title: Flow velocities after carotid artery stenting: impact of stent design. A fluid dynamics study in a carotid artery model with laser Doppler anemometry.
abstract: OBJECTIVE
  To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model.
  
  
  METHODS
  Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 mum. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles.
  
  
  RESULTS
  The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume.
  
  
  CONCLUSIONS
  Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow behavior. Depending on the stent design the flow alterations are located in different regions. All the stents tested were suitable for the carotid bifurcation. The MembraX prototype has shown promising hemodynamic properties ex vivo.
authors.affiliation: Department of Interventional Radiology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. oliver.greil@roe.med.tu-muenchen.de
authors.forename: Oliver
authors.initials: O
authors.lastname: Greil
authors.forename: Thomas
authors.initials: T
authors.lastname: Kleinschmidt
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Weiss
authors.forename: Oliver
authors.initials: O
authors.lastname: Wolf
authors.forename: Peter
authors.initials: P
authors.lastname: Heider
authors.forename: Silvio
authors.initials: S
authors.lastname: Schaffner
authors.forename: Marc
authors.initials: M
authors.lastname: Gianotti
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmid
authors.forename: Dieter
authors.initials: D
authors.lastname: Liepsch
authors.forename: Hermann
authors.initials: H
authors.lastname: Berger
mesh_terms: D000497:Alloys; D001783:Blood Flow Velocity / Q000502:physiology; D019917:Blood Vessel Prosthesis Implantation; D002339:Carotid Arteries / Q000502:physiology* / Q000601:surgery; D018056:Hemorheology; D006801:Humans; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D008567:Membranes, Artificial; D011474:Prosthesis Design; D011673:Pulsatile Flow / Q000502:physiology; D013193:Stainless Steel; D015607:Stents
chemical_list: D000497:Alloys; D008567:Membranes, Artificial; D013193:Stainless Steel; C013616:nitinol