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CARDIOLOGY

The origin of coronary stents and present life

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Expert introduction: Xia Wei Chengdu Third People’s Hospital, Department of Cardiology, deputy chief physician is mainly engaged in clinical, coronary heart disease, interventional therapy and other fields of research work.He is good at clinical diagnosis and treatment of cardiovascular diseases, and has rich clinical experience in the diagnosis and treatment of common cardiovascular diseases, frequently-occurring diseases and difficult diseases.According to the summary of the 2017 China Cardiovascular Disease Report, China’s cardiovascular disease prevention and treatment work has achieved initial results, but the prevalence, morbidity and even mortality of cardiovascular diseases are increasing year by year, and they are stable in various diseases.The first place in the incidence rate poses a serious threat to people’s physical health and life safety.Since 1977, Gruentzig of Switzerland has successfully completed the first percutaneous coronary angioplasty, which has created favorable conditions for the treatment of coronary atherosclerotic heart disease.At present, coronary interventional stenting has been widely recognized in clinical treatment for its minimally invasive, safe and effective, and is currently the most important and effective means for the treatment of coronary artery stenosis.Dilatation, and then the stent is implanted into the stenosis of the blood vessel to play the role of dredging the arterial blood vessels.However, due to the foreign body implantation and the inevitable damage to the blood vessels during the operation, the resulting stent thrombosis and restenosis are still urgent scientific problems to be solved, and the development history of the coronary stent will be briefly explained.The bare metal stent of the metal bare stent era is the first and first-generation coronary stent. Because of its good biological properties, it has strong corrosion resistance and small strain, which can improve the weight-remodeling of blood vessels and make the target vessels restenosis.The rate is reduced and is the earliest type of stent used in clinical coronary intervention.According to the shape, it can be divided into a tubular bracket, a wound bracket, a mesh bracket and a modular bracket; and the material can be divided into a nickel-titanium alloy bracket and a stainless steel bracket.The stent has axial flexibility, can pass smoothly in a coronary artery with a large branching angle and curved and detour, and its own hardness can resist the elastic force of the artery wall, and the blood vessel can be opened during the treatment process.It will not be retracted afterwards, and the stent has a longer life span.The emergence of metal-type bare stents is a rapid development in the treatment of coronary heart disease. The stent of this type is used in the expansion of a relatively simple balloon. The incidence of restenosis is reduced from 40% to 50%.15% to 25%.It was first reported in The New England Journal of Medicine in 1987.However, with long-term application observations, it has been found that the financial bare stent is prone to thrombosis in the interventional treatment, resulting in re-stenosis of the blood vessels.Mainly because metal ions are in direct contact with blood, it is easy to activate the blood coagulation system and platelets, resulting in acute thrombosis.According to relevant statistics, the probability of restenosis after bare stent is 30%~40%, which has been basically eliminated in clinical treatment, but for patients with high bleeding risk, patients who need other non-cardiac surgery in the short term, nakedThe stent has a short anti-shock time and is still an irreplaceable advantage.Bio-coated stents and drug-coated stents have been studied more and more with the in-situ stenosis caused by bare metal stents. The mechanism of continuous intimal hyperplasia has been widely recognized. In order to solve this problem, in order to effectively prevent and control financial ionsIn direct contact with the blood to cause thrombosis, the researchers thought of coating on the surface of the metal stent, thus forming a protective barrier between the stent and the blood vessel, and the bio-coating stent was born.Biocoated stents can be further divided into polymer coated stents, fibrin coated metal stents, and phosphorylcholine coated stents.Polymer-coated stents have good elasticity, less damage to blood vessels, and can reduce the formation of acute thrombosis; fibrin-coated metal stents help maintain the integrity of local vascular structures, significantly reduce the occurrence of restenosis, and fibrinIt has water solubility and biodegradability, so it can also be used as a carrier for administration; a phosphorylcholine-coated stent