Prosthetic heart valve with retention elements

Described embodiments are directed toward centrally-opening leaflet prosthetic valve devices having a leaflet frame and a leaflet construct. The leaflet construct is at least partially coupled to a leaflet frame outer side of the leaflet frame and being coupled thereto by a retention element.

FIELD

The present disclosure relates generally to prosthetic valves and more specifically flexible leaflet-type prosthetic heart valve devices.

BACKGROUND

A number of fabrication techniques have been used to couple the leaflets to a frame, including sewing individual leaflets to the frame (biological and synthetic), and for synthetic leaflets only, injection molding and dip coating a polymer onto the frame. In many cases, the resulting leaflet is supported on the frame and defines a flap having a mounting edge where the leaflet is coupled to the frame and a free edge that allows the flap to move. The flap moves under the influence of fluid pressure. In operation, the leaflets open when the upstream fluid pressure exceeds the downstream fluid pressure and closes when the downstream fluid pressure exceeds the upstream fluid pressure. The free edges of the leaflets coapt under the influence of downstream fluid pressure, closing the valve to prevent downstream blood from flowing retrograde through the valve.

Valve durability under the repetitive loads of the leaflets opening and closing is dependent, in part, on the load distribution between the leaflet and the frame. Further, substantial load is encountered on the leaflet when in the closed position. Mechanical failure of the leaflet can arise, for example, at the mounting edge, where the flexible leaflet is supported by the relatively rigid frame, particularly at the commissure posts. The repetitive loads of leaflet opening and closing leads to material failure by fatigue, creep or other mechanism, depending in part on the leaflet material. Mechanical failure at the mounting edge is especially prevalent with synthetic leaflets.

There remains a need for a more durable flexible leaflet prosthetic valve.

SUMMARY

Described embodiments are directed to apparatus, system, and methods for valve replacement, such as cardiac valve replacement. More specifically, described embodiments are directed toward flexible leaflet valve devices having biological or synthetic leaflet material and a frame, and methods of making and implanting the valve devices.

According to an embodiment, a prosthetic heart valve comprises a leaflet frame assembly. The leaflet frame assembly is an assembly of a leaflet frame, leaflet construct, and retention elements. The leaflet construct is that portion of the valve that comprises the leaflets and the structure for coupling the leaflets to the leaflet frame. In accordance with an embodiment, the leaflet construct defines a contiguous annular ring defining a plurality of leaflets and a bridge region between each of the leaflets. Each bridge region defines a bridge first end adjacent a first leaflet and a bridge second end adjacent a second leaflet. The leaflets extend radially inward from the leaflet frame when coupled to the leaflet frame. Each of the leaflets defines a fold-over portion that is folded over and lies against a leaflet frame outer side of the leaflet frame and coupled thereto such as with a securement structure, such as, but not limited to suture, adhesive, thermal bonding, or other means. Each of the bridge regions defines a bridge loop with a coaptation neck between the bridge loop and the adjacent leaflets. The coaptation neck is operable to pass through one of the post slots so that the bridge loop is adjacent to the outer portion of the leaflet frame and the leaflets extend radially inward from the leaflet frame. A retention element is disposed within the bridge loop effectively preventing the bridge loop from passing through the post slot. The retention element may be coupled to the commissure post, such as with a securement structure, such as, but not limited to suture, adhesive, thermal bonding, or other means. The fold-over portion of each of the leaflets is folded around an inflow edge of the leaflet frame and coupled thereto, such as with a securement structure, such as, but not limited to suture, adhesive, thermal bonding, or other means.

A method of making a prosthetic valve, in accordance with an embodiment, comprises obtaining a tube comprising one or more layers of expanded PTFE composite. Cutting a leaflet construct including a plurality of leaflets each being separated by a bridge region from the tube. Providing fold-over apertures in fold-over portions of the leaflets and bridge apertures in the bridge region. Obtaining a plurality of retention elements, each retention element defining retention element apertures. Folding each of the bridge regions into a bridge loop and defining a coaptation neck between each bridge loop and two adjacent leaflets, the bridge loops extending radially away from the tube axis. Disposing a retention element into each of the bridge loops. Suturing each retention element to the respective bridge loop passing suture through the bridge apertures and the retention element apertures that are aligned therewith. Cutting a leaflet frame from a metal tube defining leaflet frame windows and commissure posts therebetween where each commissure post defines a post slot dimensioned to receive a double thickness of the bridge region. Providing leaflet window frame apertures in the leaflet window frame and post apertures in the commissure posts. Disposing each coaptation neck in a respective post slot with the retention elements adjacent the post outer side and disposing the leaflets in the leaflet frame. Aligning the retention element apertures with the post apertures. Suturing each retention element to the respective commissure post passing suture through the retention element apertures and the post apertures that are aligned therewith. Folding the fold-over portions of each leaflet along the leaflet frame inflow edge and against the leaflet frame outer side aligning the fold-over apertures with the leaflet window frame apertures. And suturing each fold-over portion to the respective leaflet window frame passing suture through the fold-over apertures and the leaflet window frame apertures that are aligned therewith.

