Effect of hypertension on the delamination and tensile strength of ascending thoracic aortic aneurysm with a focus on right lateral region

Ascending thoracic aortic aneurysm (ATAA) is a degenerative vascular pathology associated with localized dilation of the ascending aorta (Coady et al., 1999, Elefteriades et al., 2015). The etiology of this disease is not yet fully understood. Besides the maximal aneurysmal diameter, patient-specific biomechanical properties of the ATAA tissue have been corroborated as an important metric to predict rupture risk (Duprey et al., 2016, Iliopoulos et al., 2009, Martin et al., 2013, Martufi et al., 2016). As the most common complication of the ATAA, aortic dissection (AD) leads to a high mortality rate if patients are not treated appropriately (Coady et al., 1999, Davies et al., 2002). AD is a devastating separation of aortic layers. From a biomechanical point of view, it occurs when hemodynamic forces exceed tissue’s adhesive strength (Ban et al., 2021, Sherifova and Holzapfel, 2019, Tong et al., 2016). Hence, biomechanical analysis of tissue delamination strength may provide us with a unique biomarker for risk of AD (Ban et al., 2021, Chung et al., 2020, Pasta et al., 2012, Wang et al., 2021).

Hypertension is regarded as a major predisposing factor to initiate thoracic aortopathy. Many studies have indicated that hypertension significantly contributes to aortic remodeling and leads to changes in tissue mechanical properties (Boutouyrie et al., 2021, Ferrara et al., 2018, Murtada et al., 2021, Rateri et al., 2014). More importantly, hypertension is the most significant risk factor for the development of ATAAs and acute AD (Howard et al., 2013). Ferrara et al. (2018) suggested that both hypertension and ageing made the ATAA tissue weaker and less extensible. Chung et al. (2020) demonstrated that delamination strength of aneurysmal ascending aortas was significantly lower for hypertensive patients than those without hypertension. Although biomechanical properties of thoracic aortic aneurysms are extensively investigated (Cebull et al., 2020, Chung et al., 2020, Deveja et al., 2018, Duprey et al., 2016, Ferrara et al., 2018, Iliopoulos and Sokolis, 2021, Pasta et al., 2012, Pichamuthu et al., 2013), effect of hypertension on the delamination and tensile strength of the ATAA tissue in the lateral regions remains unclear and relevant biomechanical data are scarce.

The aims of the present study are three-fold: i) we aim to experimentally investigate delamination strength and failure stresses of the ATAA tissue samples along the circumferential and longitudinal orientations, and to compare biomechanical data and histological characteristics between the hypertensive and non-hypertensive patients; ii) to examine whether dissection properties of the ATAA tissue are rate dependent; iii) to investigate correlations of the delamination strength and failure stresses of the ATAAs with patient ages for the hypertensive and non-hypertensive patients, respectively.

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