A new cable model formulation based on Green's theorem.

We describe an alternative formulation of the cable equation to model excitation in a cylinder of cardiac fiber. The formulation uses Green's theorem to develop equations for the extracellular and intracellular potential on either side of the excitable membrane, the dynamics of which are described by a Hodgkin-Huxley type model, without assuming that the radial current is zero. These equations are discretized to yield a system of linear equations which are solved at each instant in time. We found no qualitative differences between this approach and the standard cable model for parameters within accepted physiological limits. When the cable diameter is of the same order as the length constant the new formulation takes into account the intracellular potential change in the radial direction and gives an accurate expression of the conduction velocity.