Magnetocardiographic localization of accessory conduction pathway in patients suffering from WPW syndrome

Abstract

We have studied the group of 12 patients suffering from the Wolf-Parkinson-White (WP W ) syndrome. The noninvasive magnetocardiographic (MCG) mapping data were used to find a functional localization of accessory conduction pathway (AP) by using the current dipole source model in diflerent volume conductor models. The best reference interval for magnetic data baseline corrections as well as the onset of A P were determined automatically b y means of averaged standard deviation of magnetic recordings. The stability of MCG inverse solutions has been studied. For all cases the calculated A P spatial coordinates were compared to corresponding results obtained b y the invasive electrophysiological study (EPS). IntroductionThe result of magnetocardiographic mapping is a spatio-temporal distribution of magnetic field in the vicinity of human chest. The aim of our work is the estimation of current sources which generate the measured magnetic field. This is a biomagnetic equivalence of a well known problem in bioelectric modeling where the electric current sources inside a volume conductor are estimated from potential measurements at the thorax surface. This is known as the inverse problem for which no mathematically unique solution exists. In order to localize electrical current sources one has to introduce some models and constraints.We have tried to localize the AP in the group of 12 patients suffering from the WPW syndrome. For these patients the AP occurs between the atria and ventricles and leads to a pre-excitation of ventricles and can cause heart arrhythmia which in turn can produce sudden cardiac death. We have used a moving current dipole as a model of current source. We have tested several volume conductor models like halfspace model, elliptic cylinder and three different realistic torso models. The catheter ablation was performed in all studied patients. Before the ablation the location of AP was determined by the invasive EPS. The spatial coordinates of the tip of ablation catheter obtained by the X-ray system have been used as a reference in the evaluation procedure of current source coordinates (the onset of the AP) calculated from the noninvasive magnetic measurements. 2. MethodsIn order to find a successful solution to the inverse problem one has to solve first the forward problem for the chosen current source and volume conductor model, i.e. the mathematical relation between the source model and the corresponding magnetic field should be known in terms of finite number of parameters. The inverse problem is then solved by the parameter estimation procedure. Analytical solution for the magnetic field, generated by the current dipole, exists only for the simplest half-space model. For the volume conductor of an arbitrary shape the Boundary Element Method (BEM) has been used [l, 21. Details about our BEM approach and volume conductor models are described elsewhere [3].All MCG measurements were performed in the Berlin Magnetically Shielded Room [4] by means of 37-SQUID multichannel magnetometer system [5]. Up...

Multistage Classification of Current Density Distribution Maps of Various Heart States Based on Correlation Analysis and k-NN Algorithm

“…Magnetocardiographic mapping is performed for diagnostics of ischemic heart disease ( 4 ), Wolf-Parkinson's-White syndrome ( 5 ), and other heart failures associated with current flow changes in heart muscles. Fairly good results have been achieved in the classification of current density vector maps based on clusters analysis for coronary artery disease and ischemic heart disease detection in patients with normal or unspecifically changed ECG ( 6 ) and echocardiogram ( 7 ).…”

Current density distribution maps threshold processing

“…Cardiac-current images that include morphological information on the heart may be obtained by projecting a two-dimensional (2-D) current-arrow map (CAM), which is calculated from magnetocardiogram signals, onto a three-dimensional (3-D) standard heart model, which is intended to be applicable to all adult subjects [5]. The noninvasive magnetocardiographic mapping data is used for diagnostics and analysis of Wolf-Parkinson-White syndrome [6] and other diseases accompanied by lesions of current flow in the heart muscles.…”

Ischemic heart disease recognition by k-NN classification of current density distribution maps

“…MCG is more sensitive to intra-and extracellular activation currents than electrocardiography (ECG) [1][2]. The noninvasive magnetocardiographic mapping is used for diagnostics and analysis of ischemic heart disease [1], Wolf-Parkinson-White syndrome [3] and other diseases accompanied by lesions of current flow in the heart muscles.…”