Detection of insulation failure by gradual reduction in noninvasively measured electrogram amplitudes

Insulation failure of pacemaker leads may give rise to functional defects such as under- or oversensing, loss of capture or muscle stimulation. An increased incidence of such failures has been reported for the bipolar polyurethane-insulated Medtronic model 6972 pacing lead. It is therefore important to identify techniques that will detect such insulation defects early. A case report is presented in which diminishing electrogram amplitude at follow-up predicted lead failure several months before becoming clinically manifest. This finding suggests that routine measurement of such an electrogram may be a useful tool in predicting impending lead malfunction.