Meta-analysis of the implantable cardioverter defibrillator secondary prevention trials

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 rep orted with what might appear to be different results. The present analysis was performed to obtain the most precise estimate of the efficacy of the IC D, compared to amiodarone, for prolonging survival in patients with maligna nt ventricular arrhythmia. Methods and Results Individual patient data from the Antiarrhythmics vs Imp lantable 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 hazar d modelling of individual patient data was used to estimate hazard ratios a nd to investigate subgroup interactions. Fixed effect metaanalysis techniqu es were also used to evaluate treatment effects and to assess heterogeneity across studies. The classic fixed effects meta-analysis showed that the es timates of ICD benefit from the three studies were consistent with each oth er (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 o ver a follow-up period of 6 years. Patients with left ventricular ejection fraction <less than or equal to>35% derived significantly more benefit from ICD therapy than those with better preserved left ventricular function. Pa tients treated before the availability of non-thoracotomy ICD implants deri ved significantly less benefit from ICD therapy than those treated in the n onthoracotomy era. Conclusion Results from the three trials of the ICD vs amiodarone are consi stent with each other. There is a 28% reduction in the relative risk of dea th with the ICD that is due almost entirely to a 50% reduction in arrhythmi c death. (C) 2000 The European Society of Cardiology.