Vascular Implants

Abstract

A method and apparatus relate to the use and construction of a vascular stent. A stent assembly includes a mesh structure that is at least partially attached to a support or stent structure. The stent structure is formed of one or more struts that together form a tubular body that is sized to fit within a blood vessel. The mesh structure is formed of one or more filaments or sutures that are interwoven or braided to form a structure that is coupled to the stent structure. The mesh structure may at least partially cover the stent structure or be at least partially covered by the stent structure.

Description

[0001] This application is a divisional application of the PCT international invention patent application with application number 201880024608.4, application date February 21, 2018, and invention name “vascular implant”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Application No. 62 / 461,616, filed on February 21, 2017, the disclosure of which is incorporated herein by reference. The provisional application is incorporated by reference in its entirety. Background Art

[0004] Stents for transluminal implantation are typically made of a metal support that is inserted into a portion of the human body, such as a blood vessel. Stents are typically generally cylindrical and constructed and arranged to expand radially once in place in the body. Some stents include a graft or mesh structure that can be used to minimize or eliminate the risk of herniation during the healing phase due to the stent implanted in the body.

[0005] The mesh structure of the stent assembly increases the overall width of the stent, which may be undesirable. Therefore, it is desirable to manufacture a stent such that the mechanical attachment between the mesh structure and the stent structure is effective from a size perspective. It is also important that the mesh structure is properly and securely attached to the support portion of the stent. Summary of the invention

[0006] Disclosed herein are methods and devices related to the use and construction of a vascular stent assembly. The stent assembly includes a mesh structure positioned on and / or at least partially attached to the stent structure. Also disclosed are devices and methods for securely attaching the mesh structure to the stent structure. The stent assembly may also include or be coupled to a stent delivery system configured to deliver the stent assembly to a patient's blood vessel.

[0007] In one aspect, a stent assembly suitable for implantation in a blood vessel is disclosed, comprising: an inner stent structure formed by a plurality of interconnected struts; an outer stent structure formed by a plurality of interconnected struts, the inner stent structure being positioned within the outer stent structure to form a space therebetween, wherein the inner stent structure and the outer stent structure together form a stent body, the stent body being sized and shaped to fit within a blood vessel; and a mesh structure at least partially positioned in the space between the inner stent structure and the outer stent structure, such that the mesh structure is attached to the inner stent structure and the outer stent structure in a sandwich arrangement.

[0008] On the other hand, a method for forming a stent assembly is disclosed, comprising: forming an inner stent structure from a plurality of interconnected struts; forming an outer stent structure from a plurality of interconnected struts; positioning the inner stent structure within the outer stent structure to form a space therebetween, wherein the inner stent structure and the outer stent structure together form a stent body, the stent body being sized and shaped to fit within a blood vessel; positioning a mesh structure at least partially in the space between the inner stent structure and the outer stent structure; and clamping the mesh structure in the space between the inner stent structure and the outer stent structure to attach the mesh structure to the inner stent structure and the outer stent structure.

[0009] Other features and advantages will be apparent from the following description of various embodiments, which illustrate, by way of example, the principles of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 An exemplary bracket assembly is shown.

[0011] Figure 2 A schematic diagram of a crimping structure for attaching a mesh structure to a stent structure is shown.

[0012] Figure 3 An example is shown where a fusible polymer lead is attached to a nickel titanium (NiTi) mesh structure.

[0013] Figure 4 A schematic diagram of a stent assembly is shown, the stent assembly comprising two stent structures, the stent structure comprising an inner stent structure and an outer stent structure, the inner stent structure and the outer stent structure forming a space therebetween, in which a mesh structure can be positioned and attached.

[0014] Figure 5 An embodiment is shown in which a separate holder element is attached to the support structure.

[0015] Figure 6 An example of filaments hand-sewn through the ends of a mesh structure is shown.

[0016] Figure 7 An enlarged view of the coronary region of a stent structure with closed-loop and open-loop anchors is shown.

[0017] Figure 8 An embodiment of an anchor that may be located on the coronal portion of a stent structure is shown.

[0018] Fig. 9 An exemplary stent assembly having a teardrop-shaped aperture is shown. DETAILED DESCRIPTION

[0019] Disclosed herein are methods and devices related to the use and construction of vascular stents. Stent assembly 100 includes a mesh structure 110, which is positioned on and / or at least partially attached to a support structure or stent structure 105. The stent structure is formed by one or more struts, which together form a tubular body that is sized to fit within a blood vessel. The mesh structure is formed by one or more filaments or sutures, which are interwoven or braided to form a structure that is coupled to a stent structure according to any of the configurations described herein. The mesh structure may at least partially cover the stent structure or be at least partially covered by the stent structure.

