Early Neurological Deterioration and Time to Start Dual Antiplatelet Therapy in Patients With Acute Mild-to-Moderate Ischemic Stroke: A Pre-Specified Post Hoc Analysis of the ATAMIS Trial

Background and Purpose This study comprised a post hoc analysis of the Antiplatelet Therapy in Acute Mild to Moderate Ischemic Stroke (ATAMIS) trial aiming to determine whether the effect of dual antiplatelet therapy compared with that of monotherapy on preventing early neurological deterioration (END) differed according to the time from stroke onset to antiplatelet therapy (OTT).Methods In the ATAMIS trial, patients were divided into two subgroups: OTT from 0 to 24 hours (0–24 h group) and OTT from 24 to 48 hours (24–48 h group). We conducted multivariate regression analysis with continuous and categorical OTT to detect the effect of antiplatelet therapy. The primary outcome was END at 7 days, defined as an increase in the National Institutes of Health Stroke Scale (NIHSS) score of more than two points compared with the baseline. The safety outcomes were bleeding events and intracranial hemorrhage within 90 days.Results A total of 2,915 patients were included. With respect to END at 7 days, clopidogrel plus aspirin showed a lower proportion than aspirin alone across continuous OTT (4.8% vs. 6.7%; adjusted risk difference, -1.9%; 95% confidence interval [CI], -3.6% to -0.2%; <i>P</i>=0.03), and was lower in the 0–24 hours group (5.7% vs. 9.2%; adjusted risk difference, -3.7%; 95% CI, -5.5% to -2.0%; <i>P</i><0.01), but similar in the 24–48 hours group (3.5% vs. 2.9%; adjusted risk difference, 0.6%; 95% CI, -0.8% to 2.0%; <i>P</i>=0.40). We identified a significant interaction between the treatment effect and time subgroup with respect to the primary outcome (<i>P</i>=0.03). The occurrence of bleeding events and intracranial hemorrhage was similar in the time subgroup.Conclusion For patients with acute mild-to-moderate ischemic stroke, clopidogrel plus aspirin was associated with a lower risk of END at 7 days than aspirin alone when it was started within 24 hours of symptom onset.