Hypoattenuation on CT angiographic source images predicts risk of intracerebral hemorrhage and outcome after intra-arterial reperfusion therapy.

BACKGROUND AND
PURPOSE: Symptomatic hemorrhagic transformation (HT) is a significant complication of intravenous and catheter-based reperfusion. We hypothesized that the degree of vascular insufficiency, reflected as hypoattenuation on initial CT angiography (CTA) axial source images, is predictive of HT risk in stroke patients receiving intra-arterial reperfusion therapy.
METHODS: We examined initial CTA source images and follow-up CT scans in 32 consecutive patients. Regions of interest were semiautomatically segmented and reviewed. Mean intensity was determined in the region of maximal hypoattenuation and in normal contralateral tissue, and the arithmetic difference (deltaHU) calculated. Receiver operator characteristic (ROC) curves and cross-validation were used to identify threshold deltaHU values.
RESULTS: Thirteen patients had HT on follow-up CT (seven with parenchymal hematoma, six with hemorrhagic infarction). Patients with and those without HT did not differ in age, blood glucose level, lesion volume, or time to treatment or recanalization, though the former had a greater mean deltaHU (9.0 vs 6.3, P = .006). The ROC threshold at deltaHU > or = 8.1 was 69% sensitive and 90% specific for patients who developed HT (odds ratio = 19.1; 95% confidence interval: 2.9, 125; P = .002) and was predictive of poor clinical outcome (modified Rankin scale score > 2, P = .03). Neither HT in general nor parenchymal hematoma subtype was associated with poor outcome.
CONCLUSION: The degree of hypoattenuation on initial CTA source images is a risk factor for HT and poor clinical outcome after intra-arterial reperfusion therapy. Prospective validation of this relationship in large populations may permit feasible real-time risk stratification.