Distribution of Heart Potentials on the Thoracic Surface of Normal Human Subjects

The distribution of isopotential lines on the thoracic surface of 15 normal subjects aged 15 to 43 was determined at 10 to 20 instants of time during ventricular activation. At the beginning of the QRS interval a precordial maximum and a dorsal minimum of potential can be observed. Thereafter, the minimum migrates toward the right shoulder and appears then anteriorly in the right subclavicular fossa, while another minimum appears near the mid-sternal line. The two minima finally merge together, and the potential distribution becomes dipolar once again. During the last third of the QRS interval the maximum of potential moves toward the left axillary and dorsal region, while a new maximum appears near the upper end of the sternum. A tentative correlation between surface and intracardiac electrical events can be established on the basis of the most generally accepted descriptions of ventricular activation processes. During some phases of ventricular activation, the potential distribution on the surface of the body is of the dipolar type, and there are no measurable local components; during other phases of ventricular depolarization, however, proximity potentials do appear on the thoracic surface, yielding information about local activation waves. When the ventricular activation is altered, the location and time course of local and dipolar potentials show important modifications.