Stent

Abstract

Stent with a tubular braided structure (3) made of interwoven wire strands (1, 2), wherein at least a first wire strand (1) is formed by at least two individual wires (1.1, 1.2) that run next to one another and touch one another, wherein the first wire strand (1) winds helically in a first direction around a rotation axis of the braided structure (3) and crosses at least one second wire strand (2) that has at least one individual wire (2.1) and winds helically in a second direction around the rotation axis of the braided structure (3), and wherein the at least two individual wires (1.1, 1.2) of the first wire strand (1) have an X-ray visible core material that is coated with a sheath material that has a lower X-ray visibility than the core material, wherein the at least two, in particular both, individual wires (1.1, 1.2) of the first wire strand (1) are formed as DFT wires and the cross-sectional area of ​​the X-ray visible core material amounts to approximately 20% to 40%, in particular 30%, of the total cross-section of the DFT wire if the core material is platinum or platinum-iridium, and approximately 10% to 20% if the core material is tantalum.

Description

[0001] The invention relates to a stent with a tubular braided structure made of interwoven wire strands, wherein at least a first wire strand is formed by at least two individual wires that run alongside one another and touch one another, wherein the first wire strand winds helically in a first direction around a rotational axis of the braided structure and crosses at least one second wire strand that has at least one individual wire and winds helically in a second direction around the rotational axis of the braided structure, and wherein the at least two individual wires of the first wire strand have an X-ray-visible core material that is coated with a sheath material that has a lower X-ray visibility than the core material. Such a wire made of core material and sheath material is referred to as a DFT wire.

[0002] For example, US 2014 / 0288 637 A1 discloses a stent formed from interwoven filaments. The filaments are braided in a helical pattern around a central axis of the structure. The stent can comprise one or more X-ray-visible filaments.

[0003] Furthermore, DE 698 36 656 T2 discloses a braided stent made of filaments. A marker made of a radiopaque material and a bioabsorbable material can be woven into the filaments of the stent.

[0004] There is a need for improvement in the known stents with regard to X-ray visibility and the stability of the mesh structure.

[0005] The invention is therefore based on the object of providing a stent with a mesh structure that has a high X-ray visibility and at the same time good stability,

[0006] According to the invention, this object is achieved by a stent having the features of claim 1.

[0007] The advantage of the invention is that the X-ray-visible core material allows for positional control during stent implantation. The stent is visible along its entire length, facilitating positioning, particularly in curved vessel segments. Combining at least two wires into a first wire strand simultaneously improves the stability of the mesh structure.

[0008] In preferred embodiments, the first wire strand can consist of only two individual wires. The second wire strand can consist of only one individual wire. In general, not all wire strands wound in the same direction around the rotational axis of the braided structure need to have the same number of individual wires. Rather, the first wire strands can extend in different winding directions and intersecting one another in a helical shape around the rotational axis of the braided structure. For example, four first wire strands can be provided, which are braided between second wire strands, with two of the four first wire strands each wound in different directions around the rotational axis of the braided structure.

[0009] According to the invention, at least two, in particular both, wires of the first wire strand are designed as DFT wires, i.e., they comprise an X-ray-visible core material coated with a less X-ray-visible sheath material. This increases the X-ray visibility of the braid structure. The sheath material preferably comprises a shape memory material, in particular a nickel-titanium alloy.

[0010] The braided structure can comprise a total of four, six, or ten, preferably eight, DFT wires. In particular, all individual wires of the first wire strand can have an X-ray-visible core material coated with a sheath material that has a lower X-ray visibility than the core material. It is particularly preferred if all individual wires, in particular all individual wires of all wire strands forming the braided structure, are designed as DFT wires.

[0011] The braided structure preferably has a conical or cylindrical outer contour. It is also possible for the braided structure to have a cylindrical section and one or more conical or truncated cone-shaped sections. In particular, the braided structure can have truncated cone-shaped end sections that are connected to one another by a cylindrical section.

