• subclavian steal syndrome, also called subclavian-vertebral artery steal syndrome, refers to an altered (usually retrograde) blood flow in the vertebral artery (VA) or the internal thoracic artery (ITA) due to a proximal stenosis/occlusion of the subclavian artery (SA) or brachiocephalic trunk (BCT)
    • the upper extremity is then supplied with blood from the vertebral artery at the expense of the posterior circulation
    • subclavian steal is mostly asymptomatic and does not warrant invasive evaluation or treatment
  • a coronary variant may occur as an adverse effect of coronary artery bypass grafting (CABG) when the internal thoracic (also known as mammary) artery is used on the side of the stenotic/occluded subclavian artery

Steal phenomenon vs. steal syndrome

  • differentiate between subclavian steal phenomenon (asymptomatic, incidental finding of altered flow in the VA) and subclavian steal syndrome (steal phenomenon + clinical signs and symptoms related to the impaired blood supply to the upper extremity or posterior circulation)
    • most patients with the steal phenomenon have no clinical symptoms


Vertebral steal syndrome

  • vertebral artery steal syndrome is caused by stenosis/occlusion of the subclavian artery (SA) proximal to the origin of the vertebral artery or brachiocephalic trunk Subclavian artery occlusion; the distal segment is fed via verterbal artery  Subclavian artery occlusion on CTA
  • steal represents collateral flow from the brain in the territory of the subclavian artery
  • flow changes in the vertebral artery depend on the degree of SA stenosis
  • clinical presentation is influenced by the quality of the intracranial collateral circulation
    • symptomatic patients (steal syndrome) have poor collateral circulation and/or concurrent stenoses in the intra- or extracranial cerebral circulation
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Double steal phenomenon (carotid and vertebral)

  • can be seen in patients with severe stenosis of the brachiocephalic trunk (BCT); flow is altered in both ipsilateral VA and carotid artery (the VA and ICA usually have a higher degree of steal than the CCA)
Double steal phenomenon caused by the brachiocephalic trunk stenosis - ipsilateral steal in CCA and presteal in ICA, complete steal in VA, slow flow in ipsilateral MCA

Coronary-subclavian steal syndrome

  • the internal thoracic (mammary) artery (ITA) supplies the anterior chest wall and the breasts
  • if ITA is used in coronary artery bypass graft (CABG) surgery, subclavian stenosis/occlusion may cause cardiac steal syndrome with angina symptoms
    • during CABG, the distal end of the ITA is diverted to one of the coronary arteries
  • subclavian artery stenosis must be excluded before the CABG!


Clinical presentation

  • most commonly, no symptoms and signs from the posterior circulation are present
  • peripheral signs and symptoms (circulation problems in the upper extremity)
    • weak/absent pulse
    •  the blood pressure difference between arms (decreased on the affected side; usually  > 20 mmHg difference)
    • arm claudications (rare)
  • cerebral signs and symptoms (often provoked by the physical exercise of the affected arm)
    • presyncope/syncope
    • vertigo
    • neurologic deficits form posterior circulation (ataxia, visual field disorders, dysarthria, weakness/sensory disturbances)
    • drop attack

Diagnostic evaluation

CT angiography

  • direct detection of stenosis/occlusion of SA or BCT and other arteries (extra- and intracranial)  Subclavian artery occlusion; the distal segment is fed via verterbal artery
  • can distinguish atherosclerosis from other causes (vasculitis, compression, etc.)
  • can´t evaluate the hemodynamic consequences in the posterior circulation
    • delayed filling of the ipsilateral vertebral artery can be observed, but the flow direction cannot be determined
    • neurosonology is perfectly suited for such a task


  • detects SA stenosis + delayed retrograde filling of the ipsilateral vertebral artery


  • hemodynamic changes in the VA can be divided into the following stages:
    • presteal (latent steal) – Doppler shows systolic deceleration of flow with a split in the systolic part of the curve and a decrease in pulsatility
    • incomplete steal – biphasic flow with retrograde systole
    • complete steal – retrograde flow with increased resistance
  • always assess the V4 segment and basilar artery on TCCD in addition to the extracranial portion of the VA  Retrograde flow (complete steal) in V4 segment of vertebral artery Complete steal in the left vertebral artery (left image)), biphasic flow in the basilar artery
  • upper limb compression or stress test – in all stages of steal, the altered flow pattern will be more pronounced after the release of compression or limb relaxation
  • examination of the brachial artery is helpful – flow distal to the subclavian stenosis is blunted with loss of the triphasic curve  Blunted flow in the brachial artery in patient with ipsilateral subclavian artery stenosis. Normal flow in the brachial artery on the opposite side
Subclavian (verterbal) steal ultrasound grades
Stenosis of the right subclavian artery with a complete steal phenomenon in VA and presteal in the basilar artery. Noticeable blunted flow in the distal subclavian and brachial artery (compared to the left side)
Subclavian artery stenosis with biphasic flow in basilar artery


Steal syndrome - subclavian artery stenosis on CTA

Stenotic turbulent flow in the subclavian artery

A stenotic turbulent flow in the subclavian artery

Anterograde flow in the V4 segment of left vertebral artery

Retrograde flow the V4 segment of the right VA

Incomplete steal phenomenon with biphasic flow in basilar artery

Incomplete steal phenomenon with biphasic flow in basilar artery

Retrograde flow in V2 segment of the right vertebral artery

Retrograde flow in V2 segment of the right vertebral artery


  • aggressive management of vascular risk factors + antiplatelet therapy
    • blood pressure should be measured in both arms, and BP management should be guided by the values obtained in the unaffected arm
  • subclavian angioplasty with stenting
  • surgery

    • carotid-subclavian bypass
    • aorta-subclavian bypass

→ vertebrobasilar steno-occlusive disease

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Subclavian (vertebral) steal syndrome
link: https://www.stroke-manual.com/subclavian-vertebral-steal-syndrome/