Comparison of measured torso potentials with those simulated from epicardial potentials for ventricular depolarization and repolarization in the intact dog

Abstract

The objective of this study was to stimulate body surface potential distributions, millisecond by millisecond, from potential distributions measured directly from the epicardium of the intact dog, and to examine the resulting simulation by comparing it with measured body surface potential distributions. Included in this objective was a simulation not only of those phases of cardiac activity involving depolarization, with which previous simulations have been concerned almost exclusively, but also of times of overlapping depolarization and repolarization, and times during repolarization alone. To achieve this simulation, measurements of multiple excitation and repolarization sequences were obtained from intact dogs. Epicardial potentials were recorded from about 90 electrodes chronically implanted on the ventricular epicardium, and several electrodes on the atria. Geometric coordinates of each body surface and epicardial electrode were measured in a postmortem examination. The simulated body surface distributions were computed from the epicardial ones by means of heart to body surface transfer coefficients. These transfer coefficients were derived from the measured geometric coordinates of all the electrodes with the assumption that the volume conductor was homogeneous between the epicardium and the body surface. Results included numerous sets of isopotential distributions, each set comprising the measured epicardial and body surface distributions, and the simulated body surface distribution. At many time instants, the distribution of potentials measured from the epicardium was considerably more complicated than the distribution measured from the body surface. Nonetheless, simulated body surface distributions consistently had a high correlation with the measured body distributions. However, the simulated maps usually had larger peak to peak magnitudes. The results demonstrate that quantitative relationships between the detailed events of cardiac and body surface electrical activity can be established theoretically and confirmed by realistic experimental measurements.