What Causes a Heart Murmur in Children?

One of the extra heart sounds is a heart murmur, which usually indicates turbulent and irregular blood flow within the cavities and through the valves of the heart. A heart murmur in children can have either physiological or pathological causes. Usually, a physiological heart murmur in children disappears once the underlying condition is treated or once the child reaches their teenage years or adulthood. A pathological heart murmur in children indicates an underlying heart trouble that is usually structural in nature. It needs to be assessed and managed by a cardiologist.

Normally, the heart only produces two sounds called sound 1 (S1) and sound 2 (S2), heard as “lub-dub” on auscultation. In the presence of a murmur, these sounds are interrupted, preceded, or followed by a swishing or whistling sound, which is called a murmur. Common heart murmur types encountered in children are normal physiological, or innocent, murmurs.

Innocent murmurs are also called functional, benign, vibratory, or flow murmurs. Causes include a thin chest wall, a straight back, anemia, and fever. Children generally have thin chest walls and relatively straighter backs that make the heart closer to the surface of the chest. Blood flow is then easily heard and reported as a murmur.

When a child has a fever or anemia, the rate of his or her blood flow increases to facilitate the delivery of oxygen and nutrients to the organs. The increased blood flow leads to turbulent flow within the heart and manifests as a murmur that eventually disappears as the fever or the anemia resolves. Two innocent murmurs that are sometimes mistaken as abnormal ones include Still’s murmur and venous hum. Still’s murmur, also called musical murmur because of its musical quality, usually occurs in children between the ages 3 and 6 years. Venous hum is a soft humming murmur that can be heard over the jugular veins, also occurring in 3- to 6-year-old children.

In general, with the exception of the venous hum, heart murmurs characterized as either diastolic, holosystolic, or late systolic are abnormal in nature. A murmur that has any of these qualities should prompt the physician to search for an abnormality in the heart or blood vessels. Pathological or abnormal causes of heart murmur in children include structural abnormalities of the heart valves, heart cavities, or arteries connected to the heart. Such structural abnormalities may be congenital or acquired.

Congenital anomalies like atrial septal defect (ASD), coarctation of the aorta, tetralogy of Fallot, patent ductus arteriosus (PDA), and ventral septal defect (VSD) all manifest with murmurs. ASD, VSD, and tetralogy of Fallot are conditions wherein there is an abnormal communication between the left and right sides of the heart. Acquired conditions such as rheumatic heart disease due to untreated streptococcal infection can lead to narrowing or insufficiency of the heart valves. Narrowing leads to valvular stenosis, while insufficiency leads to valvular regurgitation. Both of these also present with heart murmurs.