ARTERIAL ENLARGEMENT IN THE ATHEROSCLEROSIS RISK IN COMMUNITIES (ARIC) COHORT - IN-VIVO QUANTIFICATION OF CAROTID ARTERIAL ENLARGEMENT

Background and Purpose The relation between arterial wall (intimal-med ial) thickness and lumen narrowing is complex and has previously been studied predominantly at autopsy. B-mode ultrasound affords the opport unity to visualize both wall and lumen of the extracranial carotid art eries in vivo. Several studies have quantified the relation of various independent variables to wall thickness of carotid arteries in popula tion-based samples, but the relation of age and wall thickness to inte radventitial and lumen diameter has not previously been investigated i n these samples. Methods We used B-mode ultrasound to quantify the rel ation of arterial lumen diameter to age, arterial wall thickness, and arterial size (interadventitial diameter) of the extracranial carotid artery in 13 711 members of the Atherosclerosis Risk in Communities (A RIC) cohort. Results Men had greater interadventitial diameters, thick er walls, and wider lumens than women. Wall thicknesses of the common carotid artery were greater by 21% in men and 22% in women aged 60 to 64 years compared with those aged 45 to 49 years (P<.001). However, lu men diameters were also greater in older individuals because interadve ntitial diameters were greater. Wall thickness of the internal carotid artery was also associated positively with age, but the lumen diamete r of the internal carotid artery was smaller in older individuals. Dia meters of the carotid artery segments also differed in their relation to arterial wall thickening. The lumen of the internal carotid artery was uniformly progressively narrower with increasing wall thickness. F or the common carotid artery greater wall thickness bare only a small correlation with narrower lumen diameter for thickening of the arteria l wall up to 1.2 mm, but the association was more marked for the range of thicknesses between 1.2 mm and 2.5 mm. Conclusions When arterial e nlargement accompanies increased wall thickness, less lumen constricti on results than expected. Quantification of these complex relations in vivo may provide new insight into the pathogenesis of symptoms relate d to vascular disease. Narrowing of the internal carotid artery lumen associated with thicker walls is consistent with the observation that stenosis develops in this region and often leads to symptoms.