The Four-Electrode Resistivity Technique as Applied to Cardiac Muscle

Abstract

Cardiac tissue consists of two conducting regions, the intracellular and the interstitial, which are separated by a plasma membrane. It therefore constitutes a bidomain, as distinct from a single (monodomain) conducting region. Each cardiac domain is anisotropic. The four-electrode technique is a useful method for measuring the resistivity of an isotropic monodomain. The technique has also been used with anisotropic monodomains. However, its applicability to the anisotropic bidomain of cardiac tissue has never been verified. This paper shows that if all anisotropy ratios are equal, then the four-electrode method can be applied in its usual form to cardiac tissue. It shows further that under this restrictive condition, a modification of (anisotropic) bulk tissue resistivity actually is measured. If the anisotropy ratios are not equal, it appears that the four-electrode method cannot be applied correctly in the usual way. Copyright © 1982 by The Institute of Electrical and Electronics Engineers, Inc.