CA1107903A

CA1107903A - Open ring valve prosthesis with velour exterior

Info

Publication number: CA1107903A
Application number: CA301,993A
Authority: CA
Inventors: Denton A. Cooley
Original assignee: COOLEY DENTON
Current assignee: COOLEY DENTON
Priority date: 1977-05-16
Filing date: 1978-04-26
Publication date: 1981-09-01
Also published as: JPS53142093A; US4164046A

Abstract

Abstract of Disclosure An improved valve prosthesis for mitral and tricuspid heart valves, the valve prosthesis being configurated as an open ring and covered with a double velour fabric having a laterally projecting fabric appendage for simultaneously facilitating suturing the prosthesis in place and improving tissue infiltration.

Description

79~3 VAI.VE PROSTHESIS
~Eecific~tion The present invention relates to an improved heart valve prosthesis for use in improving the function of the mitral and/or tricuspid heart valves.
The bicuspid or mitral valve is located in the left atrioventricular opening of the heart. It is encircled by a dense fibrous ring and consists of two valve leaflets of unequal size. The larger valve leaflet (called ventral or anterior cusp) is placed adjacent the aortic opening. The smaller leaflet is the dorsal or posterior cusp. The leaflets are composed of strong fibrous tissue which is thick in the central part but thin and translucent near the margin. The valves are constructed so as to pass blood unidirectionally from the left atrium to the left ventricle of the heart.
The tricuspid valve is located in the right atrio-~; ventricular opening and comprises three leaflets sometimes referred to as the anterior, posterior and septal cusps. The leaflets are roughly triangular inshape and attached to a fibrous ring with the apices projecting into the ventricular cavity.
Both the mitral and tricuspid valves are intended to prevent regurgitation of blood from the ventricle into the atrium when the ventricle contracts. In order to withstand the substantial back pressure and prevent -~ regurgitation of blood into the atrium during the ventricular contractio~, the cusps are held in place by delicate but strong fibrous cords which anchor the valve ~0 cusps to the muscular wall of the heart.

1~079~3 In some well recognized instances of heart disease, howe~er, valve leaflet prolapse is evident. Prolapse of the valve leaflet appears to result from a dilatation or elongation of the posterior two-thirds of the valve annulus. A number of circumstances may cause the valve defect. The result of the defect, however, is the failure of normal apposition of the leaflets. When the leaflets fail to close completely during ventricular systole, the leaflets become damaged, the cords ruptured and the atrioventricular annulus distended. The result of the valve prolapse is a syndrome often associated with chest pain, cardiac arrythmias, dyspnea, and other adverse clinical symptoms.
One obvious solution to a serious valve prolapse is total valve replacement. It is generally agreed, however, that total valve replacement is too radical except in the most advance cases. Accordin~ly, treatment of valve prolapse by ~echniques of annuloplasty have become more commonplace.
One of the more common annuloplastic techniques consists of suturing (plicating~ the two valve leaflets together at the commissures so as to reduce the size of the opening through which blood can pass. The purpose of this suture is to draw the anterior and posterior ~- cusps sufficiently close together that normal apposition will occur during ventricular systole. Experience has proved, however, that plication of the annulus at the commissures places extreme stress on the tissue adjacent ,, .
., ,~, '79(1 3 the sutures with the unfortunate result that the sutures tear from the tissue damaging the leaflets and recreating the conditions susceptible to prolapse.
A valve prosthesis for mitigating the serious valve insufficiency described above is suggested by Carpentier in the Journal of Thoracic and Cardiovascular Surgery Volume 61, No. 1~ January 1971. The prior art valve prosthesis described therein consists of a rigid circular or oval ring covered with a Teflon fabric which permits the ring to be sutured in place. The Carpentier ring was an improvement in many respects over earlier techniques. However, two inherent disadvantages in the Carpentier ring have become apparent. First, in order to secure the ring in place, suture placement is required along the anterior section of the annulus adjacent the aortic valve. Not infrequently, sutures are inadvertently passed into the aortic valve so as to interfere with the valve function. Moreover, to secure the rigid structure adjacent the largest (anterior) leaflet has the effect of interfering with mitral valve function. Second, with the passage of time sutures used for securing prior art prostheses may be subject to degeneration as a resul~ of continual heart and valve action. Suture degeneration can result in separation of the prosthesis from its secured position causing at - least partial failure of the prosthesis and risking interference with valve function.
Accordingly, it would be a significant improvement in the art to provide a heart valve prosthesis which * Trademark ~ 79M~3 restores valve function without interfering with adjacent valves and which would promote tissue adherence through natural fibroblastic growth and endotheliæation through natural processes so as to maintain the prosthesis securely in place. Such an improvement is disclosed and claimed herein.
The present invention comprises a uniquely shaped ; open ring valve prosthesis having a velour exterior for effecting mitral and tricuspid annuloplasty and for overcoming valve incompetence. The surface of the valve promotes a surprising degree of tissue infil-tration and adherence.
It is, thereforeJ a primary object of the present invention to provide an improved heart valve prosthesis.
It is another valuable object of the present invention to provide a valve prosthesis for the mitral and tricuspid valves which are configurated in the form of an open ring.
Another important object of the present invention is to provide a heart valve prosthesis having an exterior coating of velour fabric.
Another object of the present invention is to provide an open ring mitral valve prosthesis constructed to leave at least the anterior valve completely without rigid support while at the same time contracting the ~-~ valve annulus in the vicinity of the posterior leaflet and valve commissures.
Another object of the present invention is to provide a tricuspid valve prosthesis configurated as an ih~7903 open ring, the open portion of the ring being constructed to leave most of the posterior leaflet mobile while securing the tricuspid valve annulus.
In accordance with a broad aspect, the invention relates to a heart valve prosthesis comprising an open ring portion comprising: ~

