Determinants of efficacy of atrial pacing in preventing atrial fibrillation recurrences

Introduction: Several studies have shown that single or dual site atrial pa cing is effective in reducing the frequency of recurrent atrial fibrillatio n (AF) in selected patients, However, it is still unclear what the best pre dictors are of long-term efficacy of atrial pacing. Methods and Results: Forty-seven patients with paroxysmal AF requiring dema nd pacing underwent electrophysiologic study and dual chamber pacemaker imp lant. After 4 months of follow-up, patients were divided into two groups ac cording to the presence (group 1) or absence (group 2) of symptomatic AF re currences. Atrial pacing markedly reduced AF recurrences in all patients. T wenty-four patients were free of arrhythmia. The basal state conduction tim es (CTs) and. the incremental conduction times (ICTs), during programmed el ectric stimulation between the high right atrium (HRA) and the coronary sin us ostium (CSos) but not between the HRA and the His-bundle region, were si gnificantly longer in group 1. There was no statistical difference in the e ffective 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 (IC T-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, respect ively). Conclusion: Single site atrial pacing is effective in reducing AF recurrenc es, with decreasing efficacy in patients with greater right atrial conducti on delay and wider refractoriness dispersion.