Which finding would most strongly suggest coarctation of the aorta in a newborn?

• A. Very weak femoral pulse
• B. Strong brachial pulse
• C. Normal femoral pulse with tachycardia
• D. Bounding pulses in the legs

Answer: (A)

Coarctation of the aorta creates a bottleneck just after the arteries to the upper body, so blood flow to the lower body is reduced. The result is strong upper-extremity pulses but markedly weak distal pulses, especially in the legs, as the leg circulation is filtered through the narrowed segment. In a newborn, this distal under-perfusion can become even more evident as the ductus arteriosus closes, worsening the femoral pulse. That stark difference—very weak femoral pulses with relatively normal or strong arm pulses—is the finding that most strongly points to coarctation. A strong brachial pulse doesn’t fit with the expected distal reduction; normal femoral pulse with tachycardia could be due to other causes, and bounding leg pulses would not align with the decreased distal flow seen in coarctation.