Implantable devices called cardioverter-defibrillators don't appear to be associated with a reduced risk of death in women with advanced heart failure, says an article published in a recent issue of the Archives of Internal Medicine.

Heart failure affects about 5.3 million Americans, almost half of them women, according to the article, which discusses the results of an analysis of previously published research. Patients with heart failure are six to nine times more likely than the general population to experience sudden cardiac death.

In addition to medication, one of the methods of treatment for heart failure in an effort to prevent sudden cardiac death is the implantation of a cardioverter-defibrillator. This therapy is supported by numerous clinical trials, the authors note. However, questions remain regarding its benefits in certain patient groups, including women, they says.

Dr. Hamid Ghanbari and colleagues at Providence Hospital Heart Institute & Medical Center, in 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 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. 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 note. 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 might be needed to show any benefit of defibrillator implantation in women, the authors say.

"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 rate."

Because 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," they say.