Heart RateHeartBlood PressureSympathetic Nervous SystemAdrenergic beta-AntagonistsHeart Rate, FetalHeart FailureAutonomic Nervous SystemHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartElectrocardiography, AmbulatoryBaroreflexHeart AtriaElectrocardiographyHeart ValvesExercise TestMyocardial ContractionHeart BlockMyocardiumTime FactorsOxygen ConsumptionHeart Function TestsParasympathetic Nervous SystemTelemetryDogsBradycardiaPropranololStroke VolumeRespirationMyocardial IschemiaVentricular Function, LeftCardiovascular Physiological PhenomenaTachycardiaPhysical ExertionCoronary DiseaseExerciseCardiovascular SystemAtropineRestPressoreceptorsPropanolaminesCardiac OutputCardiotonic AgentsHeart Arrest, InducedNorepinephrineSinoatrial Node