Contactless localization and imaging of ventricular preexcitation in an unshielded EP laboratory with a novel 36-channel magnetocardiographic instrumentation

Multichannel Magnetocardiography (MMCG) is a contactless method, which provides non-invasive three-dimensional (3D) imaging of cardiac electrogenetic phenomena. However a multichannel system reliable in an unshielded hospital environment was needed for clinical application. We have recently installed the first 36-channel instrumentation for MMCG operating in an unshielded EP catheterization laboratory, and validated its accuracy for cardiac source localization. In this study MMCG was used for 3D imaging of ventricular preexcitation (VPX). Method: the 36-channels DC-SQUID system sensitivity is 20 fT/Hz1/2. MMCG from 36 points of the anterior chest wall (measuring grid 20 x 20 cm) lasts 90 seconds. Equivalent current dipole (ECD), Effective Magnetic Dipole (EMD) and distributed currents (DC) models are used in the inverse calculations for 3D localization and imaging of VPX. Localization results are transferred into 3D realistic heart/torso models and onto MRI images. 38 WPW pts were investigated, at least twice, to test for reproducibility. 27 pts were also studied during pacing-induced maximal VPX. The study was designed and ethically approved as a non-invasive study only. MMCG localization of VPX was compared with that achiavable with most recent ECG algorithms. Results: ECG classification of VPX was certain in 26/38 pts (68.4%), uncertain in 10/38 pts (26.3%), unreliable in 2/38 pts (5.2%). MMCG classification of VPX was certain in 35/38 pts (92.1%), uncertain in 3/38 pts, with complex activation patters during the delta wave, suggesting multiple activation pathways, unpredictable with ECG. MMCG was in agreement with ECG in 26/38 pts (68.4%). In the 12 pts unclassifiable with ECG, MMCG provided a clear-cut localization of VPX. Conclusion: This study demonstrates that 36-channel MMCG provides fast and reliable non-invasive localization of VPX also in an unshielded EP laboratory. As compared to ECG, MMCG is more accurate to classify, non-invasively, complex paraseptal VPX and to identify multiple accessory pathways. Furthermore MMCG provides quasi real-time 3D electroanatomical imaging and integration with MRI