Coronary stent with section length gradual change structure

Abstract

The invention provides a coronary stent with a gradually-changed section length structure, which adopts a degradable zinc-based material matrix and comprises the following components in percentage by mass: 0.4-0.1% of Li, 0.8-0.05% of Mn and the balance of zinc. A degradable polymer or a metal coating with drugs can be arranged on the surface of the stent base body. The stent base body is of a cylindrical net-shaped structure with gradually-changed section lengths, and the difference between the adjacent section lengths is 1-5 microns. The stent with the structure can effectively reduce the expansion speed of the stent along with the deformation of the balloon, so that the stent is stressed more uniformly in the expansion process, the influence of the dog bone effect on the stent is reduced, and the stability and the safety of the stent are improved. The preparation method comprises the steps of pipe drawing, laser cutting, cleaning, coating, electrolytic polishing, heat treatment and the like. The stent disclosed by the invention has good biocompatibility, flexibility and radial supporting force, is suitable for vascular interventional therapy, is beneficial to vascular recovery and reconstruction, and is degraded after vascular repair is completed.

Description

Technical Field

[0001] The present application relates to the technical field of medical metal materials, and in particular to a coronary stent with a gradually varying segment length structure. Background Art

[0002] Coronary heart disease is often treated clinically with percutaneous coronary intervention (PCI), which typically includes balloon angioplasty and stent implantation. Over the decades, vascular interventional angioplasty technology has continued to evolve, from balloon angioplasty to bare metal stents, to drug-eluting stents, and finally to the biodegradable stents currently under research.

[0003] Currently, biodegradable coronary stents are considered ideal stents and are divided into two main categories: biodegradable polylactic acid stents and biodegradable metal stents. Current research focuses on biodegradable metals, such as iron alloys and magnesium alloys. Zinc alloys are a new type of biodegradable biomedical material due to their excellent biocompatibility, degradation properties, and mechanical strength.

[0004] Although zinc alloy has good biocompatibility, it exhibits a "work softening" phenomenon during plastic deformation. That is, when zinc alloy is plastically deformed, the dislocation density decreases and the grains may recrystallize, resulting in a reduction in internal stress and a decrease in hardness and strength. This work softening behavior causes a series of problems in zinc alloy coronary stents, such as the inability to firmly fix the stent on the balloon during compression and gripping, easy displacement during implantation, poor wall adhesion after expansion, and even stress concentration and stress corrosion, which may lead to early failure of the stent. In addition, zinc alloy stents are prone to the "dog bone effect" during balloon expansion. That is, at the maximum filling pressure, the diameters of the proximal and distal ends of the balloon are larger than the diameters of the proximal and distal ends of the stent, resulting in uneven force on the stent, further exacerbating stress concentration and the risk of fracture. These problems seriously affect the stability and safety of the stent. Summary of the Invention

[0005] To address these issues, the present invention provides a coronary stent with a tapered segment length structure. This structure features relatively long segments at the distal end (i.e., the second and third sections) and shorter segments at the proximal end (i.e., the first section), creating a gradual transition that effectively mitigates the dog-bone effect during balloon expansion. This coronary stent not only overcomes the non-degradability and long-term complications of traditional permanent metal stents, such as their presence as a foreign body, but also addresses the softening issue of zinc alloys during processing, significantly improving the stability and safety of the coronary stent during its service life.

[0006] The present invention provides a coronary stent with a segment length gradient structure, comprising: A plurality of annular segments connected to each other, wherein the plurality of annular segments are divided into a first portion, and a second portion and a third portion located on opposite sides of the first portion; wherein the first portion comprises a plurality of first annular segments, the second portion comprises a plurality of second annular segments, and the third portion comprises a plurality of third annular segments; In the axial direction of the coronary stent with a gradual segment length variation structure, the segment lengths of the plurality of first annular segments are equal; In the axial direction from the second portion to the first portion, the segment lengths of the plurality of second annular segments gradually decrease; in the axial direction from the third portion to the first portion, the segment lengths of the plurality of third annular segments gradually decrease; Furthermore, in the axial direction of the second part toward the first part, the difference in section length between the i-th second annular section length and the i+1-th second annular section length in the second part is equal to the difference in section length between the i-th third annular section length and the i+1-th third annular section length in the third part.

[0007] Optionally, in the axial direction from the second portion toward the first portion, the difference in length between every two adjacent second annular segments is equal; Furthermore, in the axial direction from the third portion toward the first portion, the length differences between every two adjacent third annular segments are equal.

[0008] Optionally, the section length difference is 1 μm-5 μm.

[0009] Optionally, the first portion includes two of the first annular segments; The second portion includes the same number of the second annular segments as the third portion includes the third annular segments.

[0010] Optionally, in the axial direction of the coronary stent with a gradually varying segment length structure, the length of the coronary stent with a gradually varying segment length structure is 9.985 mm-10.015 mm.

[0011] Optionally, in the radial direction of the coronary stent with a gradual segment length structure, the first annular segment length, the second annular segment length and the third annular segment length are the same in size, and the size is 80 μm-100 μm.

[0012] Optionally, the coronary stent with a gradient segment length structure includes 8-10 annular segments.

[0013] Optionally, the material of the coronary stent with a gradient length structure includes zinc, lithium and manganese; The mass percentage of lithium is 0.3%-0.5%, and the mass percentage of manganese is 0.75%-0.85%.

[0014] Optionally, the coronary stent with a gradient segment length structure further comprises a degradable coating, wherein the degradable coating is attached to outer surfaces of the first annular segment length, the second annular segment length, and the third annular segment length; The thickness of the coating is 10 μm-30 μm.

[0015] Optionally, the degradable coating is made of a degradable polymer material or a degradable metal; The degradable polymer material is selected from at least one of lactic acid, polyglycolide, polyanhydride, polylactic acid copolymer, polyglycolic acid, polyhydroxypentyl butyrate, polycyanoacrylate, natural degradable polymer materials collagen, gelatin, chitosan, rapamycin, paclitaxel, emodin, and curcumin; The degradable metal is magnesium, iron or zinc.

