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S235 Poster Session III PO03-48 AGE-RELATED VARIABILITY OF P-WAVE MORPHOLOGY IN HEALTHY SUBJECTS Yan Huo, MD, Fredrik Holmqvist, MD, PhD, Jonas Carlson, PhD, Rasmus Havmöller, MD, PhD and Pyotr G. Platonov, MD, PhD, FHRS, Department of Cardiology, Lund University Hospital, Lund University, Lund, Sweden, Department of Electrophysiology, Leipzig Heart Center-University of Leipzig, Leipzig, Germany- Lund - Leipzig, Germany, Department of Cardiology, Lund University Hospital, Lund University, Lund, Sweden, Lund, Sweden, Karolinska University Hospital, Stockholm, Sweden, stockholm, Sweden Introduction: Significant differences in dominating P-wave morphology using signal-averaged ECG have been reported in patients with structural heart disease and paroxysmal atrial fibrillation in comparison with healthy and explained by deterioration of conduction over interatrial routes. However, beat- to-beat short-term variability of P-wave morphology (PMV) has not been studied in detail. This study was aimed at exploring PMV and its relation to age in healthy subjects. Methods: The study population comprised 120 healthy subjects evenly distributed in decades from 20 to 80 years of age; 60 men (50±17 y) and 60 women (50±16 y). Standard 12-lead ECG during sinus rhythm was recorded for 6 min. The ECGs were transformed to orthogonal leads, and then beat-to-beat P-wave morphology was defined automatically depending on P-wave polarity in orthogonal leads (positive/negative/biphasic) in accordance to a predefined classification algorithm. P-wave morphology that was observed in the highest number of P-waves was defined as the dominant morphology. PMV was defined as a percentage of P waves with non-dominant morphology in a 6-min sample. Results: Patients <50 years (Group 1, 20-49y, n=60) had shorter P-waves that patients ≥50 years (Group 2, 50-80y, n=60): 137 ms (range 104-188 ms) vs. 149 ms (range 116-193 ms), p=0.004. PMV varied from 0% to 49.7%. In 76 of 120 subjects (63%) all P-waves belonged to the dominating morphology class (PMV=0%). Among patients with measurable PMV (n=44, 21 from Group 1 and 23 from Group 2) younger patients had significantly higher PMV than the older ones (median 7.1% [1.3%-49.7%] vs. 2% [0.4%-31.1%], for Group 1 and Group 2 respectively, p=0.026). Further, in those with PTV>0% there was a negative linear correlation between age and PTV (R=-0.323, p=0.032). Conclusion: P-wave morphology demonstrates negligible beat- to-beat variability in the majority of healthy subjects suggesting stable interatrial conduction pattern, however in one third of subjects evenly distributed among the age groups measurable beat-to-beat P-wave polarity shift was observed. Apart from earlier reported age-related prolongation of P-wave duration, we found an attenuation of short-term variability of P-wave morphology, likely to be due to the increase in atrial fibrosis extent. PO03-49 THE IMPACT OF FASCICULOVENTRICULAR BYPASS TRACTS ON THE DIAGNOSIS AND TREATMENT OF CONCOMITANT ARRHYTHMIAS Yong-Giun Kim, MD, Gi-Byoung Nam, MD, PhD, Chang Hee Kwon, MD, Woo Seok Lee, MD, Yoo Ri Kim, MD, Ki Won Hwang, MD, Hyung Oh Choi, MD, Kee-Joon Choi, MD and You- Ho Kim, MD. Asan Medical Center, Seoul, Republic of Korea Introduction: Fasciculoventricular (FV) bypass tracts are the rarest form of ventricular preexcitation and none of them are PO03-47 THE EFFECT OF INFLAMMATION ON INCIDENT ATRIAL FIBRILLATION: RESULTS OF A SYSTEMATIC REVIEW AND META-ANALYSIS Rajeev K. Pathak, FRACP, Walter P. Abhayaratna, FRACP, Rajiv Mahajan, MD, MBBS, Christopher Wong, MBBS, Anand Ganesan, MBBS, PhD, Anthony Brooks, PhD, Muayad Alasady, FRACP and Prashanthan Sanders, MBBS, PhD. Centre for Heart Rhythm Disorders, University Of Adelaide and Royal Adelaide Hospital, Adelaide, Australia, Canberra Hospital and Australian National University, Canberra, ACT, ACT, Australia Introduction: Inflammation is considered an important component of the substrate predisposing to atrial Fibrillation (AF). Recent data suggests that inflammation may predict response to therapy and that treatment of inflammation may improve outcomes in AF. The aim of this meta-analysis was to determine the association between raised serum biomarkers and AF. Methods: Ovid and EMBASE were searched to identify prospective cohort and case-control studies that have reported an association between raised inflammatory markers and AF. Results: Of the 405 articles identified, 17 studies that enrolled a total of 3439 individuals met the inclusion criteria. Mean C-reactive protein (CRP), B-type natriuretic peptide (BNP) and IL-6 levels from each study were recorded and the standardized difference in mean and odds ratio was calculated. Using the fixed effects model (FEM), CRP and IL-6 levels were significantly higher in AF patients (odds ratio (OR) for CRP = 2.34 (CI: 1.82- 3.01); for IL6 = 2.78 (CI: 1.79-4.32)). There was no evidence of heterogeneity (p-value for CRP = 0.44; p-value for IL-6 = 0.28). Under FEM, the OR for BNP was 4.15 (CI: 3.42-5.04) and heterogeneity was present (p-value < 0.001). Using random effects model, the effect size increased to 7.08 (CI: 3.93-12.76). Publication bias was not evident. Conclusion: Raised inflammatory markers are associated with an increased risk of incident AF. The underlying mechanisms whereby inflammation may promote the genesis of AF warrant further investigation.

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S235Poster Session III

PO03-48

AGE-RELATED VARIABILITY OF P-WAVE MORPHOLOGY IN HEALTHY SUBJECTSYan Huo, MD, Fredrik Holmqvist, MD, PhD, Jonas Carlson, PhD, Rasmus Havmöller, MD, PhD and Pyotr G. Platonov, MD, PhD, FHRS, Department of Cardiology, Lund University Hospital, Lund University, Lund, Sweden, Department of Electrophysiology, Leipzig Heart Center-University of Leipzig, Leipzig, Germany- Lund - Leipzig, Germany, Department of Cardiology, Lund University Hospital, Lund University, Lund, Sweden, Lund, Sweden, Karolinska University Hospital, Stockholm, Sweden, stockholm, SwedenIntroduction: Significant differences in dominating P-wave morphology using signal-averaged ECG have been reported in patients with structural heart disease and paroxysmal atrial fibrillation in comparison with healthy and explained by deterioration of conduction over interatrial routes. However, beat-to-beat short-term variability of P-wave morphology (PMV) has not been studied in detail. This study was aimed at exploring PMV and its relation to age in healthy subjects.Methods: The study population comprised 120 healthy subjects evenly distributed in decades from 20 to 80 years of age; 60 men (50±17 y) and 60 women (50±16 y). Standard 12-lead ECG during sinus rhythm was recorded for 6 min. The ECGs were transformed to orthogonal leads, and then beat-to-beat P-wave morphology was defined automatically depending on P-wave polarity in orthogonal leads (positive/negative/biphasic) in accordance to a predefined classification algorithm. P-wave morphology that was observed in the highest number of P-waves was defined as the dominant morphology. PMV was defined as a percentage of P waves with non-dominant morphology in a 6-min sample.Results: Patients <50 years (Group 1, 20-49y, n=60) had shorter P-waves that patients ≥50 years (Group 2, 50-80y, n=60): 137 ms (range 104-188 ms) vs. 149 ms (range 116-193 ms), p=0.004. PMV varied from 0% to 49.7%. In 76 of 120 subjects (63%) all P-waves belonged to the dominating morphology class (PMV=0%). Among patients with measurable PMV (n=44, 21 from Group 1 and 23 from Group 2) younger patients had significantly higher PMV than the older ones (median 7.1% [1.3%-49.7%] vs. 2% [0.4%-31.1%], for Group 1 and Group 2 respectively, p=0.026). Further, in those with PTV>0% there was a negative linear correlation between age and PTV (R=-0.323, p=0.032).Conclusion: P-wave morphology demonstrates negligible beat-to-beat variability in the majority of healthy subjects suggesting stable interatrial conduction pattern, however in one third of subjects evenly distributed among the age groups measurable beat-to-beat P-wave polarity shift was observed. Apart from earlier reported age-related prolongation of P-wave duration, we found an attenuation of short-term variability of P-wave morphology, likely to be due to the increase in atrial fibrosis extent.

PO03-49

THE IMPACT OF FASCICULOVENTRICULAR BYPASS TRACTS ON THE DIAGNOSIS AND TREATMENT OF CONCOMITANT ARRHYTHMIASYong-Giun Kim, MD, Gi-Byoung Nam, MD, PhD, Chang Hee Kwon, MD, Woo Seok Lee, MD, Yoo Ri Kim, MD, Ki Won Hwang, MD, Hyung Oh Choi, MD, Kee-Joon Choi, MD and You-Ho Kim, MD. Asan Medical Center, Seoul, Republic of KoreaIntroduction: Fasciculoventricular (FV) bypass tracts are the rarest form of ventricular preexcitation and none of them are

PO03-47

THE EFFECT OF INFLAMMATION ON INCIDENT ATRIAL FIBRILLATION: RESULTS OF A SYSTEMATIC REVIEW AND META-ANALYSISRajeev K. Pathak, FRACP, Walter P. Abhayaratna, FRACP, Rajiv Mahajan, MD, MBBS, Christopher Wong, MBBS, Anand Ganesan, MBBS, PhD, Anthony Brooks, PhD, Muayad Alasady, FRACP and Prashanthan Sanders, MBBS, PhD. Centre for Heart Rhythm Disorders, University Of Adelaide and Royal Adelaide Hospital, Adelaide, Australia, Canberra Hospital and Australian National University, Canberra, ACT, ACT, AustraliaIntroduction: Inflammation is considered an important component of the substrate predisposing to atrial Fibrillation (AF). Recent data suggests that inflammation may predict response to therapy and that treatment of inflammation may improve outcomes in AF. The aim of this meta-analysis was to determine the association between raised serum biomarkers and AF.Methods: Ovid and EMBASE were searched to identify prospective cohort and case-control studies that have reported an association between raised inflammatory markers and AF.Results: Of the 405 articles identified, 17 studies that enrolled a total of 3439 individuals met the inclusion criteria. Mean C-reactive protein (CRP), B-type natriuretic peptide (BNP) and IL-6 levels from each study were recorded and the standardized difference in mean and odds ratio was calculated. Using the fixed effects model (FEM), CRP and IL-6 levels were significantly higher in AF patients (odds ratio (OR) for CRP = 2.34 (CI: 1.82-3.01); for IL6 = 2.78 (CI: 1.79-4.32)). There was no evidence of heterogeneity (p-value for CRP = 0.44; p-value for IL-6 = 0.28). Under FEM, the OR for BNP was 4.15 (CI: 3.42-5.04) and heterogeneity was present (p-value < 0.001). Using random effects model, the effect size increased to 7.08 (CI: 3.93-12.76). Publication bias was not evident.Conclusion: Raised inflammatory markers are associated with an increased risk of incident AF. The underlying mechanisms whereby inflammation may promote the genesis of AF warrant further investigation.

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S236 Heart Rhythm, Vol. 10, No. 5, May Supplement 2013

repolarization anomalies; Associated arrhythmias; Coronary artery disease and Coronary risk factors. SVT measures were performed: QRS, ST, QT, T wave, TCL and VA interval length. Pseudo right bundle branch block pattern was also considered. ST segment depression was defined as >2mm from the J point in >2 consecutive leads. Different ST morphologies were analyzed: Ascendant STD (ASTD), Descendant STD (DSTD), and Horizontal STD (HSTD). Two groups were compared, those who developed STD (group A) and those who didn’t (Group B).Results: Median age 52 years (IQR 32-62,5); Males 41,82%; 80% AVNRT; 20% AVRT; 41,82% developed STD (39,13% ASTD, 21,74% DSTD, 39,13% HSTD); AVRT VA median 136ms (IQR 125-150) and TCL 344ms (IQR 317-401ms); AVNRT VA median 54ms (IQR 43-90) and TCL 345ms (IQR 303-377,5ms). Group A presented higher VA (median VA 115ms; IQR 63-136ms vs. 53ms; IQR 40-84; p=0.015). No TCL differences were observed within both groups (334ms; IQR 305-376ms vs. 360ms; IQR 322-385,5; p=0.67). Median VA and TCL in ASDT were 48ms (IQR 44-66ms) and 344ms (IQR 326-402ms) respectively; VA 124ms (IQR 114-124ms) and TCL 384ms (IQR 288-420ms) in DSTD; VA 142ms (IQR 126-146ms) and TCL 322ms (IQR 300-338ms) in HSTD; VA 48ms (IQR 44-66ms) and TCL 344ms (IQR 326-402ms) in Pseudo right bundle pattern. AVNRT developed STD in 35% of cases while 72.73% of AVRTs showed STD.Conclusion: ST segment depression is conditioned by retrograde atrial activation during SVT. Retrograde P waves can distort ST segment depending on the VA interval length. This was observed at VA intervals >120ms, without depending on TCL. AVRT has higher STD rates, as VA intervals are longer than AVNRT. No TCL differences were observed between both groups, suggesting that STD is not rate dependent.

PO03-51

THE SAFETY OF DABIGATRAN VERSUS WARFARIN IN PATIENTS UNDERGOING ATRIAL FIBRILLATION ABLATIONLuis I. Garcia, MD, Kartikya Ahuja, MD, Mark A. Mascarenhas, MD, Anthony Aizer, MD, Neil Bernstein, MD, Scott A. Bernstein, MD, Steve J. Fowler, MD, Doulglas S. Holmes, MD, David S. Park, MD and Larry Chinitz, MD. New York University, New York, NYIntroduction: Dabigatran is emerging as a commonly prescribed anticoagulant in patients referred for atrial fibrillation (AF) ablation. The use of dabigatran (DG) within 24 hours pre- ablation has been associated with an increase in major bleeding and thromboembolism versus uninterrupted warfarin (WAR) therapy. The impact of alternative DG dosing strategies for the reduction of complications is currently unknown.Methods: We performed a retrospective analysis between July 2011-October 2012 of all patients undergoing an AF ablation who received uninterrupted WAR therapy (206) and the routine cessation of DG therapy (126) 4 days pre-ablation. Major safety endpoints included: pericardial effusion (requiring pericardiocentesis), peripheral thromboembolism, CVA, and groin hematoma requiring blood transfusion. Minor endpoints included pericardial effusion and groin hematoma. All patients underwent PVI isolation with an additional lesion set if warranted. Heparin was given to all patients peri-procedurally with a goal ACT >350. Dabigatran was restarted the following day after ablation.Results: Demographics and outcomes are listed in table 1. The WAR group was slightly older and had a higher CHADS score than the DG group. There were no differences in AF type, gender, BMI, repeat left atrial ablation, or additional lesion set delivery. In the DG group, there was one renal thromboembolic event 4 days post-ablation. All 8 patients who suffered a major complication

involved in reentrant tachycardia. However, they may cause diagnostic confusion if not properly understood.Methods: Seven patients with FV bypass tracts who underwent electrophysiologic studies were evaluated. The proof of FV bypass tracts relied on 1) normal AH interval and short HV interval, 2) demonstration of fixed preexcitation with decremental atrioventricular (AV) node conduction and 3) His bundle stimulation produces preexcited QRS with short HV interval.Results: One patient had a FV bypass tract with atrial fibrillation (AF), which was misinterpreted as AV bypass tract requiring emergency DC cardioversion. One patient had a FV bypass tract with complete infra-hisian AV block which mimicked slow ventricular escape rhythm. Five patients had accompanying AV bypass tracts (right lateral AV bypass tracts in 2 patients, right posteroseptal AV bypass tracts in 2 patients, and a left lateral AV bypass tract in 1 patient). Among those, 3 AV bypass tracts participated in AV reentrant tachycardias, while 2 AV bypass tracts showed short ERP producing rapid ventricular response during induced AF or atrial flutter (AFL). In two patients with AV bypass tracts, unnecessary RF application was delivered after successful ablation of the AV bypass tracts because conduction through FV bypass tract was mistaken for conduction through residual AV bypass tract (Table 1).Conclusion: FV bypass tracts were frequently accompanied by AV bypass tracts or other arrhythmias. They may cause diagnostic confusion and even unnecessary RF delivery when misinterpreted as AV bypass tracts.

PO03-50

ST SEGMENT DEPRESSION DEPENDING ON VA INTERVALS IN SUPRAVENTRICULAR TACHYCARDIASantiago Rivera, Sr., MD, Maria de la Paz Ricapito, MD, Mariano Badra Verdu, MD, Jean-François Roux, MD and Felix Ayala-Paredes, MD. CHUS, Sherbrooke, QC, CanadaIntroduction: Faster tachycardia rates during supraventricular arrhythmias are associated with high troponin levels. ST segment depression (STD) in supraventricular tachycardia has not been yet associated with shorter tachycardia cycle lengths (TCL). Our objective is to determine a possible mechanism explaining STD and its relation with the TCL.Methods: Patients admitted for SVT ablation between 2010-2012 were analyzed (n=55). AVNRT and AVRT were included. Exclusion criteria were: Bundle branch block; Ventricular

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S237Poster Session III

PO03-53

ABLATION OF LEFT-SIDED ACCESSORY PATHWAYS WITH ATRIAL INSERTION REMOVED OFF THE MITRAL ANNULUS USING AN ELECTROANATOMICAL MAPPING SYSTEMDe Yong Long, MD, Jian Zeng Dong, MD, Chen Xi Jiang, MD, Cai Hua Sang, MD, Ri Bo Tang, MD, Rong Hui Yu, MD and Chang Sheng Ma, MD. Beijing AnZhen Hospital, Beijing, ChinaIntroduction: A left-sided accessory pathway (AP) with atrial insertion removed off the mitral annulus (MA) may result in difficulty or failure of ablation along the MA. We report our initial experience of ablating this rare AP by a 3- dimensional electroanatomical mapping system (CARTO).Methods: From January of 2007 to August of 2011, 29 patients with left-sided APs who failed previous outside ablations were enrolled in this study. Left atrium (LA) was reconstructed during orthodromic atrial ventricle reentry tachycardias (AVRTs) or ventricle pacing by using a 3-dimensional electroanatomical mapping system, and the AP atrial insertion was defined as the earliest retrograde atrial activations and successful ablation of the APs at this site.Results: Among the 29 patients who had failed previous ablation, 8 patients were found to have atrial insertions removed off the MA. Of the 8 patients, the atrial insertions were at the base of the LA appendage in 5 patients, at the anterior roof of LA in 2 patients, within the distal coronary sinus in 1 patient. Ablation at the atrial insertions successfully abolished the AP conduction. The mean distance between the atrial insertion sites and the MA was 24.6±4.5 mm. No patients reported recovered AP conduction or recurrent tachycardias after at least 12-month follow-up.Conclusion: The left-sided APs may have atrial insertion removed off the MA. By using the CARTO system, the atrial insertions can be reliably identified and ablated.

PO03-54

LONG-TERM OUTCOME AFTER CRYOBALLOON PULMONARY VEIN ISOLATION: RETROSPECTIVE ANALYSIS IN 239 PATIENTSAlix Martin, MD, Peggy Jacon, MD, Radu-Eugen Moisei, MD and Pascal Defaye, MD. Chu Grenoble, Grenoble-Cedex9, FranceIntroduction: Cryoballoon ablation (CBA) for circumferential pulmonary veins isolation (PVI) has become a technique of choice for drug refractory atrial fibrillation (AF). We routinely perform this technique in our center since 2007. Accordingly, the purpose of our study was to assess long-term AF-free survival after CBA-PVI.Methods: 239 patients treated with CBA for symptomatic AF (paroxysmal n = 197, 83% - short term persistent < 6 months n = 42, 18%) were included between 2008 and 2012 (183 men, 76% - mean age 60±10 yrs). Prospective follow-up was

requiring a blood transfusion were in the WAR group.Conclusion: Cessation of dabigatran therapy 4 days pre AF ablation has a comparable safety profile to uninterrupted warfarin therapy.Demographics and Clinical Outcomes

Dabigatran (126) Coumadin (205) P value

Age (IQR) 61.7 (55.0-69.0) 65.1 (58.3-72.0) 0.003

CHADS (SD) 0.89 ±1.0 1.1 ±1.0 0.03

Total complications n (%) 4 (3.1) 13 (6.3) NS

CVA n (%) 0 0 NS

Peripheral Thromboembolism 1(0.8) 0 NSPercardial effusion AND Pericardiocentesis n (%) 2(1.6) 2(1) NSPercardial effusion NO Pericardiocentesis n (%) 0 3(1.5) NSGroin Hematoma AND Transfusion n (%) 0 6(3.0) NSGroin Hematoma NO Transfusion n (%) 1(0.8) 2(1.0) NS

PO03-52

HIGH ACCURACY UNIPOLAR LOCAL ACTIVATION TIME ASSIGNMENT TO FACILITATE ACCURATE DENSE MULTIPOLAR ELECTRODE MAPPINGSteven E. Williams, MRCP, Nick Linton, MRCP, James Harrison, MRCP, Matthew Wright, PhD, MRCP and Mark D. O’Neill, PhD, FRCP. King’s College London, Division of Imaging Sciences and Biomedical Engineering, London, United KingdomIntroduction: Multipolar electrode mapping (MEM) increases acquisition speed of local activation time (LAT) maps. Since small errors in LAT assignment may have large effects on map appearance, MEM is usually performed with bipolar electrograms but this limits the density of measurements acquired. Therefore we present an alternative method of LAT assignment utilizing unipolar electrograms.Methods: PentaRay unipolar electrograms (4kHz) were processed by zero-phase band-pass (30-500Hz) filtering the signal gradient and LAT was taken as the resulting maximum negative peak. This approach (fGrad) was tested on simulated (n=20) and clinical electrograms (n=80). For simulated data, reference activation time was the 0mV transmembrane potential time. For clinical data, mean activation time at adjacent electrodes was compared with the corresponding bipolar activation time, defined as the barycenter of a non-linear energy operator given by E(j)=x(j)^2-x(j+1)*x(j-1). Four observers annotated all clinical electrograms.Results: Simulated data showed fGrad to correlate well with cellular activation (absolute error 1.83±1.61ms). Compared with conventional LAT assignment to clinical data, inter-observer variability was significantly reduced with fGrad (mean variance 0.08ms v 1.69ms, p<0.001) and fGrad provided a significantly more accurate LAT measurement (mean absolute error 1.18ms v 2.33ms, p<0.001). Taken as a proportion of total PentaRay catheter activation time, mean LAT variance was reduced from 5.00% to 0.23% by applying fGrad.Conclusion: fGrad is a fast and reliable method of unipolar LAT assignment which could facilitate high density unipolar activation mapping.

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S238 Heart Rhythm, Vol. 10, No. 5, May Supplement 2013

PO03-56

BIOMARKERS OF MYOCARDIAL INJURY WITH DIFFERENT ENERGY SOURCES FOR ATRIAL FIBRILLATION CATHETER ABLATIONEleonora Russo, MD, Michela Casella, MD, PA, Antonio Dello Russo, MD, Martina Zucchetti, MD, Gaetano Fassini, MD, Massimo Moltrasio, MD, Fabrizio Tundo, MD, Benedetta Majocchi, MD, Osama Al-Nono, MD, Gennaro Izzo, MD, VIttoria Marino, MD, Stefania Riva, MD, Luigi Di Biase, MD, Andrea Natale, MD, FHRS and Claudio Tondo, MD. Cardiac Arrhythmia Research Centre, Centro Cardiologico Monzino IRCCS, Milan, Italy, Texas Cardiac Arrhythmia Institute at St. Davis Medical Center, Austin, TXIntroduction: Our study aims to compare acute myocardial injury biomarker rise after atrial fibrillation ablation performed with different technologies.Methods: One hundred and ten patients (pts) were treated with Pulmonary Vein (PV) isolation with 4 different technologies: open-irrigated tip RF catheter in 35 pts (Group A), cryoballoon in 35 pts (Group B), visually guided laser balloon in 20 pts (Group C), open-irrigated tip RF catheter with contact-force-sensing technology in 20 pts (Group D). Post-procedure samples of cardiac Troponin I (cTnI) and Creatinine Kinase-MB (CKMB) were collected at 19±3 and 43±3 hours after ablation.Results: At the first postprocedural sample, cTnI and CK-MB levels were found elevated in all 110 pts with a median value of 2.09 ng/mL and 8.95 ng/mL respectively. Group B pts showed cTnI levels increased (6.21±3.46 ng/mL) compared to the other groups (Group A 1.92±1.04 ng/mL, Group C 1.62±0.87 ng/mL, Group D 2.53±1.93 ng/mL; p < 0.001). Also CK-MB levels resulted higher in cryoablation (35.87±24.51 ng/mL) compared to other groups (Group A 6.20±3.18 ng/mL, Group C 7.11±2.20 ng/mL, and Group D 8.41±5.04 ng/mL; p < 0.001). No significant correlation was observed between biomarkers levels and recurrence of AF at 1, 3, 6, 12 months of follow up.Conclusion: Highest markers for myocardial injury were observed in cryoballon group. These results may reflect the role of protein denaturation and a different pattern release of biomarkers in these settings. The higher levels of cardiac biomarkers did not translate into a better outcome and its physiologic significance is unknown.

obtained by written questionnaire and collected data were: need for anti-arrhythmic drugs, AF related symptoms, and 24h-holter monitoring results. Primary end-point was a composite of AF related symptoms and/or AF recurrence.Results: At a mean follow up of 23±15 months [1.5 to 59 months], Kaplan-Meyer end-point free survival rate was 77.7% in the whole population, and raised to 93% in patients treated within 1 yr after the first episode of AF. End-point free, need for redo-procedure free, and anti-arrhythmic drugs free survival rates were 78.0 vs. 77.7% (NS), 84.3 vs 85.4% (NS), and 61.7 vs. 46.3% (P=0.08) in patients treated for paroxysmal and persistent AF respectively. After CBA for paroxysmal AF, 92% of patients without anti-arrhythmic drugs were asymptomatic and AF recurrence free. Procedure related major complication rate was 3.8% (tamponnade n=4, endocarditis n=1, severe hematomas n=3).Conclusion: In our experience, CBA for treatment of AF is safe and efficient for symptoms relief and prevention of AF recurrence, with similar results in pts with paroxysmal and short term persistent AF. Best efficacy is observed in patients treated < 1 year after first episode of AF.

PO03-55

CRYOABLATION INDUCES A SIMILAR TRANSIENT BLOOD CLOTTING ACTIVATION BUT A LOWER ENDOTHELIAL ACTIVATION WHEN COMPARED WITH RADIOFREQUENCY ABLATIONPaolo Pieragnoli, MD, Giuseppe Ricciardi, MD, Gianmarco Carrassa, MD, Luca Checchi, MD, Rossella Bani, MD, Laura Perrotta, MD, Stella Cartei, MD, Antonio Michelucci, MD, Anna Maria Gori, BS, Raffaella Priora, BS, Rossella Marcucci, BS, Rosanna Abbate, MD, Gian Franco Gensini, MD and Luigi Padeletti, MD. University of Florence, Firenze, ItalyIntroduction: Recently cryoablation (CA) emerged as an alternative procedure to radiofrequency (RF) in ablating AVNRT. Aim of this study is to compare haemostatic system alterations in patients undergoing RF or CA.Methods: Prothrombin fragment F1+2 (F1+2), Thrombin-Antithrombin complex (TAT), von Willebrand factor (vWF), and plasminogen activator inhibitor type-1 (PAI-1) were determined in 13 patients underwent CA and 15 patients underwent RF (13M/15F, mean age 51.9±16.7 years). Blood samples were obtained before the procedure (T0), immediately after (T1) and 24 hours later (T2).Results: Acute procedural success was achieved in all patients. During follow-up (68±38 days) no arrhythmias recurrences were observed. At T1 a statistically significant increase (p<0.001) in F1+2 and TAT levels occurred compared with T0 values both in CA group and RF group (table 1). At T2 F1+2 and TAT levels were similar to baseline values in both groups. At T0, T1 and T2 the comparison between RF and CA showed no significant differences in F1+2 and TAT levels. No statistically significant changes in PAI-1 and vWF plasma levels were observed in CA and RF groups. Concerning PAI-1 no significant differences were observed between CA and RF. At T2 vWF plasma levels were significantly (p<0.05) lower in CA than in RF (table 1).Conclusion: In this study we analyzed the haemostatic system in patients undergoing catheter ablation of AVNRT and we found a comparable and transient blood clotting activation in both procedures with the exception of vWF levels that were lower in CA group 24 hours after the ablation. This suggests that the CA procedure may be associated with a lower degree of endothelial damage.

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S239Poster Session III

treated with dual AAD therapy. In consecutive patients with AF admitted for a combination of AAD at our institution between 4/97 and 4/09, clinical, medication, echocardiographic data, ECG intervals including QRS and QTc interval were analyzed. Mortality was determined by the Social Security Death Index.Results: There were 79 patients admitted with AF for initiation of this combination therapy (mean age 60.3±12.1years, 60.1% male, mean LVEF 54.0±7.0%, 19% CAD, 10% ICDs and mean follow up of 18.8±26.9 months). 78.4% were on flecainide and sotalol, 6.5% were on propafenone and sotalol, 12.6% were on flecainide and dofetilide and 2.5% were on propafenone and dofetilide. There was no episodes of ventricular proarrhythmia observed during hospitalization or at follow up. Mean QTc and QRS at discharge were 440.8±58.3 msec and 116.2±33.3 msec respectively. Dual AAD therapy was stopped in 40/79 (51%) patients due to inefficacy, bradycardia and noncardiac intolerance. There was no mortality noted while on dual AAD therapy. Combination drug therapy was effective in maintaining normal sinus rhythm in 39/79 (49%) patients at the time of the last follow up visit (median time of follow up was 13 months).Conclusion: Single AAD therapy is the initial therapeutic choice for most patients with AF. However, for refractory cases, a combination of class 1 and class 3 agents appears safe in this selective group of patients when initiated in a monitored setting. These combinations could be efficacious when single drug therapy does not control the clinical arrhythmia adequately.

PO03-59

THE TIME-COURSE OF EXIT AND ENTRANCE BLOCK DURING PULMONARY VEIN ISOLATIONJason G. Andrade, MD, Paul Khairy, MD, PhD, Marc Dubuc, MD, Blandine Mondesert, MD, Nicolas Clementy, MD, Denis Roy, MD, Mario Mario, MD, Marc Deyell, MD, Matthew Bennett, MD, Lena Rivard, MD, Bernard Thibault, MD, Peter Guerra, MD and Laurent Macle, MD. Montréal Heart Institute, Montreal, QC, Canada, University of British Columbia, Vancouver, BC, CanadaIntroduction: Demonstration of entrance conduction block is considered the procedural endpoint of PVI. While the presence of entrance block appears to be effective in predicting bidirectional LA-PV conduction block, the dynamic time course of entrance and exit block during PVI is unknown.Methods: Dynamic pacing manoeuvres were performed during cryoballoon ablation of left sided pulmonary veins in ten consecutive patients with a history of drug-refractory paroxysmal AF (mean age 56 years; 63% male). In seven patients pacing was initiated in the PV at the onset of cryothermal ablation and continuously performed at 600 msec until the appearance of exit block. Once exit block with PV dissociation was clearly demonstrated, uninterrupted pacing was immediately transitioned to the distal CS catheter and continued at 600 msec throughout the rest of the cryoapplication. In two patients the opposite pacing sequence was performed. The timing of exit block, entrance block, and corresponding cryoballoon temperature were noted for all patients.Results: In the 10 pulmonary veins when real-time PV recordings were available during cryothermal ablation, and in which pacing was initiated from the PV during cryoablation, the presence of exit block was reliably demonstrated to precede entrance block by a median of 28 seconds (range 12-161 seconds; temperature at isolation -34oC; nadir ablation temperature -54oC). In the patients in which pacing was initially performed in the distal CS during cryoablation, the presence of entrance block was reliably associated with the concurrent (or pre-existing) presence of exit block.Conclusion: In PVs undergoing simultaneous circumferential PVI, ablation results in progressive pulmonary vein isolation,

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REFUTING THE ASSUMPTION OF INEVITABLE PROGRESSION TO PERSISTENT AF - THE TRUE NATURAL HISTORY OF AF FROM LONG-TERM BEAT-TO-BEAT PACEMAKER MONITORING.Conn Sugihara, MBBS, Rick Veasey, MBBS, Steve Podd, MBBS, Steve Furniss, MD, FRCP and Neil Sulke, MD, FRCP. Eastbourne General Hospital, Eastbourne, United KingdomIntroduction: Expert consensus is that AF inevitably progresses from paroxysmal (PAF) to persistent AF (PersAF). Evidence for this comes from small retrospective analyses or short-term prospective surveys, all limited by very intermittent ECG monitoring. Pacemakers (PPMs) are the gold standard in AF detection, and offer long-term beat-to-beat AF diagnostics. The definitions of PAF and PersAF result in inexorable progression from PAF to PersAF. PPM diagnostics allow for improved analysis of the natural history of AF.Methods: 247 patients with AF and PPMs capable of AF diagnostics were recruited. All medical notes, ECGs, echocardiograms and pacemaker downloads were examined, particularly for AF burden (device-detected percentage of time in AF). Those with true paroxysmal AF (‘True PAF’) were arbitrarily classified as never having 100% AF burden for more than 28 days and having greater than 10% absolute reduction in AF burden between follow up. Pts with true persistent AF (‘True PersAF’) had 100% AF burden for more than 28 days.The remainder were classified as ‘Others’.Results: There were 1329 PPM downloads, with mean 8.7 years follow up after diagnosis, 3.6 years of beat-to-beat monitoring per patient, and 5.4 downloads per patient. 46% were female, mean age 72 yrs at PPM implant. AF burden was bimodally distributed in the overall population, with a median AF burden of 14.0%.13% were classified as having ‘True PAF’. In these pts, when there was a change in AF burden between follow up downloads, the change in AF burden was normally distributed (SD 31%). The mean AF burden for this group was 25.6%.41% were classified as having ‘True PersAF’.46% were classified as ‘Others’. The mean AF burden for ‘Others’ was 1%. There was no significant difference between intensity of monitoring between the three groups throughout the follow up period.Conclusion: A clinically significant group of patients with a high burden of AF had no evidence of increasing AF burden when monitored in the long term. Most of this group would be classified as persistent AF by standard diagnostic criteria, when they actually have paroxysmal AF. Almost half of the subjects had low AF burden and did not progress to persistent AF in the long term. These data suggest that progression to persistent AF is not inevitable.

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COMBINATION OF ANTIARRHYTHMIC DRUGS IN TREATING REFRACTORY ATRIAL FIBRILLATIONSandeep Duggal, DO, Roy Chung, MD, Bryan Baranowski, MD, David O. Martin, MD, Oussama Wazni, MD, Walid Saliba, MD and Patrick Tchou, MD. Cleveland Clinic, Cleveland, OH, Cleveland Clinic Florida, Weston, FLIntroduction: Patients who have failed multiple single antiarrhythmic drug (AAD) therapies for atrial fibrillation (AF) typically can settle for rate control or pursue invasive procedure. There is presently little published data on the safety and efficacy of combining class 1 and class 3 AAD in patients with refractory AF.Methods: To assess the safety and efficacy of combination therapy, 79 patients with AF refractory to prior therapies were

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University of California, San Francisco, Division of Cardiac Electrophysiology, San Francisco, CAIntroduction: The left atrial appendage (LAA) can be a trigger for atrial fibrillation (AF). Catheter ablation for LAA isolation has been successful, but is limited by the risk of tamponade & mechanical standstill with thrombus formation. We hypothesized that epicardial LAA ligation acutely alters LAA conduction and may affect AF burden.Methods: 41 AF patients with CHADS2 score ≥ 1 underwent LAA ligation with the LARIAT suture delivery device. LAA closure was confirmed with TEE. All patients were tested for LAA conduction using unipolar recordings from the endocardial guidewire or bipolar recordings from the endo & epicardial guidwires. Electrograms were recorded pre & post ligation. 24 hr holter monitoring was performed 1 yr after ligation in 29 patients with unipolar recordings.Results: Unipolar Group - 30 pts: the mean pre & post unipolar voltage was 10.6 mV (± 5.33) & 3.1 mV (± 4.11), respectively; this was significantly different (p < 0.001, Fig 1) with a 68% mean reduction of LAA voltage. Ligation abolished & reduced LAA voltage in 10 (33%) & 27 (90%) patients, respectively. 29 patients had reduced AF symptoms. No patients had worsened AF symptoms. 1 was lost to follow up. 1 yr holter monitor revealed 8 (27%) patients with AF, and 21 (70%) patients with no AF. Bipolar Group - 11 pts: mean pre-ligation voltage = 1.12 mV (± 0.41); mean post ligation voltage = 0.45 mV (± 0.33; p = 0.001) with a 57% mean reduction of LAA voltage.Conclusion: LAA ligation acutely alters electrical conduction into the LAA. As ischemic necrosis progresses, this may translate into long-term LAA electrical isolation. These results support future studies testing whether LAA ligation and electrical isolation improves AF ablation.

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CONFIRMATION OF ENTRANCE BLOCK WITH ADENOSINE TRIPHOSPHATE IS SUFFICIENT TO EVALUATE DORMANT CONDUCTION OF PULMONARY VEINHirosuke Yamaji, MD, PhD, Takashi Murakami, MD, PhD, Shnninchi Higashiya, MD, Hiroshi Kamikawa, MD, PhD, Masaaki Murakami, MD, PhD and Kazuyoshi Hina, MD, PhD. Okayama Heart Clinic, Okayama, JapanIntroduction: Confirmation of bidirectional block of pulmonary vein (PV) is essential after PV antrum isolation (PVAI) for atrial fibrillation(AF). Adenosine Triphosphate (ATP) is useful to evaluate dormant conduction (DC) of PV after PVAI.Objective: To assess whether confirmation of bidirectional block of PV with ATP is necessary and sufficient after PAVI.Methods: We studied consecutive 100 patients who underwent PVAI (age 64±8 years, female=34, paroxysmal AF: non-paroxysmal AF=56:44). After PVAI, under coronary sinus

beginning with unidirectional exit block, and followed by entrance block. In providing verification that exit block reliably precedes, and thus is a necessary prerequisite of entrance block, we are able to provide justification for the exclusive use of entrance conduction block as the sole endpoint of PVI.

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COMPARISON OF TWO PROCEDURAL ANTICOAGULATION REGIMENS FOR PATIENTS UNDERGOING LEFT-SIDED ABLATION PROCEDURESJean-Francois Roux, MD, Santiago Rivera, MD, Felix Ayala-Paredes, MD, PhD, Mariano Badra-Verdu, MD and Charles Dussault, MD. Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, QC, CanadaIntroduction: Current guidelines for anticoagulation during left sided ablation procedures recommend the administration of unfractionated heparin with an initial bolus of 50-100U/kg, followed by continuous infusion adjusted to maintain an ACT ≥ 300 seconds. In our experience, the efficacy of this regimen to rapidly reach target ACTs is very low. Our objective was to compare the efficacy of the currently recommended heparin protocol (100 U/kg heparin bolus) to a more aggressive protocol (200 U/kg heparin bolus).Methods: We collected procedural anticoagulation data on a series of consecutive patients undergoing left sided ablation procedures at our institution. Patients with an INR ≥ 2.0 on the day of the procedure were excluded. Procedural anticoagulation was performed using one of two regimens: 1) 100 U/kg heparin bolus at the time of left sided vascular access, followed by 10 U/kg/h heparin perfusion or 2) 200 U/kg heparin bolus, followed by 20 U/kg/h heparin perfusion. The first ACT was obtained 5 minutes after left sided circulation access and then controlled every 20 minutes throughout the procedure. Heparin was titrated in order to maintain an ACT 350-400 seconds. Our primary objective was to compare the proportion of patients with an initial ACT ≥ 300 seconds in each group.Results: Overall, 71 consecutive patients were included in the study (33% females, median age 62 y.o.; median weight 84 kg): 29 patients received an initial heparin bolus of 100 U/kg and 32 patients received a bolus of 200 U/kg. The proportion of patient with an initial ACT ≥ 300 seconds was 3.4% in the 100 U/kg group compared to 81.3% in the 200 U/kg group (P < 0.001). The median initial ACT was 233 seconds (IQR 214-268 seconds) in the 100 U/kg group compared to 350 seconds (IQR 315-392 seconds) in the 200 U/kg group (P=0.02). In the 200 U/kg group, 6 patients had an initial ACT > 400 seconds (range 404 to 692 seconds) and 4 patients had an ACT < 300 seconds (range 173-290 seconds). No thromboembolic or haemorrhagic complication was observed.Conclusion: Current procedural anticoagulation guidelines for left sided ablation procedures almost universally fail to achieve an initial ACT ≥ 300 seconds. A 200 U/kg heparin bolus is much more effective in order to promptly reach the target ACT.

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THE EFFECTS OF LAA LIGATION ON LAA ISOLATION AND ATRIAL FIBRILLATIONFrederick T. Han, MD, Miguel Valderrabano, MD, Krzysztof Bartus, MD, PhD, Jacek Bednarek, MD, PhD, Nitish Badhwar, MBBS, FHRS and Randall Lee, MD, PhD. University of Utah Health Sciences Center, Salt Lake City, UT, The Methodist Hospital, Division of Cardiac Electrophysiology, Houston, TX, Department of Cardiovascular Surgery and Transplantology, Jagiellonian University, Krakow, Poland, Department of Cardiovascular Surgery and Transplantology, Jagiellonian University, krakow, Poland,

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S241Poster Session III

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LEFT ATRIAL VOLUME AND SYMMETRY CHANGES AS PREDICTORS OF LONG-TERM SUCCESS AFTER CATHETER ABLATION OF ATRIAL FIBRILLATIONSotirios Nedios, MD, Emmanuel Koutalas, MD, Sokrates Pastromas, MD, Philipp Sommer, MD, Jedrzei Kosiuk, MD, Arash Arya, MD, Sergio Richter, MD, Nikolaos Kanagkinis, MD, Sascha Rolf, MD, Christopher Piorkowski, MD, Daniela Husser, MD, Gerhard Hindricks, MD, PhD and Andreas Bollmann, MD, PhD. Department of Electrophysiology, University of Leipzig – Heart Center, Leipzig, GermanyIntroduction: Atrial fibrillation (AF) is associated with remodeling of the left atrium (LA). LA dilatation is associated with AF-progression and reduced success after catheter ablation (CA). We studied the pattern of LA asymmetry in regard to dilatation and its predictive value.Methods: We prospectively included 103 patients (72 males, 59±9 years, LAD diameter 45±6 mm) undergoing AF-CA. LA and pulmonary vein (PV) reconstruction was performed by specialized software (EnSiteVerismo,SJM,MN) and preprocedural CT data. LA volume (LAV) after exclusion of the atrial appendage (LAA) and the PV was determined. The LA was arbitrarily divided by a cutting plane, between the anterior segment of the PV ostia and LAA and parallel to the posterior wall, to anterior-(LA-A) and posterior-LA (LA-P). The ratio LA-A/LAV was defined as asymmetry index (ASI) and the ratio LA-P/LA-A as relative asymmetry index (ASI-r).Results: Patients with persistent AF (n=40) had significantly higher LAV (p<0.001,144±39ml vs. 116±27ml) and ASI (62±4% vs. 58±5%, p<0.001) but lower ASIr (62±10% vs. 75±15, p<0.001) than those with paroxysmal AF (n=63). LAV increase was associated with an ASI-increase (r=0.39, p<0.001) and ASIr-decrease (r=-0.99, p<0.001), revealing an asymmetric dilatation of LA-A in relation to LA-P. During follow-up (26±15 months), AF recurred in 31(30%) patients. Univariate analysis revealed no difference in clinical data and LAD (p=0.05, 47±5mm vs. 43±6mm), but a higher incidence of persistent AF (p=0.02, 58% vs. 30%), higher LAV (p=0.001,144±37ml vs. 120±31ml) and ASI (p=0.001,62±4% vs. 58±5%) associated with AF recurrence. Multivariate analysis showed that LA-A (p=0.01, OR=0.96, 95%CI: 0.95-0.98) and ASI (p=0.002, OR=0.85, 95%CI: 0.77-0.94) were independent predictors of AF recurrence. In patients with persistent AF, asymmetry was the strongest predictor (ASIr, p=0.03, OR=1.01, 95%CI: 1.011-1.085) independent of LA volumes. LAD correlated well with LA-A (r=0.52, p<0.01), but not with ASI (r=0.03,p=0.8) and it was not identified as independent predictor.Conclusion: Advanced AF is associated with asymmetric dilatation of LA-A in relation to LA-P, negatively affecting long-term success after CA. LA-A and ASI are new and simple independent predictors with higher value than the commonly used LAD.

