Non-invasively measured cardiac magnetic field maps improve the estimation of the current distribution

Comprehensive body surface potential mapping (BSPM) and magnetic field mapping (MFM) measurements have been carried out in order to improve the estimation of the current distribution generated by the human heart. Electric and magnetic fields and also the planar gradient of the magnetic field during the QRS complex were imaged as a time series of field maps. A model of the current distribution should explain the features of both BSPM and MFM. Simulated maps generated by a single dipole or a straight line source could be fitted satisfactorily to the BSPM, but not to the MFM. Electric potential and magnetic field maps simulated on the basis of a curved line source model are in good agreement to the measured maps. Also, curved structures in the gradient field maps are in accordance with the curved line source model. The good agreement of this model to simultaneously measured electric and magnetic data indicates the presence of a curvature component in the current density distribution. This is even more evident in the maps of the planar magnetic gradient field.