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Magnetocardiography (MCG) using a SQUID sensor is characterized by three dimensional cardiac electrical phenomena from magnetic fields, because it is hard to be affected by organ constitution of lungs and torso configuration. We have developed three-dimensional (3D) electric current density distribution analysis by a spatial filter method. At this symposium, we report clinical utility of 64-channel (64-ch) MCG. Subjects consisted of 20 normal volunteers, 10 cases with old myocardial infarction, 13 cases with atrial fibrillation (AFIB) who received surgical pulmonary (PV) isolation, and representative case with fetus premature ventricular complex (PVC). We recorded 10-min MCG data of magnetic field composition (a Bz ingredient) which was perpendicular to body surface in a magnetism shield, using 64-ch SQUID sensors (17.5 x 17.5 cm) built-in in MCG instrumentation(sampling; 500ms, total frequency characteristic; 0.1-200 Hz). We conducted 3D heart outline from electric current density calculated by magnetic field distribution. We also generated 3D functional images of the RT (activation recovery time) dispersion and spatial spectral distribution of a fibrillation wave. Increased fluctuation on RT dispersion map corresponded with space location of myocardial infarction. The mean frequency of 3D spectral map in persistent AFIB showed a higher value than that with restored a sinus rhythm (7.7 +/- 0.5 Hz vs. 6.5 +/- 0.7 Hz). We also demonstrated a fetus PVC. We concluded that 64-ch MCG can evaluate 3D spatial location of myocardial injury, 3D spectral map and characteristic frequency, and fetus arrhythmia. In future, further technical development in the fields of MCG measurement would be necessary for avoiding the used of unshielded room or liquid He.

A magnetocardiogram (MCG) can detect three-dimensional electric phenomena of the heart, because MCG does not influence the lung and torso form of the internal organs. In this symposium, we report the application of 64-channel MCG for the measurement of various arrhythmias (atrial flutter, atrial fibrillation), myocardial injury, and fetus arrhythmia. We composed function images of the conduction wave front and injured myocardium superimposed on a three-dimensional heart outline from the magnetic field. The injured myocardium was determined by a three-dimensional RT dispersion map. This algorithm allows the non-invasive determination of the space location of signal source and injured myocardium. In addition, 64-channel MCG can detect the fetal arrhythmias and autonomic nervous activity, which allows the diagnosis of fetus arrhythmia in detail before birth. Thus, MCG measurement is a useful non-invasive diagnostics procedure. However, there are several problems such as sealed room installation and the use of liquid helium. In the future, a newer technology that does not require liquid helium and a sealed room will be necessory.