HK1250325A1 - Stent - Google Patents

Abstract

The invention relates to a stent implanted into a hollow organ through a cavity,Especially blood vesselsUreterEsophagusColonIn the duodenum or biliary tract,The support comprises a substantially tubular body,The tubular body can change from a compressed state with a first cross-sectional diameter to an expanded state with an expanded second cross-sectional diameter,Wherein the bracket comprises a plurality of units,The plurality of units are defined by boundary elements formed by the tubular body;The support differs in that some of the units extend in the longitudinal direction of the support compared with the remaining units to form an inclined end face of the support.

Description

The present invention relates to a stent for transluminal implantation in hollow organs, particularly in blood vessels, ureters, esophagus, colon, duodenum or bile ducts, having a substantially tubular body which can be moved from a compressed state with a first cross-sectional diameter into an expanded state with an increased second cross-sectional diameter, wherein the stent comprises a plurality of cells defined by surrounding elements formed by the tubular body.

Such stents are used for rechanneling diseased hollow organs. In this process, the stents are introduced via an introducer catheter in a compressed state to the treatment site within the hollow organ, where they are expanded by different methods to a diameter corresponding to that of the healthy hollow organ, thereby achieving a supporting effect on the hollow organ, such as a vessel wall.

Such stents can be produced, for example, by cutting openings such as slits into the wall of a tubular body, which extend partially in the longitudinal direction of the stent, so that when the stent expands, rhombus-shaped openings are formed. An opening together with its surrounding elements is referred to as a cell.

When stents are placed near the bifurcation of a hollow organ, stents with a tapered end can be used. Such stents make it possible, for example, to support a vein from all sides up to the bifurcation, i.e., for instance, up to its opening into another vein.

In order to ensure their supporting effect, stents must be able to exert a sufficient radial expansion force that counteracts the radial force applied by the vessel wall. This is especially true in the region of the tapered end, as the radial expansion force is usually reduced there.

US 2012/024567 A1 describes a stent with a substantially tubular body that can be moved from a compressed state with a first cross-sectional diameter to an expanded state with an increased second cross-sectional diameter. The stent includes a plurality of cells defined by edge elements formed by the tubular body. Some of the cells are longer in the longitudinal direction of the stent compared to the other cells.

US 2012/24567 A1 describes a stent that is cut from a tubular material and expanded up to an expanded state.

It is the object of the present invention to create a stent of the aforementioned type which provides a high radial expansion force even in an inclined region, thereby reliably preventing the stent from kinking during its deployment.

This object is inventively achieved by a stent having the features of claim 1, and particularly by forming a portion of the cells longer in the longitudinal direction of the stent compared to the other cells, thereby creating an oblique front end of the stent.

Due to the elongated cells, a beveled end can be created. Because the cells are elongated in the longitudinal direction, no additional cells are needed to form the beveled end. Using the elongated cells, it is possible to choose a similar arrangement of cells in the beveled area as in the rest of the tubular body.

The extended cells can particularly be present only in a rigid section of the stent. Additionally, the stent may, for example, include a flexible section and/or an anchoring section. The following descriptions regarding the extended cells refer to the rigid section.

By avoiding additional cells, a stent structure is obtained that can provide particularly high radial strength. In this way, it becomes possible, for example, to reliably support blood vessels near bifurcations. An inventive stent can therefore, for example, be used in cases of venous obstructions in the area of a bifurcation, namely at the confluence of the two common iliac veins into the inferior vena cava, or in the upper part of the common iliac vein. The stent can have a diameter of greater than or equal to 12 mm. Preferably, the stent can have a diameter between 12 mm and 18 mm.

Furthermore, the omission of additional cells allows for a variable angle of the bevel, since this angle can be determined by the relative elongation of the elongated cells.

Generally, the tapered section allows reliable support of the hollow organ up to the bifurcation, without significantly protruding into the bloodstream beyond the bifurcation.

