Use of carotid intima-media thickness regression to guide therapy and management of cardiac risks

Histological evaluation disqualifies IMT and calcification scores as surrogates for grading coronary and aortic atherosclerosis

BACKGROUND/OBJECTIVES

Carotid intimal media thickness (IMT) and coronary calcium scores (CCS) are thought to reflect atherosclerotic burden. The validity of this assumption for IMT is challenged by recent meta-analyses; for CCS by absence of a relationship between negative scores, and freedom of future events. As such, we considered evaluation of the relationship between tissue IMT and CCS, and extend of atherosclerotic disease relevant.

METHODS

Analyses were performed on donor aortas obtained during renal graft procurement, and on coronary arteries collected during heart valve procurement for tissue donation. Movat pentachrome and Hematoxylin staining was performed, and the degree of atherosclerosis histologically graded. IMT and presence of calcium deposits were quantified on graded tissue sections.

RESULTS

304 aortas and 185 coronary arteries covering the full atherosclerotic spectrum were evaluated. Aortas and coronaries showed similar relationships between tissue IMT and degree of atherosclerosis, with gradual increase in tissue IMT during earlier phases of atherosclerosis (r=0.68 and r=0.30, P<0.00001 for aorta and coronaries respectively), followed by plateauing of the curve in intermediate and advanced stages. Results for tissue IMT reveal high variability, resulting in wide confidence intervals. Results for CCS are similar for aorta and coronaries, with calcium depositions limited to advanced lesions.

CONCLUSIONS

Histological IMT measurements for the aorta and coronaries show large variations around the trend and plateauing of, and possibly reductions in IMT in late stage atherosclerotic disease. These observations for the aorta and coronaries may (partly) explain the limited benefit of including carotid IMT in risk prediction algorithms.

Changing characteristics of statin-related cIMT trials from 1988 to 2006

OBJECTIVES

Changes in cIMT have not been consistently correlated with cardiovascular risk reduction in clinical studies. The variability of carotid intima media thickness (cIMT) changes in published statin LDL-C-lowering studies in relation to various baseline and study characteristics was assessed.

METHODS

This was an exploratory analysis of study-level data pooled from statin-treatment arms of 13 studies conducted during 1988-2006. Baseline mean common carotid artery (CCA)/cIMT, maximum mean CCA/cIMT and LDL-C levels, and annualized cIMT changes were estimated for the overall studies, those conducted before/after 2000, and in risk-based subgroups. Potential relationships between prespecified covariates and cIMT changes were assessed.

RESULTS

Baseline mean CCA/cIMT and LDL-C levels were higher in the combined studies conducted before year 2000 (0.8521 mm) than after 2000 (0.7458 mm), and somewhat higher in study populations of patients with coronary heart disease risk and those with greater LDL-C reductions. Mean CCA/cIMT changes were also larger for the studies conducted before 2000 (-0.0119 mm/year) than after 2000 (-0.0013 mm/year). Notably, studies conducted before 2000 were of longer duration (≥ 2 years) than after 2000 (<2 years). Heterogeneity in cIMT change was attributed to baseline and study-design characteristics. Longer study duration and greater LDL-C reductions were significantly related to larger annualized cIMT changes. Maximum cIMT results were similar.

CONCLUSION

Baseline cIMT and LDL-C levels were lower, and cIMT changes were smaller in statin cIMT trials conducted after 2000 than those before 2000. These trends are consistent with increased treatment and control of high LDL-C levels over recent years in clinical practice, and may influence the results of cIMT studies.