Pulmonary Embolism USMLE Step 1 Practice Question
A 68-year-old man with COPD and hypertension presents to the emergency department with acute dyspnea, tachycardia, and hypoxemia two days after undergoing open reduction and internal fixation of a hip fracture. Vital signs are: heart rate 122 bpm, blood pressure 92/58 mmHg, respiratory rate 30/min, and oxygen saturation 87% on room air. Physical examination reveals unilateral leg swelling and tenderness in the operative leg. Electrocardiogram shows sinus tachycardia with T-wave inversions in leads V1-V3. Serum troponin I is elevated at 0.09 ng/mL, and D-dimer is markedly elevated at 2.8 μg/mL. Chest radiograph is unremarkable. Which of the following best explains the mechanism of myocardial injury in this patient?
Answer choices
- ADemand ischemia from systemic hypoxemia and tachycardia in the setting of pre-existing coronary artery disease
- BAcute ST-elevation myocardial infarction of the anterior wall due to left anterior descending artery occlusion
- CRight ventricular strain and microinfarction secondary to acute increase in pulmonary vascular resistanceCorrect answer
- DMyocardial inflammation from surgical trauma-induced systemic inflammatory response syndrome
- ESeptic thromboembolism with direct myocardial invasion by bacterial pathogens
- FPulmonary infarction with subsequent hemorrhage into the myocardium
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.