Embryology USMLE Step 1 Practice Question
A cyanotic newborn presents with severe respiratory distress and tachycardia (HR 165/min). Chest X-ray demonstrates cardiomegaly with increased pulmonary vascular markings. Echocardiography confirms persistent truncus arteriosus with a single arterial trunk arising from the heart. Arterial blood gas shows hypoxemia (SpO2 78%) and metabolic acidosis. The infant has no dysmorphic features or cleft palate. Which of the following embryologic defects is this patient most likely to have?
Answer choices
- ADextrocardia
- BMembranous ventricular septal defectCorrect answer
- CTransposition of the great arteries
- DSecundum-type atrial septal defect
- ETetralogy of Fallot
- FCongenital diaphragmatic hernia
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