AmiodaroneHeart FailureHeartAnti-Arrhythmia AgentsHeart RateCardiac Output, LowHeart Failure, SystolicHeart Failure, DiastolicBenzofuransStroke VolumeMyocardiumHeart DiseasesCardiomyopathy, DilatedTreatment OutcomeHeart TransplantationAdrenergic beta-AntagonistsVentricular Function, LeftHemodynamicsTime FactorsAtrial FibrillationVentricular Dysfunction, LeftTreatment FailureNatriuretic Peptide, BrainChronic DiseaseCardiac Pacing, ArtificialVentricular RemodelingFollow-Up StudiesProspective StudiesTachycardiaEchocardiographyHeart AtriaCardiotonic AgentsHeart Defects, CongenitalArrhythmias, CardiacHeart Function TestsMyocardial ContractionMyocardial InfarctionElectrocardiographyDigoxinRisk FactorsDogsPropanolaminesDouble-Blind MethodTachycardia, VentricularMyocytes, CardiacCardiomyopathiesPrognosis