Embryology USMLE Step 1 Practice Question
A 3-month-old female infant presents with persistent cyanosis, poor feeding, and failure to thrive. Vital signs show HR 145 bpm, RR 42/min, SpO2 78% on room air, BP 88/54 mmHg, and temperature 37.2°C. Echocardiography demonstrates tetralogy of Fallot with right ventricular outflow tract obstruction, ventricular septal defect, overriding aorta, and right ventricular hypertrophy. No associated 22q11 deletion detected on genetic testing. This cardiac malformation results from abnormal neural crest cell migration during which embryologic process?
Answer choices
- AFailure of foramen ovale closure
- BAbnormal development of the sinus venosus
- CAbnormal atrial septation
- DInadequate development of the conotruncus and conal ridgesCorrect answer
- EInadequate endocardial cushion formation
- FEbstein anomaly
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.