Effect of strut chordae transection on mitral valve leaflet biomechanics

Strut chordae transection (SCT) has been recommended as a surgical treatment for mitral regurgitation (MR) arising from ischemic heart disease. However, little is known about the contribution of anterior strut chordae to leaflet tissue mechanics. In this study, experimental measurements of mitral valve deformation under quasi-static pressure loading were performed on isolated pig hearts before and after transecting both strut chordae. Biplane video images of markers placed on the anterior leaflet surface were used to reconstruct the 3D position of the markers. The 2D nonhomogeneous deformations in the anterior leaflet were calculated by least squares fit to the 3D marker coordinates in successive pressure loading states. Results show that the anterior leaflet undergoes large, anisotropic and nonhomogeneous deformation, with a significant radial stretch gradient and smaller, uniform circumferential stretch. Following chordal transection, the radial deformation decreases. A gradient in the circumferential stretch is observed as an increase from the annulus toward the coaptation line. Without the support provided by the strut chordae, the center portion of the anterior leaflet experienced a substantial change in shape in response to the systolic pressure, altering the load-bearing mechanism in the valvular structure. The shift of the deformation distribution suggests that additional strain energy is absorbed by the circumferentially oriented collagen fibers following SCT and may result in long-term tissue remodeling. This study provides detailed biomechanical data for interpreting the results of previous investigations of SCT, as well as for exploring a greater understanding of how SCT affects MR through computational modeling.