Repositionable covered stent

Abstract

The present invention relates to a stent (1) and a catheter system (2) comprising such a stent (1), the stent (1) comprising: a self-expandable scaffold (10) extending along an axial direction (x) comprising a plurality of open cells (11) formed by a plurality of circumferential strut structures (12) connected by axial struts (13) extending along the axial direction (x), the scaffold (10) comprising an outside facing away from an interior (14) of the stent (1) surrounded by the scaffold (10), the interior (14) forming a passage for blood through the stent (1) in an implanted state of the stent (1), a proximal end (15) configured to be connected to a catheter (3) to allow returning at least the scaffold (10) into a lumen (30) of the catheter (3), and a cover (16) arranged at least on the outside of the scaffold (10), the cover (16) being further configured to carry a drug to be administered and / or to seal a vascular rupture.

Description

[0001] Repositionable covered stent

[0002] The present invention relates to a stent, particularly to a repositionable covered stent, particularly for temporary drug delivery or occlusion of vascular ruptures or perforations. Furthermore, the present invention relates to a catheter system for delivering such a stent.

[0003] In the state of the art, balloon-expandable and self-expanding stent grafts for aneurysm, rupture and lesion treatment as permanent implants are known.

[0004] Stent grafts remain in the body as permanent implants. There is a risk of inflammatory reactions and increased restenosis due to the additional cover material, and the hemodynamics of the vessel are also permanently impaired. In the event of a severe rerestenosis of the affected vessel segment, follow-up treatment becomes difficult as a result of the implanted stent. In the case of vessel perforations or ruptures, a stent may no longer be necessary after the bleeding stops and the risk for a cardiac tamponade is eliminated. Repositionable stents (e.g. for TAVR application) must have a special, primarily closed-cell design, otherwise there is a risk of snagging of stent struts during retraction into the guiding catheter. Compared to open-cell designs, these have a high stiffness, especially bending stiffness. This can lead to alteration of the natural anatomy of the vessel (stretching of curved arteries) with associated irritation and suboptimal clinical outcomes.

[0005] Based on the above, the problem to be solved by the present invention is to provide a stent and a corresponding catheter system allowing to temporarily seal a vessel lesion and / or temporarily apply drugs hence providing the possibility of subsequent repositioning or removal of the stent, or leave the stent implanted if deemed necessary or beneficial.

[0006] This problem is solved by a stent having the features of claim 1 and a catheter system having the features of claim 9. Further aspects of the present invention relate to a method using the catheter system for implanting the stent into a patient. Preferred embodiments of these aspects are stated in the corresponding dependent claims and are described below.

[0007] According to claim 1, a stent is disclosed, comprising a self-expandable (preferably essentially cylindrical) scaffold extending along an axial direction and comprising a plurality of open cells formed by a plurality of circumferential strut structures connected by axial struts that each extend along the axial direction, the scaffold comprising an outside facing away from an interior of the stent surrounded by the scaffold, the interior of the stent forming a passage for blood through the stent in an implanted state of the stent, a proximal end of the stent configured to be connected to a catheter to allow returning at least the scaffold into a lumen of the catheter, and a cover arranged at least on the outside of the stent, the cover being further configured to carry a drug to be administered and / or to seal a vascular rupture.

[0008] The stent according to the present invention thus combines the advantages of a flexible opencell stent design with the possibility to remove the stent from the vessel after a certain implantation period (before ingrowth of the stent). A cover surrounding the stent has the function of allowing the stent to retract and also to perform new tasks, such as delivering drugs as well as closing ruptures. Such drug delivery for example is of course also possible with an open cell design, it is therefore hereby stated that the present invention and every embodiment described herein can also be implemented with an open cell design.

[0009] According to the present invention an open cell design for stents is considered as being contrary to a closed cell design. Stents are usually constituted of primary structures which have meandering substructures. Such primary structure can be rings or helices which are connected to a neighboring primary structure either directly or by connecting pieces. Such connecting pieces abut at each meandering primary structure. Meandering structures are constituted of peaks and valleys. In a closed cell design each peak or valley is either connected directly to a neighboring to a corresponding peak or valley or via a connecting piece in such a way that no free peak or valley remains in the structure. In an open cell design at least one not connected and thereby free-standing peak or valley is present in the stent pattern.

[0010] According to a preferred embodiment of the present invention, each circumferential strut structure comprises a plurality of struts connected to one another in a circumferential direction of the scaffold, each two neighboring connected struts forming an inflection point of the respective circumferential strut structure, wherein each inflection point of a minority of the inflection points of each circumferential strut structure is connected via an axial strut to a neighboring circumferential strut structure.

[0011] Particularly, in a preferred embodiment of the invention, each circumferential strut structure is connected by at most three axial struts to a neighboring circumferential strut structure. Preferably, these (e.g. at most three) axial struts are equidistantly spaced in a circumferential direction of the scaffold (e.g. by 120° in case of three axial struts).

[0012] Particularly, in a preferred embodiment, the respective circumferential strut structure comprises a meandering shape.

[0013] In comparison, a closed cell stent has every curved section of every circumferential set of strut members, except at the distal and proximal ends of the stent, attached to an axial connecting link. Consequently, closed-cell stent designs are usually stiffer compared to open-cell stent designs.

[0014] Furthermore, according to a preferred embodiment of the present invention, the scaffold is formed out of a super-elastic metal alloy, preferably a nickel titanium alloy, particularly Nitinol. Particularly, the scaffold can be laser cut out of a tube formed from such a material.

[0015] According to a preferred embodiment of the stent according to the present invention, the proximal end of the stent (i.e. the end of the stent being closer to the physician handling the stent / catheter when seen along the longitudinal axis of stent and catheter) comprises strut elements of the scaffold (preferably straight strut elements extending along the axial direction), each comprising an eyelet at a proximal end of the respective strut element for pulling on the scaffold and returning at least the scaffold or the stent into said lumen of the catheter, wherein particularly a flexible annular element extends through the eyelets for pulling on the scaffold, wherein preferably the flexible annular element comprises a diameter corresponding to a diameter of the scaffold in an expanded state of the scaffold.

[0016] Particularly, in a preferred embodiment, as flexible annular element, a thread (e.g. out of a plastic material) or a wire (e.g. out of a nickel titanium alloy such as Nitinol) or some other elongated and flexible element is threaded through the eyelets forming a closed flexible annular element with a diameter equal to that of the of the expanded scaffold. This annular element can be grasped by a suitable capturing device and enables the scaffold or stent to be withdrawn into the lumen of the catheter.

[0017] According to yet another preferred embodiment, the proximal end of the stent comprises strut elements of the scaffold (preferably straight strut elements extending along the axial direction), each strut element comprising a hook at a proximal end of the respective strut element for pulling on the scaffold and returning the scaffold or stent into said lumen of the catheter. The hooks, as a further variation, also serve to grasping of the scaffold with an appropriate capturing device.

