Abstract Body: INTRODUCTION
Gray-white matter ratio (GWR) on non-contrast head computed tomography (HCT) is a helpful tool in neuro-prognostication in post-cardiac arrest patients. Its usage is unclear for those with angiography due to residual contrast.

HYPOTHESIS
GWR remains valid for neuro-prognostication in comatose patients undergoing extracorporeal cardiopulmonary resuscitation (ECPR) followed by coronary angiography (CAG) after out-hospital cardiac arrest (OHCA).

METHODS
We performed a retrospective study of comatose OHCA adults post ECPR and CAG at University of Minnesota from January to June 2022 with dual energy HCT within 12 hours. GWR was measured at basal ganglia, centrum semiovale, and high convexity levels. Gray matter areas of interest included caudate nucleus, putamen, thalamus, and medial cortex. The white matter areas of interest included the genu of the corpus callosum, posterior limb of the internal capsule, and medial white matter. Circular regions of interest (ROI, 10-15 mm²) were placed bilaterally in corresponding areas to record the average attenuation in Hounsfield unit (HU). The basal ganglia, cerebrum, and overall GWRs were calculated as the ratio of average HU between the gray and white matter ROIs within the area. Primary outcome was inpatient death, further categorized by the primary cause being neurological or not. Logistic regression followed by receiver operating characteristic (ROC) curves was used to validate GWR in predicting death. All data analysis was performed by StataCorp Software (STATA 14).

RESULT
25 patients were included in the study. 18 (72%) were male with a median age of 60 (interquartile range (IQR): 45-67). The initial HCT was obtained at 2.08 hours (median, IQR: 1.37–2.43) post ECPR cannulation. 7 (28%) patients died from brain death or herniation and 15 (60%) died from non-neurological causes. None had intracranial bleeding. 1 patient had unilateral hypodensity on initial HCT, suggesting an acute embolic infarct. Patients who died had lower GWRs on initial HCT (Figure 1). ROC regression showed all GWRs demonstrated good prognostic performance on inpatient death with area under the curve (AUC) of 0.6970 (basal ganglia), 0.8485 (cerebrum), and 0.7576 (overall) (Figure 2).

CONCLUSIONS
GWR in early HCT has prognostic value in predicting neurological outcomes despite residual contrast. It may be used as a risk stratification tool for comatose OHCA patients undergoing ECPR and angiography.