WO1998057599A2

WO1998057599A2 - Implantable valve for blood vessels

Info

Publication number: WO1998057599A2
Application number: PCT/EP1998/003656
Authority: WO
Inventors: Sante Camilli
Original assignee: Sante Camilli
Priority date: 1997-06-17
Filing date: 1998-06-17
Publication date: 1998-12-23
Also published as: WO1998057599A3; AU8337898A

Abstract

Implantable valve for use in blood vessels, particularly veins, more particularly venous confluences comprising a first supporting element and a second operative element; said first supporting element can be in the form of a bent body or of a cut sheet; and said operative element can be joined to the first one, by known means, e.g., glueing, soldering, sewing, embedding, embodying, etc., or be integral with said first element. In the former case, the operative element can be made from a number of suitable materials, such as plastics, biological materials and of the same material as the first element; in the latter case such operative element is of the same material as the first element. A catheter-based tool for remotely removing/rescuing the eventually misplaced/mislodged valve, comprising a stiff operative probe-guide, thermally pre-shaped starting from a thermoreactive alloy wire, able to hook up the valve and to withdraw it from the body.

Description

IMPLANTABLE VALVE FOR BLOOD VESSELS Field of the invention

The present invention refers to valves for blood vessels, implantable in living bodies and in contact with the blood stream passing therethrough. More particularly the invention refers to artificial valves to be used inside veins.

Still more particularly, though not exclusively, the present invention refers to valves implantable in correspondence with a venous confluence.

The present invention also refers to the method and apparatus to implant /remove the valve into a blood vessel by means of a minimally invasive or percutaneous procedure.

Background of invention

Various types of prosthetic valves are known in the art. Among them, the heart valves can be mentioned. Such heart valves are intrinsically different from the venous ones and are unsuitable as venous valve replacement. Their unsuitability derives e.g. from their geometry, structure, size, materials and mechanical characeristics. In fact they are generally larger than the venous valves and include valve leaflets thicker and stiffer than the corresponding ones of venous valves. The thicker heart valve leaflets require a greater opening pressure and this aspect makes them unsuitable to be inserted in veins. In fact in the heart and in the vessels connected therewith, high pressures and high instantaneous flows are present; moreover, the vessels have large diameters and are protected against compression from the outside by virtue of their position inside the thorax. On the contrary, in veins there are low pressures and very variable flow which is frequently stagnant, moreover, the diameters of the veins presenting valvular incompetence are small and these veins are easily compressible from outside under various conditions. Therefore teachings derivable from the heart valves cannot be transferred to the vein valves.

As known, in the human body, pathologic conditions exist caused by venous valvular incompetence, that is to say by the failure of those valves, naturally present in veins and having the shape of flaps attached to the inner vein walls, to operate as blood flow regulators inside the veins through the variation of their position in consequence of pressure variations of the blood flow. The venous valves are essential and critical to have the unidirectional and centripetal/orthograde flow in the veins towards the heart and to prevent venous reflux. The venous reflux is a pathologic condition that leads to a disease known as Chronic Venous Insufficiency (CVI) syndrome. Such a disease involves leg heaviness, edema, pain, dermatitis, muscle cramps, ankle ulcers; it is spreadly present all over the world, with a prevalence of 10 to 30 percent in general population, and specifically in severe and invalidating forms in 3 to 5 percent of the general population.

Such pathologic conditions are known as of primary or secondary nature. Among the primary ones there are the valvular atrophia or agenesis or relaxation of the valvular leaflets. Among the secondary ones there are the destruction of the valves due to venous thrombosis or phlebitis, the so called PostPhlebitic Syndrome (PPS). The present invention is mainly to cure the venous reflux, thus preventing or curing the CVI syndrome, either from primary or secondary pathogenesis. The present invention is also to cure the venous reflux towards a side branch of the vein into with it is inserted.

