Heart Murmur

Heart Murmur

  • Normal Heart


A heart murmur is an extra, unexpected, or abnormal sound that is caused by the flow of blood through the heart.

What is going on in the body?

Except in unusual cases, a heart murmur is only noticed by a healthcare professional when he or she listens to the heart with a stethoscope. The heart normally makes certain sounds while beating. However, extra, unexpected, or abnormal sounds may also be heard. These are called murmurs. A murmur can be normal, or it can indicate the presence of a serious heart disease.


What are the causes and risks of the condition?

Normal or "innocent" heart murmurs are caused by normal blood flow. They are not a cause for concern.
Causes of abnormal heart murmurs include:
  • anemia, or low red blood cell counts
  • high levels of thyroid hormone, called hyperthyroidism
  • rheumatic fever, a complication of strep throat that can damage heart valves
  • endocarditis, an infection of the heart that can also damage heart valves
  • other types of heart valve damage or changes, such as stiffened valves from calcium deposits, which are common in the elderly. Damaged valves are often described as "leaky," which is called regurgitation, or "narrowed," which is also called stenosis. A heart attack can also cause a murmur from heart valve changes.
  • artificial heart valves
  • congenital heart disease, or heart defects present at birth, which can cause holes in the heart or deformed heart valves
  • mitral valve prolapse, which is a "leaky" heart valve that often has no known cause and is usually not serious
  • pregnancy
  • thickening of the heart muscles or enlargement of the heart, which can occur due to high blood pressure
  • heart failure, also called congestive heart failure
Other causes are also possible.


What can be done to prevent the condition?

Prevention is related to the cause. Treatment of strep throat with antibiotics can prevent cases due to rheumatic fever. Treatment of high blood pressure can prevent many cases due to congestive heart failure. Many cases cannot be prevented.


How is the condition diagnosed?

Heart murmurs are usually detected during a physical exam when the healthcare professional. The type of sound heard, and its timing during the heartbeat cycle, can usually help suggest the cause of the murmur.
Other tests may also be done to help figure out the cause of the murmur. An electrocardiogram (ECG), is commonly done. A chest x-ray may also be performed to see if the heart is enlarged or abnormal. An echocardiogram, an imaging test that uses sound waves to view the heart, may also be done. Blood tests may be used as well. A test called an arterial blood gas, for example, can measure the level of oxygen in the blood.

Long Term Effects

What are the long-term effects of the condition?

The long-term effects of heart murmurs depend on the cause. Innocent heart murmurs are normal and have no long-term effects. If the heart murmur is due to a serious cause, such as a heart attack or congestive heart failure, the underlying condition may cause death if not treated. In other cases, such as anemia or hyperthyroidism, treatment will often stop the murmur, and there may be no long-term effects.

Other Risks

What are the risks to others?

Heart murmurs are not contagious and pose no risk to others.


What are the treatments for the condition?

Treatment for heart murmurs will depend on the cause. Normal heart murmurs need no treatment. If hyperthyroidism is causing the murmur, medications or surgery may be needed to treat the thyroid condition. Anemia may be treated with iron supplements, blood transfusions, or other therapy, depending on the cause of the anemia. Mitral valve prolapse often needs no treatment. High blood pressure may be treated with blood pressure medications. Heart infections may be treated with antibiotics or surgery. If congenital heart disease is present, open heart surgery may be needed to repair the heart. Heart valve surgery can repair or replace damaged valves. Other treatments are also possible.

Side Effects

What are the side effects of the treatments?

Side effects depend on the treatments used. For example, antibiotics can cause stomach upset, allergic reactions, or other effects. Blood pressure medications may cause sleepiness or erectile dysfunction. Surgery can be complicated by bleeding, infection, or reactions to anesthesia.

After Treatment

What happens after treatment for the condition?

This depends on the cause of the murmur and the response to treatment. If anemia or hyperthyroidism are the cause and these are treated, the murmur may be "cured." However, these conditions may need further follow up or treatment. Someone who has a valve replaced may need to take medications to thin the blood, called anticoagulants, for life. A person with an artificial or damaged heart valve may also be advised to take antibiotics before any dental work or surgery. This is thought to reduce the risk of heart valve infections.


How is the condition monitored?

Heart murmurs may need close monitoring by a healthcare professional. Someone with a leaky or narrowed valve, high blood pressure, or congestive heart failure will need lifelong monitoring. A person should seek medical attention for any worsening or recurring symptoms.


Mayo Clinic Family Health Book, David E. Larson, 1996/ Professional Guide to Signs and Symptoms, Springhouse, 1997.

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