Background-Thrombotic events still occur in aspirin-treated patients with coronary artery disease. Methods and Results-To better understand aspirin "resistance," serum thromboxane B 2 (TXB 2 ) and flow cytometric measures of arachidonic acid-induced platelet activation (before and after the ex vivo addition of aspirin and indomethacin) were analyzed in 700 consecutive aspirin-treated patients undergoing cardiac catheterization. In 680 of 682 evaluable patients, serum TXB 2 concentrations were reduced compared with nonaspirinated healthy donors. Twelve patients had serum TXB 2 that was lower than nonaspirinated healthy donors but Ͼ10 ng/mL. Arachidonic acid stimulated greater platelet activation in patients with high serum TXB 2 (Ͼ10 ng/mL) than in patients with low serum TXB 2 . Addition of ex vivo aspirin reduced arachidonic acid-induced platelet activation to similar levels regardless of serum TXB 2 concentrations, which suggests that patients with high residual serum TXB 2 concentrations were either noncompliant or underdosed with aspirin. Among the remaining 98% of patients, ex vivo administration of either aspirin or indomethacin failed to prevent platelet activation across all degrees of arachidonic acid-induced platelet activation and aspirin doses. Although the patients were not randomized with respect to clopidogrel treatment, multivariate analysis showed that arachidonic acid-induced platelet activation was less in patients receiving clopidogrel. Conclusions-There is a residual arachidonic acid-induced platelet activation in aspirin-treated patients that (1) is caused by underdosing and/or noncompliance in only Ϸ2% of patients and (2) in the remaining patients, occurs via a cyclooxygenase-1 and cyclooxygenase-2 independent pathway, in direct proportion to the degree of baseline platelet activation, and is mediated in part by adenosine diphosphate-induced platelet activation. (Circulation. 2006;113:2888-2896.)
Background-Poor clinical outcome in aspirin-treated patients has been termed aspirin resistance and may result from inadequate inhibition of platelet cyclooxygenase-1 (COX-1) by aspirin. The objectives of this study were to determine prospectively whether COX-1-dependent and other platelet function assays correlate with clinical outcomes in aspirin-treated patients. Methods and Results-Blood was collected before percutaneous coronary intervention from 700 consecutive aspirintreated (81 or 325 mg for Ն3 days) patients. Platelet function was tested by (1) serum thromboxane B 2 ; (2) arachidonic acid-stimulated platelet surface P-selectin and activated glycoprotein IIb/IIIa and leukocyte-platelet aggregates; and (3) platelet function analyzer (PFA)-100 collagen-epinephrine and collagen-ADP closure time (CT). Adverse clinical outcomes of all-cause death, cardiovascular death, and major adverse cardiovascular events (cardiovascular death, myocardial infarction, hospitalization for revascularization, or acute coronary syndrome) were assessed by telephone interview and/or medical record review. Clinical outcomes information was obtained at 24.8Ϯ0.3 months after platelet function testing. By univariate analysis, COX-1-dependent assays, including serum thromboxane B 2 level, were not associated with adverse clinical outcomes, whereas the COX-1-independent assay, PFA-100 collagen-ADP CT Ͻ65 seconds, was associated with major adverse cardiovascular events (Pϭ0.0149). After adjustment for covariables (including sex, aspirin dose, Thrombolysis in Myocardial Infarction risk score, clopidogrel use), both serum thromboxane B 2 Ͼ3.1 ng/mL and PFA-100 collagen-ADP CT Ͻ65 seconds were associated with major adverse cardiovascular events. In contrast, indirect measures of platelet COX-1 (arachidonic acid-stimulated platelet markers, shortened PFA-100 collagen-epinephrine CT) were not significantly associated with adverse clinical outcomes even after adjustment for covariables. Conclusions-In this prospective study of 700 aspirin-treated patients presenting for angiographic evaluation of coronary artery disease, residual platelet COX-1 function measured by serum thromboxane B 2 and COX-1-independent platelet function measured by PFA-100 collagen-ADP CT, but not indirect COX-1-dependent assays (arachidonic acidstimulated platelet markers, shortened PFA-100 collagen-epinephrine CT), correlate with subsequent major adverse cardiovascular events. This study suggests that multiple mechanisms, including but not confined to inadequate inhibition of COX-1, are responsible for poor clinical outcomes in aspirin-treated patients, and therefore the term aspirin resistance is inappropriate. (Circulation. 2009;120:2586-2596.)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.