Known venous valves are those described in PCT/AU87/00220, PCT/US88/03175, PCT/US90/03053, however, their main drawback resides in the likelihood of clotting of blood on them, which immobilize the valves thus preventing them from operating. A further limitation of the disclosed valves resides in that they are inserted by cutting the vein and cannot be remotely implanted/removed at the desired site by a catheter. US 5,607,465 of the same applicant discloses an artificial venous valve devised to cure venous valvular insufficiency. Such valve can be axially implanted into the lumen of the vein to be treated. However, the described valve is limited in its use in that it can only be implanted inside the lumen of the vein with incompetent valves and not at the confluence of an incompetent vein into a larger or principal vein. Summary of the invention

It is an object of the present invention to provide a valve for blood vessels, particularly veins, implantable at the confluence of said vessels and in contact with a blood stream which is effective in favouring the unidirectional motion of the blood in its return path towards the heart. Said valve comprises a first supporting element in the shape of a bent body or of a cut sheet and a second operative element in the shape of a leaflet, said two elements being joined one another or the second one being integral with the first one, the valve being provided with anchor means and grip means to prevent its longitudinal slipping when it is inserted in the blood vessel.

Another object of the invention is a valve, further provided with a frame which cooperates to the positioning and fixing of said valve. Another object of the invention is to provide a valve which is economic and effective in operation and not prone to produce blood clotting.

Another object is the elastic material to be used and the process to manufacture the valve of the invention.

A further object of the invention is to provide a catheter for the remote implantation/removal of the valve.

A further object of the invention is to provide a minimally invasive or percutaneous delivery procedure to cure the venous reflux.

Additional objects will be evident from the detailed description of the invention.

Brief description of the drawings Fig. 1 is a schematic front view of a first embodiment of the valve according to the invention.

Fig. 2 is a schematic side view of the valve of Fig. 1 implanted in a principal vein, at the confluence with a confluent vein, the veins being represented with relevant walls partially cut away to show the confluence with the valve implanted to work. Fig. 3 is a schematic front view of a second embodiment of the valve according to the invention.

Fig. 4 is a schematic front view of a third embodiment of the valve according to the invention.

Fig. 5 is a schematic front view of a fourth embodiment of the valve according to the invention.

Fig. 6 is a schematic longitudinal view, partially in section, of a transport catheter for the implantation/removal of the valve according to the invention.

Fig. 7 is a schematic longitudinal perspective view of a working catheter for the implantation/removal of the valve according to the invention. Fig. 8 is a schematic longitudinal view, partially in section, of the working catheter of

Fig. 7 inserted in the transport catheter of Fig. 6.

Fig. 9 is the same view of Fig. 8 with the probe-guide in a working configuration. Detailed description of the invention

In the following detailed description reference will be made to veins only for reasons of clarity, in that it is intended that the valve according to the invention can be inserted in a generic blood vessel. In the description reference will be made to "confluence" and "confluent vein". With the term "confluence" it is intended the site where a lesser vein combines with a larger one; with the term "confluent vein" it is intended said lesser vein which intersects a principal or larger vein. The valve according to the invention comprises a first supporting element and a second operative element; said first supporting element can be in the form of a bent body or of a cut sheet; and said operative element can be joined to the first one, by known means, e.g. glueing, soldering, sewing, suturing, embedding, embodying, etc., or be integral with said first element. In the former case, the operative element can be made from a number of suitable materials, such as plastics, polymeric materials, biological materials and of the same material than the first element; in the latter case such operative element is of the same material of the first element. The bent body can be obtained from wire with circular section or other sectional shape or from a strip. The supporting element is obtained also by cutting a sheet by appropriate means and techniques. Suitable cutting techniques are, among others, laser cutting, photo-incision, shearing.

The valve is provided with anchor means and grip means to prevent longitudinal slipping when the valve is inserted in the wall of the blood vessel. The fixing or anchor means of the valve can be shaped in different way: wires, arrows, spikes, indentations and other suitable shapes, such as a sort of zig-zag shaped body. Their number, shape, position and dimension is not limiting and is related to their role of anchoring or fixing the valve to the venous wall. They can be integral with the supporting element or can be joined to it by the above mentioned known means. When the valve is not inserted in the vein, they can be in a rest position and in a linear configuration not offensive for the said vein. After insertion, they can bend into a sort of a hook configuration, thus grasping the venous wall.

