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Implantable Cardioverter Defibrillators in Primary and Secondary Prevention
A Systematic Review of Randomized, Controlled Trials
- Justin A. Ezekowitz, MB, BCh;
- Paul W. Armstrong, MD, FRCPC; and
- Finlay A. McAlister, MD, MSc, FRCPC
Abstract
Background: Sudden cardiac death is common in persons with cardiovascular disease.
Purpose: To assess the efficacy of implantable cardioverter defibrillators (ICDs) in persons at increased risk for sudden cardiac death.
Data Sources: MEDLINE (1980–2002), EMBASE (1980–2002), Cochrane Controlled Clinical Trial Registry (2002, Volume 3), other databases, and conference proceedings. Primary study authors and device manufacturers were contacted, and bibliographies of relevant papers were hand searched.
Study Selection: Randomized, controlled clinical trials evaluating ICDs versus usual care were selected.
Data Extraction: Two reviewers extracted data independently.
Data Synthesis: Eight trials were included in the final analysis (4909 patients, 1154 deaths). Compared with usual care (most commonly amiodarone therapy), ICDs significantly reduced sudden cardiac death (relative risk [RR], 0.43 [95% CI, 0.35 to 0.53]) and all-cause mortality (RR, 0.74 [CI, 0.67 to 0.82]). The included trials were divided a priori into two categories: secondary prevention (involving patients resuscitated after cardiac arrest or unstable ventricular tachycardia or ventricular fibrillation [n= 1963]) and primary prevention (involving patients at increased risk for sudden cardiac death but without documented cardiac arrest, ventricular fibrillation, or ventricular tachycardia [n= 2946]). Regardless of baseline risk, ICDs were equally efficacious in preventing sudden cardiac death in both types of trials (RR, 0.50 [CI, 0.38 to 0.66] for secondary prevention vs. 0.37 [CI, 0.27 to 0.50] for primary prevention). However, the magnitude of benefit in total mortality varied within the primary prevention trials depending on baseline risk for sudden cardiac death.
Conclusions: Implantable cardioverter defibrillators prevent sudden cardiac death regardless of baseline risk. However, their impact on total mortality is sensitive to baseline risk for arrhythmic death. Decisions about resource allocation for ICDs depend on accurate stratification of patients according to risk.
Article and Author Information
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Acknowledgments: The authors thank Dr. Terry Klassen, Dr. Brian Rowe, and Ms. Ellen Crumley for their assistance.
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Grant Support: By a CIHR Strategic Training Fellowship in TORCH (Tomorrow's Research Cardiovascular Health Professionals) (Dr. Ezekowitz) and by the Alberta Heritage Foundation for Medical Research (Dr. McAlister).
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Potential Financial Conflicts of Interest: None disclosed.
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Requests for Single Reprints: Finlay A. McAlister, MD, MSc, FRCPC, 2E3.24 Walter Mackenzie Centre, 8440 112th Street, Edmonton, Alberta T6G 2B7, Canada; e-mail, finlay.mcalister{at}ualberta.ca.
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Current Author Addresses: Drs. Ezekowitz and Armstrong: 2-51 Medical Sciences Building, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
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Dr. McAlister: 2E3.24 Walter Mackenzie Centre, 8440 112th Street, Edmonton, Alberta T6G 2B7, Canada.
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Author Contributions: Conception and design: J.A. Ezekowitz, F. McAlister.
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Analysis and interpretation of the data: J.A. Ezekowitz, P.W. Armstrong, F. McAlister.
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Drafting of the article: J.A. Ezekowitz, P.W. Armstrong, F. McAlister.
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Critical revision of the article for important intellectual content: J.A. Ezekowitz, P.W. Armstrong, F. McAlister.
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Final approval of the article: J.A. Ezekowitz, P.W. Armstrong, F. McAlister.
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Provision of study materials or patients: J.A. Ezekowitz.
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Statistical expertise: J.A. Ezekowitz, F. McAlister.
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Obtaining of funding: P.W. Armstrong.
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Administrative, technical, or logistic support: J.A. Ezekowitz, P.W. Armstrong.
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Collection and assembly of data: J.A. Ezekowitz, F. McAlister.
- Copyright ©2004 by the American College of Physicians
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