This study compared the ability of coronary artery calcium (CAC) and thoracic aortic
calcium (TAC) to predict coronary heart disease (CHD) and cardiovascular disease (CVD)
events.
Coronary artery calcium has been shown to strongly predict CHD and CVD events, but
it is unknown whether TAC, also measured within a single cardiac computed tomography
(CT) scan, is of further value in predicting events.
A total of 2,303 asymptomatic adults (mean age 55.7 years, 38% female) with CT scans
were followed up for 4.4 years for CHD (myocardial infarction, cardiac death, or late
revascularizations) and CVD (CHD plus stroke). Cox regression, adjusted for Framingham
risk score (FRS), examined the relation of Agatston CAC and TAC categories, and log-transformed
CAC and TAC with the incidence of CHD and CVD events and receiver-operator characteristic
(ROC) curves tested whether TAC improved prediction of events over CAC and FRS.
A total of 53% of subjects had Agatston CAC scores of 0; 8% 1 to 9; 19% 10 to 99;
12% 100 to 399; and 8% > or =400. For TAC, proportions were 69%, 5%, 12%, 8%, and
7%, respectively; 41 subjects (1.8%) experienced CHD and 47 (2.0%) CVD events. The
FRS-adjusted hazard ratios (HR) across increasing CAC groups (relative to <10) ranged
from 3.7 (p = 0.04) to 19.6 (p < 0.001) for CHD and from 2.8 (p = 0.07) to 13.1 (p
< 0.001) for CVD events; only TAC scores of 100 to 399 predicted CHD and CVD (HR:
3.0, p = 0.008, and HR: 2.3, p = 0.04, respectively); these risks were attenuated
after accounting for CAC. Findings were consistent when using log-transformed CAC
and TAC Agatston and volume scores. The ROC curve analyses showed CAC predicted CHD
and CVD events over FRS alone (p < 0.01); however, TAC did not further add to predicting
events over FRS or CAC.
This study found that CAC, but not TAC, is strongly related to CHD and CVD events.
Moreover, TAC does not further improve event prediction over CAC.