Mitral stenosis is an abnormal narrowing of the mitral valve, which is one of the heart valves. This "tight" valve obstructs the flow of blood within the heart.

What is going on in the body?

The human heart has 4 chambers. In the normal heart, the mitral valve helps control blood flow between 2 of these chambers, the left atrium and the left ventricle. In mitral stenosis, the valve does not open enough to allow proper blood flow into the left ventricle. This abnormal blood flow can cause changes and damage to the heart and lungs.

What are the causes and risks of the condition?

Most cases of mitral stenosis are due to the long-term consequences of rheumatic fever. Rheumatic fever can occur after group A streptococcal infections of the throat that are not treated with antibiotics. If this infection is not treated properly, mitral stenosis may occur years later. Rare causes of mitral stenosis include:

The risks of mitral stenosis are related to the "tightness" of the valve. A person with mitral stenosis may live a lifetime with no problems. However, a person with severe mitral stenosis is at increased risk of permanent heart damage. Arrhythmias, or irregular heartbeats that can lead to blood clots, may occur.