On the effects of leaflet microstructure and constitutive model on the closing behavior of the mitral valve

Abstract

Recent long-term studies showed an unsatisfactory recurrence rate of severe mitral regurgitation 3–5 years after surgical repair, suggesting that excessive tissue stresses and the resulting strain-induced tissue failure are potential etiological factors controlling the success of surgical repair for treating mitral valve (MV) diseases. We hypothesized that restoring normal MV tissue stresses in MV repair techniques would ultimately lead to improved repair durability through the restoration of MV normal homeostatic state. Therefore, we developed a micro- and macro- anatomically accurate MV finite element model by incorporating actual fiber microstructural architecture and a realistic structure-based constitutive model. We investigated MV closing behaviors, with extensive in vitro data used for validating the proposed model. Comparative and parametric studies were conducted to identify essential model fidelity and information for achieving desirable accuracy. More importantly, for the first time, the interrelationship between the local fiber ensemble behavior and the organ-level MV closing behavior was investigated using a computational simulation. These novel results indicated not only the appropriate parameter ranges, but also the importance of the microstructural tuning (i.e., straightening and re-orientation) of the collagen/elastin fiber networks at the macroscopic tissue level for facilitating the proper coaptation and natural functioning of the MV apparatus under physiological loading at the organ level. The proposed computational model would serve as a logical first step toward our long-term modeling goal—facilitating simulation-guided design of optimal surgical repair strategies for treating diseased MVs with significantly enhanced durability.

A meso-scale layer-specific structural constitutive model of the mitral heart valve leaflets

“…This is not only important to ECM mechanics but also coupling to the interstitial cell (MVIC) population. We have recently shown that simulated MVIC moduli for the four layers were found to be all within a narrow range of 4.71–5.35 kPa, suggesting that MVIC deformation is primarily controlled by each tissue layer’s respective structure and mechanical behavior rather than the intrinsic MVIC stiffness [67]. This novel result further suggests that while the MVICs may be phenotypically similar throughout the leaflet, they experience layer-specific mechanical stimulatory inputs due to distinct extracellular matrix architecture and mechanical behaviors of the four MV leaflet tissue layers.…”

Fluid–Structure Interaction Analysis of Papillary Muscle Forces Using a Comprehensive Mitral Valve Model with 3D Chordal Structure

“…Two dimensional characterization that focuses on the leaflets unfolded into a plane has been carried out with small angle light scattering (SALS). [34,35] Recent efforts have been made to map 2D SALS data to 3D image-derived models, [36] using control points and interpolation. However, these mappings exclude the mitral valve chordae and artefacts from excision such as the relaxation of collagen fibers and subsequent re-orientation remain.…”

Modelling mitral valvular dynamics–current trend and future directions

“…Wang et al reported a patient‐specific FE model of a healthy human MV reconstructed from multi‐slice CT scans with detailed leaflet thickness, chordal information, and mitral annulus dynamic motion. Micro‐CT is another widely used modality that can provide detailed MV leaflets and chordal structure for in vitro/ex vivo MV imaging but is usually unavailable with in vivo imaging when using ECHO and MRI . Manually constructing MV geometry from limited imaging data is not an optimal way, because it is highly dependent on the operators' experience, and usually associated with low reproducibility and reliability.…”