Rate-Responsive Pacing by Means of Activity Sensing Versus Single Rate Ventricular Pacing: A Double-Blind Cross-Over Study

The clinical appiicabiJity of rate-responsive pacing (RRP) by means of activity sensing has been tested in 15 patients. The patients (ages 24–85) had sinus node dysfunction (2), atrial fibrillation (7), or sinus rhythm (6) combined with complete atrioventricular block. Exercise capacity was investigated on a bicycle ergometer and on a treadmill in a double-blind cross-over study design following one week each of fixed rate ventricu/ar pacing (70 bpm) and rate-responsive pacing (60/125–150 bpm). The patients answered a questionnaire concerning subjective symptoms. A Holter ECG was recorded during 24 hours of all day activity on rate-responsive pacing. During exercise in the rate-responsive mode, heart rate increased more on the treadmill than on the bicycle. A majority of the patients (13 of 15) preferred rate-responsive pacing mainly due to less dyspnea and tiredness. Exercise capacity improved significantly both on bicycle (+7%; p < 0.01) and on treadmill (+19%; p < 0.01) during rate-responsive pacing. There were no complications during the follow-up period. In conclusion, the activitysensing pacemaker is a valuable supplement to existing types o/ pacemakers. It should be used in patients in whom an atrial electrogram cannot be used for rate triggering.