Papillary MusclesMusclesMyocardial ContractionMuscle ProteinsChordae TendineaeMuscle, SmoothMuscle, SkeletalMuscle ContractionMuscle Fibers, SkeletalMuscle, Smooth, VascularMitral Valve InsufficiencyGuinea PigsMuscle DevelopmentMitral ValveHeartFerretsAction PotentialsHeart VentriclesMyocardiumMuscle FatigueMuscle Fibers, Fast-TwitchMuscle DenervationIsometric ContractionMuscle Fibers, Slow-TwitchAequorinHeart Rupture, Post-InfarctionMyocytes, Smooth MuscleCalciumMuscle RelaxationMitochondria, MuscleRabbitsElectric StimulationCineradiographyNeck MusclesHeart RuptureOculomotor MusclesMuscle, StriatedDepression, ChemicalMuscle SpindlesCatsPurkinje FibersTime FactorsRespiratory MusclesIsoproterenolMuscle WeaknessVentricular FunctionDogsMyofibrilsMitral Valve AnnuloplastyMembrane PotentialsEndocardiumAbdominal MusclesQuadriceps MuscleMuscle CellsElectrophysiologyCross CirculationBiomechanical PhenomenaRats, WistarMasseter MuscleCardiomyopathiesAnti-Arrhythmia AgentsFacial MusclesMasticatory MusclesStimulation, ChemicalIntercostal MusclesElectromyographyOuabainHeart Conduction SystemMuscular AtrophyMicroelectrodesSatellite Cells, Skeletal MuscleRyanodineEchocardiographyDose-Response Relationship, DrugSarcolemmaSarcoplasmic ReticulumRupture, SpontaneousCarnivoraPectoralis MusclesAdrenergic beta-AgonistsRefractory Period, ElectrophysiologicalCardiotonic AgentsMyosin Heavy ChainsEchocardiography, Three-DimensionalMuscular DiseasesMitral Valve ProlapseDigitoxinRats, Sprague-DawleyQuinidinePerfusionEchocardiography, TransesophagealPotassiumHeart Valve Prosthesis ImplantationPsoas MusclesSuture TechniquesCells, CulturedTretoquinolDiacetylPolyvinyl AlcoholSodium Cyanide