Stepwise analysis of the calibration procedure of an accelerometer-based pacemaker.
The rate modulation of Relay 294-03 is individually adjusted during a 3-minute calibration test corresponding to the collection of moderate acceleration signals (MAL), which are related to a programmable moderate pacing rate (PR). Those rate/acceleration values form a calibration point in the flat part of the rate response curve (RRC). To help in a more clinically oriented analysis of this feature, the stimulator was first calibrated while strapped on a volunteer who remained seated (low MAL), walked (medium MAL), or jogged (high MAL). The device was then mechanically submitted to three calibrated to and fro movements corresponding to the sensitivity spectrum of the sensor. Each movement was repeated ten times to test the influence of the slope (1-10).


RESULTS
(1) One-way ANOVA significant effect of the MAL recorded during the calibration test on subsequent rate modulation (P = 0.0001); (2) The sensor amplifier gain was inversely related to the MAL: high MAL induced lower amplifier gain and lower PR for identical accelerations; (3) Lower amplifier gain allowed to discriminate highest acceleration magnitudes before reaching an overflow of the sensor; (4) The maximum achievable PR increased not only with the programmed slope, but also with decreasing MAL (P = 0.0055): a low MAL shifts to the left calibration point located on the part of the RRC and makes the last steep part of the RRC start earlier, thus leading to higher maximum achievable PR. In conclusion the calibration procedure is crucial not only in defining a moderate acceleration intensity but also in determining the sensor amplifier gain and the maximum achievable PR.
Mahaux
V A
VA
University of Liège, Belgium.
Verboven
Y J
YJ
Waleffe
A
A
Kulbertus
H
H
D002138:Calibration; D002304:Cardiac Pacing, Artificial; D006339:Heart Rate; D006801:Humans; D007590:Jogging; D010138:Pacemaker, Artificial; D012146:Rest; D016138:Walking