Optimal Electrode Configurations for External Cardiac Pacing and Defibrillation: An Inhomogeneous Study

We have developed an inhomogeneous two-dimensional finite element computer model of the human torso, and have used it to study electrode performance in defibrillation and external cardiac pacing. Gross individual organ effects were assessed first for different electrode configurations by creating models which included one organ at a time, and comparing the results to those obtained with a homogeneous body. Electrode placement on the body was varied in order to determine, within the limitations of the model, optimal electrode configurations for external cardiac pacing and defibrillation. Finally, the electrical and geometric parameters of a previously proposed plate electrode design were optimized for the selected external pacing position. It was found that organs of extreme resistivity, close to the body surface, and within the direct current path between two electrodes, tended to have dominant effects on the surface current density distributions. The optimum pacing position is to place the driven electrode directly over the heart and the receiving electrode on the left lateral chest wall. For defibrillation, the driven electrode is moved to the right of the sternum.