Heart valve holder that resist suture looping

An improved holder, system and method for implanting a tissue-type prosthetic mitral heart valve that prevents suture looping and may also constrict the commissure posts of the valve. The holder may include two relatively movable plates, one of which attaches to the valve sewing on the inflow end of the valve ring and the other which attaches via sutures or similar expedient to the valve commissures on the outflow end. Separation of the plates places the sutures in tension and constricts the commissures. The sutures may be strands or filaments, or may be wider bands of flexible biocompatible material. If bands are used, they desirably cover the commissure post tips to further help prevent suture looping thereover. The flexible lengths of material extend directly between commissures of the valve, or may extending radially inward from each commissure to a central upstanding member. Desirably, a slide is created by the flexible lengths of material adjacent each commissure post, for example by crossing over suture filaments at or radially inward from the commissure posts. If an upstanding member is used, the lengths of suture extend axially beyond the commissure post tips to create a tent that wards off sutures that otherwise might loop around the tips during advancement of the valve along an array of pre-implanted sutures.

FIELD OF THE INVENTION

The present invention relates generally to medical devices, and more particularly to an apparatus for facilitating the implantation of a bioprosthetic replacement heart valve, particularly a mitral valve, and associated methodology.

BACKGROUND OF THE INVENTION

In mammalian animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves and have leaflets to control the directional flow of blood through the heart. The valves are each mounted in an annulus that comprises a dense fibrous ring attached either directly or indirectly to the atrial or ventricular muscle fibers. Various surgical techniques may be used to repair a diseased or damaged valve. In a valve replacement operation, the damaged leaflets are excised and the annulus sculpted to receive a replacement valve.

Two primary types of heart valve replacements or prostheses are known. One is a mechanical-type heart valve that uses a ball and cage arrangement or a pivoting mechanical closure to provide unidirectional blood flow. The other is a tissue-type or “bioprosthetic” valve which is constructed with natural-tissue valve leaflets which function much like a natural human heart valve's, imitating the natural action of the flexible heart valve leaflets which form commissures to seal against each other to ensure the one-way blood flow. In tissue valves, a whole xenograft valve (e.g., porcine) or a plurality of xenograft leaflets (e.g., bovine pericardium) provide occluding surfaces that are mounted within a surrounding stent structure. In both types of prosthetic valves, a biocompatible cloth-covered sewing or suture ring is provided on the valve body, for the mechanical type of prosthetic valve, or on the inflow end of the stent for the tissue-type of prosthetic valve.

In placing a tissue type prosthetic valve in the mitral position, the commissure posts are on the blind side of the valve and may become entangled with pre-installed sutures, and may damage the annulus or tissue during delivery. The difficulty of the delivery task is compounded if the surgery is through a minimally-invasive access channel, a technique that is becoming more common. The problem of entanglement is termed “suture looping,” and means that the suture that is used to attach or mount the valve to the heart tissue is inadvertently wrapped around the inside of one or more of the commissure post tips. If this occurs, the looped suture may damage one of the tissue leaflets when tightly tied down, or at least may interfere with the implant procedure or valve operation and prevent maximum coaptation of the valve leaflets, resulting in a deficiency in the prosthetic mitral valve.

Some attempts have been made to overcome these problems in current holders for prosthetic mitral valves. An example of such a holder is U.S. Pat. No. 4,865,600, Carpentier, et al., incorporated herein by reference. Carpentier provides a holder having a constriction mechanism that constricts the commissure posts inwardly prior to implantation. The Carpentier device provides an elongate handle to both hold the valve/valve holder combination during implantation, as well as to cause the commissure posts to constrict inwardly. The valve is connected to the valve holder by the manufacturer using one or more sutures, and the combination shipped and stored as a unit. During the valve replacement procedure, the surgeon connects the handle to the holder and locks a locking nut to hold the commissure posts at a given constricted position. The surgeon then attaches the sewing ring of the valve to the native valve annulus with an array of sutures that has been pre-embedded in the annulus and extended outside the body. The valve is then advanced along the array of sutures to its desired implantation position and the sutures tied off. When the holder is cut free, the commissure posts are released to expand and the holder may be removed using the handle. However, even when the commissure posts are constricted, slack in the array of sutures, for example, may lead to looping of sutures around one of the cloth-covered commissure posts, which interferes with the implantation procedure.

What is needed then is an improved tissue-type prosthetic valve holder attachable to the inflow end of the valve that insures against suture looping.

