Computational Modeling of Stented Arteries: Considerations for Evolving Stent Designs
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Stents are small tubular structures that are inserted into the diseased regions of atherosclerotic arteries via a catheter. These devices are designed to prop the constricted passageway open. Clinical failures of stents occur mainly due to restenosis, which may be related to the mechanical conditions that they induce in the artery. Normal vessel response to stenting includes thrombus formation, inflammation, cell proliferation, and geometric remodeling, all of which depend on biomechanical factors. Recently developed drug-eluting stents target smooth muscle cell proliferation, and have been shown to reduce restenosis rates. The development of more effective drug-eluting and bare metal stent designs can be achieved with the continued development of realistic models. Computational modeling of stented arteries is a powerful tool that provides a means to examine issues such as efficiency of drug delivery and the stress field induced in the artery wall. Early models revealed the stress concentrations near the ends of a stent that result from the mismatch in compliance between the relatively rigid stent and the more compliant artery. This led to the design of a stent that provides gradual transitions in compliance at the ends of the stent (Compliance Matching Stent, or CMS). Computational models have shown that the CMS reduces stress concentrations. Computational models of the drug transfer into the artery wall from drug-eluting stents demonstrate the importance of even vessel coverage in the deployment process. Experimental modeling has demonstrated that important events such as thrombus formation and re-endothelialization are mediated by flow patterns that depend on stent geometry. The temporal nature of these events in vivo has led to the development of the Hybrid Dynamic Stent (HDS). The HDS incorporates biodegradable components that allow the stent to change geometry on a timeline coincident with vessel responses to stenting. Employing computational models to develop this type of technology will require more sophisticated techniques than those presently in use. Ultimately, stent design goals should include minimizing the initial trauma induced by the therapy and maximizing the efficiency of vessel recovery. Realistic modeling will necessarily incorporate the target lesion, vessel damage resulting from the stenting process, the physiologic response to damage and the mechanical (fluid and solid) environment. With the application of rapid prototyping and the further development of modeling techniques, patient specific therapies derived from modeling efforts could be the treatment option of the future. © 2006 Springer-Verlag Berlin Heidelberg.
author list (cited authors)
Moreno, M. R., Bedoya, J., Meyer, C., & Moore, J. E.