Expandable tube for deployment within blood vessel

Abstract

An expandable tube for deployment within a blood vessel is reversibly switchable from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state. The expandable tube includes: a first frame; and a second frame connected to the first frame and overlapping the first frame in the radial direction. The second frame includes a network of non-overlapping elements that do not overlap each other in the radial direction. The network of non-overlapping elements has an interconnect structure including a plurality of sub-cells repeating in a longitudinal direction. Each sub-unit of the second frame defines a closure unit, and in a radially expanded and longitudinally contracted state, the closure unit has a bulbous region in which the closure unit widens toward a circumferential end of the closure unit and away from a circumferential central region of the closure unit.

Description

Background Art

[0001] The present invention relates to an expandable tube for deployment within a blood vessel, particularly for redirecting blood flow away from an aneurysmal sac.

[0002] An intracranial aneurysm is a weak area in the wall of a cerebral artery where dilation or bulging of the artery wall may occur. Histologically, a reduction in the tunica media, the middle muscle layer of the artery, and the internal elastic lamina causes structural defects. These defects, combined with hemodynamic factors, lead to out-pouching of the aneurysm. Intracranial aneurysms are a very common disease with a prevalence of 1% to 5% in the adult population, according to autopsy studies. In the United States alone, 10 to 12 million people may have an intracranial aneurysm.

[0003] Current treatments for intracranial aneurysms include surgical clipping and endovascular coiling. In the surgical clipping method, the patient's skull is opened and surgical clips are placed across the neck of the aneurysm to block blood flow into the aneurysm sac. The risks of this method are relatively high, especially for elderly or medically complex patients. Endovascular coiling is a less invasive method that involves placing one or more coils delivered by a catheter into the aneurysm until the aneurysm sac is completely filled with coils. This helps to induce thrombosis within the aneurysm. Although endovascular coiling is considered safer than surgical clipping, it has its own limitations. First, after the aneurysm is filled with coils, it will retain its original size. Therefore, the pressure exerted by the aneurysm on the surrounding tissue will not be eliminated. Second, this procedure is not very effective for wide-necked aneurysms where the coils may protrude into the parent vessel. This problem can be alleviated by combining stents and coiling embolization, but the process is difficult and time-consuming.

[0004] Treating aneurysms using an expandable tube (sometimes called a stent) alone is a promising way to avoid the above problems. In this method, an expandable tube with a relatively low porosity area is placed across the neck of the aneurysm in a way that redirects blood flow away from the sac and triggers the formation of a thrombus within the aneurysm. Because the aneurysm itself will naturally coagulate, there is less risk of it rupturing. In addition, because no coils are involved in this method, the aneurysm will gradually shrink as the thrombus is absorbed. As a result, the pressure exerted on the surrounding tissue can be eliminated. However, it is difficult to manufacture an expandable tube with optimal properties for this application. The expandable tube must be flexible enough to pass through and adapt to the shape of very tortuous blood vessels in the brain, while providing a low enough porosity to redirect blood flow away from the aneurysm to a sufficient extent.

[0005] A known type of expandable tube is formed by braiding filaments (e.g., wires). The filaments are braided together to form a mesh tube. This type of expandable tube can be radially contracted and longitudinally expanded inside a catheter for placement in a blood vessel. When in the correct position above the neck of an aneurysm, the expandable tube is deployed from the inside of the catheter, whereupon the expandable tube radially expands and longitudinally contracts, causing it to become stuck in the blood vessel and block blood from flowing into and out of the aneurysm. However, the problem with braided filament expandable tubes is that a large number of contact points between the filaments in the braided structure create friction. In addition, each filament is free to move relative to other crossed filaments, resulting in poor radial outward force. This can cause the braided filament expandable tube to expand radially slowly and inconsistently when deployed from the catheter, making the correct placement of the expandable tube relative to the neck of the aneurysm more difficult and less reliable.

[0006] Another existing type of expandable tube is formed from a network of interconnected and non-overlapping elements. This can be formed, for example, by laser cutting from a narrow tube of a material such as a shape memory alloy. These laser cut tubes have the advantage that there are no contact points between the braided filaments to cause friction, and their deployment can be more consistent. However, it can be difficult to design a tube of this type with a low enough porosity to adequately occlude an aneurysm.

[0007] Both types of expandable tubes have additional limitations: they are generally unable to conform to tight bends in tortuous anatomy, which is particularly common in the brain, where many small blood vessels are packed closely together, and may twist or expand improperly.

[0008] The object of the present invention is to provide an expandable tube for deployment within a blood vessel, which expandable tube has improved properties, in particular with regard to the deployment of the expandable tube. Summary of the invention

[0009] According to a first aspect of the present invention, there is provided an expandable tube for deployment within a blood vessel, the expandable tube being capable of reversibly switching from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state, the expandable tube comprising: a first frame; and a second frame connected to the first frame and overlapping with the first frame in a radial direction, the second frame comprising a network of non-overlapping elements which do not overlap with each other in a radial direction, wherein: the network of non-overlapping elements has an interconnected structure comprising a plurality of sub-units repeated in a longitudinal direction; each sub-unit of the second frame defines a closed unit; and in a radially expanded and longitudinally contracted state, the closed unit has a bulbous region, wherein the closed unit widens toward the circumferential ends of the closed unit and away from the circumferential central region of the closed unit.

[0010] Using a frame defining closed cells with bulbous regions provides a longer path length of non-overlapping elements around the closed cells. This improves bending flexibility to allow the expandable tube to bend around tighter curves without kinking.

[0011] Optionally, the closed cell comprises two bulbous areas at opposite circumferential ends of the closed cell. The two bulbous areas provide greater symmetry and further improve flexibility.

[0012] Optionally, the closed cell is an area around the circumference of the second frame enclosed by the non-overlapping elements.The closed cell defines an area on the circumferential surface of the expandable tube.

[0013] Optionally, the network of non-overlapping elements includes a plurality of longitudinally extending members defining an interconnected structure, and circumferentially adjacent longitudinally extending members are connected at a connection point. The use of longitudinally extending members provides greater longitudinal flexibility, which helps to improve bending flexibility by allowing the closed cell to expand or contract longitudinally around a bend.

[0014] Optionally, in the radially expanded and longitudinally contracted state, the longitudinal direction is reversed between successive connection points along the path of each longitudinally extending member.Doubling the longitudinally extending member back on itself creates a bulbous region and increases the path length along the member.

[0015] Optionally, for each subunit that intersects the longitudinally extending member three or more times in the radially expanded and longitudinally contracted state, there is a circumferential line preferably located at the midpoint between consecutive connection points of the longitudinally extending member. This ensures that the longitudinally extending member folds back on itself to create a bulbous area and increase the path length along the member.

[0016] Optionally, the longitudinally extending member is longitudinally deformable. Extending the longitudinally extending member by deformation is a simple longitudinal extension mechanism that reduces manufacturing complexity.

[0017] Optionally, each subunit defines a plurality of enclosed cells around the circumference of the second frame, circumferentially adjacent enclosed cells being connected at a connection point; and in the radially expanded and longitudinally contracted state, the radius of curvature of the longitudinally extending member decreases as it moves away from the connection point. Connecting the longitudinally extending members together increases torsional stiffness and resists twisting of the expandable tube. The radius of curvature decreases away from the connection point so that when the longitudinally extending member is folded in half on itself, a bulbous region can be formed. In addition, the larger radius adjacent to the connection point promotes low mechanical strain in the radially contracted and longitudinally expanded state.

[0018] Optionally, the closed cells have mirror symmetry in a plane parallel to the longitudinal axis of the expandable tube and / or in a plane perpendicular to the longitudinal axis of the expandable tube. Optionally, longitudinally adjacent sub-cells have mirror symmetry in a plane perpendicular to the longitudinal axis of the expandable tube. The mirror symmetry between different structural levels improves the uniformity of the behavior of the expandable tube.

[0019] Optionally, each sub-unit defines a plurality of closed cells around the circumference of the second frame, circumferentially adjacent closed cells being connected at a connection point.Connecting the longitudinally extending members together increases torsional rigidity and resists twisting of the expandable tubular.

[0020] Optionally, circumferentially adjacent closed cells have mirror symmetry in a plane parallel to the longitudinal axis of the expandable tube.The mirror symmetry between different structural levels improves the uniformity of the behavior of the expandable tube.

[0021] Optionally, circumferentially adjacent closed cells are connected at the connection point via a bridge, optionally wherein the bridge is a rigid bridge. Optionally, the bridge extends circumferentially. The use of a bridge allows adjacent cells to remain independent and reduces the effect of the connection on the ability of non-overlapping elements to deform around the connection point.

[0022] Optionally, the bridge has a longitudinal length of at most 0.1 mm, preferably at most 0.08 mm. Optionally, the bridge has a circumferential length of at most 0.2 mm, preferably at most 0.1 mm. These dimensions have been found to be effective in joining adjacent cells while providing good torsional stiffness.

[0023] Optionally, the non-overlapping elements include straight sections at the connection points. The straight sections minimize deformation of the non-overlapping elements around the connection points, which could cause excessive mechanical strain, accelerated fatigue or damage to the connection.

[0024] Optionally, the radius of curvature of the non-overlapping elements adjacent to the straight portion is at least 0.3mm, preferably at least 0.5mm, most preferably at least 0.7mm. This ensures that the curvature away from the straight portion increases at an appropriate rate.

[0025] Optionally, the length of the straight portion is at least 0.05 mm, preferably at least 0.1 mm. This length has been found to be effective in reducing strain at the connection point.

[0026] Optionally, the closed cells widen in the bulbous region by at least 20%, preferably at least 40%, more preferably at least 60%.This level of widening provides sufficient additional path length to achieve an improvement in the bending flexibility of the expandable tube.

[0027] Optionally, the second frame is configured to drive the expandable tubular from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state. Using the second frame to drive expansion of the first frame helps the tubular to deploy more consistently and reliably, thereby reducing the likelihood of deployment failure.

[0028] Optionally, the second frame is configured to drive the expandable tube from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state by applying a force to the first frame in a radial direction. Applying a force in the radial direction means that when released from the deployment catheter, the first frame will quickly expand to its full diameter, making it easier to correctly place.