SUMMARY OF THE INVENTION

The present invention provides a holder for a tissue-type prosthetic heart valve having an inflow end and an outflow end and a flow axis therebetween. The valve includes an annular suture ring at the inflow end attached to a stent having posts circumferentially-spaced about the flow axis that support occluding tissue surfaces of the valve. In this type of valve the posts are cantilevered generally in the outflow direction.

The present invention provides an improved holder system for preventing suture looping around the commissure posts of tissue-type heart valves that are implanted in the direction where the commissure posts form the leading end of the valve. For instance, the present invention provides an improved holder for a mitral valve. In general, the invention provides improvements to an arrangement of lengths of flexible material extending between the commissure posts of the valve. Each length of flexible material extends axially, desirably through the valve, to be connected at two points to a rigid holder structure that abuts the inflow end of the valve. Severing the lengths of flexible material near one of the attachment points permits removal of the entire length of material from the valve along with the rigid structure, by virtue of the second attachment point. In a preferred embodiment, the rigid structure incorporates a mechanism for pulling the lengths of flexible material to cause the commissure posts of the valve to flex inward.

In one particular embodiment, a holder is provided that includes a plurality of lengths of flexible material extending in a taut fashion across the outflow end of the valve to prevent suture looping, each length of material having a first segment extending directly between adjacent commissure posts and crossing over each adjacent length of material adjacent to the commissure post. The lengths of flexible material may be sutures, or may comprise a band of biocompatible material, such as polyester. In the latter instance, the band of material may completely cover each commissure post, and may cross over adjacent bands of material.

In another embodiment of the invention, the holder includes a plurality of lengths of flexible material extending in a taut fashion across the outflow end of the valve to prevent suture looping, each length of material having a first segment extending in a band that a substantially wider than it is thick directly between adjacent commissure posts. Each length of flexible material may extend in second segments along two adjacent commissure posts to be attached to the rigid structure at two points. Desirably, the commissure posts are cloth covered and the second segments pass beneath the cloth covering in a configuration that is not as wide as the first segments.

In a further aspect of the present invention, the holder includes a central upstanding member passing along the axis of the valve from the inflow side to the outflow side of the leaflets. A plurality of lengths of flexible material extend in a taut fashion across the outflow end of the valve to prevent suture looping, each length of flexible material having first segments extending radially inward from one of the commissure posts to the central upstanding member. The central upstanding member may be hollow, with each length of flexible material passing into and through the member.

Alternatively, the upstanding member may be solid and include notches for receiving midpoints of the first segments of lengths of flexible material. In this case, each first segment extends from one of the commissure posts radially inward to the upstanding member and then radially outward to an adjacent commissure post via a notch. The upstanding member may include a wide base on an end that is attached to a rigid structure of the holder that abuts the sewing ring. A narrow shaft extends from the wide base and passes between and to the outflow side of the leaflets. The narrow shaft may have a non-circular cross-section, such as triangular, to reduce deformation of the leaflets from long-term storage.

The holder may include a valve abutment portion sized and shaped to abut the suture ring at the inflow end of the valve. The holder may further include a commissure post constriction mechanism adapted to constrict the commissure posts radially inward from a relaxed position to a constricted position when actuated by a handle adapted to operatively connect to the commissure post constriction mechanism. A retaining mechanism may also be provided that retains the commissure post constriction mechanism in the constricted position after the handle is removed.

In one embodiment the commissure post constriction mechanism comprises an adjusting portion and an adjusting member adapted to adjust the distance between the adjusting portion and the valve abutment portion and one or more filaments attached to the adjusting portion and sutured through the end of the commissure posts distal the adjusting portion. When the adjusting member is operated to separate the adjusting portion from the valve abutment portion the adjusting portion pulls the filaments, which in turn urge the end of the commissure posts distal the adjusting portion radially inwardly, to the constricted position.

The valve abutment portion may be of a planar shape, with the adjusting portion of a substantially complementary planar shape to the valve abutment portion. It is preferred that the planar shape of the valve abutment portion be comprised of a plurality of tangs radiating from a central body to each cover a portion of the suture ring. In this manner a sufficient amount of the suture ring is left exposed to allow for suturing the suture ring to the native annulus.

Adjustment of the distance between the valve abutment portion and the adjusting portion may be achieved by providing a central threaded aperture in the adjusting portion and an adjusting member that cooperates with this threaded aperture. In this construction the end of the adjusting member proximal the valve abutment portion abuts the valve abutment portion during operation. When the adjusting member is advanced through the central aperture of the adjusting portion it pushes the valve abutment portion and the two portions separate.

