Validation of Magnetocardiographic Localization accuracy with an amagnetic pacing catheter in Patients and in a realistic Torso Phantom

Magnetocardiography has been proposed for non-invasive localization of arrhythmias, The aim of the study was to evaluate the accuracy of magnetocardiographic (MCG) localization of an intracardiac source, which was provided by an amagnetic stimulation catheter. Methods: A pacing catheter, specially designed to produce no magnetic disturbances when performing simultaneous MCG recording and cardiac pacing, was inserted into the heart of five patients after routine electrophysio¬logical studies. Thus, the tip of the catheter was serving as a well defined dipolar current source. MCG signals were then recorded in a magnetically shielded room. Non-fluoroscopic localization of the catheter's tip was performed from measured MCG data using patient-specific boundary element torso models. The intrinsic MCG localization accuracy was evaluated by comparing the 3D localizations of the artificial pacing signal (P) with the localizations of the evoked myocardial response (EMR) 3 ms after stimuli. Results: In all five cases, the MCG localization of the catheter was in good agreement with its anatomical position as inferred from the X-ray images. The mean 3D distance between P and EMR was 4±1 mm calculated from signal-averaged data. The 95 % confidence interval of beat-to-beat localization of the tip of the catheter from 10 consecutive beats was 4±3 mm. The propagation velocity of equivalent current dipoles localized between 5 and 10 ms after the stimulus was 1.1±0.3 m/s. Conclusion: This study demonstrates that the non-invasive MCG localization of cardiac sources is sufficiently precise for making the MCG localization of arrhythmogenic substrates reliable and useful. Our amagnetic catheter can be used for simultaneous endocardial MCG pace-mapping and monophasic action potential recording. It allows to develop a new MCG-guided arrhythmia localization method with minimal use of fluoroscopy