Implant to influence blood flow

Abstract

Implant for blood vessels, for influencing blood flow in the area of ​​aneurysms (A), wherein the implant (1) has a wall formed by isolated filaments (2, 2') that are joined to form a round braid, wherein the round braid is an endless braid cut to size, adopts an elongated shape with a reduced diameter in an implantation catheter (11) and expands at the implantation point, adapting to the diameter of the vessel and increasing the surface coverage, wherein the filaments (2, 2') of the round braid have shape memory characteristics, characterized in that the round braid is adjusted such that, when the stretching forces that bring the round braid to the elongated shape disappear, it extends to such an extent that, in the area of ​​an aneurysm neck where the vessel has a larger vessel diameter compared to the adjacent healthy vessel section,It adopts a greater surface coverage compared to the adjacent healthy vessel section.

Description

Implant to influence blood flow The invention relates to a blood vessel implant, which has a wall formed by individual filaments assembled into a round braid. The implant is intended in particular to influence blood flow in the area of ​​arteriovenous malformations, such as fistulas and aneurysms. In addition, it can also be used for the treatment of ischemic stroke, for example, to restore, increase, or maintain blood flow. The implant may be designed to be retrievable. Arteriovenous malformations can lead to considerable limitations and risks, even death, in a patient. This is particularly true for arteriovenous fistulas and aneurysms when they occur in the brain. Such malformations are typically closed with implants. These implants are usually placed endovascularly, using catheters. In the case of aneurysms, the effectiveness of implanting platinum coils has been demonstrated. These coils fill the aneurysm almost completely, largely blocking blood flow and leading to the formation of a local thrombus, which fills the aneurysm and ultimately closes it. This treatment method, however, is only appropriate for aneurysms with relatively narrow access to the vascular system, known as berry aneurysms. In detached blood vessels with a secondary access point, the implanted coils again run the risk of being dislodged and causing damage to other areas of the vascular system. In these cases, it has been proposed to place a type of stent that "nets" the aneurysm opening and thus prevents the occluding coils from being expelled. Stents of this type, which have a relatively wide mesh wall, also have a number of drawbacks. On the one hand, there is the wide mesh structure, which allows unrestricted blood flow into the aneurysm. However, if the aneurysm is not sufficiently filled with the occluding material, pressure continues to act on the vessel wall without impediment. Subsequent treatment is difficult in these circumstances, as the stent limits access to the aneurysm and prevents the introduction of additional occluding materials. Another drawback is the stent's lack of adaptability to its application site. For optimal function, the stent should fit tightly against the vessel wall without exerting excessive pressure. Unlike stents designed to widen the vessel in cases of stenosis, these stents should be understood more as a kind of cuff, intended to have minimal impact on the vessel lumen and endothelial wall. Consequently, even if specifically selected for this application, these stents are only partially adaptable to the requirements. Wire-braided stents have been known for some time, particularly for use in the coronary arteries. These stents are typically manufactured as a round braid, where the individual wire strands form the stent wall in antagonistic positions in a spiral or helical pattern. This creates a mesh braid that, in the radial direction, is both supportive and permeable to blood. One problem with these stents configured as round braiding is the loose ends at the free ends which, due to their reduced diameter, can have a traumatic effect. According to US-A-4 655 771 (Wallsten), a stent of this type, configured as a round braid, is formed atraumatically at its terminals by means of U-shaped connecting elements between the loose ends. However, these U-shaped connecting elements lead to stresses that cause deformation of the stent. According to US patent 5061275 (Wallsten et al.), the loose ends of such wire stents are fused into a round shape by laser treatment to prevent traumatization. The stent described therein also consists of a round braid, in which the insulated wires in the node area have embossings to allow for tension-free fixation within the wall. US patent 2002 / 165601 shows a self-expanding braided stent. Stents of this type, configured as a round braid composed of filaments, are hydraulically expanded at the point of application with the aid of a balloon when used to treat stenosis, and are then fixed to the vessel wall. During insertion, the balloon, attached to a guide wire, acts as a delivery vehicle, onto which the stent is crimped. However, such a delivery vehicle should not be used for implants intended to influence or channel blood flow in the brain; rather, an implant that independently adjusts to the vessel diameter and is positioned within the vessel wall would be advantageous. Another problem with stents or implants made of braided wire lies in their