Is the carotid intima-media thickness really a good surrogate marker of atherosclerosis?

Aim: Intima-media thickness (IMT) is considered a surrogate measurement of atherosclerosis but this is still under debate. Methods: To evaluate the relationship between carotid IMT and atherosclerosis, postmortem specimens of the distal segments of the left common carotid artery (CCA) from 133 Korean men aged from 20 to 78 years were used for histopathology and computer-assisted morphometry. Blood lipids and atherosclerosis-associated collagen and elastin were quantitatively analyzed. Results: Correlation coefficients of IMT were smaller than those of intima thickness but IMT was well associated with age (r = 0.55, p<0.00001), atherosclerosis score (or grade, AS, r = 0.73, p< 0.00001), plaque area (PA, r = 0.72, p<0.00001), total cholesterol (TC, r = 0.69, p<0.00001), low-density lipoprotein cholesterol (LDL-c, r = 0.72, p<0.00001) and triglyceride (TG, r = 0.38, p< 0.001). Coronary artery stenosis (CAS) and coronary calcification were also well associated with age (p<0.00001), IMT (p<0.005) and PA (p<0.00001). When IMT was thicker than 1 mm, the possibility of carotid atherosclerosis accompanied with CAS and coronary calcification, TC, LDL-c and TG was much higher (CAS with coronary calcification, p<0.005; TC, p<0.00001; LDL-c, p< 0.00005; TG, p<0.00001). Collagen tended to increase while elastin tended to decrease as AS increased (p<0.005); collagen increased and elastin decreased (p<0.00001) when comparing plaque to the plaque-free area in the same segment. Conclusion: These results support that the carotid IMT in association with TC, LDL-c and TG can be used as a good surrogate marker of atherosclerosis and predictor of coronary heart disease. Plaque formation may influence significant quantitative changes in collagen and elastin.