Abstract DP139: Oxygen Extraction Fraction and Metabolism Impairment in Hyperemia and Hypoperfusion in Ischemic Stroke Post-Endovascular Therapy

Introduction: Despite successful endovascular therapy (EVT) for ischemic stroke patients, about half still progress to poor clinical outcome. The persistence of abnormal perfusion, presenting as hyperemia or hypoperfusion, is likely a contributing factor. In these abnormal regions, the tissue’s compromised ability to extract and metabolize oxygen may be a potential mechanism exacerbating impaired microvasculature perfusion. The study aim was to characterize model-based oxygen extraction fraction (OEF), cerebral metabolic rate of oxygen (CMRO2), and capillary transit heterogeneity (CTH) in areas of hyperemia or hypoperfusion in stroke patients at 24 hours following successful revascularization. Methods: Patients were included if they presented between December 2023 and July 2025, had an anterior circulation large or medium vessel occlusion, achieved successful revascularization defined as mTICI 2b/2c/3, and obtained MRI at 24 hours post-EVT, including dynamic susceptibility contrast perfusion (Cercare Medical Neurosuite). A reader evaluated cerebral blood flow (CBF) and mean transit time (MTT) for presence or absence of hyperemia and/or hypoperfusion (Figure 1). On a single slice, a region of interest (ROI) in the perfusion abnormality, a homologous contralateral ROI, and control ROIs were applied to CBF, and co-registered MTT, model-based OEF, CMRO2, and CTH (Figure 2). Signal intensity ratios (SIRs) were calculated with the ROI value divided by the contralateral ROI value. Statistical comparisons of SIRs were performed. Results: Seventy-two patients met study criteria and were included. Median age was 71 years, 29 (40%) female, and 41 (57%) patients with M1 occlusion. The mTICI was 2b for 22 (30%) patients, 2c for 17 (24%), and 3 for 33 (46%). Hyperemia was detected in 33 (46%) patients, hypoperfusion in 21 (29%), and 4 (6%) had both. For both hyperemia and hypoperfusion, the ROI SIR was significantly different compared to control for all perfusion maps (p<.01) (Figure 3). For hyperemia, CBF and CMRO2 increased, while MTT, OEF, and CTH decreased. For hypoperfusion, MTT, OEF, and CTH increased, while CBF and CMRO2 decreased. Conclusions: Oxygen extraction fraction and metabolism is dysregulated in hyperemia and hypoperfusion in ischemic stroke patients at 24 hours following successful revascularization. These findings deepen the understanding about patients experiencing persistent abnormal perfusion and the role of oxygen metabolism.