There are four heart valves. Two control the inflow of blood to the ventricles from the atria. The second set controls the outflow of blood from the heart to the body. The leaflets in the valves act as one-way doors, opening to allow the flow of blood in one direction and closing to prevent the blood from backing up into heart chambers it has just left. Healthy heart valves open easily, close securely, and do not allow blood to flow backwards.

When the valves do not open and close properly, the heart must work harder to push the blood through. Usually the valve problem is due to stenosis (valve does not fully open) or regurgitation (valve allows reverse blood flow).

Surgery for valve problems involves either repairing or replacing the valve. With valve repair, excess tissue is removed from the valve and a ring may be sewn around the opening of the valve to allow the valve to close more snugly. When a valve cannot be repaired, it may be replaced with either a biological (tissue) valve or mechanical valve. Many factors may combine to determine if a valve is repaired replaced.