Time-resolved studies of the dynamic behavior of the tendon fibers (chordae tendineae) of the human mitral valve.

Abstract

The dynamic behavior of the tendinous chords of the mitral valve of the heart was analyzed using fast x-ray diffraction combined with mechanical measurements. The tendinous chords, which have a very fine crimp, are built up of "pseudo-interwoven" fibrils [1] consisting of 80 07o type I and 20 % type III collagen. These fibrils differ f rom tendon fibrils by their twisted molecular structure [2], which is the reason for their relatively small diameter of about 45 nm. When a tendinous chord is loaded beyond the toe region of the stress/ strain curve, then the collagen fibrils also are stretched, as it is the case in tendons [3]. The stretching of the fibrils is registered via small-angle meridional x-ray diffraction spectra, whose peak intervals change with the increasing axial periodicity (D period) of the collagen fibrils (Fig. la). The tendinous chord was loaded from curves 1 to 20 and unloaded from curves 21 to 32 (Fig. 1 b). The D period increases f rom