While many small children have heart murmurs, they are generally nothing to worry about. (Bojan Kontrec)

Not long ago, I saw a 5-year-old for her yearly checkup. The girl’s growth and development were normal, but she had one physical finding that concerned her parents. She had a heart murmur, an extra whooshing sound, which had not been present at her previous checkups.

This extra whooshing sound had all the characteristics of a Still’s murmur, which is the most common normal or “innocent” murmur in young children. I was confident the murmur was not due to a problem with her heart and told her parents so.

Innocent heart murmurs are heard in 50 percent of children, most often between the ages of 3 and 8. Most children outgrow them as they enter adolescence and the chest wall becomes thicker, which makes the sound harder to hear. The percentage of adults with heart murmurs is much smaller than that of children, though most are still innocent in nature.

A heart murmur is generated by the flow of blood through the heart or its surrounding blood vessels. Murmurs typically have a whooshing or grating sound and are heard in between the “lub-DUB” sound you learned about in school. The lub-DUB comes from heart valves snapping shut as the heart muscle contracts.

In most cases, heart murmurs are the result of turbulence created as blood is being ejected from or returning to the heart. If you hold a water hose up to your ear and bend it a little, the flow of water out of the hose will speed up, creating a whooshing sound. As this happens, you will hear the water whooshing through the hose. The same principle creates heart murmurs.

In children, about half of all detectable heart murmurs are known as innocent murmurs, normal whooshing sounds made by turbulence in the cardiovascular system. Physiological changes, such as exercise, fever or anemia can increase blood flow and create a temporary, innocent murmur.

There are several types of innocent heart murmurs in childhood.

A Still’s murmur is heard when the left ventricle contracts, forcing blood into the aorta, the large artery at the top of the heart that directs oxygen-rich blood to the body. Others can be heard when blood is pumped into the lungs and blood flows back to the heart from the veins in the neck. It is not known why some people have normal heart murmurs and others do not.

Normal heart murmurs can also be caused by exercise, fever, anemia and other physiologic changes that increase blood flow. These tend resolve when the underlying problem goes away.

Evaluating heart murmurs

When a pediatrician hears a heart murmur, he or she will listen carefully to determine if it sounds like a normal murmur or one that might be structural in nature. Normal murmurs usually have a musical or vibratory quality, are brief in duration and are heard in specific locations on a child’s chest. If there is a question about the nature of the murmur, or if the parents are worried about the finding, the child will usually be referred to a cardiologist for evaluation.

Sometime ago, I saw a newborn at Sibley Hospital for his first examination. The baby was 12 hours old, and the physical exam was normal except for a heart murmur. Babies often have a murmur in the first day because a blood vessel called the ductus arteriosus, which is important during the fetal stage, closes shortly after birth. (As the ductus arteriosis is obliterated, it can create turbulence the same way an anatomic defect does, causing a murmur.)

However, this baby’s murmur was different. It was long and harsh-sounding, which suggested it was due to an anatomic abnormality. Although the baby wasn’t in distress, I thought he should be seen by a cardiologist.

A cardiologist’s evaluation commonly includes an electrocardiogram, or EKG, and echocardiogram to help pinpoint the cause of the murmur. An EKG measures the electrical activity of the heart and can detect abnormalities in the cardiac rhythm. An echocardiogram uses sound waves to evaluate the structure of the heart. They are both noninvasive tests.

In this case, the cardiologist diagnosed a ventricular septal defect (VSD), a small hole in the muscular wall that separates the left and right ventricles, the two pumping chambers of the heart. He told the parents he wanted to see the baby for a follow-up visit in a month, but he was optimistic that the hole would close on its own by the time the child entered middle school. If it didn’t close, the child might need an operation to close the defect. Fortunately, the VSD closed by the boy’s fifth birthday.

According to Roger Ruckman, a pediatric cardiologist at Children’s National Medical Center, about half of the children referred to a cardiologist for evaluation of a heart murmur are found to have an innocent murmur requiring no further attention.

Infants with murmurs are more likely than older children to have an anatomic defect, Ruckman said, though some congenital heart defects are not identified until children are older due to the mechanics of blood flow through the heart. For example, a murmur caused by an atrial septal defect (ASD), a hole between the left and right atria, may not be discovered until adolescence or early adulthood because there may be no audible sound in early childhood.

About 20 to 30 percent of congenital heart defects are discovered in utero when a routine office ultrasound of the pregnant mother picks up an abnormality within the fetal heart, according to Ruckman. In many cases, these women will be referred to a medical center for a fetal echocardiogram, which is more sensitive and better at spotting abnormalities. However, many heart defects can be picked up only after a child is born.

Even in cases where the murmur is caused by an anatomic defect, most will not require surgery. Infants who need surgery usually have complex cardiac abnormalities, problems that can’t be controlled with medication or ones that interfere with normal growth and development.

It’s not cardiac disease

If your child has a normal murmur, keep in mind that this is not cardiac disease. Your child should not be restricted from activity in any way.

Even in the case of an abnormal murmur, many children will not need restrictions, and limiting their activity may have negative psychological consequences. Discuss it with your child’s doctor.

Bennett, a pediatrician in Washington, has written numerous books for children. His Web site, www.howardjbennett.com, includes a blog on common pediatric problems.