Abstract TP295: Mechanical Thrombectomy for Medium/Distal Vessel Occlusions: Benefit in Selected Patients Defined by Age and Stroke Severity

Background: Mechanical thrombectomy (MT) is standard for large proximal occlusions, but its role in medium/distal vessel occlusions (MeVO/DiVO) remains unclear after recent trials (DISTAL, ESCAPE-MeVO, DISCOUNT) showed no overall benefit. It is suspected that certain patients with particular age and severity cutoff might still benefit. We aimed to identify these subgroups using statistical modeling. Methods: We retrospectively analyzed acute ischemic stroke patients with MeVO/DiVO (excluding proximal ICA, M1, basilar occlusions) from Rhode Island Hospital from March 2015 to June 2025. Outcome on the 90-day modified Rankin Scale (mRS) was compared between MT and medical groups using an ordinal shift analysis (proportional odds model); common odds ratios >1 indicate greater odds of a one-point shift toward a lower (better) mRS category. We fit an ordinal generalized additive modeling adjusting for age and NIHSS to estimate how MT’s common odds ratio varied by age and NIHSS, and visualized that smoothed treatment-effect with a heatmap. We additionally searched for age and NIHSS thresholds defining a subgroup with significant MT benefit (p<0.05), and confirmed it in an adjusted model. Results: We identified 218 MeVO/DiVO patients (median age 77 years, IQR 67–85; 55.5% female; 93.1% M2 occlusions; median NIHSS 14, IQR 8–19), of whom 164 (75.2%) underwent MT. The MT cohort presented with higher baseline stroke severity (median NIHSS 16 vs. 9; p<0.001) but was otherwise comparable in age and ASPECTS (p>0.05). Overall, MT showed no significant 90-day outcome advantage over medical therapy (adjusted common OR 1.21, p =0.530). However, treatment effect varied by age and NIHSS, where the benefit increased with younger age and higher NIHSS, as shown in the heatmap. Notably, among patients younger than 80 years with NIHSS ≥15 (n=58), MT was associated with significantly better 90-day mRS scores (adjusted common OR 8.66; 95% CI 1.49–50.33; p =0.016). Conclusion: Despite neutral overall trial results, MT for distal occlusions can be highly beneficial in carefully selected patients. Specifically, patients under 80 years of age with NIHSS ≥15 had markedly better outcomes with MT. These findings, enabled by both a modeling and a stratification approaches, support an individualized strategy for distal thrombectomy.