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Mental Stress More Dangerous Than Exercise for Some
Heart Patients
Anxiety restricts blood flow in some patients – more
than assumed
March 7, 2006 - The fear of public speaking might
cause some people to do more than just break out in a cold sweat and
battle stomach-churning butterflies - it could prove to have
consequences for their heart health. University of Florida cardiologists have identified
a group of heart disease patients who appear especially vulnerable to
the physical effects of mental stress.
Chronic anxiety, depression or anger are widely
recognized as raising the risk of heart attack, hospitalization or
sudden death in patients whose hearts suffer dangerous decreases in
blood flow during exercise testing. Even something as simple as public
speaking, doing mental arithmetic or recounting an argument with a loved
one can trigger a problem.
But until now, patients who trod the treadmill
without experiencing chest pain or restricted blood flow had never been
similarly scrutinized when it came to mental stress.
Yet what goes on in their heads could have
consequences for their hearts as well, UF researchers write in today's
issue of the Journal of the American College of Cardiology.
A third of the heart patients they studied
developed temporary changes in heart rhythm or restricted blood flow
when they were asked to role-play a difficult interpersonal situation,
even though their hearts responded normally to exercise.
"Recently our group and some other investigators
have started to expand the population of patients that we're looking at
to try to explore what happens when mental stress is applied," said
David S. Sheps, M.D., a professor and associate chairman of
cardiovascular medicine at UF's College of Medicine and the Malcom
Randall Veterans Affairs Medical Center.
"We believe the phenomenon of mental stress-induced
reductions in blood flow to the heart is much more common than has been
previously recognized."
In general, studies have shown that as many as
two-thirds of patients with coronary artery disease who experience
exercise-related reductions in blood flow to the heart respond similarly
to mental stress.
These bouts often produce no symptoms of chest pain
and are rarely detectable on a standard electrocardiogram. Yet last year
UF researchers found that these patients have a threefold greater risk
of dying - as large a risk factor as cigarette smoking or high
cholesterol.
Other studies have linked stress experienced after
mass disasters or natural catastrophes with a rise in heart attacks and
sudden death.
Psychological stress can leave the heart more prone
to developing arrhythmias or electrical instability and the blood more
prone to clotting.
Stress appears to raise heart rate and rapidly hike
blood pressure, increasing the heart's need for oxygen-rich blood, Sheps
said.
Yet less oxygen is supplied, in part because
coronary arteries constrict, impeding blood flow. Doctors are concerned
that this reaction to stress in the laboratory is simply a snapshot of
how patients respond to the stress of life day in and day out.
In the current study, funded by the National
Institutes of Health and Bristol-Myers Squibb, UF researchers studied 21
men and women with documented heart disease who had no signs of reduced
blood flow during exercise on the standard exercise treadmill test or on
nuclear perfusion scans of the heart.
Participants were given two minutes to prepare to
deliver a four-minute speech about a hypothetical stressful situation.
Blood pressure and electrocardiographic measurements were taken every
minute during the speech and for 10 minutes afterward.
About half an hour after the speech, participants
underwent heart imaging scans that reflected blood flow to the heart
during the stressful situation.
"These are patients who for example might have had
a severe lesion or a narrowing of one of the coronary arteries and may
have had a stent inserted; they're tested after that and found to have
no decreased blood flow with the standard type of exercise testing,"
Sheps said. "However, we found that about 30 percent of them had
evidence of decreased blood flow with the mental stressor."
In general, 20 percent to 30 percent of all
patients cardiologists see could respond in a similar fashion, Sheps
estimated. Simply warning patients to avoid stress because it's bad for
them is not enough, he added.
"All of us are leading more and more stressful
lives, and it's hard to avoid it," he said. "We as physicians need to
find better ways to treat this phenomenon to avoid having patients
develop this type of response to an increased stressor."
UF researchers are now conducting a related study
involving more than 300 patients. They are interested in replicating the
findings and determining whether these patients are more likely to
suffer a heart attack, be hospitalized or die from cardiac
complications, Sheps added.
Why does mental stress restrict blood flow in some
patients even when exercise fails to have the same effect? The effects
of mental stress could predominantly affect the heart's smaller vessels,
causing them to spasm and temporarily limiting blood flow, he
speculated. In contrast, exercise tends to affect the heart's larger
vessels.
The findings suggest patients who experience
reductions in blood flow detectable when they are experiencing mental
stress but not during standard exercise radionuclide testing may have a
worse form of heart disease than expected, cautioned David S. Krantz,
Ph.D., chairman and a professor of medical and clinical psychology at
the Uniformed Services University in Bethesda, Md.
"This patient group warrants further study since
they may have functionally more severe coronary artery disease," he
said.
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