Estimation of Left Intra-Ventricular Activation Alterations and Conduction Delay Due to Left Anterior Fascicular Block Using a Novel Magnetocardiographic Approach with 3 Directional Recordings

概要

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Using a 64-Ch magnetocardiographic (MCG) system, we analyzed left intraventricular conduction delay in patients with left anterior fascicular block (LAFB) on ECG that is hardly discernible on ECG. We repeated 3 measurements with sensors placed close to anterior, posterior, and left lateral chest wall (in the supine, prone, and lateral positions) in 7 LAFB patients with LV dysfunction and 25 volunteers (Cont). In Cont (QRS duration, QRSd=89±6 ms), we constantly recognized 2 different currents arising from separate sites (i.e., propagations via left anterior and posterior fascicle). All LAFB patients (QRSd=105±10 ms) showed quite different patterns where only upward propagation (via left posterior fascicle) was seen (no apparent downward currents via left anterior fascicle), compatible with LAFB. LV conduction time was greater in LAFB compared with Cont (74±11 vs. 51±5 ms, p<0.01). Our MCG approach could not only delineate the characteristic changes in intra-ventricular conduction due to LAFB but also quantify the subtle conduction delay which is hardly detectable on ECG.