Heart RateHeartMyocytes, CardiacHeart FailureCardiac OutputHeart DiseasesHeart Rate, FetalBlood PressureArrhythmias, CardiacHeart TransplantationHemodynamicsAutonomic Nervous SystemHeart Defects, CongenitalDeath, Sudden, CardiacMyocardiumCardiac Surgical ProceduresMyocardial ContractionFetal HeartElectrocardiographyCardiac Pacing, ArtificialTime FactorsCardiomegalyHeart AtriaHeart Function TestsHeart ValvesElectrocardiography, AmbulatoryVentricular Function, LeftAdrenergic beta-AntagonistsDogsStroke VolumeHeart ArrestEchocardiographyBaroreflexExercise TestCardiac Output, LowMyocardial IschemiaCardiac CatheterizationMyocardial InfarctionHeart BlockSympathetic Nervous SystemCardiomyopathiesOxygen ConsumptionCardiotonic AgentsHeart VentriclesBradycardiaCardiac TamponadeParasympathetic Nervous SystemVentricular RemodelingProspective StudiesCardiomyopathy, DilatedCoronary DiseaseModels, CardiovascularTelemetryVentricular Dysfunction, LeftPropranololCardiovascular SystemRats, Sprague-DawleyTachycardiaRespirationCardiovascular Physiological PhenomenaIsoproterenolRisk FactorsTreatment OutcomePhysical ExertionNorepinephrineCardiac VolumeHeart Arrest, InducedCardiac MyosinsExercisePropanolaminesMyoblasts, CardiacAtropineSinoatrial NodeFollow-Up StudiesRats, WistarDisease Models, AnimalPressoreceptorsRestSystoleHeart Conduction SystemDiastoleHeart InjuriesDose-Response Relationship, DrugHeart NeoplasmsAutonomic Nervous System DiseasesMyocardial Reperfusion InjuryPredictive Value of TestsTroponin IArrhythmia, SinusAnti-Arrhythmia AgentsCardiac GlycosidesReflexCardiac Imaging TechniquesMetoprololEpinephrineCalciumAdrenergic beta-AgonistsReference ValuesVentricular FunctionPacemaker, Artificial