Accelerometer-based adaptive-rate pacing: a multicenter study. European EXCEL Study Group.

UNLABELLED: A new adaptive rate pacemaker, using an accelerometer to detect body motion as an indicator of metabolic demand, was evaluated in 13 centers located in five countries. During the study, 55 patients with a broad range of indications were implanted with the EXCEL VR single chamber pacemaker. One month evaluations were completed on a subgroup of 37 patients. The pacemaker response was optimized before discharge using a simple walking test. An "exercise test" recording feature in the programmer eliminated the need for ECG monitoring. At nominal settings, the mean (+/- SD) pacing rate increased 29 +/- 9 ppm while walking slowly and 44 +/- 11 ppm (n = 33) during a brisk walk. This information was used to optimize the parameter settings. Without further changes to the programmed settings the patients were subsequently tested 2-4 weeks postimplant with a symptom-limited treadmill test using the chronotropic assessment exercise protocol (CAEP). Mean pacing rate increased from 74.5 +/- 2.5 ppm (n = 24) at rest to 118.6 +/- 12.2 ppm (n = 21) at 3 mph/6% grade to 143.5 +/- 3.5 ppm (n = 2) at 3.8 mph/8% grade. CONCLUSION: The individual responses were proportional to the physical exertion imposed on the patients. Pacing rates were considered to be appropriate using the chronotropic response zone as a criterion for appropriate rate modulation. A simple walking test utilizing the exercise test facility, results in appropriate optimization of the pulse generator to the individual patient.

Activity-based pacing: comparison of a device using an accelerometer versus a piezoelectric crystal.

The EXCEL VR, an accelerometer-based pacemaker (AC), and the Legend, a pacemaker utilizing a piezoelectric crystal (PZ), were compared under ergometric conditions and during stair climbing to assess the appropriateness of their rate responses. The pacemakers, programmed to the manufacturers' nominal settings in order to compare different technologically based sensors under identical conditions, were strapped over subjects' left mid-pectoral region. Placement of the devices was randomized to control for positional effects. Ten healthy subjects (55-72 years) completed a graded exercise treadmill test to 80% of maximum predicted heart rate (HR). An additional group of ten subjects (50-66 years) completed exercise protocols involving bicycle ergometry and stair climbing. Throughout all tests, pacemaker pulse rates and subjects' intrinsic HR were monitored continuously. For the treadmill exercise, the average correlations between the AC and PZ pacemakers' pulse rate and HR for the group as a whole were r = 0.92 and r = 0.82, respectively. Individual subject comparisons were also made between each pacemaker rate and intrinsic HR. The mean difference from intrinsic rate was 11 ppm for the AC pacemaker and 24 ppm for the PZ pacemaker. In addition, the PZ pacemaker's maximal pulse rate was significantly lower (105 +/- 9.6 ppm) than the other two rates (AC 137 +/- 6 ppm; intrinsic HR 129 +/- 2 beats/min). Throughout the bicycle ergometry testing, the intrinsic HR was higher than the AC and PZ pacing rates. However, the AC's rate was significantly higher than the PZ's rate. When subjects ascended stairs, the intrinsic HR and AC rate were closely correlated, but the PZ rate was significantly lower.(ABSTRACT TRUNCATED AT 250 WORDS)