Rate-adaptive AV delay and exercise performance following cardiac resynchronization therapy

Background Physiological shortening of the atrioventricular (AV) interval with increasing heart rate is well documented in normal human beings and is an established component of dual-chamber pacing for bradycardia. Objectives To assess the effect of exercise on optimal AV delay and the impact of a patient-specific rate-adaptive AV delay (RAAVD) on exercise capacity in patients with heart failure following cardiac resynchronization therapy. Methods Phase 1: We performed iterative AV optimization at rest and exercise in 52 cardiac resynchronization therapy patients in atrial-sensed mode (mean age 71.6 ± 9.2 years, 25% females). Phase 2: Subsequently, 20 consecutive volunteers from this group (mean age 69.2 ± 9.6 years, 15% females) underwent cardiopulmonary exercise testing with RAAVD individually programmed ON (RAAVD-ON) or OFF (RAAVD-OFF). Results Phase 1: In 94% of the patients, there was a marked reduction (mean 50%) in optimal AV delay with exercise. The optimal resting vs exercise AV delay was 114.2 ± 29 ms at a heart rate of 64.4 ± 7.1 beats/min vs 57 ± 31 ms at a heart rate of 103 ± 13 beats/min ( P Phase 2: With RAAVD-ON, significantly better exercise times were achieved (8.7 ± 3.2 minutes) compared with RAAVD-OFF (7.9 ± 3.2 minutes; P = .003), and there was a significant improvement in Vo 2 max (RAAVD-ON 16.1 ± 4.0 vs RAAVD-OFF 14.9 ± 3.7 mL/(kg · min); P = .024). Conclusions There was a dramatic reduction in optimal AV delay with physiological exercise in the majority of this heart failure cardiac resynchronization therapy cohort. Replicating this physiological response with a programmable RAAVD translated into a 10% improvement in exercise capacity.