Limited expansion heart valve

[0001] This application claims the benefit of U.S. Patent Application No. 62/216,936, filed Sep. 10, 2015, the entire contents of which are hereby expressly incorporated by reference herein.

[0002] The present disclosure relates to a heart valve for heart valve replacement, and more particularly to modifications to the construction of a surgical heart valve to enable receiving an expandable prosthetic heart valve therein and to expand to a limited degree.

[0003] The heart is a hollow muscular organ having four pumping chambers separated by four heart valves: aortic, mitral (or bicuspid), tricuspid, and pulmonary. Each heart valve is comprised of a dense fibrous ring known as the annulus, and leaflets or cusps attached to the annulus.

[0004] Heart valve disease is a widespread condition in which one or more of the valves of the heart fails to function properly. In a traditional valve replacement operation, the damaged leaflets are typically excised and the annulus sculpted to receive a replacement prosthetic valve.

[0005] In tissue-type valves, a whole xenograft valve (e.g., porcine) or a plurality of xenograft leaflets (e.g., bovine pericardium) can provide fluid occluding surfaces. Synthetic leaflets have been proposed, and thus the term “flexible leaflet valve” refers to both natural and artificial “tissue-type” valves. In typical surgical heart valves, two or more flexible leaflets are mounted within a peripheral support structure that usually includes posts or commissures extending in the outflow direction to mimic natural fibrous commissures in the native annulus. The metallic or polymeric “support frame,” sometimes called a “wireform” or “stent,” has a plurality (typically three) of large radius cusps supporting the cusp region of the flexible leaflets (e.g., either a whole xenograft valve or three separate leaflets). The ends of each pair of adjacent cusps converge somewhat asymptotically to form upstanding commissures that terminate in tips, each extending in the opposite direction as the arcuate cusps and having a relatively smaller radius. Components of the valve are usually assembled with one or more biocompatible fabric (e.g., DACRON® polyethylene terephthalate) coverings, and a fabric-covered sewing ring is provided on the inflow end of the peripheral support structure.

[0006] Sometimes the need for complete valve replacement may arise after a patient has already had an earlier valve replacement. For example, a prosthetic surgical heart valve that was successfully implanted to replace a native valve may itself suffer damage and/or wear and tear many years after initially being implanted. Implanting a new prosthetic heart valve directly within a previously-implanted prosthetic heart valve (a so-called valve-in-valve procedure) may be impractical since traditional prosthetic surgical heart valves may not be configured to easily receive such a valve-within-a-valve implantation in a manner which provides secure seating for the new valve while also having a large enough annulus within the new valve to support proper blood flow therethrough. Namely, conventional surgical valves have a relatively stable diameter that is not intended to be compressed or expanded during delivery, and after implant when functioning as a one-way valve.

[0007] Some attention has been paid to the problem of implanting a new valve within an old valve. In particular, the following disclose various solutions for valve-in-valve systems: U.S. Pat. No. 8,613,765, filed Jul. 7, 2011; U.S. Pat. No. 9,314,335, filed Sep. 19, 2008; U.S. Pat. No. 9,364,322, filed Dec. 20, 2013; U.S. Pat. No. 9,375,310, filed Dec. 20, 2013; and International Patent Publication No. WO 2012/018779, filed Aug. 2, 2011. The entire disclosures of these publications are expressly incorporated herein by reference.

[0008] Despite certain advances in the valve-in-valve area, there remains a need for a prosthetic heart valve which facilitates valve-in-valve procedures and simplifies manufacturing techniques.

[0009] Some embodiments provide a prosthetic surgical heart valve configured to receive a second prosthetic heart valve therein, such as a catheter-deployed (transcatheter) prosthetic heart valve. The surgical heart valves are adapted for post-implant expansion and expansion limiters that prevent over-expansion.

