|
Exercise
Testing Predicts Heart Risk
Exercise testing not only helps predict a person's risk
of death, but it can also help rule out those who don't
require aggressive treatment for cardiovascular disease,
a study says.
The stress test is a good gauge independent of another
test, angiography, which looks for diseased arteries, the
study says.
"We found that cardiac exercise testing is a good predictor
of death. It is also a very good predictor of people at
low risk who do not need aggressive treatment," says
Dr. Michael S. Lauer, a cardiologist with the Cleveland
Clinic Foundation.
Lauer and his colleagues collected data on 2,935 patients
suspected of having heart disease. The patients underwent
exercise testing followed by an angiogram. The results appear
in the current issue of the Journal of the American College
of Cardiology.
During exercise testing, patients walk on a treadmill while
their heart rate and blood pressure are measured. During
the test, the degree of difficulty is steadily increased
as the incline of the treadmill is raised. Speed is also
increased until the patient is out of breath or until the
heart rate reaches a predetermined level.
The object of the test is to see how well the patient's
heart performs under stress. The test has been used for
years to uncover heart disease.
This group of patients also underwent angiography, an invasive
procedure during which a catheter is placed in the coronary
arteries, letting doctors see if any arteries are blocked.
The researchers found that 421 of the patients had severe
heart disease, but 838 patients had abnormal heart rate
recovery after exercise testing. Lauer's team followed all
the patients for six years.
During that time, 336 patients (11 percent) died. Heart
rate recovery was a stronger predictor of risk than the
severity of coronary disease, Lauer says.
Lauer believes that measuring heart rate recovery is different
from just looking at heart disease. Measuring heart rate
recovery is assessing autonomic nervous system function,
which is different from how much blockage there is in a
coronary artery, Lauer notes. He adds this is what makes
heart rate recovery an independent predictor of death.
The most important aspect of this finding, Lauer says, is
that exercise testing can be used to identify patients who
are at low risk for heart disease.
"Using exercise testing to identify those at low risk
for heart disease is a cheap, effective way to identify
those who do not need aggressive treatment," Lauer
says.
Because doctors are too cautious, many patients are classified
as at uncertain risk for heart disease, he notes. These
patients receive unnecessary tests and medications.
Normal heart rate recovery, along with preserved functional
capacity, can identify patients at low risk. Given this
finding, "patients can be assured that exercise is
an adequate tool for assessing heart disease," he adds.
However, Dr. Bernard Chaitman, a professor of medicine and
director of cardiovascular research at St. Louis University
School of Medicine and author of a journal editorial, comments
that the implications of abnormal heart rate recovery are
unclear.
Chaitman believes the abnormal heart rate recovery is a
marker of autonomic dysfunction. "When people exhibit
this, it somehow predisposes them to heart rhythm disturbances
that lead to death," he says. "But the unanswered
question is why."
"If we knew why people had abnormal heart rate responses
to exercise, then maybe we could develop treatments to reduce
the mortality rate," Chaitman adds. "Right now
we don't know if treating them in any special way will reduce
the mortality rate."
Chaitman also does not believe that having normal heart
rate recovery alone is necessarily a sign of reduced cardiac
risk. Risk needs to be determined in the context of their
pretest risk factors as well as the results of their exercise
test, he argues.
Chaitman advises that "if your heart rate responses
to exercise are abnormal, you should want to know more as
to why and what it means, and you should consult your physician."
Another study in the same journal issue finds a new benefit
from regular exercise. European researchers have found exercise
significantly reduced markers of inflammation in patient
with chronic heart failure.
"For patients with stable chronic heart failure, regular
aerobic exercise training should not be regarded as rehabilitation
only, but as a continuing treatment with the potential to
modify the underlying disease process," Dr. Stephan
Gielen, from the University of Leipzig Heart Center, says
in a statement.
In the study, 20 men with stable heart disease were randomly
selected to undergo an exercise program or be placed in
a control group. The 10 men in the exercise group did 20
minutes of exercise a day, either on a stationary bicycle
or in a group workout.
When the researchers evaluated these men after six months
of exercise, they found that not only was there a 29 percent
increase in peak oxygen uptake, but that key inflammatory
markers, namely tumor necrosis factor-alpha, interleukin-6,
interleukin 1-beta, and nitric oxide synthase were significantly
reduced in thigh muscle.
"Exercise acts as an anti-inflammatory intervention
in the skeletal muscles in chronic heart failure. This is
especially important because inflammatory cytokines have
been linked to so-called cardiac cachexia, a chronic debilitating
wasting process which affects many heart failure patients
and leads to severe reduction in muscle mass and muscle
strength. It may therefore be hoped that training could
also help to prevent this catabolic process," Gielen
says.
Many people with heart failure complain of fatigue. And
in patients with severe heart failure, muscle-wasting, or
cachexia, can occur. The conventional wisdom has been that
these problems result from poor blood circulation.
Research has not found a connection between the ability
of the heart to pump blood and fatigue levels or the ability
to exercise. However, studies have shown that in patients
with heart failure, there is a general inflammatory response
coupled with a disruption of energy metabolism and an increase
in cell death in thigh muscles.
Although there is no current anti-inflammatory treatment
for heart failure patients, exercise might be a good option,
Gielen says. However, he notes that long-term studies are
needed to confirm that cardiac cachexia can be effectively
prevented by exercise.
Dr. Douglas Mann, from the Houston Veterans Administration
Medical Center and a professor of medicine at Baylor College
of Medicine, co-authored an accompanying editorial and comments
that the findings by Gielen's team "are provocative
but not definitive."
The results of the study seem to indicate that exercise
is good for patients with heart failure and may improve
their fatigue, Mann says. "The finding may also open
up the field for novel therapeutic interventions that might
be designed to reduce skeletal muscle inflammation and improve
[the] patient's hematology in heart failure."
Mann concludes that "exercise programs are beneficial
in heart failure and may be the mainstay of therapy for
reducing fatigue."
Read more about the exercise stress test from MedlinePlus.
Meanwhile, the Canadian
Heart and Stroke Foundation has information on heart
failure.
Article Source: HealthDay
Article Author: Steven Reinberg
Net Reference 101
|
