PROGRAMMING OF THE PACING IMPULSE IN PACEMAKERS CONNECTED TO STEROID LEAD SYSTEMS

The purpose of the study was to compare the feasibility of low amplitu de output programming (2.5 V/0.5 msec) 3 or more months after pacemake r implantation in patients receiving steroid and nonsteroid lead syste ms. Chronic pacing voltage, current, and energy thresholds were determ ined from 0.05- to 1.0-msec pulse duration in 44 patients with steroid lead systems, and in 36 patients with nonsteroid lead systems; all pa tients received pacemakers from the same manufacturer, which utilized the same programming and telemetry features. Chronaxie, pulse duration at the lowest pacing current, and energy were assessed from individua l threshold curves. Steroid-eluting leads had significantly lower paci ng voltage, current, and energy thresholds than nonsteroid leads. A 10 0% safety threshold margin could be achieved in 43 (98%) patients with steroid lead systems and in 27 (75%; P < 0.05) patients with nonstero id lead systems with output programming of 2.5 V/0.5 msec. Chronaxie ( 0.22 +/- 0.17 msec vs 0.44 +/- 0.32 msec; P < 0.05 pulse duration at l owest pacing current (0.28 +/- 0.12 msec vs 0.49 +/- 0.22 msec; P < 0. 05), and pulse duration at lowest pacing energy (0.31 +/- 0.17 msec vs 0.53 +/- 0.22 msec; P < 0.05) were significantly shorter for steroid than for nonsteroid lead systems. In 42 patients of the former group, a 100% safety margin could be maintained either with a 2.5 V/0.3 msec or with a 1.6 V/0.5 msec output. Conclusions Low amplitude output prog ramming can be obtained in almost all pacemakers connected to steroid- eluting lead systems, and in a significantly higher number of patients than when connected with nonsteroid leads systems. Moreover, in most cases, a 100% safety margin can be achieved at settings as low as 1.6 V/0.5 msec or 2.5 V/0.3 msec; these different combinations offer poten tial different opportunies to select definitive programming and reduce pacing current requirements in patients undergoing pacemaker implanta tion.