Asymmetric mechanical properties of porcine aortic sinuses

Background. Aortic sinuses are crucial components of the aortic root and important for aortic valve function. Mathematical modeling of various aortic valve or root replacements requires tissue material properties, and those of the aortic sinuses are unknown. The aim of this study is to compare the biaxial mechanical properties of the individual porcine aortic sinuses. Methods. Square specimens, oriented in the longitudinal and circumferential directions, were excised from the left coronary, right coronary, and noncoronary porcine sinuses. Tissue thickness was measured, and specimens were subjected to equibiaxial mechanical testing. Stressstrain data corresponding to a 35% stretch were fitted to a Fung strain energy function. Tissue stiffness and anisotropy were compared at 0.3 strain. Results. The circumferential direction was more compliant than the longitudinal one for left coronary (183.03 +/- 40.78 kPa versus 231.17 +/- 45.38 kPa, respectively; p=0.04) and right coronary sinuses (321.74 +/- 129.68 kPa versus 443.49 +/- 143.59 kPa, respectively; p=0.02) at 30% strain. No such differences were noted for noncoronary sinuses (331.74 +/- 129.68 kPa versus 415.98 +/- 191.38 kPa; p=0.19). Left coronary sinus was also significantly more compliant than right and noncoronary sinuses. There were no differences between right coronary and noncoronary sinus tissues. Conclusions. We demonstrate that the material properties of the porcine aortic sinuses are not symmetric. The left coronary sinus is significantly more compliant than the remaining sinuses. Realistic modeling of the aortic root must take into account the asymmetric differences in tissue material properties of the aortic sinuses.