The time dependence of antithrombin initiation in patients with non-ST-segment elevation acute coronary syndromes: Subgroup analysis from the ACUITY trial

Study objective: Antithrombins are among standard treatment agents for patients with non-ST-segment elevation acute coronary syndromes. We aimed to determine the association between time from emergency department (ED) presentation to treatment with an antithrombin and adverse cardiac events. Methods: The study cohort was a subgroup of the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial, enrolled from March 1, 2005, to December 5, 2005. The ACUITY trial enrolled patients with moderate- and high-risk non-ST-segment elevation acute coronary syndromes and who were undergoing an early invasive strategy (<72 hours from randomization). All patients received an antithrombin (unfractionated heparin, low-molecular-weight heparin, or bivalirudin), in addition to other agents. A formal ED case report form was introduced in March 2005. Time from presentation to antithrombin initiation was evaluated as a continuous variable in hours. The endpoints were defined as major ischemic events (death, myocardial infarction, unplanned revascularization) or major bleeding within 30 days, or inhospital major bleeding. Logistic regression was used to adjust for demographics, severity of disease, comorbidities, and treatment differences. Results: Of the 2,722 patients enrolled with an ED case report form, complete time data were available in 2,632 (96%). Median time to antithrombin administration was 4.87 hours (interquartile range 2.67 to 9.83). After multivariable analysis, there was no association of major ischemic events with log time (hours) to antithrombin treatment (adjusted odds ratio [OR] 0.99; 95% confidence interval [CI] 0.97 to 1.01). There was an increase in major bleeding at 30 days and inhospital major bleeding complications with longer log time (hours) to antithrombin initiation (adjusted OR 1.44, 95% CI 1.15 to 1.80; OR 1.43, 95% CI 1.13 to 1.83, respectively). Conclusion: In this study of patients with non-ST-segment elevation acute coronary syndromes who were undergoing an early invasive management strategy, we were unable to demonstrate an association between adverse ischemic outcomes with the timing of antithrombin administration. However, there was an increase in bleeding outcomes as time to antithrombin administration increased.