STENT

Description

[0001] The present invention relates to a stent for transluminal implantation into hollow organs, in particular blood vessels, ureters, esophagi, colon, duodenum, or biliary tract, comprising a substantially tubular body extending along an axial direction and capable of transitioning from a compressed state with a first cross-sectional diameter to an expanded state with an enlarged second cross-sectional diameter. The stent comprises a plurality of cells defined by rib-like rim elements formed by the tubular body. The rim elements include at least one annular support strut circumferentially around the axial direction.

[0002] Stents of this type are used for the recanalization of pathologically altered hollow organs. The stents, in their compressed state with their first cross-sectional diameter, are advanced via a delivery catheter to the site to be treated within the hollow organ. There, they are expanded by various means to a diameter corresponding to that of the healthy hollow organ, thus providing support to the hollow organ, for example, a vessel wall. After expansion, the stent has its second cross-sectional diameter.

[0003] A stent according to the preamble of claim 1 is known from US 2018 / 104044 A1. Furthermore, US 2011 / 004291 A1 describes a stent according to the preamble of claim 11.

[0004] To provide the support effect, it is necessary that the stent can generate the highest possible erection force, i.e. a force in the radial direction that, for example, presses against the wall of a blood vessel.

[0005] The object underlying the invention is therefore to further develop a stent of the type mentioned above in such a way as to provide the highest possible erection force, especially when the stent is made of relatively soft materials.

[0006] This problem is solved according to the invention by a stent having the features of claim 1 and by a stent having the features of claim 11.

[0007] The stent according to the invention is characterized in that the support strut has at least one V-shaped support section, which comprises a web angle of 90° to 150° when the stent has the second cross-sectional diameter. The V-shape of the support section can be formed by two legs. The legs can be part of the rim elements.

[0008] The invention is based on the finding that a high radial eruption force can be generated by the relatively large web angle of 90° to 150°, even if the stent is made of materials with relatively low tensile strength. In contrast to conventional coronary stents, which have web angles in the range of 60° to 80°, the invention offers a number of advantages, as will be explained in detail below.

[0009] The web angle refers specifically to the angle formed or defined by the two legs of the V-shaped support section. Unless otherwise specified herein, the web angle is always determined when the stent is in its expanded state with the second cross-sectional diameter, which is typically the nominal diameter. The nominal diameter is the diameter required for regular stent use.

[0010] In general, the stent can be formed from the aforementioned surrounding elements, which can also be referred to as stent struts, forming a lattice framework that in turn defines the tubular body of the stent.

[0011] The boundary elements preferably form a multitude of cells, wherein each cell encompasses the respective boundary element that limits it and can be connected to other cells by means of further boundary elements.

[0012] Preferred embodiments of the invention can be found in the description, the dependent claims and the drawings.

[0013] According to a first advantageous embodiment, the web angle has an angle of 90° to 140°, preferably 100° to 130°. More preferably, the web angle can have an angle of 105° to 115°. The angles specified herein are to be understood as including the stated limits. In particular, the web angle can be 110°. It has been found that a particularly high radial setting force can be achieved in the range around 110°.

[0014] For clarification, it should be noted that the aforementioned web angles refer to the state when the stent is expanded to the second cross-sectional diameter. In the first cross-sectional diameter, where the stent can be inserted into the body in a reduced size, the angle of the V-shaped support section can be significantly smaller and, in particular, even 0° if the legs are parallel. More precisely, the angle of the V-shaped support section in the compressed state with the first cross-sectional diameter can be less than 30°, preferably less than 15°.

[0015] According to the invention, the rim elements comprise, at least in some areas, a bioresorbable material consisting of or containing zinc (Zn). By using a bioresorbable material, the stent does not remain in the body indefinitely or require surgical removal. Instead, the material dissolves in the body after a few months and is absorbed and completely excreted via natural metabolic processes. In this way, biocompatibility problems and the body's own defense mechanisms, which can lead to re-occlusion of vessels (for example, due to late-stage arteriosclerosis or thrombus formation), can be minimized.