DETAILED DESCRIPTION

Although the embodiments herein may be described in connection with various principles and beliefs, the described embodiments should not be bound by theory. For example, embodiments are described herein in connection with prosthetic valves, more specifically cardiac prosthetic valves. However, embodiments within the scope of this disclosure can be applied toward any valve or mechanism of similar structure and/or function. Furthermore, embodiments within the scope of this disclosure can be applied in non-cardiac applications.

The term leaflet as used herein in the context of prosthetic valves is a flexible component of a one-way valve wherein the leaflet is operable to move between an open and closed position under the influence of a pressure differential. In an open position, the leaflet allows blood to flow through the valve. In a closed position, the leaflet substantially blocks retrograde flow through the valve. In embodiments comprising multiple leaflets, each leaflet cooperates with at least one neighboring leaflet to block the retrograde flow of blood. The pressure differential in the blood is caused, for example, by the contraction of a ventricle or atrium of the heart, such pressure differential typically resulting from a fluid pressure building up on one side of the leaflets when closed. As the pressure on an inflow side of the valve rises above the pressure on the outflow side of the valve, the leaflets open and blood flows therethrough. As blood flows through the valve into a neighboring chamber or blood vessel, the pressure on the inflow side equalizes with the pressure on the outflow side. As the pressure on the outflow side of the valve raises above the blood pressure on the inflow side of the valve, the leaflet returns to the closed position generally preventing retrograde flow of blood through the valve.

The term membrane as used herein refers to a sheet comprising a single material, such as, but not limited to, expanded fluoropolymer.

The term composite material as used herein refers to a combination of a membrane, such as, but not limited to, expanded fluoropolymer, and an elastomer, such as, but not limited to, a fluoroelastomer. The elastomer can be contained within a porous structure of the membrane, coated on one or both sides of the membrane, or a combination of coated on and contained within the membrane.

The term laminate as used herein refers to multiple layers of membrane, composite material, or other materials, such as elastomer, and combinations thereof.

The term film as used herein generically refers to one or more of the membrane, composite material, or laminate.

The term biocompatible material as used herein generically refers to any material with biocompatible characteristics including synthetic, such as, but not limited to, a biocompatible polymer, or a biological material, such as, but not limited to, bovine pericardium.

The terms native valve orifice and tissue orifice refer to an anatomical structure into which a prosthetic valve can be placed. Such anatomical structure includes, but is not limited to, a location wherein a cardiac valve may or may not have been surgically removed. It is understood that other anatomical structures that can receive a prosthetic valve include, but are not limited to, veins, arteries, ducts and shunts. It is further understood that a valve orifice or implant site may also refer to a location in a synthetic or biological conduit that may receive a valve.

As used herein, “couple” means to join, connect, attach, adhere, affix, or bond, whether directly or indirectly, and whether permanently or temporarily.

Embodiments herein include various apparatus, systems, and methods for a prosthetic valve, such as, but not limited to, cardiac valve replacement. The valve is operable as a one-way valve wherein the valve defines a valve orifice into which leaflets open to permit flow and close so as to occlude the valve orifice and prevent flow in response to differential fluid pressure.

FIGS. 1A and 1Bare outflow and inflow, respectfully, perspective views of a valve100in the form of a prosthetic heart valve, in accordance with an embodiment. The components of the valve100that are visible inFIGS. 1A and 1Binclude three flexible leaflets310, a leaflet frame200including three commissure posts210that has been covered with various material, a base frame500that has been covered with various material, and a sewing cuff600. The leaflet free edges312of the leaflets310come together at a cooptation region316in a Y-shaped pattern (when viewed from above) to close the valve100. The valve100closes in this fashion when the pressure of the blood on the outflow side (as viewed inFIG. 1A) is greater than the pressure of the blood on the inflow side of the valve (as viewed inFIG. 1B). The leaflet free edges312of the leaflets310move apart to open the valve100and to let blood flow through the valve100from the inflow side as viewed inFIG. 1Bwhen the pressure of the blood on the inflow side of the valve100is greater than the pressure on the outflow side of the valve100.

FIGS. 2-5Bshow various components that are included in the valve100, in accordance with an embodiment.

FIG. 2is a perspective view of a leaflet frame assembly234, in accordance with an embodiment, also shown inFIG. 3in an exploded view and shown inFIG. 4in an exploded view wherein the annular components have been longitudinally cut and laid open, so as to better illustrate the elements of the valve components. The leaflet frame assembly234comprises a leaflet frame200, a leaflet construct300, and a plurality of retention elements400.

Leaflet Frame

The leaflet frame200is operable to hold and support the leaflet construct300. The leaflet frame200is annular, that is it defines a cylinder having an axis X and a plurality of commissure posts210extending parallel to the axis x that are spaced from one another, each commissure post210defining a post slot217therethrough that is aligned parallel to the axis X. Between the commissure posts210is a leaflet window222that is operable to couple to and support the leaflet310around the perimeter of the leaflet310except for the leaflet free edge312.

