ABSTRACT
There is an ongoing controversy on the nature of the interaction between stresses in the myocardial tissue on the one hand and coronary pressure flow relation on the other. In terms of its mechanical behavior, the extravascular myocardial tissue consists of several components which can be grouped into two categories: the solid (muscle fibers, connective tissue fibers, and structural proteoglycans) and the interstitial fluid (primarily water). Both solid and fluid are incompressible. The mechanics of the solid-fluid myocardial tissue can thus be best analyzed along the principles of mixture theory. The most important implication of the existence of stress of the fibers (solid) is that the interaction between myocardium and intramyocardial vessel depends on the direction of the vessel. This is in contradistinction to the case in which the isotropic tissue pressure alone interacts with the vessel. In the latter case the interaction is independent of the direction of the vessel.
