Heart FailureVentricular Function, LeftHeartNeural ConductionHeart Conduction SystemVentricular Dysfunction, LeftStroke VolumeHeart RateVentricular Function, RightHeart VentriclesVentricular FunctionEchocardiographyMyocytes, CardiacMyocardiumMyocardial ContractionCardiac Output, LowHemodynamicsCardiac Pacing, ArtificialElectrocardiographyMyocardial InfarctionHeart DiseasesCardiomyopathy, DilatedCardiac OutputArrhythmias, CardiacTime FactorsVentricular RemodelingSystoleHeart Function TestsCardiomyopathiesHeart Failure, SystolicTreatment OutcomeDiastoleHeart AtriaHeart BlockCardiotonic AgentsHeart TransplantationNatriuretic Peptide, BrainAtrioventricular NodeFollow-Up StudiesHeart Failure, DiastolicCardiac CatheterizationDogsCardiomegalyProspective StudiesVentricular Dysfunction, RightMyocardial IschemiaAdrenergic beta-AntagonistsEchocardiography, DopplerHeart Defects, CongenitalCardiac Surgical ProceduresChronic DiseaseHypertrophy, Left VentricularDeath, Sudden, CardiacExercise TestVentricular PressureBlood PressureRadionuclide VentriculographyCardiac VolumeVentricular DysfunctionCoronary DiseasePredictive Value of TestsPrognosisDisease Models, AnimalCoronary CirculationTreatment FailureGated Blood-Pool ImagingRisk FactorsAtrial FibrillationRetrospective StudiesAction PotentialsHeart-Assist DevicesRadionuclide AngiographyPropanolaminesAngiotensin-Converting Enzyme InhibitorsModels, CardiovascularSeverity of Illness IndexBiological MarkersAnti-Arrhythmia AgentsDobutamineExercise ToleranceFibrosisFetal HeartPacemaker, ArtificialOxygen ConsumptionAtrial Natriuretic FactorMyocarditisMitral Valve InsufficiencyCardiac Resynchronization TherapyElectrophysiologic Techniques, CardiacRats, Sprague-DawleyAtrial Function, LeftHeart ValvesEndocardiumMyocardial Reperfusion InjuryTachycardiaDiureticsRisk AssessmentMetoprololMagnetic Resonance Imaging, CineCardiovascular Agents