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Computational Fluid Dynamics in Abdominal Aortic Aneurysm: A Diagnostic Advancement

Explore the potential of Computational Fluid Dynamics (CFD) in diagnosing and predicting abdominal aortic aneurysm (AAA). Learn about pathogenesis, operative strategies, and complications. Discover how CFD models can enhance understanding of this complex biological system, offering new insights for treatment and prognosis. This study delves into fluid dynamics, shear stress, turbulence, and hemodynamics of AAA. Gain insights into renal function implications, peripheral embolization, and acute aortic occlusion. Aims to utilize Finite Element Analysis (FEA) in modeling biological phenomena, providing a predictive tool. This comprehensive CFD research aims to enhance diagnostic and prognostic capabilities for AAA patients.

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Computational Fluid Dynamics in Abdominal Aortic Aneurysm: A Diagnostic Advancement

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  1. Computational fluid dynamics of abdominal aortic aneurysm: a potential diagnostic and prognostic tool Cristiano Spadaccio, MD CIR – Center of Integrated Research, University Campus Bio-Medico of Rome Department of Cardiovascular Surgery, University Campus Bio-Medico of Rome c.spadaccio@unicampus.it

  2. Biological Systems Complex systems

  3. Abdominal aortic aneurysm

  4. Abdominal aortic aneurysm • AAA occurs in about 1% of men who are 60 years of age or less. • The frequency increases to about 6% of men by the age of 80. The incidence is slightly less in women. • TAA is less common, affecting less than 1% of men and women; however, a rupture of a thoracic aneurysm has a greater than 97% fatality rate. Chaikof EL. et al J Vasc Surg. 2009 Oct;50(4 Suppl):S2-49.

  5. Abdominal aortic aneurysm Pathogenesis • Proteolytic degradation • Inflammatory and Immunological • Biochemical wall stress • Molecular genetics

  6. Complications Rupture Peripheral embolization Acute aortic occlusion Aortocaval fistula Aortoduodenal fistula Abdominal aortic aneurysm

  7. Operative strategy Diameter > 5cm Growth >0,5/year Abdominal aortic aneurysm • Shear stress • Turbolence • Haemodynamics Chaikof EL. et alJ Vasc Surg. 2009 Oct;50(4 Suppl):S2-49.

  8. Renal Function >60% of AAA patients presents with preoperative renal impairment Glomerular Filtration rate is a predictor of survival Abdominal aortic aneurysm Stewart R et al. Vasc Endovascular Surg 2007; 41; 225

  9. Abdominal aortic aneurysm Peripheral embolism • Presentation with acute limb embolism • Presentation with splancnic embolism Acute Supramesenteric Thrombosis of Abdominal Aortic aneurysm with deleterious embolism. Ann Vasc Eugster et al. Ann Vasc Surg 2005 19 (3): 411-413

  10. AIMS • To use FEA Finite Element analysis to model biological phenomena related with aortic abdominal with mathematical laws • Obtain a predictive and prognostic tool

  11. Previous studies • Stationary models • Simulations on 2D models • Biases on boundary conditions • Non realistic geometries Endovascular device design in the future: transformation from trial and error to computational design. Zarins CK, Taylor CA. J Endovasc Ther. 2009 Feb;16 Suppl Image-based computational fluid dynamics modeling in realistic arterial geometries. Steinman DA. Ann Biomed Eng. 2002 Apr;30(4):483-97. Review.

  12. Details • Non stationary analysis • Realistic conditions of pulsatile flow • Patient specific 3D model reconstructed from CT scans Assumptions: Blood was modeled as a newtonian, homogeneous and uncompressible fluid, with given density and viscosity values.

