Abstract DP051: Anterior vs Posterior Circulation Medium-vessel Occlusions and Response to Endovascular Thrombectomy– a Post-hoc Analysis of the ESCAPE MeVO Trial

Background: Endovascular thrombectomy (EVT) is standard care for patients with acute ischemic stroke secondary to large-vessel occlusion (LVO), but recently, three randomized controlled trials found no overall benefit in EVT treatment for medium-vessel occlusion (MeVO) compared to medical therapy alone. Given clinical and anatomical differences in anterior and posterior circulation MeVOs, we hypothesized that response to EVT treatment for MeVOs may differ according to location. Methods: We analyzed data from the ESCAPE-MeVO trial. Interaction between EVT and vessel occlusion location was assessed with the Mantel-Haenszel test of homogeneity reported as a crude combined risk ratio (RR). We further performed stratified analyses examining for a difference in treatment effect by anterior (A2, A3, M2, M3) and posterior (P2, P3) circulation occlusion. The anatomical definitions and frequencies of the different occlusion sites are shown in Figure 1. We used logistic regression to compare the odds of 90-day excellent outcomes (modified Rankin Scale mRS 0–1) within stratums. Secondary outcomes included 90-day mortality, MeVO-extended thrombolysis in cerebral infarction (meTICI) score, infarct volume, and symptomatic intracranial hemorrhages (sICH). Results are reported as adjusted odds ratios (aOR), adjusted for age, sex, baseline National Institute of Health Stroke Scale (NIHSS), intravenous thrombolysis (IVT) use, and time from symptom onset to randomization. Results: Of the 529 patients in ESCAPE-MeVO, 473 had anterior MeVOs while 56 had posterior MeVOs (Figure 1). There was no evidence of effect modification of treatment by occlusion location (test of homogeneity, p=0.45; the crude unadjusted RR JO3 was 0.97 (95%CI 0.79 – 1.18). Stratified, adjusted analyses (Figure 2) showed no benefit of EVT over medical therapy for the anterior circulation group (aOR 0.87 95% CI 0.59-1.30) and for the posterior circulation group (aOR 1.86 95% CI 0.46-7.71). Finally, there were no significant differences between EVT and medical therapy in the odds of 90-day mortality or sICH based on location. Conclusion: Anterior and posterior MeVO patients had similar responses to EVT, with neither of the two groups benefitting from it. Interpretation of our results is limited by the small sample size of patients in the posterior circulation MeVO group.