Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartTime FactorsSympathetic Nervous SystemElectrocardiography, AmbulatoryBaroreflexHeart AtriaElectrocardiographyAdrenergic beta-AntagonistsHeart ValvesExercise TestMyocardial ContractionMyocardiumHeart BlockOxygen ConsumptionDogsHeart Function TestsTelemetryParasympathetic Nervous SystemRuminococcusBradycardiaPropranololH(+)-K(+)-Exchanging ATPaseStroke VolumeMyocardial IschemiaVentricular Function, LeftCoronary DiseaseExerciseCardiovascular Physiological PhenomenaPhysical ExertionProspective StudiesTachycardiaRestCardiac OutputCardiovascular SystemAtropinePropanolaminesPressoreceptorsCardiotonic AgentsHeart Arrest, InducedReproducibility of ResultsNorepinephrineSialic AcidsMyocardial InfarctionEchocardiographyReflexSignal Processing, Computer-AssistedAutonomic Nervous System DiseasesModels, CardiovascularDose-Response Relationship, DrugPostureMyocytes, CardiacFollow-Up StudiesCardiac Output, LowArrhythmia, SinusArthroplastyCardiac Pacing, ArtificialDouble-Blind MethodMetoprololSupine PositionIsoproterenolTreatment OutcomeAge FactorsSystolePredictive Value of TestsRisk AssessmentBody TemperatureCell CycleRegression AnalysisEpinephrineCohort StudiesCardiomyopathy, DilatedModels, StatisticalAlgorithmsUnited StatesDiastoleAnalysis of VarianceRegional Blood FlowVentricular Dysfunction, LeftRats, WistarCircadian RhythmPrevalenceLinear ModelsArrhythmias, CardiacTilt-Table TestFetal MonitoringHypotensionInfant, NewbornAnti-Arrhythmia AgentsCardiomegalyAtenolol