Q: At my 10-year-old son's last checkup, his pediatrician detected a slight heart murmur. The doctor said that this is nothing to worry about and that heart murmurs are very common in children. Is there anything more I should be doing to make sure it isn't indicative of something more serious?

A: Your son's doctor is correct in saying that heart murmurs in children are very common50 to 75 percent of children may have them at some point. A murmur is defined as an extra heart sound, one that occurs in addition to the typical "lub-dub" (two heart sounds) someone would hear when listening to the heart with a stethoscope.

Murmurs may be innocent or functional (benign), but could also be due to an abnormality of the heart. The majority of heart murmurs in children are innocent and are not indicative of an underlying heart abnormality. Rather, these murmurs are a result of increased or turbulent blood flow across normal structures of the heart, resulting in a heart murmur or sound. Clinical conditions that may accentuate a heart murmur include fever, exercise, or an activity that increases the amount of blood the heart must pump. In the absence of any other findings on a clinical cardiac exam and based on the characteristics of the murmur, an innocent or benign murmur can be diagnosed. These murmurs are not associated with an underlying cardiac abnormality and often disappear over time. This seems to be the case with your son.

Murmurs can also be associated with structural abnormalities of the heart, such as thickened or leaky cardiac valves, or holes between the upper or lower chambers of the heart. The characteristics of these types of murmurs are different, though, than those of benign murmurs. These structural abnormalities are also often accompanied by other abnormal findings through a clinical cardiac exam.

The specific underlying cause of a structural murmur can be easily diagnosed by performing an echocardiogram. This test is a useful diagnostic tool when it is unclear whether a murmur is innocent or is caused by an underlying cardiac abnormality. However, this discrepancy can usually be determined through a careful medical history and physical examination. If you are looking for peace of mind, you may want to talk to your son's pediatrician about further testing to definitively rule out any serious conditions.

Stuart Berger, M.D., serves as Medical Director of Cardiology, Herma Heart Center at Children's Hospital of Wisconsin in Milwaukee. Herma Heart Center is one of the top-rated pediatric cardiology programs in the country. He also serves as professor of pediatrics (cardiology) at the Medical College of Wisconsin. Berger's areas of expertise include congenital heart disease, cardiac critical care, pediatric heart transplantation, interventional catheterization, and sudden cardiac arrest.