Multi-stent with a membrane

Abstract

The present invention relates to a multi-stent having at least two coaxially arranged stents (1, 3) and at least one membrane (2, 4), with a first stent (1) provided on the inside and a second stent (3) provided on the outside, a first membrane (2) being arranged on the inner side of the first stent (1) and / or a second membrane being arranged on the outer side of the second stent (3), and the respective membrane ends (2A, 2B; 4A, 4B) being folded over on the respective ends of the stent (1, 3) on which they are arranged, such that the membrane ends (2A, 2B; 4A, 4B) are clamped between the two stents (1, 3).

Description

Field of the Invention

[0001] The present invention relates to a multi-stent having at least two coaxially arranged stents and at least one membrane, wherein the ends of the membrane are fixed between the two stents. The multi-stent is particularly used as a stent-graft for bridging vascular malformations (such as aneurysms, for example) or shunts, but also for reinforcing unstable, fragile or thrombosed vessel walls. It is also used for reconnecting vessels branching off from the stent-supported vessels. Background Art

[0002] There are various forms of stent-grafts known for bridging vascular malformations. Generally, they consist of a fully or partially covered stent. The membrane occludes the vascular malformation, and the stent keeps the blood vessel open and ensures tight contact between the membrane and the vessel wall.

[0003] Problems encountered with such stent-grafts known from the prior art relate to securely anchoring the membrane to the stent. For example, although suturing the membrane to the stent frame is very reliable and durable, the provision of such suturing is still very time-consuming and thus expensive. Alternative developments provide for fixing the membrane to specific clip-like holding elements of the stent.

[0004] Another development in the art relates to stent-grafts in the form of so-called double stents, in which a membrane is arranged and held between two radially positioned stents (i.e., an outer stent and an inner stent). During the expansion of such a double stent, the membrane participates in the radial expansion and remains clamped between the two stents.

[0005] Such a double stent is known, for example, from the disclosure in DE 197 20 115 A1. As described above, the known double stent provides for a single-layer material or membrane to be held between the two stents.

[0006] An alternative double stent is described in DE 10 2016 120 445 A1. In this case, a second membrane is arranged on the outer stent, wherein the membrane ends of the first and second membranes are joined together at the ends of the stent, folded to the inside of the inner stent and clamped under the flexible tongue of the inner stent.

[0007] Basically, the known double stents are functional, but there is room for improvement in some aspects.

[0008] For example, for the double stent first described above, the material layer located between the two stents is subject to the friction generated between the inner stent and the outer stent during expansion, which may cause damage to the material layer. If such damage immediately or only after a period of exposure results in holes or cracks in the material layer, tightness problems may occur. Thus, for example, occlusion of the vascular malformation will no longer be achievable.

[0009] Another known variant with two membranes has, in particular, the following disadvantages: The respective membrane ends must be clamped in a flexible tongue in the lumen of the double stent in a double layer. This is not only technically very demanding but also inevitably leads to a non-negligible accumulation of material, and thus protrusions in the lumen of the stent due to the protruding clamps and possibly formed protruding membrane ends. Such protrusions are a pre-determined starting point for the formation of thrombi / clots, which can lead to blockage of the stent.

[0010] Furthermore, in the case of known double stents, it is considered substantially disadvantageous that in each case the inner lumen is formed by a bare stent without an inner cover. Thus, turbulence is generated in the blood flow due to the exposed struts of the stent, and these must therefore be regarded as another target for the formation of plaques and thrombi, which can lead to blockage of the stent. Summary of the Invention

[0011] Therefore, an object of the present invention is to provide an improved stent graft that is not affected by the disadvantages of the known double stents pointed out above.

[0012] Furthermore, an object of the present invention is to provide a stent graft that is easy to manufacture.

[0013] This object is achieved by providing a multi-stent of the type first mentioned above, which multi-stent comprises at least two coaxially arranged stents and at least one membrane, wherein a first stent is arranged on the inside and a second stent is arranged on the outside, and a first membrane is arranged on the inside of the first stent and / or a second membrane is arranged on the outside of the second stent. The respective ends of the membrane are wrapped around the respective ends of the stent to which it is attached, such that the membrane ends are clamped between the two stents.

[0014] In principle, it is thus conceivable to use devices comprising a plurality of stents and membranes arranged thereon, but the embodiments described below comprising two or three stents and one or two membranes have proven to be substantially advantageous.

