During which phase of the cardiac cycle do the coronary arteries receive blood?

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Multiple Choice

During which phase of the cardiac cycle do the coronary arteries receive blood?

During diastole the heart muscle is relaxed and the aortic valve is closed, allowing blood to flow from the aorta into the coronary ostia and fill the coronary arteries. This relaxation means the coronary vessels are not compressed, so perfusion to the myocardium, especially the subendocardial regions, is greatest then. In contrast, during systole the ventricles contract and intramyocardial pressure rises, squeezing the coronary vessels and markedly reducing blood flow. The isovolumetric contraction phase has all valves closed, so there’s essentially no coronary perfusion then. Atrial systole occurs later to aid filling but isn’t the primary period of coronary blood flow. So the coronary arteries receive blood mainly during diastole.

During diastole the heart muscle is relaxed and the aortic valve is closed, allowing blood to flow from the aorta into the coronary ostia and fill the coronary arteries. This relaxation means the coronary vessels are not compressed, so perfusion to the myocardium, especially the subendocardial regions, is greatest then. In contrast, during systole the ventricles contract and intramyocardial pressure rises, squeezing the coronary vessels and markedly reducing blood flow. The isovolumetric contraction phase has all valves closed, so there’s essentially no coronary perfusion then. Atrial systole occurs later to aid filling but isn’t the primary period of coronary blood flow. So the coronary arteries receive blood mainly during diastole.

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