Extensive thoracic aortic calcification is an independent predictor of development of coronary artery calcium among individuals with coronary artery calcium score of zero.

The predictive value of thoracic aortic calcium (TAC) scores for coronary artery calcium (CAC) conversion (CAC>0) has not been fully evaluated. 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. 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. 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.