title: Nonfluoroscopic localization of an amagnetic stimulation catheter by multichannel magnetocardiography.
abstract: This study was performed to: (1) evaluate the accuracy of noninvasive magnetocardiographic (MCG) localization of an amagnetic stimulation catheter; (2) validate the feasibility of this multipurpose catheter; and (3) study the characteristics of cardiac evoked fields. A stimulation catheter specially designed to produce no magnetic disturbances was inserted into the heart of five patients after routine electrophysiological studies. The catheter position was documented on biplane cine x-ray images. MCG signals were then recorded in a magnetically shielded room during cardiac pacing. Noninvasive localization of the catheter's tip and stimulated depolarization was computed from measured MCG data using a moving equivalent current-dipole source in patient-specific boundary element torso models. In all five patients, the MCG localizations were anatomically in good agreement with the catheter positions defined from the x-ray images. The mean distance between the position of the tip of the catheter defined from x-ray fluoroscopy and the MCG localization was 11 +/- 4 mm. The mean three-dimensional difference between the MCG localization at the peak stimulus and the MCG localization, during the ventricular evoked response about 3 ms later, was 4 +/- 1 mm calculated from signal-averaged data. The 95% confidence interval of beat-to-beat localization of the tip of the stimulation catheter from ten consecutive beats in the patients was 4 +/- 2 mm. The propagation velocity of the equivalent current dipole between 5 and 10 ms after the peak stimulus was 0.9 +/- 0.2 m/s. The results show that the use of the amagnetic catheter is technically feasible and reliable in clinical studies. The accurate three-dimensional localization of this multipurpose catheter by multichannel MCG suggests that the method could be developed toward a useful clinical tool during electrophysiological studies.
authors.affiliation: Clinical Physiology-Biomagnetism Research Center, Catholic University, Rome, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Fenici
authors.forename: J
authors.initials: J
authors.lastname: Nenonen
authors.forename: K
authors.initials: K
authors.lastname: Pesola
authors.forename: P
authors.initials: P
authors.lastname: Korhonen
authors.forename: J
authors.initials: J
authors.lastname: Lötjönen
authors.forename: M
authors.initials: M
authors.lastname: Mäkijärvi
authors.forename: L
authors.initials: L
authors.lastname: Toivonen
authors.forename: V P
authors.initials: VP
authors.lastname: Poutanen
authors.forename: P
authors.initials: P
authors.lastname: Keto
authors.forename: T
authors.initials: T
authors.lastname: Katila
mesh_terms: D000328:Adult; D018780:Body Surface Potential Mapping; D006328:Cardiac Catheterization / Q000295:instrumentation*; D003327:Coronary Disease / Q000175:diagnosis* / Q000503:physiopathology; D004558:Electric Stimulation; D004562:Electrocardiography; D004566:Electrodes; D005240:Feasibility Studies; D005260:Female; D005471:Fluoroscopy; D006339:Heart Rate; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008280:Magnetics; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results