Secondary prevention of sudden death: The Dutch Study, the AntiarrhythmicsVersus Implantable Defibrillator Trial, the Cardiac Arrest Study Hamburg, and the Canadian Implantable Defibrillator Study

Although indisputably effective in the prevention of sudden death, use of i mplantable cardioverter defibrillator (ICD) therapy may not necessarily aff ect all-cause mortality, as most patients at risk also present with severel y depressed left ventricular dysfunction. Correction of the sudden death ri sk in these patients creates a new clinical condition in need of a careful assessment. Should all-cause mortality be affected by the expected reductio n in sudden death rate associated with ICD therapy, issues of critical impo rtance such as the time extent of life prolongation and the associated qual ity of life, still remain to established. To investigate the potential bene fit of ICD therapy compared with antiarrhythmic drug treatment, 4 prospecti ve studies-the Dutch trial, the Antiarrhythmics Versus Implantable Defibril lators (AVID) study, the Cardiac Arrest Study Hamburg (CASH), and the Canad ian Implantable Defibrillator Study (CIDS)-have been conducted in which pat ients with documented sustained ventricular arrhythmia were randomized to 1 of these 2 treatment strategies. The enrollment criteria differed in these 4 studies: (1) in the Dutch trial, they included cardiac arrest secondary to a ventricular arrhythmia, old (>4 weeks) myocardial infarction, and indu cible ventricular arrhythmia; (2) in AVID and CIDS, ventricular fibrillatio n or poorly tolerated ventricular tachycardia; and (3) in CASH, cardiac att est secondary to a ventricular arrhythmia regardless of the underlying dise ase. With regard to the antiarrhythmic drugs, the Dutch trial tested class I and III agents, whereas AVID and CIDS compared ICD therapy with class III agents (mostly amiodarone). In CASH, 3 drug subgroups were investigated: p ropafenone, amiodarone, and metoprolol. All trials used all-cause mortality as the primary endpoint. Data from these trials provide support for ICD as a therapy superior to antiarrhythmic drugs in prolonging survival in patie nts meeting the entry criteria. This review briefly summarizes the methods, results, limitations, and clinical implications of these 4 studies. (C) 19 99 by Excerpta Medico, Inc.