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

OBJECTIVES

We 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.

METHODS

At 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.

RESULTS

After 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; HR(plaques at ≥ 2 sites) = 2.2; 95% CI = 1.6-3.1; p(for trend) < 0.001), contrary to mean CCA-IMT (HR(fifth vs.first quintile) = 0.8; 95% CI = 0.5-1.2; p(for 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.

CONCLUSION

Carotid plaques, but not CCA-IMT measured at a plaque-free site, were independent predictors of CHD and improved CHD risk prediction in older adults.