[0010] The present application provides a number of embodiments of prosthetic surgical heart valves adapted for post-implant expansion each defining an inflow end and an outflow end and comprise a valve member including a non-collapsible inner structural support stent having three upstanding commissure posts extending in an outflow direction and spaced evenly around a periphery of the support stent alternating with three arcuate inflow cusps midway between adjacent commissure posts. Three flexible leaflets attach along the commissure posts and inflow cusps of the support stent and are configured to ensure one-way blood flow through the valve member. The support stent periphery defined a non-collapsible delivery and implant circumference having a first diameter, wherein the support stent permits expansion of the periphery from the first diameter to a second diameter larger than the first diameter upon application of an outward dilatory force from within the support stent substantially larger than forces associated with normal physiological use. The support stent includes a structural band extending around the periphery that permits expansion of the support stent.

[0011] In a first embodiment, the structural band has overlapping free ends such that relative sliding of the overlapping free ends permits expansion of the support stent, and the valve member includes an expansion limiting spacer interposed between the overlapping free ends that engages both free ends and prevents over-expansion of the stent past the second diameter. Desirably, the overlapping free ends are located at a single one of the inflow cusps of the support stent. The expansion limiting spacer may have two fingers that are radially offset in opposite directions and extend through channels provided in respective structural band free ends. The fingers preferably terminate in enlarged heads that are wider than the channels. The expansion limiting spacer is preferably made of a lubricious material selected from the group consisting of polyester, polytetrafluoroethylene (PTFE), ultra-high-molecular-weight polyethylene (UHMWPE) and polyether ether ketone (PEEK).

[0012] In a second alternative embodiment, the structural band also has overlapping free ends such that relative sliding of the overlapping free ends permits expansion of the support stent, and a loop of one or more filaments is loosely threaded through holes in the structural band adjacent each free end such that slack in the loop permits the structural band to expand but prevents over-expansion of the stent past the second diameter. The loop preferably comprises a single suture threaded at least three times through the holes and tied off on the outside of the band. The slack in the loop may be located outside the band, and the loop and slack are hidden when the support stent is covered in cloth. Desirably, the overlapping free ends are located at a single one of the inflow cusps of the support stent.

[0013] In a third alternative embodiment, the valve member has an exterior fabric covering and an expansion limiting flexible loop having high tensile strength sewn to the fabric covering that permits the support stent to expand from the first diameter to the second diameter and prevents over-expansion of the stent past the second diameter. The flexible loop is desirably made of high tensile strength fiber. The flexible loop may be sewn to an outer edge of a suture-permeable sewing ring of the valve that surrounds the inflow cusps of the support stent, the sewing ring being compressible so as to permit the support stent to expand from the first diameter to the second diameter until the flexible loop becomes taut and limits further expansion. The flexible loop may be attached around the sewing ring with intermittent stitches or sewn in and out of the sewing ring with two free ends tied together. Alternatively, the flexible loop is sewn to a portion of the fabric covering directly around the support stent and incorporates a section of slack that permits the support stent to expand from the first diameter to the second diameter until the flexible loop becomes taut and limits further expansion. The structural band may have overlapping free ends such that relative sliding of the overlapping free ends permits expansion of the support stent. The overlapping free ends are desirably located at a single one of the inflow cusps of the support stent.

[0014] In any of the surgical heart valves having a structural band with overlapping free ends, a flexible sleeve may further surround the free ends and hold them radially together. In one embodiment, the sleeve is made of a material selected from the group consisting of polyester shrink wrap tubing and silicone rubber. Also, the sleeve may be biodegradable to maintain alignment of the two free ends for a period after implant and then degrade to permit even easier expansion of the band.

[0015] Any of the surgical heart valves may further include a unique identifier on the support stent visible from outside the body after implant that identifies the support stent as being expandable. The support stent for any of the heart valves may include the structural band concentrically disposed against a commissure band defining the three upstanding commissure posts of the support stent, the structural band being truncated at the commissure posts of the commissure band. The structural band is desirably made of a metal and the commissure band is desirably of a polymer.

[0016] Other features and advantages will become apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, certain principles and examples.