[0016] Polymeric materials, such as polylactic acid (PLA) or poly-L-lactic acid (PLLA), are particularly well-known as bioresorbable materials. However, such polymeric materials exhibit low mechanical stability, so a bioresorbable material containing zinc is preferred. The use of zinc or a zinc alloy also significantly improves the radiographic visibility of the stent compared to PLA, PLLA, or magnesium alloys. This greatly facilitates stent placement under radiographic guidance, and separate radiographic markers are not always necessary.

[0017] Other well-known bioresorbable materials are magnesium and magnesium alloys, as mentioned above. In the body, magnesium reacts adversely with the water contained in body tissue, releasing energy to form magnesium hydroxide and hydrogen. The hydrogen is then in a gaseous state and, at sufficient concentrations, can lead to life-threatening embolisms, for example, in the bloodstream. Stents made of magnesium alloys are therefore usually coated with PLLA (polypropylene lamellar) to control the degradation process. Furthermore, their mechanical properties, especially elongation at break, are inferior to those of zinc alloys.

[0018] In particular, pure zinc or a zinc alloy can be used as the bioresorbable material. The zinc alloy can be produced, for example, by adding silver (Ag) and / or titanium (Ti). Preferably, the zinc alloy can contain 90.0 to 99.95 wt% zinc and 0.05 to 10.0 wt% silver. Likewise, 0.05 to 10.0 wt% titanium can be added to the zinc alloy. Preferably, however, a proportion of 0.9 to 4.0 wt% silver and / or titanium is used, with the zinc alloy otherwise consisting of zinc. Particularly preferably, only 3.0 wt% silver and / or titanium are used in addition to zinc, especially between 2.8 and 3.2 wt%. A combination of 3.0 wt% silver and 97 wt% zinc has proven advantageous for the mechanical stability of the stents described herein.

[0019] According to a further advantageous embodiment, the bioresorbable material consists of zinc and silver, containing 90.0 to 99.95 wt% zinc and 0.05 to 10.0 wt% silver. The bioresorbable material can therefore consist exclusively of zinc and silver. Such an alloy is described in European patent application EP 16 702 899.2.

[0020] The zinc alloys of zinc and silver and / or titanium mentioned herein can, for example, exhibit a tensile strength of 180 to 210 MPa, preferably 190 to 200 MPa. This tensile strength is lower than, for example, that of stainless steel 316L, which is not bioresorbable and has a tensile strength of approximately 586 MPa. However, the web angle selected according to the invention still allows for the creation of a stent with high radial eruption force.

[0021] The zinc alloys mentioned herein can also exhibit an elongation at break in the range of 80 to 180%, for example, 80 to 100%, preferably in the range of 90 to 100%. Elongation at break indicates the percentage by which a material can be stretched before it breaks.

[0022] This high elongation at break value for the aforementioned zinc alloys allows for significantly more flexible stent support struts than would be possible, for example, with stainless steel 316L (35% elongation at break) or with pure zinc (8% elongation at break). This makes it possible, in particular, to achieve the large strut angle according to the invention and, especially, to achieve the large angular difference of the V-shaped support section between the state with a compressed first cross-sectional diameter and the expanded second cross-sectional diameter.

[0023] It should be noted that the elongation at break values ​​given herein apply to the actual bioresorbable material used in the stent. Prior to actual processing, the bioresorbable material may be processed, for example, by extrusion and / or tube drawing, which can significantly alter the elongation at break (and other material properties) compared to the pure alloy.

[0024] According to a further advantageous embodiment, the support strut comprises several V-shaped support sections, each of which has web angles in the aforementioned area, resulting in a zigzag shape of the support strut, at least in some areas. Thus, several V-shaped support sections can be arranged one behind the other in such a way that the support strut has a zigzag shape.

[0025] The "openings" of the V-shaped support sections, defined by the legs, point alternately in opposite directions.

[0026] The web angles of the individual support sections can differ, but must fall within one of the aforementioned ranges. Alternatively, the web angles can be at least partially, or all, the same, with a deviation of up to 10%, preferably up to 5%, and particularly preferably up to 3%, being considered the same. A homogeneous stent structure can be achieved by using identical or at least similar web angles. In particular, the support strut can be formed from, for example, 8, 12, or 16 V-shaped support sections.

