US researchers found that using implantable cardiac defibrillators (ICDs) in women with heart failure did not reduce their chances of sudden cardiac death.

The study was the work of principal investigator Dr Christian Machado, an electrophysiologist in the Department of Cardiology, Providence Hospital Heart Institute and Medical Center, Southfield, Michigan, and colleagues, and is published in the 14 September issue of the Archives of Internal Medicine.

Machado and colleagues carried out a meta-analysis of major randomized clinical trials that investigated the use of ICDs in 934 women with heart failure compared to women treated with medical therapy. A meta-analysis is a way of pooling together the results of several studies as if the data had come from one large study.

The results showed there was no statistically significant benefit for the women who had ICDs compared to the women who were treated with medical therapy.

Heart failure is a serious condition in which the heart is not pumping blood around the body efficiently, causing lots of problems that gradually affect tissue and organs, including malfunction and swelling.

It is not the same as a heart attack where some heart muscle dies due to lack of oxygen caused for example by a blocked artery, or cardiac arrest where the heart stops beating.

The American Heart Association estimates that about 300,000 Americans die every year from heart failure and about 5.7 million are living with the condition, with about 670,000 new cases diagnosed every year.

Machado told the press:

"Until now, the effectiveness of ICD treatment in women with heart failure had not been closely evaluated."

"As a result of clinical trials, ICD therapy for heart failure is widely accepted as a standard of care for both men and women. However, the majority of the patients involved in clinical trials have been men."

Machado said the findings show clearly that further research is needed to investigate whether men and women should received the same treatment for this condition.

For the study, the researchers searched well known medical sources, including published article databases, clinical trial registers the US Food and Drug Administration website, and papers presented at scientific meetings. In some cases, where lists were available, they searched back to 1950.

They picked out studies that reported randomized controlled trials of ICDs for preventing sudden cardiac death in heart failure patients that reported deaths from all causes and included separate figures for women. From 2,500 studies they picked out 5 trials that included a total of 934 women and put their data into the meta-analysis.

The pooled data from the 5 trials:

"Revealed no statistically significant decrease in all-cause mortality in women with heart failure who receive implantable cardioverter-defibrillators (hazard ratio, 1.01; 95 per cent confidence interval, 0.76-1.33)", wrote the authors, who concluded that:

"Implantable cardioverter-defibrillator therapy for the primary prevention of sudden cardiac death in women does not reduce all-cause mortality."

"Further studies are needed to investigate the reasons for this observation and to define the population of women who may benefit most from implantable cardioverter-defibrillator therapy," they added.

"Effectiveness of Implantable Cardioverter-Defibrillators for the Primary Prevention of Sudden Cardiac Death in Women With Advanced Heart Failure: A Meta-analysis of Randomized Controlled Trials."
Hamid Ghanbari; Ghassan Dalloul; Reema Hasan; Marcos Daccarett; Souheil Saba; Shukri David; Christian Machado.
Arch Intern Med, Vol. 169 No. 16, 1500-1506, September 14, 2009.

Sources: JAMA and Archives Journals, St John Health System.

Written by: Catharine Paddock, PhD