Detection of atrial arrhythmia in superconducting quantum interference device magnetocardiography; preliminary result of a totally-noninvasive localization method for atrial current mapping

Abstract

Map-guided surgery is the goal for treatment of atrial fibrillation (AF), because it minimizes unnecessary incisions or procedures. We propose a totally-noninvasive and even non-contact method to detect atrial arrhythmia with a superconducting quantum interference device magnetocardiography (MCG) system, and report the first clinical application case of MCG map-guided AF surgery. To detect weak atrial excitation, we utilized a high sensitive 64-channel MCG system measuring tangential magnetic field components, which is known to be more sensitive to a deeper current source. We measured the MCG signals from eight patients with chronic AF. Then, we separated the f-wave from the other components by using independent component analysis. The extracted f-wave caused by reentrant myocardial excitation was three-dimensionally localized on the mesh model of a human heart by a novel beamformer technique having a surface action potential activity as its filter output. We localized the abnormal stimulation source of an atrial arrhythmia non-invasively and visualized the current source distribution corresponding to the atrial excitation successfully on the three-dimensional atrial surface, which was separated from the ventricular excitation. Using this atrial mapping, we underwent minimal AF surgery in three patients and converted their AF to sinus rhythm successfully.

Toward cardiac electrophysiological mapping based on micro-Tesla NMR: a novel modality for localizing the cardiac reentry

“…6,16 First, I simulated heart magnetic fields generated from a cyclic excitation of transmembrane potential on the myocardial surface. 16 In biomagnetism, they generally utilize equivalent current dipoles (ECD) as its sources. As for a brain, a collective excitation of pyramidal cells on the cortex can be well-approximated by the ECD.…”

“…Therefore, I adopted the equivalent double layer (EDL) model 12 rather than the ECD because the activation of the surface membrane potential is more realistic for describing the reentrant excitation feature. 16 The EDL model states all the current sources in the myocardium can be described by epicardial action potentials on a closed surface. 12 The magnetic field generated by the surface potential was calculated by using boundary element method (BEM) on the consideration of volume currents through the various conducting media.…”

“…16 The magnetic field B( r ) at a detecting position r can be calculated from the transmembrane potential φ( r ) on the mesh surface point r by using the following equation.…”

“…Three-dimensional tissue excitation cannot be investigated by such two-dimensional measurements. 6 Non-invasively, body surface potential mapping or magnetocardiography (MCG) 16 can be applied, but the ill-posedness in inverse problems limits the accuracy of the source localization, especially for deep sources.…”

Special article Magnetocardiography in clinical cardiology. Status quo and future applications

“…By separating the f-wave time-by-time and visualizing the activity map for action potentials for each time-separated waveform, the propagation trace of the AF could be inferred. After the MCG map-guided minimal AF surgery, the patient converted to sinus rhythm, well preserved after several follow-ups [56]. Finally, Jurkko et al contributed substantially to refinement of MCG studies in AF.…”