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Lack of Effect of Aspirin in Asymptomatic Patients with Carotid Bruits and Substantial Carotid Narrowing

Robert Cote, MD; Renaldo N. Battista, MD, ScD; Michal Abrahamowicz, PhD; Yves Langlois, MD; France Bourque, RN; Ariane Mackey, MD, The Asymptomatic Cervical Bruit Study Group*
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From the Montreal General Hospital, Montreal, Quebec, Canada. Acknowledgments: The authors thank Merck Frosst Canada for providing the study medication and Ms. S. Lavigne for secretarial support. Grant Support: By the National Health and Research Development Program, Health Canada. Requests for Reprints: Robert Cote, MD, Division of Neurology, Montreal General Hospital, 1650 Cedar Avenue, Montreal H3G 1A4, Quebec, Canada. Current Author Addresses: Dr. Cote and Ms. Bourque: Montreal General Hospital, Division of Neurology, 1650 Cedar Avenue, Montreal H3G 1 A4, Quebec, Canada.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1995;123(9):649-655. doi:10.7326/0003-4819-123-9-199511010-00002
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Objective: To determine the effectiveness of aspirin in preventing ischemic events in patients with asymptomatic carotid stenosis.

Design: Double-blind, placebo-controlled trial.

Setting: University-affiliated hospitals.

Patients: 372 neurologically asymptomatic patients with carotid stenosis of 50% or more in at least one artery as determined by luminal diameter reduction on duplex ultrasonography.

Intervention: Patients were randomly assigned to receive either enteric coated aspirin, 325 mg/d, or identically appearing placebo. Duration of therapy was 2.0 years for the aspirin recipients and 1.9 years for the placebo recipients.

Outcome Measures: Patients were scheduled for a clinical examination every 6 months for assessment of the occurrence of any clinical event in the composite end point, which consisted of transient ischemic attack, stroke, myocardial infarction, unstable angina, or death.

Results: At baseline, the 188 patients receiving aspirin and the 184 patients receiving placebo had similar demographic, ultrasonographic, and laboratory characteristics. The median duration of follow-up was 2.3 years. The annual rate of all ischemic events and death from any cause was 12.3% for the placebo group and 11.0% for the aspirin group (P = 0.61). The Cox proportional-hazards analysis yielded an adjusted hazard ratio (aspirin-placebo) of 0.99 (95% CI, 0.67 to 1.46; P = 0.95). The annual rates for vascular events only were 11% for the placebo group and 10.7% for the aspirin group (P = 0.99). The multivariate analysis yielded a hazard ratio of 1.08 (CI, 0.72 to 1.62; P = 0.71).

Conclusion: Aspirin did not have a significant long-term protective effect in asymptomatic patients with high-grade (≥ 50%) carotid stenosis.

*For members of the Asymptomatic Cervical Bruit Study Group and participating institutions, see the Appendix.


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Figure 1.

Probability of event-free survival for the composite end point (all vascular events and death): Kaplan-Meier estimates (intention-to-treat analysis). Probability of event-free survival for vascular events (nonvascular deaths excluded): Kaplan-Meier estimates (intention-to-treat analysis). Values below each graph indicate the number of patients at risk in the placebo and aspirin groups.

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Figure 2.
Time dependence of the effect of aspirin on the risks for the composite end point.

The solid curve represents the estimated hazard ratio (aspirin-placebo), adjusted for the common risk factors, as a function of the duration of follow-up. The dotted curves indicate 95% CIs for the hazard ratio. The dashed horizontal line represents a hazard ratio of 1.0, which corresponds to an equal risk in the two groups. Areas below this line represent risk reduction due to aspirin; areas above the line represent risk increases.

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