Objectives: The predictive value of thoracic aortic calcium (TAC) scores for coronary artery
calcium (CAC) conversion (CAC>0) has not been fully evaluated.
Methods: We studied 1648 asymptomatic subjects (mean age 52±9 years, 54% male) with
baseline CAC=0 who underwent repeat CAC scanning 5 years later (range 3-14 years). TAC was
assessed in the ascending and descending aorta. CAC and TAC were measured using Agatston
scores. The cohort was categorized by baseline TAC scores: TAC=0 (n=1381 subjects), TAC 1-9
(n=54), TAC 10-99 (n=132) and TAC≥100 (n=81). Logistic regression was used to examine the
predictive value of baseline TAC scores for CAC>0 on repeat scans.
Results: On repeat scanning, 380 subjects (23%) developed CAC>0. The frequency of CAC>0
increased progressively across baseline TAC (TAC=0, TAC 1-9, TAC 10-99 and TAC≥100)
22%, 26%, 26% and 37%, respectively (P for trend =0.0025). Univariate analysis showed
baseline TAC ≥100 was a significant predictor of CAC>0 in repeat scans, while either TAC 1-
9 or TAC 10-99 were not, OR 2.10 [CI 1.32-3.36], P=0.002; OR 1.25 [CI 0.67-2.33], P=0.5; OR
1.24 [CI 0.82-1.87], P=0.3, respectively. In multivariable analysis, TAC ≥100 OR 1.90 [CI 1.08-
3.33], P=0.026, was a significant predictor of CAC>0, along with age, male gender, diabetes,
hypertension, hypercholesterolemia and time between scans.
Conclusions: The likelihood of conversion to CAC>0 increases with increasing TAC scores.
TAC ≥100 is an independent predictor of CAC conversion. Subjects with CAC=0 and extensive
TAC (TAC ≥100) may merit earlier repeat scanning than those with no TAC or lower TAC
scores.
