A volume conductor model of the thorax for the study of defibrillation fields

The authors develop a physiologically realistic volume conductor model for calculating epicardial potentials during transthoracic stimulation. The objective of the study is to measure cardiac potentials during a transthoracic stimulus and compare the measurements to calculated epicardial potentials obtained from the model. The results for all four stimulus configurations (anterior-posterior, neck-waist, precordial, and right-left) on the torso consistently yield correlation coefficients of about 0.90 and RMS errors of 47% between calculated and measured epicardial potentials for a homogeneous torso. Incorporating the effects of the skeletal muscle layer improves the agreement, i.e., correlation coefficients increase to about 0.914 and RMS errors decrease to about 42%. At the same time, the lungs and heart have little influence on the agreement between measured and calculated epicardial potentials. The results of the study demonstrate the importance of the skeletal muscle layer in physiologically realistic volume conductor models.