[0015] In the context and within the meaning of the present invention, outer or outside shall be understood to mean that this part of the multi-stent is arranged closer to the vessel wall, while inner or inside describes that a part of the multi-stent is arranged further away from the vessel wall and thus closer to the lumen of the multi-stent. More specific information on spatial details can also be found in the drawings.

[0016] In a first preferred embodiment, the multi-stent proposed by the present invention comprises an inner stent having a first end and a second end and an outer stent having a first end and a second end. The stents are arranged coaxially with each other.

[0017] In a first preferred embodiment, the multi-stent of the present invention further comprises an inner membrane and an outer membrane, wherein the inner membrane is arranged on the inside of the inner stent and the outer membrane is arranged on the outside of the outer stent.

[0018] The end of the membrane is folded around the end of the stent on which it is arranged, such that the corresponding end of the membrane is held in place between the stents.

[0019] In a second preferred embodiment, the multi-stent proposed by the present invention comprises an inner stent having a first end and a second end and an outer stent having a first end and a second end. The stents are arranged coaxially with each other.

[0020] In a second preferred embodiment, the multi-stent according to the present invention further comprises an inner membrane, wherein the inner membrane is arranged inside the inner stent.

[0021] The end of the inner membrane is folded around the end of the inner stent, such that the end of the inner membrane is held in place between the stents.

[0022] In a third preferred embodiment, the multi-stent proposed by the present invention comprises an inner stent having a first end and a second end and an outer stent having a first end and a second end. The stents are arranged coaxially with each other.

[0023] In a third preferred embodiment, the multi-stent according to the present invention further comprises an outer membrane, wherein the outer membrane is arranged outside the outer stent.

[0024] The end of the outer membrane is folded around the end of the outer stent, such that the end of the outer membrane is held in place between the stents.

[0025] In a variant of what is referred to as the preferred embodiment, in each case the multi-stent consists of a further third or intermediate stent arranged between the inner stent and the outer stent.

[0026] An intermediate stent may be provided to stabilize the multi-stent; however, an intermediate stent may also be provided or additionally provided in order to further fix the membrane. In order to enhance the fixation of the membrane, the intermediate stent may for example have a suitable surface structure or be made of a material that counteracts the sliding of the membrane. For this purpose, it is also conceivable that such a surface and material of the intermediate stent consists for example of a slightly rough surface to increase the friction, which would be disadvantageous for the inner stent and the outer stent since these are in direct contact with the blood vessel wall or the blood flow at least in some embodiments.

[0027] According to another variant of the described embodiments, it is conceivable that certain stents of the multi-stent (i.e. for example the inner stent and / or the intermediate stent and / or the outer stent) are not provided in the form of a uniform or continuous stent body, but rather consist of a plurality of connected or unconnected stent elements (i.e. individual stent bodies), depending on the circumstances. Overall, these stent elements may correspond to the length of the multi-stent or the length of the other stents of the multi-stent; however, they may also be generally shorter overall, such that they create a gap relative to the other stents; or generally longer overall, such that they create an overlap.

[0028] For the purposes of this further variant, terms such as "inner stent" or "outer stent" are more appropriately understood as "inner stent position" or "outer stent position" in the sense that they refer to specific positions within the multi-stent, which can be occupied by a single or continuous stent body, or alternatively by multiple connected or separate stent elements.

[0029] Preferably, in this case, at least one stent of the multi-stent is provided by a continuous or coherent stent body. This is preferably a stent on which a membrane is disposed.

[0030] The following details apply to all embodiments of the multi-stent proposed by the present invention, particularly to the preferred embodiments and the various variants outlined.

[0031] Any biological or artificial material suitable for the purpose can be used for the membrane. Generally, the membrane consists of a plastic material, preferably a plastic tube, which is pulled onto the corresponding stent. For example, a suitable material is polytetrafluoroethylene (PTFE), especially ePTFE, which has the elasticity required for the expansion process. Other plastics that are not objectionable from a medical point of view can also be used, such as polyesters, polyolefins, polyurethanes, polyurethane carbonates, etc. For example, a membrane knitted, woven or sewn from threads (especially polymer threads) is also conceivable.

[0032] The length of the membranes can be selected such that their ends overlap between the stents after being turned up. Preferably, the membranes are then 5% to 25% longer than the stents on which they are placed, more preferably 25% to 50%, further more preferably 50% to 75%, especially 75% to 100%.

[0033] However, embodiments are also conceivable in which the ends of at least one membrane overlap, which means that the length of the membrane is thus more than twice the length of the stent on which it is disposed.

