Polymeric Textile Stents: Prototyping and Modeling
Type of DegreeDissertation
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Although metal stents have been implanted for more than a decade, performance deficiencies still exist. The current study focuses on prototyping and modeling of braided structures to be used as stents, hence called ‘textile stents’. Textile stents are self-expanding stents. The objective is to establish guidelines for commercial manufacturing of textile stents which can become major substitutes for metal stents. Textile stents and bifurcated textile stents were manufactured. Manufacturing variables braid angle, braid diameter, and heatset time had statistically significant effects (p= 0.0001) on the compression force of textile stents. A chart is compiled which categorizes factors affecting the performance of textile stents. Strong correlation (adjusted R2= 0.9999) between radial and in vitro (unidirectional) compressions of textile stents was observed. Agreement between values of Young’s modulus of textile stents derived by the mechanical model (strain energy method) to those of the experimental was good (adjusted R2= 0.7955). Stress-strain curves were obtained by strip testing of textile stents on an Instron®. The empirical model showed strong correlation between theoretical and experimental values of compression force for 1.27 cm (adjusted R2= 0.8669) and 1.9 cm (adjusted R2= 0.9251) diameter textile stents. Two-Factor ANOVA showed statistically significant effect (p = 0.00051 for 0.4 cm artery diameter, p = 0.00013 for 0.8 cm artery diameter, p = 0.01716 for 1.2 cm artery diameter, p = 0.01240 for 1.6 cm artery diameter, p = 0.0309 for 2.5 cm artery diameter) of blood input velocity on exit velocity, determined by Ansys® FLOTRAN. Monofilament denier also showed statistically significant effect (p = 0.04395 for 0.4 cm, p = 0.03814 for 0.8 cm, p = 0.01491 for 1.2 cm) on exit velocity for all mentioned artery diameters except 1.6 and 2.5 cm. Textile stent entrance and exit effects and blood flow behavior in textile stented artery segment were helpful in understanding restenosis. Application of textile stents as substitute to metal stents is feasible. KEYWORDS: Vascular disease, angioplasty, stent, restenosis, prototypes, monofilaments, in vivo and in vitro tests, braiding, strain energy method, Castigliano’s theorem, empirical model, entrance and exit effects, platelets (thrombocytes), platelet plug formation. DISCLAIMER The results and applications are valid and limited only to this study. Author makes no representation, promise, or implies warranty concerning the suitability of ‘textile stents’ for implantation in any living organism. Author has no control over the information given in references and can not be held responsible for their content and authenticity.