Ultrasound assessment of carotid atherosclerosis focusing on plaque characteristics and changes over time

Abstract

In a clinical perspective better methods to identify subjects at increased cardiovascular risk are needed. Atherosclerotic plaques of the carotid arteries with low echogenicity have been related to future clinical events. However, better methods to assess plaque characteristics are needed as well as more information on the variability and change over time of echogenicity in relation to occurrence and total area of non-stenotic carotid plaques. The aims were to develop a new method for plaque assessment, study variability over time and to examine plaque characteristics in relation to diabetes mellitus and hsCRP. A population sample of 64-year-old Caucasian women (n=638) with varying degrees of glucose tolerance underwent assessment of cardiovascular risk factors and bilateral ultrasound of the carotid arteries for measurement of intima-media thickness (IMT), plaque burden and plaque echogenicity, at baseline and at 6 year follow-up. A semi-automated method to evaluate echogenicity (SAMEE) and its main feature, Percentage White (PW) were developed with the visual Gray-Weale classification as reference method. PW was then also analysed in images from the follow-up examination. The SAMEE program and its main feature, Percentage White (PW), was constructed and validated to handle different technical and artifact-related sources of variability. We showed that PW is highly reproducible and correlates to a higher extent than GSM with a number of cardiovascular risk factors. Our results suggest that the problem of multiple plaques in individual subjects in our data set is best managed by measuring the average PW of all plaques. Plaque area increased as expected during 6 years of follow-up, but this was not accompanied by a change in echogenicity. Diabetes was associated with increased plaque burden and plaque echolucency at baseline. Risk factor intervention and new medication may have impacted the findings at follow-up. hsCRP≥2mg/ml as a risk marker of future cardiovascular disease was associated with carotid bulb IMT and total plaque area among women with carotid plaques. Taken together, the SAMEE program and measurement of PW may be potentially valuable tools in the identification of subjects at increased cardiovascular risk. This has to be investigated in future studies.