Abstract 4573: Biomechanical Evidence of Reduced Wall Strength and Stiffness of Ascending Aortic Aneurysms in Females
Aim: Recent epidemiological studies have reported a prevalence of females among patients with ruptured ascending aortic aneurysms (AsAA), identifying the female sex as a predictor of negative events (dissection, rupture, and death). The objective of this study was to examine sex differences in the rupture characteristics of AsAA wall tissue.
Methods: One hundred and fifty aortic specimens were excised from the anterior AsAA wall of 25 patients (age: 67±3 years, male/female: 13/12, maximum AsAA diameter: 5.9±0.4 cm) undergoing open surgery for degenerative, non-dissecting AsAA. Specimens were grouped according to sex: male (n=79) vs. female (n=71), and direction: axial (nmale=44, nfemale=37) vs. circumferential (nmale=35, nfemale=34). Biomechanical testing up to rupture was conducted with a uniaxial tensile tester. Rupture strain (extensibility), rupture stress (strength), and peak elastic modulus (maximum stiffness) were computed.
Results: Patient age and AsAA diameter did not differ among male and female patients, as did rupture strain of both axial (0.54±0.02 vs. 0.50±0.03, P>0.2) and circumferential (0.55±0.02 vs. 0.56±0.03, P>0.2) specimens. Rupture stress and peak elastic modulus of circumferential (192.3±12.6 vs. 157.9±10.6 N/cm2, P=0.04 and 1238.6±132.1 vs. 823.5±74.9 N/cm2, P=0.05) but not of axial specimens (87.0±7.3 vs. 86.3±9.6 N/cm2, P>0.2 and 428.7±41.1 vs. 439.1±51.9 N/cm2, P>0.2) were higher in male than female patients.
Conclusions: We demonstrate sex differences in the rupture characteristics of AsAA tissue, with circumferentially-directed wall tissue being stronger and stiffer in men. Comparable results have been lately presented for abdominal aortic aneurysms and an accumulating body of evidence suggests sex-related differences in the elastic characteristics of large-conduit vessels. Particular attention should be given towards a potentially pertinent association between the increased risk of negative effects found in females and the presently-reported sex differences in strength and stiffness of AsAA, as AsAA rupture is a biomechanical phenomenon arising when the hemodynamic stresses exceed the strength of vessel wall.