Which CHD lesion is highly dependent on ductus arteriosus patency for systemic perfusion?

• A. Transposition of the great arteries
• B. Hypoplastic left heart syndrome
• C. Tetralogy of Fallot
• D. Dextrocardia

Answer: (B)

In this situation, the key idea is that ductus arteriosus patency is crucial when the systemic circulation relies on blood shunted from the right heart through the pulmonary artery into the aorta. Hypoplastic left heart syndrome leaves the left-sided structures severely underdeveloped, so the systemic output comes entirely via the ductus arteriosus from the right ventricle through the pulmonary artery into the aorta. If the ductus closes after birth, there is little to no systemic perfusion, leading to rapid deterioration. This dependence on the ductus for systemic flow is why maintaining ductal patency with prostaglandin E is essential in HLHS preoperatively.

Transposition of the great arteries, tetralogy of Fallot, and dextrocardia do not have the same single-ventricle–dependent reliance on the ductus for systemic perfusion. In TGA, survival depends on mixing between circuits (PFO/ASD, PDA), not exclusively on ductal flow for systemic output. Tetralogy of Fallot involves right-to-left shunting and RV outflow obstruction, with systemic perfusion not solely dependent on the ductus. Dextrocardia is a positional diagnosis rather than a specific hemodynamic dependence on a patent ductus.