Congenital Heart Disease USMLE Step 1 Practice Question
A 28-year-old woman with a lifelong cardiac murmur presents with progressive cyanosis and digital clubbing. She has never undergone corrective surgery for her congenital atrial septal defect. Vital signs show BP 118/76 mmHg, HR 102/min, RR 22/min, SpO2 88% on room air. Echocardiography reveals severe pulmonary hypertension (RVSP 65 mmHg) and right-to-left shunting. She denies dyspnea on exertion initially. Which mechanism best explains the change in her shunt direction?
Answer choices
- AIncreased systemic vascular resistance causing more left to right flow
- BProgressive pulmonary vascular remodeling causing right sided pressures to exceed left sided pressuresCorrect answer
- CClosure of the ductus arteriosus after birth
- DAcute papillary muscle rupture decreasing left ventricular afterload
- EFibrosis of the AV node leading to bradycardia
- FMitral stenosis developing secondary to rheumatic heart disease increasing left atrial pressure
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