Historical Reference Page
This is a historical reference page. This trial preceded the modern evidence base. It is presented as a predecessor reference. See ESCAPE (2015) for the modern successor trial that established EVT as standard of care.
MR RESCUE Trial: Penumbral Imaging to Select Patients for Mechanical Embolectomy
In patients with proximal large-vessel occlusion stroke within 8 hours, does penumbral mismatch imaging identify patients who benefit from mechanical embolectomy, and does embolectomy improve functional outcome compared with standard care?
Kidwell et al. (NEJM 2013) · doi:10.1056/NEJMoa1212793 · 118 patients
Population
Included
- Age 18 to 85 years
- Proximal anterior circulation LVO (ICA or M1 MCA) on CTA or MRA
- Penumbral imaging (MRI or CT perfusion) feasible before randomization
- Treatment achievable within 8 hours of symptom onset
- NIHSS 6 or greater
Age and neurologic status
- Patients between the ages of 18 and 85 years
- National Institutes of Health Stroke Scale (NIHSS) scores of 6 to 29
Stroke type and time window
- Large-vessel, anterior-circulation ischemic stroke randomly assigned within 8 hours after the onset of symptoms
Imaging pattern
- A favorable penumbral pattern was defined as a predicted infarct core of 90 mL or less and a proportion of predicted infarct tissue within the at-risk region of 70% or less
Prior thrombolysis allowance
- Patients treated with intravenous t-PA without successful recanalization were eligible if magnetic resonance angiography or CT angiography after the treatment showed a persistent target occlusion
Excluded
- Intracranial hemorrhage on baseline imaging
- Pre-stroke mRS greater than 2
- Established large infarct (ASPECTS below 6 or equivalent)
- Unable to undergo MRI or CT perfusion
- Posterior circulation stroke
Per protocol
- Detailed exclusion criteria are specified in the trial protocol; the Methods section of the publication does not list exclusion criteria in a dedicated format
Source: Kidwell et al., NEJM 2013· Retrieved 2026-06-09
Primary Outcome — Mean mRS at 90 Days
118 patients; mechanical embolectomy vs standard care; penumbral imaging stratified
In 118 patients with proximal anterior circulation LVO stroke randomized within 8 hours, mechanical embolectomy did not improve functional outcome compared with standard care. Mean mRS at 90 days was 3.9 in both the embolectomy group and the standard-care group. Penumbral imaging pattern (favorable mismatch vs unfavorable) did not predict benefit from embolectomy; the imaging-by-treatment interaction was not significant (p=0.56). The trial was underpowered to detect small treatment effects, and the embolectomy arm achieved successful reperfusion in only 27% of patients.
Visualization not shown for predecessor reference pages. See source paper for figures.
Trial Design
MR RESCUE enrolled patients with proximal anterior circulation LVO (ICA or M1 MCA, confirmed on CTA or MRA) within 8 hours of symptom onset and performed penumbral imaging (MRI or CT perfusion) to classify patients as having favorable mismatch (large penumbra, small core) or unfavorable pattern (large established infarct). Patients were randomized within each stratum to mechanical embolectomy or standard care. Embolectomy used the MERCI retriever or Penumbra aspiration system, first-generation devices with substantially lower reperfusion efficacy than modern stent retrievers. Only 27% of the embolectomy arm achieved TIMI 2-3 reperfusion.
Safety
Symptomatic intracranial hemorrhage occurred in 9% of the embolectomy group versus 4% of the standard-care group (not statistically significant in this small trial). Mortality at 90 days was 21% versus 17% (NS). No significant safety difference was demonstrated.