Subclavian (vertebral) steal syndrome

Created 13/12/2021, last revision 22/08/2023

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 artery steal syndrome is caused by stenosis/occlusion of the subclavian artery (SA) proximal to the origin of the vertebral artery or brachiocephalic trunk
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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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)

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!

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

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

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 filling of the ipsilateral vertebral artery can be observed, but the flow direction cannot be determined
- neurosonology is perfectly suited for such a task

performed as part of an endovascular procedure
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
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

THE STEAL PHENOMENON IN A PATIENT WITH RIGHT SUBCLAVIAN ARTERY STENOSIS

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