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hiro Nakahara, MD, PhD, Rafael J. Ramirez, PhD, Eric Buch, MD, Yoav Michowitz, MD,armar Vaseghi, MD, Carlos de Diego, MD, Noel G. Boyle, MD, PhD, FHRS, Aman Mahajan, MD, PhD,alyanam Shivkumar, MD, PhD, FHRS

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ACKGROUND Catheter ablation of the left atrium (LA) is asso-iated with potential collateral injury to surrounding structures,specially the esophagus and the right phrenic nerve (PN).

BJECTIVES The purpose of this study was to evaluate the effi-acy and feasibility of intrapericardial balloon placement (IPBP)or the protection of collateral structures adjacent to the LA.

ETHODS Electroanatomic mapping was performed in porcineearts using a transseptal endocardial approach in eight swineeighing 40–50 kg. An intrapericardial balloon was inflated inhe oblique sinus, via percutaneous epicardial access, to dis-lace the esophagus. Similarly, with the balloon positioned inhe transverse sinus, IPBP was used to displace the right PN.sophageal temperature was monitored while endocardial ra-iofrequency (RF) energy was delivered to the distal inferior PV.

ESULTS In all cases, balloon placement was successful witho significant effects on hemodynamic function. Balloon infla-ion increased the distance between the esophagus and poste-ior LA by 12.3 � 4.0 mm. IPBP significantly attenuated in-

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547-5271/$ -see front matter © 2010 Heart Rhythm Society. All rights reserved

F application (6.1 � 2.4°C vs. 1.2 � 1.1°C; P�.0001). High-utput endocardial pacing from the right superior pulmonaryein ostium stimulated PN activity. After displacement of theight PN with IPBP, PN capture was abolished in 30 (91%) of 33ites.

ONCLUSIONS These findings demonstrate that in an animalodel, IPBP is feasible in the setting of catheter ablation proce-ures and has the potential to decrease the risk of collateralamage to the esophagus and PN during LA ablation.

EYWORDS: Catheter ablation; Esophageal injury; Phrenic nervenjury

BBREVIATIONS AF � atrial fibrillation; CIPV � common inferiorulmonary vein; EA � electroanatomic; ECG � electrocardiogram;PBP � intrapericardial balloon placement; LA � left atrium;N � phrenic nerve; PV � pulmonary vein; RF � radiofrequency;SPV � right superior pulmonary vein; VT � ventricular tachycardia

Heart Rhythm 2010;7:81–87) © 2010 Heart Rhythm Society. All

reases in luminal esophageal temperature during endocardial rights reserved.

Pulmonary vein (PV) isolation by endocardial catheterblation is an established treatment for atrial fibrillationAF).1 Supplemental linear ablations have improved effi-acy in some cases, particularly for persistent AF.2,3 How-ver, a major risk associated with endocardial ablation isollateral damage to tissues near the posterior left atriumLA), which can have lethal consequences.4 Collateral dam-ge from endocardial ablation may result in atrioesophagealstula5 or phrenic nerve (PN) injury.6,7 The risk of collateralamage limits application of radiofrequency (RF) energy in

The University of California, Los Angeles, has intellectual propertyelating to this area of work. This study was supported by Nationalnstitutes of Health grant nos. IH RO1-HL084261 and HL067647 (to KS).ddress reprint requests and correspondence: Kalyanam Shivkumar,.D., Ph.D., UCLA Cardiac Arrhythmia Center, A2-237 CHS, Davideffen School of Medicine at UCLA, 10833 Le Conte Avenue, Losngeles, California 90095-1679. E-mail address: kshivkumar@mednet.

ertain areas such as the posterior LA wall and near the rightuperior PV (RSPV).

