VARIATION OF COMMON CAROTID-ARTERY ELASTICITY WITH INTIMAL-MEDIAL THICKNESS - THE ARIC STUDY

Atherosclerosis Risk in Communities (ARIC) study is a prospective inve stigation of the etiology and natural history of atherosclerosis and c ardiovascular disease in four U.S. communities. The purpose of this wo rk is to investigate the relationship between common carotid artery el asticity and intimal-medial thickness (IMT) in the four race-gender gr oups represented in the ARIC cohort. Noninvasive ultrasonic methods we re used to measure IMT and the [systolic minus diastolic] diameter cha nge (DC) of the left common carotid artery in 10,920 black and white, men and women between the ages of 45 and 64 y. The relationship betwee n DC and IMT and IMT(2) was examined after adjustment of DC for age, h eight, diastolic diameter, diastolic blood pressure and linear and qua dratic terms for pulse pressure. This adjusted value of DC was used as an index of elasticity of the common carotid artery in the ARIC cohor t with larger values of adjusted DC implying a more elastic vessel. Th e general behavior of adjusted DC with increasing IMT was observed to be qualitatively similar in all four race-gender groups. Adjusted DC r emained nearly constant or increased slightly for values of IMT betwee n approximately 0.4 and 0.8 mm, up to approximately the 90th percentil e of IMT, and then decreased above the 90th percentile of IMT. Common carotid artery elasticity, defined as adjusted DC, varies with increas ing IMT in the ARIC cohort in a manner consistent with results from pr evious studies in animals and human subjects addressing the variation of several elasticity indices with atherosclerotic involvement and ris k factor exposure in the aorta, and brachial and radial arteries. Our results suggest that thicker common carotid artery walls in middle-age d U.S. populations are no stiffer than thinner walls, except for the t hickest 10% of arteries. Since the distal common carotid artery freque ntly contains atheromatous plaques in this population, the lack of cha nge in stiffness, indeed, the reduction in stiffness per unit thicknes s, may reflect the various stages of early common carotid atherosclero sis most often found in this population. These are characterized more by destruction of arterial wall structural elements than by changes su ch as widespread or circumferential sclerosis, which would strengthen and stiffen the artery. (C) 1997 World Federation for Ultrasound in Me dicine & Biology.