MEDICAL SET, MEDICAL SYSTEM AND COVERING DEVICE FOR THE TREATMENT OF ANEURYSMS

Description

[0001] The invention relates to a medical set for treating vascular malformations, in particular aneurysms and / or fistulas. Furthermore, the invention relates to a medical system and a covering device for treating vascular malformations.

[0002] WO 2014 / 177634 A1 describes a highly flexible stent comprising a compressible and expandable lattice structure, wherein the lattice structure is formed as a single piece. The lattice structure comprises closed cells, each delimited by four lattice elements. The lattice structure has at least one cell ring comprising between three and six cells.

[0003] The applicant's practice also discloses stents with lattice structures made of a single wire. The wire is interwoven to form a tubular mesh. At the axial ends of the tubular mesh, the wire is deflected to form atraumatic loops. The axial ends can be flared in a funnel shape.

[0004] The known medical device is particularly suitable for the treatment of aneurysms in small cerebral blood vessels. Such blood vessels have a very small cross-sectional diameter and are often highly tortuous. The known stent is designed to be highly flexible, allowing it to be compressed to a very small cross-sectional diameter while also exhibiting high bending flexibility, allowing it to be delivered into small cerebral blood vessels.

[0005] To treat aneurysms in cerebral blood vessels, it is advisable to use stents that span the aneurysm and shield it from blood flow within the vessel. To achieve this, it is known to provide stents with a covering that seals off the stent cells, thus preventing blood flow into the aneurysm.

[0006] Another complementary or alternative treatment method for aneurysms is the implantation of so-called coils into the aneurysm, which cause blood clotting. The resulting thrombus then prevents blood circulation in the aneurysm and thus reduces the risk of rupture and subsequent bleeding.

[0007] However, especially in wide-necked aneurysms, the coils tend to migrate into the bloodstream during implantation, thus causing occlusion of the main vessel lumen. In the "balloon-assisted coiling" technique, catheters with "compliance balloons" are positioned within the vessel, specifically at the level of the aneurysm neck. The contrast-filled balloon closes the aneurysm neck during placement of the coils and forces the coils into a compact arrangement within the aneurysm space. Because coils are plastically deformable, they retain their shape. They do not leave the aneurysm even when the balloon is removed. However, this poses a problem, particularly due to the fact that the balloon occludes the vessel. If the procedure is prolonged (multiple coils are placed for large aneurysms, and the procedure can take several minutes), blood flow is completely interrupted.Although collateral vessels provide a supply to downstream tissue, the risk of underperfusion remains.

[0008] Furthermore, during the procedure, a catheter through which the coils are passed is "jailed," or clamped, to the side of the balloon. If it becomes necessary to replace the coil catheter (e.g., in case of damage) while the procedure is not yet complete, the balloon must be deflated to allow the catheter to be withdrawn. During this phase, the coils, which are not yet fully and compactly positioned within the vessel, may shift. This can then lead to vessel occlusion.

[0009] WO 2019 / 175 341 A1 discloses a stent with an electrospun cover intended to cover an aneurysm. US 2014 / 058 498 A1 describes a similar stent. However, such stents cannot be used to retain embolizing agents in the aneurysm. To introduce the embolizing agents, the cover must be penetrated by a microcatheter, which carries the risk that an opening remains after removal of the microcatheter, through which the embolizing agents can enter the free blood vessel.

[0010] Against this background, the object of the invention is to provide a medical kit for the treatment of vascular malformations that at least reduces the risk of vascular occlusions. A further object of the invention is to provide a medical system.

[0011] According to the invention, this object is achieved with regard to the medical set by the subject matter of patent claim 1, with regard to the medical system by the subject matter of patent claim 14 and with regard to the covering device by the subject matter of patent claim 15.

[0012] Specifically, the problem is solved by a medical set for treating vascular malformations, in particular aneurysms and / or fistulas, e.g. carotid direct cavernous fistula. The set has a permanently implantable covering device, in particular a stent, for covering the vascular malformation. The covering device has a tubular, self-expanding lattice structure and a cover made of electrospun fabric. The cover is connected to the lattice structure and at least partially covers the lattice structure in order to be placed over the vascular malformation in the implanted state. The medical set has an embolization agent which can be applied by a delivery means in the implanted state to treat the vascular malformation.The cover forms a porous membrane which can be penetrated by the delivery means for application of the embolizing agent and is adapted to adhere to the outer periphery of the delivery means when penetrated.

[0013] The medical kit according to the invention thus comprises the covering device and the embolization agent. The kit may comprise additional components.

[0014] In contrast to the medical set according to DE 10 2019 121 546 of August 9, 2019, the medical set according to the invention is intended to cover an aneurysm permanently and not just temporarily. The covering device forms a permanent implant, such as a stent. For this purpose, the permanently implantable covering device is placed over the aneurysm to be treated using a transport wire through the delivery means in a known manner. After the covering device has been completely released from the delivery means, it is released from the transport wire. The covering device is thus firmly and permanently anchored in the vessel and, in its final implanted state, can no longer be retracted into the delivery means.

[0015] For this purpose, the cover device is detachably connected to a transport wire during insertion.

[0016] The covering device is preferably a stent. Generally, the covering device has a tubular, self-expanding lattice structure. The lattice structure is open at the distal and proximal ends, i.e., at both axial ends, so that blood can flow through it in the expanded state in a conventional manner. In contrast, known thrombectomy devices for retraction into a catheter have an inwardly closing, funnel-shaped section that is firmly, i.e., non-removably, connected to the transport wire.

[0017] The covering formed from the electrospun fabric on the lattice structure has such an extension that a vascular malformation, in particular an aneurysm, can be sufficiently securely covered in the implanted state. The covering can extend over the entire circumference of the lattice structure and over a sufficiently large length in the axial direction of the lattice structure. It is also possible for the covering to extend not over the entire circumference, but only over a partial circumference of the lattice structure, in particular over an angular segment of the lattice structure, and / or over a partial length.

[0018] The cover is connected to the grid structure in such a way that it cannot detach from the grid structure when implanted. The electrospun fabric of the cover covers the grid structure.

[0019] Generally, these are embolizing agents suitable for the treatment of vascular malformations. Embolizing agents that can be introduced into the aneurysm for obliteration include, but are not limited to, one or more coils and / or embolic fluids (liquid embolics), such as viscous hydrogels.