Intrapericardial balloon retraction of the LA for preven-ion of esophageal injury during endocardial catheter abla-ion was recently reported.8 Balloon inflation9,10 or infusionf air11 into the pericardial space has also been used forrotection of the left PN during epicardial ventricular tachy-ardia (VT) ablation. Despite these case reports, no system-tic assessment of an intrapericardial balloon protection strat-gy has been performed to demonstrate protection of collateralissues during LA ablation. The purpose of this study was tossess the efficacy and feasibility of a novel intrapericardialalloon placement (IPBP) technique to displace and protect thesophagus and right PN during LA ablation.

ethodshis protocol was approved by the UCLA Animal Researchommittee and was performed according to institutional

uidelines.

. doi:10.1016/j.hrthm.2009.09.022

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nimals and preoperative preparationight pigs weighing 40–50 kg were anesthetized with 1.4g/kg Telazol (intramuscular) and then intubated. Artificial

espiration was maintained via endotracheal tube and me-hanical ventilator (Summit Medical, Bend, OR). Generalnesthesia was maintained with inhaled 1.5%–2.5% isoflu-ane. Femoral venous and arterial catheters were insertedsing modified Seldinger technique. ElectrocardiogramECG) and arterial pressure were monitored continuallyuring procedures. Luminal esophageal temperature wasonitored as described elsewhere12–14 by inserting an

sophageal catheter (Blazer II 4-mm-tip catheter, EP Tech-ologies/Boston Scientific, San Jose, CA) orally and ad-ancing to the level of the LA under fluoroscopic guidance.picardial access was obtained via subxiphoid puncturesing a Tuohy needle as described elsewhere8; an 8-Frheath (SL0, St. Jude Medical, Inc., Minnetonka, MN) or an.5-Fr deflectable sheath (Agilis, St. Jude Medical, Inc.,innetonka, MN) was advanced over a guide wire into the

ericardial space. After administration of intravenous hep-rin, a single transseptal puncture was performed to pass an-Fr SL0 sheath into the LA. A circular mapping catheterOptima, St. Jude Medical, Inc., Minnetonka, MN) and a 4m steerable electrophysiology catheter were used for map-

ing the LA and PVs endocardially.

PBPhrough the epicardial sheath, Meditech 4 cm balloon cath-ters (diameter, 12–18 mm; Meditech, Boston Scientific)ere advanced over a guide wire to the oblique sinus,

mmediately adjacent to the posterior LA. When positionedetween the LA and esophagus, the balloon was inflatedith a contrast agent using an insufflator until complete

nflation was observed radiographically. In addition to flu-roscopy, electroanatomic (EA) mapping (NavX system, St.ude Medical, Inc., Minnetonka, MN) was used to deter-ine LA geometry and analyze movement of the common

nferior PV (CIPV) antrum and the esophagus, with three-imensional geometry created by a quadripolar electrophys-ology catheter before and after balloon inflation. The meanrterial pressure and heart rate were continuously monitoredor the duration of the procedure.

In porcine hearts, the CIPV is the cardiac structure situ-ted closest to the esophagus. A nonirrigated 4-mm-tipblation catheter (Celsius, Biosense Webster, Diamond Bar,A) was positioned endocardially at the distal CIPV toeliver RF energy near the esophagus with and withoutPBP. The balloon catheter was positioned in the intraperi-ardial space between the ablation catheter and the esoph-gus. To verify reproducibility of the findings, high-powerF energy was delivered from three different positions in

he CIPV. Power was limited to 50 W with a maximal tipemperature of 60°C for 30 seconds with each application.he esophageal catheter was positioned against the anteriorsophageal wall, directly opposite the ablation catheter inhe distal CIPV, and guided by the EA map and fluoroscopic

iews. After balloon inflation, CIPV and esophageal cathe- t

ers were repositioned, if necessary, to minimize the dis-ance between them. The temperature probe’s position waserified by EA map and fluoroscopy in three planes (leftnterior oblique, right anterior oblique, and anterior-poste-ior) and adjusted frequently to compensate for any move-ents of the catheter tips. The temperature probe output was

ime tagged and annotated to the procedure log every 3econds before, during, and after RF catheter ablation.

