Heart RateCircadian RhythmHeartHeart FailureHeart Rate, FetalAutonomic Nervous SystemBlood PressureHeart DiseasesHeart TransplantationHemodynamicsHeart Defects, CongenitalElectrocardiographyFetal HeartHeart AtriaElectrocardiography, AmbulatoryTime FactorsSympathetic Nervous SystemPeriodicityBiological ClocksHeart BlockBaroreflexAdrenergic beta-AntagonistsSuprachiasmatic NucleusMyocardial ContractionHeart ValvesExercise TestTelemetryMyocardiumAtrial FibrillationRespirationBradycardiaPeriod Circadian ProteinsDogsOxygen ConsumptionHeart Function TestsActivity CyclesCircadian Rhythm Signaling Peptides and ProteinsBody TemperatureParasympathetic Nervous SystemPhotoperiodAnti-Arrhythmia AgentsStroke VolumeSinoatrial NodeCardiac Pacing, ArtificialPropranololCardiovascular Physiological PhenomenaSleep Disorders, Circadian RhythmVentricular Function, LeftArrhythmia, SinusArrhythmias, CardiacMyocardial IschemiaRestPhysical ExertionAtropineCircadian ClocksCoronary DiseaseTachycardiaPropanolaminesPressoreceptorsExerciseCardiac OutputCLOCK ProteinsCardiotonic AgentsCardiovascular SystemNorepinephrineEchocardiographyAlpha RhythmHeart Arrest, InducedProspective StudiesSignal Processing, Computer-AssistedReflexAutonomic Nervous System DiseasesMyocytes, CardiacRats, Sprague-DawleyModels, CardiovascularRisk FactorsCardiac Output, LowHeart Conduction SystemRats, WistarElectric CountershockMotor ActivityMyocardial InfarctionPostureDose-Response Relationship, DrugIsoproterenolARNTL Transcription FactorsDouble-Blind MethodTreatment OutcomeSleepMetoprololHeart ArrestCardiomyopathy, DilatedSystoleSupine PositionFollow-Up StudiesEpinephrineReference ValuesVentricular Dysfunction, LeftChronobiology DisordersDiastole