There are four valves that regulate the flow of blood within the heart: two on the left side (the aortic and mitral valves) and two on the right side (the pulmonary and tricuspid valves).
Most heart valve problems that require surgery or intervention involve the aortic and mitral valves, although problems with the other two valves can be treated.
Heart valve disorders can be caused by leaking (insufficiently or regurgitation) of the valves or narrowing (stenosis) of the valves.
When heart valves fail to open and close properly, the effects on the heart can be serious, possibly impairing the heart's ability to pump blood efficiently through the body. Heart valve problems are one cause of heart failure.