- Implantable defibrillators do not lower the risk of death in female patients.
- Previous research focused on men.
Despite their widespread use, implantable defibrillators—used to detect and then correct dangerous heart rhythms—may not protect women as well as they protect men, research shows.
The defibrillators help prevent sudden cardiac death in people with serious heart problems by delivering an electric shock to restore normal rhythm. But a study by the Providence Hospital Heart Institute in Southfield, Mich., showed that the device, technically called an implantable cardioverter defibrillator (ICD), did not significantly lower the risk of death for women, although it did for men.
“There’s no doubt that ICDs save lives,” says Christian Machado, M.D., principal investigator in the study, “but we should be candid and tell women that we just don’t know if the benefit for them is as great as for men.” The researchers analyzed results from five clinical trials carried out between 1950 and 2008. The trials involved a total of 934 women and 3,810 men with heart failure, the inability of the heart to pump blood at an adequate rate. For women, none of the trials demonstrated a benefit of ICDs over medication therapy alone, yet ICDs for heart failure are widely accepted as the standard of care for both men and women.
Machado says one of the problems with previous research is that it was biased toward men—75 percent of the subjects in the studies they analyzed were men.
“This paper points out once again that women are different from men when it comes to heart disease,” says Sharonne Hayes, M.D., of the Mayo Clinic in Rochester, Minn., who was not involved in the research. “The findings clearly warrant further study.”
The study was published in the Sept. 14 issue of the Archives of Internal Medicine.
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An implantable cardioverter defibrillator (ICD) is a battery-operated device about the size of a stopwatch that constantly monitors the heart’s rhythm. It is surgically placed under the skin, typically just below the left collarbone. Wires connect the device to the heart. If the ICD detects a rapid or chaotic heartbeat, it delivers a small pulse or shock to the heart to restore normal rhythm.
Heart failure, a chronic condition in which the heart cannot pump sufficient blood to meet the body’s needs, affects about 5.3 million Americans, half of them women. In addition to medications such as ACE inhibitors and beta-blockers, treatment for heart failure may involve implanting an ICD to prevent sudden cardiac death. Sudden cardiac death, a condition where the heart abruptly and unexpectedly stops beating, is six to nine times more common in people with heart failure than in the general population.
Nissa Simon, a health writer, lives in New Haven, Conn.