Electrode polarity effects on the shock-induced transmembrane potential distribution in the canine heart

Experimental measurements have indicated that for implantable cardioverter defibrillators (ICDs), the defibrillation threshold is different for reversed shock electrode polarity. In this research we offer a possible explanation for this observation. We examine, through large scale computer simulations, the effects of electrode polarity on the transmembrane potential distribution induced throughout the myocardium by defibrillation shock. The tissue preparation is a two-dimensional slice of ventricular myocardium across the canine heart. The transmembrane potential distribution is calculated for various defibrillation electrode systems and the percent area of direct membrane polarization is evaluated. Our simulations show that the amount of directly depolarized myocardium changes when the polarity of the shock electrodes is reversed