Biaxial mechanical properties of dilated human ascending aortic tissue

Patients with a dilated ascending aorta are at risk for life-threatening aortic dissection or rupture. It is assumed that both abnormal mechanical properties and increased stresses contribute to this risk, but the relative weights of these factors are not well understood. To assess the mechanical properties of dilated ascending aorta, we obtained specimens removed during elective surgery. We used biaxial testing to characterize the elastic properties during equibiaxial stretching of up to 30%. We found the tissue to be nonlinear at equibiaxial stretches greater than 20%. Only one specimen exhibited marked anisotropy. Thin rings of aortic tissue from three specimens were used to characterize circumferential residual stress and we found the opening angle was at least 180°