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LONG-TERM OUTCOME AND PREDICTORS FOR ARRHYTHMIA RECURRENCE AFTER REPEAT CATHETER ABLATION OF ATRIAL FIBRILLATION IN PATIENTS WHO RECURRED AFTER A SINGLE ABLATION PROCEDUREAtsuhiko Yagishita, MD, Yasuteru Yamauchi, MD, Atsushi Suzuki, MD, Hironori Sato, MD, Takamichi Miyamoto, MD, Toru Obayashi, MD, Mitsuaki Isobe, MD and Kenzo Hirao, MD. Musashino Red Cross Hospital, Tokyo, Japan, Tokyo Medical and Dental University, Tokyo, JapanIntroduction: The long-term outcome and the predictors for arrhythmia recurrence after repeat procedure of atrial fibrillation

distal (CSd) pacing (entrance block) and PV pacing with a ring catheter placed within PV(exit block), ATP was administrated to confirm DC of all PVs in all patients except with bronchial asthma. Right middle PVs were also excluded.Results: Total 392 PVs (left common trunk PV=8%) were evaluated. Local capture of PV by pacing with a ring catheter placed within PV was detected in 84% PVs (330/392). Of 330 PVs, DC under CSd pacing was observed in 26% PVs (79/330). The incidence of DC under PV pacing was same. Conversely, DC under CSd pacing was not observed in 74% PVs which was the same as the incidence of no DC under PV pacing. The incidence of entrance block and exit block with ATP administration did not differ in all PVs.Conclusion: The present results revealed that the confirmation of entrance block with ATP is necessary and sufficient to evaluate DC after PVAI.

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DO ATRIAL FIBRILLATION MONITOR CHARACTERISTICS PREDICT AF SYMPTOM SEVERITY?Nikhil Patel, BA, Eugene H. Chung, MD, FHRS, Paul J. Mounsey, MD, PhD, Jennifer D. Schwartz, MD, Irion Pursell, RN and Anil Gehi, MD, FHRS. University of North Carolina at Chapel Hill, Chapel Hill , NCIntroduction: Atrial Fibrillation (AF) is the most common arrhythmia in adults. The goal of treatment for AF is often to reduce AF burden or control heart rate. However, it remains unclear whether these AF characteristics are directly correlated with AF symptom severity.Methods: Two hundred eighty-six patients completed a questionnaire of their general health and well-being, including a detailed AF symptom assessment, followed by a 7-day continuous monitor (ACT III, LifeWatch Corp or Ziopatch, iRhythm Technologies, Inc). AF characteristics assessed from the monitor included AF burden, AF rate, sinus rhythm rate, frequency and severity of pauses, and PAC or PVC burden. Characteristics were analyzed separately for paroxysmal or persistent AF patients. Symptom severity was assessed using the University of Toronto AF symptom severity sub-scale (AFSS). Individual symptoms attributable to AF were scored on a 5-point Likert scale such that the total AFSS severity score ranged from 0-35. Individuals with a score greater than or equal to 20 (highest quartile) were classified as having severe symptoms. Student’s t-tests and multivariable regression analyses were used.Results: The mean age of the cohort was 61.8 and the majority were male (65.4%). Comorbidities included hypertension (64.5%), sleep apnea (38.4%), congestive heart failure (19.6%), and diabetes (16.4%). In unadjusted analyses, paroxysmal AF patients with severe symptoms had more pauses > 2.5 sec and a longer duration of maximum pause (p<0.05). In addition, paroxysmal AF with severe AF symptoms had a higher total AF burden (19.7% vs 11.3%, p = 0.067). Among those with persistent AF, there were no significant predictors of AF symptom severity. Heart rate in AF, heart rate in sinus rhythm, and PAC or PVC burden were not predictive of AF symptom severity in paroxysmal or persistent AF patients. After adjusting for potential cofounders (including age, gender, and comorbidities), these findings persisted.Conclusion: The number and severity of pauses as well as AF burden were predictive of severe AF symptoms in patients with paroxysmal AF. No clear feature was predictive of symptom severity in patients with persistent AF. These results may help guide therapy to relieve AF symptoms.

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Conclusion: In patients with AF and LV dysfunction with no LGE on CMR, ventricular function normalizes following the restoration of sinus rhythm. CMR may assist in the selection of AF-HF patients most likely to benefit from catheter ablation.

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THREE WEEKS ANTICOAGULATION PRIOR TO ELECTIVE CARDIOVERSION DOES NOT GUARANTEE ABSENCE OF LEFT ATRIAL THROMBUS IN HIGH RISK PATIENTS WITH PERSISTENT ATRIAL FIBRILLATIONYoungjin Cho, MD, Myung-jin Cha, MD, Eue-Keun Choi, MD, PhD, Il-Young Oh, MD and Seil Oh, MD, PHD, FHRS. Seoul National University Hospital, Seoul, Republic of Korea, Seoul National University Bundang Hospital, Seongnam-si, Gyeonggi-do, Republic of KoreaIntroduction: The current guidelines recommend 3-week period of therapeutic anticoagulation prior to elective direct current cardioversion (DCC) in patients with atrial fibrillation (AF) lasting longer than 48 hours. We sought to find out AF patients who are in high risk of left atrial (LA) thrombus despite 3-week anticoagulation before elective DCC.Methods: One hundred and seventy-eight consecutive persistent AF patients planned for elective DCC were enrolled (62 ± 10 years, 55 [31%] female). Median duration of AF was 27.4 months (inter-quartile range, 7.6 - 65.8 months). Anticoagulants were prescribed for at least 3 weeks (median duration, 149 days; inter-quartile range, 84 - 488 days) and transesophageal echocardiography (TEE) was performed before DCC to exclude LA thrombus.Results: TEE revealed LA thrombus in 6 out of 178 patients (3.4%). Patients with LA thrombus showed higher prevalence of valvular AF (3/6 [50.0%] vs. 10/172 [5.8%], p=0.005), and higher CHA2DS2-VASc score (3.7 ± 1.9 vs. 2.2 ± 1.9, p=0.021). Female gender tended to be more frequent in patients with LA thrombus (4/6 [66.7%] vs 51/172 [29.7%], p=0.074). There was no significant difference in the percentages of time in PT INR ≥ 2.0 during 3-weeks of anticoagulation prior to DCC between patients with and without LA thrombus (56.9 ± 43.8 and 75.5 ± 38.1, p=0.244). Furthermore, three patients with LA thrombus (50%) showed more than 70% of time in PT INR ≥ 2.0 (vs. 122/172 [71%] in patients without LA thrombi, p = 0.364). There was no significant difference in LA size (53.3 ± 4.0 vs. 50.6 ± 6.8 mm, p=0.333), mean CHADS2 score (1.7 ± 1.5 vs. 1.1 ± 1.1, p=0.168), and mean HAS-BLED score (2.2 ± 1.2 vs. 1.6 ± 1.0, p=0.196). In a multivariate analysis, valvular AF (odds ratio [OR], 31.9; 95% confidence interval [CI], 2.2-471; p = 0.012) and CHA2DS2-VASc ≥ 5 (OR, 20.3; 95% CI, 1.1 - 362; p = 0.041) were independent predictors of LA thrombus in TEE.Conclusion: Three weeks anticoagulation prior to DCC in persistent AF patients could not ascertain absence of LA thrombus. Patients with valvular AF or those with CHA2DS2-VASc ≥ 5 are at high risk for LA thrombus under a conventional approach to DCC, and TEE may play a role in these patients.

(AF) in patients who recurred after a single ablation procedure remains unknown.Methods: A total of 232 patients with AF (166 men; age, 61.9 ±11.4 years; 137 paroxysmal) who underwent repeat procedure for arrhythmia recurrence after a single ablation were enrolled. The long-term outcome and predictors for recurrence were determined.Results: During 54 ± 2.5 months follow-up, 68 of 232 (29.3%) patients had recurrence of AF. Patients with paroxysmal AF maintained sinus rhythm better than those with persistent AF (Log-Rank, P=0.001). Patients with sick sinus syndrome (SSS) had higher recurrence rate than those without (Log-rank, P=0.011). In multivariable analysis, both persistent AF (HR: 4.5, P < 0.001) and SSS (HR: 5.6, P < 0.001) independently predicted long-term recurrence.Conclusion: Steady decline in arrhythmia-free survival is noted after second procedure. Continued vigilance is warranted, particularly in patients with persistent AF or SSS.

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ATRIAL FIBRILLATION ABLATION IN PATIENTS WITH CARDIOMYOPATHY AND NO DELAYED ENHANCEMENT ON CARDIAC MAGNETIC RESONANCE IMAGING: SINUS RHYTHM RESTORES VENTRICULAR FUNCTIONLiang-han Ling, MBBS, Andrew J. Taylor, PhD, Andris H. Ellims, MBBS, Leah M. Iles, MBBS, Geoffrey Lee, PhD, Saurabh Kumar, MBBS, Geraldine Lee, PhD, Andrew Teh, PhD, Caroline Medi, PhD, David M. Kaye, PhD, Jonathan M. Kalmann, PhD and Peter M. Kistler, PhD. Alfred Hospital and Baker IDI Heart and Diabetes Institute, Melbourne, Australia, Royal Melbourne Hospital, Melbourne, AustraliaIntroduction: Atrial fibrillation (AF) and systolic heart failure (HF) frequently coexist. Restoration of sinus rhythm by catheter ablation may result in a variable improvement in left ventricular (LV) function. Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging identifies irreversible structural change and may predict incomplete recovery of LV function. We prospectively selected AF and HF patients (EF<50%) without LV LGE and report the impact of AF ablation on LV function.Methods: Patients with AF and HF resistant to at least one antiarrhythmic drug and prior DCR underwent contrast-enhanced CMR. LGE negative patients underwent pulmonary vein isolation and left atrial roof line with continued antiarrhythmic medications until follow-up CMR 6 months post-ablation.Results: Sixteen patients (aged 55±12 years, mean AF duration 46±41 months, LA size 44±13 ml/m2) underwent AF ablation. At 6 months 15 of 16 patients maintained sinus rhythm and underwent CMR. LV EF increased from 40±10% at baseline to 60±6% (p<0.001) and LV end systolic volume index decreased from 52±12 to 36±9 ml/m2 (p<0.001). Left atrial size decreased from 44±13 to 36±11 ml/m2 (p<0.01).

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Hamburg, Germany, Universitäres Herzzentrum Hamburg, Hamburg, Germany, Klinikum Coburg, Coburg, Germany, Klinikum Bogenhausen, München, Germany, Westpfalz Klinikum, Kaiserslautern, Germany, Klinikum Ingoldstadt, Ingoldstadt, Germany, Praxisklinik Dresden, Dresden, Germany, Evangelisches Krankenhaus Düsseldorf, Düsseldorf, Germany, Städtisches Klinikum Hildesheim, Hildesheim, Germany, Institut für Herzinfarktforschung Ludwigshafen, Ludwigshafen, GermanyIntroduction: Ablation has become a standard treatment option in therapy of atrial fibrillation. Especially patients with lone atrial fibrillation (AF) are favoured for an ablation strategy because of a very good safety and efficacy. The available data for ablation of atrial fibrillation in patients with hypertrophic cardiomyopathy (HCM) are not very comprehensive. Ablation of AF in patients with HCM is as effective as in patients with lone AF.Methods: Patient and procedural data as well as acute and long-term outcome data from pts. with ablation of AF were prospectively collected in 55 centres. One-year follow-up (1yFU) data were gathered by telephone call. Data collection and the statistical analysis were performed for the German Ablation Registry organized by the Institut für Herzinfarktforschung (IHF), Ludwigshafen, Germany.Results: 63 pts. with HCM (71,4% men, mean age 57y, 70% completed follow-up) and 4437 pts. without a structural heart disease (65,4% men, mean age 61y, 59% completed follow-up) underwent ablation for AF. Pts. with HCM had a CAD in 11,1%, in 9,5% a valve disease and in 27,8% a reduced EF(<50%). Pts. with HCM had less paroxysmal atrial fibrillation (46% vs. 68,6% p<0,01) and the ablation was performed same often for the first time (79,4% vs. 82,3% p=n.s.). There was no significant difference in acute procedural success (98,4% vs. 97,4% p=n.s.) and the recurrence rate of AF in 1yFU (45,2% vs. 46,9% p=n.s.) between the HCM pts. and the lone AF pts. All acute and long-term complication rates (MACCE, bleedings, AV-Bock II-III, thromboembolism etc.) did not differ significant. The HCM pts. had a higher procedural duration (180min vs. 165min p<0,05) without a significant difference in fluoroscopy time (29,5min vs. 27,0min p=n.s.) and in the dose area product (4083 cGy*cm2 vs. 3298 cGy*cm2).Conclusion: These results of a multicentre registry based on real-life data suggest that ablation of AF can be performed in HCM pts. with the same efficacy and safety as in pts. with lone AF especially regarding the recurrence rates in 1yFU.Limitations: -non randomized registry data-incomplete follow up (holter data)-

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NEW- ONSET ATRIAL FIBRILLATION FOLLOWING TRANS CATHETER AORTIC VALVE REPLACEMENTFnu Abhishek, MD, Jonathan Passeri, MD, E.Kevin Heist, MD, PhD, Igor F. Palacios, MD, Ignacio Inglessis, MD, Sammy Elmariah, MD, MPH, Stephan Danik, MD, Conor Barrett, MD, Joshua Baker, MD, Gus Vlahakes, MD, Jeremy Ruskin, MD and Moussa Mansour, MD. Massachusetts General Hospital, Boston, MAIntroduction: New onset atrial fibrillation (AF) has been described post-operatively after cardiac surgery.Transcatheter aortic valve replacement (TAVR) is a relatively new procedure for treating patients who are at high risk for surgical valve replacement. In our study the development of AF in post-operative period of patients undergoing TAVR was investigated.Methods: We retrospectively reviewed data from 142 patients who underwent TAVR (Edwards Sapiens Valve) between June 2008 and October 2012.Patients with prior AF were excluded (n=72). Patients undergoing TAVR were on continuous telemetry monitoring throughout their

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PREVALENCE AND CHARACTERISTICS OF MAJOR CARDIOVASCULAR EVENTS FOLLOWING ATRIAL FIBRILLATION ABLATION: A LONG-TERM COHORT STUDYYen-Chang Huang, MD, Yenn-Jiang Lin, MD, Shih-Lin Chang, MD, Li-Wei Lo, MD, Yu-Feng Hu, MD, Tzu-Fan Chao, MD and Shih-Ann Chen, MD, FHRS. Division of Cardiology, Department of Medicine, Taipei Veterans General Hospital, Taipei, TaiwanIntroduction: The purpose of this study was to evaluate the characteristics of major cardiovascular events and cardiovascular mortality following catheter ablation of atrial fibrillation (AF).Methods: This study enrolled 549 consecutive paroxysmal (80.3%) and persistent AF (19.7%) patients who underwent catheter ablation from 2004 to 2010. The major cardiovascular (CV) endpoints for the clinical follow-up included the mortality (National Death Registry database of Taiwan), stroke/TIA, acute coronary syndrome (ACS), pulmonary emboli (PE), and other peripheral vascular events requiring hospitalization.Results: With a mean follow-up duration of 45±22 months, major events occurred in 30 pts (5.2 %, 1.1% per year) with a duration of 33±20 months after the procedure, including 1 (0.5%) with cardiovascular death, 12 (2.2%) with a stroke/TIA, 16 (2.7%) with ACS, and 1 (0.2%) with a PE. Multivariate predictors of the vascular events were a higher CHADS2 score (>2, Hazard ratio, HR=4.56, 95% CI=1.26-5.56, P=0.002), and symptomatic AF recurrence (HR=2.65, 95% CI=1.26-5.57, P=0.01). In 8 patients, events occurred within 4 months after ablation and could be procedure related. In the other 22 patients, symptomatic AF recurred prior to the CV events in 16 patients (73%) with a mean duration of 8.7±18 month (range 0.1-79 month) after the first attack of AF.Conclusion: Thromboembolic events occurred with an incidence of 1.1 % per year following catheter ablation. First symptomatic AF attack (>30 seconds) occurred prior to the major thromboembolic events in most patients. This study implied the importance of symptom-based follow-up of AF recurrences, especially in patients with high CHADS2 scores (>2) following ablation.

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ABLATION OF ATRIAL FIBRILLATION IN PATIENTS WITH HYPERTROPHIC CARDIOMYOPATHY. OUTCOME FROM THE GERMAN ABLATION REGISTRYMarc Schloesser, MD, Thorsten Lawrenz, MD, Dietrich Andresen, MD, Karl-Heinz Kuck, MD, Stephan Willems, MD, Johannes Brachmann, MD, Ellen Hoffmann, MD, Burghard Schuhmacher, MD, Karl-Heinz Seidl, MD, Stephan G. Spitzer, MD, Ernst G. Vester, MD, Jürgen Tebbenjohanns, MD, Claus Jünger, MD, Jochen Senges, MD and Christoph Stellbrink, MD. Klinikum Bielefeld, Bielefeld, Germany, Vivantes Klinikum am Urban, Berlin, Germany, Asklepios Klinik St. Georg,

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values were set for age (65 years) and the LADI (24.0 mm/m2), using a receiver operating characteristic curve, the risk of AF progression was effectively stratified.Conclusion: Both the incidence of AF recurrence and AF progression were low after CA in paroxysmal AF patients.

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FOCAL IMPULSE AND ROTOR MODULATION (FIRM) ABLATION REMAINS HIGHLY SUCCESSFUL IN PATIENTS WITH UNFAVORABLE DEMOGRAPHICS FOR CONVENTIONAL ATRIAL FIBRILLATION ABLATION: A SUBSTUDY OF THE CONFIRM TRIALTina Baykaner, MD, Amir C. Schricker, MD, Gautam C. Lalani, MD, David E. Krummen, MD, Kalyanam Shivkumar, MD, PhD, Paul C. Clopton, MS, Wouter-Jan Rappel, PhD, John Miller, MD and Sanjiv M. Narayan, MD, PhD. UCSD/VA San Diego Medical Center, San Diego, CA, UCSD / VA San Diego Medical Center, San Diego, CA, UCLA Cardiac Arrhythmia Center, Los Angeles, CA, VA Medical Center, San Diego, CA, UCSD, La Jolla, CA, The Krannert Institute of Cardiology, Indiana University, Indianapolis, IN, UCSD / VA San Diego Medical Center, La Jolla, CAIntroduction: Hypertension, left atrial (LA) dilation, heart failure, obesity and sleep apnea (OSA) portend poor outcome from anatomic atrial fibrillation (AF) ablation, but for unclear reasons. We hypothesized that these demographics cause greater numbers or atypical sites for AF rotors and focal sources, but that Focal Impulse and Rotor Modulation (FIRM) of AF sources regardless of location or number will still be successful in these patients.Methods: In this prespecified analysis of the CONFIRM trial1, 107 AF patients (76 persistent, 62±9 years) received conventional ablation without (n=71) or preceded by FIRM (n=36). Patients were evaluated quarterly for recurrent AF with implanted ECGs (88% FIRM-guided patients; 44% overall).Results: Localized sources were found in 97% of patients (2.1±1.0 each). Greater source numbers were predicted by BMI (p<0.001), LA diameter (p=0.014), falling LV ejection fraction (p=0.02), OSA (p=0.016) or diabetes mellitus (p=0.039). Right atrial sources were predicted by obesity (BMI≥30 p<0.001) and persistent AF (p=0.06). Freedom from AF after the index ablation was higher for FIRM-guided vs FIRM-blinded patients for each of these demographics (see table). Notably, the presence of obesity (BMI≥30 vs <30), OSA, hypertension, and severe LA enlargement (≥47 mm) identified patients with 80-90% success rate from FIRM-Guided ablation, yet 35-50% from conventional ablation.

hospitalization.Clinical and echocardiographic parameters in 70 patients without prior AF were analyzed. Variables for analysis included patient demographics,clinical parameters, and echocardiographic variables, procedural approach (transfemoral vs. transapical) and post-operative variables such as length of hospitalization,development of new conduction block, and requirement of hemodynamic support.Results: A total of 21/70 (30 %) patients developed AF in the post-operative hospital course after undergoing TAVR.The occurrence of AF (50 %) was highest in the initial 24 hours following the procedure (1 (5 %) in the immediate post-procedure phase and 9 (45 %) within the next 24 hours). Electrical cardioversion was needed in 3 (14.3%) patients.Transapical approach was found to have a higher incidence of AF as compared to transfemoral (OR=8.0, 95 % Confidence interval [CI]:2.08 to 30.77; p=0.001).Patients with severe mitral regurgitation were also found to have a higher predisposition to develop AF (p=0.08; 95 % CI:1.38 to 5.48).Patients who developed AF had a higher requirement for hemodynamic support in the post-operative period compared to patients in sinus rhythm (47.62 % versus 22.45%; p = 0.048) and prolonged hospital stay (15.38 + 7.8 days vs. 9.06 + 4.5 days; p = 0.001).Conclusion: New onset AF occurred in 30% of patients without prior AF undergoing TAVR. The incidence of AF was observed to be higher in patients undergoing TAVR via the transapical approach as compared to transfemoral approach. Atrial fibrillation post-TAVR was associated with a higher requirement for hemodynamic support and a longer hospital stay as compared to patients in sinus rhythm.

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LONG-TERM FOLLOW-UP AFTER CATHETER ABLATION OF PAROXYSMAL ATRIAL FIBRILLATION: THE INCIDENCE OF AF-RECURRENCE AND AF-PROGRESSIONMasateru Takigawa, MD, Atsushi Takahashi, MD, Taishi Kuwahara, MD, Kazuya Yamao, MD, Naohiko Kawaguchi, MD, Yuki Osaka, MD, Emiko Nakashima, MD, Yuji Watari, MD, Keita Handa, MD, Kenji Okubo, MD, Katsumasa Takagi, MD, Kenzo Hirao, MD and Mitsuaki Isobe, MD. Yokosuka Kyosai Hospital, Yokosuka, Japan, Heart Rhythm Center, Tokyo Medical and Dental University, Tokyo, Japan, Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, JapanIntroduction: The increasing number of patients developing atrial fibrillation (AF) has resulted in catheter ablation (CA) becoming a standard treatment modality. However, the long-term outcomes of CAs have not been fully elucidated.Methods: We examined the incidence of AF recurrence and AF progression in 1220 consecutive patients (mean age, 61 ± 10 years; male, n = 940), with symptomatic paroxysmal AF, undergoing CA.Results: Acute success was achieved in all patients. The sinus rhythm (SR) maintenance rates at 1, 3, and 5 years were 72.0%, 65.4%, and 59.4%, respectively, after the initial CA, and 89.8%, 85.3%, and 81.1%, respectively, after the final CA (mean, 1.3 ± 0.6 procedures), respectively. During a mean follow-up period of 51 ± 21 months after the final CA, AF progressed from paroxysmal to persistent in 15 patients (1.2% of the total number of patients; 7.5% of those with AF recurrence). The overall AF progression rate was 0.3% per year. The duration of AF (HR 1.03, 95% CI 1.02-1.05, P < 0.0001), number of failed antiarrhythmics (HR 1.09, 95% CI 1.03-1.16, P = 0.005), and the left atrial diameter indexed by the body-surface-area (LADI; HR 1.05, 95% CI 1.02-1.07, P = 0.001) were significant predictors of AF recurrence. Patient age (HR 1.12, 95% CI 1.04-1.22, P = 0.0001) and LADI (HR 1.26, 95% CI 1.11-1.44, P = 0.0006) were significantly associated with AF progression. When cut-off

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P value (difference between above 2 rows) 0.89 0.0001Ventriculogram LVEF % for LVEF <40 (n=16) 29.9 31.8 0.12

TTE LVEF % for LVEF <40 (n=74) 29.4 39.2 <0.001

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HIGH RIGHT VENTRICULAR PACING BURDEN INCREASES THE INCIDENCE OF NEW-ONSET ATRIAL FIBRILLATIONBrett A. Faulknier, DO, Mark , Richards, MD, PhD, Xiaoyi Min, PhD, Jeffery Snell, BA and Ranjan K. Thakur, MD. FACC WVU Physicians of Charleston Dept of Electrophysiology, Charleston, WV, Northwest Ohio Cardiology Consultants, Toledo, OH, St. Jude Medical, Sylmar, CA, Thoracic Cardiovascular Institute, Lansing, MIIntroduction: Previous studies have reported adverse consequences of RV pacing leading to HF and increased AF. This analysis was conducted to assess whether, in contemporary pacemaker (PM) patients (pts) without a prior history of AF (Hx AF), %RV pacing (%RVP) burden is associated with a higher risk of developing AF.Methods: We analyzed data collected on all non-CRT PM pts without a Hx AF completing their 12 month follow up in the large observational trial of PM pts, BRADYCARE. Over the follow-up, AF was monitored clinically and documented in Case Reports Forms. Pts were distributed based upon %RVP as determined by the PM (see Table). Event-free survival from AF and a Cox proportional hazards model was used to compare the AF outcomes of these groups.Results: A total of 1512 pts were analyzed. %RVP exhibited a bimodal distribution, with peaks at 0-2% and 98-100% (see table). Over 12.9±3.0 months, 313 pts developed AF. When adjusted for age, LVEF, primary indications, NYHA functional class, and ischemic CM, the 3-97% and 98-100% groups had signifi cantly higher risks of developing AF compared to the 0-2% group (hazard ratio [HR] = 1.6, 95% CI 1.17-2.23 , p=0.004 and HR = 2.0, 95% CI 1.31-3.16, p =0.0015 respectively). The 3-97% and 98-100% groups did not have a signifi cantly different risk of developing AF (HR =1.17; 95% CI 0.8-1.68; p=0.17).Conclusion: In non-CRT pacemaker pts without a Hx AF, pts with 3-100% RV pacing exhibit a signifi cantly higher risk of developing AF compared with pts with 0-2% RV pacing.%RVP distribution groups AV Block SND Syncope 0-2% (n=599, 40% of all) 78 (13%) 400 (67%) 76 (13%)3-97% (n=278, 18% of all) 229 (36%) 322 (51%) 56 (9%)98-100% (n=635, 42% of all) 194 (70%) 45 (16%) 6 (2%)

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LONG-TERM ECG MONITORING FOR ATRIAL FIBRILLATION (AF) USING AN IMPLANTABLE LOOP RECORDER (ILR) FOLLOWING ATRIAL FLUTTER (AFL) ABLATION IN PATIENTS AT HIGH RISK FOR THROMBOEMBOLISMSuneet Mittal, MD, FHRS, Martha Ferrara, RN, Aysha Arshad, MD, Dan Musat, MD, Mark Preminger, MD, Tina Sichrovsky, MD, Alexander Romanov, MD, Evgeny Pokushalov, MD and Jonathan S. Steinberg, MD, FHRS. The Valley Health System of NY and NJ, New York, NY, The Valley Health System of NY and NJ, Ridgewood, NJ, State Research Institute of Circulation Pathology, Novosibirsk, Russian FederationIntroduction: Some patients have typical AFL but no documented AF. Following cavotricuspid isthmus (CTI) ablation, the duration of anticoagulation therapy in these patients is controversial. We sought to determine whether long-term ECG

Conclusion: FIRM Ablation retains high single procedure success rates even in patients with unfavorable demographics for conventional AF ablation. These demographics predict more sources in diverse patient-specifi c bi-atrial locations, that are missed by anatomic ablation yet identifi ed by FIRM mapping.

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NEWLY DIAGNOSED ATRIAL FIBRILLATION IN THE SETTING OF ACUTE MYOCARDIAL INFARCTION IMPAIRS RECOVERY OF LEFT VENTRICULAR FUNCTIONCyrus Wong, MD, Abhishek Jaiswal, MD, Cheng Ruan, MD, Ward Myers, MD, Omar Waheed, MD, Seth Goldbarg, MD and Andrew J. Buda, MD. New York Hospital Queens, Flushing, NYIntroduction: Atrial fi brillation (AF) occurs with higher incidence in the setting of acute myocardial infarction (AMI), and is associated with worse outcomes. The presence of AF may increase workload after acute myocardial insult, which may be manifested by prolonged recovery of stunned myocardium. We hypothesized that the occurrence of AF in the setting of AMI decreases the recovery of left ventricular function prior to discharge.Methods: We retrospectively analyzed patients presenting with AMI, who underwent percutaneous coronary intervention (PCI). Electrocardiograms and telemetry were reviewed for AF. Patients were categorized as having newly diagnosed AF or no AF. Changes in left ventricular ejection fraction (LVEF) of both groups were obtained via ventriculogram at time of PCI and pre-discharge transthoracic echocardiogram (TTE).Results: We identifi ed 397 patients from May 2008 to June 2012 who presented with AMI and received PCI. Of these patients, 53 (13.3%) had AF, 42 (10.6%) of which were newly diagnosed. New AF was seen on presenting electrocardiogram in 11 (26%) patients, and developed after PCI in 28 (74%) patients. LVEF in the AF and no AF groups are included in the table.Conclusion: Newly diagnosed AF in the setting of AMI is associated with impaired early improvement of left ventricular function. The hemodynamics of AF may be detrimental to recovery of stunned myocardium and left ventricular remodeling. Aggressive monitoring and treatment of AF may lead to an improved outcome after AMI.Comparison of patients with and without atrial fi brillation

New AF n=40

No AF n=250

P value

Anterior wall infarction 17 (43%) 120 (52%) 0.31

Single vessel disease 19 (48%) 97 (39%) 0.30

Average time from PCI to TTE (hours) 29.3 25.8 0.30

Average ischemic time (hours) 4.6 5.4 0.27

Ventriculogram LVEF % 41.9 45 0.11

TTE LVEF % 42.2 49 <0.01

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the analysis. The mean age was 66 years and 58.7% were male. There was a high prevalence of obesity (20.3%) and diabetes (16.8%). Obesity (OR 1.35, 95% CI 1.17-1.56, P<0.001) and severe obesity (OR 1.6, 95% CI 1.29-1.99, P<0.001) were independent predictors of presence of AF at admission, but diabetes was not (OR=0.92, 95% CI=0.82-1.04). Lipidomics analysis revealed that atrial TG content was substantially lower in the AF patients (P<0.05). No quantitative difference was found in the absolute content of CER, PC, LPC, PE, SM, FC, CE and DAG. AF patients had greater proportion of polyunsaturated DAG (P<0.05) while no difference was found in saturated DAG.Conclusion: Obesity but not diabetes is an independent predictor of AF. AF is associated with quantitative and qualitative alterations in atrial lipid content but not with lipotoxicity. The intracellular messenger polyunsaturated DAG may play a role in pathophysiology of AF.

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A PROSPECTIVE RANDOMIZED COMPARISON BETWEEN A FIXED “2C3L” APPROACH VERSUS STEPWISE APPROACH FOR CATHETER ABLATION OF PERSISTENT ATRIAL FIBRILLATIONChang Sheng Ma, MD, Hung-Fat Tse, MD, Cai-Hua Sang, MD, Rong-Hui Yu, MD, De-Yong Long, MD, Ri-Bo Tang, MD, Chen-Xi Jiang, MD, Xing-Peng Liu, MD, Xin Du, MD and Jian-Zeng Dong, MD. Beijing An Zhen Hospital, Beijing, China, Cardiology Division, Department of Medicine, the University of Hong Kong, Hongkong, China, Beijing Chaoyang Hospital, Beijing, ChinaIntroduction: Stepwise approach is effective for catheter ablation of persistent atrial fibrillation (AF). However, its complexity limits its wide application. We sought to compare the clinical efficacy of a fixed approach named “2C3L”, which consists of bilateral circumferential pulmonary vein antrum (CPVA) and three linear atrial ablations versus stepwise approach in patients with persistent AF.Methods: We randomized 146 patients (age 55±11 years, 76% men) with persistent AF (>3 months) to undergo 2C3L (n=73) or stepwise (n=73) approach from August 2009 to January 2011. In both groups, initial CPVA and linear ablation at the left atrial roof, mitral isthmus and cavotricuspid isthmus were performed. In the 2C3L group, cardioversion was applied and further ablation was performed to achieve conduction block over CPVA and 3 lines. In the stepwise group, ablation of complex fractionated atrial electrograms was performed to achieve AF termination, and all organized atrial tachycardias (OATs) were mapped and ablated. Further ablation was performed to achieve conduction block over CPVA and the 3 lines. The primary end point was freedom from any atrial tachyarrhythmia off antiarrhythmic drugs at 12 months follow-up.Results: There were no significant differences in the demographic features, duration of AF, left ventricular ejection fraction and left atrial dimension between the 2 groups (p>0.05). The procedural (222±42 vs. 268±43 min), fluoroscopy (41±9 vs. 55±8 min), and ablation (107±32 vs. 128±38 min) durations were shorter and the AF termination rate was lower (21 vs. 53%) with 2C3L than stepwise approach (all p<0.001). Success rates to achieve complete conduction block over CPVA and the 3 lines were similar between the 2 groups (p>0.05). At 12 months, there was no significant difference in the prevalence of sinus rhythm after 2C3L approach (49/73, 67%) vs. stepwise approach (44/73, 60%) without any AAD, (p=0.28). Furthermore, there were no differences in the AF recurrence rate (10 %vs. 11%) or OATs (23% vs. 29%) between the 2 groups (p>0.05).Conclusion: The “2C3L” strategy is a simplified with similar clinical efficacy as stepwise approach for catheter ablation of persistent AF.

monitoring could be used to limit anticoagulation to patients with ILR evidence of AF.Methods: In this pilot study, we enrolled 20 patients with typical AFL who were referred for CTI ablation. No patient had prior ECG documentation of AF and all had a CHADS2 score ≥ 2 (but no prior TIA/stroke). AFL was the only indication for anticoagulation in all patients. Immediately following ablation (open irrigated catheter; confirmed bidirectional block), a Medtronic Reveal XT ILR (using an automated algorithm for the detection of AF) was implanted. Device interrogations were used to adjudicate AF events, if detected.Results: The cohort (16 [80%] male) had a mean age of 70 ± 11 years. All patients had an EF > 40%. The CHADS2 score was either 2 (16[80%]) or 3 (4[20%]). One patient was lost to follow-up and 1 had documented symptomatic bradycardia and required a pacemaker. In the remaining 18 patients, 3 distinct patterns were identified. No AF was present in 5 (28%) patients and clear documentation of AF was present in 8 (44%) patients. In the remaining 5 (28%) patients, the ILR suggested AF ([10 min - 1 hour in 2; 1 - 4 hours in 2; 4 - 12 hours in 1)). However, these ECGs were not available to adjudicate because they were overwritten in memory by newer and shorter duration stored events, which showed only sinus rhythm with frequent premature atrial beats.Conclusion: In a carefully screened population with AFL but no AF and a high risk of thromboembolism (CHADS2 2-3), ILR-based long-term ECG monitoring following CTI ablation showed no evidence of AF in 28% and clear evidence of AF in 44% of patients. However, in 28% of patients, the Reveal XT ILR could not be used to guide clinical decision-making; in these patients, AF events of significant duration could not be adjudicated due to an absence of a stored ECG. These data have important implications on the ability to the use ILR data alone to guide decisions regarding the need for long-term anticoagulation in a cohort at high risk for thromboembolism.

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ATRIAL FIBRILLATION IN PATIENTS ADMITTED TO CORONARY CARE UNITS - THE ROLE OF OBESITY AND LIPOTOXICITYSigfus Gizurarson, MD, PhD, Marcus Stahlman, PhD, Anders Jeppson, MD, PhD, Lennart Bergfeldt, MD, PhD, Jan Borén, MD, PhD and Elmir Omerovic, MD, PhD. Toronto General Hospital, Toronto, ON, Canada, Sahlgrenska Academy, University of Gothenburg, Gothenburg, SwedenIntroduction: Atrial fibrillation is a common sustained arrhythmia. Obesity and diabetes have been linked to myocardial lipotoxicity - a condition where the heart accumulates and produces toxic lipid species. We hypothesized that obesity and diabetes may be involved in pathophysiology of AF by means of promoting a lipotoxic phenotype in atrial tissue.Methods: Our study consists of two parts. The first part is a case-control study based on the prospective data obtained from the RIKS-HIA registry from hospitals in western Sweden. All consecutive patients between 2006-2011 admitted to cardiac units with SR or AF were included in the analysis. Multivariate logistic regression and Cox proportional-hazards regression were used to test whether diabetes and obesity were independent predictors of AF at admission. In the second part we obtained atrial biopsies from 54 patients undergoing cardiac surgery and performed lipidomics analysis for a detailed qualitative and quantitative analysis of lipid species including triglycerides (TG), ceramides (CER), phosphatidylcholine (PC), lysophosphatidylcholine (LPC), phosphatidylethanolamine (PE), sphyngomyelins (SM), free cholesterol (FC), cholesterol esters (CE) and diacylglycerols (DAG).Results: Between 2006-2011, 35232 patients were included in

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ablation (CA). Data on right atrial remodeling is limited. We sought to evaluate the impact of CA on right atrial remodeling using cardiac magnetic resonance imaging (CMR).Methods: CMR was performed before and after (average 109 ± 47 days) CA in 60 patients (47 men, mean age 60 ± 10 years) with paroxysmal (70%) and persistent (30%) AF. Right and left atrial volumes (RAV and LAV, respectively) were derived using the area-length method on 2 and 4 chamber long-axis views. Atrial volumes were indexed to body surface area.Results: Table 1 summarizes the CMR findings. LAV and LAV index decreased significantly after CA from 123 ± 34 mL to 110 ± 37 mL (P < 0.01) and 58 ± 14 mL to 52 ± 15 mL (P < 0.01) respectively. RAV and RAV index also decreased significantly from 142 ± 45 mL to 118 ± 44 mL (P < 0.0001) and 67 ± 19 mL to 55 ± 19 mL (P < 0.0001) respectively. When divided into subgroups based on the type of AF, no significant difference was seen in the change in RAV or RAVI (P = 0.56 and P = 0.68, respectively).Conclusion: RA remodeling as measured by CMR occurs in AF patients and is modified by CA ablation to a greater extent than LA remodeling. Additional studies are necessary to determine its impact on clinical outcomes.

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REVERSIBLE REMODELING OF ACTION POTENTIAL PHENOTYPE, INWARD RECTIFIER K+ CURRENT AND INWARD NA+ CURRENT IN A ZEBRAFISH MODEL OF ARRHYTHMOGENIC CARDIOMYOPATHY (AC)Sudhir Kapoor, MD, Eva Plovie Buys, PhD, Angeliki Asimaki, PhD, Calum A. MacRae, MD, PhD, Jeffrey E. Saffitz, MD, PhD and André G Kléber, MD. Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, Brigham and Women’s Hospital, Harvard Medical School, Boston, MAIntroduction: It has been recently demonstrated that expression of Kir2.1 and Nav1.5 channels in the intercalated disc between cardiomyocytes involves common mechanisms of regulation. The aim of this study was to assess changes in IK1 (Kir2.1) and INa (Nav1.5) ion currents and their contribution to the action potential phenotype in a Zebrafish (ZF) model of AC, and to assess the reversibility of the changes by SB2, a compound identified in a chemical screen to rescue the AC phenotype and improve survival.Methods: We used a ZF model of AC characterized by cardiac-specific expression of the 2057del2 mutation in human plakoglobin (implicated in Naxos disease). Single cardiac ventricular myocytes were cultured from Naxos (NX) and control hearts isolated at 21 days post fertilization. To assess the effect of SB2, the drug was applied to the cultures for 36 hours. Action potentials (APs), INa and IK1 were recorded by whole-cell current- and voltage-clamp respectively. Results are expressed mean values ± S.E. from n experiments.Results: In myocytes from NX fish (vs. control), the maximal upstroke velocity of the AP, dV/dtmax, was reduced (8±1 V/s; n=8 vs. 21±3 V/s; n=12; p <0.001); AP duration (APD80) was prolonged (380±38ms; n=8 vs. 192±8ms; n=12; p <0.001), and

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IMPACT OF ADENOSINE TRIPHOSPHATE ON COMPLEX FRACTIONATED ATRIAL ELECTROGRAMS IN HUMAN ATRIAL FIBRILLATIONRikitake Kogawa, MD, Yasuo Okumura, MD, Ichirou Watanabe, MD, Masayoshi Kofune, MD, Hiroaki Mano, MD, Koichi Nagashima, MD, Kazumasa Sonoda, MD, Naoko Sasaki, MD, Kimie Okubo, MD, Toshiko Nakai, MD and Atsushi Hirayama, MD. Division of Cardiology, Department of Medicine, Nihon University School of Medicine, Tokyo, JapanIntroduction: Complex fractionated atrial electrograms (CFAEs) have been proposed as valid targets for atrial fibrillation (AF) ablation. Adenosine triphosphate (ATP) is known to promote AF through shortening of atrial refractory period. However, the influence of ATP on the characteristics of CFAEs is incompletely understood. This study, therefore, evaluated the impact on ATP on CFAEs.Methods: We recorded electrical activity with the use of 64-electrode basket catheter placed in the left atrium (LA) of paroxysmal (n=8) and persistent (n=7) AF patients presenting for AF ablation. CFAEs were calculated from each electrode pair. Off-line time domain analyses was performed from each electrode recording from 48 bipolar electrograms obtained at baseline and at the peak ATP effect (30mg, iv, R-R interval>3 sec) and CFAE mean were compared.Results: At baseline, in paroxysmal AF, CFAEs were observed in 50.4±12.7% of the total electrode pairs and in 67.0±9.0% in persistent AF (P=N.S.). In CFAE sites, ATP significantly shortened CFAEs mean interval (72.0±8.3 msec versus 63.9±7.7 msec, P<0.05) in paroxysmal AF patients. In contrast, in persistent AF patients, ATP did not affect CFAE mean (73.4±7.4 msec versus 74.4±9.8 msec, P=N.S.).Conclusion: ATP affects CFAE interval differently in paroxysmal and persistent AF patients. Those results suggest that pathogenesis of CFAEs may differ between paroxysmal and persistent AF.

