Narrowing of the mitral valve, resulting in a decrease in blood flow within the heart
- More common after the age of 40
- More common in females
- Genetics and lifestyle are not significant factors
The mitral valve sits between the upper chamber (atrium) and lower chamber (ventricle) on the left side of the heart. In mitral stenosis, the opening of this valve is narrowed, restricting the blood flow through the atrium. The heart works harder to pump blood through the narrow valve, and chronic heart failure may eventually develop. Mitral stenosis is more common in females and sometimes occurs with mitral incompetence.
What are the causes?
Mitral stenosis is almost always due to damage to the valve caused by an earlier attack of rheumatic fever. This condition is now rare in developed countries, and, in the UK, mitral stenosis is most often found in middle-aged or elderly people who had rheumatic fever during their childhood. In rare cases, mitral stenosis is present at birth.
What are the symptoms?
Symptoms usually develop gradually in adulthood and may include:
Shortness of breath, occurring during exertion at first but later also at rest.
Palpitations (awareness of an irregular or abnormally rapid heartbeat).
As the stenosis becomes worse, the symptoms of heart failure may develop, including swelling of the tissues, which is most noticeable in the ankles.
Are there complications?
Sometimes, the atria beat irregularly and rapidly (see Atrial fibrillation). Blood clots may also form on the wall of the left atrium because it does not empty fully. If fragments of clots break off, they may block a blood vessel elsewhere in the body. If the clot blocks an artery supplying the brain, the result may be a stroke.
How is it diagnosed?
Your doctor will examine you and will probably arrange for an ECG to assess the electrical activity of the heart. The inside of the heart may be imaged by echocardiography, a technique that shows the movement of the heart valves. You may also have a chest X-ray. The severity of the stenosis can be estimated by echocardiography but may need to be more accurately assessed by a procedure in which a tube called a cardiac catheter is inserted through blood vessels into the heart. The catheter is attached to a device that measures the pressure on either side of the valve.
What is the treatment?
In most cases of mitral stenosis, drug treatments are used to help to relieve the symptoms. For example, diuretics may be prescribed to remove excess fluid from the body and to relieve shortness of breath. Antiarrhythmic drugs may be given to help correct an abnormal heart rhythm. If the abnormal rhythm is atrial fibrillation, drugs that prevent blood clotting are often prescribed to reduce the risk of blood clots forming in the heart.
If drug treatment is ineffective, a balloon valvuloplasty may be performed, in which a balloon-tipped catheter is passed into the heart and the balloon briefly inflated inside the stenosed valve to widen it. Alternatively, the valve may be repaired or replaced by surgery (see Heart valve replacement).
A stenotic or replacement mitral valve is more susceptible to infection (see Infective endocarditis) than a normal valve. Your doctor will advise you to maintain good oral hygiene to reduce the risk of infection. You will also be told how to recognize symptoms of infective endocarditis so that treatment can be given promptly if it does develop.
Mitral stenosis may recur after a balloon valvuloplasty, often within a year. However, a heart valve replacement is often effective for 10 years or more.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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