The leaflet frame200defines a cylinder having a leaflet frame inner side202and a leaflet frame outer side204opposite the leaflet frame inner side202. The leaflet frame200further defines a plurality of commissure posts210. Each commissure post210has a post outer side212and a post inner side214opposite the post outer side212. The commissure post210is defined by a first post leg216and a second post leg218separated by a post slot217therebetween. A commissure tip219couples the first post leg216and the second post leg218.

In accordance with an embodiment, the leaflet frame200is annular about a central longitudinal axis X of the valve100as shown inFIGS. 2 and 3. The leaflet frame200defines a plurality of leaflet windows222that follow the shape of the leaflet310. In accordance with an embodiment, each of the leaflet windows222includes two leaflet window sides223and a leaflet window base225, defining three sides of an isosceles trapezoid, wherein the leaflet window base225is substantially flat. The leaflet base325is coupled to the leaflet window base225and each of the two leaflet sides323are coupled to one of the two leaflet window sides223. The adjacent leaflet window sides223are interconnected by a commissure post210comprising of a first post leg216and a second post leg218that extend from adjacent leaflet window sides223and meet at a commissure tip219. The commissure posts210are equally spaced from one another around the leaflet frame200. The first post leg216and the second post leg218define a post slot217therebetween.

The leaflet frame200can be etched, cut, laser cut, stamped, three-dimensional printed, among other suitable processes, into an annular structure or a sheet of material, with the sheet then formed into an annular structure.

The leaflet frame200can comprise, such as, but not limited to, any elastically deformable metallic or polymeric material that is generally biocompatible. The leaflet frame200can comprise a shape-memory material, such as nitinol, a nickel-titanium alloy. Other materials suitable for the leaflet frame200include, but not limited to, other titanium alloys, stainless steel, cobalt-nickel alloy, polypropylene, acetyl homopolymer, acetyl copolymer, other alloys or polymers, or any other material that is generally biocompatible having adequate physical and mechanical properties to function as a leaflet frame200as described herein.

Leaflet Construct

The leaflet construct300is that portion of the valve100that comprises the leaflets310and the structure for coupling the leaflets310to the leaflet frame200. In accordance with an embodiment, the leaflet construct300defines a contiguous annular ring defining a plurality of leaflets310and a bridge region330between each of the leaflets310. As used herein, contiguous means without a break or a seam, that is, seamless. Each bridge region defines a bridge first end332adjacent a first leaflet310and a bridge second end334adjacent a second leaflet310. The leaflets extend radially inward from the leaflet frame200when coupled to the leaflet frame200. Each of the leaflets310define a fold-over portion324that is folded over and lies against a leaflet frame outer side204of the leaflet frame200and coupled thereto. Each of the bridge regions330defines a bridge loop338with a coaptation neck340between the bridge loop338and the adjacent leaflets310. The coaptation neck340is operable to pass through one of the post slots217so that the bridge loop338is adjacent to the outer portion of the leaflet frame200and the leaflets310extend radially inward from the leaflet frame200.

The leaflet construct300comprising the flexible leaflets310can be made of polymer. For example, pre-shaped polymer leaflets can be made by starting from a cylinder of polymer material that has been cut into a shape like that shown inFIGS. 3 and 4.

The leaflet construct300can also be made from a sheet of polymer material that has been cut into a shape like that shown inFIGS. 3 and 4and subsequently coupled together into an annular shape. A leaflet construct300having a seam, though may not have the advantages of a contiguous, seamless construct that may exhibit a higher tensile strength characteristics. The advantages provided by the retention element400may still be realized.

Another way that the leaflet construct300may be formed (assuming the use of a material for the leaflets that is suitable for formation in this way) is by compression or injection molding.

In accordance with an embodiment, each leaflet310, at the folds326, has substantially the shape of an isosceles trapezoid having two leaflet sides323, a leaflet base325and a leaflet free edge312opposite the leaflet base325, corresponding to the two leaflet window sides223and a leaflet window base225. The two leaflet sides323diverge from the leaflet base325, wherein the leaflet base325is substantially flat.

In accordance with other embodiments of the valve100, each leaflet310includes a central region329and two side regions328on opposite sides of the central region329. The central region329is defined by a shape substantially that of an isosceles trapezoid defined by two central region sides327, the leaflet base325and the leaflet free edge312. Each of the side regions328has a shape substantially that of a triangle and each are defined by one of the central region sides327, one of the leaflet sides323, and the leaflet free edge312.

In accordance with another embodiment, the leaflet window may be described as having a U-shape. The leaflet frame generally defines a plurality of U-shaped portions as one proceeds annularly around the leaflet frame, defining a plurality of commissure posts and a plurality of leaflet window frame portions.

