WO2021018367A1

WO2021018367A1 - Medical implant for constricting a vein

Info

Publication number: WO2021018367A1
Application number: PCT/EP2019/070189
Authority: WO
Inventors: Carsten Giebmeyer; Beate Walter; Martin Bauer
Original assignee: Angiomed Gmbh & Co. Medizintechnik Kg
Priority date: 2019-07-26
Filing date: 2019-07-26
Publication date: 2021-02-04

Abstract

The present invention relates to a medical implant (10) for constricting a vein (V) used in a permanent arteriovenous access, the implant comprising: - an expandable sleeve (11), the sleeve being suitable for being arranged so as to at least partially surround the vein (V), wherein the sleeve (11) is arranged so that it can be selectively expanded to constrict the vein (V), thereby reducing the cross-sectional diameter of the vein (V).

Description

MEDICAL IMPLANT FOR CONSTRICTING A VEIN

Technical field

The present invention relates to a medical implant which can be used for constricting a vein used in a permanent

arteriovenous (AV) access.

Technical background

In patients with renal malfunctions, a haemodialysis

treatment is often performed. During that treatment, blood from the patient is led out of a vein via an injection needle and is then led to a dialysis machine. In that dialysis machine, the blood will be filtered from the waste. The cleaned blood is reintroduced into the vein ("outflow vein") via a separate needle.

Dialysis patients typically undergo three dialysis sessions per week that require three to five hours or more each to complete. There are three common ways to conduct a dialysis which are an autogenous AV access (which is commonly referred to as a "fistula") , a non-autogenous AV access (commonly referred to as a "graft") and using a central venous

catheter. A fistula or a graft AV access are established in order to reduce the duration of such a haemodialysis session down to three to five hours and to optimise the clearance values. To establish a permanent AV access with a high flow rate in the outflow vein, a vein (typically in an arm) is connected to an artery in the same arm. The joint of the vein to the artery is called an "anastomosis".

When providing an AV fistula, it is common that the vein matures over the course of several weeks and expands in its cross-section. The vein also becomes somewhat less flexible. This effect is to some extent intended and desired. However, it can be the case that the lumen of the vein increases too much in the cause of conducting the dialysis, which leads to the so-called "high flow syndrome". In such a case, a

significant proportion of the pumping performance of the heart is used for the fistula and the supply of the rest of the body with blood becomes insufficient. To compensate for this, the heart grows, which however leads to a higher risk of a heart failure ("high output cardiac failure") . A further problem is the vascular access steal syndrome.

To deal with these issues, it is known to suture parts of the expanded vein together at the junction between the artery and the vein so as to reduce its cross-sectional area.

Alternatively, some suturing material could be wrapped around the vein so as to constrict it (banding) . Further ways of dealing with such expanded veins are distal radial artery ligation (DRAL) , proximal radial artery ligation (PRAL) , and revision using distal inflow (RUDI) .

One problem with those methods is that they require,

subsequent to the establishment of the AV fistula, a separate surgical procedure, with corresponding discomfort to the patient. Furthermore, at least some of those methods do not allow for a fine adjustment of the flow rates, since the physician constricting the vein needs to make a best guess in terms of vessel reduction. Whilst it is possible, based on the physician⁷ s experience and based on flow measurements conducted prior to the procedures mentioned above, to

estimate the required flow reduction and to thereby determine the vein diameter to be achieved, it is also the case that a small reduction in vein diameter has a significant impact on flow rates. Thus, making an error in the adjustment in the vein diameter has a significant impact on the flow and, accordingly, on patient health. Accordingly, a need exists for a fine tuning of the vein diameters. Further, it is also only possible to determine the overall success of the procedure some time after the surgery has been performed. This is because during the surgery, the patient's body is in an abnormal situation, and parts of the body next to the surgical site will be swollen. This has an effect on the blood flow through the vein, so that any measurements obtained regarding blood flow during the surgery are not necessarily indicative of the situation after surgery and once swelling has receded.

Smeary of the invention

It is an object of the present invention to provide a device which is capable of adjusting the flow rates through a vein in an AV fistula after the AV fistula has been created.

The invention is defined by the medical inplant of claim 1 and by the kit of claim 10. Preferred embodiments are defined in the dependent claims.

According to the invention, a medical inplant is provided which can be used for constricting a vein used in a permanent AV access. Such a medical inplant should be made of or coated with a biocompatible material which can be implanted in a human body. Without wishing to be bound by this, suitable materials would be e.g. PTFE.

