Comparison of externally strapped versus implanted accelerometer- or vibration-based rate adaptive pacemakers during various physical activities.
The ability of externally strapped accelerometer- (Excel [Cardiac Pacemakers, Inc.]) and vibration-based (Activitrax [Medtronic, Inc.]) rate adaptive pacemakers to reproduce the rate response of the same implanted devices with identical programming was evaluated in ten patients by ambulatory Holter monitoring. The resting and postexercise external pacemaker rates closely resembled those of the respective implanted devices. During short bursts and more prolonged exercise, both types of strapped-on devices underestimated maximal implanted pacemaker rate response by 4%-10% when programmed to nominal rate adaptive settings. Studies evaluating chronotropic responses from either type of externally strapped activity sensor appear valid, provided the modest attenuation in maximal rate increase by this method is appreciated.