Magnetocardiographic Localization Of The Origin Of Ventricular Ectopic Beats

Magnetocardiographic mapping opens new perspectives for three-dimensional localization of cardiac electrical activation. Using a 37-channel SQUID magnetometer equipment with high shielding, the origin of abnormal ventricular activation was investigated in 18 patients with Wolff-Parkinson-White syndrome prior to catheter ablation and in 5 of 31 patients with coronary artery disease having a sufficient number of monomorphic ventricular extrasystoles to enable evaluation. In all WPW-patients, the site of the earliest delta-wave activation was projected onto the AV-valve plane in accordance with the MR images. The result of magnetocardiographic localization was then compared to the site of successful catheter ablation determined by digital imaging processing. After optimization of the algorithms, both sites were in the various planes at the following distance from each other: X-plane: 0.8 +/- 0.9 cm, Y-plane: 1.1 +/- 1.0 cm and Z-plane: 1.5 +/- 1.0 cm. In three-dimensional projection, the mean difference in space between both positions was calculated to be 2.1 +/- 1.7 cm. After this validation ventricular premature beats were localized in another group of patients. In 4 of 5 patients their origin was found at the border of infarct areas. In each case, the progression of the ventricular activation could be pursued. The detected structure of the magnetic field distribution of the VBP's exhibited a stable bipolar pattern, which is comparable to that of ventricular tachycardia, and its algorithms may be used to localize the origin of ventricular tachycardia. Thus, non-invasive magnetocardiographic mapping localizes abnormal ventricular activations with fair accuracy, which makes it an useful adjunct for invasive investigations as well as studies of the pathophysiology of arrhythmias.