Session M1.4

From Real-Time 3D Echocardiography to Mitral Valve Finite Element Analysis: A Novel Modeling Approach

E Votta*, A Arnoldi, M Stevanella, F Veronesi, G Tamborini,
F Alamanni, EG Caiani, A Redaelli

Politecnico di Milano
Milano, Italy

Finite element models (FEMs) represent an innovative approach for the biomechanical analysis of dynamic cardiac structures. It has been previously applied to mimic the behaviour of the mitral valve (MV) with great benefits compared to traditional animal studies. However, the existing FEMs, based on animal or ex-vivo measurements, include important simplifications: valve symmetry, idealization of leaflets free margin profile, annulus planarity and lack of contraction. Our aim was to use the morphologic information about MV annulus and papillary muscles obtained in humans by the analysis of real-time 3D echocardiographic (RT3DE) data to define a realistic FEM of the normal MV, and simulate its closure from end-diastole (ED) to systolic peak. Methods. RT3DE (iE33, Philips) was performed (frame rate 31 Hz) in a normal subject (male, age 40). At ED, 2 points were selected on papillary muscles tips to define their initial coordinates, from which their motion was estimated from experimental observations. Also, the ED position of the MV annulus was defined by 36 equally spaced manually selected points. These were then tracked frame-by-frame by custom software, allowing the integration of the dynamic annular profile in the FEM. The spatial orientation of MV leaflets was measured from RT3DE and included in the FEM. The FEM was completed with 39 branched chordae tendineae of three orders. Tissues mechanical response, based on the hyperelasticity theory and inclusive of non-linearity and anisotropy, was implemented. A physiological time-dependent pressure up to 120 mmHg was applied on the leaflets. Results. Valve dynamics and leaflets coaptation were consistent with in-vitro observations. As expected, at systolic peak leaflets stresses resulted higher in the anterior leaflet than in the posterior one, with max values of 550 kPa at the insertion of structural chordae. Leaflets strains reflected anisotropic response: in the anterior leaflet belly, stretch ratios parallel and perpendicular to the annulus were 1.09 and 1.46, respectively, in agreement with literature. Chordae tendineae tension (range .12-1.13 N) agreed with experimental findings. Conclusions. The use of RT3DE allowed to overcome most of the limitations of previous MV models, thus obtaining a realistic FEM. This approach represents the basis for the development of a patient-specific modeling tool.

(Abstract Control Number: 222)