The Steroid‐Eluting Electrode: A 10‐Year Experience

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Abstract
The benefits of steroid-eluting electrodes in reducing stimulation thresholds are well established. A question frequently asked, however, is how long does such an electrode maintain its effect on reducing stimulation threshold? Two studies were designed to answer this question by reporting a long-term prospective human implant review as well as an analytical examination of explanted leads from both humans and animals to determine the amount of remaining steroid in the silicone plug. A previously reported double-blind human study using 20 implanted unipolar ventricular leads, 10 with and 10 without steroid, was followed for 10 years. Pulse width stimulation thresholds were determined at regular intervals using a customized VVIC pulse generator programmed to 1.5-V output. Throughout the study period, the mean stimulation thresholds for the steroid-eluting leads remained almost constant, with a narrow standard deviation, whereas the leads without steroid showed an unpredictable rise and a wide standard deviation. All patients with the steroid-eluting electrodes were paced at 1.5 V, and the four surviving patients still have their original pulse generators. In the second study, the remaining steroid from 25 explanted leads (18 canine and 7 human), were analyzed and graphed against implant times that ranged from 1-350 weeks. Extrapolation of the line of best fit suggests that about 20% of the steroid is still present at 10 years and 18% at 20 years. Only small quantities of steroid are required for its stimulation threshold lowering effect, which continues clinically to at least 10 years. Sufficient quantity of steroid may well be present at 20 years.