Clinical evaluation of a dual sensor, rate responsive pacemaker.
Dual sensor pacemakers should respond more appropriately during differing exercise modes than a single sensor device. The Topaz model 515 (QT and activity count [ACT] sensing) pacemaker shows appropriate rate response during treadmill exercise testing. We postulated that adjustments to relative sensor contribution should allow fine tuning of the onset of rate response. Eleven patients with this pacemaker were studied. Three standard exercise tests were performed with adjustment of sensor blending and activity threshold between each one. We also assessed the response to isometric exercise and a false positive activity signal.


RESULTS
Times to 100 ppm (3.7 +/- 1.3, 4.4 +/- 2.0, 5.3 +/- 1.5 mins), times to peak rate (6.1 +/- 1.6, 5.6 +/- 1.4, 6.5 +/- 1.3 mins) and accelerations to peak (9.0 +/- 2.4, 9.2 +/- 5.3, 7.7 +/- 2.8 ppm/min) were measured in all three different sensor settings (QT = ACT, QT < ACT, and QT = ACT with decreased activity threshold). No significant difference in onset of rate response was seen between the three settings. Tapping (false-positive activity) provided a rapid rise in paced rate to 79 ppm from a resting value of 65 ppm. This came down to 71 ppm demonstrating satisfactory sensor cross-checking. Isometric exercise induced a moderate response from 65 ppm at rest to 74 ppm after 3 minutes.


CONCLUSIONS
Satisfactory rate response was demonstrated in most patients to treadmill testing and to isometric exercise. However, small adjustments to relative sensor contributions do not predictably alter the onset of rate response.
Sinha
S
S
Department of Cardiology, Hull Royal Infirmary, United Kingdom.
Schilling
R J
RJ
Kaye
G C
GC
Caplin
J L
JL
D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial