The natural history of coronary calcification: a meta-analysis from St Francis and EBEAT trials

Coronary artery calcium score (CACs) is an established quantitative tool for assessing subclinical atherosclerosis. The aim of this study was to assess in a meta-analysis model the natural history and reproducibility of CACs measurements obtained from St Francis and EBEAT trials.

We analysed data from 649 individuals: 443 on placebo with 2 year follow-up from St Francis trial (Study A) and 209 on 10 mg atorvastatin with 1 year follow-up of EBEAT trial (Study B). Total CACs and that in the left coronary artery (LCA) branches, left main stem (LMS), left anterior descending (LAD), left circumflex (Cx) and right coronary artery (RCA) were analysed. In view of the wide CACs spectrum, data were logarithmically transformed before the analyses and mixed model analysis was used to evaluate the change of CACs over time.

The overall agreement between the two measurements was fairly good, showing a small but significant increase in CAC: 68% of the group as a whole presented an increase in CACs, 23% of the cohort had negligible change in CACs of <10% irrespective of the baseline CACs; and the remaining 10% showed a fall in CACs. Both studies showed similar patterns. The analysis of individual coronary arteries showed significantly higher variability of measurements in the RCA than in the LCA. Males had higher baseline CACs than females, but the rate of progression was not different between genders, irrespectively of age and baseline score.

The natural history of CACs was overtime progression in the majority of subjects, irrespective of gender. The higher variability in RCA measurements could be related to the low baseline CACs or exaggerated movement of the right side atrioventricular ring, whereas those for LCA branches are influenced by the branch allocation of the CACs. Large changes to and from zero, might be related to technical limitations.