The magnetocardiogram in cardiac disorders

Magnetocardiograms of 24 normal subjects and of 31 patients with cardiac disorders have been studied with the aid of a magnetometer of the gradiometer principle which utilizes a superconducting quantum interference device (SQUID). The precordial magnetocardiograms observed are closely related to the conventional 12-lead electrocardiogram, but also reveal new information as compared with the standard ECG. There are differences between MCGs in different cardiac disorders, but the small number of cases and recording positions applied do not permit analysis of the specifity of the MCG patterns. There are certain differences between 12-lead ECG and precordial MCG in the relative sensitivity to different phases of the cardiac electromotive events. For instance, the magnitude of an S-T segment shift, as measured relative to QRS amplitude, was greater in the MCG. A part of these differences may be explained by a greater proximity effect in magnetocardiography. Magnetocardiography may prove to be of clinical value in cardiac disorders, especially in those producing primary abnormalities in the repolarization process.