Cerebral collateral flow state in acute ischemic stroke correlates with clinical functional outcomes in non-thrombectomy patients

INTRODUCTION: Hypoperfusion index ratio (HIR) measured by computerized tomography perfusion (CTP) has been shown to predict collateral flow state in acute ischemic stroke (AIS). Low HIR (<0.4) is indicative of good collateral flow state. This study tested the association between good collateral flow state and stroke severity and clinical outcome at discharge. METHODS: Data from AIS patients who underwent CTP during initial stroke evaluation were linked with Get With the Guideline database between 2018 and 2020. Patients with good collateral flow (HIR < 0.4) were compared to those with poor collateral flow (≥0.4). They were stratified based on modified Rankin Score (mRS) at discharge into good (mRS 0-2) or poor (mRS 3-6) outcomes. A collateral score of 0-3 was assigned using CTA's obtained at the time of AIS presentation. We used univariate and multivariable logistic regression analyses to test the association between good collateral flow state and good discharge outcome. RESULTS: CT perfusion data was obtained in 1442 patients. After exclusions, 391 patients (age 69 ± 14, 54% male, 48% white, 52% black/others) remained, of whom 295 (75%) demonstrated good collateral flow and 96 (25%) showed poor collateral flow. Those with good collateral flow were younger (69 ± 14 vs. 71 ± 15, p = 0.25) and lower median NIHSS [7 (25-75%ile 3-13) vs. 14 (25-75%ile 8-20), p < 0.001]. CTA collateral scores demonstrated a significant inverse correlation to HIR. Good collateral flow was associated with good outcome on discharge (OR 2.7, 95% CI 1.4-5.1). The association remained significant after adjustment for demographics and comorbidities (adjusted OR 3.2 (1.7-6.4). CONCLUSIONS: In patients presenting with AIS who were non-thrombectomy candidates, good collateral flow state measured by HIR on CTP was associated with good functional outcome at discharge after adjustment for comorbidities.