Retractable and controllable double-layer intracranial thrombectomy stent

Abstract

The application discloses a controllable double-layer intracranial thrombus-removing stent, and belongs to the intracranial thrombus-removing field. The stent comprises a stent body composed of an outer stent and an inner stent, a microcatheter, an intermediate catheter, a balloon catheter, a stent direction guide tube and a control guide wire. When reaching the thrombus position, the balloon catheter, the intermediate catheter and the microcatheter are withdrawn in sequence, and the stent body is exposed. The balloon is opened as a fixed support point. The inner and outer stent bodies are contracted or expanded by pulling the control guide wire. The stent direction guide tube is used for limiting the movement of the stent when the control guide wire is pushed and pulled. After the stent captures the thrombus and enters the microcatheter, the intermediate catheter and the balloon catheter are withdrawn in sequence, and the balloon is contracted to withdraw all the devices out of the body. The application introduces the element of the active control unit for controlling the expansion and contraction movement of the stent by using the strong and easy-to-operate deformation capacity of the special-shaped grid unit, increases the controllability of the radial force and the expansion and contraction state of the stent, and improves the thrombus fusion rate.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of intracranial thrombectomy, and particularly relates to a controllable double-layer intracranial thrombectomy stent. BACKGROUND

[0002] The brain is an extremely complex and important organ that controls various functions of the human body. When the blood vessels that deliver oxygen and nutrients to the brain are blocked, damaged or ruptured by clots, a "cerebral stroke" (also known as "stroke") occurs. If a stroke occurs, blood flow will not reach the area of the brain that controls a particular body function, which will eventually cause that part of the body to not work properly or even die. Stroke is the second most common cause of death worldwide after coronary artery disease.

[0003] Stroke is mainly divided into three categories: stroke caused by clots blocking blood flow to the brain is called "ischemic stroke" (IS); stroke caused by blood vessels rupturing to stop blood flow to the brain is called "hemorrhagic stroke" (HS); stroke caused by temporary clots causing transient ischemic attacks is called "transient ischemic attack" (TIA) or "mini stroke".

[0004] About 85% of strokes are ischemic strokes, of which acute ischemic stroke (AIS) is one of the main causes of death and disability worldwide. The latest Global Burden of Disease Study (GBD) data shows that the number of people with stroke in China has long been the highest in the world. The data also shows that the overall prevalence of stroke in China is on the rise, and the mortality rate of stroke is still at a high level.

[0005] Achieving recanalization of cerebral vessels is the key to the treatment of acute ischemic stroke. The treatment methods for stroke include drug thrombolysis and mechanical thrombectomy. The early evidence-based treatment for ischemic stroke is mainly drug thrombolysis, that is, injecting thrombolytic drugs near the site of the disease, instantaneously forming a very high concentration of thrombolytic drugs near it, accelerating the thrombus dissolution speed, and thus increasing the opportunity for recanalization of the blood vessels. However, according to authoritative research results, the treatment time window of drug thrombolysis is shorter than that of mechanical thrombectomy, only 3-6 hours, and is only suitable for small volume thrombus embolization. In addition, some patients have an adverse reaction to thrombolytic drugs, resulting in fewer patients treated by drug thrombolysis.

[0006] Mechanical thrombectomy (MT) is a method of sending a mechanical thrombectomy device to the blood vessel occlusion site through minimally invasive interventional surgery and removing the thrombus. Mechanical thrombectomy shows good therapeutic effect in the treatment of acute ischemic stroke caused by large vessel occlusion (LVO). At present, the main mechanical thrombectomy device used in the clinical treatment and research of acute ischemic stroke is stent thrombectomy. During treatment, the thrombectomy stent is sent to the embolism site through a microcatheter, and then the thrombectomy stent is released by withdrawing the microcatheter. After the thrombectomy stent obtains the thrombus at the embolism site, it is recovered, thereby removing the thrombus. Stent thrombectomy has the advantages of small size, less time limit, wide application of thrombus size, small damage to blood vessels, high recanalization rate, and ideal postoperative prognosis effect of patients.