The valve according to the present invention provides a prosthesis having the function of a venous valve, which is effective in favouring unidirectional motion of the blood in its return path towards the heart, particularly fit for operating on a venous confluence. In fact, by attaching the supporting element to a venous wall so making the operative valving element to project onto a venous confluence, the valving element itself can act as a regulator of the flow of the blood stream in the confluent vein. Specifically, when the pressure existing in the confluent vein turns out to be greater than that existing in the principal vein, the thrust becoming from the difference between said two pressures operates by bending the elastic supporting element and the operative valving element, so making the venous confluence to open. The decrease of said pressure differences makes the elasticity of the supporting element to operate according to a progressive return of the valving element to a closed position, thus preventing venous reflux in the confluent vein. Suitable materials for manufacturing the valve of the invention are selected among plastics such as Dacron®, polyesters, polyethylene, polypropylene, metals, steels such as AISI 316L, composities, alloys such as thermoreactive or thermal shape memory materials such as Nickel-Titanium alloy (Nitinol®) and other similar materials. A requirement is that such materials have to be biocompatible or rendered biocompatible with known techiques such as surface coating of the implantable device by Hepa n-like products, laluronic-like acids, Polyethylene-Oxide-like products and other available hydrophobic chemical components, all well known to the experts.

The best performances of the valve according to the invention can be obtained by selecting a specific material by which the valve can be produced. Such material is characterized in that it is a flexible material having elasticity and plasticity so as to be collapsible without deformation. Preferred materials are those characterized by thermal shape memory such as Nitinol®, which is characterized in that it has two crystallographic phases: a martensitic one, at room temperature, in which it is elastic, and an austenitic one, at a higher temperature (the temperature of the human body), in which it is rigid. By changing the temperature, therefore, it is possible to make the state and the configuration of the valve and its elements to commutate. So the temperature acts as the means for controlling the configuration of the elements which make up the valve, comprised the anchor means hereinabove described. The valve according to the invention can be obtained by using starting materials in the shape of wires, strips or sheets.

Preferred diameters for wires range between 0.10 to 0.50 mm. Preferred thickness for strips or sheets range between 0.10 to 0.50 mm. The diameter of wires and the thickness of strips and sheets can be selected in dependence of the kind and nature of blood vessel in which the valve will be inserted. Higher values for diameter/thickness can be used for larger arteries and veins, while lower values for diameter/thickness will be preferred for smaller vessels.

Wires, strips and sheets preferably made of Nitinol® or similar materials can be used to make up the support element of the valve. The operative element can be realized with a different material such as plastics, metals or biological material. In this case it can be combined to the supporting element in a suitable and known manner, e.g. glueing, soldering, sewing, suturing, embedding, embodying, etc.

In a preferred embodiment the whole valve can be made of the same material by starting from sheets. In this case the whole valve can be obtained in a single step by cutting the sheet itself in the final shape of the valve, in this case the final shape being intended the shape of the valve before the implanting step. Therefore the additional steps of glueing, soldering, sewing, etc. can advantageously be avoided, thus rendering the valve of the invention, which is per se very simple and essential, much easier to be manufactured and cheaper that the previous known ones.

The sheets can be advantageously made of a thermal shape memory material, preferred are Nitinol® and AISI 316L, or similar materials.

A possible process for producing the valve starting from a sheet, like Nitinol® or AISI

316L comprises the following steps: - to cut the sheet in its flat configuration;

- to bring the sheet to a temperature at which a martensitic→austenitic conformation occurs so that the sheet takes its "final" or operative conformation.

The sheet is preferably pre-treated and/or post-treated with known techiques in order to render it biocompatible and low or non thrombogenic according to techniques known to the experts.

Suitable cutting techniques can be the known laser cutting and photo-incision which ensure a precise and accurate cut. The invention will be illustrated by the aid of the following figures, which show some examples of the valve according to the invention and which shall not be considerd limiting the scope of the invention. Possible design modifications will be evident to the man skilled in the art and are to be considered within the scope of the invention itself.