[0016] In summary, the present invention has at least the following beneficial technical effects: The present invention provides a coronary stent with a gradually changing segment length structure, comprising a plurality of annular segments, which are further divided into a first part, a second part and a third part, wherein the first part comprises a plurality of first annular segments with equal segment lengths, the second part comprises a plurality of second annular segments with gradually decreasing segment lengths, and the third part comprises a plurality of third annular segments with gradually decreasing segment lengths, forming a coronary stent with a gradually changing segment length structure. When the stent with this structure is expanded, the force applied to it gradually transitions from the middle to both ends, which can avoid sudden increases in local stress, make the stent more evenly stressed during the expansion process, reduce the influence of the dog-bone effect on the stent, and improve the stability and safety of the stent.

[0017] The second and third ring segments on both sides are gradually shortened towards the middle area, so that the deformation of both ends of the coronary stent becomes smoother during expansion, reducing excessive expansion of the proximal / distal ends of the balloon. The first ring segment of equal length in the middle can provide stable support, and the gradual ring segment lengths on both sides release pressure step by step to avoid tearing of the two ends of the coronary stent due to uneven expansion.

[0018] In addition, the setting of gradually shortening the annular segments on both sides in the axial direction forms a "step-like" friction interface between the coronary stent and the contact surface of the balloon, which helps to improve the gripping force during compression and prevent the coronary stent from slipping during transportation. In addition, by setting the difference in the annular segment lengths of the second part and the third part to be equal, it is ensured that the forces on both sides of the coronary stent are symmetrical when the coronary stent is expanded, preventing local fracture caused by unbalanced loads. In addition, the symmetrical segment length difference on both sides can also ensure that the coronary stent is subjected to balanced forces when it retracts, reducing displacement caused by asymmetric deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 The figure shows the processing softening curve of the zinc alloy bracket in the related art proposed in the embodiment of the present application; Figure 2 An electron microscope image of the zinc alloy stent after expansion in the related art proposed in the embodiment of the present application is shown; Figure 3 A schematic diagram showing a "dog bone effect" generated by a zinc alloy stent after expansion in the related art proposed in an embodiment of the present application is shown; Figure 4 A schematic diagram showing the fracture of a zinc alloy stent after expansion in the related art proposed in an embodiment of the present application is shown; Figure 5 It shows a schematic structural diagram of a coronary stent with a gradually varying length structure proposed in an embodiment of the present application; Figure 6 It shows a schematic structural diagram of a coronary stent with equal segment length structure proposed in an embodiment of the present application; Figure 7 A schematic diagram showing the structural comparison between a coronary stent with an equal segment length structure and a coronary stent with a segment length gradient structure proposed in an embodiment of the present application is shown; Figure 8 A flow chart of a method for preparing a coronary stent with a gradually varying segment length structure proposed in an embodiment of the present application is shown; Figure 9 A cross-sectional view of the pipe proposed in Example 1 of the present application is shown; Figure 10 A schematic diagram showing ultrasonic cleaning of the stent in Example 1 of the present application is shown; Figure 11 A schematic diagram showing the polishing process of the stent in Example 1 of the present application is shown; Figure 12 A schematic diagram of the vacuum heat treatment device proposed in Example 1 of the present application is shown; Figure 13 A comparison diagram of the expansion process of the stent structure in the related art proposed in Example 1 of the present application and the stent with a gradually varying length structure is shown.

[0021] Explanation of the accompanying drawings: 1. first part; 2. second part; 3. third part; 4. annular section length; 41. crest; 42. trough; 5. flexible connector. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] In the drawings, the sizes of components, layer thicknesses, or regions may be exaggerated for clarity. Therefore, any implementation of the present disclosure is not necessarily limited to the dimensions shown in the drawings, and the shapes and sizes of components in the drawings do not reflect true proportions. Furthermore, the drawings schematically illustrate idealized examples, and any implementation of the present disclosure is not limited to the shapes or values shown in the drawings.

[0024] Coronary heart disease is often treated clinically with percutaneous coronary intervention (PCI), which typically involves balloon angioplasty and stent implantation. Over the decades, vascular interventional angioplasty technology has continuously evolved, from balloon angioplasty to bare metal stents, to drug-eluting stents, and finally to the biodegradable stents currently under research.

[0025] Currently, coronary stents are primarily composed of high-strength, corrosion-resistant, inert alloys such as 316L stainless steel, cobalt-chromium, and nickel-titanium alloys. Metal stent implantation can provide adequate mechanical support to blood vessels, prevent negative vascular remodeling, and restore their normal blood transport function. However, permanent stent placement in stenotic vessels often requires long-term antiplatelet therapy to prevent thrombosis due to long-term biocompatibility between the stent and the vessel. This also carries other potential risks, such as late stent thrombosis, allergic reactions, and in-stent restenosis. Studies have shown that stenotic vessels typically complete repair and remodeling within 6-12 months. As a support device, vascular stents are not necessary for long-term maintenance after vessel dilation and remodeling. Therefore, considering long-term safety, biodegradable stents have been investigated as a novel vascular interventional treatment. Biodegradable stents theoretically restore vascular structure and function to their natural state and are considered the "fourth technological innovation" in coronary intervention, following balloon angioplasty, bare metal stents, and drug-coated stents. Ideally, a biodegradable stent would maintain its intact shape for 1-6 months after implantation, providing effective vascular support at the lesion site. Once revascularization is complete, degradation would begin in 6-12 months, accelerating in 12-18 months, ultimately leading to complete degradation. This would address the various shortcomings and complications of current permanent metal stents, such as intimal hyperplasia, inflammation, and restenosis.

[0026] An ideal biodegradable stent (BRS) temporarily supports diseased vessels to prevent acute closure or recoil. As the vessel structure and function gradually recover, the stent is gradually absorbed. The vessel is freed from the stent's constraints, regaining pulsation and completely eliminating the long-term risks associated with permanent metal stents. Degradable coronary stents are primarily classified into two categories: degradable polylactic acid (PLA) stents and degradable metal stents. However, some studies have shown that polymer-based degradable coronary stents may present safety issues during use. Polymer stents lack mechanical strength and are prone to elastic contraction, leading to high rates of restenosis. Furthermore, polymer stents take approximately three years to fully degrade in the human body. This prolonged degradation cycle leads to the accumulation of high-molecular-weight metabolites, which may trigger allergic inflammatory reactions and lead to adverse cardiac events. Clinical studies have shown that Abbott's first-generation bioresorbable stent (absorb GT1, a polylactic acid (PLA) everolimus-coated stent) performs inferior to conventional non-degradable stents in terms of device-related composite endpoints such as target vessel myocardial infarction and late and very late stent thrombosis. The company withdrew its product from the market 14 months after its launch. Therefore, current research focuses on biodegradable metals, such as iron alloys and magnesium alloys. Research on zinc is in its infancy and there is not much research data.

