COMPARISON OF SINUS NODE RESPONSE TO EXERCISE WITH RESPONSES FROM - 2DIFFERENT ACTIVITY-BASED RATE-ADAPTIVE PACEMAKERS IN HEALTHY-SUBJECTSOF DIFFERENT AGE-GROUPS

The pacing rates from accelerometer-based (Excel(TM)) and piezoelectri c-based (Legend(TM)) activity sensing rate adaptive pacemakers, both s trapped 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 manufa cturers' nominal rate adaptive settings. Both types of activity sensin g pacemakers programmed in this way showed chronotropic deficiencies t o metabolic demand in healthy young subjects and in those matching the usual age of pacemaker implant, especially during ''burst'' activitie s. These data suggest that present recommended activity sensing rate r esponse algorithms for accelerometer and piezoelectric pacemakers are inappropriate for many physical activities.