Journal of Ultrasound in Medicine, Vol 9, Issue 4 207-213, Copyright © 1990 by American Institute of Ultrasound in Medicine
Doppler diagnosis of partial vertebral/subclavian steals convertible to full steals with physiologic maneuvers
P. S. Kotval, S. C. Babu and P. M. Shah
Department of Radiology, New York Medical College, Valhalla.
Subclavian steal syndrome has been classically described as a
unidirectional phenomenon in which retrograde flow occurs in the
ipsilateral vertebral artery in cases of high-grade proximal subclavian
stenosis. Pulsed Doppler examination in cases of subclavian stenosis shows
that partial steals with to-and-fro flow do occur. A model based on
fluctuating pressure gradients to explain the partial steal phenomenon is
discussed. The usefulness of physiologic maneuvers such as ipsilateral arm
exercise and postocclusive hyperemia in converting partial steals to full
steals is demonstrated. In cases in which surgical bypass to correct
partial steals is carried out, a relative steal can be demonstrated by
Doppler examination before and after physiologic maneuvers.