can effectively reduce adverse reactions such as thrombosis and protein adhesion.When biocoated stents are widely used in clinical practice, it has been found that although it can reduce the incidence of restenosis to a certain extent, it still stimulates local tissues and triggers inflammatory reactions.Therefore, on the basis of the bio-coated stent, a drug-eluting stent (DES) was invented, and a second-generation drug stent, that is, a drug coating on the basis of a metal stent, was applied to carry out anticoagulation and anti-tissue cells.Hyperplastic drugs.After the stent is implanted into the human body, the drug is slowly released, which can inhibit the growth of the scar tissue while keeping the coronary artery unblocked.Compared with the original metal-type bare stent, the drug-coated stent can greatly improve the anti-proliferative effect, and can achieve a good anti-inflammatory effect, reducing the probability of inflammatory reaction in patients.With the continuous advancement of medical technology, stent-loaded drugs and related technologies for drug control and release have been continuously improved and improved. The drug-coated stent can be used to mechanically support the diseased blood vessels while being able toThe release of the drug can inhibit the cell proliferation in the vascular smooth muscle, and play a certain role in the blood vessel wall that contacts the stent, which can well solve the problem of elastic retraction of the blood vessel and the endometrium.Hyperplasia plays a certain role in remodeling.Currently commonly used drug-coated stents include rapamycin coated stents and paclitaxel coated stents.With the continuous promotion of the use of drug-eluting stents, relevant clinical studies and data indicate that the mortality rate of coronary heart disease patients has increased during the use of the stents, and the safety of the stents has once again attracted widespread attention.The drug-coated stent itself and its polymer coating will remain in the human body for a long time without being absorbed, thereby affecting the vascularization of the blood vessel, thereby causing local thrombosis and inflammatory reaction and poor adhesion of the late stent, making the late or extremeThe increased incidence of late thrombosis is a serious problem that threatens the safety of patients.Therefore, the safety of clinical application of drug-coated stents has been a subject of debate.Biodesorbable scaffold (BRS) has been invented by researchers in the biodegradable stent drug-eluting stent because it eventually causes depletion of the patient.The fully degradable stent can support the vascular lumen like a bare metal stent in an effective time. After the acute phase has elapsed, the drug-coated stent can release relevant anti-proliferative drugs in the patient to prevent thrombosis.And the occurrence of restenosis, after the completion of the relevant treatment, can gradually degrade until completely disappeared, thereby effectively preventing and treating adverse reactions such as local inflammation and reducing the impact on the patient’s body.The complete absorption of the degradable stent, without the interference of permanent foreign matter, makes multiple treatments of the same lesion possible.Biodegradable stents are another major advance in the treatment of coronary heart disease, which can bring better therapeutic effects to patients with coronary heart disease.The biodegradable scaffolds that can be applied at present are degradable polymers (including poly-L-lactic acid, poly-d-lactic acid, polycaprolactone, polyglycolic acid and copolymers thereof) and degradable metals (magnesium alloys, ferroalloys).And zinc alloy, etc.) brackets.Polymer materials are limited in their application due to lack of development under X-rays, insufficient radial support strength, and poor deformability.And its mechanical properties are lower than that of metal materials. In order to improve the mechanical support force of the polylactic acid stent, it is usually necessary to increase the thickness of the stent beam, but this will affect the implantation effect.The use of degradable iron stents for treatment can prevent clogging due to adverse events such as local inflammatory reactions, thrombosis or intimal hyperplasia, and thus has better safety.However, the stent also has shortcomings, mainly because the degradation rate is too slow, and further research is needed in this aspect.The degradable magnesium stent is mainly made of medical special magnesium alloy material. Compared with other medical metal materials, the magnesium alloy has the following advantages: 1 high biosafety.Magnesium ions are intracellular cations and play an important role in the body’s metabolism.2 biodegradability.Magnesium alloys are easily degraded in body fluids.3 no magnetic, will not interfere with CT and MRI examination.4 excellent