Magnetocardiographic localization of arrhythmia substrates: a methodology study with accessory pathway ablation as reference

Abstract

In magnetocardiographic (MCG) localization of arrhythmia substrates, a model of the thorax as volume conductor is a crucial component of the calculations. In this study, we investigated different models of the thorax, to determine the most suitable to use in the computations. Our methods and results are as follows. We studied 11 patients with overt Wolff-Parkinson-White syndrome, scheduled for catheter ablation. The MCG registrations were made with a 37-channel "superconducting quantum interference device" system. The underlying equivalent current dipole was computed for the delta-wave. Three models of the thorax were used: the infinite halfspace, a sphere and a box. For anatomical correlation and to define the suitable sphere and box, magnetic resonance images were obtained. As reference we used the position of the tip of the catheter, at successful radio-frequency-ablation, documented by cine-fluoroscopy. Nine patients could be evaluated. The mean errors (range) when using the infinite halfspace, the sphere and the box were 96 (49-125), 21 (5-39), and 36 mm (20-58 mm), respectively (p < 0.0001). In conclusion, the sphere was significantly better suited than the other models tested in this study, but even with this model the accuracy of MCG localization must further improve to be clinically useful. More realistic models of the thorax are probably required to achieve this goal.

Localization of endocardial ectopic activity by means of noninvasive endocardial surface current density reconstruction

“…It is of importance to better understand the mechanisms of cardiac physiology and pathophysiology and further to develop clinically applicable, noninvasive cardiac mapping techniques. A number of efforts have been put forth in the past decades in the development of the noninvasive cardiac electrical imaging techniques to estimate the equivalent cardiac source inversely from body surface potential mappings (BSPMs, Gulrajani et al 1984a, Burnes et al 2000, He and Wu 1997, 2001, Li and He 2001, Tilg et al 2002, Zhang et al 2005), magnetocardiographic (MCG, Agren et al 1998, Leder et al 1998a, Fenicir 2003) field mappings, or directly by comparing the BSPMs (SippensGroenewegen et al . 1990, Green et al .…”

Non-Invasive Resting Magnetocardiographic Imaging for the Rapid Detection of Ischemia in Subjects Presenting with Chest Pain

“…The MCG has been used predominantly in Europe since the 1970s [2]. Most studies were done to localize arrhythmias in conditions with ventricular pre-excitation, Wolf-Parkinson-White and accessory pathways, and more recently atrial fibrillation [3,4,5,6,7,8,9,10,11]. The sensitivity and capability of the MCG for the detection of ischemia has been evaluated in only a few small clinical studies [12,13,14].…”

Noninvasive Diagnosis of Partial Atrial Standstill Using Magnetocardiograms.

“…Another advantage is that the data in MCGs are vector markers using absolute scales, whereas the data in ECGs are scalar markers using relative scales. These advantages have been explored in MCG studies of Wolff-ParkinsonWhite syndrome, 7,8 and ischemic heart disease. 9,10 The accuracy of MCGs is affected by the distance between the magnetic source and the SQUID sensor, by body motion associated with respiration and the heartbeat, and by the models used to analyze the data.…”

“…9,10 The accuracy of MCGs is affected by the distance between the magnetic source and the SQUID sensor, by body motion associated with respiration and the heartbeat, and by the models used to analyze the data. 8 The sampling data is therefore usually signal-averaged, but this is inapplicable to Af, atrial flutter and atrial tachycardia because they are complicated arrhythmias with irregular atrioventricular conduction. We have already reported that MCGs can distinguish atrial flutter caused by macro reentry from atrial tachycardia caused by other mechanisms (automaticity or micro reentry), 4 and in the present study we have developed a new algorithm for analyzing atrial activation in patients with AS and Af 6 by using QRS-T subtraction and timefrequency analysis.…”