Abstract T MP9: Analysis of MR RESCUE Dataset Employing DEFUSE 2 Target Mismatch Criteria for Defining Penumbra

Abstract

Background: The MR RESCUE trial failed to show a benefit of endovascular therapy over standard medical care for first generation thrombectomy devices within 8 hours of onset of acute ischemic stroke. We now report a subset analysis of patients enrolled with MRI, employing DEFUSE 2 criteria to define favorable penumbral pattern (target mismatch) which differed from MR RESCUE penumbral prediction criteria. Methods: Patients with large vessel, anterior circulation strokes were randomized to mechanical embolectomy (Merci Retriever or Penumbra System) or standard care. Patients were categorized as having a favorable penumbral or non-penumbral pattern employing the DEFUSE 2 criteria for target mismatch ([Tmax > 6s / thresholded ADC < 600 х 10 −6 mm 2 /s] > 1.8, thresholded ADC < 70 cc, and Tmax > 10 s < 100 cc). Results: Among 118 total patients, 94 qualified for this analysis. Mean age was 65.8, mean time to enrollment 5.6 hours, median NIHSS 17, and 47% had target mismatch. Predicted core volume using DEFUSE 2 criteria (thresholded ADC volume < 600 х 10 −6 mm 2 /s) was 18.8 cc (target mismatch) and 64.3 cc (non-target mismatch; p<0.001). Revascularization in the embolectomy group was achieved in 62% (TICI 2a-3), and 21% (TICI 2b-3). Among all patients, mean 90-day mRS scores did not differ between embolectomy and standard care (3.8 vs 3.8; p=0.92). In patients with target mismatch, embolectomy was not superior to standard care (mean mRS 3.5 vs 3.3, p=0.78). Similarly, in patients without target mismatch, embolectomy was not superior (4.1 vs 4.3, p=0.67). Furthermore, there was no interaction between pretreatment penumbral imaging pattern employing DEFUSE 2 target mismatch criteria and treatment assignment in these 90-day mRS scores (p=0.11). Conclusions: In this analysis MR RESCUE patients enrolled with pretreatment MRI, use of the DEFUSE 2 criteria for target mismatch as a definition of penumbral pattern failed to identify a subset of patients with improved outcomes when treated with embolectomy. Further randomized, controlled studies employing new generation thrombectomy devices are needed to validate target mismatch as a selection criterion for acute stroke treatments.