Assessment of subclinical atherosclerosis by carotid intima media thickness: technical issues

Abstract

Carotid intima-media thickness assessed by ultrasonography of carotid arteries is a safe, non-expensive, feasible and accurate method for detecting early signs of atherosclerosis and carotid intima-media thickness and change in carotid intima-media thickness over time reflect cardiovascular disease risk. Technical aspects impact on the measurement, variability and interpretation of carotid intima-media thickness. These include device aspects, inter- and intra-sonographer variability and the ultrasound protocol used. The mean common carotid intima-media thickness and the mean maximum common carotid intima-media thickness are the most widely used carotid intima-media thickness measurements. Common carotid intima-media thickness values of around 0.5 mm are considered 'normal' in young adults. Values are higher in men than in women, in African-Americans than Caucasians and increase with age. Carotid intima-media thickness values at or above the 75th percentile of a reference population indicate increased cardiovascular risk. Guidelines differ in their recommendations for the use of carotid intima-media thickness measurements for risk assessment in primary prevention because evidence suggesting that it improves upon conventional risk scores is inconsistent. Carotid intima-media thickness is frequently used in clinical trials as a surrogate endpoint for cardiovascular events on the assumption that regression or slowed progression of carotid intima-media thickness, induced by cardiovascular risk interventions, reflects a reduction in cardiovascular events. However, further data are required to confirm this linear relationship. No international guidelines exist on the use of carotid intima-media thickness as a research tool. Quality control in acquisition, measurement and interpretation of carotid intima-media thickness are important considerations and the carotid intima-media thickness protocol used should be determined by the research question under investigation.