ABSTRACT
FUNCTIONAL ANATOMY OF THE CORONARY ARTERIAL SYSTEM The coronary arterial system is divided into three functionally distinct main compartments. The first compartment comprises the large epicardial coronary arteries, which run onto the outer surface of the heart and have a diameter >500 m. These vessels exert a capacitance function, with practically no resistance to blood flow.1,2 An intermediate compartment comprises the prearterioles, which diameter ranges from approximately 100 to 500 m. Measurements of intracoronary pressure indicate that vessels up to 100 m are responsible for ∼45% of total coronary vascular resistance.3 As a result of their extramyocardial position and wall thickness, these vessels are not under direct vasomotor control by diffusible myocardial metabolites. The third, more distal, compartment is composed of the intramural arterioles (diameter <100 m), which are responsible for most of the resistance to coronary flow. At the level of coronary arterioles, myocardial blood flow is finely regulated to match with the tissue oxygen consumption.2