As shown inFIG. 4, each of the leaflets310has a leaflet belly portion322, and a fold-over portion324. The leaflet belly portion322of each leaflet310is the operating portion of the leaflet310when in a finished and implanted valve100. The fold-over portion324of each leaflet310is the portion that is used to secure the leaflet310to the two leaflet window sides223and the leaflet window base225of the leaflet frame200. Each leaflet window side223and a leaflet window base225of the leaflet frame200fits into a fold326that is formed between the leaflet belly portion322and the fold-over portion324of a respective one of the leaflet sides323and leaflet base325, respectively, of the leaflets310, as shown inFIG. 2. The leaflet belly portion322of each leaflet310includes enough material between the commissure posts210of the leaflet frame200so that the leaflet free edge312of the three leaflet belly portions322can come together or coapt in the interior of the valve100to close the valve100as shown inFIG. 1.

Between each of the leaflets310is a bridge region330, as shown inFIGS. 4, 5A, 5B and 8. The bridge region330is operable to be formed into a bridge loop338having a generally rectangular shape, folding about two loop fold lines336so as to contain the retention element400therein as discussed below, as shown inFIGS. 5A, 5B, 6 and 8. Due to the curvature of the annular leaflet frame200, the two loop fold lines336form an angle alpha, which corresponds to the retention element sides402as shown inFIG. 6, in accordance with an embodiment.

In accordance with an embodiment, the leaflet construct300can comprise a biocompatible material that is not of a biological source and that is sufficiently compliant and strong for the particular purpose, such as a biocompatible polymer. In an embodiment, the leaflet construct300comprises a membrane that is combined with an elastomer to form a composite material. In accordance with other embodiments, the biocompatible material that makes up the leaflet construct300comprises a biological material, such as, but not limited to, bovine pericardium.

The shape of the leaflets310are defined in part by the shape of the leaflet frame200and the leaflet free edge312. The shape of the leaflets310can also be defined by the structures and processes used to manufacture the valve100, such as, but not limited, those described below. For example, in accordance with an embodiment, the shape of the leaflets310also depends in part on molding the leaflets310using molding and trimming processes to impart a predetermined shape to the leaflet310.

The leaflets310generally flex about the leaflet base325about the leaflet window base225of the U-shaped portion as the leaflets310open and close. In an embodiment, when the valve100is closed, generally about half of each leaflet free edge312abuts an adjacent half of a leaflet free edge312of an adjacent leaflet310, as shown inFIG. 1A. The three leaflets310of the embodiment ofFIG. 1Ameet at a triple point348. The valve orifice150is occluded when the leaflets310are in the closed position stopping fluid flow.

Leaflet Construct Material

The leaflet construct300can comprise any biocompatible material sufficiently compliant and flexible, such as a biocompatible polymer. The leaflet construct300can comprise a membrane that is combined with an elastomer to form a composite material. The leaflet construct300can comprise, according to an embodiment, a composite material comprising an expanded fluoropolymer membrane, which comprises a plurality of spaces within a matrix of fibrils, and an elastomeric material. It should be appreciated that multiple types of fluoropolymer membranes and multiple types of elastomeric materials can be combined to form a composite material while remaining within the scope of the present disclosure. It should also be appreciated that the elastomeric material can include multiple elastomers, multiple types of non-elastomeric components, such as inorganic fillers, therapeutic agents, radiopaque markers, and the like while remaining within the scope of the present disclosure.

In accordance with an embodiment, the composite material includes an expanded fluoropolymer material made from porous ePTFE membrane, for instance as generally described in U.S. Pat. No. 7,306,729 to Bacino.

The expandable fluoropolymer, used to form the expanded fluoropolymer material described, can comprise PTFE homopolymer. In alternative embodiments, blends of PTFE, expandable modified PTFE and/or expanded copolymers of PTFE can be used. Non-limiting examples of suitable fluoropolymer materials are described in, for example, U.S. Pat. No. 5,708,044, to Branca, U.S. Pat. No. 6,541,589, to Baillie, U.S. Pat. No. 7,531,611, to Sabol et al., U.S. patent application Ser. No. 11/906,877, to Ford, and U.S. patent application Ser. No. 12/410,050, to Xu et al.

The expanded fluoropolymer membrane can comprise any suitable microstructure, such as pores, for achieving the desired leaflet performance. Other biocompatible polymers which can be suitable for use in leaflet include but are not limited to the groups of urethanes, silicones (organopolysiloxanes), copolymers of silicon-urethane, styrene/isobutylene copolymers, polyisobutylene, polyethylene-co-poly(vinyl acetate), polyester copolymers, nylon copolymers, fluorinated hydrocarbon polymers and copolymers or mixtures of each of the foregoing.

