Pacemaker failures characterized by continuous direct current leakage.

Pulse generator failure caused by continuous leakage of direct current through an output capacitor has not previously been appreciated. Routine post-explant electronic evaluation has identified the defect in six implanted and one external pulse generator. The constant direct current in the implantable units, 0.14 to 0.26 milliamperes, is in the range that produces ventricular arrhythmias in dogs although this did not occur in our patients. Evidence of local myocardial damage existed in four cases and of electrode deterioration in three. The implant failures occurred without warning and in four cases within 2 weeks of demonstrated normal function, blunting the predictive benefits of pacemaker monitoring programs. Capacitor discharge circuits used in many pacers are inherently capable of developing direct current leakage in the event of output capacitor short circuit. In one model of pacemakers such continuous direct current leakage caused 8.3 percent (3 of 36) of pulse generator failures, widely scattered in time at 23, 27 and 46 months after implant. Capacitor short circuit causing constant direct current leakage can masquerade as primary battery failure and should be suspected when cessation of pacer function is associated with increased threshold or poor myocardial electrogram without evidence of wire break or displacement.

Transtelephone pacemaker monitoring: five years later.

Six hundred nineteen patients have been followed by remote monitoring of pacemaker function using ECG and rate or rate alone; 278 of 280 have had battery exhaustion or electronic failure demonstrated. Ten percent of exhausted pacemakers failed prior to the average longevity of the particular model, and 32% (89 of 280) exceeded 36 months' longevity; of these, 13% (37 of 280) lasted more than 40 months and 4.6% (13 of 280) exceeded 50 months. The error rate is 0.7% (2 of 280). With pulse generator longevity increasing, monitoring is done less frequently during the first 2 years, then calls are made weekly after 24 months.