In presence of subclavian artery (SCA) steno-occlusion proximal to the origin of the vertebral artery (VA), the most important natural by-pass is represented by the ipsilateral VA: the blood is stolen by the VA from the contralateral VA (SCA steal phenomenon). This is a compensatory mechanism to increase flow to the affected extremity.
The SCA steal is a graded system showing a progressive change in the ipsilateral VA waveform: in the grade I lesions the VA flow is antegrade (with a diminished peak systolic velocity), while in the grade II lesions the VA waveform is bidirectional, and in the grade III lesions the VA waveform is completely retrograde, regardless of cardiac contractility.
While the SCA steal without a pathologic flow in the basilar artery (BA) seems only a marker of generalized atherosclerosis, the SCA steal with pathologic flow in the BA (post-stenotic, bidirectional or reverse flow) may be associated with a high risk of developing cerebrovascular accidents.
In this lesson the ultrasound parameters of the SCA with and without BA pathology are presented.
Franco Accorsi, MD
Member of the Order of Physician of Bologna n° 6728
I am a specialist in Medical Angiology and I am based in Bologna, Italy. Until 2008 (voluntary resignation) I worked at Maggiore Hospital in Bologna as "Dirigente Medico" in the Department of Internal Medicine and as Angiologist in the Angiology Unit with a position of "Alta Professionalità" in "Vascular Ecography and Angiology".
I am currently working in Bologna as an independent professional in the areas of angiology and vascular diagnostics.
I have been a speaker at national and international courses/congress and I have taught duplex ultrasound method in GIUV and SIUMB courses at the Maggiore Hospital, Bologna and courses of echocolor Doppler of extracranial and intracranial arteries at the Stroke Unit of S. Maria Nuova Hospital, Reggio Emilia.