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Carotid endarterectomy had a modest benefit for 50% to 69% stenosis after TIA or nondisabling stroke and no benefit for < 50% stenosis

ACP J Club. 1999 Mar-April;130:33. doi:10.7326/ACPJC-1999-130-2-033

Source Citation

Barnett HJ, Taylor DW, Eliasziw M, et al., for the North American Symptomatic Carotid Endarterectomy Trial Collaborators. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. N Engl J Med. 1998 Nov 12;339:1415-25.



In patients with symptomatic moderate stenosis (< 70%), does carotid endarterectomy (CE) reduce the risk for stroke?


Randomized controlled trial with 5-year follow-up.


106 clinical centers, mostly in North America.


2267 patients (median age 66 y, 70% men) who had a nondisabling stroke or symptoms of transient ischemic attack (TIA) ipsilateral to an angiographically confirmed carotid stenosis of < 70%. Exclusion criteria were lack of angiographic visualization of the artery, intracranial stenosis that was more clinically important than the cervical lesion, life expectancy < 5 years, cerebral infarction that eliminated useful function in the affected arterial territory, nonatherosclerotic carotid disease, potential cardioembolism, or previous ipsilateral CE.


Surgeons were preselected for low CE perioperative complication rates. 1118 patients were allocated to medical care, and 1108 patients were allocated to surgical care. Complete data were available for 99.7% of patients.

Main outcome measures

Any stroke ipsilateral to the stenosis studied in each patient. Data were analyzed for 50% to 69% and < 50% stenosis, and 8-year data were provided for stenosis 70% to 99%.

Main results

Analysis was by intention to treat. 1.9% of patients in the CE group did not have surgery, and 7.0% of patients in the medical group had CE. Patients with 50% to 69% stenosis who received CE had a reduced rate of ipsilateral stroke (P = 0.045), stroke (P = 0.026), stroke combined with all-cause mortality (P = 0.005), or disabling stroke combined with all-cause mortality (P = 0.032) (Table). For patients with < 50% stenosis, the groups did not differ for any outcome. For patients with 70% to 99% stenosis, 8-year data showed continuing benefit of CE.


Carotid endarterectomy modestly reduced the risk for ipsilateral stroke, any stroke, and all-cause mortality combined with either any stroke or disabling stroke when the initial, symptomatic stenosis was 50% to 69% but not when the stenosis was < 50%.

Sources of funding: National Institute of Neurological Disorders and Stroke and SmithKline Beecham.

For correspondence: Dr. H.J. Barnett, John P. Robarts Research Institute, P.O. Box 5015, 100 Perth Drive, London, Ontario N6A 5K8, Canada. FAX 519-663-3489.

Table. Carotid endarterectomy (CE) vs medical care for 50% to 69% stenosis*

Outcomes at 5 y CE Medical care RRR (95% CI) NNT (CI)
Ipsilateral stroke 13.3% 18.7% 29.1% (3.3 to 48.1) 18 (10 to 186)
Any stroke 19.8% 26.4% 25.1% (4.2 to 41.6) 15 (8 to 100)
Stroke or death 27.9% 36.4% 23.4% (2.3 to 36.4) 12 (7 to 44)
Disabling stroke or death 14.9% 20.1% 25.9% (0.7 to 44.8) 19 (10 to 783)

*Abbreviations defined in Glossary; RRR, NNT, and CI calculated from data in article.


The results of the NASCET and MRC European Carotid Surgery Trial (1) provide clinicians with excellent evidence on how best to treat patients with symptomatic carotid stenosis. With severe stenosis (i.e., ≥ 70% as defined by angiography [NASCET criteria]), CE provides substantial benefit that endures beyond 5 years. With < 50% stenosis, CE provides no benefit. With 50% to 69% stenosis, CE provides modest benefit in preventing any ipsilateral stroke, although this was about half as much in preventing ipsilateral disabling stroke (RRR 29% vs 61%).

The challenge is how best to apply these findings to particular patients with symptomatic 50% to 69% stenosis. Subgroups with different long-term benefits from surgery were defined by several factors, including the characteristics of the qualifying event, the dose of prophylactic aspirin, and the sex of the patient. For example, as in the MRC study (1), men were more likely to benefit from surgery (NNT 12 at mean follow-up of 6.1 y) than women (NNT 67). The difference may relate to women being less likely to have an ipsilateral stroke and more likely to have complications from angiography and surgery than men. Also, with less skillful surgeons than those who participated in the trial, the modest benefit for patients with 50% to 69% stenosis could be easily eroded or eliminated.

Many issues remain. The degree of stenosis and symptoms may not be enough to identify diseased carotid arteries that carry the greatest risk for subsequent ipsilateral stroke. In this trial, three quarters of patients treated medically did not have a subsequent ipsilateral stroke. Perhaps in the future, characteristics of the stenosis or plaque will allow us to identify subgroups of patients with similar degrees of carotid stenosis who will benefit more from CE. Finally, we need to develop less risky, more effective, and less costly approaches than those that are currently used for stenoses identified as being the most dangerous.

Will Longstreth, MD
University of WashingtonSeattle, Washington, USA


1. Randomized trial of endarterectomy for recently symptomatic carotid stenosis: final results from the MRC European Carotid Surgery Trial. Lancet. 1998;351:1379-87.