manufacturing. Manufacturing them as a flexible, endlessly braided tube, which is cut to the desired length, is advantageous. However, this results in loose wire ends at both ends of the cut tube, which must be deactivated in a complex manner, for example, using the connecting elements mentioned earlier. Accordingly, the task has been set to provide an implant capable of influencing blood flow within a vessel, thereby isolating aneurysms from the bloodstream as much as possible. To this end, if the implant diameter is optimally selected in relation to the vessel diameter, the implant should be able to adapt to the vessel's diameter. In areas of enlargement and de-excision, it should at most adopt its nominal diameter. Furthermore, the invention is based on providing an implant that can be positioned atraumatically, i.e., without the aid of a balloon. Such a positioning device must reliably secure the implant until its final release from the catheter and, in particular, allow for the implant to be retracted into the catheter, provided that complete release has not yet occurred. This task is solved with an implant according to claim 1. The material used for the implant according to the invention is one that has shape memory characteristics, such as nitinol. In the following description, the terms proximal end and distal end of the round braid refer to the respective end facing toward or away from the physician performing the treatment. Correspondingly, proximal and distal can be understood as facing toward or away from the guide wire of the positioning system. The implants according to the invention are described below based on a round braid to isolate an aneurysm. In the case of the implants according to the invention, they are not stents in the strict sense, as they do not provide any support. They are not used to stabilize the vessel wall but rather to channel blood flow in the area of ​​the aneurysm. For example, they must also prevent occlusive devices placed within an aneurysm from being dislodged into the vessel. They are a type of lining, inner sleeve, or flow diverter. The implants according to the invention are manufactured as a round braid from a plurality of filaments, wherein the round braid essentially forms an endless flexible tube. The required implant length can then be cut to size from this endless flexible tube. For this purpose, the individual filaments are wound in a spiral or helix shape, where the individual filaments are inserted like a mesh, i.e., crossing each other and one another. The individual filament strands are wound in this respect, normally, in two directions that intersect at a constant angle, which is cut, for example, at an angle of 90°. According to the invention, angles greater than 90° are preferred in the normal, tension-free state, particularly from 90° to 160°, where we refer to the angles open towards the ends of the implant.An inclined winding of individual filaments of this type, if sufficiently dense, can lead to a round braid with a high surface density. Under axial extension, this braid can be stretched to form considerably smaller diameters. In the absence of stretching forces and with sufficient recovery force of the filament material, the round braid returns to approximately the nominal diameter, i.e., the original stress-free state. This results in a close fit of the vessel wall to the point of insertion and a compaction of the mesh structure against the wall. This is particularly applicable in vessel expansion zones. In particular, in a round braid of this type according to the invention, the filament ends protruding from the implant's ends are joined together in at least pairs and permanently bonded. This can be done, for example, by welding, but also by mechanical crimping and gluing. Furthermore, the joined filament ends are shaped atraumatically. Normally, implants according to the invention are not enlarged and are positioned hydraulically with the aid of a balloon. It is also necessary to connect the implants with a guide wire so that they can be reliably guided. This is achieved according to the invention by means of connecting elements, which work in conjunction with a guide wire clamping element required for positioning. The ends of the round braided filament joined together are provided as such connecting elements. The branching of the vessel (bifurcations) can be taken into account, for example, in implants according to the invention, by means of areas of lower mesh density. Round braiding can, in principle, be woven in any way, but it is particularly common with multiple braids. A two-braid configuration is especially preferred. A tight weave, particularly in the case of a dense mesh, leads to a high load on the individual elements. In this respect, the multi-braid configuration is appropriate for relieving tension in the mesh, whereas excessive weaving leads to poor bonding in round braiding. The filaments can also be folded multiple times. It is especially preferred that they be folded two or three times, where two or three filaments run parallel. Because the filaments are fed from bobbins for the production of the round braid, this means that two or three filaments are fed simultaneously from the corresponding bobbin to the mandrel on which the round braid is made. According to the invention, the filament ends are joined together, particularly in pairs, where in the case of multiple