The influence of torso inhomogeneities on epicardial potentials

Describes experimental studies of the effect of thorax conductivity on both torso and epicardial electric potentials. While considerable literature exists regarding the effect of tissue inhomogeneity on the transfer of heart electrical activity to the torso surface, very little has been written about whether or not the heart itself changes with altered thorax conductivity. The authors suspended an isolated, perfused dog heart in an electrolytic tank shaped like a human torso and recorded epicardial and torso potentials while the authors varied a) global conductivity of the electrolyte, or b) local conductivity by introducing insulators into the tank. The authors results suggest that while the general topography of isopotential maps remains stable, changes in either global or local thoracic conductivity result in changes in the amplitudes of potentials on the epicardial surface. The implications of this work are important especially to forward and inverse solution modeling since it calls into doubt the implicit assumption that epicardial potentials are invariant to changes in the volume conductor