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ASSESSMENT OF RIGHT ATRIAL REMODELING USING CARDIAC MAGNETIC RESONANCE IMAGING IN PATIENTS UNDERGOING CATHETER ABLATION OF ATRIAL FIBRILLATIONLara Bakhos, MD, Mark G. Rabbat, MD, David J. Wilber, MD, Santanu Biswas, MD, Thriveni Sanagala, MD and Mushabbar A. Syed, MD. Stritch School of Medicine Heart & Vascular Institute, Loyola University Medical Center, Maywood, ILIntroduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia. It has been demonstrated that left atrial remodeling occurs in AF patients that improves after percutaneous catheter

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BOTH GAIN- AND LOSS-OF-FUNCTION MUTATIONS IN KCNQ1 IS ASSOCIATED WITH EARLY ONSET LONE ATRIAL FIBRILLATIONMorten S. Olesen, PhD, Lena Refsgaard, BSc, Annette B. Steffensen, MSc, Stig Haunsø, MD, DMSc, Jesper H. Svendsen, MD, DMSc, Søren-Peter Olesen, MD, DMSc and Nicole Schmitt, PhD. Rigshospitalet, The Heart Center, Copenhagen, Denmark, Department of Biomedical Sciences, Danish Arrhythmia Research Centre, Copenhagen, DenmarkIntroduction: Atrial fibrillation (AF) is the most frequent cardiac arrhythmia. The potassium current IKs is essential for cardiac repolarization. Gain-of-function mutations in KCNQ1, has in a linkage study been associated with familial AF, but a subsequent candidate gene study did not identify any mutations in KCNQ1 in 141 older lone AF patients. We hypothesized that early-onset lone AF is associated with a high prevalence of mutations in KCNQ1.Methods: The entire coding sequence of KCNQ1 was bidirectionally sequenced in 209 unrelated patients with early-onset lone AF (<40 years).Results: We identified four non-synonymous KCNQ1 mutations (A46T, R195W, A302V, R670K). All mutation-carriers had early-onset lone AF and no mutations were found in other genes previously associated with AF. The mutation A302V has previously been shown to influence the IKs current and are associated with long QT syndrome. In vitro electrophysiological studies of A302V displayed a pronounced loss-of-function of the IKs current, while A46T, R195W, R670K all exhibited gain of function. The patient carrying the A302V mutation was male and had a prolonged QTc (466 ms), but was extensively examined without evidence of long QT syndrome. Mutations in the IKs channel leading to gain-of-function have previously been described in familial AF, yet this is the first time a loss-of-function mutation in KCNQ1 is associated with early-onset lone AF.Conclusion: We identified a high prevalence of KCNQ1 mutations in early-onset lone AF patients. All of the mutations have been shown to modulate the IKs current supporting the hypothesis that both gain- and loss-of-function disturbances of the potassium current enhances the susceptibility to early onset lone AF.

resting membrane potential (RMP) was more positive (-67±2mV; n=8 vs. -78±1mV; n=14; p<0.001). Both INa (31±4 pA/pF, n=7 vs. 196±18 pA/pF n=22; p <0.001) and IK1 (-4.2±0.9 pA/pF n=8; vs. -17.0±2.7 pA/pF, n=8 p <0.001; values at -100mV membrane potential; EK = -43 mV) were markedly reduced. SB2 reversed the AP parameters, INa and IK1 to values not significantly different from control.Conclusion: We have previously shown that SB2 applied during the first days of embryonic development reverses the changes in AP and INa in the ZF model of arrhythmogenic cardiomyopathy after 7 weeks in culture. Here, we show a decrease in inward K+ rectifier current in this model, in addition to the decrease of INa and a full reversal of the changes in action potential, INa and IK1 by SB2 applied for 36 hours to cultured ventricular ZF myocytes expressing 2057del2 plakoglobin.

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MUTATIONS IN GENES ENCODING CARDIAC ION CHANNELS PREVIOUSLY ASSOCIATED WITH SUDDEN INFANT DEATH SYNDROME (SIDS) ARE PRESENT WITH HIGH FREQUENCY IN NEW EXOME DATALena Refsgaard, BSc, Charlotte Andreasen, BSc, Jonas B. Nielsen, MD, Ahmad Sajadieh, MD, DMSc, Bo G. Winkel, MD, PhD, Jacob Tfelt-Hansen, MD, DMSc, Stig Haunsø, MD, DMSc, Anders G. Holst, MD, PhD, Jesper H. Svendsen, MD, DMSc and Morten S. Olesen, MD, PhD. Rigshospitalet, The Heart Center, Copenhagen, Denmark, Bispebjerg Hospital, Department of Cardiology, Copenhagen, DenmarkIntroduction: Sudden infant death syndrome (SIDS) is the leading cause of death in the first six months after birth in the industrialized world. The genetic contribution to SIDS has been investigated intensively and to date, fourteen cardiac channelopathy genes have been associated with SIDS. Newly published data from NHLBI GO Exome Sequencing Project (ESP) provided important knowledge on genetic variation in the background population. Our aim was to identify all variants previously associated with SIDS in ESP in order to improve the discrimination between plausible disease causing mutations and variants most likely to be false-positive.Methods: The PubMed database was searched in order to identify SIDS-associated channelopathy variants and the prevalence of these in the ESP population (6,500 individuals) were obtained. In silico prediction tools were applied to variants present in ESP and six SIDS-associated variants (CAV3 p.C72W, p.T78M; KCNH2 p.R148W and SCN5A p.216L, pV1951L, p.F2004L) were genotyped in our own control population.Results: Nineteen missense variants previously associated with SIDS were identified in ESP. This corresponds to 1:29 individuals in the ESP population being carriers of a SIDS-associated variant. Genotyping of six SIDS-associated variants in our own controls revealed frequencies comparable with those found in ESP.Conclusion: A very high prevalence of previously SIDS-associated variants was identified in exome data from population studies. Our findings indicate that the suggested disease causing role of some of these variants is questionable. A cautious interpretation of these variants must be made when found in SIDS victims.

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pigs (15-30 kg) resulted in induction of HF (LV fractional shortening < 16% after 2-5 weeks). We monitored LV pressures, heart rate (HR) and ECG in anesthetized closed-chest pigs after pacing was halted. Inhibitors of INa,Late were given (increasing boluses followed by infusion) and If (‘funny’ current) blocker Ivabradine (0.3 mg/kg) was added in 5 animals to assess the impact of heart rate reduction.Results: Compared to controls (n=9, data not shown), HF pigs exhibited severe baseline systolic and diastolic dysfunction (see Table 1.). Ran and Mex were well-tolerated in HF pigs. Bolus injections resulted in transient reductions of HR, PMax and ±dP/dtMax. Infusions (>45 min) of either drug caused no significant change in pressures despite serum concentrations of 1-10 µM (Table 1). On average, Ivabradine reduced heart rate by 37% (p<.002), but did not alter Ran or Mex effect on hemodynamic measures.Conclusion: Suppression of INa,Late does not significantly alter LV hemodynamic function in our HF model over a wide range of heart rates, suggesting a favorable safety profile in failing hearts.

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KCNJ2 MUTATION R67Q IS ASSOCIATED WITH A CPVT PHENOTYPE AND ADRENERGIC DEPENDENT LOSS OF KIR2.1 FUNCTIONMatthew M. Kalscheur, MD, Ravi Vaidyanathan, PhD, Kate Orland, MS, Kathleen R. Maginot, MD, Craig T. January, MD, PhD, Jonathan C. Makielski, MD and L. Lee Eckhardt, MD. Inherited Arrhythmias Clinic, University of Wisconsin-Madison, Madison, WIIntroduction: KCNJ2 mutations are associated with several inherited arrhythmia syndromes, including CPVT. Previous studies by our group have shown an adrenergic-dependent loss of function of Kir2.1, encoded by KCNJ2, in a CPVT phenotype. Here we present a CPVT case and functional characterization associated with a KCNJ2 mutation, previously reported as LQTS7 related.Methods: KCNJ2 mutations were constructed using the Stratagene ExSite site directed mutagenesis kit. COS-1 cells were transiently transfected using FuGENE 6 with 2.5 μg of WT and/or mutant KCNJ2 in a pcDNA3.1 vector. For fluorescence studies, 1 μg of WT or mutant KCNJ2 DNA in pcDNA3.1-NT-GFP-TOPO was transfected into HEK293 cells using FuGENE 6.Results: A 33-year-old female was referred to the University of Wisconsin Inherited Arrhythmias Clinic with palpitations and near syncope. Cardiac evaluation demonstrated a normal echo, no CAD, and normal ECG but recurrent activity related polymorphic ventricular ectopy with tachycardia on exercise test (ET). She was treated with nadolol and flecainide. Repeat ET showed suppression of arrhythmias and resolution of symptoms. Genotype screening of the genes associated with CPVT (RYR2, KCNJ2, CASQ2) using next generation sequencing revealed heterozygous missense mutation KCNJ2 R67Q. COS-1 cells transiently transfected with cDNA from WT Kir2.1, R67Q mutated Kir2.1 or both were analyzed by whole cell patch clamp technique. From a holding potential of -60mV, step pulses from -120 to 30mV were applied to the cells in 10mV increments for 500ms. Kir2.1-WT current was typical IK1. Kir2.1-R67Q produced no current when expressed alone while co-expression

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MOG1 IS REQUIRED FOR CELL SURFACE EXPRESSION OF NAV1.5 IN THE CAVEOLIN-3 ENRICHED FRACTIONQiuyun Chen, PhD, Zhaogang Yang, PhD, Keli Hu, MD, PhD, Susmita Chakrabarti, PhD and Qing Wang, PhD. Cleveland Clinic, Molecular Cardiology, Cleveland, OH, Ohio State University, Cleveland, OH, The Ohio State University, Columbus, OHIntroduction: The voltage-gated cardiac sodium channel Nav1.5 is critical for the initiation and conduction of electrical impulses through the myocardium. Function of Nav1.5 is determined by the gating kinetics and the cell surface expression. Caveolae, the caveolin enriched microdomains, are abundantly present in the sarcolemma of cardiomyocytes. Localization of Nav1.5 in caveolae has been implicated in regulating the channel’s cell surface trafficking. However, little is known about how Nav1.5 is targeted to caveolae and how the localization of Nav1.5 in caveolae affects cell surface express. We have previously identified a small protein MOG1 that interacts with Nav1.5 and enhances membrane-localization of Nav1.5. MOG1 has been shown to interact with RAN, a GTPase with a crucial role in nucleocytoplasmic protein trafficking, and stimulates its GTP release. Recently, a MOG1 mutation was reported to be associated with Brugada syndrome. Here we investigated whether MOG1 was involved in targeting Nav1.5 to special membrane micordomains such as caveolae.Methods: HEK293 cells stably expressing Nav1.5 were transfected with a caveolin-3 plasmid and MOG1 specific siRNA. Caveolin-enriched fractions were prepared by using a detergent-free method involving sucrose gradients and ultracentrifugation. The fractions were subsequently used for Western blotting analysis with an antibody against Nav1.5, caveolin3, or MOG1.Results: Western blot analysis showed that MOG1 co-localized with Nav1.5 in the cavolin-3-rich fractions. However, MOG1 knockdown caused redistribution of Nav1.5 to non-caveolar fractions. The caveolar Nav1.5 content from caveolin-3-rich fractions was decreased significantly (84.19±8.90 % vs. 52.03±9.63%, p<0.05, n=3) when MOG1 was knocked down. These data suggest that knockdown of MOG1 expression disrupts localization of Nav1.5 onto caveolin-3-rich fractions and led to redistribution of Nav1.5 to non-caveolin-3-rich fractions.Conclusion: Ion channels are trafficked to their respective membrane subdomains to efficiently exert their functional effects. Caveolae have been implicated in the cellular trafficking of plasma membrane proteins. Our data suggest that MOG1 is involved in targeting or maintaining Nav1.5 into caveolin-3-rich membrane microdomains.

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ACUTE INHIBITION OF THE LATE NA+ CURRENT IS HEMODYNAMICALLY TOLERATED IN SEVERE SYSTOLIC HEART FAILUREMichae G. Klein, PhD, Matie Shou, MD, Craig Dobson, MD, Maureen Hood, PhD, Robert Goldstein, MD and Mark Haigney, MD. USUHS, Bethesda, MDIntroduction: Late Na current inhibitors are attractive antiarrhythmic agents for subjects in heart failure (HF), but their hemodynamic impact is uncertain; drug-induced reduction of Na+/Ca2+ exchange might worsen circulatory function. The late Na+ current (INa,Late) is significantly elevated in our swine tachycardic pacing model of HF. We tested the effects of two inhibitors of INa,Late, Ranolazine (Ran) and Mexiletine (Mex), in left ventricular (LV) hemodynamics in HF and non-HF (Control) pigsMethods: Tachycardic ventricular pacing (200 bpm) in Yorkshire

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S250 Heart Rhythm, Vol. 10, No. 5, May Supplement 2013

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GENETIC AND INFLAMMATORY PATHWAYS CONTRIBUTE INDEPENDENTLY TO ICD FIRINGJames A. Wingrove, PhD, John Blanchard, PhD, Dawood Darbar, MD, PhD, John Day, MD, Patrick Hranitzky, MD and Steven Rosenberg, PhD. CardioDx, Palo Alto, CA, Vanderbilt University Medical School, Nashville, TN, Intermountain Health, Murray, UT, Duke University Medical Center, Durham, NCIntroduction: Sudden Cardiac Death due to ventricular arrhythmia has a strong genetic component; inflammation has also been suggested as a causative factor. We previously reported that a locus at 4q22 was significantly associated with implantable cardioverter-defibrillator (ICD) firing (rs17024266, p = 7.96x10-08). Previous work has shown that elevated levels of CRP are also associated with ICD-firing; we replicate this finding and show that elevated CRP is additive to rs17024266.Methods: High-sensitivity CRP assays were performed on plasma from 350 subjects (124 cases) enrolled in DISCERN, a multi-center study designed to identify markers associated with ventricular arrhythmia. Patients had ejection fractions of < 50, 84% were male and 67% had ischemic HF. ICD firing data was captured for all subjects; cases had an adjudicated ICD firing in response to VT/VF, controls had no appropriate ICD firing within two years of ICD implant.Results: In a time-to-event analysis, elevated CRP (> 2 mg/L) was significantly associated with ICD-firing (HR 1.65, p = 0.016); CRP remained significantly associated with firing in a logistic regression model including age, sex, diabetes, BUN, hypertension, EF, NYHA class and statin use (p = 0.004). In a Cox proportional hazards model both CRP and rs17024266 were independently associated with ICD-firing; subjects with no rs17024266 risk alleles and low CRP levels (< 2 mg/L) showed the lowest ICD firing rate.Conclusion: Combining genetics with inflammatory biomarkers may provide an approach to risk stratify heart failure patients for ICD implantation.

with Kir2.1-WT showed currents equivalent to Kir2.1-WT. Following baseline recording, PKA stimulation with forskolin and 3-isobutyl-1-methylxanthine was added; Kir2.1-WT expressed alone showed a 40% increase in outward IK1 at -60 mV while co-expression of Kir2.1-WT/R67Q resulted in a 5% decrease. Immunostaining of HEK293 cells expressing Kir2.1-WT or Kir2.1-R67Q showed no change in the pattern of localization of protein.Conclusion: Phenotypic and cellular characterization of KCNJ2 R67Q mutation demonstrates a CPVT like phenotype. Treatment approach should be tailored for CPVT.

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FAMILIAL SHORT-COUPLED TORSADE DE POINTES LINKED TO A NOVEL RYANODINE RECEPTOR (RYR2) MUTATIONJim W. Cheung, MD, FHRS, Albano C. Meli, PhD, Wenjun Xie, PhD, Suneet Mittal, MD, FHRS, Steven Reiken, PhD, Anetta Wronska, MSc, Jonathan S. Steinberg, MD, FHRS, Linna Xu, MBBS, Steven M. Markowitz, MD, FHRS, Sei Iwai, MD, FHRS, Bruce B. Lerman, MD, FHRS and Andrew R. Marks, MD. Weill Cornell Medical College, New York, NY, Columbia University College of Physicians and Surgeons, New York, NY, Valley Health System of NY and NJ, New York, NY, Westchester Medical Center, Valhalla, NYIntroduction: Short-coupled torsade de pointes (TdP) has been linked to sudden cardiac death in patients with structurally normal hearts. The mechanism of short-coupled TdP remains unclear, although triggered activity has been proposed to play a role.Methods: Members of a family with short-coupled TdP were found to harbor a novel RyR2-H29D mutation. Human mutant channels were generated using site-directed mutagenesis and heterologously expressed in HEK293 cells together with calstabin2. Single channel measurements of RyR2-H29D channels and wild type RyR2-WT channels were compared at varying concentrations of cytosolic Ca2+. Binding affinities of the RyR2-H29D channels and RyR2-WT channels to calstabin2 were compared.Results: A 31-year-old female with syncope at rest and short-coupled PVCs initiating TdP was successfully treated with catheter ablation of PVCs. She was found to be heterozygous for the RyR2-H29D mutation. Her mother also had a history of syncope with short-coupled TdP and had the same mutation. At diastolic levels (150 nM and 350 nM) of cytosolic Ca2+ under non-stress conditions (absence of PKA treatment), significantly higher open probabilities and opening frequencies were seen with the RyR2-H29D mutant channel when compared to the Ry2-WT channel. This was associated with a modest but significant depletion of calstabin2 binding under resting conditions.Conclusion: The RyR2-H29D mutation is associated with a phenotype of short-coupled TdP at rest. In contrast to CPVT-associated RyR2 mutations, RyR2-H29D causes a leaky channel at diastolic levels of Ca2+ under non-stress conditions. Leaky RyR2 at rest may be a mechanism for short-coupled TdP.

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PO03-90

ROS GENERATION DURING MUSCLE STRETCH MODULATES CA2+ WAVE PROPAGATION IN INTACT RAT CARDIAC TRABECULAEMasahito Miura, MD, PhD, Mai Sasaki, BA, Tsuyoshi Nagano, MSc and Chiyohiko Shindoh, MD, PhD. Department of Clinical Physiology, Tohoku University Graduate School of Medicine, Sendai, JapanIntroduction: Ca2+ wave propagation plays a major role in the determination of delayed afterdepolarizations and causes arrhythmias in cardiac muscle. We focused on the initiation mechanism of Ca2+ waves, investigating whether their propagation velocity (V) responds differently to the changes in force by muscle stretch or by the addition of a paralyzing agent.Methods: Trabeculae were obtained from right ventricles of rat hearts. Force was measured with a strain gauge, sarcomere length with a laser diffraction technique, and [Ca2+]i with fura-2 and a CCD camera (24°C, 2.0 mM [Ca2+]o). Generation of reactive oxygen species (ROS) was measured with 2 ,7 -dichlorofluorescein diacetate (DCF) fluorescence. Ca2+ waves were induced by 2.5-Hz stimulus trains for 7.5 s. Trabeculae were exposed to a jet of solution containing 1) 10 mM Ca2+ (JH) for the induction of spontaneous Ca2+ release from the sarcoplasmic reticulum in its exposed region, and 2) 0.2 mM Ca2+ (JL) or 5 mM caffeine (JC) for Ca2+ dissociation from the myofilaments due to the regional reduction of contractile strength. Ten-percent muscle stretch was applied 10 ms after the last stimulus of the train.Results: The JH caused spatially uniform contraction, while the JL and the JC caused nonuniform contraction. Muscle stretch increased the rate of change (slope) in the DCF fluorescence and further increased the V of Ca2+ waves by the JH (P<0.05, n=9), the JL (P<0.05, n=8), and the JC (P<0.05, n=6). Preincubation with 3 μM diphenyleneiodonium, an inhibitor of NOX generation, or 10 μM colchicine, an inhibitor of microtubule assembly, suppressed the increases in both the DCF slope and the V of Ca2+ waves by the JH (n=12) during stretch, while it did not suppress the increases in the V by the JL (P<0.05, n=7) and the JC (P<0.05, n=13) during stretch. Reduction of developed force after the addition of 10 μM blebbistatin, a myosin II ATPase inhibitor, did not change the V by the JH (n=17), while it did decrease it by the JL (P<0.01, n=9) and the JC (P<0.01, n=8), irrespective of preincubation with colchicine. Conclusion: These results suggest that ROS generation modulates Ca2+ wave propagation during stretch and that in the case of nonuniform contraction, Ca2+ dissociation from the myofilaments additionally modulates it.

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PERINUCLEAR INOSITOL-3-PHOSPHATE RECEPTORS EXPRESSION AND ACTIVITY ARE ELEVATED IN ATRIAL MYOCYTES ISOLATED FROM RABBIT SUBJECTED TO RAPID ATRIAL PACINGBenoit-Gilles Kerfant, PhD, Hanneke Okkenhaug, PhD, Stijn Lumeij, BSc, Marion Kuiper, BSc, Sander Verheule, PhD, Llewelyn Roderick, H, PhD and Ulrich Schotten, MD, PhD. Maastricht University Cardiovascular Research Institute Maastricht (CARIM) Dept. of Physiology, Maastricht, Netherlands, The Babraham Institute, Cambridge, United KingdomIntroduction: Nuclear envelope-expressed type 2 inositol,1,4,5-triphosphate receptors (IP3R) participate in the regulation of Ca2+-mediated transcription pathways in cardiomyocytes. Interestingly, IP3R expression is enhanced in atrial fibrillation

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HEART RATE VARIABLITY (HRV) AFTER INDUCIBLE RE-EXPRESSION OF HEXIM1 IN THE MURINE HEARTKhyati Pandya, MD, Yee-Hsee Hsieh, PhD, Anurak Thungtong, PhD, Julian Stelzer, PhD, Margaret Chandler, PhD, Kenneth Loparo, PhD, Monica Montano, PhD, Michiko Watanabe, PhD and Thomas E. Dick, PhD. Rainbow Babies and Children’s Hospital, Case Western Reserve University, Cleveland, OH, Case Western Reserve University, Cleveland, OH, EECS Department Case Western Reserve University, Olin Room 705, Cleveland, OHIntroduction: HEXIM1, Hexamethylene-bis-acetamide-inducible protein 1 is a crucial gene for cardiovascular development. Transgenic adult mice with re-expression of HEXIM1 in cardiomyocytes had improved systolic function, and other characteristics of physiologic hypertrophy. The effects were evaluated further by analyzing heart rate variability (HRV) in detail with telemetry recordings.Methods: Data Acquisition: A radiotelemetry transmitter device to monitor heart rate in conscious, unrestrained mice was implanted intraperitoneally. Data Analysis: We selected three 2.5-min epochs (WT, n=3 and Mhc-HEXIM1, n=3) to analyze “off-line”. R-R Intervals were identified from the peak of the R-wave (Spike 2 software). Poincaré plots and fLomb periodograms were constructed for each recording.Results: 1. The mice with HEXIM1 overexpression had significantly slower heart (381±34 vs 447±39 bpm) and respiratory (176±22 vs 382±18 bpm) rates compared to the Controls 2. Dysrhythmias were detected in the mice that overexpressed HEXIM1. These were isolated prolonged pauses (500-900 ms); and occurred frequently but were not sustained. This dysrhythmia generated Poincaré plots with points distributed parallel to the axes at the baseline frequency (representative plots are in the Figure). 3. HRV: The WT mice have a tight cluster of points indicating normal HRV. HEXIM1 mice had multiple clusters of points. Poincare plots of the HEXIM1 overexpressers had greater variability in SD1 than SD2.Conclusion: This study explores HRV using complimentary analytical approaches to assess function in a murine model. An increased incidence of non-sustained, well tolerated dysrhythmias was detected in the HEXIM1 overexpressing mice compared to the Controls. Despite the lower heart rate; the power spectra had very relative power at the respiratory frequency. Future aims are to analyze conduction patterns by optical mapping to detect potential substrates for arrhythmias and repeat all cardiac function studies after 6 months to test the safety of long term induction of HEXIM1. These studies may lead to new strategies to promote physiological hypertrophy and genetically engineer a healthier heart.

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Results: Using an optical micrometry technique involving an autocorrelation algorithm we observed that sarcomere shortening was decreased in persistent AF (perAF) compared to sinus rhythm (SR) patients (at 0.5Hz: 4.8±1.5% in 10 cells from 5 perAF vs. 9.2±1.2% in 18 cells from 7 SR). With di-8ANNEPS, a specific marker for the membrane, atrial cells did not show developed t-tubules. Interestingly using line-scan confocal microscopy we observed a failure of the Ca2+ wave propagation in perAF cells (see figure), while post-rest potentiation protocol restored it. In parallel, the frequency for diastolic spontaneous Ca2+ sparks was enhanced in perAF, but only in cells not responding to field-stimulation (sparks/100μm/sec: 4.06±1.2 in 7 perAF vs. 2.05±0.4 in 9 SR, P<0.01).Conclusion: Our results show, for the first time, decreased sarcomere shortening and failing Ca2+ wave propagation in field-stimulated perAF myocytes. This spatial alteration in Ca2+ signalling should strongly participate in the contractile and electrical remodelling (e.g. Ca2+-mediated gene transcription pathways) occurring in AF. In addition, the frequency of intracellular spontaneous Ca2+ release appears to be directly correlated to the ability of cells to respond to field-stimulation.

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CARDIAC-SPECIFIC EXPRESSION OF FOG-2 INDUCES ATRIAL FIBRILLATIONMichael T. Broman, MD, PhD, Harold Olivey, PhD, Saoirse McSharry, BS and Eric Svensson, MD, PhD. University of Chicago, Chicago, IL, Indiana University Northwest, Gary, INIntroduction: Atrial fibrillation is a common cardiac arrhythmia associated with significant worldwide morbidity and mortality. Although many factors, including myocyte electrical remodeling, atrial contractile dysfunction, and structural chamber remodeling have been linked to atrial fibrillation, the molecular causes are still unclear. Previous work has demonstrated that FOG-2 (Friend of GATA-2), a transcriptional co-repressor important in early heart development, is overexpressed in the hearts of patients with heart failure who are prone to developing atrial fibrillation.Methods: We developed a novel genetic model of inducible, cardiac specific expression of FOG-2 in mice via a doxycycline-inducible transgenic system. After transgene induction, animals were followed for twelve weeks with ECG and trans-thoracic echocardiograms, and underwent electrophysiologic studies. Tissue was analyzed using Western blotting, quantitative RT-PCR, and microarray analysis, as well as histologic imaging.

(AF). We recently reported in a model for AF, rabbits subjected to rapid atrial pacing (RAP) that central-cellular, but not subsarcolemmal, Ca2+ transient was greatly reduced, likely contributing to atrial contractile dysfunction in AF. Nuclear Ca2+ transients were also reduced in RAP, suggesting that altered nuclear Ca2+ signalling may participate in the remodelling associated with AF. We hypothesize that altered perinuclear IP3R expression and IP3-induced Ca2+ release in RAP cells might underlie these observations.Methods: Using confocal microscopy we recorded transverse line-scan images in atrial cells from sham and RAP rabbits before and after 10 minutes of perfusion with L-phenylephrine (L-Phe).Results: IP3R activation elevated both nuclear and perinuclear Ca2+ release only in RAP cells (at 1Hz, L-Phe did not affect (-4.9±7%) perinuclear Ca2+ transient in 9 sham cells but enhanced it by 47.6±13% in 10 RAP cells, P<0,01). Using specific antibodies directed against type 2 IP3R, we observed that, in relation to type 2 ryanodine receptors, which were unchanged in both groups, perinuclear IP3R clusters were bigger and brighter in RAP cells (see figure).Conclusion: Our data strongly suggest enhanced IP3-dependent regulation of nuclear Ca2+ transients due to elevated perinuclear IP3R levels in RAP. These changes may affect Ca2+-mediated and IP3-dependent gene transcription pathways in tachycardia-induced remodelling.

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FAILURE OF THE CALCIUM WAVE PROPAGATION IN FIELD-STIMULATED ATRIAL MYOCYTES ISOLATED FROM PATIENTS WITH PERSISTENT ATRIAL FIBRILLATIONBenoit-Gilles Kerfant, PhD, Stijn Lumeij, BSc, Nick van Dijk, MSc, Geert Hendrikx, MSc, Hanneke Okkenhaug, PhD, Jos Maessen, MD, PhD, Llewelyn Roderick, H, PhD and Ulrich Schotten, MD, PhD. Maastricht University Cardiovascular Research Institute Maastricht (CARIM) Dept. of Physiology, Maastricht, Netherlands, The Babraham Institute, Cambridge, United Kingdom, Cardiothoracic Surgery Medical University Centre Maastricht, Maastricht, NetherlandsIntroduction: It is well established that calcium (Ca2+) signalling is altered in atrial fibrillation (AF). More specifically, global Ca2+ transient is decreased in atrial myocytes from AF patients. However, no study has explored the spatial-temporal distribution of intracellular Ca2+ in human AF. In addition since it has been suggested that spontaneous Ca2+ sparks are more numerous in AF, we also investigated Ca2+ sparks in field-stimulated cells.Methods: N/A

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Conclusion: An important factor underlying transmural AR gradients during early VF is differential IK(ATP) activation. We conclude that IK(ATP) modulation would be a stronger target for VF termination than a Purkinje based strategy.

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ACTION-POTENTIAL PROLONGATION AND ABNORMAL CA2+-HANDLING MODULATE BEAT-TO-BEAT VARIABILITY OF REPOLARIZATION DURATION IN CELLULAR AND COMPUTATIONAL MODELS OF LONG-QT SYNDROMEJordi Heijman, PhD, Antonio Zaza, MD, Daniel M. Johnson, BSc, Yoram Rudy, PhD, FHRS, Ralf L.M. Peeters, PhD, Paul G.A. Volders, MD, PhD and Ronald L. Westra, PhD. Institute of Pharmacology, University of Duisburg-Essen, Essen, Germany, Dept. of Biotechnology and Biosciences, University of Milano-Bicocca, Milan, Italy, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, Netherlands, Washington University in St. Louis, St. Louis, MO, Dept. of Knowledge Engineering, Maastricht University, Maastricht, NetherlandsIntroduction: Beat-to-beat variability of repolarization duration (BVR) is an intrinsic characteristic of cardiac function and a marker of proarrhythmia. Here, we aimed to elucidate mechanisms underlying increased BVR in long-QT (LQT) syndromes type 1-3.Methods: We developed a novel computational model of the canine ventricular myocyte (VM), simulating stochastic gating of 13 ion channels/transporters. Action-potential duration (APD) and BVR (Σ(|APDi+1 - APDi|)/[nbeats×√2]) were determined in canine VMs. LQT1-3 was mimicked in VMs and model using β-adrenergic stimulation (βAS) + IKs blockade, IKr blockade or late INa augmentation.Results: The model reproduced experimental APD and BVR properties under control and LQT1-3 conditions, suggesting that stochastic channel gating plays a role in BVR. The effect of APD on BVR followed an exponential function with no significant differences between control and LQT2 fits in model or myocytes (Fig. A), suggesting that APD is a major determinant of increased

Results: We found an approximately 7-fold increase in FOG-2 mRNA levels and a 3-fold increase in FOG-2 protein levels in the atrial tissue following gene induction. After 10 weeks of gene induction, all of these mice developed spontaneous and sustained atrial fibrillation (n=16). The onset of atrial fibrillation precedes any left ventricular systolic dysfunction, valvular disease, or elevated preload, suggesting a primary atrial mechanism. Messenger RNA microarray analysis suggested that the expression of multiple potassium channel subunits (KCNJ5, KCND2 and KCNE1) were downregulated, and these results were further confirmed by quantitative RT-PCR and in vitro promoter-reporter analysis.Conclusion: Taken together, these data suggest that FOG-2 upregulation in patients with heart failure may lead to the downregulation of potassium channel expression in atrial myocytes and the promotion of atrial fibrillation.

PO03-94

ACTIVATION RATE GRADIENTS DURING EARLY VENTRICULAR FIBRILLATION ARE DETERMINED BY TRANSMURAL IK(ATP) HETEROGENEITYEdward J. Vigmond, PhD, Patrick M. Boyle, PhD, Stephane Masse, MD and Kumaraswamy Nanthakumar, MD. University Bordeaux 1, Pessac, France, Johns Hopkins University, Baltimore, MD, Toronto General Hospital, Toronto, ON, CanadaIntroduction: Transmural activation rate gradients develop during early VF with higher frequencies colocalized with Purkinje System (PS) terminations. These gradients are suppressed by prior application of glibenclamide (an IK(ATP) blocker) which also leads to spontaneous defibrillation. However, it remains unclear whether the PS contributes to AR heterogeneity. Chemical ablation of the PS is possible experimentally but is not selective for the PS and destroys endocardium as well. We sought to use detailed computer simulations to separate IK(ATP) from PS contributions to AR gradients during VF.Methods: Ventricular computer models with either non-ungulate (endocardial) or ungulate (sub-epicardial) PS termination were constructed. Physiological IK(ATP) gradients were implemented and several seconds of VF were induced.Results: Significant AR gradients were observed in VF only for large transmural IK(ATP) gradients (see figure, bullseye AR insets). The critical determinant of AR gradient formation was refractoriness in low-IK(ATP) regions, leading to longer action potentials which blocked propagation from high-IK(ATP) regions. The PS was not invovled in establishing or maintaining AR gradients, but, increased AR heterogeneity on the endocardium or epicardium. Simulated glibenclamide application terminated VF within, at most, a few seconds, in accordance with previous experiments demonstrating cardioprotective properties of pretreatment with glibenclamide.

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for defibrillation success. However, this was an inadequate predictor here, as defibrillation failed in some instances when 100% of myocardium experienced such gradients.Conclusion: We demonstrated the feasibility of constructing electrophysiological CHD heart-torso models from clinical MRI. For the patient in this study, an S-ICD configuration was the optimal option. Φe gradients are not sufficient to predict defibrillation success.

PO03-97

UNDERLYING MECHANISMS OF LIFE THREATENING INTERACTIONS OF A COMBINATION THERAPY WITH DRONEDARONE AND DIGITALISGerrit Frommeyer, MD, Jochen Schulze Grotthoff, MSc, Lars Eckardt, MD and Peter Milberg, MD. Division of Electrophysiology, Department of Cardiovascular Medicine, Muenster, GermanyIntroduction: Dronedarone is frequently used in clinical practice. However, the PALLAS-trial was terminated early due to increased mortality in the dronedarone group. Possible interactions between dronedarone and digitalis have been discussed as probable underlying mechanisms. The aim of the present study was to assess possible proarrhythmic effects of dronedarone and digitalis in an experimental whole heart model.Methods: N/AResults: 6 female rabbits underwent chronic oral treatment with dronedarone (50mg/kg/d for 6 weeks). 10 rabbits were used as controls. Thereafter, hearts were isolated and Langendorff perfused. Eight endo- and epicardial monophasic action potentials and a 12-lead ECG showed a moderate prolongation of QT interval (+20ms)) and action potential duration at 90% of repolarization (APD90; +14ms). There was no significant increase in dispersion of repolarization. Dronedarone increased effective refractory period (ERP; +20ms) and thereby elevated post-repolarization refractoriness (PRR; +6ms).

BVR in LQT2. In agreement, reducing APD (with a stimulus current) but not removal of stochastic IKr gating reduced BVR in the model (Fig. B). Similar results were obtained for LQT3. In contrast, BVR was larger for any given APD in LQT1 + βAS and abnormal Ca2+ handling contributed to the increased BVR in model and VMs (Fig. C). Disabling stochastic gating of Ca2+-handling proteins normalized Ca2+ handling and lowered BVR without affecting APD (Fig. D).Conclusion: Different mechanisms contribute to increased BVR in LQT1 (abnormal Ca2+ handling) and LQT2-3 (APD), indicating that BVR reflects multiple potential proarrhythmic parameters.

PO03-96

PREDICTION OF OPTIMAL ICD PLACEMENT IN A PATIENT-SPECIFIC MODEL OF PEDIATRIC CONGENITAL HEART DEFECTLukas J. Rantner, MSc, Fijoy Vadakkumpadan, PhD, Jane E. Crosson, MD, Philip J. Spevak, MD and Natalia A. Trayanova, PhD, FHRS. Johns Hopkins University, Baltimore, MDIntroduction: Due to small size and varied anatomies, choosing ICD placement sites in children with congenital heart defects (CHDs) is challenging. Patient-specific heart-torso computer models offer the possibility to determine the optimal ICD placement.Methods: A biophysically-detailed heart-torso model was generated from clinical MRIs of a pediatric patient with tricuspid valve atresia (Fig A), and fiber orientation estimated using published methodology. IKs, Ito, and conductivity heterogeneities were incorporated. Since transvenous access was not possible, 3 subcutaneous (SQ) and 3 epicardial lead placement sites were identified along with 5 ICD can sites (Fig B). VF was induced, and defibrillation shocks were applied from 11 ICD configurations (Fig C) to determine defibrillation thresholds (DFTs).Results: The use of epicardial leads resulted in a lower DFT than SQ leads. Three configurations shared the lowest DFT for SQ leads (12.5% of highest DFT): 1. similar to a commercially available SQ ICD (S-ICD), 2. with two SQ leads, 3. with three SQ leads. In previous studies, extracellular potential (Φe) gradients ≥ 5 V/cm in ≥ 95% of the ventricles have been used as a surrogate

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alternans were equally important in inducing cardiac alternans during therapeutic hypothermia. SDA in APD is a more sensitive factor in predicting pacing-induced VF than SDA in Cai during therapeutic hypothermia.

PO03-99

INDUCIBILITY OF ATRIAL FIBRILLATION IN BROWN NORWAY AND SPONTANEOUS HYPERTENSIVE RATS IS NOT LINKED TO CONNEXIN 43 EXPRESSION.Junaid A. Zaman, MBChB, Pravina Patel, BSc and Nicholas Peters, MD, FHRS. Imperial College London, London, United KingdomIntroduction: It is known that atrial fibrillation (AF) and tachycardia (AT) occur in aged (1 year old) spontaneous hypertensive rats (SHR). Little is known about the molecular mechanisms but it is known that hypertrophy can alter connexin 43 (Cx43) expression. We therefore hypothesised that these changes may be evident at an earlier stage and may cause differential expression of Cx43.Methods: 10 Brown Norway (BN) and 10 Spontaneous Hypertensive Rats (SHR) aged between 12-14 weeks had their hearts perfused via Langendorff apparatus. High density recording was performed with EcoFlexMEA (32 50μm electrodes with 300μm inter-electrode distance in a square array), placed on right and left atrial appendages (RAA/LAA). Burst pacing was performed for 10s via a Micropace electrode in the right atrium from a cycle length of 150ms - 30ms in 10ms steps, with AF/AT lasting more than 30s considered ‘inducible’. Pacing was then performed from the left ventricle (LV) whilst recording RAA and LV to assess ventricular arrhythmia susceptibility. Average conduction velocity (CV) was calculated across the array using MATLAB. The hearts were snap frozen in liquid nitrogen for Western blot analysis of Cx43 expression looking at phosphorylated (P0) and dephosphorylated (P1/P2) bands.Results: Heart weight to body weight (HW:BW) ratios were significantly higher in the SHR group than the BN group (8.27 ± 2.59, n=3 vs 7.11±0.316mg/kg, n=4, p=0.04). The BN demonstrated significantly higher incidence of AF/AT than the SHR cohort (8/9 vs 2/7, p=0.03) whilst there was no difference in VT/VF susceptibility between them (2/7 vs 1/9, p=0.55). The inter-atrial conduction time (IACT) was significantly prolonged in the SHR (5.96 ± 0.46ms, n=96 vs 4.57 ± 0.36ms, n=110, p=0.0165) and CV across the array was higher in the RAA of BN vs SHR (36.44 ± 0.98 n=114 vs 31.37 ± 1.51cm/s n=92, p=0.039). Western blot analysis of atrial appendage samples showed no significant difference in P0 between species but there was an increased quantity of P1/P2 Cx43 in the BN RAA compared to LAA (p=0.01, n=5 pairs).Conclusion: Despite significant hypertrophy, SHRs at 3 months age have reduced AF/AT compared to a control species. This is accompanied by a decreased CV in the SHR and prolonged IACT but not due to changes in connexin expression.

PO03-100

IN VIVO MAPPING OF REPOLARIZATION ALTERNANS IN MAN: DOES SERCA 2A OR FIBROSIS PLAY A ROLE?Pier D. Lambiase, PhD, FRCP, Michele Orini, PhD, J. Yanni Gerges, PhD, Ben Hanson, PhD, Halina Dobrzynski, PhD, Xiao Jie, PhD, Mark Boyett, PhD, Martin Hayward, MD, FRCS and Peter Taggart, PhD, FRCP. Heart Hospital, London, United Kingdom, University College London, London, United Kingdom, University of Manchester, Manchester, United KingdomIntroduction: Action potential duration (APD) alternans is a precursor of sudden cardiac death. The cellular mechanisms

Additional application of ouabain (0.1µM and 0.2µM) resulted in a dose-dependent decrease of QT-interval, APD90, ERP and PRR in control hearts and dronedarone-pretreated hearts. Under baseline conditions, ventricular fibrillation was inducible by programmed stimulation and aggressive burst stimulation in 2 of 10 hearts (8 episodes). After application of 0.2µM ouabain 5 of 10 control hearts were inducible (20 episodes). Only 1 of 6 dronedarone-pretreated hearts (1 episode) showed ventricular fibrillation before ouabain infusion. After application of 0.2µM ouabain, 5 of 6 dronedarone-pretreated hearts were inducible (36 episodes).Conclusion: In the present study additional treatment with ouabain resulted in an increased ventricular vulnerability in chronically dronedarone-pretreated hearts. Ouabain led to a reduction of APD90, ERP and PRR. This reduction of PRR in the dronedarone group and the resulting elevated incidence of ventricular fibrillation might explain the results of the PALLAS study where an increased mortality in the dronedarone group led to an early termination of the study.