filaments, "pairs" means that two bundles formed by several filaments are respectively joined together. This bundle formation can be compact, such that all the wires are gathered into an essentially round bundle and the front ends of all the wires are fused together, resulting in a single dome. In this way, a bond is established between the wires by adding material, and the end of the bundle is made available in a non-traumatic manner. Alternatively, the wires can be guided in parallel and fused together as subdivisions on the front sides. The advantage of this embodiment is the relatively small diameter in the connection zone, compared to the concentration of filaments in bundles. Finally, as an additional option, individual strand staggering is possible; that is, the wires are cut to length in a staggered fashion. Each wire is joined to the adjacent wire via its front surface. The longest wire can then act as the connector. Staggering can be achieved with either compartmentalized or compact wire routing. In any case, the filament ends joined together are configured as joining elements to form a clamping element. As described above, in the case of the tension-free arrangement of individual filaments in the round braid, the aim is to create the densest possible implant surface. Because the braid's flexibility must be maintained, 100% surface coverage by the filaments is practically impossible. Surface coverage in the range of 30% to 80% is preferred, ideally 40% to 70%. To improve surface coverage, the round braid can be coated with a film, for example, made of Teflon, silicone, or another body-compatible synthetic material. To increase flexibility and extensibility, such a synthetic film can be grooved, with the grooves staggered and running longitudinally along the implant's perimeter. This film can be produced, for example, by immersing the implant in a suitable liquid film material (dispersion or solution) and then creating the grooves, for example, using a laser. Immersion can also be used to achieve, for example, complete or partial filling of the mesh. Alternatively, the individual filaments of the implant can be coated with such a synthetic material by immersing them in a dispersion or solution of the synthetic material, thereby increasing the filament's cross-section. In this case, the open meshes remain, but the mesh size is significantly reduced. The implant according to the invention is manufactured from a material with shape memory characteristics. Nitinol is a particular example. The implant can be coated in a known manner, both on and off the implant itself. Coating materials, in particular, include those described for stents, for example, those with antiproliferative, anti-inflammatory, antithrombogenic, growth-promoting, and / or anti-encrustation properties. A coating that promotes implant growth and neointimal formation is preferred. It may be advantageous to coat the implant externally in this way and internally with a medium that reduces adhesion, such as heparin or a derivative thereof, ASS, or suitable oligosaccharides and chitin derivatives. Nanoparticle layers, such as ultrathin layers of the polymer SiU2, which reduce adhesion, are also appropriate. The positioning of implants according to the invention is carried out in practice under X-ray guidance. For this reason, the implant should have an X-ray-proof marking material, unless it is itself made of an X-ray-proof material. Such X-ray-proof materials include, in particular, tantalum, gold, tungsten, and platinum metals, such as Pt-Ir alloys, with the latter being preferable. These markers can be attached, for example, as marking elements, in a known manner, to the ends of the filaments, but they can also be woven as marking filaments into the implant's braided structure. It is also possible to coat the individual filaments with a helix formed from platinum wire or platinum alloy wire. According to the invention, the filament ends joined together are configured as connecting elements. This can be achieved, for example, by providing these connecting elements with spherical end caps of a defined diameter, which can be manufactured by laser melting. Alternatively, connectors can be laser welded together by adding material. Mechanical joining through crimping and similar methods is also possible. A connector of this type can be configured in such a way, for example, that a spherical connector is soldered to the ends of the filament that are joined and soldered together, for example through a joining wire. It is also possible to configure the connecting elements in a non-spherical shape, for example, as anchors, rectangles, or other molded parts. In all cases, the connecting elements operate on a lock-and-key principle; that is, they work in conjunction with a fastening element that has corresponding peripheral notches or recesses. Whenever the fastening element with the integrated implant is guided into a stretched catheter with a reduced diameter, the two are held in close contact by the catheter wall. After the fastening element is withdrawn from the catheter, the implant expands to its final diameter and is thus released from the fastening element's recesses. The implant can also be secured in the notches or housings of the fixation element using a separate flexible tube, which is pulled in a geometric connection through the fixation element with integrated connectors or fasteners. Once