Artificial valve

IS 2 297 147 T3

DESCRIPTION

Artificial valve.

Field of the invention

This invention relates to medical devices for use in a body lumen.

Background

A venous valve serves to prevent retrograde blood flow and only allow forward blood flow to the heart. Referring to FIG. 1A, a healthy venous valve 12 is illustrated in a vessel 10. The valve is bicuspid, with opposing cusps 14. In the closed condition, the cusps 14 come together to prevent the retrograde flow (arrow 16) of blood. Referring to Fig. 1B, if the valve is deficient, the cusps 14 do not seal properly and a retrograde flow of blood occurs. Venous valve deficiency is considered to be caused by at least the following two medical conditions: varicose veins and chronic venous insufficiency.

WO-A-0156500 describes an implantable valve device comprising a wire frame supporting two convergent and flexible valve leaves under tension. The valve leaves are forced apart by blood flow in one direction, and forced together by blood flow in a second direction.

Summary

This invention relates to medical devices for use in a body lumen. In one aspect, the invention provides a valve cusp as defined in claim 1, including a membrane implantable in a body lumen and invertibly deformable between a first position and a second position. The membrane is invertible in response to the direction of fluid flow through the lumen and can be deformable by fluid flow through the body lumen. The membrane can be invertible with respect to a radial direction of the body lumen. The membrane can be reversibly deformable between the first position and the second position.

Implementations may include one or more of the following. The membrane may define a portion of a cone, and include an anchoring element adjacent to the apex of the cone. The membrane may include an anchoring element configured to fit within the body lumen, or alternatively configured to penetrate through the body lumen. The anchoring element can be, for example, a loop or a barb. The membrane can be formed of a polymer, for example polyurethane, polyethylene or fluoroplastic.

In another aspect, the invention provides a medical system as defined in claim 8. The system includes multiple membranes, each membrane being implantable in a body lumen and invertibly deformable between a first position and a second position. Each membrane is invertible in response to the direction of fluid flow through the lumen. System implementations may include one or more of the following. The membranes can be symmetrically implantable in the body lumen. Each membrane can be invertible with respect to a radial direction of the body lumen and can be deformable by fluid flow in the body lumen. At least one membrane can be reversibly deformable between the first position and the second position. At least one membrane may define a portion of a cone and include an anchoring element adjacent to the apex of the cone. The at least one membrane may include an anchoring element configured to fit within the body lumen, or alternatively configured to penetrate through the body lumen. The anchoring element can be, for example, a loop or a barb. At least one membrane can be formed of a polymer, for example polyurethane, polyethylene or fluoroplastic.

The embodiments may have one or more of the following advantages. One or more invertible membranes, which can act as cusps of an artificial valve, can be implanted at a site to be treated using a catheter. As such, implantation is minimally invasive and reduces the possibility of inherent complications. The membrane is made of a polymer such as polyurethane, polyethylene or fluoroplastic, whose materials are more easily accessible than natural tissue excised from an animal, and can be manufactured with a consistency and an efficiency that would be more difficult or more expensive to achieve using a natural fabric.

Other features, objects, and advantages of the invention will be appreciated from the description and drawings, and from the claims.

Description of the reinfor os

Figs. 1A and 1B are illustrations of a venous valve and a poor venous valve, respectively.

Figs. 2A, 2B and 2C are partial perspective views of one embodiment of a valve cusp.

Fig. 3 is a cross-sectional view of the valve cusp of Fig. 2A taken along the line

3- 3.

Fig. 4 is a cross-sectional view of the valve cusp of Fig. 2C taken along the line

4- 4.

Figs. 5A, 5B, 5C, 5D, and 5E are schematic views of one embodiment of a procedure for implanting a valve cusp.

Figs. 6A and 6B are partial perspective views of one embodiment of a valve cusp.

Figs. 7A and 7B are partial perspective views of one embodiment of a valve cusp.

Fig. 8 is a cross-sectional view of the valve cusp of Fig. 7A taken along line 8-8.

Fig. 9 is a cross-sectional view of the valve cusp of Fig. 7B taken along line 9-9.

Fig. 10 is a partial perspective view of an anchor element embodiment.

Fig. 11 is a partial perspective view of an anchor element embodiment.