PO03-98

ACTION POTENTIAL DURATION ALTERNANS BETTER PREDICTS THE OCCURRENCE OF PACING-INDUCED VENTRICULAR FIBRILLATION THAN INTRACELLULAR CALCIUM ALTERNANS DURING THERAPEUTIC HYPOTHERMIA IN ISOLATED RABBIT HEARTSYu-Cheng Hsieh, MD, PhD, Shien-Fong Lin, PhD, Ying-Chieh Liao, MD, Jiunn-Cherng Lin, MD, Chen-Ying Hung, MD, Chih-Tai Ting, MD, PhD and Tsu-Juey Wu, MD, PhD. Cardiovascular center, Taichung Veterans Hospital, Taichung, Taiwan, Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, INIntroduction: Hypothermia increases the vulnerability of pacing-induced ventricular fibrillation (VF) by producing spatially discordant alternans (SDA) in action potential duration (APD) during S1 pacing. Hypothermia also increases intracellular Ca (Cai) load, which in turn promotes SDA in Cai and subsequent VF. The mechanism by which SDA of APD/Cai contributes to pacing-induced VF during therapeutic hypothermia remains unclear. We hypothesize that SDA in APD is a more robust parameter in predicting pacing-induced VF than SDA in Cai during therapeutic hypothermia.Methods: Langendorff-perfused isolated rabbit hearts (n=9) were sequentially cooled to moderate hypothermia (MH, 33°C) for 30 min, and severe hypothermia (SH, 30°C) for 30 min. The hearts were optically mapped for membrane potential (Vm) and Cai. S1 pacing protocol with pacing cycle length (PCL) from 350 ms to 120 ms was used to determine alternans properties of both APD (alternans in duration) and Cai (alternans in amplitude). The alternans threshold of APD/Cai was defined as the longest S1 PCL at which APD/Cai alternans were detected. Pacing-induced VF episodes were also analyzed.Results: The thresholds for APD alternans and Cai alternans were similar during MH (233±12 ms, 240±20 ms, for APD and Cai alternans, respectively; p=ns) and SH (297±42 ms, 308±35 ms, for APD and Cai alternans, respectively; p=ns). The threshold for SDA in APD and Cai were also similar during MH (193±23 ms, 193±23 ms, for APD and Cai alternans, respectively; p=ns) and SH (277±34 ms, 245±46 ms, for APD and Cai alternans, respectively; p=0.126). A total of 20 VF episodes were induced by S1 pacing during SH. 100% (20/20) of the VF episodes were induced at PCL that produced SDA in APD. In contrast, 75% (15/20) of the VF episodes were induced at PCL of producing SDA in Cai (p=0.047).Conclusion: Given the similar threshold for APD and Cai alternans during therapeutic hypothermia, both Vm and Cai

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hearts at baseline and during E4031-perfusion (0.1µM).Results: At baseline, in vivo heart rate corrected QT intervals and ex vivo APD in LV apex-inf were longer in LQT1 (QT, ms, LQT1, 219±21 vs. WT, 181±15, p=0.0001; APD, ms, 148±16 vs. 130±9, p<0.05), and APD-restitution was steeper in LQT1 in base-anterolat (0.21±0.03 vs. 0.16±0.03, p<0.05), base-inferolat, base-inf, and apex-ant (all p<0.05). E4031 prolonged QT intervals in WT and more pronouncedly in LQT1 (ms, LQT1, 329±21 vs. WT, 255±36, p<0.0001) - leading to pseudo-AV block in 3/11 LQT1 rabbits. E4031 also significantly prolonged APD and increased APD-restitution steepness in both, LQT1 and WT (10/16 vs. 8/16 regions). Baseline peak systolic and diastolic velocities (Vr, Vz) were similar in LQT1 and WT. During E4031-infusion, however, diastolic Vr and Vz decreased more pronouncedly in LQT1 (Vr, LQT1, 9/16 vs. WT, 0/16 regions, p<0.001; e.g., base-inferolat, cm/s, -3.5±0.6 vs. -2.8±0.6, p<0.001 vs. bsl; Vz, 12/16 vs. 3/16 regions, p<0.01; -8.2±1.0 vs. -5.9±1.2, p<0.0001) - indicating an E4031-induced impaired diastolic function in LQT1.Conclusion: IKr-blocker E4031 prolongs cardiac repolarization in WT and more pronouncedly in LQT1, but impairs diastolic function only in LQT1. Phase contrast MRI in transgenic LQT1 rabbits may thus provide insights in electro-mechanical effects of IKr-blocking drugs.

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MECHANICAL VS. ELECTRICAL PACING OF LANGENDORFF-PERFUSED RABBIT HEART: MAXIMUM RATE AND SUSTAINABILITYT Alexander Quinn, PhD and Peter Kohl, MD, PHD, FHRS. Imperial College London, Harefield, United KingdomIntroduction: Mechanical stimuli cause diastolic depolarisation. This has been shown to allow mechanical pacing of the asystolic heart in experimental and emergency medicine settings. We compared maximum rate and sustainability of same-site mechanical and electrical stimulation (MS, ES; respectively) in isolated coronary-perfused hearts.Methods: Local ES (1.5×threshold voltage, 2ms bipolar pulse) and MS (1.5×threshold deformation, 10 ms contact time) was applied to the same left ventricle (LV) freewall epicardium site in Langendorff-perfused hearts (1kg rabbits; n=4), instrumented with an LV intraventricular balloon. Trains of ES, MS, and alternating ES-MS (ratio of 1:1 to 4:1) were applied. Stimulation frequency was increased, in 0.5Hz steps, from 0.5Hz above sinus rate to 6.5Hz. Two-hundred stimuli were applied at each rate, followed by 1min recovery in sinus rhythm. Surface ECG and optical mapping were used to assess heart rate and to characterize action potential propagation (20μL bolus of 27.3mM voltage-sensitive dye di-4-ANBDQPQ; 10μM excitation-contraction uncoupler blebbistatin; fluorescence excited by 640±10nm light-emitting diodes; emission collected with >690nm filter using a 128×128 EMCCD at 511Hz).Results: Activation patterns and action potential morphology with ES and MS were not different downstream of the stimulation site. Maximum pacing rates achievable with ES and MS in each heart were identical, with loss of 1:1 capture occurring between 5 and 6Hz. While ES capture was maintained at each rate, MS capture was lost after a finite number of beats, which decreased linearly with MS interval. Interestingly, replacing 1-4 out of 5 MS with ES (ES-MS protocol) had no significant effect on the total number of beats at which MS became unable to pace the heart. This was not caused by loss of LV excitability, as ES continued to pace. Loss of capture was not related to tissue damage, and same-site MS could be resumed after the recovery period.Conclusion: Local ES and MS can be used for LV pacing with similar maximum rates. However, while ES can be maintained,

of repolarization alternans (RA) in the in-vivo human heart are undetermined.Methods: 264 epicardial unipolar electrograms were recorded during cardiac surgery at 600ms-350ms cycle length. Activation Recovery Intervals (ARI), a surrogate for APD, was estimated and RA was quantified by an index incorporating both extent and persistence of beat-to-beat variations in ARI (see figure). Two myocardial biopsies were taken for mRNA analysis, each from sites of maximum & zero RA.Results: N=20 pts (mean 62 years old, 16M:4F) were studied. All pts developed RA which was regional and with considerable inter-pt variability. SERCA2A mRNA showed a trend of downregulation in RA positive regions with an inverse correlation of SERCA2A vs RA (slope=-2.1,R2=0.82,N=17). NCX1, Phospholamaban, calsequestrin 2 and Connexin43 did not show significant correlations with RA. Vimentin (fibroblast marker)(slope=1.4,R2=0.76, N=12) & Collagen type 1 mRNA (slope=45.8, R2=0.86, N=7) showed positive correlations with RA.Conclusion: In patients with coronary artery disease, ventricular regions showing RA showed increased fibrosis markers & SERCA2A downregulation compared to zero alternans regions. These preliminary data in humans are consistent with animal models and may have important implications in arrhythmogenesis.

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E4031 AFFECTS REGIONAL ELECTRICAL AND DIASTOLIC FUNCTION IN TRANSGENIC LQT1 RABBITSDavid Ziupa, MD, Marius Menza, MS, Julia Beck, Gerlind Franke, PhD, Stefanie Perez Feliz, Michael Brunner, MD, Gideon Koren, MD, Manfred Zehender, MD, Christoph Bode, MD, Bernd A. Jung, PhD, Daniela Foell, MD and Katja E. Odening, MD. University Heart Center Freiburg, Department of Cardiology and Angiology I, Freiburg, Germany, University Medical Center Freiburg, Department of Radiology, Medical Physics, Freiburg, Germany, Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Alpert Medical School of Brown University, Providence, RIIntroduction: Regionally heterogeneous prolongation of action potential duration (APD) is a major pro-arrhythmic factor in inherited and IKr-blocker-induced long QT syndrome (LQTS). Using transgenic LQT1 rabbits (loss of IKs), we aimed at assessing whether IKr-blocker E4031 also affects regional mechanical cardiac function.Methods: Male transgenic LQT1 and wild type (WT) rabbits (n=12/10) were subjected to in vivo phase contrast MRI (1.5 Tesla) at baseline and during E4031-infusion (bolus 10µg/kg, 1µg/kg/min IV) to assess regional systolic and diastolic radial and longitudinal tissue velocities (Vr, Vz). Surface ECG was recorded at baseline and during E4031-infusion (same protocol as for MRI) to detect changes in QT duration in vivo. APD und APD-restitution were examined ex vivo in Langendorff-perfused

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of AF in heart failure (HF) rabbit.Methods: HF rabbits were created by coronary ligation. Monophasic action potential recordings were performed at left atrial appendage (LAA) by a Langendorff perfusion system in normal and HF rabbits with baseline, colchicine(100µM), followed by colchicine (100µM) plus taxol (5µM) perfusion. The collagen content, PI3K/AKT/eNOS signalling pathway, mRNA and protein expressions of ionic channels were measured, respectively in LAA preparations from normal and HF rabbits with vehicle or with colchicine intraperitoneal injection for 7days.Results: Colchicine decreased action potential duration (APD,74.1±2.6 vs 91.8±3.3 ms, P<0.001), effective refractory period (ERP),and maxima slope of restitution curve (RC) in HF LAA, however this effect was reversed by taxol (n=6). The incidence of early after depolarisations (EADs), delayed after depolarisations (DADs) and induced AF were lower in colchicine perfusion compared to HF baseline and with taxolperfusion (n=6, P<0.05). Cardiac function was increased and LA fibrosiswere decreased after colchicine treatment in HF rabbits(n=6). The mRNA and protein levels of Kir2.1, Kv1.4, Kv1.5, Kv7.1, Cav1.2, SERCA2a were upregulated in HF rabbits after colchicine treatment. The mRNA expressions of PI3K, AKT and eNOS were upregulated in colchicine treated HF rabbits.Conclusion: Colchicine may regulate the gene expressions of ionic channels and decrease the fibrosis in HF rabbit through the PI3K/AKT/eNOS signalling pathway, which reverses electrical and structural remodelling, and suppress AF.

PO03-105

TRANSSEPTAL CONDUCTION AS AN IMPORTANT DETERMINANT FOR CARDIAC RESYNCHRONIZATION THERAPY, AS REVEALED BY ENDOCARDIAL MAPPING IN THE DYSSYNCHRONOUS CANINE HEART.Marc Strik, MD, Caroline J.M. van Deursen, MD, Lars van Middendorp, MD, Arne van Hunnik, MD, Marion Kuiper, MD, Agenlo Auricchio, MD, PhD and Frits W. Prinzen, PhD. University of Maastricht, Maastricht, Netherlands, University of Maastricht, Lugano, SwitzerlandIntroduction: Simple conceptual ideas about Cardiac Resynchronization Therapy (CRT) assume that biventricular (BiV) pacing results in collision of right (RV) and left ventricular (LV) pacing derived wavefronts. However, this concept is contradicted by the minor reduction in QRS duration usually observed. We investigated the electrical mechanisms of CRT by performing endocardial mapping during CRT in dyssynchronous canine hearts.Methods: N/AResults: Studies were performed in anesthetized dogs with acute left bundle branch block (LBBB, n=10) and chronic LBBB with tachypacing-induced heart failure (LBBB+HF, n=6). LV pacing increased QRS duration by ≈20% in alll dogs while BiV pacing reduced it by ≈21% in LBBB hearts but only by ≈5% in LBBB+HF hearts. The Figure shows endocardial depolarization times measured at the LV free wall (1) and at the left (2) and right (3) side of the septum. Transseptal impulse conduction was slower in LBBB+HF than in LBBB hearts and in both groups slower than transmural LV conduction. Slower transseptal conduction correlated with diminished reduction in QRS duration during BiV pacing (R=0.61). In both groups, QRS duration and vector were significantly different between LV and BiV pacing, while LV endocardial activation and LV dP/dtmax increase were similar.Conclusion: Slow transseptal conduction, especially in failing hearts, may explain why endocardial LV electrical activation sequence and hemodynamic effect is similar in LV and BiV pacing and why BiV pacing causes only a relatively small

MS demonstrates pacing rate-dependent loss of 1:1 capture. The mechanism of this rate-dependent change in the ability of MS to sustain pacing of the heart is unknown.

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IDENTIFYING CRITICAL CFE BY USING MINI-ELECTRODES PLACING WITHIN AN IRRIGATED CATHETERLi-Wei Lo, MD, Yenn-Jiang Lin, MD, Hung-Yu Chang, MD and Shih-Ann Chen, MD. Taipei Veterans General Hospital, Taipei, TaiwanIntroduction: Substrate modification has become an interest in AF ablation. Identification of critical CFE that perpetuates AF is difficult. The minielectrode (ME) is designed to provide a high-resolution signal mapping by placing 3 tiny electrodes (0.8 mm in diameter, 2.5 mm center-to-center) within a 3.5 mm irrigated ablation electrode. The study aimed to compared the CFE obtained between irrigated tip/ring electrodes (RE) & ME, and identified activation at the max CFEs (FI < 50 msec) obtained by RE & ME.Methods: Sustained AF was created in 6 dogs using continuous rapid atrial pacing (750-900 bpm, 4 wks). EnSite Array was deployed in LA & RA. Contact CFE mappings were obtained by RE & ME simultaneously. AF wavefront propagation was derived from Array isopotential maps.Results: Mean AF cycle length (CL) recorded from RA (93±4vs.81±7 msec, p=0.03) & LA (92±8vs.75±3 msec, p=0.02) were longer in ME compared to that from RE, respectively. The max CFE numbers were similar between ME & REs. But areas of max CFE were smaller in RA (5.1±2.2 vs. 12.9±5.4 cm2, p=0.04) & LA (2.2±0.5 vs. 7.3±1.6 cm2, p=0.005) from ME compared to RE, respectively. The activation of max CFE detected by ME: Surrounding PV ectopy (22%), along reentry channel (22%), slow conduction (20%), wavefront split/pivot turning (12%), random/passive activation (24%). The % of random/passive activation was higher (57%, p=0.003) in the max CFE detected from CE. Figure shows examples of CFE maps from RE (A) & ME (B) and isopotential maps (1 to 7).Conclusion: The ME improve the resolution of CFE mapping and precisely locate the critical CFE sites, contributing to usefulness in substrate modification.

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MECHANISM OF COLCHICINE ON SUPPRESSION OF ATRIAL FIBRILLATION IN HEART FAILURE RABBIT MODELRahul Singhal, MD, Shih Lin Chang, MD and Shih Ann Chen, MD. Taipei Veterans Hospital, Taipei, TaiwanIntroduction: Colchicine could reduce postoperative atrial fibrillation(AF),however, the mechanism is unclear. This study aims to investigate the mechanism of colchicineon suppression

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PO03-107

EFFECTS OF ELECTRICAL STIMULATION OF CAROTID BAROREFLEX AND RENAL DENERVATION ON ATRIAL ELECTROPHYSIOLOGYDominik K. Linz, MD, Felix Mahfoud, MD, Ulrich Schotten, MD, PhD, Christian Ukena, MD, Hans-Ruprecht Neuberger, MD, PhD and Michael Böhm, MD. Universitätsklinikum des Saarlandes, Klinik für Innere Medizin III, Homburg/Saar, Germany, CARIM, Maastricht, NetherlandsIntroduction: Electrical baroreflex stimulation (BRS) and renal denervation (RDN) reduce blood pressure and global sympathetic drive in patients with resistant hypertension. Whereas RDN decreases sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive, BRS modulates autonomic balance by activation of the baroreflex, resulting in increased vagal activation. Increased vagal tone potentially shortens atrial refractoriness resulting in a stabilization of reentry circuits perpetuating atrial fibrillation (AF).Methods: In normotensive anasthetized pigs (n=12), we compared the acute effect of BRS and RDN on blood pressure, atrial effective refractory period (AERP) and inducibility of AF. Heart rate (HR) and blood pressure were comparably reduced 30 min after bilateral RDN or during 10 minutes of electrical BRS.Results: BRS resulted in a rapid and pronounced shortening of AERP (from 162±8 ms to 117±16 ms, p=0.001) associated with increased AF-inducibility from 0% to 82%. This shortening in AERP was completely reversible after stopping BRS. After administration of atropine, AF-inducibility during BRS was attenuated. Ventricular repolarization was not modulated by BRS. In RDN, AF was not inducible, however, it did not prevent BRS-induced shortening of AERP.Conclusion: RDN and BRS resulting in comparable blood pressure and heart rate reductions differently influence atrial electrophysiology. Vagally mediated shortening of AERP, resulting in increased AF-inducibility, was observed with BRS but not with RDN.

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RENAL SYMPATHETIC DENERVATION PROVIDES VENTRICULAR RATE CONTROL BUT DOES NOT PREVENT ATRIAL ELECTRICAL REMODELING DURING ATRIAL FIBRILLATIONDominik K. Linz, MD, Felix Mahfoud, MD, Christian Ukena, MD, Ulrich Schotten, MD, PhD, Hans-Ruprecht Neuberger, MD, PhD, Klaus Wirth, MD and Michael Böhm, MD. Universitätsklinikum des Saarlandes, Klinik für Innere Medizin III, Homburg/Saar, GermanyIntroduction: Renal denervation (RDN) reduces renal efferent and afferent sympathetic activity thereby lowering blood pressure in resistant hypertension. The effect of modulation of the autonomic nervous system by RDN on atrial electrophysiology and ventricular rate control during atrial fibrillation (AF) is unknown.Methods: Here we report a reduction of ventricular heart rate (HR) in a patient with permanent AF undergoing RDN. Subsequently, we investigated the effect of RDN on AF-induced shortening of atrial effective refractory period (AERP), AF-inducibility and ventricular rate control during AF maintained by rapid atrial pacing in 12 pigs undergoing RDN (n=7) or sham procedure (n=5).Results: During sinus rhythm RDN reduced HR (RR-interval: 708±12 ms vs. 577±19 ms, p=0.0021) and increased atrio-ventricular (AV)-node conduction time (PQ-interval: 112±12

reduction in QRS duration.

PO03-106

EFFECT OF RENAL SYMPATHETIC DENERVATION ON THE INITIATION OF A SUBSTRATE FOR ATRIAL FIBRILLATION IN OBSTRUCTIVE SLEEP APNEADominik K. Linz, MD, Mathias Hohl, PhD, Alexander Nickel, PhD, Klaus Wirth, MD, Felix Mahfoud, MD, Christoph Maack, MD, Ulrich Schotten, MD, PhD and Michael Böhm, MD. Universitätsklinikum des Saarlandes, Klinik für Innere Medizin III, Homburg/Saar, Germany, CARIM, Maastricht, NetherlandsIntroduction: Obstructive sleep apnea (OSA) is associated with autonomic imbalance and the development of an arrhythmogenic electrical and structural atrial remodeling. However, the role of adrenergic influences on the initiation of an atrial substrate for atrial fibrillation (AF) in OSA is not well known.Methods: Renal sympathetic denervation (RDN) decreases sympathetic renal afferent nerve activity, leading to decreased central sympathetic drive. We studied the effect of RDN on atrial electrophysiological changes, occurrence of spontaneous AF-episodes and initiation of a structural remodeling process in a pig model with repetitive obstructive apneas for 4 hours.Results: Repetitive obstructive apneas increased spontaneous AF-episodes, which were triggered by spontaneous atrial extrabeats and maintained by shortened intra-apneic atrial refractoriness. Tracheal occlusions resulted in post-apneic blood pressure rises and increased circulating renin-angiotensin-aldosterone-system (RAAS) activation. Atrial expression of mineralocorticoid receptors (MR) and atrial aldosterone levels were not changed but 11-β hydroxysteroid dehydrogenase 2, increasing aldosterone activity via MR, was elevated. This was associated with reduced antioxidative capacity (GSH/GSSG), increased NADPH-oxidase activity and increased expression of connective tissue growth factor (CTGF). RDN prevented spontaneous AF triggered by atrial extrabeats and shortening of atrial refractoriness. Furthermore, RDN inhibited post-apneic blood pressure rises and activation of circulating RAAS while increased atrial oxidative stress together with initiation of profibrotic pathways were significantly attenuated.Conclusion: Repetitive obstructive apneas increased the trigger for AF, caused electrical remodeling and initiated a structural remodeling process in the atrium. RDN is capable to reduce occurrence of spontaneous AF and post-apneic blood pressure rises. However, increased atrial oxidative stress and subsequent initiation of profibrotic pathways were not completely prevented, suggesting a relevant role of intermittent hypoxia, which was not modulated by RDN.

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S259Poster Session III

PO03-110

ELEVATED ATRIAL TGF-β1 IN OBESITY PREDICTS ATRIAL STRUCTURAL AND ELECTROPHYSIOLOGICAL REMODELING IN AN OBESE OVINE MODELRajiv Mahajan, MD, Anthony G. Brooks, PhD, John P.M. Wood, PhD, Jim Manavis, BSc, Chrishan Samuel, MBBS, PhD, Simon Royce, PhD, Suchi Grover, MBBS, Joseph Selvanayagam, MBBS, PhD, Kurt C. Roberts-Thomson, MBBS, PhD and Prashanthan Sanders, MBBS, PhD. Royal Adelaide Hospital, Adelaide, Australia, SA Pathology, Adelaide, Australia, Department of Pharmacology, Melbourne, Australia, Discipline of Medicine, Flinders University and Flinders Medical Centre, Adelaide, AustraliaIntroduction: TGFβ superfamily is over-expressed in obesity. In addition, TGFβ1 is considered central to the mechanisms resulting in atrial fibrosis. Atrial fibrosis is an important component of structural remodeling and postulated to sustain re-entry.Methods: Thirty sheep had obesity induced by ad-libitum calorie dense diet over 18 months. Following this, animals underwent weight reduction by reducing quantity of hay over 8 months. Animals were studied in equal groups in the obese state and following 15% and 30% reduction in weight as follows: electrophysiological study, echocardiography, Cardiac MRI, DEXA, atrial fibrosis (Masson’s trichome, morphometry) and TGFβ1 protein (Western Blot). Eight lean animals served as controls.Results: Atrial TGFβ1 protein was elevated in the obese group (vs controls p<0.001) and trended toward a decrease with weight loss (p=0.06). There was significant correlation between atrial TGF-β1 and left atrial volume (r=0.45, p=0.004) and atrial fibrosis (r=0.35, p=0.07). After adjustment for mean LA pressure and LA volume, TGFβ1 still was associated with atrial conduction velocity (r=0.51, p=0.012) and conduction heterogeneity (p=0.004). The atrial pericardial adipose tissue volume significantly correlated atrial TGFβ1 expression(r=0.61, p=0.02) and this relationship remained after adjustment for total body fat (p=0.09).Conclusion: Elevated atrial TGF-β1 protein expression in obesity is associated with atrial fibrosis and electrophysiological remodeling independent of hemodynamic parameters. The strong correlation of atrial TGFβ1 with atrial pericardial adipose tissue raises the possibility of a paracrine effect which requires further investigation.

ms vs. 88±9 ms, p=0.0001). Atrial tachypacing for 30 minutes increased AF-inducibility and decreased AF-cycle length. This was not influenced by RDN. RDN reduced ventricular rate during AF-episodes by approximately 24 % (119±9 bpm vs. 158±19 bpm, p=0.0001). AF-episodes were shorter after RDN compared to SHAM (12±3 s vs. 34±4 s, p=0.0091) but AERP was not modified by RDN. RDN reduced HR and reduced AV-node conduction time during sinus rhythm and provided rate control during AF. AF-induced atrial electrical remodeling, AF-inducibility and AF-cycle length were not modified, but duration of AF-episodes was shorter after RDN.Conclusion: Modulation of the autonomic nervous system by RDN might provide rate control and reduce susceptibility to AF. Whether RDN may provide rate control in a larger number of patients with AF deserves further clinical studies.

PO03-109

ENDOVASCULAR VAGAL STIMULATION IS FEASIBLE BUT WITH EVIDENCE OF MIXED AUTONOMIC EFFECTSAlaaeldin A. Shalaby, MD, Jeffrey Balzer, PhD, John Nosbisch, RN, John Linden, RN and Samir Saba, MD. Pittsburgh VA Healthcare System, Div of Cardiology, Pittsburgh, PA, University of Pittsubrgh, Pittsburgh, PA, University of Pittsburgh, Pittsburgh, PAIntroduction: We studied the feasibility of vagal stimulation from within the right internal jugular (RIJ) or brachiocephalic (BC) vein and assessed downstream neurohormonal and cardiac electrophysiological (EP) effects.Methods: We studied patients during clinical EP procedure. After 10 min of baseline recordings, an electrode catheter was advanced to the RIJ. Stimulation at 25 Hz, 0.5 msec and varied amplitude (≤ 10 mA and without pain) was conducted while moving the catheter in random order between four positions guided by vertebral level (I: C1-C2, II: C3-C5, III: C6-T2, IV: IJ/BC junction T3-T4) or if unsuccessful a thoracic site (V: right BC/left BC junction T4-T5). Capture of the vagal nerve was confirmed by high frequency contraction of the cricothyroid muscle supplied by the recurrent laryngeal nerve. Intermittent stimulation (15 secs on, 30 secs off) was continued at capture threshold for 10 minutes at rest. EP study was then performed during the same vagal stimulation. Norepinephrine (NE) was drawn at baseline and after vagal stimulation at rest.Results: Twenty Caucasian men age 61 ± 8 years, BMI 32 ± 4 were studied under conscious sedation (6) or general anesthesia (14). In all but one, stimulation was achieved: Site I in 6 cases, II, III and IV in 4 cases each while site V was used in one. Stimulation energy was 3.6 ± 4.8 mA and fluoroscopy time for catheter placement was 1.0 ± 0. 8 minutes. Consistent with vagal effect, during sinus rhythm (19/20), PR and AH intervals prolonged and atrial refractoriness decreased. However, cycle length did not change and NE levels increased (Table).Conclusion: Endovascular vagal stimulation is feasible. However, EP and NE results may indicate mixed autonomic neuromodulation effects.

Cycle length (msec)

PR (msec)

QRS (msec)

QT (msec)

AH (msec)

HV (msec)

AVNERP (msec)

AERP (msec)

VERP (msec)

NE (pg/ml)

Baseline 958±198 185±53 103± 20 429±47 104±60 56±8 308±87 270±39 275±52 187±118

Vagal Stimulation 969±200 201 ±67 105±

20 440± 50 120±94 56±9 342±121 245±31 276±66 275±52

P value 0.7 0.025 0.5 0.13 0.029 0.7 0.12 0.015 0.9 0.035

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S260 Heart Rhythm, Vol. 10, No. 5, May Supplement 2013

Methods: The effect of siRNA specific to Cx40 (Cx40siRNA) was first confirmed in endothelial progenitor cells derived from canine peripheral blood. Then, in vivo studies were performed. After thoracotomy, the Cx40siRNA mixed with liposome was injected into the wall of canine’s left atrium (LA), including low dose injection (100 ug, N=3) and low and high dose multiple injection (200 ug, N=3). Animals injected with liposome alone were used as control (N=3). Occurrence of AF was monitored with implanted pacemaker. Open-chest electrophysiologic study was performed 2 weeks after the injection.Expression of Cx40 was evaluated.Results: Cx40 expression was reduced in LA areas injected with either high or low dose of Cx40siRNA, when compared to areas with control lipoidal injection or RA by western blots and immunostain (Fig 1). In animals receiving the Cx40siRNA injection, sustained AF was observed in 5 of 6 dogs (83%) within 2 weeks post injection (Figure 1B). 3D mapping showed reduced electrogram voltage (0.6±0.4 mV vs. 1.5±1.2 mV, P<0.01, N=30 regions) and slower conduction velocity (0.8±0.4 m/s vs. 1.8±1.2 m/s,P=0.03) when compared to the non-injection sites. During AF, the atrium with siRNA injection had a higher DF compared with the other atrium, indicating the role of AF maintenance (N=6, 100%).Conclusion: We confirmed the feasibility of knocking down of Connexin40 proteins to induce AF in canines.

PO03-113

THE RELATIONSHIP BETWEEN INTRINSIC CARDIAC AUTONOMIC GANGLIONATED PLEXI AND THE ATRIAL FIBRILLATION NESTHung-Yu Chang, MD, Li-Wei Lo, MD, Yenn-Jiang Lin, MD and Shih-Ann Chen, MD. Cheng-Hsin General Hospital, Taipei, Taiwan, Taipei Veterans General Hospital, Taipei, TaiwanIntroduction: Spectral analysis during sinus rhythm (SR) can identify high dominant frequency (DF) sites, which may play a role in the perpetuation of atrial fibrillation (AF). The relationship between cardiac autonomic nervous system (CANS) and high-DF site (AF nest) remained unclear.Methods: In 12 dogs, high frequency stimulation was applied to locate the four major left atrial (LA) ganglionated plexi (GPs). A multi-electrode array and 4-mm tip mapping catheter were delivered into the LA via LA appendage. During SR, spectral analysis was performed on the bipolar electrograms in the LA before and after epicardial GP ablation.

PO03-111

LACK OF CYCLASE-ASSOCIATED PROTEIN 2 RESULTS IN AN ARRHYTHMOGENIC CARDIOMYOPATHY WITH ALTERED CONNEXIN AND CALCIUM CHANNEL EXPRESSIONFlorian Stöckigt, MD, Vivek Peche, Angelika A. Noegel, PhD and Jan W. Schrickel, MD. Department of Medicine-Cardiology, Bonn, Germany, Department of Biochemistry, Cologne, GermanyIntroduction: Lack of cyclase associated protein 2 (CAP2) by a gene trap approach (gt) in the mouse leads to a cardiomyopathy with morphological predominance of the right ventricle resulting in an increased mortality. The purpose of our investigation was to identify potential arrhythmogenic reasons leading to this premature cardiac death.Methods: We performed in vivo electrophysiological studies in CAP2gt/+, CAP2gt/gt and corresponding wild type (WT) mice to determine surface and intracardiac ECG parameters and to test the inducibility of ventricular tachycardias (VTs). Long-term-ECG recordings were used to detect spontaneous arrhythmias. mRNA expression analysis of cardiac connexins (Cx) and ion channels were carried out as well as quantitative cardiac fibrosis determination. Immunofluorescence of Cx40 and Cx43 was performed to visualise their distribution pattern.Results: In comparison to WT, CAP2gt/gt showed marked conduction delays on atrial and ventricular level (reduced heart rate, prolonged PQ, QRS and QT time). AV-time prolongation was due to infra Hisian conduction delays. Functional testing revealed a trend towards a prolonged ventricular refractory period. The inducibility of VTs was significantly higher in the mutant mice. Long-time ECG recordings showed polymorphic premature ventricular contractions and spontaneous VTs in the CAP2 deficient mice. Compared to WT, the ventricles of CAP2gt/gt mice presented enhanced myocardial fibrosis (9.1 ± 6.7 % vs. 5.6 ± 3.3 %; p=0.01) that was found predominantly in the left ventricle. CAP2gt/gt resulted in a significant reduction of Cx40 expression (septum area) and elevated ventricular expression of Cx43, desmin and the calcium channel Cav 1.2.Conclusion: Loss of CAP2 results in marked electrophysiological disturbances leading to malignant ventricular arrhythmias. Impaired sinus node function, conduction delays, and susceptibility to arrhythmias are in accordance with a reduction in Cx40 and alterations in Cx43 and calcium channel expression. Cases of right ventricular cardiomyopathy may be due to dysfunction of CAP2, so further evaluation of its influence on cardiomyopathy and arrhythmogenesis should ensue to fully understand its functioning.

PO03-112

FEASIBILITY OF KNOCKING DOWN CONNEXIN40 PROTEINS AS A NEW CANINE MODEL OF ATRIAL FIBRILLATIONYenn-Jiang Lin, MD, PhD, Hsueh-Hsiao Wang, PhD, Li-Wei Lo, MD, Yi-Ling Yan, MS and Hung-I Yeh, MD, PhD. Taipei Veterans General Hospital, Taipei, Taiwan, Departments of Internal Medicine and Medical Research, Mackay Memorial Hospital, Mackay Medical College, New Taipei City, Taiwan, New Taipei City, Taiwan, Mackay Memorial Hospital, New Taipei City, TaiwanIntroduction: We investigated the feasibility of knocking down Connexin (Cx) 40 proteins by a novel small interfering RNA (Si-RNA) gene silencing technique in cultured EPC cells of derived from the normal canines and then in the left atrium in vivo as new model of AF.

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S261Poster Session III

Multivariate logistic regression including time from first shock, AMSA, LADrf, and CPP demonstrated time from first shock, AMSA, and CPP to be significant predictors of organized rhythm (LR chi2 = 23.3, p<0.001).Conclusion: The present study supports an independent contribution of coronary perfusion, time, and AMSA to the prediction of shock success. The intriguing decline in AMSA after having augmented coronary perfusion is the subject of ongoing research.Table (In brackets are shown the number of successes or failures in restoring an organized rhythm)

Shock #1 Shock #2 Shock #3 Shock #4 Shock #5AMSA - ALL 7.1±2.1 10.3±2.5 8.7±3.3 7.8±3.1 6.1±1.4AMSA - Success Shock 8.8 [1] 14.1 [1] 9.7±3.3 [4] 8.8±2.2 [4] 6.1±1.4 [2]AMSA - Fail Shock 6.8±2.1 [7] 9.8±2.2 [7] 7.6±3.4 [4] 3.4 [1] -LADrf - ALL 0.22±0.12 1.45±0.54 1.51±0.48 1.86±0.63 2.26±0.26LADrf - Success Shock 0.44 1.27 1.58±0.62 1.83±0.73 2.26±0.26LADrf - Fail Shock 0.19±0.09 1.48±0.58 1.43±0.39 1.96 -CPP - ALL 11±2 31±2 30±1 31±1 31±0CPP - Success Shock 14 30 30±1 32±2 31±0CPP - Fail Shock 11±1 31±2 30±1 30 -

PO03-115

TRIGGERS CONSISTENTLY LIE DISTANT TO THE ATRIAL FIBRILLATION THAT THEY INITIATEAmir A. Schricker, MD, Gautam G. Lalani, MD, David E. Krummen, MD and Sanjiv M. Narayan, MD, PHD, FHRS. UC San Diego Medical Center, La Jolla, CA, VA San Diego Healthcare System, La Jolla, CAIntroduction: Ablating atrial fibrillation (AF) triggers remains the cornerstone of ablation, yet their relationship to AF initiating mechanisms is unclear. We hypothesized that, as in all other reentrant arrhythmias, AF triggers lie at a sufficient distance for conduction slowing and block to initiate reentry.Methods: In 31 AF patients (21 parox; 62±9 yrs; LA size 42±7 mm) at ablation, we placed 64-pole basket catheters (Boston Scientific, MA) in each atrium to record spontaneous or pacing-induced AF initiations. Spatial activation maps of both atria were constructed to precisely identify trigger and AF initiating mechanisms. Basket catheter electrode locations were defined from NavX (St. Jude Medical, MN).Results: In 62 unique AF initiations, we recorded spiral waves (n=45) or repetitive focal beats (n=16) that initiated AF after a trigger. In 60/62 AF initiations, the initiation site - defined as the core of reentrant spiral waves or repetitive focal beats - did not occur at the trigger site, but 21±17 mm away. This separation was shorter for focal beats than spiral waves (15±16 vs 22±17 mm, p=0.07) but did not differ for paroxysmal vs persistent (21±19 vs 20± 11mm, p<0.02). In 12 initiations the mechanism was contralateral to its trigger. Figure A shows a trigger in the LA leading to a clockwise spiral (Figure B) that initiates AF. Distance between trigger and spiral core is 15mm.

Results: The majority of AF nests were located close to the GPs (54 sites, 51% of AF nests). The remaining AF nests were located in the PV-LA junction away from the GP (n=12, 11%), anteroseptal wall (n=11, 10%), posterior wall (n=17, 16%), and roof (n=13, 12%). After GP ablation, the mean global LA DF values decreased from 56±8Hz to 50±4Hz (p=0.012), the mean AF nest DF values decreased from 93±2Hz to 87±4Hz (p=0.001). Most of theprevious AF nest sites close to the GPs disappeared (45 sites, 83%). The mean surface area of AF nest decreased from 9±5cm2 to 3±2cm2 (p=0.001). The remaining high-DF regions were distributed at the PV-LA junction (n=15, 40%), anteroseptal wall (n=5, 13%), posterior wall (n=13, 34%), and roof (n=5, 13%). The figure showed an example of LA DF mapping before (Panel A) and after (Panel B) GP ablation.Conclusion:GP ablation decreased the mean LA DF values, AF nest DF values, AF nest areas and diminished the number of AF nests; particularly those close to the GPs. Our finding showed that CANS may play an important role in the mechanism of AF nest formation.

PO03-114

AMSA PREDICTS RETURN OF ORGANIZED RHYTHM IN A SWINE MODEL OF VENTRICULAR FIBRILLATION AND CONTROLLED CORONARY PERFUSION BY EXTRACORPOREAL CIRCULATIONChristopher L. Kaufman, PhD, Vesna Borovnik-Lesjak, MD, Kasen Whitehouse, BS, Alvin Baetiong, BS, Jeejabai Radhakrishnan, PhD and Raúl J. Gazmuri, MD, PhD. ZOLL Medical Corp., Chelmsford, MA, Rosalind Franklin University of Medicine and Science, North Chicago, ILIntroduction: Previous studies have shown that the amplitude spectral area (AMSA) method which analyzes ventricular fibrillation (VF) amplitude and frequency characteristics contains information predictive of electrical shock success. However, the underlying mechanisms are incompletely understood. We developed an open-chest swine model of VF in which “average CPR” followed by “highly effective CPR” was modeled using extracorporeal circulation (ECC).Methods: VF was induced and left untreated for 8 min in 8 pigs after which ECC was started and maintained for 10 min adjusting the flow to generate a coronary perfusion pressure (CPP) of 10 mmHg. After delivery of an initial shock, the ECC flow was increased and titrated to secure a mean aortic pressure of 40 mmHg delivering additional electrical shocks at 60 s intervals. Shock success was defined as organized rhythm lasting > 4 seconds.Blood flow in the left anterior descending (LAD) coronary artery relative to baseline LAD blood flow was determined (LADrf).Results: AMSA increased sharply after increasing CPP and the corresponding LADrf flow but progressively declined despite maintenance of adequate coronary perfusion, yet, maintaining higher values in pigs that experienced shock success (Table).

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S262 Heart Rhythm, Vol. 10, No. 5, May Supplement 2013

75.0±4.7, left inferior PV: 97.9±6.5 vs 72.9±7.7, right superior PV: 99.1±11.0 vs 74.0±67.6, right inferior PV: 96.7±11.1 vs 73.0±68.8; p <0.001). A delta ECI more than 22% pre-post PVs isolation was found in all pts. (LCOM:22.5±0.7; LSPV:25.9± 8.1; LIPV: 25.3±8.1;RSPV:28.2±8.0; RIPV: 25.3±6.9.)Conclusion: Successful PVs isolation with good contact, as monitored by the Sensei X system, is associated with a significant decrease in ECI and with delta ECI >22%. This may be used as a surrogate marker of effective lesion depth in AF ablation.

PO03-117

ATRIAL DELAYED ENHANCEMENT AT MRI: EXTENT AND DISTRIBUTION IN PATIENTS WITH AND WITHOUT ATRIAL FIBRILLATIONHubert Cochet, MD, Amaury Mouries, MD, Jatin Relan, PhD, Yuki Komatsu, MD, Frederic Sacher, MD, Nicolas Derval, MD, Arnaud Denis, MD, Khaled Ramoul, MD, Matthew Daly, MD, Laurence Jesel, MD, Stephan Zellerhoff, MD, Maxime Sermesant, PhD, Nicholas Ayache, PhD, Michel Montaudon, MD, PhD, Francois Laurent, MD, Mélèze Hocini, MD, Michel Haïssaguerre, MD and Pierre Jaïs, MD, PhD. CHU Bordeaux - Université de Bordeaux - LIRYC/INSERM U1045, Pessac, France, St Jude Medical, St Paul, MN, INRIA Sophia Antipolis, Sophia Antipolis, FranceIntroduction: Atrial delayed enhancement (aDE) at MRI has been described in pts with atrial fibrillation (AF) and correlated to post-ablation outcome. However, the determinants of aDE have not been thoroughly studiedMethods: 91 pts (58 males, age 55±7 yrs) referred for cardiac MRI underwent aDE using a 3D IR TurboFLASH free breathing method. The population was composed of 20 paroxysmal or short persistent AF, 21 long persistent AF (>1 yr), 30 pts with structural heart disease (SHD) and no history of AF, and 20 controls (no SHD nor AF). After segmentation of the left atrial wall, aDE was quantified using an adaptative thresholding algorithm. Multivariate regression analysis was performed to identify the determinants of aDE extent. Additionally, areas of aDE were registered to an atrial template to study aDE distribution in sub-populationsResults: In the total population, presence of AF and age were independently associated to aDE extent (R2=0.161, P=0.01 and R2=0.068, P=0.04). Among AF pts (N=41), female gender and AF persistence were independently associated to a higher aDE extent (R2=0.162, P=0.003 and R2=0.112, P=0.02). Extent of aDE was 21.9±8.6% in paroxysmal and short persistent AF pts, and 27.2±8.1% in long persistent AF pts (P=0.03). Among non-AF pts (N=50), presence of SHD and female gender were independently associated to a higher aDE extent (R2=0.281, P=0.001 and

Conclusion: In line with classical electrophysiological concepts, AF triggers and initiating mechanisms are not co-localized. Future studies should determine whether this ~2 cm separation explains why wide area circumferential ablation (WACA) may be more effective than lesions focused tightly on the PVs by eliminating AF initiating spirals.

PO03-116

ROBOTIC CONTACT FORCE SENSING AND ELECTRICAL COUPLING INDEX: A VALIDATION STUDY OF A COMBINED APPROACH FOR SUCCESSFUL PULMONARY VEIN ISOLATIONAntonio Dello Russo, MD, PhD, Gaetano Fassini, MD, Fabrizio Bologna, MD, Michela Casella, MD, PhD, Stefania Riva, MD, Massimo Moltrasio, MD, Fabrizio Tundo, MD, PhD, Martina zucchetti, MD, Benedetta Majocchi, MD, Vittoria Marino, MD, Daniele Colombo, MD, Ester Innocenti, MD, Gennaro Izzo, MD, Osama Al Nono, MD, Eleonora Russo, MD, Corrado Carbucicchio, MD, Pasquale Santangeli, MD, Luigi Di Biase, MD, PhD, Andrea Natale, MD, FHRS and Claudio Tondo, MD, PhD. Cardiac Arrhythmia Research Centre, Centro Cardiologico Monzino, IRCCS, Milan, Italy, Texas Cardiac Arrhythmia Institute, Austin, TXIntroduction: Contact with cardiac tissue is an important determinant of lesion efficacy during atrial fibrillation (AF) ablation. The robotic Sensei X system (Hansen Medical, CA) has been validated for contact force sensing expressed in grams. The electrical coupling index (ECI) from the EnSite Contact™ system (St Jude Medical, MN) has been validated versus histology as an indicator of tissue lesion depth. We aimed to investigate the correlation between the two in AF ablation.Methods: We enrolled 15 patients (13 males, age 59±12) with paroxysmal AF. Pulmonary vein (PV) isolation was guided by the Sensei X™ system, employing the EnSite Contact™ catheter and EnSite NavX™ electroanatomic mapping. We evaluated the ECI before, during and after ablation and compared it with force estimation in grams obtained by the robotic system. The changes in the ECI subcomponents over the course of ablation was assessed (Delta ECI).Results: A total of 56 PVs and 2 common ostia were targeted and isolated successfully, while keeping contact force in the established 20-40 grange. In all PVs the ECI was significantly reduced after ablation (left superior PV: 102.4±11.8 vs

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S263Poster Session III

PO03-119

AN ANALYSIS OF THE SPATIAL DISTRIBUTION OF LEFT ATRIAL STRUCTURAL REMODELING IN PATIENTS WITH ATRIAL FIBRILLATIONKoji Higuchi, MD, Gregory Gardner, Alan Morris, MSc, Joshua Cates, PhD and Nassir F. Marrouche, MD. University of Utah, Salt Lake City, UTIntroduction: In this study we examined the spatial distribution of left atrial (LA) structural remodeling (LASRM) in an atrial fibrillation (AF) population using LGE-MRI to detect LASRM and an automated shape modeling approach to establish LA surface point correspondence.Methods: We included 160 patients (mean age: 66±11) who underwent pulmonary vein antrum isolation in addition to posterior wall debulking for AF ablation. LGE-MRI scans were used to detect LASRM and for LA shape segmentations (Fig. A; LASRM: green; viable myocardium: blue). The presence of LASRM was tabulated at 512 surface correspondence points (Fig. B-C) for each individual and then mapped to the population mean shape; individual patient mappings and the mean shape were established with an automated shape modeling approach (ShapeWorks, SCI Institute, University of Utah). The LASRM distributions were computed for patients that recurred after ablation and those that did not.Results: Fig. C shows the histogram of LASRM on the LA, which suggests that LASRM in our study population is more localized on the posterior wall (red area) near the left inferior pulmonary vein (LIPV). In this population, 57 patients had a recurrence of AF after initial ablation. A comparison of patients with (N=57) and without (N=103) AF recurrence suggests that LASRM may be more broadly distributed on the posterior wall in patients that recur (Fig. D).Conclusion: In our study population, LASRM was highly distributed on the LA posterior wall near the LIPV. LASRM seems to be more broadly distributed on the posterior wall in patients with AF recurrence, when compared to patients without AF recurrence.

