Rethinking
the Treadmill Test
Study
finds heart function after treadmill test is best measure of risk
A recent
study proposes what could be a revolutionary change in the way cardiologists
look at exercise testing: It is what happens after the patient stops
exercising that is really important.
Current
treadmill testing focuses on "whether the ST segment [part of the electrocardiogram]
is depressed during exercise," says Dr. Michael S. Lauer, lead author
of a paper on the study in a recent issue of The New England
Journal of Medicine.
"In
fact, that is the least important item. How much the heart rate comes
down after exercise, whether there is ventricular ectopy, [abnormal
heartbeats], is a far stronger indicator of risk than what happens to
the ST segment," say researchers.
The
study looked at almost 30,000 patients who underwent exercise testing,
either because they had coronary artery disease or were suspected of
having it.
As
is customary, the testers kept the heart monitor on for a few minutes
after the person came off the treadmill to be certain the patient is
not in trouble.
However,
in this trial the researchers looked closely at the results of heart
monitoring, recording not only abnormal heartbeats but also how quickly
the heart rate returned to normal. Then they looked at the number of
cardiovascular deaths in the group, and how those deaths were related
to what happened after exercise.
Exercise
Test Does Not End When Patient Stops Exercising
"The
key message here is that the exercise test does not end when the patient
stops exercising," Lauer says. "During the first few minutes after exercise,
you can gather some extremely valuable data."
As
expected, occurrence of abnormal heartbeats during exercise increased
the risk of death over the next five years; the death rate for patients
who had those abnormalities was 9 percent, compared to 5 percent for
those who did not.
However,
the occurrence of abnormal heartbeats in the minutes after testing was
an even stronger indicator of risk: 11 percent of the patients with
those abnormalities died in the follow-up period.
"This
is a very important finding in terms of being able to assess the risk
of patients," says Dr. Richard A. Stein, a spokesman for the American
Heart Association. He is more cautious about the implications
of the study than Lauer, but does say "it could be revolutionary."
Cardiologists
will not stop looking at what happens during exercise, Stein adds, but
they will start paying more attention to the minutes after exercise.
"We
would look at that and integrate the information into the various ways
we assess risk," says Stein, who is a clinical medicine professor at
Weill-Cornell Medical Center in New York City.
Study
Implications Remain to be Seen
It
remains to be seen how the finding will be integrated into medical practice,
Stein says. Most probably, cardiologists will concentrate even more
on controlling the known risk factors in patients whose after-exercise
electrocardiograms are abnormal.
"It
will refocus our attention in exercise testing," he adds.
Always
consult your physician for more information.
Reasons
a Treadmill Test May Be Ordered
An
exercise echocardiogram, performed after you have exercised on a treadmill
or stationary bicycle, may be performed for the following reasons:
-
to
determine limits for safe exercise in patients who are entering
a cardiac rehabilitation program and/or those who are recovering
from a cardiac event, such as heart attack or heart surgery
-
to
assess leg pain with exercise (also called intermittent claudication)
in patients with suspected occlusion in the legs' circulatory system
-
to
evaluate blood pressure during exercise
-
to
assess stress or exercise tolerance in patients with known or suspected
coronary artery disease
-
to
evaluate the cardiac status of a patient about to undergo surgery
Online
Resources
American
Heart Association
National
Institutes of Health (NIH)
The
New England Journal of Medicine
|
March
2003
Study
Finds Heart Function After Treadmill Test Is Best Measure of Risk
Exercise
Test Does Not End When Patient Stops Exercising
Study
Implications Remain to be Seen
Reasons
a Treadmill Test May Be Ordered
Lower
Dose of Anti-Clotting Drug Saves Lives
Online
Resources
Find
a St. John's Mercy Physician
In
Other News About Your Heart Health:
Lower
Dose of Anti-Clotting Drug Saves Lives
Reduces
recurrence of deep vein thrombosis
The
dosage of an anti-clotting drug given to people with deep vein thrombosis
can be lowered substantially without reducing its effectiveness.
That
is the finding of a trial study on warfarin (also known as Coumadin)
that was cut short because of its impressive results.
The
trial results will be published in a recent issue of The
New England Journal of Medicine. However, the journal says
the results are being made available to physicians now "because
of the study's therapeutic implications."
This
"is going to save a number of lives," says study leader Dr. Yves
Rosenberg, a project officer at the National Heart, Lung,
and Blood Institute (NHLBI), part of the National
Institutes of Health (NIH), which funded the research.
Too
little warfarin, a blood thinner, can lead to recurrent blood clots
that at the least cause severe discomfort and at worst kill the
patient by going to the lungs and blocking the pulmonary artery.
On the other hand, too much of the drug can cause bleeding that,
at worst, occurs in the brain and can be fatal. As many as 60,000
Americans are killed each year by these pulmonary embolisms, Rosenberg
says.
The
standard treatment for patients suffering from an episode of deep
vein thrombosis or pulmonary embolism is five to 10 days of heparin,
a clot preventer given by injection, followed by three to six months
of a relatively high dose of warfarin designed to produce a blood-clotting
level of 2.0 to 3.0 in what is called the international normalized
ratio (INR). In the study, some patients were given low doses of
warfarin, just enough to achieve an INR of 1.5 to 2.0—an apparently
small difference, but very important clinically. Others were given
a placebo.
In
an average follow-up of more than four years, only 14 of the 255
patients getting low-dose warfarin had another episode, compared
to 37 of the 253 placebo patients—a reduction of 64 percent.
There were four deaths in the low-dose warfarin group and eight
in the placebo group, a reduction of nearly half.
Just
as important, the incidence of bleeding complications in both groups
was similar, the researchers report. This means patients can be
kept on low-dose warfarin for much longer than is now done, which
gives them longer-term protection. "Long-term, low-intensity warfarin
therapy can be readily implemented in clinical practice," the report
says.
Other
studies will be done to see whether the warfarin dose can be reduced
even further, Shafer says. However, what is really needed, he says,
is a new kind of anti-clotting drug that can distinguish between
harmful clots and the kind the body produces normally in response
to injury. Until that comes along, he says, "we will continue to
walk the tightrope of anticoagulant dosing."
Always
consult your physician for more information.
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