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Original Research |

Sex Differences in Implantable Cardioverter-Defibrillator Outcomes: Findings From a Prospective Defibrillator Database

Derek R. MacFadden, MD; Eugene Crystal, MD; Andrew D. Krahn, MD; Iqwal Mangat, MD; Jeffrey S. Healey, MD, MSc; Paul Dorian, MD; David Birnie, MBChB; Christopher S. Simpson, MD; Yaariv Khaykin, MD; Arnold Pinter, MD; Kumaraswamy Nanthakumar, MD; Andrew J. Calzavara, MSc; Peter C. Austin, PhD; Jack V. Tu, MD, PhD; and Douglas S. Lee, MD, PhD
[+] Article and Author Information

From the University of Toronto and Institute for Clinical Evaluative Sciences, Toronto; University of Western Ontario, London; McMaster University, Hamilton; University of Ottawa, Ottawa; Queen's University, Kingston; and Southlake Regional Health Centre, Newmarket, Ontario, Canada.


Disclaimer: The opinions, results, and conclusions are those of the authors, and no endorsement by the Ministry of Health and Long-Term Care or by the Institute for Clinical Evaluative Sciences is intended or should be inferred.

Grant Support: By an operating grant from the Canadian Institutes of Health Research (MOP 111150) and the Ontario Ministry of Health and Long-Term Care.

Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M11-1658.

Reproducible Research Statement:Study protocol: Published (19). Statistical code and data set: Not available.

Requests for Single Reprints: Douglas S. Lee, MD, PhD, Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada; e-mail, dlee@ices.on.ca.

Current Author Addresses: Drs. MacFadden, Austin, Tu, and Lee and Mr. Calzavara: Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.

Dr. Crystal: Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada.

Dr. Krahn: London Health Sciences Centre, 60 Chesley Avenue, London, Ontario N5Z 2C1, Canada.

Drs. Mangat, Dorian, and Pinter: St. Michael's Hospital, 30 Bond Street, Toronto, Ontario M5B 1W8, Canada.

Dr. Healey: Hamilton Health Sciences Centre, 237 Barton Street East, Hamilton, Ontario L8L 2X2, Canada.

Dr. Birnie: University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, Ontario K1Y 4W7, Canada.

Dr. Simpson: Kingston General Hospital, 76 Stuart Street, Kingston, Ontario K7L 2V7, Canada.

Dr. Khaykin: Southlake Regional Health Centre, 596 Davis Drive, Newmarket, Ontario L3Y 2P9, Canada.

Dr. Nanthakumar: University Health Network, 200 Elizabeth Street, Toronto, Ontario M5G 2C4, Canada.

Author Contributions: Conception and design: D.R. MacFadden, A.D. Krahn, J.S. Healey, P. Dorian, D. Birnie, Y. Khaykin, D.S. Lee.

Analysis and interpretation of the data: D.R. MacFadden, E. Crystal, J.S. Healey, P. Dorian, D. Birnie, C. S. Simpson, Y. Khaykin, A. Pinter, A.J. Calzavara, P.C. Austin, J.V. Tu, D.S. Lee.

Drafting of the article: D.R. MacFadden, Y. Khaykin, A. Pinter, D.S. Lee.

Critical revision of the article for important intellectual content: D.R. MacFadden, E. Crystal, A.D. Krahn, I. Mangat, J.S. Healey, P. Dorian, D. Birnie, Y. Khaykin, A. Pinter, K. Nanthakumar, A.J. Calzavara, P.C. Austin, J.V. Tu, D.S. Lee.

Final approval of the article: D.R. MacFadden, E. Crystal, A.D. Krahn, I. Mangat, J.S. Healey, P. Dorian, D. Birnie, Y. Khaykin, A. Pinter, K. Nanthakumar, A.J. Calzavara, P.C. Austin, J.V. Tu, D.S. Lee.

