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.