DE19531659C2 - Stent - Google Patents

Description

The invention relates to a stent for the treatment of patho logical body vessels, in the form of at least one elongated stent wire using a catheter is implantable and only at the implantation site assumes its intended helix shape.

For the treatment of pathological body and blood vessels it is known to insert stents made of metal or plastic into one to introduce diseased body vessels. Such treatments come with pathological occlusions or aneurysms, especially the aorta.

The implantation of such vascular prostheses is due to the considerable diameter of these prostheses. Mostly, only a surgical implantation of the vessel prostheses in connection with an opening of the vessel and a subsequent vascular occlusion by means of a Vascular suture possible. In the case of treatment of an aortic Aneurysms are inserted into the pelvic arteries leads. This treatment is often linked through with aortic aneurysms, stenoses of the Pelvic arteries difficult or completely thwarted.  

In the cases mentioned, but also in the case of treatment smaller vessels, such as intracranial vessels it is advantageous to use stents made by a small NEN diameter for implantation to a larger diameter knives can be expanded at the implantation site. Accordingly, balloon expandable or self-expanding Stents with a suitable catheter implanted vessels.

In this context, the use of a thermal memory wire has already been described in the article "Translumi nally-placed coilspring endarterial tube grafts, Invest Radiol 1969 , 4 , pages 329 to 332" by Charles Dotter. Thermal memory wires are mostly Nitrogen wires, i.e. nickel-titanium alloys, which harden in a predeterminable form at temperatures of 500 degrees Celsius and then remain in this form at room temperature or, depending on the alloy, at temperatures of 37 °. Under the "Thermo-Memory- Property "one understands that these wires lose their previous shape when cooled further, for example by ice water, and are then free to move and bend as elongated wire. As soon as the wire is warmed up to a temperature approximately equal to the body temperature, it jumps such a wire resiliently returns to the spatial shape specified during curing.

Charles Dotter suggests a stent made from chilled Thermo-memory wire in the form of an elongated wire to implant, which then described because of its benen thermo-memory property at the implantation site in the desired helix and prosthesis shape jumps.  

Such a procedure in animal experiments is described in the technical paper "Percutaneous Arterial Grafting" by Andrew H. Cragg et. al. from Radiology 1984 ; 150 , pages 45 to 49. According to this article, stents are implanted by means of a cooled coaxial catheter as elongated wires for the treatment of aneurysms.

However, these experiments have shown that the Treatment methods with the risk of intimal hyperpla they, that is, a pathological growth of the vessel wall treating vessels are connected. With this treatment There is therefore the possibility of a broad method ren vasoconstriction up to the vascular occlusion as well excessive thrombo-treatment of the patients to be treated Vessels.

In addition, in the case of therapeutic embolization, a vascular treatment with the aim of vascular occlusion, it is known to prevent the further supply of a tumor by implanting stainless steel filaments ("Steel Coil Embolus and Its Therapeutic Applications", Sydney Wallace et. Al ., Abrams Angiograhy, Vascular and interventional Radiology, Third Edition, Vol. III, Brown and Company, Boston 1983 ). In this case, however, completely coiled coils are placed with a guide wire in a catheter at a suitable location in the affected vessel. The helix are additional Lich covered with wool hair or Dacron fibers, which extend at least in sections radially from the helix forter, so that due to the winding of the helix in the space enclosed by the helix, a partially overlapping braid of wool hair or fibers is formed. This network is thromboized and organized up to the desired vascular occlusion through the attachment of tissue cells. In this context one speaks of embolization coils. In contrast to the previously mentioned treatment method, the mentioned embolization coils form a ball inside the body vessel, which due to its thrombogenicity causes a vascular occlusion. The stents described above keep the lumen of a body vessel open.

Furthermore, DE 43 33 836 describes a metal stent made from a helically wound wire or one with opening gene known tube known from a mesh stocking consists of flexible, tissue compatible material. In contrast to pure wire stents, the object this document through the openings of the metal stent or through the stitches of the mesh stocking adequate blood supply to the vessel wall is ensured. After Part of it is, however, that a such stents into a curved vessel through the front given shape of the mesh stocking inevitably tension or lateral forces that occur with sensitive or fragile vessels to damage the body can lead tissue. In particular, it comes as an answer on such an injury to proliferation of the smooth muscle cells involved in intimal hyperplasia unwanted narrowing of the vessel results.

