HIGH-INCIDENCE OF APPROPRIATE IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR THERAPY IN PATIENTS WITH SYNCOPE OF UNKNOWN ETIOLOGY AND INDUCIBLE VENTRICULAR ARRHYTHMIAS

Objectives. This study evaluates the hypothesis that in patients with syncope of unknown origin, inducible ventricular arrhythmias are speci fic arrhythmias and therefore should be appropriately treated. Backgro und. Although syncope is a common clinical entity, the evaluation and treatment of patients with syncope without a clear etiology are not we ll defined. Many patients with syncope of undetermined origin undergo invasive electrophysiologic evaluation. Abnormalities of the sinus nod e, prolongation of conduction times or inducible arrhythmias found at these evaluations are usually assumed to be the cause of syncope and a re therefore treated. However, whether tachyarrhythmias are truly the cause of syncope, and whether treatment of these tachyarrhythmias can prevent recurrent syncope and arrhythmic death, is unknown. Methods. T his study included 50 consecutive patients with syncope of undetermine d origin, ventricular tachyarrhythmias at electrophysiologic evaluatio n and treatment with an implantable cardioverter-defibrillator. Result s. Ventricular stimulation led to sustained monomorphic ventricular ta chycardia in 36 patients, nonsustained ventricular tachycardia in 5 an d ventricular fibrillation in 9. Over a 23 +/- 15 month (mean +/- SD) follow-up period, 18 patients received appropriate implantable cardiov erter-defibrillator shock. Actuarial probability of appropriate therap y was 22% at 1 year and 50% at 3 years, Recurrent syncope was seen in five patients, three of whom had appropriate defibrillator detections at the time of syncope. Four patients died (sudden death in one, conge stive heart failure in two). Conclusions. In patients with syncope of undetermined origin and inducible ventricular tachyarrhythmias, approp riate implantable cardioverter-defibrillator therapy is common at foll ow-up. Sudden cardiac death is uncommon. This low incidence of sudden cardiac death and high incidence of appropriate defibrillator therapy support the current practice of using implantable cardioverter-defibri llators in patients with syncope of unknown origin and inducible, vent ricular arrhythmias. (C) 1997 by the American College of Cardiology.