Computational fluid dynamics estimations of wall shear stress alterations influencing neointimal hyperplasia after stent implantation
Cardiovascular disease is a leading cause of mortality throughout the world and over one million stents are deployed annually to treat this pathology. Unfortunately, 30% of patients experience persistent narrowing of the stented region (restenosis) within six months due to neointimal hyperplasia (NH). Rates of restenosis vary with stent design and stent geometry has been identified as an important predictor of NH. Vascular geometry influences local wall shear stress (WSS) distributions as branching and curvature threaten the preferential flow environment of intravascular cells and correlate with sites of NH. Stent deployment also causes vascular damage and recent data indicates that WSS mediates the rate and location of cellular proliferation after vascular injury. Therefore, this investigation tested the hypothesis that alterations in distributions of WSS unique to the geometry of the stented portion of a vessel correlate with NH using a chronic model of stent implantation in vivo and computational fluid dynamics (CFD) modeling. The iliac artery blood flow environment 14 and 21 days after stent implantation was obtained by 3D microfocal x-ray computed tomography imaging and reconstruction of rabbit iliac arteries, and WSS determined using CFD. NH was localized to the stented region as revealed by histology. Indices of WSS were inversely related to NH. Lowest values of WSS localized to the stented area of a theoretical artery after acute implantation were incrementally increased after 14 and 21 days as NH formed within this region. Additional CFD models demonstrated that stent properties including deployment diameter, flexibility, length, stent-induced vascular deformation and strut number, width and thickness also adversely influenced indices of WSS. These results indicate that stent implantation introduces spatial and temporal alterations in WSS unique to the geometry of an implanted stent in vivo . Identifying perturbations in vascular geometry and WSS after stent placement may help delineate mechanisms associated with NH, stimulate the development of new stent designs and novel drug coatings, enhance overall stent performance and ultimately contribute to a lower rate of restenosis.
LaDisa, John F., "Computational fluid dynamics estimations of wall shear stress alterations influencing neointimal hyperplasia after stent implantation" (2004). Dissertations (1962 - 2010) Access via Proquest Digital Dissertations. AAI3153714.