Papillary MusclesMusclesMyocardial ContractionMuscle ProteinsChordae TendineaeMuscle, SmoothMuscle, SkeletalMuscle ContractionMuscle Fibers, SkeletalMitral Valve InsufficiencyMuscle, Smooth, VascularGuinea PigsMitral ValveMuscle DevelopmentHeartFerretsHeart VentriclesAction PotentialsMyocardiumMuscle FatigueMuscle Fibers, Fast-TwitchMuscle DenervationIsometric ContractionMuscle Fibers, Slow-TwitchAequorinHeart Rupture, Post-InfarctionCalciumRabbitsMyocytes, Smooth MuscleMuscle RelaxationMitochondria, MuscleElectric StimulationCineradiographyBiomechanical PhenomenaOculomotor MusclesNeck MusclesHeart RuptureTime FactorsMuscle, StriatedCatsDepression, ChemicalMuscle SpindlesVentricular FunctionDogsPurkinje FibersRespiratory MusclesIsoproterenolMuscle WeaknessMyofibrilsMitral Valve AnnuloplastyMembrane PotentialsEndocardiumElectrophysiologyAbdominal MusclesQuadriceps MuscleRats, WistarMuscle CellsEchocardiographyCross CirculationCardiomyopathiesMasseter MuscleAnti-Arrhythmia AgentsHeart Conduction SystemStress, MechanicalFacial MusclesMasticatory MusclesEchocardiography, Three-DimensionalStimulation, ChemicalMicroelectrodesIntercostal MusclesElectromyographyOuabainMuscular AtrophyModels, AnatomicDose-Response Relationship, DrugModels, BiologicalSatellite Cells, Skeletal MuscleModels, CardiovascularRyanodineRupture, SpontaneousSarcolemmaSarcoplasmic ReticulumVentricular RemodelingCarnivoraPectoralis MusclesAdrenergic beta-AgonistsRefractory Period, ElectrophysiologicalCardiotonic AgentsMitral Valve ProlapseMyosin Heavy ChainsVentricular Function, LeftRats, Sprague-DawleyElasticityHeart Valve Prosthesis ImplantationEchocardiography, TransesophagealMuscular DiseasesDigitoxinPerfusionCells, CulturedPotassium