What Is Mitral Valve Prolapse?

Mitral (MI-tral) valve prolapse (MVP) is a condition in which one of the valves of the heart, 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, 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 and form a tight seal that prevents blood from flowing back into the atria.

For more information, see the How the Heart Works section.

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, and allow blood to flow backward from the ventricle into the atrium. The backward flow of blood is called regurgitation (re-GUR-ji-TA-shun), and it can lead to symptoms and complications.

Regurgitation doesn’t occur in all cases of MVP. In fact, the majority of people with MVP don’t have regurgitation and never have any symptoms or complications. In these people, even though the valve flaps prolapse, the valve is still able to form a tight seal.

When regurgitation does occur, it can cause complications and troublesome symptoms such as shortness of breath, a racing or irregular heartbeat, or chest pain. Regurgitation can get worse over time and lead to changes in the heart’s size and higher pressures in the left atrium and lungs. Regurgitation increases the risk for heart valve infections.

Medicines can treat MVP symptoms that cause people to worry or have discomfort. Medicines are also used to prevent complications. Sometimes a person will need surgery to repair or replace the mitral valve.

Figure A shows the normal mitral valve separating the left atrium from the left ventricle. Figure B shows the 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.

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 valve was normal and there was little or no regurgitation through the valve. Now, more precise rules for diagnosing MVP with a test called an echocardiogram make it easier to identify true MVP and to detect troublesome regurgitation. Based on these new rules, it’s now believed that less than 3 percent of the population actually have true MVP, and an even smaller percentage has serious complications from it.

Outlook

In most people with MVP, the condition causes no symptoms or medical problems, and no treatment is needed. These people are able to lead normal, active lives, and they may not even know they have the condition. However, people with mild MVP may need antibiotics before dental work or certain types of surgery to prevent a heart valve infection called infective endocarditis (EN-do-kar-DI-tis). This infection is caused by bacteria that can enter the bloodstream at the time of dental work or some kinds of surgery. These bacteria can stick to and infect the heart valves in people with MVP.

Only a very small number of people with MVP have troublesome symptoms or regurgitation through the valve. They may need medicine to relieve their symptoms. A very few people with MVP may need heart valve surgery.

December 2007