The American Heart Association (AHA) has updated guidelines for carotid endarterectomy in patients with symptomatic and asymptomatic carotid stenosis. Developed by the 16-member Special Writing Group of the Stroke Council, the guidelines cover the following topics: management of risk factors, such as hypertension, cigarette smoking, serum lipid levels, alcohol consumption, postmenopausal estrogen use and antiplatelet therapy; treatment of asymptomatic and symptomatic carotid stenosis; and complications of surgery.
The first AHA guidelines for carotid endarterectomy were published in 1995; the panel members noted that only in the past five years have the indications for surgery been clarified by randomized studies. The recommendations in the guidelines are graded according to the rules of evidence used by the AHA (see the accompanying table). Reprints of “Guidelines for Carotid Endartectomy” may be obtained from the AHA, either by calling 800-242-8721 or writing Public Information, American Heart Association, 7272 Greenville Ave., Dallas, TX 75231. The guidelines are also available on the AHA Web site (http://www.amhrt.org).
|Level of evidence|
|Level I:||Data from randomized trials with low false-positive and low false-negative errors|
|Level II:||Data from randomized trials with high false-positive or high false-negative errors|
|Level III:||Data from randomized concurrent cohort studies|
|Level IV:||Data from randomized cohort studies using historical control|
|Level V:||Data from anecdotal case series|
|Strength of recommendations|
|Grade A:||Supported by Level I evidence|
|Grade B:||Supported by Level II evidence|
|Grade C:||Supported by Level III, IV or V evidence|
The following summarizes the recommendations in the guidelines.
Management of Risk Factors
Hypertension. The recommendations state that long-term care of patients who have undergone carotid endarterectomy should include careful control of hypertension (Grade A recommendation for the treatment of hypertension in general; Grade C recommendation for postendarterectomy care). In addition, careful monitoring of blood pressure is necessary immediately after carotid endarterectomy. The guidelines state that elevated blood pressure should be aggressively treated postoperatively, particularly if early symptoms of cerebral hyperperfusion syndrome occur (Grade C recommendation). Blood pressure should be monitored for several days after surgery in patients considered at risk of cerebral hyperperfusion syndrome and for seven days in patients with headaches or new neurologic symptoms. Monitoring can be performed on an outpatient basis (Grade C recommendation).
Smoking Cessation. The panel members noted that prospective studies have not been performed to assess the impact of smoking cessation after carotid endarterectomy, but postoperative care should include smoking cessation efforts (Grade C recommendation).
Lipid Levels. The recommendations specify that patients with carotid artery disease should be evaluated and treated according to the guidelines of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Grade A recommendation for carotid artery disease; Grade C recommendation for postendarterectomy care).
Alcohol Consumption. The guidelines state that heavy use of alcohol should be avoided (Grade C recommendation).
Postmenopausal Estrogen Therapy. According to the guidelines, data suggest that discontinuation of post-menopausal hormone therapy is not required after carotid endarterectomy (Grade B recommendation).
Antiplatelet Therapy. The guidelines point to data showing that antiplatelet therapy reduces the risk of stroke and other vascular events in high-risk patients (Grade A recommendation). While the panel noted that the role of antiplatelet therapy in reducing the perioperative and postoperative risk of stroke is unresolved, aspirin therapy before carotid endarterectomy is recommended in the absence of contraindications (Grade B recommendation). The optimal dose of aspirin is not known.
Asymptomatic Carotid Stenosis
According to the guidelines, the Asymptomatic Carotid Atherosclerosis Study (ACAS) broadened our understanding of asymptomatic disease. This study included 1,662 patients 40 to 79 years of age with carotid artery stenosis of 60 percent or more who were randomized to receive medical therapy or undergo carotid endarterectomy. Event rates were derived from all patients with 60 to 99 percent carotid stenosis; the study was not designed to analyze the event rates by deciles.
Because the event rate was low in this study, the panel members noted that many investigators would make carotid artery stenosis of more than 80 percent a qualifier for surgical intervention. However, the panel took a less conservative position. (The surgical risk categories mentioned in the following discussion were explained in the AHA's original carotid endarterectomy guidelines published in the January 15, 1995, issue of Circulation. Operative risk is affected by patient selection, selection of surgeon and the institution in which the operation is performed.) A summary of the panel's position follows:
For patients with a surgical risk of less than 3 percent and a life expectancy of at least five years: proven indications—ipsilateral carotid endarterectomy for stenosis of 60 percent or more, with or without ulceration and antiplatelet therapy, regardless of the status of the contralateral carotid artery (Grade A recommendation); acceptable indications—unilateral carotid endarterectomy at the time of coronary artery bypass surgery in the presence of carotid artery lesions of 60 percent or more narrowing (Grade C recommendation); uncertain indications—unilateral carotid endarterectomy for stenosis of more than 50 percent in the presence of a grade B or C ulcer, regardless of the contralateral internal carotid artery status (Grade C recommendation).
