Mechanical Thrombectomy Treatment More than 16 h after Last Known Well for Patients with Large Vessel Occlusion

INTRODUCTION: Mechanical thrombectomy (MT) has been reported to be effective within 24 h after last known well (LKW) by the DAWN (DWI or CTP Assessment with Clinical Mismatch in the Triage of Wake-Up and Late Presenting Strokes Undergoing Neurointervention with Trevo) trial and within 16 h after LKW by the DEFUSE-3 (Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3) trial. However, there have been few reports of MT more than 16 h after LKW, and the efficacy and safety of MT more than 24 h after LKW have not yet been demonstrated. We evaluated the efficacy and safety of MT more than 16 h after LKW. METHODS: Using data from the Nippon Medical School Hospital MT registry from April 2011 to August 2022, consecutive patients with anterior circulation large vessel occlusion (LVO) and prehospital modified Rankin scale (mRS) scores of 0–3 were enrolled. Patients were classified into the following three groups: early group (LKW <6 h), middle group (LKW 6–16 h), and late group (LKW >16 h). The clinical characteristics and outcomes were compared among these three groups. RESULTS: Among 778 patients in the MT registry, 624 were enrolled. The early group included 432 patients, the middle group included 123 patients, and the late group included 69 patients. The patients had a median age of 77 years (interquartile range, 68–83), and 359 were male (57.5%). The median prehospital mRS score was 1 (interquartile range, 1–1), median National Institutes of Health Stroke Scale score on admission was 17 (interquartile range, 10–23), and median Alberta Stroke Program Early CT Score was 10 (interquartile range, 8–10). Regarding safety and efficacy, the proportions of cases with successful reperfusion (modified Thrombolysis in Cerebral Infarction score of 2b–3; 85.4% vs. 92.7% vs. 88.7%; p = 0.47), symptomatic intracranial haemorrhage (6.4% vs. 5.7% vs. 7.2%; p = 0.99), mRS score ≤3 at 90 days (52.0% vs. 60.2% vs. 44.9%; p = 0.11), and mRS score of 6 at 90 days (11.3% vs. 10.6 vs. 8.7%; p = 0.37) were not significantly different between the three groups. CONCLUSION: Patients who received MT more than 16 h after LKW experienced the same safety and efficacy as those who received MT at 0–16 h after LKW. MT more than 16 h after LKW may be safe and effective for stroke patients with LVO.