[0012] Furthermore, it can be provided that the wire strands form a deflection at one longitudinal end of the braided structure, wherein the wire strands are wound in a first direction around the longitudinal axis of the braided structure before the deflection, and wherein the wire strands are wound in a second, in particular opposite, direction around the longitudinal axis of the braided structure after the deflection. The deflection essentially forms an end loop of the braided structure.

[0013] The cross-sectional area of ​​the X-ray visible core material accounts for approximately 20% to 40%, especially 30%, of the total cross-section of the DFT wire (core material plus cladding material) when the core material is platinum or platinum-iridium, and approximately 10% to 20% when the core material is tantalum.

[0014] Preferably, for DFT wires with a diameter of 35 µm (after polishing), approximately 14% to 16%, in particular 15.1%, of the cross-sectional area is occupied by the X-ray visible material, preferably a platinum-iridium alloy. For DFT wires with a diameter of 43 µm (after polishing), the cross-sectional area proportion of the X-ray visible material, in particular the platinum-iridium alloy, is preferably approximately 27% to 29%, in particular 28.1%.

[0015] The stent, particularly the braided structure, is preferably suitable for delivery via a catheter with an inner diameter of approximately 0.42 mm (0.17 inches). The cross-sectional diameter of the stent in the compressed state is adjusted accordingly. In the expanded state, the stent can have a cross-sectional diameter of 3.5 mm. Such a stent with an expanded cross-sectional diameter of 3.5 mm preferably consists of a total of 18 wire strands.

[0016] The wire strands can be deflected at one longitudinal end of the braided structure or form a deflection and be returned in an opposite direction to an opposite longitudinal end. Open wire ends are preferably arranged at an opposite longitudinal end of the braided structure ( Fig. 1). Although 18 wire strands are used to form the braided structure, the braided structure appears to consist of twice that number of wire strands, namely 36. It is also possible that the braided structure appears to consist of 32 or 40 wire strands to form a stent with an expanded cross-sectional diameter of 3.5 mm, but is actually formed by interlacing and redirecting 16 or 20 wire strands.

[0017] For a stent with an expanded cross-sectional diameter of 3.0 mm or 2.5 mm, the braided structure is preferably formed from 16 wire strands that are deflected and braided back at one longitudinal end of the braided structure. Due to the one-sided deflection of the wire strands, the braided structure then appears to consist of 32 wire strands. Alternatively, for a stent with an expanded cross-sectional diameter of 3.0 mm or 2.5 mm, the braided structure may appear to consist of 24 or 36 wire strands, although in reality, only 12 or 18 wire strands are required to form the braided structure, which are deflected and braided back along the longitudinal axis.

[0018] It is preferred if a total of eight DFT wires are provided, which have a cross-sectional diameter between 40 µm and 45 µm, in particular 43 µm, and form a total of four first wire strands. Due to the deflection of the four wire strands at one longitudinal end of the braided structure, the braided structure appears to be formed from eight wire strands, each with two DFT wires. The remaining, in particular second, wire strands can each have a single individual wire having a cross-sectional diameter of 35 µm. This is shown in the Fig. 2 and Fig. 3 recognizable.

[0019] It can also be provided that the braid structure has two, six, or ten first wire strands. In general, the cross-sectional diameter of the individual wires that are not designed as DFT wires can be 35 µm, 30 µm, or 40 µm. It is also conceivable for all individual wires to be designed as DFT wires.

[0020] The braiding style used can be 1-over-2. This means that a wire strand wound in a first direction around a longitudinal axis of the braid structure crosses over two wire strands and crosses under the following two wire strands. The 1-over-2 braiding style is Fig. 2 or Fig. 3 recognizable.

[0021] The braiding angle, i.e., the angle at which the wire strands wound in opposite directions around the rotational axis of the braided structure intersect, is preferably 140° in a central section of the braided structure. Each wire strand thus forms an angle of 70° with the longitudinal axis of the braided structure. At the transition to a deflection or end loop at one longitudinal end of the braided structure, the braiding angle is preferably approximately 130°. At this point, the respective wire strand thus forms an angle of 65° with the longitudinal axis of the braided structure.

