Women sometimes benefit more from cardiac resynchronization therapy than men

Bottom Line: Cardiac resynchronization therapy plus defibrillator implantation (CRT-D) sometimes helps women with heart failure more than men, although women are less likely to receive CRT-D than men.

Author: Robbert Zusterzeel, M.D., and colleagues at the Center for Devices and Radiological Health at the U.S. Food and Drug Administration, Silver Spring, Md.

Background: Women are underrepresented in CRT trials for heart failure, making up only about 20 percent of participants. In selected heart failure patients CRT, or biventricular pacing, is used to help improve the heart's rhythm. In addition to improving symptoms, CRT can decrease hospitalizations and reduce risk of death in patients with heart failure.

How the Study Was Conducted: The authors combined data from three large trials of CRT-D vs. implantable cardioverter defibrillator (ICD) in patients with mild heart failure (predominantly New York Heart Association Class II). The authors examined whether women with left bundle branch block (LBBB) benefit from CRT-D at a shorter QRS duration (portion of the EKG tracing that corresponds to ventricular depolarization) than men with LBBB.

Results: Women benefitted more than men and the main difference came in patients with LBBB and a QRS of 130 to 149 milliseconds. In this group, women had a 76 percent reduction in heart failure (absolute difference 23%) or death and a 76 percent reduction in death alone (absolute difference 9%), but there was no significant benefit in men. Neither sex benefitted from CRT-D at QRS shorter than 130 milliseconds and both sexes benefitted at QRS of 150 milliseconds or longer. The finding is important because recent guidelines limit the class I indication for CRT-D to patients with LBBB and QRS of 150 milliseconds or longer.

Discussion: "Overall, this study highlights the importance of sex-specific analysis in medical device clinical studies and the public health value of combining individual-patient data from clinical trials submitted to the FDA."

(JAMA Intern Med. Published online June 23, 2014. doi:10.1001/jamainternmed.2014.2717. Available pre-embargo to the media at http://media.jamanetwork.com.)

Editor's Note: This project was supported in part by the FDA Office of Women's Health and by a research fellowship from the Oak Ridge Institute for Science and Education through and interagency agreement between the U.S. Department of Energy and the FDA. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

In a related commentary, C. Noel Bairey Merz, M.D., of the Cedars Sinai Heart Institute, Los Angeles, Calif., and Vera Regitz-Zagrosek, M.D., of Charite University Medicine, Berlin, write: "There are numerous differences in cardiovascular disease (CVD) between men and women. … There are also important sex differences in use of cardiac devices."

"These results also shed light on a major contributor to the misdiagnosis and suboptimal treatment of CVD in women: guidelines are typically based on a male standard and do not address important differences in women."

(JAMA Intern Med. Published online June 23, 2014. doi:10.1001/jamainternmed.2014.320. Available pre-embargo to the media at http://media.jamanetwork.com.)

Editor's Note: This work was supported by contracts from the National Heart, Lung and Blood Institutes, grants from the National Institute on Aging and other sources. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.

Media Advisory: To contact corresponding author David G. Strauss, M.D., Ph.D., call Susan Laine at 301-796-5349 or email Susan.Laine@fda.hhs.gov. To contact commentary author C. Noel Bairey Merz, M.D., call Sally Stewart 310-248-6566 or email sally.stewart@cshs.org.