Catheter ablation near the right PVs can cause collat-ral damage to the right PN, which runs along the peri-ardium.6,7 To separate the pericardium and the PN, weositioned the intrapericardial balloon adjacent to the ante-ior aspect of the RSPV. After creating LA and PV geom-try by EA mapping, location of the right PN was identifiedround the anterior aspect of the RSPV by eliciting dia-hragmatic stimulation with bipolar pacing (10 mA, 2 msulse width) from the distal pole of the endocardial catheter.hese locations were marked on the EA map. After eachalloon placement and inflation, endocardial high-outputacing was repeated at these sites to assess for PN capture.

tatistical analysisll continuous data are expressed as mean � standardeviation. The Pearson correlation coefficient was used touantify the relationship between variables. Changes insophageal temperature were analyzed initially by repeatedeasure of analysis of variance (ANOVA), followed bytudent’s t-test to compare temperatures with and withoutPBP. A two-sided P-value of �.05 was considered statis-ically significant.

esultspproaches for positioning the intrapericardialalloonnesthesia was uneventful in all animals, and all proceduresere completed as planned. In all animals, intrapericardialalloons were successfully positioned and inflated in theblique sinus, adjacent to the posterior LA. After subxi-hoid puncture and access to the pericardial space, twopproaches were used to position the balloon near the CIPVstial region: direct posterior access and anterior accessith deflectable sheath guidance. The Tuohy needle wasirected toward the apex of the heart, and advancement ofhe guide wire indicated whether posterior or anterior accessas achieved. Movement of the guide wire to the posteriorall allowed a direct posterior approach, in which the bal-

oon catheter was advanced and positioned behind the pos-erior LA (Figure 1A). In the event of anterior advancementf the guide wire, catheter guidance from the anterior walloward the posterior LA was facilitated by use of a deflect-ble sheath (Figure 1B). Balloon placement within the peri-ardial space is shown in Figure 1C.

sophageal displacementigure 2 and Table 1 show typical results of IPBP onA-esophageal distance. After pericardial balloon inflation,

he average distance between the esophagus and atrial en-

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ocardium increased by 12.3 � 4.0 mm, calculated by EAapping and confirmed fluoroscopically (Table 1). In three

nimals, simultaneous CIPV and esophageal movement wasocumented after balloon inflation (Figures 2A–2B). Dur-ng balloon inflation, mean arterial blood pressures andeart rates did not significantly change (80.4 � 4.4 vs.6.4 � 6.4 mmHg, and 78.5 � 5.0 vs. 79.8 � 7.2 bpm,espectively; P � NS). After balloon inflation, changes inean arterial pressure (�3.8 � 6.9 vs. �4.3 � 4.7 mmHg;� NS) and heart rate (1.4 � 3.3 vs. 1.0 � 4.6 bpm; P �S) were not significantly different between small (12–14m) and large (16–18 mm) balloons.

alloon protection of esophagus during RF energypplicationn six animals, an ablation catheter was positioned in theistal CIPV close to the esophageal catheter, and an intra-ericardial balloon was successfully placed (12 mm in three,4 mm in two, and 16 mm in one animal) between theseatheters (Figure 3A). During ablation and recovery, esoph-geal temperature increased by 6.1 � 2.4°C under controlonditions, significantly more than in the presence of IPBP1.2 � 1.1°C, P �.0001; Figure 3B, top). At each time pointuring ablation and recovery, balloon inflation also signif-cantly attenuated the rise in esophageal temperatureP �.004). Temperature attenuation during IPBP was notignificantly different (P � .64) between smaller (12 mm)nd larger balloon sizes (14–16 mm). Balloon inflation didot affect mean arterial pressures or heart rates during RF

igure 1 Intraperi-ardial balloon position.nterior-posterior (AP)

nd left anterior obliqueLAO) views of the in-rapericardial balloonositioned using differ-nt approaches: A: Di-ect puncture to the pos-erior pericardial space;: anterior access witheflectable sheath guid-nce; C: postprocedural,n vivo photographs ofnflated intrapericardialalloon (yellow arrow).N along the pericar-ium is indicated byashed white arrow.SO � esophageal map-ing catheter; PV Map �ulmonary vein mappingatheter.