[0029] Optionally, the network of non-overlapping elements is integrally formed. This reduces the complexity of the manufacturing process by eliminating the need to join elements of the network. It will also reduce defects or irregularities in the surface of the second frame due to the joining between elements.

[0030] Optionally, the second frame is connected to the first frame at least at one end of the second frame.Connecting the two frames together ensures that they do not move relative to each other and that the behavior of the expandable tube is consistent and predictable.

[0031] Optionally, the second frame is further connected to the first frame at one or more points along the length of the second frame. This means that the interaction of the first frame and the second frame is uniform along the length of the expandable tube and is not only constrained at the ends of the expandable tube.

[0032] Optionally, the second frame is connected to the first frame by at least one of welding, crimping, adhesive or potting. These are particularly convenient joining methods where the first frame is formed from braided filaments.

[0033] Optionally, the second frame includes a plurality of filament receiving apertures; one or more connecting filaments are woven into the first frame; and each connecting filament passes through one or more of the filament receiving apertures. Compared to other methods (such as crimping or welding), the use of connecting filaments reduces the joint profile between the first frame and the second frame, thereby making the surface of the expandable tube more uniform.

[0034] Optionally, the connecting filaments comprise the filaments of the first framework. This means that no additional filaments are added, keeping the size of the expandable tube the same as without the connecting filaments.

[0035] Optionally, one or more radiopaque markers are attached to one or more of the connecting filaments. The connecting filaments are convenient attachment points for radiopaque markers that improve visibility of the expandable tube during deployment.

[0036] Optionally, the plurality of filament receiving apertures comprises a filament receiving aperture in a longitudinal end region of the second frame.This secures the total length of the two frames together.

[0037] Optionally, the plurality of filament receiving apertures comprises filament receiving apertures spaced apart along the length of the second frame.Including further apertures spaced apart along the second frame improves the attachment of the first frame and the second frame to each other, thereby reducing the chance of the two frames becoming detached.

[0038] Optionally, the length of the second frame is at least 50% of the length of the first frame. Optionally, the second frame overlaps the first frame over at least 50% of the length of the expandable tube. These requirements ensure that the second frame can interact with the first frame over most of its length to produce a uniform behavior of the expandable tube.

[0039] Optionally, the second frame is positioned within the first frame. Having the braided filaments on the outside of the expandable tube means that a uniform sheath is provided along the length of the expandable tube. This provides a greater radial expansion force on the first frame than if the second frame were arranged outside the first frame, thereby further facilitating proper deployment of the expandable tube.

[0040] Optionally, the radius of the second frame in an unconstrained state in which the second frame is not connected to the first frame and the second frame is radially expanded and longitudinally contracted is greater than the radius of the first frame in an unconstrained state in which the first frame is not connected to the second frame and the first frame is radially expanded and longitudinally contracted. Oversizing the second frame so that its unconstrained radius is greater than the radius of the first frame helps ensure that the second frame is able to drive the deployment of the expandable tube and minimizes the risk of radial separation between the two frames, particularly when deployed in tortuous anatomical structures. This also means that fewer fixing points are required to securely join the two frames together.

[0041] Optionally, the first elongation of the first frame is within 25% of the second elongation of the second frame, the first elongation being the ratio between the length of the first frame in an unconstrained state in which the first frame is not connected to the second frame and the first frame is radially expanded and longitudinally contracted and the length of the first frame in a radially contracted and longitudinally expanded state, and the second elongation being the ratio between the length of the second frame in an unconstrained state in which the second frame is not connected to the first frame and the second frame is radially expanded and longitudinally contracted and the length of the second frame in a radially contracted and longitudinally expanded state. Previously designed expandable tubes including braided filaments include expansion rings at one or both ends of the expandable tube to facilitate proper deployment of the ends of the braided tube. However, increasing the length of the expansion ring relative to the braided stent to facilitate proper deployment over the entire length is challenging because the expansion characteristics of the two types of frames are different. Matching the elongation ensures that no creases or warping of the first frame or the second frame will occur when the expandable tube is deployed, thereby reducing the chance of deployment complications. This further allows the second frame to be made longer relative to the first frame and further improves the consistency of deployment of the expandable tube.

[0042] Optionally, the network of non-overlapping elements includes a plurality of longitudinally deformable elements for providing longitudinal expansion and contraction of the second frame; each minimal repeating unit of the network of non-overlapping elements has a first length in the longitudinal direction in an unconstrained state in which the second frame is not connected to the first frame and the second frame is in a radially expanded and longitudinally contracted state; and the ratio between the first length and the path length along each longitudinally deformable element is within 25% of the first elongation. Correctly selecting the path length along the longitudinally deformable elements will determine the longitudinal expansion of the second frame so that it matches the first elongation of the first frame.

[0043] Optionally, the first frame comprises a shape memory alloy material, preferably nitinol. Shape memory alloys are a convenient material choice because they can be designed to return to a desired shape when freed from a constraint, thereby eliminating the need to apply an external force on the tube to cause it to expand radially.

[0044] Optionally, when the expandable tube is positioned over the opening of the aneurysm sac in a radially expanded and longitudinally contracted state in use, the first frame has a porosity to redirect blood flow away from the aneurysm sac, thereby promoting thrombosis in the aneurysm sac. This ensures that the expandable tube is operable in inducing thrombosis in the aneurysm.

[0045] Optionally, the first framework has a porosity of at most 90% in the radially expanded and longitudinally contracted state of the expandable tube. Limiting the porosity of the first framework reduces the porosity of the expandable tube such that it may induce thrombus formation in the aneurysm.

[0046] Optionally, the first framework comprises braided filaments. Braided filament frameworks are well known and their manufacture is mature. They can also provide good porosity values ​​suitable for occluding aneurysms.

[0047] Optionally, the first framework comprises at least 48 filaments. A higher filament count helps increase the pore density, which improves the ability of the expandable tube to occlude an aneurysm.

[0048] Optionally, the filaments of the first framework have a diameter of at most 30 μm. Smaller diameter filaments allow for an increased number of filaments while maintaining compatibility with appropriately sized microcatheters.

[0049] Optionally, the first framework has a braid angle of at least 50°. This advantageously allows the expandable tube 2 to conform to the tortuous anatomy of a vessel without twisting. A larger braid angle results in improved bending flexibility, smaller pores (allowing for higher pore density), and greater longitudinal flexibility.

[0050] Optionally, the first frame has a pore density of at least 20 pores / mm 2 The higher pore density improves the ability of the expandable tube to occlude the aneurysm and promotes endothelialization of the tube.

[0051] Optionally, the second frame comprises a shape memory alloy material, preferably Nitinol. Shape memory alloys are a convenient choice of material because they can be designed to return to a desired shape when freed from a constraint, thereby eliminating the need to apply an external force on the tube to cause it to expand radially.

[0052] Optionally, the second frame has a porosity of at least 70%.Since the second frame has a relatively high porosity, the first frame is the primary determinant of the porosity of the expandable tube, thereby simplifying the design of the overall performance of the expandable tube.

[0053] Optionally, the maximum radial dimension of the expandable tube in the radially contracted and longitudinally expanded state is at least 30% smaller than the maximum radial dimension of the expandable tube in the radially expanded and longitudinally contracted state. This will allow sufficient compression of the expandable tube so that it can be inserted into a catheter for deployment.

[0054] Optionally, the elongation of the expandable tube in the longitudinal direction caused by switching from the radially expanded and longitudinally contracted state to the radially contracted and longitudinally expanded state is at least 10%.Providing longitudinal expansion and contraction increases the extent to which the expandable tube can radially expand and contract.

[0055] Optionally, in the radially contracted and longitudinally expanded state, the maximum dimension of the expandable tube in the radial direction enables the expandable tube to be inserted into a catheter having an inner diameter of at most 1.0 mm. Catheters of this size are widely available and commonly used to treat cerebral aneurysms, and therefore compatibility with this catheter size is desirable.

[0056] According to a second aspect of the present invention, there is provided an expandable tube for deployment within a blood vessel, the expandable tube being capable of reversibly switching from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state, the expandable tube comprising a frame comprising a network of non-overlapping elements which do not overlap with each other in a radial direction, wherein: the network of non-overlapping elements has an interconnected structure comprising a plurality of sub-units repeated in a longitudinal direction; each sub-unit defines a closed unit; in a radially expanded and longitudinally contracted state, the closed unit has a bulbous region in which the closed unit widens toward the circumferential end of the closed unit away from the circumferential central region of the closed unit; and the closed unit has mirror symmetry in at least one of a plane parallel to the longitudinal axis of the expandable tube and a plane perpendicular to the longitudinal axis of the expandable tube.

[0057] The use of a bulbous region and symmetrical closed cells allows the expandable tube to have improved flexibility for navigating tortuous anatomy, as well as improved longitudinal stiffness for easier deployment. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which corresponding reference numerals indicate corresponding parts, and in which:

[0059] Figure 1 is a schematic diagram of an expandable tube in a radially expanded and longitudinally contracted state;

[0060] Figure 2 is a schematic diagram of an expandable tube in a radially contracted and longitudinally expanded state;

[0061] Figure 3 is a schematic diagram of an expandable tube including a first frame and a second frame in a radially expanded and longitudinally contracted state;

[0062] Figure 4 is a schematic diagram of an expandable tube including a first frame and a second frame in a radially contracted and longitudinally expanded state;

[0063] Figure 5 An expandable tube comprising a first frame and a second frame including a closed cell having a bulbous region is shown;

[0064] Figure 6 A repeating subunit defining a closed unit having a bulbous region is shown;

[0065] Figure 7 An expandable tube is shown at different levels of radial contraction and longitudinal expansion;

[0066] Figure 8 shows how the second frame accommodates the sharp bend;

[0067] Fig. 9 An aperture at the end of the second frame is shown, which can be used to connect the first frame and the second frame;

[0068] Fig.10 Details of connecting the first frame and the second frame using the apertures and connecting filaments are shown;

[0069] Fig.11 Shows Fig.10 Details of an alternative design wherein the filaments of the first frame serve as connecting filaments connecting the first frame to the second frame;

[0070] Fig.12 The addition of a radiopaque marker to the engagement filaments is shown;

[0071] Fig.13 shows the change in shape of the spaces between the braided filaments in the first frame between a radially expanded and longitudinally contracted state and a radially contracted and longitudinally expanded state;

[0072] Fig.14 Dimensions of the expandable tube are shown in a radially expanded and longitudinally contracted state and in a radially contracted and longitudinally expanded state;

[0073] Fig.15 The smallest repeating section of the second frame is shown;

[0074] Fig.16 is a schematic diagram of an expandable tube being deployed from a catheter; and

[0075] Figure 17(a)-Figure 17(c) The expandable tube is shown deployed inside a model blood vessel. DETAILED DESCRIPTION

[0076] The present disclosure provides an expandable tube suitable for deployment within a blood vessel. The expandable tube, which may also be referred to as a stent, is suitable for use in a method for treating an aneurysm. In particular, the design herein is suitable for use in a method for treating a cerebral aneurysm, where the blood vessel in which the expandable tube must be deployed is narrow and tortuous.