[0027] The present study found that the chemical activity of metallic Zn lies between that of Mg and Fe, with the standard electrode potentials of Mg, Fe, and Zn being -2.37 V (vs SCE), -0.440 V (vs SCE), and -0.763 V (vs SCE), respectively. Therefore, it can be inferred that the degradation rate of Zn is slower than that of Mg but faster than that of Fe. Zinc alloys are a novel biodegradable biomedical material due to their excellent biocompatibility, degradation properties, and mechanical strength. Zinc (Zn) is a competitive alternative to magnesium (Mg) and iron (Fe)-based alloys due to its ease of fabrication, optimal degradation rate, and biocompatibility, making it a promising alternative to biomedical applications such as stents, fracture fixation, or sutures. Zinc plays an important role in the structure and function of over 300 enzymes and other macromolecules. Zinc is a trace element necessary for the human body to maintain physiological functions. It is mainly found in muscles and bones and has osteogenesis and antibacterial effects. It is involved in almost all metabolic reactions, such as maintaining the normal activity of multiple enzymes, maintaining immune function, supporting the synthesis of proteins and DNA, etc. In addition, zinc plays an important role in cell division, cell growth, cell apoptosis regulation and wound healing.

[0028] The present invention further found that although zinc alloy has good biocompatibility, it generally has the phenomenon of softening during processing. Figure 1As shown. Usually, metals such as stainless steel will show the characteristics of "work hardening". Work hardening means that the strength and hardness of metal materials are improved during the plastic deformation process, while the plasticity and toughness decrease. The reason for this phenomenon is mainly because when the metal is plastically deformed, the grains slip, causing dislocations to entangle with each other, and changes in the grain structure such as elongation, crushing and fiberization, and the formation of residual stress inside the metal. On the contrary, work softening means that during the plastic deformation process, the dislocation density inside the material decreases, the grains may recrystallize, and then reduce the stress inside the material, reducing the hardness and strength.

[0029] The "process softening" behavior of zinc alloy can cause uneven deformation of the stent, which may manifest as the stent cannot be firmly fixed on the balloon when pressed and gripped. During the implantation and delivery process, the stent is easily displaced, resulting in failure to deliver to the correct lesion location where the support is to be released. It may also cause poor adhesion to the wall after the stent is expanded. Process softening is more likely to manifest as stress concentration and then cause stress corrosion, causing early failure of the stent during its service. The grain texture orientation of the zinc alloy stent after expansion can be seen through electron microscopy. Figure 2 As shown in the figure, some grains are oriented completely perpendicular to the direction of force, making them very susceptible to fracture during expansion. Vascular stents are very precise implantable devices, and this effect is undoubtedly fatal.

[0030] Because of this characteristic, the "dog bone effect" is very likely to occur during the process of using a balloon to expand zinc alloy biodegradable coronary stents. The dog bone effect has a greater impact on metals with processing softening characteristics. That is, when the stent delivery system is inflated to the maximum recommended filling pressure, the diameters of the proximal and distal ends of the balloon are larger than the diameters of the proximal and distal ends of the stent. This situation will cause uneven force on the stent, which can easily cause stress concentration in certain parts of the stent and then cause stress corrosion, which will subsequently lead to stent fracture and affect the service process of the stent. For reference, the dog bone effect during expansion Figure 3 As shown, the stent fracture reference Figure 4 shown.

[0031] Based on the content of related technologies, the present invention provides a coronary stent with a gradient segment length structure and a corresponding preparation method. The distal segment length of the stent with this structure is relatively long, and the middle segment length is relatively short. The gradient segment length structure formed can better cope with the dog-bone effect that occurs during balloon expansion, can effectively solve the problem of zinc alloy processing softening, and improve the stability and safety of the stent.

[0032] Specifically, refer to Figure 5 The present invention provides a coronary stent with a segment length gradient structure, comprising: a plurality of annular segments 4 connected to each other, wherein the plurality of annular segments 4 are divided into a first portion 1, and a second portion 2 and a third portion 3 located on opposite sides of the first portion 1; The first portion 1 includes a plurality of first annular segments, the second portion 2 includes a plurality of second annular segments, and the third portion 3 includes a plurality of third annular segments; In the axial direction of the coronary stent with a gradual segment length variation structure, the segment lengths of the plurality of first annular segments are equal; In the axial direction of the second portion 2 toward the first portion 1, the segment lengths of the plurality of second annular segments gradually decrease; in the axial direction of the third portion 3 toward the first portion 1, the segment lengths of the plurality of third annular segments gradually decrease; Furthermore, in the axial direction of the second part 2 toward the first part 1, the difference in section length between the i-th second annular section length and the i+1-th second annular section length in the second part 2 is equal to the difference in section length between the i-th third annular section length and the i+1-th third annular section length in the third part 3.

