Comparison of sinus node response to exercise with responses from two different activity-based rate adaptive pacemakers in healthy subjects of different age groups.

The pacing rates from accelerometer-based (Excel) and piezoelectric-based (Legend) activity sensing rate adaptive pacemakers, both strapped externally in the pectoral position, were compared with sinus rate response in normal volunteers of two different age groups (group 1, mean age 35 +/- 16 years; group 2, mean age 72 +/- 9 years) during various physical activities. Both pacemakers were programmed in manufacturers' nominal rate adaptive settings. Both types of activity sensing pacemakers programmed in this way showed chronotropic deficiencies to metabolic demand in healthy young subjects and in those matching the usual age of pacemaker implant, especially during "burst" activities. These data suggest that present recommended activity sensing rate response algorithms for accelerometer and piezoelectric pacemakers are inappropriate for many physical activities.