Active electric properties of cardiac muscle.

A model of electrical activity in the heart has been developed that treats the intracellular domain and the extracellular domain as electrical syncytia with anisotropic resistivities (bi-syncytial model). At the microscopic level, propagation is assumed to proceed primarily along the axes of individual cells. Considerations at the macroscopic level relate the transmembrane current to the intracellular and extracellular resistivity and the transmembrane potential. The result is a relationship between instantaneous extracellular potentials and cardiac action potentials.