Role of Hypoperfusion Intensity Ratio in Vessel Occlusions: A Review on Safety and Clinical Outcomes

The hypoperfusion intensity ratio (HIR) is a quantitative metric used in vascular occlusion imaging to evaluate the extent of brain tissue at risk due to hypoperfusion. Defined as the ratio of tissue volume with a time-to-maximum (Tmax) of >10 seconds to that of >6 seconds, HIR assists in differentiating between the salvageable penumbra and the irreversibly injured core infarct. This review explores the role of HIR in assessing clinical outcomes and guiding treatment strategies, including mechanical thrombectomy and thrombolytic therapy, for patients with large-vessel occlusions (LVOs). Evidence suggests that higher HIR values are associated with worse clinical outcomes, indicating more severe tissue damage and reduced potential for salvage through reperfusion. Additionally, HIR demonstrates predictive accuracy regarding infarct growth, collateral flow, and the risk of reperfusion hemorrhage. It has shown superiority over traditional metrics, such as core infarct volume, in predicting functional outcomes. HIR offers valuable insights for risk stratification and treatment planning in patients with LVOs and distal medium vessel occlusions. Incorporating HIR into clinical practice enhances patient care by improving decision-making processes, promoting timely interventions, and optimizing postintervention management to minimize complications and improve recovery outcomes.