Research

Specific ongoing/previous research projects involve:

1. Computational examination of stresses in ascending thoracic aortic aneurysms. Our biomechanical data, relating to the distributions of strength and mechanical properties of aneurysmal wall, will be used in conjunction with computational stress analyses in patient-specific geometrical models. It is expected that our findings will be employed in the clinical setting for the implementation of a more precise criterion for determination of the rupture potential of aneurysmal tissue than the maximum transverse aneurysm diameter used today.
2. Biomechanical characterization of biological soft tissues of the urinary tract (ureter, urinary bladder, urethra). Assessment of directional, regional and layer variations in the mechanical properties and their interpretation using novel structure-based constitutive models.
3. Biomechanical study of soft tissues of the gastrointestinal system (esophagus, stomach, intestine). Studies the wall mechanical properties, with particular emphasis to differences according to direction, region, and layer. Interprets the biomechanical differences by the tissue microstructure and characterizes them mathematically via complicated constitutive models.
4. The influence of aging on the mechanical properties and histological structure of the aorta. Examines changes in the biomechanical properties, composition and structure of the human aorta in relation to age. The study includes full mechanical characterization of the aortic tissue and introduction of a biaxial microstructure-based constitutive model. Gender-related differences are also to be examined.
5. Biomechanics of aortic root aneurysms. Examines the biomechanical properties of these aneurysms in comparison to healthy tissue (obtained from necropsy), and maps them in relation to the histological characteristics of root tissue, in order to better understand the mechanisms implicated in the rupture of those aneurysms.
6. Prosthetic arteriovenous fistulas for hemodialysis: Role of hemodynamics and biomechanics in graft failure and optimal graft design. Examined the contribution of hemodynamic and biomechanical factors in the development of histomorphometric alterations in the vascular wall of arteriovenous anastomoses, for the improvement of surgical procedures and graft design.
7. The chronic effect of surgically induced sympathetic denervation of the aorta in the histological structure and mechanical characteristics of its wall. Examined in an experimental animal model the geometric, structural, compositional and mechanical variations of the aortic vessel wall, from the aortic valve down to the iliac bifurcation, as a result of aortic wall sympathectomy.
8. The long-term effects of chemical sympathectomy on the elastic properties and microstructure of the thoracic aorta. Determined alterations in the tensile properties and the ultra-structural composition and architecture of the thoracic aortic wall one, two and three months following the administration of a b-blocker –regarded as pharmaceutical sympathectomy- in rats. Clinical implications were examined.
9. Characterization of the passive stress-strain relation of blood vessels under uniaxial and multiaxial loading conditions. Examined the relation between the passive tissue elements and the stress-strain relation, aiming to propose a constitutive law for blood vessel tissue, accounting for blood vessel microstructure.
10. Structural basis for the elastic characteristics of the aortic wall. Examined the effect of mechanical stress on the histological structure of the aortic wall, aiming to assess the relation between the stress-strain response and the micro-structural characteristics of the aortic wall components in uniaxial tension.
11. Biomechanics of ascending thoracic aortic aneurysms. Aimed to map the histological, mechanical and failure properties of ascending thoracic aortic wall tissue in comparison to age-matched healthy ascending aortic tissue. The influence of gender, aortic diameter, and aortic pathology on the mechanical properties and structure of the ascending thoracic aortic wall were particularly examined.
12. Comparative hemodynamic study of the intra-aortic balloon pump and left ventricular assist device. Examined the hemodynamics and arterial mechanics of experimental animals under conditions of acute ischemic left ventricular dysfunction and mechanical circulatory support by the simultaneous use of two intra-aortic balloon pumps or by use of a roller pump to increase the level of left ventricular assistance. Compared the effects of dual intra-aortic balloon pumps with the roller pump left ventricular assistance.
13. Mechanical properties and histological structure of esophagus wall. An experimental investigation was undertaken of the mechanical properties of tissue via an inflation/extension device and the experimental data were simulated with a novel constitutive model. Studied the topographical variation of mechanical in relation to structural characteristics, and the stress distribution in the healthy wall of esophagus to facilitate the understanding of its physiology.
14. Cardiovascular effects of ovariectomy and oestrogen replacement therapy. Studied the effects of ovariectomy on the biomechanical and histological characteristics of large conduit vessels, and the potential protective role of oestrogen replacement therapy.
15. In vivo antiatherogenic properties of olive oil and its separated lipid classes administration in hyperlipidemic rabbits. Investigated the effects of olive oil, olive oil neutral lipid extracts and olive oil polar lipid extracts supplementation in cholesterol-fed rabbits on atherosclerosis development.
16. Mapping the mechanical properties and histological structure of the thoracic and abdominal aorta. Stress-strain analysis and histological examination of the aortic tissue from healthy pigs was performed, to assess variations in tensile properties and aortic microstructure from the valve to the iliac arteries bifurcation. Changes in mechanical properties along the aorta were correlated with the respective changes in microstructure.
17. The role of bilateral vagotomy, assumed to be equivalent to parasympathetic denervation, in the modulation of thoracic aorta elasticity. Studied the long-term alterations in the histological characteristics, geometry and biomechanical response of the thoracic aorta, resulting from surgical parasympathetic denervation of the vessel wall.
18. Long-term effects of hyperthyroidism and hypothyroidism on the histological design and function of the aorta in rats. Studied the adaptation in biomechanical characteristics, composition and microstructure of the thoracic aortic wall in experimental animal models of hyperthyroidism and hypothyroidism. Clinical implications were sought.