In the figures similar elements, having the same function, will be indicated with same numbers, in addition the various elements of the valve are not in scale; the man skilled in the art has the knowledge to identify the suitable relative proportions of such various elements and of the whole valve. According to a first embodiment, shown in Fig.s 1 and 2, the valve or venous valvular prosthesis according to the present invention comprises a support 1 , in the shape of a stem, in a material endowed with elasticity, as for instance the ones mentioned in the above and a valving element or flap 2, supported by support 1 , in the shape of a leaflet in a non thrombogenic or minimally thrombogenic material. Support 1 is characterized in that it is made of a wire or strip shaped into a "U", substantially planar, rest configuration having a very narrow bend 1 ', with wings that extend with two extensions 1a, 1 b slightly diverging, like a "V" portion. The portion of support 1 configurated like a "U" makes up the proper stationary support; it is intended to abut against the wall of a vein V in the longitudinal sense of the blood stream of the principal vein V, and it is anchored to the venous wall through fixing means 3, 3'. The portion of support 1 configured like a "V" with its two ends 1a, 1 b makes up the movable portion of support 1 , with the function of controlling the movable valving element 2 and acting as a return or closing spring. The "U" portion and the "V" portion of the support 1 are joined to one another by a step 1". The level difference made up by step 1 " is the site in which valving element 2 is mounted. The "V" extensions 1 a and 1 b have a profile slightly bent to have the extremity of element 2 in a same plane than support 1 , as can be observed in Fig. 2. The bent portion is lightly offset with respect to the plane containing the "U" portion. Therefore, it is in this meaning that the shape of support 1 is only substantially planar, that is to say it is planar except for the specified offset.

Valving element 2 is made up of a thin lamina, of a thickness for instance, but without restriction, of 0.2 to 0.5 mm, of a suitable material, such as for instance, a flexible metallic alloy, such as nickel-titanium alloy, a plastic material, for instance a silicone Dacron® mat; or a biological material treated to render it non thrombogenic, for instance with glutaraldehyde. It can be sutured to the "V" portion of support 1 by means of a thin surgical thread, for instance in polyester or in polypropylene, with a diameter for instance of 7/0 to 8/0 USP, and has the function of occluding the outlet of venous confluence C between principal vein V and lateral vein V. Fixing means 3, 3' are made up of two double hooks, as shown in Fig. 2, fixed at 3a, 3'a to the "U" portion of the support. The fixing means 3, 3' are made by the same material of the support 1 as well as by a different material, preferably by a thermoreactive metallic alloy, by virtue of which they can be commutated between a rest configuration not offensive for the wall of the vein for the transport in it up to the positioning site, and a configuration for the attachment to the wall of the vein to stabilize it in the positioning site. As a material having thermal memory for instance Nitinol® can be used. Before the implantation, the fixing means 3, 3' present themselves in the shape of rectilinear metallic wires, as shown in Fig. 1 , which are rendered integral with support 1 through metal band soldering or glue or other means at positions 3a, 3'a. They assume the final shape of a double hook 3b, 3b'; 3'b, 3'b' after thermal stimulus. The valvular prosthesis, positioned as shown in Fig. 2, with valving element 2 in correspondence with outlet C of side vein V, impede the blood reflux in it in the rethrograde sense without obstructing the orthograde flux.

Different embodiments of the invention are shown in Fig.s 3, 4, 5. In such figures all the views show the valves in a planar configuration, however they can have a sustantially planar configuration, where "substantially" is intended with the same meaning as expressed with reference to Fig. 1. Moreover, as said in the above, the planar configuration turns into a curved one when the valves, made of thermal shape memory materials, are inserted in the blood vessels, and this aspect is indicated in the figures by a curved double arrow A.

