Electrophysiological Performance of a Bipolar Membrane‐Coated Titanium Nitride Electrode: A Randomized Comparison of Steroid and Nonsteroid Lead Designs

Abstract

The aim of this multicenter study was to investigate the performance of a new cardiac pacemaker lead with a titanium nitride cathode coated with a copolymer membrane. In particular, the electrophysiological effect of steroid dissolved in this ion-exchange membrane was evaluated by randomized comparison. Ninety-five patients were randomized either to the 1450 T (n = 51) or the 1451 T ventricular lead (n = 45) and received telemeteral VVI(R) pacemakers with identical diagnostic features. Both leads were bipolar, were passively affixed, and had a porous titanium nitride tip with a surface area of 3.5 mm2. The only difference between the two electrodes was 13 micrograms of dexamethasone added to the 1450 Ts membrane coating. Voltage thresholds (VTH) at pulse durations of 0.25, 0.37, and 0.5 ms, lead impedance, and sensing thresholds were measured at discharge, 2 weeks, 1 month, 3 months, and 6 months after implantation. Mean amplitude and the slew rate from three telemetered intracardiac electrograms, chronaxie-rheobase product, and minimum energy consumption were calculated. After a 6-month follow-up, mean voltage thresholds of 0.65 +/- 0.20 V and 0.63 +/- 0.34 were achieved for the 1450 T lead and 1451 T lead, respectively. As a result, a VTH < 1.0 V was obtained in all patients with 1450 T electrodes and in 97.7% of patients with 1451 T leads after 6 months follow-up. In both electrodes, stable VTH was reached 2 weeks after implantation, and no transient rise in threshold was observed. No differences were observed between the steroid and the nonsteroid group in respect to VTH, chronaxie-rheobase product, minimum energy consumption, and potential amplitude and slew rate. In conclusion, safe and efficient pacing at low pulse amplitudes were achieved with both leads. The tip design, independently of the steroid additive, prevented any energy-consuming increases in the voltage threshold.

A Comparison of Chronaxies for Ventricular Fibrillation Induction, Defibrillation, and Cardiac Stimulation: Unexpected Findings and Their Implications

“…The mean stimulation chronaxie of 0.15 ms for the lead tip and 0.23 ms for the coil are situated at the lower edge of the 0.2 ms to 0.6 ms chronaxie range reported for electrodes with a surface area from 2 mm 2 to 10 mm 2 30 , 32–36 . In historical data, amplitude resolution was limited, with the finest voltage step being 20% to 40% of rheobase.…”

“…The mean stimulation chronaxie of 0.15 ms for the lead tip and 0.23 ms for the coil are situated at the lower edge of the 0.2 ms to 0.6 ms chronaxie range reported for electrodes with a surface area from 2 mm 2 to 10 mm 2 . 30,[32][33][34][35][36] In historical data, amplitude resolution was limited, with the finest voltage step being 20% to 40% of rheobase. Strength-duration curves were usually reconstructed from 3 to 5 not-quite-exact data points, which introduced imprecision into the chronaxie extrapolation and spurred recent recommendations on how to improve the methodology.…”

Dexamethasone Base Conserves Hearing from Electrode Trauma‐Induced Hearing Loss

“…Mond and Stokes noted that increases in stimulation thresholds occur after electrode implantation as a direct result of the inflammatory process because of the subsequent formation of fibrosis tissue 23 . Reduction of tissue deposition lowers polarization potentials resulting in smaller electrodes and more predictable acute peak stimulation thresholds allowing for increased longevity and for improved electrode placement 23,24,33 . In a review of atrial activation fixation platinum leads, Wiegand et al noted dramatically lower long‐term reductions in stimulation thresholds in steroid‐eluting electrodes than obtained from noneluting traditional leads with results observed up to 6 years postimplantation 34 .…”

A Model of Impedance of Cardiac Pacemaker Electrodes

“…For instance, for the CapSure model 5024 Z 3 = R т ≈ 0.6 kΩ [8], for model TIR 60 UP Z 3 = R т ≈ 0.5 kΩ [9], and for model Е 1450 Т Z 2 ≈ 0.6 kΩ [10]. The values of imped ance Z 3 and Z 4 in vivo and in vitro are comparable.…”