Application of the Boundary Element Method and the Finite Element Method to the Magneto- and Electrocardiogarphic Forward and Inverse Problem

Objective:Electric anisotropy of the cardiac muscle should be taken into account for accurate treatment of the magneto- and electrocardiographic forward problem. It is also intended to study the errors caused by neglecting anisotropy in the inverse problem. Methods: A bidomain model based finite element formulation is applied for modeling the anisotropic electric properties. Current densities across the surface of the heart are considered by applying the boundary element method in the surrounding isotropic tissue (BEM-FEM coupling). Activation time imaging (ATI) is investigated as an inverse approach. Results: Body surface potentials and magnetic field maps are computed for cardiac depolarization. Results obtained by assuming anisotropy within the myocardium are compared to those obtained by assuming appropriate isotropic conductivities. Quantitative differences are relatively high (RE>43%), but field patterns are in good qualitative agreement (CC>86%). Activation times computed neglecting anisotropy are in good agreement with the reference activation sequence (RE=15%,CC=85%) Conclusions: Methods applied to the inverse problem must be stable with respect to model errors caused by neglecting anisotropy. ATI turned out to fulfill this criterion due to the additional temporal template regularization provided by the a priori knowledge about cellular action potential time course.