the implant is in its final position, the flexible tube is retracted, freeing the implant. The fixation element with guide wire, the flexible tube, and the catheter can then be retracted. Accordingly, the invention also relates to the combination of an implant of the class designated above and a guide wire, to which the implant is coupled via the fastening element. As previously mentioned, the combination of the fixation element and the implant is guided by an endovascular catheter. For this purpose, the fixation element is disc-shaped and equipped with notches around its periphery to accommodate the connecting elements. The diameter of the fixation element is designed so that it can be guided directly by a standard catheter, while the connecting elements are held by the inner wall of the catheter within these notches. A spherical configuration of the connecting elements is advantageous in this respect, as it minimizes the contact surface with the inner wall of a standard catheter, thus reducing friction and resistance to guidance. According to a preferred embodiment, the fixation element comprises two spaced fixing elements that securely hold the implant between them. In this case, the two fixing elements have corresponding housings for the implant's connecting elements, and the implant has corresponding connecting elements at both its proximal and distal ends. A fixation device configured accordingly with two fixing elements can have both fixing elements positioned at a defined distance on a single guide wire, thus subjecting the implant, with a predetermined length, to a defined stretch and tension. This ensures that extensive extension does not occur and that the restoring forces, after release into the vessel, can fully act. Alternatively, the fixing elements can be fixed to two separate guide wires, allowing the treating physician to adjust or stretch the implant, either by themselves or via a corresponding immobilization device. The second guide wire can also be configured as a guide tube. The invention is explained in more detail by the following illustrations. They show: Figure 1 shows a normal example of a round braid, as used according to the invention; Figure 2 shows filaments folded once and twice; Figure 3 shows a braid interwoven once and twice; Figure 4a shows the method of joining the ends of the filaments of a braid according to the invention; Figure 4b shows a second variant for joining two filament ends; Figure 5a shows a compact, concentrated assembly of filament ends; Figure 5b shows a compartmentalized assembly of filament ends; Figure 5c shows a staggered assembly of filament ends; Figure 6 shows the connection between the guide wire and the round braid through a clamping element; Figure 7 shows an embodiment with two fastening elements; Figure 8 shows another variant of fixing an implant to a fastening element using a flexible tube; Figure 9 is a diagram that reproduces the relationship between surface density and length variation of an implant according to the invention; and Figure 10 The arrangement of an implant according to the invention in the neck area of ​​an aneurysm. Figure 1 shows the braiding structure of an implant 1 according to the invention, which consists of individual filaments braided together. In the example shown, the individual filaments cross at an angle of approximately 120°, with the open side of the angle facing the open ends of the round braid. The braid is depicted in a slightly stretched / elongated state, i.e., with a reduced diameter. The angle theta designates the twist angle with respect to the longitudinal axis, which can be up to 80° in the slack state with the nominal diameter. During elongation of the twist in the catheter, the angle theta can be reduced to almost 7°. It is understood that the nominal diameter of the round braid is adjusted to the lumen of the target vessel at the point to be treated. The braiding is done on a conventional braiding machine and is presented as an endless braid. It is braided on a mandrel, whose outer dimensions correspond to the inner diameter of the final products. The braiding machine and its equipment determine the braiding structure, for example, the number of strands, the strand path, and the number of crossing points on the perimeter and for each lay. The number of strands depends on the number of bobbins, with each bobbin running halfway around the core of the braid in both directions. The filaments are normally made of metal, for example, nitinol. Synthetic materials with the necessary flexibility can also be used. The ideal filament thickness is 0.01 to 0.2 mm, particularly 0.02 to 0.1 mm. For high wall surface coverage, a flat strip material, for example, 0.05 to 0.5 m wide, preferably up to 0.1 mm, with the thicknesses specified above, can be used instead of wire. The round braid according to the invention can be produced from individual filaments (fold 1) or also from two (fold 2) or more filaments. Figure 2 shows nodal points 3, where two parallel guided filaments cross (fold 2) or only individual filaments 2 (fold 1). If two or more filaments are joined, they are fed through one and the same coil. Figure 3 shows a template for structures interwoven 1 and 2 times from filaments 2 of fold 2. In the structure with interweaving 1, the filament pairs are positioned alternately over and under each other. In the structure with interweaving 2, the filament