Refining thrombectomy benefit in medium vessel occlusion (MeVO) strokes using imaging and clinical enrichment

Randomized trials have not shown a clear benefit of endovascular therapy (EVT) for medium vessel occlusion (MeVO) strokes. We aimed to identify subgroups in which successful recanalization provides meaningful clinical benefit.

We retrospectively analyzed prospectively recorded consecutive patients with MeVO stroke treated with EVT at two comprehensive stroke centers. Successful recanalization was defined as expanded Thrombolysis in Cerebral Infarction (eTICI) 2b-3. The treatment effect was calculated as the difference in 90-day functional independence (modified Rankin Scale score 0-2) between recanalized and non-recanalized patients. Predicted infarct core on admission was calculated on non-contrast CT using AI-based software (AI-ICV; Methinks AI) and on CT perfusion (cerebral blood flow (CBF) <30%; IschemiaView). The hypoperfused volume (Tmax >6 s) was also obtained and the perfusion mismatch ratio was calculated (Tmax >6 s - CBF <30%)/Tmax >6 s). The treatment effect was analyzed in the overall cohort and after applying enrichment strategies based on clinical and imaging variables. Optimal cutoffs were identified by maximizing the added treatment effect while retaining ≥40% of the cohort.

Among 232 EVT-treated patients (mean age 76.1±12.3 years; median (IQR) National Institutes of Health Stroke Scale (NIHSS) score 9 (6-14)), the recanalization rate was 84.9%. The overall treatment effect was +33.3% (recanalized 53.3% vs non-recanalized 20.0%). Enrichment strategies increased the treatment effect: age ≤80 years (+13.8%), AI-ICV ≤9 mL (+9.9%), and NIHSS score ≥10 (+6.7%). Combining age, NIHSS, and AI-ICV criteria increased the treatment effect to 61.9% for an added value of +33.6%.

In MeVO stroke, the benefit of successful recanalization is substantial and can be further enhanced through pragmatic enrichment using readily available clinical and imaging variables, supporting refined patient selection and future trial design focused on enriched subgroups.