a flexible fabric spine having two ends, said spine being initially straight in configuration though bendable into said open ring configuration with the two ends spaced one from the other a distance sufficient to permi~ the positioning of at least one heart valve leaflet therebetween, the length of thè spine portion approximating the arcuate distance between commissures of a selected heart valve leaflet; and a velour sheath encapsulating the entire fabric spine portion. ~

In accordance with a further broad aspect, the invention relates to a heart ~alve prothesis comprising:

a spine portion and first and second end portions integral therewith comprising an elongated open ring, the first and second end portions ~eing appreciably arcuately configurated into a size corresponding to thç fibrous ring formed in the atrioventricular orifice, the end portions being spaced one from the other a distance which is selected to permit the unencumbered movement of a predetermined one of the heart valve leaflets which is positioned therebetween;
and a velour fabric sheath positioned upon the exterior of said elongated open ring so as to entirely cover the spine and end portions, the velour nap being exposed through the exterior and the fabric extending laterally away from the open ring to form an appendage~

In accordance wit.h a further broad aspect, the inventlon relates to a valve prosthesis for a heart valve having at least two leaflets comprising:

an elongated open ring having two ends spaced one from the other a distance sufficient to permit the positioning of at least one heart valve leaflet therebetween, the open ring presenting a velour fabric exterior.

In accordance with a further broad aspect, the invention relates to a mitral valve prosthesis comprising:
an essentially symmetrical, elongated open ring comprising a spine having opposed ends, the ends being spaced one from the other a distance which is selected to permit unencumbered movement of the anterior leaflet of the mi~ral valve between the ends when the prosthesis is in place in the mitral valve annulus; and ~..
a double ~elour fabric sheath posit~oned upon the exterior of said elongated open ring so as to substantially encapsulate the spine, the velour fabric being ~oined to the spine so as to come into direct contact with surrounding tissue when the prosth sis is in place ~ithin the mitral valve annulus.

In accordance with a further broad aspect,-the invention relates to a tricuspid valve prosthesis comprising:
an asymmetrical~ elongated open ring comprising a stiff spine ha~ing opposed ends, one of the ends bending through a greater arc than the other end and the ends being spaced one from the other a distance which is selected to permit unencum~ered movement of the septal leaflet of the tricuspid ~alve between the ends whPn the prosthesis is in place in the tricuspid valve annulus; and ~ double velour fabric ~heath positioned upon the exterior o~ said elongated open ring so as to substantially encapsulate the spine, the velour fabric being joined to the spine so as to come into direct contact with surrounding tissue when the prosthesis is in place within the tricuspid valve annulus.

