Vascular Disease USMLE Step 1 Practice Question
A 72-year-old man with chronic atrial fibrillation not on anticoagulation presents with acute left lower extremity pain and coolness. Vital signs show HR 102 and irregular, BP 138/85, RR 16, SpO2 98%. Physical exam reveals mottled skin and absent left femoral pulses. Labs show elevated D-dimer at 2.8 μg/mL. Doppler ultrasound confirms acute arterial occlusion of the left superficial femoral artery. Cardiac auscultation reveals no new murmurs. Which of the following is the most likely source of this embolus?
Answer choices
- ALeft atrial thrombus from atrial fibrillationCorrect answer
- BParadoxical embolus via PFO
- CArterial aneurysm with mural thrombus
- DIn situ thrombosis from hypercoagulability
- EAtherosclerotic plaque rupture
- FLeft ventricular thrombus from recent myocardial infarction
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.