Thrombus Perviousness Is Associated With Differential Treatment Outcomes Following IVT and EVT in MeVO Stroke

BACKGROUND: In acute ischemic stroke due to medium vessel occlusion, the relative effectiveness of intravenous thrombolysis (IVT) and endovascular therapy (EVT) remains controversial, and treatment benefits may vary across patients. We evaluated the interaction between thrombus perviousness and treatment modality on 90-day functional outcome in patients with medium vessel occlusion. METHODS: This single-center retrospective cohort study analyzed 255 patients with imaging-confirmed medium vessel occlusion treated at a stroke center in China between 2018 and 2024 (154 IVT and 101 EVT with or without prior IVT). Thrombus perviousness was quantified using the thrombus perviousness index (TPI) from noncontrast computed tomography and computed tomography angiography. Multivariable logistic regression and inverse probability of treatment weighting evaluated the TPI-by-treatment interaction for 90-day functional independence (modified Rankin Scale score ≤2). Sensitivity analyses used alternative weighting strategies and a surrogate thrombus perviousness measure. RESULTS: The 90-day functional independence rate was similar between the IVT and EVT groups (51.9% versus 51.5%; P =0.96), and TPI was not independently associated with outcome. In the inverse probability of treatment weighting-weighted model, a significant interaction between TPI and treatment modality was observed (interaction odds ratio, 0.37 [95% CI, 0.24–0.56]; P <0.001). Higher TPI was associated with a greater likelihood of functional independence in IVT-treated patients (odds ratio per 0.05-unit increase, 1.73 [95% CI, 1.19–2.53]; P =0.005), but lower odds in EVT-treated patients (odds ratio, 0.65 [95% CI, 0.49–0.87]; P =0.003). Exploratory analyses in the IVT subgroup revealed a continuous increase in functional independence as TPI increased, without a stable cutoff. Rates of symptomatic intracranial hemorrhage and 90-day mortality did not differ between groups, and TPI was not associated with hemorrhage risk. CONCLUSIONS: In medium vessel occlusion, thrombus perviousness was associated with treatment outcomes, with higher perviousness favoring IVT-related benefits, whereas the use of EVT may be relatively advantageous in patients with low-perviousness thrombi.