What Is Mitral Valve Prolapse?

Mitral (MI-tral) valve prolapse (MVP) is a condition in which one of the heart's valves, the mitral valve, doesn't work properly. The flaps of the valve are "floppy" and don't close tightly.

Much of the time, MVP doesn't cause any problems. Rarely, blood can leak the wrong way through the floppy valve, which may cause shortness of breath, palpitations (strong or rapid heartbeats), chest pain, and other symptoms.

Normal Mitral Valve

The mitral valve controls the flow of blood between the two chambers on the left side of the heart. The two chambers are the left atrium (AY-tree-um) and the left ventricle (VEN-trih-kul).

The mitral valve allows blood to flow from the left atrium to the left ventricle, but not back the other way. (The heart also has a right atrium and ventricle, separated by the tricuspid (tri-CUSS-pid) valve.)

At the beginning of a heartbeat, the atria contract and push blood through to the ventricles. The flaps of the mitral and tricuspid valves swing open to let the blood through. Then, the ventricles contract to pump the blood out of the heart.

When the ventricles contract, the flaps of the mitral and tricuspid valves swing shut. They form a tight seal that prevents blood from flowing back into the atria.

For more information about the heart, see the Diseases and Conditions Index article on How the Heart Works. This article contains animations that show how your heart pumps blood and how your heart's electrical system works.

Mitral Valve Prolapse

In MVP, when the left ventricle contracts, one or both flaps of the mitral valve flop or bulge back (prolapse) into the left atrium. This can prevent the valve from forming a tight seal.

As a result, blood may flow backward from the ventricle into the atrium. The backflow of blood is called regurgitation (re-GUR-ji-TA-shun).

Backflow doesn't occur in all cases of MVP. In fact, most people who have MVP don't have backflow and never have any symptoms or complications. In these people, even though the valve flaps prolapse, the valve still can form a tight seal.

When backflow does occur, it can cause symptoms and complications such as shortness of breath, arrhythmias (ah-RITH-me-ahs), or chest pain. Arrhythmias are problems with the rate or rhythm of the heartbeat.

Mitral Valve Prolapse

Figure A shows a normal mitral valve that separates the left atrium from the left ventricle. Figure B shows a heart with mitral valve prolapse. Figure C shows the detail of mitral valve prolapse. Figure D shows a mitral valve that allows blood to flow backward into the left atrium.

Backflow can get worse over time. It can lead to changes in the heart's size and higher pressures in the left atrium and lungs. Backflow also increases the risk for heart valve infections.

Medicines can treat troublesome MVP symptoms and prevent complications. Some people will need surgery to repair or replace their mitral valves.

MVP was once thought to affect as much as 5 to 15 percent of the population. It's now believed that many people who were diagnosed with MVP in the past didn't actually have an abnormal mitral valve.

They may have had a slight bulging of the valve flaps due to other conditions, such as dehydration or a small heart. However, their valves were normal, and there was little or no backflow of blood through their valves.

Now, diagnosing MVP is more precise because of a test called echocardiography (EK-o-kar-de-OG-ra-fee). This test allows doctors to easily identify true MVP and detect troublesome backflow.

As a result, it's now believed that less than 3 percent of the population actually has true MVP, and an even smaller percentage has serious complications from it.

Outlook

Most people who have MVP have no symptoms or medical problems and don't need treatment. These people are able to lead normal, active lives; they may not even know they have the condition.

A small number of people who have MVP may need medicines to relieve their symptoms. Very few people who have MVP need heart valve surgery to repair their mitral valves.

Rarely, MVP can cause complications such as arrhythmias (irregular heartbeats) or infective endocarditis (EN-do-kar-DI-tis). Endocarditis is an infection of the inner lining of the heart chambers and valves. Bacteria that enter the bloodstream can cause the infection.

Revised July 2009