[0020] The stent assembly may also include or be coupled to a stent delivery system that is configured to deliver the stent assembly to a patient's blood vessel. An exemplary stent delivery system includes an elongated stent delivery catheter that may be inserted into a blood vessel, for example, percutaneously. The stent assembly may be mounted on the stent delivery catheter, for example, on a distal region of the stent delivery catheter. The stent delivery catheter may then be deployed to a target site, and the stent assembly may be released from the stent delivery catheter so that the stent assembly is deployed and maintained at a target location in the blood vessel.

[0021] The stent assembly can be used for implantation in any blood vessel including the carotid artery. The mesh structure of the stent assembly can be used to minimize or eliminate the risk of herniation due to the stent during the healing phase of a patient implanted with the stent assembly (eg, in the first 30 days of implantation).

[0022] The stent assembly can be any stent, including a self-expanding stent, or a stent that can be radially expanded by inflating a balloon or expanded by an expansion member. The stent can also be made of any desired material, including metallic materials, metal alloys (e.g., nickel-titanium) or even polymer composites. The stent can have any wire or cell design. The blood vessels in which the stent of the present invention can be deployed include, but are not limited to, natural body blood vessels such as blood vessels.

[0023] Various examples of mesh configurations for coupling to a stent structure are described herein. The mesh configuration may include, for example, (1) the material of the mesh; (2) the thread configuration of the mesh; (3) the size and number of filaments forming the mesh; (4) the attachment method between the mesh and the stent, etc.; and combinations thereof. Various embodiments of stent structures for attachment to a mesh structure are also described herein.

[0024] Figure 1A perspective view of a stent assembly 100 is shown, which includes a stent body 105 (or stent structure) coupled to a mesh body 110 (or mesh structure). The stent body is formed by a plurality of interconnected struts or wires, which are attached to each other to form a plurality of cells or openings. The struts can be attached to each other in any of a variety of ways. The stent body is generally formed into a cylindrical shape, which is sized and shaped to fit within a blood vessel, such as a carotid artery.

[0025] In one embodiment, the mesh structure (sometimes referred to as a "braid") is made of a shape memory alloy, such as nickel titanium (NiTi or Nitinol). In one exemplary embodiment, the mesh structure is formed of 0.0005 inch Nitinol filaments positioned on the stent. In another exemplary embodiment, the mesh structure is formed of polyester monofilaments or multifilaments.

[0026] A stent having a polyethylene terephthalate ("PET") mesh structure can be pressed down onto the stent structure for loading onto a delivery system. The mesh structure has a wall thickness that does not increase or significantly increase the overall thickness of the entire stent assembly. In this regard, the mesh structure can be sized to have a wall thickness that is less than twice the wall thickness of the stent structure.

[0027] Various structures and methods for attaching a mesh structure to a stent structure are now described.

[0028] Attachment by adhesive

[0029] In an embodiment for attaching the mesh structure 110 to the support structure 105, a curling edge 205 is formed and used as a mechanical interface between the mesh structure 110 and the support structure 105. For example, a planar portion of the material used to form the mesh structure is turned over on itself to form such a curling edge. The curling edge defines a space into which a corresponding portion of the support structure 105 can be inserted and fixed. Figure 2 A schematic diagram of a crimping structure 205 is shown, attached to the mesh structure 110 and the support structure 105 .

[0030] A separate crimping structure 205 is attached to the mesh structure 110, for example, by sewing or gluing. The mesh structure 110 is then glued to the support structure 105 by any of a variety of methods. For example, the mesh structure may be welded to the support structure, such as by gold welding a NiTi mesh structure to the support structure. Alternatively, polymer glues, melt, solvent polymer bonding, etc., or conformal polymer coatings may be used. Figure 3 Some examples are shown where a fusible polymer lead 305 is attached to a NiTi mesh structure 110. The attached polymer portion of the mesh structure is then melted, bonded, or otherwise mechanically attached to the stent structure.

[0031] In this manner, the stent component includes a transition from a shape memory material (eg, Nitinol) to a polymer material at the ends of the stent component.

