Currently, surgical recommendations for aneurysm of the ascending aorta (AsAA) are based on the maximum diameter of the ascending aorta, but this factor is not reliable. Understanding the biomechanical properties of the aorta could lead to improve the prediction of the development of an AsAA. The aim of this study is to obtain the local patient specific elastic modulus distribution of the AsAA from a biaxial tensile test.

Pathologic ascending aortic tissue samples (n=10) were obtained from patients undergoing elective surgical repair of AsAA (Table 1). All the aortic wall samples were partitioned related to medial, posterior, lateral, and anterior quadrants. Each AsAA sample was cut in square size (15mm×15mm, n=89) with marking the circumferential and longitudinal directions. An average thickness was measured, using an electronic micrometer (Litematic VL-50, Mitutoyo®). The experiments were carried out by a biaxial tensile test machine (ElectroForce®). Each specimen was stretched at a rate of 10mm/min until rupture. Maximum Elastic Modulus was calculated for each specimen.

The longitudinal direction of the aorta is stiffer than the circumferential direction except in the medial quadrant in both tissue types. The lateral quadrant (outer curvature) of the aorta shows a higher stiffness, roughly the double value of the medial quadrant (inner curvature) (Fig. 1). The thickness of TAV and BAV tissues did not show a significant difference in the four regions of the AsAA wall.

Among the ten AsAA tissues, there are variations in the tissue stiffness according to their quadrants and the direction. It is expected to observe the regional variability in the thickness of the dilated samples corresponding the change of mechanical properties caused by valve disease. However, there was no significant correlation between the regional thickness and mechanical properties, neither TAV (r=−0.3584) nor BAV (r=−0.3107).