What is subclavian stenosis?

Subclavian Stenosis: Definition and Clinical Implications

Subclavian stenosis is a narrowing of the subclavian artery, most commonly caused by atherosclerosis, that can lead to reduced blood flow to the arm and potentially cause vertebrobasilar insufficiency through subclavian steal syndrome when the stenosis is severe enough to reverse flow in the vertebral artery.

Definition and Pathophysiology

Subclavian stenosis primarily affects the proximal portion of the subclavian artery, which is the most common location for atherosclerotic lesions in the upper extremities 1. The condition is characterized by:

• Narrowing of the subclavian artery lumen, typically due to atherosclerotic plaque
• Reduced blood flow to the affected upper extremity
• Potential for flow reversal in the ipsilateral vertebral artery (subclavian steal phenomenon)

Epidemiology

• Prevalence of asymptomatic subclavian stenosis is approximately 4.5% in adults (5.1% in males, 3.9% in females) 1
• More frequent in patients with peripheral arterial disease (11.4%) 1
• Left-sided subclavian stenosis is four times more common than right-sided 2

Clinical Presentation

Subclavian stenosis may present with various clinical manifestations:

1. Asymptomatic presentation:

   • Often detected incidentally
   • Inter-arm systolic blood pressure difference >10-15 mmHg is highly suspicious 1
   • A difference ≥15 mmHg is highly indicative of subclavian stenosis 1

2. Upper extremity symptoms:

   • Arm claudication (crampy pain on exertion)
   • Exercise-induced fatigue
   • Paresthesia
   • In severe cases with distal disease: rest pain and digital ischemia with gangrene 1

3. Subclavian steal syndrome:

   • Occurs when flow reversal in the vertebral artery causes vertebrobasilar insufficiency
   • Symptoms include dizziness, vertigo, blurred vision, alternating hemiparesis, dysphasia, dysarthria, confusion, loss of consciousness, drop attacks, ataxia, and sensory/visual disturbances 1, 3
   • Symptoms typically worsen with arm exercise 1

4. Coronary subclavian steal syndrome:

   • In patients with coronary bypass using internal mammary artery
   • Myocardial ischemia occurs when blood is diverted from coronary circulation to the upper limb 1

Diagnosis

Clinical Examination

• Bilateral blood pressure measurement (recommended for all patients) 1
• Assessment of axillary, brachial, radial, and ulnar artery pulses
• Auscultation for periclavicular or infraclavicular bruits 1
• Allen test in patients requiring radial artery instrumentation 1

Diagnostic Studies

1. Duplex ultrasonography:

   • Can differentiate occlusion from stenosis
   • Determines direction of vertebral blood flow
   • Identifies high-velocity flows in stenotic areas (50% stenosis: PSV ≥230 cm/s; 70% stenosis: PSV ≥340 cm/s) 1
   • May detect flow reversal in vertebral artery 1

2. CT Angiography or MR Angiography:

   • Provides detailed imaging of the subclavian artery and surrounding vessels
   • Helps identify the exact location and severity of stenosis 1

Management

Medical Management

• All patients should receive optimal cardiovascular risk factor modification
• Antiplatelet therapy is recommended

Revascularization

Revascularization is indicated in specific situations:

Recommended for:

• Symptomatic patients with TIA/stroke 1
• Coronary subclavian steal syndrome 1
• Ipsilateral hemodialysis access dysfunction 1
• Severe upper extremity ischemia 1
• Proximal stenosis in patients undergoing CABG using ipsilateral internal mammary artery 1

Not recommended for:

• Asymptomatic patients, regardless of stenosis severity 1
• Routine revascularization in atherosclerotic subclavian artery disease 1

Revascularization Options

1. Endovascular treatment:

   • Preferred over surgery due to lower complication rates 1
   • Options include balloon angioplasty with or without stenting
   • High technical success rates with good long-term patency 4, 2

2. Surgical options:

   • Extra-anatomic bypass (carotid-subclavian, carotid-axillary, or axillo-axillary)
   • Subclavian-carotid arterial transposition
   • Transsubclavian vertebral endarterectomy 1

Prognosis

• Generally favorable prognosis for subclavian stenosis 1
• Some patients with high-grade stenosis and mild upper-extremity claudication become asymptomatic as collateral circulation develops 1
• After endovascular treatment, restenosis occurs in approximately 26% of cases after a mean of 12 months 1
• Five-year patency after stenting approaches 97% 1

Follow-up

• All patients with subclavian artery disease should be followed for optimal cardiovascular prevention
• Tighter follow-up is required for symptomatic patients
• Post-revascularization follow-up is essential to detect and treat impending late procedural failure 1