In Vitro Evaluation of a Sensor Sensitive to Acceleration Forces Included in a New Rate Modulated Pacemaker

The characteristics of the sensor and rate adaptive algorithm included in a new dual chamber rate responsive pacemaker (Relay 294–03, Intermedics, Inc.) were studied by submitting the device to calibrated to‐and‐fro movements of specific frequencies and peak accelerations by means of a mechanical arm connected to a speed adapter. Atrial pacing rate was continuously recorded on a Holter monitor. The influences of the frequency, the magnitude, and the axis of the acceleration forces as well as the reproducibility of the rate response were evaluated. Results: (1) the sensor was sensitive to frequencies ranging from 0.5 to 7 Hz with a peak sensitivity at 3 Hz; (2) the pacing rate was not affected during movements at frequencies > 6 Hz, commonly presented as nonactivity related signals fear, bus transportation, drilling); (3) the pacing rate increased as a function of the acceleration magnitude up to 0.5 G (0.3 G for 3 Hz), then remained constant. This level of acceleration usually corresponds to high degrees of activity; (4) rate response was maximum when acceleration was directed in the anteroposterior direction; (5) reproducibility of the rate response was excellent (R2: 0.999; slope of the regression line: 0.999). Conclusion: Relay 294‐03 is a low frequency signal sensing rate modulated pacemaker using an accelerometer sensitive to motion, mainly in the anteroposterior direction.