Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Carotid endarterectomy combined with medical care and antiplatelet therapy reduced the overall incidence of ipsilateral neurologic events in men with asymptomatic carotid stenosis

ACP J Club. 1993 May-June;118:72. doi:10.7326/ACPJC-1993-118-3-072


Source Citation

Hobson RW II, Weiss DG, Fields WS, et al. Efficacy of carotid endarterectomy for asymptomatic carotid stenosis. N Engl J Med. 1993 Jan 28; 328:221-7.


Abstract

Objective

To evaluate the effectiveness of carotid endarterectomy in reducing the combined incidence of transient ischemic attack (TIA), transient monocular blindness, and stroke in patients with asymptomatic carotid stenosis.

Design

Randomized controlled trial with a mean follow-up of 48 months.

Setting

11 Veterans Affairs medical centers throughout the United States.

Patients

444 men (mean age 65 y) with asymptomatic carotid stenosis confirmed arteriographically (defined as reducing the diameter of the arterial lumen by ≥ 50%). Exclusion criteria were previous cerebral infarction, endarterectomy with restenosis, or extracranial-to-intracranial bypass; high surgical risk; long-term anticoagulant therapy or aspirin therapy at a high dose; intolerance to aspirin; life expectancy < 5 years; or a surgically inaccessible lesion.

Intervention

211 patients were randomly assigned to carotid endarterectomy with medical management, including 650 mg of aspirin twice daily (which was reduced to 325 mg daily if the larger dose was intolerable). 233 patients were assigned to medical management and aspirin alone.

Main outcome measures

Neurologic events including TIA, transient monocular blindness, and fatal and nonfatal stroke, and all-cause mortality.

Main results

190 fatal and nonfatal events occurred, including strokes, myocardial infarctions, and deaths from other causes: 87 (41%) in the surgical group and 103 (44%) in the medical group { P = 0.53}* (Table). 84 neurologic events occurred: 27 (13%) in the surgical group and 57 (25%) in the medical group, (P < 0.002) (Table). Of these 84 events, 65 were ipsilateral: 17 (8%) in the surgical group and 48 (21%) in the medical group (P < 0.001) (Table). The incidence of ipsilateral stroke alone was 10 (5%) in the surgical group compared with 22 (9%) in the medical group (P < 0.06). This difference disappeared when the 4 perioperative deaths and 3 strokes associated with arteriography were assigned to the surgical group.

Conclusions

Carotid endarterectomy combined with medical care and antiplatelet therapy reduced the overall incidence of ipsilateral neurologic events in men with asymptomatic carotid stenosis. This benefit of surgery was not observed for the combined incidence of all strokes and deaths.

Source of funding: Department of Veterans Affairs.

For article reprint: Dr. R.W. Hobson II, Section of Vascular Surgery, Medical Science Building G-532, 185 South Orange Avenue, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103, USA. FAX 973-972-5924.

* P value calculated from data in article.


Table. Carotid endarterectomy vs medical management for men with asymptomatic carotid stenosis†

Outcomes at mean 48 mos Carotid endarterectomy Medical management RRR (95% CI) NNT (CI)
Fatal and nonfatal events 41% 44% 7% (-16 to 25) Not significant
Neurologic events 13% 25% 48% (21 to 66) 9 (5 to 22)
Ipsilateral neurologic events 8% 21% 61% (35 to 77) 8 (5 to 16)

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


Revised Commentary

At the time of our last review (May/June 1993), it was recommended that asymptomatic carotid stenosis be managed conservatively, outside the Asymptomatic Carotid Atherosclerosis Study (ACAS) (1). Since then, the Asymptomatic Carotid Surgery Trial (ACST) (2) has commenced in Europe (and remains ongoing), and the ACAS results (1) have shown that patients with asymptomatic carotid stenosis of 60% to 99% who had carotid endarterectomy had a higher rate of stroke or death in the perioperative period than those treated medically (2.3% [95% CI 1.3 to 3.3%] vs 0.4% [CI 0 to 0.8%]) but an overall lower rate of ipsilateral stroke or death at 5 years (5.1% vs 11.0%, relative risk reduction 55% [22 to 72%], absolute risk reduction 5.9%).

These data indicate that carotid endarterectomy can be an effective stroke prevention strategy for some patients with asymptomatic carotid stenosis of 60% to 99%, but only if the surgeon has a prospectively audited perioperative stroke or death rate of < 3%. Even then, 100 patients need to be operated on to prevent about 6 ipsilateral strokes over the next 5 years (or 1 stroke per year), which means that more than 90 out of every 100 patients undergo carotid endarterectomy (and often angiography) unnecessarily.

Further information from ongoing trials such as the ACST are needed to determine 1) whether the results of ACAS can be generalized to most practising surgeons who have higher rates of perioperative stroke or death than ACAS (3, 4); 2) whether it is possible to accurately predict the minority of patients who may benefit (about 6%) or be harmed (about 2%) by carotid endarterectomy, and the vast majority who are operated on unnecessarily (about 90%); and 3) whether there is any net benefit from a public health viewpoint in performing carotid endarterectomy at all on neurologically asymptomatic patients referred with a positive carotid ultrasound; if so, the benefits are only likely to be realized in populations with a high pretest probability (prevalence, e.g. of about 20%) of high-grade carotid stenosis (5, 6). There is certainly no place for screening populations with a low prevalence of carotid stenosis because this is likely to lead to more false than true positive cases being exposed to angiographic or surgical risk, for no long-term benefit (5, 6).

Graeme J. Hankey, MBBS
Royal Perth HospitalPerth, Australia


References

1. Executive Committee for the Asymptomatic Carotid Atherosclerosis (ACAS). Endarterectomy for asymptomatic carotid artery stenosis. JAMA. 1995;273:1421-8.

2. Haliday AW, Thomas D, Mansfield A. The Asymptomatic Carotid Surgery Trial (ACST). Rationale and design. Steering Committee. Eur J Vasc Surg. 1994;8:703-10.

3. Wennberg DE, Lucas FL, Birkmeyer JD, Bredenberg CE, Fisher ES. Variation in carotid endarterectomy mortality in the medicare population: trial hospitals, volume, and patient characteristics. JAMA. 1998;279:1278-81.

4. Goldstein LB, Samsa GP, Matchar DB, Oddone EZ. Multicenter review of preoperative risk factors for endarterectomy for asymptomatic carotid artery stenosis. Stroke. 1998;29:750-3.

5. Hankey GJ. Asymptomatic carotid stenosis: how should it be managed? Med J Aust. 1995;163:197-200.

6. Whitty CJ, Sudlow CLM, Warlow CP. Investigating individual subjects and screening populations for asymptomatic carotid stenosis can be harmful. J Neurol Neurosurg Psychiatry. 1998; 64:619-23.