Definition of Mitral stenosis:

Mitral stenosis is a heart valve disorder that involves the mitral valve. This valve separates the upper and lower chambers on the left side of the heart. Stenosis refers to a condition in which the valve does not open fully, restricting blood flow.

Causes, incidence, and risk factors:

Blood that flows between different chambers of your heart must flow through a valve. The valve between the two chambers on the left side of your heart is called the mitral valve. It opens up enough so that blood can flow from one chamber of your heart (left atria) to the next chamber (left ventricle). It then closes, keeping blood from flowing backwards.

Mitral stenosis refers to when the valve cannot open as wide. As a result, less blood flows to the body. The upper heart chamber swells as pressure builds up. Blood may flow back into the lungs. Fluid then collects in the lung tissue (pulmonary edema), making it hard to breathe. See also: heart failure.

In adults, mitral stenosis occurs most often in those who have had rheumatic fever (a condition that may develop after strep throat or scarlet fever). The valve problems develop 5 - 10 years after the rheumatic fever. Rheumatic fever is becoming rare in the United States, so mitral stenosis is also less common.

Only rarely do other factors cause mitral stenosis in adults. These include calcium deposits forming around the mitral valve, radiation treatment to the chest, and some medications.

Children may be born with mitral stenosis (congenital) or other birth defects involving the heart that cause mitral stenosis. Often, there are other heart defects present, along with the mitral stenosis.

Mitral stenosis may run in families.