Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart Defects, CongenitalHeart TransplantationHemodynamicsFetal HeartSympathetic Nervous SystemInfant, NewbornElectrocardiography, AmbulatoryBaroreflexHeart AtriaElectrocardiographyAdrenergic beta-AntagonistsTime FactorsHeart ValvesExercise TestMyocardial ContractionHeart BlockMyocardiumOxygen ConsumptionHeart Function TestsParasympathetic Nervous SystemDogsTelemetryBradycardiaRespirationPropranololStroke VolumeMyocardial IschemiaVentricular Function, LeftCardiovascular Physiological PhenomenaTachycardiaPhysical ExertionCoronary DiseaseExerciseCardiovascular SystemAtropineRestPressoreceptorsPropanolaminesCardiac OutputCardiotonic AgentsProspective StudiesHeart Arrest, InducedPregnancyNorepinephrineSinoatrial NodeRisk FactorsEchocardiographyShaken Baby SyndromeReflexAutonomic Nervous System DiseasesMyocardial InfarctionMyocytes, CardiacArrhythmia, SinusCardiac Output, LowPostureBody TemperatureCardiac Pacing, ArtificialMetoprololDouble-Blind MethodIsoproterenolSupine PositionModels, CardiovascularDose-Response Relationship, DrugFetal MonitoringReference ValuesGestational AgeSystoleFollow-Up StudiesSignal Processing, Computer-AssistedEpinephrineCardiomyopathy, DilatedInfant, PrematureRats, Sprague-DawleyDiastoleVentricular Dysfunction, LeftRegional Blood FlowRats, WistarInfant CareArrhythmias, CardiacCircadian RhythmTilt-Table TestAtenololHypotensionCardiomegalyTreatment OutcomeCatecholaminesAnti-Arrhythmia AgentsPhenylephrinePredictive Value of TestsMyocardial Reperfusion InjuryAnesthesiaCardiomyopathiesMonitoring, Physiologic