A 62-year-old man reports left arm fatigue on exertion accompanied by brief dizziness and visual blurring that resolve with rest. Left brachial systolic pressure is 40 mmHg lower than the right. Duplex shows retrograde flow in the left vertebral artery. What is the underlying lesion?
- A Stenosis of the origin of the left subclavian artery ✓
- B Occlusion of the left vertebral artery at its origin
- C Stenosis of the left innominate artery
- D Dissection of the left vertebral artery
Correct answer: A. Stenosis of the origin of the left subclavian artery
Explanation
Subclavian steal results from a proximal subclavian stenosis proximal to the vertebral artery origin. Arm exercise lowers peripheral resistance, so blood is drawn retrograde down the ipsilateral vertebral artery from the basilar circulation, producing vertebrobasilar insufficiency. An occluded vertebral artery would not show steal physiology, and innominate stenosis would also reduce right-sided carotid flow. The pressure differential across the arms confirms the subclavian lesion.
Reference: Bailey and Love's Short Practice of Surgery, 28th ed.
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Written and medically reviewed by the StethoPrep medical team.