• subclavian steal phenomenon = an altered (usually retrograde) blood flow in the vertebral artery (VA) or the internal thoracic artery due to a proximal stenosis/occlusion of the subclavian artery (SA) or brachiocephalic trunk (BCT)
  • the upper limb is thus supplied with blood flowing down the vertebral artery at the expense of the posterior circulation

Steal phenomenon vs. steal syndrome

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

Pathophysiology

Vertebral steal syndrome

  • vertebral steal syndrome is caused by a stenosis/occlusion of the subclavian artery (SA) proximal to the vertebral artery or brachiocephalic trunk Subclavian artery occlusion; the distal segment is fed via verterbal artery  Subclavian artery occlusion on CTA 
  • steal is a consequence of collateral flow from the brain into the subclavian territory
  • flow changes in the vertebral artery depend on the degree of SA stenosis
  • clinical presentation is influenced by the quality of intracranial collateral circulation
    • symptomatic patients (steal syndrome) tend to 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 found in patients with severe stenosis of the brachiocephalic trunk (BCT); the flow is altered in both ipsilateral VA and carotid artery (the VA and ICA usually have a higher degree of a steal than the CCA)
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Coronary-subclavian steal syndrome

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

Etiology

  • atherosclerosis (most common cause)
  • external compression of a subclavian artery caused by the cervical rib or the scalene muscles (Thoracic outlet syndrome)
  • Takayasu arteritis
  • radiation-induced vasculopathy
  • congenital malformations (e.g., preductal aortic coarctation, interrupted aortic arch) and their surgical correction leading to the iatrogenic lesion of SA

Clinical presentation

  • most commonly, no symptoms and signs from the posterior circulation are present
  • peripheral signs and symptoms (circulation problems in the upper limb)
    • weak/absent pulse
    • different blood pressure values on both arms (decreased on the affected side, the usual difference is > 20 mm Hg)
    • arm claudications (rare)
  • CNS signs and symptoms (often provoked by the physical exercise of an affected arm)
    • presyncope/syncope
    • vertigo
    • neurologic deficits form posterior circulation (ataxia, visual changes, 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 enhancement of the ipsilateral vertebral artery can be observed, but flow direction can not be determined
    • neurosonology is perfect for such a task

DSA

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

Neurosonology

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STEAL PHENOMENON IN PATIENT WITH RIGHT SUBCLAVIAN ARTERY STENOSIS

Steal syndrome - subclavian artery stenosis on CTA


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


Retrograde flow in V2 segment of the right vertebral artery

Retrograde flow in V2 segment of the right vertebral artery

Management

  • a conservative approach with aggressive management of vascular risk factors + antiplatelet therapy
    • blood pressure should be measured on both arms, and blood pressure management should be guided by the values obtained on the unaffected arm
  • subclavian angioplasty with stenting
  • carotid-subclavian bypass
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