Noninvasive visualization of activated regions and current flow in the heart by analyzing vector components of a cardiac magnetic field

To enable noninvasive analysis of cardiac electric processes in the heart, we have developed two different magneto-cardiogram (MCG) display methods that use vector (normal and tangential) components. The vector components are measured and analyzed with a 64-channel superconducting quantum interference (SQUID) system. From the magnetic field pattern of the Bz component normal to the body surface, the localized current source, e.g., the location of an arrhythmia pathway, is estimated. During depolarization and repolarization phases, the position and distribution of current sources in the heart can be visualized through a two-dimensional projection of the analyzed tangential magnetic field. The location and distribution of current in the heart are visualized, and anatomical position is determined by superimposing magnetic resonance imaging (MRI) and MCG measurements. This visualization gives us new information on multiple activated regions at the beginning of QRS, on the position of the arrhythmia focus, and any abnormality in the repolarization process.