[0026] The prosthetic heart valves disclosed herein include a prosthetic valve member constructed similarly to embodiments of conventional surgical valves, with a relatively stable diameter that is not intended to be compressed or expanded during delivery and after implant when functioning as a one-way valve. The prosthetic heart valves described herein each include an internal (meaning incorporated into the valve member itself as opposed to being a supplemental element) structural stent or frame that is generally tubular in shape and that defines a flow orifice area through which blood flows from an inflow end to an outflow end. Alternatively, the shape of the internal stent can be oval, elliptical, D-shaped, irregular, or any other desired shape. The valves include flexible leaflets that selectively open and close to allow for one-way fluid flow therethrough.

[0027] Various internal stents disclosed herein have “expandable segments” that enable the stent to expand. Embodiments of the expansion can occur from the expandable segment rupturing, plastically stretching, or elastically elongating. Thus, an “expandable segment” means a location on the stent that enables it to enlarge in diameter, such as when a balloon is inflated within the stent. Examples include weak points that can rupture, thinned areas that rupture or stretch, accordion-like structures that elongate elastically or plastically, breaks in the stent that are held together with a breakable member such as a suture or spot weld, and various other means. The term, “expandable segment” thus encompasses each and every one of these alternatives, either individually or in combination.

[0028] The present application discloses specific modifications to existing surgical valves that enable manufacturers to rapidly produce a valve that accommodates valve-in-valve (ViV) procedures. Specifically, the present application contemplates retrofitting or modifying components within existing surgical valves to enable post-implant expansion, which not only converts any proven surgical valve for use in a ViV procedure, but it also reduces design and manufacturing work. Consequently, components of one popular surgical valve are described below to illustrate certain modifications thereto.

[0029] Recent publications report a drastically higher probability of annular rupture when expanding the native annulus by more than 20% by area when expanding a prosthetic heart valve therein. In light of this information, it is desirable to ensure that an expandable surgical valve expands by less than about 20% by area in some embodiments. For a 19-mm valve, a 20% increase in area corresponds to an increase in diameter of about 2 mm.

[0030] FIGS. 1A-1D are perspective and exploded views of an exemplary surgical prosthetic heart valve 20 oriented around a flow axis 22. The heart valve 20 comprises a plurality (typically three) of flexible leaflets 24 supported partly by an undulating wireform 26 as well as by a non-collapsible inner structural support stent 28. The wireform 26 and support stent 28 are visible in the figures, but are normally covered with a polyester fabric to facilitate assembly and reduce direct blood exposure after implant. The wireform 26 may be formed from a suitably elastic metal, such as a Co—Cr—Ni alloy like ELGILOY® alloy, while the support stent 28 may be metallic, plastic, or a combination of the two. As seen in FIG. 1B, outer tabs 30 of adjacent leaflets 24 wrap around a portion of the support stent 28 at so-called commissure posts of the valve that project in an outflow direction along the flow axis 22. A soft sealing or sewing ring 32 circumscribes an inflow end of the prosthetic heart valve 20 and is typically used to secure the valve to a native annulus such as using sutures.

[0031] FIGS. 1C and 1D show the inner support stent 28 in both assembled and exploded views. Although the general characteristics of the prosthetic heart valve 20 as seen in FIGS. 1A and 1B may be common to a number of different prosthetic heart valves, the illustrated support stent 28 is that used in a particular heart valve; namely, pericardial heart valves manufactured by Edwards Lifesciences of Irvine, Calif. For example, the Carpentier-Edwards PERIMOUNT® heart valves that utilize pericardial leaflets 24 feature an inner stent 28 much like that shown in FIGS. 1C and 1D. In particular, the stent 28 comprises an assembly or composite of two concentric bands: an outer band 34 surrounding an inner band 35. The bands 34, 35 are relatively thin in a radial dimension as compared to an axial dimension, and both have coincident lower edges that undulate axially up and down around the circumference. The outer band 34 exhibits three truncated peaks between three downwardly curved valleys, while the inner band 35 has generally the same shape but also extends upwards at commissure posts 36. The downwardly curved valleys are typically termed cusps 38, as seen in FIG. 1C. This undulating band shape is typical for aortic heart valves, which typically have three leaflets joined at their adjacent edges at upstanding commissures. Alternatively, the structural stent may have only one band with commissure posts.

