EXPRESS: Cerebral blood flow-oxygen metabolism uncoupling at 24 hours after stroke thrombectomy

Background Following successful endovascular therapy (EVT) for acute ischemic stroke, tissue with abnormal perfusion may have impaired oxygen extraction and metabolism. MRI model-based oxygen extraction fraction (OEFmax) and cerebral metabolic rate of oxygen (CMRO2) were characterized in hypoperfusion and hyperemia regions 24 hours post-EVT. Methods Eighty-four patients were included with anterior circulation vessel occlusion, successful recanalization, and an MRI at 24 hours post-EVT. Time-to-maximum (Tmax) and cerebral blood flow (CBF) were evaluated for hypoperfusion and hyperemia. CBF, OEFmax, and CMRO2 were quantified using i) segmentation-based and ii) single slice region of interest (ROI) analyses. Normalized CBF, OEFmax, and CMRO2 were calculated by dividing the segmentation or ROI value by the contralateral value. Results Sixty-seven (80%) patients had abnormal perfusion; hypoperfusion in 22 (26%), hyperemia in 36 (43%), and both in 9 (11%). Compared to control, hypoperfused regions demonstrated a 62% CBF decrease, 52% CMRO2 decrease, and 68% OEFmax increase (p<0.01). Hyperemic regions demonstrated a 58% CBF increase, 26% CMRO2 increase, and 25% OEFmax decrease (p<0.01). Hyperemia had no significant correlation between normalized CBF and CMRO2 (p=0.14). Conclusion Hyperemia regions demonstrated cerebral blood flow-oxygen metabolism uncoupling, suggesting the underlying mechanism as loss of cerebrovascular autoregulation rather than hypermetabolic demand.