The Causes of Heart Murmurs

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The major causes of heart murmurs revolve around issues with one or more heart valves. These causes can be serious or not and can be brought on by medical conditions or present since birth.

What is a Heart Murmur?

A heart murmur is defined by the Mayo Clinic as “abnormal sounds during your heartbeat cycle ­‑ such as whooshing or swishing – made by the turbulent blood in or near your heart.”

A heart murmur that is harmless is called an ‘innocent’ murmur. These murmurs do not require treatment. They are caused by blood flow through a healthy heart’s healthy valves.

Heart murmurs that are not innocent (abnormal) are caused by the blood flowing through one or more heart valves that are damaged or overworked. This damage can be caused by illnesses or disease. The following are some of the major causes of hear murmurs.

Congenital Heart Defects

According to WebMD, approximately 25,000 babies are born annually in the United States with heart defects. These defects can oftentimes be corrected surgically. Some of the most common congenital heart defects that cause heart murmurs are abnormalities in the heart valve, cardiac shunts and holes in the heart.

A cardiac shunt is a situation in which the blood flow between the blood vessels or chambers of the heart is abnormal. This can lead to a heart murmur.

Aortic Sclerosis

This is a condition in which the aortic valve has thickening, scarring or stiffening. This affects (according to WebMD), approximately one in every three elderly men and women. This condition may also be called valve calcification.

Mitral Valve Prolapse

This is when part of the valve does not close properly, but ‘balloons’ out instead. It can cause a clicking sound during heartbeats.

Aortic or Mitral Valve Stenosis

When the mitral or aortic valves (both on left side) narrow, it is called stenosis. This narrowing can be caused by infection or may be present at birth. This condition needs treatment to prevent heart failure.

Aortic or Mitral Regurgitation

This is the backward flow of blood caused by stenosis. The excessive workload placed on the heart by this condition can eventually lead to failure of the heart.


Another cause of heart murmur occurs when the inner lining of the valves and heart become infected or inflamed. Damage can caused by this if not treated. Generally, this is most commonly found in those patients who already have some type of abnormality in the heart.

The major causes of heart murmurs vary, but all indicate some type of problem with the heart or heart valves. If a heart murmur occurs, it is important for the cause to be determined.


Heart Murmurs. Heart Disease Health Center. WebMD. Reviewed by Robert J. Bryng, MD on September 15, 2009.

Heart Murmurs. Mayo Clinic Staff. April 9, 2010.