Treatment of Recurrent Carotid Artery Stenosis After Percutaneous Angioplasty and Stenting



Treatment of Recurrent Carotid Artery Stenosis After Percutaneous Angioplasty and Stenting



Brajesh K. Lal and Jon S. Matsumura


Carotid endarterectomy (CEA) has been proved effective at reducing the risk of stroke in large-scale landmark clinical trials. These randomized trials have established indications for CEA in selected patients with symptomatic stenosis of 50% or more and asymptomatic stenosis of 60% or more. The emergence of carotid artery stenting (CAS) has been accompanied by much deliberation. Carotid artery stenting has become an alternative to reoperation in the management of carotid restenosis after prior CEA. This approach is also recommended in the management of other subgroups of patients with carotid stenosis, including patients with significant medical comorbidities, anatomically inaccessible lesions above C2, and radiation-induced stenoses. Endovascular management of these high-risk subsets is based on acceptable post-procedural complications as well as long-term outcomes.


Among many questions that arise in the evaluation of any new technology, there is specific concern about the durability of the carotid stent in the neck, where motion occurs in several dimensions. Although the final role of CAS in carotid revascularization continues to evolve on the basis of results of recently reported and other ongoing randomized, controlled trials, it is clear that stenting will continue to be performed in subgroups of patients with carotid stenoses. Therefore, it is anticipated that there will be a corresponding increase in in-stent restenosis (ISR) cases after CAS. Considerable controversy exists regarding the clinical significance, natural history, threshold for retreatment, and appropriate intervention of recurrent carotid stenosis after stenting.



Incidence


Coronary stenting is associated with significantly lower rates of angiographic and clinical restenosis than angioplasty alone. This salutary effect may be a result of the stent’s ability to provide predictably larger arterial lumens. However, myointimal hyperplasia accompanies virtually every stent placement in the coronary, iliac, or carotid system. Intimal hyperplastic recurrence has been observed after coronary stenting in 16% to 59% of cases and after iliac stenting in 13% to 39% of reported series. A valid concern has been that CAS could be associated with similarly high rates of ISR during follow-up. Most existing studies have relatively short follow-up periods, resulting in underreporting of ISR rates.


Life-table analysis provides specific information on ISR after CAS (Figure 1). Over a follow-up period of 1 to 74 months, only five patients demonstrated high-grade ISR (≥80%), and the projected 5-year recurrence rate for ISR of 80% or more was 6.4%. In the Carotid Revascularization, Endarterectomy versus Stent Trial (CREST), of the 1086 patients receiving CAS, only 58 patients developed 70% or greater ISR, for a 2-year recurrence rate of 6.0%. The Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial, Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS), Stent-Protected Angioplasty versus Carotid Endarterectomy (SPACE) study, and the Endarterectomy versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis (EVA-3S) trial, each reported similarly low recurrence rates ranging from 2.8% over 3 years to 10.5% over 5 years. Therefore, although ISR does not appear to occur at the high rates associated with bare-metal stenting of the coronary arteries, a substantial number of patients can be anticipated to progress to moderate and high-grade ISR.




Diagnosis


Duplex ultrasonography is the standard technique for following carotid stenosis patients treated with CEA or medical therapy alone. Ultrasound velocities correlate with angiographic percentage of stenosis in the native unstented carotid artery, and the appropriate threshold velocities signifying different degrees of stenoses have been intensively analyzed and identified. However, ultrasound velocity criteria have not been well established for patients undergoing CAS. In 2004, we reported that the placement of a stent altered the biomechanical properties of the carotid territory such that compliance was reduced. The enhanced stiffness of the stent–arterial wall complex rendered the flow–pressure relationship of the carotid artery closer to that observed in a rigid tube so that the energy normally applied to dilate the artery resulted in increased velocity. We therefore proposed revised velocity criteria to serve as guidelines for other vascular laboratories when studying stented carotid arteries (Table 1). These revised criteria have been confirmed by multiple single-institution studies and have also been used to measure ISR rates in randomized, controlled trials (EVA3S and CREST).


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Aug 25, 2016 | Posted by in CARDIOLOGY | Comments Off on Treatment of Recurrent Carotid Artery Stenosis After Percutaneous Angioplasty and Stenting

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