[0007] The existing stent is mainly made of shape memory alloy and has good deformation and shape recovery ability. During the operation, the stent is stretched and contracted into the microcatheter outside the body by using the properties of the shape memory alloy material. After the microcatheter is withdrawn in the body, the stent will automatically expand and recover to its original shape. However, the intracranial cerebral vascular environment is complex and tortuous. The passive expansion of such a stent is often affected by the vascular environment, so that it cannot be fully expanded, resulting in poor fusion of the stent and the thrombus, and easy thrombus escape, which requires multiple operations to completely remove the thrombus.

[0008] In the prior art, the grid units of the hollow circular tube grid type stent are mainly evolved from regular polygons, such as water drop type evolved from triangle, spindle type evolved from quadrilateral, and honeycomb type evolved from hexagon. In order to achieve the required axial length, the existing grid type stent occupies a larger volume and length, which easily increases the resistance of the stent passing through the curved part. For example, document 1: CN113855351B discloses a thrombectomy stent composed of multiple stent bodies connected by spring rods, which realizes the ability of the thrombectomy stent to have high deformation and good structural toughness. However, the thrombectomy stent only introduces a spring rod as a conflict alleviating part, and the grid part which occupies most of the stent and plays a major role is not changed, and the grid units evolved from polygons are still used. During the axial stretching process of the stent composed of these grid units, the end points on both sides of the unit move along the symmetric axis to the two ends, thereby achieving the contraction state. However, due to the limitation of the extreme properties of the memory alloy material, the axial stretching ability of the grid unit is weak, thereby causing the radial contraction of the grid unit to be limited to a certain extent. If the stent is forcibly stretched and contracted into the microcatheter in vitro regardless of the material properties, the stent may not recover to its original shape in the body, thereby affecting the radial support force and other properties of the stent. Meanwhile, the deformation range of the spring rod is limited, which cannot well guarantee the flexibility of the stent when passing through the curved part.

[0009] Most of the stents on the market are passively self-expanding, without considering active control of the stent, so that the radial support force of the stent is uncontrollable and cannot change with the blood vessel environment. The passive expansion method makes the stent insufficiently fused with the thrombus, and cannot improve the one-time recanalization rate of the blood vessel. As document 2: a thrombus extraction device with a main body composed of a mesh stent, a central core wire and a connecting sleeve and equipped with a control handle, the core wire is controlled to move in the forward and backward directions to apply force to the stent, so that the stent expands when the button is pulled back or pulled, and the stent shrinks when the button is pushed forward or released. The purpose. Although the stent considers active control, the stent body is made of multiple metal wires, the mesh structure has weak radial support, and the shape of the expanded stent is uneven, which can easily cause thrombus escape. At the same time, only the stent at the head and tail is controlled to move, which may cause instability during the control of the stent movement or expansion. SUMMARY

[0010] The purpose of the present application is to provide an expansion and contraction controllable double-layer intracranial thrombus extraction stent, which aims to solve the technical problems of poor fusion of the stent with the thrombus and low one-time recanalization rate of the blood vessel caused by uncontrollable expansion and contraction and radial support of the stent in the prior art.

[0011] The expansion and contraction controllable double-layer intracranial thrombus extraction stent comprises a stent body composed of an outer layer stent and an inner layer stent, a microcatheter, an intermediate catheter, a balloon catheter, a stent direction guide tube and a control guide wire.

[0012] The outer layer stent comprises an outer layer stent body, an outer layer stent threaded tightening sleeve, a control unit, a control unit tightening sleeve and an encrypted mesh basket; the inner layer stent comprises an inner layer stent body and an inner layer stent threaded tightening sleeve.

[0013] The two-layer stent body is in the form of a hollow column when expanded, and the overall shape details are in the form of a hollow grid. Both layers of the stent are composed of multiple grid modules, and each grid module is composed of one or more groups of special-shaped grid units with strong axial expansion and contraction ability and radial support ability. Any two adjacent grid modules are connected by rod-shaped bridge wires, and the lengths of each bridge wire are not completely the same.

