Coronary Artery Disease USMLE Step 1 Practice Question
A 2-year-old boy presents with recurrent cyanotic episodes triggered by crying and exertion. Vital signs show HR 128/min, RR 32/min, BP 95/60 mmHg, SpO2 78% during distress. Physical examination reveals a harsh systolic ejection murmur at the left upper sternal border. Chest X-ray demonstrates a "boot-shaped" heart with right ventricular hypertrophy. The patient spontaneously assumes a squatting posture during cyanotic spells, which temporarily improves his oxygen saturation. No hepatomegaly is noted. Which embryologic defect is most closely associated with this condition?
Answer choices
- AFailure of neural crest migration causing conotruncal malalignmentCorrect answer
- BPersistence of the left superior vena cava
- CExcess apoptosis of the tricuspid leaflets
- DFailure of endocardial cushion fusion only
- EIncomplete closure of the ductus venosus
- FAbnormal development of the bulbus cordis with leftward displacement of the interventricular septum
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