Non-Invasive localization of Ventricular Preexcitation: Role of Multichannel Magnetocardiography

In clinical practice non invasive classification of ventricular preexcitation (VPX) is usually done with ECG algorithms, which however provide a qualitative localization of accessory pathways. Since 1984, single or multichannel Magnetocardiography (MMCG) has been used for 3D localization of VPX sites, however a systematic comparative study between ECG and MCG was still lacking. In this study we have compared VPX classification achieved with the 5 most recent ECG algorithms with that obtained with MCG mapping and imaging techniques. A 9 channels system was used for MMCG. 28 WPW patients (pts) were investigated, at least twice, on the same day and/or after several months, to test for the reproducibility. In 8 pts, the reproducibility of MMCG was also evaluated, with different MCG instrumentations, during maximal VPX and/or AV reentry tachycardia, induced by amagnetic transesophageal atrial pacing. Equivalent current dipole, Effective Magnetic Dipole and Distributed Currents models were used for inverse solution. MMCG classification of VPX was more accurate than that obtained with ECG and provided also additional information for the identification of paraseptal pathways. Furthermore, in pts with complex activation patterns during the delta wave, CDI evidenced two different activation patterns, suggesting multiple APs