atheter ablation application (Figure 3B, bottom). a

isplacement of right PNigure 4 and Table 2 show typical results of IPBP protectionf the right PN. At a total of 33 total sites (4.1 sites/animal),ndocardial high-output pacing around the RSPV anteriorstium resulted in PN capture before IPBP inflation (Table). These sites were tagged as PN capture sites. In allnimals, positioning of the balloon catheter for protection ofhe PN was achieved via a superior approach through theransverse sinus or via an inferior approach using a deflect-ble sheath (Figure 4). Slight anatomic differences betweennimals dictated which approach (superior or inferior) wasppropriate. Balloon inflation prevented PN capture at 3091%) of 33 tagged sites (see online movie). All animals hadormal PN capture at the end of the study, as confirmed byepeat high-output pacing and fluoroscopy after removal ofhe intrapericardial balloon, demonstrating that inflation ofhe intrapericardial balloon did not cause PN injury.

omplicationshere were no cases of hemopericardium, cardiac tampon-de, or intrapericardial balloon rupture. No other acute com-lications were observed.

iscussiono our knowledge, this is the first in vivo animal study toystematically examine the feasibility and efficacy of IPBPn the setting of LA ablation. The major findings of thistudy are as follows: (1) IPBP was technically feasible inhis animal model and did not result in acute complications;2) IPBP effectively displaced vulnerable collateral tissues;

nd (3) IPBP prevented significant esophageal heating from

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84 Heart Rhythm, Vol 7, No 1, January 2010

ndocardial RF delivery, as well as PN capture from endo-ardial pacing.

sophageal displacement and protectionver the past decade, the use of catheter ablation for the

reatment of AF has increased.15 In an effort to improverocedural outcomes, extensive LA lesion sets have beenroposed.2,3 Esophageal injury and atrioesophageal fistulare potentially life-threatening complications that may ariserom RF energy applied to the posterior LA wall.5 Oneecent study showed that an esophageal ulcer was observedy endoscopy 1–3 days after AF ablation in 36% of patientsithout luminal esophageal temperature monitoring.16 Mul-

iple strategies have been proposed to detect esophagealeating and to protect the esophagus during ablation. Thesophagus can be filled with radioopaque contrast media to

etermine its position fluoroscopically and limit RF appli- g

ation adjacent to the esophagus.17 Temperature monitoringithin the esophagus has also been used to detect esopha-eal heating during ablation.12,16 Active protection tech-iques have also been proposed, including an esophagealooling system18 and mechanical displacement of thesophagus away from the LA using an endoscopic trans-sophageal probe.19,20

More recently, other strategies aimed at increasing theistance between the heart and collateral structures haveeen proposed. Methods using intrapericardial air andaline11 or an intrapericardial balloon9 to separate theeart from the PN during ablation have been described.ur group published a case report describing the use of

n intrapericardial balloon to protect the esophagus in aatient undergoing repeat AF ablation8; the findings sug-

Figure 2 Separation of the LA and esophagusduring IPBP. A: Modified left lateral view of EAimages; B: left anterior oblique (LAO) fluoro-scopic view of the LA and contrast-filled esopha-gus, before and after balloon inflation in the sameanimal. In this case, balloon inflation caused si-multaneous movement of the CIPV and esophagusaway from each other. Esophagus and PV mapcatheter separation increased with balloon infla-tion. C: Right anterior oblique (RAO) view; D:posterior view of EA maps in the same porcineheart and esophagus shown in Figure 1A. Duringballoon inflation within the oblique sinus, theesophagus was markedly flattened (D) and shiftedaway from the posterior LA. The minimum dis-tance between the LA and esophagus increased by21 mm. ESO � esophagus; RSPV � right supe-rior PV; LSPV � left superior PV; CIPV� com-mon inferior PV; LAA � LA appendage; EPI �epicardial shell. PV map � pulmonary vein map-ping catheter located at the CIPV ostium.

