Arrhythmias, CardiacHeart FailureHeartHeart RateMyocytes, CardiacElectrocardiographyAnti-Arrhythmia AgentsMyocardiumArrhythmia, SinusDeath, Sudden, CardiacCardiac Output, LowHeart DiseasesLong QT SyndromeHeart Conduction SystemTachycardia, VentricularCardiac Pacing, ArtificialVentricular FibrillationHeart VentriclesHeart Failure, SystolicElectrocardiography, AmbulatoryMyocardial ContractionAtrial FibrillationTime FactorsCardiomyopathy, DilatedStroke VolumeVentricular Premature ComplexesVentricular Function, LeftHemodynamicsTachycardiaHeart AtriaCardiac OutputEchocardiographyMyocardial InfarctionHeart TransplantationHeart Failure, DiastolicCardiomyopathiesTreatment OutcomeCardiac Complexes, PrematureCardiomegalyDogsVentricular Dysfunction, LeftEncainideModels, CardiovascularAdrenergic beta-AntagonistsCardiotonic AgentsMyocardial IschemiaNAV1.5 Voltage-Gated Sodium ChannelFollow-Up StudiesCardiac Surgical ProceduresVentricular RemodelingNatriuretic Peptide, BrainRisk FactorsHeart Defects, CongenitalProspective StudiesDeath, SuddenEther-A-Go-Go Potassium ChannelsHeart BlockDisease Models, AnimalChronic DiseaseAction PotentialsTreatment FailureHeart Function TestsFetal HeartDigitalis GlycosidesHeart ArrestBradycardiaCardiac ElectrophysiologyMoricizinePotassium Channels, Voltage-GatedPrognosisDefibrillators, ImplantableCatheter AblationElectrophysiologic Techniques, CardiacVentricular DysfunctionAmiodaroneRetrospective StudiesKCNQ1 Potassium ChannelPredictive Value of TestsSodium ChannelsBlood PressureFlecainidePacemaker, ArtificialExercise TestAtrial FlutterTachycardia, SupraventricularDigoxinRisk AssessmentAtrial Premature ComplexesCardiac CatheterizationAutonomic Nervous SystemCalciumElectric CountershockHospitalizationChlorofluorocarbons, MethanePropanolaminesVentricular FunctionTorsades de PointesHeart-Assist DevicesAngiotensin-Converting Enzyme InhibitorsSeverity of Illness Index