Ivy Tech Anatomy and Physiology II (APHY 102) Heart Practice Test

During systole the heart muscle contracts and builds high intramyocardial pressure, which compresses the coronary vessels. This external compression raises resistance to blood flow through the coronary arteries, so perfusion to the myocardium drops while the ventricle is contracting. Most coronary blood flow occurs during diastole, when the myocardium relaxes and the vessels are relieved from compression, allowing blood from the aorta to flow into the coronary circulation more readily. Therefore, coronary blood flow to the myocardium decreases during systole (not absent, simply reduced).