Detailed description

Referring from Figs. 2A-2C through Fig. 4, a pair of valve cusps 30 located within a vessel 46, eg, a vein, is illustrated. The cusps 30 can be positioned upstream or downstream of a deficient venous valve, such as the valve depicted in FIG. 1B. Each cusp 30 of an artificial valve includes at least one anchoring element 38 attached to an invertible portion 42. In this case, the invertible portion 42 is a flexible, approximately triangular membrane with an anchoring element 38 attached to an apex 36 of the membrane. Anchor element 38 is generally configured

It is necessary to maintain the invertible portion 42 in a desired position in the vessel 46. For example, the anchor element 38 may engage within a wall 44 of the vessel 46, or penetrate through the wall to secure the vessel. cusp 30 to the glass. The invertible portion 42 may deform between a first position and a second position, for example between an open condition and a closed condition, in response to the flow of a body fluid through the vessel 46, to allow or reduce flow through the vessel.

Referring particularly to Fig. 2A and Fig. 3, the cusps 30 are shown in a position in which each cusp 30 forms an approximate semi-cone, whereby the curved surfaces of the cusps 30 form an opening 50. The opening 50 allows antegrade flow of a fluid through the vessel in the direction indicated by arrow 48. The membranes of the invertible portions 42 are relatively thin and can conform closely to the vessel wall 44 to maximize the size of the opening 50. However, each cusp 30 is also held slightly apart from the vessel wall 44 by the anchor 38, such that a gap 52 is formed between the invertible portion 42 and the wall 44.

Referring particularly to FIG. 2B, the retrograde flow of fluid (arrows 51) through the vessel can accumulate in gap 52 and exert pressure on invertible portion 42 of cusp 30. Since invertible portion 42 is flexible, it can deform. under the pressure exerted and inverted to form another approximate semi-cone, as shown in Fig. 2C. That is, each cusp 30 that forms a semi-cone in the first position can be inverted or tilted with respect to a radial axis of vessel 46 to form a second semi-cone that is approximately the mirror image of the first semi-cone. As the interior 32 of the second half cone accumulates fluid with retrograde flow, pressure is exerted on the interior of the cusp 30, causing the cusp to separate from the wall 44 of the vessel. As a consequence, the space 53 between the two cusps 30 narrows, the size of the opening 50 decreases, and the flow of fluid through the vessel and past the cusps is reduced (Fig. 4).

The cusps 30 may remain in the second position until the antegrade flow of fluid exerts sufficient pressure on the surface of the cusps 30 opposite the interior 32 and inverts the cusps to the first position. Thus the cusps 30 provide an artificial valve that automatically responds to fluid flow or pressure changes in vessel 46.

Figs. 5A to 5E show a procedure for placing cusps 30 at a site to be treated in vessel 46 using a catheter 18 that can be inserted into vessel 46 percutaneously. Catheter 18 is generally adapted to be introduced through vessel 46, for example using a guide wire. Catheter 18 includes a long, flexible body having a central portion 21, and a retractable sheath 22 above the central portion. Referring particularly to Fig. 5B, a sectional view taken along line 5-5 of Fig. 5A, there are two grooves 25 formed on either side of the central portion 21, and within each of the grooves 25 a push rod 28 is positioned. Each cusp 30 is located in a groove 25 in a compacted state and held in place by the retractable sleeve 22 until it is positioned at the site to be treated.

Catheter 18 can be guided to the site to be treated using stent placement techniques, for example by tracing a guidewire positioned with central lumen 101. At the site to be treated, retractable sheath 22 is proximally retracted to form an opening. 26 at each end of each slot 25. Referring particularly to Fig. 5C, the push rods 28 are used to push each cusp 30 distally towards the opening 26 to remove the anchoring element 38 from the opening 26. The cusps 30 are pushed through the openings 26 until the anchoring elements 38 grip the cusps 30 to wall 44 of vessel 46. For example, anchor members 38 may fit within wall 44 or pierce wall 44 and fastened to the exterior of vessel 46.

After each cusp 30 has been attached to vessel 46, retractable sleeve 22 is retracted to fully expose cusps 30 (Fig. 5D). The central portion 21 is then pulled proximally, past the flexible (and deflectable) cusps 30, and removed from vessel 46 (Fig. 5E). The cusps 30, now attached to the wall 44, can be deformed between the first and second positions, as described above.

The cusps 30 are preferably made of a biocompatible material capable of reversible deformation as described above. Each cusp 30 can be formed of a thin, flexible material, such as polyurethane, polyethylene, or fluoroplastic, eg, polytetrafluoroethylene (PTFE). The invertible portion 42 can be formed of one or more materials. For example, the invertible portion 42 may include an edge portion 40 that is relatively more flexible or more compliant than another portion of the invertible portion to help the edges meet and seal when the cusps 30 are in the second position. . The cusps 30 may include a radiopaque material such as a polymer that includes a radiopacifier, for example tantalum metal or bismuth oxychloride, to position and monitor the cusps.

