Preductal coarctation is defined as narrowing of the aorta proximal (before) to the PDA. This causes blood from the pulmonary arteries to go into the aorta.

Preductal coarctation is defined as narrowing of the aorta proximal (before) to the PDA. This causes blood from the pulmonary arteries to go into the aorta.

• A. Distal (after) the PDA
• B. Within the PDA
• C. At the level of the ductus arteriosus
• D. Proximal (before) to the PDA

Answer: (D)

Preductal coarctation means the narrowing is located before the ductus arteriosus, i.e., proximal to the PDA. Because the ductus connects the pulmonary artery to the aorta distal to the obstruction, keeping the ductus open allows blood from the pulmonary circulation to enter the aorta beyond the narrowed segment, sustaining perfusion to the lower body. This ductus-dependent flow explains why blood from the pulmonary arteries can reach the aorta when the lesion is proximal to the PDA. If the narrowing were after the PDA or at/within the ductus, the described shunt would not apply. Clinically, this is why ductus-dependent coarctation lesions require strategies to keep the ductus open (for example, prostaglandin infusion) to preserve systemic blood flow.

Preductal coarctation means the narrowing is located before the ductus arteriosus, i.e., proximal to the PDA. Because the ductus connects the pulmonary artery to the aorta distal to the obstruction, keeping the ductus open allows blood from the pulmonary circulation to enter the aorta beyond the narrowed segment, sustaining perfusion to the lower body. This ductus-dependent flow explains why blood from the pulmonary arteries can reach the aorta when the lesion is proximal to the PDA. If the narrowing were after the PDA or at/within the ductus, the described shunt would not apply. Clinically, this is why ductus-dependent coarctation lesions require strategies to keep the ductus open (for example, prostaglandin infusion) to preserve systemic blood flow.