What are the sonographic criteria for diagnosing extracranial carotid artery stenosis?
The presence and amount of carotid plaque, the PSV in the ICA and CCA, the EDV in the ICA, and the ratio of the ICA PSV to the CCA PSV are all used to detect and quantify the degree of carotid artery stenosis. Greater than 50% narrowing of the ICA is considered a stenosis, and greater than 70% narrowing is typically associated with symptoms where carotid endarterectomy is considered. The ultrasound criteria for 50% stenosis of the ICA is an ICA PSV >125 cm/sec and/or an ICA/CCA PSV ratio >2.0. The ultrasound criteria for 70% to 99% stenosis is an ICA PSV >230 cm/sec and/or an ICA/CCA PSV ratio >4.0. All of these sonographic grading criteria are based on the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Distal to a high-grade stenosis, there may be a tardus parvus waveform.
