Association of CT-Based Hypoperfusion Index With Ischemic Core Enlargement in Patients With Medium and Large Vessel Stroke.

Objective: The rate of infarct core progression in patients with acute ischemic stroke is variable and affects outcome of reperfusion therapy. We evaluated hypoperfusion index (HI) to estimate the initial rate of core progression in patients with medium-vessel-occlusion (MeVO) compared to large-vessel-occlusion (LVO) stroke and within a larger time frame since stroke onset. Methods: Core progression was assessed in 106 patients with acute stroke and CT perfusion. Using reperfusion trial core-time criteria, fast progressors had core>70-mL within 6-hours of stroke onset and slow progressors had core ≤70mL, mismatch ≥15mL and mismatch-to-core-ratio ≥1.8 within 6-24-hours. The relationship between HI and infarct core progression (core/time) was examined using receiver-operating-characteristics to determine optimal HI cut-off. The HI cut-off was then tested in overall cohort, compared between MeVO and LVO, and evaluated in patients up to 24-hours from stroke onset to differentiate fast from slow rate of core progression. HI threshold was assessed in a second independent cohort of 110 acute ischemic stroke patients. Results: In 106 patients with acute stroke, 6.6% were fast progressors, 27.4% were slow progressors, and 66% were not classified as fast or slow progressor by reperfusion trial core-time criteria. HI>0.5 was associated with fast progression and able to distinguish fast from slow progressors (AUC=0.94;95%CI=0.80-0.99). In MeVO patients (n=26) HI>0.5 had a core progression of 0.30-mL/min compared to 0.03-mL/min with HI≤0.5 (p 0.5 had a core progression of 0.26-mL/min compared to 0.02-mL/min with HI≤0.5 (p 0.5 had progression rate of 0.21-mL/min compared to 0.03-mL/min with HI≤0.5 (p 0.5 to distinguish fast and slow core progression with an AUC of 0.84(95%CI=0.72-0.97). Conclusions: HI can differentiate fast from slow core progression in MeVO and LVO patients within the first 24-hours of acute ischemic stroke. Consideration of core progression rate at time of stroke evaluation may have implications in the selection of MeVO and LVO stroke patients for reperfusion therapy that warrant further study.