[0077] Figure 1 The outer geometry of the expandable tube 2 is depicted in a radially expanded and longitudinally contracted state. Figure 2 The external geometry of the expandable tube 2 is depicted in a radially contracted and longitudinally expanded state. Figure 2 The radially contracted and longitudinally expanded state shown can be reversibly switched to Figure 1 Radially expanded and longitudinally contracted states are shown. As will be discussed further, the expandable tube 2 includes a first frame 10, optionally comprising braided filaments, and a second frame 12, comprising a network of non-overlapping elements.

[0078] The expandable tube 2 is elongated relative to the elongation axis 4. For example, the expandable tube 2 can be cylindrical. When the expandable tube 2 is cylindrical, the maximum transverse dimension is the same at all positions and angles (i.e., it is equal to the diameter). When the expandable tube 2 is not cylindrical, the maximum transverse dimension can be different at different positions and / or angles. The maximum transverse dimension defines the minimum inner diameter of a cylindrical tube (e.g., a delivery catheter) into which the frame can be inserted.

[0079] In the radially contracted state, the expandable tube 2 is significantly narrower than in the radially expanded state. Preferably, in the radially contracted and longitudinally expanded state, the maximum dimension of the expandable tube 2 in the radial direction is at least 30% smaller, more preferably at least 50% smaller than the maximum dimension of the expandable tube 2 in the radial direction in the radially expanded and longitudinally contracted state. The expandable tube 2 is radially contracted to allow the expandable tube 2 to be inserted into a narrower delivery catheter for deployment at the site of interest. It is generally desirable that the delivery catheter be as narrow as possible. This is particularly true when it is necessary to navigate a tortuous area of ​​the vascular system to reach the deployment site. This often occurs, for example, when treating cerebral aneurysms.

[0080] In the following discussion, it should be understood that the term porosity p refers to the ratio of the surface area of ​​the open area to the total external surface area occupied by the expandable tube 2, the portion of the expandable tube 2 being described, or the frame of the expandable tube 2 (to be discussed further below). The total external surface area is the sum of the surface area of ​​the open area and the surface area of ​​the area occupied by the material of the expandable tube 2 or frame. When the expandable tube 2 or frame is cylindrical, the total external surface area is simply 2πRL, where R is the radius of the cylinder and L is the length of the cylinder.

[0081] Consider the second frame 12 of the expandable tube 2, which includes elements that are not allowed to overlap each other in the radial direction. The second frame 12 has a porosity ρ in the fully radially expanded state. If the radius and length of the second frame 12 in the fully radially expanded state are R0 and L0, respectively, the minimum radius R that the second frame 12 can achieve in the radially contracted state is min (defined by the state where the porosity becomes zero) is controlled by:

[0082]

[0083] Wherein, L1 is the length of the second frame 12 in the radially contracted state.

[0084] This relationship suggests that the radius can only be reduced by a factor of ρ if the length of the second frame 12 is not allowed to change significantly. Since ρ needs to be quite low (e.g., less than 90%, preferably less than 80%, at least in low porosity areas (such as areas expected to be positioned above the opening of the aneurysm sac in use), this places a significant limitation on the extent to which the second frame 12 can be narrowed for insertion of a delivery catheter. For example, if the porosity ρ of the second frame 12 is 20% and the length of the second frame 12 is not allowed to change during radial contraction (i.e., L1=L0), the second frame 12 can only achieve a maximum 20% reduction in radius. Allowing for increases in length is also important for frames that contain braided filaments. If the length of a braided frame cannot be changed due to its braided structure, the radius of the braided frame cannot be reduced, and the greater the length may increase, the greater the radius may decrease.

[0085] Based on this understanding, an expandable tube 2 having a frame is provided which can be longitudinally expanded and allows a greater radius reduction to be achieved when the radially contracted state is adopted. For example, if the length is allowed to double, i.e. L1=2L0, for a porosity of 20%, the second frame 12 can achieve a radius reduction of 60%. Therefore, the elongation of the expandable tube 2 (or a frame forming part of the expandable tube 2) in the longitudinal direction caused by switching from a radially expanded and longitudinally contracted state to a radially contracted and longitudinally expanded state is preferably at least 10%, more preferably at least 20%, and most preferably at least 30%.

[0086] Figure 3 More details of the expandable tube 2 are shown in a radially expanded and longitudinally contracted state. The expandable tube 2 comprises a first frame 10 and a second frame 12, the first frame 10 preferably comprising braided filaments. Figure 4 Shown in radially contracted and longitudinally expanded state Figure 3 The expandable tube 2 in Figure 4 In the embodiment, the first frame 10 and the second frame 12 are both relative to Figure 3 In their state they have contracted radially and expanded longitudinally.

[0087] Figure 3 and Figure 4 An example of an embodiment of the expandable tube 2 is Figure 5 Shown in. Figure 5 It is shown in a radially expanded and longitudinally contracted state (i.e. Figure 3 The structure of the first frame 10 and the second frame 12 including the braided filaments can be clearly seen.

[0088] The first frame 10 preferably comprises braided filaments. The first frame 10 may include a plurality of filaments braided together. Figure 5 As shown, the first frame 10 includes a plurality of spirally arranged filaments. The first frame 10 includes filaments preferably having equal diameters that are arranged in both right-handed and left-handed spirals. In this way, the spiral filaments of opposite chirality overlap each other in the radial direction to form a woven structure of the first frame 10. The filaments of the first frame 10 can have substantially the same diameter. Alternatively, the filaments can include a mixture of filaments with different diameters and / or materials. For example, a mixture of filaments of different diameters can provide advantageous mechanical properties. Alternatively or additionally, having some filaments made of radiopaque material (optionally large diameter filaments) will provide radiopaqueness to allow easier positioning of the expandable tube during implantation, such as using fluoroscopic visualization.

[0089] A single filament in a first chiral helix can alternately pass under and over a filament of a second chiral (different from the first chiral) helix to form a braided structure (under and over are interpreted as being closer to and farther away from the axis of the expandable tube 2 in the radial direction, respectively). Other arrangements are also possible. For example, the filaments in a first chiral helix can alternately pass under and over a paired filament or a larger filament group (such as three, four or more filaments) in an opposite chiral helix. Passing under and over multiple filaments of opposite chiral helices can help reduce the deformation of a single filament and reduce strain and friction between the filaments. However, passing under and over too many filaments at one time may reduce the integrity of the first framework 10.

[0090] The first frame 10 (specifically, the filaments of the first frame 10) may include a shape memory alloy material, preferably Nitinol. The shape memory alloy material is conducive to driving the radial expansion of the first frame 10 because it can be configured to promote itself (self-expansion) toward a radially expanded state. Alternatively, the first frame 10 may include a polymer or other biocompatible material. Optionally, the first frame 10 can be independently self-expandable. That is, the first frame 10 is configured to self-expand from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state even when the first frame 10 is not connected to the second frame 12.

[0091] The filaments of the first frame 10 may include a radiopaque material, such as platinum. Optionally, the filaments of the first frame 10 include a core of a radiopaque material located within a covering layer of another material. The covering layer may be a shape memory alloy, preferably nitinol. For example, the filaments of the first frame 10 may include a stretched fill tube nitinol wire with a platinum core. This embodiment allows the first frame 10 to be made radiopaque, which greatly improves the visibility of the expandable tube 2 during deployment and increases the accuracy with which the expandable tube 2 can be deployed. The covering material may also be selected to have improved biocompatibility relative to the radiopaque core. The covering layer material may also be selected to have other advantageous properties, such as the self-expansion properties of the shape memory alloy.

[0092] An important characteristic of stents used to treat aneurysms is their pore density, i.e., the number of pores per unit area of ​​the vessel wall. Increased pore density is associated with greater flow reduction within the aneurysm sac and more rapid re-endothelialization of the vessel to the stent, both of which lead to better and more reliable patient outcomes. Therefore, increasing the pore density in stents has been a goal of stent designers for some time.

[0093] For frames made of braided filaments (such as the first frame 10), the pore density can be increased by using narrower filaments and increasing the number of filaments (the total number of filaments around the diameter of the frame). However, narrower filaments are less stiff, and frames made from narrower filaments have poorer expansion characteristics. Therefore, attempts to increase the pore density in a braided frame by using narrower filaments will generally compound the already unsatisfactory expansion performance of the braided frame.

[0094] Increasing the number of filaments without reducing the filament diameter may provide some benefits without degrading the expansion characteristics, but will increase the diameter of the stent in the radially contracted state. This makes the stent incompatible with standard sized catheters used to deploy stents to treat intracranial aneurysms, which are widely available and well known to physicians. Therefore, the problem of increasing the density of pores in a stent without increasing the diameter of the stent in the radially contracted state has not been satisfactorily solved for some time.

[0095] As will be discussed further below, in the present invention, the second frame 12 can be expanded more easily and consistently than the first frame 10. Therefore, the second frame 12 can be configured to drive the expandable tube 2 from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state, that is, so that the expansion characteristics of the expandable tube 2 are primarily determined by the second frame 12. The favorable expansion characteristics of the second frame 12 allow the first frame 10 to be manufactured using filaments having narrower diameters, because the first frame 10 is not relied upon to cause expansion of the expandable tube 2. The use of narrower diameter filaments allows the number of filaments of the first frame 10 to be increased relative to conventional braided stents without the need to increase the diameter of the expandable tube 2 in the radially contracted and longitudinally expanded state.

