A randomized study on the effects of pacemaker programming to a lower output on projected pulse generator longevity.

The programmability of cardiac pacemakers enables the physician at follow-up to adjust the pacing pulse under consideration of the 100% safety margin with respect to the individual pacing threshold. The purpose of reducing the output is to prolong pacemaker longevity. The aims of this prospective, randomized trial were to compare the effects of nominal output versus a lower output on projected pacemaker longevity in single and dual chamber pacemakers. The secondary aim was to assess how many patients can be programmed to 2.5 V/0.4 ms instead of the nominal 3.5-V setting with > or = 100% safety margin. The patients received the same types of VVI or DDD pacemakers that were connected in the ventricle to the steroid-eluting, high impedance pacing lead. At the 3-month follow-up, patients with ventricular pacing thresholds < or = 0.15 ms at 2.5-V pulse amplitude were randomized to 3.5 V or 2.5 V amplitude at 0.4-ms pulse duration. Lead function and projected device longevity were assessed with the pacemaker's telemetry 6 and 12 months after implantation. Of patients implanted with a VVI pacemaker, at the 3-month follow-up, 3 patients had pacing thresholds > 0.15 ms at 2.5 V and 139 patients could be randomized. A reprogramming to a higher output was necessary in one patient. The mean percentage of ventricular pacing was about 40% throughout the study time. The programming to 2.5-V output resulted in an insignificant increase of device longevity from 117.9 +/- 18.7 months in the nominal group to 123.7 +/- 11.9 months at the 12-month follow-up (P = 0.16). Of patients implanted with a DDD pacemaker, 166 patients underwent randomization. The mean percentage of ventricular pacing was 85% in the ventricle and 35% in the atrium. The 2.5-V setting significantly prolonged pacemaker longevity from 98.1 +/- 21.3 to 112.0 +/- 13.6 months (P < 0.0001). In three (1%) patients a late increase of the pacing threshold was observed. Due to the low ventricular pacing thresholds, the 2.5-V/0.4-ms setting provided, 3 months after implantation, a > or = 100% safety margin in 99% of the patients. Programming to a lower output slightly increased projected pacemaker longevity compared to the nominal 3.5-V setting. Longevity increasedfor 5% in patients with single andfor 14% in dual chamber pulse generators.