Subclavian steal with severe carotid stenosis

Case contributed by Dr Michael P Hartung


Carotid bruit

Patient Data

Age: 70
Gender: Male

Diminished velocities with tardus parvus waveforms in the right common and internal carotid arteries, with reversal of diastolic flow in the common carotid artery. This suggests high-grade proximal narrowing.

Left internal carotid artery: 70% stenosis to near occlusion. Peak systolic velocity 548 cm/s.

Vertebral arteries: Intermittent reversal of flow of the right vertebral artery, which can be seen in the setting of subclavian steal. This is supported by the tardus parvus waveform within the right common and internal carotid arteries and reversal of flow in the right common carotid artery, suggesting that narrowing is at the level of the brachiocephalic artery. Normal velocities with tardus parvus waveform of the left vertebral artery. 

CT angiography of the neck is recommended for full characterization. Vascular surgery consultation is also recommended for further management in this high-risk patient.     

No contrast opacification of the proximal innominate artery measuring approximately 2.7 cm in length. Reconstitution of flow distally just prior to the bifurcation into the subclavian and right common carotid artery. There is delayed enhancement of these arterial vessels, likely related to a combination of high-grade stenosis/occlusion and retrograde flow through collateral vessels secondary to steal phenomenon.

High-grade stenosis of left common carotid artery is estimated at 65-70%. Atherosclerotic stenosis involving the left subclavian artery just proximal to the vertebral artery origin is estimated at approximately 90%.

Dense atherosclerotic calcification of the carotid bulbs and bifurcations bilaterally with estimated stenosis measuring 65-70% on the right and approximately 60% on the left.

Delayed contrast enhancement of the diminutive right vertebral artery with dense atherosclerotic calcification at its origin likely related to reversal of flow due to steal phenomenon.

Bulky plaque narrowing the origin of the left vertebral artery. 


Case Discussion

This is a very complicated case, but contains illustrates many important vascular ultrasound concepts which were subsequently confirmed with CT angiography.

Regarding the ultrasound, key findings include:

  • tardus parvus waveforms with diminished velocities of the right common and internal carotid arteries, indicating proximal stenosis.
  • intermittent reversal diastolic flow in the common carotid artery (in this setting, hemodynamically significant stenosis of the internal carotid artery cannot be reliably commented on)
  • diminished velocities of the right vertebral artery with intermittent flow reversal
  • severely elevated velocities of the left internal carotid artery, which is likely a combination of stenosis and compensatory flow given the proximal right narrowing
  • tardus parvus configuration of the left vertebral artery, suggesting proximal narrowing

Regarding the CTA findings, key findings include:

  • segmental occlusion/near occlusion of the right brachiocephalic artery
  • diminished contrast enhancement within the right subclavian, common and internal carotid, and vertebral arteries (this is due to the delayed, retrograde opacification from the left circulation/steal phenomenon)
  • high-grade narrowing of the left internal carotid artery and proximal left vertebral arteries, placing this patient at very high risk for catastrophic cerebral vascular insult
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Case information

rID: 59552
Published: 14th Apr 2018
Last edited: 16th Apr 2018
System: Vascular
Inclusion in quiz mode: Included

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