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If you have an innocent heart murmur, you likely will not have any signs or symptoms. An abnormal heart murmur may not cause obvious signs or symptoms either, except the unusual sound your physician may hear. It's important to do further investigating to determine the underlying cause and the severity of the problem.

What Causes Heart Murmurs?

Innocent Heart Murmurs

Why some people have innocent heart murmurs and others do not isn't known. Innocent murmurs are simply sounds made by blood flowing through the heart's chambers and valves, or through blood vessels near the heart.

Extra blood flow through the heart also may cause innocent heart murmurs. After childhood, the most common cause of extra blood flow through the heart is pregnancy. This is because during pregnancy, women's bodies make extra blood. Most heart murmurs that occur in pregnant women are innocent.

Abnormal Heart Murmurs

Congenital heart defects or acquired heart valve disease often are the cause of abnormal heart murmurs.

Congenital Heart Defects

Congenital heart defects​ are the most common cause of abnormal heart murmurs in children. These defects are problems with the heart's structure that are present at birth. They change the normal flow of blood through the heart.

Congenital heart defects can involve the interior walls of the heart, the valves inside the heart, or the arteries and veins that carry blood to and from the heart. Some babies are born with more than one heart defect.

Heart valve problems, septal defects (also called holes in the heart), and diseases of the heart muscle such as hypertrophic cardiomyopathy are common heart defects that cause abnormal heart murmurs.

Heart Defects That Can Cause Abnormal Heart Murmurs

Illustratin of a Heart Murmur

Acquired Heart Valve Disease

Acquired heart valve disease​ often is the cause of abnormal heart murmurs in adults. This is heart valve disease that develops as the result of another condition.

Many conditions can cause heart valve disease. Examples include heart conditions and other disorders, age-related changes, rheumatic fever, and infections.

Heart conditions and other disorders. Certain conditions can stretch and distort the heart valves, such as:

  • Damage and scar tissue from a heart attack or injury to the heart
  • Advanced high blood pressure and heart failure​ which can enlarge the heart or its main arteries

Age-related changes. As you get older, calcium deposits or other deposits may form on your heart valves. These deposits stiffen and thicken the valve flaps and limit blood flow. This stiffening and thickening of the valve is called sclerosis.

Rheumatic fever. The bacteria that cause strep throat, scarlet fever, and, in some cases, impetigo also can cause rheumatic fever. This serious illness can develop if you have an untreated or not fully treat streptococcal (strep) infection.

Rheumatic fever can damage and scar the heart valves. The symptoms of this heart valve damage often don't occur until many years after recovery from rheumatic fever.

Infections. Common germs that enter the bloodstream and get carried to the heart can sometimes infect the inner surface of the heart, including the heart valves. This rare but sometimes life-threatening infection is called infective endocarditis, or IE.

IE is more likely to develop in people who already have abnormal blood flow through a heart valve because of heart valve disease. The abnormal blood flow causes blood clots to form on the surface of the valve. The blood clots make it easier for germs to attach to and infect the valve.

IE can worsen existing heart valve disease.

Other Causes

Some heart murmurs occur because of an illness outside of the heart. The heart is normal, but an illness or condition can cause blood flow that's faster than normal. Examples of this type of illness include fever, anemia, and hyperthyroidism.

What are the Signs and Symptoms of a Heart Murmur?

People who have innocent (harmless heart murmurs don't have any signs or symptoms other than the murmur itself. This is because innocent heart murmurs aren't caused by heart problems.

People who have abnormal heart murmurs may have signs or symptoms of the heart problems causing the murmurs. These signs and symptoms may include:

  • Poor eating and failure to grow normally (in infants)
  • Shortness of breath, which may occur only with physical exertion
  • Excessive sweating with minimal or no exertion
  • Chest pain
  • Dizziness or fainting
  • A bluish color on the skin, especially on the fingertips and lips
  • Chronic cough
  • Swelling or sudden weight gain
  • Enlarged liver
  • Enlarged neck veins

Signs and symptoms depend on the problem causing the heart murmur and its severity.

Source: National Heart, Lung, and Blood Institute; National Institutes of Health; U.S. Department of Health and Human Services.

If you have a history of heart murmurs or are experiencing symptoms, schedule an appointment with your physician or a cardiologist. They will work with you, run the appropriate test for diagnosis, and create the right treatment plan, if necessary. If you are in need of a trusted physician, call 1.855.819.7482.

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