Many normal conditions may cause the blood to flow through the heart with turbulence, so that a healthcare provider hears a murmur when listening with a stethoscope. This does not mean something is abnormal, or that the child’s health is in danger.
Among the conditions that may cause a normal, or innocent, heart murmur are:
- Small blood vessels to the lung arteries (called pulmonary arteries) in newborn children. This is called physiologic peripheral pulmonary stenosis, or PPS. Before birth, there is little blood flow to the lungs. As soon as the baby is born and begins to breathe air, blood flow to the lungs increases tremendously. As it travels through the relatively small lung blood vessels, it may flow turbulently as the main lung artery divides into the two main branch arteries going to each lung, causing a heart murmur. This type of heart murmur typically disappears when the baby reaches about 6 to 9 months of age.
- Blood flow through the aortic valve and pulmonary valve. Blood flow across these two heart valves can be heard in some children. The sound may be the result of a child’s normally faster heart rate, and does not indicate a problem. Also, children have thinner chest walls than adults, which allow sounds to be more readily heard. This is typically called an innocent flow murmur.
- Still’s murmur: This innocent murmur is most commonly initially heard between 3 and 6 years of age, but can occasionally be heard in infants as well. It is heard in a typical location and has a different sound than a pathologic murmur. It usually disappears by 10 to 12 years of age.
- Venous hum. Sometimes blood flowing through the large veins from the neck and upper chest as it returns back to the heart can naturally be heard.
- "Mammary soufflé.” Occasionally, when girls go through puberty and breast tissues develop, blood flow in the arteries supplying the rapidly developing breast tissue may be heard through a stethoscope.