[0033] It should be noted that the annular segment length 4 refers to the smallest structural unit constituting the coronary stent; The material of each ring segment length 4 can be zinc alloy; refer to Figure 5 The axial direction of the coronary stent with a gradual length variation structure refers to the direction in which the coronary stent extends in the horizontal direction x; The first portion 1 is located at the center of the coronary stent in the horizontal direction x, and the second portion 2 and the third portion 3 are respectively arranged on both sides of the first portion 1 with the center of the coronary stent in the horizontal direction x as an axis; A plurality of first annular segment lengths, a plurality of second annular segment lengths, and a plurality of third annular segment lengths constitute a plurality of annular segment lengths 4, and the plurality of annular segment lengths 4 constitute a coronary stent with a gradient segment length structure; The first annular segment, the second annular segment and the third annular segment have the same shape, which is configured as a corrugated shape. Each annular segment 4 includes a plurality of crests 41 and a plurality of troughs 42. Each annular segment 4 includes an even number of wave crests 41 and an even number of wave troughs 42; The crests 41 and troughs 42 of every two adjacent annular segments 4 are aligned one by one in the direction of the crests 41 convex; Each adjacent two annular segments 4 are connected in sequence toward the direction of the wave crest 41 by a flexible connector 5; The flexible connecting piece 5 between each two adjacent annular segments 4 is integrally formed with the annular segments 4 during preparation; The two ends of the flexible connector 5 between each two adjacent annular segments 4 are respectively connected to the connecting line between the wave crest 41 and the wave trough 42; At least two flexible connectors 5 are provided between each two adjacent annular segments 4; The number of flexible connectors 5 provided between each two adjacent annular segments 4 may be an even number; refer to Figure 5 ,exist Figure 5 In the x-direction shown, the flexible connectors 5 are staggered, which helps to suppress the occurrence of the "dog bone" effect when the stent is expanded; There are three wave crests 41 or three wave troughs 42 between every two flexible connectors 5; The first portion 1 may include an even number of first annular segments; The first part 1 may include two, four or more first annular sections; the second part 2 may include two, three, four or more second annular sections; the third part 3 may include two, three, four or more third annular sections; The second portion 2 may also include an even number of second annular segment lengths, and the third portion 3 may also include an even number of third annular segment lengths; The lengths of the multiple first annular segments are equal, which means: Figure 5 , in the horizontal direction x, the length of each first annular segment is the same; The axial direction of the second portion 2 toward the first portion 1 refers to the direction in which the second annular segment length, which is farthest from the first annular segment length in the second portion 2, faces the first annular segment length. For example, it can be Figure 5 The x direction indicated in ; The lengths of the plurality of second annular segments gradually decrease, which means that the second annular segment farthest from the first annular segment in the second portion 2 has the largest length, and the second annular segment closer to the first annular segment has a smaller length. In the axial direction of the third portion 3 toward the first portion 1 , it means: the third annular segment length in the third portion 3 that is farthest from the first annular segment length is toward the first annular segment length; The lengths of the plurality of third annular segments gradually decrease in length, which means that the second annular segment farthest from the first annular segment in the third portion 3 has the largest length, and the third annular segment closer to the first annular segment has a smaller length. The coronary stent composed of the first annular segment length, the second annular segment length and the third annular segment length takes the center position of the horizontal direction x as the axis, and its length gradually increases along the axis toward both ends, forming a coronary stent with a segment length gradient structure; The segment length difference refers to the difference between the lengths of two adjacent second ring segments or two adjacent third ring segments in the horizontal direction x. The i-th and (i+1)-th refer to two adjacent second annular segment lengths in the second part 2 , or two adjacent third annular segment lengths in the third part 3 .

[0034] In practice, the coronary stent provided by the present invention is pressed against a balloon. When the balloon expands, the first central annular segment initially experiences uniform pressure. The second and third annular segments on either side gradually adapt to changes in vessel curvature or diameter, reducing the formation of stress concentration points. During service, the uniform central annular segments provide stable coverage of the lesion, while the gradually varying annular segments on either side adapt to the natural transition of the vessel, reducing geometric mismatch between the stent and the vessel.

[0035] In the present invention, a coronary stent with a segment length gradient structure is provided in the axial direction, wherein the segment length of the middle section is constant and the segment lengths on both sides decrease step by step, so that the coronary stent can form an asymmetric distribution when expanded. The middle section provides uniform support, and the segment lengths on both sides gradually decrease to form a flexible transition zone. This arrangement can effectively reduce the local stress concentration in the contact area between the two ends of the balloon and the coronary stent, so that the balloon expansion pressure is more evenly transmitted to the middle section of the stent, and the occurrence of size mismatch caused by excessive expansion of the proximal and distal ends. Compared with traditional stents, the segment length gradient structure provided in the present invention can be more firmly fixed on the balloon when pressed and gripped, and the stent is not easily displaced during implantation and delivery, and can be more accurately delivered to the correct lesion location where the support is to be released, so it is less likely to cause poor wall adhesion after the stent is expanded.

[0036] refer to Figure 6 and Figure 7 ,exist Figure 7 In the figure, "a" represents a conventional zinc alloy stent of uniform length, and "b" represents the coronary stent with a tapered segment length structure provided by the present invention. Conventional zinc alloy stents of uniform length are prone to inducing preferred grain orientation due to uniform deformation during expansion. The tapered segment length structure of the present invention, however, creates a non-uniform strain field, promoting the activation of diverse dislocation slip systems, breaking up the single-orientation texture, thereby enhancing the coordinated deformation capability of multiple slip systems and avoiding brittle fracture caused by grains perpendicular to the force direction.

[0037] In summary, the coronary stent with a gradient length structure provided by the present invention can effectively solve the problems existing in related technologies such as processing softening, poor wall adhesion, and "dog bone" effect, and greatly improve the stability and safety of the stent during its service stage.

[0038] In some embodiments, reference Figure 5 The coronary stent with a gradient segment length structure includes 8-10 annular segments of length 4.

[0039] It should be noted that the 8-10 annular segments 4 included in the coronary stent with a gradual segment length structure are composed of a plurality of first annular segment lengths, a plurality of second annular segment lengths, and a plurality of third annular segment lengths; In specific implementation, the coronary stent with a gradient segment length structure may include 8, 9, or 10 ring segments of length 4.

[0040] In the present application, the number of annular segments 4 is preferably an even number, for example, 8 or 10, so that the stent is numerically symmetrical in both the axial and radial directions. This numerical symmetry helps to achieve a more balanced stress distribution during stent expansion, avoiding asymmetric stress concentration caused by an odd number of annular segments, ensuring a more uniform stress distribution in the stent, and achieving optimal expansion results for the zinc alloy stent with work-softening properties.

[0041] In some embodiments, reference Figure 5 , the first part 1 includes two of the first annular sections; The number of the second annular segments included in the second portion 2 is the same as the number of the third annular segments included in the third portion 3 .

