Tissue-type Heart Valve With A Graft Support Ring Or Stent

Abstract

A tricuspid valve and a graft support ring or stent therefor. The frame of the stent comprises three wire arcs, each formed along a circular or elliptical cylindrical surface. Each arc has an upstanding end portion that blends into a line parallel to the axis of the cylinder. Preferably, each arc is a separate wire, and, an elastomeric coating or a cloth pledget may lie over the meeting ends, which may be welded together. A fabric covering completely surrounds and encloses the frame, the coating or pledget preventing later strike-through of the fabric by the metal during use. The fabric covering preferably provides a pair of radial wings at each post, one extending inwardly and the other one outwardly, and it also provides a continuous projection along the length of the wires for stitching. To this graft support ring is sutured living tissue, preferably autologous or homologous, by stitches to the wings and the continuous projection. A plurality of such tissue members, e.g., fascia lata, is used, one for each wire arc, shaped to provide a cusp-type valve. The tissue covers essentially all the surfaces of the fabric on both the inner and outer. faces, so that essentially nothing but tissue is in contact with the blood and body tissues after the valve is installed.

Description

BACKGROUND OF THE INVENTION

This invention relates to an improved heart valve, to a graft support ring or stent therefor, and to a frame for the graft support ring or stent.

Various types of homograft and heterograft valves have already been proposed. In many of them a substantial area of fabric is exposed, and this exposure has tended to result in serious conditions, such as problems of thromoembolism and hemolysis, for the fabric, though organically inactive, is not equivalent to living tissue. Vascularization of the valve, even when a part of it is living tissue, is slowed down by the presence of exposed fabric, and the lack of direct contact of the graft tissue with the body tissue.

In the prior art, relatively massive frames of metal have been completely covered with Dacron or Teflon cloth, and a single-piece cylinder of tissue has been placed on the outer face only of such valves. The inner section of cloth was therefore in contact with the blood being pumped, and usually there was no direct contact of the heart wall with the fascial tissue. Other problems were encountered in making the valve, for the sizing of the tissue cylinder was done away from the stent or support ring, so that the size and shape of the cusp tended often to be somewhat inaccurate.

The present invention overcomes many of these difficulties and provides an improved heart valve. A specially structured wire frame covered with cloth provides minimal bulk, and in the completed valve all the fabric surfaces are covered with live tissue. Hence, the completed valve can be sewn into the heart tissue at the proper location with the valve's tissue in contact with the heart wall and with the blood, enabling more rapid vascularization of the valve's tissue. The size and shape of the cusp tissue can be determined before it is affixed to the stent, and it becomes possible to provide a device for holding the stent or graft support ring in position while affixing the tissue.

BRIEF SUMMARY OF THE INVENTION

The stent of the invention has a frame with three wire arcs for a tricuspid valve, preferably a separate wire for each arc. Each wire is formed along a segment of a circular or elliptical cylindrical surface so that the assembled frame is generally circular or elliptical in shape, though not lying in a single plane. Each of the wire arcs has an upstanding portion at each end then that blends into a line which is parallel to the axis of the cylinder and has an arcuately dipped intermediate portion. The impression given is that of a curve along one-third of a cylinder, for example. In this tricuspid valve, each wire is in line radially with an end of a succeeding wire, and the ends preferably overlap only radially, so that the stent frame is no wider along the surface of the cylinder than the wire thickness. The ends of the wire may be secured together by electron beam welding or spot welding, providing a post. Preferably each post of the stent frame where the two wires meet is tipped with elastomer or with a cloth pledget to prevent the raw ends of the wire from striking through the fabric or the tissue which is going to cover the stent frame. A fabric covering completely surrounds the stent frame and encloses it. At each post of the stent the fabric covering preferably provides a pair of radial wings, one extending radially inwardly and the other one radially outwardly, to provide a good anchor for the stitching to be done later. Also, the fabric covering provides an extension going beyond the covering of the wires to provide an anchor for stitching along the arcs.

