Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartSympathetic Nervous SystemElectrocardiography, AmbulatoryBaroreflexHeart AtriaElectrocardiographyTime FactorsAdrenergic beta-AntagonistsExercise TestHeart ValvesMyocardial ContractionMyocardiumHeart BlockOxygen ConsumptionHeart Function TestsDogsTelemetryParasympathetic Nervous SystemBradycardiaPropranololRespirationStroke VolumeMyocardial IschemiaVentricular Function, LeftExerciseCardiovascular Physiological PhenomenaCoronary DiseaseTachycardiaPhysical ExertionRestCardiovascular SystemProspective StudiesAtropineCardiac OutputPressoreceptorsPropanolaminesCardiotonic AgentsHeart Arrest, InducedRisk FactorsNorepinephrineSinoatrial NodeEchocardiographyMyocardial InfarctionReflexAutonomic Nervous System DiseasesDouble-Blind MethodPostureMyocytes, CardiacArrhythmia, SinusCardiac Output, LowCardiac Pacing, ArtificialDose-Response Relationship, DrugMetoprololFollow-Up StudiesReproducibility of ResultsTreatment OutcomeSignal Processing, Computer-AssistedReference ValuesModels, CardiovascularIsoproterenolSupine PositionSystoleRats, Sprague-DawleyBody TemperatureEpinephrineCardiomyopathy, DilatedDiastoleVentricular Dysfunction, LeftRegional Blood FlowRats, WistarPredictive Value of TestsCircadian RhythmAnalysis of VarianceArrhythmias, CardiacHypotensionAtenololTilt-Table TestFetal MonitoringCardiomegalyCatecholaminesAnti-Arrhythmia AgentsCross-Over StudiesPhenylephrineChronic DiseaseAnesthesiaMonitoring, PhysiologicMyocardial Reperfusion InjuryOxygenCardiomyopathiesHypertension