Preoperative information has helped in the planning of ablative therapy. Malignant ventricular tachyarrhythmias after myocardial infarction have low-amplitude high-frequency electromagnetic activity, so called late fields, at the end of the ventricular depolarization phase.
These signals are absent in patients without arrhythmic events after myocardial infarction. Similar abnormal ventricular activity can also be found in patients with cardiomyopathy and ventricular tachyarrhythmias. Long-QT patients have an inhomogeneous pattern of repolarization in MCG, clearly distinguishable from the normal pattern of their healthy relatives. In summary, multichannel MCG seems a powerful new clinical tool for identifying risk and for locating the foci in patients with life-threatening arrhythmias.