The heart valve is made by attaching to this graft support ring three tissue members, such as fascia lata or other suitable tissue, preferably homologous or autogenous. The pieces of tissue are secured to the graft support ring at the wings and at the extension along the wires, and they completely cover all the fabric, which has itself completely covered the stent. Thus, all exposed surface is live tissue, the tissue pieces being lapped so that both the inner and outer surfaces of the ring are covered. Hence, the blood and the tissues in the body in which the valve is implaced do not come into contact with any cloth fabric or wire. In insertion of the valve into the body, the wings and extensions again provide anchors for the stitches that secure the valve to the body.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a top plan view of a tricuspid heart valve embodying the principles of the invention.

FIG. 2 is a top plan view of a wire frame for the stent used in the heart valve of FIG. 1 and embodying the principles of the invention. Coatings or pledgets over the post ends are shown in phantom.

FIG. 3 is a view in side elevation of the wire frame of FIG. 2, the pledgets or coatings again being shown in phantom.

FIG. 4 is a view in side elevation similar to FIG. 3 of the completed graft support ring or stent, with the fabric covering thereon.

FIG. 5 is an enlarged view in section taken along the line 5--5 in FIG. 4, showing the fabric extension.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS

The frame of the stent is preferably made from a plurality of wire segments. Although it is possible to make it from a single wire, such a frame is usually less satisfactory because of the bulk at the posts, and a much better stent, lighter and thinner at the posts, can be made from the segmented type of structure.

A Tricuspid Valve (FIGS. 1 to 5)

FIGS. 2 and 3 show a wire frame 10 made from three wires 11, 12, 13. Each wire lies along what is substantially a cylindrical surface, and the general effect in plan, as shown in FIG. 2, is that of a circle. The stent frame 10 need not be truly circular, since the stent 10 is preferably formed into a shape equivalent to the outside of the cusps of an aortic or mitral valve. Each wire 11, 12, 13 has two end portions, so that the wire 11 has end portions 14 and 15, the wire 12 has end portions 16 and 17, and the wire 13 has end portions 18 and 19. These end portions 14, 15, 16, 17, 18, and 19 are generally upstanding, with a straight upper portion blending into a curved or generally arcuate portion 21, 22, or 23, respectively, that joins the ends of the wires 11, 12, and 13. Each end itself blends in with a line which is parallel to the axis of the cylinder around which the segment lies.

A very important feature of the invention as applied to a tricuspid valve is that the meeting ends 14, 19 and 15, 16 and 17, 18 of each two wires 11, 13 and 11, 12 and 12, 13, while lapped, do not extend beyond each other along the cylinder of envelopment, and they lie radially in line. Thus, the ends 14 and 19 are radially in line, and the end 14 lies radially within the end 19, and the same is true of the ends 15, 16 and the ends 17, 18, so that there is no widening along the cylinder as a result of the ends joining together. The ends 14, 19 and 15, 16 and 17, 18, when properly located, are welded together, preferably by electron beam welding to prevent adulteration, to form posts 24, 25, and 26, which are preferably straight but can incline outwardly up to about 10.degree..

Each of the posts 24, 25, and 26 is preferably covered by a shield or cap 27, 28, 29, comprising either a coating of elastomer such as silicone rubber, or a pledget of fabric such as Teflon or Dacron. These caps or shields 27, 28, 29 cover the ends of the wires 11, 12, and 13 and the weldments joining them and provide a very smooth surface, so that the likelihood of strike-through of the cloth covering and of the tissue during use is greatly diminished or substantially eliminated. Thus is the frame 10 completed.

The stent or graft support ring 30, as shown in FIG. 4 is made by covering the frame 10 with a fabric covering 31. As shown in FIG. 5, the covering 31 may be all one piece and may include a tubular portion 32 and an extension portion 33. The extension portion 33 may comprise a pair of folded sections 34 and 35 held to the tubular portion 32 by a line of sewing 36 and held to each other near the outer edge by a line of sewing 37. The extension 33 provides an anchor for stitches when securing tissue to the graft support ring 30 and when sewing the valve into the heart.

