Indications and Patient Selection

There is irrefutable evidence that for certain patient populations CEA offers an advantage over best medical treatment (BMT) alone. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) generated prospective, randomized data demonstrating symptomatic patients with carotid stenosis greater than 70% and a perioperative stroke or death rate below 6% are best treated by CEA over BMT alone.^13,14 The Veterans Affairs Cooperative Studies Program (VACSP) also found a beneficial effect of CEA when compared to BMT.¹⁵ The Asymptomatic Carotid Atherosclerosis Study (ACAS) proved asymptomatic patients with carotid stenosis of greater than 60% could benefit from CEA with a reduction in 5-year ipsilateral stroke risk, provided that their perioperative stroke or death rate was less than 3% and their modifiable risk factors were aggressively treated.¹⁶ Based on the preceding results, the Stroke Council of the American Heart Association has published guidelines and indications for CEA.¹⁷ However, these key trials excluded patients deemed to be high risk for CEA. The initial indications for CAS were some of the key exclusion criteria from NASCET, VACSP, and ACAS, including restenosis after CEA, contralateral internal carotid artery (ICA) occlusion, previous neck irradiation, advanced age, renal failure, chronic obstructive pulmonary disease, and severe cardiopulmonary disease. The increasing use of CAS has led investigators to question whether either revascularization procedure is more beneficial over the other. Over the last 10 years, multiple studies have attempted to answer that question; however, variability in study design, technology used, and patient selection have made a comparison between CAS and CEA difficult.^12,18–22 It is beyond the scope of this chapter to detail individual study design flaws, results, and criticisms; however, several study trials have helped influence patient selection for CAS in my practice. The trial that led to U.S. Food and Drug Administration approval for CAS was the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE). The SAPPHIRE study led to a general sense that CAS was at least equivalent to CEA in high-risk patients. SAPPHIRE 30-day myocardial infarction (MI), stroke, and death rates were 4.8% in the CAS arm versus 9.8% in the CEA arm (P = 0.09).¹² One-year MI, ipsilateral stroke, and death rates were 12.2% in CAS versus 20.1% in CEA (P = 0.048). The 3-year incidence of stroke was 7% for both CAS and CEA. The Carotid Revascularization Endarterectomy versus Stenting Trial (CREST) randomized 1326 symptomatic and 1196 asymptomatic patients to CAS or CEA with a median follow-up period of 2.5 years. This study recently concluded that among patients with symptomatic or asymptomatic carotid stenosis, the risk of the composite primary outcome of stroke, MI, or death did not differ significantly in the groups treated by CAS from those treated by CEA.¹⁸ This study did find a higher risk of periprocedural stroke with stenting (4.1% vs. 2.3%, P = 0.01) and periprocedural MI with endarterectomy (1.1% vs. 2.3%, P = 0.03). Further, quality-of-life analyses among survivors at 1 year indicated that stroke had a greater adverse effect than did MI on a range of health-status domains. It is the current practice of my colleagues and I to offer CAS to asymptomatic or symptomatic patients who would benefit from CEA but are deemed to be too high a surgical risk for CEA.

Preoperative Preparation

All patients in our surgical practice undergoing CAS are reported in ongoing clinical registries. Pretreatment patient evaluation consists of a noninvasive study suggesting carotid stenosis and a neurologic assessment performed by a neurologist or neurosurgeon. On the day of the procedure, the patient’s National Institutes of Health Stroke Scale is assessed and recorded. Preoperative laboratory results include hematocrit, hemoglobin, platelet count, white blood cell count, serum creatinine, prothrombin time, and activated partial prothrombin time obtained within a week of intervention. My colleagues and I also routinely obtain a baseline 12-lead electrocardiogram. Further cardiac or pulmonary evaluation is performed case by case as deemed medically necessary. MI is always a primary or secondary endpoint for clinical trials; thus, postprocedure creatine kinase, creatine kinase-MB, and troponin-I levels are routinely collected the morning after the procedure. All patients have a baseline brain computed tomography or magnetic resonance imaging to document preexisting infarctions.

In our practice, all patients considered for CAS are started on aspirin at a dosage of 325 mg daily at least 5 days prior to the procedure. My colleagues and I also start clopidogrel at least 24 hours prior to the procedure but preferably 3 to 5 days prior to intervention. Clopidogrel is loaded as a 300-mg dose the day before or 75 mg daily 5 days prior to intervention. Some evidence suggests the combination of aspirin and clopidogrel decreases restenosis by inhibiting myointimal proliferation.^23–25 In emergent cases in which patients are not pretreated, patients are loaded the day of surgery with aspirin at 325 mg and clopidogrel at 300 mg. After the angiogram is completed and the determination to proceed with CAS is made, 4000 U of heparin is administered intravenously and redosed at 1000 U every hour until completion of the stenting procedure. Although not a standard of care, many surgeons check activated coagulation times with the practice of anticoagulating to achieve the goal of doubling these times.

Anesthesia and Intraoperative Monitoring

CAS can be performed under monitored anesthesia care (MAC) or conscious sedation in the majority of cases, with only the rare need to convert to general endotracheal anesthesia. In my practice, my colleagues and I have not needed to convert to general anesthesia in any case. MAC allows us to monitor the patient’s neurologic status throughout the case; thus, we have not found the need to use other physiologic monitoring, such as electroencephalogram or intraoperative transcranial Doppler. MAC is also preferable because many candidates we evaluate for CAS are high-risk surgical patients due to an underlying cardiopulmonary disease rather than an anatomic consideration. The decision on arterial line blood pressure monitoring is based on the patient’s cardiopulmonary status, but all arterial lines are removed immediately after the procedure.

Procedure