Results of Mechanical Thrombectomy 6 Hours after Stroke Onset: Analysis of Multiple Stroke Centers in Fukushima Prefecture.

Objective: The purpose of this study was to examine the efficacy and safety of mechanical thrombectomy in patients with acute occlusion of a large cerebral artery in the anterior circulation beyond 6 hours of the time last known to be well using the real-world clinical data collected from non-urban areas of Japan. Methods: We analyzed a retrospective multicenter database collected at 10 thrombectomy capable primary stroke centers in Fukushima Prefecture. In all, 188 patients were presenting a large cerebral artery occlusion in the anterior circulation, that is, internal carotid and middle cerebral artery (M1 and M2 segment). In all, 158 patients received mechanical thrombectomy within 6 hours from symptom onset (early time window), and 30 patients exceeded 6 hours (late time window). We compared the patient background, outcomes, and safety variables between the two groups. The modified Rankin Scale (mRS) score of 0-2 at 90 days after treatment and the incidence of symptomatic intracranial hemorrhage were compared between groups to evaluate treatment efficacy and safety. Results: There was no significant difference in the proportion of mRS score 0-2 at 90 days after treatment (51.3 vs. 46.7%: P = 0.644). However, symptomatic intracranial hemorrhage was more frequent in the late time window group (7.0 vs. 16.7%: P = 0.081). Symptomatic intracranial hemorrhage was a significant factor of a poor functional outcome in the late time window group (P = 0.022). Conclusion: This study reflects the real-world results of mechanical thrombectomy in the non-urban areas of Japan. The treatment efficacy in the late time window patients was equivalent to that in the early time window patients. On the other hand, the incidence of symptomatic intracranial hemorrhage showed a trend to high in patients beyond 6 hours, which was a significant factor related to a poor functional outcome.