[0042] It should be noted that the reference Figure 5 , the two first annular segments included in the first part 1 are arranged side by side in the horizontal direction x; the second annular segments included in the second part 2 are arranged side by side in the horizontal direction x; the third annular segments included in the third part 3 are arranged side by side in the horizontal direction x; The second portion 2 may include an even number of second annular segments; and the third portion 3 may include an even number of third annular segments.

[0043] In the present invention, by dividing the stent into two first annular segments in the middle and second annular segments and third annular segments symmetrical in number on both sides, a symmetrical distribution is formed in the axial direction, so that the stress distribution of the stent is more balanced when it expands, avoiding local stress concentration caused by the asymmetric structure, and making the stent fit more closely to the blood vessel wall.

[0044] In some embodiments, the material of the coronary stent with a gradient length structure includes zinc, lithium and manganese; The mass percentage of lithium is 0.3%-0.5%, and the mass percentage of manganese is 0.75%-0.85%.

[0045] It should be noted that the material of the coronary stent with a gradient segment length structure refers to the material of each annular segment length 4, and also the material of each first annular segment length, second annular segment length, and third annular segment length; Materials including zinc, lithium and manganese refer to: zinc alloy materials made by doping lithium and manganese with zinc as the main material; In a specific implementation, the mass percentage of lithium can be 0.3%, 0.35%, 0.4%, 0.45%, and 0.5%; the mass percentage of manganese can be 0.75%, 0.8%, and 0.85%.

[0046] In the invention, the addition of lithium to the zinc material helps improve the work hardening ability of the zinc alloy and increase the yield strength of the bracket. The addition of manganese helps further refine the grain size and improve the fatigue resistance of the zinc alloy material.

[0047] In the segment-length gradient coronary stent made of this zinc alloy material, the combined effects of lithium and manganese can inhibit the dynamic recrystallization and body temperature aging process of the zinc alloy, thereby increasing the work hardening index of the stent during expansion. At the same time, it improves the stability of the material in service at body temperature, and its softening resistance is further improved compared to pure zinc alloy. The addition of lithium and manganese can inhibit the excessive release of zinc ions through the galvanic cell effect, avoiding inflammatory reactions caused by excessive local ion concentrations when the material degrades. Lithium ions also promote the proliferation and migration of endothelial cells, while manganese ions can enhance the antioxidant capacity of endothelial cells. Lithium ions can promote osteoblast differentiation, while manganese ions have antibacterial effects, reducing the risk of infection after stent implantation.

[0048] In some embodiments, the coronary stent with a gradient segment length structure further comprises a degradable coating, wherein the degradable coating is attached to the outer surfaces of the first annular segment length, the second annular segment length, and the third annular segment length; The thickness of the coating is 10 μm-30 μm.

[0049] It should be noted that a degradable coating refers to a coating that can degrade along with the zinc alloy stent after the service life of the coronary stent ends; The thickness of the coating can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm.

[0050] In this invention, the biodegradable coating forms a biological barrier during the initial stent implantation phase, reducing direct contact between the stent and the vessel wall and significantly reducing the release of inflammatory factors. Furthermore, precise control of the coating thickness ensures uniform distribution across the stent surface, avoiding performance variations caused by areas of excessive thickness or thinness.

[0051] In some embodiments, the degradable coating is made of a degradable polymer material or a degradable metal; The degradable polymer material is selected from at least one of lactic acid, polyglycolide, polyanhydride, polylactic acid copolymer, polyglycolic acid, polyhydroxypentyl butyrate, polycyanoacrylate, natural degradable polymer materials collagen, gelatin, chitosan, rapamycin, paclitaxel, emodin, and curcumin; The degradable metal is magnesium, iron or zinc.

[0052] In the present invention, the combination of gelatin and rapamycin in the selected coating materials can promote endothelial cell proliferation and migration and accelerate the process of vascular endothelialization; the combination of rapamycin and paclitaxel can be continuously released after stent implantation to inhibit smooth muscle cell proliferation; the combination of curcumin and emodin has anti-inflammatory and antioxidant effects; the degradation cycle of polylactic acid and magnesium matches that of the stent body (zinc-lithium-manganese alloy), ensuring that the coating remains intact during the stent support period and gradually degrades after the vascular repair is completed; the degradation products of collagen and zinc are biocompatible substances, such as amino acids, Zn 2+ , will not cause local toxicity or allergic reactions; the combination of polyglycolide and gelatin forms a smooth layer on the surface of the stent, reducing friction resistance during delivery and improving the accuracy of stent release; the combination of polyhydroxybutyrate and rapamycin can inhibit platelet adhesion and activation, reducing the risk of thrombosis.

[0053] In some embodiments, reference Figure 5 , in the axial direction of the second portion 2 toward the first portion 1, the length difference between each two adjacent second annular segments is equal; Furthermore, in the axial direction from the third portion 3 toward the first portion 1 , the length differences between every two adjacent third annular segments are equal.

[0054] It should be noted that the reference Figure 5 , the axial direction of the second portion 2 toward the first portion 1 means that: the second annular segment length farthest from the first annular segment length in the second portion 2 in the horizontal direction x points in the direction of the first annular segment length; refer to Figure 5 The length difference between each two adjacent second ring segments refers to the difference between the lengths of the two adjacent second ring segments in the horizontal direction x. The same applies to the third part 3. The length differences of the segment lengths are set to be equal, so that in the axial direction of the second part 2 toward the first part 1 , the length differences of the segment lengths of the plurality of second annular segments form an arithmetic progression, and the same is true for the third part 3 .

[0055] In the present invention, by setting the length difference between each two adjacent annular segments 4 to be equal, the bracket forms a continuous rigid transition in the axial direction (rigid transition refers to the ability of the structure to resist deformation, and the transition emphasizes the continuous change of properties (such as stiffness) in space or structure, rather than sudden changes). In this way, when the bracket is expanded, the stress change will be more gentle, reducing the risk of bracket fracture. The setting of equal-difference segment lengths can also ensure that the degree of deformation of each second annular segment length and the third annular segment length increases uniformly during expansion, thereby improving the overall deformation coordination of the bracket. The uniform strain gradient helps to slow down the softening process of zinc alloy processing and ensure the stability of mechanical support force during service (6-12 months). In addition, the setting of equal-difference gradient annular segment lengths can produce a uniform strain field, promote the diversification of grain orientation inside the material, and reduce the tendency of brittle fracture caused by a single orientation.

