Magnetocardiography of Direct Currents: S-T Segment and Baseline Shifts during Experimental Myocardial Infarction

Magnetocardiograms with a bandwidth of 0 to 40 hertz were recorded from intact dogs undergoing myocardial infarction. This was done with a superconducting magnetometer in a magnetically shielded room. The purpose was to look for the steady currents of injury from the heart which supposedly produce much of the S-T segment shifts during infarction. These heart currents cannot be measured with surface electrodes because of direct-current interference from other sources, such as from the contact potential between electrode and skin. The magnetocardiograms showed both S-T segment shifts and direct currents as a result of infarction. However, they also showed that the S-T segment shifts were not produced by the direct currents. It is unlikely that these direct currents originated from the infarcted area, and their exact origin is not yet known.