A handle may be operatively connected to the adjusting member to turn it by providing a handle that has an externally threaded end portion and an adjusting member having a central longitudinal threaded bore sized to receive the threaded end of the handle. When the handle is introduced into the bore it is rotated in a first direction and will seat in the threaded bore of the adjusting member. Further rotation of the adjusting member separates the adjusting portion from the valve abutment portion, as recited above, and causes the commissure posts to constrict inwardly.

A further understanding of the nature and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an improved heart valve holder for tissue-type prosthetic heart valves that facilitates implantation and reduces the chance of suture entanglement. The holder of the present invention is particularly useful for prosthetic mitral heart valves having commissure posts on the outflow side supporting flexible leaflets therebetween. The mitral position is such that the outflow side (and commissure posts) projects distally toward the left ventricle during implantation, and thus the holder must be attached to the inflow (i.e., accessible) side of the valve. Delivery of the valve to the mitral position involves sliding the valve down a plurality or array of sutures that have been pre-installed around the annulus and then passed through the valve sewing ring. The holder of the present invention constricts the commissure posts radially inward and thus helps prevent the posts from becoming entangled in the array of pre-installed sutures. This benefit is thus especially advantageous where the outflow side and commissure posts of the heart valve extend distally during delivery, forming the leading end of the valve, which is the case in a prosthetic mitral valve implantation. Nonetheless, the holder of the present invention may prove useful for the implantation of heart valves in other than the mitral position, and thus the invention may be applicable thereto.

With reference now toFIG. 1an exemplary holder20of the present invention is shown attached to a tissue-type heart valve22. The heart valve22includes an annular sewing ring24on an inflow side, and a plurality of commissure posts26projecting generally axially in the outflow direction. The holder20attaches to the sewing ring24on the inflow side of the valve22, which also is the proximal (i.e., accessible) side during implantation. That is, the commissure posts26project distally toward the outflow side of the valve22, defining the leading end of the valve during implantation.

The heart valve22further includes a plurality of flexible leaflets28that are supported by and extend between the commissure posts26. The leaflets28provide the occluding surfaces of the valve22, and may be made of individual pieces of bovine pericardium, for example. Alternatively, the leaflets28may be part of an entire xenograft, or homograft. In the former instance, natural porcine (pig) valves are particularly useful. Therefore it should be understood that the leaflets28may be formed of a variety of materials, none of which is limiting with respect to the present invention. In addition, there are preferably three such leaflets28corresponding to three commissure posts26.

Various constructions for the heart valve22are known, which may include metallic or plastic stent elements, a silicone or urethane insert for the sewing ring24, biocompatible fabric (i.e., polyester) covering around one or more of the elements, etc. In a preferred embodiment, the heart valve22includes an internal metallic wireform (not shown) having an undulating shape with a plurality of arcuate cusps connected by upstanding commissures. The wireform commissures provide internal structure for the commissure posts26of the valve, and are somewhat flexible so as to be able to flex or cantilever inward. The holder20of the present invention facilitates this flexing, though the invention may be practiced in its broadest sense without causing inward movement of the commissure posts. It should be noted that other internal constructions of heart valve22having movable commissure posts are available with which the holder20of the present invention may function equally as well.

An exemplary holder20of the present invention includes a rigid structure of three relatively movable elements. A plate-like valve abutment portion40lies against the inflow side of the sewing ring24, and includes a plurality of through holes around its periphery. A plate-like commissure adjusting portion44generally mirrors the shape of the valve abutment portion40, and also includes a plurality of peripheral through holes46. The adjusting portion44further includes a centrally located and internally threaded boss48that projects in a proximal direction from the otherwise generally planar adjusting portion. Finally, an adjusting member50having external threads thereon is sized to mate with the internal threads of the boss48. It should be understood that the function of the holder20in constricting the valve commissures may be accomplished with different structures than the one shown.

A plurality of lengths of flexible material60is shown inFIGS. 1–3partly extending between the tips62of the commissure posts26. In the preferred embodiment, the lengths of flexible material60comprise mono- or poly-filament sutures, and that exemplary nomenclature will be used herein. Because there are three commissure posts26, there are at least three lengths of sutures60extending therebetween in an equilateral triangular configuration. Each length of suture60includes a first segment61spanning between two of the commissure posts26. Second segments63of each length of suture60extend axially in a proximal direction from the tips62and along the post26, the segments passing through the sewing ring24and attaching to the holder20. This is seen best in the perspective view ofFIG. 1. Specifically, both second segments63pass through the holes in the valve abutment portion40and attach to the adjusting portion44at discrete attachment points, for example by tying the free ends of each suture. In this manner, each length of suture60may be severed close to one of its points of attachment to the adjusting portion44and pulled free of the valve22along with the holder20by virtue of its remaining attachment point. Further specifics of this arrangement can be seen in co-pending U.S. application Ser. No. 09/626,570, filed Jul. 27, 2000, and in a continuation-in-part of the 09/626,570 application filed on even date herewith, the entire disclosures of which are hereby expressly incorporated by reference.

