Mental Stress Reduces Blood Flow To The Heart In Patients With Gene Variation
University of Florida researchers have identified a
gene variation in heart disease patients who appear especially
vulnerable to the physical effects of mental stress - to the point where
blood flow to the heart is greatly reduced.
"Searching for the presence of this gene may be one way to better
identify patients who are at an increased risk for the phenomenon," 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.
Those with the gene variation are three times more likely to experience
dangerous decreases in blood flow to the heart - a condition doctors
call ischemia - than heart disease patients without it. Ischemia
increases the chance these patients will suffer a heart attack, heart
rhythm abnormalities or sudden death, UF researchers report in the April
14 issue of Archives of Internal Medicine.
"There’s no question that in certain populations it is associated with
worse prognosis than in patients who do not have mental stress-induced
ischemia in terms of overall adverse events and also mortality," Sheps
said. "And it has become apparent that it is far more prevalent than we
initially thought. Most of the studies that have been published to date
have involved populations of patients who had coronary disease and
positive exercise stress tests. But recently we and other investigators
have shown that a much broader category of patients also are prone to
mental stress ischemia."
Past 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 previous UF research has shown 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 on a daily basis.
An estimated 10 percent of all patients with coronary disease experience
detectable mental stress-induced reductions in blood flow to the heart.
In some subsets of patients the phenomenon may be even more prevalent,
involving up to 40 percent of these patients.
UF researchers studied 148 patients with coronary artery disease who
were on average about 65 years old. Participants were asked to perform a
public speaking test designed to induce stress. Images were taken of
blood flow to the heart at rest and during the speech task. Blood
samples also were collected and analyzed for five common gene
variations.
About a fourth of the patients experienced mental stress-induced reduced
blood flow to the heart, and about two-thirds of them harbored a
particular variation of the adrenergic beta-1 receptor genotype that was
associated with a three-fold increased risk of this phenomenon, said
Mustafa Hassan, M.D., the study’s lead author and a research fellow in
UF’s division of cardiovascular medicine. This receptor typically helps
the body respond to stress by regulating blood pressure and heart rate,
but a common variability in its gene may make certain patients more
vulnerable to the effects of psychological stress.
The study was funded by the National Heart, Lung and Blood Institute and
also was supported by the Department of Veterans Affairs Medical Center
and the Buy lexapro pills UF colleges of Pharmacy and Dentistry.
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, Sheps speculated. In
contrast, exercise tends to affect the heart’s blood supply through
different mechanisms.
"We should focus our research on two areas," he said. "One is better
identification of patients who are prone to have this problem and two is
looking for effective treatments once we know they have it. We need to
know whether we can reverse this phenomenon. We are embarking on other
treatment studies fairly soon."
UF researchers are hunting for other genetic subtypes that could
identify other patients at increased risk, he added.
"One of the advantages of detecting these sorts of things is that we may
be able to in the future be more specific about what kind of treatment
might work better in certain patients depending on their genetic
makeup," Sheps said. "That is one of the important things happening in
many fields of medicine. There are many diseases that already have been
shown to respond differently to different types of treatment based on
genetic differences."
The University of Florida Health Science Center - the most comprehensive
academic health center in the Southeast - is dedicated to high-quality
programs of education, research, patient care and public service. The
Health Science Center encompasses the colleges of Dentistry, Public
Health and Health Professions, Medicine, Nursing, Pharmacy and
Veterinary Medicine, as well as the Veterinary Medical Teaching Hospital
and an academic campus in Jacksonville offering graduate education
programs in dentistry, medicine, nursing and pharmacy. Patient care
activities, under the banner UF&Shands, are provided through teaching
hospitals and a network of clinics in Gainesville and Jacksonville. The
Health Science Center also has a statewide presence through satellite
medical, dental and nursing clinics staffed by UF health professionals;
and affiliations with community-based health-care facilities stretching
from Hialeah and Miami to the Florida Panhandle.
University of Florida Health Science Center
Buy fosamax without prescription | Buy diflucan pills | Buy synthroid without prescription