[0096] This, in turn, increases the pore density of the first frame 10 while still allowing the expandable tube 2 to be compatible with standard-sized catheters that are widely used in deploying the expandable tube 2 to treat intracranial aneurysms. For example, in the radially contracted and longitudinally expanded state, the maximum dimension of the expandable tube 2 in the radial direction may be such that the expandable tube 2 can be inserted into a catheter having an inner diameter of at most 1.0 mm. Preferably, the maximum dimension of the expandable tube 2 in the radial direction enables the expandable tube 2 to be inserted into a catheter having an inner diameter of 0.69 mm (0.027 inches) or 0.53 mm (0.021 inches) or less.

[0097] Optionally, the first frame 10 comprises at least 48 filaments, preferably at least 64 filaments, more preferably at least 72 filaments, most preferably at least 96 filaments. Optionally, the diameter of the filaments of the first frame 10 is at most 30 μm, preferably at most 25 μm, more preferably at most 20 μm. Optionally, the pore density of the first frame 10 is at least 20 pores / mm 2 , preferably at least 40 holes / mm 2 , more preferably at least 50 holes / mm 2 , most preferably at least 60 holes / mm 2 .

[0098] Another important characteristic of the first frame 10 is the braiding angle, i.e., the angle between the longitudinal direction of the first frame 10 and the individual filaments of the first frame 10. The bending flexibility of the braided filaments of the first frame 10 increases as the braiding pitch decreases (i.e., as the braiding angle increases). This is advantageous in allowing the expandable tube 2 to conform to the tortuous anatomical structure of the blood vessel without twisting. A larger braiding angle results in improved bending flexibility, smaller pores (allowing a higher pore density), and improved longitudinal flexibility. Optionally, the braiding angle is at least 50°, preferably in the range of 50°-80°.

[0099] Existing stent designs typically only achieve 48 filaments or a maximum of 64 filaments, with a hole density of up to 20 or a maximum of 30 holes / mm2 Attempts to further increase the number of filaments in prior art devices have been unable to maintain compatibility with standard sized 0.69 mm (0.027 inch) catheters and have required custom and / or larger sized catheters for deployment.

[0100] Dual layer stents have been considered before. However, existing designs have two layers made of conventional braided filament layers. Such designs offer some advantages. However, the two braided layers do not provide the same improvement in reliability and consistency of expansion as provided by having one braided frame and one non-overlapping element frame.

[0101] Moreover, in the braided frame, each filament overlaps with other filaments at the intersection. This results in a cross-sectional profile of 2*filament diameter (i.e., the effective thickness of the frame wall in the radial direction). For a double-layer device with only a braided frame, the cross-sectional profile is further increased to 2*filament diameter of the inner frame + 2*filament diameter of the outer frame. This increased cross-sectional profile is associated with higher thrombogenicity and is undesirable. The present invention can have a reduced cross-sectional profile, which is due to its ability to use thinner filaments and include a second frame 12 containing non-overlapping elements. When the expandable tube 2 is positioned above the opening of the aneurysm sac in a radially expanded and longitudinally contracted state in use, the first frame 10 can have a porosity to redirect blood flow away from the aneurysm sac, thereby promoting thrombosis in the aneurysm sac. For example, in the radially expanded and longitudinally contracted state of the expandable tube, the first frame 10 can have a porosity of up to 90%, preferably up to 80%, more preferably up to 70%, more preferably up to 60%, and most preferably up to 50%. Porosity can also be expressed as surface coverage, which is the inverse of porosity (i.e., 90% surface coverage represents 10% porosity). If the porosity of the first framework 10 alone is low enough to redirect blood flow away from the aneurysm, this reduces the design constraints on the second framework 12, allowing the second framework 12 to have a higher porosity.

[0102] The expandable tube 2 further comprises a second frame 12. The second frame 12 comprises a network of non-overlapping elements, wherein the non-overlapping elements do not overlap each other in the radial direction. This is not the case for the braided filaments of the first frame 10, which overlap each other in the radial direction. Figure 6 and Figure 8 An exemplary design of a network of non-overlapping elements is shown in . The friction between elements that would otherwise occur at overlapping points is avoided by the network of non-overlapping elements of the second frame 12. In turn, this reduces the resistance to radial expansion of the second frame 12, allowing the second frame 12 to expand quickly and uniformly during deployment when released from the catheter.

[0103] The network of non-overlapping elements can be integrally formed (i.e., the non-overlapping elements are connected together to form the network) so that there are no material interfaces between any of the elements. This can be achieved by forming the second frame 12, for example by laser cutting a hollow tube or by other techniques known in the art for making such structures. An integrally formed network of non-overlapping elements is preferred because there are no joints between the elements that could increase friction, create possible failure points, or similar problems. However, this is not required, and the network of non-overlapping elements can be formed by, for example, welding together a plurality of individual elements or the like.

[0104] The second frame 12 and in particular the non-overlapping elements may comprise a shape memory alloy material, preferably Nitinol. Optionally, the second frame 12 may have a porosity of at least 70%, preferably at least 80%, preferably at least 85%, more preferably at least 90%, most preferably at least 95%. This allows the second frame 12 to have a less dense network of non-overlapping elements, thereby reducing the likelihood that the elements interfere with each other during expansion and contraction of the frame, and simplifying the design of the network. This also means that the porosity of the expandable tube 2 as a whole is more completely determined by the first frame 10 alone, thereby allowing the determination of the overall characteristics of the expandable tube 2 to be simplified. Optionally, the second frame 12 may be independently self-expandable. That is, the second frame 12 is configured to self-expand from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state even when the second frame 12 is not connected to the first frame 10.

[0105] The network of non-overlapping elements of the second frame 12 has an interconnected structure comprising a plurality of subunits repeated in the longitudinal direction. The advantage of this feature is that the length of the expandable tube 2 can be easily changed to suit any particular application by adding more subunits. Longitudinally adjacent subunits can have mirror symmetry in a plane perpendicular to the longitudinal axis of the expandable tube 2.

[0106] Each subunit of the second frame 12 defines a closed unit 32 . Figure 6 Two adjacent closed cells 32 of the second frame 12 are shown. A closed cell 32 is an area around the circumference of the second frame 12 enclosed by non-overlapping elements. In other words, a closed cell 32 is a portion of the outer surface area of ​​the second frame 12 defined by a network of non-overlapping elements.

[0107] In the radially expanded and longitudinally contracted state, the closing cell 32 has a bulbous region 34, wherein the closing cell 32 widens toward the circumferential ends of the closing cell 32 and away from the circumferential center region of the closing cell 32. The closing cell 32 may widen in the bulbous region 34 by at least 20%, preferably at least 40%, and more preferably at least 60%.

[0108] The circumferential end portion refers to the end portion of the closed unit 32 in the circumferential direction around the second frame 12 (i.e., around the outer surface of the second frame 12). Similarly, the circumferential central region is a region located between (e.g., approximately equidistant from) the circumferential end portions of the closed unit 32 in the circumferential direction. Figure 6 As shown, the closed cell 32 may include two bulbous regions 34 at opposite circumferential ends of the closed cell 32. Figure 6 In the example of , the network of non-overlapping elements includes a series of s-shaped segments to define the bulbous region 34 of the closed cell 32. The closed cell design of the second frame 12 provides greater torsional rigidity and resistance to torsional rotation.

[0109] The closed cell 32 may have mirror symmetry in one or both of a plane parallel to the longitudinal axis of the expandable tube 2 and a plane perpendicular to the longitudinal axis of the expandable tube 2. Figure 6 In the example of , the enclosed cell 32 has mirror symmetry in a plane defined by the longitudinal axis of the expandable tubular and a line drawn through each other connection point 30 along the longitudinally extending member. Figure 6 The closed cell 32 also has a mirror symmetry in a plane perpendicular to the longitudinal axis of the expandable tube 2 , the plane being drawn through the connection points 30 at the two opposite circumferential ends of the closed cell 32 .

[0110] The network of non-overlapping elements may comprise a plurality of longitudinally extending members 8 defining an interconnected structure. Preferably, the longitudinally extending members 8 are longitudinally deformable. Figure 6 In the example of FIG. 8 , this means that each closed cell 32 is defined by two circumferentially adjacent longitudinally extending members 8 .

[0111] The longitudinally extending member may be configured such that Figure 6 The angle marked "A" in the figure is greater than 180 degrees. This means that, in the radially expanded and longitudinally contracted state, the longitudinal direction is reversed between consecutive connection points 30 along the path of each longitudinally extending member 8. In the radially expanded and longitudinally contracted state, each subunit has a circumferential line that intersects the longitudinally extending member 8 three or more times. The circumferential line is preferably located at the midpoint between consecutive connection points 30 of the longitudinally extending member 8, but generally also exists at a series of longitudinal positions around the midpoint, depending on the degree to which the longitudinal member bends back on itself between the connection points.

[0112] Angles "A" greater than 180 degrees enable longer path lengths for longitudinally extending members 8. This s-shaped configuration between consecutive connection points 30 causes longitudinally extending members 8 to reverse their direction of curvature, resulting in better bending flexibility, longitudinal flexibility and lower strain amplitudes on non-overlapping elements.

[0113] Each subunit of the second frame 12 can define a plurality of closed cells 32 around the circumference of the second frame 12, so that the closed cells 32 are repeated in the circumferential direction. Circumferentially adjacent closed cells 32 can be connected at a connection point 30 (i.e., non-overlapping elements defining circumferentially adjacent closed cells 32 are connected at the connection point). In the case where the second frame 12 includes a plurality of longitudinally extending members 8, circumferentially adjacent longitudinally extending members 8 are connected at the connection point 30. In this case, the structure of the network of non-overlapping elements can repeat itself in the longitudinal direction and the circumferential direction. The circumferential repetition of the unit allows the radius of the expandable tube 2 to be easily adjusted according to the requirements of a specific application.

