Clinical study of a new activity sensor for rate adaptive pacing controlled by electrical signals generated by the kinetic energy of a moving magnetic ball.

A new rate adaptive pacemaker (Sensorithm) controlled by an activity sensor providing electrical signals induced by a magnetic ball moving freely in an elliptical cavity surrounded by two copper coils, was implanted in ten patients; mean age of 75 years (range 64-89). Six patients had atrioventricular block and four had sinus node disease. In auto-set testing procedure during a 1-minute walk in the corridor, a slope resulting in a maximum rate of 95 beats/min was selected in every patient, and a medium reaction time was programmed. During graded treadmill exercise tests the heart rate increased 63 +/- 7 beats/min to 135 +/- 6 beats/min in rate adaptive pacing mode (VVIR), and 15 +/- 6 beats/min (P < 0.0001) in ventricular pacing mode (VVI). The symptom-limited exercise time was 9.1 +/- 1.1 minutes and 8.2 +/- 1.2 minutes (P = NS), and the exercise distance was 501 +/- 95 meters and 428 +/- 92 meters (P < 0.05) in VVIR and VVI pacing mode, respectively. The maximum oxygen uptake was 20.6 +/- 2.6 mL/kg per minute in VVIR pacing and 18.1 +/- 2.1 mL/kg per minute (P < 0.05) in VVI pacing. The delay time until the pacing rate increased 10% of the total rate increase at onset of treadmill exercise was 4.4 +/- 0.7 seconds.(ABSTRACT TRUNCATED AT 250 WORDS)