Parametric analysis of flow in the intramyocardial circulation.

A simple mathematical model of the intramyocardial circulation has been utilized to provide a better understanding of coronary blood flow. The model includes three myocardial layers, each characterized by a three-parameter windkessel with one capacitance and two resistances. The effects of the beating heart are taken into account by means of an intramyocardial pump and the possible collapse of the vessels by an elevated backpressure. The three basic parameters that govern the flow are a normalized time constant, tau, the total resistance, Rt, and a parameter, alpha, which specifies the resistance distribution in the intramyocardial circulation. Both the normal beating heart and prolonged diastole have been investigated analytically as well as numerically. It is shown that each of these parameters has its own special significance. Calculated pressure-flow relationships and zero-flow pressures for the case of prolonged diastole show a high sensitivity to tau and alpha.