NEUROIMAGING / NEUROSONOLOGY
Subclavian (vertebral) steal syndrome
Created 13/12/2021, last revision 25/12/2022
- 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 limb is thus supplied with blood flowing down the vertebral artery at the expense of the posterior circulation
- subclavian steal is mainly asymptomatic and does not warrant invasive evaluation or treatment
- a coronary variant can occur as an adverse effect of coronary artery bypass graft (CABG) when the internal thoracic (also known as mammary) artery on the side of the stenotic/occluded subclavian artery is used
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 symptoms
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
- 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) 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 artery bypass surgery, cardiac steal syndrome with angina symptoms may occur with subclavian stenosis/occlusion
- 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!
Etiology
- atherosclerosis (the 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)
- cerebral 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)
- 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
Management
- a conservative approach with 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 on the unaffected arm
- subclavian angioplasty with stenting
- carotid-subclavian bypass