Implantable Defibrillators Not Providing Women Equal
Protection from Heart Failure
Study cannot find a reduced risk of death for women
with advanced heart failure
Sept. 14, 2009 - Implantable cardioverter-defibrillators
do not appear to be associated with a reduced risk of death in women
with advanced heart failure, according to a meta-analysis of previously
published research in the September 14 issue of Archives of Internal
Medicine, one of the JAMA/Archives journals.
Heart failure affects about 5.3 million Americans,
almost half of them women. Patients with heart failure are six to nine
times more likely than the general population to experience sudden
cardiac death.
One of first studies to focus on senior citizens and
ICDs finds older people are good candidates for ICDs to prevent death
from arrhythmias; but benefit diminishes when age combined with multiple
disease conditions
FDA has drug in priority review; approves first
ablation catheters for the treatment of atrial fibrillation, which
affects mainly senior citizens over age 65
In addition to medication, treatment for heart
failure involves preventing sudden cardiac death through the
implantation of a cardioverter-defibrillator. This therapy is supported
by numerous clinical trials, the authors of this study point out.
However, there have been questions regarding the benefits in certain
patient subgroups, including women.
Hamid Ghanbari, M.D., and colleagues at Providence
Hospital Heart Institute and Medical Center, Southfield, Mich., searched
for randomized clinical trials of implantable defibrillator therapy for
heart failure patients published between 1950 and 2008 that included
data on the risk of death for female patients.
Five eligible trials that included 934 women were
identified.
None of the five trials demonstrated a significant
benefit of defibrillator implantation over medical therapy for women.
When the researchers pooled the data and performed
a meta-analysis, the implantable cardioverter-defibrillator was not
associated with decreased all-cause mortality in women.
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About Implantable Cardioverter
Defibrillators
What is Heart Failure
Among the 3,810 men in the studies, however, a
statistically significant decrease in death rate was found in each of
the five trials alone and in the combined meta-analysis.
There are several possible reasons for the sex
differences in these results, the authors say.
Among patients with heart disease, women have about
one-fourth the risk of sudden cardiac death as men. This may be because
women have different patterns of arrhythmias and also because they have
more co-occurring illnesses that may increase their risk of death from
other causes. Therefore, a larger study population may be needed to show
any benefit of defibrillator implantation in women.
"Most clinical trials have been heavily weighted
toward men; therefore, generalization of the results to women remains
questionable," the authors write.
The best answer to this problem would be to
perform a clinical trial that specifically targets women with heart
failure to test the hypothesis of whether implantable
cardioverter-defibrillator implantation reduces their overall mortality
[death] rate.
Because clinical guidelines already recommend
defibrillator treatment to prevent sudden cardiac death, such a trial
may be difficult to propose, they note. "However, on the basis of our
findings it seems that a trial targeting women is needed, and a
meta-analysis such as ours may be an appropriate first step to explore
this hypothesis."
Editorial: What's Good for the Gander May Not Be
Good for the Goose
"Approximately 30 percent of implantable
cardioverter-defibrillator recipients are women. However, data
supporting the efficacy of implantable cardioverter-defibrillators for
primary prevention in women is sparse," writes Rita F. Redberg, M.D., of
University of California, San Francisco, and editor of Archives of
Internal Medicine, in an accompanying editorial.
"In other words, implantable
cardioverter-defibrillators are being implanted in hundreds of thousands
of women without substantial evidence of benefit, apparently based on
the assumption that, to paraphrase the old saying, 'What's good for the
gander is good for the goose.'"
"It is important to know the benefits of
implantable cardioverter-defibrillator use in women, especially
considering the known risks of morbidity and mortality," Dr. Redberg
continues. "Ghanbari et al rightly conclude that further studies are
needed. Part of the reason for the lack of sex-specific data for devices
may be related to the lack of Food and Drug Administration guidance in
this area. There is reason to be optimistic that this deficit will start
to be corrected in the near future."
"Until then, meta-analyses such as the one by
Ghanbari et al are the best way to determine if the goose is doing as
well as the gander," she concludes.
Implantable Cardioverter Defibrillator
An implantable cardioverter defibrillator is used
in patients at risk for recurrent, sustained ventricular tachycardia or
fibrillation.
The device is connected to leads positioned inside
the heart or on its surface. These leads are used to deliver electrical
shocks, sense the cardiac rhythm and sometimes pace the heart, as
needed. The various leads are tunnelled to a pulse generator, which is
implanted in a pouch beneath the skin of the chest or abdomen.
These generators are typically a little larger than
a wallet and have electronics that automatically monitor and treat heart
rhythms recognized as abnormal. Newer devices are smaller and have
simpler lead systems. They can be installed through blood vessels,
eliminating the need for open chest surgery.
When an implantable cardioverter defibrillator
detects ventricular tachycardia or fibrillation, it shocks the heart to
restore the normal rhythm. New devices also provide overdrive pacing to
electrically convert a sustained ventricular tachycardia, and "backup"
pacing if bradycardia occurs. They also offer a host of other
sophisticated functions (such as storage of detected arrhythmic events
and the ability to do "noninvasive" electrophysiologic testing).
Implantable cardioverter defibrillators have been
very useful in preventing sudden death in patients with known, sustained
ventricular tachycardia or fibrillation.
Studies are now being done to find out how best to
use them and whether they may have a role in preventing cardiac arrest
in high-risk patients who haven't had, but are at risk for,
life-threatening ventricular arrhythmias.
According to the American Heart Association Heart
and Stroke Statistical Update, in 1998 (the most recent statistics
available) there were 26,000 ICD procedures.
Heart failure is a chronic, progressive condition
in which the heart muscle is unable to pump enough blood through the
heart to meet the bodys needs for blood and oxygen. Basically, the
heart cant keep up with its workload.
At first the heart tries to make up for this by:
● Enlarging. When the heart chamber enlarges, it
stretches more and can contract more strongly, so it pumps more blood.
● Developing more muscle mass. The increase in
muscle mass occurs because the contracting cells of the heart get
bigger. This lets the heart pump more strongly, at least initially.
● Pumping faster. This helps to increase the
heart's output.
The body also tries to compensate in other ways:
● The blood vessels narrow to keep blood pressure
up, trying to make up for the heart's loss of power.
● The body diverts blood away from less important
tissues and organs to maintain flow to the most vital organs, the heart
and brain.
These temporary measures mask the problem of heart
failure, but they don't solve it. Heart failure continues and worsens
until these substitute processes no longer work.
Eventually the heart and body just can't keep up,
and the person experiences the fatigue, breathing problems or other
symptoms that usually prompt a trip to the doctor.
The body's compensation mechanisms help explain why
some people may not become aware of their condition until years after
their heart begins its decline. (It's also a good reason to have a
regular checkup with your doctor.)
Heart failure can involve the heart's left
side, right side or both sides. However, it usually affects the left
side first.
Sept. 14, 2009 - Implantable cardioverter-defibrillators
do not appear to be associated with a reduced risk of death in women
with advanced heart failure, according to a meta-analysis of previously
published research in the September 14 issue of Archives of Internal
Medicine, one of the JAMA/Archives journals. 
An implantable cardioverter defibrillator is used
in patients at risk for recurrent, sustained ventricular tachycardia or
fibrillation. 