title: The hemodynamic impact of misalignment of fenestrated endografts: a computational study.
abstract: OBJECTIVE
  The hemodynamic consequences of misaligned stent-grafts (SG) in fenestrated endografts (EG) have not been adequately studied. Our aim was to study the hemodynamic effects of positional variations of SG, investigating the potential influence on the total displacement forces acting on the EG and the shear stress values at the stented segments.
  
  
  METHODS
  This was a computational study. An idealized EG model with two renal fenestrations was computationally reconstructed and centrally extended up to the suprarenal level to treat a suprarenal aneurysm. The misalignment of SG was represented by a variable take-off angle between the SG and the EG centerline axis, corresponding to angles of 90°, 176°, 142°, 38°, and 4°, respectively. Accordingly, the maximum EG displacement forces and the shear stress within the stented segments were calculated, using commercially available software.
  
  
  RESULTS
  The variable positions of the SG caused no effect on the maximum displacement force acting on the EG, being quite steady and equal to 5.55 N. On the contrary, the values of maximum shear stress acting on the stented segments were influenced by their orientation. The narrow transition zone between the distal end of the mating stent and the target artery showed higher stresses than any other segment. The right-angle take off SG position (90°) was associated with the lowest stresses (12.5 Pa), whereas the highest values were detected at 38° and 142° (16.5 and 16.1 Pa, respectively). The vessel segments distal to the SG exhibited constantly lower stress values (1.9-2.2 Pa) than any other segment.
  
  
  CONCLUSIONS
  We detected differences in the values of shear stress exerted on the stented arteries, depending on different positions that SG can adapt after the deployment of fenestrated EG. The pathophysiologic implication of our findings and their potential association with clinical events deserve further investigation and clinical validation.
authors.affiliation: Department of Vascular Surgery, "Democritus" Medical School, University Hospital of Alexandroupolis, Greece. Electronic address: efstratiosgeorg@gmail.com.
authors.forename: E
authors.initials: E
authors.lastname: Georgakarakos
authors.affiliation: Fluids Section, School of Mechanical Engineering, National Technical University of Athens, Athens, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Xenakis
authors.affiliation: Department of Vascular Surgery, "Democritus" Medical School, University Hospital of Alexandroupolis, Greece.
authors.forename: G S
authors.initials: GS
authors.lastname: Georgiadis
authors.affiliation: Department of Vascular Surgery, "Democritus" Medical School, University Hospital of Alexandroupolis, Greece.
authors.forename: C
authors.initials: C
authors.lastname: Argyriou
authors.affiliation: Department of Vascular Surgery, Hellenic Red Cross Hospital, Athens, Greece.
authors.forename: G A
authors.initials: GA
authors.lastname: Antoniou
authors.affiliation: Department of Vascular Surgery, "Democritus" Medical School, University Hospital of Alexandroupolis, Greece.
authors.forename: N
authors.initials: N
authors.lastname: Schoretsanitis
authors.affiliation: Department of Vascular Surgery, "Democritus" Medical School, University Hospital of Alexandroupolis, Greece.
authors.forename: M K
authors.initials: MK
authors.lastname: Lazarides
mesh_terms: D001012:Aorta, Abdominal / Q000503:physiopathology / Q000601:surgery*; D017544:Aortic Aneurysm, Abdominal / Q000503:physiopathology / Q000601:surgery*; D001783:Blood Flow Velocity; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D003198:Computer Simulation; D057510:Endovascular Procedures / Q000009:adverse effects / Q000295:instrumentation*; D006439:Hemodynamics; D006801:Humans; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D012039:Regional Blood Flow; D015607:Stents; D013314:Stress, Mechanical; D016896:Treatment Outcome
keywords: Displacement forces; Endovascular; Fenestrated endografts; Hemodynamics; Shear stress; Suprarenal aortic aneurysms