Comparative Fluid–Structure Interaction Analysis of Polymeric Transcatheter and Surgical Aortic Valves' Hemodynamics and Structural Mechanics

Abstract

Transcatheter aortic valve replacement (TAVR) has emerged as an effective alternative to conventional surgical aortic valve replacement (SAVR) in high-risk elderly patients with calcified aortic valve disease. All currently FDA-approved TAVR devices use tissue valves that were adapted to but not specifically designed for TAVR use. Emerging clinical evidence indicates that these valves may get damaged during crimping and deployment- leading to valvular calcification, thrombotic complications, and limited durability. This impedes the expected expansion of TAVR to lower-risk and younger patients. Viable polymeric valves have the potential to overcome such limitations. We have developed a polymeric SAVR valve, which was optimized to reduce leaflet stresses and offer a thromboresistance profile similar to that of a tissue valve. This study compares the polymeric SAVR valve's hemodynamic performance and mechanical stresses to a new version of the valve- specifically designed for TAVR. Fluid-structure interaction (FSI) models were utilized and the valves' hemodynamics, flexural stresses, strains, orifice area, and wall shear stresses were compared. The TAVR valve had 42% larger opening area and 27% higher flow rate versus the SAVR valve, while wall shear stress distribution and mechanical stress magnitudes were of the same order, demonstrating the enhanced performance of the TAVR valve prototype. The TAVR valve FSI simulation and Vivitro pulse duplicator experiments were compared in terms of the leaflets' kinematics and the effective orifice area. The numerical methodology presented can be further used as a predictive tool for valve design optimization for enhanced hemodynamics and durability.

On the Modeling of Patient-Specific Transcatheter Aortic Valve Replacement: A Fluid–Structure Interaction Approach

“…On the other one, a comparison between structural FE and FSI approach on a generic tri-leaflets transcatheter aortic valves was performed, confirming the more realistic representations of the valve behavior when applying the FSI method [28]. TAVR was also compared to the conventional surgical valve replacement with FSI simulations in terms of leaflet stresses and thromboresistance profile [59]. To the best of our knowledge, there are only two FSI works on the complete TAVR procedure [48,54].…”

Principles of TAVR valve design, modelling, and testing

“…Fluid-structure Interaction (FSI) analysis is capable of simulating leaflets mechanical response to blood flow and vice versa by solving the fluid and structural mechanics governing equations simultaneously [91]. It is commonly employed to study the prosthetic valves hemodynamics, and examine leaflets kinematics and maximum stress magnitudes [44, 92, 93, 94, 95, 96]. Wu et al (2015) were the first to develop an FSI model to study a self-expandable TAVR valve deployed in a patient-specific aortic root geometry [94].…”

“…This model, however, did not include the calcified native leaflets, which could affect the flow analysis. Ghosh et al (2017) implemented an ALE-FSI model to compare the PolyNova TAVR and SAVR valve’s hydrodynamics together with leaflets mechanical stresses during the cardiac cycle [96]. This SAVR valve was also studied using an “operator-split” FSI approach, which was used to evaluate the valve thrombogenicity [44].…”

New Insights into Valve Hemodynamics

“…18 Nevertheless, several such devices are currently being developed and have demonstrated promising experimental results. 16,[19][20][21][22] However, even if polymeric valves do achieve the hemodynamic capabilities of current bioprosthetic valves-with the durability of mechanical valvestheir inability to grow makes them problematic for pediatric use. Tissue-engineered heart valves may, potentially, be able to adjust to both tissue growth and remodeling, therefore ensuring prolonged durability.…”