Congenital Heart Disease USMLE Step 1 Practice Question
A 2-day-old male presents with cyanosis, tachypnea (RR 58/min), and poor feeding. Vital signs show HR 165/min, BP 62/38 mmHg, SpO2 78% on room air, and temperature 37.2°C. He has hepatomegaly but no murmur. Chest X-ray demonstrates cardiomegaly with increased pulmonary vascular markings. Echocardiography reveals a single arterial trunk arising from the heart with a large ventricular septal defect. Which embryologic mechanism best explains this presentation?
Answer choices
- AFailure of the aorticopulmonary septum to formCorrect answer
- BPremature closure of the ductus arteriosus
- CUnderdevelopment of the left fourth aortic arch
- DFailure of the tricuspid valve to canalize
- EFailure of the septum primum to close the foramen ovale
- FFailure of the neural crest cells to migrate to the conotruncus
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