Leakage of blood back through the mitral valve of the heart
- In some cases, the condition is inherited
- Age, gender, and lifestyle as risk factors depend on the cause
The mitral valve sits between the upper chamber (atrium) and the lower chamber (ventricle) on the left side of the heart. In mitral incompetence, the valve fails to close properly and allows blood to leak back into the atrium. This increases the pressure in the blood vessels leading to that chamber. The left side of the heart has to work harder to pump blood around the body, and eventually chronic heart failure develops. Mitral incompetence can occur in conjunction with mitral stenosis.
What are the causes?
In rare cases, mitral incompetence is present at birth, sometimes as a result of the rare genetic disorder Marfan’s syndrome. Any condition that damages the mitral valve can lead to mitral incompetence. Rheumatic fever was once a major cause of the disorder but is now rarely seen in developed countries, mainly because of the widespread use of antibiotics. A more common cause is an infection of the valve (see Infective endocarditis). Hypertrophic cardiomyopathy, in which the wall of the left ventricle is thickened, may distort the valve, causing incompetence. The condition can also be a consequence of a heart attack if the heart muscle attached to the valve is affected (see Myocardial infarction). In some cases, mitral incompetence occurs in conjunction with mitral valve prolapse.
What are the symptoms?
Symptoms of mitral incompetence usually develop gradually over months or years but may appear suddenly if the cause is a heart attack or valve infection. The symptoms include:
Shortness of breath during exertion.
Palpitations (awareness of an irregular or abnormally rapid heartbeat).
Eventually, symptoms of chronic heart failure may occur, such as shortness of breath at rest as well as during exertion, due to fluid in the lungs. The build-up of fluid in the body tissues also causes swelling of the ankles.
Are there complications?
The backward blood flow into the left atrium may enlarge it, leading to an irregular heartbeat (see Atrial fibrillation). If the atrium is so large that it cannot empty fully with each heartbeat, a blood clot may form. If a clot passes into an artery supplying the brain and blocks it, the result may be a stroke. Another potential complication is infection of the leaky mitral valve after dental treatment or surgery on the digestive or urinary tracts.
What might be done?
Your doctor may suspect mitral incompetence if he or she hears characteristic sounds known as heart murmurs. Tests to assess the function of the heart and lungs may be carried out, including an ECG to monitor the electrical activity of the heart and a chest X-ray. The interior of the heart may be imaged by echocardiography to confirm the diagnosis. This procedure can show the movements of the mitral valve.
If heart failure develops, drugs such as diuretics may be prescribed to relieve the symptoms. If the left atrium becomes enlarged, you may also be given drugs that prevent blood clotting to lessen the risk of clots in the atrium. Severe mitral incompetence may need to be treated surgically to repair the valve or implant a heart valve replacement. An abnormal 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.
The outlook for people with mitral incompetence is good if treatment is given before the heart has become badly damaged.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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