ested that IPBP may allow safe and effective delivery of

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F energy to the targeted tissues. The present study is therst systematic experimental evaluation of such an IPBP

echnique.These data demonstrate that the IPBP approach is tech-

ically feasible in porcine hearts. Appropriate balloon align-ent was achieved using one of two approaches, and bal-

oon position within the pericardial space was stable afteralloon inflation. In all animals, the esophagus was dis-laced from its original position by intrapericardial balloonnflation. In some cases, both the esophagus and the PVere displaced. Nevertheless, no significant hemodynamic

onsequences resulted from impaired LA filling, and noignificant complications were observed. Optimization of

able 1 Separation of esophagus and atrium before and after I

nimal no. ApproachBalloonsize, mm

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Anterior, deflectable sheath 12 10Posterior puncture 12 11Anterior, deflectable sheath 12 10Anterior, deflectable sheath 14 8Anterior, deflectable sheath 14 11Posterior puncture 16 13Anterior, deflectable sheath 16 14Posterior puncture 18 21

verage � SD 14.3 � 2.3 12.3

igure 3 Luminal esophageal temperature. A: Fluoro-copic images of the positions of each electrode without IPBPcontrol, upper panel) and with balloon inflation (IPBP, mid-le panel) in the LAO fluoroscopic views. LAO EA imageslower panel). ESO � esophageal catheter; ABL � endocar-ial ablation catheter. B: Time courses of luminal esophagealemperature, mean arterial pressure (MAP), and heart rateHR) during RF catheter ablation (RFCA) at the distal CIPVnd during recovery. Temperature increased during controlonditions (no IPBP, white circles) but was unchanged withalloon inflation. Overall temperature increased significantlyn control conditions compared with in IPBP groups for allalloon sizes (P�.0001, ANOVA). At each time point duringFCA application and over 30 seconds of recovery, control

emperatures were significantly greater than IPBP groupsP�.004, Student’s t-test). There were no significant differ-nces in the esophageal temperature between the smaller (12m, blue circles) and larger balloons (14–16 mm, red cir-

les; P � .64, ANOVA). During RFCA application andecovery phases, MAP and HR did not change significantly.

ize and shape for intrapericardial balloons warrants furthertudy.

The mechanism of esophageal injury or fistula during RFblation is not completely understood. Thermal injury is theost likely cause (with an area of necrosis surrounded by

nflammatory cells), although an ischemic mechanism haslso been proposed.5,21,22 Shorter distance and increasedontact force might increase the risk of esophageal injury.23

he IPBP method has potential advantages for the preven-ion of esophageal injury during RF application. In additiono displacement of the esophagus, the presence of the inter-ening liquid-filled balloon likely conferred additionalhielding of surrounding tissues from RF energy. For diffi-

ntus, mm

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ult balloon catheter approaches, the deflectable sheathroved valuable for precise positioning in the pericardialpace.

ight PN displacementhe PN has an epicardial course (Figure 1C), and PN

njury has been reported after percutaneous catheter ab-

able 2 Displacement of PN

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ation procedures for accessory pathways,24 inappropriateinus tachycardia,25 and AF.6,7,26 The anterior wall of theSPV is less than 2 mm from the right PN in 32% of

ubjects based on autopsy data.27 The reported prevalencef PN injury as a complication of AF ablation is 0.11%–.48%.7,28 Methods to prevent left PN injury during epicar-ial catheter ablation for VT have been proposed.9–11 Tour knowledge, there have been no reports describing anffective displacement technique of the right PN in theetting of LA ablation. Our experimental observations sug-est that two balloon approaches (superior and inferior)ith a deflectable sheath appear to be feasible for displace-ent and protection of the right PN in this animal model. In

ddition, the balloon catheter was easily repositioned fromn esophageal protection site in the oblique sinus, to thenterior aspect of the RSPV for protection of the right PN,uggesting that IPBP provides a flexible approach for col-ateral protection during LA ablation.

imitationshe present study was performed in a limited number oforcine hearts, which have anatomic differences from hu-an hearts. The porcine esophagus is usually positioned

