A critical appraisal of indications for the implantable cardioverter defibrillator (ICD).

The implantable cardioverter defibrillator (ICD) is a remarkably effective therapy for reducing sudden cardiac death in patients with malignant ventricular arrhythmias. The indications for implantation of the ICD were approved in 1985 by the United States Food and Drug Administration; it could be implanted in patients who have experienced cardiac arrest or in those with recurrent ventricular arrhythmias which are not suppressed by anti-arrhythmic drugs in the electrophysiology laboratory. These established indications have not changed in the last seven years. In the near future, the release of third-generation ICDs (with antitachycardia pacing) will likely further expand indications for the device. Many patients with stable ventricular tachycardia who have not had syncope or cardiac arrest will receive a third-generation defibrillator. Also, three clinical trials now in progress--CABG-PATCH, Multicenter Automatic Defibrillator Implantation Trial (MADIT) and Multicenter Unsustained Tachycardia Trial (MUSTT)--are studying "pre-event" patients with low ejection fraction and electrical instability; some of the patients in each trial are being prospectively randomized to the ICD. Within the next five years we will have a better understanding of the role of ICD therapy in such patients. Until these studies are completed, it is important that the indications for the ICD not be expanded.