What are innocent heart murmurs?
Innocent heart murmurs are sounds made by the blood circulating through the heart's chambers and valves or through blood vessels near the heart. They're sometimes called other names such as "functional" or "physiologic" murmurs. Many heart murmurs are considered to be “innocent” or harmless.
Are innocent heart murmurs normal?
Innocent murmurs are common in children and are quite harmless. In any group of children, a large percentage is likely to have had one at some time. Innocent murmurs also may disappear and then reappear. Most innocent murmurs disappear when a child reaches adulthood, but some adults still have them. When a child's heart rate changes, such as during excitement or fear, the innocent murmurs may become louder or softer. This still doesn't mean that the murmur is abnormal.
Sometimes, when a doctor first hears the murmur through a stethoscope, he or she may want to have other tests done to be sure the murmur is innocent. After that, there's no need for a cardiac reevaluation unless the patient or doctor has more questions. The child doesn't need medication, won't have cardiac symptoms, and doesn't have a heart problem or heart disease. A parent doesn't need to pamper the child or restrict his or her diet or activities. The child can be as active as any other normal, healthy child. Read more about innocent murmurs.
What causes heart murmurs?
Heart murmurs are often caused by defective heart valves. A stenotic heart valve has a smaller-than-normal opening and can't open completely. 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.
Murmurs also can be caused by certain congenital defects and other conditions such as pregnancy, fever, thyrotoxicosis (a diseased condition resulting from an overactive thyroid gland) or anemia.
A murmur that occurs when the heart muscle relaxes between beats is called a diastolic murmur. A systolic murmur is one that occurs when the heart muscle contracts. Systolic murmurs are graded by intensity (loudness) from one to six. A grade 1/6 is very faint, heard only with a special effort. A grade 6/6 is extremely loud. It's heard with a stethoscope slightly removed from the chest.
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This content was last reviewed December 2015.