[0114] The non-overlapping elements may include straight line portions 36 at the connection points 30. Figure 6 In the example of the embodiment of the present invention, the straight portion 36 has a length "L". The straight portion 36 minimizes the deformation of the non-overlapping elements at the connection point 30. This can greatly reduce fatigue-related failures of the expandable tubular 2 because the additional material and / or joints at the connection point 30 may not bend well. The length of the straight portion 36 can be at least 0.05 mm, preferably at least 0.1 mm. The straight portion 36 is preferably centered about the connection point 30. The straight portion 36 does not need to be completely straight, but the radius of curvature of the non-overlapping elements in the straight portion 36 should be substantially larger than the radius of curvature of the non-overlapping elements outside the straight portion 36, such as 25% larger, preferably 50% larger, and more preferably 100% larger. Preferably, the non-overlapping elements will not bend too tightly next to the straight portion 36 to further reduce the strain at the connection point 30. The radius of curvature of the non-overlapping elements adjacent to the straight portion 36 can be at least 0.3 mm, preferably at least 0.5 mm, and most preferably at least 0.7 mm.

[0115] Circumferentially adjacent closed cells 32 in each sub-unit may have mirror symmetry in a plane parallel to the longitudinal axis of the expandable tube 2. Figure 5 and Figure 6 In the example of , the closed cell has mirror symmetry in a plane defined by the longitudinal axis of the expandable tube and a line drawn along the longitudinally extending member 8 through every other connection point.

[0116] In the case where the sub-units include a plurality of closed cells 32 connected at a connection point 30, the second frame 12 may be configured such that in the radially expanded and longitudinally contracted state, the radius of curvature of the longitudinally extending member 8 decreases as it moves away from the connection point 30. The decrease in the radius of curvature may be substantially continuous or may be provided by two or more sections of the longitudinally extending member 8 having different radii of curvature.

[0117] exist Figure 6In the example of FIG. 1 , the two sections are indicated as R1 and R2. The radius of curvature of section R1 is greater than the radius of curvature of R2. This minimizes the strain of the longitudinally extending member at R1 and at and immediately around the connection point 30. This results in the deformation of the longitudinally extending member 8 coming primarily from the R2 section. Using such a design with two or more radii of curvature enables lower strain values ​​to be achieved in non-overlapping elements.

[0118] Circumferentially adjacent closed cells 32 (or longitudinally extending elements 8 defining closed cells 32) can be connected at connection points 30 via bridges. The bridges are preferably rigid bridges. The closed cell design using bridges connecting longitudinally extending members 8 provides greater longitudinal rigidity for the second frame 12. This allows the expandable tube 2 to be more easily pushed out of the delivery catheter by the delivery guidewire, and can allow the expandable tube 2 to be more easily and consistently delivered from a wider range of delivery system designs. The bridge preferably extends circumferentially. The longitudinal length of the bridge can be at most 0.2 mm, preferably 0.1 mm, more preferably at most 0.08 mm, and most preferably at most 0.05 mm. The bridge can have a circumferential length of at most 0.1 mm.

[0119] Figure 7 The expandable tube 2 is shown Figure 5 The radial expansion and longitudinal contraction state shown is switched to Figure 4 The schematic diagram shows the process of radial contraction and longitudinal expansion. Figure 7 In the figures, the expandable tube 2 has been placed inside a tapered glass funnel so that its behavior can be seen at different levels of radial contraction and longitudinal expansion.

[0120] exist Figure 5 In the state shown, the expandable tube 2 has its maximum diameter so that it can engage the wall of the vessel in which the expandable tube 2 is deployed. This corresponds to Figure 7 The state of the radial expansion region 40 is the state.

[0121] exist Figure 7 In the middle region 42 in the expandable tube 2, the porosity is greatest because the spaces between the filaments in the first frame 10 have their largest area. The closed cells 32 of the second frame 12 have been longitudinally elongated and circumferentially contracted so that they no longer exhibit the bulbous regions 34 that were present in the radially expanded and longitudinally contracted state.

[0122] exist Figure 7In the radial contraction region 44 in the expansion tube 2, the expandable tube 2 has its minimum diameter so that it can be inserted into a catheter for deployment into a blood vessel. In this process, the spaces between the filaments of the first frame 10 are transformed from rhombuses with the major axis oriented circumferentially to rhombuses with the major axis oriented longitudinally. The closed cells 32 of the second frame 12 further contract circumferentially and expand longitudinally. As shown in the figure, most of the deformation of the longitudinally extending member 8 occurs away from the connection point 30, thereby reducing the mechanical strain around the connection point 30.

[0123] Figure 8 Some beneficial effects of the second frame 12 are demonstrated, wherein the closed cell 32 has a bulbous region 34. The closed cell structure provides greater torsional stiffness to resist twisting in tortuous anatomical structures. The open cell design can cause elements of the frame (struts) to protrude into the vessel lumen around the bend. This may cause partial obstruction of the vessel lumen and may lead to thromboembolic complications. Conversely, the closed cell design also improves the apposition of the expandable tube 2 in tortuous anatomical structures, which is particularly useful in neurovascular applications.

[0124] The longer path length of non-overlapping elements provided by the bulbous region 34 in the closed cell design also improves bending flexibility on the outer curve without requiring any substantial change in the diameter of the expandable tube 2. Figure 8 As shown, the closing unit 32 can be opened on the outer curve and closed on the inner curve without any element protruding significantly into the surrounding space. Figure 8 It is also shown that the second frame 12 can have flared ends (i.e., the diameter of the second frame 12 increases in one or both end regions of the second frame 12). The flared ends improve engagement of the second frame 12 with the vessel wall, maintain wall apposition around curves, and prevent "fishmouthing" of the first frame 10. This is where the ends of the first frame 10 do not fully expand in the radial direction due to poor radial forces and poor structural compliance (particularly where the first frame 10 includes braided filaments).

[0125] The second frame 12 is described herein as a portion of an expandable tube 2 that includes the second frame 12 and the first frame 10. However, the second frame 12 can also be configured to deploy an expandable tube within a blood vessel independently of the first frame 10. In some cases, such as when the low porosity of the expandable tube is not important, this may be preferred. When provided as an expandable tube independent of the first frame 10, the second frame 12 can have any applicable structural features described herein.

[0126] When arranged together with the first frame as part of the expandable tube 2, the second frame 12 overlaps the first frame 10 in the radial direction. That is, for at least some points along the axis of elongation 4, a line perpendicular to the axis of elongation 4 will pass through the first frame 10 and the second frame 12. The second frame 12 may overlap the first frame 10 over at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably at least 80% of the length of the expandable tube 2. Figures 3 to 5 In the example of , the first frame 10 and the second frame 12 overlap substantially over their entire length. Having a substantial overlap between the first frame 10 and the second frame 12 ensures that the characteristics of the expandable tube 2 are the same along the expandable tube 2, making the behavior of the expandable tube 2 predictable. Figure 3 In the embodiment, the second frame 12 is positioned within the first frame 10. However, this is not required, and in other embodiments, the first frame 10 may be within the second frame 12. If the first frame 10 is within the second frame 12, this may further require that one or more points in the second frame 12 are connected to the first frame 10 along the length of the second frame 12.

[0127] The length of the second frame 12 may be at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably at least 80% of the length of the first frame 10. Figures 3 to 5 In the example of the first frame 10 and the second frame 12 have substantially the same length. This also helps to ensure that the characteristics of the expandable tube 2 remain consistent along the length of the expandable tube 2. The overlap requirement and the relative length requirements of the first frame 10 and the second frame 12 will also allow the first frame 10 and the second frame 12 to be connected together at the end of the expandable tube 2, which may be preferred in some embodiments.

[0128] The second frame 12 is connected to the first frame 10. The connection can be achieved in any suitable manner. For example, the second frame 12 can be connected to the first frame 10 by at least one of welding, crimping, adhesive, weaving or braiding, or encapsulation. Connecting the first frame 10 and the second frame 12 by encapsulation at some point can be achieved by locally coating the adjacent portions of the first frame 10 and the second frame 12 with a suitable material, such as a biocompatible polymer (such as PTFE).

[0129] In a preferred embodiment, the second frame 12 is connected to the first frame 10 using connecting filaments 16 . Figures 9 to 12 Various aspects of the frames being connected together using connecting filaments 16 are shown. Figures 10 to 12 In the design of the network of non-overlapping elements of the second frame 12, Figures 6 to 8 However, the method of connecting the two frames is equally applicable to any design of the second frame 12.

[0130] To facilitate the connection between the two frames, the second frame 12 includes a plurality of filament receiving apertures 18. One or more connecting filaments 16 are woven into the first frame 10, and each connecting filament 16 passes through the one or more filament receiving apertures 18.

[0131] The advantage of using the connecting filament 16 compared to other methods such as crimping or welding is that the joint profile between the first frame 10 and the second frame 12 is reduced, thereby making the surface of the expandable tube 2 more uniform. The filament can also join the laser cut structure to a continuous braid (i.e., a braid with a continuous pitch). Further, the filament 16 is able to deform during the expansion and contraction of the expandable tube 2. Therefore, the use of the connecting filament 16 enables a smooth transition between a radially contracted and longitudinally expanded state and a radially expanded and longitudinally contracted state, while fixing the first frame 10 and the second frame 12 together at the location of the filament receiving orifice 18.

[0132] Fig. 9 An example of a longitudinal end region of the second frame 12 in an embodiment is shown, wherein the plurality of filament receiving apertures 18 include filament receiving apertures 18 located in the longitudinal end region of the second frame 12. The longitudinal end region may include an area within a distance of the end of the expandable tube 2 of at most 10%, preferably at most 5%, of the length of the expandable tube 2. The second frame 12 may include filament receiving apertures 18 in one or both end regions of the expandable tube 2. Fig. 9 The filament receiving aperture 18 in the embodiment is located on the longitudinally distalmost element of the network of interconnected elements of the second frame 12. Although not shown, Fig. 9 The filament receiving apertures 18 in the embodiment of are also located on the longitudinally most proximal element of the network of interconnected elements of the second frame 12 .

[0133] like Fig.10 and Fig.11 As shown, one or more connecting filaments 16 are woven into the first frame 10 , and each connecting filament 16 passes through one or more filament receiving apertures 18 .