[0020] According to the invention, the cover, specifically the electrospun fabric of the cover, forms a porous membrane. The entire cover, specifically the electrospun fabric of the cover, can form the porous membrane. It is also possible for only a portion of the cover to form the porous membrane. The porous membrane is designed such that it can be penetrated by the delivery means for applying the embolization agent. In other words, the porous membrane is designed such that the delivery means can be probed radially or at an acute angle outwards through the membrane from the inner lumen of the implanted lattice structure. The delivery means pierces or penetrates the membrane or the electrospun fabric of the cover without irreversibly damaging the cover or the tissue. It is possible for individual pores in the tissue to expand or enlarge considerably.

[0021] It has been shown that the electrospun fabric is sufficiently flexible that the pores present in the electrospun fabric, or a pore, can be elastically expanded by the delivery agent when the delivery agent penetrates the electrospun fabric. The pores, or the pore and the membrane material arranged around the pores, deform elastically enough to create a sufficiently large opening for the delivery agent. The delivery agent itself has a diameter that is orders of magnitude larger than the diameter of the pores. The electrospun fabric or porous membrane is elastic enough to allow sufficient deformation of the pores to allow the delivery agent to pass through.

[0022] An example of the diameter of the feeder is based on pore sizes (inscribed circle diameter) of the cover or covering of 5-20µm for a 1-minute spun grid structure or pore sizes (inscribed circle diameter) of 1-5µm for a 2-minute spun grid structure. Where the unit "inch" is used in the description, the following conversion applies: 1" = 25.4mm

[0023] The outer diameter of the suitable delivery device, e.g. a guidewire with a subsequent microcatheter, can be described as follows: Outer diameter of the guidewire: approx. 0.36 mm (0.014") Outer diameter of the microcatheter: approx. 2.1 Fr (0.70 mm) Inner diameter of the microcatheter (ID): approx. 0.42 mm (0.0165")

[0024] Smaller combinations of outer diameter of the guide wire of approximately 0.254mm (0.010") and outer diameter of the microcatheter of approximately 1.5 Fr (0.5 mm), ID: 0.33mm (0.013") are possible.

[0025] The above-mentioned size ratios are examples. Other size ratios of pores and feed medium are possible.

[0026] In this state, i.e. when the delivery agent penetrates the membrane, the porous membrane of the cover or electrospun fabric adheres to the outer circumference of the delivery agent, thus sealing it off from the vascular malformation, in particular the aneurysm. The embolization agent can then be transported through the membrane into the aneurysm by the delivery agent. The delivery agent is arranged in the lumen of the cover device or stent. Due to the membrane function of the cover or fabric, it is possible for the embolization agent to be introduced into the aneurysm with the aid of the delivery agent through the lumen of the cover device radially or at an acute angle from the inside to the outside through the wall or the lattice structure of the cover device.

[0027] The sealing of the delivery agent by the tissue or the cover prevents the embolizing agent from entering the bloodstream when it is introduced into the aneurysm.

[0028] Once the aneurysm is sufficiently filled with the embolizing agent, the delivery agent can be removed through the lumen of the mesh structure. The flexibility of the cover or electrospun fabric helps this process, allowing the delivery agent to be removed without the embolizing agent escaping from the aneurysm.

[0029] The membrane function of the cover or fabric can be described as follows: On the one hand, the cover or fabric is so slightly porous that the embolizing agent is retained in the aneurysm when the cover device is implanted. On the other hand, the cover or fabric is so open-pored and flexible that a delivery device, such as a microcatheter, can be guided through the cover or fabric without destroying the cover or fabric or detaching it from the stent support structure or the lattice structure in general.

[0030] In electrospun fabrics, pores are typically irregularly shaped. The manufacturing process certainly doesn't allow for a patterned arrangement or design of pores. However, the pore sizes can be adjusted using the process parameters to ensure that at least some of the pores have a certain minimum size.

[0031] For example, the electrospinning process can be performed directly on the grid structure, so that a bond to the grid structure is created simultaneously during the formation of the cover. The cover can be bonded to the grid structure by a material bond. For example, the cover can be bonded to the grid structure by an adhesive bond. The adhesive bond can be created using an adhesion promoter. The adhesion promoter can, for example, comprise or consist of polyurethane.

[0032] The cover, made of electrospun fabric, is also extremely thin and flexible, which has little to no impact on the flexibility of the lattice structure. In particular, unlike previously known covers made of textile materials, the cover barely prevents the lattice structure from compressing. Overall, the entire covering device can be compressed to a significantly smaller cross-sectional diameter and thus guided into particularly small blood vessels via small catheters. This is particularly relevant for the treatment of aneurysms in cerebral blood vessels, for which the invention is particularly suitable.

[0033] The medical set according to the invention therefore also enables treatments in blood vessels that cannot be achieved with previous medical devices featuring a grid structure and a cover. Due to the high compressibility of the cover device, very low delivery forces occur during delivery through a catheter or, in general, through a delivery means. In particular, the delivery forces with the cover device can even be the same as when delivering a grid structure without a cover.

[0034] Furthermore, the covering device, which is conveniently arranged at the treatment site, i.e. at the level of the aneurysm, can prevent the coils from migrating out of the aneurysm during and after the coils have been placed, so that the risk of vascular occlusion caused by the coils can also be at least greatly reduced and preferably excluded.

[0035] The covering is porous and, in particular, permeable to blood. Porous in this context means that the covering or electrospun fabric is designed as a net. The idea behind this is that the cells located in the area of the covering can be supplied with blood and thus nutrients, thus preventing a shortage of nutrients during or after the coils are inserted.

[0036] The medical set according to the invention thus enables effective shielding of an aneurysm to retain the embolization agent, e.g., coils, inserted into the aneurysm, while simultaneously allowing nutrient supply to the aneurysm. Nutrient supply to branching blood vessels and adjacent vessel walls, which are covered by the cover, is also achieved by the medical set. The cover, which is formed from the electrospun fabric, enables coverage of an aneurysm while simultaneously allowing a certain degree of permeability to blood. This permeability is useful for supplying the cells of the aneurysm wall with nutrients. This prevents cell degeneration and a potentially resulting rupture of the aneurysm.

[0037] The advantages of the invention are not only evident in the treatment of aneurysms, but also in other vascular malformations such as fistulas, e.g. Carotid Direct Cavernous Fistula.

[0038] The invention has several other advantages.

[0039] With conventional treatment methods using devices such as flow diverters, the introduction of coils or embolic fluids can only be planned in advance. This typically involves inserting a second catheter into the aneurysm first, before placing the stent or flow diverter in front of the aneurysm neck and over the second catheter. The second catheter is located radially outside the stent or flow diverter, between the catheter wall and the vessel wall. Coils or liquid embolic fluids can then be introduced into the aneurysm through the second catheter. Once the aneurysm is sufficiently filled, the second catheter is removed.

[0040] Subsequent coiling or delivery of liquid embolic agents is no longer possible, as it is no longer possible to reach the aneurysm without the second catheter.

