The effect of chordal replacement suture length on function and stresses in repaired mitral valves: a finite element study.

BACKGROUND AND AIMS OF THE STUDY: Replacement of ruptured mitral valve chordae using expanded polytetrafluoroethylene (ePTFE) sutures is becoming an increasingly utilized repair technique. However, setting the proper length of the replacement suture is technically challenging, and the effect of a non-optimal suture length is undefined. The purpose of this study was to assess how varying the length of replacement sutures affects mitral valve function and stresses.
MATERIALS AND METHODS: We employed a finite element model of the mitral valve used extensively in our laboratory. Seven different valve conditions were simulated using this model: (i)normal valve, (ii) chordal rupture without repair, and (iii-iv) chordal replacement using ePTFE sutures that were equal in length to the replaced chordae (equal length), 10% longer (Long10), 3% longer (Long3), 3% shorter (Short3), and 10% shorter (Short10) than the replaced chordae. Each model was loaded to physiologic pressures.
RESULTS: Both the Long10 and chordal rupture models achieved complete valve closure, but chordal stresses were nearly double normal values. The Long3 model also demonstrated complete valve closure, but chordal stresses were increased to only one-third more than normal. Using sutures equal to or shorter than the length of the replaced chordae prevented complete valve closure, and produced stress concentrations at the anterior leaflet free edge. The resulting gaps and stress concentrations were most significant in the Short10 model and least significant in the equal length model.
CONCLUSIONS: These models demonstrate that replacement sutures equal to, or slightly longer than the replaced chordae optimize function and stresses in the repaired valve.