Abstract
Introduction
The prevalence of valvular heart disease is growing due to the improved survival of an aging population. Rheumatic heart disease remains the most common cause of heart disease, with a largely under-reported 40.5 million cases globally and 306,000 global deaths in 2019 [1]. In the UK, approximately 5000 aortic heart valve replacements are carried out annually, which is only predicted to increase [2]. The patented Wheatley Heart Valve (WHV) is a polymeric valve with a novel hemodynamic design. It’s been modelled such, that it washes out blood in the aortic root during the diastolic phase, thus clearing debris and likely irradicating the need of blood-thinners [3,4].
For the WHV to be fully realized, the leaflet material needs to have appropriate characteristics and manufacturability; polycarbonate urethane (PCU) has been investigated in this study as a promising candidate. Multiple approaches to characterization and manufacturing have been explored – transitioning to spin casting, from injection molding. Different grades and samples of PCU were subjected to tensile and hemocompatibility testing. Additionally, the mechanical data generated will be fed into a computer model to assess the hemodynamics of the proposed valve design.
Methods
Polycarbonate urethane (PCU) (grades: AC-4095A and PC355D) were dissolved using Dimethylacetamide (DMAc) solution and cast to form films, 50-200 µm thick. Test samples were laser cut. Samples underwent uniaxial tensile testing to determine the Young’s modulus. In a separate test, samples were exposed to bovine blood under agitation for 90 minutes at room temperature. The blood samples were centrifuged and spectrophotometric analysis of the plasma, in combination with the Harboe method, assessed the amount of free hemoglobin present and indicated hemolysis occurrence.
Results & Discussion
The Young’s modulus for the materials at thicknesses were found to be between 24.37 MPa and 35.46 MPa. It found that a thinner AC-4095A had a higher Young’s Modulus than its thicker counterpart. The hemolysis testing showed no significant amount of hemolysis which is more promising than previous studies, which have been done on different PCU grades [5].
Conclusion
By investigating the mechanical properties of this material at different thicknesses, we aim to contribute valuable insights towards the development of safer and more durable mechanical heart valve replacements. Future work will focus on refining manufacturing techniques, identifying the spin speed curve for spin casting, and the influence of material thickness and the application of diamond-like carbon coatings (DLCs) on mechanical properties will be compared.
Acknowledgments
There are no conflicts of interest.
References
1. S. Coffey. et al. Nature Reviews Cardiology 2021
2. M. Baghai et al. J. f Cardio-Thoracic Surgery 60 (2021) 1353–1357, 2021
3. S. McKee, et al. J Biomech Eng, 143(8), 2021
4. H. Oliveira, et al. Int J Numer Method Biomed Eng, 2024
5. S. F. Melo, et al. Biomater. Sci., 12, 2149-2164, 2024
The prevalence of valvular heart disease is growing due to the improved survival of an aging population. Rheumatic heart disease remains the most common cause of heart disease, with a largely under-reported 40.5 million cases globally and 306,000 global deaths in 2019 [1]. In the UK, approximately 5000 aortic heart valve replacements are carried out annually, which is only predicted to increase [2]. The patented Wheatley Heart Valve (WHV) is a polymeric valve with a novel hemodynamic design. It’s been modelled such, that it washes out blood in the aortic root during the diastolic phase, thus clearing debris and likely irradicating the need of blood-thinners [3,4].
For the WHV to be fully realized, the leaflet material needs to have appropriate characteristics and manufacturability; polycarbonate urethane (PCU) has been investigated in this study as a promising candidate. Multiple approaches to characterization and manufacturing have been explored – transitioning to spin casting, from injection molding. Different grades and samples of PCU were subjected to tensile and hemocompatibility testing. Additionally, the mechanical data generated will be fed into a computer model to assess the hemodynamics of the proposed valve design.
Methods
Polycarbonate urethane (PCU) (grades: AC-4095A and PC355D) were dissolved using Dimethylacetamide (DMAc) solution and cast to form films, 50-200 µm thick. Test samples were laser cut. Samples underwent uniaxial tensile testing to determine the Young’s modulus. In a separate test, samples were exposed to bovine blood under agitation for 90 minutes at room temperature. The blood samples were centrifuged and spectrophotometric analysis of the plasma, in combination with the Harboe method, assessed the amount of free hemoglobin present and indicated hemolysis occurrence.
Results & Discussion
The Young’s modulus for the materials at thicknesses were found to be between 24.37 MPa and 35.46 MPa. It found that a thinner AC-4095A had a higher Young’s Modulus than its thicker counterpart. The hemolysis testing showed no significant amount of hemolysis which is more promising than previous studies, which have been done on different PCU grades [5].
Conclusion
By investigating the mechanical properties of this material at different thicknesses, we aim to contribute valuable insights towards the development of safer and more durable mechanical heart valve replacements. Future work will focus on refining manufacturing techniques, identifying the spin speed curve for spin casting, and the influence of material thickness and the application of diamond-like carbon coatings (DLCs) on mechanical properties will be compared.
Acknowledgments
There are no conflicts of interest.
References
1. S. Coffey. et al. Nature Reviews Cardiology 2021
2. M. Baghai et al. J. f Cardio-Thoracic Surgery 60 (2021) 1353–1357, 2021
3. S. McKee, et al. J Biomech Eng, 143(8), 2021
4. H. Oliveira, et al. Int J Numer Method Biomed Eng, 2024
5. S. F. Melo, et al. Biomater. Sci., 12, 2149-2164, 2024
| Original language | English |
|---|---|
| Publication status | Published - 7 Sept 2024 |
| Event | BioMedEng24 - Queen Mary University of London, London, United Kingdom Duration: 5 Sept 2024 → 6 Sept 2024 https://biomedeng.org/biomedeng24/ |
Conference
| Conference | BioMedEng24 |
|---|---|
| Country/Territory | United Kingdom |
| City | London |
| Period | 5/09/24 → 6/09/24 |
| Internet address |
Keywords
- Wheatley heart valve
- hemolytic assessments