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Systematic Review: Implantable Cardioverter Defibrillators for Adults with Left Ventricular Systolic Dysfunction

Justin A. Ezekowitz, MB, BCh, MSc; Brian H. Rowe, MD, MSc; Donna M. Dryden, PhD; Nicola Hooton, MPH; Ben Vandermeer, MSc; Carol Spooner, BScN, MSc; and Finlay A. McAlister, MD, MSc
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From the University of Alberta Evidence-based Practice Center, Edmonton, Alberta, Canada.

Disclaimer: The authors of this report are responsible for its content. Statements in the report should not be construed as endorsement by the AHRQ or the U.S. Department of Health and Human Services.

Acknowledgments: The authors thank the members of the technical expert panel for this AHRQ report: Dr. Gillian Sanders (Duke University, Durham, North Carolina), Dr. Mark Hlatky (Stanford University, Stanford, California), Dr. Richard Page (University of Washington School of Medicine, Seattle, Washington), Dr. William Abraham (Ohio State University, Columbus, Ohio), and Mary Nix (AHRQ, Rockville, Maryland), who provided direction for the scope and content of the review. They also thank the librarians (Carol Friesen and Tamara Durec) and the external reviewers who submitted written comments on earlier drafts of this report: Dr. David Atkins (AHRQ), Dr. Eric Fain (St. Jude Medical, St. Paul, Minnesota), Dr. Martin Fromer (Centre Hospitalier Universtaire Vaudois, Lausanne, Switzerland), Dr. Gordon Moe (University of Toronto, Toronto, Ontario, Canada), Dr. Robert Rea (Mayo Clinic College of Medicine, Rochester, Minnesota), Dr. John Spertus (University of Missouri–Kansas, Kansas City, Missouri), Bob Thompson (Medtronic, Minneapolis, Minnesota), and Dr. Clyde Yancy (Baylor Heart and Vascular Institute, Dallas, Texas).

Grant Support: This manuscript is based on an evidence report produced by the University of Alberta Evidence-based Practice Center under contract 290-02-0023 from the AHRQ, U.S. Department of Health and Human Services. Dr. Ezekowitz is supported by the Canadian Institutes of Health Research Randomized Controlled Trials Program. Dr. Rowe is supported by the 21st Century Canada Research Chairs program through the Government of Canada. Dr. McAlister is a Population Health Scholar supported by the Alberta Heritage Foundation for Medical Research, is a New Investigator of the Canadian Institutes of Health Research, and holds the Merck Frosst/Aventis Chair in Patient Health Management at the University of Alberta, Edmonton. Drs. Ezekowitz, Rowe, and McAlister are also supported by the Faculty of Medicine and Dentistry, University of Alberta, Edmonton, and the Capital Health Authority, Edmonton.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Finlay A. McAlister, MD, MSc, University of Alberta Hospital, 2E3.24 WMC, 8440 112th Street, Edmonton, Alberta T6G 2R7, Canada; e-mail, Finlay.McAlister@ualberta.ca.

Current Author Addresses: Dr. Ezekowitz: 2C2 Cardiology WMC, University of Alberta Hospital, 8440 112th Street, Edmonton, Alberta T6G 2B7, Canada.

Dr. Rowe: Department of Emergency Medicine, University of Alberta Hospital, 1G1.42, 8440 112th Street, Edmonton, Alberta T6G 2B7, Canada.

Dr. Dryden, Ms. Hooton, Mr. Vandermeer, and Ms. Spooner: University of Alberta Evidence Based Practice Center, Aberhart Centre, 11402 University Avenue, Edmonton, Alberta, T6G 2J3, Canada.

Dr. McAlister: University of Alberta Hospital, 2E3.24 WMC, 8440 112th Street, Edmonton, Alberta T6G 2R7, Canada.

Ann Intern Med. 2007;147(4):251-262. doi:10.7326/0003-4819-147-4-200708210-00007
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Background: Patients with left ventricular (LV) systolic dysfunction have an increased risk for ventricular arrhythmias.

Purpose: To summarize the evidence about benefits and harms of implantable cardioverter defibrillators (ICDs) in adult patients with LV systolic dysfunction.

Data Sources: A search of electronic databases (including MEDLINE, EMBASE, Cochrane Central, and U.S. Food and Drug Administration reports) from 1980 through April 2007, not limited by language of publication, was supplemented by hand searches and contact with study authors and device manufacturers.

Study Selection: Two reviewers independently selected studies on the basis of prespecified criteria. They selected 12 randomized, controlled trials (RCTs) (8516 patients) that reported on mortality and 76 observational studies (96 951 patients) that examined safety or effectiveness.

Data Extraction: Data were extracted in duplicate and independently by 2 reviewers.

Data Synthesis: In adult patients with LV systolic dysfunction, 86% of whom had New York Heart Association class II or III symptoms, ICDs reduced all-cause mortality by 20% (95% CI, 10% to 29%) in the RCTs and by 46% (CI, 32% to 57%) in the observational studies. Death associated with implantation of ICDs occurred during 1.2% (CI, 0.9% to 1.5%) of procedures. The frequency of postimplantation complications per 100 patient-years included 1.4 (CI, 1.2 to 1.6) device malfunctions, 1.5 (CI, 1.3 to 1.8) lead problems, and 0.6 (CI, 0.5 to 0.8) site infection. Rates of inappropriate discharges per 100 patient-years ranged from 19.1 (CI, 16.5 to 22.0) in RCTs to 4.9 (CI, 4.5 to 5.3) in observational studies.

Limitations: Studies were of short duration and infrequently reported nonfatal outcomes. Few studies evaluated dual-chamber ICDs. Lack of individual-patient data prevents identification of subgroup-specific effects.

Conclusions: Implantable cardioverter defibrillators are efficacious in reducing mortality for adult patients with LV systolic dysfunction, and this benefit extends to nontrial populations. Improved risk stratification tools to identify patients who are most likely to benefit from ICD are needed.


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Figure 1.
Flow diagram of study identification and selection.

RCT = randomized, controlled trial.

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Figure 2.
Effect of implantable cardioverter defibrillator (ICDs) on all-cause mortality in randomized trials.

AMIOVIRT = Amiodarone vs. Implantable Defibrillator Randomized Trial; AVID = Antiarrhythmics Versus Defibrillators; CABG Patch = Coronary Artery Bypass Graft Patch Trial; CASH = Cardiac Arrest Study Hamburg; CAT = Cardiomyopathy Trial; CIDS = Canadian Implantable Defibrillator Study; COMPANION = Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure Trial; DEFINITE = Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation; DINAMIT = Defibrillator in Acute Myocardial Infarction Trial; MADIT = Multicenter Automatic Defibrillator Implantation Trial; RR = relative risk; SCD-HeFT = Sudden Cardiac Death in Heart Failure Trial.

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Figure 3.
Effect of implantable cardioverter defibrillators (ICDs) on all-cause mortality in observational studies with contemporaneous control groups.

MUSTT = Multicenter Unsustained Tachycardia Trial; RR = relative risk.

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Figure 4.
Scatter plot of all-cause mortality versus length of follow-up for recipients of implantable cardioverter defibrillators who were enrolled in different types of studies.

Circle = prospective cohort study; square = randomized, controlled trial; triangle = retrospective cohort study. Size of plotting character is proportional to the square root of the sample size of study.

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