Abstract Body: BACKGROUND:
Despite recent advances in endovascular treatment for acute ischemic stroke (AIS), continued infarct growth and poor functional outcome has been reported in 20-50% of patients despite successful reperfusion. Oxygen extraction fraction (OEF) has shown promise as a method to evaluate ischemic tissue viability and can now be quantified from dynamic-susceptibility-contrast (DSC) perfusion MRI. We aimed to determine the association of OEF alterations on pretreatment DSC perfusion MRI with infarct growth among stroke patients that achieved successful reperfusion.

METHODS:
In this retrospective study, we included patients with anterior circulation LVO, who achieved successful reperfusion (TICI ≥ 2b), and had pretreatment DSC perfusion and posttreatment MRI within 48 hours from reperfusion. DSC perfusion was analyzed using the Cercare Medical Neurosuite (Cercare Medical). OEF values were quantified from the segmented ischemic core (ADC ≤620 ×10^-6 mm²/s) and penumbra tissue (Tmax >6 sec) on pretreatment MRI and normalized to the contralateral hemisphere (rOEF). Infarct growth was determined if the final infarct volume was ≥ 10 mL larger than baseline ischemic core volume. The association between rOEF in conjunction with demographic, clinical, other imaging variables and infarct growth were evaluated by univariate and multivariate analysis.

RESULTS:
Among 94 patients who achieved successful reperfusion, 30 (32%) patients had infarct growth ≥ 10 mL. While there was no significant difference in rOEF values measured in the ischemic core between patients with and without infarct growth, the OEF values were significantly (p=0.004) higher in penumbral tissue of patients without infarction growth. ROC analysis showed an AUC: 0.70, sensitivity of 62.1% and specificity of 70.5% for penumbra-rOEF values at threshold of ≥ 1.8. Multivariate logistic regression analysis revealed penumbra-rOEF (p= 0.002) as an independent variable for prediction of infarct growth ≥ 10 mL (p=0.002) with Odds ratio of 0.057 (95%CI: 0.010-0.321).

CONCLUSION:
Infarct growth occured in about 1/3 of patients despite successful recanalization. Low rOEF values in the penumbra tissue could be predictive of infarct growth while elevation of rOEF ≥1.8 could be protective.