SAN FRANCISCO – Women who were referred to an electrophysiologist were just as likely as men to get an implantable cardioverter-defibrillator, but women developed more complications and were less likely to receive an appropriate ICD shock or appropriate ICD-delivered therapy, a study of 6,902 patients found.
Previous studies have suggested that women are less likely than men are to get ICDs. If that’s true, the disparity may be happening before patients are referred for consideration of ICD implantation, Dr. Derek R. MacFadden said at the annual meeting of the American College of Physicians.
Dr. Derek R. MacFadden
He and his associates analyzed data from a prospective registry of all 6,902 patients in the province of Ont., Canada, who were referred for consideration of an ICD or had one implanted between February 2007 and July 2010. Men and women were equally likely to be among the 5,450 patients who received ICDs and the 571 who did not receive ICDs (because they did not meet implantation criteria, refused implantation, or deferred a decision until after therapy could be optimized), reported Dr. MacFadden of the University of Toronto. The analysis excluded 881 patients with missing data.
Previous studies have reported higher risks for complications in women who get ICDs, as well as sex differences in arrhythmia patterns after implantation. Follow-up data on complications at 45 days in the current study were available in 4,830 patients, and an analysis of outcomes and complications at 1 year included 5,213 patients (Ann. Intern. Med. 2012;156:195-203).
At 45 days, rates of any major or minor complication were significantly higher in women (5.4% and 5.8%), compared with men (3.3% and 3.8%), Dr. MacFadden reported. These included significantly higher rates of lead replacement in women, compared with men (1.9% vs. 0.7%, respectively), and of pulmonary edema (0.6% and 0.2%, respectively).
At the 1-year follow-up, women were 91% more likely than were men to have a major complication, 56% more likely to have a minor complication, and 55% more likely to have any complication, compared with men, after researchers adjusted for confounding factors.
Women were significantly less likely at 1 year to have received an appropriate shock (5%) or appropriate therapy (11%), compared with men (8% and 15%, respectively). When appropriate shocks or therapy were delivered, men received it significantly sooner than did women, he said. The rates of inappropriate shocks (3%) or death (3%) were similar between the sexes.
"Greater risk of complications and the possibility of decreased therapeutic benefit should be considered in women who are referred for ICD implantation," Dr. MacFadden said.
The higher rates of complications in women may be due to bodily differences or physical characteristics, compared with men, he speculated.
At the time of referral for consideration of an ICD, the women were significantly younger than the men were (63 years vs. 65 years). Women had a significantly higher left ventricular ejection fraction (31% vs. 29%). Rates for many cardiac and noncardiac conditions differed significantly by sex. Women were less likely to have had percutaneous coronary intervention, coronary artery bypass graft surgery, atrial fibrillation, dyslipidemia, hypertension, stroke, and peripheral vascular disease, and they were more likely to have a family history of sudden cardiac death, severe valvular disease, or inactive cancer.
The ICDs were implanted for primary prevention in 3,822 patients and for secondary prevention in 1,628 patients.
Women account for approximately 43% of sudden cardiac deaths. Guidelines for ICD implantation to prevent sudden cardiac death are the same for women and men, and are based on randomized, controlled trials with only small percentages of women in their cohorts, he said.
Dr. MacFadden reported having no financial disclosures. Some of his associates reported financial relationships with Biosense, Boehringer, Boston Scientific, Medtronic, and Sanofi.
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