Background:In stroke patients with large vessel occlusion and extensive early ischemic change, the role of bridging thrombolysis prior to endovascular thrombectomy (EVT) is still to be determined.Aim:To examine the impact of ischemic change on the efficacy and safety of bridging thrombolysis in patients treated with EVT.Methods:Consecutive anterior circulation EVT patients from a prospectively collected registry were included in this retrospective analysis. Alberta stroke programme early CT scores (ASPECTS) were evaluated from initial non-contrast CT scan with lower score indicating larger areas of early ischemic change. Outcome measures included symptomatic intracranial hemorrhage and functional independence (modified Rankin scale score 0-2) at day 90. Multivariable logistic regression models with interaction terms between ASPECTS and bridging thrombolysis were created. ASPECTS was treated as numeric variable in the primary analysis and trichotomized (ASPECTS ≤5, 6-8, 9-10) in a sensitivity analysis.Results:872 EVT patients (384 female, mean ± SD age of 67 ± 15, baseline NIHSS 16 [IQR 11-20], median ASPECTS 8 [range 2-10]) were included. 436 (50%) received bridging intravenous thrombolysis with alteplase. There was no significant main effect of ASPECTS on sICH (main effect OR 0.73 95%CI 0.45-1.21, p=0.24) and no modifying effect of thrombolysis (interaction p=0.65). With decreasing numeric ASPECTS, the probability of functional independence reduced (main effect OR 1.34 95%CI 1.20-1.49, p<0.001), and this the reduction was steeper in those without bridging thrombolysis (interaction p=0.035). The interaction was not significant when ASPECTS was split into the 3 categories (p=0.28).Conclusion:In anterior circulation patients treated with EVT, bridging thrombolysis was associated with a higher probability of functional independence in those with more extensive early ischemia as determined by ASPECTS. These results suggest patients with large ischemic cores may still benefit from bridging thrombolysis, but this will need to be evaluated in further studies.