The inplant comprises an expandable sleeve which can be arranged so as to at least partially surround the vein. That is, the sleeve can be formed to at least partially wrap around the vein, even though it does not need to entirely wrap around the vein - it suffices if it is wrapped so as to be capable of constricting that vein when being expanded. The sleeve is expandable, that is, it can be made to increase in its volume. The sleeve is arranged so that it can be selectively expanded to constrict the vein, thereby reducing the cross-sectional diameter of that vein. When the sleeve is provided so as to at least partially surround the vein, an expansion of that sleeve will compress the vein. This will reduce its cross- sectional diameter.

By implanting the medical implant when providing the AV access, one provides a means of, subsequent to the surgery for providing the AV access, accurately reducing the diameter of the vein post-surgery. For example, one can, by means of an externally provided means, cause the sleeve to expand so as to constrict the vein. When externally monitoring the flow rate using flow control by ultrasound some time after

surgery, it becomes possible to adjust the flow rate without the flow rate being affected by swelling of the body close to the implant. It is also to be noted that the implant can also be implanted some time after the fistula has been created, for example in a minimally invasive surgical procedure.

It is particularly preferred if the expansion capability of the sleeve is also reversible, that is, if one can not only expand the sleeve but also contract it. This would give even more flexibility in the adjustment of the flow rate through the vein. By providing a medical implant which is adjustable from outside of the body, i.e. when the implant is implanted, one has the possibility of an accurate external adjustment of the flow through the vein in an AV access.

It is preferred that the sleeve is arranged to be wrapped around the vein to thus form a tube so that, in the tubular state, the wrapped-over end of the sleeve can be affixed to the remainder of that sleeve. I.e • / the sleeve itself has, in the state in which it is shipped and prior to implanting in the patient's body, an essentially flat shape and only assumes an essentially tubular shape during implantation.

Such a medical implant is easy to ship and is also very versatile, since it can be adjusted in its diameter to the diameter of the vein it is to be used with. Further, since it is provided in a flat shape and since it is only wrapped around the vein during surgery, it does not need to be slid over a severed end of the vein but could, in principle, also be arranged over an intact vein.

By the wrapped-over end of the sleeve being affixed to the remainder of the sleeve, it is meant that the wrapped-over end is permanently fixed to the remainder of the sleeve. This could be achieved by suturing the ends of the sleeve to each other to thereby obtain a tube. However, an affixation by means of an adhesive or by welding or by any other suitable means is also possible. It is preferred that the wrapped-over and is to be sutured to the remainder of the sleeve since suturing is a technique which is widely used in surgery. By the affixation of the wrapped-over end to the remainder of the sleeve, a tubular shape is formed. This tube can then be used for constricting the vein.

In an alternative preferred variant, the sleeve further comprises a scaffolding structure. This scaffolding structure is arranged to retain the sleeve in a configuration where it at least partially surrounds the vein. By providing such a scaffolding structure, one avoids the need to affix one end of the sleeve to the remainder of the sleeve, which makes implanting the implant easier. The scaffolding structure could be incorporated into the sleeve and could, for example, be made of a shape memory alloy such as nitinol. This

scaffolding could, when made from such a material, cause the sleeve to automatically assume a configuration which at least partially wraps around a vein, thus simplifying the placement of the implant.

It is also possible that the scaffolding is provided

separately from the expandable sleeve and is only subsequent to the placement of the sleeve provided so as to surround the sleeve and so as to hold the sleeve in place in the form of a frame. The scaffolding would then have a C-shaped cross- sectional shape, which would then cause the sleeve to have the same shape. In such a configuration, the medical implant would surround the vein as a bracket. The sleeve would be held shut by means of the spring force of the scaffolding and would not need to be sutured shut or would need to have its ends otherwise affixed to each other to form a tube. Whilst in such a configuration, a closed tube is unlikely going to be achieved, the compressive forces exerted by the expandable sleeve on the vein would nevertheless be sufficient for the intended purpose of constricting the vein.

An alternative preferred embodiment would be that the sleeve is formed in a tubular configuration which can be slid over a vein. This avoids the need to provide a tubular (or

essentially tubular) configuration during implant placement.

In a preferred variant, the sleeve comprises one or more balloons which can be inflated and deflated by a fluid to expand and contract the sleeve. Providing such balloons inside the sleeve allows for an easy to implement way of making the medical implant expandable and contractible. The fluid with which they are to be inflated could be a

physiological sodium chloride solution. However, other fluids (e.g. silicone oil) are equally possible.

