Reversal of vertebral artery blood flow demonstrated by Doppler ultrasound.

Vertebral artery blood flow was studied by a Doppler ultrasound technique in two patients with the subclavian steal syndrome. The Doppler probe was positioned in the region of the Chassaignac tubercle. The direction of vertebral artery flow corresponded with the angiographic flow direction preoperatively. Postoperatively, the technique was used to confirm the patency of a carotid-subclavian graft, and also to study the hemodynamic effects of axillary-axillary grafting. Reversal of vertebral flow direction was easily demonstrated by this technique, which is simpler to perform than previously described methods.