Coronary calcium progression rates with a zero initial score by electron beam tomography

Background: A review of existing literature shows that for individuals with initial coronary calcium scores (CCS) of zero it would be reasonable to consider follow-up scanning no sooner than 3 years from the initial evaluation, however the data is very limited. In this study, we sought to determine the rate of new calcifications in patients initially presenting with a zero initial score on electron beam tomography (EBT). Methods and results: We evaluated 710 physician-referred participants (253 women and 448 men, mean age = 56 ± 9 years [range = 29 to 93]) with no coronary artery calcium (CAC) at baseline electron beam tomography (EBT) scan. The participants underwent a follow-up scan at least 12 months apart. In our study, 248 (35%) were followed for 1-3 years, 256 (36%) for 3-5 years and 204 (29%) for > 5 years, respectively. Overall, more than half of the individuals (62%) did not develop any CAC (score remained zero) in the interim period, whereas only 2% had CAC progression > 50 during the follow-up. The overall median (interquartile range) and mean ± S.D. change/year in these individuals was 0 (0-0.8) and 1 ± 3, respectively. Only 11 (2%) had CAC progression/year of 11-50, whereas 3 (1%) had CAC change/year > 50. It is interesting to note that even among individuals with long-term follow-up (> 5 years), very few individuals (2%) had CAC progression > 50. Individuals with follow-up 3-5 years did not have a significantly higher odds ratio for CAC change > 10 (p = 0.17) as compared to the reference group (follow-up of 1-3 years). All the other individuals who had a longer follow-up (> 5 years) had a significantly higher likelihood of CAC progression > 10 (OR = 6.6, 95% CI = 2.6-16.9, p < 0.0001) compared to the reference group. Conclusion: In individuals with no detectable coronary calcium on an initial EBT scan, a repeat scan can be recommended no sooner than 5 years.