Core/perfusion Mismatch Prevalence According To ASPECT Score In Acute Ischemic Stroke With Large Vessel Occlusion.

Background: In acute ischemic stroke (AIS) with large vessel occlusion (LVO), core/perfusion mismatch modifies the effect of mechanical thrombectomy (MT) on clinical outcome, MT appears to have greater benefit in patients with significant mismatch. We aimed to study the prevalence of core/perfusion mismatch according to ASPECT score in a large population of LVO-related AIS imaged either with MRI or CT. Methods: Retrospective study including AIS patients with ICA/M1 occlusion and baseline perfusion imaging (MRI or CT) performed within 24hrs from last seen well. To avoid selection bias, patients were selected from (1) the registries of 3 comprehensive centers with systematic use of MRI- or CT-perfusion imaging and including both MT-treated and untreated patients, and (2) one thrombectomy trial where MT decisions were performed blinded to the results of MRI perfusion imaging. Core/perfusion mismatch was defined as mismatch ratio (Tmax>6s volume/ core volume) >1.8 and volume (Tmax>6s - core volume) >15 mL. ASPECT score was rated on diffusion weighted imaging (DWI) or non-contrast CT blinded from the perfusion imaging. Results: Overall, 580 and 350 patients were included in the MRI and CT cohorts. Last-seen-well to imaging time was 4.8hrs (IQR 3.0-8.7) and 3.2hrs (1.3-8.0) in the MRI and CT cohorts, respectively, median ASPECT score was 7 (5-8) and 8 (7-9), and core/perfusion mismatch was present in 393/580 (68%) and 315/350 (90%) patients. In both cohorts, 75% of patients were treated with MT following imaging. In the MRI cohort, mismatch prevalence was 44% (75/170) and 92% (378/410) for DWI-ASPECTS 0-5 and 6-10, respectively. In the CT cohort, mismatch prevalence was 47% (15/32) and 94% (300/318) for ASPECTS 0-5 and 6-10, respectively. Conclusion: About 90% of patients with ASPECTS 6-10 have a core/perfusion mismatch regardless of imaging type. However, patients with ASPECTS ≤5 are heterogeneous in terms of mismatch status. Therefore, perfusion imaging may be particularly useful to select appropriate MT candidates with low ASPECT scores, regardless of imaging type, which has implications for large core trials.