The invention has for its object to provide a stent improved physical tolerance, especially in the rear look at the danger of creating intimal hyperplasia. The stent according to the invention is also intended to be the tissue education, especially in connection with the treatment of aneurysms, accelerate along the stent wall.

This object is achieved in that the stent the preamble of claim 1 of the stent wire at least partially with one beyond its outer circumference protruding tissue structure and / or with itself radially from the this stent is provided with extending fibers,  that the tissue is in the intended spiral shape structures and / or the fibers between the individual adjacent coils formed by the stranded wire at least partially overlap.

This stent continues to offer the benefit of a lighter implantation as an elongated wire through a corresponding catheter. By this principle, only egg ne small opening with a small diameter necessary to the Insert stent wire into the body. The more voluminous Helix shape only arises at the implantation site where the Stent wire due to its thermo-memory property or due to its elasticity in its intended Shape jumps. The latter can be used in particular of a plastic wire.

In its intended position, the stent then has the Form of a wire loop skeleton, the single one Loops through the fabric structure connected to the wire structures or fibers are shielded from the vessel wall and due to the overlapping fabric structures or fibers are connected to each other. So it is not the entire stent body is formed from wire, but be partly also consists of fiber or fabric sections. This is the total length of the implant Stent wire shortened compared to pure wire stents. In in any case, however, is the wire loop skeleton of the stent completely shielded from the vessel wall. Hereby the body tolerance of the stent is improved.

A decisive advantage of the stent according to the invention However, it is that, in contrast to the previously be knew wire stents with adjacent wire sockets now in the area of the fabric and fiber sections Walls of the new stent membrane properties, for example have a diffusibility. The vascular wall conditions can initially be diffused  be worried. In addition, any medication is given not affected by the new stent wall. This creates the risk of intimal hyperplasia of the vessel walls to be treated drastically reduced.

Another advantage is seen in the fact that a increased attachment of connective tissue cells or a increased thrombo-area in the area of tissue or Fiber sections of the stent wall results. The difference the inventor forms part of the well-known embolization spiral stent according to the invention a fiber-provided tube that leaves the vessel lumen open. Because of the described Cell attachment is gradually due to the thrombogenesis biological structure Wall formed. In this way, for example, aneurysms men from the normal blood flow, with what the risk of rupture of the aneurysm continues to act sam is prevented.

A particularly gentle and simple implantation of the Stenting is particularly possible if the patient is using te stent wire is a thermo-memory wire. Because of ner known thermal memory property is in this The use of nitinol wires is particularly related Cheap. However, there are also plastic filaments suitable for use Thermo memory properties.

The stent wire made from a thermo-memory wire should be through one with physiological saline cooled catheters to be implanted to avoid that the stent wire is already inside the catheter voluminous spiral shape jumps and thereby the the Im friction between the stent wire and the inner wall of the catheter is enlarged.

Instead of the spiral made of thermo-memory wire wires can also be highly to super-elastic  Wires are used as stent wire, which as a result their elastic properties at the implantation site in get their intended spiral shape. A derar Tiger stent wire can be made of appropriate plastics but also be made of nitinol.

According to claims 5 and 6, the fabric structures to create the diffusible membrane sections just as much from a textile as from a metal structure be made. In case of using textile fabrics weave the membrane sections have smaller pores and Larger pores if metal mesh is used on. For a solution with small-pored tissue sections the thrombosis and organization of the brought structures accelerated. Metal mesh structures may have the advantage of a higher cross stability on.

The transverse stability of such a stent can also be increased by the fact that the tissue structures at least are cut in fringes in sections. The Tissue structures can vary in length the fringes interlocking, stiffening and sealing.

