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What are heart murmurs?

Most heart murmurs are harmless, but some can be signs of trouble. They should always be checked out by a doctor.

A healthy heart, heard through a stethoscope, makes steady, rhythmic sounds known as beats. But sometimes other sounds come from the heart too. They often sound like a swishing or whooshing, and they're known as murmurs.

Most murmurs are nothing to worry about, according to the National Heart, Lung, and Blood Institute (NHLBI), but others can be signals that the heart isn't working properly.

Just a sound

Heart murmurs occur naturally in many people, especially children. These murmurs are harmless—also called innocent, functional or physiologic.

Murmurs may also occur when an unusually large amount of blood is moving through the heart, or when blood is moving through the heart very quickly. This can happen during pregnancy, a fever, or when someone has a deficiency of iron or an overactive thyroid. In these cases, the murmur should go away when the pregnancy ends, the fever subsides, or the iron or thyroid problem is remedied.

More than noise

In some cases heart murmurs can be the result of more serious problems. Called abnormal heart murmurs, they result from problems with the heart's structure or function.

In children, abnormal murmurs are most often caused by congenital heart defects—problems with heart structure that a child has at birth. In adults they can usually be traced to the effects of infections, disease or aging of heart valves.

Specific problems that can lead to abnormal heart murmurs include:

Mitral valve prolapse. Also known as click-murmur syndrome, Barlow's syndrome, balloon mitral valve and floppy valve syndrome, this type of murmur occurs when the mitral valve (which lies between the two left chambers of the heart) doesn't close correctly.

Aortic stenosis. This condition affects the aortic valve, which opens to let blood flow out of the heart. A valve affected by stenosis doesn't open wide enough to allow a normal amount of blood out into the body.

Aortic regurgitation. This happens when the aortic valve doesn't close properly, allowing blood to leak back into the heart.

Some abnormal murmurs can be managed with medicines that help prevent heart damage. Others don't need any treatment. But some will need to be corrected with surgery to implant an artificial heart valve.

Warning signs

Abnormal murmurs usually cause more than strange sounds. Most often, they come with symptoms of a heart problem. According to the NHLBI, these symptoms can include:

  • Bluish skin.
  • Chronic cough.
  • Heavy sweating.
  • Chest pain.
  • Dizziness.
  • Shortness of breath.
  • Fainting.
  • Fatigue.
  • In infants, poor eating and failure to grow normally.
If you notice any of these symptoms in yourself or your child, talk to your doctor. A physical examination, carefully listening to the heart, and a couple of quick and painless tests can reveal a heart murmur that should be watched or treated.

Reviewed 2/18/2021

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