Etiology: stenosis of (usually) L subclavian artery –> reversal of flow through the “vertebral artery loop” to supply blood to distal L subclavian.
- Carotids: bruits, pulse quality
- Subclavians: bruits, pulse quality, pulse delays
- Vertebrals: auscultate suboccipital region for bruits
- Thoracic outlet syndrome: Adson test (abduction and external rotation of arm causes decrease in radial pulse) – not a great test, high rate of false positives.
- Blood pressure differential – >15 mmHg – affected side lower
- Pulse differential (weaker or delayed on affected side)
- Takayasu’s arteritis
Confirmatory: U/S or CTA imaging.