EFFECT OF SADDLE-SHAPED ANNULUS IN REDUCING MITRAL VALVE STRESS: A COMPUTATIONAL STUDY

Abstract

Purpose of Study: The effect of saddle-shaped annulus in mitral valve (MV) stress remains unclear. All previous studies using finite element analyses were made on MV model with flat annulus. This research aimed to study the effect of annulus shape (flat vs. saddle) in MV leaflet stress. Methods: Sonomicrometry crystals were implanted in sheep in-vivo to obtain the three-dimensional MV asymmetric model with saddle-shaped annulus (model S). Flat annulus asymmetrical model (model F) were created artificially by flattening the annulus of model S into two-dimensional plane. Both models were imported into ANSYS for simulation. A static analysis was performed at ventricular pressure of 0.01MPa. Results: Model S had two evident high stress points on the trigones of anterior annulus, and a U-shape high stress concentration pattern on the anterior leaflet. These observations are consistent with the existence of trigones in a real mitral valve. Model F, however, showed irregular stress pattern. It was found that the saddle annulus has made a reduction of 13.2% and 3.4% in the maximum and minimum leaflet stresses respectively. Conclusion: The saddle-shaped annulus shows advantage in terms of reducing the total leaflet stress, and directs the annulus stress towards the trigones; such that the remaining annulus stress would be minimized. This analysis shows significant reason of preserving the saddle-shaped during valve reconstruction, repair or designing a mitral prostheses in the future.