BradycardiaTachycardiaTachycardia, VentricularTachycardia, SupraventricularTachycardia, Atrioventricular Nodal ReentryTachycardia, SinusTachycardia, ParoxysmalTachycardia, Ectopic AtrialElectrocardiographyCatheter AblationTachycardia, Ectopic JunctionalHeart RatePostural Orthostatic Tachycardia SyndromeCardiac Pacing, ArtificialHeart Conduction SystemTachycardia, ReciprocatingElectrophysiologic Techniques, CardiacTachycardia, Sinoatrial Nodal ReentryAnti-Arrhythmia AgentsAtrioventricular NodeArrhythmias, CardiacBundle of HisHeart BlockBody Surface Potential MappingVentricular FibrillationVagus NerveApneaSyncopeWolff-Parkinson-White SyndromeBlood PressureElectrocardiography, AmbulatoryHypotensionSinoatrial NodeAmiodaroneHeart AtriaDefibrillators, ImplantablePacemaker, ArtificialArrhythmia, SinusReflexFlecainideVentricular Premature ComplexesAtropineAtrioventricular BlockBundle-Branch BlockCryosurgeryAtrial FlutterHeart VentriclesProcainamideHeartEndocardiumElectrophysiologySick Sinus SyndromeDogsElectric CountershockPre-Excitation SyndromesBaroreflexTreatment OutcomeSotalolDeath, Sudden, CardiacAccessory Atrioventricular BundleCardiac Complexes, PrematureAtrial FibrillationHemodynamicsAdrenergic beta-AntagonistsFollow-Up StudiesDivingTilt-Table TestBiguanidesPropranololReflex, OculocardiacTime FactorsCardiovascular SystemEpicardial MappingHeart ArrestAnesthesiaTorsades de PointesAutonomic Nervous SystemRecurrenceSympathetic Nervous SystemAtropine DerivativesCardiomyopathiesRespirationVagotomyLong QT SyndromeFetal DiseasesPressoreceptorsHydrops FetalisSyncope, VasovagalArrhythmogenic Right Ventricular DysplasiaDecerebrate StateVerapamilAtenololHeart Rate, FetalRetrospective StudiesIsoproterenolDisopyramideClonidineParasympathetic Nervous SystemAdenosineInjections, Intravenous