Ischemic core thresholds change with time to reperfusion: A case control study

Abstract

Introduction: We aimed to identify if acute ischemic stroke patients with known complete reperfusion after thrombectomy had the same baseline CTP ischemic core threshold to predict infarction as thrombolysis patients with complete reperfusion. Methods: Patients who underwent thrombectomy were matched by age, clinical severity, occlusion location, and baseline perfusion lesion volume to patients who were treated with intravenous alteplase alone from the International Stroke Perfusion Imaging Registry. A pixel-based analysis of co-registered pre-treatment CT perfusion (CTP) and 24 hour diffusion-weighted imaging (DWI) was then undertaken to define the optimum CTP thresholds for the ischemic core. Results: There were 132 eligible thrombectomy patients and 132 matched controls treated with alteplase alone. Baseline National Institutes of Health Stroke Score (median 15, IQR 11-19), age (median 65, IQR 59 - 80) and time to IV treatment (median 153min, IQR 82- 315min) were well-matched (all p>0.05). Despite similar baseline CTP ischemic core volumes using the previously validated measure (rCBF <30%), thrombectomy patients had a smaller median 24 hour infarct core of 17.3mL (IQR 11.3-32.8mL) versus 24.3 mL (IQR 16.7-42.2mL, p=0.011) in alteplase-treated controls. As a result, the optimal threshold to define the ischemic core in thrombectomy patients was rCBF <20% (AUC 0.89, 95% CI: 0.84, 0.94), while in alteplase controls the optimal ischemic core threshold remained rCBF <30% (AUC 0.83, 95% CI: 0.77, 0.85). Interpretation: Thrombectomy salvaged tissue with lower CBF, likely due to earlier reperfusion. For patients who achieve rapid reperfusion, a stricter rCBF threshold to estimate the ischemic core should be considered. This article is protected by copyright. All rights reserved.

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