ABSTRACT NUMBER: ESOC2026A18 DOES THROMBUS STIFFNESS DETERMINE THROMBECTOMY SUCCESS IN ACUTE ISCHEMIC STROKE? A PROSPECTIVE OBSERVATIONAL STUDY

Abstract Background and aims Endovascular thrombectomy (EVT) is standard care for acute ischemic stroke (AIS), yet nearly 40% of patients fail to achieve complete revascularization on the first pass, strongly affecting recovery and mortality. Thrombus mechanical properties may underlie these differences in outcomes. This study examined the relationship between thrombus stiffness and age, sex, occlusion location, and its association with EVT success, measured as modified first-pass reperfusion (mFPR, eTICI≥2b). Methods Thrombi were collected from 73 EVT-treated patients. Stiffness was measured by compression testing, and histological composition assessed using Martius-Scarlett-Blue staining and CD42b+ immunostaining. Linear mixed-effects regression (LMR) identified determinants of stiffness accounting for multiple samples per patient; generalized LMR assessed associations with mFPR, adjusting for age, sex, occlusion site, and first pass EVT technique. Results Thrombus stiffness decreased progressively from ICA (1.106 kPa, 95% CI: 0.571–2.147) to M1 (0.760 kPa, 95% CI: 0.498–1.162) to M2 (0.236 kPa, 95% CI: 0.138–0.405), independent of thrombus composition. The adjusted probability of achieving mFPR was 75.2% (95% CI: 52.2–89.3) for ICA thrombi, 93.3% (95% CI: 83.6–97.4) for M1 occlusions, and 57.9% (95% CI: 39.8–87.1) for proximal M2 occlusions. The interaction between thrombus stiffness and occlusion site in predicting EVT success was not significant (P = 0.126). Conclusions Thrombi in distal vessels are softer than in proximal occlusions, suggesting occlusion location as a surrogate for thrombus stiffness. First-pass EVT success is lower for the stiffest thrombi in ICA and for the softest thrombi in M2 occlusions, supporting patient-specific EVT strategies and informed device selection. Conflict of interest LB, BF, FG received funding from the European Union’s Horizon Europe research and innovation programme under the grant agreement No 101136438 (GEMINI). All authors: nothing to disclose. Figure 1 - belongs to Results