title: Flow and wall shear stress characterization after endovascular aneurysm repair and endovascular aneurysm sealing in an infrarenal aneurysm model.
abstract: Endovascular aneurysm repair (EVAR) with a modular endograft has become the preferred treatment for abdominal aortic aneurysms. A novel concept is endovascular aneurysm sealing (EVAS), consisting of dual endoframes surrounded by polymer-filled endobags. This dual-lumen configuration is different from a bifurcation with a tapered trajectory of the flow lumen into the two limbs and may induce unfavorable flow conditions. These include low and oscillatory wall shear stress (WSS), linked to atherosclerosis, and high shear rates that may result in thrombosis. An in vitro study was performed to assess the impact of EVAR and EVAS on flow patterns and WSS.
  
  
  
  Four abdominal aortic aneurysm phantoms were constructed, including three stented models, to study the influence of the flow divider on flow (Endurant [Medtronic, Minneapolis, Minn], AFX [Endologix, Irvine, Calif], and Nellix [Endologix]). Experimental models were tested under physiologic resting conditions, and flow was visualized with laser particle imaging velocimetry, quantified by shear rate, WSS, and oscillatory shear index (OSI) in the suprarenal aorta, renal artery (RA), and common iliac artery.
  
  
  
  WSS and OSI were comparable for all models in the suprarenal aorta. The RA flow profile in the EVAR models was comparable to the control, but a region of lower WSS was observed on the caudal wall compared with the control. The EVAS model showed a stronger jet flow with a higher shear rate in some regions compared with the other models. Small regions of low WSS and high OSI were found near the distal end of all stents in the common iliac artery compared with the control. Maximum shear rates in each region of interest were well below the pathologic threshold for acute thrombosis.
  
  
  
  The different stent designs do not influence suprarenal flow. Lower WSS is observed in the caudal wall of the RA after EVAR and a higher shear rate after EVAS. All stented models have a small region of low WSS and high OSI near the distal outflow of the stents.
authors.affiliation: Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands; Department of Vascular Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands; Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands. Electronic address: j.boersen@antoniusziekenhuis.nl.
authors.forename: Johannes T
authors.initials: JT
authors.lastname: Boersen
authors.affiliation: Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands; Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Groot Jebbink
authors.affiliation: Department of Physics of Fluids, Faculty of Science and Technology, Technical University of Twente, Enschede, The Netherlands.
authors.forename: Michel
authors.initials: M
authors.lastname: Versluis
authors.affiliation: MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, The Netherlands.
authors.forename: Cornelis H
authors.initials: CH
authors.lastname: Slump
authors.affiliation: School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Ga.
authors.forename: David N
authors.initials: DN
authors.lastname: Ku
authors.affiliation: Department of Vascular Surgery, St. Antonius Hospital, Nieuwegein, The Netherlands.
authors.forename: Jean-Paul P M
authors.initials: JPM
authors.lastname: de Vries
authors.affiliation: Department of Surgery, Rijnstate Hospital, Arnhem, The Netherlands.
authors.forename: Michel M P J
authors.initials: MMPJ
authors.lastname: Reijnen
mesh_terms: D000465:Algorithms; D001012:Aorta, Abdominal / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D017544:Aortic Aneurysm, Abdominal / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D001783:Blood Flow Velocity; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000295:instrumentation*; D057510:Endovascular Procedures / Q000295:instrumentation*; D006439:Hemodynamics; D006801:Humans; D007083:Iliac Artery / Q000503:physiopathology; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D012039:Regional Blood Flow; D012077:Renal Artery / Q000503:physiopathology; D013314:Stress, Mechanical; D013997:Time Factors