Figure 4 PN protection. A, B: left and rightanterior oblique, respectively, fluoroscopic imagesof the same porcine heart shown in Figure 1B. A16 mm by 4 cm balloon was inflated near theanterior aspect of the RSPV via the transversesinus (superior approach). A mapping catheter(Map) was positioned at the endocardial RSPVostium for high-output pacing. Fluoroscopic AP(C) and right lateral EA (D) images of a secondporcine heart show a 12 mm by 4 cm ballooninflated near the anterior aspect of the RSPV viaan inferior approach. Red circles indicate siteswith PN capture before balloon inflation.

lightly further away from the posterior LA than in humans.

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87Nakahara et al IPBP for Prevention of Damage during Ablation

owever, it can be argued that the closer proximity betweenhe esophagus and posterior LA in humans suggests thatPBP may be even more useful in humans than in ournimal model. For this technique, epicardial access is re-uired, which is not performed in all ablation centers andarries its own inherent risks. Our studies used an imped-nce-based EA mapping system. Balloon inflation may haveaused a small change in the thoracic impedance field,hich could alter the EA map. However, no changes in

ardiac geometry (PVs, left appendage, and LA wall) wereetected, and catheter position was confirmed by fluoro-copic imaging. Our study did not address the minimumolume or ideal shape of the balloon for attenuating the risen temperature in the esophagus. Further studies are war-anted to elucidate the potential significance of IPBP in alinical setting and to optimize balloon shapes and sizes.

onclusionsur experimental observations suggest that the IPBP con-

ept is feasible and might decrease the risk of collateralamage that would otherwise occur during RF catheterblation of the LA. Deflectable sheath guidance may facil-tate the optimal positioning of the intrapericardial balloon.f the results in this animal study are borne out in humans,he IPBP method might one day serve as a tool to improvehe safety and efficacy of catheter ablation procedures forA arrhythmias such as AF.

cknowledgmentshe authors thank Dr. Tara Bourke, Nikhil Sunny Patel, andelly A. Walker for their assistance with porcine experi-ents.

ppendixupplementary dataupplementary data associated with this article can beound, in the online version, at doi:10.1016/j.hrthm.2009.9.022.

eferences1. Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibril-

lation by ectopic beats originating in the pulmonary veins. N Engl J Med1998;339:659–666.

2. Jais P, Hocini M, Hsu LF, et al. Technique and results of linear ablation at themitral isthmus. Circulation 2004;110:2996–3002.

3. Hocini M, Jais P, Sanders P, et al. Techniques, evaluation, and consequences oflinear block at the left atrial roof in paroxysmal atrial fibrillation: a prospectiverandomized study. Circulation 2005;112:3688–3696.

4. Cappato R, Calkins H, Chen SA, et al. Prevalence and causes of fatal outcomein catheter ablation of atrial fibrillation. J Am Coll Cardiol 2009;53:1798–1803.

5. Cummings JE, Schweikert RA, Saliba WI, et al. Brief communication: atrial-esophageal fistulas after radiofrequency ablation. Ann Intern Med 2006;144:

572–574.

6. Bai R, Patel D, Di Biase L, et al. Phrenic nerve injury after catheter ablation:

should we worry about this complication? J Cardiovasc Electrophysiol2006;17:944–948.

7. Sacher F, Monahan KH, Thomas SP, et al. Phrenic nerve injury after atrialfibrillation catheter ablation: characterization and outcome in a multicenterstudy. J Am Coll Cardiol 2006;47:2498–2503.

8. Buch E, Nakahara S, Shivkumar K. Intra-pericardial balloon retraction of the leftatrium: a novel method to prevent esophageal injury during catheter ablation.Heart Rhythm 2008;5:1473–1475.

9. Buch E, Vaseghi M, Cesario DA, et al. A novel method for preventing phrenicnerve injury during catheter ablation. Heart Rhythm 2007;4:95–98.

0. Fan R, Cano O, Ho SY, et al. Characterization of the phrenic nerve course withinthe epicardial substrate of patients with nonischemic cardiomyopathy and ven-tricular tachycardia. Heart Rhythm 2009;6:59–64.

