Implantable defibrillators benefit women as much as men after heart attack

Women who have had a heart attack get as much survival benefit as men from implanted cardioverter defibrillators (ICDs), devices designed to monitor the heart's pumping rhythm and shock it back to normal when needed, according to a study published in the December edition of the Journal of Cardiovascular Electrophysiology.

ICDs are designed to counter arrhythmias, electrical malfunctions that throw the heart out of rhythm and are a major cause of sudden cardiac death (SCD) in 450,000 Americans each year. Many confuse SCD with heart attack, a crisis brought on when a blocked artery damages heart muscle. The two problems come together when scar tissue left behind by a heart attack interferes with the heart's electrical system, bringing on arrhythmia.

Beta blockers in combination with ACE-inhibitors and statins are the treatment of choice for heart attack survivors, but fail to reduce risk of arrhythmia in many cases. ICDs have been gaining ground since the 2002 MADIT II study (Multicenter Automatic Defibrillator Implantation Trial II) found that the devices could reduce mortality by 31 percent in patients who had a heart attack. Led out of the University of Rochester Medical Center, the landmark study changed medical guidelines nationwide and made a hundred thousand heart attack survivors eligible for ICD therapy.

Some experts have since questioned, however, whether the ICD benefit extends to women, who were underrepresented in past studies and continue to be undertreated for heart disease in general, according to the American Heart Association. Until now, little data has been available to either support or debunk their use specifically in women. To address the gap, researchers at the University of Rochester Medical Center re-analyzed the MADIT II data, pulling out the data on women comparing the effects of ICD therapy in women and men.

The analysis found that women have similar risk of both overall mortality and SCD following heart attack as men. The study also found that both genders get a similar benefit from ICD therapy, which reduced mortality risk in women by an estimated 43 percent, and in men by 34 percent.

"Studies show that women received just 9,000 of 46,000 ICDs implanted in 2001," said Wojciech Zareba, M.D., Ph.D., lead author on the study and associate professor of Medicine (Cardiology) within the Cardiology Unit at the medical center. "Some physicians may be biased, perceiving that women have a lower cardiac mortality rate. Our study provides evidence that this perception needs to change if we are to better prevent sudden death in women after their heart attack."