Implantable Cardioverter Defibrillators May Reduce Mortality for Adults With Left Ventricular Systolic Dysfunction

August 22, 2007 — Implantable cardioverter defibrillators (ICDs) are effective in reducing mortality for adult patients with left ventricular systolic dysfunction, according to the results of a systematic review published in the August 21 issue of Annals of Internal Medicine.
"Patients with left ventricular (LV) systolic dysfunction have an increased risk for ventricular arrhythmias," write Justin A. Ezekowitz, MB, BCh, MSc, from the University of Alberta Evidence-based Practice Center in Edmonton, Alberta, Canada, and colleagues.
The objective of this review was to summarize available evidence concerning the benefits and disadvantages of ICDs in adults with LV systolic dysfunction. The investigators searched MEDLINE, EMBASE, Cochrane Central, US Food and Drug Administration reports, and other electronic databases from 1980 through April 2007. This search was not limited by language of publication, and the reviewers also did searches by hand and contacted study authors and device manufacturers.
Based on prespecified criteria, 2 reviewers independently selected studies and extracted data in duplicate. The selected studies consisted of 12 randomized controlled trials (RCTs) enrolling a total of 8516 patients and reporting on mortality, as well as 76 observational studies enrolling a total of 96,951 patients and evaluating safety or effectiveness.
New York Heart Association class II or III symptoms were present in 86% of adult participants with LV systolic dysfunction. Use of ICDs was associated with a 20% reduction in all-cause mortality (95% confidence interval [CI], 10% - 29%) in the RCTs and a 46% reduction in all-cause mortality (95% CI, 32% - 57%) in the observational studies.
Death associated with ICD implantation was reported during 1.2% of procedures (95% CI, 0.9% - 1.5%). Per 100 patient-years, postimplantation complications included 1.4 device malfunctions (95% CI, 1.2 - 1.6), 1.5 lead problems (95% CI, 1.3 - 1.8), and 0.6 site infections (95% CI, 0.5 - 0.8). Per 100 patient-years, there were 19.1 inappropriate discharges (95% CI, 16.5 - 22.0) in RCTs and 4.9 inappropriate discharges (95% CI, 4.5 - 5.3) in observational studies.
Limitations of the review were primarily those of the reported studies, namely, short duration, nonfatal outcomes being reported infrequently, dual-chamber ICDs being evaluated in few studies, and inability to determine subgroup-specific effects because of lack of individual patient data.
"Implantable cardioverter defibrillators are efficacious in reducing mortality for adult patients with LV systolic dysfunction, and this benefit extends to nontrial populations," the authors write. "Improved risk stratification tools to identify patients who are most likely to benefit from ICD are needed."
The Agency for Healthcare Research and Quality, US Department of Health and Human Services, supported this study. Some of the authors have disclosed various financial relationships with the Canadian Institutes of Health Research Randomized Controlled Trials Program, 21st Century Canada Research Chairs program, Alberta Heritage Foundation for Medical Research, the University of Alberta, and the Capital Health Authority, Edmonton.
Ann Intern Med. 2007;147:251-262.