Carotid high-low flow ratio most accurately predicts significant stenosis.
The Doppler quantitative carotid blood flow technique is a dynamic, physiologic tool that measures carotid blood flow, velocity, and vessel diameter. A high-low flow ratio that reflects variation in side-to-side carotid flow is calculated. We determined the accuracy of this method for the detection of carotid stenosis in 70 patients with cerebrovascular disease in whom cerebral angiography was the gold standard. The most sensitive measure proved to be high-low flow ratio, which was abnormal in 19 of 23 patients (82.6% sensitivity). The patients with high-grade stenosis had contralateral elevated flow compared with that of patients without high-grade stenosis and age-specific normal subjects. The quantitative carotid blood flow technique reflects compensatory alterations in flow produced by significant carotid disease, with an abnormal high-low flow ratio having the highest positive predictive value. This technique can be used independently to screen for carotid stenosis and as an adjuvant to carotid duplex scanning in the investigation of extracranial carotid disease.