Abstracts S185

Canadian Cardiovascular Society (CCS) PosterPOSTER - CLINICAL ELECTROPHYSIOLOGY

Friday, October 18, 2013

247SUBOPTIMAL TIME IN THERAPEUTIC RANGE (TTR) FORINTERNATIONAL NORMALIZED RATIO (INR) MEASUREMENTSOBSERVED IN AN OUTPATIENT CARDIOLOGY CLINIC: IMPACTOF GENDER, ETHNICITY, DISEASE ETIOLOGY, CHADSVASCSCORE, PHYSICIANS AND CLINIC SITE

N Singh, S Premji, S Chandra, D Song, L Yan, D Suh

Atlanta, Georgia

BACKGROUND: TTR correlates inversely with ischemic strokerisk. Novel anticoagulants benefit most those patients (pts)with poor TTR. Variations in TTR are common with a rangeof between 55-60% being the norm and > 70% beingoptimal. It is not known what factors impact TTR most in thecommunity cardiology setting.METHODS: Retrospective chart review of all pts beingtreated with warfarin in a single, multi-site suburban,outpt cardiology practice for 1 yr between Jul 2011 and Jul2012 .RESULTS: In the 523 pts being followed, mean age was 69.6yrs with 51% males. Hypertension (73%), hyperlipidemia(49%) were common, while diabetes (21%), smoking (6%),alcohol (21%) and aspirin use (20%) were less. The mean EFwas 54 + 13%. Atrial fibrillation was the most commonreason for treatment (75%) followed by mechanical valves(5%) venous system disease (15%) and arterial system disease(5%). An average of 12+5 INR readings/pt were done over theyear. Average time on warfarin was 35+18 months. TTR forthe overall group was 44.5 + 22.3%.

There was no difference in TTR for males (44.2%) vsfemales (44.9%), p¼0.51. There were 44% Caucasians, 38%African Americans and 13% Asians. TTR for these ethnicitiesvaried significantly, 49.0% vs 37.7% vs 50.3% respectively,p¼0.000001. INR's were managed by 7 physicians withsignificant differences (TTR range 39.9% to 49.0%,p¼0.025). TTR also varied significantly between 4 clinic sites(TTR range 36.4% to 51.9%, p¼0.04). The meanCHADSVasc score was 2. No difference in TTR was seenbased on CHADSVasc score p¼0.4. Clinics and physicianshaving a higher proportion of African American pts tended tohave lower TTR. TTR was worse in pts with arterial (36.9%)and venous disease (40%) vs atrial fibrillation (46.5%) andmechanical valves (47.6%), p¼0.02. Bleeding rates were lowover the year (4%). For atrial fibrillation pts, only 11% hada documented discussion about using novel anticoagulants asa treatment option.CONCLUSION: Our findings suggest that TTR may besubstantially worse in clinical practice than previouslypublished literature would suggest. Ethnicity, physicians,clinic site and disease etiology may all contribute to poor

TTR. Novel anticoagulants should be discussed moreoften, especially in afib pts at higher risk for poor TTR.Confirmation of these findings in a broader populationcould have significant implications for future anti-coagulation management and stroke prevention.

248CLINICAL ECG AUDIT: A USEFUL QUALITY ASSURANCE TOOL

A Khosla, J Kornder, K Bhagirath

Vancouver, British Columbia

BACKGROUND: The ECG is a vital diagnostic clinical tool.Important decisions regarding treatment often depend onaccurate interpretation, and therefore competency in ECGreading is of utmost importance.

A formal process to measure ongoing competency inECG interpretation is not outlined by the Royal Collegeof Physicians and Surgeons of Canada (RCPSC), althoughthis would fall under the College's Maintenance ofCertification program; a mandatory requirement forspecialists. The 2001 American College of Cardiology(ACC) Competence Statement on Electrocardiographyrecommends routine participation in quality improvement,specifically advocating for “activities such as havinga number of ECGs over-read by colleagues and partici-pating in periodic discussions of systemic issues involvingECG interpretation.”METHODS: The Division of Cardiology at Surrey MemorialHospital designed a pilot clinical audit of 53 ECG readersthroughout the Fraser Health Authority. The audit wasdesigned to retrospectively review 740 adult ECGs inter-preted and reported by cardiologists and internists using theMUSE system (General Electric). Fourteen ECGs per inter-preting physician were randomly selected and de-identified.The ECGs were over-read by one reviewer (JK) who wasblinded to the patient, site and interpreting physician name.Upon review of the ECG and the initial interpretation, thereviewer classified each into one of three groups outlinedbelow:

All moderate or significant discrepancies were reviewed ina blinded fashion by at least 3 further reviewers. Anyremaining difference of opinion resulted in the ECG reclas-sified as Group 1 “no discrepancy”.RESULTS: Of the 740 ECGs randomly selected, 7 werepediatric ECGs and were excluded from the clinical audit. Intotal, 87.3% (640) were found to have none or minordiscrepancies, 10% (74) were classified in the moderatecategory, and 2.7% (19) had a significant discrepancy.Amongst the 53 ECG readers, there was an average

S186 Canadian Journal of CardiologyVolume 29 2013

concordance of 87.3% in initial interpretation. Furtheranalysis of each reader's individual concordance with theirpeers and frequency of each type of discrepancy was evaluatedand provided to the participants.CONCLUSION: This pilot clinical audit demonstrates thatthere can be major clinically relevant discrepancies inECG interpretation in up to 3% of cases, thus providingimpetus for the development and implementation ofa regional ECG audit program. This program can actas a quality assurance tool for administrators and iseasily scalable to other regional and provincial healthauthorities.

