Symptomatic intracranial hemorrhage mediates the association between eosinophils and 90-day outcomes after mechanical thrombectomy for acute ischemic stroke

Background Decreased eosinophil level is associated with poor outcomes after mechanical thrombectomy in patients with acute ischemic stroke (AIS), but the underlying mechanism of this association is elusive. We aimed to assess the mediation effect of symptomatic intracranial hemorrhage (sICH) on the aforementioned association. Methods A total of 328 consecutive AIS patients undergoing mechanical thrombectomy between May 2017 and March 2021 were analyzed. SICH was defined as any evidence of brain hemorrhage on CT scan with neurological deterioration. Regression analysis was used to assess the effect of eosinophils on sICH, and its effect on poor outcome. Mediation analysis was performed to assess the proportion of total effect by sICH on the association between eosinophils and poor outcome. Results Multivariate analysis revealed an independent association between eosinophil count and sICH after adjusting for potential confounders (odds ratio, 0.00; 95% CI, 0.00–0.01; P = 0.0141), which is consistent with the result of eosinophil count (dichotomous) as a categorical variable (odds ratio, 0.22; 95% CI, 0.11–0.46; P < 0.0001). Eosinophil count was negatively associated with poor outcome (odds ratio, 0.00; 95% CI, 0.00–0.02; P = 0.0021). Mediation analysis revealed that sICH partially mediated the negative relationship between eosinophil count and poor outcome (indirect effect=-0.1896; 95%CI: -0.3654 – -0.03, P < 0.001). Conclusion This study showed an important effect of sICH on the association between eosinophils and poor outcome.