In the event that the stent wire at least in sections is provided with radially extending fibers, it is advantageous to determine the length of the fibers of each Select application accordingly. For example wise in connection with the treatment of aneurysms conceivable to measure the length of the fibers so that the Braid these fibers preferably in the appropriate Vessel sack protrudes into the area increased vascular thrombosis takes place. This would result in a continuous thrombo acceleration of the pathological vascular sacking accelerated. It is also conceivable that the fibers preferably in the Interior of the stent protrude to an anastomosis with a  to form the underlying stent. That is the verb The second stent is inserted into the this training better sealed.

The stent can be used without the use of extraneous glue fe which are also of dubious durability are such be made that at least one stent wire under Inclusion of the fabric structures or fibers encased and / or is wrapped. This wrapping or wrapping can be done with another textile or thread. An additional attachment of the fabric structures or Fibers are not required.

In a further embodiment, the attachment of the Ge weave structures or protruding fibers simply because of it done that as a stent wire one of several wires th entangled stent wire is used, whereby within the entanglements of the stent wire, the Ge weave structures or fibers are kept. This one too Execution is the use of additional glue or other fasteners can be dispensed with.

According to claim 11, the stent can be particularly advantageous in Connection with the "kissing stent method" for treatment the abdominal aorta. With this me method are already implan into the distal lumen of a main stents on the distal side, each via an artery femoralis two secondary stents in the distal lumen of the Main stents inserted and then expanded. At this treatment method has the problem that the ancillary stents inserted on the distal side are not that Lumen of the main stent already implanted completely fill out so that in the area of this branch of the Stents results in an undesirable leakage. In connection with this "kissing stent method" it is therefore advantageous adheres to a stent that has fibers at its distal end  is provided, which preferably protrude into the stent interior. This results in an accelerated vascular occlusion in the area of anastomosis if such a stent as Main stent is used.

According to the statements according to claims 12 and 13 the risk of leakage in the area of the distal ver branch of the main stent is also noticeably reduced.

The fact that the stent wire ver with stiffening struts see that is parallel and during implantation standing across the stent wire after implantation an additional transverse stiffening of the stent is given. A special stiffening effect is always then achieved when the length of each wire section like this it is dimensioned that at least two adjacent loops of the stent overlapped by a stiffening strut will. A possible realization of such Cross bracing of the stent turn is given by the fact that the stiffening struts have a larger diameter have than the stent wire and thus after leaving the catheter only in its intended position if the stent is otherwise already manufactured. The proper expansion of the stent as a result of the Ela stity or the thermal memory property of the stent wire is therefore not due to the stiffening struts with special needs.

Another shortening of the stent to be implanted wire results from a double-helix structure is implanted.

In another version, the Thermo-Memory-Eigen shaft of the thermo-memory wire or the elasti of a plastic wire is also used in this way be that individual loops of a stent attached to  a guidewire are attached after Implantation within the vessel to be treated in unfold the desired spiral shape.

According to claim 17, this embodiment can me can be supported mechanically during the implan tation of the stent with a loop detachable apron in their attached to the guide wire folded position can be kept.

In an embodiment according to claim 18 there is a improved spring action in the longitudinal direction of the stent. As a result, the body tolerance of the stent can especially with an implantation in the curve or flexion rich in vessels. Through the waveform The stent wires can also have additional teeth the spiral loops can be reached with each other and this increases the transverse stiffness of the stent.

The implantation of such a stent and its location correct placement can be facilitated by the fact that the stent wire is provided with special markings, which is the observation of the stent on the x-ray screen facilitate.

A durable attachment of the fabric structures or company is possible if the strent wire has a longitudinal oval or rectangular cross-section, since this is a extensive contact of the fabric or the fibers with the Results in stent wire.

