BradycardiaMyocytes, CardiacHeart RateCardiac OutputHeartArrhythmias, CardiacVagus NerveApneaCardiac Surgical ProceduresDeath, Sudden, CardiacCardiac Pacing, ArtificialElectrocardiographyBlood PressureHypotensionHeart ArrestReflexSinoatrial NodeMyocardiumMyocardial ContractionCardiomegalyHeart DiseasesArrhythmia, SinusHeart BlockPacemaker, ArtificialCardiac TamponadeHemodynamicsCardiac CatheterizationHeart VentriclesAtropineReflex, OculocardiacBaroreflexSyncopeTime FactorsDivingBiguanidesSick Sinus SyndromeCardiovascular SystemDogsTachycardiaCardiomyopathiesHeart FailureAnesthesiaHeart Conduction SystemRespirationEchocardiographyAutonomic Nervous SystemMyoblasts, CardiacAtrioventricular BlockCardiac Output, LowCardiac MyosinsVagotomyHeart AtriaCardiac Imaging TechniquesAnti-Arrhythmia AgentsRats, Sprague-DawleyMyocardial InfarctionPressoreceptorsAtropine DerivativesCardiac GlycosidesFetal HeartParasympathetic Nervous SystemVentricular Function, LeftRats, WistarCardiotonic AgentsOut-of-Hospital Cardiac ArrestTreatment OutcomeHeart Defects, CongenitalAdrenergic beta-AntagonistsSyncope, VasovagalStroke VolumeCardiac VolumeMedulla OblongataVentricular RemodelingHeart TransplantationChemoreceptor CellsLong QT SyndromeTroponin IParasympatholyticsCardiopulmonary ResuscitationCarotid SinusProspective StudiesClonidineDecerebrate StateImmersionIntraoperative ComplicationsCardiovascular Physiological PhenomenaDisease Models, AnimalModels, CardiovascularIsoproterenolTorsades de PointesMyocardial IschemiaSympatholyticsHeart Rate, FetalPropranololDose-Response Relationship, DrugCardiac Resynchronization TherapyElectrocardiography, AmbulatoryHeart Function TestsRetrospective StudiesTroponin T