Further examples of leaflet construct materials include: wherein the leaflet construct comprises at least one fluoropolymer membrane layer; wherein the leaflet construct comprises a laminate having more than one fluoropolymer membrane layer; wherein the at least one fluoropolymer membrane layer is an expanded fluoropolymer membrane layer; wherein an elastomer is contained within the expanded fluoropolymer membrane layer; wherein the elastomer comprises perfluoromethyl vinyl ether and tetrafluoroethylene; wherein the expanded fluoropolymer membrane layer comprises ePTFE; wherein the leaflet construct comprises a composite material having at least one fluoropolymer membrane layer having a plurality of pores and an elastomer present in the pores of at least one of the fluoropolymer membrane layers; wherein the composite material comprises fluoropolymer membrane by weight in a range of about 10% to 90%; wherein the elastomer comprises (per)fluoroalkylvinylethers (PAVE); wherein the elastomer comprises a copolymer of tetrafluoroethylene and perfluoromethyl vinyl ether; wherein the elastomer is silicone; wherein the elastomer is a fluoroelastomer; wherein the elastomer is a urethane; and wherein the elastomer is a TFE/PMVE copolymer; wherein the TFE/PMVE copolymer comprises essentially of between about 40 and 80 weight percent perfluoromethyl vinyl ether and complementally 60 and 20 weight percent tetrafluoroethylene; and wherein the leaflet construct comprises silicone.

Retention Element

The retention element400is an element that is operable to be disposed within the bridge loop338formed by the bridge region330of the leaflet construct300, which effectively prevents the bridge loop338from passing through the post slot217, and therefore the leaflet construct300is mechanically coupled to the commissure post at the post outer side. The retention element400has a width that is larger than a width of the post slot217. With the retention element400being disposed in the bridge loop338, the bridge loop338will be prevented from passing through the post slot217. The size of the bridge loop338should correspond closely to the size of the retention element400to prevent a portion of the bridge region330from extending through the post slot217to the valve orifice150in case of the suture loosening or failing.

In accordance with an embodiment, the retention element400defines a relatively flat generally rectangular shape so as to have a low profile on the post outer side212of the commissure post210. Due to the curvature of the annular leaflet frame200, the sides of the retention element400are formed at an angle corresponding to the two loop fold lines336that form an angle alpha, as shown inFIG. 8, in accordance with an embodiment.

In accordance with embodiments, the retention element400can be flat, relatively flat, or concave on the inside (toward the center of the valve) to correspond with the radially outer convexity of commissure post210that the retention element400will be adjacent to. Each retention element400has a plurality of retention element apertures408that align with commissure post apertures209wherein the retention element400is placed against the post outer side212of the commissure post210with a portion of the bridge region330therebetween. A securement structure, such as, but not limited to suture700, may be used to couple the retention element400to the commissure post210. Suture may be of any suitable material, such as PTFE, PET, and nylon, among others. Stitching comprising suture700may be passed through these aligned commissure post apertures209and retention element apertures408and the bridge region330to hold each retention element400and the bridge region330to the commissure post210. Some or all of this suture700may pass through the fold-over portion324of the leaflet310. In that event, this suture700will contribute to securing the leaflet belly portion322of the leaflets310to the leaflet frame200.

Examples of suitable materials for the retention elements400include various biocompatible alloys such as titanium, Elgiloy, MP35N, stainless steel, nitinol, etc., and various biocompatible engineering plastics such as acetyl polymers, PTFE, and PEEK.

Leaflet Frame Assembly

A leaflet frame assembly234is the assembly of the leaflet frame200, leaflet construct300, and the retention elements400. The leaflet construct300is that portion of the valve100that comprises the leaflets310and the structure for coupling the leaflets310to the leaflet frame200. In accordance with an embodiment, the leaflet construct300defines a contiguous cylinder defining a plurality of leaflets310and a bridge region330between each of the leaflets310. Each bridge region defines a bridge first end332adjacent a first leaflet310and a bridge second end334adjacent a second leaflet310. The leaflets extend radially inward from the leaflet frame200when coupled to the leaflet frame200. Each of the leaflets310defines a fold-over portion324that is folded over and lies against a leaflet frame outer side204of the leaflet frame200and coupled thereto, such as with securement structure, such as, but not limited to suture, adhesive, thermal bonding, or other means. Each of the bridge regions330defines a bridge loop338with a coaptation neck340between the bridge loop338and the adjacent leaflets310. The coaptation neck340is operable to pass through one of the post slots217so that the bridge loop338is adjacent to the outer portion of the leaflet frame200and the leaflets310extend radially inward from the leaflet frame200. A retention element400is disposed within the bridge loop338effectively preventing the bridge loop338from passing through the post slot217. The retention element400may be coupled to the commissure post210, such as with suture, adhesive, thermal bonding, or other means. The fold-over portion324of each of the leaflets310is folded around an inflow edge of the leaflet frame200and coupled thereto, such as with suture, adhesive, thermal bonding, or other means.

In accordance with an embodiment, each bridge region330is wrapped around a retention element outer side412to the retention element inner side414of one of the retention elements400with the bridge first end332wrapped across the retention element inner side414to adjacent a dividing line416that vertically bisects the retention element400, from a first direction and the bridge second end334wrapped across the retention element inner side414to adjacent the dividing line416from an opposite direction, wherein the bridge first end332and bridge second end334are adjacent to each other to define a coaptation neck340.

