Clinical application of magnetocardiogram by a high temperature superconducting quantum interference device

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We evaluated whether the cardiac electrical current could be visualized by displaying the current, density and whether the conduction velocity of electrical currents can be deduced obtained by a high temperature superconducting quantum interference device (high Tc-SQUID) using liquid nitrogen.Magnetic fields from heart were measured using a 32-channel high Tc-SQUID (Sumitomo Electric) in a magnetically shielded room. From the magnetic isofield maps, three-dimensional locations of dipolar currents during atrial or ventricurar depolarization phase were computed. Vector currents were obtained at 32 lead points based on the magnetic gradient, and a current density map were constructed.The conduction velocity during atrial depolarization was about 0.67 m/sec. The conduction velocity of dipolar current was about 0.85 m/sec at the initial ventricular depolarization phase. In a current distribution map obtained during ventricular depolarization, left and right ventricular electromotive forces could be visualized separately.Differing from ECG, magnetocardiography facilitates the accurate localization of the origin of electric current at mm-units, and conduction velocities of dipole can non-invasively deduced using this high Tc SQUID system. Previously, the detection of magnetic field from the heart required an expensive SQUID system using liquid helium. However, this system was characterized by its relative higher cost effectiveness and excellent spatial resolution. In addition, few studies have been done on the map which displays cardiac current density, which can potentially provide important information on electromotive forces. Therefore, this system can be clinically applied because it facilitates the detection of detailed cardiac electrical current.