Clinical study
Effectiveness of implantable defibrillators for preventing arrhythmic events and death: A Meta-Analysis

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Abstract

Objectives

The aim of this study was to compare the effectiveness of the implantable cardioverter defibrillator (ICD) and medical strategies for prevention of arrhythmic events and death.

Background

The ICD is a potential strategy to reduce mortality in patients at risk of sudden death.

Methods

The MEDLINE, EMBASE, and Cochrane Library electronic databases were searched from January 1966 to April 2002. All published randomized controlled trials comparing ICD implantation with medical therapy were reviewed. Four independent reviewers extracted data on all-cause mortality, nonarrhythmic death, and arrhythmic death using a standardized protocol.

Results

Nine studies including over 5,000 patients were synthesized using both fixed-effects and random-effects models. The primary and secondary prevention trials showed a significant benefit of the ICD with respect to arrhythmic death, with relative risks (RR) of 0.34 and 0.50, respectively (both p < 0.001). The mortality benefit of the ICD was entirely attributable to a reduction in arrhythmic death (all trials: p < 0.00001). Whereas the secondary prevention trials exhibited a robust decrease in all-cause ICD mortality (RR 0.75; p < 0.001), the pooled primary prevention trials demonstrated decreased all-cause ICD mortality (RR 0.66; p < 0.05) which was dependent on selected individual trials. The disparity in ICD-related mortality reductions in the primary prevention trials was related to variability in the incidence of arrhythmic death between individual studies.

Conclusions

Although the ICD decreases the risk of arrhythmic death, its impact on all-cause mortality is related to the underlying risk of arrhythmia-related death relative to competing causes. Given the cost of the device strategy, policies of targeted intervention based on the future risk of arrhythmia are warranted.

Abbreviations

AAD
antiarrhythmic drugs
AVID
Antiarrhythmics Versus Implantable Defibrillators study
CABG Patch
Coronary Artery Bypass Graft Patch trial
CASH
Cardiac Arrest Study Hamburg
CAT
Cardiomyopathy Trial
CI
confidence interval
CIDS
Canadian Implantable Defibrillator Study
ICD
implantable cardioverter defibrillator
LV
left ventricular
LVEF
left ventricular ejection fraction
MADIT
Multicenter Automatic Defibrillator Implantation Trial
MUSTT
Multicenter Unsustained Tachycardia Trial
RCT
randomized controlled trial
RD
risk difference
RR
relative risk

Cited by (0)

Dr. Lee is a research fellow of the Heart and Stroke Foundation of Canada/Canadian Institutes of Health Research. Dr. Liu is supported in part by grants from the Heart and Stroke Foundation of Ontario, the Canadian Institutes of Health Research, and the Heart & Stroke/Polo Chair Professor of Medicine at the University of Toronto. Dr. Tu is supported by a Canada Research Chair in Health Services Research and by the Canadian Institutes of Health Research. Dr. Alter is supported by the Canadian Institutes of Health Research and the Heart and Stroke Foundation of Canada.