[0027] According to the invention, a longitudinal connector is attached to the support strut in the region of the web angle, which connects the support strut to at least one further support strut. The longitudinal connector can, in particular, be attached at the point where the two legs of the V-shaped support section meet. The web angle is preferably determined without taking the longitudinal connector into account.

[0028] Preferably, the longitudinal connector extends at least substantially parallel to the axial direction and thus preferably at approximately a right angle to the support strut. The longitudinal connector is, in particular, a boundary element, wherein two longitudinal connectors and the associated sections of the support struts span or define a cell.

[0029] The longitudinal connector preferably has a position marker that is approximately circular or elliptical in plan view. The position marker may comprise or consist of a thickening of the bioresorbable material. The position marker can, in particular, facilitate positioning of the stent on a catheter. The position marker is preferably arranged adjacent to or near the support strut.

[0030] Along the axial direction of the support strut, the web angle can alternately lie on a side facing away from the longitudinal connector and on a side facing the longitudinal connector. If the web angle lies on the side facing the longitudinal connector, the longitudinal connector can be located approximately in the middle of the web angle.

[0031] Furthermore, a longitudinal connector can only be attached in the area of ​​every second web angle. Viewed along the circumference of a support strut, the longitudinal connectors can be alternately attached to opposite sides of the support strut. In other words, there can be more V-shaped support sections per support strut than longitudinal connectors. Alternatively, there can be exactly the same number of V-shaped support sections as longitudinal connectors.

[0032] Preferably, several longitudinal connectors, in particular exactly two or three longitudinal connectors, can be attached to each support strut on the same side. This means that two adjacent support struts are connected to each other by exactly two or three longitudinal connectors. The connection with two or three longitudinal connectors makes it possible to design the stent flexibly, so that it can adapt well to the curvatures and curves of the hollow organ being supported. At the same time, the support struts provide a high radial erection force.

[0033] The stent may, in particular, have a central section consisting solely of support struts and the longitudinal connectors that join these struts. Viewed axially, the central section is located between the two ends of the stent.

[0034] According to a further advantageous embodiment, the support strut extends radially around the axial direction, at least substantially, such that the axial direction forms a normal vector to the plane defined by the support strut. For determining the plane defined by the support strut, a zigzag shape of the support strut is disregarded, but rather averaged out if necessary. In other words, the support strut is not arranged laterally, obliquely, or at an angle to the axial direction. Instead, the axial direction is perpendicular to the plane defined by the support strut. Consequently, the support struts do not intersect. Preferably, all support struts are arranged in this manner.

[0035] According to a further advantageous embodiment, the stent can be expanded to a third cross-sectional diameter, which is larger than the second cross-sectional diameter, wherein the web angle increases to at least 120°, preferably to at least 140° or 160°, when the stent has the third cross-sectional diameter. In particular, the web angle of at least 165° or 170° can also be present at the third cross-sectional diameter. The web angle of the third cross-sectional diameter can also be at least 10° or 20° larger than that of the second cross-sectional diameter.

[0036] For example, in the coronary arteries, it may be necessary to temporarily enlarge the stent to the third diameter during insertion. This ensures that the stent is better embedded in the blood vessel and maintains a sufficiently large lumen to guarantee unimpeded blood flow. This suppresses the adhesion of platelets, which could otherwise lead to thrombosis.

[0037] The third cross-sectional diameter can be at least 7 to 20% (e.g., 10% or 14%) larger than the second cross-sectional diameter. Particularly due to the zinc alloy mentioned herein, the stent material can be sufficiently flexible to achieve the aforementioned web angles for the third cross-sectional diameter without material failure. The maximum web angle for the third cross-sectional diameter can be 170°, preferably a maximum of 150°.

[0038] According to a further advantageous embodiment, the stent has a uniform structure except for its axial end regions. This means that the stent is identical throughout and may only deviate from this uniform structure at its ends. The axial end regions are understood to be those where, for example, blood enters or exits the stent if it is used in a single-branch blood vessel.

[0039] Alternatively, it is also possible that within a predefined vessel branch area, the rim elements have a lower mass than the rim elements in another area of ​​the same size, with the lower mass being achieved, for example, by using thinner rim elements. The predefined vessel branch area is a curved surface that results when the stent is in its expanded state with the second cross-sectional diameter.

