What are the symptoms and management of subclavian steal syndrome?

Subclavian Steal Syndrome: Symptoms and Management

Subclavian steal syndrome is characterized by vertebrobasilar insufficiency symptoms including dizziness, syncope, vertigo, ataxia, visual disturbances, and arm claudication, and should only be treated with revascularization if symptomatic or if the ipsilateral internal mammary artery is required for coronary bypass. 1

Clinical Presentation

Symptoms

• Vertebrobasilar insufficiency symptoms:

  • Dizziness and vertigo
  • Syncope
  • Ataxia
  • Visual disturbances (diplopia, blurred vision)
  • Dysphasia and dysarthria
  • Facial sensory deficits
  • Headache
  • Neurological deficits

• Upper extremity symptoms:

  • Arm claudication (exercise-induced fatigue and pain)
  • Paresthesia
  • Rest pain (in severe cases)
  • Digital ischemia (in severe cases with distal disease)

• Important clinical finding: Symptoms typically worsen with exercise of the affected arm, which amplifies flow reversal in the vertebral artery 1, 2

Physical Examination Findings

• Asymmetrical upper limb blood pressure (>10-15 mmHg difference)
• Periclavicular or infraclavicular bruit
• Reduced or absent pulses in the affected arm 1

Diagnosis

Initial Assessment

• Bilateral arm blood pressure measurement (difference ≥15 mmHg is suspicious) 1, 3
• Auscultation for periclavicular or infraclavicular bruit 1

Diagnostic Studies

1. Duplex ultrasonography:

   • Detection of high-velocity flows in stenotic areas (50% stenosis: PSV ≥230 cm/s, PSVr ≥2.2; 70% stenosis: PSV ≥340 cm/s, PSVr ≥3.0)
   • Monophasic post-stenotic waveforms
   • Flow reversal in the ipsilateral vertebral artery (present in >90% of patients with ≥50% stenosis) 1

2. Advanced imaging:

   • CT angiography (CTA) or MR angiography (MRA) of the aortic arch to identify and characterize subclavian artery stenosis 1, 3

Management

Conservative Management

• Most asymptomatic patients with subclavian steal phenomenon require no specific intervention 1, 2
• Secondary prevention strategies for atherosclerosis:
  • Antiplatelet therapy (aspirin 75-325 mg daily)
  • Aggressive cardiovascular risk factor modification
  • Lipid-lowering therapy aiming at >50% LDL-C reduction 1, 3

Indications for Revascularization

1. Symptomatic patients with:

   • TIA/stroke
   • Coronary subclavian steal syndrome
   • Ipsilateral hemodialysis access dysfunction
   • Severe upper extremity ischemia 1

2. Asymptomatic patients:

   • When the ipsilateral internal mammary artery is required for myocardial revascularization 1, 3
   • Cases of ipsilateral hemodialysis arteriovenous access 1

3. Routine revascularization in asymptomatic patients is NOT recommended 1

Revascularization Options

1. Endovascular approach:

   • Angioplasty with or without stenting
   • Lower complication rates compared to surgery
   • Primary patency rates: 93% at 1 year, 70% at 5 years 1, 3

2. Surgical options:

   • Carotid-subclavian bypass
   • Subclavian-carotid arterial transposition
   • Excellent long-term patency rates: 100% at 1 year, 96% at 5 years 3

Post-Revascularization Management

• Antiplatelet therapy:
  • After surgical bypass: long-term aspirin
  • After endovascular stenting: dual antiplatelet therapy for at least 30 days 1, 3
• Regular follow-up with serial noninvasive imaging at 1 month, 6 months, and annually 3

Clinical Pearls and Pitfalls

Important Considerations

• Most cases of subclavian steal are asymptomatic (subclavian steal phenomenon) and do not require intervention 1, 2
• Symptoms typically occur only during arm exercise, which increases demand for blood flow 2, 4
• The severity of symptoms correlates with the degree of blood pressure difference between arms 2

Common Pitfalls

• Failing to measure bilateral arm blood pressures in patients with unexplained vertebrobasilar symptoms
• Attributing isolated dizziness or vertigo to other causes without considering vascular etiologies 5
• Unnecessary revascularization in asymptomatic patients 1
• Overlooking subclavian steal syndrome in patients undergoing coronary bypass with internal mammary artery grafts 1, 3