Biaxial Strain Analysis of Various Fixation Models in Porcine Aortic and Pulmonary Valves

Cho, Sungkyu; Kim, Yong Jin; Kim, Soo Hwan; Choi, Seung Hwa

Abstract

BACKGROUND: The function of a bioprosthetic heart valve is determined largely by the material properties of the valve cusps. The uniaxial tensile test has been studied extensively. This type of testing, however, does not replicate the natural biaxial loading condition. The objective of the present study was to investigate the regional variability of the biaxial strain versus pressure relationship based on the types of fixation liquid models. MATERIAL AND METHOD: Porcine aortic valves and pulmonary valves were assigned to three groups: the untreated fresh group, the fixed with glutaraldehyde (GA) group, and the glutaraldehyde with solvent (e.g., ethanol) group. For each group we measured the radial and circumferential stretch characteristics of the valve as a function of pressure change. RESULT: Radial direction elasticity of porcine aortic and pulmonary valves were better than circumferential direction elasticity in fresh, GA fixed, and GA+solvent fixed groups (p=0.00). Radial and circumferential direction elasticity of pulmonary valves were better than aortic valves in GA fixed and GA+solvent fixed groups (p=0.00). Radial and circumferential direction elasticity of aortic valves were decreased after GA and GA+solvent fixation (p=0.00), except for circumferential elasticity of GA+solvent fixed valves (p=0.785). The radial (p=0.137) and circumferential (p=0.785) direction of elasticity of aortic valves were not significantly different between GA fixed and GA+solvent fixed groups. Radial (p=0.910) and circumferential (p=0.718) direction of elasticity of pulmonary valve also showed no significant difference between GA fixed and GA+solvent fixed groups.
CONCLUSION
When fixing porcine valves with GA, adding a solvent does not cause a loss of mechanical properties, but, does not improve elasticity either. Radial direction elasticity of porcine aortic and pulmonary valves was better than circumferential direction elasticity.