In accordance with an embodiment, the leaflet frame assembly234is provided with means for coupling to a native tissue annulus, and thus the leaflet frame assembly234is a prosthetic heart valve100. In an embodiment, a sewing cuff600is coupled to the leaflet frame assembly234, where the sewing cuff is operable to be sutured to the native tissue annulus. In another embodiment, a base frame500comprising a sewing cuff600is coupled to the leaflet frame assembly234.

One possible way to characterize the benefits of some embodiments presented herein is the effect of the bridge region330being a continuous member, that is, no seams or breaks. Any force tending to pull or extract the bridge region330through the post slot217is countered by the tensile strength of the material that the bridge region330comprises. The forces on the leaflets310during use are greatest at the commissure posts210tending to pull the leaflets310away from the commissure posts210. The coupling of the leaflet construct300to the leaflet frame200at the commissure posts210, in accordance with these embodiments, does not rely solely on the suture700but also the retention element400that prevents the bridge region330from passing through the post slot217. It is understood that sutures, in general, tend to loosen and fail over a period of time, especially in regions of high stress. In these embodiments, the suture700that couples the bridge region330to the commissure post210may loosen or fail but the retention element400continues to prevent the bridge region330from passing through the post slot217preventing failure of the valve100.

Further, the retention element400provides a clamping force between a portion of the bridge region330and the post outer side212of the commissure post210during operation of the valve100. This clamping force is the result of the retention element400being larger than the post slot217which prevents the bridge region330from passing through the post slot217. The clamping force does not rely on the strength of the suture700or the tension of the suture on the bridge region330and the commissure posts210.

This clamping force may tend to distribute the forces on the bridging region330reducing peak stresses that might be applied at the suture700and apertures999. Further the clamping force is the primary mode of transferring the forces from the leaflets130to the leaflet frame200rather than merely relying on the stitching of the leaflets310to the leaflet frame200. Further, the angle alpha of the two loop fold lines336allows for a substantially equal distribution of stresses over the coaptation neck340between the bridge loop338and the adjacent leaflets310whereby reducing the peak stresses in the coaptation neck340.

In accordance with these embodiments, the leaflets310extend perpendicular from the leaflet frame200, as shown inFIG. 5. The leaflets310extend from the post slot217in a direction perpendicular to the post inner side214As such, the leaflets310exhibit a bias toward the closed position. This is beneficial in that the valve100will tend to close earlier during the phase of the cardiac cycle where the blood is decelerating or reversing. An earlier closure will tend to reduce back flow through the valve100.

The design and manufacturing process (including the various components and the way of assembling those components) greatly reduce possible stress concentration at the leaflet frame-leaflet junction by distributing the load more evenly. These design and manufacturing process aspects also (1) reduce the burden of extensive and demanding suturing, (2) increase the consistency of valve manufacturing results, and (3) increase the service life of a resulting valve as a consequence of all of the foregoing factors.

Instead of or in addition to suture, chemical bonds and/or adhesives can be used between the leaflet frame200and the fold-over portion324of the leaflet construct.

The bridge regions330are passed through the post slot217in a number of ways. In accordance with an embodiment, the bridge region330is formed into a narrow bridge loop338which is passed through the post slot217from the leaflet frame inner side202to the leaflet frame outer side204. A retention element400may then be inserted into the bridge loop338preventing the bridge loop338from being passed back through the post slot217.

In accordance with embodiments, the leaflet frame200, leaflet construct300and the retention elements400have matching and radially aligned apertures for receiving suture. The fold-over portion324and the bridge regions330containing a retention element400are coupled to the leaflet frame by suturing through these matching apertures. The dashed lines inFIG. 7show an illustrative suture pattern. The suturing work-load is very light and not skill-demanding.

Base Frame

The base frame500is a generally annular member defining a base frame lumen550having a base frame inner side502and a base frame outer side504, as shown inFIGS. 3 and 4. The base frame500may provide structural, load-bearing support to the leaflet frame200. In addition, the base frame500can be configured to provide positive engagement to the recipient tissue at the implantation site.

In accordance with an embodiment, the base frame500defines a plurality of triangular regions526extending away from the base frame inflow edge520. The leaflet frame200may comprise corresponding triangular openings256defined by two leaflet window sides223of adjacent leaflet windows222of the leaflet frame200define two sides of an isosceles triangle on the leaflet frame inflow edge220. The triangular openings256are operable to receive the triangular regions526of the base frame500therein.

The base frame500can comprise any metallic or polymeric material that is generally biocompatible. For example, the base frame500can comprise a material, such as, but not limited to nitinol, cobalt-nickel alloy, stainless steel, and polypropylene, acetyl homopolymer, acetyl copolymer, ePTFE, other alloys or polymers, or any other biocompatible material having adequate physical and mechanical properties to function as described herein.

The base frame500can be etched, cut, laser cut, or stamped into a tube or a sheet of material, with the sheet then formed into an annular structure.

In accordance with embodiments, the base frame500can be configured to provide positive engagement to an implant site. In an embodiment, the valve100further includes a sewing cuff600coupled about the base frame500, as shown inFIGS. 1A and 1B, that is operable to accept suture so as to be sewn to a tissue orifice. It is understood that conventional, surgical techniques to implant prosthetic valves can be used to implant the valve100, in accordance with embodiments.

