Illustration by Maria Rendon
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Keeping the Beat
By Melissa Hendricks, March-April 2004
These new heart tests could save your life
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Mort Libov knew smoking was bad for you. He just didn't think it was bad
for him. After indulging in a pack and a half daily for 50 years, the
retired television producer and director felt no chest pain, no shortness of
breath, no cough—none of the symptoms the habit is known to cause. So he
didn't pay much mind to the doctors and loved ones urging him to quit.
"Everybody thinks they're bigger than life," says Libov, 68.
Then he took the test that changed his life—and may have saved it.
Last August, Libov's doctor in Baltimore, Maryland, ordered an ultra-fast
CT scan as part of a routine checkup. The cross-sectional images showed white
flecks—calcium deposits—in the arteries, which are a sign of
atherosclerosis.
"If you want to be a patient of mine for a short time, continue to
smoke," Libov's doctor told him. "Or, if you want to be a patient
of mine for a long time, stop smoking immediately." In other words, there
was a good chance some plaque would soon dislodge from the sludge, float free,
and then jam one of the arteries leading to his heart, triggering a heart
attack.
Libov did not need to hear more. Immediately after his appointment, he
collected his cigarettes and drove to the golf course, where he gave away all
but one. "I smoked the last cigarette on the 15th hole," he says,
"and that was it." He has not had a cigarette since that day.
Libov is a lucky man, no doubt about it. But it wasn't just luck that
altered his life. The test that alerted him to the danger lurking in his own
body could herald the future of cardiovascular disease diagnosis. Thanks to
breakthrough research being done at government, private, and university labs
around the country, in the coming decade asymptomatic patients who are at known
risk of heart disease, as well as folks who are unaware they are at any risk at
all, will increasingly be directed to one of a slew of new tests that can catch
the killer before it strikes.
"Absolutely, this is a new era," says Stanley Hazen, M.D., Ph.D.,
head of preventive cardiology at the Cleveland Clinic. "We're
identifying how atherosclerosis occurs and understanding the basic science of
heart disease. We've seen the tip of the iceberg. There's a lot more to
come."
But along with this new understanding comes a host of new questions: When
will a test provide useful information, and when will it cause needless
worry—or a false sense of security? Which tests provide new data to
doctors, and which repeat what another test has already shown? And most
important, which patients should get which tests—especially when
insurance might not pay?
In treating heart disease, the key word is risk: the patient's odds of
having a heart attack. The higher the risk, the more aggressively doctors seek
to lower it with drugs, diet, and exercise.
The best way to learn your own risk is to see your doctor, who will weigh a
variety of factors, including your blood pressure, cholesterol levels, and
personal and family health histories.
For people without diagnosed heart disease or diabetes (which damages the
cardiovascular system), the most popular way to calculate risk is to use a
formula developed from the Framingham Heart Study, the federal government's
long-term investigation of heart disease, conducted in Framingham,
Massachusetts. Into the formula go your age, cholesterol levels, and other
vital statistics. Out come your chances of having a heart attack or dying from
cardiovascular disease in the next 10 years. (You can perform a
rough version of this calculation at the American Heart Association
website.)
At the other end of the risk spectrum are people who are actually
experiencing the chest pain of angina. For that group, scientists recently
developed a new method of predicting whether a heart attack will occur within
the next six months. The test, for an enzyme in the blood called
myeloperoxidase, is highly accurate.
Ideally, heart specialists would like a similar test to predict a
patient's long-term risk of heart disease, before the person starts
experiencing symptoms. Using new techniques such as those described below,
doctors are beginning to hone their understanding of which patients need which
treatments. By intervening in time, they may be able to cut the patient's
risk and even save a life.
Uncovering Arterial Plaque Through Imaging
Researchers are refining technologies such as the CT scan, MRI, and
ultrasound to make more revealing pictures of the arteries and heart. The tests
are noninvasive and can uncover atherosclerosis that would otherwise go
undetected.
The National Institutes of Health is sponsoring a study that may help
scientists decide how and when to use the new tests. While the main goal of the
10-year Multi-Ethnic Study of Atherosclerosis (MESA) is to learn how heart
disease develops, the investigators hope to discover which tests best predict
risk. Project leaders expect the first results of the study in two to three
years.
Advanced imaging tests are generally most helpful for those who have a
medium or uncertain risk of heart disease, as determined by the standard tests
of cholesterol, blood pressure, and other markers. A positive finding could
inspire more aggressive treatment to protect the heart. These tests also could
benefit people such as Libov who are at high risk of heart disease but
don't yet have symptoms.
Clearly, though, these frontier-science methods are not yet for everybody.
The first problem is cost. An ultrafast CT scan of the heart costs $175 to $500
or more, a fee not generally covered by insurance. MRIs cost even more. To
justify its expense, a test should provide information that goes beyond other
more affordable methods of assessing risk. So far, few studies have looked into
the cost-effectiveness of the new imaging tests.
