A 5-year-old with a harsh murmur at the left lower sternal border; which condition is most likely?

A 5-year-old with a harsh murmur at the left lower sternal border; which condition is most likely?

• A. Aortic stenosis
• B. Pulmonic stenosis
• C. Patent ductus arteriosus
• D. Tricuspid atresia

Answer: (B)

In children, where a murmur is heard and how it sounds helps narrow the likely heart defect. A harsh systolic murmur heard along the left lower sternal border points most toward an outflow tract obstruction, with pulmonic stenosis being the best fit. Narrowing at the pulmonic valve or infundibulum causes the blood to be forcefully ejected during systole, producing that harsh quality we hear best in that region. Other choices don’t match as well: aortic stenosis is usually heard best at the right upper sternal border; a patent ductus arteriosus presents with a continuous, machine-like murmur typically best heard under the left clavicle; tricuspid atresia often features cyanosis early in life and a murmur pattern not centered on a harsh left-lower-sternal-border systolic murmur.

In children, where a murmur is heard and how it sounds helps narrow the likely heart defect. A harsh systolic murmur heard along the left lower sternal border points most toward an outflow tract obstruction, with pulmonic stenosis being the best fit. Narrowing at the pulmonic valve or infundibulum causes the blood to be forcefully ejected during systole, producing that harsh quality we hear best in that region.

Other choices don’t match as well: aortic stenosis is usually heard best at the right upper sternal border; a patent ductus arteriosus presents with a continuous, machine-like murmur typically best heard under the left clavicle; tricuspid atresia often features cyanosis early in life and a murmur pattern not centered on a harsh left-lower-sternal-border systolic murmur.