Complex sentence: Myxomatous degeneration of the mitral valve is more common in women as well as with advancing age which causes a stretching of the leaflets of the valve and the chordae tendineae.
Split into simpler sentences: Myxomatous degeneration of the mitral valve is more common in females, and is more common in advancing age. This causes a stretching out of the leaflets of the valve and the chordae tendineae.