Below, the invention is based on several in the attached drawing schematically illustrated Ausfüh Examples explained. Not to scale show:

Fig. 1 is a stent,

Fig. 2 is a connected to a fabric structure stent wire

Fig. 3 shows a cross-section of the stent wire along the line III-III in Fig. 2,

Fig. 4 shows the stent wire of FIG. 3 within a Ka theters,

5 shows a connected with a frangible web structure stent wire.,

Fig. 6 shows a stent wire portion of tangled wires enclosed-fiber structure,

Fig. 7 shows a stent wire coated with encapsulated fiber structure,

Fig. 8 in a sectional view of a kissing stent in longitudinal section,

Fig. 9 shows the Kissing stent of Fig. 6 with Innenfaserung at the distal end in cross-section,

Fig. 10 is a longitudinal oval kissing stent in cross-section,

Fig. 11 is a kissing stent constriction in cross-section,

Fig. 12 shows a stent wire having transverse ribs,

Fig. 13 is a stent with appropriate Querverrippung,

Fig. 14 a stent having an undulating wire stent,

Fig. 15 is a stent with retractable wire loops and

Fig. 16 is a double-barreled stent.

Fig. 1 shows a stent 1 immediately after its implantation, which is still connected to a catheter 2 .

A stent wire 3 is advanced through the catheter 2 during implantation by means of a pusher, not shown. This stent wire 3 optionally consists of a thermo-memory wire, such as Nitinol, or an elongated, flexible wire made of highly elastic plastic, which is pushed through the catheter 2 and exits from the catheter 2 at the proximal end within the vessel to be treated and because of the called Thermo-Me mory property or the elasticity of the wire jumps into the desired helical shape of the stent 1 .

In the case of using a thermal memory wire, the catheter 2 should be flushed with a cooled physiological saline solution to prevent the stent wire 3 from jumping inside the catheter 2 into the helical shape. Otherwise, the advancement of the stent wire 3 within the catheter 2 disabling frictional force would by the bulky stent wire 3 considerably increased. To this end, the catheter 2 may be provided an inlet valve for the phy siologische solution at distalsei-side end and also on the proximal malseitigen end of the catheter 2, a lock valve to be sorted, which although allowing the physiological Kochsalzlö leak solution without hindrance, but conversely the A occurs by warm body fluids prevented.

The stent wire 3 is connected to a fabric or metal structure 4 . The structure 4 can be glued to the stent wire 3 , for example. The stent can be manufactured in that the stent wire 3 is glued in its Wen delform with a structure 4 that the closed coil shown in Fig. 1 is formed. On closing the closed helix structure can along the formed of the stent wire 3 wire loops 5 are cut so that the unwound stent wire 3 is each connected to a both sides protruding bonded fabric structure 4 shown in Fig. 2 Darge provides. In this elongated form, the stent wire 3 can be implanted through the catheter 2 .

In the case of the implanted spiral stent 1, it is therefore possible to distinguish between the wire loops 5 and the membrane sections 6 formed by the tissue or metal structure 4 . The membrane sections 6 are diffusible due to their porosity. In the case of textile fabric structures, the membrane sections 6 are very fine-pored and in the case of using Metallge weave very large-pored. The decision to use a textile or metal structure depends on the desired stiffness of the stent and the required diffusion properties.

The rectangular cross-section shown in Fig. 3 of the stent wire 3 makes it clear that due to this cross-sectional shape of the stent wire, a flat contact of the tissue structure 4 to the stent wire 3 is given. This is particularly advantageous when using an adhesive connection between the stent wire 3 and the tissue structure 4 .

According to FIG. 4, the flexible fabric structure 4 is a space-saving folded around the stent wire 3 during the implantation by the catheter 2. This facilitates the implantation of the stent 1 .

The fabric or metal structure 4 can additionally be cut like a fringe according to FIG. 5. In an advantageous embodiment of this embodiment, the fabric fringes 7 of adjacent wire loops 5 overlap in the manner of a piano tape such that an additional transverse stiffening for the stent 1 is given. The tightness of the membrane sections 6 in this embodiment depends essentially on the width of the incisions in the fabric or metal structure 4 .

In another embodiment of the stent 1 , the stent wire 3 is provided with fibers 10 that extend radially from the stent wire 3 forterstrec. The fibers are mostly made of Dacron material and can be of different lengths in sections or depending on the preferred direction.

