Abstract W P113: Prolonged Use of Clopidogrel and Aspirin and Stroke Risk in Intracranial Stenosis in SAMMPRIS

Abstract

Background: In the SAMMPRIS trial, the use of combination aspirin and clopidogrel for 90 days after enrollment could be one reason that the outcome of patients in the medical arm was better than expected. The SAMMPRIS protocol required stopping clopidogrel after 90 days unless the patient had a non-neurological indication for continued use. We sought to compare outcomes in patients on vs. off clopidogrel beyond 90 days. Methods: For patients who did not have a primary endpoint within 90 days after enrollment (n = 397), we compared baseline features (t and Fisher’s exact tests), survival curves for the primary endpoint beyond 90 days after enrollment (the logrank test), and major hemorrhages (Fisher’s exact test) in patients on vs. off clopidogrel in the medical arm and stenting arms. Results: In the medical and stenting groups combined, baseline factors that were significantly (p<0.05) different between those on vs. off clopidogrel beyond 90 days (all higher in on clopidogrel group) were: age, diabetes, lipid disorder, coronary disease, SBP, and on antithrombotic agent at qualifying event. The table shows the primary endpoints and major hemorrhages in patients on vs. off clopidogrel in both treatment groups. Conclusion: This analysis, which was underpowered to detect even very large differences in event rates, suggests that prolonged use of clopidogrel plus aspirin may lower the risk of stroke in medically treated patients with intracranial stenosis, but increase the risk of major hemorrhage. Further studies with higher statistical power are needed to test this hypothesis.