Does myxomatous mitral valve disease selectively affect the chordae? A mechanical and biochemical analysis

It is unclear how the process of myxomatous disease leads to mitral valve regurgitation. We performed mechanical and biochemical tests to measure the differences between leaflets and chordae from myxomatous and normal human mitral valves. Uniaxial tensile tests and assays for uronic acid (glycosaminoglycans or GAGs) indicated that the myxoid tissues were more extensible, had lower stiffness and failure strength, and increased GAG concentration. Additional DNA assays suggest that the cells in myxoid valves are producing higher levels of GAGs than normal. Furthermore, all differences between the myxoid and normal tissues were far more pronounced in the chordae than in the leaflets. These findings support reported observations that myxoid-related chordal rupture is the leading cause of mitral valve regurgitation