Entity

Time filter

Source Type

Ymittos Athens, Greece

Iliopoulos D.C.,National and Kapodistrian University of Athens | Iliopoulos D.C.,Athens Medical Center | Kritharis E.P.,Foundation of Biomedical Research | Sokolis D.P.,Foundation of Biomedical Research
IFMBE Proceedings | Year: 2011

To properly understand the natural history of ascend ing thoracic aortic aneurysms (ATAA) and better assess their risk of rupture, stress analyses asking for biaxial biomechanical data of the tissue are necessary, but information on this matter is restricted in the literature. The present study addressed the role of ATAA on the biomechanical response of vessel wall. Degenera tive ATAA were excised from patients during graft replacement and non-aneurysmal age-matched vessels during autopsy. Uniaxi al tensile-tests were conducted on circumferential (CIRC) and longitudinal (LONG) tissue strips. The experimental recordings were reduced by a Fung-type strain-energy function that was found to be appropriate for characterization of the vessel's biome chanical response. The material parameters and rupture proper ties disclosed that ATAA and non-aneurysmal aorta were aniso tropic, i.e. stronger and stiffer in the CIRC direction. ATAA had no influence on tissue strength, but caused stiffening and exten sibility reduction. Our findings may serve as input data for the implementation of finite element models to be used as improved surgical intervention criteria. © 2011 Springer-Verlag Berlin Heidelberg.


Sokolis D.P.,Foundation of Biomedical Research | Krithais E.P.,Foundation of Biomedical Research | Giagini A.T.,Foundation of Biomedical Research | Lampropoulos K.M.,Foundation of Biomedical Research | And 3 more authors.
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2012

Ascending thoracic aortic aneurysms (ATAA) were resected from patients during graft replacement and non-aneurysmal vessels during autopsy. Tissues were histomechanically tested according to region and orientation, and the experimental recordings reduced with a Fung-type strain-energy function, affording faithful biomechanical characterisation of the vessel response. The material and rupture properties disclosed that ATAA and non-aneurysmal aorta were stiffer and stronger circumferentially, accounted by preferential collagen reinforcement. The deviation of microstructure in the right lateral region, with a longitudinal extracellular matrix and smooth muscle element sub-intimally, reflects the regional differences in material properties identified. ATAA had no effect on strength, but caused stiffening and extensibility reduction, corroborating our histological observation of deficient elastin but not collagen content. Our findings may serve as input data for the implementation of finite element models, to be used as improved surgical intervention criteria, and may further our understanding of the pathophysiology of ATAA and aortic dissection. © 2012 Taylor & Francis.


Kritharis E.P.,Foundation of Biomedical Research | Kritharis E.P.,National Technical University of Athens | Kakisis J.D.,National and Kapodistrian University of Athens | Peroulis M.,National and Kapodistrian University of Athens | And 3 more authors.
IFMBE Proceedings | Year: 2011

Numerous investigations have addressed the influence of hemodynamics on the formation of intimal hyperplasia and the ensuing graft dysfunction in arteriovenous fistulas for hemodialysis, but study of the intramural biomechanical factors is lagging behind. In the present communication, arteriovenous fistulas were created in a porcine model between the right carotid artery and ipsilateral jugular vein, and the biomechanical adaptation of venous wall was examined with inflation/extension testing. In vivo measurements at the proximal veins disclosed an almost three-fold increase in blood pressure and flow after fistula creation, remaining so until termination. In response to hemodynamic overload, the principal morphological finding in anastomosed veins was wall thickening, serving to restore hoop stresses close to normal levels, and a less significant radial enlargement, steadily normalizing shear stresses. Compared to control, the compliance and distensibility of anastomosed veins were lower at the individual mean pressure. We conclude that the vein wall becomes thicker and stiffer post-fistula creation, aiming to restore the hemodynamic stresses to homeostatic values. © 2011 Springer-Verlag Berlin Heidelberg.

Discover hidden collaborations