Abstract
Aim: This paper aims to compare the mechanical performance of metallic (Xience) and bioresorbable polymeric (Elixir) stents during the process of crimping and deployment. Methods: Finite element software ABAQUS was used to create the geometrical models and meshes for the balloon, stent and diseased artery. To simulate the crimping of stents, 12 rigid plates were generated around the stent and subjected to radially enforced displacement. The deployment of both stents was simulated by applying internal pressure to the balloon, where hard contacts were defined between balloon, stent and diseased artery. Results: Elixir stent exhibited a lower expansion rate than Xience stent during deployment. The stent diameter achieved after balloon deflation was found smaller for Elixir stent due to higher recoiling. Lower level of stresses was found in the plaque and artery when expanded by Elixir stent. Reduced expansion, increased dogboning and decreased vessel stresses were obtained when considering the crimping-generated residual stresses in the simulations. Conclusion: There is a challenge for polymeric stents to match the mechanical performance of metallic stents. However, polymeric stents impose lower stresses to the artery system due to less property mismatch between polymers and arterial tissues, which could be clinically beneficial.
Highlights
Coronary interventionalists have been asking for stents designed with thinner struts
Medtronic has reduced strut dimensions for each new generation of modular stents, with the S7 stent representing the ultimate in strut thinness attainable in a 316L stainless steel design
Achieving even thinner struts required challenging the fundamental aspects of modular stent design and replacing 316L stainless steel with a cobalt-based alloy that offers several important advantages
Summary
The introduction of the Driver Coronary Stent marks the first use of a cobalt-based alloy in a modular stent design. Why did Medtronic choose a cobalt-based alloy for its new Driver Coronary Stent?. Medtronic has reduced strut dimensions for each new generation of modular stents, with the S7 stent representing the ultimate in strut thinness attainable in a 316L stainless steel design. Achieving even thinner struts required challenging the fundamental aspects of modular stent design and replacing 316L stainless steel with a cobalt-based alloy that offers several important advantages. The alloy is denser than 316L stainless steel, such that good radiopacity is maintained despite the thinner strut dimensions. Superb vessel support and good radiopacity, the Driver design is the foundation for the Medtronic drug-eluting stent program
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