[0041] In contrast, the invention offers the advantage that the electrospun fabric takes on a membrane function. This allows the user greater flexibility directly during application or even months or years later: The covering device covered with the electrospun fabric, in particular the covered stent, is first placed over the aneurysm neck. Subsequently (or if necessary at a later point in time), the delivery means, in particular a microcatheter, which was already used to deliver the stent, can be used to pass through the covered fabric layer. For this purpose, for example, a guide wire, preferably in the 0.014" or 0.012" or 0.010" stiff version, is inserted into the microcatheter and previously shaped at the tip as desired (e.g. 90° bend, tight radius). Any stent cell orGenerally, a cell of the lattice structure covering the aneurysm neck is probed with the guidewire. Once the cell has been successfully probed, the microcatheter on the guidewire can be advanced through the cell into the aneurysm. The guidewire is then removed, allowing coils or liquid embolizes to be delivered through the catheter.

[0042] The tissue reacts like a membrane that wraps tightly around the guide wire or microcatheter and at the same time prevents embolization agents, such as coils or embolic material, from escaping into the bloodstream.

[0043] The introduction of the embolizing agent into the aneurysm using the set according to the invention occurs after the implantation of the covering device. The time interval is variable and can even be months or years. A second catheter placed before implanting the covering device is no longer necessary. Optionally, the microcatheter can be used directly after deployment of the stent to probe the membrane and deliver the embolic agent or, in general, the embolizing agent. The invention thus considerably facilitates the introduction of the embolizing agent into the aneurysm because the implantation of the covering device and the introduction of the embolizing agent into the aneurysm can be performed using one and the same delivery device.

[0044] According to the independent system claim 14, the combination of the set according to the invention with the feeding system is disclosed and claimed.

[0045] The covering device according to the invention according to independent claim 15 is disclosed and claimed independently of the embolization agent and the delivery means. The covering device according to the invention according to independent claim 15 is therefore limited neither to the embolization agent nor to the delivery means.

[0046] Preferred embodiments, further developments and variants are the subject of the subclaims.

[0047] Thus, the porous membrane of the cover can be adapted to at least partially regress an opening formed by the feed means when it penetrates the membrane after the feed means has been removed.

[0048] Once the aneurysm has been sufficiently filled with coils / embolic agent, the delivery device, particularly the microcatheter, can be safely withdrawn from the aneurysm. The properties of the membrane lead to an immediate closure of the opening of the lattice cell, particularly the stent cell, to prevent the coils or embolic agent from leaking into the cerebral vessel. The lattice cell does not need to be completely closed to achieve this effect.

[0049] In other words, as soon as the delivery agent has been completely removed from the aneurysm and thus pulled out of the cover or tissue, the cover or tissue at least partially closes again. The flexible opening in the cover or tissue that was widened to allow the delivery agent to pass through shrinks at least partially due to the elasticity of the tissue, so that the tissue forms an essentially closed, albeit porous, cover that securely retains the embolizing agent located in the aneurysm. The cover thus forms a porous membrane that can be pierced or penetrated by the delivery agent to introduce the embolizing agent into the aneurysm, sealing the aneurysm during introduction. After the delivery agent has been removed, the membrane closes again to retain the embolizing agent in the aneurysm. The closure does not have to be complete to retain the embolizing agent.In a further preferred embodiment, it is provided that the porous membrane of the cover is adapted to reduce the opening to at most 80%, in particular at most 60%, in particular at most 40%, in particular at most 20% of the diameter of the supply means.

[0050] The regressed opening is smaller than the outer diameter of the feed medium with which the feed medium penetrated the membrane.

[0051] Preferably, the cover is so slightly porous that it retains the applied embolization agent when implanted.

[0052] The lattice structure expediently comprises a shape memory alloy, in particular nitinol or another shape memory alloy, or is preferably formed from such a material. The lattice structure can be braided or produced by laser cutting. For cerebral applications, a braided lattice structure is preferred.

[0053] In order to achieve sufficient flexibility of the cover, it is preferably formed from irregularly arranged net-like threads which have a thread thickness between 0.1 µm and 3 µm, in particular between 0.2 µm and 2 µm, in particular between 0.5 µm and 1.5 µm, in particular between 0.8 µm and 1.2 µm.

[0054] The threads may preferably have a thread thickness of at most 2 µm, in particular at most 1.5 µm, in particular at most 1 µm, and a thread thickness of at least 0.3 µm

[0055] The cover expediently has a porosity of at most 70%, in particular at most 50%, in particular at most 40%, in particular at most 30%. This increases the stability of the cover with respect to the force exerted by the coils or, in general, the embolization agent, which, for example, presses on the cover when inserted into the aneurysm. Furthermore, the stability of the cover is advantageously optimized with regard to fracture stability.

[0056] In one embodiment, the cover has a porosity of at least 5%, in particular of at least 10%, in particular of at least 20%, in particular of at least 30%, in particular of at least 40%, and in particular of at least 45%. This embodiment is based on the idea that an existing porosity at the aforementioned percentages—as already mentioned above—ensures the supply of, for example, side vessels or vessel walls near the aneurysm during and after placement of the embolization agent.

[0057] Furthermore, due to its porosity, the cover is particularly suitable for microcatheters, as the cover is compressible and can therefore be inserted and removed through the microcatheters to the treatment site with lower friction forces. A microcatheter is defined as a catheter with an inner diameter in the range of 0.3 mm to 0.75 mm.

[0058] The above upper and lower limits can be combined to form ranges (see also claims 5 and 6), where appropriate.

[0059] According to a practical embodiment, the cover extends over the entire circumferential surface of the grid structure. This advantageously optimizes the aforementioned advantages, particularly with regard to the stability of the cover and thus of the grid structure.

[0060] According to an expedient further development, the cover extends over a part, in particular at most 70%, in particular at most 60%, in particular at most 50%, in particular at most 40%, in particular at most 30% of the circumference of the lattice structure. The cover therefore preferably extends only over the treatment site, for example over an opening in the aneurysm. This further development ensures that, on the one hand, an opening in the aneurysm is sufficiently closed to fix the coils placed therein. On the other hand, it is ensured that, in particular, cells and / or side vessels located at the level of the aneurysm can be better and continue to be supplied with blood and thus with nutrients due to the lack of cover.

[0061] According to a supplementary or alternative embodiment, the cover extends over at least 80%, in particular over at least 90%, and in particular over 100% of the length L of the lattice structure. The length L corresponds to the total length of the covering device, in particular of the implant.

