Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartSympathetic Nervous SystemElectrocardiography, AmbulatoryTime FactorsBaroreflexHeart AtriaElectrocardiographyAdrenergic beta-AntagonistsHeart ValvesExercise TestMyocardial ContractionMyocardiumHeart BlockOxygen ConsumptionHeart Function TestsTelemetryDogsParasympathetic Nervous SystemBradycardiaPropranololGerminal CenterRespirationStroke VolumeMyocardial IschemiaVentricular Function, LeftCardiovascular Physiological PhenomenaProspective StudiesTachycardiaCoronary DiseaseExercisePhysical ExertionCardiovascular SystemRisk FactorsAtropineRestPressoreceptorsPropanolaminesCardiac OutputCardiotonic AgentsChild Day Care CentersHeart Arrest, InducedSinoatrial NodeNorepinephrineTreatment OutcomeEchocardiographyReflexAutonomic Nervous System DiseasesFollow-Up StudiesPostureMyocardial InfarctionMyocytes, CardiacCardiac Output, LowArrhythmia, SinusDouble-Blind MethodCardiac Pacing, ArtificialRetrospective StudiesMetoprololIsoproterenolDose-Response Relationship, DrugSupine PositionModels, CardiovascularSignal Processing, Computer-AssistedSystoleReference ValuesCardiomyopathy, DilatedEpinephrineBody TemperatureRats, Sprague-DawleyVentricular Dysfunction, LeftDiastoleRats, WistarArrhythmias, CardiacRegional Blood FlowTertiary Care CentersCommunity Health CentersCircadian RhythmPredictive Value of TestsHypotensionTilt-Table TestTrauma CentersAtenololAnti-Arrhythmia AgentsFetal MonitoringCatecholaminesCardiomegalyOxygenAnesthesiaPhenylephrineCardiomyopathiesAnalysis of Variance