Computing and visualizing electric potentials and current pathways in the thorax

The long-term goal of electrocardiography is to relate electric potentials on the body surface with activities in the heart. Many previously reported studies have focused on direct links between heart and body surface potenti als. The goals of this study were first to validate computational methods o f determining volume potentials and currents with high-resolution experimen tal measurements and then to use interactive visualization of thoracic curr ents to understand features of the electrocardiographic fields from measure d cardiac sources. We developed both simulation and experimental studies ba sed on a realistic shaped torso phantom containing an isolated, perfused do g heart. Interventions included atrial pacing, single pacing and simultaneo usly pacing at multiple locations on the ventricles. Simulated torso volume potentials closely matched measured potentials in the torso-tank preparati on (mean correlation coefficients of 0.95). Simulation further provided a m eans of estimating the current field in the torso from the computed torso v olume potentials and the local geometric and conductive properties of the m edium. Applying these techniques to the torso electric fields under a varie ty of pacing conditions, we have further demonstrated that thoracic current can provide many insights into the relationship between heart surface pote ntial and body surface potentials. Specifically, we have shown that geometr ic factors including cardiac source configuration and location play an impo rtant role in determining to what extent electric activity in the heart is directly visible on the body surface electrocardiogram. The computation and visualization toolkit we developed in this study to explore current fields associated with cardiac events may provide new insights into electrocardio logy.