As mentioned, the abutment portion40, adjusting portion44, and adjusting member50are relatively movable. That is, the adjusting portion50is adapted to cause relative axial displacement between the abutment portion40and the adjusting portion44(preferably by connecting a handle52thereto). Because the abutment portion40remains against the sewing ring24, the adjusting portion44translates proximally away from the abutment portion, and attached valve22. Because the lengths of suture60attach to the adjusting portion44, they are also pulled in the proximal direction. Moreover, because the first segment61of each length of suture60spans between two of the commissure posts26, proximal movement of the adjusting portion44and attached second segments63causes radially inward movement of the tips62, with the commissure posts26generally flexing inward from their structural point of attachment within the valve22adjacent the sewing ring24.

It should be clearly understood that the inward flexing of the commissure post tips62reduces the chance of suture looping around the tips, but that certain aspects of the present invention reduce suture looping even without tip flexing. That is, the lengths of suture60may attach to the rigid structure of a holder that simply abuts the valve, without the relatively moving elements that cause commissure deflection.

With reference toFIGS. 1–3, the arrangement of the discrete lengths of sutures60will now be described. There are desirably three equal lengths of suture60, each secured at its two free ends to the adjusting portion44. As mentioned, the second segments63pass through the aligned holes46in the adjusting portion44and abutment portion40, and then through the sewing ring24to a first commissure post26. From there, the second segments63continue generally axially to the tips62of adjacent commissure posts26, and the first segment61spans obliquely across the outflow side of the valve22structurally coupling the two tips. It should be noted that each of the commissure posts26desirably has a fabric covering, and the lengths of suture60pass at least once through the fabric covering at the tip62or along each post26. For example,FIG. 3shows the first segments61passing below the fabric covering at the tip62, andFIG. 1shows the second segments63threading at least once through the fabric. This threaded path guides the lengths of suture60along their predetermined paths. It is a simple matter to remove the lengths of suture60from the valve22along with the holder by puling them free from the fabric cover.

As seen best inFIGS. 2 and 3, the first segment61of each length of suture60extends from a circumferential side of the respective commissure post tip62that is farthest away from the destination tip. That is, three lengths of sutures60a,60b,60care seen inFIG. 2extending between three commissure post tips62a,62b,62c, using a clockwise nomenclature. The first segment61of the first length of suture60aextends from a counter-clockwise side of the first commissure post tip62ato a clockwise side of the second suture post tip62b. The other two lengths of sutures are arranged accordingly such that each two adjacent lengths of suture cross over (i.e., intersect) just prior to being threaded into (i.e., just radially inward from) the respective commissure post tips62. This intersection of the sutures60defines a plane or slide closely adjacent to each commissure post tip62. The plane or slide formed by the crossed sutures60helps prevent suture looping because a barrier of sorts is provided that guides loose sutures over each post tip62.

As mentioned and as seen inFIG. 1, the second segment63of each length of suture60continues axially along the respective commissure posts26and may be threaded into and out of the cloth covering thereover. Desirably, a second crossover of the second segments63is provided in the commissure posts26to insure that each end is secured to the adjusting portion44in the proper orientation. As seen inFIG. 1, therefore, the length of suture60that is seen extending between the two visible commissure posts26extends upward through the valve22and holder20to emerge from the closest aligned holes46(as shown) and be secured in the cutting guide. This dual crossover thus helps a surgeon identify which lengths of sutures60extend between which commissure posts26.

FIGS. 4 and 5illustrate a second embodiment of heart valve holder of the present invention for preventing suture looping which also provides a planar guard over the commissure tips, similar to the crossed-over lengths of filament-like material ofFIGS. 1–3. In general, the holder ofFIGS. 4–5is identical to the holder described above, with the substitution of flexible bands70a,70b,70cinstead of lengths of suture60. The bands70may be made of polyester tape, or other suitable biocompatible material similar to sutures. In one embodiment, the bands70are substantially wider than they are thick (e.g., formed in a tape or flat strip), and desirably have a width that is approximately equal to the circumferential width of the each of the commissure post tips62.

