Heart Stimulation by Time-Varying Magnetic Fields

Abstract

A strong magnetic stimulator adopted for cardiac muscle was constructed with the stored energy of 50 kJ. Pulsed magnetic fields were applied to dog hearts with normal activity from outside of the body. The magnetic stimulus triggered on the T wave of the electrocardiograph caused arrhythmias in the first and second beats after the stimulus. It has been confirmed that this magnetic effect is due to a direct stimulation of cardiac muscle, not to an indirect stimulation on the vagus nerve. The threshold strength was determined for different pulse durations. The obtained strength-duration relationship is comparable to that for the electric stimulation of the dog heart.