  13. Reconstruction

  14. Finite ElementsAnalysis

  15. Finite ElementsAnalysis Mesh generation 11929 elements, 59263 dof

  16. Navier-Stokes eq. Continuity eq. Physicalmodel Solved with Comsol Multiphysics

  17. Boundaryconditions Inlet  Inflow Physiological pulsed regime (at rest)

  18.  From experimental data  ? ? = ? v(t) wasrescaled in ordertogive Rem = 300, whichis a suitablevalueforrestconditions

  19. Inlet

  20. Profile at the inlet Flat profile Parabolic profile

  21. Inletspeed Source inlet Wave guide 1 cm 2 cm 3 cm

  22. No slip Boundaryconditions No slipping boundaries assumption

  23. Outlet 1) 2) Outflow Systemic pressure

  24. Simulation • Simulation was carried out for 3 cycles • Results presented for 3rd cycle • Systolic acceleration • Systolic deceleration • Diastole • Late diastole

  25. Velocityfield (m/s) t=0.31 s attached flow patterns

  26. Velocityfield (m/s) t=0.42 s Perturbation in correspondance of a small radius of curvature

  27. Velocityfield (m/s) t=0.52 s (flow inversion) Vortex extends to the proximal portion of the aneurism

  28. Velocityfield (m/s) t=1.00 s

  29. Velocityfield (m/s) t=0.20 s Vortex reaches its maximum dimension, before dissolving at the new systole

  30. Pressure at walls (kPa) t=0.20 s

  31. Pressure at walls (kPa) t=0.31 s Massimo gradiente di pressione

  32. Pressure at walls (kPa) t=0.42 s

  33. Pressure at walls (kPa) t=0.52 s

  34. Pressure at walls (kPa) t=1.00 s

  35. Results • Velocity profiles show the potential for retrograde embolization • Pressure profile demonstrates higher wall stress on anterior and posterior aortic wall.

  36. The literature • The management of abdominal aortic aneurysms in patients with concurrent renal impairment. Bown MJ, Norwood MG, Sayers RD. Eur J Vasc Endovasc Surg. 2005 Jul;30(1):1-11 • Renal dysfunction and abdominal aortic aneurysm. Losito A, Fagugli RM, Caporali S, Verzini F, Giordano G, Cao PG. Contrib Nephrol. 1994;106:63-7. • Renal artery stenosis and renal parenchymal damage in patients with abdominal aortic aneurysm proven by autopsy.Nakamura S, Ishibashi-Ueda H, Suzuki C, Nakata H, Yoshihara F, Nakahama H, Kawano Y. Kidney Blood Press Res. 2009;32(1):11-6. Epub 2009 Jan 29.

  37. Renal artery stenosis and renal parenchymal damage in patients with abdominal aortic aneurysm proven by autopsy. Nakamura et al Conclusions: We demonstrated that renal parenchymal damage and deteriorated kidney function are closely associated in the patients with AAA. Treatment of these patients in view of protection of the kidney is thus relevant. Kidney Blood Press Res. 2009;32(1):11-6

  38. Acute Supramesenteric Thrombosis of Abdominal Aortic aneurysm with deleterious embolism. Eugster et al A 55-year-old man was admitted with severe pain, paralysis of both legs and absent femoral pulses. Computed tomographic scan demonstrated a 6 cm juxtarenal abdominal aortic aneurysm (AAA) with thrombosis starting at the level of the celiac trunk. At immediate operation, thrombectomy of visceral arteries was performed and distal neovascularization was achieved with a bifurcated prosthesis. It was revealed that all major arteries were occluded with debris. Embolectomy did restore flow in major vessels, but organ perfusion was not achieved due to occlusion of smaller vessels. The patient died with multiorgan failure. This is the first description in the literature of an acutely thrombosed AAA at the supramesenteric level. Ann Vasc Surg 2005 19 (3): 411-413

  39. Results • Results agree with other data reported in the literaturei • Synthesis of previous works in a patient specific approach, that migth be merged with physiological blood velocity and pressure • Might represent an innovative tool for the prediction of aneurism rupture or clot formation

  40. Thanks for your attention c.spadaccio@unicampus.it

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