IMPLANT FOR PROVIDING A SHUNT WITH ADJUSTABLE FLOW

Description

[0001] The invention relates to an implant for providing a shunt with adjustable flow and to a system comprising such an implant and a suitable actuating element.

[0002] In order to have a sufficient amount of blood available in the patient's vein for a successful dialysis treatment, the vein to be punctured is usually surgically connected to an adjacent artery via a shunt (usually on the forearm between the A. radialis and the V. cephalica This connection is then permanently open, meaning it remains open even between dialysis treatments, and a large amount of blood constantly flows into the vein at high pressure. This can potentially lead to adverse effects on the patient, such as cardiac problems due to increased reflux through the vein or circulatory disorders in the limbs beyond the connection point, as too much blood flows directly from the artery into the vein via the shunt.

[0003] In the state of the art, implants are proposed for providing generic shunts which allow the flow to be adjusted.

[0004] For example, US Pat. No. 8,057,421 B2 discloses a shunt in which the blood flow through the shunt can be controlled using two rotary valves in the inlet and outlet of the shunt. Each spring-loaded rotary valve is adjusted against the spring force using a hydraulic fluid, thereby changing the flow through the shunt. The hydraulic fluid is added and withdrawn via an access port using a syringe.

[0005] US Pat. No. 8,652,084 B2 discloses a further development of this system, in which one of the rotary valves is replaced by a slide valve with an opening and various sensors. The slide valve can also be hydraulically actuated and can restrict or completely interrupt the flow through the shunt. The sensors are located on the side of the slide valve facing the blood vessel and supply control electronics for regulating the slide valve position.

[0006] The published patent application US 2010 / 0056978 A1 discloses several embodiments of a shunt with means for narrowing the shunt and reducing the flow. In one variant, a rubber ring is provided that can be moved from the skin surface within the valve with a finger and brought into a defined position in which it narrows the shunt. If the ring is pushed back, more blood can flow through the shunt. In a second variant, the valve consists of a solid valve body, and a fluid is injected from the outside between the valve body and the shunt using a syringe. This narrows the shunt and reduces the flow. To increase the flow, the fluid must be suctioned out again. In another variant, the valve comprises a cage made of a special metal and two metal rings connected to it.Using an electromagnetic field, a current is induced in the metal rings, which heats the cage, causing the valve body to change its shape, which affects the flow.

[0007] WO 2012 / 104848A1 discloses an implant with a collapsible plunger. US 2010 / 030322A1 discloses an implant with a self-expanding shunt that can be constricted using a cuff. Furthermore, US 2006 / 129083A1 discloses implants in which the flow cross-section can be varied using inflatable bladders or movable membranes.

[0008] Since increased blood flow to the vein is practically only necessary for the duration of dialysis, for example, three times a week for approximately five hours, it would be desirable to open or dilate the shunt only during this time. During the remaining time, the connection could be at least partially closed to reduce the negative effects. However, the state-of-the-art solutions presented above are only suitable for this purpose to a limited extent. Adjusting the fluid volume using a syringe before and after each dialysis treatment would be just as impractical as using a valve with complicated sensors or delicate mechanics.

[0009] The object of the invention is to provide a concept with which a closure or partial closure of a shunt between dialysis treatments can be realized in an improved manner.

[0010] Against this background, the invention relates to an implant for providing a shunt with adjustable flow, wherein the implant comprises a valve element with a passage, wherein the valve element comprises a plunger movable between a passage position and a closed position, which plunger has a permanent magnet and is spring-loaded such that it is biased into its closed position. The implant can be designed such that the flow can be regulated or controlled.

