The Risk Predictive Value of the Coronary Artery Calcification Score in Middle-Aged Healthy Men
The Risk Predictive Value of the Coronary Artery Calcification Score in Middle-Aged Healthy Men
Abstract & Commentary
By Harold L. Karpman, MD, FACC, FACP, Clinical Professor of Medicine, UCLA School of Medicine. Dr. Karpman reports no financial relationship to this field of study.
Synopsis: In middle-aged, asymptomatic men, the presence of coronary artery calcification proved to have substantial, cost-effective, independent prognostic value that was incremental to measured coronary risk factors in its ability to predict incident coronary artery disease.
Source: Taylor AJ, et al. Coronary Calcium Independently Predicts Incident Premature Coronary Heart Disease Over Measured Cardiovascular Risk Factors Mean Three-Year Outcomes in the Prospective Army Coronary Calcium (PACC) Project. J Am Coll Cardiol. 2005;46:807-814.
The framingham risk score (frs) is an excellent coronary artery heart disease (CHD) risk prediction tool.1-4 In addition, recent guidelines have outlined the potential use of anatomically based CHD risk assessments, especially using electron-beam computed tomography (CT) to detect coronary artery calcium (CAC)5,6 however, controversy still exists regarding whether, and to what extent, detection of CAC provides any incremental risk prediction beyond conventional CHD risk factor tools such as the FRS.
The Prospective Army Coronary Calcium (PACC) project was a prospective cohort study of US Army personnel which was designed to examine whether there was any incremental value of the CAC score above and beyond the FRC for the determination of CHD prognosis. CAC was found in 22.4% of men and 7.9% of women between the ages of 40 and 50 years (mean age, 43 years). Annual telephonic contacts over 1 to 6 years with the 2000 subjects were made and it was determined that 7 acute events occurred among the 364 men with CAC (CAC score of 10-44 in 2 subjects and > 45 in 5 subjects) and in only 2 of the 1263 men without CAC resulting in an 11.8-fold increase risk for incident CHD in subjects with CAC controlling for the FRS. These findings were highly significant suggesting that the presence of CAC in relatively young asymptomatic men provided substantial, cost-effective, independent prognostic value that was incremental to measured coronary risk factors in predicting incident CHD.
Commentary
The independent predictive value of CAC had been in question since electron-beam computed tomography was introduced many years ago. The value of global coronary risk scoring algorithms such as the FRC in evaluating CHD risk has been fully accepted by most cardiologists however, there are some who feel that the FRC incompletely identifies CHD risk and may lead to systematic over estimation of risk especially in lower-risk populations.7 A meta-analysis which examined the relationship between CAC, coronary risk factors and CHD events noted that many of the studies reported an independent relationship between CAC and either mortality or CHD events but that there was a substantial degree of variability in the reported strength of this relationship. The observed variability was thought to be due to the manner of risk factor assessment, the adjudication of outcomes and the inclusion of women in the cohort and therefore, the PACC project was designed to compare CAC scanning scores to measured risk factors in order to ascertain the true incremental value of CAC scanning in middle-aged men.
Generally expressed concerns about cost-effectiveness of CAC screening are certainly appropriate. The potential advantages of screening men age 40-50 included a generally lower prevalence of CAC in this age group thereby limiting the potential for over-detection of individuals identified as being at risk because of the dominant relationship between age and CAC score. The PACC study was underpowered to exclude relationships between CAC and CHD events in women; however, one study did suggest that such a relationship existed between CAC score and total mortality.8 Obviously, further studies in larger female cohorts are needed but, for the time being, the incremental predictive value of CAC over conventional risk factors for premature CHD outcomes in middle-aged men appears to be meaningful although prospective, carefully controlled trials with larger numbers of both men and women are needed before CAC screening can be recommended for widespread use. Because of the obvious clinical benefit of detecting early CHF and because the cost effectiveness analysis suggested significant overall benefit, payers should consider paying for this screening tool, at least for asymptomatic men older than age 40, at this time.
Reference
1. Taylor AJ, et al. 34th Bethesda Conference: Executive summary--can atherosclerosis imaging techniques improve the detection of patients at risk for ischemic heart disease? J Am Coll Cardiol. 2003;41:1860-1862.
2. Greenland P, et al. Prevention Conference V: Beyond secondary prevention: identifying the high-risk patient for primary prevention: noninvasive tests of atherosclerotic burden: Writing Group III. Circulation. 2000;101:E16-E22.
3. Grundy SM, et al. Implications of recent clinical trials for the national cholesterol education program adult treatment panel III guidelines. Circulation. 2004;110:227-239; Erratum in: Circulation. 2004 Aug 10;110:763.
4. Greenland P, et al. Improving coronary heart disease risk assessment in asymptomatic people: role of traditional risk factors and noninvasive cardiovascular tests. Circulation. 2001;104:1863-1867.
5. O’Malley PG, et al. Prognostic value of coronary electron-beam computed tomography for coronary heart disease events in asymptomatic populations. Am J Cardiol. 2000;85:945-948.
6. Pletcher MJ, et al. Using the coronary artery calcium score to predict coronary heart disease events: a systematic review and meta-analysis. Arch Int Med. 2004;164:1285-1292.
7. Grover SA, et al. Identifying adults at increased risk of coronary disease. How well do the current cholesterol guidelines work? JAMA. 1995;274:801-806.
8. Raggi P, et al. Gender-based differences in the prognostic value of coronary calcification. J Womens Health (Larchmt). 2004;13:273-283.
In middle-aged, asymptomatic men, the presence of coronary artery calcification proved to have substantial, cost-effective, independent prognostic value that was incremental to measured coronary risk factors in its ability to predict incident coronary artery disease.Subscribe Now for Access
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