[0014] The inner and outer layer stent threaded tightening sleeves are used to tighten and fix the proximal end and the distal end of the inner and outer layer stent bodies. The inner layer stent threaded tightening sleeve is placed in the outer layer stent threaded tightening sleeve, which is used to adjust the relative position of the inner and outer layer stent bodies and balance the axial deformation difference caused by the different diameters of the inner and outer layer stents.

[0015] The control unit is located at the middle part of the outer layer stent body, is used for controlling the expansion and contraction of the stent body, and is integrally processed with the outer layer stent, and then the control unit is fixed in the inner contraction sleeve, the inner contraction sleeve is provided with a plurality of connection points of the control guide wire, preferably 2-4, and is uniformly distributed.

[0016] The control guide wire passes through the inner and outer layer stent threaded contraction sleeves, the outer layer stent threaded contraction sleeve is provided with a clamping groove as a movement limiting point of the inner layer stent threaded contraction sleeve, and the outer layer stent threaded contraction sleeve is provided with a fixed connection point of the control guide wire.

[0017] The outer layer stent body is provided with an encryption net basket at the distal end, which is realized through the grid design of the distal end of the outer layer stent, and is used for reducing the escape of broken thrombus; the outer layer stent body is provided with a slide-shaped structure at the proximal end, so as to facilitate the thrombus to enter the catheter.

[0018] The stent body is located in the microcatheter, the microcatheter is located in the intermediate catheter, and the intermediate catheter is located in the balloon catheter. The control guide wire is connected with the head and tail control points of the stent body and the connection points of the control unit in sequence, and the expansion and contraction of the stent is realized through the push-pull operation of the control guide wire, specifically:

[0019] When the expandable and contractible double-layer intracranial thrombus extraction stent reaches the position of the thrombus, the balloon catheter, the intermediate catheter and the microcatheter are withdrawn in sequence, and the stent body is exposed; when the balloon catheter is withdrawn to the preset position, the balloon is opened, and the balloon serves as a fixed support point after the device reaches the lesion, and is used to assist the controllable expansion and contraction movement of the inner and outer layer stents in the body; at this time, the proximal end of the stent body is fixed, the expansion of the control unit of the stent body is realized by pulling the control guide wire backward, so as to drive the slow expansion of the inner and outer layer stent bodies in the body;

[0020] The contraction of the control unit of the stent body is realized by pushing the control guide wire forward, so as to drive the contraction of the inner and outer layer stent bodies, and when the contraction reaches the preset value of the stent, the control guide wire is pulled backward to drive the whole stent to move to the microcatheter until the microcatheter is entered. After the stent body is exposed, the expansion and contraction degree and state of the stent can be adjusted at any time by pushing and pulling the control guide wire, so as to better fuse with the thrombus.

[0021] The stent direction guide tube is used for limiting the movement of the stent when the control guide wire is pushed and pulled, after the thrombus captured by the stent enters the microcatheter, the microcatheter is withdrawn to the intermediate catheter, the intermediate catheter withdraws the balloon catheter, the balloon is contracted, and the balloon catheter is pulled to withdraw all the devices out of the body.

[0022] The advantages of the present application are that:

[0023] 1. A double-layer intracranial thrombus extraction stent with controllable expansion and contraction, the special-shaped grid unit adopted by the stent body has strong axial and radial deformation capability in the expansion and contraction operation, which can more favorably facilitate the stent to enter the distal end of the cerebral blood vessel for surgical operation.

[0024] 2. A double-layer intracranial thrombus extraction stent with controllable expansion and contraction, the special-shaped grid unit structure is stable, the stent composed of the unit in series arrangement has strong radial support force, and the cylindrical stent composed of the unit has fewer sharp corners, and the stimulation damage to the blood vessel wall is also reduced.

