Calcification of coronary atherosclerotic plaques (which cause coronary artery disease) can occur as early as the second decade of life. With advancing age and atherosclerosis, deposition of calcium increases, occurring via an active process resembling bone formation.
Coronary artery calcium (CAC) has been assessed with computed tomography (CT), initially with electron-beam CT and more recently with multi-detector CT. Calcium can be easily recognised with CT, since it has the density of bone, differing from fat, water (blood) or muscle (myocardium).
In the study Nikolaos Alexopoulos from Emory University, Atlanta, measured the coronary artery score in a population of 14,789 adult asymptomatic patients referred for CAC screening because of risk factors for atherosclerosis. Patients with symptomatic coronary artery disease or prior history of CVD were excluded from the study. The mortality data were gathered using the social security death index (SSDI), which was accessed after an average of five years following the initial scan.
Results show that in a proportional hazards survival analysis, both chronological and arterial age were significant predictors of mortality. Arterial age, however, conferred additional predictive information. In a receiver operating characteristics (ROC) curve arterial age provided enhanced classification of mortality over and above chronological age (p<0.0001). The area under the curve was 0.77 (95% CI 0.75-0.79, p<0.0001) for chronological age and 0.81 (95% CI 0.79-0.83, p<0.0001) for arterial age. Increased ratio of arterial to chronological age was associated with decreased survival.
“CAC scores are likely to be especially useful in screening young asymptomatic patients since it can be used to improve risk prediction. The beauty of this method is that it's a very simple concept for everyone to grasp,” said Alexopoulos, adding that the cost of CAC scoring in the USA was $100-150, making it a financially feasible.