Magnetocardiography: supraventricular arrhythmias and preexcitation syndromes.

Magnetocardiography is an elegant non-invasive method with which to study the electrical activity of the heart. The localization of cardiac electric sources, such as arrhythmia foci, would, in particular, be an interesting clinical application. In addition the detection of different abnormalities that could lead to cardiac depolarization and repolarization gives insight into how cardiac arrhythmias and arrhythmia mechanisms are generated. We have studied patients with supraventricular arrhythmias, especially those suffering from the Wolff-Parkinson-White (WPW) syndrome. Magnetocardiographic localization of the preexcitation site was performed in 26 WPW patients, with an average accuracy of 2 +/- 1 cm in comparison to the results obtained by invasive catheter mapping. By inspection of spatial isofield maps during atrial depolarization, the risk of atrial fibrillation was classified correctly in 11/20 (55%) patients with documented atrial fibrillation, and in 4/6 (67%) patients without atrial fibrillation. In a case of focal atrial tachycardia, magnetocardiographic localization of the origin of the arrhythmia was performed during tachycardia. In addition, the level of conduction block was successfully determined in six patients with third-degree congenital atrioventricular block.