Novel Heart Valve Leaflet Design: Research Based on High-Stiffness Polymeric Materials and Biomimetic Kinematics

Academic Background

Heart valve disease is a significant global health issue, with over 850,000 patients requiring heart valve replacement surgery annually. Currently, the heart valves used in clinical practice are mainly divided into two categories: mechanical valves and bioprosthetic valves. Mechanical valves, made of carbon or titanium, offer long-term durability but have poor hemodynamic performance, which can lead to flow cavitation, and patients require lifelong anticoagulation therapy. Bioprosthetic valves, made from bovine or porcine pericardial tissue, do not require long-term anticoagulation but have limited durability, often leading to valve degeneration and structural failure over time. Therefore, developing a new type of heart valve that offers both long-term durability and excellent hemodynamic performance has become a key focus of current research.

In recent years, fully polymeric heart valves (PHVs) have gained attention due to their flexible material design and simplified manufacturing processes. However, existing polymeric valves still face challenges in terms of biostability and durability. This study aims to explore a novel leaflet design using high-stiffness polymeric materials, such as polyether ether ketone (PEEK), to improve the hemodynamic performance and durability of heart valves.

Source of the Paper

This paper was co-authored by Caroline C. Smid, Georgios A. Pappas, Nikola Cesarovic, Volkmar Falk, and Paolo Ermanni, affiliated with ETH Zürich (Swiss Federal Institute of Technology Zurich) and Deutsches Herzzentrum der Charité (Charité – Universitätsmedizin Berlin, Germany). The paper was published online on November 26, 2024, in the journal Bio-design and Manufacturing, with the DOI 10.1007/s42242-024-00309-y.

Research Process and Results

1. Leaflet Design and Conceptualization

The study began with benchmarking existing single-curvature leaflet designs and proposed a new concept of double-curvature leaflet design. The double-curvature design reduces the effective flexural stiffness by increasing the radius of curvature of the leaflets, thereby improving the valve’s opening performance. The research team designed five different double-curvature leaflet variants (V1-V5) and evaluated these designs through finite element analysis (FEA) and in vitro experiments.

2. Material Selection

Two materials were selected for comparison: traditional soft polyurethane (PU) and high-stiffness PEEK. The Young’s modulus of PEEK is approximately 2400 MPa, significantly higher than that of natural leaflet tissue (4-15 MPa). The research team manufactured PEEK leaflets using vacuum forming technology and optimized their thickness.

3. Finite Element Analysis

The study used Abaqus software to conduct quasi-static implicit analysis on six valve designs. The leaflets were meshed using shell elements (S4R) to simulate the opening and closing behavior of the valves under physiological flow conditions. The study also calculated the bending and membrane strain energy ratios to assess the impact of different materials on valve performance.

4. In Vitro Experiments

The research team developed a custom-built pulse duplicator (PD) to simulate physiological flow conditions in vitro. Using high-resolution cameras and pressure sensors, the team recorded the opening pressure (OP), effective orifice area (OA), and transvalvular pressure gradient (ΔP) in real-time. The experimental results showed that the double-curvature leaflet design significantly improved the valve’s opening performance, especially for high-stiffness materials like PEEK.

5. Results and Discussion

The results demonstrated that the double-curvature leaflet design exhibited significant advantages in terms of opening pressure. The best-performing variant (V2) reduced the opening pressure by 47% (based on numerical analysis) and 44% (based on experimental data) compared to the traditional single-curvature design. Additionally, the transvalvular pressure gradient of PEEK valves was comparable to that of existing bioprosthetic valves, indicating competitive hemodynamic performance.

Conclusion and Significance

This study is the first to propose a double-curvature leaflet design based on high-stiffness polymeric materials, significantly improving the opening performance of heart valves. This design is not only suitable for high-stiffness materials like PEEK but also provides new insights for the future optimization of heart valve designs. The results show that the double-curvature design effectively reduces the opening pressure while maintaining excellent hemodynamic performance, highlighting its potential for clinical applications.

Research Highlights

1. Innovative Design: The first to propose a double-curvature leaflet design, significantly improving the opening performance of high-stiffness material valves.
2. Material Selection: The use of high-stiffness polymeric materials like PEEK, combined with biomimetic kinematics, enhances the durability and hemodynamic performance of valves.
3. Experimental Validation: The effectiveness of the design was validated through numerical simulations and in vitro experiments, providing reliable data support for future heart valve optimization.

Additional Valuable Information

The research team also developed an automated image processing tool for real-time tracking of the effective orifice area (OA) of the valves. This tool not only improves the accuracy of experimental data but also provides new technical means for future heart valve research.

This study offers new perspectives on heart valve design and material selection, with significant scientific value and clinical application potential.