[0134] exist Fig. 9 In the example of the second frame 12, the second frame 12 comprises two filament receiving apertures 18 on the same element of the second frame 12. In this case, the angle between the line between the filament receiving apertures 18 on the same element and the longitudinal axis 4 of the expandable tube 2 is preferably the same as the braiding angle of the braided filaments of the first frame 10. Thus, the connecting filaments 16 passing through the filament receiving apertures 18 on the same element of the second frame 12 will extend parallel to the filaments of the first frame 10. This facilitates the braiding of the connecting filaments 16 into the first frame 10.

[0135] The connecting filaments 16 are woven into the first frame 10. In this way, the connecting filaments 16 alternately pass from above and below the filaments of the first frame 10 (below and above are interpreted as being closer to and farther away from the axis of the expandable tube 2 in the radial direction, respectively). Other arrangements are also possible. For example, the connecting filaments 16 can alternately pass from below and above the paired filaments or larger filament groups (such as three, four or more filaments) of the first frame 10. Passing from below and above the multiple filaments of the first frame 10 can help reduce assembly time. Alternatively, passing from below and above the fewer filaments of the first frame 10 can help increase the bonding strength of the first frame 10 to the second frame 12. The arrangement of the connecting filaments 16 can match the arrangement of the filaments of the first frame 10, or it can be different. For example, if the connecting filaments 16 have a larger diameter than the filaments of the first frame 10, it can be expected that the connecting filaments 16 pass from above and below the filament group that is larger than the filaments of the first frame 10 themselves.

[0136] In embodiments where the plurality of filament receiving apertures 18 includes filament receiving apertures 18 in the longitudinal end regions of the second frame 12 , the connecting filaments 16 may be woven into the first frame 10 around the circumference of the first frame 10 . Fig.10 An example of such an embodiment is shown in . In this case, the connecting filaments 16 are bent at regular intervals to alternately follow the filaments of the right-handed spiral and the left-handed spiral of the first frame 10. To facilitate this, the connecting filaments 16 can be bent into the desired shape before being woven into the first frame 10. This helps to maintain the bend in the correct position and angle after the connecting filaments 16 have been woven into the first frame 10. In the case where the connecting filaments 16 include wires, the wires can be shaped to achieve bends at desired positions to facilitate the transition between a radial contraction structure and a radial expansion structure. The embodiment in which the connecting filaments 16 are woven into the first frame 10 around the periphery of the first frame 10 can also improve the expansion characteristics of the expandable frame 2, because the connecting filaments 16 at the ends of the expandable tube 2 can help promote radial expansion when the expandable tube 2 is deployed from the catheter.

[0137] The connecting filaments 16 may comprise the same material and / or have the same diameter as the filaments of the first frame 10. Optionally, the connecting filaments 16 comprise the filaments of the first frame 10. Fig.11 In this embodiment, joining the first frame 10 and the second frame 12 together may include unraveling one or more filaments of the first frame 10 to use as the connecting filaments 16. The connecting filaments 16 are then passed through the apertures 18 in the second frame 12 and woven back into the other woven filaments of the first frame 10.

[0138] Alternatively, the connecting filaments 16 may have a different diameter than the filaments of the first frame 10 or be made of a different material than the filaments of the first frame 10. The connecting filaments 16 may include nitinol wire. The connecting filaments 16 may include a material typically used for medical sutures. In this embodiment, the two ends of the suture can be tied to secure the two frames together.

[0139] Optionally, the plurality of filament receiving apertures 18 comprises filament receiving apertures 18 spaced apart along the length of the second frame 12. The filament receiving apertures 18 may be spaced apart along the length of the second frame 12, preferably spaced apart at equal intervals. The spacing between the filament receiving apertures 18 may be at most 50%, preferably at most 25%, more preferably at most 10% of the length of the expandable tube 2. Optionally, each longitudinal expandable element 8 of the second frame 12 comprises a filament receiving aperture.

[0140] Including the filament receiving apertures 18 spaced apart along the second frame 12 improves the attachment of the first frame 10 and the second frame 12 to each other, thereby reducing the chance of the two frames becoming separated. This also means that the connecting filaments 16 do not need to be Fig.10 10, but can follow the helical path of the braided filaments of the first frame 10 along the entire length of the first frame 10. This is advantageous because the connecting filaments 16 are under less tension than when bent. A plurality of connecting filaments 16 can be provided following the right-handed and left-handed helices of the braided filaments of the first frame 10.

[0141] Preferably, the apertures 18 are arranged so that when the connecting filaments 16 pass through the apertures 18, each connecting filament 16 follows the braiding angle of the braiding filaments of the first frame 10. To achieve this, in the case where a plurality of filament receiving apertures 18 are provided on the same element of the second frame 12, the angle between the line between the filament receiving apertures 18 on the same element and the longitudinal axis 4 of the expandable tube 2 is preferably the same as the braiding angle of the braiding filaments of the first frame 10. This also reduces unnecessary bending of the connecting filaments 16 and reduces tension in the connecting filaments 16.

[0142] The connecting filament 16 can help improve visibility of the expandable tube 2 during deployment. For example, the connecting filament 16 can include a radiopaque material. Alternatively or additionally, as Fig.12 As shown, one or more radiopaque markers 19 may be attached to one or more connecting filaments 16 .

[0143] The connection should be made in a biocompatible manner so that it does not affect the ability of the expandable tube 2 to be inserted into the human or animal body. The expandable tube 2 can stay in the body for a long time after deployment, usually indefinitely. Therefore, it is also important that any material used for the connection is biocompatible.

[0144] The second frame 12 may be connected to the first frame 10 at least at one end of the second frame 12. Connection at the end of the second frame 12 may be convenient because the ends of the elements of the second frame 12 may be joined to the first frame 10, such as the ends of the filaments of the first frame 10. The second frame 12 may also be connected to the first frame 10 at one or more points along the length of the second frame 12. Joining the first frame 10 and the second frame 12 at other points along the length of the second frame 12 will help prevent the first frame 10 and the second frame 12 from separating or preventing warping or creasing at any point along the length of the expandable tube 2. This is particularly relevant when the expandable tube 2 is expanding or contracting. Separation of the first frame 10 and the second frame 12 may result in improper deployment or damage to the expandable tube 2. However, joining at multiple points along the length of the expandable tube 2 will increase the complexity of the manufacture of the expandable tube 2 and may therefore not be preferred in all embodiments.

[0145] The connection between the first frame 10 and the second frame 12 can also be designed to reduce the possibility of damaging the blood vessel (where the expandable tube 2 is deployed). For example, the ends of the braided filaments of the first frame 10 and the elements of the second frame 12 can be included in the termination element. The termination element is configured to reduce the possibility of damaging the interior of the blood vessel, for example, by preventing any sharp points or other sharp surfaces at the ends of the filaments from contacting the inner wall of the blood vessel. The termination element itself can have a smooth and / or curved surface to prevent any damage to the blood vessel.

[0146] Optionally, the second frame 12 is configured to drive the expandable tube 2 from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state. As described above, the problem with prior art expandable tubes consisting only of braided filaments is that they do not always expand uniformly or reliably due to friction between the filaments. By including a second frame 12 configured to drive the expandable tube 2 to expand radially and contract longitudinally, the behavior of the expandable tube 2 can be made more reliable and consistent. Optionally, the second frame 12 is configured to drive the expandable tube 2 from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state by applying a force to the first frame 10 in a radial direction. Consistent radial expansion is important so that the expandable tube 2 expands to its final size and engages with the inner wall of the blood vessel in which it is deployed. In other embodiments, the second frame 12 can drive the expandable tube 2 from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state by applying a force to the first frame 10 in a longitudinal direction. However, this is generally not preferred because the drive to expand the expandable tube 2 radially is only indirect, and there may not be much improvement in the consistency of radial expansion when deployed.

[0147] Optionally, the radius of the second frame 12 in the unconstrained state in which the second frame 12 is not connected to the first frame 10 and the second frame 12 is radially expanded and longitudinally contracted is greater than the radius of the first frame 10 in the unconstrained state in which the first frame 10 is not connected to the second frame 12 and the first frame 10 is radially expanded and longitudinally contracted. Both the first frame 10 and the second frame 12 are configured to push themselves toward the radially expanded and longitudinally contracted state, and will have their maximum radius obtained when they are unconstrained. When the first frame 10 and the second frame 12 are connected together to form an expandable tube, their respective maximum radii in the radially expanded and longitudinally contracted state of the expandable tube 2 will be limited to the same, i.e., the smaller of the radii of the first frame 10 and the second frame 12 in their unconstrained states. By designing the second frame 12 so that its radius in the unconstrained state is greater than the radius of the first frame 10 in the unconstrained state, the second frame 12 will drive the first frame 10 to expand to its maximum radius and minimize the risk of radial separation between the two frames, especially when deployed in a tortuous anatomical structure. This will improve the consistency of radial expansion of the first frame 10 including braided filaments. This feature also means that fewer fixing points are required to securely join the two frames together.

[0148] Optionally, at least one of the first frame 10 and the second frame 12 may be provided with a hydrophilic coating and / or an anti-thrombotic coating.

[0149] The design of the multi-layer expandable tube 2 including the first frame 10 and the second frame 12 relies on the first frame 10 and the second frame 12 to expand and contract longitudinally and radially together with each other. The extent of longitudinal and radial expansion and contraction of the expandable tube 2 is mainly determined by the braided structure of the first frame 10, and the second frame 12, for example, containing longitudinal and circumferential independent elements, accommodates the longitudinal and radial movement of the braided structure.