Similarly, anchor element 38 is preferably biocompatible. Anchor member 38 can be formed of a relatively rigid material, such as a polymer having a suitable hardness, for example, acrylonitrile-butadiene-styrene (ABS). Other materials can be used, such as metals (eg, tantalum, tungsten, or gold), alloys (eg, stainless steel or Nitinol), and ceramics. Anchor elements 38 may include a radiopaque material to position and monitor cusps 30. The anchor element may be embedded in the invertible portion or affixed to a surface of the invertible portion with, for example, an adhesive.

Other realizations

In other embodiments, any number of cusps may be anchored to wall 44 of vessel 46 to act as a valve to prevent retrograde flow of blood through blood vessel 46.

Referring to Figs. 6A and 6B, a single cusp 60 can be used. Cusp 60 can be transported to the site to be treated and anchored to wall 44 of a vessel 46, in the same manner as described above, using a catheter. In a first position, the cusp

ES 2 297 147 T3 forms an approximate semi-cone, with the edges 63 of the semi-cone facing towards the wall 44 opposite to the place where the cusp 60 is anchored to the wall 44. The interior of the cone forms a channel 64 that allows the fluid to pass the cusp 60. Anchoring member 65, attached to cusp 60 at apex 61, keeps cusp 30 slightly spaced from wall 44, whereby a gap 66 is formed between cusp 60 and wall 44. Backflow fluid can accumulate in gap 66 and exert pressure on cusp 60, deforming cusp 60 and widening gap 66 until pressure on cusp 60 reverses the cusp. Referring particularly to FIG. 6B, in an inverted position, the cusp 60 forms an approximate cone with the wall 44 and accumulates fluid with retrograde flow in a pocket 68 formed within the cone. The accumulated fluid can exert pressure on the cusp 60, causing the cusp 60 to move away from the wall 44. As a consequence, the space 66 between the cusp 60 and the wall 44 opposite the anchor element narrows, until the cusp 60 touch wall 44, in a second position, as shown. In the second position, the flow past the cusp 60 is less than the flow that was when the cusp 60 was in the first position. The cusp 60 remains in the second position until the pressure exerted on the cusp 60 by the forward flow of fluid is sufficient to reverse the cusp 60 to the first position.

Referring to Figs. 7A-7B, three cusps 70a-70c can be symmetrically attached to the wall 44 of a vessel 46 in a manner similar to that described above. Referring particularly to Fig. 7A, cusps 70a-70c are shown in a first position that does not substantially impede the flow of a fluid through vessel 46. As shown in Fig. 8, the surfaces of the cusps 70a-70c conform to the wall 44 of the vessel 46, allowing a substantial opening 72 for flow past the cusps 70a-70c. Each cusp 70a-70c is kept separated from the wall 44 by anchoring elements 71a-71c, so that a gap 76 is formed between each cusp and the wall 44. As described above, backflow fluid accumulates in gap 76 and exerts pressure on cusp 70, causing the cusp to deform away from wall 44, until the cusp reverses.

Referring particularly to Fig. 7B, in an inverted position, the interior of each cusp 70a-70c accumulates fluid with retrograde flow. The application of pressure on the cusps causes them to move towards each other, until the cusps 70a-70c meet in a second position and reduce the flow that exceeds the cusps 70a-70c with respect to that existing when the cusps 70a- 70c are in the first position. Referring to Fig. 9, opening 72 is significantly reduced, thereby restricting fluid flow. The cusps 70a-70c remain in the second position until the pressure exerted on the cusps 70a-70c by the forward flow of the fluid reverses the cusps to the first position.

Although the above embodiments describe a device having between one and three cusps, any number of cusps can be used to prevent retrograde flow through a vessel. The cusps can be arranged symmetrically, as shown, or they can be arranged in any other configuration.

Although the embodiments described above included cusps of similar size and configuration, cusps of different sizes and configurations can be used in conjunction with each other.

The anchoring member can take a number of different shapes that allow the end of the cusp to penetrate the wall of a blood vessel and prevent the end of the cusp from re-entering the vessel. For example, the anchor element can be a barb element, as shown in the embodiments described above. Alternatively, the anchor element may be a harpoon device 80 as shown in Fig. 10, in which the harpoon 80 penetrates the wall of a vessel and the tips 82 prevent the anchor from re-entering the vessel. In another embodiment, the anchor member may define a loop 84, as shown in FIG. 11, in which the looped end 86 prevents the anchor from re-entering the vessel.

In other embodiments, a cusp can include more than one anchor element. A cusp can have other polygonal configurations. For example, a generally rectangular cusp can be attached to a vessel using two anchoring elements adjacent to two corners of the cusp. The cusp can form a half cylinder.

There are other embodiments within the scope of the following claims.