[0034] Insofar as more than one membrane is arranged in the multi-stent, the membranes can be made of different materials and have different lengths.

[0035] When multiple membranes are provided, they can have the same length or have different lengths. The membranes can be arranged symmetrically or provided in some other configuration.

[0036] The stents can be balloon-expandable or self-expandable. In addition, the stents can be braided or cut from a tube of suitable diameter using laser cutting technology. They have a mesh or lattice structure.

[0037] The multi-stent principle according to the present invention inherently results in a relatively high wall thickness of the construct, which may limit the operability of the patient's vascular system. This can be offset by selecting a tube with a low wall thickness from which the stent is cut or a small-diameter wire for stent braiding (e.g., in the range between 0.05 and 0.50 mm, preferably between 0.10 and 0.20 mm, especially approximately 0.15 mm). The mesh width can also be reduced, for example, to between 0.05 and 0.50 mm, preferably between 0.10 and 0.20 mm, especially approximately 0.15 mm. By using at least two stents, a high radial force can be achieved even with a low wall thickness or wire diameter.

[0038] Stents can generally be made of conventionally known materials, such as medical steel, cobalt-chromium alloy, and nickel-titanium alloy or their optional combinations. Plastics (polymers) can also be used, such as resorbable plastic materials, including various polylactates known in the prior art, as well as combinations consisting of metal stents and plastic stents. In this regard, the arrangement and materials to be used for the stents are selected by those skilled in the art to suit the corresponding application at hand. For example, the inner stent can thus include metal, and the outer stent can include plastic, or vice versa. However, all stents can also be made of the same material.

[0039] It should be understood that different stents can have different thicknesses and different lengths, and at least the inner stent and the outer stent of the multi-stent of the present invention are preferably arranged symmetrically relative to each other.

[0040] However, the following embodiments are also conceivable: According to the embodiments, the stents are arranged staggered with respect to each other or have different lengths, as long as this ensures that the required clamping effect can still be achieved.

[0041] Similarly, the stents can have different designs. Therefore, it is preferred that, for example, the stent located further away from the outside or the outer stent is provided with a smaller mesh than the stent located further away from the inside or the inner stent. In this way, compressive stress is generated during expansion, which has a beneficial effect on the radial force and coherence of the construct. This ensures that high strength and durability of the construct can be achieved.

[0042] The nominal diameter of the stent located more inwardly or the inner stent is at least as large as the nominal diameter of the stent arranged more outwardly, but preferably, the nominal diameter of the stent located more inwardly should be selected to be slightly larger than the nominal diameter of the stent arranged more outwardly in order to achieve a greater clamping effect.

[0043] Clamping the ends of the membrane in place between the stents results in reliable anchoring of the membrane and can be easily implemented because there is no need to manufacture and operate small-scale clamping elements or perform complex and delicate suturing work.

[0044] In another development of the multi-stent according to the present invention, the stent is particularly suitable for multi-lumen implants. A multi-lumen implant is defined as an implant intended for implantation into the vascular system and includes branches to be adapted to the patient's vascular morphology. Typically, these are multi-lumen stent grafts.

[0045] Multi-lumen implants are usually provided in a kit because individual vascular morphologies can vary from patient to patient, and custom design and manufacturing are both expensive and time-consuming. In this case, during or before the intervention, the individual branches of the multi-lumen implant are selected to match the corresponding diameters of the blood vessels to be treated. A key factor in this regard is that the individual components must be connected safely and easily.

[0046] Therefore, the said another development provides that the retaining element is arranged at least at one end or edge region of the multi-stent, and the multi-stent is fixed in the multi-lumen implant by the element. For example, the retaining element can be provided in the form of a hook-shaped and radially outwardly directed element. The hook-shaped and radially outwardly directed element can preferably be part of a bare stent (i.e., an uncovered stent).

[0047] Certain reshaping or modification of the stent end or edge region of the stent can also be used as a retaining element. For example, it is conceivable that at least one end of at least one stent forming part of the multi-stent expands outward. For this purpose, for example, the struts arranged at the end of the stent can be specially shaped, and in particular, they can be made longer than other struts to facilitate this modification.

[0048] It can also be considered that hook-shaped retaining elements are provided in particular for a dual function, that is, they are provided on the covered stent, and in addition to their retaining function in the multi-lumen implant, they are also capable of additionally fixing the membrane at the folding point. In any case, the retaining elements must be arranged such that they protrude far enough from the multi-stent to allow sufficient anchoring in the multi-lumen implant.

