Radioisotopic Pacemaker: Long-Term Clinical Results

In order to prolong the service life of the generator, the isotopic pacemakers, powered by Pu238, have been developed and implanted since 1970. We report the follow‐up of 325 patients (mean age 39 ± 18 years) implanted with an isotopic pulse generator (Medtronic 9000/9090) between April 1970 and July 1982. The mean follow‐up was 12 years (range 6 days to 18.5 years). The generator was highly reliable; the mean value of pacing rate between implantation and last follow‐up decreased significantly but no more than 1 beat/min (72.7 vs 71.8 beats/ min; P < 0.001) and the pulse width did not change significantly. The actuarial survival of the device was 97% at 18.5 years. During the follow‐up period, 122 reoperations were performed in 85 patients: 88 explanations of the entire pacing system and 34 modifications of the lead system. Lead dysfunction accounted for 68% of the 122 reoperations, generator failure for 6%, and miscellaneous reasons for 26%. However, 72% of patients remain free of intervention during the follow‐up period and 61 patients (20%) died during this period. Most deaths (52%) were of nonsudden cardiovascular origin, 17% were related to cancer, and 13% to sudden death. After 5, 10, and 18.5 years, 94%, 89%, and 73% of the patients were alive, respectively. No side effect could be attributed to the radioisotope. We conclude that this isotopic pacemaker demonstrated its reliability for long‐term cardiac pacing.