[0032] In the exemplary PERIMOUNT® valves, the outer band 34 is metallic and is formed from an elongated strip of metal closed to the generally circular shape and the ends joined together, for example, by welding, as at 40. In contrast, the in band 35 is formed of a biocompatible polymer such as polyester (e.g., polyethylene terephthalate (PET)) or polyacetal (e.g., DELRIN® polyacetal), which may be molded, and also may be formed as a strip, closed into a circular shape and the ends joined together, for example, by welding (not shown). Both the outer and inner bands 34, 35 feature a series of through holes that register with each other so that the assembly can be sewn together, as schematically illustrated in FIG. 1C at a commissure region. The wireform 26 and the commissure posts 36 of the inner band 35 provide flexibility to the commissures of the valve, which helps reduce stress on the bioprosthetic material of the leaflets 24. However, the inflow end or base of the valve 20 surrounded by the sewing ring 32 comprises the relatively rigid circular portions of the support stent 28. The combination of the metallic outer and plastic inner bands and 34, 35 presents a relatively dimensionally stable circumferential base to the valve, which is beneficial for typical surgical use. However, the same characteristics of the support stent 28 that provide good stability for the surgical valve resist post-implant expansion of the valve. Consequently, the present application contemplates a variety of modifications to the support stent 28 to facilitate expansion thereof.

[0033] The exemplary surgical valve 20 described above may thus be modified for post-implant expansion. Furthermore, a similar surgical valve structure is used in the commercial Edwards INTUITY® valve system, and the same modifications can be made in the valve component of that system so that it may be easily expanded post-implant.

[0034] FIGS. 2A and 2B are perspective and elevational views of a first band 50 for use in an exemplary combination of structural bands to replace existing support bands and to enable post-implantation expansion thereof. The first band 50 again has a relatively small radial thickness relative to its axial height, and includes an undulating annular shape having downwardly curved cusps 52 intermediate upwardly projecting commissure posts 54. In a preferred embodiment, the first band 50 comprises a polymer material begins as a flat strip that is then curved into a circular shape and the two free ends joined together, for example, welded, as at 56.

[0035] The first band 50 includes weakened areas located below each of the commissure posts 54 that enable the band to rupture and easily expand along with the rest of the prosthetic heart valve. The first band 50 comprises a series of vertically-spaced through holes 60, 62 at each of the commissure posts 54. In particular, a first pair of through holes 60 is located closely adjacent to a lower edge 64 of the band. A vertical score line 66 through the thickness of band 50 extends vertically upwards from just above the first pair of through holes 60 to an upper through hole 62, which is located about midway up the commissure post 54. Preferably, the score line 66 connects with the upper through hole 62. The through holes 60, 62 may be circular, as shown, or may be slightly elongated such as in a teardrop shape so as to focus any tensile forces generated from expansion of the band 50 to a certain point, such as vertically upward, or may have any other suitable shape, for example, diamond, triangular, elliptical. Because of the relatively weak polymer material and the weakened areas provided by the through holes 60, 62 and score line 66, the first band 50 tends to split apart at three locations below the commissure posts 54. As explained above, the flexible leaflets are often secured to the upper ends of the commissure posts 54, which remain substantially unchanged above the upper through hole 62. Although the prosthetic heart valve in which the first band 50 is assembled is supplanted by a secondary valve, maintenance of the general integrity of the valve is desirable to avoid any loose components.

[0036] FIGS. 3A and 3B are perspective and elevational views of a second band 70 that can be coupled with the first band 50 of FIGS. 2A and 2B to form a composite structural band for use in various prosthetic heart valves to enable post-implantation expansion thereof. In particular, when assembled in a heart valve, the second band 70 is concentrically located around the first band 50 in intimate contact therewith, as seen in FIG. 4. The second band 70 also has an undulating annular shape with lower-arcuate cusp regions 72 alternating with upwardly extending commissure regions 74. The two bands differ mainly in that the commissure regions 74 of the second band 70 are truncated, extending only up a portion of the commissure posts 54 of the first band 50.