[0040] The vascular branching surface area is designed to be positioned at a vascular branch, where the reduced mass in this area facilitates dilation of the branch. This allows for the creation of a recess in the vascular branching surface area, enabling, for example, unimpeded blood flow at the branch point.

[0041] To achieve the reduced mass, the mass per unit length of the edging elements can be, for example, at least 15%, preferably at least 25%, smaller than that of the other edging elements. Accordingly, the edging elements, and thus, for example, also a section of a support strut that runs through the vessel branching area, can be, for example, 25% thinner or narrower.

[0042] According to a further advantageous embodiment, no longitudinal connectors are arranged within the vessel branch area. In other words, only support struts, e.g., with their V-shaped support sections, are provided within the vessel branch area. By omitting the longitudinal connectors, the mass of the surrounding elements is also reduced. This further simplifies the expansion of the branch, while maintaining radial strength.

[0043] According to a further advantageous embodiment, one or more radiopaque markers are arranged within and / or adjacent to the vessel branching area. The radiopaque markers can be made of a radiopaque material, for example, tantalum. The radiopaque material can be held in an eyelet-shaped structure of the surrounding elements. In particular, for example, four radiopaque markers can be provided, each arranged at regular intervals at the border of the vessel branching area. The radiopaque markers arranged in this way significantly facilitate the correct positioning of the stent or the vessel branching area at a vessel branch under radiographic guidance.

[0044] According to a further advantageous embodiment, the rim elements are at least partially coated with a drug, the drug being preferably released by the stent over a predetermined period. The drug can have an antiproliferative effect to prevent tissue overgrowth of the stent. For example, antiproliferatives of the Limus group, statins, P2Y12 antagonists, or thrombin antagonists can be used as the drug.

[0045] According to a further advantageous embodiment, the boundary elements have a wall thickness of at most 4%, preferably at most 2%, and more preferably at most 1.5%, of the second cross-sectional diameter. The width of the boundary elements, i.e., the dimension viewed in the circumferential direction, can preferably have a maximum of 4%, more preferably at most 2%, and particularly preferably at most 1.7%, of the second cross-sectional diameter. The boundary elements can, for example, have a width of about 105 to 120 µm and a wall thickness of 90 to 115 µm.

[0046] The stent can thus include rim elements that are approximately 25 to 40% narrower and / or thinner than the rim elements of conventional bioresorbable PLLA stents. These particularly thin and narrow rim elements further reduce the risk of thrombosis by hindering platelet adhesion.

[0047] In particular, the stent may be a coronary stent whose second cross-sectional diameter is, for example, a maximum of 2 mm or 4 mm.

[0048] A further object of the invention is a stent for transluminal implantation into hollow organs, in particular blood vessels, ureters, esophagi, colon, duodenum, or biliary tract, comprising a substantially tubular body extending along an axial direction and capable of transitioning from a compressed state with a first cross-sectional diameter to an expanded state with an enlarged second cross-sectional diameter. The stent comprises a plurality of cells defined by rib-like rim elements formed by the tubular body. The rim elements include at least one annular support strut circumferentially around the axial direction, wherein a longitudinal connector is attached to the support strut, which connects the support strut to at least one further support strut.The stent is characterized by the fact that no longitudinal connectors are arranged within a predefined vessel branching area and the surrounding elements comprise, at least in some areas, a bioresorbable material which includes zinc.

[0049] By omitting the longitudinal connectors, the mass of the surrounding elements is reduced, and dilation of the branch is simplified, as explained above. In other words, only support struts, e.g., with V-shaped support sections, are provided within the vessel branch area.

[0050] The vessel branching area can be, in particular, the size of an artery or vein that enters a blood vessel supported by the stent in the area of ​​the stent.

[0051] According to one embodiment, one or more X-ray markers or position markers are arranged within the vessel branching area and / or adjacent to the vessel branching area.

[0052] According to one embodiment, the border elements within the predefined vessel branch area have a lower mass than the border elements in another area of ​​the same size, the lower mass being achieved, for example, by thinner border elements.