Fig. 6 shows an embodiment in which the stent wire 3 is made of intertwined wires 11 and 12 . The partial wires 11 and 12 also consist of thermo-memory wire or highly elastic plastics. Dacron fibers 10 are held between the individual wires 11 and 12 by means of the interlacing of these wires 11 and 12 . This version does not require any foreign adhesives with doubtful or limited durability.

In another embodiment of the stent 1 , a stent wire 3 is wrapped in a covering 13 . This cover 13 can also consist of a textile or metal fabric structure 4 . However, it can also be an auxiliary thread or auxiliary wire. Also in this embodiment, the sheath 13 is wrapped around the stent wire 3 such that Dacron fibers 10 which extend radially from the stent wire are additionally closed.

The fibers 10 extending from a stent wire 3 in accordance with the exemplary embodiments according to FIGS . 6 and 7 also serve to form membrane sections 6 between the individual wire loops 5 of the stent 1 . The braid formed by the overlap of the individual fibers 10 can, however, also be used very specifically to produce thromboses, for example within a pathological vascular sac, such as an aneurysm.

According to another embodiment, the fibers 10 can also protrude specifically into the interior of the stent 1 in order to accelerate a vascular occlusion.

Figs. 8 to 11 show a stent for a particular method of treatment for vascular diseases in the range of arterial branches. The pelvic arteries that branch off from the aorta-abdominalis are often affected, particularly in the case of the aorta-abdominalis due to infrarenal aneurysms. A stent used to treat these vascular diseases must also have a corresponding branch. The so-called "kissing stent method" is successfully used for this purpose. Here, a larger main stent 14 is implanted in the branching vessel and then a further auxiliary stent 17 , 17 'is inserted distally on the distal side into the initially implanted stent. In the case of a pathological abdominal aorta, an auxiliary stent 17 , 17 'is inserted through the aorta-femoralis into the distal lumen of the main stent 14 already implanted. So far, it has been problematic that there was a leak in the region of the branching of the two distal-side inserted auxiliary stents 14 , since the auxiliary stents 17 , 17 'inserted laterally on the distal side did not fill the entire lumen of the originally implanted main stent 14 . In the case of the sectional arrangement of inwardly projecting fibers according to FIG. 9 at the distal end of the main stent 14 , the leakage described can be effectively combated by accelerating thrombo-isolation within the leakage zones.

According to FIG. 10, the leakage can also be limited in that the main stent 14 has a longitudinal oval lumen at the distal end or is provided with a central constriction 15 according to FIG. 9. Combinations of the stent solutions shown in FIGS. 9 to 11 for carrying out the kissing stent method are of course also conceivable
According to FIG. 12 of the stent wire 3 may additionally be Ver steifungsstreben with 15 is connected. The Versteifungsstre ben 15 could, for example, be welded onto the thermo memory wire Nitinol wire sections. Another method for fastening such stiffening struts is so-called "crimping".

Ideally, the stiffening struts 15 lie parallel to the stent wire 3 during the implantation through the catheter 2 . Only at the implantation site within the vessel to be treated do the stiffening struts 15 move due to their thermal memory properties or due to their elasticity into their intended position across the wire loops 5 of the stent 1 . Ideally, the length of the stiffening struts 15 is dimensioned such that the adjacent wire loops 5 are covered. This results in an additional transverse reinforcement of the stent 1 .

An improved spring property of the stent in the longitudinal direction can be achieved in that the stent wire 3 jumps into a waveform at the implantation site as shown in Fig. 14. The individual wire loops 5 are then made of wavy bent stent wires 3
educated. An additional cross-stiffening effect results if the wavy bulges of the stent wire 3 overlap one another in a manner not shown.

In a further embodiment according to FIG. 15, the individual wire loops 5 are fastened to a guide wire 16 . During the implantation, the wire loops 5 are placed as closely as possible on the guide wire 16 and then jump after implantation at the implantation site due to their thermal memory property or their elasticity into the desired helical shape. During the implantation, the individual wire loops can additionally be held in their folded position by a detachable crochet.

If according to FIG. 16 two parallel stent wires 3, 3 may be 'bonded to a fabric structure 4 a dop pelläufiger stent can be produced. As a result, the length of the stent wires 3 , 3 'to be implanted is shortened for the same stent length.

