The rationale for prophylactic implantation of a defibrillator in "high risk" patients

The increasing technological developments have made it possible to have implantable defibrillators with a wide range of diagnostic and therapeutic capabilities, which can be implanted without the need for a thoracotomy. It is not surprising, therefore, that the indications for implantation of a defibrillator have rapidly evolved. Defining populations of patients in whom a true "prophylactic" implantation (before the first episode of ventricular tachycardia or ventricular fibrillation) may be justified is still difficult. However, the time has certainly come to provide a cardioverter defibrillator to all patients who have suffered from one episode of ventricular tachycardia or ventricular fibrillation and who are at real risk of sudden arrhythmic death. Identification of these patients is relatively easy. It can be done using simple variables from the clinical history. Results from an ongoing multicenter trial testing the hypothesis that clinical variables can indeed be used to stratify the risk of sudden death and to select candidates for a defibrillator have proven the validity of this approach. There is no medical justification to withhold implantation of a cardioverter defibrillator in the truly "high risk" patient. One has to realize, however, that the concept of "high risk" is relative, and that the indications for the implantable defibrillator will continue to broaden.