[0053] The statements made herein relating to the first-mentioned stent shall apply mutatis mutandis to the further disclosed stent, in particular with regard to advantages and preferred embodiments.

[0054] The invention is described below by way of example only, with reference to the drawings. These show: Fig. 1: An external view of a stent in its expanded state; Fig. 2: An external view of the stent ofFig. 1 , where the stent is in an overexpanded state; Fig. 3 the stent of Fig. 1 in a compressed state; and Fig. 4 a vessel branching area of ​​the stent.

[0055] The Fig. 1 Figure 1 shows a section of a stent 10 in an expanded state with a second cross-sectional diameter corresponding to the nominal diameter of the stent 10. The stent 10 comprises a tubular body 12 extending along an axial direction A. The figures show the stent 10 from a view perpendicular to the axial direction A. The stent 10 is formed by a plurality of boundary elements 14, which together form a lattice-like structure. The stent 10 extends to the left and right of the Fig. 1 continued the shown section.

[0056] Part of the surrounding elements 14 forms ring-shaped support struts 16 circumferentially around the axial direction A. The support struts 16 comprise several V-shaped support sections 18, which are arranged one behind the other such that the support struts 16 have a zigzag-shaped structure in the circumferential direction. Each V-shaped support section 18 comprises two legs 20, between which a web angle 22 is defined. In the illustrated embodiment, the web angle 22 is approximately between 105° and 110°.

[0057] In the area of ​​the web angle 22, the support struts 16 are connected to each other by means of longitudinal connectors 24, wherein, in the circumferential direction, only every second support section 18 is coupled to a longitudinal connector 24. Viewed in the circumferential direction, the longitudinal connectors 24 are alternately attached to opposite sides of the support strut 16.

[0058] The zigzag shape of the support struts 16 is chosen such that adjacent support struts 16 run approximately parallel, i.e., they are not offset or twisted relative to each other. This means that the connection points of each pair of legs 20 of different support struts 16 run approximately along a straight line, with the web angles 22 being arranged on the same side of the support struts 16 along this straight line.

[0059] The stent 10 shown is made of a bioresorbable material consisting of 97% zinc (Zn) and 3% silver (Ag). The choice of this zinc alloy allows the large web angles 22 shown to be achieved without the risk of fracture of the surrounding elements 14.

[0060] As in Fig. 2As shown, it is even possible to temporarily bring the stent into an overexpanded state in which the cross-sectional diameter is at least 7 to 20% larger than the aforementioned second cross-sectional diameter. Such a state is in Fig. 2 shown. As in Fig. 2 As shown, in this state the bridge angle 22 can be more than 120°.

[0061] In contrast, it shows Fig. 3 The stent 10 in its compressed state with a first cross-sectional diameter. In this state, the legs 20 are approximately parallel, so that the web angle 20 does not exist or is approximately 0°.

[0062] Fig. 4 Finally, it shows a different section of stent 10 than in the Figs. 1-3 shown. Fig. 4 shows a section of the stent 10 with a vessel branching area 28 that is approximately circular in plan view.

[0063] The support struts 16 are 25% thinner within the vessel branching area 28 than in the rest of the stent 10. Furthermore, no longitudinal connectors 24 are arranged within the vessel branching area 28, which is indicated by the (non-existent) longitudinal connectors 24 shown with dashed lines. It is understood that the support struts 16, which run through the vessel branching area 28, are coupled by longitudinal connectors 24 arranged outside the vessel branching area 28. These are in Fig. 4not shown. The omission of the longitudinal connectors 24 and the thinner design of the support struts 16 result in easier dilatability of the stent in the area of ​​the vessel branching surface 28, so that the support struts 16 can be bent outwards in the area of ​​a vessel branching, i.e., bent to the edge of the vessel branching surface 28, for example to improve blood flow through the vessel branching.

