The Contribution of Core Muscle Fibers to the Surface Depolarization Signals on Cable-Like Cardiac Tissue Preparations - A Computer Simulation Study

Abstract

Small tissue samples of the heart such as the Papillary muscles in the ventricles or Pectinate muscles in the atria are widely used in experimental studies. Unlike with larger tissue samples or whole organ preparations, where perfusion is the method of choice to supply the tissue with oxygen, for practical reasons superfusion is considered to be a more appropriate method for small tissue samples. In this case, oxygen diffuses into the superficial tissue layers, but supply with oxygen decreases with depth leaving the core of a preparation without adequate oxygenation. It is unclear as to which degree pathological conditions in deeper tissue layers affect extracellular signals recorded close to the intact and viable surface of a preparation. To assess the contribution of sources within the depth of myocardial tissue sample and the impact of the absence of these sources under pathological conditions, computer simulations were conducted. A 3D-computer model of a cylindrically shaped tissue sample, immersed in an infinite volume conductor, was established. The contribution of deeper layers was evaluated by removing the current sources of co-axial cylindrical cores of variable radius. Results suggest that the pattern of activation remained essentially unchanged, although subtle effects on the extracellular potentials were detectable. The superficial viable tissue layers clearly dominate the potential distribution near the tissue surface during depolarization.