Carotid Endarterectomies— When are They Indicated?
Abstract & Commentary
Synopsis: Enthusiasm for this operation is justified but restraint is indicated unless patients are properly selected and sent to appropriate surgeons who are associated with appropriate surgical facilities.
Source: Barnett HJM, et al., for the North American Symptomatic Carotid Endarterectomy Trial. N Engl J Med 1998;339:1415-1425.
The number of carotid endarterectomies rose by 95% between 1980 and 1985 as enthusiasm for this procedure blossomed. By 1985, 170,000 carotid endarterectomies were being performed annually in the United States; however, reports of high complication rates, questions about the appropriateness of patients selected to undergo the procedure, and the absence of data from carefully controlled clinical studies were all evaluated and summarized in two negative trials, which quickly dampened the enthusiasm for this procedure, resulting in a dramatic decrease in the volume of these procedures that were performed in that year.1,2 A series of large and complex randomized, controlled trials were then mounted to address the many questions about the efficacy and safety of the procedure and, as the results of these trials became available, the number of carotid endarterectomies performed increased by 94% between 1991 and 1996.
Barnett and colleagues representing the North American Symptomatic Carotid Endarterectomy Trial Collaborative recently published a paper in the New England Journal of Medicine reporting on the results of the last remaining cohort of a large, randomized, controlled trial of symptomatic patients with carotid stenosis. They report that performing carotid endarterectomies in patients with symptomatic moderate (50-69%) carotid stenosis yielded only a moderate reduction in the risk of stroke. Patients with stenosis of less than 50% did not benefit from surgery at all, whereas patients with severe stenosis (i.e., > 70%) had a durable benefit from endarterectomy at eight years. It should be noted that the protocol included only hospitals with perioperative complication rates of 6% or less.
In the same issue, Tu and colleagues calculated the annual rate of carotid endarterectomies in California, New York, and in the Canadian province of Ontario.3 They also found a dramatic fall and then rise in the rates of carotid endarterectomy in both the United States and Canada, which correlated with the publication of first an unfavorable and later favorable clinical studies. The recent increase in numbers of carotid endarterectomies was found to be similar in high mortality rate hospitals as it was in those hospitals with low mortality rates suggesting that many patients, even if they were appropriately selected, did not receive the full risk/benefit of the carotid endarterectomy procedure3 because the surgeon and/or the hospital they selected for the procedure had a higher complication rate than did other surgeons and hospitals.
Comment by Harold L. Karpman, MD, FACP
The first carotid endarterectomies were performed successfully in 1954 on patients who had symptoms suggesting that a stroke was imminent.4 Since that time, the numbers of carotid endarterectomies performed had been a rollercoaster curve reflecting when the procedure would either fall in or out of favor. Initially, there was a great deal of confusion about the results, but over the past 14 years, a series of large and complex randomized, controlled trials have addressed the many questions about the efficacy of this procedure in both symptomatic and asymptomatic patients. These studies have demonstrated absolute risk reductions of statistically significant degrees among symptomatic patients with stenoses of 60% or greater. In asymptomatic patients, the data on efficacy is less clear; however, one major study, the Asymptomatic Carotid Atherosclerosis Study (ACAS) demonstrated a statistically significant absolute reduction of 5.9% in the five-year risk of stroke or death. The surgical complication rate in this study was only 2.3%, but, even with this low complication rate and even under the ideal circumstances of the trial, the net benefit for asymptomatic patients is much less clear than it is for the symptomatic patients.
It is obviously critical that referring physicians are fully familiar with the complication rates of the surgical team and the hospital to which they refer potential candidates for carotid endarterectomies in order to ensure that the patients receive the full benefit of the surgical procedure especially in those cases with severe symptomatic carotid stenosis. It is also essential to carefully assess whether a specific patient will benefit at all from this surgical procedure—that is, whether the patient belongs to a sub group for whom the potential benefit is remote. All risk factors should be evaluated especially for patients who are in the 50-69% stenosis range as they are being considered for an endarterectomy. These patients will benefit statistically on a long-term basis only if they are carefully selected since it has been demonstrated that the risk of stroke with medical treatment is higher for men than it is for women, for patients who have had a stroke in the past than it is for those who have had simple transient ischemic attacks, and for patients with hemispheric symptoms rather than for those who simply have retinal artery symptomatology. Also, published studies have demonstrated that the risk of perioperative stroke or death is increased in patients with diabetes, elevated blood pressure, contra-lateral occlusion, left-sided hemispheric disease or a lesion that is evident on either computed tomography scanning or magnetic resonance imaging studies.
Because the enthusiasm for carotid endarterectomy is increasing at this time, it becomes doubly important to recognize that many patients with symptomatic stenosis of less than 70% are not appropriate candidates for endarterectomy when the risk and benefits are carefully weighed. The benefits of the randomized controlled trials will not be fully realized until mechanisms have been established to ensure that those patients who are not likely to benefit from carotid endarterectomy do not undergo the procedure and that those who have been appropriately selected receive the full benefit of the procedure (but only in the proper surgical environment performed by the proper surgeons). In other words, the carotid endarterectomies have excellent outcomes when patients are appropriately selected and when operations are performed by those surgeons who have a high volume of patients and low complication rates, but the risk of peri-operative stroke or death is significantly increased for those patients in whom the indications are not appropriate and who are afflicted with complicating medical conditions such as diabetes, elevated blood pressure, contralateral carotid stenosis or occlusions, or perhaps even with those with lesions that are evident on computed tomography and magnetic resonance imaging. In conclusion, enthusiasm for this operation is justified but restraint is indicated unless patients are properly selected and sent to appropriate surgeons who are associated with appropriate surgical facilities.
References
1. Fields WS, et al. JAMA 1970;211:1993-2003.
2. Shaw DA, et al. Neurol Sci 1984;64:45-53.
3. Tu JV, et al. N Engl J Med 1998;339:1441-1447.
4. Eastcott HH, Pickering GW, Rob CG. Lancet 1954;267:994-996.
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