[0022] Crimped sleeves can be provided at the ends as additional X-ray markers. Advantageously, one, two, or three X-ray markers are arranged at each longitudinal end of the braided structure. The X-ray markers can be formed by crimp sleeves, each of which is crimped to a single wire or a wire strand made up of several, in particular two, single wires.

[0023] The stent preferably has a length between 10 mm and 25 mm, preferably between 15 mm and 20 mm.

[0024] The stent is suitable for the treatment, particularly for flow barriers, of aneurysms in arteries. The surface of the wires is preferably coated with an anti-corrosive coating. One or both stent ends or braid ends can be shaped atraumatically by forming end loops. The stent is preferably retractable into a catheter. One or both stent ends or braid ends can include a flaring, i.e., a truncated cone-shaped expansion.

[0025] To deliver the stent into a blood vessel, the stent, in particular the braided structure, can be connected to a transport wire. The connection can be produced in a form-fitting manner. The connection can be designed such that the stent is positively secured to the transport wire in the compressed state, with the connection being released automatically upon expansion of the stent. The transport wire preferably has a flexible tip. The flexible tip can also be bent or curved to have an atraumatic effect. This is Fig. 4 shown as an example.

[0026] The attached drawings show the following: Fig. 1 is a side view of a stent according to a preferred embodiment of the present invention; Fig. 2 a detailed view of a middle section of the mesh structure of the stent according to Fig. 1; Fig. 3 a detailed view of an end section of the braided structure of the stent according to Fig. 1; and Fig. 4 a perspective partial view of the stent according to Fig. 1 with a transport wire for delivering the stent into a blood vessel.

[0027] The reference numbers in the drawings are assigned to the following components / elements of the invention: - “1” denotes a first wire strand of the braid structure, - “2” denotes a second wire strand of the braid structure, - “1.1” denotes a first single wire which is designed as a DFT wire, - “1.2” denotes a second single wire designed as a DFT wire, - “3” denotes the braid structure, - “4” denotes a deflection or end loop, - “5” denotes a transport wire, and - “6” indicates a flexible, curved tip of the transport wire.

Claims

[1] Stent with a tubular braided structure (3) made of interwoven wire strands (1, 2), wherein at least a first wire strand (1) is formed by at least two individual wires (1.1, 1.2) which run next to one another and touch one another, wherein the first wire strand (1) winds helically in a first direction around a rotation axis of the braided structure (3) and crosses at least one second wire strand (2) which has at least one individual wire (2.1) and winds helically in a second direction around the rotation axis of the braided structure (3), and wherein the at least two individual wires (1.1, 1.2) of the first wire strand (1) have an X-ray visible core material which is coated with a sheath material which has a lower X-ray visibility than the core material, wherein the at least two, in particular both, individual wires (1.1, 1.2) of the first wire strand (1) are formed as DFT wires and the cross-sectional area of ​​the X-ray visible core material amounts to approximately 20% to 40%, in particular 30%, of the total cross-section of the DFT wire if the core material is platinum or platinum-iridium, and approximately 10% to 20% if the core material is tantalum. [2] Stent according to claim 1, characterized by that all individual wires (1.1, 1.2) of the first wire strand (1) have an X-ray visible core material which is coated with a sheath material which has a lower X-ray visibility than the core material. [3] Stent according to one of the preceding claims, characterized by that the individual wires (1.1, 1.2) of all wire strands (1, 2) have an X-ray visible core material which is coated with a sheath material which has a lower X-ray visibility than the core material. [4] Stent according to one of the preceding claims, characterized bythat the braid structure (3) has a conical or cylindrical outer contour. [5] Stent according to one of the preceding claims, characterized by in that the wire strands (1, 2) form a deflection at one longitudinal end of the braided structure, wherein the wire strands (1, 2) are wound in a first direction around the longitudinal axis of the braided structure (3) before the deflection (4), and wherein the wire strands (1, 2) are wound in a second direction around the longitudinal axis of the braided structure (3) after the deflection (4). [6] Stent according to one of the preceding claims, characterized by that the sheath material comprises a shape memory material, in particular a nickel-titanium alloy.

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