Heart Disease Health Center

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Heart Murmurs

Heart Murmur Causes

Most heart murmurs are innocent: They are caused by blood flowing through healthy valves in a healthy heart and do not require treatment. However, heart murmurs can be caused by blood flowing through a damaged or overworked heart valve. Heart valve defects may be present at birth or heart valve disease may result from other illnesses, such as rheumatic fever, heart disease, heart attacks, or infective endocarditis.

Types of Heart Valve Disease

Mitral valve prolapse: Normally your mitral valve closes completely when your left ventricle contracts, preventing blood from flowing back into your left atrium. If part of the valve balloons out so that the valve does not close properly, you have mitral valve prolapse. This causes a clicking sound as your heart beats. Often, this common condition is not serious. However, in rare cases it leads to infective endocarditis or mitral regurgitation (backward blood flow through the valve); both can be serious.

Mitral valve or aortic stenosis: Your mitral or aortic valves, both on the left side of your heart, can become narrowed by scarring from infections, such as rheumatic fever, or may be narrow at birth. Such narrowing or constriction is called stenosis. In mitral valve or aortic stenosis, the heart has to work harder to pump enough blood to satisfy your body's oxygen needs. If untreated, stenosis can wear out your heart and can lead to heart failure.

Aortic sclerosis: One in three elderly people have a heart murmur due to the scarring, thickening, or stiffening (sclerosis) of the aortic valve. This condition is generally not dangerous; typically, the valve can function for years after the murmur is detected. Aortic sclerosis is usually seen in people with atherosclerosis, or hardening of the arteries.

Mitral or aortic regurgitation: Regurgitation (backward flow) of blood can occur with mitral valve prolapse or mitral valve or aortic stenosis. To counteract this back flow, the heart must work harder to force blood through the damaged valve. Over time, this can weaken and/or enlarge the heart and can lead to heart failure.

Congenital heart defects: About 25,000 babies are born each year with heart defects, such as holes in heart walls or misshapen heart valves. Many congenital heart defects can be corrected by surgery.

Other Possible Causes of Heart Murmurs

Some common conditions can force your heart to beat faster, changing the rate and amount of blood moving through your heart and resulting in heart murmurs. You and your doctor should monitor all of these conditions:

Pregnancy
Anemia
High blood pressure
Overactive thyroid
Fever

Tests for Heart Murmurs

Usually heart murmurs are detected during a physical exam. Your doctor will be able to hear your heart murmur when listening to your heart with a stethoscope.

Your doctor may order one or more of the following tests to see whether your heart murmur is innocent or whether it is caused by acquired valve disease or a congenital defect: