Heart Murmurs

two boys talking

Your doctor listens to your child’s heart with a stethoscope to detect heart murmurs.

"Innocent" heart murmurs

Innocent heart murmurs are sounds made by blood circulating through the heart’s chambers and valves, or through blood vessels near the heart. Innocent murmurs are common in children and are harmless. These heart murmurs are also called “normal” or “physiological” murmurs.

Innocent heart murmurs are so common that most children are likely to have one at some time. Innocent murmurs may disappear and then reappear. When a child’s heart rate changes, such as during excitement or fear, these innocent murmurs may become louder or softer. This still doesn’t signal that the murmur is cause for concern.

If your doctor hears a murmur when listening to your child’s heart, they may recommend additional testing, such as an electrocardiogram (ECG) or echocardiogram (echo). This is to confirm the murmur is innocent. Unless testing suggests otherwise, no additional steps are needed.

With an innocent heart murmur, your child won’t need medication, and doesn't have a heart problem or heart disease. You will not need to restrict your child’s activities or diet. They can lead an active, healthy life!

Most innocent murmurs disappear when a child reaches adulthood, but in some adults the murmur remains for life.

Read more about innocent murmurs.

Other causes

Non-innocent (or abnormal) heart murmurs are often caused by defective heart valves. For example, a stenotic heart valve has a smaller-than-normal opening and can’t open completely. Or a valve may also be unable to close completely. This leads to regurgitation, which is blood leaking backward through the valve when it should be closed.

Certain congenital defects and other conditions such as pregnancy, fever, anemia or thyrotoxicosis (a condition caused by an overactive thyroid gland) can also cause murmurs.

A murmur that occurs when the heart muscle relaxes between beats is called a diastolic murmur. A systolic murmur occurs when the heart muscle contracts.

Systolic murmurs are graded by intensity (loudness) from 1 to 6. A grade 1 is faint, heard only with a special effort. It's softer than the normal heart sounds. A grade 6 is extremely loud, and can be heard with no contact between stethoscope and the chest.

En español: Read about heart murmurs (PDF)