Effect of Thrombolytics on Delayed Reperfusion After Incomplete Thrombectomy: Target Trial Emulation

Background and ObjectivesMore than half of the endovascularly treated ischemic stroke patients with incomplete reperfusion (expanded Thrombolysis in Cerebral Infarction [eTICI] <3) show delayed reperfusion (DR) on 24-hour perfusion imaging, which is associated with favorable clinical outcome. The effect of intravenous thrombolysis (IVT) on the rates of DR remains unclear. This study aimed to assess the treatment effect of IVT on the occurrence of DR.MethodsPooled data from 3 randomized controlled trials (EXTEND-IA and EXTEND-IA TNK parts 1 and 2) and 2 comprehensive stroke centers (University Hospitals Graz and Bern) were analyzed. Only patients with a final reperfusion score of eTICI 2a-2c and available perfusion imaging at follow-up of 24 ± 12 hours were included. The primary outcome was the presence of DR on 24-hour follow-up CT/MRI perfusion imaging, defined as the absence of any focal perfusion deficit on perfusion imaging, despite incomplete reperfusion on the final angiography series during thrombectomy. For the secondary analysis, we explored the association between the primary outcome (DR) and the time elapsed between start of IVT and the end of an intervention. To address confounding in observational data, we performed a target trial emulation.ResultsOf 832 included patients with eTICI 2a-2c (median age 74 years, 49% female), 511 (61%) had DR. There was an independent treatment effect of IVT on DR (standardized risk ratio [sRR] 1.1, 95% CI 1.0-1.3; standardized risk difference [sRD] 8.2%, 95% CI 0.2%-16.1%), after adjusting for age, sex, atrial fibrillation, number of device passes, collateral score, and eTICI. Among those patients who have received IVT (n = 524/832, 63%), when adjusting for the aforementioned covariates, there was a causal effect of shorter time between administration of thrombolytics and end of the intervention on DR (sRR 0.93%, 95% CI 0.87-0.98; sRD -5.2%; 95% CI -9.1% to -1.3%, per hour increase).DiscussionExposure to thrombolytics showed independent treatment effect on the occurrence of DR among patients with incomplete reperfusion after thrombectomy who undergo perfusion imaging at the 24-hour follow-up. The effect of thrombolytics on DR was observed if there was a high chance of therapeutic concentrations of thrombolytics at the time point when the proximal vessel was recanalized, but distal occlusions persisted and/or occurred.Classification of EvidenceThis study is rated Class III because it is a nonrandomized study and there are substantial differences in baseline characteristics of the treatment groups.