[0025] 3. A double-layer intracranial thrombus extraction stent with controllable expansion and contraction, the strong and easy-to-operate deformation capability of the special-shaped grid unit is utilized, an active control unit element is introduced for controlling the expansion and contraction movement of the stent, the controllability of the radial force and the expansion and contraction state of the stent is increased, the thrombus fusion rate is improved, and the active control unit and the stent body are integrated and can be machined at the same time, without the need for secondary splicing and assembly, thereby reducing the machining difficulty.

[0026] 4. A double-layer intracranial thrombus extraction stent with controllable expansion and contraction, the stent is connected with the grid module through the bridge to achieve sparse and dense combination, so as to ensure the flexibility of the stent in the curved blood vessel. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a general schematic view of the double-layer intracranial thrombus extraction stent with controllable expansion and contraction.

[0028] Figure 2 It is a structural schematic view of the outer stent body of the double-layer intracranial thrombus extraction stent with controllable expansion and contraction.

[0029] Figure 3 It is a structural schematic view of the inner stent body of the double-layer intracranial thrombus extraction stent with controllable expansion and contraction.

[0030] Figure 4 It is a three-dimensional structural schematic view of a special-shaped grid unit of the outer stent.

[0031] Figure 5 It is a planar development view of a special-shaped grid unit of the outer stent.

[0032] Figure 6 It is a special-shaped grid unit expansion process schematic view of the outer stent.

[0033] Figure 7 It is a structural schematic view of the outer thrombus extraction stent in the contraction and stretching state.

[0034] Figure 8 It is a schematic view of the thrombus extraction device provided by the embodiment of the present application in operation.

[0035] Figure 9The schematic diagram of the structure of the middle control unit of the outer layer frame body before processing of the application;

[0036] Figure 10 The schematic diagram of the structure of the middle control unit of the outer layer frame body of the application;

[0037] Figure 11 The schematic diagram of the position relationship between the components in the stent retrieval device of the application

[0038] In the figure: 1-outer layer stent, 1.1-outer layer stent threaded tightening sleeve, 1.2-control unit, 1.2.1-control unit tightening sleeve, 1.3-encryption net basket, 2-inner layer stent, 2.1-inner layer stent threaded tightening sleeve, 3-micro catheter, 4-intermediate catheter, 5-balloon catheter, 6-distal stent direction guide tube, 7-control guide wire DETAILED DESCRIPTION

[0039] In order to facilitate those skilled in the art to understand and implement the application, the application will be further described in detail below in combination with the drawings and examples. Obviously, the described examples are only part of the examples of the application, not all examples, and all other examples obtained by those skilled in the art without creative labor based on the examples in the application shall belong to the protection scope of the application.

[0040] The application discloses a controllable intracranial double-layer stent retrieval device with adjustable expansion and contraction and adaptability to complex and variable blood vessels, which is composed of inner and outer double-layer stents, adopts special-shaped grid units which are relatively flexible and stable in axial deformation and radial deformation, arranges the grid units in series to form multiple grid modules, connects the modules through bridge ribs, and increases control units which are not separated from the stent at the end of each module; the frame bodies of the inner and outer stents are collected into screw sleeves with adjusting function at the head and tail ends, and also pass through control guide wires as head and tail control points; the stent device further comprises a distal stent direction guide tube, a proximal micro catheter, an intermediate catheter and a balloon catheter; the application adopts wire driving, the control guide wire is connected with the head and tail control points and the control unit in the middle of the stent, and the expansion and contraction of the stent are realized through push-pull operation of the control guide wire. The application has the advantages of simple motion control, integration of the control unit and the stent, convenient production and processing, control of the shape and radial support force of the stent through operation of the control guide wire in the operation, expansion of the operation space and improvement of the adaptability of the stent retrieval device to the operation environment.

[0041] In the application, "proximal end" and "distal end" are used to refer to the distance between the surgical equipment and the doctor during minimally invasive operation, the proximal end refers to the end closer to the doctor, and the distal end refers to the end farther away from the doctor and first entering the human body.

[0042] As Figure 1As shown, the retrievable double-layer intracranial thrombus extraction stent comprises a stent body composed of an outer stent 1 and an inner stent 2, a microcatheter 3, an intermediate catheter 4, a balloon catheter 5, a stent direction guide tube 6 and a control guide wire 7.

