ACUTE AND CHRONIC PERFORMANCE OF A STEROID ELUTING ELECTRODE FOR VENTRICULAR PACING

Studies have demonstrated consistently low stimulation thresholds in the first months following implantation of steroid eluting electrodes. There have been no reported cases of exit block. There is little information on the long-term performance of these leads. Data were collected on 15 patients in whom Medtronic steroid eluting leads (5023 and 4003) had been implanted in 1987. Stimulation thresholds were measured at implantation and at weeks 1, 2, 3, 4, 5, 6 and 12. Stimulation threshold, lead impedance and sensing thresholds were monitored periodically for 3 yr using the telemetered function of the pulse generator. Three-month follow-up was obtained in all the patients and 3-yr follow-up in 10. Stimulation thresholds remained low throughout the follow-up period in all but one patient who developed exit block necessitating the replacement of the pacing system. In the remaining patients there was a significant increase in mean stimulation threshold from implantation to week 1 (mean stimulation threshold at implantation = 0.106 ms, mean ST at week 1 = 0.182 ms; p = 0.05), and also a gradual increase in the stimulation threshold over the first 2 yr of follow up (mean stimulation threshold 1 week = 0.182 ms, mean stimulation threshold months 13 - 24 = 0.243 ms; p = 0.05). Lead impedance showed no significant change over the follow-up period (mean change in impedance = 4.3 OMEGA, SD 163.2, p = 0.97). Unlike many conventional electrodes, steroid eluting leads show no early peak in stimulation threshold but exit block can occur. Stimulation thresholds show a small but significant rise over time.