A Comparison of Segment-Specific and Composite Measures of Carotid Intima-Media Thickness and their Relationships with Coronary Calcium

Aims: The utility of carotid intima-media thickness (cIMT) as a marker for coronary heart disease is under heavy debate. This is predominantly due to the lack of a standard definition of cIMT, leading to inconsistent results. We investigated and compared the relationships of five different measures of cIMT with coronary calcium. Methods: Japanese men aged 40-79y (n-869) from Shiga Epidemiological Study of Subclinical Atherosclerosis were examined. Mean cIMT was measured in three segments of the carotid arteries: common carotid artery (CCA(mean)), internal carotid artery (ICA(mean)) and bifurcation (Bif(mean)). Mean cIMT of average values (Mean cIMT) and mean cIMT of maximum values (Mean-Max cIMT) of all segments combined were assessed. Coronary calcium was assessed as coronary artery calcification (CAC). Ordinal logistic regression was used to determine the odds ratio (OR) of higher CAC per I standard deviation higher cIMT measure. Analyses were adjusted for cardiovascular covariates and stratified by age quartiles. Results: All cIMT measures had positive associations with CAC (p < 0.001): [OR, 95% Confidence Interval]: ICA(mean) [1.23, 1.07-1.42], CCA(mean) [1.27, 1.08-1.49], Bif(mean) [1.33, 1.15-1.53], Mean cIMT [1.42, 1.22-1.66], and Mean-Max [1.50, 1.28-1.75]. In age-stratified analyses, only Mean-Max cIMT maintained a significant relationship with CAC in every age quartile (p < 0.05), while CCA(mean) had some of the weakest associations among age quartiles. Conclusions: Mean-Max cIMT had consistently stronger associations with coronary calcium, independent of important confounders, such as age. The most oft-used measure, CCA(mean), was no longer associated with coronary calcium after age-adjustment and stratification.