Why coronary perfusion takes place during diastole?

Coronary perfusion primarily occurs during diastole because this is when the heart muscle relaxes, allowing the coronary arteries to fill with blood. During systole, the contraction of the heart compresses the coronary vessels, reducing blood flow. Additionally, the aortic valve is closed during diastole, which helps to maintain higher pressure in the coronary arteries, facilitating blood flow to the myocardium. Thus, diastole is crucial for adequate oxygen and nutrient delivery to the heart muscle.