Comparison of Mechanical Properties of Human Ascending Aorta and Aortic Sinuses

Background Computational finite element models of the aortic root have previously used material properties of the ascending aorta to describe both aortic sinuses and ascending aorta. We have previously demonstrated significant material property differences between ascending aorta and sinuses in pigs. However, it is unknown whether these regional material property differences exist in humans. The main objective of this study was to investigate biomechanics of fresh human ascending aorta and aortic sinuses and compare nonlinear material properties of these regions. Methods Fresh human aortic root specimens obtained from the California Transplant Donor Network (Oakland, CA) were subjected to displacement-controlled equibiaxial stretch testing within 24 hours of harvest. Stress-strain data recorded were used to derive strain energy functions for each region. Tissue behavior was quantified by tissue stiffness and a direct comparison was made between different regions of aortic root at physiologic stress levels. Results All regions demonstrated a nonlinear response to strain during stretch testing in both circumferential and longitudinal directions. No significant difference in tissue stiffness was found between anterior and posterior regions of the ascending aorta or among the three sinuses in both directions. However, our results demonstrated that human ascending aorta is significantly more compliant than aortic sinuses in both circumferential and longitudinal directions within the physiologic stress range. Conclusions Significant material and structural differences were observed between human ascending aorta and aortic sinuses. Regionally specific material properties should be employed in computational models used to assess treatments of structural aortic root disease.