Heart FailureHeartVentricular Function, LeftVentricular FunctionHeart VentriclesPhenylisopropyladenosineRubidium RadioisotopesMyocardiumVentricular Function, RightVentricular Dysfunction, LeftStroke VolumeHeart RateEchocardiographyGuinea PigsMyocytes, CardiacMyocardial ContractionHemodynamicsCardiac Output, LowMyocardial InfarctionHeart DiseasesCardiac OutputCardiomyopathy, DilatedVentricular Dysfunction, RightVentricular RemodelingCardiac Pacing, ArtificialSystoleTime FactorsHeart Function TestsHeart Failure, SystolicHeart Septal Defects, VentricularTreatment OutcomeCardiomyopathiesElectrocardiographyDiastoleCardiotonic AgentsHeart TransplantationNatriuretic Peptide, BrainHeart Failure, DiastolicArrhythmias, CardiacCardiac CatheterizationFollow-Up StudiesCardiomegalyProspective StudiesHeart Defects, CongenitalEchocardiography, DopplerCardiac Surgical ProceduresAdrenergic beta-AntagonistsMyocardial IschemiaHeart AtriaChronic DiseaseHypertrophy, Left VentricularDogsExercise TestVentricular PressureBlood PressureDeath, Sudden, CardiacRadionuclide VentriculographyCardiac VolumeCoronary DiseaseVentricular DysfunctionPrognosisPredictive Value of TestsDisease Models, AnimalTreatment FailureGated Blood-Pool ImagingCoronary CirculationRisk FactorsRetrospective StudiesHeart-Assist DevicesRadionuclide AngiographyAngiotensin-Converting Enzyme InhibitorsPropanolaminesSeverity of Illness IndexPacemaker, ArtificialBiological MarkersDobutamineExercise ToleranceFetal HeartAtrial Natriuretic FactorOxygen ConsumptionFibrosisMitral Valve InsufficiencyMyocarditisHeart BlockHeart ValvesDiureticsMagnetic Resonance Imaging, CineCardiac Resynchronization TherapyMyocardial Reperfusion InjuryRisk AssessmentEchocardiography, Doppler, PulsedEchocardiography, Doppler, ColorMetoprololCardiovascular AgentsCoronary Artery BypassAtrial Function, LeftHypertrophy, Right VentricularRats, Sprague-DawleyCoronary AngiographyHospitalization