On old dogs and new tricks: CT perfusion predicts hemorrhagic transformation after thrombectomy

Introduction Hemorrhagic transformation is a major complication of large vessel occlusion (LVO) recanalization after mechanical thrombectomy in acute ischemic stroke. The hypoperfusion index ratio (HIR) quantifies the severity of cerebral hypoperfusion in the setting of an acute ischemic stroke using CT perfusion (CTP) to compare the volume of severely hypoperfused tissue (time-to-maximum Tmax > 10 s) to total hypoperfused tissue (Tmax >6 s), and has emerged as a potential predictor of ischemic core growth and poor outcomes. We investigated whether computed tomography perfusion (CTP) derived hypoperfusion index ratio correlates with the rate of hemorrhagic transformation. Methods We conducted a retrospective cohort analysis of a prospectively maintained patient database. Included patients underwent mechanical thrombectomy for large vessel ischemic stroke from January 2019 to December 2022 at a single comprehensive stroke center. Patients were separated into 2 groups depending on whether hemorrhagic transformation developed. Hemorrhagic transformation included any hemorrhage that could be classified according to the ECASS criteria as hemorrhagic infarction (HI)1, HI2, parenchymal hematoma (PH)1 and PH2. Hypoperfusion index ratio on admission CTP was determined using VizAI software. Data were analyzed using Chi-square and Mann-Whitney U tests. Results Among the 289 patients included (median age, 72.5; 41.5% female), 55 (19%) had hemorrhagic transformation. Patients with hemorrhagic transformation had a significantly higher hypoperfusion index ratio (median, 0 vs 0.2; P = 0.004) compared with those with no hemorrhagic transformation. Multivariable analysis showed that for every 0.1 increase in the hypoperfusion index ratio, there was a significant 4.64-fold increase in hemorrhagic transformation (OR 4.64; 95% CI 1.40 to 15.18; p = 0.011). Conclusion In patients with LVO who underwent mechanical thrombectomy, a higher hypoperfusion index ratio on admission CTP was associated with an increased rate of hemorrhagic transformation. This suggests that the hypoperfusion index ratio could be used as a predictor for hemorrhagic transformation after mechanical thrombectomy.