[0043] The outer stent 1 comprises an outer stent body, an outer stent threaded tightening sleeve 1.1, a control unit 1.2, a control unit tightening sleeve 1.2.1 and an encryption net basket 1.3; the inner stent comprises an inner stent body and an inner stent threaded tightening sleeve 2.1.

[0044] Preferably, the inner and outer stent bodies of the stent body each have 3-5 segments; the two-layer stent body is in the shape of a hollow column when expanded, and the overall shape is in the form of a hollow grid. Both the two-layer stent bodies are composed of multiple grid modules, and each grid module is composed of one or more groups of special-shaped grid units with strong axial stretching and radial support capabilities. Any two adjacent grid modules are connected by rod-shaped bridge ribs, and the lengths of each bridge rib are not completely the same.

[0045] The inner and outer stent threaded tightening sleeves are respectively used to tighten and fix the proximal end and the distal end of the inner and outer stent bodies. The inner stent threaded tightening sleeve is placed in the outer stent threaded tightening sleeve to adjust the relative position of the inner and outer stent bodies and balance the axial deformation difference caused by the different diameters of the inner and outer stents.

[0046] As shown in Figure 2 and Figure 3 , they are respectively the outer stent body and the inner stent body structure schematic diagram provided by the present embodiment. The present embodiment adopts a special-shaped grid unit with round heads at both ends and a concave middle part. The perspective view and the plane expansion view are respectively shown in Figure 4 and Figure 5 . The grid unit has a strong axial deformation capability within the elastic limit of the material and can ensure recovery to the original state. The deformation of the special-shaped grid unit during the axial stretching of the stent is shown in Figure 6 . The special-shaped grid involves many design parameters, such as the grid arc radius, length, width and inclination angle, etc. The required stent diameter and length can be achieved by changing the design parameters of the special-shaped grid. When the stent is stretched, it is equivalent to stretching the two ends of the special-shaped grid. The special-shaped grid will present different grid shapes due to deformation. Preferably, the special-shaped grid within these shape ranges can be used as the variation range of the grid design shape. After reasonable design, within the material deformation range, the stent composed of this unit can achieve an axial deformation of 150% when the stent is radially contracted to 50% of the radius, greatly improving the operation space of the stent near the intracranial lesions.

[0047] In one example, one heteromorphic grid unit of the outer layer stent is composed of 4 heteromorphic grids connected by short straight strut bridges, one grid module is composed of 2-4 heteromorphic grid units connected in series, and every two adjacent grid modules are connected by strut bridges. For the outer layer stent, each grid module is provided with a control unit at the end, and the control unit is an integral whole with the stent grid unit. The control unit in this example is initially formed as two independent horn-shaped grid units, as shown in Figure 9 , which is connected only with the previous grid module, and the two horn-shaped grid units are merged into a sleeve to form a control unit, as shown in Figure 10 , for controlling the passage of a guide wire. The proximal end of the outer layer stent in this example is provided with a meniscus structure to facilitate the sliding of thrombus at the proximal microcatheter, and the meniscus structure is retracted into the proximal spiral sleeve after processing. The proximal spiral sleeve needs to be placed in the microcatheter.

[0048] In one example, the heteromorphic grid unit of the inner layer stent is composed of 2 heteromorphic grids identical to the outer layer stent connected by short straight strut bridges, one grid module is composed of 2-4 heteromorphic grid units connected in series, and every two adjacent grid modules are connected by strut bridges. The length of the bridge needs to be adjusted according to the design of the outer layer stent to avoid interference between the outer control unit and the inner layer stent. Similarly, the first and last grid modules of the inner layer stent will add two bridge segments to the two ends, respectively, and the two bridge segments need to be retracted into the first and last spiral sleeves, respectively.

