Angiography­based quantitative flow ratio for functional assessment of intracranial atherosclerotic disease.

ABSTRACT

BACKGROUND: Intracranial atherosclerotic stenosis (ICAS), an important cause of stroke, is associated with a considerable stroke recurrence rate despite optimal medical treatment. Further assessment of the functional significance of ICAS is urgently needed to enable individualised treatment and, thus, improve patient outcomes. AIMS: We aimed to evaluate the haemodynamic significance of ICAS using the quantitative flow ratio (QFR) technique and to develop a risk stratification model for ICAS patients. METHODS: Patients with moderate to severe stenosis of the middle cerebral artery, as shown on angiography, were retrospectively enrolled. For haemodynamic assessment, the Murray law-based QFR (µQFR) was performed on eligible patients. Multivariate logistic regression models composed of µQFR and other risk factors were developed and compared for the identification of symptomatic lesions. Based on the superior model, a nomogram was established and validated by calibration. RESULTS: Among 412 eligible patients, symptomatic lesions were found in 313 (76.0%) patients. The µQFR outperformed the degree of stenosis in discriminating culprit lesions (area under the curve [AUC] 0.726 vs 0.631; DeLong test p-value=0.001), and the model incorporating µQFR and conventional risk factors also performed better than that containing conventional risk factors only (AUC 0.850 vs 0.827; DeLong test p-value=0.034; continuous net reclassification index=0.620, integrated discrimination improvement=0.057; both p<0.001). The final nomogram showed good calibration (p for Hosmer-Lemeshow test=0.102) and discrimination (C-statistic 0.850, 95% confidence interval 0.812-0.883). CONCLUSIONS: The µQFR was significantly associated with symptomatic ICAS and outperformed the angiographic stenosis severity. The final nomogram effectively discriminated symptomatic lesions and may provide a useful tool for risk stratification in ICAS patients.