A cell can be connected to one or more other cells via a connection section or multiple connection sections. The length of a cell can be understood as the distance in the longitudinal direction between two connection sections, taking into account the center of each respective connection section. A cell includes the mentioned recess as well as its respective surrounding elements, wherein the connection sections belong to the surrounding elements.

In a stent according to the invention, the cells can be connected to each other via a plurality of connecting sections, at least partially. In particular, three or four connecting sections can be provided respectively in the tapered region and/or in the elongated cells. Thus, the supporting effect can be particularly high due to the radial expansion force achievable in this way.

The stent can be made of a shape-memory metal that takes on a stored shape at a certain threshold temperature.

Preferred embodiments of the invention are to be found in the description, the dependent claims, and the drawings.

According to a first advantageous embodiment, at least a portion of the extended cells are arranged along a straight or approximately straight line, which particularly runs parallel or approximately parallel to the longitudinal direction. This means, for example, that at least one or two cells arranged in a row along the straight line can be provided. With more than two cells, at least two connection sections of at least one of these cells can be directly connected to two further extended cells. In particular, two connection sections of the extended cells are located on the straight line.

According to another advantageous embodiment, the extended cells can be divided into several groups, in particular into nine groups, wherein the cells of each group are arranged along a straight or substantially straight line, and these lines are particularly parallel or substantially parallel to the longitudinal direction. In total, the stent can have twelve groups of cells, of which nine groups include extended cells. With such a definition of groups, the spaces between the groups can also form cells.

The arrangement of the cells can thus be chosen such that the respective cells are arranged along straight or approximately straight lines. Additionally, the cells can be symmetrically formed with respect to one of these lines. Therefore, in particular, there are no cells that are tilted or rotated relative to the other cells. In this way, a weakening of the structure caused by such rotated cells can be avoided.

In particular, all cells within a group can each have the same or approximately the same length when viewed in the longitudinal direction. Alternatively, a group can also include cells of different lengths.

The lines formed by the cells of different groups preferably run parallel or nearly parallel to each other.

Further preferred is that, from a cross-sectional plane extending perpendicular to the longitudinal axis up to the beveled end, each group is provided with an equal number of cells. By providing an equal number of cells in each group, a radial expansion force can be achieved which is essentially constant along the length of the stent. Preferably, in the rigid section of the stent, each group can be provided with an equal number of cells.

In particular, when using a large number of cells, angles can be formed by the connection sections of the cells, which are visible in the so-called unfolding of the stent. The angles are defined by the circumferential direction (which is a straight line in the unfolding) and a straight line, with the straight line passing through the connection sections of the cells. This means that the connection sections of the cells lie at least partially on straight lines in the unfolding. The angles can be larger the closer they are to the tapered end of the stent, preferably four, five, or six angles being provided.

At the beveled end itself, the ends of the cells in the unfolded state cannot form a straight line, but instead define a curve that approximates a sine wave. Such a sine curve in the unfolded state leads to a beveled section (the beveled area) on the three-dimensional stent, featuring an exactly flat cut surface.

The cells can be arranged such that a first angle lies within a range of 20° to 24°, a second angle within a range of 37° to 44°, a third angle within a range of 48° to 52°, a fourth angle within a range of 60° to 64°, a fifth angle within a range of 63° to 67°, and a sixth angle within a range of 69° to 73°. The largest angle may particularly be located closest to the beveled end of the stent, whereas the smallest angle is located the farthest from the beveled end. Moreover, an angle of 0° can be provided, which means that there exists a position on the stent in the unrolled state where connection sections are arranged along the circumferential direction. The 0° angle can be provided at a transition from the rigid section to the flexible section. The cells of a group can have different lengths in order to form the described angles.

For such a selection of angles, it has been shown that a very stable stent can be created, which exhibits particularly long durability.

According to another advantageous embodiment, the length of the cells of adjacent groups varies in the circumferential direction from a maximum to a minimum. In particular, cells with maximum length are opposite to cells with minimum length relative to a central axis of the stent. Such an arrangement can produce the beveling.

