Agatston Coronary Calcium Score Research Articles

Comparison of the coronary calcium score with the estimated coronary risk

The role of coronary calcium scoring in coronary risk estimation is not well established. Calcium scoring could provide additional information in a certain subgroup of patients where the calcium score does not match the conventional Framingham risk estimates. We explored the characteristics of such a subgroup. The study participants were 1653 asymptomatic persons who underwent routine health screening and calcium scoring using the 16-slice multidetector computed tomography. Risk stratification was performed in five categories both by 10-year Framingham coronary risk and the Agatston coronary calcium score. Risk stratifications by coronary calcium score and absolute risk showed a large discrepancy (difference > or =3 classes) in about 9% of participants. The proportion increased with age (P for trend <0.0001). An exploratory analysis revealed that age (partial R=0.109, P<0.0001) and the presence of the metabolic syndrome (partial R=0.025, P<0.001) were independent variables that accounted for the variance of the residual of regression between the log-transformed value of coronary calcium score and the absolute risk. Calcium scoring may be clinically more useful in older (> or =50 years) participants and/or in participants with the metabolic syndrome because of the relatively higher probability of obtaining additional information that the conventional Framingham risk estimation cannot provide.

The latest on the calcium story

Coronary calcium scanning is no longer restricted to specialized centers but has become widely available as a test that can easily be performed in clinical practice. There have been parallel developments in scientific evaluation of coronary calcium scanning in numerous research studies and the practical use of this test. A number of reports have clarified the relation between the unstable coronary plaque and coronary calcium. Whereas calcium is a frequent feature of plaque rupture, there is too much overlap with more stable plaques to be specific. However, data are accumulating to indicate that calcium is associated with coronary atherosclerotic disease activity. Indeed, reports presented within the past year have demonstrated that very high calcium scores, in particular those >1,000, indicate a significantly increased cardiovascular risk. The advent of cardiac spiral computed tomography (CT) has made coronary calcium scanning widely available. As this methodology is continuously evolving, a number of challenges regarding standardization of test ordering, performance, and interpretation have arisen. Currently, 4-slice spiral CT scanners are most widely used. Protocols with prospective or retrospective electrocardiographic triggering are used, which appear to yield results similar to the Agatston coronary calcium score compared with electron-beam CT, despite the technical differences. New scoring algorithms are being evaluated. With electron-beam and spiral CT we have, for the first time, a readily available test for direct diagnostic visualization of the coronary arteries in clinical practice. This represents the opportunity and the challenge of a proof of principle.

Impact of motion artefact on the measurement of coronary calcium score.

Reports have shown that total coronary calcium (CC) measured by electron beam CT (EBCT) correlates well with atheroma extent, and this in turn is a reliable indicator of risk for future ischaemic events. Although total CC may be measured using a conventional CT scanner, image quality is degraded by cardiac motion artefact. Errors in CC measurement owing to slice misregistration between adjacent breath-holds affect both conventional CT and EBCT. The latest generation conventional CT scanners have acquisition times of 500 ms or shorter, and, when combined with ECG triggering, quantitative CC measurement without reliance upon EBCT becomes a real possibility. We investigated the effect of motion on the measured calcium score using a moving phantom. Our results show that use of ECG triggering with conventional CT improves reproducibility of Agatston calcium score measurement. Increasing motion time during image acquisition results in an apparent increase in the Agatston CC score. Alternative measures of the amount of CC may be less susceptible to motion-induced bias, but have a similar reproducibility.