In which phase does normal flow in the coronary arteries occur?

Normal flow in the coronary arteries primarily occurs early in ventricular diastole. During this phase, the pressure within the ventricles decreases significantly after the heart has ejected blood during systole. As the pressure in the ventricles falls, the aortic valve closes, and the pressure in the aorta remains higher than in the ventricles. This pressure gradient allows blood to flow into the coronary arteries, which supply the heart muscle with oxygen-rich blood.

Additionally, the period immediately after ventricular contraction allows for this retraction of the vessel walls, leading to increased perfusion pressure in the arteries, further promoting flow into the coronary circulation. Understanding the timing of coronary artery perfusion is crucial for recognizing the heart's physiological function and the importance of diastolic filling time for myocardial oxygen delivery.