[0049] To achieve this, the end of the stent provided with the retaining element can be, for example, slightly longer and thus already protrude from the multi-stent, which is particularly advantageous if one of the inner stents is equipped with a retaining element.

[0050] If the outer stent is equipped with a hook-shaped retaining element, especially for the said second embodiment, it is preferred to arrange the uncovered outer stent to be shorter in total length than the inner covered stent, resulting in the outer stent being completely covered by the inner stent or the membrane provided on the stent with respect to the vascular lumen.

[0051] In addition to the hooks mentioned here, other designs of the retaining element can be envisaged, such as designs particularly adapted to the relevant connection points in the multi-lumen implant, similar to the key-lock principle or the hook-eye principle.

[0052] The combination of the inner stent and the outer stent with the adventitia and / or the intima results in an implant that has surprising stability while still providing a high degree of flexibility. The membrane and at least the double-stent configuration contribute to stabilizing the multi-stent and allowing the stent walls to remain relatively thin. However, the multi-stent exhibits good radial force. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further illustration of the present invention is provided by the drawings showing preferred embodiments of the present invention. It goes without saying that the features shown in the drawings should in each case be regarded separately as part of the present invention and should not be understood only in the context of the other features shown in the drawings, where

[0054] Figure 1 shows a schematic structure of a first embodiment of a multi-stent according to the present invention;

[0055] Figure 2 shows Figure 1 Detail B of, which shows the arrangement of the stent and the membrane of a first embodiment of a multi-stent according to the present invention;

[0056] Figure 3 shows a schematic structure of a second embodiment of a multi-stent according to the present invention;

[0057] Figure 4 shows Figure 3 Detail B of, which shows the arrangement of the stent and the membrane of a second embodiment of a multi-stent according to the present invention;

[0058] Figure 5 shows a schematic structure of a third embodiment of a multi-stent according to the present invention;

[0059] Figure 6 shows Figure 5 Detail B of, which shows the arrangement of the stent and the membrane of a third embodiment of a multi-stent according to the present invention;

[0060] Figure 7 shows the application of a multi-stent according to the present invention in a multi-lumen implant;

[0061] Figure 8 is a detailed view of another development of the multi-stent provided with a holding element according to the present invention for a multi-lumen implant; DETAILED DESCRIPTION OF THE INVENTION

[0062] Figure 1Shows a first embodiment of a multi-stent M according to the present invention, which has an inner stent 1 with a first end 1A and a second end 1B and an outer stent 3 with a first end 3A and a second end 3B, wherein the stents 1, 3 are arranged coaxially with each other. The multi-stent M is shown in a non-expanded state. An inner membrane 2 is arranged inside the inner stent 1, and an outer membrane 4 is arranged outside the outer stent 3.

[0063] The membranes 2, 4 are folded around the ends 1A, 1B, 3A, 3B of the stents 1, 3 such that their ends are respectively clamped between the stents 1, 3.

[0064] The stents 1, 3 can be provided as balloon-expandable or self-expandable, and all known materials are suitable for use. The stents 1, 3 can be made of different materials. The nominal diameter of the inner stent 1 is at least as large as the nominal diameter of the outer stent 3; preferably, the nominal diameter of the inner stent 1 should even be selected to be slightly larger than the nominal diameter of the outer stent 3 to achieve a higher clamping effect.

[0065] The membranes 2, 4 can be made of the widest range of known materials, but preferably the tubular membrane is made of ePTFE. The membranes 2, 4 can also be provided with different materials.

[0066] Figure 2 Shows Figure 1 a detailed view B, which is a closer view of the arrangement of the stents 1, 3 and the membranes 2, 4 relative to each other. The inner membrane 2 and the outer membrane 4 are folded around the ends 1A, 1B, 3A, 3B of the stents 1, 3 where they are respectively located inside and outside with their two ends 2A, 2B, 4A, 4B in the region between the stents 1, 3. Thus, the ends 2A, 2B, 4A, 4B (or more precisely, the end regions) of the membranes 2, 4 are clamped in place between the two stents 1, 3. As shown, the membranes 2, 4 can have different lengths, but they can also have the same length. As shown, the lengths of the membranes 2, 4 can be selected such that the corresponding ends 2A, 2B or 4A, 4B between the stents 1, 3 do not touch or overlap, but the lengths of the membranes 2, 4 can also be selected such that the corresponding ends 2A, 2B or 4A, 4B between the stents 1, 3 touch or overlap.

