Which congenital lesion best explains diminished lower-extremity perfusion and cold legs with preserved upper-extremity flow?

• A. Coarctation of the aorta
• B. Aorta atresia
• C. Pulmonary stenosis
• D. Patent ductus arteriosus

Answer: (A)

This question tests how obstruction in the aorta can create a split in blood flow between the upper and lower parts of the body. When the aorta is narrowed just after the arteries that supply the arms branch off, the blood pressure and flow to the upper body remain relatively normal, but the descending aorta beyond the obstruction can’t deliver as much blood to the legs. The result is diminished perfusion of the lower extremities with cold legs, while perfusion in the arms and head stays preserved.

This pattern fits coarctation of the aorta well because the narrowing typically lies distal to the left subclavian artery, producing higher pressures and pulses in the arms but weaker femoral pulses and cooler legs. In contrast, aorta atresia would block flow more globally and usually not preserve upper-body perfusion. Pulmonary stenosis affects the pulmonary circulation and right heart output rather than systemic perfusion to the legs. Patent ductus arteriosus causes a left-to-right shunt between the aorta and pulmonary artery and does not inherently create isolated leg hypoperfusion with intact upper-extremity flow.