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Senior Citizen Health & Medicine
Catch 22: Implantable Defibrillators Reduce
Deaths but Increase Heart Failure
More
attention needed to prevent heart failure in those who get ICD
 June
12, 2006 Is there a Catch 22 with implantable cardioverter
defibrillators? These ICDs do reduce the risk of sudden cardiac death
but they may increase the risk of heart failure in those who live
longer. A new study says more attention must be paid to heart failure
prevention in those who get ICDs.
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Some patients whose lives were prolonged by ICDs
were sicker and more prone to develop heart failure, said Ilan
Goldenberg, M.D., research assistant professor at the University of
Rochester Medical Center and lead author of the latest report from the
Multicenter Automatic Defibrillator Implantation Trial-II (MADIT-II).
The ICD kept them alive by preventing sudden
cardiac death as their heart disease naturally progressed to heart
failure.
Patients who developed heart failure had almost
four times the increase in risk of death during follow up. This study
should direct more attention to the prevention of heart failure in
patients receiving an ICD.
The study is published in Circulation: Journal of
the American Heart Association.
The MADIT-II trial included 1,232 heart attack
patients with an ejection fraction of 30 percent or less who had a heart
attack at least a month before enrollment. Researchers randomly
assigned patients to ICD (single or dual chamber) or best medical care.
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About Implantable Defibrillators |
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Pacemakers and Implantable Cardioverter
Defibrillators (ICDs) are used to treat arrhythmias
a condition of heart rhythm problems that occurs when the electrical
impulses that coordinate your heartbeats dont function properly,
causing your heart to beat too fast, too slow or irregularly. The Left
Ventricular Assist Device (LVAD) helps maintain the pumping ability of
your heart.
Implantable cardioverter defibrillator (ICD)
On an acute basis, many life-threatening tachycardias can be stopped by
giving the heart an electric shock or by rapid "overdrive" pacing with
an electrode catheter. Implantable devices can provide automatic
electrical therapy on a chronic basis for patients with recurrent
tachycardias. The greatest advance in this area is the implantable
cardioverter defibrillator (ICD). It's used in patients at risk for
recurrent, sustained ventricular tachycardia or fibrillation.
The American Heart Association recommends that
before a patient is considered to be a candidate for an implanted
defibrillator, the arrhythmia in question must be life-threatening.
Remediable causes of the arrhythmia must be ruled out.
Read more from the American Heart Association
Click Here
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Ejection fraction is a measure of the hearts
ability to efficiently pump blood to other parts of the body. An
ejection fraction of 60 percent is healthy, so the MADIT-II patients
were pumping blood at about half the rate of healthy people.
Compared to patients who received only medical
therapy, those who had ICDs implanted after a heart attack were 39
percent more likely to have a first hospitalization for heart failure.
And, they were 58 percent more likely to be hospitalized for recurrent
heart failure during an average 20-month follow up.
The overall survival benefit was 42 percent for
patients who received a single chamber ICD and 51 percent for those with
a dual chamber.
Researchers analyzed data from 1,224 study
patients, including 402 who received single-chamber devices and 313 who
were implanted with dual-chamber devices.
Twenty-three percent of patients who received ICDs
in the MADIT-II trial were hospitalized for HF during 20 months of
follow-up versus 17 percent of patients who received only medical
therapy.
Patients who received single-chamber devices did
not suffer a reduced survival benefit if they developed heart failure.
However, patients who were implanted with dual-chamber devices had a
significant reduction in survival benefit after heart failure,
Goldenberg said.
Resynchronization therapy with a biventricular ICD
is currently being evaluated as a preventive strategy to reduce the risk
of heart failure in ICD treated patients in a follow-up study to MADIT-II,
he said.
Co-authors are Arthur J. Moss, M.D.; W. Jackson
Hall, Ph.D.; Scott McNitt, M.S.; Wojciech Zareba, M.D., Ph.D.; Mark L.
Andrews, B.B.S.; and David S. Cannom, M.D.
MADIT-II was funded in part by Guidant
Corporation. This sub analysis of MADIT-II was not funded.
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