Coronary Calcium Screening Seen Useful Beginning Between Age 40 and 50

J Am Coll Cardiol. 2005;46:807-814

Sept. 23, 2005 - In healthy, asymptomatic men and women 40 to 50 years of age, the presence of coronary artery calcification "provides substantial, cost-effective, independent prognostic value" in predicting coronary events above and beyond that gained from traditional coronary risk factors such as blood pressure and cholesterol.
Washington, D.C.-based investigators, who report this finding in the Journal of the American College of Cardiology for September 6th, note that recent guidelines and position statements on coronary artery calcium (CAC) testing largely advocate the test for individuals over age 50 who are at intermediate-risk for coronary heart disease [CHD] and CHD events.
"The PACC (Prospective Army Coronary Calcium) project data support this general concept and challenge the notion that plaque burden assessments should not be applied to younger populations at lower absolute CHD risk," Dr. Allen J. Taylor and colleagues from Walter Reed Army Medical Center write.
"One thing about coronary calcium, if you scan folks in their 50s and 60s you find so many have subclinical calcium in their arteries ? practically one in two come out with an abnormal test result ? and there is concern that that leads to over detection," Dr. Taylor said in an interview with Reuters Health.
When a younger-age population is screened, about one in five men have an abnormal finding. "That, I think, is useful because you don't over-activate the population, but you find that small subpopulation ? 20% ? that has the highest risk," Dr. Taylor continued.
In the PACC study, 2000 men and women with a mean age of 43 years underwent standard coronary risk assessment and coronary artery calcium detection by electron beam computed tomography.
"The principal finding," Dr. Taylor said, "is that coronary calcium was associated with a nearly 12-fold increased risk of heart disease events in men at a mean of 3 years follow-up after adjusting for other measured risk factors such as BP [blood pressure] and cholesterol."
"This study gives us additional confidence that calcium scanning is additive to measured BP and measured blood cholesterol, which is really standard for detecting coronary risk," Dr. Taylor noted.
The other principal finding, he said, was that CAC testing in the 40 to 50-year-olds appears to be moderately cost-effective, on the assumption that the test will identify some individuals at higher risk who will then be appropriately treated and, as a result, coronary events will be prevented.
Summing up, Dr. Taylor said the study "really brings to bear that people are developing the precursors of heart attacks at a very young age and extends what we knew about coronary calcium testing ? that even screening at a younger age could be effective in identifying folks that have increased risk."
The researcher cautioned, however, that the subjects in the PACC study are primarily Caucasian and that similar information needs to be developed for ethnic subpopulations, because their rates of coronary calcium are not the same and the relationship between events and calcium has not been shown. More data for women are also needed, he added.

Clinical Context

CACs seen on EBCT studies can predict an increased risk of CHD events, and these lesions also correlate with other cardiac risk factors. In a study by Mahoney and colleagues of 384 subjects who underwent an evaluation for cardiac risk factors in the teenage and young adult years, 31% of men and 10% of women were found to have CACs in their fourth decade. The study, which was published in the February 1996 issue of the Journal of the American College of Cardiology, demonstrated that elevated BP, lower high-density lipoprotein (HDL) cholesterol levels, and increased body size in youth were associated with a later increased risk of CACs.
The current research examines whether the presence of CACs can augment cardiac risk assessment beyond traditional risk factors. The current authors also examine whether assessment with computed tomography may be cost-effective.

Study Highlights

Study participants included U.S. Army personnel between the ages of 40 and 50 years. Patients with a history of CHD or angina pectoris were excluded from participation.
All subjects underwent a thorough history and physical examination as well as laboratory evaluation to determine cardiac risk. Participants also underwent EBCT to evaluate for a CACs. The EBCT scans were read by an experienced radiologist blinded to the patient history.
A patient was considered to have a positive EBCT result if any significant calcifications were found in the coronary arteries.
All subjects were followed up for the incidence of CHD, defined by sudden cardiac death, myocardial infarction, or unstable angina pectoris. CHD events were tracked through contact with study participants, and medical records were reviewed to confirm events. The planned follow-up period for the research is 5 years, and the current report is a planned interim analysis after three years of follow-up.
1,999 adults entered the study, and follow-up data were available for 1,983 persons. 82% of subjects were men, and the mean age was 42 years old. 71.8% of participants were Caucasian. The most prevalent cardiac risk factors were hypertension (30.8% of the cohort), family history of CHD (31.7%), and active tobacco use (6.9%).
CAC was found in 22.4% of men and 7.9% of women. 72 men had a Framingham risk score of more than 10%, and one third of these subjects were found to have CACs on EBCT.
Nine CHD events occurred during the follow-up period, and all of these events occurred in men. The mean age of participants at the time of the CHD event was 43 years. 4 events occurred in men with a Framingham risk score less than 6%, and 5 events occurred in men with a Framingham risk score between 6% and 10%.
The adjusted relative risk of a CHD event associated with a positive EBCT result was 11.8. There was an incremental increase in the risk of CHD events associated with higher degrees of coronary calcifications, with each increasing quartile of coronary calcification burden associated with a hazard ratio of 4.3.
Incorporating EBCT into traditional cardiac risk factor assessment was judged to be cost-effective. The authors calculate that an added $37,633 estimated expenditure translated into one additional quality-adjusted life year for patients.