Role of Rate Control and Regularization Through Pacing in Patients With Chronic Atrial Fibrillation and Preserved Ventricular Function: The VRR Study

AIM: High heart rates in chronic atrial fibrillation (CAF) is one of the factors responsible for hemodynamic alterations and may lead to tachycardiomyopathies. The ventricular rate regulation (VRR) study evaluates the effect of ventricular rate regularization in CAF patients with preserved ventricular function, marked ventricular rate variability, and indications for pacemaker (PM) implantation owing to symptomatic pauses. Rate regularization was achieved using VRR algorithm (INSIGNIA pacemakers, Guidant Corp., St. Paul, MN, USA). METHODS: One month after PM implantation, 58 patients followed two 3-month crossover periods (VRR-OFF; VRR-ON) in which the VRR algorithm was randomized and compared to fixed rate stimulation at 60 ppm. During follow-up visits a 6-minute walk test was performed under partially inhibited conditions (PM at 40 ppm) and ventricular response was recorded. The following parameters were measured: mean ventricular rate (MR), rate variability (RR30), rate recovery after exercise (SLOPE = (R-END - R-REC)/(R-END - 40)), R-END being the rate at end of walk and R-REC the rate 1 minute after exercise. RESULTS: The VRR algorithm decreased rate variability (RR30: -7.36 +/- 8.8; P < 0.01) without increasing ventricular rate (MR: -1.11 +/- 8.3 P = NS), while SLOPE improved significantly (SLOPE: +15.41 +/- 16.8 P < 0.01). CONCLUSIONS: VRR effectively stabilizes rate, without increasing pacing rate above spontaneous rhythm and helps achieve a more favorable autonomic balance, improving rate recovery after exercise.