"The subclavian steal" is a retrograde flow of blood from the vertebral-basilar system into the subclavian artery. The vertebral arteries participate in the collateral circulation around the first portion of the subclavian artery. This syndrome occurs when the first portion of the subclavian artery is occluded. The blood pressure in the distal subclavian artery is decreased to the point where it is lower than the pressure in the vertebral-basilar system and therefore blood flows in a retrograde fashion.
This paper is a report of two cases of occlusion of the right subclavian artery proximal to the origin of the vertebral artery. One patient exhibited a reversal of blood flow so as to siphon blood from the brain to the arm. The second patient demonstrated a similar anatomic picture but not the retrograde vertebral artery flow. Both patients were studied by arteriograms and treated by reconstituting the blood flow to the
PARROTT JC. The Subclavian Steal Syndrome. Arch Surg. 1964;88(4):661-665. doi:10.1001/archsurg.1964.01310220151023