An infant with marked cyanotic heart defect with decreased pulmonary vascularity should be treated with:

Correct Answer: B

Rationale: Prostaglandin E1 maintains the patency of the ductus arteriosus, allowing blood to bypass obstructed or underdeveloped pulmonary circulation, improving oxygenation in cyanotic congenital heart diseases like pulmonary atresia or transposition of the great arteries.

Correct Answer: B

Rationale: Aplastic anemia results in low reticulocyte counts due to the bone marrow's inability to produce red blood cells.

Correct Answer: D

Rationale: Milrinone is a phosphodiesterase inhibitor primarily used for heart failure, not acute shock, where dopamine and dobutamine improve cardiac output.

Correct Answer: D

Rationale: Cardiogenic shock is more common in later stages of KD.

Correct Answer: D

Rationale: A large atrial septal defect has low turbulence and pressure gradients, making it less likely to develop infective endocarditis compared to high-pressure lesions such as VSDs or valvular regurgitations.