[0150] Optionally, the first elongation of the first frame 10 is within 25%, preferably within 15%, more preferably within 10%, and most preferably within 5% of the second elongation of the second frame 12. The first elongation of the first frame 10 is the ratio between the unconstrained length of the first frame 10 and the length of the first frame 10 in a radially contracted and longitudinally expanded state. The unconstrained length of the first frame is the length of the first frame 10 in an unconstrained state, in which the first frame 10 is not connected to the second frame 12 and the first frame 10 is radially expanded and longitudinally contracted. The second elongation is the ratio between the unconstrained length of the second frame 12 and the length of the second frame 12 in a radially contracted and longitudinally expanded state. The unconstrained length of the second frame 12 is the length of the second frame 12 in an unconstrained state, in which the second frame 12 is not connected to the first frame 10 and the second frame 12 is radially expanded and longitudinally contracted. The radially contracted and longitudinally expanded state mentioned refers to the radially contracted and longitudinally expanded state of the first frame 10 or the second frame 12 when the first frame 10 or the second frame 12 is part of the expandable tube 2 (i.e., connected to the second frame 12) and the expandable tube 2 is in its radially contracted and longitudinally expanded state. This can be, for example, when the expandable tube 2 is inside a catheter ready for deployment. Previously designed expandable tubes including braided filaments include expansion rings at one or both ends of the expandable tube to facilitate proper deployment of the ends of the braided tube. However, it is challenging to increase the length of the expansion ring relative to the braided stent to facilitate proper deployment over the entire length because the expansion characteristics of the two types of frames are different. Matching the first elongation with the second elongation ensures that the chance of warping of the first frame 10 or the second frame 12 or separation of the first frame 10 from the second frame 12 is reduced. This further allows the second frame to be made longer relative to the first frame and further improves the consistency of deployment of the expandable tube.

[0151] In order to define the dimensional inputs for designing the second frame 12, the elongation of the first frame 10 needs to be analytically determined. Two methods for determining the first elongation of the first frame 10 are outlined below, and the elements of the second frame can be designed so that the second elongation matches the first elongation to a desired degree. The first method outlines a detailed method by determining the change in length and height of a single hole of the first frame 10 between a radially expanded and longitudinally contracted state and a radially contracted and longitudinally expanded state. A hole is a single space defined by adjacent filaments in the first frame 10, such as Fig.13 Schematically shown. The radially contracted and longitudinally expanded state can also be referred to as the loaded state, because this is the state of the expandable tube 2 when it is loaded into the catheter before being deployed into the blood vessel. The second method provides a simpler way to estimate the total length change of the first frame 10 between the radially expanded and longitudinally contracted state and the radially contracted and longitudinally expanded state.

[0152] like Fig.14 As shown in (a), the first method starts with the diameter of the expandable tube 2 in a radially expanded and longitudinally contracted state. and the braiding angle θ braid . Braiding angle θ braid is the angle between the longitudinal direction of the first frame 10 and a single filament of the first frame 10. This angle will change depending on whether the expandable tube 2 is in a radially expanded and longitudinally contracted state or in a radially contracted and longitudinally expanded state. The circumference C of the expandable tube 2 can then be calculated using Formula 1.

[0153]

[0154] The circumferential distance Dc between the filaments in the first frame 10 can be calculated using Equation 2.

[0155]

[0156] Among them, N wire is the number of filaments in the first frame 10 .

[0157] The hole of the first frame 10 has a diamond shape, wherein the length of each side of the hole remains constant as the diameter of the first frame 10 decreases, resulting in a decrease in hole height and an increase in hole length, as shown in FIG. Fig.13 as shown in (b).

[0158] Use Equation 3 to calculate the longitudinal length L of the hole pore .

[0159] L pore =2a sin(90°-θ braid ) Formula 3

[0160] The circumferential height H of the hole can be calculated using Equation 4 pore .

[0161] H pore =2a cos(90°-θ braid ) Formula 4

[0162] The total number of holes N around the circumference can be calculated using Formula 5 c .

[0163]

[0164] Equation 6 may be used to calculate the total number of holes Nh in a single row along the length of the first frame 10 .

[0165]

[0166] Among them, L expandedis the length of the first frame 10 in the radially expanded and longitudinally contracted state, such as Fig.14 As shown in (a). Using the number N of holes around the circumference c , the circumferential height H of each hole under loading can be calculated using Formula 7 loaded .

[0167]

[0168] Among them, D catheter is the inner diameter to which the expandable tube 2 must be reduced to enable deployment, such as the inner diameter of a delivery catheter. The braiding angle θ in the loaded state can be calculated using Equation 8: loaded .

[0169]

[0170] Then, the longitudinal length L of each hole in the loaded state can be calculated using Equation 9: loaded pore .

[0171] L loaded pore =2a cos(90°-θ loaded ) Formula 9

[0172] like Fig.14 As can be seen in (b), the length L of the first frame 10 in the loaded state can then be calculated using Formula 10 loaded .

[0173] L loaded =N h L loaded pore Formula 10

[0174] Finally, the first elongation ∈ can be determined using Equation 11.

[0175]

[0176] The second method is a simpler method applied to estimate the elongation of the first frame 10 assuming that the length of a single filament in the first frame 10 is equal to the length of the first frame 10 in the loaded state.

[0177] The first step is to use Equation 12 to calculate the braid and the pitch P of the helix of circumference C.

[0178]

[0179] The limited length L of each filament in the first frame 10 in the radially expanded and longitudinally contracted state is expanded The number of turns N turns It can be determined using Equation 13.

[0180]

[0181] Assuming that the length of the filament in the first frame 10 is equal to the length of the first frame in the loaded state, Equation 14 can be applied.

[0182]

[0183] For the first method, Equation 11 can be used to determine the first elongation. In addition, the number of subunits N can be determined by applying Equation 15 cells .

[0184]

[0185] It should be noted that the number of subunits in the second frame 12 should be an integer, which must be taken into account when selecting the parameters of the first frame 10 to ensure that the lengths of the first frame 10 and the second frame 12 remain the same in the radially expanded and longitudinally contracted state and in the radially contracted and longitudinally expanded state.

[0186] Once the first elongation of the first frame 10 is known, the geometry of the minimum repeating unit of the second frame 12 can be defined, such as Fig.15 The second frame 12 is designed to match the diameter and length variation characteristics of the first frame 10 to ensure uniform performance of the expandable tube 2. This is done for an embodiment in which the sub-units of the network of non-overlapping elements of the second frame 12 repeated in the longitudinal direction themselves comprise a plurality of units repeated in the circumferential direction (as described above).

[0187] Fig.15 Shows Figure 5-Figure 9 The minimum repeating unit of the closed cell design shown in . This repeating unit is repeated longitudinally to produce longitudinally extending members 8, which are themselves repeated circumferentially to form the complete second frame 12. Note that for this reason, the minimum repeating unit is different from the sub-unit of the second frame 12, because each minimum repeating unit does not individually define a closed cell 32. The unit length L cell Given by:

[0188]

[0189] Among them, L path is the path length along the minimal repeating unit, and, as mentioned above, ∈ is the first elongation of the first frame. Fig.15 The half-cell height H shown (ie, half of the circumferential height of a single closed cell 32) is cell Given by:

[0190]

[0191] Wherein, C is the circumference of the expandable tube 2 .

[0192] Thus, by ensuring that the path length L along each longitudinally extending member 8 is path and the first length L cell The longitudinally extending members 8 are designed to match the elongation of the first frame 10 (i.e., the longitudinal length of each minimum repeating unit in the radially expanded and longitudinally contracted state) in proportion to the first elongation of the first frame 10. Optionally, the ratio between the first length and the path length along each longitudinally deformable element 8 is within 25% of the first elongation, preferably within 15%, more preferably within 10%, and most preferably within 5%.

[0193] The expandable tube 2 may be configured for use in a delivery system 20, such as Fig.16 The delivery system shown. The delivery system 20 includes a tubular member 24 (also referred to as a catheter) and an elongated body 22 (also referred to as a guidewire). The elongated body 22 is positioned within the tubular member 24, and the expandable tube 2 is positioned between the tubular member 24 and the elongated body 22. The expandable tube 2 is engaged inwardly with the elongated body 22 and outwardly with the tubular member 24. The delivery system 20 is positioned at an appropriate position near the aneurysm in the blood vessel, and the elongated body 22 extends beyond the end of the tubular member 24. The longitudinal engagement force between the elongated body 22 and the expandable tube 2 and between the expandable tube 2 and the tubular member 24 is such that the expandable tube is also longitudinally moved and deployed to the outside of the tubular member 24. The expandable tube 2 radially expands and longitudinally contracts, thereby disengaging from the elongated body 22 and deploying into the blood vessel. Once the expandable tube 2 is fully deployed outside the tubular member 24, the delivery system 20 can be withdrawn from the blood vessel, so that the expandable tube 2 is in place.

[0194] FIG. 17 shows the use of Fig.16 The delivery system shown deploys the expandable tube 2 into the blood vessel model. In FIG. 17 (a), the expandable tube is still completely contained within the tubular member 24. In FIG. 17 (b), the distal portion of the expandable tube 2 has been deployed from the tubular member 24, while the proximal portion remains within the tubular member 24. The elongated body 22 has been further extended beyond the end of the tubular member 24 to deploy the expandable tube 2. In FIG. 17 (c), the expandable tube 2 is fully deployed and fully released from the delivery system. The tubular member 24 and the elongated body 22 can then be withdrawn from the blood vessel, leaving the expandable tube 2 in place.

[0195] Although this type of delivery system is preferred, the expandable tube 2 may also be used with other suitable types of conventional delivery systems. For example, the expandable tube 2 can be deployed using a delivery system that does not include an elongated body that engages outwardly with the expandable tube 2. The expandable tube 2 can be deployed using a delivery system that pushes the expandable tube 2 from the proximal end. This type of delivery system is generally not suitable for expandable tubes that include a network of non-overlapping elements. This is particularly true when these expandable tubes are designed to have high longitudinal flexibility, such as for neurovascular applications, and therefore have poor longitudinal stiffness. However, because the first frame 10 provides a higher filament density, the hybrid design of the expandable tube 2 allows deployment using this type of delivery system.

[0196] Other aspects of the expandable tube disclosed above may be described by the following numbered clauses. These clauses are not claims of the present application under the claim headings. However, these clauses provide other aspects that may be combined with features in the claims.

[0197] 1. An expandable tube deployed in a blood vessel, the expandable tube being capable of reversibly switching from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state, the expandable tube comprising: a first frame; and a second frame connected to the first frame and overlapping with the first frame in a radial direction, the second frame comprising a network of non-overlapping elements which do not overlap with each other in a radial direction, wherein: the network of non-overlapping elements has an interconnected structure comprising a plurality of sub-units repeated in a longitudinal direction; each sub-unit of the second frame defines a closed unit; and in the radially expanded and longitudinally contracted state, the closed unit has a bulbous region in which the closed unit widens toward a circumferential end of the closed unit and away from a circumferential central region of the closed unit.