With particular reference to Fig. 3, this figure illustrates the same valve of Fig.1 the difference residing in the fixing means. In this case the fixing means 3 are in the shape of a zig-zag shaped body, which can be divided in two branches ending in B and C or continuous if the ends B and C join together. The zig-zag can be made of wire or strip and can be fixed to the support 1 by a band 3a. The length of the zig- zag is not critical and is such that it adapts itself inside the wall vessel thus occupying the whole section of the vessel, when it is continuous, or part of it, when it is divided in two branches.

In a further not shown embodiment the support 1 , the extensions 1a and 1 b, the zig- zag 3 and the band 3a consitute the same body obtainable starting from a sheet by cutting techniques.

With particular reference to Fig. 4, it is illustrated a further embodiment of the valve, the difference from the valve illustrated in Fig. 3 is that the leflet 2 is integral with support 1 and zig-zag 3. Preferably the whole valve is obtained starting from sheet by cutting techniques.

Another embodiment is illustrated in Fig. 5, with the leaflet 2 integral with the supporting element. In this case the support element of the valve is a sort of a substantially quadrangular frame 4. From the middle of one side of said frame 4 depart two diverging extensions 1 'a, 1 'b connected each to the respective adjacent side of frame 4. Fixing means 3' are in form of spikes integral with frame 4. The leaflet 2 is connected to the two extensions 1'a, 1'b by the bridges 5, the number of which is not critical. The above whole assembly can be obtained by shearing or cutting a sheet. The length of the frame and generally speaking the dimensions of the single elements of which the valve is made up can be adjusted to the previewed circumference of the selected vein.

The valve can be implanted in a generic blood vessel or it can be inserted in a principal vein at the confluence with a confluent vein, arranged with the leaflet element in such a position as to interest all the confluence opening of the confluent vein into the principal vein to prevent the blood stream refluxes onto said confluent vein itself.

Once in place and owing of the nature of the material endowed with elasticity and flexibility of which it is made, the valve, from a flattened position, will take on a substantially curved, cylindrical or tubular or conical configuration, lining the inner wall of the vessel with the valvular element preferably fit in front of the venous confluence. Such curving cooperates with the walls of the blood vessel in that it matches them and supports the same. The valve of the invention can be combined with the artificial venous valve described in US 5,607,465 thus rendering the latter able to work at confluences. The valve can be inserted through a surgical incision and preparation of the site of the vein to be treated, or, preferably, it can be inserted into the human body in a percutaneous or mininvasive manner, through a known catheter, such the one described in US 5,607,465. When misplacements or displacements of the valve occur, the valve can be replaced in the correct position by using the catheter hereinbelow described, fit for remote removal and replacement of the valve. The valve according to the invention can be supplied in a sterile packaging ready for use and can be part of an operating kit further comprising a delivery system, such as the catheter described in US 5,607,465 of the same applicant, and the catheter described hereinbelow for the removing.

Advantages of the valve according to the invention resides in its low costs and easy manufacture; the valve is also easy to be remotely inserted in a human body. Another advantage resides in that the valve takes the shape of the vein and supports it and is low thrombogenic, thanks to its simple and essential shape. The valve of the present invention allows to cure the long as well the short saphenous incompetent vein and the incompetent perforating veins; so it allows to cure even the relatively small incompetent veins (with more than 3 mm in diameter) and in deep position located. This performance is obtained by placing the valvular device in a principal or larger vein, with more consistent diameter. Moreover, the eventual malfunction of the valvular device will not obstruct the normal vein into which it is inserted, while the incompetent vein will be obstructed only. This non expected final result will produce anyhow a benefit for the patient, like by a surgical high ligation of the long saphenous vein.

The present invention includes a catheter-based tool apt for remote removing or rescueing of the valve above described eventually misplaced or not working. The tool is illustrated in Fig.s 6 to 9 and it is characterized in that inside a working catheter 14 (of about one millimeter in internal lumen) a probe-guide 14' is arranged having a stem15, a goose-neck portion 16 and a terminal segment or tip 17. The probe-guide 14' is a stiff pre-shaped assembly manufactured using a shape memory material like Nitinol® or AISI 316L or similar material. Its pre-shaped configuration is the one illustrated in Fig. 9. This tool is inserted in a larger catheter 10, also called transport catheter, inside which the tool is made to slide forwards and backwards thanks to manual or mechanical push/pull external movements. Also the probe-guide 14' inserted Into the internal working catheter 14, is provided with means (not shown) for pushing/pulling it. The external, transport catheter 10 has inner cavity (principal lumen 11 ) and comprises a balloon 12 fed with a saline solution S and controlled by a channel 13 in the lumen 11 through a hole 12' in the wall of the transport catheter itself. Both catheter 10 and 14 can be made of conventional plastic materials like polyethylene. Preferred length of the gooseneck portion and of the tip are each about 1cm.

