Characterization of Aortic Tissue Fracture Toughness and Stiffness under Cyclical Fatigue Loading

An ascending aortic aneurysm is an asymptomatic disease that, if left untreated, could lead to death through its eventual rupture. Current clinical management practices are based primarily on the monitoring of an aneurysm's growth, followed by surgical resection of the affected aortic segment when its diameter reaches 5 to 5.5 centimetres. Unfortunately, this method is based solely on clinical observations and is frequently inaccurate in predicting the risk of an imminent rupture. More sophisticated tools have been developed and do not depend on aneurysm size alone, but these have focused mostly on the distribution of stresses within an aneurismal aortic wall and do not give clinicians an estimate of the time to failure.;This work constitutes the first tentative steps towards the development of a clinical tool that can evaluate the fracture toughness of aneurismal aortic tissues and predict the temporal likelihood of aneurismal rupture.;This present work incorporates the temporal aspect by examining the effects of fatigue on aortic wall properties, and adopts an energetics approach to evaluating the aorta's resistance to rupture. Tissue samples from porcine aortas were fatigued and were subjected to both biaxial and guillotine tests to assess stiffness and fracture toughness. The experiments indicate that both properties decreased according to a power function. After 1 000 000 loading cycles, the final/initial stiffness ratio dropped to 0.85, while its toughness counterpart fell to 0.80.