A boundary element formulation of the forward problem of electrocardiology utilising discontinuous elements

The forward problem of Electrocardiology is the determination of the body surface potential distribution given a specified potential distribution on the surface of the heart. The governing equation for the electric potential distribution inside a realistic torso containing the internal heart chambers is solved via the boundary element method using over 4000 linear quadrilateral elements. Due to the complex shapes involved in the model, it is necessary to divide complex regions into convex subregions to maintain numerical accuracy. The use of linear elements requires the use of discontinuous elements to accurately account for the direction of normals to intersecting surfaces inside the thorax. The aim of developing this model is to gain an understanding of current flow within the thorax due to various conditions affecting the heart and to correlate these conditions with observed changes in the body surface electrocardiogram. Two different cardiac events are considered. Firstly, there is a comparison of body surface maps resulting from endocardial and epicardial ischaemia and, secondly, a series of maps looking at pre- and post-epicardial breakthrough.