[0011] The closed position corresponds to the rest position of the plunger, which it assumes due to the spring load, provided no opposing force is applied. When the plunger is in its closed position, the cross-section of the passage is reduced, thus impeding or preventing flow through the passage or a line or blood vessel located therein. The valve element is therefore designed so that it is closed in its basic position. During dialysis treatment, the valve element can be temporarily opened by applying an external magnetic field and its interaction with the plunger's permanent magnet. After dialysis treatment, the external magnetic field can be removed, so that the valve element closes again automatically due to the spring load on the plunger. This principle is very simple and not prone to errors.No intervention into the patient's body is required to manipulate the valve. It is sufficient to apply an external magnetic field, for example, by placing a magnetic cuff on the patient's arm before the start of dialysis treatment. The plunger can contain one or more permanent magnets.

[0012] In one embodiment, the implant comprises a conduit running through the passage, with at least partially flexible walls. Suitable conduits include flexible tubing made of plastics such as polyethylene terephthalate (PET, brand name Dacron), polytetrafluoroethylene (PTFE, brand name Gore-Tex), or silicone. The conduit preferably extends a certain length beyond the passage of the valve element on both sides, thus enabling easier connection to the patient's blood vessels.

[0013] In one embodiment, the plunger is spring-loaded by a compression spring, such as a helical compression spring, a disc spring, or a rubber spring. Such mechanical springs are simple and less prone to failure. They are available in highly miniaturized form and require little space. One or more such springs can act on the plunger.

[0014] In one embodiment, the plunger protrudes into the passage in its closed position. The plunger thus directly changes the cross-section of the passage and, if a line is present through the passage, presses directly against the line. In its open position, the plunger can either not protrude into the passage at all or only to a lesser extent. The decisive factor is that in its closed position, the plunger protrudes further into the passage than in its open position, and thus the cross-section of the passage is reduced by the body of the plunger in its closed position.

[0015] In one embodiment, the valve element comprises a hydraulic system with an engagement area and an effective area arranged at the passage. The plunger, in its closed position, exerts pressure on the engagement area such that hydraulic fluid is displaced and causes a reduction in the cross-section of the passage at the effective area of ​​the hydraulic system. In this variant, the plunger indirectly causes a change in the cross-section of the passage by acting on a hydraulic system. The hydraulic fluid can be, for example, table salt. Such indirect activation is also very simple, miniaturizable, and error-resistant.

[0016] In one embodiment, the hydraulic system has a protrusion in the area of ​​action, which protrudes into the passage when the plunger, in its closed position, exerts pressure on the engagement area. The hydraulic system can thus discharge directly into the passage via an opening, with the hydraulic fluid remaining separated from the passage by a preferably flexible membrane. When the plunger exerts pressure on the engagement area of ​​the hydraulic system, the membrane is expanded by the displaced fluid and protrudes into the passage. Such a protrusion can achieve a very gentle narrowing of the passage or line, preventing mechanical damage to blood components.By means of such a protrusion, a multi-sided narrowing of the passage can also be achieved in that the opening of the hydraulic system closed by the membrane extends over a certain minimum angular range of the passage circumference, for example over at least a quarter circle or at least a semicircle.

[0017] In one embodiment, the valve element has a closing mechanism arranged at the passage, and the plunger is connected to this closing mechanism in such a way that the cross-section of the passage is reduced when the plunger is in the closed position. In this variant, the plunger indirectly ensures a change in the cross-section of the passage by acting on a suitable closing mechanism. Using a closing mechanism, for example, a multi-sided narrowing of the cross-section can be achieved.

[0018] In one embodiment, the closing mechanism comprises an iris diaphragm with several blades that can be pivoted together into the aperture via a mechanism. Such diaphragms are known from cameras. Using such a mechanism, the cross-section of the aperture can be adjusted with a fixed center and a continuous circular opening. The plunger can cause the rotation.

[0019] In one embodiment, it can also be provided that the tappet acts directly or indirectly on a control bore of the valve element through which blood flows during use, in order to change its cross-section. In this way, the arterial blood pressure can have a supporting effect on the actuation of the valve, i.e., on the cross-sectional adjustment of the passage.

