In aortic valve regurgitation, the aortic valve does not close completely. The valve lets blood leak back (regurgitate) into the heart.

In a normal heart, the aortic valve opens to allow oxygen-rich blood to flow from the left ventricle into the aorta. The aortic valve closes completely when the heart rests between beats, and stops blood from flowing backward into the heart. But in aortic valve regurgitation, the aortic valve does not close completely. So, with each heartbeat, some of the blood pumped into the aorta leaks back into the left ventricle.