[0062] This embodiment is particularly suitable for fusiform or long-necked aneurysms in which a longer section is to be covered. Fusiform aneurysms are defined as aneurysms that extend over at least 50%, in particular over at least 75%, of the entire circumference or over the entire circumference of a blood vessel.

[0063] In one embodiment, the cover extends over a maximum of 80%, in particular over a maximum of 60%, in particular over a maximum of 40% of the length of the lattice structure, wherein the cover is spaced from the distal and / or proximal end of the lattice structure. The length L corresponds to the total length of the covering device, in particular of the implant. By not completely covering the cylindrical region of the lattice structure, it is ensured that any vessels in the vicinity of the aneurysm, and especially in the vicinity of the aneurysm opening, continue to be perfused, i.e. supplied with blood. This embodiment has also proven particularly suitable for aneurysms with adjacent side branches and for smaller aneurysms.

[0064] The proximal spacing is particularly important with regard to locking on the guide wire due to the open proximal cells. If the proximal edge cells are open, i.e., unclamped, the applicant's locking system, the so-called "crown sleeve," of the transport wire, can be securely engaged. An upper limit of 80% of the clamped length is sufficient for this. Remaining 10% of the total length L with open edge cells per axial side should be sufficient.

[0065] In one embodiment, the cover has at least 10 pores with a size of at least 15 µm² over an area of 100,000 µm². During the production of the cover, the minimum pore size can be adjusted, in particular by the duration of the electrospinning process. This combination of a certain minimum number of pores and a minimum pore size has proven particularly beneficial in practice for ensuring sufficient blood permeability of the cover while simultaneously maintaining a good covering effect.

[0066] The cover is preferably made of a plastic material, in particular a polymer, and preferably polyurethane. Such materials are particularly lightweight and can be easily produced in fine threads using an electrospinning process. The plastic material therefore makes it possible, on the one hand, to produce a particularly thin and fine-pored cover. On the other hand, the plastic material is inherently highly flexible, so that a high compressibility of the medical set is achieved. Alternatively, the cover can also be made of polyethylene, fluoropolymers or, for example, thermoplastic polyurethanes based on polycarbonate. Furthermore, it can be provided, for example, alternatively or additionally, that fillers, such as anti-thrombogenic substances, are embedded in the aforementioned materials of the cover before the cover is formed with them using the electrospinning process.Alternatively or additionally, the cover is coated with such substances, for example, antithrombogenic substances. For this purpose, the surface of the cover is then provided with a nanocoating.

[0067] Preferably, the cover is formed from a plastic material, in particular a polymer, preferably polyurethane, which preferably has a Shore hardness of at least 80A, in particular at least 90A, in particular at least 55D, in particular at least 65D, in particular at least 75D. These material values have proven advantageous for the membrane function of the cover.

[0068] In a further embodiment, the cover is arranged on an outer side and / or an inner side of the grid structure. In a configuration in which the cover is arranged on the outer side of the grid structure, the grid structure forms a support structure that exerts sufficient radial force to fix the cover against a vessel wall. The grid structure thus supports the outer side of the cover.

[0069] Alternatively or additionally, the cover can be arranged on an inner side of the grid structure. In particular, it is possible for the grid structure to be embedded between two covers, each formed by an electrospun fabric. The grid elements of the grid structure can thus be completely encased by the electrospun fabric. Specifically, it can be provided that the electrospun fabric of a cover on the inner side of the grid structure extends through the cells of the grid structure and is connected to the electrospun fabric of a cover on the outer side of the grid structure. The grid elements that delimit the cells are thus encased on all sides by electrospun fabric.

[0070] According to a preferred embodiment, the grid structure is formed from webs that are integrally connected to one another, i.e., monolithically, and define closed, particularly diamond-shaped cells. Preferably, the grid structure has 3 to 9, particularly 4 to 6, cells arranged one behind the other in the circumferential direction, forming a circumferential cell ring.

[0071] The grid structure can thus generally be designed as a one-piece grid structure. In this respect, preferred embodiments provide for the grid elements to form webs that are integrally coupled to one another by web connectors (one-piece grid structure).

[0072] It is also possible for the lattice structure to be formed from interwoven wires. The wire mesh can consist of a single wire that is deflected and returned at the longitudinal ends of the mesh structure. The wire can be intertwined with itself to form the mesh structure. The mesh structure can also consist of multiple wires that are intertwined. The multiple wires can be deflected and returned at one axial longitudinal end, while the opposite axial longitudinal end can have wire ends that are open. It is also possible for the interwoven wires to have open wire ends at both axial longitudinal ends.

[0073] The grid structure can therefore comprise a mesh which is braided from at least one wire, in particular from several wires to form meshes, wherein the wire or wires are movable relative to one another at crossing points.

[0074] The embolization agent can comprise at least one deformable wire, in particular a coil, and / or an embolization fluid. Specifically, the embolization fluid is an embolization fluid that can be delivered through a microcatheter with an outer diameter of no more than 2 Fr (inner diameter of no more than 0.017" / 0.43 mm).

[0075] The wire can have an X-ray-visible core material and a sheath material made of a shape memory alloy. In particular, it is provided that the volume ratio between the core material, preferably platinum, and the volume of the entire composite wire is between 20% and 40%, in particular between 25% and 35%. While a braided lattice structure is characterized by particularly high flexibility, in particular bending flexibility, a one-piece lattice structure has a comparatively thin wall thickness, so that the lattice structure has less of an impact on blood flow within a blood vessel. The webs furthermore preferably have a thickness in the range between 30 µm and 60 µm. The cells are furthermore each delimited by a total of four webs, wherein the basic geometry of the cells is essentially diamond-shaped in the preferred design.In particular, each cell is bounded by two pairs of webs, with the webs that are substantially parallel to each other or opposite and not directly connected forming a web pair. Such a design is already described in the . Fig. 1and paragraphs

[0041] to

[0046] of the applicant's patent specification DE 10 2011 009 371 B3, to which reference is made in this regard. The webs of a first pair of webs have a smaller web width than the webs of a second pair of webs. This arrangement of the webs with different web widths increases the flexibility of the mesh structure and thus facilitates the introduction of the medical device into human vessels, particularly when these have pronounced vessel curvatures. The increased flexibility improves attachment to the vessel wall and thus prevents the formation of congestive areas that promote thrombosis. The good flexibility and the resulting good insertability in and / or through the catheter is particularly important in combination with a biological coating, preferably fibrin, preferably fibrin, preferably fibrin including heparin.

[0076] In addition to the pores formed by electrospinning, the fabric can be perforated at least in certain regions by additional pores that are formed in the electrospun fabric through processing of the fabric, in particular by laser cutting or thermal expansion using a laser. This achieves a targeted and, if desired, regional increase in porosity or enlargement of the pores after the electrospinning process. For example, laser-cut, defined pores or pores thermally enlarged with a laser beam can be formed over the entire circumference or just over a portion of it.

