The purpose of this study was to evaluate predictors of appropriate therapy in patients with implantable cardioverter-defibrillators (ICD) for primary prevention of sudden cardiac death. A retrospective cohort of 321 patients with systolic heart failure undergoing ICD placement for primary prevention of sudden cardiac death was queried with a mean follow-up period of 2.6 years. Appropriate ICD therapy was defined as therapy delivered for termination of a ventricular tachyarrhythmia. Appropriate ICD therapy was delivered in 142 (44%) of the patients. In a multivariate model, body mass index >/=28.8 kg/m(2), chronic kidney disease, left ventricular ejection fraction =20% and metabolic syndrome were found to be independent predictors of appropriate ICD therapy. Appropriate ICD therapy was associated with higher cardiovascular mortality. These findings show the importance of identification of risk factors, especially metabolic syndrome, in patients following ICD implantation as aggressive treatment of these co-morbidities may decrease appropriate ICD therapy and cardiovascular mortality.