Final answer:
Prostaglandin E1 is used to keep the ductus arteriosus open in certain heart defects, which is necessary for proper blood circulation in infants with congenital heart issues until surgical repair can be performed.
Step-by-step explanation:
The substance used to keep the ductus arteriosus open (patent) in certain heart defects is Prostaglandin E1 (B). This treatment is vital for maintaining blood flow in conditions where the ductus arteriosus needs to remain open to ensure an adequate mix of oxygenated and deoxygenated blood until the defect can be addressed more permanently, such as surgical intervention.
Prostaglandin E1 functions by inhibiting the natural constriction of the ductus arteriosus that would occur after birth. In contrast, other options like oxygen therapy (A) are not designed to keep the ductus arteriosus patent, and nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin (D) can actually promote its closure by blocking prostaglandin synthesis. Nitric oxide (C) is typically used to relax the smooth muscle of blood vessels but is not specifically used for maintaining patent ductus arteriosus.