The Eccentric Spheres Model as the Basis for a Study of the Role of Geometry and Inhomogeneities in Electrocardiography

To study the role of internal geometry and inhomogeneities in the "forward problem" of electrocardiography (ECG), a mathematical model was constructed which permitted manipulation of these variables. The model, which consists of two eccentric systems of concentric spheres, contains all the important torso compartments, namely the blood cavity, the myocardium, the pericardium, the lung region, the surface muscle layer, and the subcutaneous fat. An analytic solution is found in the form of a double series expansion in Legendre polynomials. The integrated effect of the inhomogeneities on the surface potential distribution is investigated. The model demonstrates the importance of interactions between the various torso components in determining the potential distribution at the surface.