Abstract 66: Optimal Delay Time to Initiate Anticoagulation After Ischemic Stroke in Atrial Fibrillation: Primary Results of the START Trial

Abstract

Introduction: Clinical practice guidelines recommend initiation of anticoagulation within 2 weeks after stroke due to atrial fibrillation (AF). It is unknown whether there is an optimal day within that 14-day period that balances the risks of recurrent embolic vs serious hemorrhagic events. Methodology: The Lone Start Stroke START trial is a pragmatic, prospective, multi-center, response-adaptive randomized Phase 2 study of 200 patients prescribed a direct oral anticoagulant (DOAC) for secondary prevention of stroke due to AF. Patients were randomized into one of 4 Arms: Day 3-4 from stroke onset, Day 6, Day 10, or Day 14. The primary outcome was an ischemic (stroke or systemic embolus) or hemorrhagic (ICH or major systemic hemorrhage) event observed within 30 days from the index stroke time of onset. Posterior probabilities that each arm was the best were calculated at predefined intervals and randomization allocations were adjusted to favor the Arms with higher probabilities. Results: The median age was 75 (IQR 65-81), median NIHSS at presentation was 7 (IQR 4-14), median lesion diameter was 3.1 cm (IQR 2.0-4.4) at the time of randomization. The sample was 50% female, 17.5% non-white, and 16.5% Hispanic. Apixaban was the prescribed DOAC in 89% of the patients. No ischemic events were observed for Arm 1, and no hemorrhage events were observed for Arm 4. Arm 1 (3-4 days) had a posterior 41.1% probability of being the best among the four, with probabilities of 26.4%, 17.1%, and 15.4 % respectively, for the other arms. Response adapted randomization was feasible and favored the earlier two arms. Expected event rates for each arm are presented in the Table. The timing and severity of the outcome events will be presented at the conference. Conclusion: Although the START trial did not identify a clearly superior day to initiate DOAC for secondary stroke prevention in AF, the evidence suggests that initiating DOAC early is better than at later times within the first 2 weeks after stroke onset.