Hypotension in the lower extremities may indicate the presence of

• A. Patent ductus arteriosus
• B. Ventricular septal defect
• C. Coarctation of the aorta
• D. Hypoplastic left heart syndrome

Answer: (C)

Lower-extremity hypotension points to reduced blood flow to the legs due to a fixed narrowing of the aorta after the vessels to the head and arms. This pattern is classic for coarctation of the aorta, where the upper body maintains higher pressures while the lower body receives less perfused, lower-pressure blood. In newborns, the ductus arteriosus can temporarily help perfuse the lower body, but once it closes, leg perfusion can deteriorate quickly, leading to weak femoral pulses and hypotension in the legs.

This presentation is not typical of the other defects. A patent ductus arteriosus tends to cause a continuous murmur and wide pulse pressures with relatively good distal perfusion, rather than a targeted drop in leg pressures. A ventricular septal defect mainly causes left-to-right shunting and pulmonary overcirculation with less emphasis on differential leg versus arm perfusion. Hypoplastic left heart syndrome involves severely limited systemic output and overall poor perfusion, not a pattern focused on lower-extremity hypotension.