These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawing.
Figure 1 is a schematic illustration of the prior art technique of effecting annuloplasty through plication of annulus at the commissures.
Figure 2 is a presently preferred mitral valve prosthesis embodiment.
Figure 3 is a cross section taken along lines 3-3 of Figure 2.
Figure 4 is a schematic illustration of a presently preferred tricuspid valve prosthesis. Figure 5 is a ; cross section taken along lines 5-5 of Figure 4.
Fi~ure 6 is an illustration of the mode of implan-tation of the mitral valve embodiment of Figure 2.
Figure 7 i5 a schematic illustration of the mitral valve embodiment of Figure 2 sutured in place upon a mitral valve.
- Figure ~ is a graphical illustration of the - surprisingly improved tissue adhesion effected through the use of the double velour fabric utilized by the prosthesis embodiments of this invention.
Figure 9 is a schematic plan view of a flexible valve prosthesis embodiment, the broken line portion representing the configuration into which the prosthesis 079~)3 will be bent upon securement to the mitral valve annulus.
Figure 10 is a schematic cross-sectional view of the embodiment of Figure 9 in a state of partial dis-assembly to reveal interior construction.
The present invention, as represented by the pres-ently preferred embodiments disclosed herein, provide a valve collar prosthesis which restores valve competence and at the same time promotes a surprising degree of fibroblastic growth and endotheliazation to assure that the prosthesis will remain in place and continue its function even if the sutures should degenerate over tlme.
Referring now to ~igure 1, a schematic illustration of one widely recognized prior art technique for valve annuloplasty is illustrated. In ~igure 1, a mitral - valve generally designated 12 is illustrated. The mitral valve has an anterior leaflet 14 and a smaller posterior leaflet 16. For convenience, the left atrium 18 is illustrated schematically.
At the eommissures 20 and 22, the leaflets 14 and 16 are secured together with sutures 24 for the purpose of reducing the enlarged opening between the leaflets 14 - and 16. It is the stretched and enlarged opening between the leaflets which permits prolapse of the valve under pressure from the blood. Unfortunately, however, the sutures 24 tend to tear from the delicate tissue forming the leaflets 14 and 16 under the significant back pressure exerted by the blood.

~ ~ 79N33 In accordance with the present invention, one preferred embodiment of which is illustrated in Figure

2, an open ring valve prosthesis generally deslgnated 26 can be used to effect annuloplasty of a distended mitral valve. Referring now more particularly to Figure 2, it will be observed that the valve prosthesis is shaped as an open ring having an elongated central member 28 and integral, coplanar ends 30 and 32 which are bent each toward the other. As shown best in Figure 3, the prosthesis 26 preferably includes a spine comprising comparatively stiff interior rod 34, preferably formed of metal such as titanium. Clearly, other suitable stiff or semirigid materials could be used to form rod - 34. The exterior of the rod 34 is encapsulated in a - sheath 3~ of double velour fabric. The term "double `
- velour" fabric, as used herein means fabric having a velour nap on both front and back surfaces. The ends of the double velour fabric are joined together and project laterally away from the rod 34 to form an appendage 38 of fabric. While any suitable velour fabric could be used, a double velour knitted material formed of Dacron polyester has been found highly effective.
The velour fabric has two significant advantages.
First, it provides a convenient medium thrcugh which suture can be placed to secure the prosthesis ~6 to the surrounding fibrous tissue. Second, the velour fabric has been found surprisingly effective in encouraging endotheliazation. In order to adequately fill the desirable criteria for a valve prosthesis, the encapsu-Trademark , -~s Ir--,~ .~, ,, ~ilO79C~3 lating fabric should be strong, durable and biocompatible and at the same time permit long term healing and incorporation into surrounding tissues. The "velour" construction has tiny loops of polyester fabric presenting a soft surface with high pile and more pliable consistency which facilitates passage of the suture. Notably, the velour surface of the fabric is present entirely around the rod 34 to permit tissue infiltration from any direction. It was determined that the double velour fabric exhibited surprising resistance to separation from the infiltrated tissue (adventitia).
These surprising results were evidenced in part by laboratory investigations comparing double velour, warp knitted fabric and woven Dacron fabric of the low porosity type (see Figure 8).
In conducting the investigations, anesthetized dogs were intubated endotracheally for respiratory support and the abdominal aorta was exposed by a midline laparotomy. The aorta from just below the renal arteries to the trifurcation was removed and replaced by grafts of the double velour, knitted and woven types.
Anastomoses were made with 5-0 polypropylene continuous sutures. The peritoneum was closed over the graft and ~ the abdominal incision was repaired. Intramuscular -~ streptomycin was given for prophylaxis against infection. The dogs were well attended, fed and exercised during the ensuing six weeks and then sacrificed.
* Trademark s; ~ , .

