Alterations in wall shear stress predict sites of neointimal hyperplasia after stent implantation in rabbit iliac arteries

Abstract

Rates of restenosis vary with stent geometry, but whether stents affect spatial and temporal distributions of wall shear stress (WSS) in vivo is unknown. We tested the hypothesis that alterations in spatial WSS after stent implantation predict sites of NH in rabbit iliac arteries. Antegrade iliac artery stent implantation was performed under angiography, and blood flow was measured before casting 14 or 21 days after implantation. Iliac artery blood flow domains were obtained from three-dimensional microfocal X-ray computed tomography imaging and reconstruction of the arterial casts. Indexes of WSS were determined using three-dimensional computational fluid dynamics. Vascular histology was unchanged proximal and distal to the stent. Time-dependent NH was localized within the stented region and was greatest in regions exposed to low WSS and acute elevations in spatial WSS gradients. The lowest values of WSS spatially localized to the stented area of a theoretical artery progressively increased after 14 and 21 days as NH occurred within these regions. This NH abolished spatial disparity in distributions of WSS. The results suggest that stents may introduce spatial alterations in WSS that modulate NH in vivo.computational fluid dynamics; restenosis; computational modeling; computed tomography; image reconstruction; wall shear stress RESTENOSIS after stent implantation remains a persistent clinical problem (1,6,8,28,40,45). The mechanisms of restenosis are incompletely understood, but direct endothelial and smooth muscle cell damage, reduced compliance, and alterations in the distributions of wall shear stress (WSS) within the stented region have been implicated as potential triggering events that stimulate neointimal hyperplasia (11,19,44,47). Vascular damage to the vessel during implantation may be minimized by using an appropriate stent-to-artery deployment ratio (11,46). The rigid framework of the stent causes differences in compliance between the stented and native regions of the artery, but this stent rigidity provides structural scaffolding that is associated with reduced restenosis rates compared with angioplasty alone (4,8). Novel stent designs that reduce compliance mismatch at the proximal and distal edges of the stent have also been developed (2). Previous studies have suggested that there may be a correlation between stent-induced alterations in WSS and neointimal hyperplasia during pathological processes including primary atherogenesis and restenosis after angioplasty (17,18,20,21,30). However, few studies have examined detailed time-and space-dependent distributions of WSS or attempted to correlate these alterations in WSS with neointimal hyperplasia after stent implantation in vivo. Moreover, it is well known that restenosis varies with stent geometry (11,32,35,50), but the geometric influence of stent properties on spatial and temporal WSS patterns has not been thoroughly investigated. Thus we tested the hypothesis that local alterations in spatial WSS associated with stent implantation temporally pr...

Sequential Structural and Fluid Dynamics Analysis of Balloon-Expandable Coronary Stents: A Multivariable Statistical Analysis

“…Following coronary stent deployment, sites of aggressive neointimal hyperplasia also correspond to sites subjected to non-physiological flow conditions, and this has been attributed to increased endothelial dysfunction and permeability. 6,17,18,20,21,52,71,79,88 The hemodynamic impact of the investigated stents was evaluated in terms of the relative residence time distribution predicted upon the lumen surface during the third cardiac cycle. The RRT accounts for temporal variations in both the magnitude and the orientation of the instantaneous wall shear stress vector and is calculated as follows:…”

“…6,17,18,20,21,52,71,79,88 In light of these observations, a significant body of research has been carried out in this area. Due to the difficulty involved in the evaluation of these phenomena in an in vivo setting however, a large portion of this research has been carried out using computational methods of analysis.…”

Wall Shear Stress in Intracranial Self-Expanding Stents Studied Using Ultra-High-Resolution 3D Reconstructions

“…The importance of even minor asymmetries in stent deployment has been clearly demonstrated in vascular cross-sections from high-resolution histologic studies (LaDisa et al, 13 …”

“…11 Recent computational hemodynamic (CHD) studies on the effects of stents on arterial hemodynamics have generally used idealized mathematic modeling of the artery and superimposed stent. [12][13][14][15][16][17] These simulations have provided some useful information about the local WSS behavior near the struts and cell centers as a function of strut dimensions, stent porosity, and flow rates. Although more detailed analysis of flow over stent struts has been undertaken by using 2D models, 18 which have also been used to predict deposition rates for drug-eluting stents, 19 the importance of 3D hemodynamic behavior near the struts and wall has recently been recognized.…”

Computational replication of the patient-specific stenting procedure for coronary artery bifurcations: From OCT and CT imaging to structural and hemodynamics analyses

“…A number of studies proved that neointima thickening (NT), which can lead to in-stent restenosis, is related to increased wall stress poststenting (Timmins et al, 2011) and to altered local fluid dynamics (e.g. low and oscillating wall shear stress; WSS) provoked by the stent presence within the coronary artery (LaDisa et al, 2005 andMalek et al, 1999).…”