The use of carotid artery stenting to treat carotid bifurcation stenosis remains a topic of recent investigation and vigorous debate regarding safety and efficacy. Multiple prospective randomized controlled trials have compared carotid endarterectomy (CEA) with carotid artery stenting (CAS) and have shown comparable outcomes in asymptomatic patients. There are certain complications that are more frequent or specific to the use of closed versus open cell nitinol carotid artery stents. This chapter focuses on clinical evidence describing the complications as well as the clinical decision making and preoperative evaluation to limit these complications.
Complications following CAS with closed and open cell nitinol stents can be divided into periprocedural and late. Periprocedural complications include inability to cross the lesion with the stent, severe residual stenosis, and postprocedure stroke. Late complications include stent fracture and/or deformation, restenosis, and late stroke.
Inability to cross the carotid stenosis has multiple etiologies that include tortuous artic arch and a tortuous common carotid artery. The flexibility of the stent can be an important determinant in successfully negotiating tortuous vessels. In general, the open cell stents such as the PRECISE (Cordis, Hialeah, FL) and ACCULINK (Abbott Laboratories, Chicago, IL) are more flexible than the closed cell XACT stent and may cross tortuous aortic arch–carotid anatomy, which the XACT (Abbott Laboratories, Chicago, IL) may not successfully track despite the use of stiffer embolic protection delivery wires.
Residual stenosis following stent placement can usually be successfully treated with poststent balloon angioplasty. However, in certain critically stenotic lesions, especially in the presence of calcification of the carotid bifurcation, residual carotid stenosis can be a problem. The higher radial force of the closed cell XACT stent may be more resistant to compressive forces at the bifurcation when compared with open cell nitinol stents and may be beneficial in limiting residual stenosis.
Postprocedure stroke severity and timing during CAS may be related to stent design. Closed cell stents have a lower cell area compared with open cell stents and may provide better coverage of the atherosclerotic lesion ( Fig. 46.1 ). In a study by Cao and coworkers in which they reviewed 505 CAS procedures, all but one major stroke occurred during catheterization of the target vessel or crossing the lesion with the embolic protection device (EPD). No major strokes occurred in the postprocedure period. Thirteen of 16 minor strokes, however, occurred within 24 hours of the CAS procedure. Minor strokes following CAS are related to embolic material extruding through the stent architecture and subsequent embolization. Theoretically, an open cell stent has a higher chance of atheromatic plaque material extruding into the arterial lumen. Although controversial, there are data suggesting that stents with the lowest stent cell area are at lower risk of postprocedure stroke. The closed cell nitinol XACT stent has a lower cell surface area compared with the PRECISE and ACCULINK and in some studies has been shown to have a lower postprocedure incidence of stroke. However, there have been two large randomized trials comparing CAS with CEA: the CREST and ACT-1 trials. The ACCULINK open cell stent was used in the CREST Trial and the closed cell nitinol XACT stent was used in the ACT-1 Trial. In asymptomatic patients, the primary endpoint of 30-day stroke, death, myocardial infarction, and late stroke occurred in 5.6% of patients in the CREST trial compared with 3.8% of patients in the ACT-1 trial ( Table 46.1 ). The concept of improving coverage of the atherosclerotic plaque by lowering cell surface area has resulted in the ongoing development of stents with superimposed mesh on the stent framework to provide widespread coverage of the lesion and potentially limit postprocedure stroke.
|ACT-I: Primary endpoint||3.8%||3.4%||0.11|
|CREST: Primary endpoint||5.6%||4.9%||0.562|
|ACT-I: 30 days stroke, MI, death||3.3%||2.6%||0.60|
|CREST: 30 days stroke, MI, death||3.5%||3.6%||0.96|
|ACT-I: 30 days stroke, death||2.9%||1.7%||0.33|
|CREST: 30 days stroke, death||2.5%||1.4%||0.15|