[0049] The inner diameter of the first and last threaded sleeves of the outer layer stent in this example is also threaded, and the inner diameter is consistent with the outer diameter of the first and last spiral sleeves of the inner layer stent. In this example, the inner layer stent and the outer layer stent are composed of the same heteromorphic grid, but due to the different number of heteromorphic grids, the diameter of the inner layer stent is smaller than that of the outer layer stent, and the length of the inner layer stent is also different from that of the outer layer stent. Different diameters and lengths will result in different axial deformation lengths of the inner and outer layer stents, as shown in Figure 11 , the length L will change with the expansion and contraction state of the stent. This design is to adjust the balance of such differences.

[0050] The control unit is located at the middle part of the outer layer stent body, used for controlling the expansion and contraction of the stent body, and can be processed on the same circular pipe material as the outer layer stent, and then retracted inward to be fixed in the control unit tightening sleeve. This greatly reduces the complexity and stability of stent processing. The control unit tightening sleeve is provided with a connection point for controlling the guide wire; preferably 2-4, and uniformly distributed.

[0051] The control guide wire passes through the inner and outer layer stent thread tightening sleeves simultaneously, the outer layer stent thread tightening sleeve is provided with a clamping groove as a movement limiting point of the inner layer stent thread tightening sleeve, and the outer layer stent thread tightening sleeve is further provided with a fixed connecting point of the control guide wire.

[0052] The grid module at the tail end of the outer layer stent body in the example is followed by a basket structure formed by an encrypted grid, which is used to capture the escaped thrombus in the thrombus capturing process, and the tail end of the basket structure also needs to be fixed by a distal end spiral sleeve, which needs to be placed in a distal end guide tube for controlling the direction of the stent. Meanwhile, the proximal end of the outer layer stent body is provided with a slide structure to facilitate the thrombus entering the catheter.

[0053] The stent body is located in a micro catheter, the micro catheter is located in an intermediate catheter, and the intermediate catheter is located in a balloon catheter. The control guide wire is connected through the control point positions of the first and last spiral sleeves of the stent body and the connecting points of the control unit in sequence, and the stent is expanded and contracted by pushing and pulling the control guide wire, and is limited by the control guide wire at the same time.

[0054] Specifically,

[0055] As shown in Figure 8 When the expandable and contractible double-layer intracranial thrombus capturing stent reaches the position of the thrombus, the balloon catheter, the intermediate catheter and the micro catheter are withdrawn in sequence, and the stent body is exposed; when the balloon catheter is withdrawn to the preset position, the balloon is opened as a fixed support point after the device reaches the lesion, which is used to assist the expandable and contractible movement of the inner and outer layer stents in the body; at this time, the proximal end of the stent body is fixed, and the expansion of the control unit of the stent body is realized by pulling the control guide wire backward, thereby driving the slow expansion of the inner and outer layer stent bodies in the body;

[0056] As shown in Figure 7 The contraction of the control unit of the stent body is realized by pushing the control guide wire forward, thereby driving the contraction of the inner and outer layer stent bodies, and when the contraction reaches the preset value of the stent, the control guide wire is pulled backward to drive the whole stent to move to the micro catheter until it enters the micro catheter. After the stent body is exposed, the expansion and contraction degree and state of the stent can be adjusted at any time by pushing and pulling the control guide wire, so as to better fuse with the thrombus.

[0057] The stent direction guide tube is used to limit the movement of the stent when the control guide wire is pushed and pulled, and after the stent captures the thrombus and enters the micro catheter, the micro catheter is withdrawn to the intermediate catheter, the intermediate catheter withdraws the balloon catheter, the balloon is contracted, and the balloon catheter is pulled to withdraw all the devices out of the body.

[0058] In this example, the stent body is placed into the microcatheter after being stretched and contracted in vitro to the right position. After entering the body, the balloon of the balloon catheter is opened, the microcatheter is withdrawn, and the stent is released. At this time, the stent is in a fully contracted state, the control point at the distal end of the stent, i.e. the control point in the inner layer stent distal end spiral sleeve, is at the maximum distance from the microcatheter, and the length depends on the length of the outer layer stent. After the stent in this example is in place, the control wire can be pushed and pulled by a surgical control device such as a handle to change the expansion and contraction state of the stent.

