A 68-year-old man experiences recurrent dizziness and visual blurring when using his left arm for overhead work. Left radial pulse is weaker than right, and left brachial blood pressure is 30 mmHg lower than the right. Duplex shows retrograde flow in the left vertebral artery. Which vessel is stenosed?
- A Left subclavian artery proximal to the vertebral artery origin ✓
- B Left common carotid artery at its origin
- C Left vertebral artery at its origin
- D Innominate artery
Correct answer: A. Left subclavian artery proximal to the vertebral artery origin
Explanation
Subclavian steal occurs when proximal subclavian stenosis creates low pressure distally, so the vertebrobasilar circulation is siphoned retrograde down the ipsilateral vertebral artery during arm exercise, causing posterior circulation symptoms. Stenosis of the vertebral origin itself would reduce antegrade flow rather than produce steal. The innominate would also affect the right carotid circulation.
Reference: Bailey and Love's Short Practice of Surgery, 28th ed.
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Written and medically reviewed by the StethoPrep medical team.