A Study of the Human Heart as a Multiple Dipole Electrical Source

A model for the electrical activity of the heart during depolarization, in which the ventricles were represented by 12 dipoles and the thorax by an inhomogeneous conductor, was evaluated. Potentials measured at 126 locations on the thoracic surface were used to determine the dipole strengths as a function of time for 58 normal sedentary subjects. Most of the dipole strengths had the form of a single pulse in time, the dipole onset sequence being consistent with the depolarization sequence found by others. Dipole activities (DA), obtained for each dipole by time integration of its strength, varied considerably between subjects. However, much of this variation arose from a systematic decrease of DAs with age. The separate DAs were summed to obtain the DAs of the septum and left and right ventricular free walls. The proportions of the summed DAs agreed with the cardiac component weights found by others. When the variation with the subject's age was removed, the total DA fluctuated by ±13% (standard deviation of the mean) in this series.