For patients with a surgical risk of 3 to 5 percent: proven indications—none; acceptable but not proven indications—ipsilateral carotid endarterectomy for stenosis of 75 percent or more in the presence of contralateral stenosis ranging from 75 percent to total occlusion; proven inappropriate indications—none defined. The guidelines state that uncertain indications exist in the setting of ipsilateral carotid endarterectomy for stenosis of 75 percent or more, with or without ulceration, regardless of the contralateral artery status (no stenosis to occlusion) and in the setting of coronary artery bypass surgery in patients with bilateral asymptomatic stenosis of more than 70 percent or unilateral carotid stenosis of more than 70 percent.
For patients with a surgical risk of 5 to 10 percent: proven indications—none; acceptable indications—none; uncertain indications—unilateral carotid endarterectomy in the setting of coronary artery bypass surgery when bilateral asymptomatic carotid stenosis of more than 70 percent is present or when unilateral carotid stenosis of more than 70 percent is present. For this surgical risk category, the recommendations also describe two proven inappropriate indications—ipsilateral carotid endarterectomy for stenosis of 75 percent or more or for stenosis of 50 percent or less, with or without ulceration and regardless of the contralateral internal carotid artery status.
Symptomatic Carotid Stenosis
According to the guidelines, three clinical trials of carotid endarterectomy demonstrate that the procedure improves the outcome in symptomatic patients with severe carotid stenosis. The European Carotid Surgery Trial (ECST) revealed that the risk of ipsilateral stroke and perioperative death was 10.3 percent in patients who underwent surgery and 16.8 percent in patients who did not undergo surgery. The risk of death due to carotid endarterectomy or stroke during three years of follow-up was 12.3 percent for surgically treated patients and 21.9 percent for medically treated patients. Data from a subgroup of 1,590 patients with moderate stenosis (30 to 60 percent narrowing) indicate that no benefit is derived from carotid endarterectomy during a four- to five-year postoperative period.
The North American Symptomatic Carotid Endarterectomy Trial (NASCET) revealed that the cumulative risk of ipsilateral stroke at two years was 9 percent in surgically treated patients, compared with 26 percent in medically treated patients. These statistics were derived from 659 patients with 70 to 90 percent stenosis; 328 of these patients underwent carotid endarterectomy. The incidence of major or fatal ipsilateral stroke was 2.5 percent in the surgically treated group and 13.1 percent in the medically treated group. The NASCET investigators concluded that carotid endarterectomy is highly beneficial in patients with severe ipsilateral carotid stenosis and recent hemispheric ischemia or retinal transient ischemia.
The third study, the Carotid Endarterectomy and Prevention of Cerebral Ischemia in Symptomatic Carotid Stenosis study, was designed to determine whether carotid endarterectomy confers protection against cerebral ischemia in men with ischemic cerebral hemispheric symptoms and more than 50 percent stenosis of the ipsilateral internal carotid artery. This study, however, was terminated when the results of ECST and NASCET were known. It did show a stroke rate of 7.9 percent in the surgical patients with more than 70 percent stenosis, compared with a stroke rate of 25.6 percent in the medically treated patients.
Unlike the section on carotid endarterectomy for asymptomatic stenosis, the section on symptomatic lesions does not contain a breakdown of proven indications, acceptable indications and unproven indications for different surgical risk categories. The recommendations state that carotid endarterectomy in symptomatic patients is beneficial in patients with a recent nondisabling event and ipsilateral stenosis of 70 to 90 percent (Grade A recommendation). Whether potential benefit is derived in symptomatic patients with 30 to 60 percent stenosis is unknown. The guidelines state that carotid endarterectomy is not beneficial in symptomatic patients with zero to 29 percent stenosis (Grade A recommendation). According to the guidelines, the potential benefit in symptomatic patients with 30 to 69 percent stenosis is not yet known. Data from ECST do not support surgical intervention in patients with less than 50 percent stenosis. NASCET data for this subgroup are not yet available.