Said probe-guide 14' works as follows. When the catheter 14 is pushed partially away from the catheter 10, owing to the preshaped bent configuration of the probe- guide 14', the tip 17 deviates from the longitudinal axis of the catheter 14 more or less depending on the length of the goose-neck itself with respect to the pushed catheter 14. Consequently, the probe-guide tip 17 goes out from the catheter 14 and directs itself towards the vessel wall (Fig. 8), thus scraping said wall in consequence of pushing/pulling movements. The probe-guide is moved backwards and forwards until the tip 17 hooks up the target, consisting in the valve to be removed. Then a further pushing movement permits the probe-guide 14' to recover the preshaped configuration, the valve being hooked, and the tip 17 lining near the catheter (Fig. 7). Afterwards the transport catheter 10 is pushed forwards until the tip 17 inserts into it (Fig. 9). At this point the valve is firmly secured to the probe-guide which is extracted together with the transport catheter from the body. All the procedure is made under fluoroscopy control or videoscopy or ultrasound technique or a combination of the above, well known to the experts.

Claims

1. Implantable valve for blood vessels, particularly veins, comprising a first supporting element and a second operative element in the shape of a leaflet; said first supporting element being in the form of a bent body or of a cut sheet; and said operative element being joined to the first one or being integral with said first element and made of the same material of it.

2. Implantable valve according to claim 1 wherein the joining is performed by glueing, soldering, sewing, suturing, embedding, embodying.

3. Implantable valve according to claim 1 wherein the operative element is made from a number of suitable materials, such as plastics or biological materials.

4. Implantable valve according to claim 1 wherein the operative element is of the same material of the first element.

5. Implantable valve according to claim 1 wherein the bent body is in the shape of wire or strip of dimensions ranging between 0.10 to 0.50 mm.

6. Implantable valve according to claim 1 further provided with a frame.

7. Implantable valve according to claim 1 characterized in that the supporting element is manufactured starting from a sheet.

8. Implantable valve according to claim 1 characterized in that the whole valve is made of the same material and manufactured starting from a sheet of said material.

9. Implantable valve according to claim 8 wherein the thickness of the sheet ranges between 0.10 to 0.50 mm.

10. Implantable valve according to claim 1 further provided with fixing means to prevent longitudinal slipping when the valve is inserted in the blood vessel.

11. Implantable valve according to claim 10 wherein the fixing means are shaped as wires, arrows, spikes and like a zig-zag shaped body.

12. Implantable valve according to claim 11 wherein the fixing means are integral with the supporting element .

13. Implantable valve according to claim 1 characterized in that it is made of a material selected among plastics such as Dacron┬«, metals, steels such as AISI 316L, composities, alloys, the requirement being that such materials be biocompatible.

14. Implantable valve according to claim 1 characterized in that it is made of a flexible material having elasticity and plasticity so as to be collapsible without deformation, said material being characterized by thermal shape memory.

15. Implantable valve according to claim 1 characterized in that it is made of Nickel- Titanium alloy.

16. Implantable valve according to claim 1 characterized in that it is made of AISI 316L.

17. Implantable valve according to claim 1 wherein the supporting element is obtained by a wire or strip of a material having elasticity and being shaped into a "U", substantially planar, rest configuration having a bend and two wings, that extend into two respective "V" diverging extensions; the leaflet element being connected to the support element in correspondence with said extensions, the valve being further provided with means for fixing it in a blood vessel.

