Fracture properties of porcine versus human thoracic aortas from tricuspid/bicuspid aortic valve patients via symmetry-constraint Compact Tension testing

Abstract

AbstractAneurysm rupture is a life-threatening event, yet its underlying mechanisms remain largely unclear. This study investigated the fracture properties of the thoracic aneurysmatic aorta (TAA) using the symmetry-constraint Compact Tension (symconCT) test and compared results to native and enzymatic-treated porcine aortas’ tests. With age, the aortic stiffness increased, and tissues ruptured at lower fracture energy $$D$$. Patients with bicuspid aortic valves were more sensitive to age, had stronger aortas and required more $$D$$ than tricuspid valves individuals (peak load: axial loading 4.42 $$\pm$$ 1.56 N vs 2.51 $$\pm$$ 1.60 N; circumferential loading 5.76 $$\pm$$ 2.43 N vs 4.82 $$\pm$$ 1.49 N. Fracture energy: axial loading 1.92 $$\pm$$ 0.60 kJ m-2 vs 0.74 $$\pm$$ 0.50 kJ m-2; circumferential loading 2.12 $$\pm$$ 2.39 kJ m-2 vs 1.47 $$\pm$$ 0.91 kJ m-2). Collagen content partly explained the variability in $$D$$, especially in bicuspid cases. Besides the primary crack, TAAs and enzymatic-treated porcine aortas displayed diffuse and shear-dominated dissection and tearing. As human tissue tests resembled enzymatic-treated porcine aortas, microstructural degeneration, including elastin loss and collagen degeneration, seems to be the main cause of TAA wall weakening. Additionally, a tortuous crack developing during the symconCT test reflected intact fracture toughening mechanisms and might characterize a healthier aorta.