Heart RateHeartHeart Rate, FetalHeart FailureAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHeart Defects, CongenitalHemodynamicsFetal HeartSympathetic Nervous SystemElectrocardiography, AmbulatoryBaroreflexHeart AtriaElectrocardiographyAdrenergic beta-AntagonistsHeart ValvesExercise TestMyocardial ContractionHeart BlockMyocardiumTime FactorsOxygen ConsumptionHeart Function TestsParasympathetic Nervous SystemTelemetryDogsBradycardiaPropranololStroke VolumeRespirationMyocardial IschemiaVentricular Function, LeftCardiovascular Physiological PhenomenaTachycardiaPhysical ExertionCoronary DiseaseExercise