18. Implantable valve according to claim 17 characterized in that the means for fixing comprise attaching means connected to the supporting element in correspondence with said "U" wings, in a material endowed with thermal memory virtue of which they can be commutated between a rest configuration not offensive for the wall of the blood vessel for the transport in it up to the positioning site, and a configuration for the attachment to said wall to stabilize it in the positioning site.

19. Implantable valve according to claim 17 characterized in that the means for fixing in the rest position are in the shape of rectilinear wires and in the attachment configuration are in the shape of double hooks by the bending of end tracts of said rectilinear wires.

20. Implantable valve according to claim 1 characterized in that it comprises fixing means in the shape of a zig-zag shaped body, which are continuous or divided in two branches and are connected to the supporting element by means of a band.

21. Implantable valve according to claim 20 wherein the support, the zig-zag 3 and the band constitute the same body obtainable starting from a sheet by cutting techniques.

22. Implantable valve according to claim 21 characterized in that the operative element integral with the support and the zig-zag and the whole valve is obtained starting from sheet by cutting techniques.

23. Implantable valve according to claim 1 characterized in that the operative element is integral with the supporting element, which is in the shape of a sort of a substantially quadrangular frame 4, from the middle of one side of said frame departing two diverging extensions connected each to the respective adjacent side of frame 4, fixing means being further provided, the operative element being connected to the two extensions and the whole assembly being obtained by cutting a sheet.

24. Catheter-based tool apt for remote removing or recovering of implanted valves characterized in that inside a working catheter (14) a probe-guide (14') is arranged having a stem (15), a goose-neck portion (16) and an terminal segment or tip (17), the probe-guide (14') being made of a stiff pre-shaped assembly manufactured using a shape memory material, the tool being inserted in a larger transport catheter (10), inside which the tool is made to slide forwards and backwards thanks to manual or mechanical push/pull external movements and the probe-guide (14') being inserted Into the internal working catheter (14) and provided with pushing/pulling means.

25. Catheter according to claim 24 in which the external, transport catheter (10) has an inner cavity (11 ) and comprises a balloon (12) fed with a saline solution and controlled by a channel (13) in the lumen (11 ) through a hole (12') in the wall of the transport catheter (10).

26. Operating kit comprising the valve according to claim 1.

27. Operating kit comprising the catheter according to claim 24.

28. Process for producing the valve according to claim 1 starting from a sheet of a Nickel-Titanium alloy or similar material comprising the following steps:

- to cut or shear the sheet in its flat configuration;

- to bring the sheet to a temperature at which a martensiticΓåÆaustenitic transformation occurs so that the sheet takes its "final" or operative conformation.

29. Process to adjust the misplacements of the valve according to claim 1 or to remove said valve from the human body in a percutaneuos or mininvasive manner, through the catheter of claim 24 under fluoroscopic or videoscopic or echografic monitoring or a combination of the available monitoring systems.

30. Process to implant the valve according to claim 1 characterized in that the valve is fixed to the wall of a blood vessel, i.e. a vein, so that the blood being in a confluent vein V, when it reaches a pressure higher than in a corresponding principal vein V, operates against the operative element to an open position, thus flowing towards the^" heart; conversely, when the blood pressure being in the principal vein V becomes higher than in the confluent vein V, it operates against the operative element to a closed position, thus preventing reflux into the confluent vein V.

31. Process to implant the valve according to claim 1 characterized in that the valve is fixed to the wall of a principal vein V at the confluenence with a confluent vein V so that the leaflet element faces the venous confluence, the leaflet acting as a regulator of the flow of the blood stream in the confluent vein and being operated by the differential pressure instantly present on both two sides of the operative element and such pressure elastically deflecting or bringing back the leaflet element of the valve, alternatively closing or opening the venous confluence, thus rendering the blood flow in the confluent vein V substantially unidirectional towards the heart.

32. Use of themperature shape memory materials to manufacture the valve according to any of the claims 1-23.

33. Use of Nickel-Titanium alloys to manufacture the valve according to any of the claims 1-23.

34. Use of AISI 316L to manufacture the valve according to any of the claims 1-23.