Non invasive Study of Preexcitation by Multichannel Magnetocardiography

Multichannel Magnetocardiography (MMCG), is a contactless method for non invasive localization of ventricular preexcitation (VPX). We have evaluated its reliability in an unshielded EP cathlab. Method: 9 channels DC-SQUID MMCG system (sensitivity is 20 fT/Hz1/2) (CMI, USA), measuring grid 20 x 20 cm. 22 WPW patients (pts), investigated at least twice, to test for reproducibility. In 14 pts the second procedure was carried out on the same day, in 12 MMCG was repeated after approximately 3 months. In 6, MMCG was also repeated during transesophageal atrial pacing-induced maximal VPX and/or AV reentry tachycardia. VPX localization with ECG algorithms and MMCG was compared. Results: MMCG classification of VPX was in agreement with ECG in 18/22 (81.8%). In 4/22 (18%) with conflicting results, MMCG provided a clear-cut localization in all and demonstrated complex activation patters during the delta wave in 3/4. Current density reconstruction and imaging in those cases suggested multiple activation pathways, unpredictable on the basis of ECG, in 1/4. Conclusion: MMCG is possible, reproducible and reliable also in an unshielded EP cathlab. As compared to ECG, it is optimal for non invasive 3D localization of paraseptal and multiple pathways.