A 62-year-old man reports dizziness and visual blurring when using his right arm overhead, together with right arm claudication. Right radial pulse is weaker than the left, and systolic blood pressure is 40 mmHg lower in the right arm. Duplex shows reversed flow in the right vertebral artery. What is the underlying lesion?

• A Occlusion of the right common carotid artery
• B Stenosis of the right vertebral artery at its entry into the transverse foramen
• C Stenosis of the right subclavian artery proximal to the vertebral artery origin ✓
• D Dissection of the innominate artery distal to the carotid origin

Explanation

Proximal subclavian stenosis creates a low-pressure sink in the arm, so the ipsilateral vertebral artery flow reverses to supply the limb, stealing blood from the vertebrobasilar circulation during arm exercise. The diagnostic triad is arm claudication, interarm systolic pressure difference greater than 20 mmHg, and reversed vertebral flow on duplex. A vertebral artery lesion itself would reduce brainstem perfusion but cannot reverse flow direction in that vessel.

Reference: Schwartz's Principles of Surgery, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.