What are the symptoms and management of subclavian steal syndrome?

Symptoms and Management of Subclavian Steal Syndrome

Subclavian steal syndrome occurs when proximal subclavian artery stenosis or occlusion causes retrograde blood flow in the ipsilateral vertebral artery, leading to posterior cerebral circulatory insufficiency and upper extremity symptoms. 1, 2

Clinical Presentation

Neurological Symptoms (Vertebrobasilar Insufficiency)

• Dizziness, lightheadedness, and syncope 1
• Vertigo and ataxia 1, 2
• Visual disturbances including blurred vision and diplopia 1, 2
• Dysphasia and dysarthria 1, 2
• Alternating hemiparesis and motor deficits 2, 3
• Confusion and loss of consciousness 2, 4
• Drop attacks 4, 5
• Facial sensory deficits 1

Upper Extremity Symptoms

• Arm claudication (exercise-induced crampy pain and fatigue in the affected arm) 1
• Muscular fatigue in the affected arm 1, 4
• Paresthesia 1
• In severe cases, rest pain and digital ischemia with potential gangrene 1

Cardiac Symptoms

• Myocardial ischemia (coronary-subclavian steal) in patients with coronary bypass using the internal mammary artery 1, 4, 6

Key Clinical Feature

• Symptoms typically worsen with exercise of the ipsilateral arm, which amplifies flow reversal 1

Diagnostic Findings

Physical Examination

• Asymmetrical blood pressure between arms (difference of >15 mmHg is highly suspicious for subclavian stenosis) 1, 2
• Periclavicular or infraclavicular bruit 1, 4
• Decreased or absent pulses in the affected arm 1, 4
• Blood pressure tends to fall further in the affected limb after arm exercise 1

Diagnostic Testing

• Duplex ultrasonography: identifies reversal of flow in the vertebral artery 1
  • Intrastenotic high-velocity flows (50% stenosis: peak systolic velocity ≥230 cm/s) 1, 4
  • Monophasic post-stenotic waveforms 1, 4
• CT angiography or MR angiography: definitive identification of stenosis of the subclavian artery 1
• Dynamic examination with cuff compression of the upper arm can demonstrate vertebral flow direction changes 1

Management

Conservative Management

• For asymptomatic patients: no specific intervention needed other than secondary prevention strategies for systemic atherosclerosis 1
• Bilateral arm blood pressure measurement for all patients with peripheral arterial disease 1, 4

Indications for Revascularization

• Symptomatic ischemia involving upper-extremity claudication 1
• Recurrent vertebrobasilar symptoms despite optimal medical management 1
• When the ipsilateral internal mammary artery is required for coronary bypass 1
• Ipsilateral hemodialysis arteriovenous access dysfunction 1

Revascularization Options

• Endovascular treatment (angioplasty ± stenting): may be preferred due to lower complication rates despite similar long-term outcomes 1, 4
• Surgical options (carotid-subclavian bypass): excellent long-term patency (96-100% at 5 years) 4, 5

Important Considerations

Risk Factors

• Higher prevalence in patients with peripheral arterial disease (11.4% vs. 4.5% in general population) 1, 4
• Atherosclerosis is the most common cause, but other etiologies include Takayasu arteritis, giant cell arteritis, fibromuscular dysplasia, and radiation-induced arteriopathy 1

Prognosis

• Generally favorable prognosis for subclavian artery stenosis 1
• Many patients with high-grade stenosis and mild upper-extremity claudication become asymptomatic as collateral blood supply develops 1
• Not all patients with flow reversal in the vertebral artery will be symptomatic (>90% of patients with at least 50% proximal subclavian stenosis have flow reversal, but many remain asymptomatic) 1, 4

Common Pitfalls

• Bilateral subclavian disease may not present with asymmetrical blood pressures 1
• Vertebrobasilar insufficiency can have numerous other causes that mimic subclavian steal syndrome symptoms 1
• An inter-arm systolic blood pressure difference >25 mmHg doubles prevalence and independently predicts mortality 4