Heart FailureArrhythmias, CardiacVentricular Function, LeftHeartVentricular Dysfunction, LeftHeart RateStroke VolumeVentricular Function, RightHeart VentriclesMyocytes, CardiacEchocardiographyMyocardiumVentricular FunctionElectrocardiographyMyocardial ContractionHemodynamicsMyocardial InfarctionCardiac Output, LowHeart DiseasesCardiomyopathy, DilatedCardiac Pacing, ArtificialCardiac OutputArrhythmia, SinusTime FactorsVentricular RemodelingCardiomyopathiesHeart Function TestsSystoleTreatment OutcomeDeath, Sudden, CardiacHeart Failure, SystolicDiastoleCardiotonic AgentsMyocardial IschemiaFollow-Up StudiesHeart TransplantationProspective StudiesAdrenergic beta-AntagonistsNatriuretic Peptide, BrainTachycardia, VentricularAnti-Arrhythmia AgentsVentricular Dysfunction, RightCardiomegalyHeart Failure, DiastolicDogsCardiac CatheterizationHeart AtriaHeart Defects, CongenitalCardiac Surgical ProceduresVentricular DysfunctionEchocardiography, DopplerExercise TestHypertrophy, Left VentricularChronic DiseaseBlood PressureCoronary DiseasePredictive Value of TestsVentricular PressureVentricular FibrillationPrognosisAtrial FibrillationRadionuclide VentriculographyElectrocardiography, AmbulatoryDisease Models, AnimalCardiac VolumeRisk FactorsHeart Conduction SystemCoronary CirculationTachycardiaTreatment FailureRetrospective StudiesGated Blood-Pool ImagingPacemaker, ArtificialDefibrillators, ImplantableMyocardial Reperfusion InjuryPropanolaminesHeart BlockHeart-Assist DevicesVentricular Premature ComplexesRadionuclide AngiographyAngiotensin-Converting Enzyme InhibitorsSeverity of Illness IndexModels, CardiovascularBiological MarkersDobutamineFibrosisExercise ToleranceHeart ArrestFetal HeartRisk AssessmentMyocarditisOxygen ConsumptionAtrial Natriuretic FactorMagnetic Resonance Imaging, CineMitral Valve InsufficiencyDiureticsMetoprololElectrophysiologic Techniques, CardiacHeart ValvesDigoxin