What is mitral valve stenosis?

Mitral valve stenosis is a heart condition in which the mitral valve fails to open as wide as it should. Although it has no immediate effect on health, eventually mitral valve stenosis can cause irregular heartbeats and possibly heart failure or other complications, including stroke, heart infection, pulmonary edema, and blood clots.

See a picture of an open and closed mitral valve.

What is the purpose of the mitral valve?

The mitral valve is one of four valves in the heart. It regulates blood flow from the left atrium into the left ventricle, the heart's main pumping chamber. A normal mitral valve has two flaps, or leaflets. When the heart pumps, blood forces the flaps open, and blood flows from the left atrium (upper chamber) to the left ventricle (lower chamber). Between heartbeats, the leaflets close tightly so that blood does not leak backwards through the valve.

But with mitral valve stenosis, the two leaflets and related structures become stiff, scarred, or partially fused together. As a result, the mitral valve gradually narrows, restricting blood flow to the left ventricle, increasing the volume and pressure of blood in the left atrium, and causing blood to back up into the lungs.

See a picture of the heart and its chambers, valves, and blood flow.

See a picture of mitral valve stenosis.

What causes mitral valve stenosis?

Virtually all cases of mitral valve stenosis are caused by rheumatic fever, which can follow an untreated strep throat infection. But many people who have mitral valve stenosis don't realize they had rheumatic fever.

What are the symptoms?

Although mitral valve stenosis is a lifelong disease, symptoms usually do not develop for 10 to 20 years and may take as long as 40 years.^{1, 2} Early symptoms, such as shortness of breath with exertion, are often mild and hard to distinguish from normal breathing during exercise. Symptoms may not be noticeably abnormal until late in the disease.

In the later stages of mitral valve stenosis, the left atrium may not be able to keep pumping the same volume of blood into the left ventricle. Blood will begin to back up into the lungs, causing symptoms such as shortness of breath at rest or with only mild-to-moderate exertion, fatigue, weakness, and pounding of the heart.

How is mitral valve stenosis diagnosed?

Because early symptoms may be mild or unnoticeable, mitral valve stenosis may not be diagnosed in its early stages.

A review of your medical history and a physical examination will help your doctor determine how seriously your mitral valve is affected. To help check it, your doctor may order one or more of the following tests:

• An electrocardiogram, a test that measures the electrical signals that control the rhythm of your heartbeat
• An echocardiogram, which is an ultrasound examination used to study the heart
• A chest X-ray

How is it treated?