249UNUSUALLY HIGH RATE OF HYPERTHYROIDISM OBSERVED INPATIENTS EXPOSED TO AMIODARONE IN CALGARY

PT Pollak, N Vijayaratnam

Calgary, Alberta

BACKGROUND: The high iodine content of amiodaroneprecludes its use at any dose without at least a magnitudeincrease in exposure to iodine. A 200 mg tablet contains 75mg of iodine, or which 7.5 mg is bioavailable, rapidlydwarfing the normal total body content of 14 mg.Hyperthyroidism is observed in about 3.3% of individualsin populations exposed to an increase in environmentaliodine through increased salt fortification, water purifica-tion or seaweed ingestion. Study of linked prescription/clinical databases confirms that patients taking amiodaroneand thus exposed to excess iodine, also experience hyper-thyroidism at a rate of 3-4%. This suggests they arereacting to iodine rather than the peripheral pharmaco-logical effect of amiodarone on thyroxine conversion totriiodothyronine. We studied the incidence of hyperthy-roidism in patients enrolling in the Calgary AmiodaroneClinic and compared it to personal experience in otherCanadian cities.METHODS: Serial thyroid indices (Thyroid StimulatingHormone, Free Thyroixine-T4 and Total Triiodothyronine-T3), ALT and serum amiodarone concentrations werecollected every six months on 115 patients enrolled in clinicfor amiodarone dose adjustment and monitoring of hepaticand thyroid function.RESULTS: During three years of follow-up, 12 patientsdeveloped FreeT4>30 pmol/L with an mean time of onset of914 days of therapy and a mean FreeT4 of 44 pmol/L. Serumamiodarone concentration was not high at a mean of 1.04mcmol/L (target < 2.2 mcmol/L) and there was no evidenceof any drug toxicity in the 12 patients with a mean ALT of 37U/L and no ocular, neurological, pulmonary or dermalsymptoms. All cases resolved within 6 months of initiatingmethimazole therapy (usually 5 mg p.o. TID) without stop-ping amiodarone.

CONCLUSION: The observed rate of hyperthyroidism ina sample of Calgary patients receiving amiodarone was 10.4%,about 3 times that predicted by epidemiology and our expe-rience in London and Halifax. What determines this deviationfrom the norm remains to be discovered. The literaturesuggests that hyperthyroidism incidence varies geographicallyby iodine intake. One might speculate that like the WupperValley in Europe, the population of Alberta may have adaptedto low environmental iodine and react more vigorously toiodine supplementation from amiodarone. The answer may liein studying iodine exposure in various cities in Canada bymeasuring urinary iodine output in patients not receivingamiodarone.

250EVALUATION OF EXERCISE-INDUCED CHANGES IN QT INTERVALUNRELATED TO HEART RATE ACCELERATION - THE STRESS QTSTUDY

L Laroussi, H Nguyen Thanh, B Dube, A Vinet, V Jacquemet,R Leblanc, G Becker, T Kus, R Nadeau, M Sturmer

Montréal, Québec

BACKGROUND: The QT interval is heart rate dependent. Itdecreases as heart rate increases. Several correction modelshave been proposed to normalize its value at an RR intervalof 1000 ms. In addition, the autonomic nervous systemmay affect QT interval duration independently of heartrate.AIM: To compare QT durations during a physiological stresstest and during atrial pacing at the same RR intervals.METHODS: We recruited ten ambulatory patients with dualchamber pacemakers or ICDs who were rarely paced in theventricle. While wearing a Holter monitor in supineposition, subjects were stimulated in AAI mode at heartrates of 100 bpm (RR¼600 ms) and 120 bpm (RR¼500ms) for 2 minutes at each step. Subsequently, theywalked on a treadmill to reach comparable average heartrates. The analysis of QT intervals excluded prematureventricular contractions, ventricular paced beats andartifacts.RESULTS: During the stress test, 7 patients were able to reachstable RR intervals close to 100 and 120 bpm for at least 30seconds. These 7 patients were considered for statisticalanalysis using 2-way repeated measure ANOVA (PE effect:pacing vs effort, FR effect: 100 vs 120 bpm). The mean RRintervals were similar during pacing and stress for each step(601.8�0.8 vs 601.7�9.4 ms and 500.3�1.6 vs 503.4�9.9ms, PE effect: p ¼ 0.635). The mean QT intervals showeda statistically significant difference (341.0�16.4 vs334.6�14.2 ms and 319.0�14.1 vs 308.6�15.0 ms)according to both frequency (FR effect, p < 0.001) and pacevs effort (PE effect: p ¼ 0.049), but not according to theirinteraction (PE*FR effect: p ¼ 0.290).