The effect of anterior chordal replacement on mitral valve function and stresses. A finite element study.

During the past 10 years chordal replacement with expanded polytetrafluoroethylene (ePTFE) suture has become an acceptable mitral valve repair technique. Unfortunately, its effect on the mechanical function of the valve is unclear. The purpose of this study was to test whether replacement of ruptured anterior leaflet chordae with ePTFE suture restores mitral valve function and stresses to normal ranges. To answer this question, the authors' existing finite element model of the mitral valve was modified to simulate six different valve conditions: 1) normal, 2) rupture of anterior chordae, 3) replacement using two 4-0 ePTFE sutures, 4) replacement using four 4-0 ePTFE sutures, 5) replacement using two 5-0 ePTFE sutures, and 6) replacement using four 5-0 ePTFE sutures. Physiologic pressures representing ventricular systole from the onset of isovolumic contraction to peak left ventricular pressure were applied to each model. It was found that after rupture, coaptation was impaired and stresses increased dramatically in chordae adjacent to the rupture site. Replacement with two ePTFE sutures restored proper coaptation and lowered stresses to near normal. Using four sutures also restored coaptation and lowered stresses even further. There was minimal difference between 4-0 and 5-0 suture. In conclusion, the replacement of ruptured anterior leaflet chordae with ePTFE suture restores both mitral valve function and stresses to normal ranges.