It is particularly preferred if the implant further comprises a conduit having one end connected to the sleeve, with the other end of the conduit preferably being connected to a port. The conduit is arranged to allow a fluid to be

introduced into or extracted from the one or more balloons to thereby inflate or deflate them. Having such a conduit makes it easier to inflate those balloons. If one end of the conduit is connected to a port, it becomes possible to provide this port close to a patient's skin so that the implant can, if need be, easily inflated or deflated by accessing that port. This make inflating or deflating the sleeve much less invasive. The conduit can be made of a thin flexible plastic tube (again preferably made of or coated with a biocompatible material) , with the port being placed directly underneath the skin of a patient.

It is particularly preferred if the sleeve comprises a plurality of balloons which are separated from each other. By having a plurality of balloons, it becomes possible to vary the pressure on the vein. It is preferred that the balloons are arranged so that they can be wrapped around the vein - i .e • / the balloons are provided so that each such balloon will at least partially encircle the vein, rather than being aligned parallel to the vein. This makes it easier to control the diameter of the vein. The balloons could be made of or could be coated by PTFE, which is a well known biocompatible material .

It is also preferred that some and preferably all of the balloons are fluidically connected to each other. This means that a fluid can pass from one balloon to the other balloon. This makes it possible to inflate all of the balloons at the same time simply by introducing a fluid into one of the balloons the fluid will then also enter into the further balloons. It is preferred that the balloons are fluidly connected to each other by valves which are arranged to let the fluid pass between the balloons in one direction only. By such a configuration, it also becomes possible to only inflate one balloon if one wants to do so, namely by

introducing, via a potential conduit, a tube which enters into the respective balloon to be inflated. The valve will then prevent the fluid from entering into the neighbouring balloons. This allows for a greater flexibility in inflating the implant.

It is also preferred that when there are several such

separated balloons, there are membrane portions between the balloons which can be affixed to each other. Since those membrane portions are not meant for being inflated, it becomes possible to suture them to each other without puncturing the balloons.

According to a further aspect of the invention defined in claim 10, a kit is provided which comprises an implant as defined in one of the preceding claims and an inflatable balloon which is suitable for being introduced into the vein which is to be constricted by the implant. In such a kit, the vein diameter which is to be achieved after the flow

reduction procedure can be set up by placing the balloon (which is typically part of a catheter such as an PTA

catheter) inside the vein close to the anastomosis to the artery. After the balloon is placed inside the vein close to the anastomosis to the artery, and after the PTA

("percutaneous transluminal angioplasty") balloon is inflated to the intended diameter, the sleeve can be wrapped tight on top of the catheter of the balloon and the excess vein wall material will be sutured to the outside of the vein together with the balloon material of the implant. In that

configuration, the sleeve has a somewhat tubular form.

Afterwards, the PTA catheter is removed. Some time after the surgery, the diameter of the tubular implant can be adjusted by means of inflating or deflating the sleeve. By inflating the sleeve, the inner diameter of the wrapped sleeve will decrease, whilst by evacuating the chambers, the inner diameter of the sleeve will increase. Accordingly, a fine adjustment of the vein diameter can be achieved. If one then conducts continuous flow measurements during the vein

diameter adjustment procedure, the physician can be informed of the achieved flow rate. Accordingly, one can, with a high degree of accuracy, adjust the flow for each patient

individually. Brief description of the drawings

Figure 1 shows an AV fistula with an attached implant.

Figure 2 shows an implant according to the invention in the Undeployed configuration.

Figure 3 shows an implant in a tubular configuration.

Figure 4 shows an implant having a scaffolding structure.

Figure 5 shows a method of using the implant with a balloon catheter.

Figure 6 shows steps which can be taken in the use of the implant shown in Figure 3.

Detailed description of the drawings

Figure 1 shows schematically an implant 10 in the implanted state. As can be seen from that drawing, an artery A has been joined to the vein V at a junction (anastomosis) J. This has been achieved by severing the vein V and joining one of its ends to the artery A. The remaining dead end DE of the vein V has been cauterised.

Wrapped around the vein V close to the junction J is the implant 10. This implant 10 comprises an expandable sleeve 11 which is wrapped around the vein V. This sleeve 11 in turn comprises three balloons 16', 16 9 9 , 16 9 9 9 which also wrap around the vein V and which are separated by membrane

portions 18. These membrane portions 18 are affixed to each other so as to cause the expandable sleeve 11 to assume the tubular shape.

