Heart valves regulate the flow of blood through the heart's four chambers. The two small, round upper chambers are the atria and the two larger, cone-shaped lower chambers are the ventricles. Each valve consists of flaps (cusps or leaflets), which open and close like one-way swinging doors.

The heart valves can malfunction either by leaking resulting in regurgitation. They may also not open adequately, thus blocking the flow of blood, resulting in stenosis. Stenosis and regurgitation can affect any of the heart valves. Either problem will greatly interfere with the heart's ability to pump blood. Sometimes a valve has both problems.