Optimal energy steering for an implantable defibrillator

Abstract

Epicardial-patch electrodes for defibrillation are efficient in deliverying electrical energy accurately to the necessary tissue and in minimizing electrical losses, but they are risky and costly because their implantation requires major surgery. Intravenous implantation of endocardial-coil electrodes, such as right-ventricular-apex (RVA) and superior-vena-cava (SVC) electrodes, by means of cardiac catheters, on the other hand, involves simpler procedures. Also, implantation of a subcutaneous-patch (SUB) electrode or of a pulse-generator housing (CAN, subject to co-pending application) electrode requires comparatively minor surgery. Using these last four electrodes, however, involves accepting electrical losses in intervening tissue, relatively inefficient current directions in some cases, and unfavorable energy distributions among paralleled paths. The present invention achieves more favorable energy and current distribution by introducing lossy elements in one or more paths, or by capacitor-switching methods, where RVA is given one polarity, and at least two of the other electrodes are given opposite polarity, yielding at least two pathways. The present invention also achieves current and energy steering by means of differing pulse durations in different paths.