Experimental/numerical study to assess mechanical properties of healthy and Marfan syndrome ascending thoracic aorta under axial and circumferential loading

Abstract

Ascending thoracic aortic aneurysm (ATAA) can be a life threatening disease as it leads to a lack of function in most of the connective tissues. Marfan syndrome is a congenital connective tissue disorder that may have influence on the cardiovascular system. It has been shown that Marfan syndrome invokes a degradation of the elastin and collagen content of the aortic wall and, consequently, a remarkable weakness in the mechanical strength of the arterial wall. However, so far, the mechanical properties of the aortic wall due to Marfan syndrome have not been determined. Therefore, this study was aimed to perform a comparative experimental study to quantify the linear elastic and non-linear hyperelastic mechanical properties of the healthy and Marfan syndrome ATA. Eight healthy and Marfan aorta tissues were excised from the human body during invasive cardiac surgery and autopsy respectively. The tissue samples were subjected to the longitudinal and circumferential loadings until breakage occurred. The elastic modulus, maximum stress and strain of the ATA tissues were calculated. The non-linear mechanical behaviour of the ATA tissues was also computationally investigated using Mooney–Rivlin hyperelastic material model. The results showed that the healthy ATA tissues are stiffer in the longitudinal direction compared to the circumferential direction. The highest elastic modulus (764.10 N cm− 2) and maximum stress (298.18 N cm− 2) were observed for the Marfan ATA wall in the longitudinal direction, while the healthy ATA tissues showed the axial elastic modulus and maximum stress of 367.08 and 220.14 N cm− 2 respectively. The hyperelastic material model also well defined the non-linear mechanical behaviour of the ATA tissues. These results may have implications not only for understanding the mechanical properties of the healthy and Marfan ATA tissues but also for a wide range of clinical applications, including valve repair or replacement.