[0056] In some embodiments, reference Figure 5 , the section length difference is 1 μm-5 μm.

[0057] It should be noted that the reference Figure 5 The segment length difference refers to the difference between the length values of two adjacent second ring segments in the horizontal direction x, and the difference between the length values of two adjacent third ring segments in the horizontal direction x.

[0058] In a specific implementation, the length difference of the section length can be 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm.

[0059] In the present application, by setting the segment length difference to a micron-scale difference of 1 μm-5 μm, the axial deformation of the stent is made smoother, avoiding the problem of local stress concentration caused by sudden changes in segment length due to excessive differences.

[0060] In some embodiments, reference Figure 5 In the axial direction of the coronary stent with gradually varying segment lengths, the length of the coronary stent with gradually varying segment lengths is 9.985 mm-10.015 mm.

[0061] It should be noted that the reference Figure 5 The axial direction of the segment length gradient coronary stent refers to Figure 5 The horizontal direction x in The length of the coronary stent with a gradual segment length structure refers to the distance between the end of the second annular segment length, which is farthest from the center line of the two first annular segments, and the end of the third annular segment length; In a specific implementation, the length of the coronary stent with a gradient length structure can be 9.985 mm, 9.990 mm, 9.995 mm, 10.000 mm, 10.005 mm, 10.010 mm, or 10.015 mm.

[0062] In the present invention, by controlling the stent length within an extremely narrow tolerance range (±0.015 mm), the stress distribution of the stent during expansion is made more uniform.

[0063] In some embodiments, in the radial direction of the coronary stent with a gradient segment length structure, the first annular segment length, the second annular segment length, and the third annular segment length are the same in size, and the size is 80 μm-100 μm.

[0064] It should be noted that the reference Figure 5 , the radial direction of the segment length gradient structure coronary stent refers to Figure 5 The direction pointed by y in ; The dimensions of the first annular segment length, the second annular segment length, and the third annular segment length refer to: the thickness dimension in the vertical direction y; In a specific implementation, the size can be 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

[0065] In the present invention, by controlling the radial dimension of the annular segment length 4 within a narrow range of 80 μm-100 μm and making each annular segment length 4 the same in size, the stent is subjected to more balanced force during balloon expansion, thus avoiding local over-support or under-support.

[0066] The present invention also provides a method for preparing the above-mentioned coronary stent with a gradual length variation structure, referring to Figure 8 , the preparation method comprises: Step S1: drawing the zinc alloy into a tube; Step S2: Preloading the drawing through the program and driving the femtosecond laser to cut the tube material to form a coronary stent with a tubular lattice structure and a gradient length structure; Step S3: Place the tubular grid structure in a water bath at 35°C-45°C for ultrasonic cleaning for 5 min-10 min.

[0067] It should be noted that zinc alloy drawing into tubes refers to the process of pulling a zinc alloy billet through a die of a specific shape using external force (mechanical or hydraulic), reducing its cross-sectional area and increasing its length to form a tube. During the drawing process, the material undergoes plastic deformation, refining the internal grain structure, and improving strength and surface finish. When drawing into a tube, the drawing speed is 0.5 m / min-2 m / min, and the drawing temperature is 100 ℃-300 ℃; Femtosecond laser refers to a laser that emits laser light in femtoseconds (1 femtosecond = 10 -15 Ultrafast laser technology with a pulse width of 1000 seconds. In pipe cutting, it uses the high peak energy of extremely short pulses to interact with the material to achieve high-precision, low-heat-damage cold processing; When cutting, the laser power is 10 W-50 W, the pulse frequency is 100 kHz-500 kHz, and the cutting speed is 0.1 mm / s-1 mm / s; Tubular grid structure refers to a hollow structure with a certain wall thickness and a hollow structure in the middle of the pipe. The tubular grid structure can be placed in a water bath at 35°C, 38°C, 40°C, 43°C, and 45°C for ultrasonic cleaning for 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min.

[0068] In this method, zinc alloy is drawn into tubing, ensuring uniform wall thickness and providing high-quality raw material for subsequent laser cutting. The drawing process also refines the tubing's grain size, improving its mechanical properties and fatigue resistance. Femtosecond laser cutting technology, with pre-programmed drawings, achieves micron-level machining accuracy, ensuring precise formation of structures with gradually varying lengths.

[0069] Placing the tubular grid structure in a water bath at 35°C-45°C for ultrasonic cleaning for 5-10 minutes can effectively remove attached impurities such as microparticles, oxide scale, and oil stains generated during the cutting process, thereby improving the surface smoothness of the tubular grid structure.

[0070] In some embodiments, after ultrasonically cleaning the tubular grid structure in a water bath at 35° C. to 45° C. for 5 to 10 minutes, the method further comprises: Step S11, spraying a degradable polymer material or a degradable metal on the tubular grid structure to form a degradable coating on the surface of the tubular grid structure; Step S21: electrolytically polishing the coated stent.

[0071] It should be noted that the degradable polymer material can be selected from at least one of lactic acid, polyglycolide, polyanhydride, polylactic acid copolymer, polyglycolic acid, polyhydroxybutyrate, polycyanoacrylate, natural degradable polymer materials collagen, gelatin, chitosan, rapamycin, paclitaxel, emodin, and curcumin; The degradable metal can be magnesium, iron, or zinc; The thickness of the coating can be 10 μm-30 μm.

[0072] In specific implementation, the electrolytic polishing process also includes: Step S111, phosphoric acid and anhydrous ethanol are mixed in a ratio of 1:2-1:1 to prepare a polishing liquid; Step S211: Set the polishing voltage to a DC voltage of 10 V, ensure that the polishing current is less than 1 A, determine the number of polishing turns required according to the wall thickness required for clinical application, and perform the mortgage polishing process; Step S311: annealing the polished tubular lattice structure. The annealing temperature is determined according to the type of zinc alloy. After annealing, a coronary stent with a segment length gradient structure is obtained.

