Middle Cerebral Artery M2 Thrombectomy in the STRATIS Registry

Background and Purpose: The safety and benefit of mechanical thrombectomy in the treatment of acute ischemic stroke patients with M2 segment middle cerebral artery occlusions remain uncertain. Here, we compare clinical and angiographic outcomes in M2 versus M1 occlusions in the STRATIS (Systematic Evaluation of Patients Treated With Neurothrombectomy Devices for Acute Ischemic Stroke) Registry. Methods: The STRATIS Registry was a prospective, multicenter, nonrandomized, observational study of acute ischemic stroke large vessel occlusion patients treated with the Solitaire stent-retriever as the first-choice therapy within 8 hours from symptoms onset. Primary outcome was defined as functional disability at 3 months measured by dichotomized modified Rankin Scale. Secondary outcomes included reperfusion rates and rates of symptomatic intracranial hemorrhage. Results: A total of 984 patients were included, of which 538 (54.7%) had M1 and 170 (17.3%) had M2 occlusions. Baseline demographics were well balanced within the groups, with the exception of mean baseline National Institutes of Health Stroke Scale score which was significantly higher in the M1 population (17.3±5.5 versus 15.7±5.0, P ≤0.001). No difference was seen in mean puncture to revascularization times between the cohorts (46.0±27.8 versus 45.1±29.5 minutes, P =0.75). Rates of successful reperfusion (modified Thrombolysis in Cerebral Infarction≥2b) were similar between the groups (91% versus 95%, P =0.09). M2 patients had significantly increased rates of symptomatic ICH at 24 hours (4% versus 1%, P =0.01). Rates of good functional outcome (modified Rankin Scale score of 0–2; 58% versus 59%, P =0.83) and mortality (15% versus 14%, P =0.75) were similar between the 2 groups. There was no difference in the association of outcome and onset to groin puncture or onset to successful reperfusion in M1 and M2 occlusions. Conclusions: In the STRATIS Registry, M2 occlusions achieved similar rates of successful reperfusion, good functional outcome, and mortality, although increased rates of symptomatic ICH were demonstrated when compared with M1 occlusions. The time dependence of benefit was also similar between the 2 groups. Further studies are needed to understand the benefit of mechanical thrombectomy for M2 occlusions. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT02239640.