[Progression of coronary calcium]

The progression of coronary atherosclerosis is determined by risk factor exposure. It is also an important predictor of future cardiac events in its own right. Coronary calcium represents an integral part of coronary atherosclerosis. Accurate measurements can be obtained by using electron-beam computed tomography (EBT) or recently developed multidetector spiral CT scanners which are in the state of evaluation. The variability of EBT-derived quantification of coronary calcium is < 10% and thus suitable for determining the progression of coronary calcium.

In the healthy general population, the annual progression measures approximately 24%, whereas in untreated, asymptomatic high-risk patients, it is 40-50%. Similar values are observed in symptomatic patients with modern pharmacological therapy. There is a considerable amount of inter-individual variability in the progression of coronary calcium, probably as a result of the complex interplay of numerous factors which influence the process. Progression of coronary calcium is observed at typical predilection sites of atherosclerosis in the coronary tree. Changes in overall coronary calcium result from uniform changes at these sites. This uniform pattern of change suggests that the development of calcified plaque disease is a coronary systemic process. The baseline amount of coronary calcium is significantly associated with its progression. In patients with a high baseline calcium score, absolute progression is enhanced. LDL-cholesterol is the most important risk factor influencing progression. Indeed, the effect of medical therapy on coronary atherosclerosis can be assessed. Preliminary data indicate that clear-cut progression of coronary calcium is associated with an increased risk of cardiac events.

For the first time, EBT-derived measurements of the progression of coronary calcium enable direct assessment of the activity of coronary calcified atherosclerosis. The interaction between therapeutic measures, progression of anatomical disease, and clinical course can be appreciated.