Reversed Vertebral Artery Flow

Abstract

It has been demonstrated that the direction of blood flow through the vertebral artery can be reversed by stenosing or occluding the subclavian artery proximal to the subclavian-vertebral junction. This was observed first in man as a result of naturally occurring disease¹ and has been produced experimentally in animals.² In man it has been designated brachial-basilar insufficiency³ or the "Subclavian Steal,"⁶ but for animals a more appropriate term would be reversed vertebral artery flow. In this syndrome blood from the opposite vertebral, the basilar, and probably the external caroticovertebral and segmental vertebrovertebral anastomotic circulations is diverted into one vertebral artery and shunts distally to the limb (Fig 1). This shunt may be asymptomatic but has been observed to be associated with signs and symptoms of cerebral vascular insufficiency and with intermittent claudication of the limb during exercise. It seemed to us that fluctuations in systemic blood