Heart RateHeartHeart FailureMyocardiumHeart Defects, CongenitalFetal HeartHeart Rate, FetalHeart DiseasesElectrocardiographyMyocardial ContractionBlood PressureHemodynamicsHeart TransplantationHeart ValvesAutonomic Nervous SystemHeart AtriaDogsHeart VentriclesCardiomegalyElectrocardiography, AmbulatoryCardiomyopathiesHeart BlockCardiomyopathy, DilatedVentricular Function, LeftMyocytes, CardiacAdrenergic beta-AntagonistsCardiac Pacing, ArtificialArrhythmias, CardiacHeart Conduction SystemTricuspid AtresiaEchocardiographyTime FactorsTachycardia, VentricularMyocardial IschemiaExercise TestOxygen ConsumptionVentricular Premature ComplexesSympathetic Nervous SystemModels, CardiovascularArchivesBaroreflexDeath, Sudden, CardiacStroke VolumeMyocardial InfarctionVentricular FibrillationCardiotonic AgentsAnti-Arrhythmia AgentsPhysical ExertionCardiac Output, LowCardiac OutputCoronary DiseaseTachycardia, SinusCoronary CirculationIsoproterenolVentricular Dysfunction, LeftVentricular RemodelingHeart Function TestsParasympathetic Nervous SystemTelemetrySystoleReference ValuesBradycardiaHeart SeptumVentricular PressurePropranololPerfusionElectrophysiologic Techniques, CardiacSyncopeDiastoleRespirationProspective StudiesDisease Models, AnimalEndocardiumCardiac VolumeCardiovascular Physiological PhenomenaTachycardiaPacemaker, ArtificialRats, WistarVentricular Function, RightCatecholaminesExerciseMyocardial Reperfusion InjuryHypertrophy, Left VentricularCardiovascular SystemHeart MurmursAtropineRestPericardiumPressoreceptorsVentricular FunctionPropanolaminesRabbitsBlood Flow VelocityEchocardiography, DopplerHeart Arrest, InducedRats, Sprague-DawleyNorepinephrineSinoatrial NodeCatheter AblationCardiomyopathy, Hypertrophic