~ 9~ 3 The grafts were opened longitudinally and examined.
Peel tests were performed using a modified Instron tensile strength testing device to ascertain the degree of adherence of the three graft types to the surrounding external tissue. The results of the investigation are illustrated in Figure 8. The double velour fabric proved to be strikingly more adherent to the surrounding tissue demonstrating more than ten times the force of adherence of the non-double velour fabrics. It is believed that the profound adherence of the double velour grafts to surrounding tissue is the result of-rapid fibrous tissue infiltration.
Insertion of thè mitral valve prosthesis, as will be understood by persons skilled in the art, is performed by using a standard midline sternotomy.
Temporary cardiopulmonary bypass with hemodilution is employed and the mitral valve i8 exposed through an incision medial to the right pulmonary veins. The distance between the peripheral extent of the commissures or the actual width of the anterior leaflet is measured or estimated and a prosthesis 26 of appropriate size is selected. Typical of adequate sizes for the prosthesis 26 would include 25, 30 and 35 millimeters maximum diameter.
The prosthesis 26 is positioned such that the anterior leaflet 14 of the mitral valve 12 is situated in the free zone between the ends 30 and 32 of the prosthesis 26. As shown best in Figure 6, mattress sutures are symmetrically placed around the prosthesis trademark ~3 .

79{1 3 26 and thro~gh the fabric 36 to maintain proper spacing.
A double-needle suture of braided 2-0 polyester is used with a Teflon felt pledget 40 attached individually to the ends of the suture 42.
Use of alternating colored sutures facilitates identification and separation of the suture for tying.
The sutures are placed carefully into the fibrous portion 44 of the annulus but not deeply enough to encircle or injure the underlying circumflex branch of the left coronary artery or the coronary sinus. When all of the sutures are tied, the distended annulus is constricted to its normal size and the mitral valve has ` renewed competence with free action of the anterior : leaflet 14. Figure 7 illustrates the prosthesis in its fully implanted position.
Another valve prosthesis embodiment generally designated 50 is illustrated in Figures 4 and 5. This `~ collar ring prosthesis 50 has a configuration which differs from the configuration of the embodiment of 20 Figure 2 primarily to accommodate annuloplasty of a -tricuspid valve. The prosthesis 50 has an enlarged coplanar ascending portion 52 which turns inwardly at 54 and terminates at end ~6. The opposite end 58 traverses a slight bend which, by contrast to the embodiment of Figure 2, is significantly less than the angle traversed by the end 56. The prosthesis 50, as shown in Figure 5, has a spine comprising an interior rod 60 which is circumscribed by a velour fabric 62. The rod 60 is ;~
preferably formed of titanium metal, however, any Trademark x~

