Chronic mitral regurgitation is a long-term disorder in which the heart's mitral valve does not close properly, causing blood to flow backward (leak) into the upper heart chamber when the left lower heart chamber contracts. The condition is progressive, which means it gradually gets worse.

See also: Acute mitral regurgitation

Mitral regurgitation is the most common type of heart valve insufficiency. After 55 years of age, some degree of mitral regurgitation is found in almost 20% of men and women who have an echocardiogram.

Any disorder that weakens or damages the mitral valve or causes the left lower chamber of the heart (ventricle) to become widened may lead to mitral regurgitation. Over time, more blood backs up into the left upper chamber of the heart (atrium) from the left ventricle, and the heart has to work harder to pump blood to the rest of the body. This may lead to congestive heart failure.

Mitral regurgitation becomes chronic when the condition persists rather than occurring for only a short time period. Chronic mitral regurgitation should be distinguished from acute mitral regurgitation.

Mitral valve prolapse is a relatively common cause of chronic mitral regurgitation.

About one-third of all cases of chronic mitral regurgitation are caused by rheumatic heart disease, a complication of untreated strep throat that is becoming less common.

Congenital (present from birth) mitral regurgitation is rare if it is not part of a more complex heart defect or syndrome.

Chronic mitral regurgitation can also be caused by:

• Atherosclerosis
• Endocarditis
• Heart tumors
• High blood pressure
• Marfan syndrome
• Swelling of the left lower heart chamber
• Untreated syphilis (rare)

Risk factors include an individual or family history of any of the disorders mentioned above and use of fenfluramine or dexfenfluramine (appetite suppressants banned by the FDA) for 4 or more months.