pairs, as depicted, are guided respectively through two opposing filament pairs before being guided through and under two opposing filament pairs. A two-part fold, or one with even more parts, results in a higher surface density of the round braid, while simultaneously reducing its longitudinal extension during compression. This increased surface density, however, comes at the expense of flexibility, also due to increased friction and tension. This can be countered by increasing the interweaving; that is, a structure with two or more interweavings provides increased flexibility. According to the invention, a two-part interweaving and a two-part fold are preferred. After being divided into product-specific units, the braid must be closed at the ends. This is necessary to ensure the stability of the braid's shape and to prevent damage to the vessel. This also requires the placement of the structure at the ends of the round braid. Figure 4a shows the joining of two filaments 2, 2' at the end of the round braid to form a pair of filaments 4, where 1 and 2' are filaments running in opposite directions. The filaments are curved axially for this purpose and welded together distally. In this respect, the filaments located one above the other at the edge nodes are joined together. The nodal points are located, for example, at the points where the horizontally drawn auxiliary lines intersect the perpendicular nodal plane AA. Figure 4b shows another variant of joining two filaments 2 and 2' to form a pair of filaments 4, which is joined to filaments 2, 2' via two arms 2" and 2'' and solder points 8. The two arms of the joining piece 4 are joined at a solder point 8'. The pair of filaments 4 can be prefabricated and allows for a uniform termination that does not disturb the path of filaments 2, 2'. Figure 5a shows variations for closing the braid, as generally described in Figure 4. According to Figure 5a, a bundle of four filaments 2 is welded together end-to-end, for example, by laser welding. This results in a permanent bond between the individual filaments, preventing the round braid from unraveling and, at the same time, producing a non-traumatic shaping of the filament tips, which could otherwise cause injury. According to a preferred embodiment, the welding points 5 can be switched to a sphere or a molded body, which can be used as joining elements. Figure 5b shows a subdivision-shaped guidance of a filament bundle 4, in which the individual filaments are joined together distally through a common solder point 5. Finally, Figure 5c shows a staggered exit of the individual filaments of the filament bundle 4 with individual solder points 5, which establish the joint between each other. In this variant, the wires are cut to size in a staggered fashion. The longest wire can serve as the connector and accommodate, for example, a molded element at its tip. All the shorter wires are joined by adding material, with their front surface touching the adjacent wire. In this embodiment, the smaller diameter of the connection area is of particular interest. In a braided structure with 2 interweavings of the fold 2, with a total of 16 double threads, this leads to a total of eight welded joints of the type shown in Figure 5 (others are conceivable), which can be used as eight joining elements for connecting the implant according to the invention to a fastening element. Figure 6 shows a combination according to the invention consisting of an implant 1, which is attached to a guide wire 10 via a clamping element 12 and guided within a catheter 11. The implant 1 is attached proximally to the clamping element 12 via filament bundles 7, which are welded together at their ends and shaped to form connectors 6. The clamping element 12 has notches around its periphery in which the connectors 6, which have a spherical head, are integrated. The clamping element 12, which has a disc-shaped cross-section, is adapted to the inner diameter of the catheter 11, such that the connectors 6 arranged in the notches 13 are prevented from dislodging from the notches by the inner wall of the catheter. If the implant 1 is guided out of the end of the catheter 11 using the guide wire 10, it expands under distension and increases in diameter. In this process, the connectors 6 dislodge from the notches 13, freeing the implant, and allowing the guide wire and the securing element 12 to retract. During expansion, the implant 1 comes into close contact with the vessel wall and can thus shield an arteriovenous malformation such as an aneurysm. Figure 7 shows another variant of the combination shown in Figure 6 between guide wire, clamping element and implant in a catheter 11. According to this variant, it is possible to tension the implant between a proximal clamping element 12 and a distal clamping element 12' on the peripheral notches, in which the bundles of filaments 7 are integrated, joined by welding at the ends through the connectors 6. The braid 1 located in the middle can undergo greater or lesser elongation, depending on the separation of the clamping elements 12, 12', which can be used to facilitate transport through the catheter. To achieve relative movement, two self-contained guidance systems are required. This can be accomplished, for example, using two separate guide wires. Another option is to connect the proximal clamping element 12 to a flexible tube and the distal clamping element 