Magnetic field excitation of peripheral nerves and the heart: a comparison of thresholds.

Time-varying magnetic fields can theoretically excite the heart or peripheral nerves. Relative excitation thresholds of nerve and heart are compared using ellipsoidal representations of the human torso. Relative magnetic thresholds depend on the excitability of nerve and cardiac tissue, the geometric positions of anatomical features, stimulus waveform features and the direction and spatial distribution of the incident magnetic field. Minimum electric field thresholds for excitation of nerve and heart do not differ greatly. Nevertheless, nerve and heart magnetic thresholds may be disparate because of factors related to body geometry and the dependence of excitability on the stimulus waveform.