[0073] It should be noted that the coating preparation method may also include immersion, encapsulation, co-solution and grafting; To ensure the uniformity of the stent, the number of polishing circles must be an even number; for example, the number of polishing circles can be 20-30 circles; specifically, the number of polishing circles can be 20 circles, 22 circles, 24 circles, 26 circles, 28 circles, and 30 circles; In the present invention, the type of zinc alloy is zinc-lithium-manganese alloy, and the annealing temperature can be 150°C-300°C; specifically, the annealing temperature can be 150°C, 180°C, 200°C, 250°C, or 300°C.

[0074] In this invention, a degradable coating with a thickness of 10 to 30 μm is applied to the surface of the tubular grid structure through a spraying process. This ensures a uniform coating thickness (±2 μm) to avoid performance variations caused by areas of excessive thickness or thinness. Electrolytic polishing further smoothes the coating surface, removing any microparticles and uneven areas that may have been generated during the spraying process.

[0075] In order to enable those skilled in the art to more clearly understand the present invention, the coronary stent with a gradient segment length structure according to the present invention will be described in detail through the following examples.

[0076] Example 1 (1) Zinc-lithium-manganese alloy tubes were prepared by drawing process. The mass percentage of lithium in zinc-lithium-manganese alloy was 0.5%, the mass fraction of manganese was 0.85%, the outer diameter of the tube was set to 1.6 mm, the average wall thickness was 7120 μm, and the extreme wall thickness was 25 μm. The cross-sectional view of the tube is shown in Fig. Figure 9 ; (2) Using a laser cutting machine (model: Kunshan Situo TLS-HT1200), according to a pre-designed CAD drawing, the drawing content includes the first part, the second part and the third part, wherein the first part includes two first annular segments arranged in parallel in the axial direction and having a length of 1.05 mm, the second part includes three second annular segments with lengths of 1.20 mm, 1.15 mm and 1.10 mm, and the third part includes three third annular segments with lengths of 1.20 mm, 1.15 mm and 1.10 mm, respectively. The second annular segments and the third annular segments of the same length are located at the same position on both sides of the center line of the two first annular segments, respectively. The above-mentioned tube is precisely cut by femtosecond technology to obtain a coronary stent with a tubular lattice structure and a gradient length structure (hereinafter referred to as the stent). The working parameters of the laser cutting machine are set, wherein the power is 15 W and the frequency division is between 8 and 10; (3) After the stent is cut, impurities such as oil, oxide scale, etc. often remain on its surface. In order to ensure the cleanliness of the stent surface, immerse the stent in a beaker filled with anhydrous ethanol and place the beaker in an ultrasonic cleaning machine for cleaning (refer to the cleaning steps). Figure 11 The cleaning time was controlled within 8 min, and the water temperature was maintained at 40 °C. After cleaning, the surface was inspected under a microscope to ensure that there were no residual impurities on the surface of the stent. (4) Phosphoric acid: anhydrous ethanol is prepared into polishing liquid in a ratio of 1:2. Since anhydrous ethanol is volatile, the polishing liquid is connected to the power supply, rectifier, electrolytic cell and supporting facilities, and the bracket is firmly fixed with a clamp to ensure that the bracket can remain stable and evenly stressed during the polishing process. The polishing temperature is room temperature, and the polishing voltage is set to DC voltage 10 V. The current should be kept below 1 A during the polishing process, and the maximum current cannot exceed 1.5 A. Polish 30 times. After polishing one round, remove the bracket and turn it around to polish the next round. To ensure the uniformity of the bracket, the number of polishing rounds must be an even number. The polishing process refers to Figure 10 As shown; (5) Place the polished bracket into the processing chamber of the vacuum heat treatment furnace for preheating. Figure 12 As shown, the furnace is preheated to raise the temperature to 250 ℃. After the furnace is heated to 250 ℃, the furnace is slowly moved to wrap the processing chamber. When the processing chamber is slowly heated to 250 ℃, heat treatment (i.e., low-temperature annealing treatment) begins. The processing chamber temperature is maintained at 250 ℃ for 3600 s. After the heat treatment is completed, the furnace is removed and the processing chamber is air-cooled. After cooling to room temperature, a section length gradient structure bracket is obtained.

[0077] A coronary stent with a gradient segment length structure is prepared based on Example 1, and a method for applying the stent is provided, including: When the stent is ready for use, if conducting in vitro experiments, heat the water bath to 37°C and maintain a constant temperature. Completely submerge the balloon in water and inflate it using the balloon pressure inflator. During the inflation process, slowly adjust the pressure pump until it reaches approximately 8 atmospheres, ensuring that the balloon is inflated to 3 mm or another predetermined diameter.

[0078] If an in vivo experiment is conducted, the stent prepared by the present invention is delivered to the site of vascular lesions via a guidewire, and then the balloon is expanded using a balloon pressure inflator so that it remains in the blood vessel cavity to assist in the recovery and reconstruction of the blood vessels at the lesion site. The stent degrades after the vascular repair and reconstruction is completed.

[0079] Specifically, the application methods include: 1. Place the coronary stent obtained after the annealing treatment above onto a 2.5mm diameter balloon and crimp it using a crimping machine (model: Blockwise SC700), ensuring it is positioned exactly in the center of the balloon. Use the crimping machine to crimp it to 1.35mm, then push the crimping machine further to crimp it to 0.9mm. After removing the stent, inspect the crimped position and ensure there are no broken rods or abnormal deformations. Seal and store. 2. When the stent is needed, the guidewire is used to deliver the stent to the site of vascular lesions, and then the balloon is expanded by the balloon pressure inflator to remain in the lumen to assist in the restoration and reconstruction of the lesion site, and the stent is degraded after the vascular repair and reconstruction is completed.

[0080] Based on the above experimental content, the expansion process of the stent structure in the related art and the length gradient structure proposed in the present invention is referred to as follows: Figure 13 As shown, it is proved that the segment length gradient structure provided by the present invention unfolds more slowly during expansion and is less susceptible to the dog-bone effect.

