Curriculum in CardiologyCoronary artery calcium scanning: Clinical paradigms for cardiac risk assessment and treatment
Section snippets
Brief overview of CAC
Electron beam computed tomography uses a rotating electron beam to acquire triggered, tomographic x-ray images acquired over 100 milliseconds at 3-mm intervals, in the space of a 30- to 40-second breath-hold, and quantifies the calcified plaque in the epicardial coronary arteries. Multidetector computed tomography uses a rotating gantry with a special x-ray tube and variable number of detectors (from 4 to 64), with images acquired over 165 to 420 milliseconds at 0.5- to 3.0-mm intervals, and
Key studies
The final report of the NCEP guidelines29 made the following recommendation, based on the data of Raggi et al3, 30: “Therefore, measurement of coronary calcium is an option for advanced risk assessment in appropriately selected persons. In persons with multiple risk factors, high coronary calcium scores (e.g., >75th percentile for age and sex) denotes advanced coronary atherosclerosis and provides a rationale for intensified low density lipoprotein (LDL)–lowering therapy.” Raggi et al30
Patient selection
Recommendations for CAC scanning are not based on age and sex alone. Rather, the Framingham Risk Score, which incorporates both age and sex, is recommended as the initial step in selecting the appropriate test populations. Asymptomatic patients in the 10%-20% Framingham 10-year risk category (moderately high risk) comprise the group that presents the greatest challenge to the treating physician and are those in whom the application of CAC scoring is most appropriate. Although this application
Limitations
As with any diagnostic method, CAC testing has limitations. It does not evaluate the degree of coronary stenosis; the specificity for obstructive disease of any CAC >0 is in the 40% range.54 In addition, the specificity of CAC for cardiac events is quite low, as only a minority of patients with CAC experience events. However, the specificity of CAC for the identification of atherosclerosis is nearly 100%. Coronary artery calcium does not visualize soft plaque, and patients with exclusively
Conclusions
The increasing use of CAC scanning for risk assessment is now supported by extensive evidence in appropriately selected patients. Critical to its implementation is the ability of the practitioners to understand the data and the limitations of the test, as outlined in this review, and to appropriately use this knowledge in applying the test results to the care of their patients.
References (54)
- et al.
Coronary artery calcium evaluation by electron beam computed tomography and its relation to new cardiovascular events
Am J Cardiol
(2000) - et al.
Prediction of coronary events with electron beam computed tomography
J Am Coll Cardiol
(2000) - et al.
Coronary calcification, coronary risk factors, C-reactive protein and atherosclerotic cardiovascular disease events: the St. Francis Heart Study
J Am Coll Cardiol
(2005) - et al.
Coronary calcification in the diagnosis of coronary artery disease
Am J Cardiol
(1979) - et al.
Comparison of electron beam computed tomography with intracoronary ultrasound and coronary angiography for detection of coronary atherosclerosis
J Am Coll Cardiol
(1997) - et al.
Quantification of coronary artery calcium using ultrafast computed tomography
J Am Coll Cardiol
(1990) - et al.
Age and gender distributions of coronary artery calcium detected by electron beam tomography in 35,246 adults
Am J Cardiol
(2001) - et al.
Ethnic differences in coronary atherosclerosis
J Am Coll Cardiol
(2002) - et al.
African Americans and Caucasians have a similar prevalence of coronary calcium in the Dallas Heart Study
J Am Coll Cardiol
(2004) - et al.
Use of electron beam tomography data to develop models for prediction of hard coronary events
Am Heart J
(2001)