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Implantable cardioverter defibrillators in primary and secondary prevention: a systematic review of randomized,
Justin A Ezekowitz1, Paul W Armstrong, Finlay A McAlister
1University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
Insights
Implantable cardioverter defibrillators (ICDs) significantly reduce sudden cardiac death and all-cause mortality in high-risk patients. ICD efficacy in preventing sudden cardiac death is consistent across risk levels, but total mortality benefits vary.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Sudden cardiac death (SCD) is a significant cause of mortality in individuals with cardiovascular disease.
- Identifying individuals at increased risk for SCD is crucial for timely intervention.
Purpose of the Study:
- To evaluate the effectiveness of implantable cardioverter defibrillators (ICDs) in preventing sudden cardiac death (SCD).
- To assess the impact of ICDs on all-cause mortality in at-risk populations.
Main Methods:
- Systematic review and meta-analysis of randomized controlled trials (RCTs) comparing ICDs with usual care.
- Inclusion of eight trials with 4909 patients and 1154 deaths.
- Data extraction and analysis performed by two independent reviewers.
Main Results:
- ICDs significantly reduced sudden cardiac death (RR, 0.43) and all-cause mortality (RR, 0.74) compared to usual care.
- ICD efficacy in preventing sudden cardiac death was consistent in both secondary prevention (RR, 0.50) and primary prevention (RR, 0.37) groups.
- The benefit of ICDs on total mortality varied within primary prevention trials based on baseline risk.
Conclusions:
- Implantable cardioverter defibrillators are effective in preventing sudden cardiac death irrespective of a patient's baseline risk.
- The impact of ICDs on overall mortality is influenced by the patient's risk for arrhythmic death.
- Accurate patient risk stratification is essential for optimizing resource allocation for ICD implantation.
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.
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