[0037] The second band 70 is desirably metallic, such as a cobalt-chromium alloy, for example, a Co—Cr—Ni alloy, for example, ELGILOY® alloy (Elgiloy Specialty Metals, Elgin, Ill.), and preferably formed initially as a flat band that is circularized into an annular shape. In the illustrated embodiment, two free ends 76a, 76b of the band 70 overlap and engage each other for limited expansion. One preferred example of such engagement is shown in FIGS. 3B and 5A-5C. Because the first band 50 comprises a polymer material and the second band 70 is metallic, the second band may be termed the “structural band” inasmuch as it provide greater resistance to any dimensional changes to the support stent formed by the assembly of the two, and prosthetic valve in which the support stent is used. The first band 50 may be termed a “commissure post band” because it provides the commissure posts 54 to which the valve leaflets attach. It should also be understood that these two concentric bands may be combined into one structural band with commissure posts, and the two free ends desirably provided at a cusp region.

[0038] As seen in FIGS. 5A-5C, the two free ends 76a, 76b in this example are radially separated by a sliding insert or “spacer” 78, shown in more detail in FIGS. 6A-6C. For example, the spacer 78 is formed of a lubricious material such as polyester, polytetrafluoroethylene (PTFE), ultra-high-molecular-weight polyethylene (UHMWPE). The spacer 78 is primarily formed as a radially thin rectangular body 80 that has a curvature the same as or similar to the curvatures of the two free ends 76a, 76b. A pair of offset interlocking fingers 81 having enlarged tabs 82 are cut from and project on either radial side of the body 80, as see in FIGS. 6A and 6C. The fingers 81 commence near the middle of the body 80, project away from each other and are angled radially away from opposite sides of the body. Each finger 81 is generally rectangular and terminates in the enlarged tabs 82, which is also illustrated as rectangular. The spacer 78 is desirably made from about 0.1 mm (about 0.004″) thick polyester (e.g., PET) and is die-cut, or could be cut or molded from other, stronger materials if needed, such as polyether ether ketone (PEEK). The spacer can also be a composite, for example, including a stronger central layer and lubricious outer layers.

[0039] The two free ends 76a, 76b are each distinguished from the rest of the band at a pair of shoulders 84 that reduce the axial height of an intermediate portion 86 having a central circumferential slot 87. Each free end 76a, 76b terminates in an axially enlarged head 88 (or oppositely-directed axial bumps) having an axial height that is approximately the same as the majority of the band 70, or the same as the two non-expandable cusp regions of the band. The fingers 81 on the sliding spacer 78 extend through the circumferential slots 87 on respective free ends 76a, 76b, as best see in FIGS. 5B and 5C.

[0040] The assembly of the two free ends 76a, 76b and spacer 78 seen in FIG. 5A is held together by a flexible sleeve 89 which surrounds the free ends 76a, 76b and holds them radially together. The sleeve 89 desirably comprises polyester (e.g., PET) shrink wrap tubing, or may be an elastic material, such as silicone rubber, and is shown transparent to illustrate the mating free ends 76a, 76b. The two free ends 76a, 76b may slide apart a predetermined distance while remaining overlapping. The flexible sleeve 89 provides a small or minimum amount of friction against the axially enlarged heads 88, and generally serves to maintain alignment of the free ends 76a, 76b.

[0041] The assembly of the first band 50 in intimate contact with the second band 70, as seen in FIG. 4, provides good stability for the prosthetic valve leaflets when in use, and an advantageous expandable structure if and when a valve-in-valve procedure is necessary. The flexible sleeve 89 nominally maintains the diameter of the band so that it is stable during manufacturing, but allows it to easily open up or expand when a valve-in-valve procedure is performed. Moreover, the sleeve 89 may be biodegradable to maintain alignment of the two free ends 76a, 76b for a period after implant and then degrade to permit even easier expansion of the band 70 when desired.