PO03-120

COMPLEX FRACTIONATED ATRIAL ELECTROGRAMS RELATED TO LEFT ATRIAL WALL THICKNESSJin Wi, MD, Hee-Sun Mun, MD, Jae-Sun Uhm, MD, Jaemin Shim, MD, Jong-Youn Kim, MD, PhD, Hui-Nam Pak, MD, PhD, Moonhyoung Lee, MD, PhD and Boyoung Joung, MD, PhD. Severance Cardiovascular Hospital, Yonsei University Health System, Seoul, Republic of KoreaIntroduction: The mechanism of complex fractionated atrial electrogram (CFAE) in patients with atrial fibrillation (AF) remains

R2=0.085, P=0.007). Extent of aDE was 20.7±7.7% in pts with SHD and no AF history, and 12.3±5.1% in controls (P<0.0001). In terms of distribution, aDE was more frequent in the posterior vs anterior wall. In the posterior wall, aDE was more likely found around and below left inferior pulmonary vein ostium, and to a lesser extent in the left isthmus and around the right veins ostia. In the anterior wall, aDE was more likely found below the right veins, in the septum. This distribution was stereotyped, regardless of the underlying condition.Conclusion: The presence of AF and its persistence are the strongest determinants of aDE extent. However, aDE is also related to age, sex, and to the presence of SHD. The distribution of aDE is stereotyped regardless of the underlying condition. aDE is more frequent in the posterior wall and particularly in the area adjacent to the left inferior pulmonary vein ostium

PO03-118

STRUCTURAL AND FUNCTIONAL STATUS OF THE ATRIA 5 YEARS AFTER SUCCESSFUL ABLATION FOR PERSISTENT ATRIAL FIBRILLATION: AN MRI STUDYHubert Cochet, MD, Daniel Scherr, MD, Yuki Komatsu, MD, Frederic Sacher, MD, Nicolas Derval, MD, Arnaud Denis, MD, Khaled Ramoul, MD, Matthew Daly, MD, Laurence Jesel, MD, Stephan Zellerhoff, MD, Michel Montaudon, MD, PhD, Francois Laurent, MD, Mélèze Hocini, MD, Michel Haïssaguerre, MD and Pierre Jaïs, MD, PhD. CHU Bordeaux - Université de Bordeaux - LIRYC/INSERM U1045, Pessac, FranceIntroduction: The long term functional outcome of the atria after successful ablation for persistent atrial fibrillation has not been thoroughly studied.Methods: We studied 27 patients (54±8 years, 3 women) referred for ablation for persistent AF using the stepwise approach and with no recurrence for over 3 years since last procedure. LA and RA scar burden were quantified using delayed-enhanced MRI. LA and RA volumes, ejection fraction (EF), and inter-appendage delay were quantified using cine imaging. Trans-mitral and trans-tricuspid flows were analyzed using velocity encoded imaging to quantify E/A ratios. Structural and functional MRI parameters were correlated to patients baseline characteristics and procedural records.Results: Uninterrupted AF duration was 12.0±8.6 months. Patients had undergone 2.3±0.8 procedures for a total RF duration of 97±29 min. Mean follow-up since last procedure was 63±24 months. At MRI, LA and RA scar extent were 29.3±7.5 and 4.8±3.8%, respectively. LA and RAEF were 23.9±6.3 and 45.3±7.7%, respectively. Mean delay between LAA and RAA activation was 81±47ms (range 39-217). LAA activation occurred after mitral valve closure in 2 patients, and complete LAA isolation was found in 3 patients. These 5 patients had higher LA scar extent (36.5±5.2 vs 26.9±6.3, P=0.002), and lower LAEF (16.2±3.7 vs 26.1±5.1, P<0.0001). Mean E/A ratios were 5.6±2.3 and 1.1±0.6 on trans-mitral and trans-tricuspid flows, respectively. A wave was absent in 8/27 patients on trans-mitral flow, and in none of the patients on trans-tricuspid flows. LA scar extent was higher when A wave was absent (37.6±3.6 vs 25.7±5.8, P<0.0001). LA scar extent was poorly correlated to RF duration and uninterrupted AF duration (R=0.35 and 0.35, respectively). LAEF correlated better to LA scar extent (R=-0.67), than to RF duration and uninterrupted AF duration (R=-0.23 and -0.21).Conclusion: Various degrees of LA dysfunction are observed 5 years after successful persistent AF ablation. Mechanical delay and isolation of the LAA should be recognized as it might have embolic consequences. LA impairment seems more closely related to LA scar burden than to AF duration or procedural RF delivery. Further studies are needed to identify factors contributing to scar extent.

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Figure 1 shows B-mode ICE images (A) and ARFI images (B) during linear RFA at the LA roof. The LA myocardial thickness is approximately 8 mm. The RFA catheter is visualized in the B-mode images (ACC = catheter-tissue contact site). The color bar represents microns of maximum ARFI-induced tissue displacement. Tissue displacements are greater before (no lesion (NL)) than after RFA, demonstrating RFA-induced increases in tissue stiffness. Panel 3B shows tissue changes consistent with contiguous and trans-mural RFA lesions.Conclusion: Intra-procedure ARFI imaging during LA RFA is feasible and can provide near real-time visualization of tissue changes coincident with RFA. This is the first demonstration of ARFI imaging of RFA treated myocardium in humans.

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CHANGES OF LEFT ATRIAL VOLUME AND TRANSPORT FUNCTION IN PATIENTS WITH SINUS RHYTHM AFTER SUCCESSFUL RADIOFREQUENCY CATHETER ABLATION FOR ATRIAL FIBRILLATION: 1-YEAR FOLLOW-UP COMPUTED TOMOGRAPHY STUDYHong Euy Lim, MD, PhD, Seung Yong Shin, MD, Hwan Seok Yong, MD, PhD, Seok Man Moon, BS, Sung Il Im, MD, Jin Oh Na, MD, PhD, Cheol Ung Choi, MD, PhD, Jong Il Choi, MD, PhD, Jin Won Kim, MD, PhD, Eung Ju Kim, MD, PhD, Seong Woo Han, MD, PhD, Sang Weon Park, MD, PhD, Chun Hwang, MD, PhD and Young-Hoon Kim, MD, PhD. Cardiovascular Center, Korea University Guro Hospital, Seoul, Republic of Korea, Cardiovascular Center, Chung-Ang University Hospital, Seoul, Republic of Korea, Department of Radiology, Korea University Guro Hospital, Seoul, Republic of Korea, Cardiovascular Center, Korea University Anam hospital, Seoul, Republic of Korea, Department of Cardiology, Hallym University Hangang Sacred Heart Hospital, Seoul, Republic of Korea, Division of Cardiology, Utah Valley Regional Medical Center, Provo, UTIntroduction: Although radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF) is an effective treatment option to maintain sinus rhythm (SR), structural changes after successful RFCA has not been fully elucidated. The aim of this study is to evaluate whether left atrial transport function is improved in patients with SR after successful AF ablation.Methods: 93 patients (paroxysmal AF=51) who had SR during 1 year after successful RFCA were consecutively enrolled. LA volume (LAV) and LA emptying fraction (LAEF) were assessed by multi-slice computed tomography at baseline and 1 year after RFCA. Improved LAEF was defined as the change of LAEF of >2.5% and worsened LAEF was defined as the change of LAEF of <-2.5%. Cardiac enzyme including Troponin-T was analyzed at one day after RFCA.Results: LAV (P<0.001) was significantly decreased in all subjects. 50 patients (53.8%) had worsened LAEF and 30

controversial. This study investigated the relationship between CFAE and left atrial (LA) thickness.Methods: We measured CFAE of LA in 31 patients (25 men, 56.8 ± 9.1 years) with paroxysmal (n = 12) and persistent (n = 19) AF before catheter ablation. The LA wall thickness measurements were obtained in a total of 31 preselected sites, including 3 roof, 9 anterior, 9 posterior, 3 floor, 1 anterior appendage base, 3 lateral, and 3 septal sites in each patient using multi-detector CT. The LA wall thickness was measured in the thickest muscular segments (fat was excluded based on difference in Hounsefield Units of fat as compared with muscle) within 5 mm of each reference point. In 15 patients including 13 PeAF, CFAE mapping was performed before and after PV isolation (PVI).Results: There was a large range of LA wall thickness (average 2.41 ± 0.41 mm, range 1.49-3.12 mm) between patients. In addition, there were significant regional differences in LA wall thickness. The anterior appendage base had the thickest wall (3.40 ± 1.20 mm) and the lateral wall was thinnest (1.45 ± 0.42 mm). Each patient had average 7.3 ± 3.5 CFAE sites among 31 sites. In a total of 961 sites, the mean LA wall thickness of 227 sites with CFAE was thicker than 734 sites without (3.04 ± 0.96 vs. 2.19 ± 0.91 mm, p<0.001). This finding was also observed in patients with both PAF (3.16 ± 1.04 vs. 2.09 ± 0.85 mm, p<0.001) and PeAF (2.97 ± 0.91 vs. 2.26 ± 0.95 mm, p<0.001). In 23 (74%) out of 31 patients, including 10 PAF and 13 PeAF patients, the LA wall thickness and CFAE area were well matched, showing CFAE at thicker LA regions. Among 227 CFAE sites, there was no difference in LA wall thickness between patients with PAF and those with PeAF. However, among 734 non-CFAE sites, LA wall was thicker in patients with PeAF than in those with PAF (2.26 ± 0.95 vs. 2.08 ± 0.85 mm, p=0.008). There was a tendency that CFAE sites without change after PVI had thicker LA wall than those with change (2.55 ± 0.78 vs. 2.28 ± 0.58 mm, p=0.069) in patients with PeAF.Conclusion: The LA wall thickness and CFAE area were well correlated suggesting that the mechanism of CFAE was related to LA wall thickness.

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ACOUSTIC RADIATION FORCE IMPULSE IMAGING REVEALS TISSUE CHANGES AFTER LEFT ATRIAL ABLATION IN HUMANSTristram D. Bahnson, MD, FHRS, Stephanie A. Eyerly, MS, Douglas M. Dumont, PhD, Gregg E. Trahey, PhD and Patrick D. Wolf, PhD. Duke Center for Atrial Fibrillation, Duke University Medical Center, and Division of Cardiovascular Medicine, Duke University, Durham, NC, Dept of Biomedical Engineering, Duke University, Durham, NC, Dept of Biomedical Engineering, Duke University and Dept of Radiology Duke University Medical Center, Durham, NCIntroduction: Acoustic radiation force impulse (ARFI) imaging can identify myocardial stiffness changes coincident with radiofrequency ablation (RFA). This feasibility study was undertaken to determine whether ARFI imaging can identify RFA treated myocardium in humans.Methods: Five adult patients undergoing RFA for drug refractory AFIB were imaged during left atrial (LA) ablation using a software modified S2000 ultrasound scanner (Siemens Healthcare) and standard 8 Fr AcuNav intracardiac echocardiography (ICE) catheter (Biosense Webster) positioned in the LA within 2.5 cm from the endocardial surface. Diastolic-gated ARFI images of RFA sites were acquired before and after RF energy delivery during normal sinus rhythm.Results: All image pairs acquired in this way showed increased tissue stiffness at the ablation catheter contact site after RFA.

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PROSPECTIVE EVALUATION OF SHANNON ENTROPY MAPPING AS AN ADJUNCTIVE ATRIAL FIBRILLATION ABLATION STRATEGY TO FACILITATE TARGETING OF AF ROTORSAnand N. Ganesan, MBBS, PhD, Pawel Kuklik, PhD, Anthony Brooks, PhD, Rajiv Mahajan, MD, Sachin Nayyar, MD, Rajeev Pathak, MBBS, Lauren Wilson, BSc, Kurt Roberts-Thomson, MBBS, PhD and Prashanthan Sanders, MBBS, PhD. University of Adelaide, Adelaide, AustraliaIntroduction: Rotors are postulated to be critical to the maintenance of atrial fibrillation (AF). In preclinical studies, we have demonstrated that the bipolar electrogram Shannon entropy (ShEn) distinguishes the pivot from periphery of AF rotors in computer simulation and animal models. We hypothesized targeted ablation of high Shannon entropy regions might therefore lead to AF termination and or AF cycle length slowing.Methods: In this prospective single centre open label pilot study, we undertook of targeted ablation of regions of high Shannon entropy in 8 patients with persistent AF(LA size 45±6mm, LVEF 52±5%). Patients were in spontaneous or induced AF lasting>10 minutes before mapping which was undertaken using a a 20-pole PentaRay catheter and the NavX system (616±285 points/pt). After map acquisition, points were exported to a PC in the control room where a ShEn map was constructed. The top 10% of regions of ShEn were identified, and annotated on the NavX map to guide ablation. Ablation or pre-identified ShEn regions was performed after wide antral circumferential ablation (WACA) with an endpoint of pulmonary vein isolation. No additional CFAE or linear ablation was performed. Pre-specified endpoints were: (i) AF cycle length change (≥5ms); and (ii) AF termination.Results: AF termination occurred in 6/8 cases, with 2/8 cases requiring cardioversion to sinus rhythm. 3/8 cases terminated during WACA, with 2/3 of these cases coinciding with pre-specified high ShEn. 3/8 cases terminated during ablation in pre-specified high ShEn regions. Mean AF cycle length change post PV isolation was 12.3±15ms (p=0.07), and AF cycle slowing post-ShEn ablation was 32.7±26ms (p=0.02). Sites of ShEn region termination included the anterior base of LA appendage (1), anterior to the right PVs (1), roof (1), posterior wall (1), and left superior PV ridge (1). 7/8 cases remained in sinus rhythm at median follow-up 186 days (IQR 212 days).Conclusion: Directed ablation of high ShEn regions, as a marker of the pivot zone of AF rotors, may be associated with termination of AF and/or AF cycle length slowing in selected AF patients, and requires further investigation as an adjunctive strategy in AF ablation.

(32.3%) had improved LAEF. Subjects were divided into 2 groups (worsened=50 vs. preserved=43). Compared with preserved group, there were more paroxysmal AF, smaller LAV, and greater LAEF in worsened group. The change of LAEF was significantly correlated with ablation time (R=0.303, P=0.032) and troponin-T level (R=0.575, P < 0.001) in worsened group.Conclusion: LAEF was decreased in more than half of patients with SR after successful RFCA, although LAV was significantly diminished. Worsening of LAEF was associated with the amount of myocardial damage. Minimized ablation strategy might be helpful to prevent functional deterioration, especially in patient who had lesser structural remodeling.

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ANATOMIC CHARACTERIZATION OF CAVOTRICUSPID ISTHMUS (CTI) BY THREE-DIMENSIONAL TRANSESOPHAGEAL ECHOCARDIOGRAPHY (3D-TEE) IN PATIENTS WITH DIFFICULT CTI ABLATIONFrançois D. Regoli, MD, PhD, Francesco F. Faletra, MD, Marta Acena, MD, Maria Cristina Dequarti, MD, Agne Drasutiene, MD, Evelina Faragasso, MD, Elena Pasotti, MD, Tiziano Moccetti, MD and Angelo Auricchio, MD, PhD. Fondazione Cardiocentro Ticino, Lugano, SwitzerlandIntroduction: CTI-dependent atrial flutter is common. Although catheter ablation is the treatment of choice, procedural data vary greatly between patients. This study aimed to characterize CTI anatomy by 3DTEE to identify anatomic determinants of difficult ablation.Methods: Thirty consecutive patients (mean age 66.8±11.1 years, 21 males) underwent CTI-ablation procedure. Before ablation, TEE was performed and 3DTEE images were acquired to evaluate CTI anatomy (Figure, panel A). CTI ablation was performed according to standard procedure (8 mm ablation catheter, settings: 65°C, 80 Watts). EP operators were blinded to 3DTEE data. RF time >11 minutes to achieve bidirectional CTI block defined difficult ablations (Group 1, n=14); otherwise, ablation was straightforward (Group 2, n=16).Results: Bidirectional block was achieved in all patients. No procedural complications occurred. Mean ablation time for group 1 was 14.0±8.9 minutes compared to 6.3±1.4 minutes for group 2 (p=0.010). Isthmus length (I), presence of Eustachian valve (EV) and ridge (ER) as well as presence of abundant pectinate muscle did not differ significantly between groups (Figure, panel B). In group 1, 11/14 patients presented a pouch compared to 5/16 patients in group 2 (p=0.014); antero-posterior end-diastolic length (25.1±5.8 mm vs. 19.0±6.7 mm, p=0.029) and depth (12.8±4.4mm vs 7.0±1.4mm, p<0.001) of the pouch were significantly greater in group 1. Most patients in group 1 (11/14) were found to present >1 septal anatomic feature compared to group 2 (2/16, p<0.001).Conclusion: Pre-procedural 3DTEE identified presence of a large pouch combined with prominent EV and/or ER as main anatomic determinants of difficult CTI ablation.

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years; males=23 (92%); ejection fraction=54±12%; LA diameter=46±4mm) who underwent radiofrequency (RF) ablation of multi-loop AT. Multi-loop AT was defined as a tachycardia that required ablation of >1 distinct isthmus/site prior to termination to sinus rhythm. If there was no change in the tachycardia cycle length (TCL) or p-wave, or atrial activation after ablation of the first isthmus, entrainment mapping was performed to determine whether another isthmus was involved. These patients were compared to those in a control group with AT from a single isthmus/site.Results: The CL of the multi-loop and single loop AT was 235±52 ms and 260±90 ms, respectively (p=0.08). A total of 113 critical isthmi/sites were involved (4±1.7 per patient) in patients with multi-loop AT. The most common sites included the LA roof (68%), mitral isthmus (64%), and the LA appendage (36%). There was no change in the CL, p wave, or activation in 13 patients (52%) with multi-loop AT after ablation at the first isthmus. Despite a lack of change in these parameters, entrainment mapping showed that the initial isthmus was no longer engaged (PPI-TCL>30 ms whereas before RF, PPI≈TCL). RF ablation terminated the AT to sinus rhythm in 92% and 93% of the cases of multi-loop and single loop AT. After a mean follow up of 32±18 months after the last procedure, 16 patients (64%) with multi-loop AT remain arrhythmia-free without anti-arrhythmic medications as compared with 22 patients (88%) with single-loop AT (p=0.04).Conclusion: Multi-loop ATs following AF ablation are complex arrhythmias often involving up to 4 distinct isthmi/sites. In half of the cases, there is a seamless transition from one isthmus to another, despite a lack of change in the CL, p-wave, or activation. Entrainment mapping is critical in determining whether the culprit isthmus has been eliminated. Long-term outcomes are inferior in patients with multi- as compared to single-loop AT.

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SAFETY AND EFFICACY OF CONTINUOUS PERIPROCEDURAL RIVAROXABAN FOR PATIENTS UNDERGOING CATHETER ABLATION PROCEDURES: A RETROSPECTIVE REGISTRY ANALYSISRoger Dillier, MD, Sonia Ammar, MD, Tilko Reents, MD, Heribert Pavaci, MD, Alessandra Buiatti, MD, Patric Schoen, MD, Susanne Kathan, MASc, Monika Hofmann, MD, Verena Semmler, MD, Carsten Lennerz, MD, Christoph Kolb, MD, Gabriele Hessling, MD and Isabel Deisenhofer, MD. Deutsches Herzzentrum München, Munich, GermanyIntroduction: Catheter ablation procedures (CAP) require optimal periprocedural anticoagulation for minimizing bleeding and thromboembolic complications. Rivaroxaban, a factor Xa inhibitor, was recently approved for prevention of stroke or systemic embolism in patients with nonvalvular atrial fibrillation (AF). However, the safety and efficacy of rivaroxaban as a periprocedural anticoagulant for CAP are unknown. The purpose of this study was to evaluate the safety and efficacy of periprocedural rivaroxaban during CAP.Methods: We performed a retrospective analysis from our data base including all CAP between February 2012 and November 2012. A total of 170 patients (mean age 62 years, 29 % female) taking periprocedurally rivaroxaban were included in the study. 149 (88 %) were left and 21 (12 %) were right atrial procedures. Rivaroxaban 20 mg per day was taken 2 to 12 hours before the procedure. During left atrial procedures, heparin was given to maintain an activated clotting time at 270-300 seconds. Any bleeding requiring blood transfusion, hematomas requiring surgical intervention, and pericardial effusions requiring drainage (tamponade) were considered as major bleeding complications.

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EFFECT OF ELECTROGRAM RECORDING CONDITIONS ON SHANNON ENTROPY LOCALIZATION OF THE PIVOT ZONE OF ATRIAL FIBRILLATION ROTORSAnand N. Ganesan, MBBS, PhD, Pawel Kuklik, PhD, Anthony G. Brooks, PhD, Mathias Baumert, PhD, Wei-Wen Lim, BSc, Shivshankar Thanigaimani, BSc, Sachin Nayyar, MD, Rajiv Mahajan, MD, Kurt Roberts-Thomson, MBBS, PhD and Prashanthan Sanders, MBBS, PhD. University of Adelaide, Adelaide, AustraliaIntroduction: The pivot is critical to the rotors postulated to maintain AF. Recently, we have shown that high Shannon entropy (ShEn), a statistical measure of information uncertainty, localizes to the pivot of rotors recorded with bipolar electrograms, in computer simulation and animal experimental models. In addition, targeted ablation of high ShEn EGMs is associated with slowing and or termination in human AF.The aim of this study was to evaluate the ability of ShEn to colocalize the pivot zone of under simulated AF rotors conditions.Methods: Bipolar EGM recordings were studied in the Courtemanche human atrial myocyte models. Rotors were simulated in 2-dimensional. sheets. Each model mesh contained 100x100 elements with 0.5 mm spatial distance (resulting in 5cm x 5cm sample size). Mesh elements were diffusively coupled (no-flux boundary conditions). Unipolar EGMs were calculated, at each mesh element, which were used to construct bipolar EGMs. The pivoting trajectory of the spiral wave tip was phase integration. ShEn was calculated as an index of amplitude distribution for each bipole for each rotor. We simulated the effects of: (i) bipolar EGM inter-electrode distance, (ii) EGM filtering, with simulated high-pass Butterworth filters with cutoffs at 0.5,10,and 30Hz, and (iii) ShEn box size.Results: In each of the model systems, the highest region of ShEn colocalized with the pivoting region identified by the spiral wave tip trajectory. ShEn was inversely correlated with distance from the visual pivoting centre in each model system. ShEn was inversely correlated with distance from the pivot zone (Pearson’s r=-0.61, p<0.001). The region of maximum ShEn remained colocalized with the pivot zone over simulated inter-electrode spacing from 0.5mm-8mm. Max ShEn colocalized with the pivot zone in ShEn box size from 0.01mV-1mV. Max ShEn remained colocalized with the pivot over a range of bipolar EGM cut-off frequencies.Conclusion: These data confirm ShEn as a mechanistically-based potential tool to map locally stable rotors with bipolar electrogram data. ShEn mapping is currently under investigation as an adjunctive ablation strategy in clinical AF ablation.

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MULTI-LOOP ATRIAL TACHYCARDIA AFTER CATHETER ABLATION OF ATRIAL FIBRILLATION.Aman Chugh, MD, Diego Belardi, MD, Rakesh Latchamsetty, MD, Hamid Ghanbari, MD, Wouter Saint-Phard, MD, Thomas Carrigan, MD, Arisara Suwanagool, MD, Mohamad Sinno, MD, Robert Kennedy, MD, Siddarth Mukherji, MD, Mark Bowers, MD, Thomas Crawford, MD, Krit Jongnarangsin, MD, Eric Good, MD, Frank Bogun, MD, Frank Pelosi, MD, Hakan Oral, MD and Fred Morady, MD. University of Michigan, Ann Arbor, MIIntroduction: Although atrial tachycardias (AT) after left atrial (LA) ablation of atrial fibrillation (AF) have been reasonably well described, little is known about multi-loop tachycardias that require ablation of multiple isthmi/sites prior to restoration of sinus rhythm.Methods: Twenty-five consecutive patients (Age=61±7

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of 70% and specificity of 75%. A CFAE area also provided arrhythmogenic milieu of AT occurring after AF ablation.

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CLINICAL CHARACTERISTICS AND LONG-TERM FOLLOW-UP AFTER ABLATION OF RIGHT ATRIAL MACRO-REENTRANT TACHYARRHYTHMIAS FOLLOWING SURGICAL REPAIR OF CONGENITAL AND ACQUIRED HEART DISEASEIgnasi Anguera, MD, Paolo Dallaglio, MD, Miguel Alvarez, MD, Javier Jimenez-Candil, MD, Mari Fe Arcocha, MD, Rafael Peinado, MD, Javier García Seara, MD, Benito Herreros, MD, Aurelio Quesada, MD, Antonio Hernandez-Madrid, MD and Xavier Sabate, MD. Hospital de Bellvitge, Barcelona, Spain, Hospital Virgen de las nieves, Granada, Spain, Hospital Universitario de Salamanca, Salamanca, Spain, Hospital de Basurto, Bilbao, Spain, Hospital Universitario La Paz, Madrid, Spain, Hospital Clinico Universitario de Santiago de Compostela, Santiago de Compostela, Spain, Hospital Universitario Río Hortega, Valladolid, Spain, Hospital General Universitario de Valencia, Valencia, Spain, Hospital Universitario Ramón y Cajal, Madrid, SpainIntroduction: The surgical repair of congenital (CHD) and acquired (AHD) heart disease (both ischemic and valvular heart disease) involves the creation of lines of block that generate a complex pathophysiological substrate, promoting atrial reentry. Radiofrequency catheter ablation (ABL) can treat these atrial tachyarrhythmias. The aim of our study was to describe the long-term follow-up of patients with previous cardiac surgery undergoing right atrial macro-reentrant tachyarrhythmia ablation.Methods: Multicenter study. Clinical characteristics, long-term follow-up and predictors of atrial fibrillation (AFib) development were analyzed.Results: A total of 372 patients were included (69% men), 111 of them had undergone surgical repair of CHD (42% ostium secundum atrial septal defect), while 261 were postoperative of AHD (isolated CABG in 38%, isolated valve disease in 51% and mixed procedures in 11%). Mean age was 61 years (IQ range 52-73y). Cavo-tricuspid isthmus-dependent atrial flutter (CTI-AFL) was observed in 300 patients: 239 (92%) patients with AHD and 61 (55%) patients with CHD; and intra-atrial re-entrant tachycardia (IART) in 72 patients. Ablation was successful in 349 cases (94%) (95% of CTI-AFL and 89% of IART). After a median follow-up was 51 months (IQ 18-72), 119 (32%) patients developed AFib. AFib rates were higher in AHD than CHD patients (35% vs 24%, p=0.04). Hospital admission for heart failure was required in 67 (18%) patients. A total of 55 (15%) patients required pacemaker implantation. At the end of follow-up, 255 (69%) patients were in sinus rhythm and 81 (22%) in AFib. Overall mortality was 14.5%. Multivariate analysis showed that female gender (OR 2.3, 95% IC 1.4-3.8), surgery for AHD (OR 95% 2.7, 95% IC 1.4-4.9), left (OR 1.8, 95% IC 1.1-3.1) and right (OR 1.7, 95% IC 1.05-3.1) atrial dilation were independent predictors of long term AFib presentation.Conclusion: Radiofrequency ablation of right atrial macro-reentrant tachyarrhythmias after surgical correction of acquired and congenital heart disease is associated with high rates of acute efficacy. Atrial fibrillation and heart failure were common events during follow-up, especially in patients operated for acquired heart disease and with dilated atrial chambers.

Minor bleeding complications included small hematomas and pericardial effusions not requiring an intervention (non-tamponade). The primary endpoint was safety of the procedure including major bleedings and thromboembolic events whereas the secondary endpoint was minor bleedings.Results: CAP included treatment of paroxysmal AF (n = 76, 45 %), persistent AF (n = 40, 23 %), atrial tachycardia (n = 33, 19 %) and typical atrial flutter (n = 21, 12 %). The mean procedure time was 147 ± 64 min and the mean total heparine dosage per body weight was 116 ± 48 IU/kg. In addition, 23 patients (14 %) were taking aspirin, 2 patients (1 %) clopidogrel and another 2 patients (1 %) were on dual antiplatelet therapy with aspirin and clopidogrel. No major bleedings or thromboembolic events occurred. Minor bleedings in terms of groin hematoma (> 5 cm) were found in 12 (7 %) patients.Conclusion: In this large study, CAP under continuous periprocedural rivaroxaban (20 mg per day) seems to be safe and effective.

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RELATIONSHIP OF COMPLEX FRACTIONATED ATRIAL ELECTROGRAMS DURING ATRIAL FIBRILLATION WITH CRITICAL SITES OF ATRIAL TACHYCARDIA DEVELOPED AFTER CATHETER ABLATION OF ATRIAL FIBRILLATIONJi-Eun Ban, MD, PhD, Dae-In Lee, MD, Yung-Lung Chen, MD, Yae-Min Park, MD, Hwan-Cheol Park, MD, Jong-Il Choi, MD, PhD, Hong-Euy Lim, MD, PhD, Sang-Weon Park, MD, PhD and Young-Hoon Kim, MD, PhD. Korea university medical center, Seoul, Republic of KoreaIntroduction: Complex fractionated atrial electrogram (CFAE) is one of targets of substrate modification in patients with atrial fibrillation (AF). However, it remains to be determined whether CFAE also provides arrhythmogenic grounds of atrial tachycardia (AT) developed after AF ablation. The aim of this study was to evaluate the relationship of CFAEs and critical site of AT occurred after CFAE guided ablation.Methods: Seventy two patients showing AT after pulmonary vein isolation and further ablation (58±12 years, male/female 59/13, paroxysmal AF/non-paroxysmal AF 5/67, mean left atrial size 43.2±6.1mm) guided by automated 3-D CFAE (NavX) map were included. Ninety five ATs out of 72 patients were analyzed. The termination site of AT and the highest density of CFAE clustering areas were annotated on color-coded CFAE cycle maps. Range of CL of border zone of CFAE area was 120- 200ms, which was color coded from red to green.Results: Among a total of 95 ATs (52 converted ATs and 43 induced ATs) occurring after ablation of AF, 61 ATs (64.2%) were found to have a termination site at the border zone of CFAE (n=55) and highly densed CFAE area (n=6). The main mechanism responsible for AT was macroreentry. The CL of AT, which was terminated during ablation at CFAE area, was significantly shorter than those which terminated at irrelevant to CFAE area (259±45ms vs. 299±75ms, P=0.01). The cut-off CL of AT terminated at CFAE area was 270ms, with sensitivity/specificity of 70%/75%. In 41 (67.2%) of 61 ATs, anterior wall near the LA appendage (LAA), septum and roof areas were the major critical sites of AT among CFAE area, while peri-mitral isthmus was the most common termination site of AT irrelevant to CFAE area (12/34 ATs, 35.3%).Conclusion: The CFAEs and their junction with non-CFAE areas, especially at the anterior wall near the LAA, septum and roof, were frequently associated with successful termination of ATs developed after CFAE guided ablation of AF. Mean CL of AT, of which critical sites are located at the CFAEs, was significantly shorter than those terminated at irrelevant to CFAE area. The cut-off value of mean CL of AT was 270ms with sensitivity

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uptake prior to and after cardioversion. This study prospectively evaluated the change in oxygen kinetics and cardiopulmonary performance parameters after catheter ablation for asymptomatic long-standing persistent AF patients.Methods: Sixteen consecutive consenting patients with long-standing persistent AF (age 69±8 years, BMI 32±6, 88% male) undergoing catheter ablation were enrolled in this pilot prospective study. Cardiopulmonary exercise tests were performed using a modified version of Balke’s incremental treadmill protocol at baseline and after 12 weeks of blanking period post-procedure. Maximal oxygen consumption (VO2max), metabolic equivalent of oxygen uptake (MET), maximum heart rate (HRmax), exercise grade, exhaled minute ventilation at body temperature and pressure saturated (VEBTPS) were recorded at pre-ablation (baseline) and follow-up visits. Exercise data for three patients experiencing recurrence after the blanking period were not included in this analysis.Results: The post-ablation assessment showed substantial improvement in exercise capacity as evident in most of the indices. Peak VO2max improved 19% (1.95±0.54 (median 1/91) to 2.42±1.5 (median 2.1) L/min, p=.024). The corresponding METs increased from 5.4±1.2 to 7.0±4.5 METs (p=0.034). The highest treadmill grade attained by the patients increased from 7.7±3 (median 8) to 9.2±2.6 (median 9.5) minutes (p=.021). Although the average increase of 15.2 L/min in VEBTPS (66.9±12 (median 62.5) to 82.1±48 (median 70.1) L/min, p=.17) did not reach statistical significance, it signaled a positive trend. There was no significant change in BMI, and HRmax.Conclusion: The results from the present study indicate that maximal aerobic capacity and exercise tolerance improve substantially in asymptomatic patients with long-standing persistent AF following successful catheter ablation.

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MANIFESTATIONS OF CORONARY ARTERIAL INJURY DURING CATHETER ABLATION OF ATRIAL FIBRILLATION AND RELATED ARRHYTHMIASAman Chugh, MD, Akash Makkar, MD, Baskaran Sundaram, MD, Miki Yokokawa, MD, Hamid Ghanbari, MD, Thomas Carrigan, MD, Wouter Saint-Phard, MD, Frank Pelosi, MD, Hakan Oral, MD and Fred Morady, MD. University of Michigan, Ann Arbor, MIIntroduction: Case reports have described arterial injury in patients undergoing catheter ablation of atrial fibrillation (AF). The prevalence and culprit sites in a series of patients have not been described in detail.Methods: Among 5,709 patients undergoing catheter ablation of AF and post-AF atrial tachycardia (AT), 8 patients (0.14%) developed arterial injury as a result of radiofrequency (RF) ablation. There were 5 men, 7 with persistent AF, 4 with structural heart disease, with a mean age of 60±6 yrs, ejection fraction of 56±19%, and left atrial (LA) diameter of 50±6 mm.Results: In 5 patients, the clinical manifestation of arterial injury was apparent within 2-30 minutes of RF energy delivery, and in the other 3, it was 6 hours, 18 hours, and 2 months. Three patients developed ventricular fibrillation requiring immediate defibrillation. All 3 underwent angiography, which showed occlusion of the proximal (n=2) or distal circumflex (Cx) artery (n=1). Two of the 3 patients had undergone RF ablation in the distal coronary sinus (CS) for perimitral flutter (20 W) and the other at the base of the LA appendage (35 W). Two of the 3 underwent coronary stenting. In the other patient, the distal Cx was too small for intervention. The 5 remaining patients developed acute sinus node (SN) dysfunction. In 4/5 patients, the culprit site was immediately subjacent to the SN artery (as seen retrospectively on computed tomography) coursing over the high

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IMPACT OF CATHETER-TISSUE CONTACT FORCE ON PULMONARY VEINS ISOLATION ACUTE PROCEDURAL PARAMETERSGiuseppe Stabile, MD, Francesco Solimene, MD, Leonardo Calò, MD, Matteo Anselmino, MD, PhD, Antonio Castro, MD, Caludio Pratola, MD, Roberto De Ponti, MD, FHRS, Alberto Bandini, MD, Nicola Bottoni, MD, Antonio De Simone, MD, Giuseppe Grandinetti, MD and Emanuele Bertaglia, MD. Clinica Mediterranea, Napoli, Italy, Clinica Montevergine, Avellino, Italy, Policlinico Casilino, Rome, Italy, Az. Ospedaliero Universitaria S.Giovanni Battista di Torino, Torino, Italy, Ospedale Sandro Pertini, Rome, Italy, Arcispedale S.Anna, Ferrara, Italy, Ospedale di Circolo e Fondazione Macchi, Università Insubria, Varese, Italy, Az. Unità Sanitaria Locale di Forlì, Forlì, Italy, Az. Ospedaliera di Reggio Emilia, Reggio Emilia, Italy, Clinica S.Michele, Caserta, Italy, Az. Ospedaliera Universitaria Policlinico di Bari, Bari, Italy, Az. Ospedaliera di Padova, Padova, ItalyIntroduction: Catheter-tissue contact is critical for effective lesion creation in radiofrequency catheter ablation (RFCA). We assessed, in a multicenter prospective study, the impact of direct catheter force measurement on acute procedural parameters during RFCA of atrial fibrillation (AF).Methods: One hundred-four consecutive patients with paroxysmal AF underwent their first RFCA procedure. A new open-irrigated tip catheter with contact force measurement capabilities (SmartTouchTM, Biosense Webster Inc. CA) was used. All patients underwent antral pulmonary vein (PV) isolation, aiming at entry and exit block in all PVs. Comprehensive contact force data were available for 94/104 patients (mean age 58±11 years, male 84%, heart disease 60%, mean left atrium diameter 41±5 mm) in which four PVs were identified and effectively isolated.Results: Mean overall procedure time was 138±69 min with a mean fluoroscopy time of 14.5±11.1 min. Mean ablation time (radiofrequency time needed for PV isolation) was 34.4±22.5 min, and mean contact force (mean contact force during all the radiofrequency application) was 12.1±4 g. Patients in which the mean contact force was maintained > 20 g required shorter procedural time (92±23 min vs 160±67 min, p=0.02), fluoroscopy time (9.2±5.1 min vs 15.3±10 min, p=0.15) and ablation time (25±10.1 min vs 37.7±30.6 min, p=0.32) as compared with patients in which the mean contact force was < 10 g. Only 4 groin haematoma were observed. No stroke/TIA, pericardial effusion, or tamponade were observed in both groups.Conclusion: Contact force during RFCA for PV isolation impacts procedural parameters significantly reducing the procedure time, without increasing acute periprocedural complications.

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IMPACT OF CATHETER ABLATION ON EXERCISE CAPACITY IN ASYMPTOMATIC PATIENTS WITH LONG-STANDING PERSISTENT ATRIAL FIBRILLATIONSanghamitra Mohanty, MD, Prasant Mohanty, MBBS, Luigi Di Biase, MD, PHD, FHRS, Mohammed Alkatan, BS, Chintan Trivedi, MD, MPH, Rong Bai, MD, FHRS, David Burkhardt, MD, Joseph G. Gallinghouse, MD, Rodney Horton, MD, Javier E. Sanchez, MD, Shane Bailey, MD, Jason Zagrodzky, MD, Hirofumi Tanaka, PhD and Andrea Natale, MD, FHRS. St. David’s Medical Center, Austin, TX, University of Texas at Austin, Austin, TXIntroduction: Earlier researches have demonstrated adverse effects of AF on exercise capacity by comparing peak oxygen

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Recently, left atrial appendage closure (LAAC) was shown to be non-inferior to VKA. We therefore combined LAA occlusion with AF ablation in a single procedure to determine feasibility and stroke incidence during 1 yr follow-up.Methods: 45 Pts with drug refractory AF were included if their CHADS2 score exceeded 1 and/or they had a contraindication for VKA, and pre-procedure TEE excluded LAA thrombus. Procedures were performed under general anesthesia, in a drug-free state, under TEE guidance. The Phased RF multi-catheter ablation system was used for ablation, followed by Watchman LAAC. Pts stayed on OAC post-ablation until TEE at 60 days showed effective LAAC, then switched to ASA 1dd100 mg/daily. Outpatient clinic visits occurred at 3,6 and 12 mo. Rhythm follow-up was performed with ECG and 48h-Holter.Results: Between Feb 2010-Apr 2012, 45 pts were included (30 male), average age of 63 yrs (range 48-79 yrs). Median CHADS2 score was 3, 75% had a prior ischemic stroke, while 26% had a contraindication VKA due to bleeding or failure to achieve adequate INR. PAF/PersistentAF was present in 34 pts (75%), while 13 had longstanding persistent AF. PAF pts were treated with PVAC PVI, while in the others additional LA CFAE ablation was performed with the MASC and MAAC catheter. After ablation, LAAC was performed under TEE guidance. The Watchman was successfully implanted with complete acute occlusion in all pts, with a median number of 1 device (1-3). Average total procedure time was 90 min, of which 42 min were needed for LAAC. At 60 days, all pts met the criteria for successful sealing. Within the first year of follow-up, 30% of pts had documented AF recurrence of AF. In 6 pts a redo PVI was performed successfully, without any interference of the LAAC. No thromboembolic events occurred during 1 yr follow-up with an anticipated pre-procedure stroke rate of 8% in this population.Conclusion: Watchman LAAC occlusion can successfully and safely be combined in a single procedure, and does not preclude a redo PVI. In this high risk population, no strokes occurred during 1 yr follow-up.

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GREATER MYOCARDIAL BIOMARKER RELEASE USING THE NOVEL 28MM CRYOBALLOON - A LINK TO INCREASED PROCEDURAL EFFICACY?Stefano Bordignon, MD, Boris Schmidt, MD, FHRS, Anne Klemt, Melanie Gunawardene, Britta Schulte-Hahn, MD, Marie-Christine Boehmer, MD, Verena Urban, MD, Bernd Nowak, MD, Alexander Fuernkranz, MD and Kyong Ryul Julian. Chun, MD. CCB - Cardioangiologisches Centrum Bethanien, Frankfurt a.M., GermanyIntroduction: Recently, a novel second generation (G2) cryoballoon (CB) was introduced. Preliminary reports suggested improved procedural efficacy as compared to the first generation (G1) CB. Comparative analysis of myocardial biomarker release (G1 vs. G2) has not been studied.Objective: To compare myocardial biomarker release using the 28mm G1 Vs G2 CB.Methods: In patients (pts) treated with the single big cryoballoon (SBCB) strategy for pulmonary vein isolation (PVI), myocardial biomarkers (TnT, CK, LDH) were measured at 12, 24 and 48 hours after PVI. Two groups were defined: group 1 (G1; freezing-time: 300s), group 2 (G2; freezing-time: 240s). Mean biomarker peak values were compared. An index calculated as peak biomarker release divided by the total freezing time was calculated.Results: 66 consecutive CB PVI procedures (G1: 33 pts, G2: 33 pts) were analyzed. PVI was achieved in all pts using SBCB only. Mean freezing time (51 ± 10 min vs. 33 ± 6 min, p<0,01) was significantly shorter in G2. Ice cap formation was noticed in G1 and

anterior LA (n=3) or the septal base of the RA appendage (n=1). In 2/5 patients with acute SN dysfunction, 35-45 W were required for AT termination at the high anterior LA and in 3/5 patients, sinus tachycardia was seen during RF energy delivery at this site. Two of the 5 patients required a permanent pacemaker. In 1, SN dysfunction resolved after 48 hours.Conclusion: Clinically apparent injury to the coronary arteries during LA ablation for AF and related arrhythmias is rare. However, it may be associated with potentially life-threatening ventricular arrhythmias and acute SN dysfunction requiring permanent pacing. The culprit sites seem to be in the distal CS and the anterior LA. Vigilance and utilizing low power settings are important in minimizing the risk of arterial injury. Sinus tachycardia during RF ablation at the anterior LA maybe a harbinger of injury to the SN artery.

