During diastole, what is the role of the coronary arteries?

• A. They are perfused during diastole when the aortic pressure flows into the coronary vessels
• B. They are perfused during systole
• C. They are closed during diastole
• D. They receive blood from the coronary veins

Answer: (A)

During diastole the heart muscle is relaxed, and the aortic pressure continues to push blood into the coronary ostia, supplying the coronary arteries. The contracting myocardium during systole actually compresses the small vessels, limiting perfusion then, so most coronary blood flow occurs in diastole. That’s why the statement about the coronary arteries being perfused during diastole when the aortic pressure flows into them is the best description. The other ideas don’t fit: perfusion isn’t greatest during systole, the arteries aren’t closed during diastole, and blood is supplied to the myocardium by the arteries, while the veins drain blood away, not supply it.