Contact Simulation And Hemodynamic Analysis Of The Coronary Stent In Curved Blood Vessels

In reality,the blood vessels are often curved,and long straight blood vessels exist only in the ideal state.At the same time,implanting the stent in curved vessels is clinically challenging.It is often accompanied by plaque prolapse and stroke complications that eventually lead to In-Stent Restenosis(ISR).Therefore,it is practical and very useful to study the stress deformation of stent implantation in curved blood vessels.However,at present,in the simulation of stent implantation,the simulated blood vessels are usually straight and the curved blood vessels are not considered.In order to make the simulation results reliable,the simulation model should be closer to the actual situation.Based on the Pro/E modeling software,this article establishes an "curved blood vessels-stent contact model" in which curved coronary arteries(30°?45°?60°,curved blood vessels)and stents(curved stents)are assembled closer to the actual situation.Based on the Ansys finite element simulation software,the "curved blood vessels-stent flow field model" was established through Boolean operations,meanwhile the contact simulation analysis and hemodynamic analysis were performed on these two models respectively.In the contact simulation analysis,for the sake of comparison,a model in which the long straight blood vessels in contact with the stent is established,ie,the straight blood vessels-stent contact model.The equivalent stress and displacement deformation data of the stent and blood vessels are compared in the two cases.It is concluded that the stent implanted in the curved blood vessels is more likely to fail than the straight blood vessels.This requires a higher support performance of the curved stent,especially on the inner side of the curved stent,which provides guidance for the optimal design of stent in the curved blood vessels.In order to reduce the damage to the blood vessel when the stent is in contact with the blood vessels,the flexibility of the curved stent is further studied based on the simulation analysis of the straight stent compliance.By simulating the model after implanting the blood vessels with good flexibility curved stents and poorly flexible curved stents,it was confirmed that the flexible stents can reduce the damage to the curved blood vessels and reduce the ISR.This provides a theoretical basis for the choice of clinical curved stent.In performing hemodynamic analysis,a flow field model in which a long straight blood vessel coupled to a stent was established,ie,a straight blood vessels-stent flow field model was used as a comparison.Through the flow simulation of the curved blood vessels-stent flow field model and the straight blood vessels-stent flow field model,the Wall Wear Stress(WSS)of the corresponding low WSS region is compared,ie the proportion of the WSS<0.5 Pa and the size of the flow resistance(FR).The following results are obtained:?The area of WSS<0.5 Pa accounted for 16.14%of the total area in the straight vessel-stent flow field model,while they are25.21%?28.65%?26.63%in the curved vessels-stent(30°?45°?60°).That means the rate of ISR in the curved vessels-stent were relatively high;? The Flow Resistance(FR)of the curved vessels-stent model(30°?45°?60°)was greater than that of the straight vessel-stent model[1.5 0,1.82,2.17,1.03 N · s2/(kg · m)].Which explained the relatively high rate of ISR in clinically curved blood vessels.In general,this article establishes "the curved blood vessels-stent contact model"and "the curved blood vessels-stent flow field model" that are closer to the actual situation,making the simulation results more reliable.Through the contact simulation analysis and hemodynamic analysis of these two models respectively,comparing the straight blood vessels,the stents implanted in the curved blood vessels were found to be more prone to failure,stabbing blood vessels and causing ISR.This requires an curved stent:?Higher support performance,especially on the inside of the curved stent;?Better flexibility to reduce the stent's damage to blood vessels;?Reduce the low WSS zone in the curved blood vessels after stent implantation,especially on the inside of the curved stent.These will provide important guidance for the optimal design of the curved stent and provide a theoretical basis for the selection of the curved stent in clinical practice.