BackgroundThe significance of early venous filling (EVF) after mechanical thrombectomy (MT) in acute ischemic stroke (AIS) is not fully understood. In this study, we aimed to investigate the impact of EVF after MT. MethodsFrom January 2019 to May 2022, AIS patients with successful recanalization (modified Thrombolysis in Cerebral Infarction score (mTICI) >= 2b) after MT were retrospectively reviewed. EVF was evaluated on final digital subtraction angiography runs after successful recanalization and was categorized into phase subgroups (arterial phase and capillary phase) and pathway subgroups (cortical veins subgroup and thalamostriate veins subgroup), respectively. The impact of EVF subgroups on functional outcomes after successful recanalization were both investigated. ResultsA total of 349 patients achieving successful recanalization after MT were included, including 45 patients in the EVF group and 304 patients in the non-EVF group. Multivariable logistic regression analysis showed the EVF group had a higher rate of intracranial hemorrhage (ICH; 66.7% vs 22%, adjusted odds ratio (aOR) 6.805, 95% CI 3.389 to 13.662, P<0.001), symptomatic ICH (sICH; 28.9% vs 4.9%, aOR 6.011, 95% CI 2.493 to 14.494, P<0.001) and malignant cerebral edema (MCE; 20% vs 6.9%, aOR 2.682, 95% CI 1.086 to 6.624, P=0.032) than the non-EVF group. Furthermore, the cortical veins subgroup of EVF had a higher rate of mortality than the thalamostriate veins subgroup (37.5% vs 10.3%, P=0.029). ConclusionsEVF is independently associated with ICH, sICH and MCE after successful recanalization of MT, but not with favorable outcome and mortality.