The potential utility of sensor-driven pacing in DDD pacemakers.

Sensor-driven pacemakers have clinically improved symptomatology over ventricular pacemakers. Adding rate responsiveness to DDD pacing would theoretically benefit patients with an inability to increase their atrial rate. We evaluated 20 patients who had long-term implanted DDD pacemakers as to the utility of an added effect of rate responsiveness. The pacemakers had been implanted for an average of 34 months. This patient group included 15 patients with atrioventricular (AV) block and five patients with sick sinus syndrome. All patients were exercised on the treadmill until they were fatigued and were monitored to determine their intrinsic heart rate response. A sensor-driven pacemaker was strapped to the patients and was connected to an ECG to measure its rate response. It was set to activity threshold of medium, with a rate response of 7. The 20 patients exercised for an average of 5.9 minutes, with a range of 1.7 to 10 minutes. The maximum intrinsic atrial response averaged 110 beats/min, ranging from 60 to 150 beats/min. The maximum achieved activity rate averaged 99 beats/min, ranging from 60 to 118 beats/min. In 7 of the 20 of patients (35%), the activity pacemaker reached a higher rate than the patient's intrinsic rate. Six had AV block and one had sick sinus syndrome. In these seven patients the peak activity rate response averaged 102 beats/min and their intrinsic activity averaged to 78 beats/min. There was an increase in rate by the addition of rate responsiveness in 35% of our DDD patients.(ABSTRACT TRUNCATED AT 250 WORDS)