AbstractBackgroundHypoperfusion Intensity Ratio (HIR) is associated with collaterals and outcome in acute ischemic stroke (AIS). We investigated whether a combined assessment of HIR and collaterals could provide an added value.MethodsRetrospective single‐center study, including AIS patients with large vessel occlusion and endovascular treatment 0–24 h from onset. Predictors of FIV and outcome (90 days modified Rankin Scale 0–1) were investigated with linear and logistic regression respectively. Subjects were stratified in three groups: poor collaterals (grade 0–3) with poor HIR (≥.4), good collaterals (grade 4–5) with poor HIR/poor collaterals with good HIR (<.4) and good collaterals with good HIR.ResultsWe included 337 patients (median age 77, 53.1% males), of whom 100 (29.7%) had excellent outcome. One hundred and forty five patients with favourable collateral and HIR profiles had smaller infarct (median poor collaterals with poor HIR 41 mL, good collaterals with poor HIR/poor collaterals with good HIR 21 mL and good collaterals with good HIR 11 mL, p <.001) and higher rates of excellent outcome (poor collaterals with poor HIR 15.7%, good collaterals with poor HIR/poor collaterals with good HIR 26.2% and good collaterals with good HIR 39.3% p =.001). Logistic regression showed that patients with favourable collateral and HIR profiles had the highest odds of good outcome (OR: 3.83, 95% CI 1.62–9.08, p =.002).ConclusionCollaterals and HIR are independent predictors of final infarct lesion and outcome in stroke patients and their integration provides an added value. These findings might inform clinical practice and future trials.