[0018] The number of the strut elements (either with eyelets or hooks) described above, can range from three to a maximum number corresponding to the number of crowns (i.e., inflection points) of the scaffold at the corresponding proximal end of the stent.

[0019] According to yet another preferred embodiment of the stent, the proximal end of the stent is a unilaterally tapered proximal end of the stent terminating with a docking site for capturing the proximal end of the stent. According to a preferred embodiment the docking site is one of: a loop, a magnet. Other docking sites are also conceivable.

[0020] Furthermore, according to a preferred embodiment of the present invention, the cover covers at least 90% of the outside of the scaffold, wherein preferably the cover covers the outside of the scaffold completely. Further, according to a preferred embodiment of the present invention, the cover comprises or is made out of one of the following materials: a biocompatible plastic material, a biological tissue.

[0021] According to a preferred embodiment of the present invention, the cover of the stent is preferably made of a biological material, which has distinct advantages over a polymeric cover, particularly for small vessel diameters, including intrinsic low thrombogenicity. The design of the biological cover preferably supports removability of the stent, i.e. withdrawing the latter into the lumen of the catheter.

[0022] Furthermore, according to a preferred embodiment, the cover is a one-piece (e.g. monolithic) cover, particularly a biological cover, that is particularly configured to prevent ingrowth in general or that is particularly configured to prevent at least ingrowth during a time period during which the stent is residing temporarily in a patient, and wherein the scaffold is configured to be returned into the catheter together with the cover after said time period has lapsed.

[0023] Ingrowth is the process in which cellular processes in the tissue of the vessel wall adjacent to the cover cause a partial dismantling and reconstruction of the biological cover and cells and extracellular matrix migrate into and / or onto the matrix of the cover.

[0024] On the other hand, the biological cover is preferably prevented from growing. The term "growth" refers to the process by which proliferation of the tissue of the vessel wall adjacent to the cover fills open portions of the cover and causes a mechanical interlocking between the vessel wall and the biological cover.

[0025] Here, preferably, the proximal end of the stent is configured to be connected to a catheter to allow pulling on the stent and returning at least the scaffold or the complete stent (including the cover) into a lumen of the catheter.

[0026] In a preferred embodiment, collagen-containing tissue of animal origin (e.g., pericardium) or bacterial nanocellulose are selected as material of the cover. Both materials can be provided in a dry state on the stent after processing of the respective material. Particularly, pericardium chemically cross-linked with glutaraldehyde cannot be enzymatically converted in the body, which is why ingrowth is not possible. According to a preferred embodiment, the cover of the stent is therefore made from pericardium cross-linked with glutaraldehyde, particularly under high pressure. The crosslinking under high pressure results in a very thin cover with a very smooth surface similar to a polymer film. The crosslinking is preferably performed on the outside of the scaffold without additional sutures, which also prevents stable adhesion. This is followed by the process of stabilized drying of pericardium.

[0027] Furthermore, bacterial nanocellulose cannot be degraded or converted in the body due to the absence of cellulases in the body, which is why ingrowth is also not possible. The cover for the stent is preferably made by directly growing and processing bacterial nanocellulose on the scaffold. Furthermore, the growth on silicone surfaces or growth on a rotating mold in a bioreactor is possible. Additional seams are also not necessary, since a three-dimensional form-fit is achieved with the scaffold of the stent in a preferred embodiment. The thickness of the material can be controlled via the cultivation time. Due to the final drying without stabilizers, the cellulose is permanently reduced in thickness.

[0028] According to a further preferred embodiment of the stent according to the present invention, the cover is configured to allow ingrowth of the vessel wall into the cover during a time period during which the stent resides in the vessel of a patient, wherein the scaffold is configured to be returned into the catheter without the cover. Here, in a preferred embodiment, the proximal end of the stent, which proximal end is formed by the scaffold, is configured to be connected to a catheter to allow pulling on the scaffold and returning the scaffold into a lumen of the catheter while the ingrown cover remains implanted, i.e., in the vessel.

[0029] According to a preferred embodiment, collagen-containing tissue of animal origin (e.g. pericardium) is used as material for the cover, which is explicitly not treated with a chemical crosslinker, but is natively processed according to the process of stabilized drying. A exemplary process for stabilized drying is described in US 11,590,261 B2. After implantation, the stabilizers are flushed from the pericardium and the remaining rehydrated collagen-containing extracellular matrix provides an excellent substrate for proliferation of cells of the vessel wall. The use of native dried tissue allows complete ingrowth of the cover, which thus stably attaches to the vessel wall and remains in the body upon withdrawing the scaffold into the catheter. According to an embodiment, the natively dried pericardium is produced by the process of stabilized drying and additionally maximally reduced in thickness by a subsequent pressing step. Preferably, very thin pericardium from young animals is used to achieve a thickness of less than 80 micrometers. Furthermore, according to an embodiment, stable fixation of the cover is achieved by classical suturing (degradable suture material) of the cover (e.g. a shaped part cut e.g. by a CCh-laser) to the scaffold.

[0030] Furthermore, according to a preferred embodiment of the stent, the cover comprises an inner part and an outer part covering and surrounding the inner part, the outer part forming an outer surface of the cover for contacting the vessel wall, wherein the outer part is configured to allow ingrowth of the vessel wall into the outer part during a time period during which the stent is residing in a vessel of a patient to connect the vessel wall to the outer part of the cover, and wherein the scaffold is configured to be returned into the catheter together with the inner part and without the outer part. Here, preferably, the proximal end of the stent is configured to be connected to a catheter to allow pulling on the scaffold and / or the inner part of the cover to return the scaffold together with the inner part into a lumen of the catheter while the ingrown outer part of the cover remains in the vessel / implanted.

[0031] According to a preferred embodiment, in case of an outer part that remains in the vessel as described above, both collagen-containing tissue of animal origin (e.g., pericardium) as well as bacterial nanocellulose, also in combination, are suitable and can be used for the inner and outer part of the cover.

[0032] According to a preferred embodiment of the preset invention, the inner part and the outer part of the cover are made out pericardium, respectively, or comprise pericardium, respectively. Preferably, the respective (inner or outer) part comprises a thickness of less than 50 pm. Particularly, since the two parts of pericardium are superimposed, very thin pericardium selected from preferably young animals is preferably used to achieve a thickness of less than 50 pm. Particularly, according to an embodiment, an ultrathin pericardium chemically crosslinked under pressure with glutaraldehyde is attached as inner part of the cover to the scaffold without the use of any suture material. Subsequently, an outer part of the cover, which outer part is formed out of very thin natively dried pericardium is applied to the scaffold using degradable suture material. After implantation, the outer part of the cover grows in completely, while the inner part of the cover forms a barrier and allows explantation of the repositionable stent.

