• The benefit of IV alteplase (tPA) beyond the conventional window of 3 hours after onset of stroke symptoms was established by the randomized ECASS III Trial, which compared treating acute ischemic stroke with IV alteplase versus placebo, between 3 and 4.5 hours (median 4 hours).
• The study found a significantly more favorable outcome amongst participants who received alteplase (odds ratio 1.34, 95% CI 1.02 - 1.76).  The overall number needed to treat was 14.
• The standard exclusion criteria used in this study differed from those of others, and these characteristics must be taken into account when deciding which patients are eligible for treatment at up to 4.5 hours.
• Therefore, data from ECASS III can not be used to support treating at up to 4.5 hours in the following types of patients:

              -- Age > 80 years old

              -- NIH Stroke Scale > 25

              -- History of combination of previous stroke and diabetes

              -- On anticoagulation medication, regardless of INR

References

• Hacke W; Kaste M; Bluhmki E; et al. Thrombolysis with alteplase 3 to 4.5 hours after acute ischemic stroke. New England Journal of Medicine 208; 359:1317.
• Bluhmki E; Chamorro A; Davalos A; et al. Stroke treatment with alteplase given 3.0-4.5 hours after onset of acute ischaemic stroke (ECASS III): Additional outcomes and subgroup analysis of a randomised controlled trial. Lancet Neurology 209; 8:1095.