The benefit of favorable venous outflow profiles is mediated through the reduced risk of intracranial hemorrhage in acute ischemic stroke patients undergoing endovascular treatment.

Background: Favorable venous outflow (VO) has been recognized as an independent predictor of excellent clinical outcomes in acute ischemic stroke caused by anterior circulation large vessel occlusion (AIS-LVO) patients who received endovascular treatment (EVT). However, the reasons why VO affects clinical outcomes have not been fully explained. In this study, we aimed to identify the potential mediators of VO affecting prognosis.

Methods: We conducted a multicenter retrospective cohort study of consecutive patients with AIS-LVO who underwent EVT. Baseline computed tomographic angiography (CTA) was applied to assess VO by the Cortical Vein Opacification Score (COVES). The primary outcome was functional independence at 90 days (modified Rankin Scale (mRS) score of 0-2). Classifying subtypes of intracranial hemorrhage (ICH) to explore the relationship between ICH subtypes and VO. Multivariate logistic regression and causal mediation analyses were used to evaluate the relationship among VO, functional independence, and potential mediators.

Results: Among 860 AIS-LVO patients undergoing EVT, a total of 515 patients were included in the present study after strict screening. In multivariate logistic regression analysis, favorable VO profiles (defined as COVES 3-6) were significantly associated with a lower incidence of ICH (24.2% vs 46.9%, adjusted odds ratio (aOR) 0.48, 95% confidence interval (CI) 0.30 to 0.77, P=0.002) and a higher proportion of functional independence (58.9% vs 15.0%, aOR 4.07, 95% CI 2.41 to 6.88, P<0.001). Mediation analysis showed that favorable VO profiles significantly reduced the incidence of parencuymal hematoma (PH) 2 accounting for 8.0% (95% CI 0.9% to 19.0%) of its beneficial effect on functional independence.

Conclusion: This study demonstrated the potential mediating effects of severe ICH for the beneficial effect of favorable VO on clinical prognosis among patients with AIS-LVO who underwent EVT.