Determinants of efficacy of atrial pacing in preventing atrial fibrillation recurrences

Introduction: Several studies have shown that single or dual site atrial pacing is effective in reducing the frequency of recurrent atrial fibrillation (AF) in selected patients, However, it is still unclear what the best predictors are of long-term efficacy of atrial pacing. Methods and Results: Forty-seven patients with paroxysmal AF requiring demand pacing underwent electrophysiologic study and dual chamber pacemaker implant. After 4 months of follow-up, patients were divided into two groups according to the presence (group 1) or absence (group 2) of symptomatic AF recurrences. Atrial pacing markedly reduced AF recurrences in all patients. Twenty-four patients were free of arrhythmia. The basal state conduction times (CTs) and. the incremental conduction times (ICTs), during programmed electric stimulation between the high right atrium (HRA) and the coronary sinus ostium (CSos) but not between the HRA and the His-bundle region, were significantly longer in group 1. There was no statistical difference in the effective refractory period (ERP) recorded at the HRA, the low right atrium (LRA), and the CSOS between the two groups, whereas the differences between the greatest and. least recorded ERPs measured from tbe HRA, LRA, and CSOS (Delta ERP) mere significantly greater In group 1 patients. Two parameters were selected by discriminant multivariate analysis, namely Delta CTOS (ICT-CT between HRA and CSOS) and Delta ERP. The first had a greater relative importance in predicting AF recurrence (r(2) = 0.33 and r(2) = 0.1, respectively). Conclusion: Single site atrial pacing is effective in reducing AF recurrences, with decreasing efficacy in patients with greater right atrial conduction delay and wider refractoriness dispersion.