Heart RateHeartArrhythmia, SinusSympathetic Fibers, PostganglionicSympathetic Nervous SystemPeroneal NerveRespirationElectrocardiographyInhalationSinoatrial NodeModels, CardiovascularMyocardial ContractionHeart FailurePressoreceptorsBlood PressureSignal Processing, Computer-AssistedRestHeart DiseasesMyocardiumHeart TransplantationHeart Defects, CongenitalTime FactorsOxygen ConsumptionFetal HeartAction PotentialsHeart VentriclesHeart AtriaHeart ValvesHeart BlockAlgorithmsHemodynamicsHeart Function TestsPregnancyHeart Arrest, InducedMyocardial IschemiaDogsCardiac Pacing, ArtificialVentricular Function, LeftMyocytes, CardiacCoronary DiseaseVentricular Premature ComplexesStroke VolumeCiliaCardiac Output, LowPerfusionAdrenergic beta-AntagonistsHeart Rate, FetalCardiotonic AgentsCardiomyopathy, DilatedTachycardiaElectrocardiography, AmbulatoryAutonomic Nervous SystemEchocardiographyMyocardial InfarctionExercise TestCardiomegalyHeart SeptumVentricular Dysfunction, LeftCardiomyopathiesHeart, ArtificialHeart Failure, SystolicBaroreflexRisk FactorsMyocardial Reperfusion InjuryAtrial Premature ComplexesVentricular PressureAnti-Arrhythmia AgentsHeart ArrestHeart InjuriesProspective StudiesRheumatic Heart DiseaseHeart Valve ProsthesisIsoproterenolSystoleFollow-Up StudiesVentricular RemodelingHeart Failure, DiastolicPropanolaminesAtrioventricular NodeDiastoleAmerican Heart AssociationVagus NervePacemaker, ArtificialDisease Models, AnimalArrhythmias, CardiacRats, Sprague-DawleyRats, WistarTreatment OutcomeChronic DiseaseAtrial Fibrillation