Abstract TP81: A Closer Look at MRI-Based Core in Patients With Large Vessel Occlusion Within 6 Hours From Onset

Abstract

Introduction: Recent clinical trials including EXTEND-IA and SWIFT PRIME utilized CT and MRI imaging to exclude large core patients from endovascular therapy (EVT) presenting within 6 hours from onset. We hypothesize that patients with clinical-core mismatch, retrospectively defined as admit NIHSS ≥ 6 and core volume ≤20 mL, were more likely to have early neurological improvement versus those who did not. Methods: Patients included had confirmed large vessel occlusion in the anterior circulation, presented within 6 hours from last known normal, were screened pre-EVT with multimodal MRI, treated with EVT between January 2015 through July 2019, and consented to Natural History of Stroke Study. Core volumes were calculated using a fully automated algorithm, “coretool”, based on processed DWI and ADC maps thresholded at ≤620 μm 2 /sec. Perfusion deficit volumes were calculated by thresholding Tmax maps at >6 sec delay. Early neurological improvement (ENI) was defined as a decrease in NIHSS≥8 points or NIHSS of 0-1 at 24 hours. Results: Fifty-four patients met study criteria with median age 54 years, 59% female, admit NIHSS=19 [13-23], onset=117 min [59-155], onset to groin=212 min [171-265], core volume=9mL [4-31], Tmax volume=82mL [50-107], mismatch volume=51mL [30-86], mismatch ratio=7.5 [2.6-11.9], and 90 day mRS=3 [1-5]. Of the 54 patients, 61% (n=33) had clinical-core mismatch while 39% (n=21) did not. Patients with mismatch had smaller core volumes, median 6 versus 39mL (p<0.001) and larger mismatch ratios, median 8.9 versus 2.6, (p=0.003), but no differences in age, sex, IV tPA treatment, onset time, onset to groin time, admit NIHSS, complete recanalization rate, Tmax volume, mismatch volume, or day 90 mRS. Fifty-five percent (18/33) of patients with clinical-core mismatch had ENI at 24 hours versus 24% (5/21) without (p=0.026). Conclusions: Patients with clinical-core mismatch had a significantly higher rate of early neurological improvement at 24 hours post EVT. However, some patients without mismatch but with complete recanalization still did well. Alternative definitions of mismatch, outside of current guidelines, may identify patients that will benefit more from EVT.