Between January 1990 and October 1992, we implanted 16 steroid-eluting ventricular epicardial pacing leads (Medtronic 10295A and 10295B/4965) in 12 patients. There were 8 males and 4 females ranging in age from 3 months to 49 years (mean +/- , median years). Structural cardiac disease was present in 11 of 12 patients. Follow-up ranged from 3-73 months postimplant (mean +/- , median months). Lead fracture (10295A) occurred in 1 of 12 patients. Of the remaining 11 patients, 8 of 11 have very low long-term pacing thresholds. Unexpectedly, 3 patients demonstrated precipitous threshold increases from 3 months to years postimplant. Although no deaths resulted in these exit block patients, 1 of 3 exit block patients developed marked worsening of congestive heart failure. We reviewed and analyzed the data obtained at 4 weeks postimplant for all of the 10295A and 4965 patients in the entire Medtronic clinical study database. Using the criterion of a 4 week postimplant pacing threshold > or = ms (5 V), we found that the long-term risk of eventual exit block was % for the 10295A lead (P = ) and % for the 10295B/4965 lead (P = ). We, therefore, recommend that in patients implanted with the 4965 steroid-eluting epicardial lead, ventricular pacing thresholds > or = ms (5 V) measured at 4 weeks postimplant should prompt frequent threshold testing to detect late and potentially sudden ventricular pacing threshold increases.
The DEXTRUS pacing lead is an extendable-retractable, active fixation lead designed to provide a larger electrically-active surface area for enhanced threshold performance. The lead features a familiar feel with durable and predictable helix extension-retraction performance and an inner coil designed for predictable torque response. The DEXTRUS lead is designed for an easy lead implant experience with mapping capability, a radiopaque helix and tip extension indicator and a flexible tip designed for flexible placement options within the right atrium and right ventricle.
This paper reports on the drug release mechanisms of silicone structures with embedded steroids applied in pacing leads. Different derivatives of the steroid dexamethasone, which is associated with the reduction of acute stimulation thresholds, were evaluated together with different matrix based release control mechanisms with the target to potentially match optimal drug release rates during the first month after implantation. By incorporating dexamethasone-21-dihydrogen phosphate in silicone matrices in combination with release rate adaption layers, almost continuous release rates were obtained under physiological test settings.