Coronary vessels supplying the left ventricle originate at the output of the left ventricle ending into the right atrium. The coronary network is developed by lumped parameters representation based on the intramyocardial pump concept. In the model, coronary circulation was approximated using three parallel vascular branches, simulating the microvascular network of the subendocardial (upper network), middle (middle network) and subepicardial (lower network) layers of the left ventricular wall. The three parallel branches "epi", "mid" and "endo" with an identical structure have different values of resistance and extravascular compression.The large cardiac vessels are included in the model. The epicardial arteries, together with epicardium microcirculation, are included in the epicardium layer (R_Aepi, C_AM1 and R_AM1). Coronary veins and coronary sinus are included as well in epicardium layer (R_VM1 and C_VM1).

A time-varying intramyocardial pressure, different for each layer, was applied through the intramyocardial capacitances C_Myo1, C_Myo2 and C_Myo3. Intramyocardial pressure, decreasing from subendocardium to subepicardium, is assumed to be proportional to left ventricular pressure (LVP). This effect was reproduced in the numerical model by changing the constant values (K_1ENDO, K_1MID and K_1EPI). This way the model mimics (in all the layers) the decrease of arterial inflow and the increase of venous outflow in systole, by permitting also the reversal arterial inflow. The compliances C_VM1, C_VM2 and C_VM3 are related to intramyocardial compression through a linear dependence (by the constants K_2ENDO, K_2MID, and K_2EPI) on left ventricular pressure. This representation could give the possibility of mimicking severe pathophysiological conditions.