Around each of the posts 24, 25, and 26, the fabric covering is preferably provided with a pair of radially extending webs or wings 41, 42 and 43, 44 and 45 (the third outer wing not showing in FIG. 4). This provides additional anchors for stitching the graft tissue. As noted before, the shields or caps 27, 28 and 29, of silicone rubber or fabric pledgets, prevent strike-through of the cloth 31 and protect it from the ends of the posts 24, 25 and 26.

In making the heart valve 50 of FIG. 1, the graft support ring 30 provides the support for three pieces 51, 52, and 53 of tissue, such as fascia lata or periocardial tissue from the patient or from a donor or dura mater tissue from a donor. The type of tissue is not critical to the present invention. When the tissue is cut from the patient, it is cut into three strips and placed on the holder and is then draped on to the graft support ring 30 without tension, preferably with a straight trimmed edge 54, 55, 56, 57 and 58, 59 at each coaption area. The assembly may be retained at first by the holding device with the aid of some needles, if desired, then the three prepared sections 51, 52, 53 are brought together and clamped, the ring 30 slipped into the holder and pushed into place. Sutures 60, 61, 62 are then taken on either side or both sides of the posts through the wings 41, 42, 43, 44 45, 46 and passed through the overlying tissue sections 51, 52, 53. Serially, each tissue section 51, 52, 53 is cut along the edge which determines the amount of fascia or tissue needed to lap over the cloth 31 at the cusp base. The fascia is folded over the frame and sutured by multiple stitches 63, 64, and 65 along the cloth portion 32 covering the frame 10 and the extension 33 and again by other stitches to the wings 41, 42, 43, 44, 45 and 46. The tissue is brought inside the frame for stitching in order to leave the action of the cusps free.

In implantation of the valve, whether in the aorta or in the atrioventricular position, the cloth extension 33, though covered with tissue, is used as the sewing ring with stitches taken through the tissue material, the cloth, and the heart tissue at the same time. The close approximation of the tissue and the heart wall enables early vascularization to take place and also improves the probability of long term stability of the fascia or other tissue acting as the valve cusps.

In this tricuspid valve, the radial disposition of each pair of wire ends 14, 19 and 15, 16 and 17, 18, as shown in FIGS. 2 and 3, enables the cuspid tissue to coapt better, and the wings 41, 42, 43, 44, 45, and 46 enable better attachment of the tissue.

The valve 50 thus includes a lightweight frame 10, which is constructed to enable complete coverage with tissue, thereby enabling better vascularization of the tissue valve when it is attached to the heart muscle. The valve 50 provides for direct tissue-to-tissue contact and this, in turn, prolongs the life and potency of the valve, affords little or no fibrotic buildup, a phenomenon which tends to occur when the heart tissue is in contact with cloth, as in prior art valves. Also, the tendency toward thrombosis is greatly reduced. In addition, it is noted that there is better coaption of the cusps than in prior art valves.

The type of frame 10 and stent 30 may be used to provide complete covering with tissue for both homograft and heterograft transplantation, but of course in general autogenous tissue is preferred.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

Claims

We claim:

1. A heart valve stent frame of metal wire formed along a closed-curve cylindrical surface and comprising a plurality of upstanding posts blending into a plurality of arcuately dipped portions, each said post comprising two wire portions, one radially within the other so that the circumferential thickness of each said post is only the width of one said wire portion.

2. The stent frame of claim 1 having a smooth shield covering each said post.

3. The stent frame of claim 2 wherein said shield comprises an elastomeric coating.

4. The stent frame of claim 2 wherein said shield comprises a fabric pledget.

5. A tricuspid heart valve stent frame, comprising three metal wires, each formed generally along a segment of a closed-curve cylindrical surface, each wire having an upstanding portion at each end parallel to the axis of the cylinder and also having an arcuately dipped intermediate portion, each end of each wire being in-line radially with the end of another said wire and secured to it, whereby the meeting ends lie with one end radially within the other and without increasing the thickness along the cylindrical surface beyond the wire thickness.

6. A tricuspid heart valve stent frame, comprising

three identical curved wires disposed in a circular closed figure around a circular cylindrical surface,

each wire having an upstanding vertical portion at each end parallel to the axis of the cylinder and having an arcuately dipped intermediate portion,

the wire ends of each adjacent pair of wires being welded together radially in line, whereby the meeting ends lie with one end radially within the other without increasing the thickness along the cylindrical surface beyond the wire thickness.

