Long-term observation of pacemaker electrodes. A follow-up study of 328 consecutive patients treated between 1959 and 1967.

Epicardial electrodes implanted in 20 patients between 1959 and 1962 had a short-term effectiveness. A change to endocardial stimulation was later necessary in 15 of these patients. Endocardial electrodes inserted between 1962 and 1967 in 306 patients were included in this study; 121 (40%) of these patients survived for 10 years or more. Seventy-five (62%) of the long-term survivors had no problems with their electrodes. In 39 of these patients the stimulation thresholds were measured after both 5 and 10 years and found to be 2.3 +/- 0.6 volts and 2.2 +/- 0.8 volts, respectively. Hence, long-term complication-free endocardial pacing can be accomplished.