**Author details**

Efstratios Georgakarakos, George S. Georgiadis, Konstantinos C. Kapoulas, Evagelos Nikolopoulos and Miltos Lazarides *"Democritus" University of Thrace Medical School, Alexandroupolis, Greece* 

Antonios Xenakis *Fluids Section, School of Mechanical Engineering, National Technical University of Athens, Athens, Greece* 

#### **7. References**

166 Aneurysm

Mohan 2002).

**6. Conclusion** 

endografts are exposed to.

Efstratios Georgakarakos, George S. Georgiadis,

*Fluids Section, School of Mechanical Engineering, National Technical University of Athens, Athens,* 

Konstantinos C. Kapoulas, Evagelos Nikolopoulos and Miltos Lazarides

*"Democritus" University of Thrace Medical School, Alexandroupolis,* 

**Author details** 

Antonios Xenakis

*Greece* 

*Greece* 

large retrograde component in end-systole (Chong and How, 2004) and formation of recirculating zones. The profiles are significantly more disturbed in the deceleration phase

Finally, local geometric factors play a role in the determination of velocity values and flow patterns (recirculating zones, flow separation, skewed flow, vortices and Dean flows) with the out-of-plane endograft geometry determining greatly the outlet flow rates, flow patterns and drag forces (Morris 2006). Extrinsic constriction (due to calcified or stenosed iliac vessels) or excessive kinking in the iliac limbs can lead either to thrombosis of the graft limbs or altered flow patterns that induce excessive disturbances in shear stresses (not shown in our model), leading also to recirculating zones and prolonged transit times of platelets with consequent apposition and formation of thrombus in the endografts. The latter constitutes a rather common incidental finding, occurring more frequently that previously assumed (Wu et al, 2009). Finally, the study and understanding of the hemodynamic alterations and the parameters that influence them, could lead to better designs of endovascular grafts, in order to eliminate the factors that predispose to endograft migration as well as to generation of endoleaks (Figueroa 2009 and 2010, Liffman 2001,

Aortic endografts are subject to hemodynamic alterations that determine the flow patterns within the different parts of the endografts and influence the values and distribution of pressures and stresses onto their surface during the different phases of the cardiac cycle. Certain geometric factors such as the inlet-to-outlet ratio of the graft as well as the out-ofplane configuration of the main body and iliac limbs have been implicated as major determinants of the aforementioned hemodynamic alterations. Computational simulation techniques can help towards the understanding of these interactions and help us further design better endografts with greater resistance to migration, endoleaks and dislocation of modular stent-grafts, all of which are influenced by the hemodynamic environment that

than at maximum velocity (Chong and How, 2004).


**Chapter 9** 
