redundant normally refers to the chordae, the chords which connect to the leaflets, are stretched. This means they won't allow the leaflet to work correctly.
I see your point. However, in medical terms the word 'degenerated' often means less functional. In the case of Myxomatous degeneration the proteins making the chordae and leaflets form incorrectly, and causes thickening.
My heart scan result says that the mitral valve shows some redundant thickening. Please can you advise what does the redundant thickening mean here?