[0059] In this example, a fixing device is provided at the connection between the microcatheter and the proximal end spiral sleeve of the outer layer stent. The control can be performed by introducing a screw with the same outer diameter as the proximal end threaded sleeve of the outer layer stent inside the microcatheter, or a microcatheter with a limiting device can be customized or purchased. For the positioning of the microcatheter, a limiting device needs to be added to the intermediate catheter. The positioning of the intermediate catheter is the same. The balloon catheter is used to fix and determine the overall positioning of the entire device. Therefore, in this example, the extension distance of the proximal end spiral sleeve of the outer layer stent relative to the microcatheter is predetermined, and the distances of the microcatheter relative to the intermediate catheter and the intermediate catheter relative to the balloon catheter are also predetermined, as shown in FIG. 1B, the lengths L1, L2 and L3 are all preset constant values. Figure 11

[0060] In this example, since the hollow grid circular tube type stent will elongate during the contraction process, in order to prevent the outer layer stent from being too long during contraction and causing the stent to lose stability during expansion, the distance between adjacent control points is set to an equal value during design to facilitate control.

[0061] Preferably, after the stent is processed and formed, a hydrophobic coating can be added to the surface to increase the flexibility of the stent in the body. The development point of the stent can be added at the control point. If a clearer development effect is needed, a development point can be added to the bridge of the outer layer stent. Most preferably, platinum wire can be added during stent processing to achieve the effect of whole-body development.

[0062] The connecting bridge of the outer layer stent grid module in this example is a straight rod. The bridge can also be replaced with a triangular function shaped wave-shaped bridge to reduce the pre-shrinkage of the stent and improve the stability of the stent during movement. The inner layer stent is used to improve the fusion of the stent and the thrombus and to quickly open the blood vessel passage. The design of the inner layer stent is constrained by the outer layer stent, so the length of the bridge connecting the inner layer stent grid module can be different, and the bridge shape can also be changed according to needs.

[0063] ​The catheter in the balloon catheter in the example is a common catheter, which can be replaced by a suction catheter of matching size to reduce the thrombus escape phenomenon near the catheter port during the stent withdrawal process and improve the one-time recanalization rate of the blood vessel.

[0064] The control unit in the middle part of the outer layer of the stent body has 2-4 control points, plus the control points at the head and tail of the stent, a total of 4-6 control points, and these control points are as evenly distributed as possible, that is, the distance between adjacent points is as consistent as possible, thereby ensuring the stability of the stent movement and expansion process.

[0065] The material of the stent body is a shape memory alloy, preferably a nickel-titanium alloy, and the stent is cut from a round tube by laser.

