Examining the fraction of intrathoracic current that enters the heart during transthoracic defibrillation of the human torso

The objective of this study is to compute the amount of current entering the heart during transthoracic defibrillation by utilizing a physiologically realistic volume conductor model of the thorax which simulates defibrillation fields. The volume conductor model is constructed from intact human geometry and boundary integral equations. The model computes the total amount of intrathoracic current and transcardiac current from a knowledge of defibrillation shock strength, defibrillation electrode location, and the relative conductivities of the interior thorax. Simulations have been performed using an inhomogeneous torso and rectangular defibrillation electrodes with a surface area of 60 cm² and an aspect ratio of 2:1. Results for anterior posterior, precordial, and right-left defibrillation electrode configurations indicate that the transcardiac current fraction is 22%, 18%, and 11%, respectively