Traditional risk-factor scoring fails to identify
approximately one-third of women likely to develop coronary
heart disease, the leading cause of death of women in the
United States, according to a pair of reports from
cardiologists at Johns Hopkins.
"Our best means of preventing coronary heart disease
is to identify those most likely to develop the condition
and intervene with lifestyle changes and drug treatment
before symptoms start to appear," said the senior author of
both studies, cardiologist Roger Blumenthal, an associate
professor and director of the
Ciccarone Preventive Cardiology Center at the School of
Medicine and its
Heart Institute. "The goal is to strongly consider
therapies, such as aspirin, cholesterol-lowering
medications and, possibly, blood pressure medications for
individuals at higher risk so that heart attacks will be
less likely to occur in the future."
The Johns Hopkins findings, the latest of which appear
in the American Heart Journal online Dec. 16, is believed
to be one of the first critical assessments of the
Framingham Risk Estimate as the principal test for early
detection of heart disease. The researchers wanted to
determine why many of these women at risk for heart disease
are not identified earlier.
The Framingham Risk Estimate, or FRE, is a total
estimate of how likely a person is to suffer a fatal or
nonfatal heart attack within 10 years, and it is based on a
summary estimate of major risk factors for coronary heart
disease, such as age, blood pressure, blood cholesterol
levels and smoking.
However, Blumenthal said, many women with
cardiovascular problems go undetected despite use of the
Framingham score. While the death rate for men from
cardiovascular disease has steadily declined over the last
20 years, the rate has remained relatively the same for
women, he said.
In their latest report, the Johns Hopkins researchers
examined the risk of premature coronary heart disease in
women whose average age was 50 and who were participating
in the Sibling and Family Heart Study, a long-term study of
how heart disease develops among family members. Study
subjects had no symptoms of heart disease but had a sibling
who had been hospitalized for a coronary event, such as a
heart attack before age 60.
The researchers calculated each woman's Framingham
score and found that 98 percent of the study subjects were
gauged to be at very low risk for future coronary heart
disease, with an FRE of less than 6 percent, while only 2
percent of participants were judged to be at intermediate
risk for future coronary heart disease, with an FRE between
10 percent and 20 percent.
When the results were contrasted with evidence gleaned
from CT-scan measurements of calcium buildup in the
arteries, the researchers found that one-third of women
originally classified as very low risk actually had
coronary atherosclerosis, a hardening and narrowing of the
arteries that can lead to heart attacks if not controlled
with drug therapy along with diet, exercise and other
lifestyle changes. Indeed, 12 percent of women in the study
had advanced stages of atherosclerosis, while another 6
percent had severe calcium buildup.
"We wanted to verify if the Framingham score truly
captured who was most at risk, but it turns out to have
underestimated a large number of those who should be
considered for preventive therapies," Blumenthal said.
According to the researchers, performing cardiac CT
scans on everyone with a low Framingham score is not a
practical option for improving upon traditional risk-factor
screening. To better determine who should get scanned, even
if they have a low risk assessment, the Johns Hopkins team
began to search for additional predictors of who was most
at risk. They found that people with two or more risk
factors, such as obesity, smoking or metabolic syndrome,
plus a family history of heart disease, were those most
likely to have a high calcium score. It is this group, the
researchers said, who should be considered for a fast
cardiac CT scan, regardless of low Framingham scores, if
the physician or patient is unsure about the need to go on
long-term preventive therapies.
In a related second investigation, published online in
the May edition of the journal Atherosclerosis, the
Johns Hopkins team analyzed the Framingham scores of 2,447
women ages 45 to 65 who were participating in a long-term
study in Ohio of adults referred by a physician for a
cardiac risk assessment.
Again, when the FRE results were compared to calcium
scores, 84 percent (408 of 489) of those classified as low
risk by FRE actually had some coronary atherosclerosis.
Twenty percent of those who were classified at intermediate
risk by FRE had signs of advanced atherosclerosis.
"Our results show that if a CT scan had not been
performed in addition to traditional risk-factor scoring, a
large number of women would have missed the chance to begin
preventive therapies," said cardiologist Erin Michos, a
clinical research fellow at Johns Hopkins and its Heart
Institute. Michos led both studies.
"For some women, especially those with a family
history of heart disease and multiple risk factors for it,
additional screening using CT scan and calcium scoring may
be warranted," she said.
Funding for these studies, whose data analyses took
place between January 2003 and November 2004, was provided
by the National Institutes of Health, including the
National Institute of Nursing Research and the National
Heart, Lung and Blood Institute; the Johns Hopkins General
Clinical Research Center; and the Maryland Athletic Club
Other researchers involved in the two studies were
Khurram Nasir, Joel Braunstein, John Rumberger, Matthew
Budoff, Wendy Post, Chandra Vasamreddy, Diane Becker, Lisa
Yanek, Taryn Moy, Elliot Fishman and Lewis Becker.
— Gary Stephenson