The subclavian steal syndrome is cerebral or brain stem ischaemia that results from diversion of blood flow from the basilar artery to the subclavian artery. This is due to occlusive disease of either the subclavian artery or the innominate artery before they branch off at the vertebral artery. It is very rare.
In the patient with subclavian steal syndrome the subclavian artery is fed by retrograde flow from the vertebral artery via the carotids and the circle of Willis.
Haemodynamic stability is possible until there is excessive demand in the upper limb. In this situation blood is 'stolen' - diverted - from the cerebral circulation resulting in transient cerebral ischaemia. This may be suspected clinically by the absence of a pulse or by a difference in blood pressure (> 20 mm Hg) between the two arms. Vertigo and syncope may result.
The condition is often demonstrated incidentally by Doppler or angiography.
Treatment is by surgical reconstruction or bypass of the subclavian artery.
Last reviewed 01/2018