Which innocent murmur commonly found in low-birth-weight infants radiates to the axilla and back?

• A. Pulmonary flow murmur
• B. Mitral flow murmur
• C. Systolic ejection murmur
• D. Aortic flow murmur

Answer: (A)

In preterm or low-birth-weight infants, a benign flow murmur often comes from increased blood flow through the pulmonary outflow tract. This pulmonary flow murmur is a soft systolic ejection murmur heard best at the left upper sternal border and can radiate to the back and to the left axilla due to the jet of flow through the pulmonic valve. It’s common in this group because pulmonary vascular resistance is relatively high at birth and then falls with maturation, causing the murmur to decrease and usually disappear over the first months. This radiating pattern to the axilla and back, in a LBW infant, fits the typical benign profile of a pulmonary flow murmur.