Clinical predictors of implantable cardioverter-defibrillator shocks (results of the CASCADE trial)

Abstract

The Cardiac Arrest in Seattle, Conventional Versus Amiodarone Drug Evaluation (CASCADE) study evaluated antiarrhythmic drug therapy in high-risk survivors of out-of-hospital ventricular fibrillation. Antiarrhythmic drug therapy for 228 patients was randomized to amiodarone or conventional antiarrhythmic drugs. Additional therapy with an implantable cardioverter-defibrillator was provided to 105 of these patients. Clinical predictors of shocks were evaluated for the 88 patients with coronary artery disease (amiodarone 46, conventional 42), treated with an implantable cardioverter-defibrillator. Survival free of all shocks at 2 years was 77% for patients taking amiodarone and 42% for those receiving conventional therapy (p = 0.014). Two-year survival free of syncopal shocks was 98% for amiodarone-treated patients and 81% for those receiving conventional agents (p = 0.01). Multiple clinical factors were evaluated by Cox analysis for potential clinical predictors of shocks. The independent clinical predictors of shocks were low ejection fraction (p = 0.002), female gender (p = 0.007) and conventional antiarrhythmic drug therapy (p = 0.015). The only independent predictor of a shock associated with syncope was conventional antiarrhythmic drug therapy (p = 0.035). Patients treated with amiodarone receive fewer shocks than patients treated with conventional drug therapy.