Study Finds Defibrillators are More Beneficial to Women

Cardiac resynchronization therapy defibrillators made by Boston Scientific Corp. are more beneficial to women than men, according to clinical trial data.

An analysis of results from a study of 1,800 patients showed that twice as many women as men experienced a reduction in heart failure events (70 percent for women, compared with 35 percent for men). Additionally, women who had a cardiac synchronization device combined with a defibrillator (CRT-D) implanted experienced a 72 percent reduction in death from any cause. According to the study, there was no evident reduction in death for men.

“These findings are noteworthy because CRT-D therapy has historically been underutilized in women compared to men with the same level of heart disease,” said Kenneth Stein, M.D., chief medical officer, CRM, for Boston Scientific’s Cardiology, Rhythm and Vascular Group.

The study is a sub-analysis of the MADIT-CRT trial, which was published last year in The New England Journal of Medicine. The gender-based analysis follows a U.S. Food and Drug Administration advisory panel recommendation that the device be approved for use in patients with mild heart failure. The device is already approved to treat patients with severe heart failure. If approved for the new prevention of heart failure indication, nearly 4 million additional people could be receive CRT-D treatment.

“Anecdotally, we know that women are offered devices to treat heart failure less often than men,” said Wojciech Zareba, M.D., Ph.D., professor of Medicine at the University of Rochester Medical Center (in Rochester, N.Y.) and co-author of the study. “We’re hopeful that these results will change the mindset of physicians and that they will apply this type of therapy as indicated in women as well as in men.”

The study’s authors attribute the disparate gender results to various factors, including the higher incidence of non-ischemic heart disease in women. Non-ischemic heart disease typically is characterized by inflammation of the heart muscle and can lead to reduced pumping strength, abnormal heart rhythms (arrhythmias) and disturbances in the heart’s electrical system. In many cases, non-ischemic disease affects the entire heart rather than a single region of the organ.

Another factor contributing to the lopsided results is the fact that women are more likely to have left bundle branch block, a condition that results in disorganized electrical activity throughout the heart, including unsynchronized contractions. Because left bundle branch block and non-ischemic disease lead to diffuse, as opposed to localized heart problems, researchers believe women may be more responsive to CRT-D therapy, which strengthens the overall mechanical pumping action of the heart and coordinates the heart’s electrical activity.

“Another issue to consider is that women often put their own health lower down on their list of priorities, after taking care of their family, managing their career, and so on,” Zareba noted. “This may translate into women showing up at the physician’s office later than men, with more advanced disease, in which case they might see a greater benefit from CRT-D therapy.”

Men, on the other hand, are more likely to suffer from ischemic heart disease— otherwise known as coronary artery disease—where narrowed arteries restrict the flow of blood and oxygen to the heart. Ischemic disease often leads to localized problems (a clogged artery restricts blood flow and causes damage to a particular region of the heart, for instance). Researchers believe the more localized problems men typically experience may render them somewhat less responsive to CRT-D therapy.

CRT-D therapy combines two functions found in current devices. It combines an implantable cardioverter defibrillator (ICD), which is designed to prevent sudden, rhythm-related cardiac death, with cardiac resynchronization therapy, which works to reduce heart failure and associated symptoms.