[0081] refer to Figure 13 , after comparative analysis, when expanded to 3 atmospheres, the stent structure in the related art has been fully deployed, and the expansion speed is relatively fast; when expanded to 4 atmospheres, the segment length gradient structure provided in Example 1 of the present invention is fully deployed. This result shows that the expansion process of the segment length gradient structure provided by the present invention requires a longer time. Traditional zinc alloys are prone to processing softening during rapid deformation, which leads to stent fracture. The segment length gradient structure provided in Example 1 of the present invention can slow down the expansion speed of the stent as the balloon deforms, so that the stent is more evenly stressed during the expansion process, thereby effectively reducing the impact of the dog-bone effect on the stent. In addition, in terms of the mechanical properties of the stent, the segment length gradient structure does not affect the radial support performance of the stent, and there is no significant difference in radial support force from ordinary stents, which meets the clinical thin-walled stent standards.

[0082] Example 2 Steps (1) to (4) of Example 2 are identical to those of Example 1. Example 2 further includes the following preparation steps: (5) Using ultrasonic atomization spraying technology, spray drug coating, polymer coating or other functional coating on the surface of the cleaned stent body to form a degradable coating on the surface of the tubular lattice structure. Specifically, polylactic acid, polyglycolic acid, polylactic acid-glycolic acid copolymer polyglycolide, polyanhydride, polylactic acid copolymer, polyhydroxybutyrate, polycyanoacrylate, etc. can be sprayed. The drugs in the coating are not limited to rapamycin, paclitaxel, emodin, curcumin, etc.; (6) The stent, including the coated stent, is electropolished. First, phosphoric acid and anhydrous ethanol are mixed in a ratio of 1:2 to form a polishing solution. Since anhydrous ethanol is volatile, the polishing solution is connected to the power supply, rectifier, electrolytic cell and supporting facilities, and the stent is firmly fixed with a clamp to ensure that the stent can remain stable and evenly stressed during the polishing process. The polishing temperature is room temperature, and the polishing voltage is set to a DC voltage of 10 V. The current should be kept below 1 A during the polishing process, and the maximum current cannot exceed 1.5 A. Polish 30 times. After polishing one round, remove the stent and turn it around to perform the next round of polishing. To ensure the uniformity of the stent, the number of polishing rounds must be an even number. The polishing process is shown in Reference 10; (7) The polished bracket is placed in the processing chamber of the vacuum heat treatment furnace and preheated. The vacuum heat treatment instrument is shown in Figure 11. The furnace is preheated to raise the temperature to 250 °C. After the furnace is heated to 250 °C, the furnace is slowly moved to wrap the processing chamber. When the processing chamber is slowly heated to 250 °C, heat treatment (low-temperature annealing treatment) is started. The processing chamber temperature is maintained at 250 °C for 3600 s. After the heat treatment is completed, the furnace is removed and the processing chamber is cooled by air. After cooling to room temperature, a bracket with a gradient length structure is obtained.

[0083] Example 2 aims to improve the biocompatibility of the stent, control drug release, and enhance the performance of the stent by providing a coating.

[0084] In summary, the present invention provides a coronary stent with a gradient segment length structure. This stent utilizes a degradable zinc-based material matrix, wherein the mass percentage of Li in the zinc alloy is 0.4-±0.1%, the mass percentage of Mn is 0.8±0.05%, and the balance is zinc. This stent has a gradient cylindrical mesh structure with adjacent segment lengths varying by 1 μm-5 μm, enabling uniform expansion and reducing the dog-bone effect. A drug-loaded coating can be provided on the surface, and the stent is manufactured through processes such as drawing, laser cutting, and polishing. This stent combines excellent biocompatibility, flexibility, and support strength, and can degrade after vascular repair.

[0085] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0086] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0087] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements that are inherent to such process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "comprises a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0088] The above is a detailed introduction to a coronary stent with a gradient length structure provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A coronary stent with a gradually varying segment length structure, characterized in that: include: A plurality of annular segments connected to each other, wherein the plurality of annular segments are divided into a first portion, and a second portion and a third portion located on opposite sides of the first portion; wherein the first portion comprises a plurality of first annular segments, the second portion comprises a plurality of second annular segments, and the third portion comprises a plurality of third annular segments; In the axial direction of the coronary stent with a gradual segment length variation structure, the segment lengths of the plurality of first annular segments are equal; In the axial direction from the second portion to the first portion, the segment lengths of the plurality of second annular segments gradually decrease; in the axial direction from the third portion to the first portion, the segment lengths of the plurality of third annular segments gradually decrease; Furthermore, in the axial direction of the second part toward the first part, the difference in section length between the i-th second annular section length and the i+1-th second annular section length in the second part is equal to the difference in section length between the i-th third annular section length and the i+1-th third annular section length in the third part.

2. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: In the axial direction from the second portion to the first portion, the difference in length between every two adjacent second annular segments is equal; Furthermore, in the axial direction from the third portion toward the first portion, the length differences between every two adjacent third annular segments are equal.

3. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: The difference in section length is 1 μm-5 μm.

4. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: The first portion includes two of the first annular segments; The second portion includes the same number of the second annular segments as the third portion includes the third annular segments.

5. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: In the axial direction of the coronary stent with a gradually varying segment length structure, the length of the coronary stent with a gradually varying segment length structure is 9.985 mm-10.015 mm.

6. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: In the radial direction of the coronary stent with a gradual segment length structure, the first annular segment length, the second annular segment length and the third annular segment length are the same in size, and the size is 80 μm-100 μm.

7. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: The coronary stent with a gradient segment length structure includes 8-10 annular segments.

8. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: The material of the segment length gradient structure coronary stent includes zinc, lithium and manganese; The mass percentage of lithium is 0.3%-0.5%, and the mass percentage of manganese is 0.75%-0.85%.

9. The coronary stent with a gradually varying segment length structure according to claim 1, characterized in that: The coronary stent with a gradient segment length structure further includes a degradable coating, which is attached to the outer surfaces of the first annular segment length, the second annular segment length, and the third annular segment length; The thickness of the coating is 10 μm-30 μm.

10. The coronary stent with a gradually varying segment length structure according to claim 9, characterized in that: The degradable coating is made of a degradable polymer material or a degradable metal; The degradable polymer material is selected from at least one of lactic acid, polyglycolide, polyanhydride, polylactic acid copolymer, polyglycolic acid, polyhydroxypentyl butyrate, polycyanoacrylate, natural degradable polymer materials collagen, gelatin, chitosan, rapamycin, paclitaxel, emodin, and curcumin; The degradable metal is magnesium, iron or zinc.

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