[0033] According to a further alternative embodiment, the inner part is made out of cellulose or comprises cellulose, and the outer part is made out of pericardium or comprises pericardium. According to an embodiment, first, an inner part of the cover of bacterial nanocellulose is grown and processed on the scaffold. Particularly, the cultivation time is selected in such a way that the cover of bacterial nanocellulose stably envelops the scaffold and forms a continuous barrier. Furthermore, particularly, the cellulose grown in this way is then dried without stabilizers and permanently reduced in thickness. Particularly, in the dried state, thicknesses of 30 micrometers are achievable and sufficient. Subsequently, as described above, an outer part of the cover formed of natively dried pericardium is then applied on the inner part. After implantation, the outer part of the cover grows in completely, while the inner part of the cover forms a barrier and allows explantation of the repositionable stent.

[0034] According to a further alternative embodiment, both the inner part and the outer part of the cover are made out of cellulose or comprise cellulose. According to a preferred embodiment, first, an inner part of the cover of bacterial nanocellulose is applied to the scaffold. Preferably, drying of the inner part of the cover, optionally under radial pressure, results in a mechanically and structurally long-term stable layer of bacterial nanocellulose. Subsequently, the stent thus obtained, covered with an inner part of the cover of cellulose, is coated with an outer part of the cover by growing a layer of bacterial nanocellulose on the inner part of the cover. Preferably, the inner and the outer part of the cover are formed such that between the two layers of cellulose there is no connection by cellulose fibers, but the bond exists only due to a positive between the inner and outer part of the cover and hydrogen bridge bonds. Preferably, the cellulose grown in this way on the scaffold is rinsed. Both parts / layers of cellulose are then preferably dried without stabilizers. Particularly, drying is conducted in surface-structured press molds under radial pressure. As a result, surface structures are imprinted only in the outer part of the cover, which allow the outer part of the cover to adhere to the vessel wall. Particularly, the surface structures are stable over the long term due to drying without stabilizers.

[0035] According to a preferred embodiment, the surface structures are one of the following: grooves, spirals, irregularly distributed grooves, irregularly distributed spirals, depressions, irregularly distributed depressions. These surface structures enhance adhesion. Furthermore, according to a preferred embodiment, both biological tissues (pericardium and cellulose) are formed from a matrix of biological fibers. Microscopically, both tissues represent spongelike structures, which can be optionally loaded with one or several drugs. The loading can also take place immediately prior to implantation in the course of rehydration. Alternatively, an additional drug coating of the dried tissues on the outside of the outer part of the cover is also possible.

[0036] Furthermore, according to yet another preferred embodiment, the stent is a temporary occlusion implant, wherein the cover closes the interior of the stent.

[0037] According to an embodiment, if pericardium is used as cover material, an additional molded part is used for occluding the interior of the stent for the passage of blood, e.g. in the form of a sack, which can be sewn into the interior of the stent. In alternative embodiment, when cellulose is used as cover material, an additional sack-like material portion is arranged inside the free interior of the stent together with the cover on the scaffold and particularly without the need for sutures. This can be achieved, for example, by using two rods whose ends are shaped in such a way that they can be inserted into the stent structure, with a gap between the two ends into which bacterial cellulose can grow into. In this way, it is possible to simultaneously envelop the scaffold by the cover and have the interior of the stent closed.

[0038] According to yet another aspect of the present invention, a catheter system is disclosed, the catheter system comprising a stent according to the present invention and a catheter comprising a lumen configured to deliver the stent to an implantation site, wherein the catheter is configured to be connected to a proximal end of the stent to allow returning at least the scaffold into a lumen of the catheter.

[0039] A capture and retraction mechanism of the catheter system can be designed in several versions. According to a preferred embodiment, the catheter comprises a capturing device configured to assume a collapsed state and an expanded state, wherein the capturing device is configured to be inserted into the interior of the stent in the collapsed state and to be brought into the expanded state when residing in the interior of the stent so that the capturing device engages with the flexible annular element (or a corresponding element or docking site) extending through said eyelets of the proximal end of the stent when being retracted, wherein when the capturing device is subsequently brought to its collapsed state, the proximal end of the stent is radially contracted so that it can be returned into the lumen of the catheter. Particularly, depending on the employed cover (see above), the scaffold or stent can thus be returned into the lumen of the catheter. Particularly, the capturing device can be an umbrella comprising legs pivoted away from one another in said expanded state to engage with the flexible annular element.

[0040] According to yet another preferred embodiment of the catheter system, the capturing device comprises several arms which are configured to be inserted into the interior of the stent, each arm having an end portion configured to engage with the flexible annular element extending through said eyelets of the proximal end of the stent when the arms are subsequently retracted into the catheter, wherein the arms are configured to move towards one another so that the proximal end of the stent is radially contracted and can be returned into the lumen of the catheter. Particularly, depending on the employed cover (see above), the scaffold or stent can thus be returned into the lumen of the catheter.

[0041] According to a further preferred embodiment of the catheter system, the capturing device comprises an inflatable balloon which is configured to be inserted into the interior of the stent, the balloon having separately inflatable hook elements protruding from an outer surface of the balloon, wherein the hook elements are configured to engage with the flexible annular element (or an alternative docking site) when the balloon and the hook elements are inflated and the balloon is retracted, wherein the balloon is configured to be deflate while the hook elements remain inflated so that the proximal end of the stent is radially contracted and can be returned into the lumen of the catheter. Particularly, depending on the employed cover (see above), the scaffold or stent can thus be returned into the lumen of the catheter.

[0042] Furthermore, according to yet another embodiment of the catheter system, the capturing device comprises a foil formed out of a super-elastic metal alloy (such as a nickel titanium alloy, e.g., Nitinol), wherein the foil is rolled up into a spiral shape and is configured to be rotated around the axial direction (e.g. longitudinal axis) of the stent so as to successively move the foil over the proximal end of the stent, wherein due to the spiral shape the proximal end of the stent is radially contracted and can be returned into the lumen of the catheter upon retracting the foil together with the proximal end of the stent into the lumen of the catheter. Particularly, depending on the employed cover (see above), the scaffold or stent can thus be returned into the lumen of the catheter.

[0043] Particularly, an outer edge of the foil can be crimped over the proximal end of the stent and is rotated around the axial direction (e.g. longitudinal axis of the scaffold / stent) in such a way that a strut arm of the scaffold at the proximal end of the stent moves inwards into the spiral-shaped foil and is thus pushed radially towards a center of the spiral-shaped foil. At the same time, the outer edge of the foil, which continues to rest against the vessel wall, slides over the next strut arm of the scaffold and so on. Thus, with multiple rotations of the foil about its axial direction, the proximal end of the stent is completely pulled into the spiralshaped foil and undergoes a radial contraction.

