Women Less Likely Than Men to Receive Implantable Cardioverter-Defibrillators for Prevention of Sudden Cardiac Death

Among Medicare patients, men are about 2-3 times more likely than women to receive an implantable cardioverter-defibrillator for the prevention of sudden cardiac death, according to a study in the October 3 issue of JAMA.1

 Sudden cardiac death is a leading cause of death in the United States. Overall, the risk of sudden cardiac death increases with age and is higher in men than in women, although the sex difference narrows and eventually disappears after age 85 years, according to background information in the article. Research has shown the effectiveness of implantable cardioverter-defibrillators (ICDs) in preventing sudden cardiac death, and Medicare coverage of ICDs has expanded, but many eligible patients still do not receive them.

Lesley H. Curtis, Ph.D., of Duke University School of Medicine, Durham, N.C., and colleagues examined the differences between men and women in the receipt of ICDs for the primary and secondary prevention of sudden cardiac death. Data for the study came from a five percent national sample of files from the U.S. Centers for Medicare & Medicaid Services for the period 1991 through 2005. Patients in the study were age 65 years or older with Medicare fee-for-service coverage and diagnosed with a heart attack and either heart failure or cardiomyopathy (a disorder of the heart muscle), the primary prevention cohort: 136,421 patients; n = 65,917 men and 70,504 women; or with cardiac arrest or ventricular tachycardia (a cardiac arrhythmia), the secondary prevention cohort: 99,663 patients; n = 52,252 men and 47,411 women, from 1999 through 2005.

In the 2005 primary prevention group, 32.3 per 1,000 men and 8.6 per 1,000 women received ICD therapy within 1 year of entering the study. Men in this group were about 3.2 times more likely than women to receive an ICD. Among men and women alive at 180 days after group entry, the risk of death in the subsequent year was not significantly lower among those who received ICD therapy.

In the 2005 secondary prevention group, 102.2 per 1,000 men and 38.4 per 1,000 women received ICD therapy. After controlling for various factors, men in this group were about 2.4 times more likely than women to receive ICD therapy. Among men and women alive at 30 days after entry in this group, the risk of death in the subsequent year was 35 percent lower among patients who received ICD therapy.

 “In this longitudinal analysis of Medicare beneficiaries at high risk for sudden cardiac death, we found significant sex differences in the use of ICD therapy from 1999 through 2005. Our findings in this cohort of elderly patients differ from an earlier study that suggested a narrowing of the gap between men and women, and they highlight the need for an improved understanding of sex differences in patterns of care,” the authors conclude.

A study in the same issue of JAMA shows that many eligible heart-failure patients do not receive ICDs, and that rates of use are lower among women, and black patients. 2 The study showed that fewer than 40 percent of potentially eligible patients hospitalized for heart failure receive ICDs, and women and black patients are significantly less likely than white men to receive an ICD.

Half of all deaths from heart failure are sudden events thought to be attributable primarily to lethal arrhythmias, according to background information in the article. Studies have shown that ICDs reduce the risk of death for certain heart failure patients. The influence of sex and race on ICD use among eligible patients is unknown.

 Adrian F. Hernandez, M.D., M.H.S., of Duke University School of Medicine, Durham, N.C., and colleagues examined the overall use of ICD therapy in patients with heart failure who were at risk for sudden cardiac death. The analysis included 13,034 patients admitted with heart failure and left ventricular ejection fraction of 30 percent or less (a measure of how well the left ventricle of the heart pumps with each contraction). Patients were treated between January 2005 and June 2007 at 217 hospitals participating in a quality improvement program.

Among patients eligible for ICD therapy, 4,615 (35.4 percent) had ICD therapy at discharge. ICDs were used in 375 of 1,329 eligible black women (28.2 percent), 754 of 2,531 white women (29.8 percent), 660 of 1,977 black men (33.4 percent), and 2,356 of 5,403 white men (43.6 percent). After adjustment for patient characteristics and hospital factors, compared with white men, the odds of ICD use were: 27 percent lower for black men; 38 percent lower for white women; and 44 percent lower for black women.

“There are several potential factors that may explain the disparities observed in this study. System inequities may exist in the identification of eligible patients and delivery of ICD therapy. Physicians may consider certain subgroups more prominently due to a large number of white men in clinical trials. Patients may also differ in preferences for ICD therapy across sex and race subgroups …” the authors write.

“Further research is needed to understand the reasons for the disparities at the patient, physician, and hospital levels. Programs for awareness and promotion of evidence-based use of medical devices in heart failure are needed overall and for the important subgroups studied here. Publicly reported measures regarding ICD therapy should be considered.”

In an accompanying editorial in the journal, Rita F. Redberg, M.D., M.Sc., of the University of California-San Francisco Division of Cardiology, comments on studies regarding the use of ICDs. “… the multibillion-dollar question is: Are too few ICDs for primary prevention being implanted in women (and minorities) or are too many ICDs being implanted in (white) men? The important clinical and policy question may be not why women and black Medicare beneficiaries are less likely to get an ICD, but which Medicare beneficiaries will benefit from ICD at all? To answer this question, studies must look beyond reporting only process measures, such as implantation rates, and must include clinical outcomes, such as survival and quality of life after ICD implantation for primary and secondary prevention. By reporting the first outcomes data for ICD in the Medicare population, the study by Curtis et al should stimulate national dialogue on this crucial question.”

“Thus, in addition to their findings regarding disparities in ICD use, the studies by Curtis et al and Hernandez et al raise, perhaps inadvertently, a more serious concern. Their reports are important, but only first steps in understanding how to optimize delivery of cardiovascular health care in the United States. Their work highlights the importance of outcomes data for new therapies such as ICDs, reported according to sex and race/ethnicity subgroups, to determine if all patients are benefiting from health care advances.”



1. JAMA. 2007; 298(13):1517-1524                                                              

2. JAMA. 2007; 298(13):1525-1532.

3. JAMA. 2007; 298(13):1564-1566.