Mitral valve regurgitation is classified as primary and secondary. Primary mitral regurgitation is caused by an abnormality in the mitral valve; secondary is caused by an abnormality in the left ventricle of the heart.

Possible causes of mitral valve regurgitation include:

  • Mitral valve prolapse. In this condition, the leaflets and tendon-like cords supporting the mitral valve weaken and stretch so that with each contraction of the left ventricle, the valve leaflets bulge (prolapse) into the left atrium. This common heart defect can prevent the mitral valve from closing tightly and lead to regurgitation.
  • Damaged tissue cords. Over time, the tissue cords that anchor the flaps of the mitral valve to the heart wall may stretch or suddenly tear, especially in people with mitral valve prolapse. A tear can cause substantial leakage through the mitral valve relatively suddenly and may require repair by heart surgery. Trauma to the chest also can rupture the cords.
  • Rheumatic fever. Rheumatic fever — a complication of untreated strep throat and once a common childhood illness in the United States — can damage the mitral valve, leading to mitral valve regurgitation later in life. Rheumatic fever is rare in the United States, but still common in developing countries.
  • Endocarditis. The mitral valve may be damaged by an infection of the lining of the heart (endocarditis) that can involve heart valves.
  • Heart attack. A heart attack can damage the area of the heart muscle that supports the mitral valve, affecting the function of the valve. If the damage is extensive enough, a heart attack can cause sudden and severe mitral valve regurgitation.
  • Abnormality of the heart muscle (cardiomyopathy). Over time, certain conditions, such as high blood pressure, can cause your heart to work harder, gradually enlarging your heart's left ventricle. This can stretch the tissue around your mitral valve, which can lead to leakage.
  • Congenital heart defects. Some babies are born with defects in their hearts, including damaged heart valves.
  • Certain drugs. Prolonged use of certain drugs, such as ergotamine, used to treat migraines and other conditions, can cause mitral valve regurgitation.

How the heart works

The heart, the center of your circulatory system, consists of four chambers. The two upper chambers, the atria, receive blood. The two lower chambers, the ventricles, pump blood.

Four heart valves open and close to let blood flow in only one direction through your heart. The mitral valve — which lies between the two chambers on the left side of your heart — comprises two flaps of tissue called leaflets.

The mitral valve opens when blood flows from the left atrium to the left ventricle. Then the flaps close to prevent the blood that has just passed into the left ventricle from flowing backward.

In mitral valve regurgitation, the mitral valve doesn't close tightly. With each heartbeat, blood from the left ventricle flows backward into the left atrium instead of moving forward into the aorta.

Aug. 28, 2014

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