The atrial defibrillator: A stand-alone device or part of a combined dual-chamber system?

Atrial fibrillation (AF) is an extremely common arrhythmia seen in clinical practice. Because of the limited efficacy of traditional therapeutic strat egies to restore and maintain normal sinus rhythm, several nonpharmacologic options have evolved. The promising results achieved with internal atrial defibrillation have facilitated the development of an implantable atrial de fibrillator. Preliminary results obtained from an initial study on a small number of highly selected patients with refractory AF suggest that atrial d efibrillation can be performed effectively and safely with adequate patient tolerance by using a stand-alone device. The extension of this therapy wil l depend on the results of well-designed prospective studies comparing this new therapeutic option with traditional methods. Several acute studies hav e shown that internal conversion of AF is feasible at low energies with cur rent endocardial transvenous lead configurations primarily designed for ven tricular defibrillation, bur long-term efficacy has, to date, only been dem onstrated with atrial implantable defibrillator lead systems. As AF is a fr equent arrhythmia in implantable cardioverter defibrillator (ICD) recipient s, it would seem desirable to incorporate the capability for atrial defibri llation into an ICD. Clinical studies have shown that an atrial defibrillat or, as part of a combined dual-chamber ICD system, may not require a potent ially complicated switching network for establishing different electrode co nfigurations for atrial and ventricular tachyarrhythmia. The efficacy in at rial cardioversion of such a combined, less complex device seems to be as h igh as reported for a pure atrial defibrillator, but generally at somewhat higher energy requirements. The results of further investigations will show whether a dual-chamber cardioverter defibrillator would be of clinical rel evance in patients with ventricular and supraventricular tachyarrhythmia. ( C) 1999 by Excerpta Medica, Inc.