[0077] The fabric is preferably perforated by the additional pores over at least 25%, in particular at least 40%, and in particular at least 50% of the circumference of the lattice structure. This allows, for example, the area opposite the aneurysm neck to be perforated in a targeted manner.

[0078] The fabric can be free of further pores over at least 25%, in particular at least 40%, in particular at least 50% of the circumference of the lattice structure. In other words, a portion of the fabric is not post-treated or subsequently perforated. In this portion of the fabric, no further pores are introduced into the fabric in addition to those formed by electrospinning. In this region, the fabric consists only of the pores formed by electrospinning. The region of the fabric free of further pores can be arranged in the region of the aneurysm neck in the implanted state. This can be desired, for example, if the porosity of the electrospun fabric remains advantageous for the treatment of the aneurysm.

[0079] A combination of areas of unaltered electrospun fabric and subsequently perforated electrospun fabric is possible.

[0080] The additional pores can be formed in both axial directions, starting from the axial center of the lattice structure. In a further embodiment, additional pores can be arranged on the proximal or distal side within the covering or fabric.

[0081] The length over which the further pores can be distributed corresponds to at least 25% of the axial length of the cover or fabric, in particular at least 30%, in particular at least 40%, in particular at least 50% of the axial length of the cover or fabric.

[0082] In order to promote the flow, the size of the additional pores can be at least 50µm, in particular at least 100µm, in particular at least 200µm, in particular at least 300µm.

[0083] Regarding the geometry of the subsequently added pore enlargement, it is generally added that the shape of the additional pores can be round or oval. It is also possible that the additional pores have no recognizable shape pattern.

[0084] The distances between the additional pores can be at least 1 times the diameter of the additional pores, in particular at least 1.5 times the diameter, in particular at least 2 times the diameter, in particular at least 2.5 times the diameter. A distance of 1 times the diameter corresponds to the diameter of one additional pore.

[0085] In a particularly preferred embodiment, the peripheral contour of the cover is marked at least in sections, in particular over its entire circumference, with an X-ray-visible medium. This can be achieved, for example, by radiopaque wires woven into the grid structure along the contour of the cover. It is also possible to achieve the contour of the cover by arranging a series of radiopaque sleeves, for example, Pt-Ir sleeves or crimped C-sleeves.

[0086] The position of the covering or fabric is thus visible under X-rays so that the doctor can place the device safely - also in the correct rotational position.

[0087] The fabric itself can contain an X-ray-opaque agent. For example, the threads of the fabric can be filled with a radiopaque material, especially with a minimum of 10% up to a maximum of 25% radiopaque material, e.g., barium sulfate BaSO4. The basic color of the fabric threads can be transparent; with the addition of barium sulfate BaSO4, they can appear white / yellowish.

[0088] A secondary aspect of the invention relates to a medical system for treating aneurysms using a medical set. The set is the medical set already described above. The system further comprises a delivery means, in particular a microcatheter, with which the cover can be perforated to introduce the embolization agent.

[0089] According to the invention, the cells of the lattice structure, in the expanded state, have an inscribed circle diameter, or can be expanded to an inscribed circle diameter, that corresponds at least to the outer diameter of the delivery means. The inscribed circle diameter is the diameter of the largest possible circle that can be inscribed in the pore. In other words, the inscribed circle diameter of the pore corresponds to the outer diameter of a cylinder that can just barely be pushed through the pore. If the delivery means, in particular the catheter, is not aligned at an angle of 90° to the pore of the cover or to the cell of the lattice structure during application, an oval opening is created that occupies more surface area.

[0090] This ensures, particularly in the embodiment of the medical system explained above, that the delivery means can be easily introduced into the aneurysm through the cover or the tissue.

[0091] The embolization agent is preferably formed by a deformable wire, in particular a coil wire, in particular a coil as already mentioned above, or by a liquid, e.g., a hydrogel. Such embodiments of the embolization agent have proven particularly suitable for the treatment of aneurysms.

[0092] The advantages and preferred embodiments listed with regard to the medical kit apply analogously to the medical system, and vice versa. All dimensional specifications listed with regard to the medical kit and the medical system apply to an expanded state of the lattice structure, unless otherwise stated.

[0093] The invention is explained in more detail using exemplary embodiments with reference to the attached schematic drawings.

[0094] The Figures 1 to 8the use of a medical set according to an embodiment of the invention, wherein the embolization means is a coil. Figures 9 to 16 show a further possible use of the medical set according to an embodiment of the invention, wherein the embolization agent is an embolizate.

[0095] Specifically, the figures show: Fig. 1 shows a side view of a cover device of a medical set according to the invention according to a first embodiment in the implanted state (step 1); Fig. 2 shows a side view of the cover device according to Fig. 1 with a delivery means and a guide wire penetrating the cover of the cover device (step 2); Fig. 3 a side view of the cover device according to Fig. 1 , wherein the feeding means penetrates the cover (step 3); Fig. 4 a side view of the covering device according to Fig. 1, with the guide wire retracted (step 4); Fig. 5 a side view of the cover device according to Fig. 1 , wherein a coil wire is advanced by the feeding means (step 5); Fig. 6 a side view of the covering device according to Fig. 1 , wherein the coil wire is inserted into the aneurysm (step 6); Fig. 7 a side view of the covering device according to Fig. 1 , wherein the feed means is removed from the vessel and the remaining opening is greatly reduced after removal of the feed means (step 7); Fig. 8 a side view of the covering device according to Fig. 1in the final state, wherein the cover retains the coil wire arranged in the aneurysm and the remaining opening is greatly reduced after removal of the delivery means (step 8); Fig. 9 a side view of a cover device of a medical set according to the invention according to a second embodiment in the implanted state (step 1); Fig. 10 a side view of the cover device according to Fig. 9 with a feeding means and a guide wire penetrating the cover of the cover device (step 2); Fig. 11 a side view of the cover device according to Fig. 9 , wherein the feeding means penetrates the cover (step 3); Fig. 12 a side view of the covering device according to Fig. 9 , with the guide wire retracted (step 4); Fig. 13 a side view of the cover device according to Fig. 9 , wherein an embolization fluid is transported by the supply means (step 5); Fig. 14 a side view of the covering device according to Fig. 9 , wherein the embolization fluid is introduced into the aneurysm (step 6); Fig. 15 a side view of the covering device according to Fig. 9 , wherein the feed means is removed from the vessel and the remaining opening is greatly reduced after removal of the feed means (step 7); Fig. 16 a side view of the covering device according to Fig. 1 in the final state, wherein the cover retains the embolization fluid arranged in the aneurysm and the remaining opening is greatly reduced after removal of the delivery means (step 8); Fig. 17 shows a side view of a cover device of a medical set according to the invention according to a further embodiment in the implanted state, and Fig. 18 shows a side view of a cover device of a medical set according to the invention according to a further embodiment in the implanted state.