[0032] Mechanical attachment via interlayer

[0033] In another embodiment for attaching the mesh structure 110 to the support structure 105, the mesh structure 110 is sandwiched between the inner support structure 105a and the outer support structure 105b. That is, the support assembly includes two support structures, including the inner support structure 105a and the outer support structure 105b. Figure 4 Schematically shown. A space is formed between the support structures 105a and 105b, and the mesh structure 110 can be at least partially positioned in the space. In this way, the mesh structure 110 is inserted or sandwiched between the support structures 105a and 105b to form a secure attachment therebetween.

[0034] In one example, the following specifications may be used for the inner and outer support structures:

[0035] 0.003" outer support structure and 0.006" inner support structure on NiTi mesh structure;

[0036] · 0.002" outer support structure and 0.008" or 0.009" inner support structure on NiTi mesh structure.

[0037] like Figure 5 As shown, in another sandwich embodiment, a separate clamp element 505 is added only on the coronal end of the stent structure. Figure 5 Shown in.

[0038] The sandwich embodiment is now further described. The inner support structure and the outer support structure can encapsulate the mesh structure by placing the mesh structure between them. The inner support structure applies a radial strength or radial outward force higher than the outer support structure, so that the net force between the inner support structure and the outer support structure pushes the entire stent assembly device toward the vessel wall (e.g., radially outward) when implanted. In terms of length, the inner support structure and the outer support structure are both longer than the length of the mesh structure. In one embodiment, except for two parameters, the inner support structure and the outer support structure have the same specifications. The first parameter is the strut length (SL) of the struts of the stent structure. The second parameter is the wall thickness (wt) of the stent structure.

[0039] In one example, the SL of the inner stent structure is about 15% shorter and the SL of the outer stent structure is about 15% longer. That is, all strut lengths of the inner stent structure are less than the shortest strut of the outer stent structure. The net difference in SL between the inner stent structure and the outer stent structure is 30%. By having a shorter SL, the radial strength becomes higher. By having a longer SL, the radial strength becomes lower. Therefore, the radial strength of the entire stent assembly device applies its radial strength outward (i.e., toward the vessel wall).

[0040] The wt of the inner stent structure is 0.006" and the wt of the outer stent structure is 0.003". By having a thinner wt, the radial strength becomes lower. By having a thicker wt, the radial strength becomes higher. Therefore, the radial strength of the composite device applies its radial strength outward (e.g., toward the vessel wall). In addition, the net wt of the composite device is equal to or below the 0.009" threshold wt. By adjusting the wt and SL of the inner and outer stents to accommodate higher or lower radial strengths, respectively, the net radial strength of the composite device applies an outward force toward the vessel wall.

[0041] Attachment by machine sewing

[0042] As described above, a crimp may be formed on the mesh structure. The mesh may be formed using a sewing machine and the crimp attached to the support structure. The mesh structure may also be mechanically sewn directly to the struts of the support structure. According to this process, filaments are used to form a stitch pattern that attaches the mesh structure to the support structure. The sewing stitch pattern may be formed by any type of filament, including, for example, 205 hand stitches and 301 lock stitches. The stitch may be formed in a circumferential direction along the struts of the support (or just across the struts of the support). The stitch width may be constant, or vary around the circumference of the device.

[0043] The stitches may have a constant or variable stitch length. For example, the stitches may be tighter at a certain number of discrete locations along the stent structure and slightly less tight at other locations. The braided structure may also form holes of various shapes and sizes.

[0044] Attached by hand sewing

[0045] In another embodiment, the mesh structure is attached to the support structure by hand sewing the ends of the mesh structure to itself and / or the support. Preferred sewing patterns can be used with custom features on the support to make it easier to attach sutures to the support. Exemplary sewing patterns include 301 lock stitch and 205 hand stitch for testing.

[0046] Figure 6An example of a filament 605 hand-sewn through the end of the mesh structure 110 is shown. The mesh structure is then attached to the coronal portion of the stent structure using a separate multiple loop suture. The filament is sewn so that it goes in and out of the multiple loops. The number of loops can vary. In one embodiment, there are 10 to 100 loops.

[0047] In one embodiment, a filament (eg, PET filament) is sewn through the ends of the NiTi mesh structure and connected to the stent structure. The filament is sewn through one or more loops of the mesh structure and also through annular holes or openings along the coronal portion of the stent structure.

[0048] Attached by hand sewing with suture anchors

[0049] The coronal region of the stent assembly may include one or more types of suture anchors. The coronal portion of the stent includes a first type of suture anchor having a "split O" configuration, wherein the suture anchor forms a partial ring with a gap or opening along its circumference. The gap or opening provides a channel for the suture to be inserted into the anchor.

