Safety and Efficacy of MCA‐M2 Thrombectomy in Delayed Time Window: A Propensity Score Analysis From the STAR Registry

Background Mechanical thrombectomy of middle cerebral artery M2 segment occlusion of the middle cerebral artery has reported safety and efficacy in recent post‐hoc and observational studies. However, there is no known benefit of mechanical thrombectomy for patients with M2 segment occlusions in the delayed time window (>6 hours). Methods The Stroke Thrombectomy and Aneurysm Registry (STAR) is a prospective, multicenter, nonrandomized observational study registry for acute ischemic stroke thrombectomy and aneurysm treatment. We analyzed all patients who underwent mechanical thrombectomy within the late time window (>6 hours from symptom onset) involving isolated M2 occlusions. We used propensity score matching to select a comparison group of patients who underwent mechanical thrombectomy for M1 occlusion in the same time window. Results Of 1083 consecutive patients analyzed, propensity matching yielded 180 well matched M1 and M2 pairs. Baseline demographics were well balanced between the groups (M1 and M2). Alberta stroke program early CT score (7.6±1.7 versus 8.3±1.5; P