Furthermore, the cells are preferably at least partially connected to each other via connecting sections, wherein the connecting sections are extended between the elongated cells, particularly only between the longest cells. Due to the extended or enlarged connecting sections, the openings of the longest cells can be shortened, thereby enabling a uniform buckling of all cells when the stent is expanded. Such a uniform buckling in turn can result in a uniform distribution of the radial crimping force and lead to a particularly robust stent.

Particularly preferred is a marker extending in the longitudinal direction away from the beveled end, at least in the form of a loop, wherein the marker has an asymmetric shape. A marker can be a section of the stent that exhibits increased radiopacity, i.e., is particularly visible in an X-ray image. In particular, the marker can be a loop that is filled or coated, for example, with tantalum. Due to its asymmetric shape, the marker can also be arranged in the beveled area, as the marker can extend away from the bevel.

In other words, the marker can be arranged within a range between the longest and the shortest extent of the stent in the longitudinal direction. Due to the asymmetric shape, the marker can be made large enough to be particularly well visible in the X-ray image. Additionally, another marker can be provided, for example, at the tip of the bevel. Yet another marker can, for example, be attached at the shortest part of the stent on the bevel.

According to another advantageous embodiment, at least two asymmetric markers are provided at the beveled end, wherein the markers are opposite each other with respect to the stent's axis, in particular. Thus, the two markers can be symmetrically arranged relative to a plane of the stent that passes through the stent's axis and the tip of the bevel. Due to such an arrangement, the asymmetric markers can be superimposed in an X-ray image, for example. As a result, the position of the stent can be particularly clearly visible in the X-ray image.

According to another advantageous embodiment, the stent includes a flexible section connected to the rigid section. The flexible section is opposite the beveled end. The flexible section can have cells that, when expanded, occupy a larger area than the cells of the rigid section. Due to the larger cells, the flexible section can be more bendable, thereby allowing the flexible section to easily adapt to the contour shape of a hollow organ. Preferably, the cells of the flexible section can have a tooth-like boundary.

According to another advantageous embodiment, the stent includes an anchoring section connected to the flexible section. The cells of the anchoring section may correspond to the cells of the rigid section and, for example, be shaped like rhombuses. Due to the rhombus-shaped cells, the anchoring section may have a certain degree of flexibility and thus fix the stent at its position within the hollow organ. The anchoring section can form a straight end of the stent, at which markers can be attached that extend away from one end of the stent. The markers can have the shape of loops and, for example, can also be coated or filled with tantalum. When introducing the stent into the hollow organ, the stent can be fixed within an introduction catheter by means of the markers of the anchoring section.

The described stent can be used in a method wherein: a) the stent is cut from a tubular material, b) the stent is expanded up to its expanded state, and c) in the expanded state, the shape of the stent's cells is changed and fixed.

By changing the shape of the cells, each individual cell can be formed in such a way that a uniform expansion behavior of the individual cells is achieved. In this way, the risk of fracture can be reduced, especially for short and medium-length cells near the slanted area, which typically tend to expand asymmetrically and excessively due to an inhomogeneous force distribution during expansion.

For example, in rhombus-shaped cells with up to four connection sections at the respective corners of the rhombus, the sharp angles can be reduced or modified so that they are smaller than 70°, preferably smaller than 60°. This leads to the stent being better able to withstand large external forces in the area of the beveled section through a homogeneous force distribution across the structure, and the risk of stent collapse or stent fracture is significantly reduced.

Moreover, the method makes it possible to prevent excessive cell expansion, thereby avoiding pre-damage to connection sections.

A core can be used to expand the stent, to which fastening elements are attached in order to change and fix the shape of the stent's cells. Thus, with these fastening elements, the expansion behavior of each individual cell can be adjusted. Consequently, the shape of the cells is altered compared to pure expansion using, for example, a cylindrical core. Such a cylindrical core can also include a conical section that facilitates the stent's deployment. Moreover, the expansion can be performed by applying heat.