[0050] The second type of suture anchor is a "solid circle" or closed loop, wherein the suture anchor forms a completely closed loop. Figure 7 An enlarged view of the coronary region of a stent structure is shown with closed loop anchors 705 and open loop anchors 710. Sutures may be passed through the open loop anchors and secured in a splint-like manner, wherein the sutures also extend through the open loop anchors. The sutures may alternately be looped around the closed loop anchors and also wrapped around the base of the anchors to further secure the sutures thereto.

[0051] Ideally, the mesh structure is fixed to the stent structure in such a manner that the mesh structure is fixed to the stent structure against forces applied in the distal and proximal directions along the longitudinal axis of the stent structure, that is, the mesh structure will remain fixed and will not detach from the stent structure regardless of the direction of the relative forces between the stent structure and the mesh structure.

[0052] Figure 8 An embodiment of an anchor 805 that can be located on the coronal portion of a stent structure is shown. The anchor forms an open loop and includes one or more "ears", prongs, barbs or projections 810 that serve as structures to further secure the suture to the anchor. Figure 8 As shown, suture 110 (actually the figure should be modified, 110 is modified to 805) can pass through the open loop and also be wrapped around the ear to fix the suture thereto and prevent it from detaching from the stent structure during loading and / or removing the stent assembly from the delivery system. It should be understood that the ear structure is only an example, and other structures can be used to further fix the suture to the stent structure.

[0053] Mechanical attachment via interconnect features

[0054] In another embodiment, the mesh is mechanically interconnected to features of the stent. A variety of methods can be used to mechanically attach the mesh structure to the stent structure. For example, the ends of the mesh structure can be wrapped around the ends of the stent structure, or the mesh structure forms a ring inside itself, where the two braided layers are on the outside of the stent. The two braided layers can then be bonded or sewn together with the construction.

[0055] Optionally, the ends of the braid can be "finished" so that the filaments used for the braid do not loosen or unravel. The ends of the braid are secured using any of the methods described in the present disclosure. Next, the ends of the mesh structure are looped around some features of the stent. These features may include crowns or finger-like protrusion structures of the stent. The protrusions may face away or outward to help the mesh structure engage more easily.

[0056] Attachment via polymer coating

[0057] In another embodiment, a polymer coating can be used to finish the ends of the mesh structure and / or to attach the mesh structure to the stent structure. A thin polymer layer is added to the ends of the mesh structure to prevent the mesh structure from unraveling before being attached to the stent structure.

[0058] Alternatively, the polymer coating is used to help "finish" the ends of the mesh structure and also serve as a mechanism for disposable attachment of the mesh stent struts. For this example, the polymer may be sprayed only on the ends of the stent assembly, leaving the center of the stent / mesh structure free of any polymer. The polymer coating may be applied to one or more rows of braid elements, less than one row of braid elements, one or more strut-rung element, or less than one strut-rung element. In order to coat only the ends of the braid, it may be necessary to mask the center of the stent structure with a masking agent that can be removed after the coating process is complete.

[0059] Polymer coating can be achieved using a dipping or spraying process with various solid contents. Multiple cycles may be required to achieve adequate coating. It is critical to encapsulate the entire braided filament-stent strut element with the coating to ensure it is adequately attached.

[0060] Various polymer gluing or coating options for securing the mesh ends and / or bonding to the stent are shown in the table below.

[0061]

[0062]

[0063] Other materials that may be used include, for example:

[0064] Parylene C: Conformal coating formed by vapor deposition. With a long history in medical devices.

[0065] PEVA: Rubbery copolymer. Available in a variety of vinyl acetate series. Very low VA content (less than 10%) is difficult to dissolve. Higher VA (18-33%) will be very flexible and sticky.

[0066] PBMA: Tough material. Not as flexible as PEVA. Soluble in many solvents.

[0067] SIBS: Tough rubber material. Soluble in several solvents.

[0068] PC: Tends to form self-assembled monolayers.

[0069] PVP: water-soluble polymer.

[0070] Polyvinylidene fluoride / hexafluoropropylene: melt processable.

[0071] Attachment by welding

[0072] In another embodiment, the mesh structure can also be welded to the support structure. For example, the following materials can be used in the welding process:

[0073] - Niti wire (from braid) for Niti bracket welding: laser welding, resistance welding

[0074] -Polymer filaments for Niti stent welding (from braid)

[0075] A variety of mesh configurations may be used. A circular weave approach may be used, wherein the apertures may be formed by any one or a combination of a variety of polymer or metal fibers. Exemplary NiTi or PET fibers are approximately 0.001", 0.00075", 0.0005" diameter wires.

