Carotid intima-media thickness in plaque-free site, carotid plaques and coronary heart disease risk prediction in older adults. The Three-City Study

ObjectivesWe sought to address the respective association between carotid intima-media thickness (IMT) in plaque-free sites and plaques with coronary heart disease (CHD) and their usefulness for CHD risk prediction in the Three-City Study.MethodsAt baseline, 5895 CHD-free adults aged 65-85 years underwent a bilateral ultrasound examination of carotid arteries. Mean IMT was measured in the far wall of the right and left common carotid arteries (CCA) at plaque-free site while the presence of focal plaques was assessed in the near and the far walls of the CCAs, the bifurcations and the origin of the internal carotid arteries.ResultsAfter a median follow-up of 5.4 years, 223 subjects had a first ever CHD event. In multivariate analysis, carotid plaques were independent predictors of CHD (Hazard ratio (HR)plaques at 1 site = 1.5; 95% confidence interval (CI) = 1.0-2.2; HRplaques at ≥2 sites = 2.2; 95% CI = 1.6-3.1; pfor trend < 0.001), contrary to mean CCA-IMT (HRfifth vs. first quintile = 0.8; 95% CI = 0.5-1.2; pfor trend < 0.48). Adding carotid plaques to conventional risk factors significantly improved CHD risk prediction as measured by the area under the ROC curve (from 0.728 to 0.745; p = 0.04), the Harrell's c (from 0.748 to 0.762; p < 0.001), and the integrated discrimination improvement (IDI = 0.007; p = 0.002)/net reclassification improvement (NRI = 13.7%; p < 0.001) indices.ConclusionCarotid plaques, but not CCA-IMT measured at a plaque-free site, were independent predictors of CHD and improved CHD risk prediction in older adults.