From cell to body surface: a fully coupled approach

Different types of equivalent cardiac sources are often used in the forward problem of electrocardiology. These may not be adequate to accurately reproduce the body surface potentials that are the result of cellular electrical activity, because they do not guarantee current conservation across the myocardial surfaces. Presented here are the outlines of 2 new coupling techniques that seek to overcome this problem by creating a continuous electrical pathway from the cellular level through to the body surface. The first technique directly couples the extracellular cardiac bidomain region to the surrounding passive torso regions creating a single system of equations without the need for matrix inversions. The second technique uses a fixed point iteration across each myocardial surface that has the goal of matching the potential fields and current flows across the cardiac boundaries into the neighbouring tissues. These techniques can be combined, directly coupling some regions and iterating across other region boundaries. Simulations on a transverse two-dimensional slice through a human male torso are presented, showing the convergence of these methods.