The fastening elements can be pins or spikes that are inserted into holes of the core. The pins or spikes can, for example, be extended outward from the core or inserted inward from the outside. For this purpose, an automated process using robots or hydraulics, but also a manual adjustment of the cells, can be carried out.

The modified shape of the stent's cells can be permanently fixed by means of a heat process. Such fixation is particularly advantageous when using memory metals, which regain the shape stored during the heat process when the temperature increases. Permanent fixation refers to fixing the shape of the stent's cells in the expanded state of the stent, wherein the shape of the cells is maintained even if the stent is temporarily compressed. When the stent is introduced into the body, the stent and its cells can then regain the shape learned during the manufacturing process due to body heat.

The invention will be described below with reference to preferred embodiments and the accompanying drawings. They show: Fig. 1: a stent according to the invention in the expanded state, in side view; Fig. 2: the stent of Figure 1 in the expanded state, in top view; Fig. 3: the stent of Figure 1 in a cross-sectional representation projected into a plane; and Fig. 4: the cross-sectional representation of Fig. 3 with a representation of angles defined by connecting sections.

Fig. 1 and Fig. 2 show a stent 10. The stent 10 has a tubular shape and includes a rigid section 12, a flexible section 14 connected to the rigid section 12, and an anchoring section 16 connected to the flexible section 14.

The rigid section 12 is formed by rhombic (closed) cells 18, each connected to other rhombic cells 18 via three or four connecting sections 20. The rhombic cells 18 are defined by web-like edge elements 22, which are formed from a metal.

Section 12 includes a beveled portion 24, which allows the use of the stent 10 at a (not shown) bifurcation of a hollow organ.

The beveled section 24 forms an end of the stent 10 and is created by elongating a portion of the rhombic cells 18 in the longitudinal direction L. The longest rhombic cells 18 are marked with the reference numeral 18a, whereas the shortest rhombic cells 18 are marked with the reference numeral 18b. In the rigid section 12, three of the shortest rhombic cells 18b and three of the longest rhombic cells 18a are provided in the longitudinal direction L. The longest rhombic cells 18a are arranged opposite to the shorter rhombic cells 18b relative to a central axis of the stent 10. Three groups of the longest and the shortest rhombic cells 18a, 18b are provided side by side (i.e., adjacent in the circumferential direction).

In the flexible section 14, open cells 26 with a zigzag or tooth-like outline are arranged, wherein, when viewed in the circumferential direction of the stent 10, fewer open zigzag cells 26 are provided compared to rhombic cells 18. By using fewer open zigzag cells 26, the flexible section is more deformable in the longitudinal direction L and can thus easily adapt to the course of a blood vessel or similar structure.

The anchoring section 16 is formed by rhombic cells 18, which contribute to an increased stiffness of the anchoring section 16, thereby enabling the stent 10 to reliably maintain its position within a hollow organ.

Both at the tapered section 24 and at the end formed by the anchoring section of the stent 10, four eye-shaped markers 28 are provided, three of which are visible in Fig. 1. In Fig. 2, all four markers 28 of the tapered section 24 can be seen.

Two of the markers 28, which are mounted in the tapered region 24 at the locations of the longest and shortest extension of the stent 10, are symmetrically designed. Two additional markers 28 are attached to the tapered region 24 where the stent 10 has its average length. These two markers 28 are designed as asymmetric markers 28a, wherein the area of the asymmetric markers 28a extends toward the shortest extension of the stent.

Fig. 3 shows the rigid section 12 of the stent 10 from Fig. 1 and Fig. 2 in a so-called cutaway view. Consequently, Fig. 3 shows a projection of cuts introduced into a raw material of the stent onto a plane. A line thus indicates a cut. Several parallel but offset cuts can, when the stent 10 is expanded, be widened into the rhombus-shaped cells 18 shown in Fig. 1 and Fig. 2.