[0076] Exemplary cell patterns for mesh or scaffold structures

[0077] exist Fig. 9In the illustrated embodiment, the braid or mesh structure may be formed and / or post-processed to form a paired hole or unit pattern. For example, the mesh structure forms a plurality of teardrop-shaped holes 905, which have an enlarged circular area at the first end and a smaller sharp angle area at the second end. In the paired pattern, the enlarged circular areas of at least two teardrop-shaped holes contact or abut each other. The teardrop-shaped holes may extend along the long axis, wherein the circular area of ​​the hole is positioned at the first end along the axis, and the sharp angle area is positioned at the second end along the axis, wherein the axis is straight. The holes may be arranged in rows so that the larger areas of the two holes are in direct contact in a "paired" arrangement, while the smaller areas of the two holes are spaced apart from each other. A series of holes (e.g., holes 905a and 905b) are coaxial along a common long axis. One way to achieve this pattern is to weave a tubular braided structure with a single plurality of holes, wherein at least some of the holes are generally circular, square, or rectangular in shape. The tubular braid may be stretched longitudinally onto a smaller diameter mandrel to produce elongated pores in a paired or teardrop pattern; the structure may then optionally be heat set to retain the shape.

[0078] The teardrop-shaped hole arrangement described above enables smaller hole diameters to be achieved with certain wires to form stent components and holes, such as Nitinol wires with diameters ranging from 0.0005" to 0.001". In one exemplary embodiment, the "matched" hole configuration enables a minimum hole width of 100-250um and an aspect ratio ranging from 3:1 to 10:1.

[0079] Although this specification contains many details, these details should not be interpreted as limitations on the scope of the claimed or claimable invention, but as descriptions of features specific to a particular embodiment. Certain features described in the context of a single embodiment in this specification may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments. In addition, although the above-mentioned features may be described as working in certain combinations or even initially claimed, one or more features in the claimed combination may be deleted from the combination in some cases, and the claimed combination may involve a sub-combination or a variation of the sub-combination. Similarly, although operations are illustrated in a particular order in the accompanying drawings, this should not be understood as requiring the operations to be performed in the particular order shown or in sequence, or to perform all the operations shown, to achieve the desired result. Only a few examples and implementations are disclosed. The described examples and implementations and other implementations may be modified, improved and enhanced based on the disclosed content.

Claims

1. A method of forming a stent assembly, comprising: forming a stent structure by positioning an inner stent structure within an outer stent structure to form a space therebetween, wherein the inner stent structure is formed of a plurality of interconnected struts and the outer stent structure is formed of a plurality of interconnected struts, the inner stent structure and the outer stent structure together forming a stent body sized and shaped to fit within a blood vessel; longitudinally stretching a tubular braided structure having a plurality of holes onto a mandrel to form a plurality of teardrop-shaped holes in the tubular braided structure, wherein at least one hole of the plurality of holes transitions from a first shape to a teardrop shape; heat setting the tubular braided structure to form a mesh structure; positioning the mesh structure at least partially in a space between the inner support structure and the outer support structure; sandwiching the mesh structure in the space between the inner support structure and the outer support structure to attach the mesh structure to the inner support structure and the outer support structure, The coronary region of the stent structure has closed-loop anchors and open-loop anchors, wherein sutures extend through the open-loop anchors and are secured in a splint-like manner, and wherein the sutures are also alternately looped around the closed-loop anchors and wrapped around the base of the closed-loop anchors.

2. The method of claim 1, further comprising forming a curled edge on the mesh structure. 3 . The method of claim 2 , further comprising positioning at least a portion of one of the inner support structure and the outer support structure within the bead.

4. The method according to claim 2, wherein: Forming a bead on the mesh structure includes attaching the bead to the mesh structure.

5. The method according to claim 2, wherein: Forming a bead on the mesh structure includes folding a portion of the mesh structure upon itself.

6. The method of claim 1, further comprising forming a plurality of teardrop-shaped holes in the mesh structure.

7. The method according to claim 1, wherein: The teardrop-shaped holes are arranged such that at least two teardrop-shaped holes have an enlarged circular area at a first end and a smaller area at a second end, and wherein the enlarged circular areas of at least two teardrop-shaped holes contact each other.

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