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IMPROVED PROCEDURAL EFFICACY OF PULMONARY VEIN ISOLATION USING THE NOVEL SECOND-GENERATION CRYOBALLOONKyong Ryul Chun, MD, Alexander Fürnkranz, MD, Stefano Bordignon, MD, Britta Schulte-Hahn, MD, Bernd Nowak, MD and Boris Schmidt, MD. Markus Krankenhaus, Frankfurt am Main, GermanyIntroduction: The cryoballoon technology has the potential to isolate a pulmonary vein (PV) with a single energy application. However, using the first-generation cryoballoon (CB-1G) repeated freezing or additional focal ablation is often necessary. The novel second-generation cryoballoon (CB-2G) features a widened zone of optimal cooling comprising the whole frontal hemisphere. The aim of this study was to investigate the impact of the novel design on procedural efficacy of cryoballoon PV isolation (CB-PVI).Methods: N/AResults: Single transseptal CB-PVI using an endoluminal spiral mapping catheter was performed in 60 consecutive patients (CB-1G, 28 mm, 300 sec. application time: 30 patients; CB-2G, 28 mm, 240 sec. application time: 30 patients). When compared to the CB-1G, using the CB-2G increased single-shot PVI rate from 51% to 84% (p<0,001); and decreased procedure duration (128±27 vs 98±30 min., p<0,001) and fluoroscopy exposure time (19,5±7,4 vs 13,4±5,3 min., p=0,001); Effective CB-2G PVI could be performed with increased real-time PVI visualization rate (49% vs. 76%, p < 0,001). Time to PVI (TPVI) was shorter in the CB-2G group (79±60 vs. 52±36 sec., p=0,049). Procedure-related complications occurred in 2 patients in the CB-1G group and 1 patient in the CB-2G group.Conclusion: The CB-2G significantly improved procedural efficacy compared to the CB-1G and provided reliable TPVI measurements. TPVI may be used to adjust application time and number individually in future studies.

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STROKE REDUCTION BY COMBINING CATHETER ABLATION AND LEFT ATRIAL APPENDAGE CLOSURE IN HIGH RISK PATIENTSMartin Swaans, MD, Selcuk Karadavut, MD, Arash Alipour, MD, PhD, Martijn Post, MD, PhD, Benno Rensing, MD, PhD and Lucas Boersma, MD, PhD. St.Antonius Hospital, Nieuwegein, NetherlandsIntroduction: Although symptomatic AF is increasingly being treated with catheter ablation disappointing long term freedom of AF has been reported. Moreover, pts at high risk of stroke may remain at risk unless Vit.K antagonists (VKA) are continued.

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AF differed significantly: At dense DE areas and their borders, 74% of wavelets showed slow conduction (0.1-0.5m/s) with evidence of pivot and channel conduction. At dense DE, we found functional collisions at 21% of mapped beats. Regions without dense DE correlate to continuous CFAE sites and show higher conduction velocity (0.62-0.85m/s, p<0.01) with evidence of functional wave collision at 41% of mapped AF waves/beats (p<0,05). Less than 20% of dense DE areas display continuous CFAE. Mean EGM voltage is lower at dense DE vs other sites (0.63+/-0.5mV vs. 0.85+/-0.7mV, p<0.001).Conclusion: A minority of DE regions display continuous CFAE. Slow conduction, channel and pivoting occur with high frequency at LA sites with DE. These sites may represent the arrhythmogenic atrial substrate in patients with persistent AF.

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WHICH IS THE BEST CATHETER TO PERFORM ABLATION OF ATRIAL FIBRILLATION? A COMPARISON BETWEEN STANDARD THERMOCOOL, SMARTTOUCH AND SURROUND FLOW CATHETERLuigi Sciarra, MD, Paolo Golia, MD, Ermenegildo De Ruvo, MD, Serena Dottori, PhD, Andrea Natalizia, PhD, Lucia De Luca, MD, Antonio Scarà, MD, Alessio Borrelli, MD, Marco Rebecchi, MD, Fabrizio Guarracini, MD, Alberto Bandini, MD, Ernesto Lioy, MD and Leonardo Calò, MD. Cardiology - Policlinico Casilino, Roma, Italy, Cardiology - Morgagni Hospital, Forlì, Italy, Biosense Webster, Italy, Milan, ItalyIntroduction: Radiofrequency catheter ablation (RFCA) is an established therapy for atrial fibrillation (AF). However, the rate of complication is still significant and procedural and fluoroscopic times may be considerable. Two aspects seem to be crucial to improve the efficacy/risk ratio: the contact force of the ablation catheter over the atrial wall and the efficiency in RF delivery to the tissue. The SmartTouchTM catheter (STc) provides information about catheter tip to tissue contact force. The Surround Flow catheter (SFc) provides a more uniform cooling of the tip. Aim of our study: to analyze the impact of ST and SF catheters on RFCA of paroxysmal AF.Methods: 63 patients (pts) (mean age 57.6±9.8 years, 53 males) underwent to encircling/de-connection of pulmonary veins (PVs) (Carto3-Lasso technique) for paroxysmal AF. Pts were randomized to ablation with standard Navistar Thermocool catheter (TCc) (Biosense Webster Inc) or with STc, or with

G2 in 0/33 pts Vs 13/33 pts (p<0,001). All biomarker levels tend to be higher in G2 vs G1. The indexed biomarkers values were significantly higher in G2: -TnT: 18,8±8,5 pg/l/min Vs 32,3±13,6 pg/l/min (p<0,01); -CPK: 6,7±2,7 U/l/min vs 11,7±3,9 U/l/min (p<0,01); -LDH: 5,2±1,0 U/l/min vs 9,1±2,7 U/l/min (p<0,01). A linear regression analysis revealed a significant time/biomarker profile diffenrence between G1 G2 (p<0,001). During 90 days follow up, G2 showed a lower AF recurrence (10/33 Vs 5/33).Conclusion: Despite a shorter freezing time the second generation cryoballoon is associated with an increased myocardial biomarker release suggesting an enhanced efficacy in lesion formation.

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IMPACT OF ATRIAL FIBROSIS ON WAVE PROPAGATION IN HUMAN ATRIAL FIBRILLATION - EVIDENCE FOR REGIONAL CHANNEL, PIVOT AND SLOW CONDUCTION AT DELAYED ENHANCED SITESAmir Jadidi, MD, Steve Kim, Eng., Hubert Cochet, MD, Shinsuki Miyazaki, MD, Heiko Lehrmann, MD, Chan-il Park, MD, Michel Haissaguerre, MD, Thomas Arentz, MD and Pierre Jais, MD. Universitaets-Herzzentrum Freiburg Bad Krozingen, Rhythmologie, Bad Krozingen, Germany, SJM, St Paul, MN, Hopital Cardiologique du Haut-Leveque, Pessac-Bordeaux, FranceIntroduction: We assessed the impact of atrial fibrosis (delayed enhancement MRI (DE)) on AF wave propagation in pts with persistent AF.Methods: LA sites of dense DE and patchy DE at MRI of 10 patients (64+/-6yo, 7 long persist. AF) were segmented/registered with the LA NavX geometry, to assess propagation during AF at sites of dense vs patchy vs no DE. AF wavelets were mapped at DE and CFAE boundaries using 2 high density 40-pole catheters, allowing to map simultaneously a surface area of 30cm2 (AFocus II, SJM and Pentaray, BW). In each LA region, we categorized wave propagation by evaluation of 10 AF beats: 1. slow conducting channels, 2. pivots, 3. wave collision and 4. conduction block. In addition, the mean regional beat-to-beat conduction velocity was assessed during AF.Results: A total of 300 AF beats were analysed at dense DE, patchy DE and non-DE LA regions. Wave propagation during

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difference in the rate of early adverse events (<30 days), 12 % vs 21 %, p=0.17 and the rates of late adverse events were 5.6 % vs 8.8 %, respectively. After 67±42 months 84% of PRIM patients were free from AF vs 74 % after 62±42 months in the CONC group, N.S. Eight pts died during follow-up, 3 in the CONC group.Conclusion: In spite of significant preoperative differences, the PRIM and CONC patients did not differ in their long-term efficacy. The Cox maze III procedure is a valid option also for patients with concomitant open heart surgery.

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LONG-TERM OUTCOMES AFTER CATHETER ABLATION IN PATIENTS WITH PAROXYSMAL ATRIAL FIBRILLATION AND BRADYCARDIA-TACHYCARDIA SYNDROME.Masateru Takigawa, MD, Atsushi Takahashi, MD, Taishi Kuwahara, MD, Yuki Osaka, MD, Naohiko Kawaguchi, MD, Kazuya Yamao, MD, Emiko Nakashima, MD, Yuji Watari, MD, Keita Handa, MD, Kenji Okubo, MD, Katsumasa Takagi, MD, Kenzo Hirao, MD and Mitsuaki isobe, MD. Yokosuka Kyosai Hospital, Yokosuka, Japan, Heart Rhythm Center, Tokyo Medical and Dental University, Tokyo, Japan, Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, JapanIntroduction: Although catheter ablation (CA) is considered as the treatment for paroxysmal atrial fibrillation (PAF) and bradyacardia-tachycardia syndrome (BTS), long-term effect in these patients remains unknown. The aim of this study was to clarify the long-term clinical outcomes after CA in patients with PAF and BTS.Methods: Consecutive symptomatic 111 PAF patients with prolonged sinus pauses on termination of PAF (54 drug-induced BTS and 57 non-drug-induced BTS, mean age: 64 ± 10 years, 36 females) undergoing CA in our institution were included in this study. The incidence of the AF-recurrence and the pacemaker implantation (PMI) were examined.Results: Acute success was achieved in all patients. Sinus rhythm (SR) maintenance rate at 1,3, and 5 year was 62.0%, 50.9%, and 49.1% after the initial CA, and 87.2%, 78.6%, and 75.5% after the final CA (mean 1.5±0.7 procedures), respectively. PMI-avoidable-rate at 1,3, and 5 year was 83.8%, 81.3%, and 78.6% during a mean follow-up of 36±24 months after the initial CA. By multivariate analysis, age (HR 1.10, 95% CI 1.03-1.18, P=0.005), diabetes (HR 3.55, 95% CI 1.21-9.27, P=0.02), and AF-recurrence after the initial CA procedure (HR 6.08, 95% CI 2.20-21.4, P=0.0003), were the significant predictors of the incidence of PMI.Conclusion: Although CA is an effective therapy for the patients with PAF and BTS, PMI is still required in approximately 20% patients during a long-term follow-up.

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CONTACT FORCE GUIDED CATHETER ABLATION SIGNIFICANTLY REDUCES THE INCIDENCE OF ADENOSINE INDUCED DORMANT CONDUCTION POST PULMONARY VEIN ISOLATIONGeorge Monir, MD, Jennifer Forsyth, RN, Leann Goodwin, RN and Scott Pollak, MD. Florida Hospital Cardiovascular Institute, Arrhythmia and Ablation Center, Orlando, FLIntroduction: Recurrences of atrial fibrillation (AF) after initial successful pulmonary vein isolation (PVI) procedures are usually due to pulmonary vein to left atrium (PV-LA) re-conduction. Optimal catheter tip-to-tissue contact force (CF)

SFc. In the STc group the RF was delivered when the contact force was between 5 and 40g. Measured parameters: total procedural, fluoroscopy, and RF delivery times; percentage of PVs reconnection at 30 min; percentage of isolated PVs.Results: The 3 groups were comparable in terms of age (TCc 54.6±11.0 vs STc 59.7±9.1 vs SFc 58.4±8.8 years; p=NS), sex distribution (86% vs 86% vs 81%; p=NS), mean left atrial diameter (36±6 vs 35±7 vs 37± 8mm p=NS), antiarrhythmic drugs tested (1.6±0.7 vs 1.8±0.8 vs 1.9±0.5; p=NS). A mild groin hematoma was observed in the TCc group. The percentage of PVs isolated (end procedure) was comparable in the groups (TCc 96% vs STc 98%; vs SFc 96% P=NS). Percentage of deconnected PVs at 30 min was lower in TCc group (89%) than in STc (95%) and in SFc (95%) group (p<0.05). Both the use of STc and SFc was correlated to a reduction of fluoroscopy time (TCc 34±18 min; STc 20±10 min p<0.001 vs TCc; SFc 21±13min p=0.02 vs TCc) and RF time (TCc 33±18 min; STc 20±10 min p=0.013 vs TCc; SFc 21±13min p<0.01 vs TCc). Only the STc was correlated to a significant reduction of the total procedural time (TCc 181±53 min; STc 140±53 min p<0.001 vs TCc; SFc 170±51min p=NS vs TCc).Conclusion: both the STc and the SFc allowed to significantly simplify RFCA of paroxysmal AF. Future technological developments combining the features of both catheters could be of benefit

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COX MAZE III IN COMBINATION WITH OTHER OPEN HEART SURGERY - AN OPTION?Birgitta Johansson, MD, PhD, Nils Edvardsson, MD, PhD, Oskar Vaart, MD, Britta Nyström, BSc, Thomas Karlsson, MSc, Henrik Scherstén, MD, PhD and Eva Berglin, MD, PhD. Sahlgrenska University Hospital/Östra, Gothenburg, Sweden, Sahlgrenska Academy at Sahlgrenska University Hospital, Gothenburg, Sweden, Sahlgrenska University Hospital, Gothenburg, Sweden, Sahlgrenska Academy at Sahlgrenska University Hospital, Gothenburg, SwedenIntroduction: Cox maze III surgery with the “cut-and-sew” technique is an established treatment for primary drug refractory atrial fibrillation (AF). We studied the results in patients (pts) with indications for concomitant open heart surgery, appearing during the preoperative work-up.Methods: In all, 232 consecutive patients (pts) underwent the Cox maze III procedure between 1997 and 2009. Severely symptomatic AF was the primary indication for surgery, but concomitant surgery (CONC) was performed in 34 pts. Follow-up data were obtained from a patient questionnaire, patient files and 12-lead ECGs.Results: Patients with primary AF (PRIM), (n=198, 85%) were younger, 56±8 years, than those who underwent CONC (n=34, 15%), 60±7 years, p=0.02. CONC consisted of CABG (n=16), atrial septal patch (n=1), mitral valve surgery (n=8), aortic valve surgery (n=2), tricuspid valve surgery (n=3) and combinations of these (n=4). Persistent/permanent AF was present in 108 pts (55 %) versus 21 pts (62 %), N.S., with a mean duration of 7.6±6.7 years vs 5.5±6.4 years, p=0.03, respectively. There were significant differences in comorbidity; hypertension 18% vs 41%, p=0.005, diabetes mellitus 3% vs 12%, p=0.03, history of embolic stroke/TIA 6% vs 18%, p=0.02. The preoperative NYHA class for CONC was worse than for PRIM, p=0.02. A mean of 3 antiarrhythmic drugs had been tried and 55% vs 35% had been on a class I antiarrhythmic drug, p=0.04. The ECC times, 139±24 min vs 173±42 min, and the aortic clamp times 96±21 min vs 120±24 min, were both significantly longer in the CONC group, both p<0.0001. CONC patients stayed longer in the intensive care unit for, 2.3±0.9 vs 3.4±4.4 days, p=0.008. There was no

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prior stroke, left ventricular dysfunction (ejection fraction < 50%), and Chads(2) score-2 had more risk of chronic-phased thromboembolisms as shown in Figure1. AF recurrences (HR 5.64, 95% CI 1.52-23.8, P=0.01), prior stroke (HR 11.9, 95% CI 1.45-117.1, P=0.02), and left ventricular dysfunction (ejection fraction < 50%) (HR 30.9, 95% CI 5.25-195.9, P=0.0003), were independent predictors of chronic-phased thromboembolisms by the multivariate analysis.Conclusion:The incidence of AF recurrences and thromboembolisms was low after CA for PAF.

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A SIMPLE AND NOVEL RISK SCHEME TO PREDICT MAJOR BLEEDING IN PATIENTS WITH ATRIAL FIBRILLATIONMayumi Yamamoto, MD, Eiichi Watanabe, MD, Tomohide Ichikawa, MD, Hiroto Harigaya, MD, Yoshihiro Sobue, MD, Kentaro Okuda, MD and Yukio Ozaki, MD. Fujita Health University School of Medicine, Toyoake, JapanIntroduction: Atrial fibrillation (AF) is increasingly becoming a health concern worldwide, since it contributes to the increased risk of stroke and heart failure. Currently, anticoagulation by warfarin is the most effective therapy for the prevention of stroke. However, major bleeding is a feared complication of warfarin anticoagulation in patients with non-valvular atrial fibrillation (NVAF), and then optimal decision making regarding warfarin use for NVAF requires estimation of bleeding risk. Several bleeding risk scores such as HAS-BLED (Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile international normalized ratio, Elderly, Drugs/alcohol concomitantly) or ATRIA (anemia, severe renal disease, age>75 years, prior bleeding, hypertension) are not so handy scheme because they constitute of many clinical variables. The aim of the present study was to develop a simple risk stratification scheme to predict major bleeding in NVAF patients undergoing warfarin anticoagulation.Methods: We prospectively enrolled 522 patients (age 72+/-12 years, male 62%) who were diagnosed NVAF at our hospital visit and undergoing warfarin anticoagulation therapy.Results: During a 1-year follow up, we observed 35 (6.7%) major bleeding defined by the criteria of International Society on Thrombosis and Haemostasis. A multivariate Cox proportional-hazard regression model revealed the three independent variables and weighted by regression coefficients; concomitant antiplatelet therapy (1 point), kidney dysfunction (creatinine clearance <30 ml/min, 1 point), and prior bleeding (1 point). The annual bleeding rate increased with increasing risk variables. The predictive accuracy (c-index) for the continuous risk score of our new scheme named AKB was 0.71, which was higher than that in ATRIA (0.64, p = 0.01), but was similar to that in HAS-BLED (0.68, p = 0.50).

during radiofrequency (RF) lesion delivery is believed to result in adequate lesion formation and decrease the likelihood of producing reversible thermal lesions and hence improve clinical efficacy of catheter ablation for AF. Adenosine infusion post PVI can unmask dormant conduction resulting in acute transient PV-LA re-conduction. We hypothesized that CF guided RF ablation would reduce the incidence of Adenosine induced acute recurrence of PV-LA conduction post PVI.Methods: Two consecutive groups of patients with drug refractory AF were studied. Ipsilateral wide circumferential antral PVI for each PV pairs was performed using CARTO® electroanatomical 3-dimensional mapping system, irrigated-tip radiofrequency ablation catheter and a circular mapping catheter (LASSO®). Entrance and exit block for PV-LA conduction was achieved in all PV pairs. In group-I, RFA was delivered using a NAVISTAR® THERMOCOOL® catheter, while in group-II, a THERMOCOOL® SMARTTOUCH™ catheter was used with CF working range between 5-50 grams. RF power was limited to 25W for 20-30 seconds in the posterior wall and 30-35 W for 30-60 seconds in the anterior wall and ridge. After a waiting period of at least 20 min, 12-18 mg of adenosine was given and repeated to unmask dormant conduction and PV recurrent conduction (PVRC) in all PV pairs. Adenosine effect was confirmed by the presence of temporary atrio-ventricular block.Results: A total of 53 patients (35 M, 58 ± 12 years) with drug refractory AF were studied. Wide Circumferential isolation with entrance and exit block was achieved in all of the 106 Pairs of PVs studied. In Group-I (N=28, 17 M, 56 ± 12 years) adenosine infusion unmasked dormant conduction and PVRC in 12/56 pairs (21%) of PVs compared to 4/ 50 pairs (8%) of PVs in Group II (N=25, 18 M, 59 ± 12 years) ( (p<0.05).Conclusion: Use of CF to optimize RF applications during PVI for AF, significantly reduced adenosine induced transient PVRC. Long-term clinical outcome study is needed to evaluate the potential improvement in long-term maintenance of sinus rhythm

PO03-141

THE INCIDENCE AND PREDICTORS OF THROMBOEMBOLISMS IN PATIENTS WITH PAROXYSMAL ATRIAL FIBRILLATION UNDERGOING CATHETER ABLATIONMasateru Takigawa, MD, Atsushi Takahashi, MD, Taishi Kuwahara, MD, Yuki Osaka, MD, Naohiko Kawaguchi, MD, Kazuya Yamao, MD, Emiko Nakashima, MD, Yuji Watari, MD, Keita Handa, MD, Kenji Okubo, MD, Katsumasa Takagi, MD, Kenzo Hirao, MD and Mitsuaki Isobe, MD. Yokosuka Kyosai Hospital, Yokosuka, Japan, Heart Rhythm Center, Tokyo Medical and Dental University, Tokyo, Japan, Department of Cardiovascular Medicine, Tokyo Medical and Dental University, Tokyo, JapanIntroduction: Because of increasing number of patients with atrial fibrillation (AF), catheter ablation (CA) has recently become a standard treatment. However, the long term effect of CA on the prevention of thromboembolisms has not been fully elucidated.Methods: We studied 1220 consecutive patients (61+10 years, 940 males, CHADS(2) score 0.8+1.0) who were referred to our institution for CA for symptomatic paroxysmal AF (PAF).Results: Acute success was achieved in all patients. Sinus rhythm (SR) maintenance rate at 1,3, and 5 years was 72.0%, 65.4%, and 59.4% after the initial CA, and 89.8%, 85.3%, and 81.2% after the final CA (mean 1.3±0.6 procedures), respectively. Among 1594 procedures for these 1220 patients, 64 (5.2%) procedure-related complications occurred including 9 (0.6%) thromboembolisms. Chronic-phased thromboembolisms occurred in 10 (0.8%) patients during a mean follow up of 48.2+22.0 (range 1 to 112.8) months after the final CA. Kaplan-Meier analysis revealed that patient with AF-recurrence,

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assessed. Twelve consecutive PVC coupling intervals were recorded. Mean CI and ΔCI (max-min CI) were assessed.Results: We studied 51 PTS (age 51±17 years, 61% male, EF 50±13%). The PVC origin was right ventricular outflow or left ventricle (RV-LV) in 33 (65%), GCV in 4 (8%) and SOV 14 (27%). The PVC was successfully ablated in 47 (92%) but deferred due to location near a coronary artery in 3 (6%). The mean CI in the RV-LV PVCs was 516±109 ms vs 481±70 ms in the SOV/GCV patients (P<0.0001). There was a significant difference between the ΔCI of RVOT/LV PVCs (mean 30±15 ms) vs those from the SOV/GCV (106± 49) (p<0.0001) (figure 1) No RV-LV PVCs had >60 ms ΔCI and only 2 of the SOV/GCV PVCs had <60ms ΔCI. A ΔCI of>60 ms had an 89% sensitivity, 100% specificity, 100% positive predictive value and 94% negative predicitve value for SOV/GCV origin. Two (4%) PTS (both with SOV PVCs) had documented cardiac arrest.Conclusion: ΔCI is greater in PVCs originating from the SOV or GCV, possibly due to lack of surrounding myocardial tissue that is present in PVCs from the RV-LV. ΔCI of 60 ms helps discriminate the origin of PVCs and better plan ablation. More variable CI may predispose to higher risk of future R-on-T phenomena.

PO03-146

FEVER NOT ONLY UNMASKS BRUGADA-TYPE ECG BUT ALSO EXAGGERATES DEPOLARIZATION ABNORMALITYHiroshi Morita, MD, PhD, Tadashi Wada, MD, Kohei Miyaji, MD, PhD, Koji Nakagawa, MD, PhD, Masamichi Tanaka, MD, PhD, Nobuhiro Nishii, MD, PhD, Satoshi Nagase, MD, PhD, Kazufumi Nakamura, MD, PhD, Kusano Kengo, MD, PhD and Hiroshi Ito, MD, PhD. Dept. of Cardiovascular Therapeutics, Okayama University Graduate School of Medicine, Okayama, Japan, Dept. of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Okayama, Japan, Dept. of Cardiovascular Medicne, Okayama University Graduate School of Medicine, Okayama, JapanIntroduction: Although it has been reported that fever unmasks Brugada-type ECG, it is still unknown the electrophysiological mechanism of occurrence of ventricular fibrillation (VF) during a febrile illness in patients with Brugada syndrome. We objective to clarify electrophysiological changes promoting the Brugada-type ECG during a febrile illness by analyzing ECG change in patients with Brugada syndrome.Methods: The subjects of this study compromised 25 patients with fever induced Brugada-type ECG. We analyzed clinical characteristics (symptoms, family history of sudden death and SCN5A), 12-lead ECG parameters (Brugada-ECG type of Consensus Reports, PQ, RR, QRS, and QT intervals, ST level, fragmentation of QRS (number of spikes within QRS complex),

Conclusion: This simple, 3-variable novel risk scheme (AKB) provides a practical tool to assess the major bleeding risk of patients with NVAF undergoing warfarin anticoagulat.

PO03-144

COST EFFECTIVENESS OF CATHETER ABLATION VERSUS A RATE CONTROL STRATEGY FOR TREATMENT OF PERSISTENT ATRIAL FIBRILLATION IN PATIENTS WITH ADVANCED HEART FAILURE. AN ANALYSIS OF THE CAMTAF STUDYGeoffrey Lee, MBChB, Ross Hunter, MBBS, TJ Berriman, R. Kamdar, Victoria Baker, F. Goromonzi, V. Sawhney, Steven Page, MBBS, B. Unsworth, J. Mayet, M. Dhinoja, MBBS, Mark Earley, MBBS, PhD, Simon Sporton, MBBS and Richard Schilling, MBBS, PhD. Barts and the London NHS, London, United KingdomIntroduction: Persistent atrial fibrillation (PerAF) and heart failure (HF) both result in significant morbidity, reduction in quality of life and substantial utilization of healthcare resources. The aim of this study was to evaluate the cost effectiveness of catheter ablation (CA) compared to a rate control strategy in patients with PerAF and HF as performed in the randomized controlled study CAMTAF.Methods: We performed an economic analysis looking at direct health care cost and quality adjusted life year (QALY) data obtained from the CAMTAF. An incremental cost effective ratio analysis (ICER) was performed at 6 months. Costs for each patient were individually determined using National Health Service reimbursement tariff data.Results: 26 patients underwent CA for PerAF and 25 patients underwent a rate control strategy. Baseline characteristics were similar between the two arms. Freedom from AF was achieved in 21/26 (81%) in the CA group at 6 months. CA was associated with a greater improvement in QALY at 6 months compared to a rate control strategy (0.76±0.17 vs. 0.59±0.19, p<0.05). Improvements were sustained at one-year follow up. There was an absolute improvement in QALY of 0.209 for CA at an additional cost of £3833.10. The incremental cost effective ratio cost of CA vs. a rate control strategy was £31,637. This is comparable to similar cost effective interventions such as renal dialysis (ICER=£21,970) or TAVI (ICER=£36, 326)Conclusion: Catheter ablation of PerAF in patients with HF is a cost-effective strategy that leads to restoration of sinus rhythm, improvement in quality of life and left ventricular function compared to a rate control strategy.

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COUPLING INTERVAL PREDICTS THE ORIGIN OF IDIOPATHIC PVCSJason Bradfield, MD, FHRS, Mohamed Homsi, MD, Kalyanam Shivkumar, MD, PHD, FHRS and John M. Miller, MD, FHRS. UCLA Cardiac Arrhythmia Center, David Geffen School of Medicine at UCLA, Los Angeles, CA, Krannert Institute of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, INIntroduction: Premature ventricular complexes (PVCs) occur at relatively fixed coupling intervals (CI) from the preceding normal QRS in most patients (PTS). We observed PTS with PVCs originating in unusual areas (aortic sinuses of Valsalva [SOV], great cardiac vein [GCV]) in whom the PVC CI was highly variable. We hypothesized that PVC from these areas occur seemingly randomly due to lack of “restraining effect” of surrounding myocardium.Methods: Consecutive PTS referred for PVC ablation were

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1.1), or CAD (n=3592,32.9%) (RR;1.0, 95% CI 0.8-1.2).Conclusion: ER in the inferior leads of the 12-lead ECG predicts the occurrence of arrhythmic death and near-fatal arrhythmic events but not AF or non-arrhythmic cardiac events in the middle-aged subjects, suggesting that this ECG pattern is a specific sign of increased vulnerability to ventricular tachyarrhythmia but not a sign of subclinical structural cardiac disease increasing the risk of non-arrhythmic mortality or morbidity.

PO03-148

PLEOMORPHIC VENTRICULAR TACHYCARDIA MAY INDICATE INFLAMMATORY PHASE IN PATIENTS WITH CARDIAC SARCOIDOSISSubha N. Panda, Sr., MD, Lawrance Jesuraj. masilamani, MD, Sridevi C, MD, Sharada K, MD, Nalla Swapna, MD, Krishna Lalukota, MD and Calambur Narasimhan, MD. CARE Hospital, Hyderabad, IndiaIntroduction: To analyze the ECG morphology in patients presenting with Ventricular Tachycardia (VT ) during inflammatory phase of cardiac sarcoidosis(CS)Methods: Morphology of VT of 21 consecutive patients diagnosed to have active CS was analyzed. The 12 lead ECGs were analyzed by two independent observers and classified into Monomorphic (MONO group)and Pleomorphic VT (PLEO group) according to definition of EHRA/HRS expert consensus on catheter ablation of ventricular arrhythmias 2009. VT with a similar QRS configuration from beat to beat was labeled as Monomorphic VT. When there was more than one morphologically distinct QRS complex occurring during the same episode of VT, it was labelled as Pleomorphic VT. 18FDG PET-CT was performed in 85% of patients in both the groups and was analyzed by an independent observer.Results: Pleomorphic morphology of VT was noted in 7/21(33%) patients .Among the patients with VT in the MONO group mean left ventricular ejection fraction( LVEF) was better preserved and there are areas of limited myocardial involvement in18FDG PET-CT .However PLEO group had multiple areas of myocardial involvement and have mildly depressed LVEF. Comparison between two groups has been shown in the table 1Conclusion: Our results indicate that pleomorphic ventricular tachycardia can be a mode of presentation in active sarcoidosis. This feature seems to indicate multiple sites of myocardial involvement.

PO03-149

LYMPHOCYTIC CELL INFILTRATION OF MYOCARDIUM IS ASSOCIATED WITH VF EPISODE IN PATIENTS WITH BRUGADA SYNDROMEMasamichi Tanaka, MD, Kazufumi Nakamura, MD, Tadashi Wada, MD, Daiji Miura, PhD, Aya Miura, PhD, Koji Nakagawa, MD, Nobuhiro Nishii, MD, Satoshi Nagase, MD, Kohno Kunihisa, MD, Hiroshi Morita, MD, Kengo Kusano, MD, Chikao Yutani, MD and Hiroshi Ito, MD. Department of Cardiology, Okayama University Graduate School of Medicine, Dentistry

and inferolateral early repolarization (ER)) during a febrile and an afebrile states.Results: At a febrile (body temperature: 38.4 ± 1.0 °C), type 1 ECG appeared in all patients, whereas type 1 ECG remains in only 5 patients at an afebrile (p<0.01); 14 had non-type 1 ECG and 4 patients did not have any Brugada-like ECG at an afebrile. Two patients suffered from VF episodes and a patient had frequent premature ventricular contractions during a febrile illness. Fever increased heart rate (febrile: 84 ± 13 bpm vs. afebrile: 69 ± 11 bpm, p<0.01), and promoted more prominent ST elevation in right precordial leads than did afebrile (ST level in V2: febrile: 0.47 ± 0.27 mV vs. afebrile: 0.21 ± 0.15 mV, p<0.01). QTc interval was prolonged in right precordial leads (febrile: 425 ± 49 ms, vs. afebrile: 366 ± 36 ms, p<0.01) but not in left precordial leads at a febrile. Fever enhanced ER in lateral leads (p<0.05). Fever also exaggerated depolarization parameters: more prolonged PQ and QRS intervals (QRS: febrile: 111±14 ms vs. afebrile: 102 ± 15 ms, p<0.01) and more fragmentation of QRS complex at febrile (total number of QRS spikes of V1-V3: febrile: 6.2 ± 1.4 spikes, vs. afebrile: 5.0 ± 1.6 spikes, p<0.01).Conclusion: Fever not only unmasked Brugada-type ECG but also enhanced depolarization parameters. Exaggeration of both the repolarization (ST elevation, ER and QT prolongation) and the depolarization (QRS widening and fragmentation) abnormalities promoted the occurrences of VF during a febrile illness in Brugada syndrome.

PO03-147

EARLY REPOLARIZATION AS A PREDICTOR OF ARRHYTHMIC VS.NON-ARRHYTHMIC CARDIACEVENTS IN MIDDLE-AGED SUBJECTSHeikki V. Huikuri, MD, Jani T. Tikkanen, MD, Olli Anttonen, MD, Aapo L. Aro, MD, Tuomas Kerola, MD, Harri A. Rissanen, MSc, Paul Knekt, MD and Juhani MJ. Junttila, MD. Institute of Clinical Medicine, University Central Hospital of Oulu, Oulu, Finland, Päijät-Häme Central Hospital, Department of Internal Medicine, Lahti, Finland, Helsinki University Central Hospital, Division of Cardiology, Department of Medicine, Helsinki, Finland, National Institute For Health and Welfare, Helsinki, FinlandIntroduction: Early repolarization (ER) in leads other than V1-V3 predicts mortality in middle-aged subjects, but it is not known whether ER is a specific sign of increased risk of arrhythmic vs. non-arrhythmic events.Methods: We assessed the prognostic significance of ER in a community-based general population of 10,846 middle-aged subjects (mean age 44±8 years). The endpoints were sudden arrhythmic death, non-arrhythmic cardiac death, non-fatal ventricular tachycardia, ventricular fibrillation or resuscitated cardiac arrest (VT-VF), symptomatic new onset atrial fibrillation needing hospital visit (AF), and hospitalization for congestive heart failure (CHF) or coronary event (CAD) during a mean follow-up of 30±11 years. ER was defined as ≥0.1 mV elevation of J-point in either inferior or lateral leads.Results: Inferior ER was present in 3.5% and lateral in 2.4% of subjects. After including all risk factors of cardiac mortality and morbidity in Cox regression analysis, such as age, gender, history of cardiovascular disease, blood pressure, cholesterol, cardiovascular medication, and smoking, ER in lateral leads did not predict any of the endpoints. However, ER in the inferior leads predicted arrhythmic death (n=802, 7.4%) with an adjusted relative risk (RR) of 1.5 (95% CI 1.1-2.0, p=0.01) and non-fatal VT-VF (n=108, 1.0%) with a RR of 2.2 (95% CI 1.1.-4.5, p=0.03), but not the non-arrhythmic cardiac death (n=1235, 12.2%) (RR; 1.2, 95% CI 0.9-1.6), occurrence of AF (n=1659, 15.2%) (RR; 0.9, 95% CI 0.7-1.2), CHF (n=1752,16.1%) (RR;0.9, 95% CI 0-7-

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53%. Isolated LV disease was seen in 7%. The most frequent RV abnormality was focal dyskinesis of the basal inferior wall (96%) followed by the basal anterior wall (84%). The remainder of the RV including the apex was involved in advanced disease. The most common LV abnormality was epicardial fat infiltration in the posterolateral wall (76%). Similar to CMR data, voltage maps revealed scar (<0.5 mV) in the RV basal inferior wall (100%), followed by the RV basal anterior wall (68%) and LV posterolateral wall (45%). All 16 RV VTs originated from the basal inferior wall (56%) or basal anterior wall (44%). Of 3 LV VTs, 2 localized to the posterolateral wall.Conclusion: Genetic ARVD exhibits a previously unrecognized unique pattern of biventricular disease involving the basal RV and posterolateral LV. Arrhythmias also arise from both ventricles and localize to the diseased regions. Our data provide unique insights for diagnosis, management and understanding the disease mechanism in desmosomal myopathies.

PO03-151

ECG-GATED CARDIAC CT FOR ACCURATE DIAGNOSIS OF ARRHYTHMOGENIC RIGHT VENTRICULAR DYSPLASIA - HIGH SENSITIVITY OF A NON-INVASIVE IMAGING MODALITYGregor Pache, MD, Heiko Lehrmann, MD, Chan-il Park, MD, Reinhold Weber, MD, Philipp Blanke, MD, Jochen Schiebeling-Roemer, MD, Juergen Allgeier, MD, Thomas Arentz, MD and Amir Jadidi, MD. Section of Cardiovascular Radiology, University Heart Centre Bad Krozingen, Bad Krozingen, Germany, Department of Rhythmology, University Heart Centre Freiburg - Bad Krozingen, Bad Krozingen, Bad Krozingen, GermanyIntroduction: Despite the use of MRI diagnosis of ARVC often remains unclear. Moreover MRI cannot be applied in patients with ICD implants and has limited spatial resolution as compared to CT. Thus we sought to assess the diagnostic value of a novel cardiac CT (CCT) 4D imaging in patients with inconclusive Echo/MRI or ineligibility for MRI.Methods: Ten patients with electrical storm underwent electro-anatomical substrate (EAS) mapping of the RV at high density. CCT [3D&4D; 0.6 mm slices] was performed due to ICD (n=6), inconclusive Echo/MRI (n=7) and claustrophobia (n=1). CT images were analyzed for RV dyskinesia, fatty infiltrations or microaneurysms. Twenty 4D-CCTs of non-ARVC patients served as control.Results: ARVC was diagnosed in 10/10 pátients based on EAS-RV. In all patients, CT imaging revealed dyskinetic regions, fat infiltrations or microaneurysms in identical regions as pathological findings at EAS-mapping (low voltage, late potentials). In the control group no similar abnormalities were detected. In 7/10 patients (3 with ICD) previous imaging studies had not revealed RV abnormalities. In 3 patients CT diagnosis of ARVC was only possible when 4D-Imaging was applied. Mean

and Pharmaceutic, Okayama, Japan, Department of Cardiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama, Japan, Department of Cardiovascular therapeutics, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama, Japan, Department of Life Science, Okayama University of Science, Okayama, JapanIntroduction: The existence of myocarditis in endomyocardial biopsy sample in patients with Brugada syndrome is still debated. The aim of the present study was to investigate by endomyocardial biopsy whether the presence of lymphocytic cell infiltration of myocardium and its association with clinical features in patients with Brugada syndromeMethods: We studied consecutive 73 patients (71 males; mean age 48±11 years) with Brugada syndrome. All patients underwent cardiac ultrasonography, coronary and ventricular angiography, endomyocardial biopsy from right ventricular septum, electrophysiological (EP) study, and DNA screening of the SCN5A gene. The lymphocytic cell infiltration of myocardium was determined by the presence of over five inflammatory cell infiltration by CD45RO immunohistochemical staining associated with necrosis or degeneration of adjacent myocytes in high power field image.Results: SCN5A mutation was detected in 15 patients. VF episode was detected in 17 patients. Lymphocytic cell infiltration of myocardium was detected in 7 patients (2 patients with SCN5A mutation and 5 without SCN5A mutation). Lymphocytic cell infiltration of myocardium was detected in 4 patients of 17 patients with episode of VF. Univariate analysis showed that the existence of lymphocytic cell infiltration was associated with the VF episode in patients with Brugada syndorome (P=0.047), but not with SCN5A mutation, syncope, family history, or VF induction in EP study.Conclusion: Lymphocytic cell infiltration was detected in patients with Brugada syndrome in both of SCN5A positive and negative group. And the existence of lymphocytic cell infiltration is associated with VF episode in patients with Brugada syndrome.

PO03-150

CARDIAC PHENOTYPE OF ARRHYTHMOGENIC RIGHT VENTRICULAR DYSPLASIAAnneline S. te Riele, MD, Cynthia A. James, PhD, Binu Philips, MD, Neda Rastegar, MD, Aditya Bhonsale, MD, Judith A. Groeneweg, MD, Brittney Murray, MS, Crystal Tichnell, MS, Daniel P. Judge, MD, Jeroen F. van der Heijden, MD, PhD, Maarten J. Cramer, MD, PhD, Birgitta K. Velthuis, MD, PhD, David A. Bluemke, MD, PhD, Stefan L. Zimmerman, MD, Ihab R. Kamel, MD, PhD, Richard NW. Hauer, MD, PhD, Hugh Calkins, MD and Harikrishna Tandri, MD. University Medical Center Utrecht, Utrecht, Netherlands, Johns Hopkins Hospital, Baltimore, MD, National Institute of Health Clinical Center, Bethesda, MDIntroduction: Arrhythmogenic Right Ventricular Dysplasia (ARVD) is a cardiomyopathy that is traditionally regarded to be confined to the RV involving the triangle of dysplasia. This concept predates genetic testing and excludes biventricular phenotypes. The purpose of this study was to re-examine the cardiac phenotype of ARVD.Methods: We reviewed Cardiac Magnetic Resonance (CMR) of 81 mutation positive ARVD patients for regional abnormalities on a 5 segment RV and 17 segment LV model. The location of electroanatomic endo- and epicardial scar and site of successful VT ablation was recorded in 11 ARVD subjects.Results: Of 81 subjects, 59 (73%) had an abnormal CMR. The RV was abnormal in 93%, with additional LV involvement in

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THE ROLE OF 18F-FLUORODEOXYGLUCOSE POSITRON EMISSION TOMOGRAPHY IMAGING IN PREDICTING VENTRICULAR ARRHYTHMIC EVENTS IN PATIENTS WITH CARDIAC SARCOIDOSIS AND PRESERVED LEFT VENTRICULAR EJECTION FRACTIONNitesh Sood, MD, Nishant Patel, MD, Gary Heller, MD, MPH and Christopher A. Clyne, MD. Lahey Clinic, Tufts Univeristy Medical Center, Burlington, MA, Hartford Hospital, Univeristy of Connecticut School of Medicine, Hartford, CT, Univeristy of Connecticut School of Medicine, Farmington, CTIntroduction: Autopsy studies have estimated the prevalence of cardiac involvement to be at least 25% in the patients with systemic sarcoidosis. Recently, 18F-FDG PET Imaging has been used to identify the presence of cardiac sarcoid activity. The use of 18F-FDG PET to determine myocardial sarcoid activity and severity burden to predict ventricular arrhythmia and sudden cardiac death has not been well studied.Methods: Twenty two consecutive patients who met the modified MHLW criteria for diagnosis of cardiac sarcoidosis with a positive 18F-FDG PET were evaluated for subsequent cardiac events. A blinded read of a previously described 13-segment model for analysis of 18F-FDG PET imaging for cardiac sarcoidosis was done by two independent readers.Focal FDG cardiac uptake was considered positive for active inflammatory sarcoid lesions. Following the FDG PET study patients were followed for the presence of sustained ventricular arrhythmia (>30sec) or ICD therapy (shock and ATP for ventricular arrhythmia) and were considered to be significant arrhythmic events (SAE). Patients were followed for mean 1.6 ± 1.2 years.Results: Patients were categorized by the total score as high burden of inflammation, 18F FDG PET score ≥ 10 (≥25% myocardial involvement) and patients with PET score <10 were classified as low burden of inflammation. Patients with PET score ≥ 10 (N= 8, 36%) had statistically significantly higher incidence of SAE (4, 50%) vs. 0 events in patients with PET score <10 (P value = 0.01).Conclusion: Quantification of myocardial sarcoid burden with 18F FDG PET may be useful in risk in predicting risk of ventricular arrhythmia beyond left ventricular ejection fraction in patients with cardiac sarcoidosis.

effective dose was 8.9±4.4 [range 3.1-14.6] mSv.Conclusion: Novel CCT high resolution 3D&4D imaging shows excellent sensitivity for the diagnosis of ARVC. CT findings showed high correlation to abnomalities on invasive EAS mapping.

