Magnetic Study of the His?Purkinje Conduction System in Man

It has recently been suggested that depolarization of the entire His-Purkinje conduction system of the heart produces a characteristic waveform in the surface electrocardiogram. The magnetic probe offers a different and, in some respects, advantageous means of observing such waveforms, and extensive records of the surface magnetic field generated by the human heart have been obtained for four normal subjects. A first-order SQUID gradiometer was employed havinAthe lowest noise level yet reported in any biomagnetic study (6 X 10-15 T/?Hz). Using an on-line computer, 100 beat averages were taken at 49 positions over the chest on a 1 in square grid. The fields observed have a characteristic symmetry and provide support for the suggestion that events associated with depolarization of the conduction system may be observed at the surface of the torso.