It is appreciated that other elements or means for coupling the valve100to an implant site are anticipated. By way of example, but not limited thereto, other means, such as mechanical and adhesive means may be used to couple the valve100to a synthetic or biological conduit.

In another embodiment, the valve100further comprises a base frame500, as shown inFIGS. 3 and 4. The base frame500is coupled to a leaflet frame inflow edge220of the leaflet frame200. The base frame500is provided with base frame apertures508that may be used to suture the base frame500to the leaflet frame200using suture700. An advantage of a separate leaflet frame200and base frame500is that they may have different physical characteristics. By way of example, a relatively less stiff leaflet frame200supporting the leaflets310can be more likely to reduce the loading encountered by the opening and closing leaflets130as compared to a stiffer leaflet frame200. The leaflet frame200having a relatively less stiff property may reduce leaflet accelerations and reduce the closing stresses on the leaflets310. Wherein the base frame500may be more stiff which would be more suitable for suturing to the native tissue orifice. The base frame500may resist the compressive forces that may be encountered at the implant site, for example.

In embodiments of the valve100, the inclusion of a base frame500and a leaflet frame200provides a means for providing different physical properties for each of the base frame500and the leaflet frame200suitable for a particular purpose. In accordance with an embodiment, the base frame500is stiffer as compared with the leaflet frame200. The base frame500, when engaged to the implant site, such as, but not limited to a tissue orifice, is rigid enough to not significantly deform under physiological loading.

The physical properties of the base frame500and the leaflet frame200depends, in part, on the size, shape, thickness, and material property of the base frame500and the leaflet frame200.

Stiff and stiffness, as used herein and as is commonly used in engineering, is a measure of the resistance to deformation given by a base. Stiff and stiffness is a function of, among other things, material properties, the shape of the object, and the boundary conditions on the object. Stiffness of the leaflet frame200(seeFIG. 1A) may be measured by any number of methods known in the art. In accordance with one method, cables may be coupled to each of the three commissure posts210and brought together so as to allow the cables to be pulled simultaneously along the axis of the leaflet frame, with the leaflet frame held by the base frame500. The amount of force on the cables required to deflect the three commissure posts toward the axis provides a measure of stiffness. The same may be done with the base frame500with the cables coupled to three equally spaced points on the base frame, such as an apex of the triangular region526, as shown inFIG. 4.

Sewing Cuff

The valve100may be provided with a sewing cuff600adjacent the base frame500, as shown inFIGS. 1A and 1B. The sewing cuff600is operable to provide structure that receives suture for coupling to the implant site. The sewing cuff600may comprise any suitable material, such as, but not limited to, double velour polyester and silicone. The sewing cuff600may be located circumferentially around the base frame500or perivalvular depending from the base frame500. The sewing cuff600may comprise a filler material, such as, but not limited to, a silicone ring and/or PTFE felt.

Methods

A method of making a prosthetic valve, in accordance with embodiment, comprises obtaining a tube comprising one or more layers of expanded PTFE composite. Cutting a leaflet construct including a plurality of leaflets each being separated by a bridge region from the tube. Providing fold-over apertures in fold-over portions of the leaflets and bridge apertures in the bridge region. Obtaining a plurality of retention elements, each retention element defining retention element apertures. Folding each of the bridge regions into a bridge loop and defining a coaptation neck between each bridge loop and two adjacent leaflets, the bridge loops extending radially away from the tube axis. Disposing a retention element into each of the bridge loops. Suturing each retention element to the respective bridge loop passing suture through the bridge apertures and the retention element apertures that are aligned therewith. Cutting a leaflet frame from a metal tube defining leaflet frame windows and commissure posts therebetween where each commissure post defines a post slot dimensioned to receive a double thickness of the bridge region. Providing leaflet window frame apertures in the leaflet window frame and post apertures in the commissure posts. Disposing each coaptation neck in a respective post slot with the retention elements adjacent the post outer side and disposing the leaflets in the leaflet frame. Aligning the retention element apertures with the post apertures. Suturing each retention element to the respective commissure post passing suture through the retention element apertures and the post apertures that are aligned therewith. Folding the fold-over portions of each leaflet along the leaflet frame inflow edge and against the leaflet frame outer side aligning the fold-over apertures with the leaflet window frame apertures. And suturing each fold-over portion to the respective leaflet window frame passing suture through the fold-over apertures and the leaflet window frame apertures that are aligned therewith.

In accordance with an embodiment the method may further comprise providing strips of fabric, wrapping and sewing the fabric on the leaflet frame to provide a cushion between the leaflet frame and the leaflet construct, and trimming the fabric to approximately 3 mm from the leaflet frame outflow edge of the leaflet frame.

In accordance with an embodiment the method may further comprise cutting a base frame from a metal tube defining base frame apertures, and coupling the base frame to the leaflet frame inflow edge of the leaflet frame.

