MR RESCUE

The timely concurrent publication of Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE) with the International Management of Stroke Trial III and the Local Versus Systemic Thrombolysis for Acute Ischemic Stroke (SYNTHESIS) Expansion trials confirmed that endovascular therapy was not superior to standard care for patients with acute ischemic stroke.1–3 The novel conclusion from MR RESCUE was that, "…a favorable penumbral pattern on neuroimaging did not identify patients who would differentially benefit from endovascular therapy." Some have interpreted this finding to support a pessimistic (glass half-empty) view of advanced imaging selection for acute reperfusion therapy. We disagree with this viewpoint and argue that the results of MR RESCUE should not dampen enthusiasm for the concept of imaging-based selection. Key limitations of MR RESCUE that hinder the generalizability of the conclusions of the study include enrollment bias, with a preponderance of patients having large infarct cores, and late times to endovascular therapy combined with very low rates of adequate early reperfusion. Lessons learned from this important study should help guide future trials.MR RESCUE was a phase IIb randomized, controlled, open-label, blinded outcome, multicenter study. Patients were assigned within 8 hours after the onset of large-vessel anterior circulation stroke to undergo embolectomy (with the first-generation Merci or Penumbra devices) or standard care (37% of patients received IV recombinant tissue plasminogen activator). Based on MRI (80%) or multimodal computed tomography, randomization was stratified according to whether the patient had a favorable penumbral pattern (infarct core <90 mL and substantial salvageable tissue) or a nonpenumbral pattern (large core and small or absent penumbra). Notably, only 118 patients eligible for the primary analyses were enrolled across 22 high-volume North American Stroke Centers over nearly a decade (2004–2011). The median predicted infarct core volume at the time of baseline …