[0020] In one embodiment, the valve element is a servo valve comprising a valve chamber arranged in the passage, which is separated by a passage diaphragm both from a section of the passage forming the feed line and from a section of the passage forming the return line. The passage diaphragm rests detachably on the passage section forming the return line and has two return openings which connect the valve chamber to this passage section. One of the return openings is detachably closed by a closing element connected to the tappet, and the passage diaphragm further has a feed opening which connects the valve chamber to the passage section forming the feed line. The feed opening preferably has approximately the same cross-sectional area as the return opening not closed by the closing element.

[0021] Furthermore, the invention relates to a system comprising an implant according to the invention and a magnetic actuating element. The actuating element serves to activate the plunger magnet, thereby generating a counterforce to the spring tension and opening the valve.

[0022] In one embodiment, the magnetic actuating element is an arm cuff with a counter magnet. The cuff is suitable for application to a patient's forearm. For example, it can be a Velcro cuff made of a flexible textile material, as is known from blood pressure monitors. The counter magnet can be incorporated into the cuff. It can be, for example, a permanent magnet.

[0023] Using the implant and system according to the invention, a method for treating a dialysis patient can be implemented. Before the start of dialysis treatment, an external magnetic field is applied to the patient's arm to open the valve element and thus allow a high blood flow through the shunt. After the dialysis procedure is completed, the magnetic field can be removed, allowing the valve element to close itself and the blood flow through the shunt to be throttled or prevented again until the next treatment session.

[0024] The implant according to the invention can be inserted into a patient during an operation. It is conceivable that the implant is inserted into an arteriovenous fistula or is placed onto an arteriovenous fistula in such a way that the fistula runs through the passage. If the implant comprises a conduit, this conduit can be connected at both ends to the patient's natural blood vessels and form at least part of the fistula. The arteriovenous fistula is usually created during the same operation. However, subsequent insertion of the implant is also conceivable. The fistula is preferably located in the forearm between the A. radialis and the V. cephalic.

[0025] Further details and advantages of the invention will become apparent from the following exemplary embodiments illustrated with reference to the figures. The figures show: Figure 1: a schematic representation of a first embodiment of an implant according to the invention; Figure 2: a schematic representation of a second embodiment of an implant according to the invention; Figure 3: a schematic representation of another possible embodiment of a valve of an implant according to the invention; and Figure 4: a schematic representation of yet another possible embodiment of a valve of an implant according to the invention.

[0026] In Figure 1 a first embodiment of an implant according to the invention is shown in two states, namely with a narrowed passage in the inactive state ( Figure 1a ) and with extended passage in the active state ( Figure 1b ).

[0027] The implant 1 comprises a valve body 2 and a passage 3 through which a flexible line 4 made of a woven PTFE material is guided. The line 4 represents an arteriovenous fistula in the patient's forearm between the A. radialis and the V. cephalic represents.

[0028] To regulate the diameter of the passage 3 and thus the flow cross-section of the line 4 accommodated therein, a tappet 5 is accommodated in the valve body 2, which can be moved translationally between a closed position ( Figure 1a ) and a pass position ( Figure 1b ) can be moved. The plunger 5 comprises several permanent magnets 6 distributed evenly over its surface and is held against the closed position ( Figure 1a ) prestressed.

[0029] The plunger 5 protrudes in its closed position ( Figure 1a) directly into passage 3 and exerts pressure on line 4, narrowing its flow cross-section. This at least partially closes the shunt. In its passage position ( Figure 1b ), the plunger 5 does not reduce the flow cross-section of the line 4. It does not protrude into the passage 3.

[0030] As this is Figure 1b As shown schematically, the plunger 5 can be moved from the closed position ( Figure 1a ) into the pass position ( Figure 1b ) because the magnetic attraction force between the permanent magnets 6 of the plunger 5 and the external counter magnet 8 exceeds the opposing spring force of the helical compression springs 7. If the counter magnet 8 is removed, the plunger 5 moves back to its original position due to the restoring force of the helical compression springs 7.

[0031] In Figure 2a second embodiment of an implant according to the invention is shown in two states, namely with a narrowed passage in the inactive state ( Figure 2a ) and with extended passage in the active state ( Figure 2b ). Corresponding elements are provided with identical reference numerals as in Figure 1 .

