Clinical outcomes and independently adjudicated results of M2 aspiration thrombectomy: A subgroup analysis from the Imperative Trial

Background: The ESCAPE-MeVO (Endovascular Treatment to Improve Outcomes for Medium Vessel Occlusions) and DISTAL (Endovascular Therapy plus Best Medical Treatment vs Best Medical Treatment Alone for Medium Vessel Occlusion Stroke) trials failed to demonstrate the superiority of endovascular thrombectomy over best medical management for medium and small vessel occlusions. Potential limitations of these trials include older patient populations, lower presenting National Institutes of Health Stroke Scale (NIHSS) scores, higher rates of premorbid disability, delayed revascularization times, inclusion of both medium and small vessel occlusions, and widespread use of stent retrievers. Here we present M2 occlusion data from the Imperative Trial, evaluating aspiration thrombectomy with the Zoom System. Methods: The Imperative Trial is a prospective, multicenter, single-arm trial with independent core lab and safety board adjudication, evaluating aspiration thrombectomy with the Zoom System (Imperative Care, Campbell, CA, USA) for large vessel, including M2, occlusions. This subanalysis includes patients with primary M2 occlusions. Angiographic outcomes were defined as modified Treatment in Cerebral Infarction (mTICI) score ≥2b (good) and ≥2c (excellent). Clinical outcomes were defined as modified Rankin Scale score (mRS) 0-2 (good) and 0-1 (excellent) at 90 days. Safety was assessed by all-cause mortality, symptomatic intracranial hemorrhage (sICH), and all hemorrhage. Results: Of 260 enrolled patients, 25% (65/260) had primary M2 occlusions. Median age was 69 years; median NIHSS was 13. Good and excellent reperfusion were achieved in 88% (57/65) and 66% (43/65), respectively. At 90 days, good and excellent clinical outcomes occurred in 62% (39/63) and 56% (35/63), respectively. Mortality, sICH, and any hemorrhage were 4.6% (3/65), 1.5% (1/65), and 18% (12/65), respectively. Conclusions: The Zoom System demonstrated excellent safety and efficacy in M2 occlusions. These findings support aspiration thrombectomy for M2 occlusions as a viable treatment in well-selected patients.