Heart BlockArrhythmias, CardiacHeartAdams-Stokes SyndromeHeart RateElectrocardiographyArrhythmia, SinusPacemaker, ArtificialAtrioventricular NodeHeart Conduction SystemBradycardiaAtrioventricular BlockCardiac Pacing, ArtificialHeart Defects, CongenitalRNA, Small CytoplasmicFetal HeartFetal DiseasesAntibodies, AntinuclearHeart FailureBundle of HisHeart DiseasesHeart Rate, FetalTachycardia, VentricularBundle-Branch BlockElectrocardiography, AmbulatoryAnti-Arrhythmia AgentsMyocardiumHeart AtriaVentricular FibrillationSyncopeSinoatrial NodeMaternal-Fetal ExchangeEchocardiographyRibonucleoproteinsCardiomyopathiesNerve BlockSteroids, FluorinatedCatheter AblationHeart TransplantationHeart SeptumVentricular Premature ComplexesMyocytes, CardiacKearns-Sayre SyndromeElectrophysiologic Techniques, CardiacTime FactorsEndocardial FibroelastosisMyocardial InfarctionTachycardiaDogsHeart Septal Defects, VentricularMagnetocardiographyFollow-Up StudiesPregnancyDeath, Sudden, CardiacInfant, NewbornCardiomyopathy, DilatedHeart VentriclesCardiac Complexes, PrematureLupus Erythematosus, CutaneousAtrial FibrillationAutoantigensAutoantibodiesLong QT SyndromeMyocardial IschemiaHemodynamicsTreatment OutcomeCardiac CatheterizationHydrops FetalisSick Sinus SyndromeLupus Erythematosus, SystemicHeart ValvesTachycardia, SupraventricularDefibrillators, ImplantableRisk FactorsPregnancy ComplicationsCardiomyopathy, HypertrophicMyocardial ContractionProspective StudiesAtrial FlutterMyocarditisUltrasonography, PrenatalTransposition of Great VesselsAutoimmune DiseasesRetrospective StudiesVentricular DysfunctionAction PotentialsMyocardial Reperfusion InjuryCardiac Surgical ProceduresImmunity, Maternally-AcquiredMetoprololCollagen DiseasesExercise TestPrenatal DiagnosisDisease Models, AnimalPrognosisModels, CardiovascularBetamethasoneHeart Valve ProsthesisHeart AuscultationFlecainide