Abstract
Recent concern for local drug delivery and withdrawal of the first Food and Drug Administration-approved bioresorbable scaffold emphasizes the need to optimize the relationships between stent design and drug release with imposed arterial injury and observed pharmacodynamics. In this study, we examine the hypothesis that vascular injury is predictable from stent design and that the expanding force of stent deployment results in increased circumferential stress in the arterial tissue, which may explain acute injury poststent deployment. Using both numerical simulations and ex vivo experiments on three different stent designs (slotted tube, corrugated ring, and delta wing), arterial injury due to device deployment was examined. Furthermore, using numerical simulations, the consequence of changing stent strut radial thickness on arterial wall shear stress and arterial circumferential stress distributions was examined. Regions with predicted arterial circumferential stress exceeding a threshold of 49.5 kPa compared favorably with observed ex vivo endothelial denudation for the three considered stent designs. In addition, increasing strut thickness was predicted to result in more areas of denudation and larger areas exposed to low wall shear stress. We conclude that the acute arterial injury, observed immediately following stent expansion, is caused by high circumferential hoop stresses in the interstrut region, and denuded area profiles are dependent on unit cell geometric features. Such findings when coupled with where drugs move might explain the drug–device interactions.
Highlights
The proliferation of drug-eluting stent designs has been accompanied by the need to understand more fully the relationship between stent design and acute arterial injury [1]
finite element analysis (FEA) predictions were investigated as to whether high tensile hoop stress in the interstrut region correlated with sites of endothelial denudation
The predictions were compared with representative histological stains for endothelial denudation relating to the deployment of each stent design
Summary
The proliferation of drug-eluting stent designs has been accompanied by the need to understand more fully the relationship between stent design and acute arterial injury [1]. Arterial geometry is an issue for all aspects of the interaction between stent, drug elution, and vascular response to injury. Understanding the relationship between stent design and acute arterial injury has become. Stent-Induced Vascular Injury even more vital as the number of patients receiving these endovascular implants increases [>3 million globally annually [2]]. The precise interaction of acute vascular injury and stent geometrical features that may control this biological response is understudied. Understanding the precise mechanical initiators of acute vascular injury may permit control of these variables for optimal drug delivery and directly guide the design and evaluation of stent geometries that minimize undesired mechanical injury [9]. Several different mechanisms of injury have been reported including chronic stress from the stent struts normal to the vessel resulting in partial laceration [10], chronic changes in surface shear stress from altered blood flow that may trigger maladaptive remodeling [11, 12], and scraping of the vessel wall at the ends of the stent caused by end-first expansion [13]
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