Alterations in regional vascular geometry produced by theoretical stent implantation influence distributions of wall shear stress: analysis of a curved coronary artery using 3D computational fluid dynamics modeling

Ladisa, Olson, Douglas, Warltier, Kersten, Pagel

Description

The success of stent implantation in the restoration of blood flow through areas of vascular narrowing is limited by restenosis. Several recent studies have suggested that the local geometric environment created by a deployed stent may influence regional blood flow characteristics and alter distributions of wall shear stress (WSS) after implantation, thereby rendering specific areas of the vessel wall more susceptible to neointimal hyperplasia and restenosis. Stents are most frequently implanted in curved vessels such as the coronary arteries, but most computational studies examining blood flow patterns through stented vessels conducted to date use linear, cylindrical geometric models. It appears highly probable that restenosis occurring after stent implantation in curved arteries also occurs as a consequence of changes in fluid dynamics that are established immediately after stent implantation. Methods In the current investigation, we tested the hypothesis that acute changes in stent-induced regional geometry influence distributions of WSS using 3D coronary artery CFD models implanted with stents that either conformed to or caused straightening of the primary curvature of the left anterior descending coronary artery. WSS obtained at several intervals during the cardiac cycle, time averaged WSS, and WSS gradients were calculated using conventional techniques. Results Implantation of a stent that causes straightening, rather than conforms to the natural curvature of the artery causes a reduction in the radius of curvature and subsequent increase in the Dean number within the stented region. This straightening leads to modest skewing of the velocity profile at the inlet and outlet of the stented region where alterations in indices of WSS are most pronounced. For example, time-averaged WSS in the proximal portion of the stent ranged from 8.91 to 11.7 dynes/cm 2 along the pericardial luminal surface and 4.26 to 4.88 dynes/cm 2 along the myocardial luminal surface of curved coronary arteries as compared to 8.31 dynes/cm 2 observed throughout the stented region of a straight vessel implanted with an equivalent stent. Conclusion The current results predicting large spatial and temporal variations in WSS at specific locations in curved arterial 3D CFD simulations are consistent with clinically observed sites of restenosis. If the findings of this idealized study translate to the clinical situation, the regional geometry established immediately after stent implantation may predispose portions of the stented vessel to a higher risk of neointimal hyperplasia and subsequent restenosis.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2006
• Nombre de lectures: 5
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

BioMedical Engineering OnLine

BioMedCentral

Open Access Research Alterations in regional vascular geometry produced by theoretical stent implantation influence distributions of wall shear stress: analysis of a curved coronary artery using 3D computational fluid dynamics modeling 1,2,5 5 2 John F LaDisa jr , Lars E Olson , Hettrick A Douglas , 2,3,4,5 2,4 2,5 David C Warltier , Judy R Kersten and Paul S Pagel*

1 2 Address: Department of Pediatrics (Division of Cardiology), Stanford University, Stanford, California, USA, Department of Anesthesiology, the 3 Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin, USA, Department of Medicine (Division of Cardiovascular Diseases), the Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs Medical Center, Milwaukee, 4 Wisconsin, USA, Department of Pharmacology and Toxicology, the Medical College of Wisconsin and the Clement J. Zablocki Veterans Affairs 5 Medical Center, Milwaukee, Wisconsin, USA and Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, USA Email: John F LaDisa  [e-mail]; Lars E Olson  [e-mail]; Hettrick A Douglas  [e-mail]; David C Warltier  [e-mail]; Judy R Kersten  [e-mail]; Paul S Pagel*  [e-mail] * Corresponding author

Published: 16 June 2006 Received: 17 February 2006 Accepted: 16 June 2006 BioMedical Engineering OnLine2006,5:40 doi:10.1186/1475925X540 This article is available from: http://www.biomedicalengineeringonline.com/content/5/1/40 © 2006 LaDisa et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Background:The success of stent implantation in the restoration of blood flow through areas of vascular narrowing is limited by restenosis. Several recent studies have suggested that the local geometric environment created by a deployed stent may influence regional blood flow characteristics and alter distributions of wall shear stress (WSS) after implantation, thereby rendering specific areas of the vessel wall more susceptible to neointimal hyperplasia and restenosis. Stents are most frequently implanted in curved vessels such as the coronary arteries, but most computational studies examining blood flow patterns through stented vessels conducted to date use linear, cylindrical geometric models. It appears highly probable that restenosis occurring after stent implantation in curved arteries also occurs as a consequence of changes in fluid dynamics that are established immediately after stent implantation.

Methods:In the current investigation, we tested the hypothesis that acute changes in stent induced regional geometry influence distributions of WSS using 3D coronary artery CFD models implanted with stents that either conformed to or caused straightening of the primary curvature of the left anterior descending coronary artery. WSS obtained at several intervals during the cardiac cycle, time averaged WSS, and WSS gradients were calculated using conventional techniques.

Results:Implantation of a stent that causes straightening, rather than conforms to the natural curvature of the artery causes a reduction in the radius of curvature and subsequent increase in the Dean number within the stented region. This straightening leads to modest skewing of the velocity profile at the inlet and outlet of the stented region where alterations in indices of WSS are most pronounced. For example, timeaveraged WSS in the proximal portion of the stent ranged 2 2 from 8.91 to 11.7 dynes/cm along the pericardial luminal surface and 4.26 to 4.88 dynes/cm along

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