Subclavian and Vertebral Artery Stenosis

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.

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