[0032] In contrast to the first embodiment, the plunger 5 in the second embodiment also protrudes in its closed position ( Figure 2a ) does not enter the passage 3. Instead, a hydraulic system 9 is provided in the valve body 2, which comprises a reservoir 9a connected to the plunger and an operating area 9b located at the passage 3. The hydraulic system 9 is filled with a suitable solution, which is preferably biocompatible, such as saline solution.

[0033] In its closed position ( Figure 2a), the plunger 5 exerts pressure on the reservoir 9a of the hydraulic system 9, so that hydraulic fluid is displaced from the reservoir 9a. This causes a diaphragm at the effective area 9b of the hydraulic system 9 to protrude into the passage 3. This protrusion exerts pressure on the line 4, so that its flow cross-section is narrowed. Thus, the shunt is at least partially closed.

[0034] In its through position ( Figure 2b ), the plunger 5 does not exert any pressure on the reservoir 9a of the hydraulic system 9. The protrusion at the effective area 9b of the hydraulic system 9 shrinks back and no longer protrudes into the passage 3.

[0035] The structure and mechanics of the plunger 5 are essentially identical to the first embodiment.

[0036] In dialysis patients, increased blood flow from the A. radialis in the V. cephalicaonly necessary for the duration of dialysis. It is not necessary between treatments and may even lead to complications. Using the implants 1 presented here, it is possible to expand the flow cross-section of the line 4 serving as a shunt only during dialysis treatment by the approach of an external magnet 8, for example, by applying a magnetic Velcro cuff, while remaining constricted between dialysis treatments.

[0037] Figure 3 shows a valve suitable for use in an implant according to the invention, the closing mechanism of which comprises an iris diaphragm 10 with several slats 11, which can be pivoted together into the passage via a mechanism. Figure 3a the narrowed normal state is shown, while in Figure 3bthe expanded state that can be assumed during dialysis treatment is shown. The valve body 2 encloses the shunt line 4 and the slats 11 narrow the passage 3 to a defined extent depending on the state of the iris diaphragm 10 and in doing so compress the circular and flexible shunt line 4 evenly from all sides so that the circular shape of the shunt line 4 is maintained when narrowed and the center point does not change. The slats 11 are connected to a plunger 5 on the outer circumference of the iris diaphragm 10, wherein the closing mechanism is designed such that a movement of the lever along the circumference of the iris diaphragm 10 leads to a narrowing or widening of the passage 3. The plunger 5 carries a permanent magnet 6 so that a movement of the plunger 5 can be triggered by the approach of an external magnet 9.The blades 11 of the iris diaphragm 10 are connected by a circular return spring 12, so that when the external magnet 9 is removed, the plunger 5 and thus the blades 11 return to their original position. The configuration of the iris diaphragm 10 is such that the original position (. Figure 3a ) a narrowing of the passage 3 and the activated position ( Figure 3b ) corresponds to an extension of passage 3.

[0038] Figure 4shows another valve suitable for use in an implant according to the invention, which is a servo valve. The servo valve comprises as its central components a valve body 2 in which a valve chamber 13 is formed. A passage membrane 14 separates the chamber 13 both from a line 3a of the passage 3 forming the supply line and from a line 3b of the passage 3 forming the return line. The line 3b forming the return line is accommodated in the line 3a forming the supply line in the sense of a pipe-in-pipe arrangement, wherein the line sections 3a and 3b are separated by the passage membrane 14 resting on the opening of the inner tube or line section 3b.The passage membrane 14 has three openings, namely a supply opening 14a, which connects the valve chamber 13 to the line 3a forming the supply line, and two return openings 14b and 14c, which connect the valve chamber 13 to the line 3a forming the return line. A first return opening 14b has a flow cross-section that approximately corresponds to the flow cross-section of the supply opening. The flow cross-section of the further return opening 14c is preferably larger.

