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Mitral Stenosis


Updated February 12, 2013

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Mitral stenosis (MS) is a relatively uncommon heart valve abnormality that can cause significant cardiac problems if it is not treated appropriately.

The mitral valve separates the two left chambers of the heart -- the left atrium and the left ventricle. When the left atrium contracts, the mitral valve opens to allow blood to flow into the left ventricle. When the left ventricle subsequently contracts, the mitral valve closes to prevent a backflow of blood into the other chamber.

With mitral stenosis, the heart's mitral valve becomes thickened and immobile, and does not completely open as a result. When this occurs, the blood tends to back up in the left atrium, leading to increased pressure in the chamber. Over a long period of time, significant problems can result.

What Are The Causes of Mitral Stenosis?

Several cardiac conditions can produce MS:
  • Rheumatic heart disease is the most common cause of MS. Because rheumatic heart disease is becoming uncommon in developed countries, MS is now seen much less frequently than it was in past decades.
  • Some forms of congenital heart disease can include MS. In these cases, the mitral valve fails to develop normally.
  • Mitral annular calcification (a condition in which calcium deposits form on the mitral valve, usually in association with with aging or kidney disease) can cause MS. While mitral annular calcification is a fairly common condition, it only rarely produces MS.
  • Infectious endocarditis (infection of the heart valves) very rarely results in MS.

What Problems Does Mitral Stenosis Cause?

When MS is caused by rheumatic heart disease (the most common cause), the valve problem develops slowly, over a period of years, and symptoms appear gradually. In most cases, the MS is first diagnosed 15 to 20 years after rheumatic fever has occurred.

During this time, the pressure within the left atrium gradually increases, and it eventually becomes enlarged. The increased pressure is transmitted to the blood vessels in the lungs, and eventually to the pulmonary artery. Pulmonary artery hypertension, high pressure in the pulmonary artery, eventually results.

Pulmonary artery hypertension can eventually cause heart failure affecting the right side of the heart. Right-sided heart failure is commonly associated with extreme fatigue and massive fluid accumulation (edema) in the legs, and often in the belly.

Atrial fibrillation, rapid and irregular heart arrhythmia caused by chaotic electrical impulses in the upper two chambers of the heart, is extremely common in MS. It is estimated that 30% to 70% of people with MS will eventually develop this problem.

Thromboembolism (blood clots within blood vessels or the heart that break off and cause tissue damage, such as stroke) is a risk in anybody with atrial fibrillation, but that risk is especially high when the atrial fibrillation is associated with MS. In fact, because of the damming-up of the blood in the left atrium seen in MS, blood clots can develop in the atrium (a condition called left atrial thrombus) even without atrial fibrillation.

What Are the Symptoms of Mitral Stenosis?

The most common symptoms caused by MS are shortness of breath (possibly accompanied by cough) and fatigue. People with MS are most likely to experience these symptoms any time the workload of the heart is increased, such as during exertion of any type, emotional stress, fever or other illness, or pregnancy.

Just as the MS develops very gradually, so does the shortness of breath. In many cases, people with MS avoid symptoms by subconsciously reducing their activity levels over a period of years, eventually becoming quite sedentary. Because they are so inactive, they often will not actually notice the breathing issue, and may not report this symptom to their doctors.

When MS becomes severe, patients may develop persistent symptoms, even at rest, and may also develop severe edema and cough up blood.

Arial fibrillation can produce palpitations and lightheadedness, and can make all the symptoms associated with MS much worse.

How is Mitral Stenosis Diagnosed?

The diagnosis is often first suspected after the doctor performs a physical examination and notices the soft, rumbling heart murmur characteristic of MS. Usually, MS can be easily confirmed or ruled out with an echocardiogram.

Treating Mitral Stenosis

If you have been diagnosed with MS, the most important things you and your doctor will have to consider are whether/when to perform a surgical intervention to relieve the MS, and what steps need to be taken to prevent thrombosis.


Bonow, RO, Carabello, BA, Chatterjee, K, et al. 2008 Focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. Circulation 2008; 118:e523.

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