Background and objectives: Data from randomized trials on the treatment effect of pure thrombolysis in patients with vessel occlusion are lacking. We examined data from a corresponding subsample of patients from the multicenter, randomized, placebo-controlled WAKE-UP trial to determine whether MRI-guided IV thrombolysis with alteplase in unknown-onset ischemic stroke benefits patients presenting with vessel occlusion.
Methods: Patients with an acute ischemic lesion visible on MRI diffusion-weighted imaging but no marked parenchymal hyperintensity on fluid-attenuated inversion recovery images were randomized to treatment with IV alteplase or placebo. The primary end point was a favorable outcome defined by a modified Rankin Scale score of 0-1 at 90 days after stroke. We investigated the interaction between vessel status and treatment effect using an unconditional logistic regression model. Treatment effects (adjusted odds ratio [aOR]) and their 95% CI were compared in patients with and without any vessel occlusion (AVO) and large vessel occlusion (LVO).
Results: 185 patients (mean age 64.5 years, 46% female, median NIH Stroke Scale score 9, median time between last seen well and MRI 10.26 hours) received treatment and presented with an occlusion. 98 (20%) had LVO (defined as occlusion of the internal carotid artery, middle cerebral artery trunk, or combination). A favorable outcome was observed in 30 of 94 patients with AVO (31.9%) in the alteplase group and in 18 of 91 (19.8%) in the placebo group (aOR 2.04, 95% CI 1.00-4.18). In the subgroup of patients with LVO, a favorable outcome was observed in 16 of 53 (30.2%) in the alteplase group and in 7 of 44 (15.9%) in the placebo group (aOR 2.08, 95% CI 0.71-6.10). Treatment with alteplase was associated with higher odds of favorable outcomes with no heterogeneity of treatment effect between patients with AVO and patent vessel (p = 0.56), or between patients with and without LVO (p = 0.69).
Discussion: Although the WAKE-UP study was not powered to demonstrate treatment efficacy in patient subpopulations, this subgroup analysis points to a benefit of MRI-guided thrombolysis in patients with unknown-onset ischemic stroke, independent of vessel occlusion.
Clinical trial registration: Registered at ClinicalTrials.gov with unique identifier NCT01525290 (clinicaltrials.gov/study/NCT01525290). The study was first posted on February 2, 2012; the first patient was enrolled on September 24, 2012.
Classification of evidence: This study provides Class II evidence that for patients with unknown-onset ischemic stroke with AVO, MRI-guided treatment with IV tissue plasminogen activator improves outcomes.