• Niaz Ahmed, Lars Kellert, Kennedy R Lees, Robert Mikulik, Turgut Tatlisumak, Danilo Toni, and SITS Investigators.
• Department of Clinical Neurosciences, Karolinska Institutet. niaz.ahmed@karolinska.se
• JAMA Neurol. 2013 Jul 1;70(7):837-44.

ImportancePooled analysis of randomized controlled trials of intravenous thrombolysis shows no statistically significant benefit beyond 4.5 hours, with the possible advantage perhaps offset by risk.ObjectiveTo compare the outcomes of patients who were treated within 4.5 to 6 hours or within 3 to 4.5 hours of the onset of an ischemic stroke with the outcomes of patients who were treated within 3 hours in the SITS-ISTR.DesignAn observational study based on SITS-ISTR data during the period from 2002 to 2011.SettingAcute and emergency care.ParticipantsOf 29 618 patients with acute ischemic stroke, 283 (1.0%) were treated within 4.5 to 6 hours of onset, 4056 (13.7%) were within 3 to 4.5 hours of onset, and 25 279 (85.4%) were treated within 3 hours of onset, in compliance with other European Union approval criteria.ExposureIntravenous thrombolysis with alteplase.Main Outcomes And MeasuresFunctional independence (modified Rankin Scale score of 0-2) and mortality at 3 months and symptomatic intracerebral hemorrhage (SICH). P values are based on comparisons between patients treated within 4.5 to 6 hours or within 3 to 4.5 hours of onset against patients treated within 3 hours of onset.ResultsResults are presented as within 4.5 to 6 hour vs within 3 to 4.5 hours vs within 3 hours. Median time from stroke onset to treatment was 295 vs 210 minutes vs 138 minutes (P < .01), median age was 65 vs 67 vs 68 years (P < .01), and median baseline National Institutes of Health Stroke Scale score was 9 vs 9 vs 12 (P < .01). Rate of functional independence was 61.3% (P = .40) vs 62.7% (P < .01) vs 58.4%; mortality rate was 11.8% (P = .99) vs 11.1% (P = .21) vs 11.8%; and rate of SICH was 2.6% (P = .17) vs 1.8% (P = .27) vs 1.5%. Multivariate analysis detected no significant difference in SICH (P > .05), mortality (P > .05), or independence (P > .05). Time from stroke onset to treatment as a continuous variable was significantly associated with higher rates of SICH and poor 3-month outcome after adjustment for age and National Institutes of Health Stroke Scale score.Conclusions And RelevanceThe treatment remains safe and effective for patients treated within 3 to 4.5 hours compared with patients treated within 3 hours. Our selected group of patients treated within 4.5 to 6 hours of stroke onset did not have worse outcomes than patients treated within 3 hours. An inevitable limitation of our observational study is the possible nonequivalence of the cohorts, particularly the 4.5- to 6-hour cohort relative to the other 2 cohorts.

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