Abstract WP32: Mechanical Thrombectomy for Mild Acute Ischemic Stroke with Large Vessel Occlusion: Results from the MISTWAVE Prospective Study

Introduction: Endovascular therapy (EVT) for emergent large vessel occlusion (ELVO) is standard of care for disabling strokes. There is no sufficient prospective data evaluating EVT for mild ischemic stroke with ELVO. Retrospective data suggests that many patients may not have favorable outcomes without intervention. We present our initial data investigating safety and outcomes of EVT in patients with ELVO and initial NIHSS of < 6. Methods: Our single arm prospective study (Mild acute Ischemic Stroke With lArge Vessel occlusion - MISTWAVE) recruited patients in 2 large tertiary care centers. Inclusion criteria included anterior circulation or basilar artery ELVO within 24 hours of onset. We excluded patients with ASPECTS score ≤ 6 on pre-intervention imaging, prior intracranial hemorrhage, or current anticoagulant use. Our primary endpoints were symptomatic cerebral hemorrhage within 24 hours, and/or change in NIHSS by ≥ 4 points within 72 hours or during hospitalization. Secondary endpoints included angiographic recanalization grade, NIHSS and disability assessment at discharge, 30 days, or on last follow-up. Results: We screened over 50 patients, and enrolled 20 as of November 2018 (mean age 65.6 ± 12.3 years; 55% males; 12 M1 occlusions, 8 M2 occlusions). Main reasons for exclusion were: outside treatment window, worsening NIHSS to >5, tandem or extracranial carotid occlusion, and inability to obtain consent. TICI 2B/3 thrombectomy was achieved in 95% of patients. The median NIHSS on presentation was 3 (range 0-5), and at last available follow-up it was 0 (0-10). The majority of patients (85%) were discharged home with minimal or no residual deficits. The average follow-up was 60.9 days (range 9-210 days), and mRS 0-2 was achieved in 90%. None of the patients suffered symptomatic cerebral hemorrhage. One patient (5%) had neurologic worsening within 24 hours despite TICI 3 recanalization. There were no other periprocedural complications. Conclusion: This is one of the first truly prospective studies designed to assess the safety and feasibility of EVT in patients with low NIHSS and ELVO. Our results are preliminary, but suggest excellent radiographic and clinical outcomes, and no significant procedural complications.