Phantom Validation of Multichannel Magnetocardiography Source Localization

Abstract

Multichannel magnetocardiography (MMCG) is used clinically for noninvasive localization of the site of origin of cardiac arrhythmias. However, its accuracy in unshielded environments is still unknown. The aim of this study was to test the accuracy of three-dimensional localization of intracardiac sources by means of MMCG in an unshielded catheterization laboratory using a saline-filled phantom, together with a nonmagnetic catheter designed for multiple monophasic action potential recordings in a clinical setting. A nine-channel direct current superconducting quantum interference device (DC-SQUID) system (sensitivity fT/Hz0.5) was used for MMCG from 36 points in a measuring area of 20 x 20 cm. The artificial sources to be localized were dipoles embedded in the distal end of the catheter, placed 12 cm below the sensor's plane. Equivalent current dipoles, effective magnetic dipoles, and distributed currents models were used for the inverse solution. The localization error was estimated as the three-dimensional difference between the physical position of the tip of the catheter and the three-dimensional localization of the dipoles derived by means of the inverse solution calculated from MMCG data. The reproducibility was tested by repeating the MMCG after repositioning the phantom and the measurement system. The average location error of the catheter dipole was 9 +/- 4 mm and was due primarily to imprecise depth estimation. Localization was reproducible within 0.73 mm. The distributed currents model provided an accurate image of current distribution centered over the catheter tip. The authors conclude that MMCG estimation is accurate enough to guarantee proper localization of cardiac dipolar sources even in an unshielded clinical electrophysiological laboratory.

Contactless magnetocardiographic mapping in anesthetized Wistar rats: evidence of age-related changes of cardiac electrical activity

“…Since the early 1970s, MCG has been proposed as the magnetic alternative to ECG and BSPM for the noninvasive study of cardiac electrophysiology (1,20,28,51,62,69,75). In humans, multichannel MCG systems provide simultaneous multipoint cardiac mapping, with spatial and temporal resolution adequate to reveal electrophysiological markers for risk of life-threatening arrhythmias (43,44,74).…”

“…Multichannel MCG mapping measures the magnetic fields (MF) generated by cardiac activation currents, with minimal distortion due to the shape and conductivity of the lungs and torso (20,28). The advantages of contactless MCG mapping are as follows: 1) the ability to study conscious animals without movement artifacts (65), 2) the potential to provide diagnostic information not revealed by ECG (1,29,36,37,41,43,44,51,54,62,64,69,71,74,75), 3) the fixed-sensors geometry (42), which minimizes errors in localization of intracardiac sources (30) and three-dimensional electroanatomic imaging of arrhythmogenic phenomena (77), and 4) the localization of VR heterogeneities associated with areas of myocardial injury (50).…”

Angiotensin II-induced sudden arrhythmic death and electrical remodeling

“…CMFM signals have several advantages: 1) they are little influenced by the tissues between skin and heart, 2) they are sensitive to tangential currents that arise in the border zones of cardiac tissue with different electrophysiological properties such as ischemia, and 3) they consider the track of electrical vortex currents (10). The technical feasibility of recording CMFM signals in small animals has already been shown (31).…”

Body Surface Two-Dimensional Spectral Map of Atrial Fibrillation Using Vector-Projected 187 Channel Electrocardiography

“…17) Representative positions are shown in Figure 1 as previously reported. 13,14) In brief, we proposed 11 parallel, equispaced transverse levels with 2-inch spacing between the levels. Level 5 coincides with the second intercostal space and level 6 with the heart center.…”

“…11,12) Previously, we reported a 3D spectral map of the atrial fibrillation generated by 64ch cardiomagnetic fields B in the z direction using a space filter. 13) Recently, we developed a 187 channel vectorprojected ECG (187ch VP-ECG) that could evaluate 2-dimensional (2D) characteristics of recovery time dispersion and high frequency late potentials. [14][15][16] We hypothesized that AF cycle length may be correlated locally with atrial refractoriness and globally with the degree of atrial organization.…”