Effectiveness of implantable defibrillators for preventing arrhythmic events and death
A Meta-Analysis
Douglas S. Lee, MD, FRCPC*  ,
Lawrence D. Green, MD*,
Peter P. Liu, MD, FRCPC ,
Paul Dorian, MD, MSc, FRCPC||,
David M. Newman, MD, FACC||,
F. Curry Grant, MD, MSc, FRCPC,
Jack V. Tu, MD, PhD, FRCPC*¶ and
David A. Alter, MD, PhD, FRCPC#,*
* Department of Health Policy, Management and Evaluation/Clinical Epidemiology, Toronto, Canada
Institute for Clinical Evaluative Sciences, Toronto, Canada
Division of Cardiology, University Health Network-Toronto General Hospital, Toronto, Canada
Heart and Stroke/Richard Lewar Centre of Excellence and Toronto General Hospital, Toronto, Canada
|| Electrophysiology and Arrhythmia Service, Division of Cardiology, St. Michael’s Hospital, Toronto, Canada
¶ Department of Medicine, Sunnybrook and Women’s College Health Science Centre, Toronto, Canada
# Division of Cardiology, Schulich Heart Centre, Sunnybrook and Women’s College Health Science Centre, Toronto, Canada
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Figure 1 QUOROM flow diagram of search results and the process of identification of randomized controlled trials (RCTs) meeting inclusion criteria. ICD = implantable cardioverter defibrillator.
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Figure 2 Plot of left ventricular ejection fraction (LVEF) in the defibrillator intervention (horizontal axis) and control arms (vertical axis) of the included randomized trials. Error bars are the reported standard deviations of LVEF in trial publications. Most of the points lie on the diagonal, suggesting that the trials were balanced for LVEF in the study arms. MADIT I and CABG Patch point estimates overlap. MUSTT and Wever et al. point estimates overlap. No standard deviation of LVEF was reported in MUSTT; only the point estimate is shown. AVID = Antiarrhythmics Versus Implantable Defibrillators study; CABG Patch = Coronary Artery Bypass Graft Patch Trial; CASH = Cardiac Arrest Study Hamburg; CAT = Cardiomyopathy Trial; CIDS = Canadian Implantable Defibrillator Study; MADIT = Multicenter Automatic Defibrillator Implantation Trial; MUSTT = Multicenter Unsustained Tachycardia Trial.
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Figure 3 Death from all causes in the primary prevention defibrillator trials, pooled in a random effects model. For each randomized trial, the number of deaths (n) and the number assigned (N) are shown. The rectangles represent the point estimates of the relative risk (RR) for individual studies, and the 95% confidence intervals (CI) are shown as bars. The overall pooled RR is 0.66 with a 95% CI of 0.46 to 0.96, which significantly favors treatment with the defibrillator (p = 0.03). The horizontal tips of the black diamond represent the 95% CI, and the midpoint of the diamond represents the point estimate of the RR. df = degrees of freedom; other abbreviations as in Figure 2.
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Figure 4 All-cause mortality in pooled secondary prevention defibrillator trials. For each randomized trial, the number of deaths (n) and the number assigned (N) are shown. The rectangles represent the point estimates of the relative risk (RR) for individual studies, and the 95% CI are shown as bars. The overall pooled RR is 0.75 with a 95% CI of 0.64 to 0.87, which significantly favors treatment with the defibrillator (p = 0.0002). The study results were not heterogeneous (p = 0.26), and together demonstrated significant reduction in death from any cause with the implantable cardioverter defibrillator. The horizontal tips of the black diamond represent the 95% CI, and the midpoint of the diamond represents the point estimate of the RR. AVID = Antiarrhythmics Versus Implantable Defibrillators study; CASH = Cardiac Arrest Study Hamburg; CIDS = Canadian Implantable Defibrillator Study; df = degrees of freedom.
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Figure 5 Impact of the randomized defibrillator trials on arrhythmic death. For each randomized trial, the number of arrhythmic deaths (n) and the number assigned (N) are shown. All studies showed consistent benefit in reducing arrhythmic death with the implantable cardioverter defibrillator (ICD), and there was no statistical heterogeneity between studies (p = 0.18). Over all studies reporting arrhythmic deaths, the defibrillator reduced the risk of arrhythmic death significantly (pooled relative risk 0.43; 95% CI 0.35 to 0.54). The ICD effect was a highly significant reduction in risk of arrhythmic death (p < 0.00001). The horizontal tips of the black diamond represent the 95% CI, and the midpoint of the diamond represents the point estimate of the RR. CABG Patch = Coronary Artery Bypass Graft Patch Trial; MADIT = Multicenter Automatic Defibrillator Implantation Trial; MUSTT = Multicenter Unsustained Tachycardia Trial. Other abbreviations as in Figure 4.
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