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Contact:
cfeheley@acc.org; 800-253-4636; 301-581-3425
December 4, 2002
A
"Cool" New Addition to Heart Attack Treatment
Trial demonstrates practical method
for quickly lowering body temperature during angioplasty.
Researchers to test potential to reduce heart attack damage
(BETHESDA,
MD)—Catheter devices that can cool a patient's body from
the inside out can be used without interfering with standard
angioplasty treatment of heart attacks and may offer a novel
way to preserve heart muscle, according to a new
study in the Dec. 4, 2002, issue of the Journal of
the American College of Cardiology. "This is the
first reported experience of using cooling in patients with
heart attacks," said Dr. Simon Dixon of the William Beaumont
Hospital in Royal Oak, Michigan. Experience in animals and
with heart transplants and certain neurosurgical procedures
suggests that cooling has the potential to reduce damage due
to the restricted blood flow to the heart muscle that occurs
during a heart attack.
Researchers
at nine centers in the U.S., Australia and Germany cooled
20 heart attack patients by inserting heat-exchange balloon
catheter devices into the patients' inferior vena cava. When
a patient's body temperature was reduced from normal (37 degrees
Celsius, 98.6 degrees Fahrenheit) to 33 degrees Celsius (91.4
degrees Fahrenheit), doctors performed angioplasty, stenting
or other conventional heart attack treatment to restore blood
flow to the affected heart muscle. Another 21 patients underwent
conventional treatment without cooling.
Dr.
Dixon noted that this study was intended to prove that patients
could be cooled rapidly and without disrupting conventional
heart attack treatment, to prepare for further studies of
whether cooling can protect heart muscle, thus reducing the
damage of a heart attack. "It is feasible to initiate
cooling in patients with acute infarct. Secondly, it is safe
to do so from a hemodynamic standpoint. And thirdly, the protocol
we used to reduce shivering in these patients is effective
and allows cooling to be applied," Dr. Dixon said. Shivering
was suppressed with a combination of drugs and skin warming.
Cooling
appears to protect muscle tissue in part by reducing metabolism
rates, in essence slowing the clock in terms of the damaging
effects of blood flow blockages, but questions remain about
the beneficial effects of hypothermia. The researchers reported
that scans indicated the scar tissue area in the heart muscle
appeared to be smaller on average in the cooled patients than
in conventionally-treated patients, but Dr. Dixon cautioned
that the trial design and small number of patients mean that
they could not draw conclusions about any protective effect
of cooling. A larger trial of effectiveness, the "COOLing
for Myocardial Infarction" (COOL MI) trial, is currently
underway.
The
researchers said that lowering the body temperature of heart
attack patients using ice packs or cooling blankets simply
isn't practical, so the researchers were encouraged by the
fact that they were able to integrate catheter-based cooling
into their angioplasty protocol.
Dr.
Spencer King of the Emory University Hospital in Atlanta,
Georgia, who was not part of the research team, agreed that
the study results demonstrate the feasibility of the new catheter-based
cooling technique. "This is clearly an exciting possibility
for reducing the size of myocardial infarctions, if it turns
out that the mechanism is from a slowing of the metabolic
processes in the myocardium and the microcirculation, preserving
heart muscle, Dr. King said. "What I'm seeing from this
experience is leading me to believe that this may be of substantial
help for people who otherwise might have very large myocardial
infarctions."
Unlike
current heart attack treatments, which focus on restoring
blood flow to the heart muscle, cooling attempts to protect
the heart muscle against the damaging cascade of cellular
events that occur when blood flow is cut off. "It's really
taking it to a new kind of level in terms of the heart muscle,
the myocardium itself, in addition to getting the best results
we can with angioplasty and stents. We hope this will lead
to further salvage of the myocardium where the infarct has
occurred, limit the infarct size and lead to a better prognosis
for these patients," Dr. Dixon said.
The
American College of Cardiology, a 28,000-member nonprofit
professional medical society and teaching institution, is
dedicated to fostering optimal cardiovascular care and disease
prevention through professional education, promotion of research,
leadership in the development of standards and guidelines,
and the formulation of health care policy.
The
American College of Cardiology (ACC) provides
these new reports of clinical studies published
in the Journal
of the American College of Cardiology as a
service to physicians, the media, the public,
and other interested parties. However, statements
or opinions expressed in these reports reflect
the view of the author(s) and do not represent
official policy of the ACC unless stated so.
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