CHICAGO (Reuters) – Despite their widespread use, implantable defibrillators to protect against deadly heart rhythms do not prevent deaths in women with advanced heart failure, US researchers said last week.

They said implantable defibrillators – which detect abnormal heart rhythms and offer a life-saving shock to restore a regular heartbeat – do not appear to protect men and women equally. "There seems to be much less significant benefit" in women, said Dr. Hamid Ghanbari of Providence Hospital Heart Institute and Medical Center in Michigan, whose study appears in the Archives of Internal Medicine.

"Implantable cardioverter-defibrillators are being implanted in hundreds of thousands of women without substantial evidence of benefit," Dr. Rita Redberg of the University of California, San Francisco, wrote in a commentary in the journal.

Nearly 22 million people worldwide suffer from heart failure, a chronic condition in which the heart struggles to pump blood. Heart failure affects about 5.3 million Americans, and nearly half are women. People with heart failure are six to nine times more likely than most people to suffer sudden cardiac death, a dangerous heart rhythm in which the heart quivers but does not pump blood to the organs. Implantable defibrillators can detect this rhythm and deliver a shock to restore a normal heart beat. Many clinical trials have found implantable defibrillators save lives and are cost-effective; but too often, the studies are overpopulated with men, Ghanbari said.