A heart murmur is an abnormal heart sound that results from the turbulent flow of blood through the heart. Heart murmurs are usually detected by a physician using a stethoscope to listen to the heartbeat. Most heart murmurs are harmless or “innocent,” which means they are not associated with a disease or condition of the heart. Many, if not most, children will have a heart murmur at some point in their lives. However, heart murmurs may also be the result of an underlying heart condition, such as the narrowing of one of the heart’s four valves (valvular stenosis) or heart disease that has been present from birth (congenital heart disease). The underlying cause of a heart murmur is usually diagnosed through painless tests such as an echocardiogram and (if necessary) a minimally invasive test such as a cardiac catheterization. A treatment plan will be designed based on the underlying condition.