[0039] The valve comprises a plunger 5, which is mounted in the housing 2 such that it can be translated therein. The plunger 5 is fixedly connected to a permanent magnet 6 and has a closing element on its active surface, which, when the plunger 5 is in the rest position, covers and thus closes the preferably larger return opening 14c of the passage diaphragm 14.

[0040] In Figure 4aThe normal operation of the valve is shown, in which the plunger 5 is in its initial position determined by spring tension. Normal operation corresponds to operation without dialysis, in which only a small blood flow is to occur through the shunt. A blood flow symbolized by the arrow through the supply section 3a enters the chamber 13 via the supply opening 14a and exits it again through the uncovered, smaller return opening 14b.

[0041] If the plunger 5 is lifted from the rest position by an external magnet 9, as in Figure 4bAs shown, the larger return opening 14c of the passage membrane 14 opens. This leads to the blood flowing out of the chamber 13 into the return line 3b through the now two opened return openings 14b and 14c faster than it can flow through the supply opening 14a. This results in a pressure difference between the chamber 13 and the supply line 3a, through which the passage membrane 14 is lifted from the opening of the line section 3b, as shown in Figure 4c In this state, a large amount of blood can flow directly from the supply line 3a into the return line 3b without having to pass through the chamber 13. This corresponds to the desired state for dialysis treatment.

[0042] To return the valve to its initial position, the external magnet 9 is removed, as shown in Figure 4dThe plunger 5 then springs back to its original position, closing the larger return opening 14c again and equalizing the pressure above and below the diaphragm 14. Due to the larger effective area at the top, i.e., on the chamber side, and the inherent tension of the diaphragm 14, this also returns to its original position and closes the short circuit between the supply line 3a and the return line 3b.

Claims

1. An implant for providing a shunt having an adjustable flow rate, wherein the implant comprises a valve element having a passage, characterized in that the valve element comprises a plunger that is travelable between a pass position and a closed position, that has a permanent magnet, and that is spring loaded such that it is preloaded into its closed position.

2. An implant in accordance with claim 1, characterized in that the implant comprises a line extending through the passage and having flexible walls at least sectionally.

3. An implant in accordance with one of the preceding claims, characterized in that the plunger is spring loaded by means of a compression spring such as a helical compression spring, a plate spring, or a rubber spring.

4. An implant in accordance with one of the preceding claims, characterized in that the plunger projects into the passage in its closed position.

5. An implant in accordance with one of the claims 1 to 3, characterized in that the valve element has a hydraulic system having a zone of attack and having an effective zone arranged at the passage, wherein the plunger exerts pressure on the zone of attack in its closed position such that hydraulic fluid is displaced and effects a reduction in the cross-section of the passage at the effective zone of the hydraulic system.

6. An implant in accordance with claim 5, characterized in that the hydraulic system has a protuberance in the effective zone that projects into the passage when the plunger exerts pressure on the zone of attack in its closed position in this manner.

7. An implant in accordance with one of the claims 1 to 3, characterized in that the valve element has a closing mechanism that is arranged at the passage; and in that the plunger is connected to this closing mechanism such that the cross-section of the passage is reduced in the closed position of the plunger, with provision preferably being made that the closing mechanism comprises an iris diaphragm having a plurality of blades that can be pivoted together into the passage via a mechanism.

8. An implant in accordance with one of the claims 1 to 3, characterized in that the valve element is a servo valve that comprises a valve chamber that is arranged in the passage and that is separated by a passage membrane both from a section of the passage forming the feed and from a section of the passage forming the return, with the passage membrane lying releasably on the passage section forming the return and having two return apertures that connect the valve chamber to this passage section, with one of the return apertures being releasably closed by a closing element connected to the plunger, and with the passage membrane furthermore having a feed aperture that connects the valve chamber to the passage section forming the feed.

9. A system comprising an implant in accordance with one of the preceding claims and a magnetic actuation element.

10. A system in accordance with claim 9, characterized in that the magnetic actuation element is an arm cuff having a counter-magnet.