SummaryCatheter ablation has been established to be an effective therapy for drug-refractory paroxysmal AF and is recommended as the treatment of choice for many patients, including those with a permanent pacemaker (PM). However, the clinical efficacy of catheter ablation of paroxysmal AF in patients with a permanent PM for atrioventricular block (AVB) is not clear. Twenty-nine patients with a permanent PM for AVB (AVB + PM group), and 145 age-and gender-matched control patients (on a 1:5 basis) without AVB and without a permanent PM (no-AVB + no-PM group), were included in this study. Atrial fibrillation (AF) recurrence was defined as the occurrence of confirmed atrial tachyarrhythmia lasting more than 30 seconds beyond 3 months after catheter ablation in the absence of any antiarrhythmic treatment. During a mean follow-up period of 14.2 ± 8.6 months (range, 3-30 months), 54 patients (31.0%) developed recurrence of AF. The recurrence rate was higher in the AVB + PM group than in the no-AVB + no-PM group (48.3% versus 27.6%, P = 0.005). Cox regression analysis with adjustment for age, valvular heart disease, AVB and a PM together, left atrial (LA) diameter and PV isolation identified LA diameter (hazard ratio 1.054, 95% confidence interval 1.001-1.110, P = 0.047) and AVB and a PM together (hazard ratio 2.095, 95% confidence interval 1.109-3.960, P = 0.023) as two independent predictors of recurrence of AF. Patients with a permanent PM for AVB were at an increased risk of recurrence of AF after catheter ablation. (Int Heart J 2014; 55: 489-493) Key words: Recurrence A trial fibrillation (AF) is a common cardiac arrhythmia in the general population 1) and is associated with increased cardiovascular morbidity and mortality.2,3) A recent study showed that AF is the most frequent tachyarrhythmia in patients with a permanent pacemaker (PM), occurring in up to 37% of patients implanted due to atrioventricular block (AVB).4) Catheter ablation has been established to be an effective therapy for drug-refractory paroxysmal AF and is recommended as the treatment of choice for many patients, including those with a permanent PM. However, there is still a risk of recurrence after ablation. Our previous study evaluated the clinical efficacy of catheter ablation of paroxysmal AF in patients with a permanent PM for sick sinus syndrome (SSS) and showed that SSS and the use of a pacemaker together was an independent predictor of recurrence of AF. 5) SSS is primarily a disease of the elderly and is presumed to be due to senescence of the sinus node and atrial muscle. 6) Thus, SSS likely reflects an underlying atrial disease, which may be associated with an increased rate of recurrence of AF. In AVB patients with a permanent PM, although AVB may contribute little to the development of AF recurrence, the cumulative percentages of ventricular pacing may be higher in AVB patients than in SSS patients. Whether these patients also have an increased risk of recurrence of AF after catheter ablation is not clear. This retrospective study ...