ULTRASONIC MEASUREMENT OF THE ELASTIC-MODULUS OF THE COMMON CAROTID-ARTERY - THE ATHEROSCLEROSIS RISK IN COMMUNITIES (ARIC) STUDY

Background and Purpose: The Atherosclerosis Risk in Communities Study is a prospective investigation of the etiology and natural history of atherosclerosis and the etiology of clinical disease in four US communities. Methods: Noninvasive ultrasonic methods were used to determine mean wall thickness (WT), radius (R), and circumferential arterial strain (CAS) in the left common carotid artery of 3,321 white male and female study participants between the ages of 45 and 64 years. The mean and standard deviation of Young's elastic modulus (Y) in 5-year age groups were determined for each sex by combining the ultrasonic data with concurrent noninvasive measurements of pulse pressure (PP) in the right brachial artery using the equation Y=(R/WT) x (PP/CAS). Results: Significant (p=0.0001) age group differences in Y were observed in both sexes, with the mean value increasing from 701 kPa in women and 771 kPa in men in the 45-49-year-old age group to 965 and 983 kPa, respectively, in the 60-64-year-old age group. Significant (p=0.0001) age group differences were also observed for WT, the WT/R ratio, PP, CAS, and the PP/CAS ratio in both sexes. A sex difference in Y was detected (male>female, p=0.0006) only in the 45-49-year-old age group. Significant (p<0.0001) sex differences were found, with men having a greater lumen diameter calculated as 2 x (R-WT), a greater WT, and a greater 2R in all age groups. The WT/R ratio did not differ in both sexes in all age groups. Conclusions: Knowledge of the arterial wall elastic modulus and the parameters required for its determination can provide important insight into structural changes occurring within the arterial wall with age and sex, and possibly with the onset of very early arterial disease.