[0044] According to a further preferred embodiment of the catheter system, the capturing device comprises a tubular structure comprising a plurality of lamellae mounted on top of one another, so as to overlap in a circumferential direction of the tubular structure, which lamellae are configured to move relative to one another in a circumferential direction of the tubular structure to reduce an inner diameter of the tubular structure, wherein an end section of the tubular structure is configured to move out of the catheter to be slid over the proximal end of the stent, wherein the lamellae are configured to be pushed over one another when the catheter is advanced relative to the end section of the tubular structure so that the inner diameter of the tubular structure is reduced allowing the tubular structure to grab the proximal end of the stent for retracting the proximal end of the stent into the lumen of the catheter. Particularly, depending on the employed cover (see above), the scaffold or stent can thus be returned into the lumen of the catheter.

[0045] According to a further preferred embodiment of the catheter system, the proximal end of the stent is configured to be connected to the catheter during a time period during which the stent is temporarily implanted into a vessel to seal a rupture of the vessel, wherein the catheter is configured to remain connected to the proximal end of the stent during said time period to allow returning the stent into the lumen of the catheter after lapsing of said time period when the bleeding of the vessel has stopped. Advantageously, during said time period, blood flow is maintained through the vessel via the stent. By maintaining blood flow in the vessel through the stent’s interior, the physician has a longer period of time to seal the vessel than with e.g. a balloon dilatation.

[0046] According to a preferred embodiment of the catheter system, the proximal end of the stent is permanently connected to the catheter. Particularly, this connection can only be released by way of destruction.

[0047] According to a preferred embodiment of the catheter system, the proximal end of the stent is connected to the catheter by means of a pull cord. The pull cord can be any elongated flexible element such as a rope or a wire.

[0048] According to yet another preferred embodiment of the catheter system, the stent is configured to be completely detached from the catheter so as to remain in the vessel as permanent implant. This is especially useful in case the bleeding cannot be stopped within a pre-defined time period (e.g. usually several minutes after implantation of the stent). Since no capture mechanism is required in this embodiment, the proximal end of the stent does not need to be especially modified and extended to include appropriate hook or eye elements.

[0049] According to a preferred embodiment of the catheter system, the pull cord is threaded through open cells of the scaffold at the proximal end of the stent, or through through- openings provided in the scaffold at the proximal end of the stent. According to a preferred embodiment, the pull cord comprises two ends, so that pulling at the two ends at once (or pulling on one end with the other end being fixed) causes the proximal end of the stent to radially contract so that the proximal end of the stent can be retracted into the lumen of the catheter.

[0050] According to yet another preferred embodiment of the catheter system, for permanent release of the stent, the pull cord is threaded such through the open cells / through-openings of the scaffold that the pull cord can be pulled out of the open cells / through-openings entirely by pulling on one end of the pull cord, while having the other end free.

[0051] According to yet another aspect of the present invention, a method is disclosed, wherein the method uses a catheter system according to the present invention, wherein the method comprises the steps of:

[0052] Implanting the stent into a vessel to seal a vessel rupture and / or administer a drug using the catheter, and

[0053] - Retracting the scaffold or the stent into the lumen of the catheter after a time period when a bleeding of the vessel due to said rupture has stopped and / or the drug has been administered, or releasing the stent from the catheter to permanently implant the stent into the vessel.

[0054] The present invention allows to achieve the following advantages. According to the paradigm generally accepted in VI and postulated by physicians which are widely considered to be Key Opinion Leaders (KOLs): "Leaving nothing behind" (bailout stenting only in case of flow-limiting dissections or high recoil after balloon dilatation), the covered stent remains in the vessel only as long as necessary to fulfill its therapeutic purposes. Due to its higher flexibility, it minimizes vessel irritation. At the end of therapy, the stent can be removed and the vessel regains its undisturbed mobility.

[0055] Improved long-term clinical results can thus be expected. New areas of application are becoming possible with this basic design: Vessels, lumens, cavities can be temporarily occluded when the stent is internally closed, e.g., as an alternative method for sterilization. Furthermore, unwanted side drains can be temporarily occluded and heal if the stent remains open on the inside. Furthermore, fractures for nasal septum correction can be temporarily supported from the inside and at the same time allow breathing. With appropriately strong stents, constrictions of the trachea / esophagus can be temporarily kept open and at the same time ensure local drug delivery. Further, the covered stent can be provided with a second outer cover that remains in the body and is, e.g., degradable, contains an active ingredient or is impregnated with an active ingredient.

[0056] Two covered stents could temporarily press the bypass graft at the connection points to the Vessel wall to achieve bypass grafting without suturing. The temporary covered stent could be equipped with a sensor that records physiological data over a period of time. Further applications are: Retaining gallstones / bladder stones with filter, drug-filled bladder (depot) equipped by physician on a situational basis, keeping clogged fallopian tubes temporarily open, sealing of fallopian tubes instead of coil, application in children: temporary stents of advantage in growth.

[0057] In the following embodiments of the present invention as well as further features and advantages of the present invention are described with reference to the Figures, wherein

[0058] Fig. 1 shows an embodiment of a stent according to the present invention having an open-cell scaffold, a cover arranged on the scaffold as well es strut elements at the proximal end of the stent, which strut elements comprise proximal ends in the form of eyelets through which a flexible annular element is threaded for engaging with a capturing device,

[0059] Fig. 2 shows a modification of the embodiment shown in Fig. 1, wherein instead of eyelets and an annular element threaded therethrough, the strut elements comprise hooks at their respective proximal end for engaging with a capturing device,

[0060] Fig. 3 shows an embodiment of a stent according to the present invention having an open-cell scaffold and a cover arranged thereon, wherein the stent comprises a docking site at its proximal end in form of a loop for engaging with a capturing device,

[0061] Fig. 4 shows an embodiment of a catheter system according to the present invention comprising a stent according to the embodiment of Fig. 1, wherein the catheter system comprises a capturing device for engaging with the flexible annular element; Fig. 4 shows insertion of the capturing device into the interior of the stent as well as bringing the capturing device into its expanded state to interact with the flexible annular element upon retraction of the capturing device,

[0062] Fig. 5 shows the capturing device of Fig. 4 engaged with the flexible annular element and in its collapsed state for withdrawing the proximal end of the stent into the lumen of the catheter,

[0063] Fig. 6 shows a further embodiment of a catheter system according to the present invention comprising a stent according to the embodiment of Fig. 1, wherein the catheter system comprises a capturing device having multiple arms for engaging with the flexible annular element; Fig. 6 shows engagement of said arms of the capturing device with the flexible annular element upon retraction of the capturing device in an expanded state of the capturing device,

