Abstract Body: Background: Absence of a perfusion Mismatch (MM) profile suggests that the volume of salvageable penumbral tissue is small or absent. There is uncertainty regarding the benefit of endovascular therapy (EVT) in large ischemic core patients without MM. Although these patients were eligible for recent prospective randomized trials, few ultimately were enrolled. We sought to compare the expected percentage of MM versus No MM encountered in clinical practice compared to enrollment in large core clinical trials stratified by time since last known well.

Methods: We used a retrospective multicenter international study of patients with anterior circulation large vessel occlusion strokes, baseline MR or CT perfusion (MRP, CTP), and definitive last known well (LKW) within 24 hours. We compared this to the SELECT2 and ANGEL-ASPECT randomized clinical trials of EVT in large core ischemic stroke. A MM profile was defined as mismatch ratio ≥1.2 and penumbral volume ≥10ml. Large core was defined as ≥50ml on CTP (volume of relative cerebral blood flow <30%) or MRP (volume of apparent diffusion coefficient value of <620 x 10-⁶mm²/s), in keeping with the SELECT2 trial enrollment criteria. We used the Cochran-Armitage Trend Test to evaluate for trends in MM presence over time. There was potential bias in favor of a higher proportion of MM in our dataset because one hospital’s transfer patient acceptances were based on favorable CTP profiles at spoke hospitals.

Results: Of 2,012 patients, 444 had core ≥50ml. Among these patients, 161 (36%) had a No MM profile, median core infarct size was 112ml (IQR 68-137). 53% were male, median age was 72 (59-81), median baseline NIH Stroke Scale was 19.5 (16-24), median time from LKW was 4.3 hours (2-8.7), and 35.8% had CTP as baseline perfusion modality. Figure 1 shows a trend toward decreasing MM over time since LKW (P=0.01). By comparison, 29 of 352 (8%) patients enrolled in the SELECT2 trial had a No MM profile, 8 of whom were randomized to EVT (Figure 2). 31 of 426 (7%) patients enrolled in ANGEL-ASPECTS had a No MM profile; 15 underwent EVT, only 2 in the 12-24 hour since LKW well epoch (Figure 3).

Conclusions: The proportion of patients with No MM enrolled in large core trials was substantially smaller than encountered in routine clinical practice, particularly in the late time windows. Additional data on the response to EVT in these patients, who have evidence of a potentially completed or nearly completed infarct, is needed.