Introduction: The relative effectiveness of the implantable cardioverter defibrillator (ICD) and antiarrhythmic drugs (AADs) varies with left ventricular ejection fraction (LVEF). However, once an ICD or AAD treatment strategy is chosen, the degree to which the LVEF influences survival is unknown. This article addresses that question. Methods and Results: Using patient data from the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial, the impact of LVEF on prognosis of patients who were treated with either an ICD or AAD was assessed. Survival within each quintile of LVEF was estimated by the method of Kaplan-Meier for patients treated with either the ICD or AADs. The Cox proportional hazards model was used to investigate the prognostic value of LVEF for estimating survival after adjustment for other baseline covariates among all patients in the subgroups treated by ICD or AAD. In the highest two quintiles of LVEF, survival was comparable in AAD-treated and ICD-treated patients. In the AAD-treated patients, higher LVEF was significantly and independently associated with survival free of all-cause mortality and arrhythmic death. In the ICD-treated patients, however, the statistical significance of the association was lost and only a trend toward greater survival was present. Death due to congestive heart failure remained independently and significantly associated with survival in both AAD-treated and ICD-treated patients. Conclusion: In patients treated with AADs but not patients treated with ICDs, survival is strongly associated with LVEF. The absence of a statistically significant association in the ICD patients is likely related to the effectiveness of the ICD in treating malignant ventricular arrhythmias, but a chance lack of association cannot be excluded.
- Implantable cardioverter defibrillator
- Sudden cardiac death
- Ventricular arrhythmia