Incremental benefit of rate adaptive pacing on exercise performance during cardiac resynchronization therapy

Abstract

BACKGROUND: Cardiac resynchronization therapy (CRT) improves exercise capacity in patients (pts) with left bundle branch block (LBBB) and heart failure. However, pharmacologic treatment with -blockers and/or coexisting chronotropic incompetence frequently limit an increase in heart rate during exercise in pts with heart failure, which may have negative effect on the exercise capacity. The potential incremental benefits of using rate adaptive sensor and atrioventricular interval (AVI) adaptation in CRT during exercise have not been studied. METHODS AND RESULTS: We studied the exercise performance in 21 pts (15 males, mean age: 70 9 years) with LBBB (mean QRS duration 176 22 ms) and heart failure (76% nonischemic cardiomyopathy, mean ejection fraction: 24 10%) implanted with CRT for 12 months. All pts received stable medications (86% on -blockers) and their device AVI was optimized by using Ritter’s formula (mean 101 21 ms). All pts underwent cardiopulmonary exercise treadmill test with their pacemaker programmed to 1) DDD mode with fixed AVI (DDD-off); 2) DDD mode with adaptive AVI algorithm on (DDD-on) and 3) DDDR mode with adaptive AVI algorithm on (DDDR-on) in a randomized fashion. The minimum AVI was 76 11 ms using adaptive AVI algorithm at the maximum exercise heart rate. The maximum heart rate achieved during peak exercise was significantly higher with DDDR-on mode than DDD-off and DDD-on mode (Figure 1). Both DDD-on and DDDR-on mode increased the exercise time compared to DDD-off mode (Figure 2). However, the use of DDDR-on mode further increased peak oxygen consumption (VO2 max) compared to DDD-off and DDD-on mode (Figure 3). CONCLUSIONS: In heart failure pts implanted with CRT, the use of rate adaptive pacing and adaptive AVI algorithm can further enhance their exercise performance by reducing chronotropic incompetence during exercise.