PO03-152

AUTOMATIC MYOCARDIAL FAT QUANTIFICATION AT CONTRAST-ENHANCED CARDIAC MDCT IN ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY: INITIAL VALIDATION VS CONTROLSHubert Cochet, MD, Yuki Komatsu, MD, Amir Sherwan Jadidi, MD, Arnaud Denis, MD, Frederic Sacher, MD, Nicolas Derval, MD, Khaled Ramoul, MD, Matthew Daly, MD, Laurence Jesel, MD, Stephan Zellerhoff, MD, Jatin Relan, PhD, Maxime Sermesant, PhD, Nicholas Ayache, PhD, Michel Montaudon, MD, PhD, François Laurent, MD, Mélèze Hocini, MD, Michel Haïssaguerre, MD and Pierre Jaïs, MD, PhD. CHU Bordeaux - Université de Bordeaux - LIRYC/INSERM U1045, Pessac, France, Herzzentrum Bad Krozingen, Bad Krozingen, Germany, St Jude Medical, St Paul, MN, INRIA Sophia Antipolis, Sophia Antipolis, FranceIntroduction: ARVC is characterized by fibro-fatty infiltration. Myocardial fat can be assessed at CT as areas of low density. We compared RV myocardial fat extent and distribution in ARVC pts vs controlsMethods: 21 pts (age 45±15 yrs, 7 women) with ARVC and 21 age and sex-matched controls underwent contrast-enhanced ECG-gated cardiac CT. Controls were referred at CT for the assessment of aortic valve disease and had no RV dysfunction. A 2 mm-thick RV free wall layer was automatically segmented using region grow segmentation of the RV endocardium, secondarily dilated. Myocardial fat was defined as pixels with density between -120 and -10 HU. Fat extent was automatically computed and expressed in % of the RV free wall (< 5 min processing/pt). Patient-specific segmentations were registered to an RV template to compute epicardial maps displaying fat likelihood over the RV free wall in each groupResults: Myocardial fat extent was 15.5±6.6% (range 4.7-29.6) in ARVC and 3.0±1.7% (0.5-6.7) in controls (P<0.0001). RV end-diastolic volume was 251±91mL (113-483) in ARVC and 121±33mL (74-195) in controls (P<0.0001). Fat extent diagnosed ARVC with Se/Sp values of 0.95/0.95 using a 6.7% cut-off. RV volume diagnosed ARVC with Se/Sp values of 0.86/0.86 using a 169mL cut-off. In ARVC, fat extent correlated strongly to RV volume (R=0.69) and not to age (R=0.12) while it was the opposite in controls (R=-0.19 and R=0.38). Fat Distribution was different in ARVC vs controls (fig)Conclusion: This study introduces a fully automatic method for the quantification of fat in the RV free wall from CT images. Fat quantification with CT performs better than RV volume for the diagnosis of ARVC while at the same time enabling substrate mapping

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potentials (LP) and long stimulus to QRS duration (S-QRS) during pace-mapping (PM) have been used to guide SM, however, whether these two methods identify the same areas of abnormal substrate is not clear. We sought to explore the relation between LPs and S-QRS.Methods: A total of 257 data points were obtained from 5 male pts with IHD (mean LVEF 28%) undergoing LV endocardial SM. Data obtained from scar areas where PM was attempted included BiV, presence of LPs, and time from QRS onset to LP. When capture occurred, the S-QRS and which EGM(s) captured were recorded. A far field late potential (FFLP) was defined as either 1). a LP at baseline that did not capture or 2). a LP seen remote from the captured EGM during pace-mapping.Results: LPs were seen at 81/257 (32%) sites. Pacing captured at 192/257 (75%) sites. Pacing demonstrated that the LP was actually a FFLP at 60 pacing sites. Of 124 sites with no LP at baseline where pacing captured, 24 (19%) exhibited LPs during pacing, consistent with poorly coupled myocardium. At sites with capture, those with LPs had longer S-QRS intervals (91 +/- 44 vs 67+/- 48 msec, p=0.0003) and lower BiV (0.31 +/- 0.23 vs 0.43 +/- 0.26 mV, p=0.02) than those without LPs. Within the LP sites, areas of FFLP also had significantly longer S-QRS times (115 +/- 53 vs 63 +/- 38 msec, p<0.0001), and lower BiV (0.32 +/- 0.40 vs 0.50 +/- 0.40 mV). Interestingly, the FFLP sites had a shorter interval from QRS onset to LP than other LP sites (183 +/- 138 vs 287 +/- 204 msec, p=0.006).Conclusion:Pacing indicates that many LPs in scar are far-field, and associated with more conduction delay during pacing than sites where the LP is near field and captures. The procedural significance of FFLP however, remains to be defined, and further studies are warranted. Pacing provides information that is complimentary to EGM analysis for substrate mapping.

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CT SCAN SEGMENTATION OF MYOCARDIAL HYPODENSITY TO GUIDE VENTRICULAR TACHYCARDIA ABLATION IN ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHYYuki Komatsu, MD, Amir Jadidi, MD, Hubert Cochet, MD, Frédéric Sacher, MD, Arnaud Denis, MD, Patrizio Pascale, MD, Laurent Roten, MD, Daniel Scherr, MD, Matthew Daly, MD, Khaled Ramoul, MD, Ashok Shah, MD, Heiko Lehrmann, MD, Reinhold Weber, MD, Jochen Schiebeling-Römer, MD, Gregor Pache, MD, Thomas Arentz, MD, Jatin Relan, PhD, Maxime Sermesant, PhD, Nicholas Ayache, PhD, François Laurent, MD, Nicolas Derval, MD, Mélèze Hocini, MD, Michel Haïssaguerre, MD and Pierre Jaïs, MD. CHU Bordeaux, Hôpital du Haut-Lévêque, Bordeaux, France, University Heart Center Freiburg/Bad Krozingen, Bad Krozingen, Germany, INRIA Sophia Antipolis, Sophia Antipolis, FranceIntroduction: Myocardial fatty-infiltration, the milieu for ventricular tachycardia (VT) in arrhythmogenic right ventricular cardiomyopathy (ARVC), can be depicted as a myocardial hypodensity (MH) at contrast-enhanced multi-detector computed tomography (MDCT). The purpose of this study was to assess the relationship between the MH and VT substrate in ARVC.Methods: We studied 13 patients with ARVC who underwent ablation after MDCT. Imaging data was integrated with 3D electroanatomic mapping (3D-EAM), and registered to high-density endo- and epicardial maps (617±348 and 711±354 points/map, respectively) in sinus rhythm. Analysis of the locations of low-voltage and MH included the following 7 regions in each endo- and epicardium: apex, mid (anterior, lateral, inferior), and basal (anterior, lateral, inferior). The location of local abnormal ventricular activities (LAVA) was compared with the MH.

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A 3-TESLA MRI-BASED REAL-TIME ELECTROPHYSIOLOGY MAPPING AND ABLATION SYSTEM WITH ACUTE VISUALIZATION OF ABLATION LESIONSRavi Ranjan, MD, PhD, Eugene Kholmovski, PhD, Sathya Vijayakumar, MS, Greg Gardner, BS, Nelly Volland, PhD, Joshua Blauer, BS, Dennis Parker, PhD, Rob MacLeod, PhD and Nassir Marrouche, MD. University of Utah, Salt Lake City, UTIntroduction: Current fluoroscopy based electrophysiology (EP) systems lack confirmation of tip tissue contact and when ablating there is no direct feedback of ablation related tissue changes. We describe a 3-Tesla MRI EP system providing imaging based tip tissue contact confirmation and direct feedback of acute tissue changes from ablation.Methods: The real time MRI-EP system consisted of a 3T MRI scanner with custom pulse sequences, navigation and visualization software, and catheters with active tracking coils and tip cooling. Test studies (n=15) in adult mini-pigs began by creating an endocardial shell from MR angiograms for catheter guidance. The catheter was maneuvered using the shell, surface ECG and local electrogram and placed on the endcoardial wall. We then verified tip tissue contact using MR real-time images and adjusted the catheter if a gap was detected until good contact was confirmed.Results: Ablation was successful in all 15 animals. EP study was carried out recording 35 +/-19 point coordinates and local electrograms per study. The RV bipolar electrogram was 5.8 +/- 2.5 mV when using traditional measures of good tip tissue contact and 8.0 +/- 2.7 mV when contact was confirmed using MR imaging. Ablation lesions were acutely visualized using late gadolinium enhancement and confirmed using gross pathology.Conclusion: We have shown the real time MRI guidance of ablation is entirely feasible. Our system provides confirmation of tip tissue contact, acute lesion visualization, and elimination of ionizing radiation. The system also shows that relying on traditional markers like robust bipolar electrogram amplitude is not sufficient for good tip tissue contact.

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SUBSTRATE MAPPING IN ISCHEMIC CARDIOMYOPATHY: PACING PROVIDES COMPLIMENTARY INFORMATION TO ELECTROGRAM ANALYSIS OF LATE POTENTIALSJustin J. Ng, MBBS, Thomas Tadros, MD, Chirag Barbhaiya, MD, Nagesh Chopra, MD, Tobias Reichlin, MD, Eyal Nof, MD, Roy John, MD, William Stevenson, MD and Usha Tedrow, MD. Brigham and Women’s Hospital, Boston, MAIntroduction:Substrate modification (SM) for catheter ablation of VT includes identifying slow conduction, potential channels, and exits for reentry in regions of low bipolar voltage (BiV) scar, during sinus or paced rhythm. Analysis of EGMs, including late

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delayed’’ LAVA from the far-field ventricular electrogram.

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CHARACTERIZATION OF CONTACT FORCE IN DIFFERENT REGIONS OF THE ENDOCARDIUM AND EPICARDIUM DURING SUBSTRATE MAPPING FOR VT ABLATIONLaurence Jesel, MD, Frederic Sacher, MD, Yuki Komatsu, MD, Matthew Daly, MD, Wislane Ambri, Nicolas Derval, MD, Khaled Ramoul, MD, Arnaud Denis, MD, Stephan Zellerhoff, MD, Mélèze Hocini, MD, Michel Haissaguerre, MD and Pierre Jais, MD. CHU Bordeaux, Hôpital du Haut-Lévêque, Bordeaux-Pessac, France, Biosence Webster, Issy-les-moulineaux Cedex 09, FranceIntroduction: The optimal contact force during endocardial and epicardial ventricular mapping and ablation has not been yet validated. The aim of the study was to assess the contact force (CF) in different endocardial and epicardial regions during ventricular tachycardia (VT) substrate mapping using a CF catheter (Smartouch, Biosense Webster).Methods: Two experienced operators performed endocardial and epicardial ventricular mapping blinded to CF information. During RF delivery, CF and force vector orientation (VO) were carefully monitored. We analysed 11 epicardial and 7 left ventricular endocardial maps, containing 3145 epi- and 957 endocardial mapping points. Endocardial maps were performed via a retrograde aortic approach. The CF and VO were assessed among the following endo- and epicardial regions: anterior, lateral, inferior and right ventricle (epi)/septal (endo). Each region was divided into basal and apical segments. VO was defined as ‘correct’ epicardially when the vector was pointing towards the heart and endocardially when pointing towards the epicardium.Results: During epicardial mapping, 49% of the points showed correct VO. Mean CF of correct VO in the epicardium was 11±9 g. There was no difference in CF nor proportion of correct VO between the 8 epicardial regions. When VO was not correct, mean CF was significantly higher at 19±11 g (p<0.001). During endocardial mapping, 89% of VO were correct. Mean CF of correct VO in endocardium was significantly higher than in epicardium (17± 11 vs 11± 9; p<0.0001). The CF in the antero-basal and antero-apical regions was lower compared to the other endocardial regions (p<0.05).Conclusion: During epicardial mapping, in half of the points the catheter was oriented in the inadequate direction. Lower CF in epicardium compared to endocardium is observed in case of good catheter orientation. CF was similar in all epicardial regions. The CF catheter provides information which may optimize safety and efficacy during epicardial VT substrate mapping and ablation.

Results: MH was found in all and successfully integrated with 3D-EAM. Registration of MDCT allowed direct visualization of coronary arteries used to avoid coronary damage during epicardial RF delivery. The κ agreement test demonstrated a high concordance between the epicardial low voltage and MH (κ=0.636, p<0.001), but not with the endocardium (κ=0.166, p=0.060). The majority of LAVA (353/469 [75%]) were located within the MH. Of them, 328/353 (93%) were not farther than 20mm from the MH border. In the deep inside severe MH, LAVA were less frequently detected.Conclusion: The integration of myocardial hypodensity with 3D-EAM in ARVC provides valuable information on the extent and dispersion of epicardial VT substrate and demonstrates LAVA clustering in the border zone.

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ELECTROPHYSIOLOGIC CHARACTERISTICS OF LOCAL ABNORMAL VENTRICULAR ACTIVITIES IN ISCHEMIC AND NON-ISCHEMIC VENTRICULAR TACHYCARDIA DEPEND ON SCAR LOCATIONYuki Komatsu, MD, Matthew Daly, MD, Frédéric Sacher, MD, Nicolas Derval, MD, Hubert Cochet, MD, Amir Jadidi, MD, Patrizio Pascale, MD, Laurent Roten, MD, Daniel Scherr, MD, Arnaud Denis, MD, Khaled Ramoul, MD, Laurence Jesel, MD, Stephan Zellerhoff, MD, Ashok Shah, MD, Mélèze Hocini, MD, Michel Haïssaguerre, MD and Pierre Jaïs, MD. CHU Bordeaux, Hôpital du Haut-Lévêque, Bordeaux, FranceIntroduction: Local abnormal ventricular activities (LAVA) in scar-related ventricular tachycardia (VT) may appear at any time during or after the far-field electrogram in sinus rhythm. That is, while they may be separated from the far-field signal by an isoelectric line and extend beyond the end of the surface QRS, they may also appear fused or buried within the QRS. We sought to characterize LAVA with regard to their locations.Methods: We studied 44 patients (ischemic cardiomyopathy: 28, non-ischemic dilated cardiomyopathy:16) who underwent mapping and ablation of scar-related VT with 3D electro-anatomic mapping system. Among a total of 31,059 electrograms mapped during sinus rhythm, 1,364 LAVA (endocardium: 846, epicardium: 518) were identified and analyzed.Results: The interval from surface QRS-onset to local electrogram onset (EGM-onset) was longer in the postero-lateral endocardium (18ms [11ms, 26ms]) and in the epicardium (27ms [18ms, 36ms]) than in the antero-septal endocardium (1ms [-8ms, 10ms]). LAVA lasting beyond the surface QRS-end were common in the epicardium (485/518 [94%]), while they were less likely to be found in the antero-septal endocardium (182/344 [53%]). There was a significant positive correlation between timing of EGM-onset and LAVA lateness as estimated by the interval from surface QRS-onset to LAVA-end (r=0.44, p<0.001).Conclusion: The lateness of LAVA is affected by their locations, primarily owing to the timing of the activation wavefront in sinus rhythm. In the endocardial septal scar, ventricular pacing maneuvers may frequently be needed to separate the ‘‘non-

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RFCA failed.Methods: The records of 28 consecutive pts with rTOF who underwent RFCA of VT from two centres were reviewed. Ablation targeted anatomical isthmuses containing VT re-entry circuits identified by 3D substrate, pace and/or entrainment mapping. A left-sided approach was considered appropriate if (1) RFCA from the right ventricular side failed to prevent VT induction and/or isthmus transection and/or VT recurrence, (2) part of the circuit was located in the LV or aortic root and (3) RFCA on the left side prevented VT induction and recurrence. Complete procedural success was defined as non-inducibility of any VT and transection of the isthmus.Results: In four of 28 pts with rTOF right-sided RFCA failed and left-sided RFCA was required. These pts (52±13 years, 75% male) were inducible for 2.0±1.4 VTs with a cycle length of 328±46 msec. In 3 pts, diastolic activity and/or concealed entrainment could be demonstrated in the aortic root. RFCA at that site terminated VT and prevented VT induction in all 3. In the fourth pt with heart failure and a biventricular ICD, a good pace map was found in the LV just above the VSD patch with recording of diastolic activity during VT. RFCA at that spot prevented VT induction but resulted in complete heart block. The critical isthmus could likely not be transected from the right side due to hypertrophy in 2, the pulmonary homograft in 1 and the VSD patch in 1. The left-sided approach resulted in complete procedural success and prevention of VT recurrence during follow-up (20±16 months) in all. However the fourth pt received one ICD shock for VF.Conclusion: Successful RFCA of VT in rTOF targeting anatomical isthmuses bordering on the septum required a left sided approach in 14% of the pts. However, the proximity of the specific conduction system needs to be considered.

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PREDICTORS OF DIFFICULT ELIMINATION OF LOCAL ABNORMAL VENTRICULAR ACTIVITIES IN ISCHEMIC AND NON-ISCHEMIC VENTRICULAR TACHYCARDIAYuki Komatsu, MD, Frédéric Sacher, MD, Hubert Cochet, MD, Matthew Daly, MD, Laurence Jesel, MD, Nicolas Derval, MD, Amir Jadidi, MD, Ashok Shah, MD, Isabelle Nault, MD, Patrizio Pascale, MD, Laurent Roten, MD, Daniel Scherr, MD, Arnaud Denis, MD, Khaled Ramoul, MD, Stephan Zellerhoff, MD, Mélèze Hocini, MD, Michel Haïssaguerre, MD and Pierre Jaïs, MD. CHU Bordeaux, Hôpital du Haut-Lévêque, Bordeaux, FranceIntroduction: The elimination of local abnormal ventricular activities (LAVA) yields superior survival free from recurrent ventricular tachycardia (VT) or death during long-term follow-up. However, their complete abolition is sometimes challenging. The aim of this study was to identify factors predicting difficult-to-eliminate LAVA in patients with VT due to ischemic cardiomyopathy (ICM) and non-ischemic dilated cardiomyopathy (NICM).Methods: We studied 85 consecutive patients (ICM=58, NICM=27) who underwent VT ablation with the goal and ideal endpoint of complete elimination of LAVA. The relative difficulty of LAVA elimination was assessed according to the radiofrequency (RF) duration required to achieve it.Results: LAVA was ablated with an average RF duration of 29±17 min. Electrophysiologic variables were compared between patients with complete LAVA elimination using RF<30min (group1, n=27 [ICM=19, NICM=8]) and patients with LAVA elimination requiring RF>30min or incomplete elimination (group2, n=58 [ICM=39, NICM=19]). No significant difference was found in the difficulty in LAVA elimination between ICM and NICM. Scar size, assessed in 28 ICM patients who underwent

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ELIMINATION OF ABNORMAL ELECTROGRAM-BASED ABLATION STRATEGY: COULD IT YIELD BETTER OUTCOME IN SCAR-RELATED RIGHT VENTRICULAR OUTFLOW TRACT ARRHYTHMIAS?Fa-Po Chung, MD, Yenn-Jiang Lin, MD, Li-Wei Lo, MD, Shih-Lin Chang, MD, Yu-Feng Hu, MD, Tze-Fan Chao, MD and Shih-Ann Chen, MD, PHD, FHRS. Taipei Veterans General Hospital, Taipei, TaiwanIntroduction: Abolition of late potential activity provided favorable outcome in dilated cardiomyopathy and ischemic ventricular tachycardia(VT). Abnormal electrograms(Eg), including fragmented and late signals, could be identified in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and predict further arrhythmic events. The study aimed at clarification prognostic value of abnormal electrograms-based ablation strategies in patients with scar-related RVOT ventricular arrhythmias.Methods: A total of 97 consecutive patients(mean age 44.4±12.7, 30 male, 51 definite ARVC, 12 borderline ARVC, 34 possible ARVC) undergoing catheter ablation for right ventricular outflow tract arrhythmias[41(53.9%) for VT, 35(46.1%) for ectopy] were consecutively enrolled and categorized into two groups: 31 patients(40.8%, group 1) with and 45(59.2%, group 2) without completely abnormal Eg(fragmented or late potentials after QRS during sinus rhythm) abolition. High density electroanatomic mapping (EAM) was obtained in all patients. Abnormal Egs were explored for analysis. End points was defined as recurrence of VT or ventricular ectopy>500 beats/day.Results: Baseline characteristics were similar between two groups. Of 97 EAMs, scar(<0.5 mV) or low voltage zone(<1.5 mV) were identified in all patients. Fragmented Egs were present in 51 patients(52.6%) and late potentials in 21 patients(21.6%). Endocardial ablation was performed in 96 patients(30 in group 1 and 45 in group 2) and epicardial approaches for 3 patients(3 in group 1). After a mean follow-up of 15.0±5.5 months, a total of 20 patients(20.6%) documented recurrences[3(3.1%) with VT recurrence and 17(17.5%) with recurrence of ventricular ectopy], including 4 (12.9%) in group 1 and 16 (35.6%) in group 2 (p=0.04). After multivariate analysis, completely abolition of abnormal electrograms prevented further recurrences (p=0.048, Hazard ratio:0.33, 95% CI:0.11~0.99).Conclusion: Completely elimination of abnormal Egs within RVOT in RV cardiomyopathy provided favorable prognosis. Ablation based on abnormal Egs within scar/low voltage zone could be one useful strategy for further clinical application in patients with scar-related RVOT ventricular arrhythmias.

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LEFT-SIDED ABLATION OF VENTRICULAR TACHYCARDIAS IN ADULTS WITH REPAIRED TETRALOGY OF FALLOT: A CASE SERIESGijsbert F. Kapel, MD, Tobias Reichlin, MD, PhD, Adrianus P. Wijnmaalen, MD, PhD, Usha B. Tedrow, MD, Sebastiaan R. Piers, MD, Martin J. Schalij, MD, PhD, William G. Stevenson, MD, PhD and Katja Zeppenfeld, MD, PhD. Leiden University Medical Center, Leiden, Netherlands, Brigham and Women’s Hospital Boston, Boston, MAIntroduction: Radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in patients (pts) with repaired Tetralogy of Fallot (rTOF) is a favourable option. However, the critical isthmus of VT in rTOF may be difficult to transect due to hypertrophied myocardium or prosthetic material. A left-sided approach might be required in patients in whom right-sided

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Tedrow, MD, William G. Stevenson, MD and Roy M. John, MD. Brigham and Women’s Hospital, Boston, MAIntroduction: Idiopathic ventricular arrhythmias originating from the left ventricular outflow tract (LVOT) are a frequent cause of symptoms. Successful ablation can be limited by proximity to coronary arteries or inaccessibility. Reasons for failures and their frequency are not well described.Methods: A consecutive series of 69 patients undergoing mapping/ablation procedures at a tertiary referral center for idiopathic ventricular arrhythmias originating from the LVOT region were analyzed. Mapping of both outflow tracts, the coronary venous system and the aortic root were performed. Procedural success was defined as absence of any arrhythmia following ablation, while procedural failure included patients with unaffected or only reduced arrhythmias as well as patients in whom no ablation was performed at all.Results: Median age of the patients was 53 years, 58% were male and the median EF was 55%. A prior ablation attempt had failed in 33/69 patients (48%). Acute success was achieved in 42 patients (61%) and failure occurred in 27 patients (39%). Failure was due to close proximity to a coronary artery in 14/27 pts (52%), a deep inaccessible origin in 10/27 pts (37%), proximity to the phrenic nerve in 1/27 pts (4%) and mixed reasons in 2/27 pts (7%). After catheter ablation failure, 3 highly symptomatic patients (two with an origin too close to a coronary artery and one with an origin in an inaccessible area) subsequently underwent successful surgical cryoablation. Coronary artery injuries occurred in 2 (4%) patients: occlusion of a diagonal branch from catheter RF ablation in the Great Cardiac Vein; and LAD stenosis presenting as angina 12 weeks after surgical cyroablation.Conclusion: In this referral population, catheter ablation failed in 39% of LVOT arrhythmias, largely due to anatomic obstacles. Surgical cryoablation is an option after failed catheter ablation, but coronary injury can still occur.

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AN EXTREMELY LOW VOLTAGE AREA-TARGETED ENDOCARDIAL LINEAR ABLATION CAN SUPPRESS POSTINFARCTION VENTRICULAR TACHYCARDIA IN THE LONG TERM: RESULTS OF THE MULTICENTER J-PIVT-STUDYKenji Kuroki, MD, Yukio Sekiguchi, MD, Kazutani Kaitani, MD, Takashi Koyama, MD, Masayuki Igawa, MD, Junichi Nitta, MD, Yasuteru Yamauchi, MD, Takeshi Machino, MD, Yoko Ito, MD, Hiro Yamasaki, MD, Dongzhu HU, MD, Miyako Igarashi, MD, Nobuyuki Murakoshi, MD and Kazutaka Aonuma, MD. University of Tsukuba, Tsukuba, Japan, Tenri Hospital, Tenri, Japan, University of Akita, Akita, Japan, Tsukuba Memorial Hospital, Tsukuba, Japan, Saitama Red Cross Hospital, Saitama, Japan, Musashino Red Cross Hospital, Tokyo, JapanIntroduction: Several substrate guided ablation methods for postinfaction ventricular tachycardia (VT) have been recently advocated. Some aggressive ablation strategies including epicardial approach in high volume centers have demonstrated relatively good outcome. However, we hypothesized that the low invasive strategy targeting an extremely low voltage area in the endocardium can be feasible particularly in postinfarction ventricular tachycardia.Methods: Catheter ablation (CA) was performed in 56 consecutive patients (65±9 years old, 4 female) with post-infarction VT in 6 Japanese institutions. VT storm was present in 27 patients (48%). Left ventricular ejection fraction measured 36±11 %. Strict voltage criteria of an electroanatomical mapping were defined as: non-arrhythmogenic area, >0.6 mV; low voltage area (LVA), >0.1 to ≤0.6 mV; scar, ≤0.1 mV. Using these criteria,

electro-anatomic mapping, was smaller in group1 than in group2 (66±34cm2 vs. 106±52cm2, p<0.05), while it was comparable in NICM between the groups (47±25cm2 vs. 41±22cm2, p=NS). There was a significantly lower prevalence of septal scar in group1 than in group2 (2/27 [7%] vs. 21/58 [36%]).Conclusion: Larger scars are associated with difficult LAVA elimination in ICM, but not in NICM. The successful ablation of predominantly septal substrate is a challenge in both ICM and NICM, suggesting the possible presence of intramural substrate.

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LOCALIZATION AND ABLATION OF VENTRICULAR ARRHYTHMIAS IN BILEAFLET MITRAL VALVE PROLAPSE SYNDROMEChenni S. Sriram, MBBS, Michael J. Ackerman, MD, PhD, Faisal F. Syed, MBChB, Rick A. Nishimura, MD, Samuel J. Asirvatham, MD and Bryan C. Cannon, MD. Mayo Clinic, Rochester, MNIntroduction: The specifics about ventricular ectopy (VE) and potential for ablation in patients (pts) with the recently described arrhythmogenic bileaflet mitral valve prolapse (bi-MVP) syndrome are unknown. Females with bi-MVP, complex VE, and abnormal T waves represent the syndrome tetrad. We hypothesized that mechanical irritation stemming from bi-MVP on adjacent ventricular structures is arrhythmogenic.Methods: We retrospectively reviewed our ablation experience (1/06-11/12) in bi-MVP syndrome pts with symptomatic VE refractory to medications.Results: Seven females with bi-MVP syndrome (median age 31[24-67] yrs, ejection fraction 64%[45-67]) underwent electrophysiology study with characterization of dominant and/or ventricular fibrillation-triggering VE. All pts had a high VE burden on Holter (median PVC/hour 5245[728-31335], ventricular tachycardia or VT episodes 24[1-54]). Four pts with a prior ICD had received multiple appropriate shocks (3[2-20]). VE was mapped to left ventricular papillary muscle/fascicles in all and included anterior (n=2) and posterior-septal fascicles (n=2) as well as anterolateral (n=3) and posteromedial (n=4) papillary muscles. Fascicular pre-potentials always preceded fascicular ectopy and were noted in 4/7 sites of papillary muscle PVCs. The substrate specifically included the conduction tissue in proximity to papillary muscle. 3/7 pts had concurrent ablation of right (n=2) and left (n=1) ventricular outflow tract ectopy. Over a median follow-up of 15[1-65] months, 6/7 pts reported minimal/ no symptoms. Follow up Holter on 5 pts showed a trend towards decreased VE (median PVC/hour 1687[483-10960] p= 0.06, VT episodes 0[0-5]). None experienced ICD shocks.Conclusion: The arrhythmic substrate in bi-MVP syndrome appears to originate in both conduction tissue and myocardium related to papillary muscle as well as outflow tract. Myocardial PVCs although common, may result in malignant arrhythmias with fascicular involvement. Outflow tract ectopy is a feature of this syndrome and may stem from the outflow tract papillary muscle. Ablation here may be necessary to prevent malignant ventricular arrhythmias. Ablation is feasible for reducing ICD shocks and can be guided by fascicular prepotential mapping of ectopic beats in most case

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FAILURE OF CATHETER ABLATION FOR IDIOPATHIC ARRHYTHMIAS FROM THE LV OUTFLOW TRACT: FREQUENCY, REASONS AND SURGICAL OPTIONSTobias Reichlin, MD, Michifumi Tokuda, MD, Koichi Nagashima, MD, Eyal Nof, MD, Justin Ng, MD, Chirag Barbhaiya, MD, Gregory F. Michaud, MD, Bruce A. Koplan, MD, Usha B.

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T-WAVE ALTERNANS IS USEFUL FOR PREDICTING ADVERSE OUTCOMES OF HOSPITALIZED PATIENTS WITH HEART FAILUREShinya Yamada, MD, Hitoshi Suzuki, MD, Takashi Kaneshiro, MD, Yoshiyuki Kamiyama, MD, Shu-ichi Saitoh, MD and Yasuchika Takeishi, MD. Department of Cardiology and Hematology Fukushima Medical University, Fukushima, JapanIntroduction: The impairment of autonomic nervous control is associated with worsening heart failure (HF). However, the clinical significance of ventricular repolarization abnormality has not been fully elucidated in worsening HF. Thus, we investigated the association between ventricular repolarization abnormality by using T-wave alternans (TWA) and worsening HF.Methods: We studied 89 chronic HF patients (60 males, mean age 66 years) with reduced left ventricular ejection fraction (<45%) by echocardiography. All patients were hospitalized for the treatment of acute decompensated HF. After optimal medications, electrocardiogram (QRS duration and QTc interval) and Holter monitoring (heart rate variability, heart rate turbulence and TWA) were performed. Positive TWA was defined as over 65 μV. During follow-up period (10.8 ± 6.6 months), re-hospitalization due to worsening HF or cardiac death (cardiovascular events) occurred in 18 patients (20%). All subjects were divided into two groups based on whether cardiovascular events occurred (n=18, Group-A) or not (n=71, Group-B). Parameters from echocardiography, electrocardiogram and Holter monitoring were compared between the two groups. We then investigated the relationship between these measured parameters and the incidence of cardiovascular events.Results: The ratio of positive TWA was significantly higher in Group-A than in Group-B (83% vs. 41%, P<0.01). In heart rate variability, standard deviation of all R-R intervals (SDNN) and standard deviation of the 5-min mean R-R intervals (SDANN) were significantly lower in Group-A than in Group-B (SDNN, 75.6 ± 35.6 ms vs. 100.1 ± 35.8 ms; SDANN, 67.4 ± 34.5 ms vs. 86.6 ± 32.4 ms, P<0.05, respectively). Multivariate Cox proportional hazards analysis identified positive TWA as an only independent predictive factor for future cardiovascular events (odds ratio 11.4; 95% confidence interval, 1.13-114.7; P<0.05).Conclusion: These results suggest that ventricular repolarization abnormality rather than the impairment of autonomic nervous control might be a more effective predictor of future cardiovascular events in chronic HF. Thus, TWA is useful for the risk stratification of chronic HF patients.

CA targeted every possible arrhythmogenic region inside the LVA (≤0.6 mV). Linear ablation inside the LVA was repeated until VT inducibility was suppressed to a maximum extent. An epicardial approach was not attempted in all patients. Patients were classified into 3 groups according to the acute results of CA: Compete success (CS; any VT was not inducible, n=34), Partial success (PS; clinical VT was not inducible, n=19), and Failure (n=3).Results: During mean follow-up of 31±28 months, Kaplan-Meiyer VT-free survival rate after 1st CA procedure was 96, 90, 68% at 1,2, and 5 years. VT-free survival rate depended on VT inducibility just after ablation with the CS group the highest, followed by the PS and Failure group in this order (p=0.0005 for the log-rank test). 2nd CA procedure was performed 8 of 10 patients with recurrences. VT-free survival rate after mean 1.1±0.4 CA procedure was 100, 97, 92% at 1,2, and 5 years.Conclusion: An extremely low voltage area-targeted linear ablation was an effective therapy for postinfarction ventricular tachycardia at long-term follow up. In postinfarction patients, ventricular tachycardia is curable from endocardial site using this method, although some of them need repeated procedures.

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HIGH FREQUENCY STIMULATION (HFS) OF PULMONARY ARTERY FOR THE INDUCTION OF IDIOPATHIC RVOT VPC/VTMinseok Choi, MD, Sung-Hwan Kim, MD, Tae-Seok Kim, MD, Woo-Seung Shin, MD, Ji-Hoon Kim, MD, Sung-Won Jang, MD, Yong-Seog Oh, MD, PhD, Man Young Lee, MD, PhD and Tai-Ho Rho, MD, PhD. Sun General Hospital, Dea-Jeon, Republic of Korea, The Catholic University College of Medicine, Seoul, Korea, Seoul, Republic of KoreaIntroduction: Catheter ablation has been used to cure for symptomatic VPC. However, in some patients with RVOT VPC, clinical VPC rarely occurs in the EP lab and ablation cannot be done on those patients. High frequency stimulation (HFS) has been used for the induction method of RVOT VT in animal model, so, we hypothesized HFS might induce clinical VPC in humans and systematically evaluated the effects of HFS.Methods: In the EP lab, clinical VPC was recorded before the insertion of diagnostic catheters in 6 patients with symptomatic RVOT VPC. Voltage mapping of RVOT and pulmonary artery(PA) was done with Carto3 and was merged with CT image. PA was divided into 5 portions(Anterior: left, distal, and proximal PA; Posterior: left, and proximal PA), and HFS was performed for the induction of clinical VPC with Navistar SF catheter connected to Grass S48 Stimulator(5V, 10V, and 15V in each site; Duration: 5000ms).Results: HFS was performed in 6 patients with the total 113 sites of PA(Anterior: left(24), distal(34), and proximal PA(27); Posterior: left(9), and proximal PA(19)). No response was observed in 5V of HFS. Ventricular and Atrial arrhythmias were developed at above 10V of HFS. Clinical VPC was not induced but non-clinical VPC/VT were observed in 2 patients at the anterior proximal part of PA. Atrial arrhythmias(APC, AT, and AF) were shown during/right after HFS at the posterior proximal part of PA in all 6 patients. Also, hiccup response was seen in 6 patients at posterior left PA.Conclusion: HFS is not a useful method for the induction of clinical VPC. Non clinical VPC/VT could be induced at the anterior proximal part of PA and atrial arrhythmia(APC, AT, and AF) would be inducible in posterior PA area.

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HETEROGENEITY OF VENTRICULAR REPOLARIZATION IN PATIENTS WITH END STAGE RENAL DISEASE AND RENAL REPLACEMENT THERAPYAhmed K. Talib, IV, MD, PhD, Nobuyuki Sato, MD, PhD, Junko Chinda, MD, Kazutoshi Abe, MD, Naoki Nakagawa, MD, Tomoya Hirayama, MD, Takayuki Fujino, MD, Yuichiro Kawamura, MD, PhD, Jun Maruyama, MD and Naoyuki Hasebe, MD, PhD. Asahikawa Medical University, Asahikawa, Japan, Asahikawa Rehabilitation Hospital., Asahikawa, Japan, Kitasaito Hospital, Asahikawa, JapanIntroduction: Patients with end stage renal disease (ESRD) who undergo hemodialysis (HD) and peritoneal dialysis (PD) are at great risk for sudden cardiac death (SCD). Several factors are known to predispose ESRD patients to SCD such as volume overload, electrolyte abnormalities and importantly, substrate changes that alter the repolarization properties. Recently, important ventricular repolarization parameters such as the T-wave peak to end interval (Tp-e), Tp-e/QT ratio and QT/RR slope have been considered as useful markers for repolarization instability.Methods: After excluding those with organic heart disease (OHD), atrial fibrillation, atrioventricular block, and wide QRS complexes, we identified 111 subjects; 18 patients with HD, 13 PD patients, and 80 healthy controls (C). Ambulatory ECG-derived parameters including the QT,Tp-e interval, Tp-e/QT ratio and QT/RR slope were calculated and statistically compared.Results: Although there was no significant difference in the heart rate and QT interval among the groups, the Tp-e interval, and Tp-e/QT ratio were significantly increased in the HD and PD groups compared to that in the C group. Similarly both the QTapex/RR and QTend/RR slopes were significantly large in the HD and PD groups (Table).Conclusion: (1) Even in the absence of OHD, the novel markers of repolarization heterogeneity, Tp-e and Tp-e/QT, were significantly increased in the ESRD patients indicating an enhanced transmural dispersion of repolarization. (2) An abnormal QT adaptation to heart rate changes in the ERSD patients, reflecting changes in the myocardial vulnerability, may contribute to the increased risk of arrhythmic events and SCD in such a high risk cohort of patients.

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IMPAIRED VENTRICULAR REPOLARIZATION DYNAMICS IN EARLY REPOLARIZATION SYNDROME: AN INSIGHT INTO THE PATHOPHYSIOLOGY OF SUDDEN CARDIAC DEATHAhmed K. Talib, IV, MD, PhD, Nobuyuki Sato, MD, PhD, Muhib Sharifi, MD, Makoto Aita, MD, Naoko Kawabata, MD, Akira Asanome, MD, Ayumi Date, MD, Eitaro Sugiyama, MD, Takeshi Nishiura, MD, Naka Sakamoto, MD, Hisanobu Ota, MD, Yasuko Tanabe, MD, Toshiharu Takeuchi, MD, Kazumi Akasaka, MD, Yuichiro Kawamura, MD, PhD and Naoyuki Hasebe, MD, PhD. Asahikawa Medical University, Asahikawa, JapanIntroduction: Almost all current investigations on early repolarization syndrome (ERS) have focused on the J-wave characteristics and ST-segment configuration; however, few have reported on ventricular repolarization indexes in ERS. On the other hand, contemporary data has shown the peak incidence of sudden cardiac death (SCD) in ERS patients is at night from 0-6 A.M.Methods: A total of 145 subjects were enrolled: 10 ERS patients with history of aborted SCD, 45 uneventful ER pattern (ERP) subjects and 90 healthy controls without J-waves or ST-segment elevation. Ambulatory ECG-derived parameters (QT, QTc(B), QTc(F), and QT/RR slope) were measured and statistically compared.Results: Among the groups, there was no significant difference in the average QT and QTc(B); however, ERS patients had the shortest QTc(F). Importantly, the 24-hour QT/RR slope was significantly smaller in the ERS than ERP and control groups. When analyzing the diurnal and nocturnal QT/RR slopes, ERS patients had small diurnal and nocturnal QT/RR slopes while the ERP and control groups had large diurnal and small nocturnal QT/RR slopes. Moreover, intra-nocturnal analysis showed the lowest QT/RR slopes were from 0-6 A.M (Table 1).Conclusion: (1) In contrast to uneventful ERP subjects, ERS patients had a continuously depressed diurnal and nocturnal adaptation of the QT interval to the heart rate. Such abnormal repolarization dynamics might provide a substrate for reentry and be an important element for developing ventricular fibrillation in the ERS cohort. (2) Importantly, the QT/RR maladaptation was most evident at midnight which may explain the propensity of ERS patients to develop SCD during this critical period.

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43.5±12.8; 50 male, 33.1%) underwent an RFCA for RVOT VA successfully were consecutively enrolled. Pre-ablation, 6-month and yearly post-ablation 24-hour Holter examinations were obtained free from antiarrhythmic drugs. Recurrence was defined by progressive increasing in premature ventricular complexes (PVC) >10% of total daily beats (TDB) or the presence of ventricular tachycardia (VT) clinically. The characteristics of ventricular arrhythmias of 6-month Holter examination were explored for further analysis.Results: Of 151 patients, 96 patients (63.6%) received ablation for VT and 55 (36.4%) for symptomatic PVCs. During a mean follow-up duration of 50 months (11-160), 56 of 151 patients (37.1%) had recurrences of ventricular arrhythmias, including 21 (13.9%) with recurrent VT and 35 (23.2%) with recurrent PVCs. Baseline characteristics of patients with and without recurrences were similar. For recurrent patients, mean PVC burden before RFCA (30.6±14.6% per day) decreased to (2.2±3.0% per day, and returned to 28.5±19.1% (at median follow-up of 31.7±8.3 months, P<0.001). After multivariate Cox logistic regression analysis, PVC burden within 6 months predicted further progressive very long-term recurrence (p<0.001, HR: 68.4, 95%CI: 16.5~282.8) with a cut-off value of PVC burden>0.42% (sensitivity 96.7%, specificity 97.2%) or 484 beats/day (sensitivity 98.3%, specificity 98.1%).Conclusion: There is a wide variation of recurrence state one year after catheter ablation of RVOT VA. Even with short-term successful ablation results, late recurrences of ventricular arrhythmias ensued 6 months after ablation. The 6-month Holter monitoring with PVC burden >0.42% of total daily beats or 484 beats per day predicts late recurrence.

