Ultrasonographic Morphology Assessment of Low-grade Carotid Stenosis

Plain-language summary

Internal carotid artery (ICA) is intended to supply blood to brain. The carotid bulb located upstream of ICA origin is prone to atherosclerosis. This is an accumulation of fat and calcium in the wall forming a plaque that gradually thickens and leads to carotid stenosis (CS), which causes a decrease in blood flow. The risk of CS is stroke caused either by carotid artery thrombosis (occlusion) or by atherosclerotic plaque fragmentation, some components of which may leak into the brain (embolism). When diagnosing CS, an Echo-Doppler is performed to determine bulb and ICA origin obstruction rates. The reference method of quantifying CS is based on hemodynamic criteria that only allow the diagnosis of high grade stenosis thresholds (50%-70%). Below 50%, low-grade stenosis, patient follow-up is limited and could be based on morphological criteria; ultrasound imaging being a reference technique for human body structures morphological assessment, especially vessels. Two methods of CS morphological quantification with Doppler ultrasound currently exist. Calibre reduction at the maximum of stenosis can be measured by relating the smallest luminal diameter to the vessel diameter at stenosis site (ECST method) or to the downstream ICA diameter (NASCET method). As bulb diameter measures ≈1.8 times that of ICA, ECST appears to be more suitable for CS quantification. For high-grade stenosis, morphological quantification performance is impaired due to extensive calcification of large atheromatous plaques. However, it is possible that less calcified nature of low-grade stenosis and the use of a rigorous methodology will allow reproducible assessment in routine practice. This technique has not yet been evaluated, although it is a frequent situation in patient follow-up.

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