Randomized Controlled Trial of Fixed Rate Versus Rate Responsive Pacing After Radiofrequency Atrioventricular Junction Ablation:

INTRODUCTION: Ablation of the AV junction is a widely accepted treatment of drug-refractory atrial fibrillation. Long-term pacing of the right ventricular (RV) apex following AV junction ablation can result in adverse cardiac remodeling. However, anecdotal studies report that pacing too slowly following AV junction ablation was associated with propensity to sudden cardiac death. The aim of this study was to provide information about the balance between measures of quality of life versus measures of electrical remodeling achieved by pacing with different rate modalities in a randomized pilot clinical trial. METHODS AND RESULTS: Patients with permanent atrial fibrillation were randomized to VVI (80 beats/min) versus VVIR (minimum rate 80 beats/min), whereas patients with paroxysmal atrial fibrillation were randomized to DDI versus DDDR pacing at discharge from hospital. Serially, measurements of exercise capacity, quality of life, cycle length dependence of QT dispersion (QTdisp), RV refractoriness, and the incidence of nonsustained ventricular tachycardia were made in 28 patients over a 6-month follow-up period. Time-dependent increases in QTdisp were observed in patients randomized to the rate responsive mode (RR-ON) but only when paced at 40 beats/min. This was paralleled by time-dependent increases in RV refractoriness (270 +/- 11 ms at baseline to 302 +/- 5 ms at 6 months) in patients with RR-ON. RR-ON also was associated with trends to an increasing incidence of episodes of nonsustained ventricular tachycardia and worsening of some measures of quality of life. Exercise capacity was not substantially different in the randomized groups. CONCLUSION: Rate responsive pacing results in electrical remodeling of the ventricle following AV junction ablation, but exercise capacity was similar in groups with RR-ON or RR-OFF.