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. 2017 Nov:75:486-494.
doi: 10.1016/j.jmbbm.2017.08.013. Epub 2017 Aug 9.

Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

Andrés Caballero  1 , Fatiesa Sulejmani  1 , Caitlin Martin  1 , Thuy Pham  1 , Wei Sun  2
Affiliations

Evaluation of transcatheter heart valve biomaterials: Biomechanical characterization of bovine and porcine pericardium

Andrés Caballero et al. J Mech Behav Biomed Mater. 2017 Nov.

Abstract

Objective: Bovine pericardium (BP) has been identified as a choice biomaterial for the development of surgical bioprosthetic heart valves (BHV) and transcatheter aortic valves (TAV). Porcine pericardium (PP) and younger BP have been suggested as candidates TAV leaflet biomaterials for smaller-profile devices due to their reduced thickness; however, their mechanical and structural properties remain to be fully characterized. This study characterized the material properties of chemically treated thick (PPK) and thin (PPN) PP, as well as fetal (FBP), calf (CBP) and adult (ABP) BP tissues in order to better understand their mechanical behavior.

Methods: Planar biaxial testing and uniaxial failure testing methods were employed to quantify tissue mechanical responses and failure properties. Fiber characteristics were examined using histological analysis.

Results: ABP and CBP tissues were significantly stiffer and stronger than the younger FBP tissues. Histological analysis revealed a significantly larger concentration of thin immature collagen fibers in the FBP tissues than in the ABP and CBP tissues. While PP tissues were thinnest, they were stiffer and less extensible than the BP tissues.

Conclusions: Due to comparable mechanical properties but significantly reduced thickness, CBP tissue may be a more suitable material for TAV manufacturing than ABP tissue. FBP tissue, despite its reduced thickness and higher flexibility, was weaker and should be studied in more detail. Although PP tissues are the thinnest, they were least extensible and failed at earlier strain than BP tissues. The differences between PP and BP tissues should be further investigated and suggest that they should not be used interchangeably in the manufacturing of TAV.

Keywords: Aging; Biaxial testing; Bovine pericardium; Collagen; Porcine pericardium; Transcatheter aortic valve; Uniaxial testing.

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Figures

Fig. 1
Fig. 1
a) Orientation of biaxial samples, b) Representative equibiaxial stress-strain curve and calculated parameters, c) Dimensions of dog-bone uniaxial sample. SM60: Secant modulus at 60 kPa, SM250: Secant modulus at 250 kPa, SM500: Secant modulus at 500 kPa. Extensibility for both X1 and X2 directions.
Fig. 2
Fig. 2
Equibiaxial response data for BP and PP testing groups, presented as mean ± standard error bars.
Fig. 3
Fig. 3
Mean and SD of stiffness measurements calculated as secant modulus at three stress levels for all testing groups. (*) indicates a statistically significant difference, (**) indicates a high statistically significant difference.
Fig. 4
Fig. 4
Mean and SD of extensibility measurements for all testing groups. (*) indicates a statistically significant difference, (**) indicates a high statistically significant difference.
Fig. 5
Fig. 5
Mean and standard deviation of a) UTS measurements and b) UTE measurements for all testing groups. (*) indicates a statistically significant difference, while (**) indicates a high statistically significant difference.
Fig. 6
Fig. 6
Representative picrosirius red-stained cross-sections for a) ABP, b) CBP and c) FBP.
See this image and copyright information in PMC

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