[0198] 2. An expandable tubular according to clause 1, wherein the second frame is configured to drive the expandable tubular from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state.

[0199] 3. An expandable tubular according to clause 2, wherein the second frame is configured to drive the expandable tubular from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state by applying a force to the first frame in a radial direction.

[0200] 4. An expandable tube according to any of the preceding clauses, wherein the network of non-overlapping elements is integrally formed.

[0201] 5. An expandable tube according to any of the preceding clauses, wherein the second frame is connected to the first frame at least at one end of the second frame.

[0202] 6. An expandable tube according to clause 5, wherein the second frame is further connected to the first frame at one or more points along the length of the second frame.

[0203] 7. An expandable tubular according to clause 5 or 6, wherein the second frame is connected to the first frame by at least one of welding, crimping, adhesive, weaving or braiding or potting.

[0204] 8. An expandable tubular according to any of the preceding clauses, wherein: the second frame comprises a plurality of filament receiving apertures; one or more connecting filaments are woven into the first frame; and each connecting filament passes through one or more of the filament receiving apertures.

[0205] 9. An expandable tube according to clause 8, wherein the connecting filaments comprise filaments of the first frame.

[0206] 10. An expandable tube according to clause 8 or 9, wherein one or more radiopaque markers are attached to one or more of the connecting filaments.

[0207] 11. An expandable tubular according to any of clauses 8 to 10, wherein the plurality of filament receiving apertures comprises filament receiving apertures in a longitudinal end region of the second frame.

[0208] 12. An expandable tubular according to any of clauses 8 to 11, wherein the plurality of filament receiving apertures comprises filament receiving apertures spaced apart along the length of the second frame.

[0209] 13. An expandable tube according to any of the preceding clauses, wherein the length of the second frame is at least 50% of the length of the first frame.

[0210] 14. An expandable tube according to any of the preceding clauses, wherein the second frame overlaps the first frame over at least 50% of the length of the expandable tube.

[0211] 15. An expandable tube according to any of the preceding clauses, wherein the second frame is located within the first frame.

[0212] 16. An expandable tube according to any of the preceding clauses, wherein the radius of the second frame in an unconstrained state in which the second frame is not connected to the first frame and expands radially and contracts longitudinally is greater than the radius of the first frame in an unconstrained state in which the first frame is not connected to the second frame and expands radially and contracts longitudinally.

[0213] 17. An expandable tube according to any of the preceding clauses, wherein a first elongation of the first frame is within 25% of a second elongation of the second frame, the first elongation is the ratio between the length of the first frame in an unconstrained state in which the first frame is not connected to the second frame and the first frame is radially expanded and longitudinally contracted and the length of the first frame in a radially contracted and longitudinally expanded state, and the second elongation is the ratio between the length of the second frame in an unconstrained state in which the second frame is not connected to the first frame and the second frame is radially expanded and longitudinally contracted and the length of the second frame in a radially contracted and longitudinally expanded state.

[0214] 18. An expandable tube according to claim 17, wherein: the network of non-overlapping elements includes a plurality of longitudinally deformable elements for providing longitudinal expansion and contraction of the second frame; each minimum repeating unit of the network of non-overlapping elements has a first length in the longitudinal direction in an unconstrained state in which the second frame is not connected to the first frame and the second frame is in a radially expanded and longitudinally contracted state; and the ratio between the first length and the path length along each longitudinal deformable element is within 25% of the first elongation.

[0215] 19. An expandable tube according to any of the preceding clauses, wherein the first frame comprises a shape memory alloy material, preferably Nitinol.

[0216] 20. An expandable tube according to any of the preceding clauses, wherein, when the expandable tube is positioned above the opening of the aneurysm sac in a radially expanded and longitudinally contracted state during use, the first frame has a porosity to redirect blood flow away from the aneurysm sac, thereby promoting thrombosis in the aneurysm sac.

[0217] 21. An expandable tube according to any of the preceding clauses, wherein the first frame has a porosity of at most 90% in a radially expanded and longitudinally contracted state of the expandable tube.

[0218] 22. An expandable tube according to any of the preceding clauses, wherein the first framework comprises braided filaments.

[0219] 23. An expandable tube according to clause 22, wherein the first framework comprises at least 48 filaments.

[0220] 24. An expandable tube according to clause 22 or 23, wherein the filaments of the first framework have a diameter of at most 30 μm.

[0221] 25. An expandable tube according to any of clauses 22-24, wherein the braiding angle of the first frame is at least 50°.

[0222] 26. An expandable tubular according to any of the preceding clauses, wherein the pore density of the first frame is at least 20 pores / mm2 .

[0223] 27. An expandable tube according to any of the preceding clauses, wherein the second frame comprises a shape memory alloy material, preferably Nitinol.

[0224] 28. An expandable tube according to any of the preceding clauses, wherein the second frame has a porosity of at least 70%.

[0225] 29. An expandable tube according to any of the preceding clauses, wherein the maximum dimension of the expandable tube in the radial direction in the radially contracted and longitudinally expanded state is at least 30% smaller than the maximum dimension of the expandable tube in the radial direction in the radially expanded and longitudinally contracted state.

[0226] 30. An expandable tube according to any of the preceding clauses, wherein the elongation of the expandable tube in the longitudinal direction caused by switching from the radially expanded and longitudinally contracted state to the radially contracted and longitudinally expanded state is at least 10%.

[0227] 31. An expandable tube according to any of the preceding clauses, wherein, in the radially contracted and longitudinally expanded state, the maximum dimension of the expandable tube in the radial direction enables the expandable tube to be inserted into a conduit having an inner diameter of at most 1.0 mm.

Claims

1. An expandable tube for deployment in a blood vessel, the expandable tube being capable of reversibly switching from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state, the expandable tube comprising: First frame; as well as a second frame connected to the first frame and overlapping the first frame in a radial direction, the second frame comprising a network of non-overlapping elements which do not overlap each other in the radial direction, wherein: The network of non-overlapping elements has an interconnected structure comprising a plurality of subunits repeated in a longitudinal direction; Each subunit of the second frame defines a closed cell; and In the radially expanded and longitudinally contracted state, the closing cell has a bulbous region in which the closing cell widens toward circumferential ends of the closing cell and away from a circumferential center region of the closing cell.

2. The expandable tube according to claim 1, wherein: The closing unit includes two bulbous areas at two opposite circumferential ends of the closing unit.

3. The expandable tube according to claim 1 or 2, wherein: The closed cell is an area around the circumference of the second frame enclosed by the non-overlapping elements.

4. An expandable tube according to any one of the preceding claims, wherein: The network of non-overlapping elements includes a plurality of longitudinally extending members defining the interconnected structure, and circumferentially adjacent longitudinally extending members are connected at connection points.

5. The expandable tube according to claim 4, wherein: In the radially expanded and longitudinally contracted state, the longitudinal direction is reversed between successive connection points along the path of each longitudinally extending member.

6. The expandable tube according to any one of claims 4 to 5, wherein: For each subunit that intersects the longitudinally extending member three or more times in the radially expanded and longitudinally contracted state, there is a circumferential line that is preferably located midway between consecutive connection points of the longitudinally extending member.

7. The expandable tube according to any one of claims 4 to 6, wherein: The longitudinally extending members are longitudinally deformable.

8. The expandable tube according to any one of claims 4 to 7, wherein: Each sub-unit defines a plurality of closed cells around the circumference of the second frame, circumferentially adjacent closed cells being connected at a connection point; and In the radially expanded and longitudinally contracted state, the radius of curvature of the longitudinally extending member decreases away from the connection point.

9. An expandable tubular according to any one of the preceding claims, wherein: The closed cell has mirror symmetry in a plane parallel to the longitudinal axis of the expandable tube and / or in a plane perpendicular to the longitudinal axis of the expandable tube.

10. An expandable tubular according to any one of the preceding claims, wherein: Longitudinally adjacent subunits have mirror symmetry in a plane perpendicular to the longitudinal axis of the expandable tube.

11. An expandable tubular according to any one of the preceding claims, wherein: Each sub-unit defines a plurality of closed cells around the circumference of the second frame, and circumferentially adjacent closed cells are connected at connection points.

12. The expandable tube according to claim 11, wherein: Circumferentially adjacent closed cells have mirror symmetry in a plane parallel to the longitudinal axis of the expandable tube.

13. An expandable tube according to claim 11 or 12, wherein: Circumferentially adjacent closed cells are connected at said connection points via bridges, optionally wherein said bridges are rigid bridges.

14. The expandable tube according to claim 13, wherein: The bridge extends circumferentially.

15. An expandable tube according to claim 13 or 14, wherein: The bridge has a longitudinal length of at most 0.1 mm, preferably at most 0.08 mm.

16. An expandable tube according to any one of claims 13 to 15, wherein: The bridge has a circumferential length of at most 0.2 mm.

17. An expandable tube according to any one of claims 11 to 16, wherein: The non-overlapping elements include straight line portions at the connection points.

18. The expandable tube according to claim 17, wherein: The radius of curvature of the non-overlapping elements adjacent to the straight portion is at least 0.3 mm, preferably at least 0.5 mm, most preferably at least 0.7 mm.

19. An expandable tube according to claim 17 or 18, wherein: The length of the straight portion is at least 0.05 mm, preferably at least 0.1 mm.

20. An expandable tubular according to any one of the preceding claims, wherein: The closed cells widen in the bulbous region by at least 20%, preferably by at least 40%, more preferably by at least 60%.

21. An expandable tube for deployment within a blood vessel, the expandable tube being reversibly switchable from a radially contracted and longitudinally expanded state to a radially expanded and longitudinally contracted state, the expandable tube comprising a frame, the frame comprising a network of non-overlapping elements that do not overlap each other in a radial direction, wherein: The network of non-overlapping elements has an interconnected structure comprising a plurality of subunits repeated in a longitudinal direction; Each subunit defines a closed unit; In the radially expanded and longitudinally contracted state, the enclosing cell has a bulbous region in which the enclosing cell widens toward the circumferential ends of the enclosing cell away from the circumferential center region of the enclosing cell; and The closed cell has mirror symmetry in at least one of a plane parallel to a longitudinal axis of the expandable tube and a plane perpendicular to the longitudinal axis of the expandable tube.

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