Comparative biomechanical and structural evaluation of region-specific stented and non-stented ex vivo perfused human...

The aim of this study is to characterize the mechanical properties of the human thoracic aorta after thoracic endovascular aortic repair (TEVAR). While patient-specific in silico models are becoming increasingly important for preoperative planning, their accuracy depends on reliable mechanical properties. However, the biomechanics of stented aortas remains poorly understood. To address this knowledge gap, the TEVAR-aorta interaction was first simulated under in vivo-like loading conditions using a custom-made mock circulation loop. After perfusion and stenting, tissue samples were obtained from thirteen healthy human thoracic aortas, and biaxial extension tests were performed under various stretch ratios to evaluate the effects of stent placement. Subsequently, a material model was employed to support in silico simulations of TEVAR-induced mechanical changes. Multi-photon imaging was used to assess the morphology of elastic lamellae in representative regions to provide structural insights, strengthening the mechanical findings. The results revealed region-specific mechanical alterations. The proximal (ascending) aorta exhibited a 32% decrease in the k₂ parameter of the material model, while the distal region exhibited a 73% increase. This can lead to overstretching and rupture of the fibers proximally, while increased fiber recruitment occurs distally. Imaging showed that the elastic lamellae were 7.0% thinner proximally at the strut imprints, while they appeared 7.4% thicker distally. Although the changes in the obtained constitutive parameter did not result in statistically significant differences, they are consistent with these significant structural findings. Given the 159 biaxial specimens investigated, the observed mechanical differences are likely due to the intervention. This study improves stent graft design and patient-specific modeling by highlighting region-dependent alterations, thus supporting surgical planning and outcome prediction. Statement of Significance: Thoracic endovascular aortic repair (TEVAR) is a common interventional treatment for aortic diseases, yet its effects on the mechanical behavior of the human aorta remain poorly understood. Using ex vivo perfused human thoracic aortas, this study examined the effects of stent grafts on the structure and mechanics of the thoracic aortic wall. Combining mechanical testing, state-of-the-art imaging, and material modeling, region-specific changes in tissue behavior were identified. Overall, our findings demonstrate softening proximal to the heart (proximal/ascending aorta) and stiffening distally. These findings may help explain stent-tissue interaction and potentially influence surgical outcomes. The results can be used to improve stent design and support patient-specific computer simulations to assist surgeons in planning safer and more effective interventional procedures.