[0064] Fig. 7 shows the capturing device of Fig. 6 engaged with the flexible annular element and moved into its collapsed state by withdrawing its arms into the lumen of the catheter for withdrawing the proximal end of the stent into the lumen of the catheter,

[0065] Fig. 8 shows a further embodiment of a catheter system according to the present invention comprising a capturing device in form of a spiral-shaped foil, Fig. 9 shows a further embodiment of a catheter system according to the present invention comprising a capturing device having multiple overlapping lamellae,

[0066] Fig. 10 shows a further embodiment of a catheter system according to the present invention comprising a capturing device having an inflatable balloon comprising separately inflatable hook elements,

[0067] Fig. 11 shows a further embodiment of a catheter system according to the present invention comprising a capturing device having multiple loops for engaging with hooks of strut elements of the stent’s scaffold at the proximal end of the stent,

[0068] Fig. 12 shows a further embodiment of a catheter system according to the present invention, wherein the catheter comprises a chamfer formed on an inside region of the catheter which inside region delimits an opening of the catheter through which opening the lumen of the catheter is accessible,

[0069] Fig. 13 shows a further embodiment of a catheter system according to the present invention, wherein the catheter comprises a pull cord for connecting the stent to the catheter and for retracting the proximal end of the stent into the lumen of the catheter,

[0070] Fig. 14 shows details of the pull cord of the embodiment of Fig. 13, wherein the pull cord is connected to the scaffold so as to particularly allow a radial compression of the scaffold (e.g. when pulling on both ends of the pull cord),

[0071] Fig. 15 shows a further detail of the pull cord of the embodiment of Figs. 13 and 14, according to which the pull cord can be threaded through open cells of the stent’s scaffold at the proximal end of the stent or through through-openings, each through-opening being formed in the vicinity of an inflection point at the proximal end of the stent (i.e. where two adjacent struts meet to form a crown),

[0072] Fig. 16 shows a further embodiment of a catheter system according to the present invention comprising a stent that is permanently connected to the catheter, wherein the stent is configured to be implanted for a certain time period and to be retracted by means of the catheter after lapsing of said time period; here, the stent is permanently connected to the catheter even during the time period during which it is implanted in the vessel (e.g. to seal a rupture in the vessel wall).

[0073] Fig. 17 shows a further embodiment of a catheter system according to the present invention comprising a stent that can be released and completely detached from the catheter and thereafter re-captured and returned into the lumen of the catheter (e.g. to adjust the position at which the stent is to be implanted or to remove the scaffold or stent from the vessel entirely).

[0074] Fig. 1 shows an embodiment of a stent 1 according to the present invention, the stent comprising a self-expandable scaffold 10 extending along an axial direction x of the stent 1 / scaffold 10 and comprising a plurality of open cells 11 formed by a plurality of circumferential strut structures 12 connected by axial struts 13 extending along the axial direction x. Preferably, each circumferential strut structure 12 comprises a plurality of struts 120 connected to one another in a circumferential direction of the scaffold 10, each two neighboring connected struts 120 forming an inflection point 121 of the respective circumferential strut structure 12, wherein a minority of the inflection points 121 of each circumferential strut structure 12 is connected via an axial strut 13 to a neighboring circumferential strut structure 12. According to Fig. 1, the respective circumferential strut structure 12 comprises a meandering shape, in particular.

[0075] Furthermore, the scaffold 10 comprises an outside facing away from an interior (or lumen) 14 of the stent 1 surrounded by the scaffold 10. This interior 14 forms a passage for blood through the stent 1 in an implanted state of the stent 1. Further, the stent 1 comprises a proximal end 15 configured to be connected to a catheter 2 to allow returning at least the scaffold 10 into a lumen 20 of the catheter 2. Finally, the stent 1 comprises an (e.g. cylindrical) cover 16 arranged at least on the outside of the scaffold 10, the cover 16 being further configured to carry a drug to be administered to the patient having the stent implanted and / or to seal a vascular rupture of the patient.

[0076] According to a preferred embodiment, straight strut elements 17 of the scaffold 10 are provided at the proximal end 15 of the stent 1, wherein the strut elements 17 are provided with eyelets 18 at their respective proximal end. The number of strut elements 17 / eyelets 18 can range according to an embodiment from three to a maximum of the number of crowns (inflection points 121) at the corresponding proximal end 15 of the stent 1. Through the eyelets 18, a flexible annular element 19 is threaded (e.g. a plastic thread or a flexible nitinol wire or any other suitable flexible elongated element) forming a closed ring with a diameter equal to that of the of the expanded stent 1. This is configured to be grasped by a suitable capturing device of a catheter and enables the scaffold 10 or stent 1 to be withdrawn into a lumen of the catheter.

[0077] As shown in Fig. 2, instead of eyelets 18, also hooks 18a may serve to grasping of the scaffold 10 / stent 1 with an appropriate capturing device of a catheter.

[0078] Furthermore, as an alternative to Figs. 1 and 2, the covered open-cell scaffold 10 may also be unilaterally tapered according to Fig. 3 and may terminate with a single docking site 18b at the proximal end 15 of the stent 1 for capturing the tip of the stent 1 at its proximal end 15. Particularly, as shown in Fig. 3, the docking site 18b can be a loop.

[0079] The cover 16 of the retractable covered stent 1 is preferably made of a biological material, which has distinct advantages over a polymeric cover, particularly for small vessel diameters, including intrinsic antithrombogenicity. The design of the biological particularly supports removability of the implant 1 from the implantation site / vessel. To this end, the biological cover 16 is preferably prevented from growing in according to an embodiment of the present invention. On the other hand, the biological cover is preferably prevented from growing (see also above).

[0080] To ensure the removability of the stent 1, there are three preferred general examples that are described in the following:

[0081] (i) A one-piece biological cover that does not show significant ingrowth or ingrowth during the implantation period;

[0082] (ii) A one-piece biological cover that grows tightly with the vessel wall (ingrowth) and, in particular, only the scaffold carrying the cover initially is removed during explantation;

[0083] (iii) A two-part biological cover, in which the outer part connects to the vessel wall during the time period during which the stent is implanted / resides in the vessel and the inner part of the cover allows explantation of the stent.

[0084] Regarding the one-piece biological cover (i) that does not show significant ingrowth or ingrowth during the implantation period, both collagen-containing tissue of animal origin (e.g., pericardium) and bacterial nanocellulose are suitable for this option. Both materials are dry on the implant after processing. Pericardium chemically cross-linked with glutaraldehyde cannot be enzymatically converted in the body, which is why ingrowth is not possible. The cover for the re-sheathable stent is therefore made from ultra-thin pericardium cross-linked with glutaraldehyde under high pressure. The crosslinking under high pressure results in a very thin cover with a very smooth surface similar to a polymer film. The crosslinking can be performed directly on the outside of the scaffold without additional sutures, which also prevents stable adhesion. This is preferably followed by the process of stabilized drying of pericardium.

