Abstract
Physiological responsive pacing includes the application of sensors to measure physiologic variables, which in turn are used to control pacemaker rate. Six such systems are evaluated based on a comparison of (1) speed of response, (2) sensor reliability, and (3) system specificity. Although there is not a clear-cut solution, and every system has some weaknesses, several sensors seem more feasible than others. Much research remains to be done, and the indications and patient benefits must be established.