Congenital Heart Disease USMLE Step 1 Practice Question
A 3-day-old male infant presents with cyanosis and severe respiratory distress. Vital signs show HR 165 bpm, RR 58/min, BP 58/40 mmHg, SpO2 78% on room air, and temperature 36.8°C. Physical examination reveals a single S2 and systolic ejection murmur. Chest X-ray demonstrates an "egg-on-string" appearance with decreased pulmonary vascular markings. Arterial blood gas shows PaO2 42 mmHg. The infant has not received prostaglandin E1. Which of the following is the most likely diagnosis?
Answer choices
- AHypoplastic left heart syndrome
- BTotal anomalous pulmonary venous return
- CTetralogy of Fallot
- DTransposition of the great arteriesCorrect answer
- ETruncus arteriosus
- FPulmonary atresia with intact ventricular septum
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.