Connected to all of the balloons 16' , 16 9 9 , 16 9 9 9 is a conduit 12 which terminates in a port 26. Through the port 26, a fluid can be introduced into the conduit 12. The fluid flowing inside the conduit 12 will then be led to the

balloons 16' , 16 9 9 , 16 9 9 9 to thereby inflate them. It is also possible to extract a fluid from the conduit 12 via port 26 to thereby deflate the balloons 16', 16 9 9 , 16 9 9 9 By

inflating the balloons 16', 16 9 9 , 16 9 9 9 , the medical implant 10 reduces the cross-sectional diameter of the vein V so as to reduce blood flow, which can be used for treating the high flow syndrome.

Even though not shown in the drawings, the port 26 will be placed close to the patient's skin so that it is accessible by means of an injection needle connected to a syringe. A suitable port for such a purpose is the low-profile access port disclosed in US 2014/0207086 Al, the contents of which are incorporated by reference. A receiving cup of that port would be placed just underneath the patient's skin and could be accessed by piercing the skin using a hypodermic needle. The other end of the port would be connected to that part of the conduit 12 which is distal to the sleeve 11. When

introducing a fluid into the receiving cup of the access port, this fluid will then inflate the balloons 16', 16 9 9 16''' of the sleeve 10 so as to constrict the vein V. The port 26 itself will become overgrown by skin so that it is entirely within the patient's body. A corresponding

configuration is shown in Fig. 2 of US 2014/0207086 Al and is described in paragraph [0028] of that document.

Figure 2 shows a medical implant 10 in the non-implanted configuration. The implant 10 comprises an expandable sleeve 11 which is, in the non-implanted configuration, flat and has, in the present embodiment, an essentially rectangular shape (even though other shapes are possible) . The sleeve 11 is made of a membrane and comprises three elongated balloons 16', 16 9 9 , 16 9 9 9 . Those elongated balloons 16', 16 9 9 , 16 9 9 9 are connected by a conduit 12 which is also extended to the outside of the sleeve 11. Provided between the balloons 16', 16", 169 9 9 are membrane portions 18. By means of introducing a fluid into conduit 12, the balloons 16', 16 9 9 , 16 9 9 9 can be inflated. Between adjacent balloons, a valve 20 is provided. This valve 20 allows a fluid to flow from balloon 16 9 9 to balloon 16' but does not allow generally a fluid flow from balloon 16' to 16 9 9 unless the valve 20 is forced open (e.g. by means of a tube extending through valve 20) . Likewise, the valve 20 provided between balloon 16 9 9 and 16 ' ' ' allows a fluid flow from balloon 16 9 9 9 to balloon 16 9 9 but does not allow a fluid flow from balloon 16 9 9 to balloon 16 9 9 9 unless it is forced open.

By those valves 20, all of the balloons 16'- 16 9 9 9 can be inflated by means of introducing a fluid into the conduit 12. However, it also becomes possible to only expand balloon 16' by introducing a narrow tube via conduit 12 through the valves 20 into balloon 16' . This balloon could be inflated individually whilst the valve would prevent any fluid from also being led into balloon 16 I I . Likewise, if the further conduit (not shown) is introduced into balloon 16 9 9 , balloon

16' ' and balloon 16' can be inflated, without inflating balloon 16 9 9 9 , for similar reasons as set out previously. Accordingly, the configuration shown in Figure 2 allows for a selective inflation of the balloon 16', 16 9 9 and 16 9 9 9 . The valves 20 could be made of membranes.

Figure 3 shows the implant 10 of Figure 2 in a tubular configuration. The ends 22, 24 have been sutured together by stitches 30 so as to provide a tubular configuration. A vein can then be introduced into lumen 28 of the tubular sleeve 11 shown in Figure 3. The balloon 16'- 16 9 9 9 are, for the sake of simplicity, not shown in Fig. 3.

Figure 4 shows an arrangement where a scaffolding structure 40 keeps the sleeve 11 wrapped around the vein V. The sleeve 11 is an inflatable sleeve as discussed with respect to

Figures 1 to 3, with the main difference being that its ends are not sutured to each other so that it assumes a configuration having a C-shaped cross section. In order to keep the sleeve 11 on the vein V, a scaffolding structure 40 is provided, which can, for example, be made of a memory metal. The scaffolding structure 40 is sufficiently resilient so that the sleeve is kept on the vein V during physiological conditions and that it can also withstand the forces exerted when inflating the sleeve 11 so as to compress the vein.

The tubular sleeve 11 can be used in the configuration shown in Figure 5. This figure shows the placement of the implant 10 around a vein V. The main diameter which should be

achieved after the flow reduction procedure will be set up by placing a PTA balloon 30 inside the vein V close to the anastomosis of the artery. After the PTA balloon 30 is placed inside the vein V close to the anastomosis to the artery, the membrane 11 will be wrapped tight on top of the PTA catheter 30 and the excess vein wall material will be sutured at the outside of the vein V together with the membrane sleeve 11. The diameter of the balloon 30 can then be adjusted by means of the conduit 36 connected to a syringe 34 by which a fluid can be introduced or extracted from the balloons forming part of the sleeve 11.

