A mechanical model of the dynamics of the coronary circulation in dog

A mechanical model of the coronary circulation, including a capacitive extramyocardial compartment and a collapsible intramyocardial vascular bed has been described. The phasic coronary blood flow (CBF) in the circumflex artery of 11 anesthetized open chest dogs was studied in control conditions and during thoracic aortic constriction and arteriovenous fistula (AVF). We measured pressures in aortic and left ventricle, phasic CBF by pulsed Doppler flowmetry and in three dogs, pressure in the left anterior descending coronary artery. After aortic and AVF unclamping, we observed a major reverse flow in the circumflex artery. This reverse flow may be explained by the displacement of the collapse point of the intramyocardial compartment, due to the relative distribution of the intramyocardial tissue pressure and the intravascular coronary pressure. The specific role of the epicardial capacitive coronary compartment and of the intramyocardial pump action has been illustrated during coronary artery clamping, ectopic beats and changes in myocardial contractility. Under all the experimental conditions, the reported results demonstrated the ability of the model to describe the patterns of the dynamic of the coronary circulation.