In this experimental study we measured the magnetocardiograms (MCGs) of 17 normals at 42 measuring sites in a plane near the chest. The recordings were made in an unshielded environment with a single channel second-order SOUID gradiometer. From these recordings spatial maps were constructed of the atrial depolarisation and repolarisation. The two series of maps were found to be dipolar, but opposite in sign for 14 of the 17 subjects. The relatively small change in the amplitude and pattern of the atrial repolarisation maps built up out confidence in the method of subtracting a computed mean repolarisation map from the maps obtained during the last 40 ms before the QRS-onset. This method of separating His-Purkinje activity from atrial repolarisation led to distinct dipolar patterns in 9 out of the 17 cases. The direction and location of the associated electric current dipole was in good agreement with what can be expected electrophysiologically for His-Purkinje activation.
- Magnetic isofield contour maps
- Atrial repolarisation