Subclavian Steal

Subclavian steal refers to the phenomenon where retrograde flow of vertebral artery occurs to supply distal subclavian in cases of proximal subclavian stenosis or occlusion. This can give rise to syncope and neurological deficits due to blood flow "stolen" from posterior circulation, as well as blood pressure differential in arms.

Subclavian Steal Syndrome: The result of occlusion or stenosis of the subclavian artery proximal to the origin of the vertebral artery. This leads to retrograde flow in the vertebral arteries and possible concomitant neurological symptoms resulting from cerebral ischemia. However subclavian steal is often asymptomatic and may not require aggressive treatment. Lesions are 3:1 more common on the left side versus the right.

Risk Factors: Smoking, Hypertension, Family History of Vascular Disease, Diabetes, Hyperlipidemia, and Takayasu’s arteritis.

Symptoms: A provoking event, usually exercising of the upper limb on the ipsalateral side, is often linked to the symptoms and this effect is often reproducible. Patients may report various symptoms related to ischemia of the vertebrobasilar or posterior circulations. Such symptoms may include but are not limited to: vertigo, dizziness, visual loss, ataxia, sensory hemianaesthesia, syncope, and arm claudication.

Signs: Reduced blood pressure of >15mm Hg in the ipsilateral arm. Auscultation of the carotid artery may reveal a bruit.

Differential Includes: Atherosclerosis, Temporal Arteritis, Takayasu’s Arteritis, Aortic Dissection, Multiple Sclerosis, Seizures, Cardiac Arrhythmias.

Investigations: Continuous wave Doppler or Duplex Ultrasonography is usually the first investigation and will demonstrate retrograde flow through the vertebral artery. Other noninvasive investigations include MRI, MRA, and CT angiography

Management: Several treatments exist including angioplasty, carotid subclavian bypass, carotid subclavian transposition, axilloaxillary bypass, carotid endartectomy, and subclavian arterectomy.

Case #1. TRICKS angiogram of patient with Takayasu's arteritis: absence of opacification of  occluded proximal left subclavian, with distal subclavian being supplied by the left vertebral. Note also stenosis of the descending aorta. Takayasu's is a large artery granulomatous vasculitis.