Implantable defibrillators not too effective in women

Researchers from the Michigan University conducted five studies that together included 3810 men and 934 women with heart failure during the time period from 1950 to 2008.

In some patients, ICDs were implanted through surgery while others got medical care that didn’t require surgical implantation.

The clinical trial’s results turned out to be biased towards men. Nearly 22 percent men who got ICDs were less likely to die of cardiac arrests than men who didn’t get ICDs.

But none of the studies nor the combined data showed any survival advantage for women, irrespective of whether they had ICDs or not. According to reports, 30 percent of people who get the ICDs transplanted are women.

Reasons for the absence of mortality benefit in women
The researchers could not find any specific reason for women being at a disadvantage. One reason could be that the women enrolled in the five clinical trials were older and had a worse clinical status than men -- more severe heart failure, higher systolic blood pressure, and a higher incidence of diabetes.

Dr. Christian Machado, director of electrophysiology at Providence Hospital Heart Institute, in Southfield, Michigan speculated that the reasons why women derived lesser benefits from the ICDs could be due to different anatomy of a man and a woman and the differing hormonal factors.

"We need to find a way to study more women in order to be able to identify what subgroups truly benefit from this therapy," Dr. Machado said.

Hamid Ghanbari, MD, of Providence Hospital Heart Institute and Medical Center in Southfield, Michigan said that the best answer to this problem would be to perform a clinical trial that specially targets women suffering from heart diseases and test the hypothesis of whether ICD implantation reduces their overall mortality rate or not.

As to the implantation rates among the two sexes, the researchers said, “The exact reasons for the significant sex differences in ICD implantation rates are not well established, but perhaps some of this disparity is driven by the paucity of data for women in randomized clinical trials of ICD therapy.”

Presently, there are no such recommendations to use the ICDs based on gender.

Rita F. Redberg, MD, editor of Archives of Internal Medicine wrote, “ICDs 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.”

The report of the study appears in the Archives of Internal Medicine.

Reasons of heart failure
Heart failures happen when the heart muscles are not able to pump enough blood in the body. People with heart failures are at a higher risk of suffering sudden cardiac death.

However, such people can get the ICDs implanted to prevent sudden cardiac death. These devices achieve this by detecting the quivering rhythm and delivering a shock to the heart to restore the normal heart-beat.