[0064] In the area of ​​the omitted longitudinal connectors 24, a total of four circular or elliptical position markers 26 are attached to the support struts 16. The position markers facilitate the positioning of the stent 10 on a catheter (not shown). Reference symbol list

[0065] 10 Stent 12 Tubular body 14 Rim element 16 Support strut 18 V-shaped support section 20 Leg 22 Web angle 24 Longitudinal connector 26 Position marker 28 Vessel branch area Aaxial direction

Claims

1. A stent (10) for transluminal implantation into hollow organs, in particular into blood vessels, ureters, esophagi, the colon, the duodenum or the biliary tract, comprising a substantially tubular body which extends along an axial direction (A) and which can be converted from a compressed state having a first cross-sectional diameter into an expanded state having an enlarged second cross-sectional diameter, wherein the stent (10) comprises a plurality of cells which are defined by strut-like bordering elements (14) formed by the tubular body, wherein the bordering elements (14) comprise at least one support strut (16) revolving in a ring shape about the axial direction (A), and wherein the support strut (16) has at least one V-shaped support section (18) which comprises a strut angle (22) of 90° to 150° when the stent (10) has the second cross-sectional diameter, characterized in that a longitudinal connector (24) is attached to the support strut (16) in the region of the strut angle (22) and connects the support strut (16) to at least one further support strut (16) and the bordering elements (14) at least regionally comprise a bioresorbable material which comprises zinc.

2. A stent (10) in accordance with claim 1, characterized in that the strut angle (22) has an angle of 100° to 130°, preferably of 105° to 115°.

3. A stent (10) in accordance with claim 1 or claim 2, characterized in that the bioresorbable material consists of zinc and silver, wherein the bioresorbable material includes 90.0 to 99.95 mass % zinc and 0.05 to 10.0 mass % silver.

4. A stent (10) in accordance with at least one of the preceding claims, characterized in that the support strut (16) at least substantially revolves radially about the axial direction (A) such that the axial direction forms a normal vector to the plane defined by the support strut (16).

5. A stent (10) in accordance with at least one of the preceding claims, characterized in that the stent (10) is expandable to a third cross-sectional diameter which is larger than the second cross-sectional diameter, with the strut angle (22) increasing to at least 120°, preferably to at least 140° or 160°, when the stent (10) has the third cross-sectional diameter.

6. A stent (10) in accordance with at least one of the preceding claims, characterized in that the bordering elements (14) have a smaller mass within a predefined vessel branching areal region (28) than the bordering elements (14) in another areal region of the same size, with the smaller mass, for example, being achieved by thinner bordering elements (14).

7. A stent (10) in accordance with claim 6, characterized in that no longitudinal connectors (24) are arranged within the vessel branching areal region (28).

8. A stent (10) in accordance with claim 6 or claim 7, characterized in that one or more X-ray markers are arranged within the vessel branching areal region (28) and / or adjacent to the vessel branching areal region.

9. A stent (10) in accordance with at least one of the preceding claims, characterized in that the bordering elements (14) are at least regionally provided with a medicine.

10. A stent (10) in accordance with at least one of the preceding claims, characterized in that the bordering elements (14) have a wall thickness of at most 4%, preferably of at most 2%, further preferably of at most 1.5%, of the second cross-sectional diameter.

11. A stent (10) for transluminal implantation into hollow organs, in particular into blood vessels, ureters, esophagi, the colon, the duodenum or the biliary tract, comprising a substantially tubular body which extends along an axial direction (A) and which can be converted from a compressed state having a first cross-sectional diameter into an expanded state having an enlarged second cross-sectional diameter, wherein the stent (10) comprises a plurality of cells which are defined by strut-like bordering elements (14) formed by the tubular body, wherein the bordering elements (14) comprise at least one support strut (16) revolving in a ring shape about the axial direction (A), and wherein a longitudinal connector (24) is attached to the support strut (16) and connects the support strut (16) to at least one further support strut (16), characterized in that no longitudinal connectors (24) are arranged within a predefined vessel branching areal region (28), and the bordering elements (14) at least regionally comprise a bioresorbable material which comprises zinc.

12. A stent (10) in accordance with claim 11, characterized in that one or more X-ray markers or position markers (26) are arranged within the vessel branching areal region (28) and / or adjacent to the vessel branching areal region.

13. A stent (10) in accordance with claim 11 or claim 12, characterized in that the bordering elements (14) have a smaller mass within the predefined vessel branching areal region (28) than the bordering elements (14) in another areal region of the same size, with the smaller mass, for example, being achieved by thinner bordering elements (14).