CONGRESS ABSTRACT

Background: Evaluation of Stress-Strain curve to analyze mechanical properties of aortic wall hasbecome a frequent practice. Under low (physiological) loading the properties of aortic walldepends on the elastic fi bers (elastin-based properties) while at supra physiological loading (tillrupture) depends on the collagen fi bers. Relationship between two components of the stress-strain curve are still unclear especially in pathological conditions (aortic aneurysm/aorticdissection). In this study we sought to clarifi ed if histological alterations of aortic diseases couldcause a signifi cant modifi cation of intrinsic relationship between elastin and collagen basedaortic wall mechanical properties. Materials and Methods: Ex vivo mechanical properties test were obtained in 238 samplesharvested from 52 patients undergoing cardiac surgery at our hospital and divided in 3 groups(Aortic aneurysm n.28; Aortic dissection n.12; Control group n.20). All tests were conducted onfresh samples within 48 hours from collection. Stress-Strain curve was extracted for each sampleand two Elastic modulus were calculated, representing the behavior at low physiological loading(elastin-based properties) and at maximum load until rupture (collagen-based properties). Resultsat low and maximum loading were correlated between them and between study's groups. Results: As summarized in fi g 1a mechanical properties at low and maximum loading wereusually signifi cantly increased (orange box) in patients without aortic diseases (control groupfrom heart transplant) except for maximum elastic modulus. Furthermore, as shown in greensquare, aortic wall strain at both low and maximum loading was signifi cantly reduced in patientswith aortic dissection (brown box) compared to those with chronic aortic aneurysm (bleu box).Analyzing the correlation between elastin and collagen based phase of mechanical properties,fi nally, we founded linear correlation for all three parameters in all study's groups (fi g 1b). Conclusions: Mechanical properties of aortic wall, at low and maximum loading are signifi cantlypreserved in patients without aortic diseases. In patients with aortic dissection aortic wall strain, ,was further impaired compared to patients with non-dissected aneurysm either at low andmaximum loading. Mechanical properties at low and maximum loading, fi nally, showed linearcorrelation without alteration of elastin-based and collagen-based properties ratio