Abstract WP75: Ischemic Core Volume Modifies the Association Between ASPECT Score and Clinical Outcome

Background: While CT ASPECT scores predict clinical outcomes, the association between the scores and ischemic lesion volume is not linear as the subcortical regions involve small volumes while the cortical areas often involve large volumes. We evaluated whether ASPECTS and CTP ischemic core volume, modify each other’s association with clinical outcome in patients undergoing endovascular thrombectomy (EVT). Methods: In a prospective multicenter cohort study of imaging selection (SELECT), anterior circulation large vessel occlusion patients up to 24 hours from last known well were enrolled at 9 centers. All patients received a unified imaging profile (NCCT, CTA, and CTP with ischemic core volume [rCBF <30%] by RAPID software). A blinded core lab adjudicated all images. Results: Of 445 enrolled, 284 received EVT and are included in this analysis. Median (IQR) ASPECTS was 8 (7-9), median (IQR) ischemic core volume 10 ml (0-33). Both ASPECTS and ischemic core volume independently correlated with good outcome after EVT. For ASPECTS, the probability of good outcome decreased by 14% per point (aOR 1.18, 95% CI 1.01-1.38, p=0.03). For CTP mRS 0-2 probability dropped by 25% for each 10 ml increase in core volume (aOR 0.75, 95% CI 0.67-0.84, P<0.001). The correlation between ASPECTS and good outcome was substantially altered when adjusted for ischemic core size (fig 1). Outcomes were poor irrespective of ASPECTS in patients with large core lesions while outcomes were generally favorable in patients with a small ischemic core, even with lower ASPECTS. In contrast, the relationship between CTP ischemic core and favorable outcome was not altered when adjusted for ASPECTS (pre-ASPECTS aOR: 0.75 (0.67-0.84), p<0.001 vs post-ASPECTS aOR: 0.75 (0.67-0.85), p<0.001) (fig 2). Conclusion: ASPECTS association with clinical outcome after EVT was strongly modified by ischemic core volumes. Favorable outcomes were achieved in patients with small ischemic core volume despite low ASPECTS.