[0067] Figure 3 Shows a second embodiment of a multi-stent M according to the present invention, which has a first inner stent 1 with a first end 1A and a second end 1B and a second outer stent 3 with a first end 3A and a second end 3B, wherein the stents 1, 3 are arranged coaxially with each other. The multi-stent M is shown in a non-expanded state. In this embodiment, only one membrane 2 is arranged inside the inner stent 1.

[0068] The membrane 2 is folded around the ends 1A, 1B of the inner stent 1 such that the membrane is clamped between the stents 1, 3 with its ends.

[0069] The stents 1, 3 can be provided as balloon-expandable or self-expanding, and all known materials are suitable for use. The stents 1, 3 can be made of different materials. The nominal diameter of the inner stent 1 is at least as large as the nominal diameter of the outer stent 3; preferably, the nominal diameter of the inner stent 1 should even be selected to be slightly larger than the nominal diameter of the outer stent 3 to achieve a higher clamping effect.

[0070] The membrane 2 can be made of the widest range of known materials, but preferably the tubular membrane is made of ePTFE.

[0071] Figure 4 Shows Figure 3 A detailed view B of the arrangement of the stents 1, 3 and the membrane 2 relative to each other, which is a closer view. The inner membrane 2 is folded with its two ends 2A, 2B around the ends 1A, 1B of the inner stent 1 into the region between the stents 1, 3 respectively. Thus, the ends 2A, 2B of the membrane 2 are clamped in place between the two stents 1, 3. As shown, the length of the membrane 2 can be selected such that its ends 2A, 2B between the stents 1, 3 do not touch or overlap; however, the length of the membrane 2 can also be selected such that its ends 2A, 2B between the stents 1, 3 touch or overlap.

[0072] Figure 5 Shows a third embodiment of a multi-stent M according to the present invention, which has a first inner stent 1 with a first end 1A and a second end 1B and a second outer stent 3 with a first end 3A and a second end 3B. The stents 1, 3 are arranged coaxially with each other. The multi-stent M is shown in a non-expanded state. In this embodiment, only one membrane 4 is arranged on the outer side of the outer stent 3.

[0073] The membrane 4 is folded around the ends 3A, 3B of the outer stent 3, such that the ends of the membrane are clamped between the stents 1, 3.

[0074] The stents 1, 3 can be provided as balloon-expandable or self-expanding, and all known materials are suitable for use. The stents 1, 3 can be made of different materials.

[0075] The nominal diameter of the inner stent 1 is at least as large as the nominal diameter of the outer stent 3; preferably, the nominal diameter of the inner stent 1 should even be selected to be slightly larger than the nominal diameter of the outer stent 3 to achieve a higher clamping effect.

[0076] The membrane 4 can be made of the widest range of known materials, but preferably the tubular membrane is made of ePTFE.

[0077] Figure 6 Shows Figure 5Detailed view B, which is a closer view of the arrangement of the stents 1, 3 and the membrane 4 relative to each other. The outer membrane 4 is folded with its two ends 4A, 4B around the ends 3A, 3B of the outer stent 3 into the region between the stents 1, 3. Thus, the ends 4A, 4B of the membrane 4 are clamped in place between the two stents 1, 3.

[0078] As shown, the length of the membrane 4 can be selected such that its ends 4A, 4B between the stents 1, 3 do not touch or overlap; however, the length of the membrane 4 can also be selected such that its ends 4A, 4B between the stents 1, 3 touch or overlap.

[0079] Figure 7 Another development of the multi-stent M proposed by the present invention is shown in its application in a multi-lumen implant ML (i.e., a branched stent-graft).

[0080] Figure 8 Is shown in detail the end region of another development of the multi-stent M according to the invention used in the multi-lumen implant ML as shown in Figure 7 The other development provides that the retaining element 5 is arranged at least at one end of the multi-stent M; with the aid of this element, the multi-stent M can be fixed in the multi-lumen implant ML. The multi-lumen implant ML is usually provided in a kit, in which the individual branches of the multi-lumen implant ML are selected to match the corresponding diameters of the blood vessels to be treated. The key in this case is the connection of the individual components. Taking this into account, the other development preferably provides that the retaining element 5 consists of hook-shaped and radially outwardly pointing elements 5. Preferably, these can be part of an uncoated stent, since the ends of the coated stent are covered by the folded membrane. Piercing the membrane by the retaining element would cause unnecessary material damage. It is also conceivable that the retaining elements 5 are provided for a dual function, i.e., they are provided on the coated stent and, in addition to their retaining function in the multi-lumen implant ML, are also able to fix the membrane additionally at the folding points. In any case, the retaining elements 5 must be arranged such that they project far enough from the multi-stent to allow sufficient anchoring in the multi-lumen implant.

