title: Disturbed flow in radial-cephalic arteriovenous fistulae for haemodialysis: low and oscillating shear stress locates the sites of stenosis.
abstract: BACKGROUND
  Despite recent clinical and technological advancements, the vascular access (VA) for haemodialysis still has significant early failure rates after arteriovenous fistula (AVF) creation. VA failure is mainly related to the haemodynamic conditions that trigger the phenomena of vascular wall disease such as intimal hyperplasia (IH) or atherosclerosis.
  
  
  METHODS
  We performed transient computational fluid dynamics simulations within idealized three-dimensional models of 'end-to-side' and 'end-to-end' radio-cephalic anastomosis, using non-Newtonian blood and previously measured flows and division ratio in subjects requiring primary access procedure as boundary conditions.
  
  
  RESULTS
  The numerical simulations allowed full characterization of blood flow inside the AVF and of patterns of haemodynamic shear stress, known to be the major determinant of vascular remodelling and disease. Wall shear stress was low and oscillating in zones where flow stagnation occurs on the artery floor and on the inner wall of the juxta-anastomotic vein.
  
  
  CONCLUSIONS
  Zones of low and oscillatory shear stress were located in the same sites where luminal reduction was documented in previous experimental studies on sites stenosis distribution in AVF. We conclude that even when exposed to high flow rates, there are spot regions along the AVF exposed to athero-prone shear stress that favour vessel stenosis by triggering IH.
authors.affiliation: Department of Biomedical Engineering, Laboratory of Biomedical Technologies, Mario Negri Institute for Pharmacological Research, Ranica, Italy. bogdan@marionegri.it
authors.forename: Bogdan
authors.initials: B
authors.lastname: Ene-Iordache
authors.forename: Andrea
authors.initials: A
authors.lastname: Remuzzi
mesh_terms: D001166:Arteriovenous Shunt, Surgical / Q000009:adverse effects*; D002408:Catheters, Indwelling; D003198:Computer Simulation; D003251:Constriction, Pathologic; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D011673:Pulsatile Flow / Q000502:physiology; D006435:Renal Dialysis / Q000009:adverse effects* / Q000295:instrumentation*; D033081:Shear Strength; D013314:Stress, Mechanical; D017539:Tunica Intima