Claims

1. A retrievable controllable double-layer intracranial thrombectomy stent, characterized in that, Specifically comprising: The stent body, the microcatheter, the intermediate catheter, the balloon catheter, the stent direction guide tube and the control guide wire are composed of the outer layer stent and the inner layer stent; The stent body is located in the microcatheter, the microcatheter is located in the intermediate catheter, and the intermediate catheter is located in the balloon catheter; The outer layer stent comprises an outer layer stent frame, an outer layer stent threaded tightening sleeve, a control unit, a control unit tightening sleeve and an encryption net basket; the inner layer stent comprises an inner layer stent frame and an inner layer stent threaded tightening sleeve; The inner layer stent threaded tightening sleeve is placed in the outer layer stent threaded tightening sleeve, the two ends of the two stent frames are fixed through the respective threaded tightening sleeves, and the control guide wire fixing connection points are arranged in the inner and outer layer stent threaded tightening sleeves; The control unit is located at the middle part of the outer layer stent frame and is used for controlling the expansion and contraction of the stent frame, and is integrally processed with the outer layer stent and is fixed inwardly through the control unit tightening sleeve; the control unit tightening sleeve is provided with a control guide wire fixing connection point; The control guide wire passes through the inner and outer layer stent threaded tightening sleeves and the control unit simultaneously, is sequentially connected with the head and tail fixing connection points of the stent body and the fixing connection points of the control unit, and the expansion and contraction of the stent are realized through the push-pull operation of the control guide wire, specifically as follows: When the stent reaches the position of the thrombus, the balloon catheter, the intermediate catheter and the microcatheter are withdrawn in sequence, and the stent body is exposed; when the balloon catheter is withdrawn to the preset position, the balloon is opened as a fixed support point to assist the inner and outer layer stents to perform controllable expansion and contraction movement in the body; at this time, the proximal end of the inner and outer layer stent frames is fixed, the control unit is expanded by pulling the control guide wire backward, thereby driving the slow expansion of the inner and outer layer stent frames in the body; The control unit is contracted by pushing the control guide wire forward, thereby driving the contraction of the inner and outer layer stent frames; when the contraction reaches the preset value of the stent, the control guide wire is pulled backward to drive the whole stent to move to the microcatheter until it enters the microcatheter; after the stent body is exposed, the expansion and contraction degree and state of the stent can be adjusted at any time by pushing and pulling the control guide wire, so as to better fuse with the thrombus; The stent direction guide tube is used to limit the movement of the stent when the control guide wire is pushed and pulled; after the stent captures the thrombus and enters the microcatheter, the microcatheter is withdrawn to the intermediate catheter, the intermediate catheter withdraws the balloon catheter, the balloon is contracted, and the balloon catheter is pulled to withdraw all devices out of the body.

2. The retrievable controllable double-layer intracranial stent-riever of claim 1, wherein, The stent body is in the form of a hollow column when it is expanded, and the outer shape is in the form of a hollow grid; the two layers of stents are composed of a plurality of grid modules, and each grid module is composed of one or more groups of special-shaped grid units which have strong axial expansion and contraction ability and radial support ability; any two adjacent grid modules are connected through a rod-shaped bridge.

3. The retrievable controllable double-layer intracranial stent-riever of claim 1, wherein, ​ 4. The retrievable controllable double-layer intracranial stent-riever of claim 2, wherein, The design parameters of the special-shaped grid unit include: grid arc radius, length, width and inclination angle, the required stent diameter and length are realized by changing the design parameters of the special-shaped grid unit; when the inner and outer layer stent bodies are stretched, it is equivalent to stretching the two ends of the special-shaped grid unit, due to the deformation, the special-shaped grid unit presents different grid shapes, which can be used as the change range of the grid design shape, within the reasonable deformation range of the material, when the stent is radially contracted to 50% of the radius, the axial deformation can reach 150%.

5. The retrievable controllable double-layer intracranial stent-riever of claim 1, wherein, The inside of the outer layer stent thread tightening sleeve is also threaded, and the inner diameter is consistent with the outer diameter of the inner layer stent spiral sleeve; the diameter of the inner layer stent is smaller than that of the outer layer stent, and the length of the inner layer stent also differs from that of the outer layer stent, and the different diameters and lengths will result in different axial deformation lengths of the inner and outer layer stents.

6. The retrievable controllable double-layer intracranial stent-riever of claim 2, wherein, The connecting bridge of the grid module of the outer layer stent is: a straight rod or a wave-shaped bridge; the design of the inner layer stent is constrained by the outer layer stent, so the lengths of the bridges connecting the grid modules of the inner layer stent are selected to be different or the shapes of the bridges are changed according to the requirements.

7. The retrievable controllable double-layer intracranial stent-riever of claim 1, wherein, The catheter in the balloon catheter is a size-matched suction catheter.

8. The retrievable controllable double-layer intracranial stent-riever of claim 1, wherein, The stent is provided with 4-6 fixed connection points at the head and tail, and the control unit is provided with 2-4 control units, which are uniformly distributed, that is, the distance between adjacent points is consistent.

9. The retrievable controllable double-layer intracranial stent-riever of claim 1, wherein, The material of the stent body is shape memory alloy, and the stent is cut from a circular tube by laser.

10. The retrievable controllable double-layer intracranial stent-riever of claim 9, wherein, The shape memory alloy is nickel-titanium alloy.

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