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Women experience greater complications and less life-saving therapy from ICD implantation: study


Women who undergo Implantable Cardioverter-Defibrillator (ICD) surgery are more likely to develop complications after the procedure than men according to new research from the Institute for Clinical Evaluative Sciences (ICES). The research was conducted in collaboration with 18 major cardiac centres in Ontario and shows that complications increased by 55 per cent in women who undergo ICD implantation up to one year after the operation compared to men.

The ICD works by recognizing serious heart rhythm disorders and treating them automatically with an electrical shock or heart pacing. While women were more likely to experience complications, they were also less likely to receive potentially life-saving shocks from the ICD. Approximately 10,000 women currently have an ICD in Ontario. Women were 31 per cent less likely to receive an appropriate defibrillator shock than men. Women were also 27 per cent less likely to receive an appropriate shock or heart pacing therapy from the device.

“While women make up a smaller proportion of all referred patients, they were equally likely to be implanted with an ICD after referral to an electrophysiologist. However, women were less likely to experience life-saving defibrillator shocks from the ICD,” says Dr. Douglas Lee, author of the study, ICES Scientist and Peter Munk Cardiac Centre (PMCC) Cardiologist.

Sudden cardiac death is a major cause of mortality, contributing to approximately 500,000 deaths annually in North America. ICDs have been shown to reduce mortality as primary prevention among those with myocardial infarction or heart failure, and as secondary prevention after cardiac arrest. An estimated 2,000 Ontarians undergo new ICD device procedures annually.

The findings of this study suggest that women should be aware of the potential risk of early complications, and they should seek the care of their physician if such events occur. These symptoms may include swelling or tenderness at the surgical site or difficulty breathing. However, some complications, which can impact how well the ICD works, can only be detected by regular checks of the defibrillator by the doctor in the clinic. Regular attendance at follow-up clinics is essential.

“The results reported by the investigators emphasize the ongoing need for inclusion of large numbers of women in randomized prospective clinical trials. Indeed these results suggest that in certain circumstances “women only” clinical trials may be required,” says Dr. Stephanie Brister, cardiac surgeon at PMCC.

The study of 6,021 patients who were referred for an ICD in 18 major cardiac centres in Ontario from February 2007 to July 2010 found:

  •  Among those referred for an ICD, rates of implantation were similar in men and women.
  •  Women experienced a 78 per cent increase in the odds of a major early complication occurring within 45 days after ICD implantation.
  • In longer-term follow-up, 13.9 per cent of women followed for up to one year developed major complications compared to 7.4 per cent of men – an increase in risk of 91 per cent in women compared to men.
  • Women who were implanted with an ICD were 31 per cent less likely to receive an appropriate defibrillator shock and 27 per cent less likely to receive an appropriate therapy from the device.

“The study findings add to the growing literature about important sex differences” says Pat Campbell, CEO, Echo: Improving Women’s Health in Ontario. “Recognition of sex differences in complication rates will support women and their care providers in making important decisions about appropriate care and underline the importance of examining for sex and gender differences.”

The Ontario ICD database, funded by the Ontario Ministry of Health and Long-Term care, is one of the most comprehensive ICD databases in the world. While ICDs can be life-saving devices for many patients, these data suggest that patient, operator and system factors contribute to risk of complications in patients facing ICD implantation procedures. Identifying factors contributing to complications may permit identification of high-risk individuals that warrant incremental monitoring and therapy to attenuate risk.

The study “Sex differences in Implantable Cardioverter Defibrillator outcomes: Findings from a prospective defibrillator database” is in the February 7, 2012 edition of Annals of Internal Medicine.

The Ontario Implantable Cardioverter Database (ICD) is funded by the Ontario Ministry of Health and Long-Term(MOHLTC) and involves a collaborative effort between ICES and all 18 hospitals in Ontario involved in the implantation and follow-up of patients who receive ICDs in Ontario visit ICD website. The results and conclusions are those of the authors, and should not be attributed to the MOHLTC.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.

The Peter Munk Cardiac Centre is the premier cardiac centre in Canada. Since it opened in 1997, the Centre has saved and improved the lives of cardiac and vascular patients from around the world. Each year, approximately 17,000 patients receive innovative and compassionate care from multidisciplinary teams in the Peter Munk Cardiac Centre, and the Centre trains more cardiologists, cardiovascular surgeons and vascular surgeons than any hospital in Canada. The Centre is based at the Toronto General Hospital and the Toronto Western Hospital – members of University Health Network, which also includes Princess Margaret Hospital and Toronto Rehabilitation Institute. All three sites are research hospitals affiliated with the University of Toronto. For more information please visit Peter Munk Cardiac Center website.



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