[0081]

[0082] 1 Inner (first) stent (1A, 1B: ends of the inner stent)

[0083] 2 Inner (first) membrane (2A, 2B: ends of the inner membrane)

[0084] 3 Outer (second) stent (3A, 3B: ends of the outer stent)

[0085] 4 Outer (second) membrane (4A, 4B: ends of the outer membrane)

[0086] 5 Retaining element

[0087] M multi-stent

[0088] ML multi-lumen implant

Claims

1. A multi-stent, comprising at least two coaxially arranged stents and at least one membrane, wherein, The first stent is arranged on the inside and the second stent is arranged on the outside, characterized in that a first membrane is arranged on the inside of the first stent and / or a second membrane is arranged on the outside of the second stent, wherein the respective membrane ends are folded around the respective ends of the stent on which they are arranged such that the membrane ends are guided between the first stent and the second stent.

2. The multi-stent according to claim 1, wherein The more inwardly arranged stent has a nominal diameter that is at least the same size as the more outwardly arranged stent, wherein the more inwardly arranged stent has a larger nominal diameter than the more outwardly arranged stent.

3. The multi-stent according to claim 1 or 2, characterized in that, The at least one membrane is provided in tubular form.

4. The multi-stent according to claim 1 or 2, characterized in that, The at least one membrane is 5% to 25% longer than the stent on which it is arranged.

5. The multi-stent according to claim 1 or 2, characterized in that, The length of the at least one membrane is more than twice the length of the stent on which it is arranged such that the folded membrane ends overlap between the stents respectively.

6. The multi-stent according to claim 1 or 2, wherein, The membrane is made of a thin film or provided in a form knitted, woven or sewn from threads.

7. The multi-stent according to claim 1 or 2, comprising two coaxially arranged stents and two membranes, wherein, The first stent is provided on the inside and the second stent is provided on the outside, characterized in that the first membrane is arranged on the inside of the first stent and the membrane ends of the first membrane are folded to the outside of the first stent, and the second membrane is arranged on the outside of the second stent and the membrane ends of the second membrane are folded to the inside of the second stent such that the membrane ends are clamped in place between the stents.

8. The multi-stent according to claim 1 or 2, comprising two coaxially arranged stents and a membrane, wherein, The first stent is provided on the inside and the second stent is provided on the outside, characterized in that the membrane is arranged on the inside of the first stent and the membrane ends are folded to the outside of the first stent such that the membrane ends are clamped in place between the stents.

9. The multi-stent according to claim 1 or 2, having two coaxially arranged stents and a membrane, wherein, The first stent is provided on the inside and the second stent is provided on the outside, characterized in that the membrane is arranged on the outside of the second stent and the membrane ends are folded to the inside of the second stent such that the membrane ends are clamped in place between the stents.

10. The multi-stent according to claim 1 or 2, comprising three coaxially arranged stents and two membranes, wherein, The first stent is arranged on the inside, the second stent is provided on the outside, and a third stent is provided between the first stent and the second stent, characterized in that the first membrane is arranged on the inside of the first stent and the membrane ends of the first membrane are folded to the outside of the first stent and are clamped in place between the first stent and the third stent, and the second membrane is arranged on the outside of the second stent and the membrane ends of the second membrane are folded to the inside of the second stent and are clamped in place between the second stent and the third stent.

11. The multi-stent according to claim 1 or 2, wherein, Retention elements are provided at least at one end of one of the stents of the multi-stent.

12. The multi-stent according to claim 11, wherein, The retention element is provided as an extension of at least one end of at least one of the stents of the multi-stent.

13. The multi-stent according to claim 11, wherein, The retention element is provided with a hook-shaped configuration and points radially outwards.

14. The multi-stent according to claim 1 or 2, characterized in that, At least one of the stents of the multi-stent comprises a plurality of individual stent elements.

15. The multi-stent according to claim 1 or 2, characterized in that, The at least one membrane is 25% to 50% longer than the stent on which it is arranged.

16. The multi-stent according to claim 1 or 2, characterized in that, The at least one membrane is 50% to 75% longer than the stent on which it is arranged.

17. The multi-stent according to claim 1 or 2, characterized in that, The at least one membrane is 75% to 100% longer than the support on which it is disposed.

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