Cardiac Resynchronization TherapyHeart FailureCardiac Resynchronization Therapy DevicesCardiac Pacing, ArtificialPacemaker, ArtificialDefibrillators, ImplantableVentricular Dysfunction, LeftBundle-Branch BlockCoronary SinusStroke VolumeVentricular RemodelingTreatment OutcomeHeart VentriclesEchocardiographyVentricular Function, LeftCardiac Output, LowElectrocardiographyCardiomyopathy, DilatedProsthesis ImplantationEchocardiography, DopplerElectrodes, ImplantedArrhythmias, CardiacHeart Conduction SystemVentricular DysfunctionCicatrixElectric CountershockHeartCardiomyopathiesFollow-Up StudiesCardiography, ImpedancePredictive Value of TestsMitral Valve InsufficiencyProspective StudiesAtrioventricular NodeHeart Failure, SystolicMyocardial ContractionHeart RateTime FactorsEchocardiography, Doppler, ColorPatient SelectionSystoleHemodynamicsVentricular Function, RightNatriuretic Peptide, BrainSeverity of Illness IndexEchocardiography, Three-DimensionalElectrophysiologic Techniques, CardiacHeart-Assist DevicesExercise TestMyocardial IschemiaPrognosisExercise ToleranceElectric InjuriesRetrospective StudiesVentricular Dysfunction, RightDeath, Sudden, CardiacKaplan-Meier EstimateDextrocardiaAtrial FibrillationCardiac OutputTachycardia, VentricularHeart AtriaAdrenergic beta-AntagonistsEquipment FailureRecovery of FunctionCardiac Imaging TechniquesPhlebographyTherapy, Computer-AssistedChronic DiseaseTreatment FailureHospitalizationBody Surface Potential MappingRisk AssessmentEchocardiography, Doppler, PulsedMyocardiumReproducibility of ResultsHeart Function TestsSensitivity and SpecificitySleep Apnea, CentralEndocardiumGated Blood-Pool ImagingEquipment DesignFluoroscopyAtrioventricular BlockRandomized Controlled Trials as TopicOxygen ConsumptionRisk FactorsHeart DiseasesSurvival AnalysisFeasibility StudiesPhrenic NerveSurvival RateSingle-Blind MethodDogsCheyne-Stokes RespirationObserver VariationMyocytes, CardiacProportional Hazards ModelsVena Cava, SuperiorCardiac Volume