Claims (20)

1. stent for the treatment of pathological body vessels, which can be implanted in the form of at least one elongated stent wire ( 3 ) by means of a catheter ( 2 ) and only assumes its intended helix shape at the implantation site after the implantation has been carried out, characterized in that the stent wire ( 3 ) is at least partially provided with a fabric structure ( 4 ) projecting beyond its outer circumference with fibers ( 10 ) extending radially from the stent wire ( 3 ) such that the fabric structures ( 4 ) and / or the fibers ( 10 ) are in the intended helical shape. overlap at least partially between the individual, adjacent coils formed by the stent wire ( 3 ). 2. Stent according to claim 1, characterized in that the stent wire ( 3 ) is a thermal memory wire, in particular made of nitinol. 3. Stent according to claim 2, characterized in that the implanted catheter ( 2 ) has an inlet valve located outside the body for a cooled physiological saline solution and a shut-off valve located inside the body, which prevents the entry of body fluids into the catheter ( 2 ) . 4. Stent according to claim 1, characterized in that the stent wire ( 3 ) is a highly to super-elastic wire, in particular made of plastic. 5. Stent according to one of the preceding claims, characterized in that the fabric structure ( 4 ) is at least partially a textile structure. 6. Stent according to one of claims 1 to 4, characterized in that the fabric structure ( 4 ) is at least partially made of metal mesh. 7. Stent according to claim 5 or 6, characterized in that the fabric structure ( 4 ) is cut at least in sections like a fringe. 8. Stent according to one of the preceding claims, characterized in that the fibers ( 10 ) extending radially from the stent wire in sections and / or depending on the radial preferred direction are of different lengths. 9. Stent according to one of claims 1 to 8, characterized in that at least one stent wire ( 3 ) is enclosed and / or wrapped with the inclusion of protruding tissue structures ( 4 ) and / or radially projecting fibers ( 10 ). 10. Stent according to claim 9, characterized in that a plurality of part wires ( 11 , 12 ) including projecting over the tissue structures ( 4 ) or protruding fibers are intertwined to form a stent wire ( 3 ). 11. Stent according to claim 8, characterized in that a main stent ( 14 ) has at least at one end fibers ( 10 ) which preferably protrude into the interior of the stent. 12. Stent according to claim 11, characterized in that the main stent ( 14 ) has an oval lumen at least at its distal end. 13. Stent according to claim 11, characterized in that the main stent ( 14 ) is constricted at least at its distal end in such a way that its lumen at this point has at least approximately the shape of an eight. 14. Stent according to one of the preceding claims, characterized in that the stent wire ( 3 ) with stiffening struts ( 15 ) is provided for transverse stiffening of the stent, which are parallel to the stent wire ( 3 ) during implantation and after successful implantation. 15. Stent according to one of the preceding claims, characterized in that in each case two stent wires ( 3 , 3 ') through the fabric structure ( 4 ) to form a double-stranded spiral structure of the stent ( 1 ) are firmly connected to one another. 16. Stent according to one of the preceding claims 1 to 14, characterized in that the individual loops ( 5 ) of a stent ( 1 ) are formed by individual stent rings which, during implantation, on a guide wire ( 16 ) or on a guide wire ( 16 ) insertable guide tube can be folded and can be opened into the respective spiral shape after the intended implantation. 17. Stent according to one of the preceding claims, characterized in that the stent ( 1 ) is initially stretched to carry out the implantation and is then held in this stretching by means of a releasable constriction. 18. Stent according to one of the preceding claims, characterized in that the stent wire ( 3 ) after the intended implantation is swung at least in sections within the lateral surface of the stent ( 1 ) in such a way that the helix of the implanted stent ( 1 ) at least in sections is formed from a wave-shaped curved stent wire ( 3 ). 19. Stent according to one of the preceding claims, characterized in that the stent wire ( 3 ) is provided with markings which facilitate observation of the stent ( 1 ) on the X-ray screen. 20. Stent according to one of the preceding claims, characterized in that the stent wire ( 3 ) has a longitudinal oval or rectangular cross section.