Subclavian steal syndrome

Overview

Subclavian steal syndrome (SSS) is a vascular condition in which blood flow is reversed in the vertebral artery due to significant narrowing or occlusion of the proximal subclavian artery. This reversal “steals” blood from the posterior cerebral circulation, diverting it to supply the affected arm. The syndrome can lead to symptoms related to cerebral ischemia as well as arm ischemia.

SSS is an uncommon but important cause of vertebrobasilar insufficiency and upper limb ischemic symptoms. It often affects middle-aged or older adults with atherosclerotic disease but can also occur due to other vascular pathologies.

Causes

The main cause of subclavian steal syndrome is stenosis or occlusion of the proximal subclavian artery, proximal to the origin of the vertebral artery. Common causes include:

• Atherosclerosis: The most frequent cause, leading to plaque buildup and narrowing of the subclavian artery.

• Takayasu arteritis: A chronic inflammatory condition affecting large arteries, especially in younger patients.

• Radiation-induced arterial injury: Previous chest or neck radiation therapy may damage the vessel walls.

• Congenital vascular anomalies or trauma: Rarely cause subclavian artery obstruction.

Symptoms

Symptoms arise from insufficient blood flow to the brain or the arm and may vary based on the severity of the occlusion and collateral circulation:

Neurological Symptoms (Vertebrobasilar Insufficiency)

• Dizziness or vertigo

• Syncope or near-fainting episodes

• Visual disturbances such as diplopia or blurred vision

• Ataxia and balance problems

• Drop attacks (sudden falls without loss of consciousness)

• Headache and confusion in severe cases

Arm Ischemic Symptoms

• Claudication or pain in the affected arm during exertion

• Weakness or fatigue of the arm

• Coolness, numbness, or paresthesia of the hand or fingers

• Blood pressure discrepancy between arms (lower on the affected side)

Diagnosis

Diagnosis of subclavian steal syndrome involves a combination of clinical examination and imaging studies:

• Physical exam: Detection of blood pressure difference between arms (>15-20 mmHg), diminished pulses, and neurological assessment.

• Doppler ultrasound: Non-invasive evaluation showing reversed vertebral artery flow on the affected side.

• CT angiography (CTA) or MR angiography (MRA): Visualization of subclavian artery stenosis and collateral circulation.

• Conventional angiography: Considered the gold standard for diagnosis and used when intervention is planned.

• Additional tests: ECG and echocardiography to rule out cardiac causes of symptoms.

Treatment

Treatment depends on symptom severity and underlying cause, ranging from conservative management to surgical intervention:

Conservative Management

• Risk factor modification: controlling hypertension, diabetes, hyperlipidemia, and smoking cessation

• Antiplatelet therapy (e.g., aspirin) to reduce thrombotic risk

• Physical therapy for mild arm symptoms

Endovascular Treatment

• Percutaneous transluminal angioplasty with or without stenting to restore subclavian artery patency

• Minimally invasive and often preferred for suitable lesions

Surgical Treatment

• Bypass grafting (e.g., carotid-subclavian bypass)

• Endarterectomy of the subclavian artery

• Reserved for cases unsuitable for endovascular therapy or with recurrent symptoms

Prognosis

The prognosis of subclavian steal syndrome is generally good with appropriate treatment. Many patients experience symptom relief after revascularization. Untreated, the syndrome can lead to recurrent neurological events and progressive arm ischemia.

Regular follow-up is important to monitor for restenosis or progression of atherosclerosis. Early recognition and management improve quality of life and reduce the risk of stroke and limb complications.