The material areas represented as white regions between the lines become connection sections 20 or border elements 22 after expansion. Fig. 3 shows only the rigid section 12 of the stent 10.

As shown in Fig. 3, it can be seen that extended connecting sections 20a are provided between the longest diamond-shaped cells 18a, which lead to a more uniform bulging of all diamond-shaped cells 18 when the stent is expanded.

Fig. 4 shows the view of Fig. 3 with the angles marked, which are formed by connection sections 20 with respect to a circumferential direction. Six angles α1, α2, α3, α4, α5, α6 are shown, which gradually increase from an angle of approximately 22° (α1) through angles of approximately 40° (α2), 50° (α3), 62° (α4), and 65° (α5) up to an angle of approximately 71° (α6). A straight end line 30, arranged at the transition from the rigid area 12 to the flexible area 14, extends in the circumferential direction through the connection sections 20 and thus defines an angle of 0°.

Reference list

10 Stent 12 rigid section 14 flexible section 16 anchoring section 18, 18a, 18b bulb-shaped cell 20, 20a connection section 22 rim element 24 beveled area 26 open serrated cell 28, 28a marker 30 end line L longitudinal direction α angle

Claims (12)

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, having a substantially tubular body 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 (18, 18a, 18b) which are defined by bordering elements (22) formed by the tubular body, wherein some of the cells (18, 18a) are formed as elongated in the longitudinal direction of the stent (10) in comparison with the other cells (18b) to form a chamfered front face end (24) of the stent (10), characterized in that at least some of the elongated cells (18, 18a) are arranged along a straight line or an approximately straight line which extends in parallel or approximately in parallel with the longitudinal direction (L).
2. A stent (10) in accordance with claim 1, characterized in that the elongated cells (18, 18a) can be divided into a plurality of groups, in particular into nine groups, with the cells (18, 18a) of each group being respectively arranged along a straight line or an approximately straight line, with the lines in particular extending in parallel or approximately in parallel with the longitudinal direction (L).
3. A stent (10) in accordance with claim 2, characterized in that the lines extend in parallel or approximately in parallel with one another.
4. A stent (10) in accordance with claim 2 or claim 3, characterized in that a respective equal number of cells (18, 18a, 18b) is provided in each group from a cross-sectional plane extending perpendicular to the longitudinal axis up to the chamfered front face end (24).
5. A stent (10) in accordance with at least one of the claims 2 to 4, characterized in that the length of the cells (18, 18a, 18b) of adjacent groups decreases from a maximum to a minimum in the peripheral direction.
6. A stent (10) in accordance with at least one of the preceding claims, characterized in that cells having a maximum length (18a) are disposed opposite cells having a minimal length (18b) with respect to a central axis of the stent (10).
7. A stent (10) in accordance with at least one of the preceding claims, characterized in that at least some of the cells (18, 18a, 18b) are connected to one another by means of connection sections (20, 20a); and in that the connection sections (20a) are formed as elongated between the elongated cells (18, 18a), in particular only between the longest cells (18a).
8. A stent (10) in accordance with at least one of the preceding claims, characterized in that at least one marker (28, 28a), in particular in the form of an eyelet, extends away from the chamfered end (24) in the longitudinal direction (L), with the marker (28, 28a) having an asymmetrical shape.
9. A stent (10) in accordance with claim 8, characterized in that the marker (28, 28a) is arranged in a region between the longest and the shortest extent of the stent (10) in the longitudinal direction (L).
10. A stent (10) in accordance with claim 8 or claim 9, characterized in that at least two markers (28, 28a) are provided at the chamfered end, with the markers (28, 28a) being disposed opposite one another with respect to an axis of the stent (10).
11. A stent (10) in accordance with claim 1 which is cut out of a tubular material and in which the shape of the cells (18, 18a, 18b) can be fixed in the expanded state.
12. A stent in accordance with claim 11, characterized in that the cells (18, 18a, 18b) of the stent (10) can be permanently fixed in a changed shape by means of a heating process.