Provision of study materials or patients: E. Crystal, A.D. Krahn, I. Mangat, J.S. Healey, P. Dorian, C. S. Simpson, K. Nanthakumar, D.S. Lee.

Statistical expertise: A.J. Calzavara, P.C. Austin, D.S. Lee.

Obtaining of funding: A.D. Krahn, K. Nanthakumar, J.V. Tu, D.S. Lee.

Administrative, technical, or logistic support: E. Crystal, A.D. Krahn, D.S. Lee.

Collection and assembly of data: E. Crystal, A.D. Krahn, I. Mangat, J.S. Healey, P. Dorian, D. Birnie, C. S. Simpson, Y. Khaykin, K. Nanthakumar, D.S. Lee.


Ann Intern Med. 2012;156(3):195-203. doi:10.7326/0003-4819-156-3-201202070-00007
Text Size: A A A

Background: Sex differences in the use and outcomes of implantable cardioverter-defibrillators (ICDs) have not been fully studied.

Objective: To examine potential sex differences in ICD implantation and device outcomes.

Design: Health payer–mandated, prospective study of patients referred for ICD implantation, with comprehensive, longitudinal follow-up for complications, deaths, and device outcomes.

Setting: 18 ICD implantation and follow-up centers in Ontario, Canada.

Patients: 6021 patients (4733 men) referred for ICD implantation from February 2007 to July 2010.

Measurements: Multivariate-adjusted ICD implantation rate, complications up to day 45, multivariate-adjusted complications, device outcomes (including appropriate shocks and therapies), and deaths occurring during 1-year follow-up.

Results: Rates of ICD implantation were similar in men and women (relative risk, 0.99 [95% CI, 0.97 to 1.02]; P = 0.60). However, women were significantly more likely to experience major complications by 45 days (odds ratio, 1.78 [CI, 1.24 to 2.58]; P = 0.002) and 1 year (hazard ratio [HR], 1.91 [CI, 1.48 to 2.47]; P < 0.001) after implantation. Occurrence of any major or minor complication was also increased in women at both 45-day follow-up (odds ratio, 1.50 [CI, 1.12 to 2.00]; P = 0.006) and 1-year follow-up (HR, 1.55 [CI, 1.25 to 1.93]; P < 0.001). After implantation, women were less likely than men to receive appropriate ICD shock (HR, 0.69 [CI, 0.51 to 0.93]; P = 0.015) or appropriate therapy via shock or antitachycardia pacing (HR, 0.73 [CI, 0.59 to 0.90]; P = 0.003). Total mortality among defibrillator recipients did not differ between men and women (HR, 1.00 [CI, 0.64 to 1.55]; P = 0.99).

Limitation: The differential effects of sex on prereferral events were not examined.

Conclusion: Although ICD implantation rates were similar after referral to an electrophysiologist, women who underwent ICD implantation had greater risks for complications and were less likely to experience appropriate ICD-delivered therapies than men.

Primary Funding Source: Canadian Institutes of Health Research and Ontario Ministry of Health and Long-Term Care.

Figures

Grahic Jump Location
Figure 1.
Study flow diagram.

ICD = implantable cardioverter-defibrillator.

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Figure 2.
Time to first appropriate or inappropriate shock.
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Figure 3.
Time to first appropriate antitachycardia therapy.
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Summary for Patients

Implantable Cardioverter-Defibrillators in Women

The full report is titled “Sex Differences in Implantable Cardioverter-Defibrillator Outcomes: Findings From a Prospective Defibrillator Database.” It is in the 7 February 2012 issue of Annals of Internal Medicine (volume 156, pages 195-203). The authors are D.R. MacFadden, E. Crystal, A.D. Krahn, I. Mangat, J.S. Healey, P. Dorian, D. Birnie, C.S. Simpson, Y. Khaykin, A. Pinter, K. Nanthakumar, A.J. Calzavara, P.C. Austin, J.V. Tu, and D.S. Lee.

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