NHLBI Study Finds Implanted Defibrillator Reduces Heart Failure Deaths
An implantable cardiac defibrillator (ICD) significantly reduces
deaths in heart failure patients, according to a new study supported
by the National Heart, Lung, and Blood Institute (NHLBI), one of
the National Institutes of Health. The study also found that treatment
with the antiarrhythmic drug amiodarone does not reduce deaths in
Preliminary results from the study called "Sudden Cardiac
Death in Heart Failure" (SCD-HeFT) are being presented today
at the American College of Cardiology Annual Scientific Session
2004 in New Orleans, LA.
"These findings should have a big impact on the treatment
of heart failure patients," said NHLBI Acting Director Dr.
Barbara Alving. "Until now, it was not known if implanted defibrillators
would help such a wide range of heart failure patients, including
those whose heart failure may not have been caused by a heart attack.
The study had a relatively high percentage of women and minorities,
and was larger and lasted longer than earlier trials of sudden death
in heart failure patients."
"When these findings are put into practice, they will prolong
the lives of many heart failure patients," said Dr. Gust Bardy,
SCD-HeFT study director and President of the Seattle Institute for
Cardiac Research in WA. "The results give physicians vital
information for better managing the care of their heart failure
Heart failure affects about 5 million Americans. It develops over
time as the heart loses its ability to pump blood through the body.
It can be caused by various conditions, including heart attack.
Symptoms include feeling tired, having trouble breathing, and swelling
(edema), usually in the legs and ankles.
It is estimated that about 50 percent of deaths in heart failure
are sudden deaths and are probably due to a ventricular tachyarrhythmia,
or rapid heartbeats in one of the lower chambers. In sudden death,
the heart stops abruptly.
SCD-HeFT tested whether an ICD that provides a shock without pacing
impulses or an antiarrhythmic drug would help prevent sudden death
in heart failure patients. An ICD is put under the skin of the chest
and sends an electric signal to correct a potentially fatal arrhythmia.
An antiarrhythmic drug works by preventing the occurrence of an
The study involved 2,521participants, who were randomly assigned
to one of three treatment arms 847 in a placebo group, 845 in the
amiodarone group, and 829 in the ICD group. The mean follow-up was
almost 4 years.
Patient enrollment began in September 1997 and patient follow-up
ended in October 2003. Participants were enrolled through 148 hospitals,
clinics, and academic centers in the United States, Canada, and
New Zealand. The study's Clinical Coordinating Center is at the
Seattle Institute for Cardiac Research; the Data Coordinating Center
is at the Duke Clinical Research Institute at Duke University in
Durham, NC. The study biostatistician is Dr. Kerry Lee, Director
of Biostatistics at Duke Clinical Research Institute.
The participants had moderate to severe heart failure New
York Heart Association classes II and III. Classes range from I
to IV. Class II patients have trouble breathing or feel tired after
exercise, such as climbing stairs; class III patients have such
heart failure symptoms while performing minimal activities, such
as walking on level ground.
Study participants ranged in age from 19 to 90; the median age was
60. Seventy-seven percent were men and 23 percent women. Seventy-seven
percent were white, 17 percent African American, and about 6 percent
Fifty-two percent had heart failure caused by heart attack (myocardial
infarction) and 48 percent had heart failure due to a different
cause, such as a viral infection of the heart. Thirty percent had
diabetes and 15 percent had had at least one episode of diagnosed
atrial fibrillation when they entered the study.
At the end of the study, there were 666 deaths overall 182 (22
percent) in the ICD group, 240 (28 percent) in the amiodarone group,
and 244 (29 percent) in the placebo group.
Results showed that:
- In those with heart failure, implantable defibrillator therapy
significantly reduced deaths, but amiodarone therapy did not.
- The benefit from implantable defibrillator therapy appeared to
be strongest in those with moderate heart failure at enrollment. Amiodarone therapy appeared
to have a detrimental effect in those with severe heart failure at enrollment.
- Implantable defibrillator therapy reduced deaths for patients whether
their heart failure resulted from heart attack or a different cause.
To interview an NHLBI scientist on this study, contact the NHLBI
Communications Office at (301) 496-4236.
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