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 these patients.
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 patients.”
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 irregular heartbeat.
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 other
minorities.
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.
NHLBI press releases and other materials are available
online at www.nhlbi.nih.gov
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