**Core Concept**
Congenital heart disease often involves abnormalities of the ductus arteriosus, a vital shunt in fetal circulation. In certain conditions, maintaining patency of the ductus arteriosus (PDA) is crucial for survival.

**Why the Correct Answer is Right**
The correct answer is a prostaglandin E1 analogue (e.g., alprostadil), which is commonly used to keep the PDA patent in neonates with congenital heart disease. This is because prostaglandin E1 maintains ductal patency by inhibiting the enzyme prostaglandin endoperoxide synthase-1 (PGHS-1), which is involved in the constriction of the ductus arteriosus.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect because digoxin is primarily used in the treatment of atrial fibrillation and heart failure, not in maintaining PDA patency.
* **Option B:** This is incorrect because furosemide is a diuretic used to manage fluid overload in heart failure, not to keep the PDA patent.
* **Option C:** This is incorrect because nitric oxide is used as a vasodilator in pulmonary hypertension, not specifically to maintain PDA patency.

**Clinical Pearl / High-Yield Fact**
Prostaglandin E1 analogues are essential in neonatal cardiology for maintaining ductal patency in congenital heart disease. Always consider their use in neonates with cyanotic heart disease or those requiring cardiac surgery.

**Correct Answer:** A. Alprostadil