[Observation of magnetic fields from three directions, and the moving image of the heart in a normal subject].
Three components of the magnetic field generated by the heart over the anterior aspect of the chest in a normal subject were detected using a Superconducting Quantum Interference Device (SQUID) magnetometer with a single detecting coil in a magnetically shielded room. Contour maps and color density maps of the field were prepared by computer. Movies of sequential magnetic fields of the vertical component on the anterior aspect of the chest were made from these maps. In the movies, the maximum moved from the upper central portion to right lower portion in the early stage of ventricular excitation. It moved to the central portion in the middle stage, then returned to the upper central portion in the late stage. Three-dimensional maps of instantaneous magnetic fields over the anterior portion of the chest were derived from maps of three components of the field, and from presumed heart vectors and were drawn as arrows, based on the Viot-Savart theorem. Heart vectors from these field maps corresponded well with septal forces in the early stage, left ventricular free wall force in the middle stage and the basal force in the late stage, respectively. However, large circulating vectors in the form of clockwise rotation in the central portion were also presumed. These circulating heart vectors did not correspond with the sequence of cardiac excitation as reported by Durrer et al. This discrepancy may have been caused by the fact that the vertical electric current could not be expressed from our display for presuming an electric force. Therefore, new displays and interpretations may be required for the expression of heart vectors.
D006321:Heart / Q000502:physiology*; D006801:Humans; D008280:Magnetics