12' to a guide wire 10 running within that tube. To ensure the system's flexibility, the tube 14 and the guide wire 10 can be made of nitinol. Before the implant is released, the system must be positioned distally. After distal release, the guide wire 10 with the distal clamping element 1' can first be retracted into the catheter 11. Then, the implant 1 can also be released proximally by retracting the catheter 11, and the proximal clamping element 12 can be retracted along with the tube 14. The release system according to Figure 8a shows another variant of a combination according to the invention, comprising an implant 1, which is attached to a guide wire 10 via a clamping element 12 and is guided in a catheter not shown herein. The implant 1 is attached proximally to the clamping element 12 via connectors 6 welded at their ends, such that the connector spheres 6 are integrated into notches 13 of the clamping element 12. A flexible tube 15, which is pulled over the clamping element 12 and in which the guide wire 10 runs, secures the connectors 6 in the notches 13. Figure 8a shows the combination of implant, clamping element, guide wire and flexible tube with the implant fixed, and Figure 8b shows the implant released from the clamping element 12 after pulling back the flexible tube 15. Because the guide wire 10 and the flexible tube 15 can move relative to each other within a catheter (not shown), it is possible to first position the implant at the implantation site, then retract the catheter, and then, by retracting the flexible tube 15, release the implant. The flexible tube 15 and the guide wire 1 with clamping element 12 can then be retracted into the catheter and withdrawn from the vessel along with it. An implant that has not yet been detached, but has been released distally, can be reinserted for repositioning or further withdrawal. Sufficiently tensile-resistant flexible tubing is well-known. To ensure the necessary flexibility, even in the case of longer flexible tubing, it may be advisable to equip the tubing with slots or other openings, especially in the distal area. This increases flexibility and allows for the removal of air from the tubing before application of the system. Other variations of this release system are conceivable, in which, for example, the connector spheres 6 can be replaced by other types of connecting elements and are fixed in position to the clamping element 12 by means of the catheter 11, a tube 14 or a flexible tube 15. It is understood that the fixation shown here of an implant to a holding element with the help of a tube, a flexible tube or within the catheter can also be used for other forms of implants. Figure 9 finally shows a diagram, which reproduces the relationship between surface density and length variation of a braided stent, such as the one that is the subject of the invention. In the fully expanded state (resting state), an implant according to the invention, with a braid diameter of 100%, has a longitudinal extension of 0%. As elongation increases, the braid diameter decreases, and its length doubles with a 4% reduction in diameter, or triples with a 15% reduction in diameter. This means that an inner lining according to the invention, for transport via a microcatheter to be implanted in the blood vessel near the target site, must be considerably elongated. In parallel with this, the braid density reaches 100% with full expansion, i.e., 0% longitudinal extension. The braid density is reduced by 46% with a 4% reduction in braid diameter (100% longitudinal extension), resulting in a braid density of 40% with a braid diameter of only 85%. The diagram reproduces the theoretical values ​​for an idealized cylindrical braid. However, it is necessary to consider that blood vessels do not have an ideal cylindrical shape and that, particularly in the area of ​​an aneurysm neck, which is intended to be covered, they often have a larger vessel diameter compared to the adjacent healthy vessel section, also due to the opening. This characteristic of the malformation allows the braid of the implant's inner lining to locally adopt a higher surface density and, in this way, reduce or stop blood flow in the aneurysm. A surface density / braid density of approximately 40% to 70% of the fully expanded state will normally be set. However, in well-integrated implants according to the invention, or in the case of significant vessel diameter widening in the aneurysm zone, values ​​clearly exceeding 70% of the theoretical value can also be achieved. Figure 10 shows a schematic representation of the implantation of the invention in a vessel, in the neck region of an aneurysm A. The braid 1 has reached its maximum expansion in the aneurysm A region, with a braiding angle theta of approximately 68°. Correspondingly, the filament or braid density has increased. In the region of the edge of the round braid 1, with a normal vessel lumen, the braiding angle theta is 60°, with a correspondingly reduced filament density. By increasing the filament density in the aneurysm A zone, the permeability of the round braid according to the invention is reduced, which corresponds to the intention of channeling blood flow in the aneurysm A zone and "isolating" the aneurysm A from the blood flow. This isolation can be further enhanced, for example, by filling the aneurysm A space outside the implant 1 with an occlusion coil or other occlusion device.

