Characterization of Biomechanical Properties of Mitral Valve Chordae Tendineae

Objective: Mitral regurgitation and prolapse are the two most common diseases of the mitral valve and result in the leakage of blood back into the left atrium during systole. Rupture of the chordae tendinae is the most common cause of mitral insufficiency. The goal of this study was to characterize the biomechanical properties of the mitral valve chordae tendineae of aged human and ovine hearts. Materials and Methods: A total of 115 chordae specimens from fresh ovine hearts (n=18, weight = 374.833 47.947g, age of 1-2 year old), and 152 from human hearts (n=14, weight = 516.538 125.718g, mean age of 76.29 10.35 years old) were subjected to uniaxial tensile tests using marker tracking technology. The elastic and failure properties of five types of chordae tendineae were characterized, namely the anterior strut, anterior marginal, anterior basal, posterior marginal, and posterior basal chordae. The elastic properties were fitted with the nonlinear hyperelastic Ogden material model. The microstructure of the chordae samples was assessed through histology. Results: Human anterior basal and strut chords were significantly larger than the corresponding ovine chords. The mechanical properties of human chords were all similar while there were variations in the mechanical properties among ovine chords of differing type. The human chords were significantly stiffer and less extensible, yet stronger, than the corresponding ovine chords. These findings can be explained by histology results: collagen fibers in the human chords were nearly straight which resulted in reduced extensibility, while the collagen fibers in the ovine chords were highly crimped which resulted in high extensibility. Conclusions: Aged human and ovine chordae tendinae have significantly different structure and material properties