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Mental Stress Testing Detects Patients at High Risk for Cardiac Events Missed by Standard Exercise Testing

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Duke Health News 919-660-1306

DURHAM, N.C. -- Patients with a history of coronary artery
disease who test positive on experimental mental stress tests
are almost three times more likely to suffer a serious cardiac
event than those who don't, according to a new study by Duke
University Medical Center researchers.

The researchers concluded that treadmill tests, the method
most commonly used by cardiologists to determine the risk of
future heart attacks, missed many heart patients who were at
the greatest risk. In this group of patients, treadmill tests
were not a strong predictor of future cardiac events.

The findings are published in the June 5 issue of the
Journal of the American Medical Association.

Of 126 heart patients followed for up to five years, Duke
researchers found that more than 27 percent of those who
responded adversely to mental stress testing experienced a
significant cardiac event, compared to only 12 percent of those
who did not.

The cardiac events included death, heart attack and unstable
or progressive angina, or chest pain requiring surgery or
coronary angioplasty.

"Our data suggest that there is a large subgroup of at-risk
heart patients who are not being identified by standard
treadmill testing," said psychologist James Blumenthal, lead
investigator of the study. "If the results are confirmed by
larger studies, it would suggest that physicians should
reconsider the way we evaluate patients with heart disease.

"Another implication of our study suggests that stress
management techniques might be an effective strategy in
potentially reducing the risk of future cardiac events in this
group of patients."

The study was supported by grants from the National
Institutes of the Health.

Using radiologic and electrophysiologic tests on all study
participants, the Duke researchers measured a condition known
as myocardial ischemia, which occurs when heart muscle does not
receive enough oxygen-rich blood. The lack of blood flow, when
prolonged, may ultimately cause damage or death to the heart
muscle starved of oxygen.

While ischemia caused by exercise is often felt as chest
pain by heart patients, ischemia caused by mental stress is
almost always "silent," Blumenthal said. "During exercise, such
as the treadmill test, ischemia is largely due to the fact that
the body cannot keep up with the increased demand of the heart
for more blood and oxygen."

"However, with mental stress, reduced supply of blood may be
more critical," said Dr. Wei Jiang, one of the study's
cardiologists. "For reasons that are not entirely clear, the
blood vessels supplying the heart constrict during mental
stress. This type of ischemia normally occurs at low heart
rates and goes largely unnoticed by patients."

While the exact cause of this constriction is not known for
certain, Jiang said that stress hormones may be to blame.

Because mental stress-induced ischemia goes unfelt by
patients, Blumenthal said it is especially important to be able
to predict which patients are at greatest risk.

The mental stresses used in the study were induced in the
laboratory through a battery of five prototype tests, each
lasting about three minutes. Patients were asked to:

Give a speech on a current events topic to a group of
observers. Read a short passage from a magazine. Participate in
a standardized interview to assess "Type A" personality. Trace
the outline of a star from its reflection on a mirror. Perform
a series of complex serial additions.

In the last two tests, patients were continually encouraged
to perform at an increasingly faster rate without making
mistakes.

Data published last year in the journal Circulation by the
Duke researchers showed a strong correlation exists between the
mental stress induced in a research laboratory and the stresses
of everyday life.

Currently, the Duke team is evaluating the effectiveness of
different behavioral strategies on those patients involved in
the current study who demonstrated mental stress-induced
ischemia to determine if there is any beneficial effect on
future cardiac events.

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