Mechanical properties and ultrastructure of normal human tricuspid valve chordae tendineae.

The mechanical properties and ultrastructure of normal human tricuspid valve chordae tendineae were examined. Mechanical studies showed that these chordae exhibited less extensibility than normal mitral valve chordae of comparable size. The non-linear stress-strain curve of the tricuspid chordae, however, can be attributed to their microstructure. Under scanning electron microscopy these chordae were found to consist of fairly straight collagen bundles that were made up of networks of collagen fibrils. Transmission electron microscopical studies showed that the distribution of collagen fibril size was bimodal with an average fibril diameter of 441 A (S.E. = 2A) while the average fibril density was 198.4 (S.E. = 8.4) per 10(-8) cm2. These data data from the transmission electron micrographs were found to be different from those already reported for the mitral valve chordae. Thus, fine structural differences exist between chordae from both the mitral and tricuspid valves. These differences in fine structure could be due to the fact that these valves are under different in vivo mechanical stresses and they may account for the less extensible nature exhibited by the tricuspid chordae tendineae.