suitably biocompatible stiff or semirigid material could be used. The ends of the fabric are joined together to form an appendage 64. Thus, the entire exterior surface of the prosthesis 50 is covered with velour fabric.
Preferably the velour fabric is a double velour having nap on both sides thereof.
The tricuspid prosthesis 50 is secured in essen-tially the same manner as that described in connection with Figure 6. In the prosthesis 50, however, the ends 56 and 58 are positioned on either side of the posterior or septal leaflet such that the septal leaflet is ~;~ situated in the free zone between ends 56 and 58 of prosthesis 50. As with the mitral valve prosthesis 26, the prosthesis 50 does not interfere with leaflet function.
Referring to Figures 9 and lO, still another ; presently preferred heart valve prosthesis generally designated 70 is illustrated. The prosthesis 70 differs : from the embodiments illustrated in Figures 2 and 4 primarily in that the prosthesis has a more flexible construction. With particular reference to Figure 10, the prosthesis 70 is interiorly provided with a flexible interior spine 78 preferably formed of braided dactron tape. The flexible spine 78 is sutured at 79 to a velour fabric 8G. Preferably, the fabric 80 is a double velour fabric for maximizing the advantages of early endotheliazation.
The first fabric spine 78 is desirably folded axially and rolled into the velour fabric 80. The Trademark ,, , '79~3 velour ~abri 80 is suEEiciently greater in lateral climension that the entire spine fabric 78 is sheathed within the velour fabric 80. The velour fabric 80 is then sutured as at 77 along the forward edge of the prosthesis 70.
The flexible prosthesis 70 thus constructed, can be easily configurated in any one of a variety of suitable heart valve configurations including both of those illustrated in Figures 2 and 4. The broken line position illustrated in Figure 9 represents the configuration into which the prosthesis would be configurated upon placement during mitral valve annuloplasty. The length of the prosthesis 70 is specifically constructed such that the ends 72 and 74, when displaced into the proper configuration, will be spaced so as to correspond essentially to the arcuate distance between commissures of the mitral heart valve leaflet. Clearly, the length of the prosthesis 70 may be varied to correspond to any selected heart valve subject to valvular annuloplasty. This flexible prosthesis embodiment has been found highly effective in restoring valve function by constricting the valve annulus without interfering with leaflet mobility.
The invention may be embodied in other specific forms without departing from its spirit or essential ~ ~
characteristics. The described embodiments are to be ~ -considered in all res~ects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than 79~3 by the foregoing description. All changes which come within the meaning and range of equivalency of the c~aims are to be embraced within their scope.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A heart valve prosthesis comprising an open ring portion comprising:
a flexible fabric spine having two ends, said spine being initially straight in configuration though bendable into said open ring configuration with the two ends spaced one from the other a distance sufficient to permit the positioning of at least one heart valve leaflet therebetween, the length of the spine portion approximating the arcuate distance between commissures of a selected heart valve leaflet; and a velour sheath encapsulating the entire fabric spine portion.

2. A heart valve prosthesis comprising:
a spine portion and first and second end portions integral therewith comprising an elongated open ring, the first and second end portions being appreciably arcuately configurated into a size corresponding to the fibrous ring formed in the atrioventricular orifice, the end portions being spaced one from the other a distance which is selected to permit the unencumbered movement of a predetermined one of the heart valve leaflets which is positioned therebetween;
and a velour fabric sheath positioned upon the exterior of said elongated open ring so as to entirely cover the spine and end portions, the velour nap being exposed through the exterior and the fabric extending laterally away from the open ring to form an appendage.

3. A heart valve as defined in claim 2 wherein said spine portion and end portions are fabricated from flexible fabric which is covered with a double velour sheath.

4. A heart valve as defined in claim 2 wherein said spine portion and end portions are fabricated from stiff metal which is covered with a double velour sheath.

5. A valve prosthesis for a heart valve having at least two leaflets comprising:
an elongated open ring having two ends spaced one from the other a distance sufficient to permit the positioning of at least one heart valve leaflet therebetween, the open ring presenting a velour fabric exterior.

6. A prosthesis for a heart valve is defined in claim 5 wherein said ring comprises a spine formed of essentially stiff titanium metal.

7. A prosthesis for a heart valve as defined in claim 5 wherein said open ring comprises a spine of stiff material and wherein said spine is covered with double velour fabric, the double velour fabric being joined in a laterally extending appendage.

8. A mitral valve prosthesis comprising:
an essentially symmetrical, elongated open ring comprising a spine having opposed ends, the ends being spaced one from the other a distance which is selected to permit unencumbered movement of the anterior leaflet of the mitral valve between the ends when the prosthesis is in place in the mitral valve annulus; and a double velour fabric sheath positioned upon the exterior of said elongated open ring so as to substantially encapsulate the spine, the velour fabric being joined to the spine so as to come into direct contact with surrounding tissue when the prosthesis is in place within the mitral valve annulus.

9. A tricuspid valve prosthesis comprising:
an asymmetrical, elongated open ring comprising a stiff spine having opposed ends, one of the ends bending through a greater arc than the other end and the ends being spaced one from the other a distance which is selected to permit unencumbered movement of the septal leaflet of the tricuspid valve between the ends when the prosthesis is in place in the tricuspid valve annulus; and a double velour fabric sheath positioned upon the exterior of said elongated open ring so as to substantially encapsulate the spine, the velour fabric being joined to the spine so as to come into direct contact with surrounding tissue when the prosthesis is in place within the tricuspid valve annulus.