Contrast delay on perfusion CT as a predictor of new, incident infarct: a retrospective cohort study.

Background And Purpose: The purpose of this study was to determine if the assessment of intracranial collateral circulation by CT angiography and/or perfusion CT (PCT) can predict the risk of future ischemic stroke in a large, retrospective cohort study.

Methods: We identified 135 consecutive patients who underwent CT angiography of the head and neck and PCT of the brain at baseline and with subsequent follow-up brain imaging. Clinical and demographic information and carotid wall features were collected. Collateral circulation was assessed anatomically at CT angiography and functionally by measuring the mean transit time delay at PCT. The clinical, carotid, CT angiography, and PCT variables were compared between those with and without new incident infarct at follow-up imaging using mixed effect logistic statistical models.

Results: During the follow-up period, 15 patients developed a new infarct and 120 patients did not. Clinical features associated with the stroke risk were age, hypertension, hyperlipidemia, and atrial fibrillation. The carotid features associated with stroke risk were wall thickness. Anatomic assessment of collaterals on CT angiography was not associated with stroke risk, whereas the functional assessment of collaterals (mean transit time delay on PCT) was associated with stroke risk. In a multivariate model, age, atrial fibrillation, and mean transit time delay (OR, 22.8; P<0.001) were the only covariates that were independent predictors of future ischemic stroke.

Conclusions: The mean transit time delay on PCT contains important physiological information and should not be discarded. Along with age and atrial fibrillation, this functional assessment of intracranial collateral circulation predicts the risk of future hemispheric infarct.