[0085] Further, bacterial nanocellulose cannot be degraded or converted in the body due to the absence of cellulases in the body, which is why ingrowth is also not possible. The cover 16 for the re-sheathable stent can be made out of bacterial nanocellulose directly grown and processed on the scaffold. For this purpose, growing the nanocellulose on silicone surfaces or on a rotating mold in a bioreactor is possible. Additional seams are also not necessary, since a three-dimensional form-fit is achieved with the scaffold 10 of the stent 1. The thickness of the material can be controlled via the cultivation time. Due to the final drying without stabilizers, the cellulose is permanently reduced in thickness.

[0086] Furthermore, regarding said one-piece biological cover that grows tightly with the vessel wall (ii), collagen-containing tissue of animal origin (e.g. pericardium) is suitable, which is explicitly not treated with a chemical crosslinker, but is natively processed according to the process of stabilized drying. After implantation, the stabilizers are flushed from the pericardium and the remaining rehydrated collagen-containing extracellular matrix provides an excellent substrate for proliferation of cells of the vessel wall. The use of native dried tissue allows complete ingrowth of the cover, which thus stably attaches to the vessel wall and remains in the body upon explantation. The natively dried pericardium is produced by the process of stabilized drying and additionally maximally reduced in thickness by a subsequent pressing step. Preferably, very thin pericardium from young animals is used to achieve a thickness of less than 80 micrometers (thickness of synthetic polymers currently used for covered stents). Stable fixation of the cover is possible by classical suturing (degradable suture material) of a shaped part of the cover, that is cut e.g. by a CCh-laser, with the scaffold of the stent.

[0087] Regarding the afore-mentioned two-part biological cover (, both collagen-containing tissue of animal origin (e.g., pericardium) as well as bacterial nanocellulose, also in combination, are suitable.

[0088] Example a): “Both inner and outer part of the cover from pericardium”

[0089] Since two layers of pericardium are superimposed (i.e. an outer and an inner part of the cover), very thin selected pericardium from young animals is used to achieve a thickness of less than 50 pm. First, as described in (i) above, an ultrathin pericardium chemically crosslinked under pressure with glutaraldehyde pericardium without suture material is attached as a cover to the scaffold. Subsequently, as described above in (ii), an additional outer part of the cover of very thin natively dried pericardium is applied with degradable suture material. After implantation, the outer part of the cover grows in completely, while the inner part of the cover forms a barrier and allows explantation of the repositionable stent. Example b): “Inner part of cover made of cellulose, outer part of cover made of pericardium” First, as described in (i) above, a cover of bacterial nanocellulose is grown and processed on the scaffold. The cultivation time is selected in such a way that the cover of bacterial nanocellulose stably envelops the scaffold and forms a continuous barrier. The cellulose grown in this way is then dried without stabilizers and permanently reduced in thickness. In the dried state, thicknesses of 30 micrometers are achievable and sufficient. Subsequently, as described in example a), an outer cover of natively dried pericardium is then applied as described in example a). After implantation, the outer part of the cover completely grows in, as in example a), while the inner part of the cover forms a barrier and allows explantation of the repositionable stent.

[0090] Example c): “Both the inner and the outer part of the cover made of cellulose”

[0091] First, as described in example b), an inner cover of bacterial nanocellulose is applied to the scaffold. Drying, optionally under radial pressure, results in a mechanically and structurally long-term stable layer of bacterial nanocellulose. Subsequently, the scaffold thus obtained, covered with a layer of cellulose (inner part), is coated with a second layer of bacterial nanocellulose as described in (i) above. Preferably, between the two (inner and outer) parts of the cover there is no connection by cellulose fibers, but a bonding is merely accomplished by positive fit and hydrogen bonds. The cellulose grown in this way on the scaffold is rinsed. Both layers of cellulose (inner and outer part) are then dried without stabilizers. Drying takes place in surface-structured press molds under radial pressure. As a result, surface structures are imprinted only in the outer part of the cover, which allow the outer cellulose layer to adhere to the vessel wall. The surface structures are stable over the long term due to drying without stabilizers. The surface structures can be in the form of grooves, spirals, irregularly distributed depressions, etc., in order to enable the best possible adhesion.

[0092] Both biological tissues (pericardium and cellulose) are preferably formed from a matrix of biological fibers. Microscopically, both tissues represent sponge-like structures, which can optionally be loaded with drugs. The loading can also take place immediately prior to implantation in the course of rehydration. Alternatively, an additional drug coating of the dried tissues on the outside is also possible. According to different preferred embodiments of the present invention, several capture and retraction mechanism can be realized in conjunction with the stent 1 according to the present invention.

[0093] Fig. 4 shows a catheter system 2 comprising a stent 1 according to the present invention (e.g., as shown in Fig. 1), wherein the catheter system 2 further comprises a catheter 3 (not shown, but used in the same manner as in Figs. 6 and 7) having a capturing device 4, which can be shaped as an umbrella 4. The umbrella 4 can be advanced out of a lumen 30 (not shown, but used in the same manner as in Figs. 6 and 7) of the catheter 3 in a direction D into the interior 14 of the stent 1 / scaffold 10 in a collapsed state of the umbrella 4 (cf. Fig. 4). The interior 14 is the region / lumen surrounded by the scaffold 10 (including the strut elements 17 if present). When the proximal ends of the pivotable umbrella legs are positioned behind the flexible annular element 19 threaded through the eyelets 18, the umbrella 4 can be stretched open (expanded state of umbrella 4) and will become engaged with the flexible annular element 19 when retracted in the opposite direction D’. By expanding the umbrella 4 the surface plane xx got accordingly expanded and reaches through the outer circumference of the stent 1 / scaffold 10 to engage it. When it is subsequently closed again (collapsed state), the proximal end 15 of the stent 1 is radially contracted and can be returned into the catheter in direction D' as shown in Fig. 5.

[0094] Figs. 6 and 7 show a further embodiment of a catheter system 2 having a capturing device 4 for capturing a stent 1 according to the present invention having said flexible annular element 19, wherein the capturing device 4 comprises multiple arms 40, each arm 40 comprising an end portion 41 (e.g. in form of a barb). These end portions 41 are pushed between the scaffold 10 and the vessel wall and hook into the flexible annular element 19 during retraction in direction D. Due to the closing of the arms 40 during the retraction into the lumen 30 of the catheter 3, the stent 1 is also radially contracted proximally.

