Noninvasive Classification of Ventricular Preexcitation with Unshielded Magnetocardiography and Transesophageal Atrial Pacing and Follow-Up

Background: Ventricular preexcitation (VPx) is usually localized noninvasively by means of electrocardiogram (ECG) algorithms, which vary in their concordance levels. Contactless magnetocardiography (MCG) has been used as an alternate 3-dimensional (3D) method of accessory pathways (AP) localization. The sensitivity of MCG can be increased for preoperative evaluations and planning of ablation procedures by combining it with transesophageal pacing (TEP) and electrophysiological (EP) studies. This study compared the accuracy of VPx localization with MCG with ECG algorithms, and examined the increment in diagnostic accuracy achievable with TEP. Methods: Multisite mapping from the anterior chest wall was performed with a 36-channel MCG system. TEP allowed the evaluation of anterograde conduction properties and inducibility of arrhythmias. The reproducibility of the test and follow-up was examined in 88 patients with Wolff-Parkinson-White (WPW) syndrome. The accuracy of MCG localization was reevaluated during pacing-induced maximal VPx in 36 patients in whom, during MCG, the degree of VPx was highest during TEP. The gold standard for validation was effective ablation of the AP. Results: The MCG classification of VPx was accurate in 94% of AP, versus 64% and 67% with ECG, during sinus rhythm and during pacing-induced maximal VPx, respectively. In 4.5% of cases with unclear ECG localization, MCG suggested a complex septal VPx. In all patients with successful ablations, the 3D MCG localization of the AP corresponded to the ablation site. Conclusions: MCG was more accurate than ECG for the classification of VPx and provided additional information in the non-invasive EP assessment of patients with WPW syndrome