Claims

1. Implant for blood vessels, for influencing blood flow in the area of ​​aneurysms (A), wherein the implant (1) has a wall formed by isolated filaments (2, 2') that are joined to form a round braid, wherein the round braid is an endless braid cut to size, adopts an elongated shape with a reduced diameter in an implantation catheter (11) and expands at the implantation point, adapting to the diameter of the vessel and increasing the surface coverage, wherein the filaments (2, 2') of the round braid have shape memory characteristics, characterized in that the round braid is adjusted in such a way that, when the stretching forces that bring the round braid to the elongated shape disappear, it extends to such an extent that, in the area of ​​an aneurysm neck in which the vessel has a larger vessel diameter compared to the adjacent healthy vessel section,1. An implant adopts a greater surface coverage compared to the adjacent healthy vessel section.

2. An implant according to claim 1, characterized in that the filaments (2, 2') are at least partially composed of nitinol.

3. An implant according to any of the preceding claims, characterized in that at the proximal and / or distal end of the round braid, the filament ends are joined together in at least pairs and permanently bonded to each other, wherein the joined filament ends are shaped atraumatically and configured as connecting elements (6) to form a fastening element (12).

4. An implant according to claim 3, characterized in that the connecting elements (6) are spherical caps of a defined diameter, arranged at the filament ends.

5. An implant according to claims 3 or 4,characterized in that the joining elements (6) are welded to the filament ends.

6. Implant according to any of the preceding claims, characterized in that the filament ends are welded together.

7. Implant according to any of the preceding claims, characterized in that the filament ends are brought together in an axial direction and joined together.

8. Implant according to any of the preceding claims, characterized in that the braid structure has a surface coverage across the filaments (2, 2') in a range of 30% to 80%.

9. Implant according to claim 8, characterized in that the surface coverage is from 40% to 70%.

10. Implant according to any of the preceding claims, characterized in that the filaments (2, 2') of the round braid are coated with synthetic material.

11. Implant according to any of the preceding claims,characterized in that the round braid is coated with a sheet, or has meshes filled totally or partially with synthetic material.

12. Implant according to any of the preceding claims, characterized in that the implant contains marking elements.

13. Implant according to claim 12, characterized in that the marking elements are platinum filaments or platinum alloys, which are interwoven in the round braid or helically surround filaments (2, 2') of the round braid.

14. Combination of an implant according to any one of claims 1 to 13 and a guide wire (10), to which the implant (1) is coupled via the fastening element (12).

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