Subclavian steal syndrome

Subclavian steal syndrome (SSS) and subclavian steal phenomenon both result from occlusion or severe stenosis of the proximal subclavian artery resulting in retrograde flow in the ipsilateral vertebral artery.

Subclavian steal phenomenon refers to steno-occlusive disease of the proximal subclavian artery with retrograde flow in ipsilateral vertebral artery.

Subclavian steal syndrome refers to steno-occlusive disease of the proximal subclavian artery with retrograde flow in ipsilateral vertebral artery and associated cerebral ischaemic symptoms.

There is an increased incidence with age and the greater male predilection with a M:F ratio of 2:1. It is commoner on the left side with L:R ratio of ~3:1.

  • ipsilateral upper limb
    • weak or absent pulse
    • decreased blood pressure (>20 mmHg)
    • arm claudication (rare due to collateral perfusion)
  • neurological (exacerbated by arm exercise)
    • dizziness / vertigo / syncope
    • ataxia
    • visual changes
    • dysarthria
    • weakness / sensory disturbances

Subclavian artery steno-occlusive disease results in decreased perfusion to the ipsilateral arm and hand. Subclavian artery branches distal to the obstruction act as collateral pathways to maintain upper limb perfusion. 

If the level of stenosis or occlusion is proximal to the vertebral artery, reversal of flow in the vertebral artery may occur, thereby stealing blood from the posterior circulation. When the upper limb is exercised, blood is diverted away from the brain to the arm. Whether or not this steal phenomenon causes cerebral ischemic symptoms depends on the adequacy of intracranial collateral circulation, especially the posterior communicating arteries. Patients with adequate intracranial collateral circulation are usually asymptomatic; 80% symptomatic patients have lesions elsewhere in the intracranial or extracranial cerebral circulation.

Patients in whom the left vertebral artery arises directly from the aortic arch are protected from subclavian steal syndrome on the left.

  • retrograde flow in ipsilateral vertebral artery
  • early changes prior to reversal of flow: decreased velocity, biphasic flow (in vertebral artery)
  • changes can be augmented with arm exercise or inflation of BP cuff above systolic pressure
  • proximal subclavian artery usually cannot be seen well enough to assess
  • distal subclavian artery shows parvus-tardus waveform and monophasic waveform
  • subclavian artery stenosis or occlusion is easily identified
  • delayed enhancement of ipsilateral vertebral artery
  • direction of flow in vertebral artery cannot be determined
  • other intracranial or extracranial cerebral vascular lesions can be identified
  • subclavian artery stenosis or occlusion easily identified
  • delayed enhancement of ipsilateral vertebral artery
  • retrograde direction of flow in ipsilateral vertebral artery
  • other intracranial or extracranial cerebral vascular lesions can also be identified
  • performed at the time of endovascular intervention
  • subclavian artery stenosis or occlusion easily identified
  • delayed filling of ipsilateral vertebral artery (which fills retrogradely)
  • other intracranial or extracranial cerebral vascular lesions can also be identified
  • endovascular: angioplasty +/- stenting
  • surgical: bypass surgery
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Article information

rID: 5012
Section: Syndromes
Tag: refs
Synonyms or Alternate Spellings:
  • Sub-clavian steal syndrome
  • Subclavian steal phenomenon
  • Subclavian steal syndrome (SSS)

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    Subclavian steal
    Case 3: following endoluminal repair
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    Case 4: biphasic flow in left vertebral artery
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    Case 4: 3D reconstruction
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    Case 5: time resolved 3D CE-MRA
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    Case 6: high grade stenosis of the left subclavian artery
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    Case 9: on right
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