Cardiac Resynchronization Therapy DevicesCoronary SinusElectrodes, ImplantedCardiac Resynchronization TherapyProsthesis ImplantationPacemaker, ArtificialCardiac Pacing, ArtificialHeart VentriclesHeart FailureEquipment FailureBundle-Branch BlockFluoroscopyDefibrillators, ImplantablePhlebographyVentricular Dysfunction, LeftPhrenic NerveTreatment OutcomeVentricular Function, LeftEquipment DesignVentricular SeptumElectrocardiographyEchocardiographyElectric InjuriesStroke VolumeHeart BlockSick Sinus SyndromeForeign-Body MigrationFollow-Up StudiesDevice RemovalAtrioventricular BlockVena Cava, SuperiorElectrophysiologic Techniques, CardiacElectric CountershockElectrodesFeasibility StudiesHypertrophy, Left VentricularTime FactorsProspective StudiesAtrial Function, Left