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6 — Ultrasound Following Surgery and Intervention
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be indicated with further workup before velocities reach the PSV threshold for a high-grade stenosis.
For CAS, Armstrong et al. uses a schedule simi- lar to CEA with 6-month surveillance for the first 18 months.24 Patients are then monitored annually if, by velocity criteria, they have less than a 50%
stenosis. Patients will remain on a 6-month interval if they have lesions greater than 50% on the CAS side or on the contralateral side. Should the lesions become symptomatic on either side or the disease on either side progress asymptomatically to the high- grade lesion, they are considered for intervention.
SUMMARY
Issues associated with CEA and CAS remain in flux. CEA remains the traditional approach toward treating the bifurcation lesion and, although new techniques are evolving, its issues are relatively stable. Issues in CAS are poorly defined but given recent findings in CAS, the vascular sonographer should anticipate the volume of CAS to increase, possibly at the expense of CEA. It is important for vascular sonographers to recognize that significant differences exist in the duplex evaluation of CEA and CAS patients seen in follow-up. They should also recognize that the results of diligent post-CAS surveillance will determine the future of CAS. Duplex ultrasound will be the most important way of characterizing the behavior of this implanted device over time.
Critical Thinking Questions
1. You are asked to do a carotid ultrasound in the recovery room on a patient who just underwent a CEA. What approach would you use to image the CEA site and why?
2. You perform an ultrasound examination on a patient who is 2 weeks post- CEA. You observe echogenic material along the wall of the vessel with color aliasing and elevated velocities. What is the most likely cause of the stenosis?
3. When scanning patients who have had a CAS or CEA, will either patient group present a problem with acoustic shadowing and why?
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