Activity-mode cardiac pacing: clinical considerations.

In the past, pacemaker candidates with "chronotropic incompetence" or chronic atrial arrhythmias have been treated with fixed-rate cardiac pacing. During physical exertion, however, increased cardiac output is often limited by this fixed rate. A physiologic pacemaker that increases the cardiac pacing rate as a response to physical activity is now available. The benefits of this pacemaker are increased heart rate during physical activity and increased exercise tolerance.