Investigations on the Nature of Electrical Sources of the BSP and MCG

The relationship between the primary electrical sources within a human heart model and the simulated magnetocardiogram (MCG) including an boundary-element (BE) thorax model for the inverse problem is investigated. A cellular automaton model of the entire human heart considering 15 different tissue types and the dependence of the refractory period and conduction velocity on the cycle length is adopted. Anisotropy of the conduction velocities and optionally of the electrical conductivities in the ventricles is assumed. The Huygen´s propagation principle is applied for calculating the isochrones. The primary current dipoles are computed by the bidomain theory. The heart model is positioned inside the BE thorax model. The MCG is calculated closely above the thorax surface at 74 observation points. In case of the UDL theory (the PCDs are perpendicular to the wavefront) no MCG can be detected outside the thorax as long as the excitation wave does not reach the heart´s surfaces (epi- or endocardium). In case of the ODL theory (the PCDs are directed oblique to the wavefront), an additional contribution to the MCG is generated. In case of electrical isotropy the real signal generators are located on the heart´s surfaces only (i.e. the transmembrane potential distribution). Reconstructing sources from the MCG one can consequentely try to estimate the transmembrane potential distribution or the activation time map on the endo- and epicardium.