Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartSympathetic Nervous SystemElectrocardiography, AmbulatoryBaroreflexTime FactorsHeart AtriaElectrocardiographyAdrenergic beta-AntagonistsHeart ValvesExercise TestMyocardiumMyocardial ContractionHeart BlockOxygen ConsumptionHeart Function TestsParasympathetic Nervous SystemTelemetryDogsBradycardiaPropranololNasal ObstructionStroke VolumeRespirationMyocardial IschemiaVentricular Function, LeftCardiovascular Physiological PhenomenaTachycardiaPhysical ExertionCoronary DiseaseExerciseCardiovascular SystemAtropineRestDose-Response Relationship, DrugPressoreceptorsPropanolaminesCardiac OutputCardiotonic AgentsHeart Arrest, InducedNorepinephrineSinoatrial NodeEchocardiographyReflexAutonomic Nervous System DiseasesMyocardial InfarctionRats, Sprague-DawleyMyocytes, CardiacArrhythmia, SinusRats, WistarCardiac Output, LowProspective StudiesCardiac Pacing, ArtificialPostureMetoprololIsoproterenolRisk FactorsDisease Models, AnimalSupine PositionModels, CardiovascularDouble-Blind MethodSystoleSignal Processing, Computer-AssistedEpinephrineCardiomyopathy, DilatedBody TemperatureDiastoleVentricular Dysfunction, LeftSneezingReference ValuesRegional Blood FlowArrhythmias, CardiacCircadian RhythmTilt-Table TestAtenololHypotensionCardiomegalyFetal MonitoringCatecholaminesAnti-Arrhythmia AgentsTreatment OutcomeFollow-Up StudiesOxygenPhenylephrineRabbitsMyocardial Reperfusion InjuryAnesthesiaCardiomyopathiesHeart Failure, SystolicAnalysis of VarianceCross-Over Studies