Subclavian Steal Syndrome

Proximal subclavian artery stenosis/occlusion → causes reversal of blood flow in the vertebral artery → “Steals” blood from the posterior cerebral circulation

Aetiology

Most Common Cause
  • Atherosclerosis
Other Causes
  • Large vessel vasculitis (e.g., Takayasu arteritis)
  • Congenital anomalies
  • Post-surgical (e.g., CABG with LIMA graft)

Pathophysiology

  • Proximal subclavian stenosis
  • ↓ pressure distal to stenosis
  • Blood flows retrograde from vertebral artery
  • Blood diverted away from brain → arm
Result
  • Vertebrobasilar insufficiency
  • Upper limb ischemia
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Epidemiology

  • More common in:
    • Elderly
    • Patients with vascular risk factors
  • Left side more commonly affected

Clinical presentation

Neurological Symptoms (Vertebrobasilar Insufficiency)
Common Symptoms
  • Dizziness / lightheadedness
  • Vertigo
  • Syncope or presyncope
  • Visual disturbances:
    • Blurred vision
    • Diplopia
  • Ataxia / imbalance
  • Confusion (rare)
Mechanism
Blood is diverted from brain to arm → transient posterior circulation ischemia
Upper Limb Ischemic Symptoms
  • Arm claudication (pain with use)
  • Fatigue or weakness
  • Cold sensation
  • Paresthesia
Combined Presentation (Classic Pattern)
  • Neurological symptoms + arm symptoms
  • Triggered by using the affected arm
Physical Examination Findings
Blood Pressure Difference
>15–20 mmHg between arms (very important clue)
Pulse Findings
Weak or delayed radial pulse on affected side
Bruit
Over supraclavicular/subclavian region
Limb Findings
  • Cool extremity
  • Reduced perfusion signs

Investigations

Duplex Ultrasound (First-Line)
  • Detects:
    • Reversed vertebral artery flow (hallmark)
    • Subclavian stenosis
Digital Subtraction Angiography (Gold Standard)
  • Confirms diagnosis
  • Allows intervention
CT Angiography / MR Angiography
Defines:
  • Location and severity of stenosis
 

Management

Core Principle
  1. Treat underlying cause (usually Atherosclerosis)
  1. Relieve symptoms (neurologic + arm ischemia)
  1. Prevent cerebrovascular events
Conservative Management (First-Line in Asymptomatic)
  • Risk factor modification
    • Smoking cessation
    • Blood pressure control
    • Diabetes management
    • Lipid control (statins)
  • Antiplatelet therapy
    • Aspirin or clopidogrel
Appropriate for asymptomatic or mild cases
Indications for Intervention
  • Symptomatic patients:
    • Vertebrobasilar symptoms (dizziness, syncope)
    • Arm claudication affecting function
  • Significant inter-arm BP difference
  • Compromised cerebral circulation
Revascularization (Definitive Treatment)
Endovascular (Preferred First-Line)
  • Percutaneous angioplasty ± stenting
Advantages
  • Minimally invasive
  • High success rate
  • Short recovery time
Surgical Options
Used if endovascular fails or not feasible:
  • Carotid–subclavian bypass
  • Subclavian–subclavian bypass
  • Endarterectomy