Predicted early failure of cardiac pacemakers

This paper describes a study on pacemaker longevity carried out on 65 subjects using mostly the Telectronics model 171 and model 173 pacemakers and based on an analysis of pacing rate reduction as a function of time since implant. Three different modes of rundown were observed. The shortest predicted lifetime was 23 months for a model 171 unit. This study was undertaken after the manufacturer and battery companies clearly delineated the existence of the problem and steps to be taken in the follow-up of patients. Careful analysis of medical records of the patients did not yield any correlation between sex, age, indications for implantation, initial pacing threshold, or amount of use of the pacemaker, and the early rundown of these pacemakers. Our study indicated that, in general, the model 173 had a shorter expected lifetime than the model 171. Using a reduction in pacing rate of 5.5 bpm from the rate at implant as the end-of-life indicator, the study showed that 16% of the model 173 pacemakers would need to be replaced within 3 years of implant and 78% within 6 years of implant. In the case of the model 171 units, 10% would need to be replaced within 3 years of implant and 48% within 6 years. Follow-up of patients with these units should be scheduled to monitor closely the rate of rundown in order to predict replacement dates.