7. The stent frame of claim 6 wherein said welded ends are covered with a smooth shield.

8. The stent frame of claim 7 wherein said shield comprises a coating of silicone elastomer.

9. The stent frame of claim 7 wherein said shield comprises a fabric pledget.

10. A tricuspid graft support ring for valve fabrication and implantation, including in combination:

a frame of metal wire encircling a closed-curved cylindrical surface and having a plurality of upstanding posts blending into a plurality of arcuately dipped intermediate portions,

each post comprising two substantially parallel wire portions in-line radially so that the thickness of each post along the circumferential distance is only that of one said wire portion, and

a fabric covering completely surrounding said frame and enclosing the frame and providing extension portions for anchoring stitches.

11. The ring of claim 10 for a tricuspid valve having three posts and three arcuately dipped portions and being generally circular in shape.

12. The ring of claim 10 wherein said extension portions of said fabric covering comprise a pair of radial wings at each post, one extending inwardly and one outwardly and a continuous portion along each arcuately dipped portion.

13. The ring of claim 10 wherein said upstanding posts are smoothly covered by shield means to prevent the metal from striking through the fabric.

14. The ring of claim 13 wherein the smooth covering shield means is an elastomeric coating on the wire.

15. The ring of claim 13 wherein the smooth covering shield means is a cloth pledget.

16. The ring of claim 10 wherein said frame comprises three wires secured together, their ends meeting at the posts.

17. A graft support ring for valve transplantation, including in combination:

a frame made up of three metal wires, each formed generally along a segment of a circular cylindrical surface, each wire having an upstanding portion at each end parallel to the axis of the cylinder and having an arcuately dipped intermediate portion, each end of each wire being in line radially with the end of another said wire and secured to it, so that the meeting ends lie with one radially within the other and without adding to the thickness along the cylindrical surface, said meeting ends forming three posts,

a shield over each said post, and

a fabric covering completely surrounding said frame and enclosing the frame, said shield preventing later strikethrough of the cloth by the metal during use, said fabric covering providing a pair of radial wings at each post for receiving stitches, one extending inwardly and one outwardly, and providing a stitch-receiving projection along said arcuately dipped portions.

18. A tricuspid heart valve, comprising

a metal frame formed along a closed-curve cylindrical surface and comprising three upstanding posts blending into three arcuately dipped intermediate portions,

each said post comprising two wire portions disposed so that one lies radially within the other so that each post is only as wide in a circumferential direction as one said wire portion,

a fabric covering completely surrounding said frame and enclosing the frame and providing extension portions for receiving stitches, and

three tissue members, one for each said dipped portion shaped to meet in a cusp and provide a tricuspid valve and covering all surfaces of said fabric and frame both inside and out and sutured to said fabric.

19. The heart valve of claim 18 wherein said extensions comprise a substantially continuous extension along each said dipped portion and a pair of radially extending wings at each said post, one extending in radially and the other extending out radially.

20. A heart valve, comprising

a frame made up of a plurality of wires, each formed along a circular cylindrical surface, each wire having an upstanding portion at each end blending into a line parallel to the axis of the cylinder and having an arcuately dipped intermediate portion, each end of each wire being in line radially with the end of an adjacent said wire, so that when the ends meet, they lie with one radially within the other and meet without forming a thickness greater than their wire thickness along the cylindrical surface, said meeting ends forming posts,

a smooth covering over each said post,

a fabric covering completely surrounding said frame and enclosing the frame, said smooth covering preventing later strike-through of the cloth by the metal during use, said fabric covering providing a pair of radial wings at each post, one extending inwardly and one outwardly, and providing a continuous projection along each said arcuately dipped portion, for sewing attachment, and

a plurality of tissue members, one for each said wire, shaped to provide a cuspid valve and covering substantially all surfaces of said fabric and wires, both inside and out, and sutured to said fabric wings and said projection.

21. The valve of claim 20 wherein there are three said wires with three equally spaced posts and three tissue members.