Progression to Chronic Atrial Fibrillation After theInitial Diagnosis of Paroxysmal Atrial Fibrillation:Results From the Canadian Registry of AtrialFibrillationKerr CR, Humphries KH, Talajic M, et al. Am Heart J2005;149:489 –96.

Study Question: How often does paroxysmal atrial fibrilla-tion (PAF) progress to chronic atrial fibrillation (CAF)?Methods: A group of 757 patients (mean age 61 years) withPAF were enrolled in a registry at the time that PAF was firstdocumented. The patients were evaluated on an annualbasis and followed for a median of 8 years. CAF was definedas atrial fibrillation (AF) present for �1 year. Therapy wasat the discretion of the treating physician.Results: The rate of progression to CAF was 8.6% at 1 yearand 25% at 5 years of follow-up. The strongest independentpredictors of progression to CAF were moderate/severeaortic stenosis (relative risk [RR] 3), left atrial diameter �45mm (RR 2.7), cardiomyopathy (RR 2.4), left atrial diameter40–45 mm (RR 2.1), moderate/severe mitral regurgitation(RR 1.7), and age (RR 1.4 for 10-year increments).Conclusions: Approximately one-fourth of patients whopresent with PAF develop CAF within 5 years. The stron-gest predictors of progression to CAF are valvular disease,cardiomyopathy, left atrial enlargement and age.Perspective: Approximately 40% of patients in this registrywere treated with an antiarrhythmic medication after thediagnosis of PAF. Of note is that the use of antiarrhythmicmedications had no effect on progression to CAF. This mayreflect the poor long-term efficacy of rhythm-control med-ications and/or the inability to alter the natural history of AFby drug therapy, even when PAF is suppressed or made lessfrequent. FM

Comparative Assessment of Right, Left, andBiventricular Pacing in Patients With PermanentAtrial FibrillationBrignole M, Gammage M, Puggioni E, et al. Eur Heart J2005;26:712–22.

Study Question: Does left ventricular (LV) or biventricular(BiV) pacing have any long-term advantages over rightventricular (RV) pacing after atrioventricular junction cath-eter ablation (AVJCA) in patients with chronic atrial fibril-lation (CAF)?Methods: Both RV and LV leads were implanted in 56 pa-tients (mean age 70 years) with CAF who underwentAVJCA. Using a 3-month randomized crossover design, RVpacing was compared to LV and BiV pacing. The primaryend points were quality of life (QoL) and exercise capacityat the end of each 3-month study period.Results: No significant differences existed in QoL or exer-cise capacity between RV and LV pacing. Compared to RVpacing, BiV pacing was associated with a modest (�15%)

improvement in QoL, and with a similar degree of improve-ment in exercise capacity. The results were similar in pa-tients with an ejection fraction �40% and �40%.Conclusions: In patients with CAF who undergo AVJCA,neither LV nor BiV pacing provides any clinically meaning-ful advantages over RV pacing.Perspective: Over the past 24 years that AVJCA has beenperformed in patients with atrial fibrillation and an uncon-trolled ventricular rate, multiple studies have demonstrateda significant improvement in QoL and exercise capacitywith RV pacing. This useful study shows that, despite theventricular dysynchrony induced by RV pacing, there is noreason to routinely use BiV pacing after AVJCA. This isprobably because the beneficial effects of rate control andrate regularization after AVJCA overshadow the deleteriousaffects of dysynchrony induced by RV pacing. FM

Focal Atrial Tachycardia From the Ostium of theCoronary Sinus. Electrocardiographic andElectrophysiological Characterization andRadiofrequency Ablation

Kistler PM, Fynn SP, Haqqani H, et al. J Am Coll Cardiol2005;45:1488 –93.

Study Question: What are the characteristics of focal atrialtachycardia (FAT) arising at the coronary sinus (CS) os-tium?Methods: Activation mapping was performed in 193 pa-tients with FAT. Thirteen patients (6.7%, mean age 41years) in whom the site of origin was at the CS ostium werethe subjects of this study. Radiofrequency ablation (RFA)was performed, and the patients were followed for a medianof 25 months.Results: In 7 patients FAT was inducible by pacing and wasspontaneous in 5 patients. The mean FAT cycle length was360 ms. During FAT, the P waves were inverted in theinferior leads, isoelectric in lead I, and upright in aVL andaVR. Endocardial activation at the CS ostium was recordeda mean of 36 ms before the P wave. The RFA was acutelysuccessful in 11 of 13 patients (85%). One patient requiredrepeat RFA. During long-term follow-up, 11 patients (85%)remained off antiarrhythmic medications and had no fur-ther episodes of FAT.Conclusions: Approximately 7% of FATs arise at the CSostium. The RFA of these FATs has a high long-term successrate.Perspective: Right atrial FATs most commonly arise alongthe crista terminalis or tricuspid annulus. These types ofFAT generate P waves that are distinct from the P waves ofFAT arising at the CS ostium. When the P waves duringFAT have a morphology similar to that of typical atrialflutter (in which the atrial exit site is at the CS ostium), a siteof origin at the CS ostium should be suspected. FM

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