The effect of variations of ventricular volume on the electrocardiogram. A comparison of two model simulations

Two previously published models of the electrocardiogram are compared and evaluated to determine the causes and nature of the relationship between variations in ventricular volumes and surface potential. Both models included a relatively high conductivity spherical heart in a spherical torso, but in one the source was a single dipole, while in the other the source was a double-layer spherical cap. Volume conductor effects (that is the change in electrical conductivity of the torso associated with ventricular volume changes) caused a decrease in surface potential with increase in ventricular volume. Changes in position of the heart and of the strength of the activation wavefront with increases in volume may explain the increase in surface potential with ventricular volume observed in experimental studies.