[0042] When a dilatory force such as an expanding balloon is applied within the heart valve, the free ends 76a, 76b slide apart and one or more of the weakened areas on the first band 50 located below each of the commissure posts 54 rupture so that the main circular support for the valve expands. The wireform 26 or other structure of the valve easily flexes apart. The preferably metal outer band 70 only expands at one location, while the preferably polymer band 50 can expand at all three commissures. The outer band 70 is able to slide within the surrounding cloth coverings and relative to the other components such that the valve expands generally uniformly around its perimeter. That is, the commissure areas of a wireform to which the leaflets attach and commissure areas of the metal band 70 are initially aligned, or registered. As the metal band 70 expands, the registered commissure areas become misaligned since the wireform 26 expands at all three commissures and the metal band only expands at the one cusp. However, the valve becomes obsolete, having been replaced with a transcatheter valve, and so this misalignment is of no consequence. The wireform maintains the upstanding commissure posts of the expanded valve in roughly the same locations as when they were functional, which are intermediate the surrounding coronary ostia, and thus valve expansion will not end up blocking critical blood flow to the coronary arteries.

[0043] Interference between the interlocking fingers 81 on the sliding spacer 78 and the circumferential slots 87 on the free ends 76a, 76b limits total expansion of the band 70. FIG. 5A shows the band in its unexpanded configuration with the free ends 76a, 76b nearly completely overlapping. FIG. 5B shows the free ends 76a, 76b separating, such as if a dilating device, for example, a balloon, expands within the prosthetic heart valve in a ViV procedure. Each of the enlarged tabs 82 on the fingers 81 remains on a respective side of the associated circumferential slot 87, ultimately preventing the free ends 76a, 76b from separating completely. As such, the sliding spacer limits total expansion of the band 70, such as to a pre-determined amount, about 2 mm for example. The geometry of the interlocking fingers 81 and slots 87 may be dimensioned to limit expansion of the band 70, and valve, to one or two valve sizes, for example, with 2 mm between each valve size.

[0044] The particular configuration of the sliding spacer 78 with fingers 81 that interlock with both free ends 76a, 76b is exemplary only and may take other forms. For example, the enlarged tabs 82 may be shaped differently such as being square or rounded rather than rectangular. Further, the sliding spacer 78 may be eliminated in favor of interlocking elements on the respective free ends 76a, 76b. In some examples in which the band is metallic, the polymer spacer 78 reduces sliding friction and/or possible detrimental sloughing of material that may result from metal-on-metal contact. Still further, alternative constructions for limiting expansion of the internal valve structure are shown and described below.

[0045] It should also be noted that although there is preferably a single point of expansion at the free ends 76a, 76b at one of the cusp regions of the band 70, as shown, the two non-expandable cusp regions of the band may also have similar points of expansion. In that instance, the overall magnitude of expansion at each cusp region will be less than needed for a single point of expansion, such as one third of the desirable increase in diameter of 2 mm. Further, providing three points of expansion will help reduce any misalignment of the existing valve commissures that may occur from expanding at only one cusp.

[0046] The band 70 preferably includes an identifying trait visible using external imaging and signifying it is expandable. In the embodiment illustrated in FIG. 4, a pattern of three holes 90 is provided at each commissure region 74. Again, this permits a surgeon contemplating a replacement operation to quickly confirm that a valve-in-valve procedure is a possibility. The band 70 may also include a valve size indicator visible using external imaging, such as having a valve size number, for example, a valve size in millimeters, laser cut though the band.

[0047] Another concept for limiting the expansion of prosthetic heart valves is shown in FIG. 7A. Specifically, a stent including a structural band 100 is shown, which is much like the band 70 of FIG. 3A and which is shaped to mate with a secondary band having commissure posts, such as band 50 of FIG. 2A. Alternatively, the structural band 100 may feature commissures and be shaped to function as a stent on its own. As before, the structural band 100 includes three cusps 102 between three commissures 104 in an undulating pattern which is conventional for aortic heart valves.

