A 66-year-old woman with atrial fibrillation not on anticoagulation suddenly develops a cold, pale, pulseless right leg. There was no preceding claudication, the right leg was previously entirely well, and the left leg pulses are strong. Sensation is reduced below the ankle and power is intact. Which combination best supports embolism rather than in situ thrombosis as the cause?

• A Sudden onset, known arrhythmia source, normal contralateral pulses, absence of prior claudication ✓
• B Gradual onset over days, previous intermittent claudication, absent contralateral pulses
• C Pain out of proportion to findings and a normal neurovascular examination
• D Elevated D-dimer and a history of previous deep vein thrombosis

Explanation

Embolic acute limb ischaemia is characterised by instant maximal onset, a documented cardiac source such as atrial fibrillation, previously normal pulses in the affected limb, and normal contralateral limb pulses, since the native arteries are healthy. In situ thrombosis on pre-existing atherosclerosis presents more gradually, often with prior claudication and absent pulses in the opposite leg reflecting diffuse disease. This distinction matters because embolism demands urgent embolectomy plus anticoagulation, whereas extensive thrombosis may need catheter-directed thrombolysis or bypass. D-dimer elevation occurs in both and discriminates nothing here.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.