[0096] In the figures, parts with the same function are shown with the same reference numerals.

[0097] The Fig. 1 to 8 The schematically illustrated medical set 2 is used to treat aneurysms 4, or generally vascular malformations such as fistulas, and is in Fig. 1 shown in a state arranged within a vessel 6.

[0098] The medical set 2 comprises a covering device 12 that can be moved through a catheter (not shown) to a treatment site 10. The treatment site 10 is preferably the location along the vessel 6 where the aneurysm 4 is formed. The covering device 12 serves to permanently cover the aneurysm 4. This means that the covering device 12, once completely released from the catheter, can no longer be retracted into it but remains permanently in the vessel. Specifically, the covering device 12 is a permanent implant, in particular a stent.

[0099] Temporary draping devices, which are removed from the vessel after treatment, must be distinguished from permanent draping devices. Another distinguishing feature of permanent draping devices is the detachable connection to the transport wire, which is necessary to decouple the draping device or grid structure from the delivery system after it has been completely released from the delivery system. This is not the case with temporary draping devices, which are firmly connected to the transport wire for retraction into the delivery system.

[0100] The covering device 12 comprises a self-expanding lattice structure 14. For this purpose, the lattice structure 14 is preferably made of a shape memory material. The lattice structure 14 is tubular or hollow-cylindrical and open at the proximal longitudinal end 16 and the distal longitudinal end 18. This means that the lattice structure 14 has a flow cross-section at both longitudinal ends 16, 18 that is free of the lattice structure 14. The flow cross-section is the cross-section through which flow can pass transversely to the longitudinal axis of the lattice structure 14, which is delimited radially outwardly by the vessel or by the lattice structure 14. This distinguishes the permanently implantable covering device or the lattice structure 14 from the lattice structure 14 of a temporarily implantable covering device, in which the lattice structure protrudes into the flow cross-section in a funnel-shaped manner, at least at the proximal longitudinal end.In the permanently implantable covering device 12, however, the grid structure 14 lies against the vessel wall along its entire length and applies a radial force to it.

[0101] Furthermore, the lattice structure 14 is at least partially provided with a cover 20. The cover 20 is made of an electrospun fabric and forms a porous membrane. The electrospun fabric is adapted to impart a membrane function to the cover. The porous membrane is designed such that it can be penetrated by the delivery means for applying the embolization agent. Furthermore, the membrane is adapted to adhere to the outer periphery of the delivery means when the membrane is penetrated.

[0102] This applies to all covers 20 in this application.

[0103] There are various options for the shape of the cover 20.

[0104] The cover 20 can, for example, as shown in the Figures 1 to 16 shown, extend along a partial length of the lattice structure 14 or over a part, in particular over at most 80%, in particular over at most 60% and especially in particular over at most 40% of the total length L of the lattice structure 16. The total length L of the lattice structure is shown in the figures and extends between the outermost axial longitudinal ends along the center line of the lattice structure.

[0105] This ensures that the cover 20, in the implanted state, is located only within the region of the opening 28 of the aneurysm 4, so that cells and / or side vessels adjacent to the aneurysm 4 are not covered by the cover 20. Thus, the cells and / or side vessels can continue to be supplied with blood and thus with nutrients due to the lattice structure 14 formed with cells.

[0106] As can be clearly seen in the figures, the cover 20 is arranged substantially centrally, i.e., in the region of the axial center of the lattice structure 14. In other words, the axial longitudinal ends of the cover 20 are approximately equidistant from the proximal and distal longitudinal ends 16, 18 of the lattice structure 14.

[0107] The contour of the longitudinal ends of the cover 20, which extends in the circumferential direction of the lattice structure 14, substantially corresponds to the contour of the proximal and distal longitudinal ends 16, 18 of the lattice structure. This feature is disclosed and claimed both in connection with the specific embodiments and generally in connection with further embodiments not shown here.

[0108] In the case of the covers 20 shown in the figures, this extends over the entire circumference of the grid structure 14. It is also possible, as for example in the Figures 17, 18shown that the cover 20 covers only a partial segment of the lattice structure 14 in the circumferential direction, i.e. an angular segment.

[0109] The cover 20 serves, in particular when placing an embolizing agent 40 within the aneurysm 4, to ensure that the embolizing agent 40 cannot escape from the aneurysm 4 after placement until the blood within the aneurysm 4 has clotted due to the embolizing agent 40 and the aneurysm 4 is thus reliably closed.

[0110] Based on the Figures 1 to 8 It is explained how the corresponding embodiment of the medical kit comprising the covering device 12 and the embolization agent 40 is used to treat an aneurysm. The treatment of other vascular malformations is possible accordingly.

[0111] In Fig. 1The cover device 12 is shown, for example, in the form of a stent in a permanently implanted state, i.e., after complete release from the delivery system (step 1). The cover device 12 is arranged with the cover 20 over the aneurysm opening 28. The cover 20 covers the aneurysm opening 28. The X-ray markers 56 at the two axial longitudinal ends 16, 18 mark the position of the cover device 12.

[0112] As in Fig. 2 As can be seen, in step 2, a delivery means 44 in the form of a microcatheter is introduced through the lumen of the covering device 12. For this purpose, a guide wire 22 is also arranged in the lumen of the covering device 12 in a manner known per se, through which the delivery means 44 is guided to the treatment site. The guide wire 22 penetrates the covering 20 in the region of the aneurysm opening 28, as in Fig. 2clearly visible. This is where the membrane function of the cover 20 comes into play. Due to the pores formed by the electrospun fabric, this enables the perforation or expansion or widening of the pores of the cover by the guide wire 22. The guide wire 22 penetrates the material of the cover 20, whereby the corresponding pore or pores penetrated by the guide wire 22 are widened. This forms the opening 24 through which the guide wire 22 is pushed into the interior of the aneurysm 4.

[0113] In Fig. 3It is shown that the delivery means 44 is pushed further forward into the aneurysm 4 via the guide wire 22. In this state, the delivery means 44, specifically the distal free end of the delivery means 44, projects into the aneurysm 4. In doing so, the delivery means 44 penetrates the cover 20 in the region of the opening 24 already formed by the guide wire 22. The opening 24 is further widened by the delivery means 44 to the outer diameter of the delivery means 44. The widened opening 24 fits closely against the outer contour of the delivery means 44 and thus seals the aneurysm 4 against the lumen of the cover device 12.

