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Subclavian steal and vertebral artery disease

Stenosis or occlusion of the subclavian artery before the origin of the vertebral artery causes reversed flow in the vertebral artery ("steal"); most patients are asymptomatic and are found by an inter-arm blood pressure difference, and treatment is given only for symptoms — arm claudication, posterior circulation symptoms, or angina in a patient with a LIMA bypass — usually with a stent.

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Why it matters in the exam

The left subclavian artery is affected more than the right. When the stenosis is proximal to the vertebral origin, arm pressure is low, and blood is "stolen" from the brain: it rises in the opposite vertebral artery and descends in the vertebral artery of the affected side to the arm. Most patients feel nothing, and the leading finding is a difference in systolic blood pressure between the arms — a difference of more than 15 mmHg is considered significant — and a weak pulse in one arm. Measuring blood pressure in both arms also matters so as not to miss hypertension (measure in the arm with the higher pressure). Possible symptoms: arm claudication and fatigue on exertion, and dizziness, visual disturbance or syncope during arm activity (posterior circulation symptoms). Duplex shows reversed vertebral flow, and CTA or MRA shows the stenosis.

A special and dangerous situation is "coronary-subclavian steal" in a patient after coronary bypass with the left internal thoracic artery (LIMA): stenosis of the left subclavian artery before the LIMA origin causes angina or myocardial ischaemia, sometimes when the patient uses the arm. So before a LIMA bypass the inter-arm pressure difference is checked and significant stenosis is treated, and before TEVAR covering the left subclavian origin, it is revascularised in a dependent patient. Treatment: an asymptomatic patient — best medical therapy only (antiplatelet, statin, risk factor control). A symptomatic patient — a stent in the stenosis as first choice; for a long occlusion or failure — carotid-subclavian bypass or subclavian-to-carotid transposition, with durable results. In disease of the vertebral artery itself treatment is first medical, and stenting is kept for patients with recurrent symptoms despite optimal therapy, because randomised trials showed no clear benefit of stenting.

An inter-arm pressure difference is also a marker of increased cardiovascular risk, so such a patient needs a global risk assessment.

Key points

• Reversed flow in the vertebral artery.
• Pressure difference above 15 mmHg.
• No symptoms — medical therapy.
• Symptoms — stent; long occlusion — bypass or transposition.
• LIMA — check before bypass and suspect with angina.

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Sources

• ESVS Clinical Practice Guidelines on the Management of Atherosclerotic Carotid and Vertebral Artery Disease, 2023 — Vertebral and subclavian artery disease
• ESC Guidelines for the management of peripheral arterial and aortic diseases, 2024 — Upper extremity artery disease
• Rutherford's Vascular Surgery and Endovascular Therapy, 10th edition (2022) — Upper extremity arterial disease and subclavian steal

Sources are given for further reading; the text is written afresh and not copied from them.

Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.