Thrombus Compositional Balance Is Associated with Complete Reperfusion After Mechanical Thrombectomy

Background/Objectives: Thrombus composition has been associated with the response to mechanical thrombectomy (MT), but previous studies have largely evaluated individual components separately or classified thrombi using component-rich categories. We investigated whether the relative compositional balance among red blood cells (RBCs), platelets, and fibrin was associated with endovascular outcomes after MT. Methods: We retrospectively analyzed 312 patients at a single center who underwent MT for acute intracranial large-vessel occlusion between 2017 and 2021 and had retrieved thrombi available for histological analysis. RBC, platelet, and fibrin proportions were quantified immunohistochemically. An isometric log-ratio transformation was used to derive a compositional balance contrasting RBCs with platelets and fibrin, with higher values indicating greater relative RBC predominance. Endovascular outcomes were compared across quartiles of compositional balance, and exploratory logistic regression analyses were performed to further characterize the observed association with complete reperfusion (modified Thrombolysis in Cerebral Infarction [mTICI] 3). Results: Complete reperfusion was achieved in 65.7% of patients. Rates were 56.4%, 62.8%, 73.1%, and 70.5% from the lowest to the highest quartile (Q1-Q4) of compositional balance (p for trend = 0.030). Compositional balance was not associated with successful reperfusion, first-pass effect, or the number of thrombectomy passes. Higher compositional balance was associated with greater odds of complete reperfusion both continuously (adjusted odds ratio [OR] per 1-unit increase, 1.31; 95% confidence interval [CI], 1.03-1.67; p = 0.027) and across increasing quartiles (adjusted OR per quartile increase, 1.41; 95% CI, 1.11-1.80; p = 0.005). The association remained consistent after excluding thrombi with a platelet proportion < 1%. Conclusions: In this exploratory analysis, greater relative RBC predominance over platelets and fibrin was associated with a higher likelihood of complete reperfusion after MT. The relative balance among thrombus components may provide additional insight into how thrombus composition relates to the completeness of endovascular reperfusion after MT.