Research On Structure Optimization And Mechanical Properties Of Coronary Stents

With the improvement of people’s quality of life,the incidence of coronary heart disease has been at a high level for many years.As an important implanted device of Percutaneous Transluminal Coronary Angioplasty,the research of the mechanical properties of coronary stent have become one of the key factors that determine the therapeutic effect of surgery.The processes of stenting are as follows: Firstly deliver the stent crimped into the micro-catheter to the vascular lesion site along the bending blood vessel,and then expand the stent by pressuring the balloon to resist the press from atheromatous plaque.Because of the different structural performance requirement of the above stages,various factors need to be taken into account in the exploiture process of stents.To propose the optimization model,the following work is carried out in this paper:1.Discussion and comparison of finite element modeling methodsA single stent model with direct load applied on the stent and an integrative model considering the influence of balloon and catheter are respectively established.And then,the finite element method is used for studing the mechanical properties of cobalt-chromium alloy bare stent Ⅱ-38 by above models.As a result,the experimental results show that the integrative model is more accurate,which could be regarded as a reference for method selection.2.Study on the effect of strut parameters on the mechanical properties of stentsStrut is the main part of supporting the blood vessel in the coronary stent.This paper researches the effect of strut parameters on the mechanical properties of stents taking strut number and strut length as variables.Result shows that the stent with more struts or longer strut has smaller plastic deformation,lower stress level,a better shortening rate performance of axial length and better expansion inhomogeneity.Among them,the influence of strut number on axial shortening rate is relatively significant.On the contrary,the recoil rate performance of radial diameter and the radial support capacity of above stents are weakened.Furthermore,Changes in strut parameters have little effect on the flexibility of the stent,so that the optimization of this performance should be considered from the change of link.3.Study on the effect of link form on the mechanical properties of stentsLink is the important part of connecting struts together.In this paper,three kinds of stents with different link forms(“I” style,“C” style and “S” style)are modeled.The results indicated that the stent with “C” link and “S” link has a better performance of flexibility.What’s more,the stent with “C” link has a better shortening rate performance of axial length,so that it is easier to locate in the lesion site.Besides,other performances are not significantly affected by link forms.4.Proposing optimization model and performance analysisProposing the optimization model using the rules summarized above as evidence,then,researching the stress distribution and performance indexes of the stent using finite element method.After that,by comparing with the data results of other stents,advantages of the optimization model are verified.Furthermore,Goodman chart method is used to prove that the fatigue life of the scaffold meets the service requirements.To sum up,this paper can be regarded as a reference for the optimal design of coronary stent.