Heart RateHeartHeart FailureHeart Rate, FetalBlood PressureAutonomic Nervous SystemHeart DiseasesTime FactorsReproducibility of ResultsHemodynamicsHeart TransplantationHeart Defects, CongenitalFetal HeartSympathetic Nervous SystemElectrocardiographyElectrocardiography, AmbulatoryBaroreflexHeart AtriaOxygen ConsumptionExercise TestAdrenergic beta-AntagonistsProspective StudiesMyocardiumMyocardial ContractionDogsRisk FactorsHeart ValvesReference ValuesTelemetrySensitivity and SpecificityHeart BlockHeart Function TestsRespirationStroke VolumeParasympathetic Nervous SystemAlgorithmsCardiac OutputVentricular Function, LeftBradycardiaExercisePredictive Value of TestsPropranololCoronary DiseaseMyocardial IschemiaPhysical ExertionFollow-Up StudiesCardiovascular Physiological PhenomenaAnalysis of VarianceRestSignal Processing, Computer-AssistedRegression AnalysisPostureTachycardiaEchocardiographyTreatment OutcomeModels, BiologicalDose-Response Relationship, DrugCardiovascular SystemModels, CardiovascularLinear ModelsBlood Flow VelocityAtropineAge FactorsPropanolaminesCardiotonic AgentsModels, StatisticalMyocardial InfarctionPressoreceptorsCohort StudiesNorepinephrineRegional Blood FlowOxygenHeart Arrest, InducedObserver VariationRisk AssessmentMonitoring, PhysiologicDouble-Blind MethodComputer SimulationRats, Sprague-DawleySystoleSinoatrial NodeUnited StatesBody TemperatureBody WeightReflexInfant, NewbornBiological MarkersSupine PositionAutonomic Nervous System DiseasesMyocytes, CardiacCardiac Output, LowCase-Control StudiesCircadian RhythmDiastoleRats, WistarRetrospective StudiesCardiac Pacing, ArtificialHypertensionArrhythmia, SinusPrevalence