[0095] Fig. 8 shows a further embodiment of a catheter system 2 having a capturing device 4 for capturing a stent 1 according to the present invention. Here, partial crimping of the proximal end 15 of the stent 1 is achieved for capturing the stent 1. For this purpose, the capturing device 4 comprises a foil 45 (e.g. made from a nickel titanium alloy such as Nitinol) that is rolled up into a spiral. The outer edge of the spiral-shaped foil 45 is crimped over the proximal end 15 of the stent 1 and is rotated around the axial direction x of the stent 1 in such a way that a stent portion at the proximal end 15 moves inwards into the spiral-shaped foil 45 and is thus pushed radially towards the center of the spiral-shaped foil 45. At the same time, the outer edge, which continues to rest against the vessel wall, slides over an adjacent stent portion of the proximal end 15 of the stent 1, etc. Thus, with multiple rotations of the foil 45 about the axial direction x, the proximal end 15 of the stent 1 is completely pulled into the spiral-shaped foil 45 and undergoes a radial contraction.

[0096] Fig. 9 shows another variant of this active principle of a capturing device 4 of a catheter system 2 according to the present invention. Here, the capturing device 4 comprises multiple thin lamellae 42 mounted on top of each other so as to overlap in the circumferential direction of the catheter 3. These lamellae 42, similar to an iris diaphragm, can be moved relative to one another in the circumferential direction, thus reducing an inner diameter of the tubular structure they form. When this tubular structure is fully opened, the inner diameter essentially corresponds to the outer diameter of the proximal end 15 of the stent 1, so that the lamellae 42 can be slid over the stent 1. By advancing the catheter 3 the lamellae 42 are pushed over each other again, thus reducing the inner diameter of the tubular structure they form and the proximal end 15 of the stent 1 is grasped by the lamellae 42.

[0097] Furthermore, Fig. 10 shows an embodiment of a catheter system 2 according to the present invention having a capturing device 4 comprising an inflatable balloon 43 with separately fillable hook elements 44 on its surface. When the balloon 43 and the hook elements 44 are inflated, the hook elements 44 become entangled in the flexible annular element 19 during retraction. If the balloon 43 is deflated, the hook elements 44 remain inflated, and the balloon 43 will radially contract the proximal end 15 of the stent 1 and allow retraction into the lumen 30 of the catheter 3.

[0098] In the above, the flexible annular element 19 can be replaced by a similar element that can engage with the capturing device 4, this element may also be formed by a portion of the stent or scaffold itself. Furthermore, as shown in Fig. 11, in case of a stent 1 according to the embodiment shown in Fig. 2, the hooks 18a may also engage with loops 46 of flexible elongated elements 4 such as ropes or wires in order to connect the stent 1 to the catheter 3 for retraction of the stent 1.

[0099] Furthermore, as shown in Fig. 12, in all embodiments described herein, the catheter 3 preferably comprises a chamfer 33 formed on an inside region 31 of the lumen 30 of the catheter 3, which inside region 31 delimits an opening 32 of the catheter 3 through which opening 32 the lumen 30 of the catheter 3 is accessible, i.e., for advancing the stent 1 out of said lumen 30. Particularly, the chamfer 33 reduces the risk of damaging the stent 1 upon retraction into the lumen 30.

[0100] Fig. 13 shows in conjunction with Fig. 14 a catheter system 2 according to the present invention that allows in principle to implant a covered stent 1 according to the present invention, wherein the stent 1 can stay connected to the catheter 3 while being implanted allowing to retract the stent 1 at any time. However, due to the design of the catheter system 2, the system 2 also allows to permanently release the stent 1 in the vessel and leave it at the implantation site as a permanent implant.

[0101] Thus, the present embodiment is intended for use in two scenarios, wherein the main difference to other embodiments of the present invention is, that the covered stent 1 can remain permanently in the vessel if necessary.

[0102] In the first scenario, the stent 1 is implanted in the area of the rupture of the vessel by advancing it out of the lumen 30 of the catheter 3 using an inner shaft 5 that comprises a stop for the proximal end 15 of the stent 1, wherein the stent 1 remains there for e.g. several minutes. The inner shaft 5 is slidably arranged in the lumen 30 of catheter 3. By maintaining blood flow in the vessel through the stent’s interior 14, the physician has a longer period of time to seal the vessel than with balloon dilatation. Once the bleeding has stopped after e.g. several minutes, the stent 1 can be retracted into the lumen 30 of the catheter 3 using a pull cord 4 according to the embodiment shown in Figs. 13 to 15, which pull cord 4 runs through the catheter 3 and allows to pull the proximal end 15 of the stent against the stop 50, wherein the proximal end 15 is radially contracted upon pulling it into the (preferably chamfered) opening 32 of the catheter 3. As shown in Fig. 15, the pull cord 4 comprises two ends 400 and is threaded through open cells 11 at the proximal end 15 of the stent 1 or through through-openings 110 formed in the scaffold 10 at the proximal end 15 of the stent 1. Thus, when pulling on the two ends 400 of the pull cord 4, the proximal end 15 of the stent 1 radially contracts with support of the stop 50 and chamfer 33.

[0103] However, if bleeding has not stopped after e.g. several minutes of being sealed by the stent 1, the stent 1 is completely released and detached from the catheter 3, remaining permanently in the vessel as a stent graft.

[0104] Since no capture mechanism is required in this design, the proximal end 15 of the stent 1 does not need to be specially modified and extended to include appropriate hook or eye elements. The open cells 11 at the proximal end 15 can be used for retraction by means of the pull cord 4 as described above. When both ends 400 of the pull cord 4 are pulled simultaneously (or one end 400 is pulled with the other end 400 being fixed), the proximal end 15 of the stent 1 contracts radially and can be retracted into the catheter 3. For complete and permanent release of the stent 1, the pull cord 4 is pulled out of the scaffold (cf. lower portion of Fig. 14) by releasing one end 400 and pulling on the other end 400 of the pull cord 4.

[0105] Furthermore, Fig. 16 shows an embodiment of the catheter system 2, wherein the stent 1 is permanently connected to the inner sheath 5 of the catheter 3. In this embodiment, the stent 1 is implanted only temporarily, e.g. for sealing a vessel rupture and / or for applying a drug. Afterwards, the stent 1 is retracted into the lumen 30 of the catheter 3 by means of the inner sheath 5 that is connected to the stent 1 and removed from the vessel.

[0106] Furthermore, Fig. 17 shows a further embodiment of a catheter system 2 according to the present invention (cf. Fig. 17 (a)) that allows to release a stent 1 according to the present invention at the implantation side in a vessel, capture and retract it into the lumen 30 of the catheter 3 (cf. Fig. 17 (b)-(d)), for instance for the purpose of repositioning the stent, and to release it again (cf. Fig. 17 (e)-(h)). The inner shaft / capturing device 4 can be used to engage with a docking site 19 of the stent 1 for retracting the stent 1 into the lumen 30 of the catheter 3. The docking site 19 can e.g. the flexible annular element 19 described earlier or other suitable structures. For releasing the stent 1, the capturing device / inner shaft 4 can be used to push the stent 1 out of the lumen 30 of the catheter 3. As indicated in Fig. 17, the capturing device / inner shaft 4 can comprise a hook at its distal end to engage with the docking site 19.

