EFFECTS OF LOCAL STEROID ELUTION ON CHRONIC PACING THRESHOLD AND IMPEDANCE OF ENDOCARDIAL PACEMAKER LEADS

To study the effects of steroid elution on chronic pacing threshold an d impedance, a 4-mm(2) surface area lead with steroid (030-368, Telect ronics; n = 9) was compared to the same lead without steroid (030-359, Telectronics; n = 9) 3 months after implantation. The pulse duration thresholds of the steroid lead were significantly lower at 0.8, 1.6, 2 .5, and 5.0 V. Impedance measured by telemetry at 0.8, 1.6, 2.5, 5.0 a nd 8.0 V pulse amplitude, and 0.05, 0.25, 0.5 and 1.0 ms pulse duratio n was imilar for the two leads. Mean impedance was about 650 Omega and did not change from 0.8 to 8.0 V. The local steroid elution reduced t he pacing threshold, but had no influence on the impedance. The stable impedance indicates that the impedance of this lead was not modified by pulse-dependent variables and, therefore, can also be correctly det ermined at pulse amplitudes below 5.0 V.