Mitral Stenosis

Mitral stenosis is a narrowing of the mitral valve in the heart. This forces the heart to work harder to pump blood from the left atrium into the left ventricle. The most common cause of this condition is rheumatic fever. When symptoms are present, they can include fatigue, shortness of breath, and irregular heart rhythms. People with a mild case may not require any immediate treatment. More severe cases of this condition may be treated with lifestyle changes, medications, or surgery to repair or replace the mitral valve.

What Is Mitral Stenosis?

The valves of the heart are like doors that open and close. They open to allow blood to flow into the next chamber of the heart or into one of the arteries, and then they shut to keep blood from flowing backwards.

The mitral valve is on the left side of the heart. It separates the left atrium and the left ventricle. Normally, the mitral valve opens when the left atrium contracts. This allows blood to flow down into the left ventricle. The mitral valve is closed when the left ventricle contracts -- allowing blood to flow out to the rest of the body through the aortic valve.

In mitral stenosis, the mitral valve is narrowed. This forces the heart (left atrium) to pump harder to get blood through the mitral valve and into the left ventricle. Over time, the left atrium enlarges because of the extra workload. As the left atrium thickens, it becomes less effective at pumping blood through the mitral valve. This can cause blood to back up into the lungs.

What Causes It?

The most common cause of mitral stenosis is rheumatic fever. Mitral stenosis often occurs with aortic valve problems like aortic stenosis or aortic regurgitation, which are also associated with rheumatic fever. The condition can also be caused by:

Conditions people are born with (congenital defects)
Other rheumatoid diseases, though this is more rare.

Mitral stenosis is more common in women than in men.

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