SPATIAL POTENTIAL AND CURRENT DISTRIBUTIONS ALONG TRANSVENOUS DEFIBRILLATION ELECTRODES - VARIATION OF ELECTRODE CHARACTERISTICS

The therapeutic efficacy of an endocardial defibrillation lead system can be improved by controlling the profile of current delivery through a suitable choice of electrode characteristics, which include the len gth, radius, number of conductor elements, electrode resistance, and p oint of connection to the voltage source. Such control will minimize t issue and lead damage during long-term use. In this study, a semianaly tical model was developed to study cylindrical electrodes of different constructions in an idealized electrolytic medium. Simulations were p erformed to investigate the effects of varying the electrode character istics on the spatial voltage and current distributions and interelect rode resistance for cylindrical electrodes of different constructions. The results show that, for transvenous electrodes of realistic dimens ions, the current distributions are determined largely by edge effects . The edge effects increase as the aspect ratio of the electrode (leng th/radius) decrease. The multiple edges resulting from wrapping conduc tor elements over a nonconducting base are found to increase the nonun iformity and the current density over the conductor-covered surface. T he model is used to demonstrate two techniques of controlling the curr ent distribution. The first method involve modifying the electrode res istivity profile and point of connection. In the second approach, the electrode surface is covered with a thin film having a model-computed resistance profile. By using either methods to produce isocurrent elec trodes, the interelectrode resistance is found to increase.