On the pressure flow relationship of the coronary collaterals: a model study

The pressure-flow relationship of the collaterals is investigated by using an electrical analog model which combines the coronary epicardial tree with the nonlinear characteristics of the intramyocardial circulation. The study aims to examine some issues concerning the collateral circulation, including the location and transmural distribution of the collaterals, the nature of the wall of the collateral vessels, the effects of the muscle contraction, the effect of microcirculatory embolization and the causes for the nonlinearity of the collateral pressure-flow relationship. The study was carried out by simulating the two basic experimental setups: the free-flow and the back-pressure. The analysis shows that the nonlinear relationship between retrograde flow and perfusion pressure depends heavily on the experimental setup and is a function of the distensibility of the collaterals, which are distributed mainly on the epicardial surface, and of the nonlinear contraction characteristics of the myocardium