Noninvasive classification of ventricular preexcitation with unshielded magnetocardiography and transesophageal atrial pacing and follow-up

Non-invasive classification of ventricular preexcitation (VPX) is usually done with ECG algorithms, which provide only a qualitative localization of accessory pathways (APs). Alternatively contactless multichannel magnetocardiography (MMCG) has been used for three-dimensional localization (3D) of APs. In combination with transesophageal pacing (TEP) MMCG can be performed also during TEP-induced atrio-ventricular reentry tachycardia (AVRT), thus it be an alternative to invasive electrophysiological (EP) study, for preoperative localization of VPX and planning of the ablation approach, especially in the case of paraseptal VPX. This study was aimed to compare the accuracy of VPX localization obtained with MMCG and with ECG algorhytms, and evaluate the diagnostic improvement achievable with TEP. Method: A 36-channel MMCG system (sensitivity is 20 fT/Hz0.5) was used for sequential recordings from 36 points on the anterior chest wall, within an area 20 x 20 cm. TEP provided EP evaluation of antegrade conduction properties and arrhythmias inducibility. 86 patients with Wolff-Parkinson-White syndrome were repetitively examined, months to years apart, to test for the reproducibility of the measurements and EP follow-up. In 35 patients, the accuracy of magnetocardiographic localization was assessed also during maximal VPX and/or atrioventricular reentrant tachycardia induced by Simultaneous TEP via an amagnetic catheter. The goldstandard for validation was effective ablation of the APs. Results: MMCG classification of VPX was found to be more accurate than ECG, with appropriate localization in 90% of the cases, versus only 52.3% and 77% obtained with ECG, in SR and during pacing-induced maximal VPX respectively. 10% of cases, with uncertain or impossible MCG localization, had multiple APs. When ablation was performed, MMCG 3D localization of VPX coincided with the ablation site Conclusions: MMCG 3D localization and imaging of VPX is highly reproducible. MMCG is feasible also in combination with amagnetic TEP and can provide also 3D imaging of retrograde atrial activation during AVRT. As compared to ECG, MMCG is more accurate and in combination with TEP represents a powerful tool to avoid invasivity in WPW patients requiring a diagnostic EP assessment, but not ablation