On the Independence of Magnetic and Electric Body Surface Recordings

Recent papers have shown that the ECG depends on the flow sources of the impressed field in the heart while the MCG is a function of its vortex source distribution. It has consequently been suggested that body surface electric and magnetic recordings yield completely independent information about the physiological generators. Such independence would be of enormous significance wherever present diagnostic procedures rely heavily on the ECG or EEG. This paper points out that the independence of the flow and vortex sources is only a mathematical possibility. It demonstrates that two important physical constraints are operating which require the flow and vortex sources to be, in effect, one-to-one with each other. Consequently, the electric and magnetic fields arising from excitable tissue in an assumed homogeneous volume conductor are fundamentally interdependent.