Dissection mechanics of tissue components in human aorta

Abstract

This study investigates the mechanical properties of the aneurysmatic ascending aorta through radial tensile testing, focusing on the behavior of different anatomical regions and layers of the aortic wall. The primary aim is to examine how rupture propagates between the intima-media and media-adventitia layers, and to assess how these mechanical properties vary across four anatomical regions (anterior, right lateral, posterior, and left lateral) of the aorta. Specimens from twelve patients were subjected to direct tension tests, with force-displacement curves used to analyze key mechanical parameters, including maximum force (Fmax), yield force (Fyield), strain, and elastic modulus. The samples were collected from patients at Hygeia Hospital between September 2023 and February 2024. The experimental procedures were conducted at the Center of Clinical, Experimental Surgery & Translational Research at the Biomedical Research Foundation of the Academy of Athens (BRFAA). For the mechanical testing, a fully automated Vitrodyne V1000 Universal tensile testing machine was used, equipped with specially developed specimen grips to ensure precise and consistent measurements during the direct tension tests. The results were contextualized within the framework of existing literature on the mechanical behavior of the aortic wall, particularly in relation to rupture initiation and propagation. The study found that the intima-media interface exhibits significantly higher mechanical resistance, with greater Fmax and elastic modulus values compared to the media-adventitia interface, indicating that the inner layers of the aorta are stronger and more resistant to rupture. In contrast, the outer layers showed greater variability and lower mechanical resistance, making them more prone to rupture initiation. These findings align with previous studies that have demonstrated the mechanical vulnerability of the media-adventitia interface in pathological conditions such as aortic dissections. Furthermore, regional differences were observed, with the posterior and right lateral regions exhibiting higher mechanical resistance compared to the anterior and left lateral regions, suggesting that the structural integrity of the aorta varies across different anatomical locations. Patient-specific factors such as age, gender, and valve morphology also influenced the mechanical behavior of the aortic wall. Younger patients exhibited higher mechanical strength, while patients with bicuspid aortic valves (BAV) showed lower resistance to rupture compared to those with tricuspid aortic valves (TAV). These findings emphasize the importance of considering individual patient characteristics when assessing rupture risk and planning treatment. In conclusion, this study provides valuable insights into the layer-specific and region-specific mechanical properties of the aneurysmatic ascending aorta, highlighting the critical role of the intima-media interface in maintaining aortic integrity. The findings have significant implications for the clinical management of aortic aneurysms and dissections, particularly in terms of identifying patients at higher risk of rupture and tailoring interventions accordingly. Future research should focus on integrating mechanical testing with histological analyses to further explore the structural factors that influence aortic wall failure.