MONDAY, Sept. 14, 2009 (HealthDay News) -- Widely used implantable cardioverter-defibrillators may not actually help women with advanced heart failure.
A new analysis turns up no evidence that the devices, used to detect and then correct abnormal heart rhythms, actually lowered the risk of death among female patients, despite the fact that this is routine therapy for all patients with heart failure.
"We do not know of the benefits of defibrillators when used as primary prevention," said Dr. Christian Machado, senior author of a paper appearing in the Sept. 14 issue of the Archives of Internal Medicine. "We just do not know how much women benefit from this therapy."
Yet, according to an accompanying editorial, 30 percent of people getting implantable cardioverter-defibrillators, also called ICDs, are women.
In fact, there are even guidelines supporting the practice, said Machado, who is director of electrophysiology at Providence Hospital Heart Institute, in Southfield, Mich.
ICDs are intended to prevent sudden cardiac death in heart failure patients, who have a high risk for such an event. And while clinical trials do support the practice, those trials tend to be biased towards men.
Here, a search of medical literature databases turned up only five relevant randomized clinical trials between 1950 and 2008. The trials involved a total of 934 women and 3,810 men, a clear indication that women are underrepresented in this type of study even though women make up almost half of the 5.3 million Americans who have heart failure.
None of the studies on their own showed any survival advantage for women of having a defibrillator implanted, nor did the combined data show any benefit.
But there was a reduction in death rates for men in each trial, as well as when the results were pooled together.
"We need to find a way to study more women in order to be able to identify what subgroups truly benefit from this therapy," Machado said.
But that could be difficult. Given that current guidelines recommend the use of ICDs, it would be unethical to propose a trial that randomized some women to go without one, Machado explained.
And this data is certainly not likely to change cardiac care procedures. "I don't think this is going to change anyone's practice," said Dr. Seth Keller, associate director of cardiac electrophysiology at Lenox Hill Hospital in New York City. "Practice guidelines are pretty well-established in terms of ICDs. But this does raise a lot of questions."
"If it is true that women don't benefit from primary prevention with ICDs, then why not?" he added.
Machado speculated that reasons for women deriving different or less benefit from ICDs could range from different anatomy to hormonal factors to how women's bodies use calcium.
"I'm sure there's more than one factor leading to such a less dramatic benefit in women from this therapy," he said.
In fact, the devices might even cause harm. The editorial referenced one analysis that found that women have a 70 percent greater risk of problems after receiving an ICD than men.
"Let's question the dogma," Machado said. "Let's figure out how to change our recommendations."
But one expert urged caution.
Dr. Wojciech Zareba, director of the Heart Research Follow-Up Program at the University of Rochester Medical Center, felt that this meta-analysis, along with most papers in this form, was fraught with methodological problems that weakened the validity of the findings.
"I believe that we don't have evidence at this moment which would preclude using ICDs in women," Zareba said. "This is unfortunately only stirring the water and doesn't provide any useful clues."
The American Heart Association has more on women and heart disease.