Mitral Stenosis

In mitral stenosis, the opening of the mitral valve becomes narrow.

When mitral stenosis develops, blood flow from the left atrium into the left ventricle is impaired. Pressure in the left atrium increases, stretching and enlarging it. These changes commonly result in an irregular, fast heart rhythm called atrial fibrillation. Also, blood clots may form in the atrium. Part of a clot may break off and block an artery elsewhere in the body. Occasionally, a stroke results.

Severe mitral stenosis tends to be diagnosed and treated in younger people. Thus, mitral stenosis in older people is uncommon and tends to be milder.

Causes

Mitral stenosis almost always results from rheumatic fever, a childhood illness. Rheumatic fever is now rare in regions where antibiotics are widely used to treat strep throat and thus prevent rheumatic fever. Less commonly, mitral stenosis develops in older people when calcium accumulates on the valve.

Symptoms and Diagnosis

Mild mitral stenosis causes few or no symptoms. If the disorder is moderate or severe, people may notice an irregular, fast heartbeat (indicating atrial fibrillation). At first, they may feel short of breath only during physical activity. But if the disorder worsens, they may feel short of breath during rest (indicating that heart failure is developing). Some people can breathe comfortably only when propped up with pillows or sitting upright. Some people cough up blood.

Mitral stenosis is more likely to cause atrial fibrillation and blockages due to blood clots in older people than in younger people.

Doctors usually suspect the diagnosis based on symptoms, abnormal heart sounds, and the results of echocardiography. Occasionally, mitral stenosis is first diagnosed in people who have had a stroke due to a blood clot.

Treatment and Outlook

Most people with mild to moderate mitral stenosis can be treated with drugs, such as beta-blockers, and thus avoid surgery. Heart failure and atrial fibrillation, if present, are treated. Warfarin (an anticoagulant) is usually given to prevent clots from forming.

If mitral stenosis causes symptoms and is worsening, the mitral valve may be repaired or replaced. The outlook for people with mitral stenosis depends on the severity of the disorder. If heart failure develops, the outlook is worse. When the valve is repaired or replaced, symptoms are generally relieved, and people can function much better.