Frequency of Thrombectomy in Early and Late Postonset Time Windows Among Emergency Medical Services Patients With...

With recent trials demonstrating benefit of endovascular thrombectomy (EVT) up to 24 hours from last known well time (LKWT), emergency medical services systems must consider stroke center routing for patients with LKWT ≤24 hours. We sought to determine the frequency of thrombectomy by prehospital-determined LKWT using retrospective data from a tiered regional stroke care system.

During the July 2018 to March 2019 study period, patients with potential large-vessel occlusion, based on a Los Angeles Motor Scale of 4 or 5, were routed directly to a designated EVT center if within 30 minutes. We determined the frequency of thrombectomy by time intervals from prehospital-determined LKWT to first medical contact.

Emergency medical services transported 830 patients with acute ischemic stroke with documented prehospital-determined LKWT ≤24 hours to EVT centers. The ≤6 hours, >6 to ≤16 hours, and >16 to ≤24 hours epochs accounted for 75%, 20%, and 5% of transports to EVT centers, respectively. Men accounted for 47% of the study population, with a median age of 77 years (interquartile range, 64-86 years) and National Institutes of Health Stroke Scale median of 11 (interquartile range, 4-20). Overall, 28.2% (234/830) received EVT. Time window-specific EVT frequencies were: ≤6 hours (29.8% of patients [187/627]); >6 to ≤16 hours (24.1% of patients [39/162]); and >16 to ≤24 hours (19.5% of [8/41]).

In this regional stroke system with 2-tiered routing, patients in the >6- to 24-hour postonset window accounted for nearly one fourth of transports to EVT centers and 23% received thrombectomy.