Claims

Claims1. A stent (1), comprising: a self-expandable scaffold (10) extending along an axial direction (x) comprising a plurality of open cells (11) formed by a plurality of circumferential strut structures (12) connected by axial struts (13) extending along the axial direction (x), the scaffold (10) comprising an outside facing away from an interior (14) of the stent (1) surrounded by the scaffold (10), the interior (14) forming a passage for blood through the stent (1) in an implanted state of the stent (1), a proximal end (15) configured to be connected to a catheter (3) to allow returning at least the scaffold (10) into a lumen (30) of the catheter (3), and a cover (16) arranged at least on the outside of the scaffold (10), the cover (16) being further configured to carry a drug to be administered and / or to seal a vascular rupture.

2. The stent according to claim 1, wherein the proximal end (15) of the stent (1) comprises strut elements (17) of the scaffold (10), each strut element (17) comprising an eyelet (18) at a proximal end of the respective strut element (17) for pulling on the scaffold (10), wherein particularly a flexible annular element (19) extends through the eyelets (18) for pulling on the scaffold (10).

3. The stent according to claim 1, wherein the proximal end (15) of the stent (1) comprises strut elements (17) of the scaffold (10), each strut element (17) comprising a hook (18a) at a proximal end of the respective strut element (17) for pulling on the scaffold (10).

4. The stent according to one of the preceding claims, wherein the cover (16) covers at least 90% of the outside of the scaffold (10), wherein preferably the cover (16) covers the outside of the scaffold (10) completely.

5. The stent according to one of the preceding claims, wherein the cover (16) comprises or is made out of one of the following materials: a biocompatible plastic material, a biological tissue.

6. The stent according to one of the preceding claims, wherein the cover (16) is a one- piece cover, that is configured to prevent ingrowth or that is configured to prevent ingrowth during a time period during which the stent is residing in a patient, and wherein the scaffold (10) is configured to be returned into the catheter (3) together with the cover (16).

7. The stent according to one of the claims 1 to 5, wherein the cover (16) is configured to allow ingrowth of the vessel wall into the cover during a time period during which the stent (1) resides in the vessel of a patient, wherein the scaffold (10) is configured to be returned into the catheter (3) without the cover (16).

8. The stent according to one of the claims 1 to 5, wherein the cover (16) comprises an inner part and an outer part covering and surrounding the inner part, the outer part forming an outer surface of the cover (16) for contacting the vessel wall, wherein the outer part is configured to allow ingrowth of the vessel wall into the outer part during a time period during which the stent (1) is residing in a vessel of a patient to connect the vessel wall to the outer part of the cover (16), and wherein the scaffold (10) is configured to be returned into the catheter (3) together with the inner part and without the outer part.

9. A catheter system (2) comprising a stent (1) according to one of the preceding claims, and a catheter (3) comprising a lumen (30) configured to deliver the stent (1) to an implantation site, wherein the catheter (3) is configured to be connected to a proximal end (15) of the stent (1) to allow returning at least the scaffold (10) into the lumen of the catheter (3).

10. The catheter system according to claim 9, wherein the catheter (3) comprises a capturing device (4) configured to assume a collapsed state and an expanded state, wherein the capturing device (4) is configured to be inserted into the interior (14) of the stent (1) in the collapsed state and to be brought into the expanded state when residing in the interior (14) of the stent (1) so that the capturing device (4) engages with the flexible annular element (19) extending through said eyelets (18) of the proximal end (15) of the stent (1) when being retracted, wherein when the capturing device (4) is subsequently brought to its collapsed state, the proximal end (15) of the stent is radially contracted so that it can be returned into the lumen (30) of the catheter (3).

11. The catheter system according to claim 9, wherein the capturing device (4) comprises several arms (40) which are configured to be inserted into the interior (14) of the stent (1), each arm (40) having an end portion (41) configured to engage with the flexible annular element (19) extending through said eyelets (18) of the proximal end (15) of the stent (1) when the arms (40) are subsequently retracted into the catheter (3), wherein the arms (40) are configured to move towards one another so that the proximal end (15) of the stent (1) is radially contracted and can be returned into the lumen (30) of the catheter (3).

12. The catheter system according to claim 9, wherein the capturing device (4) comprises an inflatable balloon (43) which is configured to be inserted into the interior (14) of the stent (1), the balloon (43) having separately inflatable hook elements (44) protruding from an outer surface of the balloon (43), wherein the hook elements (44) are configured to engage with the flexible annular element (19) when the balloon (43) and the hook elements (44) are inflated and the balloon (43) is retracted, wherein the balloon (43) is configured to be deflated while the hook elements (44) remain inflated so that the proximal end (15) of the stent (1) is radially contracted and can be returned into the lumen (30) of the catheter (3).

13. The catheter system according to claim 9, wherein the capturing device (4) comprises a foil (45) formed out of a super-elastic metal alloy, wherein the foil (45) comprises aspiral shape and is configured to be rotated around the axial direction (x) of the stent (1) so as to successively move the foil (45) over the proximal end (15) of the stent (1), wherein due to the spiral shape, the proximal end (15) of the stent (1) is radially contracted and can be returned into the lumen (30) of the catheter (3) upon retracting the foil (45) together with the proximal end (15) of the stent (1) into the lumen (30) of the catheter (3).

14. The catheter system according to claim 9, wherein the capturing device (4) comprises a tubular structure comprising a plurality of lamellae (42) overlapping one another and configured to move relative to one another in a circumferential direction of the tubular structure to reduce an inner diameter of the tubular structure, wherein an end section of the tubular structure is configured to move out of the lumen (30) of the catheter (3) to be slid over the proximal end (15) of the stent (1), wherein the lamellae (42) are configured to be pushed over one another when the catheter (3) is advanced relative to the end section of the tubular structure so that the inner diameter of the tubular structure is reduced allowing the tubular structure to grab the proximal end (15) of the (1) stent for retracting the proximal end (15) of the stent into the lumen (30) of the catheter (3).

15. The catheter system according to claim 9, wherein the proximal end (15) of the stent is configured to be connected to the catheter (3) during a time period during which the stent (1) is temporarily implanted into a vessel to seal a rupture of the vessel and / or to administer a drug, wherein the catheter (3) is configured to remain connected to the proximal end (15) of the stent (1) during said time period to allow returning the stent (1) into the lumen (30) of the catheter (3) after lapsing of said time period when the bleeding of the vessel has stopped, or wherein the stent (1) is configured to be completely detached from the catheter (3) so as to remain in the vessel as a permanent implant.

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