Description

• A condition that results from stenosis or occlusion of the subclavian artery proximal to the origin of the vertebral artery; blood is drawn from the contralateral vertebral basilar or carotid artery regions into the low-pressure ipsilateral upper limb vessels, “stealing” the blood flow from the circle of Willis.
• The term was reported for the first time by Fisher in 1961. It is a normal pattern of collateral response to proximal subclavian artery occlusion.

Epidemiology

• Predominant age:
  • Age >55 years—atherosclerotic etiology
  • Age <30 years—90% of patients with Takayasu arteritis
• Predominant sex: Female > Male
• More frequent in African Americans and non-Hispanic whites when compared with Hispanics and Chinese Americans

• Present in 6% of the patients with asymptomatic carotid bruit
• Hemodynamically significant left subclavian artery stenosis is present in ~2.5% of patients undergoing coronary revascularization (1).

Risk Factors

• Smoking
• Hypertension
• Diabetes
• Hyperlipidemia
• Radiotherapy

Pathophysiology

• With a left subclavian occlusion, maintenance of blood flow to the left arm occurs with reversal of flow from the basilar artery via the left vertebral artery.
• Symptoms are associated with the degree and location of a second extracranial vessel occlusion.

Etiology

• Arteriosclerosis obliterans of the proximal subclavian artery in 95% of cases
• Lesions are 4:1 more common on the left side.
• Less common causes of obstruction:
  • Dissecting aneurysm of aortic arch
  • Trauma
  • Embolus
  • Radiotherapy induced
  • Takayasu arteritis
  • Giant cell arteritis
  • Fibromuscular dysplasia
  • May happen after Blalock-Taussig procedure for tetralogy of Fallot

Commonly Associated Conditions

• Carotid artery disease
• Coronary artery disease is present in 30–60% of patients.
• Arteriosclerosis

Geriatric Considerations
Older patients are more likely to have arteriosclerosis.