Implantable cardioverter-defibrillator therapy improves long-term survival in patients with unexplained syncope, cardiomyopathy, and a negative electrophysiologic study

Objectives: The purpose of this study was to evaluate the long-term outcomes of patients with unexplained syncope, ischemic or nonischemic cardiomyopathy, and a negative electrophysiologic study (EPS). Background: EPS is frequently performed to evaluate syncope in patients with left ventricular dysfunction. Limited long-term data evaluating all-cause mortality in patients with no inducible arrhythmia or examining the potential benefits from implantable cardioverter-defibrillator (ICD) therapy are available. Methods: We evaluated 102 consecutive patients with unexplained syncope, cardiomyopathy, and a negative EPS from September 1996 to December 2000. A blinded matched case-control analysis utilized 51 of these patients (19 treated with an ICD and 32 matched controls treated with conventional therapy). We compared primary endpoint of death and documented cardiac arrest of patients treated with ICD therapy to matched controls. Results: Baseline characteristics were similar between groups. There were 14 primary events among the study population during a follow-up period of 44.3 ± 20 months: 2 in the ICD group and 12 in the conventional therapy group. The hazard ratio for the risk of event in the ICD group compared with the conventional therapy group was 0.18 (95% confidence interval, 0.04-0.85; P = .04). Other comorbid conditions, including age, sex, ischemic etiology of heart failure, ejection fraction, and antiarrhythmic use, did not predict outcome. Appropriate ICD shocks occurred in 26% of patients at 2 years. Conclusions: This study suggests that empiric ICD therapy improves long-term outcomes in patients with unexplained syncope, ischemic or nonischemic cardiomyopathy, and negative EPS.