mechanical properties.The mechanical properties of magnesium alloys such as elastic modulus, tensile strength and plasticity are superior to those of polymer materials.5 resources are abundant and the price is low.The degradable magnesium scaffold is completely degraded for a shorter period of time than the degradable polymer scaffold and is fully degradable in about 4 h.However, it can have the disadvantage of being easily corroded.Therefore, in order to improve its corrosion resistance, it is usually necessary to achieve corrosion resistance by micro-arc oxidation, addition of other elements, surface coating of polymers, and the like.Micro-arc oxidation is a technique that mainly deals with the surface of degradable magnesium scaffolds, and produces a highly corrosion-resistant ceramic coating on its surface.Applying a polymer coating to the surface of the degradable magnesium stent can effectively reduce the corrosion rate of the stent and prevent corrosion from being too fast.Due to the continuous advancement of surface treatment technology for degradable magnesium stents, it has broad application prospects in replacing traditional stent materials in the future.The use of biodegradable materials in scaffolds is epoch-making.The vessel of the stenosis is supported by a stent that can be completely degraded for a predetermined period of time and then completely absorbed by the body.This is a qualitative leap compared to the transformation of traditional metal brackets.However, the degradation time of degradable stents lacks an exact standard.If the degradation time is too short, elastic retraction may occur, and the probability of stenosis will increase greatly.If the degradation time is too long, the intimal hyperplasia may be excessive in the stent, and the possibility of stent thrombosis may increase.The drug-coated degradable stent can inhibit intimal hyperplasia, but the release rate and duration of the drug and the degradation rate of the stent still need to find a balance point.Otherwise, the promotion of degradable stents may still be limited..
The safety of bioabsorbable stents is of great concern to us. Some recent studies have not been satisfactory, especially in the early stent thrombosis rate. The meta-analysis showed that stent thrombosis occurred in the bioabsorbable stent group.The rate is significantly higher than the traditional drug-coated stent.In a meta-analysis, a total of 10510 patients were enrolled, of whom 2159 were implanted with drug-eluting stents and 8351 were implanted with bioabsorbable stents. The study found that patients in the bioabsorbable stent group compared with patients in the drug-eluting stent group.The incidence of late stent thrombosis was significantly increased.Therefore, although the bioresorbable stent has been marketed in Europe, the current research suggests that the bioabsorbable stent may have problems such as a higher risk of late stent thrombosis and a “collapse” of the stent due to the unsynchronized absorption of the stent itself. Based on this, the US FDAOn March 18, 2017, a warning was given to the black frame of the degradable stent produced by Abbott.Since then, Poco has decided to abandon the project of bioresorbable stents under study.Also based on patient safety considerations, in September 2017, Abbott, the largest producer of bioabsorbable stents, announced that it would stop the sale of all clinically degradable stents. The decision of the two companies will undoubtedly give way to the exploration stage.Bioabsorbable stents have a huge negative effect, and bioabsorbable stents have a longer way to go for clinical use.Conclusion The coronary stent has gone through a long process from conception to manufacturing to practical application. Under the background of economic development and continuous advancement of science and technology, coronary stent technology has been continuously improved and developed from the initial development of bare metal stents.Up to now, the biodegradable stent has been continuously breakthrough and developed in terms of technology and safety, and has brought good effects to the treatment of coronary artery disease.However, the realization of “interventional non-implantation” revascularization is an ideal. Any new technology will experience almost complete setbacks in the exploration and the process of continuous improvement.We are looking forward to the biodegradable stent and calmly thinking. We believe that there is a lot of room for improvement, both in terms of the product itself and the operation technology and the exploration of applicable lesions.The development of biodegradable stents is more than just the development of a new stent. In addition to the innovation of materials science, multidisciplinary cooperation and comprehensive technical exploration are needed.

ouyangshaoxia

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