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COMPARISON BETWEEN FLECAINIDE AND AJMALINE CHALLENGE IN BRUGADA SYNDROME PATIENTS.Vincent Probst, MD, Frederic Sacher, MD, Philippe Mabo, MD, Jean-Baptiste Gourraud, MD, Jacques Mansourati, MD, Dominique Babuty, MD and Herve le Marec, MD. l’institut du thorax, Nantes, France, Nantes, France, Service De Rythmologie, CHU De Bordeaux, Bordeaux, France, Service De Rythmologie, CHU De Bordeaux, Rennes, France, l’institut du Thorax, Nantes, France, Nantes, France, Service De Rythmologie, CHU De Bordeaux, Brest, France, Service De Rythmologie, CHU De Bordeaux, Tours, FranceIntroduction: Flecainide and ajmaline challenges are used to unmask the aspect of Brugada syndrome. There is no direct comparison of the electrocardiographic modification induced by these two drugs in the large population of patients. These two drugs are used in our reference center which allows a comparison of results.Methods: Injections are performed by continuous infusion over a period of 10 minutes at 1mg/kg dose for ajmaline and 2 mg / kg for flecainide. Tests were performed in case of absence of type 1 aspect on the resting ECG and in absence of major conduction defectsResults: The flecainide test (F) was performed in 412 patients and ajmaline test (A) in 311. Mean age was 41 +/-16 years and 42 F +/- 16 years in A (p = 0.2) and there was 194 women in group F (47%) vs 152 in group A (48%), NS. All patients were in sinus rhythm in both groups. Heart rate was similar 70 + / - 12 vs 71 + / - 12 bpm (p = 0.17). There was no difference between the two groups for heart rate 70+/-12 vs 71+/-13 bpm (p=0.17), PR 161 +/- 28 ms vs 162 +/-29 ms (p=0.63), QRS 95 +/-20 ms vs 96+/-13 ms (p= 0.94). The QTc appears to be longer in the F than in the A group 409+/-29 vs 418+/-28 ms (p<0.001). During the test, HR increase in both groups 74 +/- 12 vs 78 +/- 12 bpm but the increase was more pronounce in A (p< 0.001).

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ECG-BASED SCREENING OF YOUNG ATHLETES OF A FIRST DIVISION BELGIAN SOCCER TEAMBenjamin Berte, MD, Juliana Elices, MD, Liesbeth Timmers, MD, Frederic Van Heuverswyn, MD, Roland Stroobandt, MD, PhD, Ann Neyrinck, MD, Jan De Neve, MD, Yves Vandekerckhove, MD, Rene Tavernier, MD, PhD and Mattias Duytschaever, MD, PhD. AZ Sint Jan hospital, Brugge, Belgium, University hospital UZ Ghent, Ghent, Belgium, AZ Sint Lucas hospital, Bruges, BelgiumIntroduction: We analysed (1) the feasibility, (2) time, (3) cost and (4) reproducibility of ECG-based screening protocols in the youth division (<18 years) of a first division soccer team.Methods: We prospectively screened 138 male athletes (median age 14yrs [IQR12-16], Caucasian n=98, Black African n=24, Maghrebian n=11) using: (1) the AHA-questionnaire (QST), (2) a physical examination (PE), and (3) an ECG. The ECG was categorized as normal/abnormal by a panel (BB, MD, RT) according to ESC 2010 criteria according to Corrado et al in European Heart Journal (E) or the 2011 recommendations by Uberoi et al in Circulation (U). In case of any abnormality, further disease specific examinations were performed. We calculated the time spent by the health care providers and the cost for society. In addition all ECGs were categorised by 6 other cardiologists according to the ESC 2010 criteria.Results: Out of 138 young athletes, 29 (21%) had abnormal findings: QST=5 (positive familial history n=4, palpitations n=1), PE=8 (cardiac murmur ≥2/6 in all) and ECG=18 (13%) [E n=13 (9.5%); U n=15 (11%)] with following abnormalities: T wave inversion=9 (E n=7; U n=8), pathologic Q waves=4 (E n=2; U n=4), RVH=2 (E n=2; U n=0), LAHB =1 (E n=1; U n=1), ST depression=2 (E n=2; U n=2) and pre-excitation=1. Except for the asymptomatic intermittent pre-excitation, no pathology was found. Nobody was excluded from further sport participation. The total time spent for screening was 69,5 hours (30min/athlete), the total cost was 10031€ (72,7 €/athlete). Out of 138 ECGs, 97 were classified as normal and 3 as abnormal by all cardiologists; in 38 ECGs there was disagreement (27.5%).Conclusion: At a club level, ECG-based screening in young athletes is feasible and affordable. In very young athletes (<18 yrs) we did not observe a reduction in ECG abnormalities using the Uberoi recommendations compared to the 2010 ESC criteria. Furthermore, there is a low reproducibility in the ECG interpretation of young athletes. These data add up to the general concern that ECG-based screening is of limited value in screening for sudden cardiac death in young athletes.

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LONG-TERM RECURRENCE OF RIGHT VENTRICULAR OUTFLOW TRACT VENTRICULAR ARRHYTHMIAS AFTER CATHETER ABLATION: PROGNOSTIC VALUE OF HOLTER EXAMINATION DURING LONGITUDINAL FOLLOW-UPFa-Po Chung, MD, Yenn-Jiang Lin, MD, Li-Wei Lo, MD, Shih-Lin Chang, MD, Yu-Feng Hu, MD, Tze-Fan Chao, MD, Satoshi Higa, MD and Shih-Ann Chen, MD, PHD, FHRS. Taipei Veterans General Hospital, Taipei, Taiwan, Division of Cardiovascular Medicine, Makiminato Central Hospital, Japan, JapanIntroduction: Radiofrequency catheter ablation (RFCA) was effective in elimination of right ventricular outflow tract (RVOT) tachycardia. However, long-term follow-up demonstrated high recurrence rate. Current study investigated the prognostic value of 24-hour Holter examination within 6 months after RFCA for RVOT VA during long-term follow-up.Methods: From 1999 to 2011, a total of 151 patients (mean age

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Seoul, Republic of Korea, Asan Medical Center, Seoul, Republic of KoreaIntroduction: Although apical hypertrophic cardiomyopathy (HCM) has been considered to be more benign than asymmetric HCM, there have been few studies that directly compare clinical features. We compared the electrocardiographic data and long-term outcomes between patients with apical HCM versus asymmetric HCM. Methods: This retrospective study enrolled 796 patients (243 apical HCM and 553 asymmetric HCM). We assessed long-term all-cause and cardiac mortalities using an inverse probability of treatment weighted (IPTW) method and propensity score matched (PSM) analysis.Results: In patients with asymmetric HCM, QT prolongation, QRS widening, PR prolongation and pathologic Q wave were significantly more frequent. The incidence of early repolarization were similar (11% in apical and 12% in asymmetric HCM, P=0.19). The median follow-up duration was 6.5 years. There was a borderline significant difference in overall survival rates between apical and asymmetric HCM groups (73% versus 69%, log rank P=0.38, IPTW: P=0.05, PSM: P=0.05). Regarding cardiac death, asymmetric HCM was more hazardous than apical HCM (89% versus 77%, log rank P=0.04, IPTW: P=0.03, PSM: P=0.03). There was no electrocardiographic predictor for the long-term outcomes.Conclusion: Abnormal electrocardiographic findings were more prevalent in patients with asymmetric HCM, but they had no long-term significance. The overall survival rate of apical HCM was as high as that of asymmetric HCM, but cardiac survival rate was significantly lower in patients with asymmetric HCM.

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PROCAINAMIDE CHALLENGE INDUCES ELECTROCARDIOGRAM CHANGES IN ALL PEDIATRIC SUBJECTSChristopher Jordan, MD, Charles I. Berul, MD, FHRS, Jeffrey P. Moak, MD and E. Anne. Greene, MD. Children’s National Medical Center, Washington, DCIntroduction: Brugada syndrome (BrS), marked by right precordial ST segment elevation and right bundle branch block (RBBB) on ECG, is difficult to diagnose in children. Presentations include sudden cardiac death (SCD), syncope, palpitations, asymptomatic with abnormal ECG, or family history of SCD. Procainamide (Proc) is a sodium channel blocker used to unmask the hallmark ECG seen with BrS. The current study analyzes the first exclusively pediatric case series of Proc challenge for diagnosis of BrS.Methods: This is a retrospective review of children <20 years undergoing Proc challenge (10-15mg/kg). Investigators blinded to clinical diagnoses analyzed and measured ECGs.Results: 9/37 patients (24%) had positive Proc response consistent with BrS. Patients undergoing Proc infusion had prolongation of PR (mean +14%; 0-45%), QRS (+13%; 2-49%) & QTc (+15%; 4-30%) intervals. QTc >460 occurred in 21/29 (72%) negative tests and 8/9 (89%) positive tests. Right precordial ST elevation in patients with a positive test averaged +0.12mV. No differences in intervals occurred between positive

There was no difference for PR 190 +/- 33 ms vs 187 +/- 36 ms (p=0.4) and QRS 114 +/-20 ms vs 115+/-23 ms (p= 0.35). The QTc remains longer in the A than in the F group 451+/-33 vs 438+/-34 ms (p<0.001). The number of positive tests F 123/412 (30%) vs 121/311 (39%) were slightly higher in A group even if this difference was not significant. During the tests arrhythmic complications were rare (VPBs 5vs 2 and VT 1 vs 3).Conclusion: In this large population of patients, the results of Flecainide and Ajmaline challenge are similar for conduction parameters and risk of ventricular arrhythmias. The proportion of positive tests seems slightly higher in the A group.

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QUANTIFICATION OF LOW AMPLITUDE QRS FRAGMENTATION RELATES TO MYOCARDIAL SCAR SIZE AND PREDICTS ARRHYTHMIC EVENTS IN PATIENTS WITH CARDIOMYOPATHYMoloy Das, MBBS, Adrian M. Suszko, MSc, Feng Jin, PhD, Sridhar Krishnan, PhD and Vijay S. Chauhan, MD, FRCP. Toronto General Hospital, Toronto, ON, Canada, Ryerson University, Toronto, ON, CanadaIntroduction: QRS fragmentation (fQRS) is currently assessed qualitatively from visually apparent, large amplitude peaks but its prognostic utility has been inconsistent in patients with cardiomyopathy (CM). We hypothesized that narrow, lower amplitude peaks may provide a better definition of arrhythmogenic substrate by reflecting small regions of aberrant conduction. Our aim was to quantify fQRS in patients with CM and relate it to (i) heterogeneous gray-zone scar and (ii) arrhythmic events.Methods: We prospectively studied 40 patients (61±10 years, LVEF 28±7%) with ischemic (n=24) or dilated (n=16) CM receiving ICDs. Signal intensity thresholding was used to quantify core and gray-zone scar (as a % of LV mass) from late gadolinium enhanced MRI images. Precordial lead ECG recordings were taken post-implant during sinus rhythm and V pacing at 100bpm and 110bpm. The degree of fQRS for each lead (fVn) was defined by automatically detecting the number of positive peaks of <15ms duration within the QRS complex of the de-noised ECG. Patients with arrhythmic events (cardiac arrest, sustained VT or appropriate ICD therapy) were identified.Results: In sinus rhythm, fV3 correlated with both core% (r=0.44, p=0.006) and gray-zone% (r=0.35, p=0.031). During V pacing at 100bpm, fV4 correlated solely with gray-zone% (r=0.41, p=0.008). This relationship improved at 110bpm (r=0.62, p=0.004). Arrhythmic events were seen in 7 patients (18%) at 30±14 months follow-up. Mean fV4 during V pacing was higher in patients with events compared to those without (2.9±1.2 vs 1.5±1.1, p=0.008). fV4 was the only independent predictor of events in a multivariate logistic regression model that included fV4, gray-zone%, age, LVEF and intrinsic QRS duration (Odds Ratio 2.30, 95% CI 1.12-4.69, p=0.023).Conclusion: In patients with CM, fV4 during V pacing is associated with heterogeneous gray-zone scar, particularly at higher rates. For each peak detected, the risk of arrhythmic events independently increases 2.3-fold. This novel risk marker may reflect localized regions of delayed conduction which increase arrhythmia vulnerability.

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LONG-TERM COMPARISON OF APICAL VERSUS ASYMMETRIC HYPERTROPHIC CARDIOMYOPATHYSung-Hwan Kim, MD, Yong-Seog Oh, MD, PhD, Ki Won Hwang, MD, Gi-Byoung Nam, MD, PhD, Kee-Joon Choi, MD, PhD and You-Ho Kim, MD, PhD. Seoul St. Mary’s Hospital, Cardiology,

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SD TTP* ≥ 60 ms (dyssynchronous)

11 (38% of total) 2 (7%)

SD TTP < 60 ms (non-dyssynchronous) 1 (3%) 15 (52%) <0.01

*Standard deviation of the time to peak

Conclusion: Significant LV activation delay, by the classic pattern, was frequently identified in this healthy VP population and was associated with LV dysfunction and longer QRS duration, but not with pacing site or duration. LV dysfunction was surprisingly common and weakly correlated with pacing duration.

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FLECAINIDE SAFETY AND TRENDS IN USE IN PEDIATRIC PATIENTS WITH CONGENITAL HEART DISEASE OR CARDIOMYOPATHYJeffrey J. Kim, MD, Philip J. Lupo, Ph.D (c), MPH, Santiago O. Valdes, MD and Brady S. Moffett, PharmD. Texas Children’s Hospital, Houston, TXIntroduction: Flecainide (FLEC) is frequently used for the treatment of cardiac arrhythmias in children. Due to extrapolation of data from the Cardiac Arrhythmia Suppression Trial finding increased mortality in adults receiving FLEC after myocardial infarction, there has been hesitancy to use FLEC in children with congenital heart disease (CHD) or cardiomyopathy (CM). The purpose of this study was to describe trends in use of FLEC in children with CHD or CM and assess its possible association with cardiac arrest or death.Methods: Data from 42 freestanding children’s hospitals contained in the Pediatric Health Information System database from 2004 to 2011 were analyzed. All pts with CHD or CM receiving enteral antiarrhythmic therapy for supraventricular arrhythmias were reviewed. Trends in FLEC use in this population were analysed, and the incidence of cardiac arrest or death was compared to pts receiving other enteral antiarrhythmics.Results: During the study period, there were 3544 pts with CHD or CM who received enteral antiarrhythmic therapy (median age 73 days; IQR 1 day - 4.4 yrs). FLEC was administered in 231 pts (6.5%). There was a trend towards increased use of FLEC in this population over time, increasing from 4.6% in 2004 to 8.7% in 2011 (p=0.07). In those receiving FLEC, cardiac diagnoses included ASD or VSD in 57%, TGA in 6%, Ebstein’s anomaly in 6%, and TOF in 5%. Single ventricle physiology was noted in 4% and 15% had a diagnosis of CM. The incidence of cardiac arrest in pts with CHD or CM receiving FLEC was 3.0% with an overall mortality of 4.3%. The mortality was 2.9% in pts with CM and no pts with single ventricle physiology died. Based on multi-variate analysis, when compared to pts with CHD or CM receiving other anti-arrhythmics, there was no difference in the incidence of cardiac arrest (p= 0.31) or death (p=0.28).Conclusion: FLEC use in children with CHD or CM has increased in recent years. The incidence of cardiac arrest or death with FLEC administration in this cohort is comparable to other anti-arrhythmic agents that are commonly employed. This suggests that FLEC may be a safe alternative for treatment in this population.

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IN-HOSPITAL ARRHYTHMIA DEVELOPMENT AND OUTCOMES IN PEDIATRIC PATIENTS WITH MYOCARDITISChristina Y. Miyake, MD, Sarah Teele, MD, Liyuan Chen, BS, Kara S. Motonaga, MD, Anne M. Dubin, MD, Sowmya Balasubramanian, MD, David N. Rosenthal, MD, Edward P. Walsh, MD, Mark E. Alexander, MD and Douglas Y. Mah, MD.

or negative tests. QRS prolongation alone did not account for total QTc prolongation. There was excellent intraobserver and interobserver consistency. No induced arrhythmias or adverse events occurred.Conclusion: Proc infusion is safe in children as a diagnostic evaluation for BrS. Proc prolonged PR, QRS, & QTc in all patients, but ST elevation was only observed in patients with positive studies. Proc induces increases of >20% for PR, QRS, and QTc in some children without adverse events. The amount of QTc prolongation suggests an undescribed pharmacodynamic effect of Proc in this population.

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FREQUENT DYSFUNCTION & DYSSYNCHRONY IN VENTRICULAR-PACED, COMPLETE AV BLOCK IN YOUNG ASYMPTOMATIC PATIENTS HAVING NORMAL CARDIAC ANATOMYDavid Gamboa, MD, Daniel Forsha, MD, Niels Risum, MD, P. Andrea. Kropf, MD, Christoph P. Hornik, MD, Joseph Kisslo, MD and Ronald J. Kanter, MD. Duke University Medical Center, Durham, NCIntroduction: Cardiac resynchronization therapy improves LV dysfunction and dyssychrony due to ventricular pacing (VP), but 1/3 of pts do not respond. A newly described strain analysis, termed “classic pattern,” identifies electrical activation delays that predict CRT response in LBBB (>90% sensitivity and specificity). This is the initial study of the classic pattern in chronic VP patients with complete AV block (CAVB).Methods: We identified 60 asymptomatic pts with non-surgical CAVB. Criteria of chronic VP (> 90% of beats) and a quality 4-chamber echo view were met by 29 pts (27 congenital CAVB). LVEF, longitudinal strain, and two methods of dyssynchrony analysis (classic pattern, standard deviation of the time to peak) were analyzed with TomTec 2D CPA. History, ECG, and CXR were reviewed. Continuous variables were reported as median (25-75 %ile). Analyses included Spearman’s rank and Fisher’s exact tests.Results: Median age was 18.4 years (9.8-22.5); 55% male; heart rate 70 bpm (64-86); and all had prolonged QRS duration. Classic pattern was seen in 41% (12/29). RV pacing site (septal vs apical) was associated with site of earliest LV contraction (p=0.006) but not with classic pattern (p=0.7 ). Global peak strain (GPS) correlated with LVEF (r=-0.8) and pacing duration (r=0.4).

Classic Pattern No Pattern P

valueTotal Number 12 (41%) 17 (59%)

LV Ejection Fraction (%) 38.7 (31.9-44.3)

48.9 (40.8-52.6) 0.009

Total Duration Paced (years) 9.4 (5.6-15.1) 7.7 (5.0-10.9) 0.38

QRS Duration (ms) 163 (147-173) 140 (126-158) 0.04

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Methods: This was a prospective randomized controlled study of patients undergoing surgery for CHD. Thirty patients were randomized to receive either unipolar or bipolar temporary epicardial pacing leads in the ventricles at the time of surgery. The pacing threshold (mA) and sensing threshold (mV) were recorded daily until the removal of leads or for a maximum duration of 7 post-operative days (PODs).Results: Patients were randomized to bipolar (n=16, males=9, age=2.85±1.19 years) and unipolar (n=14, males=7, age=3.68±1.32 years). There was no statistical difference in the sensing or pacing thresholds between the 2 groups for the first three PODs (Figure). However, the mean sensing and pacing thresholds were superior for bipolar leads when compared to unipolar leads from POD 3. There were no sensing or pacing failures of bipolar or unipolar leads.Conclusion: The bipolar temporary pacing leads tend to have superior sensing and pacing thresholds from POD3 when compared to unipolar leads in patients undergoing surgery for CHD.

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PROSPECTIVE RANDOMIZED COMPARISON OF 6-MM-TIP VERSUS 8-MM-TIP CRYOABLATION OF ATRIOVENTRICULAR NODAL REENTRANT TACHYCARDIA IN CHILDRENVolkan Tuzcu, MD, Yakup Ergul, MD, Enes E. Gul, MD, Emine F. Dalgic, MD and Celal Akdeniz, MD. Istanbul Medipol University, Istanbul, Turkey, Istanbul Mehmet Akif Ersoy Research and Teaching Heart Hospital, Istanbul, TurkeyIntroduction: Cryoablation (Cryo) for atrioventricular nodal reentrant tachycardia (AVNRT) is more commonly preferred over radiofrequency ablation in children in the recent years. Recent studies with 6 and 8-mm tip catheters are demonstrating high long-term success rates comparable to radiofrequency ablation. There is no previously published data comparing 6 and 8-mm tip Cryo of AVNRT. The aim of this study was to compare efficacy and safety of 8-mm-tip versus 6-mm-tip Cryo of AVNRT in children.Methods: A total of 70 consecutive patients over 25 kg of weight with AVNRT were randomized to treatment with 8-mm-tip or 6-mm-tip Cryo treated. EnSite system (St.Jude Medical, St Paul, MN, USA) was used to reduce or eliminate fluoroscopy.Results: Acute procedural success was 97% (34/35) and 100% (35/35) for 6-mm-tip and 8-mm-tip catheters, respectively (p=0.51). Procedure duration was shorter in 8-mm-tip group. Both fluoroscopy time and number of complete lesions were comparable between the groups (Table). No fluoroscopy was used in 63 patients. Kaplan-Meier survival analysis demonstrated no significant difference between the treatment groups in terms of recurrence rate (6% [2/33] vs. 6% [2/31]; log-rank test p=0.81) at a mean follow-up of 7±4 months. No complications occurred.Conclusion: Cryo of AVNRT is safe and effective with comparable acute and mid-term follow-up success using 6-mm and 8-mm-tip catheters in children. Procedure duration is shorter with 8-mm-tip Cryo. Longer follow-up is necessary for evaluation of long-term recurrence risk.

Stanford University, Palo Alto, CA, Boston Children’s Hospital, Boston, MAIntroduction: Cardiac arrhythmias are a complication of myocarditis. There have been no previous studies of in-hospital arrhythmia development and outcomes in this patient population.Methods: Retrospective two-center review of pts ≤ 21 yrs hospitalized with myocarditis between 1996-2012. Fulminant myocarditis was defined as need for inotropic support within 48 hours of presentation. Acute arrhythmias occurred at presentation and subacute after admission.Results: A total of 85 pts (59% male) presented at a median age of 10 yrs (1 day - 17 yrs). Arrhythmias occurred in 45 pts (52%) and were more common in the fulminant (60%) vs. non-fulminant group (41%) (p=0.057). Of 59 arrhythmias, 63% presented acutely and 37% subacutely. CPR was required in 3 pts and direct current cardioversion in 8 pts due to subacute arrhythmias. Development of subacute arrhythmias was associated with ST changes >0.1mV (p=0.0014), whereas low-voltages, troponin, AST/ALT, lactate and myocardial function were not. Arrhythmias were associated with worse outcomes (mechanical support, death, or orthotopic heart transplant (OHT), p=0.0087), with death/OHT occurring only in the fulminant group (Figure 1). All pts surviving to discharge (37/45,82%) had resolution of their arrhythmias prior to discharge (11 pts on antiarrhythmics) with 1 exception (CHB requiring pacemaker). At 1 yr follow-up, there was no arrhythmia related mortality.Conclusion: Arrhythmias are common on admission for myocarditis, but nearly 40% can develop after presentation and are associated with ST changes. Early identification of pts who develop subacute arrhythmias may help management. A majority of pts do not require continued post-discharge arrhythmia treatment.

PO03-178

CLINICAL RELIABILITY OF BIPOLAR VERSUS UNIPOLAR TEMPORARY EPICARDIAL PACING LEADS IN PATIENTS AFTER SURGERY FOR CONGENITAL HEART DISEASE: INTERIM RESULTS OF A PROSPECTIVE, RANDOMIZED, CONTROLLED STUDYNivedita Mohari, MD, Joanne P. Starr, MD, Richard N. Gates, MD, Michele B. Domico, MD and Anjan S. Batra, MD, FHRS. CHOC/H-UCLA, Torrance, CA, CHOC, Orange, CAIntroduction: There have been no studies comparing the clinical reliability of bipolar vs. unipolar temporary epicardial pacing leads in patients after surgery for congenital heart disease (CHD). This study was undertaken to compare the sensing and pacing thresholds of unipolar vs. bipolar temporary epicardial pacing leads in patients after surgery for CHD over time.

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PO03-181

CHARACTERIZATION OF RIGHT VENTRICULAR ACTIVATION IN PATIENTS WITH TETRALOGY OF FALLOT AND RIGHT BUNDLE BRANCH BLOCKZakaria Jalal, MD, Frederic Sacher, MD, Pierre Bordachar, MD, PhD, Hubert Cochet, MD, Nicolas Derval, MD, Sylvain Ploux, MD, Michel Haissaguerre, MD, PhD, Jean-Benoit Thambo, MD, PhD and Pierre Jais, MD, PhD. C.H.U de Bordeaux, Pessac, FranceIntroduction: Presence of prolonged QRS duration in patients with tetralogy of Fallot (TOF) is considered as a risk factor for sudden death and may be a possible target for CRT. It has been suggested that QRS duration mainly reflects abnormalities of the RV outflow tract (RVOT) rather than the RV body itself. We characterized the RV activation pattern in these patients to better understand the electrophysiological background for arrhythmias and RV dysfunction.Methods: RV activation sequence was studied in 28 adults (QRS duration 153±21ms) referred for either catheter ablation or pulmonary valve replacement late after ToF repair, with application of 3D contact mapping (201 ± 32 sites per patient; Carto 3 - Biosense Webster).Results: TOF patients showed a single RV breakthrough in the septum (mid-septal in 79%, septo-basal in 14% and apico-septal in 7%) recorded 28±23 ms after the beginning of the earliest QRS complex traducing a slow left-to-right transseptal activation time and absence of direct RV Purkinje activation. Two distinct patterns of activation proceeded slowly from the breakthrough site: 1) the first one from the septum to the outflow tract and to the basal portion of the RV free wall; we observed, at the level of the RVOT, presence of fragmented, low voltage, or multiphasic components corresponding to the surgical scars and patches; 2) the second one, from the breakthrough site to the apex and the mid RV free wall with prolonged conduction velocities likely as a result of cell-to-cell conduction and/or anisotropic conduction. Despite major abnormal electrical signals detected at the level of the RVOT, this scared area did not influence the localization of the last activated segments. Indeed, the RV activation ended at the mid portion of the RV free wall after a mean RV activation time of 127±20 ms. This RV activation time was correlated to QRS duration (r=0,72; p<0,001).Conclusion: In adults with repaired TOF, we observed slow conduction velocities in the whole RV cavity with slow left-to-right transseptal activation time, a similar pattern of activation of the RV as that observed in the LV in patients with left bundle branch block. This may have important implications in the understanding of the risk of sudden death, the decision to implant a CRT device and the determination of the optimal pacing sites

PO03-182

FETAL VENTRICULAR ECTOPY ASSOCIATED WITH VENTRICULAR WALL DEFECTS AND A CORONARY ARTERY ANOMALYJanette F. Strasburger, MD, Carli Peters, BS, Annette Wacker-Gussmann, MD, Bettina Cuneo, MD, Nina Gotteiner, MD and Ronald T. Wakai, PhD. Children’s Hospital of Wisconsin-Milwaukee, Milwaukee, WI, University of Wisconsin Madison, Madison, WI, University Children’s Hospital, Tubingen, Germany, Heart Institute for Children, Hope Children’s Hospital, Oak Lawn, IL, Lurie Children’s Hospital, Chicago, ILIntroduction: Congenital ventricular wall defects (ventricular aneurysms (CVA) and diverticula (CVD)), and congenital coronary artery anomalies (CAA) are rare and represent potentially life-threatening fetal and neonatal conditions.Methods: In a five year period, 9 fetuses were referred for evaluation because of frequent ventricular ectopy on fetal

Comparison of 6-mm vs. 8-mm-tip Cryo6-mm-tip(n=35)

8-mm-tip(n=35) p Value

Age, years 13±3 15±4 0.11Weight, kg 51±17 53±13 0.72Acute procedural success 34/35 (97%) 35/35 (100%) 0.51Fluoroscopy time, min 0.73±2.4 0.32±1.2 0.38Procedure duration, min 148±41 126±28 0.01Number of lesions, median 6 (4-11) 5.5 (3-11) 0.54Follow-up duration, months 8±4 7±3 0.65Recurrence rate 2/33 (6%) 2/31 (6%) 0.81

PO03-180

WPW-LIKE QRS PATTERN IN PATIENTS WITH DANON DISEASE IS NOT LINKED TO THE PRESENCE OF AN ACCESSORY PATHWAYTorsten Konrad, MD, Sebastian Sonnenschein, MD, Hanke Mollnau, MD, Frank P. Schmidt, MD, Ewald Himmrich, MD, Thomas Münzel, MD, Cathrin Theis, MD and Thomas Rostock, MD. II. Medical Clinic, Department for Electrophysiology, Johannes-Gutenberg University, Mainz, Germany, II. Medical Clinic, Johannes-Gutenberg University, Mainz, GermanyIntroduction: Danon disease is a rare X-linked dominant lysosomal disease causing deficiency of the lysosome-associated membrane protein 2 (LAMP2). The defects in LAMP2 protein cause insidious glycogen accumulation in skeletal and cardiac muscle cells resulting in cardiac hypertrophy. Previous publications suggested an association of Danon disease with WPW syndrome due to a characteristic preexcitation-like QRS pattern. However, a systematic electrophysiological investigation of Danon patients is lacking thus far.Methods: At our institution, 7 patients with Danon disease (4 males, 33±11 y; 3 females, 47±20 y) from 3 different families were studied. In all patients, Danon disease was confirmed by western blot or genetic testing. ECG, Holter-ECG, echocardiography and ICD interrogation (if implanted) were performed. All male patients underwent electrophysiological investigation (EP study).Results: Left ventricular hypertrophy was present in all patients (mean thickness of intraventricular septum in males 20±13mm, in females 17±2mm). Ventricular tachycardia in Holter-ECG was documented in 6 of 7 patients. Moreover, 4 of 7 patients suffered from atrial fibrillation. One male patient suffered from stroke at an age of 30 years. In all male patients, the initial QRS-complex showed a slurring upstroke and shortened PQ-interval mimicking WPW pattern. However, the presence of an accessory pathway could be excluded by an EP study. In female patients, initial QRS-complex slurring was significantly less distinct. One patient underwent cavotricuspid isthmus ablation for common type atrial flutter. In 4 patients, ICD implantation was performed for primary prevention.Conclusion: This is the first systematic electrophysiological characterization of patients with Danon disease. A WPW-like QRS pattern is not associated with the presence of an accessory pathway in these patients. Myocardial hypertrophy and reduction of conduction velocity may result in an initial QRS slurring causing a WPW-like pattern. Furthermore, atrial fibrillation is common in Danon patients and associated with a substantial risk of stroke in the young.

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procedures over the past decade. Given the increasing epidemic of AF, this data has critical implications for health policy assessing the adequacy of expenditure, infrastructure, training and funding for AF ablation services.

PO03-184

NOVEL USE OF ADENOSINE TO FACILITATE RESUMPTION OF ACCESSORY PATHWAY CONDUCTIONAndrew W. Teh, MBBS, PhD, Marc A. Miller, MD, Jorge E. Velásquez, MD and Andre d’Avila, MD, PhD. Mount Sinai Medical Center, New York, NYIntroduction: Adenosine is used to confirm the elimination of accessory pathway (AP) conduction after ablation (RFA) by prolonging AV nodal conduction time and/or causing transient AV block favoring AP conduction. In this case, AP VA conduction was inhibited by mechanical trauma. Resumption of AP conduction was only seen following adenosine administration.Methods: NAResults: A 62 year old man presented with symptomatic wide complex tachycardia (LBBB-morphology). EP study baseline findings: AH=100 ms and HV=59 ms. LBBB tachycardia was induced with ventricular stimulation (cycle length 390 msec). During tachycardia, VA=92 ms and earliest atrial activation was at the proximal His. Ventricular overdrive pacing yielded a V-A-V response, PPI-TCL=66ms and SA-VA=40ms. His refractory ventricular extrastimuli advanced the subsequent A or terminated tachycardia without reaching the A. During mapping, there was loss of VA conduction due to mechanical trauma to the AP (Fig 1A). 12 mg of iv adenosine resulted in: 1) AV block (Fig 1B) followed by 2) Transient recovery of VA conduction (Fig 1B) and 3) Loss of VA conduction as adenosine wore off (Fig 1C). The AP was successfully ablated using repeated boluses of adenosine to facilitate retrograde conduction over the AP.Conclusion: This report provides a novel finding of transient restoration of accessory pathway conduction during adenosine administration allowing successful RFA. Adenosine may be useful in cases where mechanical trauma renders a pathway unmappable or to confirm successful RFA in the absence of VA conduction.

echocardiogram, representing 2% of fetal magnetocardiography (fMCG) studies. Of these, 5 had structural abnormalities (CVA-3, CVD-2, and CAA-1). A series of 10 minute fMCG recordings were performed at UW-Madison Biomagnetism Lab using a 37-channel SQUID magnetometer within a highly permeable magnetically shielded room. The literature was reviewed for these 3 rare congenital conditions.Results: Electrophysiologic abnormalities are shown in Table I.EP Abnormalities in Fetal CVA, CVD, and CAA

CVD(n=2) CVA(n=3) CAA (n=1)Sinus Tachycardia 1 1Monomorphic Bigeminy 1 3 1Couplets 1QRS Prolongation 2ST-T abnormality 1 1Increased P:QRS ratio (amplitude) 1 2PVC response with fetal movement ↓,- ↓,↑,↓ ↓

Conclusion: Ventricular wall defects and coronary artery anomalies are associated with incessant monomorphic ventricular arrhythmias in the fetus. Precise electrophysiologic diagnosis can now be made, including the complexity of ventricular ectopy, arrhythmic response to fetal movement, presence of QRS or ST-T wave abnormalities, and atrial amplitude increases. Fetuses with ventricular ectopy should be closely evaluated prior to and at the time of birth.

PO03-183

MARKED GROWTH OF CATHETER ABLATION PROCEDURES FOR ATRIAL FIBRILLATION OVER THE PAST DECADE: A NATIONWIDE STUDY WITH IMPLICATIONS FOR HEALTH CARE POLICY, INFRASTRUCTURE AND SPENDINGJonathan M. Kalman, MBBS, PhD, Saurabh Kumar, MBBS, Tomos E. Walters, MBBS, Graham Hepworth, PhD, Peter M. Kistler, MBBS, PhD, Prashanthan Sanders, MBBS, PhD and Joseph B. Morton, MBBS, PhD. Royal Melbourne Hospital, Melbourne, Australia, University of Melbourne, Melbourne, Australia, Alfred Hospital and Baker IDI, Melbourne, Australia, Centre for Heart Rhythm Disorders (CHRD), University of Adelaide, Royal Adelaide Hospital, Adelaide, AustraliaIntroduction: Catheter ablation is a class I indication for treatment of drug refractory AF. We examined nationwide temporal trends in the provision of catheter based AF ablation over the past decade.Methods: We performed a review of the numbers of catheter based AF ablations from 2000/1 to 2009/10 from three sources: the Australian Institute of Health, Welfare and Aging (AIHW), Medicare Australia database (MA), and local records at a high volume tertiary referral center (TR) for AF ablation. For comparison, we also examined nationwide trends in all cardiovascular procedures and percutaneous coronary interventions (PCIs). Linear regression models were fitted comparing population-adjusted trends in procedural numbers.Results: Catheter-based AF ablation showed a 30.9%, 23.2% and 39.8% per year population adjusted increment over 10 years from the AIHW, MA and TR sources respectively (P<0.001 for all). In contrast, there was a 5.1% per year population adjusted increment in PCIs over 10 years from both, the AIHW and MA sources respectively (P<0.001). This was similar to the growth rate of all cardiovascular procedures (AIHW: 5.1% vs. 3.8%/year, P=0.27). Growth of AF ablations was significantly higher than PCIs (P<0.001 for AIHW and MA sources) and all cardiovascular procedures (AIHW: 30.9% vs. 3.8%/year, P<0.001: Figure).Conclusion: AF ablation procedures have had a marked growth exceeding the growth of PCIs and of all cardiovascular

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ablation of frequent PVC exhibiting left bundle branch morphology and inferior axis with a transitional zone of V3 and the width of r wave in lead V1 of 60 ms, characteristic of the origin of LVOT. Chest X-ray and echocardiography demonstrated no evidence of structural heart disease. Activation mapping of PVC and pace mapping was performed. The optical site for ablation was not found in the right ventricular OT, pulmonary artery (PA), LVOT and aortic cusps of Valsalva, but the earliest activation site (arrow in Panel A) with V-QRS of -15 ms (Panel B) was detected in the anterior wall of AsAo, faced to PA, 25 mm above right coronary cusp, where spiky ventricular electrogram (filled arrow) following far-field ventricular electrogram during sinus rhythm and prepotential (unfilled arrow) preceding PVC, consistent with VME activation were detected (Panel B) and a high output pacing exhibited excellent pacemap with a spike-QRS delay. Radiofrequency delivery at this site eliminated the PVC.Conclusion: This is the first case report of successful ablation of PVC originating from VME extended into AsAo. Retrograde VME potential during sinus rhythm and the earliest VME potential preceding PVC should be targeted for mapping and ablation.

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SUCCESSFUL ABLATION OF PREMATURE ATRIAL CONTRACTIONS ORIGINATING FROM THE LEFT CORONARY CUSPDavid Steckman, MD, Russell Heath, MD, David F. Katz, MD, Jaime E. Gonzalez, MD, Matthew Zipse, MD, Raphael K. Sung, MD, Paul D. Varosy, MD, Ryan G. Aleong, MD, Duy T. Nguyen, MD, Joseph L. Schuller, MD, William H. Sauer, MD and Wendy S. Tzou, MD. University of Colorado, Denver, COIntroduction: Left ventricular outflow tract atrial tachycardias are uncommon but usually originate from the non-coronary cusp (NCC). We present a case of paroxysmal atrial tachycardia originating from the left coronary cusp (LCC).Methods: N/AResults: A 44 year old female with history of symptomatic drug refractory frequent premature atrial contractions (PAC) and failed right parahisian PAC ablation was referred for repeat ablation. Electroanatomic activation mapping confirmed that the region of earliest right atrial activation was near the His and diffusely early (~25 ms pre-P wave). Left atrial activation demonstrated a similarly diffuse although somewhat less early activation area (20 ms pre-P wave). Mapping was then performed in the aortic root. The activation on the NCC was slightly earlier (~30 ms pre-P wave). High-power ablation at this site led to late suppression of PACs. However, PACs recurred. Intracardiac echocardiography demonstrated that the aorto-mitral continuity (AMC) was

PO03-185

ASPIRATION OF RIGHT ATRIAL THROMBUS THROUGH A STEERABLE SHEATH GUIDED BY INTRACARDIAC ECHOCARDIOGRAPHY PRIOR TO TRANSSEPTAL PUNCTUREBernhard Strohmer, MD, Franz Danmayr, MD, Mathias Brandt, MD and Uta Hoppe, MD. Salzburger Landeskliniken (SALK), Salzburg, AustriaIntroduction: Atrial fibrillation (AF) predisposes to formation of blood clots typically within the left atrial (LA) appendage. TEE is generally used to screen for LA thrombi in pts who are at risk of stroke prior AF ablation. The objective is to present a case that illustrates the value of monitoring a LA redo-procedure with intracardiac echo (ICE) detecting a thrombus despite adequate anticoagulation.Methods: N/AResults: A 55 year-old man presented with LA flutter (CL 250 ms) refractory to amiodarone and cardioversion. Ablation of long-standing persistent AF was performed 15 mos ago (WACA, roof line, LA isthmus) with restoration of SR for one year. His previous illnesses were hypertension, renal insufficiency, tuberculosis, but no structural heart disease (normal CT). The pt was on oral anticoagulation and bridged with LMWH. The redo-procedure was performed with help of ICE (AcuNav 10F) to guide transseptal (TS) puncture. Despite heparinization (ACT >200 sec) a filiform clot was observed when positioning the TS needle at the fossa ovalis. Due to progressive thrombus formation the TS puncture was abandoned and the sheath withdrawn. The serpiginous thrombus floated within the dilated RA, but did not embolize through the tricuspid valve. A steerable sheath (Agilis NxT medium curl, 11.5F) was introduced and directed towards the ICE catheter which seemed to anchor parts of the clot. All thrombus material was aspirated through the large lumen (8.5F) of the sheath and photo-documented. The procedure was stopped because of the hypercoagulable state. No complications occurred and the pt was put on acencoumarol. Three mos later curative ablation of LA flutter was performed around the RSPV and no intraatrial thrombus formation was detected with ICE.Conclusion: This case highlights the fact that periprocedural formation of intraatrial thrombi can occur despite therapeutic anticoagulation with heparin and warfarin in pts undergoing LA ablation. The use of ICE helped to detect potentially serious thromboembolic complications and prompted early interventions for effective thrombus removal. Monitoring all steps of AF ablation procedure with ICE may increase the safety and efficacy of complex LA interventions.

PO03-186

SUCCESSFUL ABLATION OF PREMATURE VENTRICULAR CONTRACTIONS ORIGINATING FROM ASCENDING AORTAMio Tamura, MD, Yoshiaki Kaneko, MD, PhD, Tadashi Nakajima, MD, PhD, Tadanobu Irie, MD, Masaki Ota, MD, Takafumi Iijima, MD, Takashi Iijzuka, MD, Syuntaro Tamura, MD, Akihiro Saito, MD, PhD and Masahiko Kurabayashi, MD, PhD. Gunma University Graduate School of Medicine, Maebashi, Gunma, JapanIntroduction: Catheter ablation of premature ventricular contractions (PVC) originating from left ventricular outflow tract (LVOT) still remains challenging. Anatomical investigators suggested the presence of ventricular myocardial extension (VME) into ascending aorta (AsAo) beyond ventriculo-arterial junction.Methods: N/AResults: A 60-year-old woman was admitted for catheter

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contiguous with the LCC. Additional mapping revealed that the area of earliest activation was on the LCC, near the LCC-NCC junction. Ablation at this site yielded immediate acceleration and then termination of the PAC within 8 seconds. Several high-power consolidation lesions were delivered in this area. The PAC did not recur during a 45 minute waiting period on isoproterenol, and the AT was no longer inducible.Conclusion: This case demonstrates that PACs may originate from the LCC. Careful mapping in the aortic root for PACs should include LCC mapping, especially when the AMC is adjacent to the LCC.

PO03-188

PERSISTENT COMPLETE HEART BLOCK AFTER ADMINISTRATION OF REGADENOSONJacqueline Eubany, MD and Hans Moore, MD. George Washington University, NW, DC, Veterans administrations hospital, DC, NW, DCIntroduction: Regadenoson is a pharmacologic stress agent used for myocardial perfusion scintigraphy in patients, who are unable to perform an exercise stress test. Regadenoson is an adenosine receptor agonist that causes coronary vasodilation and increases coronary blood flow through its low agonistic affinity for A2A adenosine receptor. Regadenoson’s simple rapid bolus administration, short duration of hyperemic effect and high patient tolerance, makes it an ideal agent for stress testing . There were no incidence of second or third degree heart block reported in phase 3 clinical trials of this medication. However, 8 cases of complete heart block were reported in post marketing surveillance in the FDA database. We are presenting a case of a delayed presentation of complete heart block after administration of regadenoson, persistent up to 4 hours post administration.Methods: N/AResults: 66 year old male with history of ischemic cardiomyopathy presented to the ER with nausea, vomiting, lightheadedness. Patient was in the hospital that morning undergoing a pharmacologic nuclear examination. Within 45 minutes after completion of stress test where he received regadenoson, he developed acute onset of nausea, vomiting, presyncope and fell to the ground. He was taken immediatelyto the emergency room where an ECG showed sinus rhythm with complete heart block and a ventricular escape rate of 38bpm. Because of ongoing severe symptoms, the patient was given aminophylline to reverse the effects of regadenoson four hours after receiving regadenoson. This resulted in an almost immediate resumption of sinus rhythm at 90bpm, and an immediate resolution of all symptoms. He remained in sinus rhythm for the duration of his hospital stay.Conclusion: Regadenoson is eliminated from the body in 3 phases. The first 2 phases occur within minutes, but the third phase has a T1/2 of approximately 2hrs . Most of it is eliminated unchanged from the urine, while the rest is excreted in bile. In our patient, heart block did not become evident until 45mins post administration and persisted for 4 hours until aminophylline was given. This should call for more studies to evaluate appropriate duration of monitoring of this drug post administration.