Another problem: the findings are imperfect. For example, plaque causes
trouble when it ruptures, but not all plaque is prone to rupture, says Ann
Bolger, M.D., professor of clinical medicine at the University of California at
San Francisco. The CT scan could show plaque, but if it is stable, it may never
cause anything but worry. At present, there's no test to distinguish
between these two types of plaque.
On the other hand, an ultrafast CT scan ignores plaque that has not
calcified. So the test results might give a patient dangerous reassurance.
"Some patients who learn they have no calcium will go straight to
McDonald's," says Bolger. "But they may be the ones who are most
at risk."
Bottom line: If you have a low risk of heart disease based on conventional
risk factors such as weight and lifestyle, you would do just as well to stick
with the more traditional tests given to predict heart health, such as
cholesterol levels and blood pressure. If, on the other hand, you have reason
to be concerned, you might want to consult your doctor about whether any of the
new imaging tests would be appropriate for you.
Blood Tests That Reveal a Predator's Tracks
Scientists from labs around the world have discovered that other substances
in the blood may indicate heart disease as well as, or better than,
cholesterol. One that has attracted the most attention is C-reactive protein
(CRP).
The liver produces CRP in response to inflammation. Many experts now believe
that cardiovascular disease is at least in part an inflammatory condition, in
which the body's immune system produces an excess of proteins that trigger
atherosclerosis. They continue to puzzle over exactly what infection, injury,
or other factor sparks the inflammation. Growing evidence suggests that the
higher your CRP level, the higher your risk of heart attack—even if you
have no other indicators of heart disease.
At about $40, the CRP test could be an economical way to find people at risk
of heart disease. So who should have their CRP level tested? As with the
ultrafast CT scan, medical experts say the test could help people who have a
medium risk of heart disease, because those with high and low risk already know
where they stand. (Medium risk means a 10 to 20 percent chance of heart disease
in the next 10 years. This is a broad category of people that would include,
for example, a 50-year-old nonsmoking man with borderline high cholesterol,
borderline high blood pressure, and a close relative who has had a heart
attack.)
Again, some doctors warn against widespread use of the test. Many different
factors can cause CRP levels to spike. Having a cold can boost CRP, as can
cigarette smoking, inflammatory diseases such as rheumatoid arthritis, and
physical inactivity. As a result, doctors advise patients who receive a high
CRP result to repeat the test.
Also, medical experts have not yet demonstrated what people with high CRP
readings should do to protect their hearts. Logic suggests that reducing CRP
with cholesterol-lowering drugs called statins will reduce the risk of heart
disease, but scientists have not yet demonstrated that. The ongoing JUPITER
trial, which is following more than 15,000 healthy North Americans with high
CRP levels taking either a statin drug or a placebo, is testing the theory.
The Hunt for Dangerous Genes
At the forefront of efforts to refine heart disease risk are the researchers
who are hunting for genes that predispose a person toward a strong or a weak
cardiovascular system. Everyone knows the medical anomalies: Composer Eubie
Blake, who started smoking at age six and lived to be 100. Jim Fixx, the
running aficionado who died of a heart attack at age 52. Genes that make people
more or less susceptible to heart disease could explain these exceptions to the
rules as we now understand them.
Researchers have discovered only a few genes that are related to heart
disease, but they will undoubtedly find more. Sharon Kardia, Ph.D., an
assistant professor of epidemiology in the University of Michigan Public Health
Genetics program, is studying how patients with high blood pressure respond to
various drugs based on their genes. She recently reported that people who have
a version of a gene called adducin 2 achieved greater declines in blood
pressure with drugs called beta blockers than did people without that type of
gene.
Which means that genetic testing might one day help doctors decide which
blood pressure drug to prescribe, Kardia says. It might also show that one
patient would benefit more from trying a diet to reduce high blood pressure,
while another could lower blood pressure faster by taking medication.
Promising as these new tests are, we already know a great deal about the
risks associated with heart disease. After analyzing the results of three
long-term studies involving thousands of volunteers, Philip Greenland, M.D.,
professor of preventive medicine at Northwestern University, concluded that 90
percent of heart attacks occur in people who have at least one of the known
risk factors: high cholesterol, high blood pressure, diabetes, or smoking.
So while the tools for discovering and understanding heart disease may be
rapidly expanding, the prescription for protecting your heart hasn't
changed: keep your "bad" cholesterol level and your blood pressure
down, reduce your risk of diabetes by watching your weight and exercising, and
do not smoke. Science can go only so far in diagnosing and repairing a damaged
heart. The most effective treatment, as always, is prevention.
Melissa Hendricks wrote about hormone replacement therapy in the
November-December 2002 issue.
Now, review our guide to different types of heart tests that might benefit
you.
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