1. Matsuo S, Jais P, Knecht S, et al. Images in cardiovascular medicine. Noveltechnique to prevent left phrenic nerve injury during epicardial catheter ablation.Circulation 2008;117:e471.

2. Redfearn DP, Trim GM, Skanes AC, et al. Esophageal temperature monitoringduring radiofrequency ablation of atrial fibrillation. J Cardiovasc Electrophysiol2005;16:589–593.

3. Perzanowski C, Teplitsky L, Hranitzky PM, et al. Real-time monitoring ofluminal esophageal temperature during left atrial radiofrequency catheter abla-tion for atrial fibrillation: observations about esophageal heating during ablationat the pulmonary vein ostia and posterior left atrium. J Cardiovasc Electro-physiol 2006;17:166–170.

4. Cummings JE, Schweikert RA, Saliba WI, et al. Assessment of temperature,proximity, and course of the esophagus during radiofrequency ablation withinthe left atrium. Circulation 2005;112:459–464.

5. Noheria A, Kumar A, Wylie JV, Jr., et al. Catheter ablation vs antiarrhythmicdrug therapy for atrial fibrillation: a systematic review. Arch Intern Med 2008;168:581–586.

6. Singh TM, d’Avila A, Doshi SK, et al. Esophageal injury and temperaturemonitoring during atrial fibrillation ablation. Circ Arrhythm Electrophysiol2008;1:162–168.

7. Yamane T, Matsuo S, Date T, et al. Visualization of the esophagus throughoutleft atrial catheter ablation for atrial fibrillation. J Cardiovasc Electrophysiol2006;17:105.

8. Berjano EJ, Hornero F. A cooled intraesophageal balloon to prevent thermalinjury during endocardial surgical radiofrequency ablation of the left atrium: afinite element study. Phys Med Biol 2005;50:N269–279.

9. Herweg B, Johnson N, Postler G, et al. Mechanical esophageal deflection duringablation of atrial fibrillation. Pacing Clin Electrophysiol 2006;29:957–961.

0. Chugh A, Rubenstein J, Good E, et al. Mechanical displacement of the esoph-agus in patients undergoing left atrial ablation of atrial fibrillation. Heart Rhythm2009;6:319–322.

1. Dixit S, Marchlinski FE. How to recognize, manage, and prevent complicationsduring atrial fibrillation ablation. Heart Rhythm 2007;4:108–115.

2. Sanchez-Quintana D, Cabrera JA, Climent V, et al. Anatomic relations betweenthe esophagus and left atrium and relevance for ablation of atrial fibrillation.Circulation 2005;112:1400–1405.

3. Nakagawa H, Ikeda A, Shah DC, et al. Role of contact force in esophageal injuryduring left atrial radiofrequency ablation. Heart Rhythm 2008;15:S68.

4. Rumbak MJ, Chokshi SK, Abel N, et al. Left phrenic nerve paresis complicatingcatheter radiofrequency ablation for Wolff-Parkinson-White syndrome. AmHeart J 1996;132:1281–1285.

5. Durante-Mangoni E, Del Vecchio D, Ruggiero G. Right diaphragmparalysis following cardiac radiofrequency catheter ablation for inap-propriate sinus tachycardia. Pacing Clin Electrophysiol 2003;26:783–784.

6. Lee BK, Choi KJ, Kim J, et al. Right phrenic nerve injury following electricaldisconnection of the right superior pulmonary vein. Pacing Clin Electrophysiol2004;27:1444–1446.

7. Sanchez-Quintana D, Cabrera JA, Climent V, et al. How close are the phrenicnerves to cardiac structures? Implications for cardiac interventionalists. J Car-diovasc Electrophysiol 2005;16:309–313.

8. Cappato R, Calkins H, Chen SA, et al. Worldwide survey on the methods,

efficacy, and safety of catheter ablation for human atrial fibrillation. Circulation2005;111:1100–1105.