Rate-responsive pacing improves exercise tolerance in heart transplant recipients: a pilot study

Area of Science:

• Cardiology
• Exercise Physiology
• Transplantation Medicine

Background:

• Chronotropic incompetence limits exercise capacity in heart transplant recipients.
• Late or incomplete cardiac reinnervation may not restore appropriate heart rate response during exercise.
• Rate-responsive pacing is a potential intervention to improve cardiovascular function post-transplant.

Purpose of the Study:

• To evaluate the efficacy of rate-responsive pacing on peak heart rate and exercise capacity.
• To compare exercise performance with and without rate-responsive pacing in heart transplant recipients.

Main Methods:

• Eight male heart transplant recipients with pacemakers underwent two maximal graded exercise tests (GXT) using the Naughton protocol.
• Pacemakers were tested in a bradycardia support mode (unpaced) and a rate-responsive mode (paced).
• Beta-blockade with metoprolol was administered prior to the paced GXT to minimize endogenous catecholamine influence.

Main Results:

• Paced GXT showed significantly higher peak heart rate (149 vs. 129 bpm).
• Peak oxygen uptake, time to exhaustion, and minute ventilation were also significantly increased during paced GXT.
• All measured exercise parameters demonstrated statistically significant improvements with rate-responsive pacing (P < 0.05).

Conclusions:

• Rate-responsive pacemakers enhance peak heart rate and exercise capacity in heart transplant recipients.
• Activity-based sensor programming in pacemakers provides superior chronotropic support compared to circulating catecholamines.
• This technology offers a significant benefit for improving functional capacity after heart transplantation.