In the hemodynamic stenosis of the subclavian artery (SCA) a significantly elevated velocity is present, with change of the waveform from the normal triphasic to monophasic appearance.
The hemodynamic stenosis of the SCA proximal to the vertebral artery (VA) origin may cause characteristic changes in the ipsilateral VA waveform: a mild to moderate SCA stenosis may cause, in the ipsilateral VA, characteristics waveforms with antegrade or bidirectional flow, while, in case of severe proximal SCA disease, a complete reversal of ipsilateral VA flow appears. In case of occlusion, or high grade pre-vertebral SCA stenosis, a completely retrograde waveform in the VA is present.
The VA stenosis may be distinguished by the detection of focal velocities > 100 cm/s. accompanied by disturbed flow in the more distal segment of the VA.
The absence of color/flow in the VA is suggestive of occlusion: in this case the distal VA recanalization is possible for the activation of collateral circulation. A tardus parvus distal VA waveform is suggestive of significant proximal VA stenosis or occlusion
In this lesson the ultrasound parameters of the SCA and VA stenosis 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.