Visualization of Cardiac Excitatory Process by Magnetocardiogram Using the Newest 64-channel SQUID System

We tried to visualize cardiac excitatory process using newly developed 64-channel Superconducting Quantum Interference Device(SQUID)system. The magnetocardiogram was measured in six healthy men by SQUID system installed in Tsukuba University Hospital. After the signals were averaged, we constructed two-dimensional isomagnetic and vector arrow maps from spatial derivatives of the normal(Bz)component in the tangential direction. In all subjects, we could measure the magnetic field of the heart. The distribution of current arrows was similar in each case, which was summarized as follows:During the P weve, current arrows were directed to lower left at the sinus node. At the beginning of the QRS wave, the current arrows were directed to the lower right at the intraventricular septum. These arrows changed direction anticlockwise and were directed to the left or lower left portion at the left ventricle. Then arrows were directed gradually to the upper or right upper at the basal portion of the heart. During the T weve, current arrows were directed to the left or left lower portion. These results were qualitatively similar compared with previous our study measuring tangential magnetocardiogram directly. This simplified SQUID system, having fewer SQUIDs and measuring circuits than previous system, was thought to make a new step for the clinical use.