MAGNETOCARDIOGRAPHIC PACEMAPPING FOR NONFLUOROSCOPIC LOCALIZATION OF INTRACARDIAC ELECTROPHYSIOLOGY CATHETERS

The purpose of the study was to validate, in patients, the accuracy of magnetocardiography (MCG) for three-dimensional localization of an am agnetic catheter (AC) for multiple monophasic action potential (MAP) w ith a spatial resolution of 4 mm2. The AC was inserted in five patient s after routine electrophysiological study. Four MAPs were simultaneou sly recorded to monitor the stability of endocardial contact of the AC during the MCG localization. MAP signals were band-pass filtered DC-5 00 Hz and digitized at 2 KHz. The position of the AC was also imaged b y biplane fluoroscopy (XR), along with lead markers. MCG studies were performed with a multichannel SQUID system in the Helsinki BioMag shie lded room. Current dipoles (5mm: 10mA), activated at the tip of the AC , were localized using the equivalent current dipole (ECD) model in pa tient-specific boundary element torso. The accuracy of the MCG localiz ations was evaluated by: (2) anatomic location of ECD in the MRI, (2) mismatch with XR. The AC was correctly localized in the right ventricl e of all patients using MRI. The mean three-dimensional mismatch betwe en XR and MCG localizations was 6 +/- 2 mm (beat-to-beat analysis). Th e coefficient of variation of three-dimensional localization of the AC was 1.37% and the coefficient of reproducibility was 2.6 mm. In patie nts, in the absence of arrhythmias, average local variation coefficien ts of right ventricular MAP duration at 50% and 90% of repolarization, were 7.4% and 3.1%, respectively. This study demonstrates that with a dequate signal-to-noise ratio, MCG three-dimensional localizations are accurate and reproducible enough to provide nonfluoroscopy dependant multimodal imaging for high resolution endocardial mapping of monophas ic action potentials.