On the Possibility of Directly Relating the Pattern of Ventricular Surface Activation to the Pattern of Body Surface Potential Distribution

A system of three 320-element spheres was employed to represent the endocardial and epicardial surfaces of the left ventricle and the body surface. The two inner (heart) spheres were considered electrogenic, and each active subunit was given an onset time and a monophasic action potential; these subunits were treated as source dipoles for successive instants in time. The potential distribution at any instant resulting on the outer (torso) surface was calculated from adding together the corresponding proportionate effects of all active subunits, each treated as dipolar sources. This result was compared to multipolar reduction of simultaneous endocardial and epicardial action potential patterns which, when combined, gave a net multipolar generator content enabling outer pattern approximation. The identity between the patterns of torso surface potential, systematically calculated from multiple dipoles, and those produced from the multipolar reduction provided three insights: 1) the whole surface treatment of the multipolar method is faster, 2) both show an offset term related to the monophasic nature of the sources and similar to that found in live data, and 3) such a model may provide a vehicle for experimentally testing the contribution of intramural sources to body surface potential maps.