[0114] This is made possible by the membrane-like design of the cover 20, specifically by the electrospun fabric, which has such elasticity that the material around the penetrated pore(s) or the opening 24 is sufficiently elastically deformed.

[0115] According to Fig. 4 In step 4, the guide wire is withdrawn from the delivery means 44 so that the delivery means 44 is placed with the free end in the aneurysm 4 and has a free lumen for the application of the embolization agent 40.

[0116] In Fig. 5 It is shown that in step 5 the embolization agent 40, specifically a coil wire 42, is supplied to the aneurysm through the supply means 44 and the opening 24 in the cover 20.

[0117] In step 6, as in Fig. 5 As shown, the aneurysm 4 is filled with the embolizing agent 40 or the coil wire 42. Even in this state, the cover 20 retains the embolizing agent 40 in the aneurysm. Furthermore, the cover 20 seals the aneurysm 4 against the lumen of the cover device 12 in the region of the opening 24, since the opening 24 fits tightly against the outer diameter of the delivery means 44. This prevents the embolizing agent 40 from escaping during application.

[0118] After the aneurysm is sufficiently filled with the embolizing agent 40, the delivery agent 44 is removed from the lumen of the cover device 12, as shown in Fig. 7 shown (step 7). In Fig. 7It is clearly visible that the opening 24 is shrinking. The shrunken opening 24 has a smaller diameter than the outer diameter of the delivery means 44. As a result, the embolization agent 40 is securely retained in the aneurysm 4. It is not absolutely necessary for the opening 24 to shrink completely and return to its original pore size. It is sufficient if the opening 24 shrinks to such an extent that no embolization agent 40 can enter the lumen of the covering device 12 through the shrunken opening 24. The coils / hydrogels delivered through the delivery means, or generally the delivered embolization agent, correspond or approximately correspond to the inner diameter of the delivery means. If the opening becomes smaller after the delivery means is removed, the embolization agent, i.e. neither the coil nor the hydrogel, can escape through the opening.

[0119] Fig. 8shows the final state after the delivery means 22 has been completely removed and the covering device 12 retains the embolization agent 40 in the aneurysm 4.

[0120] It is possible to perform steps 1 to 8 in the same operation, ie in immediate succession and contiguously. It is also possible to initially only remove the covering device, as in Fig. 1 shown, without first performing steps 2 to 8. If it turns out that the treatment is not yet sufficiently successful, the aneurysm can be treated subsequently with an embolization agent 40 without any problems. This means that steps 2 to 8 are carried out in a second, later operation. The medical set comprising the covering device and the embolization agent thus enables a flexible and targeted treatment method for aneurysms.

[0121] Another example is shown in the Figures 9 to 16 This embodiment differs from the embodiment according to the Figures 1 to 8 in that instead of the coil wire 42, another embolization agent 40 is used, namely an embolization fluid 46. The application of the embolization fluid 46 is carried out in the same way as the application of the coil wire 42. In this respect, reference is made to the explanations of the Figures 1 to 8 referred to.

[0122] In this embodiment, the opening 24 can be reset so that after removal of the delivery means 44, a sufficiently small opening remains in the cover 20 through which the embolization fluid 46 cannot escape. Here, too, the opening 24 does not have to close completely to achieve the intended purpose.

[0123] Fig. 17shows the lattice structure 14 of an embodiment according to the invention in the implanted state, wherein the cover 20 is arranged on the lattice structure 14 in the region of the aneurysm neck and covers it. The cover 20 is arranged on a partial circumference or on an angular segment of the lattice structure 14. In the example, the fabric or the cover 20 covers approximately half the circumference of the lattice structure 14 or the stent. A different degree of covering, i.e. more or less than half the circumference of the lattice structure 14, is possible.

[0124] This further optimizes the supply of cells and / or lateral vessels adjacent to the aneurysm 4, since this preferably only covers the opening 28 of the aneurysm 4, and cells and / or lateral vessels located at the same level as the aneurysm 4 can continue to be supplied with blood and nutrients. Thus, for example, a lateral vessel located opposite the aneurysm 4 can be supplied with blood.

[0125] As in Fig. 17 to see are - in contrast to Fig. 18 - no additional pores are provided in the fabric other than those formed by electrospinning. The properties of the fabric are therefore determined solely by the pores formed during the electrospinning manufacturing process.

[0126] Fig. 18 shows a further embodiment of the invention, in which the grid structure 14, as in Fig. 17, is implanted to treat an aneurysm. In contrast to Fig. 17 The covering 20, in particular the fabric, is applied over its entire circumference to the lattice structure 14 by electrospinning. A portion of the covering 20, specifically the portion of the covering 20 opposite the aneurysm neck, is perforated in addition to the pores 52 formed during electrospinning. This is achieved by post-treating the fabric, for example, by laser cutting or thermal expansion using a laser. The additional pores 54 thus formed in the fabric are larger than the pores 52 formed by electrospinning, as shown in Fig. 18 In the example according to Fig. 18Four additional pores 54 are formed per cell. The number of additional pores 54 can vary. Unlike the pores 52 formed by electrospinning, the additional pores 54 are geometrically defined, for example, round. This is made possible by laser cutting, thermal expansion, or thermal melting using a laser.

[0127] The additional perforation of the tissue allows for a targeted influence on the permeability of the tissue, for example to improve the blood supply in side branches without compromising the treatment of the aneurysm.

[0128] As in Figs. 17, 18As can be clearly seen, X-ray markers 56 are provided in the medical set 2 and especially in the grid structure 14. The X-ray markers 56 are arranged at the cell tips of the edge-side cells of the grid structure 14. Specifically, the X-ray markers 56 can be formed as X-ray-visible sleeves, for example made of platinum or gold, which are crimped onto the cell tips of the edge-side cells. Figs. 17, 18 that three X-ray markers 56 are arranged at each longitudinal end of the lattice structure 10.

[0129] The covering devices 14 according to Fig. 17 and Fig. 18 are combined with an embolization agent 40 to form a medical set. The set can in turn be combined with a delivery agent 44 to form a system.

