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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.