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A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation
Published on: February 28, 2012
Meta-analysis of the implantable cardioverter defibrillator secondary prevention trials. AVID, CASH and CIDS studies.
S J Connolly1, A P Hallstrom, R Cappato
1Hamilton Health Sciences Corporation, Hamilton, ON, Canada.
Insights
The implantable cardioverter defibrillator (ICD) significantly reduces the risk of death by 28% in patients with malignant ventricular arrhythmias compared to amiodarone. This survival benefit is primarily driven by a 50% reduction in arrhythmic death.
Area of Science:
- Cardiology
- Clinical Trials
- Medical Device Therapy
Background:
- Malignant ventricular arrhythmias pose a significant risk of sudden cardiac death.
- Implantable cardioverter defibrillators (ICDs) and antiarrhythmic drugs like amiodarone are used for prevention.
- Previous randomized trials reported seemingly disparate results regarding ICD efficacy.
Purpose of the Study:
- To precisely estimate the efficacy of ICD therapy compared to amiodarone in prolonging survival.
- To analyze pooled individual patient data from multiple ICD trials.
Main Methods:
- Individual patient data from the AVID, CASH, and CIDS trials were merged.
- Proportional hazard modeling and fixed-effect meta-analysis were employed.
- Treatment effects and subgroup interactions were investigated.
Main Results:
- Meta-analysis confirmed consistent ICD benefit across studies (P heterogeneity=0.306).
- ICD therapy significantly reduced all-cause mortality (HR 0.72, P=0.0006) and arrhythmic death (HR 0.50, P<0.0001).
- Survival was extended by a mean of 4.4 months; greater benefit observed in patients with LVEF ≤35% and in the non-thoracotomy era.
Conclusions:
- Results from the three trials are consistent, supporting ICD efficacy.
- ICD therapy offers a 28% relative risk reduction in death, largely due to a 50% reduction in arrhythmic death.
Aims:
Three randomized trials of implantable cardioverter defibrillator (ICD) therapy vs medical treatment for the prevention of death in survivors of ventricular fibrillation or sustained ventricular tachycardia have been reported with what might appear to be different results. The present analysis was performed to obtain the most precise estimate of the efficacy of the ICD, compared to amiodarone, for prolonging survival in patients with malignant ventricular arrhythmia.
Methods And Results:
Individual patient data from the Antiarrhythmics vs Implantable Defibrillator (AVID) study, the Cardiac Arrest Study Hamburg (CASH) and the Canadian Implantable Defibrillator Study (CIDS) were merged into a master database according to a pre-specified protocol. Proportional hazard modelling of individual patient data was used to estimate hazard ratios and to investigate subgroup interactions. Fixed effect meta-analysis techniques were also used to evaluate treatment effects and to assess heterogeneity across studies. The classic fixed effects meta-analysis showed that the estimates of ICD benefit from the three studies were consistent with each other (P heterogeneity=0.306). It also showed a significant reduction in death from any cause with the ICD; with a summary hazard ratio (ICD:amiodarone) of 0.72 (95% confidence interval 0.60, 0.87;P=0.0006). For the outcome of arrhythmic death, the hazard ratio was 0.50 (95% confidence interval 0.37, 0.67;P<0.0001). Survival was extended by a mean of 4.4 months by the ICD over a follow-up period of 6 years. Patients with left ventricular ejection fraction < or = 35% derived significantly more benefit from ICD therapy than those with better preserved left ventricular function. Patients treated before the availability of non-thoracotomy ICD implants derived significantly less benefit from ICD therapy than those treated in the non-thoracotomy era.
Conclusion:
Results from the three trials of the ICD vs amiodarone are consistent with each other. There is a 28% reduction in the relative risk of death with the ICD that is due almost entirely to a 50% reduction in arrhythmic death.
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