[0130] The aforementioned embodiments, in particular with regard to an extension of the cover 20 along a length L of the grid structure 14 and with regard to an extension of the cover 20 along a circumference of the grid structure 14, can be designed and combined in any desired combination. For example, a configuration is also possible in which the cover 20 extends over the entire length L of the grid structure, but also extends only over part of the circumference of the grid structure 14. List of reference symbols

[0131] 2Medical set 4Aneurysm 6Vessel 8Free 10Treatment site 12Cover device 14Grid structure 16Proximal longitudinal end 18Distal longitudinal end 20Cover 22Guide wire 24Opening 26Free 27Circumferential surface 28Aneurysm opening 30Free 32Free 34Struts 36Cell 40Embolization agent 42Coil wire 44Delivery agent 46Embolization fluid 48Free 50Free 52Pore 54Other pores 56X-ray marker LLength

Claims

1. A medical kit for the treatment of vascular malformations, in particular aneurysms and / or fistulas, with: - a permanently implantable covering device (12), in particular a stent, for covering the vascular malformation, wherein the covering device (12) has a tubular, self-expandable mesh structure (14) and a covering (20) formed from an electrospun fabric, wherein the covering (20) is connected to the mesh structure (14) and at least partially covers the mesh structure (14) in order to be placed over the vascular malformation in the implanted state, and - an embolization means (40) which, in the implanted state, is appliable by a delivery means (44) for the treatment of the vascular malformation, wherein the covering (20) forms a porous membrane, characterized in that the mesh structure (14) has cells (36) or meshes which, in the expanded state, have an inscribed diameter (D) or are expandable to an inscribed diameter (D) which corresponds to at least the external diameter (A) of the delivery means, and the covering (20) is penetrable by the delivery means (44) for the application of the embolization means (40) and is adapted to lie against the outer circumference of the delivery means (44) in the penetrated state, wherein the porous membrane is adapted to at least partially contract an opening (24) formed by the delivery means when the membrane is penetrated after the removal of the delivery means, and wherein the delivery means has a distal external diameter of at most 0.7 mm.

2. The medical kit as claimed in claim 1, characterized in that the porous membrane of the covering (20) is adapted to contract the opening (24) by at most 80%, in particular at most 60%, in particular at most 40%, in particular at most 20% of the diameter of the delivery means.

3. The medical kit as claimed in any of the preceding claims, characterized in that the covering (20) is slightly porous, in a manner such that in the implanted state, it retains the applied embolization means, and / or in that the covering (20) has a porosity of at most 70%, in particular at most 50%, in particular at most 40%, in particular at most 30%, and / or in that the covering (20) has a porosity of at least 5%, in particular at least 10%, in particular at least 20%, in particular at least 25%, in particular at least 30%, in particular at least 40%, in particular at least 45%.

4. The medical kit as claimed in any of the preceding claims, characterized in that the covering (20) extends over the entire circumference of the mesh structure (14), or in that the covering (20) extends over a portion, in particular at most 70%, in particular at most 60%, in particular at most 50%, in particular at most 40%, in particular at most 30%, of a circumference of the mesh structure (14).

5. The medical kit as claimed in any of the preceding claims, characterized in that the covering (20) extends over at most 80%, in particular over at most 60%, in particular over at most 40% of the length (L) of the mesh structure (14), wherein the covering (20) is at a distance from the distal end (18) and / or from the proximal end of the mesh structure (14).

6. The medical kit as claimed in any of the preceding claims, characterized in that the covering (20) has at least 10 pores (52) with a size of at least 15 µm2 over an area of 100000 µm2, and / or in that the electrospun fabric of the covering (20) has filaments with a filament thickness of at most 2 µm, in particular at most 1.5 µm, in particular at most 1 µm, and with a filament thickness of at least 0.3 µm, and / or in that the covering (20) is formed by a plastic material, in particular a polymer, preferably polyurethane, which preferably has a Shore hardness of at least 80A, in particular at least 90A, in particular at least 55D, in particular at least 65D, in particular at least 75D.

7. The medical kit as claimed in any of the preceding claims, characterized in that the covering (20) is disposed on an outside and / or on an inside of the mesh structure (14), and / or in that the embolization means (40) comprises at least one deformable wire (42), in particular a coil, and / or a liquid embolic.

8. The medical kit as claimed in any of the preceding claims, characterized in that the mesh structure (14) is formed from struts (34) which are connected together in one piece and delimit closed, in particular diamond-shaped cells (36), or in that the mesh structure (14) comprises a braid which is braided from at least one wire, in particular from a plurality of wires with the formation of meshes, wherein the wire or the wires are movable relative to each other at points of intersection.

9. The medical kit as claimed in any of the preceding claims, characterized in that in addition to the pores (52) formed by electrospinning, the fabric is perforated, at least in regions, by further pores (54) which are formed in the electrospun fabric by processing the fabric, in particular by laser cutting or thermal widening by means of a laser, in particular wherein the fabric is perforated by the further pores over at least 25%, in particular over at least 40%, in particular over at least 50% of the circumference of the mesh structure (10).

10. The medical kit as claimed in claim 16 or claim 17, characterized in that the fabric is free from further pores over at least 25%, in particular over at least 40%, in particular over at least 50% of the circumference of the mesh structure (10) and / or in that the further pores are formed in both axial directions outwards from the axial centre of the mesh structure (10).

11. The medical kit as claimed in any of claims 16 to 19, characterized in that the size of the further pores is at least 50 µm, in particular at least 100 µm, in particular at least 200 µm, in particular at least 300 µm.

12. The medical kit as claimed in any of claims 16 to 19, characterized in that the distances between the further pores in relation to the diameter of the further pores are at least 1 time the distance, in particular at least 1.5 times the distance, in particular at least 2 times the distance, in particular at least 2.5 times the distance.

13. The medical kit as claimed in any of the preceding claims, characterized in that the circumferential contour of the covering (20) is marked by a radiopaque means, at least in sections, in particular entirely circumferentially, and / or in that the fabric per se has a radiopaque means.

14. A medical system for the treatment of vascular malformations with a medical set as claimed in any of the preceding claims, and a delivery means, with which the covering (20) is penetrable in order to introduce the embolization means.

15. A permanently implantable covering device (12), in particular a stent, for the treatment of vascular malformations, in particular aneurysms and / or fistulas, in particular in order to cover the vascular malformation, wherein the covering device (12) has a tubular, self-expandable mesh structure (14) and a covering (20) formed from an electrospun fabric, wherein the covering (20) is connected to the mesh structure (14) and at least partially covers the mesh structure (14) in order to be placed over the vascular malformation in the implanted state, wherein the covering (20) forms a porous membrane which is penetrable by a delivery means (44) for the application of an embolization means (40) and is adapted to lie against the outer circumference of the delivery means (44) in the penetrated state, wherein the porous membrane of the covering (20) is adapted so as to contract an opening (24) formed by the delivery means upon penetration of the membrane by at most 80%, in particular at most 60%, in particular at most 40%, in particular at most 20% of the diameter of the delivery means after removal of the delivery means, and wherein the covering (20) comprises at least 10 pores (52) which have a size of at least 15 µm2 over an area of 100000 µm2.