Most “risk calculators” used by clinicians to gauge
a patient’s chances of suffering a heart attack and
guide treatment decisions appear to significantly
overestimate the likelihood of a heart attack,
according to results of a study by investigators at
Johns Hopkins and other institutions.
Physicians commonly use standardized risk assessment
systems, or algorithms, to decide whether someone
needs care with daily aspirin and
cholesterol-lowering drugs or just watchful waiting
and follow-up exams. These algorithms calculate
heart attack probability using a combination of
factors, such as gender, age, smoking history,
cholesterol levels, blood pressure and diabetes,
among others.
The new findings, reported Feb. 17 in Annals of
Internal Medicine, suggest four out of five widely
used clinical calculators considerably overrate risk,
including the most recent one unveiled in 2013 by
the American Heart Association and the American
College of Cardiology amid controversy about its
predictive accuracy.
The results of the study, the research team says,
underscore the perils of overreliance on
standardized algorithms and highlight the importance
of individualized risk assessment that includes
additional variables, such as other medical
conditions, family history of early heart disease,
level of physical activity, and the presence and
amount of calcium buildup in the heart’s vessels.
“Our results reveal a lack of predictive accuracy in
risk calculators and highlight an urgent need to
reexamine and fine-tune our existing risk assessment
techniques,” says senior investigator Michael Blaha,
M.D., M.P.H., director of clinical research at the
Johns Hopkins Ciccarone Center for the Prevention of
Heart Disease.
“The take-home message here is that as important as
guidelines are, they are just a blueprint, a
starting point for a conversation between patient
and physician about the risks and benefits of
different treatments or preventive strategies,”
Blaha adds.
In addition to patient safety, risk overestimation
has important public health and economic
ramifications, the investigators say.
“For example, cholesterol-lowering medicines, while
clearly cost-effective in high-risk patients, are
less so among low-risk patients,” says lead author
Andrew Paul DeFilippis, M.D., M.Sc., assistant
professor of medicine at the University of
Louisville and adjunct assistant professor of
medicine at the Johns Hopkins Ciccarone Center for
the Prevention of Heart Disease. “Therefore,
overestimation of risk could lead to more health
care spending, less health gain, and unnecessary
exposure to drug side effects.”
Prevention and treatment decisions are
straightforward in some people, but many have
borderline risk scores that leave them and their
clinicians in a gray zone of uncertainty regarding
therapy. Under the American Heart Association’s most
recent guidelines, people who face a 7.5 percent
risk of suffering a heart attack within 10 years are
urged to consider preventive therapy with a
cholesterol-lowering medication. Risk overestimation
could be particularly problematic for those with
marginal risk scores estimates, because it can put a
person with a relatively low-risk profile into the
“consider treatment” group. This is why patients
with such borderline scores could benefit from
further risk assessment with tests like CT scans
that visualize the degree of calcification in the
arteries of the heart.
“Additional testing could be a much-needed
tiebreaker in the all-too-common ‘to treat or not to
treat’ dilemmas,” says study co-author Roger
Blumenthal, M.D., professor of medicine and director
of the Johns Hopkins Ciccarone Center for the
Prevention of Heart Disease. “Such testing should be
considered in all patients with marginal risk scores
— those in whom the decision to treat with long-term
statin and aspirin remains unclear.”
The new findings stem from an ongoing study known as
the Multi-Ethnic Study of Atherosclerosis, or MESA,
following some 7,000 men and women nationwide, ages
45 to 84, from different ethnic backgrounds without
preexisting cardiovascular disease.
To check the accuracy of each one of five risk
calculators, the investigators compared the number
of predicted versus actual heart attacks and strokes
among a group of more than 4,200 MESA participants,
ages 50 to 74, followed over a decade. All people
involved in the research were free of cardiovascular
symptoms at the beginning of the study and had no
history of heart attacks and strokes.
Four out of five risk scores analyzed in the study
overestimated risk by anywhere from 37 percent to
154 percent in men and 8 percent to 67 percent in
women.
The new American Heart Association calculator
overestimated risk by 86 percent in men and by 67
percent in women. In the group with a predicted risk
score between 7.5 to 10 percent — the threshold at
which initiation of stain is recommended — the
actual rate of heart attacks and strokes was only 3
percent in men and 5 percent in women, well below
the risk level at which statins should be considered.
The least flawed prediction of heart attack risk was
generated by the Reynolds risk score, which
overestimated risk among men by only 9 percent, but
underestimated it by 21 percent among women. In
addition to age, gender, smoking, diabetes,
cholesterol and blood pressure, the Reynolds score
includes family history of early heart disease.
While not the subject of the current study, the
researchers say the overestimation of risk likely
stems from the fact that calculators, including the
newest one, use risk reference data obtained decades
ago, when more people were having heart attacks and
strokes.
“The less-than-ideal predictive accuracy of these
calculators may be a manifestation of the changing
face of heart disease,” Blaha says. “Cardiac risk
profiles have evolved in recent years with fewer
people smoking, more people having early preventive
treatment and fewer people having heart attacks or
having them at an older age.”
The Reynolds risk equation, for example, was based
on data from a more recent group of patients
compared with other calculators, which may explain
its superior accuracy, the researchers say.
“Our next step is to explore the impact of multiple
cardiovascular risk factors on risk score accuracy,”
DeFilippis says. “Such an analysis will generate
important insights about which factors need to be
recalibrated and what new variables should be
considered as we develop new risk scores for today’s
patients.”
Atherosclerotic heart disease or atherosclerosis — a
condition marked by the buildup of fatty plaque and
calcium deposits inside the major blood vessels — is
the main cause of heart attacks and strokes,
claiming the lives of some 380,000 people in the
United States each year.
For more information
Annals
of Internal Medicine
Johns Hopkins Medicine
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