In accordance with an embodiment the method may further comprise providing a fabric tube and inserting the fabric tube through the base frame along its flow axis. Folding the fabric outflow edge of the fabric over the base frame outflow edge of the base frame. Sewing the fabric into place using suture through the base frame apertures in the base frame. Inverting the fabric inflow edge of the fabric tube over the base frame. Sewing the fabric tube into place using suture through base frame apertures along the inflow edge of the base frame. Disposing a sewing cuff insert inside a pocket defined by the inverted fabric tube and tucking the fabric tube in between the base frame and the sewing cuff insert such that all the slack of the fabric tube is removed around the sewing cuff. Placing the leaflet frame coaxially with and adjacent to the base frame and inside the fabric tube. Trimming the fabric tube approximately 5 mm from the leaflet frame outflow edge and suturing the leaflet frame to the base frame at the leaflet window base using suture passing through the respective leaflet window frame apertures and the base frame apertures. Folding the trimmed edge of the fabric tube over the leaflet frame outflow edge, tucking the trimmed edge underneath itself to conceal any frayed edges, and sewing the fabric tube to the fabric on the leaflet frame.

Example

By way of example, one embodiment of a valve was made as follows:

A surgical prosthetic heart valve was constructed in the following manner. A leaflet construct300, including fold-over apertures308and bridge apertures309, was cut from the leaflet coupon using a CO2 laser according to the pattern shown inFIG. 3.

Three retention elements400made from PEEK, shown inFIG. 3, were sewn onto the bridge loop338of the bridge region330of the leaflet construct300, as shown inFIGS. 5 and 6. The retention element400is provided with retention element apertures408that align with bridge apertures309on the leaflet construct300. A partial view of the resulting assembly is shown inFIG. 2.

A leaflet frame200and base frame500were laser cut, including leaflet frame apertures208and base frame apertures508, respectively, and electropolished from a tube of cobalt chromium (MP35N) with a 25 mm OD and 0.4 mm wall thickness, as shown inFIG. 3. The frames were cleaned in an ultrasonic bath of ethanol to remove contaminants. Three strips of polyester knit fabric were wrapped and sewn on the leaflet frame, to provide a cushion between the leaflet frame200and the leaflet construct300. A post slot217of the commissure post210large enough (approximately 0.254 mm) to accommodate a double thickness of the leaflet construct300at the bridge region330was provided. The remaining polyester knit fabric was trimmed off approximately 3 mm from the leaflet frame outflow edge224of the leaflet frame200shown inFIG. 4. The leaflet construct300with retention elements400was placed onto the leaflet frame200by sliding each coaptation neck340in the post slot217with the retention elements400on the post outer side212, as shown inFIG. 2. The retention element apertures408were aligned with leaflet frame apertures208on the leaflet frame200and were sewn into place with suture700, as shown inFIG. 6. The leaflet construct300includes fold-over portions324and fold-over apertures308along attachment edges. The fold-over portions324were folded along the leaflet frame inflow edge220of the leaflet frame200up against the leaflet frame outer side204where fold-over apertures308in the fold-over portions324coincide with leaflet frame apertures208of the leaflet frame200and were sewn into place with suture700as shown inFIG. 7.

A tube of polyester knit fabric about 24 mm in diameter and at least 10 cm in length was inserted through the base frame500along its flow axis. The fabric outflow edge of the polyester knit fabric was folded over the base frame outflow edge524of the base frame500and sewn into place using suture700through base frame apertures508in the base frame500(not shown). The fabric inflow edge of the polyester knit fabric tube was inverted over the base frame500and sewn into place using suture700through base frame apertures508along the base frame inflow edge520of the base frame500. A silicone sewing cuff insert was placed over the base frame500and inside of the inverted polyester knit fabric tube. The polyester knit fabric tube was tucked in between the base frame500and the sewing cuff insert such that all the slack was removed around the sewing cuff600.

The leaflet frame assembly234comprising the leaflet frame200, the leaflet construct300and retention elements400was coaxially placed adjacent the base frame and inside the polyester knit fabric tube. The polyester knit fabric tube was trimmed approximately 5 mm off the leaflet frame outflow edge224. The leaflet frame200was sutured to the base frame500at the leaflet window base225, with three sutures700at each of the three leaflet window bases225of the leaflet frame200. The trimmed edge of the polyester knit fabric was folded over the leaflet frame outflow edge224. The trimmed edge was tucked underneath itself to conceal any frayed edges and sewn to the polyester knit fabric on the leaflet frame.

Numerous characteristics and advantages have been set forth in the preceding description, including various alternatives together with details of the structure and function of the devices and/or methods. The disclosure is intended as illustrative only and as such is not intended to be exhaustive. It will be evident to those skilled in the art that various modifications can be made, especially in matters of structure, materials, elements, components, shape, size and arrangement of parts including combinations within the principles of the disclosure, to the full extent indicated by the broad, general meaning of the terms in which the appended claims are expressed. To the extent that these various modifications do not depart from the spirit and scope of the appended claims, they are intended to be encompassed therein.