As seen best inFIG. 5, first segments72of the bands70extend between the commissure post tips62in a flattened configuration and cross over each adjacent band at or slightly inward from the tip. After extending to the outside of the commissure post tip62, each band70is folded, twisted, or otherwise narrowed in second segments74to pass through one or more fabric tunnels76along the commissure posts26. Ultimately, each narrowed second segment74passes through aligned holes in the abutment portion40and adjusting portion44and is secured to the adjusting portion, as described above. The mechanism for the holder20ofFIGS. 4–5is similar to that described above in that separation of the abutment portion40and adjusting portion44pulls the narrowed second segments74of the bands70to shorten the flattened first segments72between the commissure post tips62. As each second segment74is pulled, the first segment72follows and is folded or otherwise narrowed as it passes through the fabric cover of the commissure post26. Moreover, when the holder is removed, one of the second segments74of each band70is severed close to its point of attachment to the holder and the band70may then be pulled free from the valve by virtue of its remaining attachment to the holder. In this regard, the bands70may be TEFLON (PTFE) to facilitate sliding through the fabric tunnels in the valve.

Because of the flattened or otherwise planar configuration of the bands70, suture looping around the commissure post tips62is greatly reduced. That is, sutures that contact the bands70will be guided over and to the outside of each commissure post tip62. The bands70provide slides of sorts that guide the loose sutures over the commissure post tips62, and in the preferred embodiment, the bands completely cover the tips to present a smooth, even surface.

FIGS. 6–8illustrate a further embodiment of a heart valve holder for preventing suture looping. As seen best inFIG. 7, a plurality of lengths of sutures80extends between the commissure post tips62across the outflow side of the valve as before, although first to a central upstanding member82elevating the lengths of sutures above the commissure post tips. The upstanding member82has an upper end84with a plurality of grooves or notches therein through which the lengths of suture80are threaded. Although the upstanding member82is shown as being elevated axially beyond the commissure post tips62, some of the benefits of reduced suture looping may be realized if the member has the same axial height as the post tips.

An exemplary embodiment of the upstanding member82is illustrated inFIGS. 8A–8C. The member82includes a wide base86and a narrow shaft88terminating in the upper end84. Three generally radial grooves90are formed in the upper end84distributed about 120 degrees with respect to each other. These grooves90are each aligned with one of the commissure post tips62to receive a length of suture80extending therefrom. A lower pin92in the upstanding member82fits within a central bore provided in the center of the abutment portion40. Alternatively, the upstanding member82may be integrally molded with the abutment portion40. The wide base86strengthens the upstanding member82, and the shaft88has a length that projects axially above the commissure posts26.

As seen inFIG. 7, threading the lengths of suture80through the grooves90in the upper end84of the upstanding member82provides a tent of sorts. This suture tent helps to prevent suture looping around the commissure post tip62. That is, errant sutures that contact any of the angled lengths of suture80are guided up and over the nearest commissure post tip62.

An alternative embodiment of an upstanding member82′ is illustrated inFIG. 8D. As in the earlier embodiment, the member82′ includes a wide base86′ and a narrow shaft88′ terminating in an upper end84′ having three generally radial grooves90′ distributed about 120 degrees with respect to each other. The shaft88′ has a triangular as opposed to circular cross-section so as to better mate with the surrounding leaflets in the assembly of the valve and holder. That is, the three leaflets come together in an equilateral triangle, desirably at the axis of the valve, and the upstanding member82′ will be oriented such that the corners of the triangular shaft88′ project toward each valve commissure, thus bifurcating two leaflets. In this way the midpoint of each leaflet free edge abuts the flat sides of the shaft88′, minimizing any deformation of the leaflet at that midpoint from the extended contact with the shaft88′ during long term storage in a preservative solution.

FIGS. 9 and 10illustrate a further heart valve holder of the present invention that also makes use of a central upstanding member100, although the member is hollow and the lengths of suture102extend axially through the member to be connected to either the abutment portion40or adjustment portion44. The lengths of suture102may be filaments or strands, or may be wider bands as described above with respect toFIGS. 4–5. The upstanding member100maybe a hollow tubular structure fastened within or molded with the abutment portion40. Again, the axial height of the upstanding member100is greater than the axial height of the commissure posts26such that the lengths of suture102are tented across the outflow end of the valve

It will be appreciated that the invention has been described hereabove with reference to certain examples or preferred embodiments as shown in the drawings. Various additions, deletions, changes and alterations may be made to the above-described embodiments and examples without departing from the intended spirit and scope of this invention. Accordingly, it is intended that all such additions, deletions, changes and alterations be included within the scope of the following claims.