Hypoperfusion intensity ratio to differentiate between stroke etiologies in patients with a large vessel occlusion

Background: Collateral circulation plays a key role in acute ischemic stroke. We sought to determine the association between the arterial collateral status, estimated by the Hypoperfusion Intensity Ratio (HIR) on perfusion MRI, and stroke etiology in anterior circulation large vessel occlusion (LVO). Methods: We retrospectively analyzed anterior circulation LVO acute stroke patients with a baseline perfusion MRI performed within 24 h from symptom onset. To avoid selection bias, patients were chosen from (1) the prospective registry of one comprehensive stroke center that included both thrombectomy-treated and untreated patients with systematic use of perfusion MRI and (2) one prospective thrombectomy study where perfusion MRI was acquired per protocol, but treatment decisions were made blinded to the results. Stroke etiology was evaluated according to the TOAST classification. HIR, defined as the proportion of time-to-maximum (T max ) > 6 s with T max > 10 s volume, was measured on perfusion imaging. The relationship between stroke etiology (large artery atherosclerosis [LAA]) versus cardioembolism [CE]) and HIR was assessed by bivariate then multivariable binary logistic regression analyses. Results: Among the 310 included patients, stroke etiology was CE in 178 (57%) and LAA in 51 (16%). Patients with CE stroke etiology had higher HIR (0.43 vs 0.31, p < 0.001) than those with LAA etiology. Higher HIR, indicating worse collateral circulation, remained independently associated with CE etiology following adjustment for the main confounders (adjusted OR = 1.5 [95%CI 1.24–1.81] per 0.1-point increase, p < 0.001). Conclusion: CE etiology is associated with worse collateral circulation in LVO-related acute stroke patients.