Effect of Right Ventricular Outflow Tract Material Properties on Simulated Transcatheter Pulmonary Placement

TL;DR

This study tackles how uncertainties in right ventricular outflow tract (RVOT) tissue properties and transannular patch characteristics affect finite element (FE) simulations of self-expanding transcatheter pulmonary valve (TPV) deployment. It employs an uncoupled Holzapfel-Gasser-Ogden (HGO) material model within FEBioUncertainSCI to perform a polynomial chaos expansion (PCE)–based uncertainty analysis on a patient-specific RVOT geometry, while also evaluating two patch locations and four patch stiffness levels. Key findings show that the ground matrix shear modulus $c$, fiber modulus $k_1$, and fiber orientation $\gamma$ predominantly influence 95th percentile stresses, with $c$ also driving Lagrangian strain; patch stiffness and location shift peak stresses to patch interfaces and alter local strains, though the total stent-enclosed volume remains stable. Overall, FE simulations prove a robust framework for assessing TPVR outcomes and guiding device selection, even in the face of tissue-property uncertainties and patch heterogeneity, though further validation and incorporation of hemodynamics are warranted.

Abstract

Finite element (FE) simulations emulating transcatheter pulmonary valve (TPV) system deployment in patient-specific right ventricular outflow tracts (RVOT) assume material properties for the RVOT and adjacent tissues. Sensitivity of the deployment to variation in RVOT material properties is unknown. Moreover, the effect of a transannular patch stiffness and location on simulated TPV deployment has not been explored. A sensitivity analysis on the material properties of a patient-specific RVOT during TPV deployment, modeled as an uncoupled HGO material, was conducted using FEBioUncertainSCI. Further, the effects of a transannular patch during TPV deployment were analyzed by considering two patch locations and four patch stiffnesses. Visualization of results and quantification were performed using custom metrics implemented in SlicerHeart and FEBio. Sensitivity analysis revealed that the shear modulus of the ground matrix (c), fiber modulus (k1), and fiber mean orientation angle (gamma) had the greatest effect on 95th %ile stress, whereas only c had the greatest effect on 95th %ile Lagrangian strain. First-order sensitivity indices contributed the greatest to the total-order sensitivity indices. Simulations using a transannular patch revealed that peak stress and strain were dependent on patch location. As stiffness of the patch increased, greater stress was observed at the interface connecting the patch to the RVOT, and stress in the patch itself increased while strain decreased. The total enclosed volume by the TPV device remained unchanged across all simulated patch cases. This study highlights that while uncertainties in tissue material properties and patch locations may influence functional outcomes, FE simulations provide a reliable framework for evaluating these outcomes in TPVR.

Figures (5)

• Figure 1: Transannular patch embedded in the RVOT vessel wall at two locations, a distal (position 1) and proximal (position 2) location with respect to the undeformed TPV device.
• Figure 2: Mesh convergence analysis. (A) intramural strain vs. distance ratio at a distal location and (B) at a proximal location where the TPV device impinges the RVOT wall. (C) 95th%ile and 99th%ile strains in the entire RVOT at complete TPV device expansion. Based on the mesh convergence plots, the model containing 4 mesh layers in the RVOT wall was chosen for the subsequent simulations.
• Figure 3: (A) Total and first-order sensitivity indices for the HGO material parameters for 95%ile and mean 1st principal stress and Lagrangian strain in the RVOT. (B) Raincloud plot showing the distribution of 1000 sampling combinations of HGO material parameters for 95th%ile and mean stress and strain in the RVOT vessel wall at maximum TPV device expansion. (C) Mean 1st principal stress and Lagrangian strain distribution across all simulations conducted for sensitivity analysis. (D) Geometric comparison metrics calculated across the 133 completed sensitivity simulations using a baseline simulation with vessel material parameters defined as per donahue_finite_2022donahue_finite_2024. Plot depicts the maximum and minimum values across all samples.
• Figure 4: (A) 1st principal stress and (B) 1st principal Lagrangian strain distribution across baseline, patch position 1, and patch position 2 simulations for stiffness 1 and stiffness 4 conditions.
• Figure 5: (A) 1st principal stress and 1st principal Lagrangian strain distribution across baseline, patch position 1, and patch position 2 simulations in the entire RVOT and only the transannular patch. (B) Enclosed volume by the stent across simulated conditions, separated by the distal region of the stent, the middle region of the stent, and the proximal region of the stent.