By means of the conduit 12 and the associated port 26, the inner diameter of the sleeve 11 can be adjusted subsequent to the placement of the implant 10 which can then be used to control the inner diameter of the vein V.

Figure 6 shows in a flowchart steps which can be taken to implant 10 shown in Figure 3.

As a first step S10, a surgeon creates an anastomosis between an artery A and a vein V. Thus, the overall arrangement of the artery A and the vein V is as shown in Figure 1. Subsequently (step S12), the sleeve 11 is wrapped around the vein V close to junction J. The ends 22, 24 of the sleeve 11 are overlapped with each other so that the sleeve 11 assumes a tubular configuration which encircles the vein V.

In the next step (step S14) , the overlapping ends 22, 24 of the sleeve 11 are affixed to each other so that they are permanently attached. This could be done by suturing (so that the configuration shown in Figure 3 is arrived at) , however, it is also possible to affix them by an adhesive or by welding. The skilled person will appreciate that other types of affixation are equally possible.

Subsequently (step S16), the port 26 of the conduit 12 is positioned in a location close to but underneath the

patient's skin and the wound which was created for placing the implant 10 is closed. The port 26 is provided at a position close to the patient's skin so that it can be accessed from the outside so as to inflate the sleeve with minimal discomfort to the patient.

Finally (step S18), typically some time after step S16 so that the wound had time to heal, the port 26 is accessed so as to inflate the sleeve 11. This can, for example, be done by means of an injection needle piercing the skin and

accessing the port 26. By means of that needle, the sleeve 11 can be inflated so as to adjust blood flow through the vein V. This adjustment of the blood flow serves to avoid or ameliorate the potential medical issues discussed before.

Claims

1. Medical implant (10) for constricting a vein (V) used in a permanent arteriovenous access, the implant comprising:

- an expandable sleeve (11), the sleeve being suitable for being arranged so as to at least partially surround the vein (V) ,

wherein the sleeve (11) is arranged so that it can be selectively expanded to constrict the vein (V) , thereby reducing the cross-sectional diameter of the vein (V) .

2. Medical implant according to claim 1, wherein the sleeve (11) is arranged to be wrapped around the vein to thus form a tube so that, in the tubular state, the wrapped-over end (24) of the sleeve is arranged for being affixed to the remainder (22) of the sleeve (11) .

3. Medical implant according to claim 1, the sleeve (11) further comprising a scaffolding structure (40) arranged to retain the sleeve in the configuration where it at least partly surrounds the vein (V) .

4. Medical implant according to claim 1, the sleeve (11) being formed in a tubular configuration which can be slid over the vein.

5. Medical implant according to one of the preceding claims, wherein the sleeve comprises one or more balloons (16' , 16 9 9 , 16 9 9 9 ) which can be inflated and deflated by a fluid so as to expand and contract the sleeve (11) .

6. Medical implant according to claim 5, further comprising a conduit (12) having one end connected to the sleeve (11), the other end of the conduit preferably being connected to a port (26), the conduit (12) being arranged for allowing a fluid to be introduced into or extracted from the one or more balloons (16', 16", 169 9 9 ) to thereby inflate or deflate the one or more balloons (16', 16 9 9 , 16 ' ' '

7. Medical implant according to one of claims 5 and 6, wherein the sleeve (11) comprises a plurality of balloons (16' , 16 9 9 , 16 9 9 9 ) which are separated from each other, wherein one or more, preferably all of the balloons (16', 16", 16 9 9 9 ) are arranged for being wrapped around the vein

(V) .

8 . Medical implant according to claim 7, wherein some, preferably all of the balloons (16', 16 9 9 , 16 9 9 9 ) are

fluidically connected to each other, wherein they are

preferably fluidically connected to each other by valves (20) which are arranged to let a fluid pass between the balloons (16', 16 9 9 , 16 9 9 9 ) in one direction only.

9. Medical implant according to claim 7 or 8, when

depending on claim 2, the sleeve having, in the area between the balloons, membrane portions (18) which are arranged so that the membrane portions (18) can be affixed, preferably sutured, to each other to thereby cause the sleeve (11) to assume a tubular shape.

10. Kit, comprising an implant according to one of the preceding claims, preferably an implant according to claim 9, and an inflatable balloon which is arranged for being

introduced into the vein (V) .