Extracellular (volume conductor) effect on adjoining cardiac muscle electrophysiology

Abstract

The paper describes the effect of the extracellular volume conductor on the electrophysiological behaviour of an adjoining multifibred cardiac muscle preparation, where the fibres are parallel to the interface and to each other. It is shown how, at any given depth from the interface, an approximating linear-core conductor model can be formulated, where the interstitial resistance per unit length depends on the depth. At the surface the interstitial resistance is zero whereas at the greatest depth it approaches the value that results when the preparation is in oil. Because of this varying total axial resistance with depth, and because of the effect of the total axial resistance on velocity, action potential foot, and maximum rising-phase slope, the wavefront and waveform will also vary with depth. Furthermore these qualities will be anisotropic, since the tissue conductivities are anisotropic. Numerical examples are presented to show that the hypotheses are consistent with experimental results.