Flow Velocities After Carotid Artery Stenting: Impact of Stent Design. A Fluid Dynamics Study in a Carotid Artery Model with Laser Doppler Anemometry
To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model.
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 μm. 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.
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.
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.
KeywordsCarotid flow model Experimental fluid dynamics Laser Doppler anemometry Experimental carotid artery stenting Stent design Stent membrane
This study was supported in part by the DFG under contract Li 256-49. Abbott Company provided us with the stent designs and application systems.
- 1.Barr, JD, et al. 2003Quality improvement guidelines for the performance of cervical carotid angioplasty and stent placementJ Vasc Interv Radiol14S321S335Google Scholar
- 2.Ahmadi, R, Willfort, A, Lang, A, et al. 2001Carotid artery stenting: Effect of learning curve and intermediate-term morphological outcomeJ Endovasc Ther8539546Google Scholar
- 3.Veith, FJ, Amor, M, Ohki, T, et al. 2001Current status of carotid bifurcation angioplasty and stenting based on a consensus of opinion leadersJ Vasc Surg3311116Google Scholar
- 4.Wholey, MH, Wholey, M 2003Current status in cervical carotid artery stent placementJ Cardiovasc Surg44331339Google Scholar
- 5.Ku, DN, Giddens, DP 1985Hemodynamics of the normal human carotid bifurcation: In vitro and in vivo studiesUltrasound Med Biol111326Google Scholar
- 6.Kerber, CW, Liepsch, D 1994Flow dynamics for radiologists. I. Basic principles of fluid flowAJNR Am J Neuroradiol1510651075Google Scholar
- 7.Kerber, CW, Liepsch, D 1994Flow dynamics for radiologists. II. Practical considerations in the live humanAJNR Am J Neuroradiol1510761086Google Scholar
- 8.Greil, O, Pflugbeil, G, Weigand, K, Weiss, W, Liepsch, D, Maurer, PC, Berger, H 2003Changes of carotid artery flow velocities after stent implantation: A fluid dynamics study with laser-Doppler-anemometryJ Endovasc Ther10275284Google Scholar
- 9.Müller-Hülsbeck, S, Jahnke, T, Stolzmann, P, Paulsen, F, Wenke, R, Heller, M 2003A new concept for covered stent protected carotid angioplasty: An ex vivo studyRoFo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr17516341638Google Scholar
- 10.Liepsch, D, Moravec, St, Baumgart, R 1992Some flow visualization and laser Doppler-velocity measurements in a true-to-scale elastic model of a human aortic arch. A new model techniqueBiorheology29563580Google Scholar
- 11.Ohki, T 2003The dark side of embolic protection devicesEndovasc Today95460Google Scholar
- 13.Glagov, S, Zarins, C, Giddens, DP, Ku, DN 1988Hemodynamics and atherosclerosis. Insights and perspectives gained from studies of human arteriesArch Pathol Lab Med11210181031Google Scholar
- 14.Ma, P, Li, X, Ku, DN 1997Connective mass transfer at the carotid bifurcationJ Biomech30565571Google Scholar
- 15.Zhao, SZ, Xu, XY, Hughes, AD, Thom, SA, Stanton, AV, Ariff, B, Long, Q 2000Blood flow and vessel mechanics in a physiologically realistic model of a human carotid arterial bifurcationJ Biomech33975984Google Scholar
- 16.Davies, PF 1995Flow-mediated endothelial mechanotransductionPhysiol Rev75519551Google Scholar
- 17.Davies, PF 1997Mechanisms involved in endothelial responses to hemodynamic forcesAtherosclerosis1311517Google Scholar
- 18.Davies, PF 1997Overview: Temporal and spatial relationships in shear stress-mediated endothelial signalingJ Vasc Res34208211Google Scholar
- 19.Barbee, KA, Davies, PF, Lal, R 1994Shear stress-induced reorganisation of the surface topography of living endothelial cells imaged by atomic force microscopyCirc Res74163171Google Scholar
- 20.Liepsch, DW, Pflugbeil, G, Maurer, PC, Weigand, C 1994LDA measurements in anatomically distensible carotid artery models under physiological conditionsLiepsch, DW eds. Biofluid mechanics. Proceedings of the 3rd International Symposium 17VDI Verlag, Reihe Biotechnik593602Google Scholar