[0048] The band 100 is contiguous except at two overlapping free ends 106a, 106b located at about the middle of one of the cusps 102. As before, the free ends 106a, 106b are adapted to slide with respect to one another and thus permit expansion of the stent upon application of an outward dilatory force such as in a ViV procedure. In the illustrated embodiment, the two free ends 106a, 106b are shaped somewhat like the free ends 76 described above. A sliding insert or “spacer” 112 is interposed between the two free ends 106a, 106b to reduce sliding friction therebetween. For example, the spacer 112 is formed of a lubricious material such as polyester, PTFE, or UHMWPE. The assembly of the two free ends 106a, 106b and spacer 112 may be held together by a flexible sleeve (not illustrated), which surrounds the free ends 106a, 106b and holds them radially together, such as was described above with respect to the sleeve 89. The flexible sleeve also provides a small or minimum amount of friction against the free ends 106a, 106b.

[0049] Expansion of the band 100 is limited by a loop 120 of one or more filaments loosely threaded through holes 122 in the band 100 adjacent each free end 106a, 106b. The loop 120 may comprise a suture or any other flexible biocompatible member. In the illustrated embodiment the loop 120 is formed by a single suture threaded three times through the holes 122 and tied off on the outside of the band. A certain amount of slack in the loop 120 permits the band 100 to expand in a ViV procedure, for example, but expansion is limited thereby. The loop 120 is hidden when the assembly is covered in cloth, and its slack would preferably be located outside the band 100. Upon expansion of the heart valve, the loop 120 becomes taut at a predetermined diameter of the band 100 to prevent further expansion, as shown in FIG. 7C. For example, the loop 120 may be dimensioned to limit expansion of the band 100, and valve, to about 2 mm, or about one valve size.

[0050] Although the preceding configurations for limiting expansion of prosthetic heart valves by one or two sizes have been successfully tested, each require modification to a design of an already expandable valve. FIGS. 8-11 illustrate still further variations for limiting valve expansion that do not require significant modification of existing valves by introducing exterior loops of filament that can be easily sewn into the fabric covering the valves.

[0051] FIG. 8 shows a typical heart valve 130 much as described above having three flexible leaflets 132 supported by an internal stent structure (not shown) covered in biocompatible fabric 134. In the illustrated embodiment the valve 130 has a sewing ring 136 disposed circumferentially about an inflow end thereof. A loop 140 of flexible material such as a suture is added around the sewing ring 136 to limit the ability of the valve to expand. More particularly, the loop 140 is attached around the sewing ring 136 with intermittent stitches 142. The loop 140 may be made of high tensile strength fiber (e.g., DYNEEMA® UHMWPE, SPECTRA® UHMWPE, or KEVLAR® aramid), and is flexible so that it follows the scalloped-shape contour and is placed at a distance away from or spaced from the inner surface of the sewing ring 136. The distance from the inner surface of the sewing ring 136 permits some compression of the sewing ring from valve expansion but ultimately limits the amount of expansion and defines the final expanded diameter.

[0052] It should be understood that expansion-limiting solutions utilizing loops oaf material attached (e.g., sewn) to the exterior of the heart valve can be implemented across various expandable surgical valve designs, since it is independent of the internal structure of the valve. That is, the heart valves disclosed herein may be utilized without a secondary expansion-limiting solution within the valve structure, or any other expandable valve such as disclosed in U.S. Pat. No. 8,613,765, U.S. Pat. No. 9,314,335, U.S. Pat. No. 9,364,322, U.S. Pat. No. 9,375,310, and International Patent Publication No. WO 2012/018779, the disclosures of which are expressly incorporated herein by reference.

[0053] The loop 140 can be constructed as a separate piece and attached/sewn to the sewing ring 136. Alternatively, the loop 140 can be constructed by sewing the high tensile strength fiber in and out of the sewing ring 136 and tying the ends together, such as shown in FIG. 9. The loop 140 is completed when the free ends of the high tensile strength fiber are tied in a knot or crimped. In some examples, the loop 140 is a separately manufactured closed loop that does not require knotting or crimping during assembly of the prosthetic valve, which facilitates uniform sizing and/or simplified manufacturing.

[0054] FIG. 10 shows another version of a loop 150 for limiting expansion of the heart valve 130. In this version, the loop 150 attaches around an upper portion of the fabric-covered internal stent, described above, and includes built-in relief or slack 152 that permits expansion of the valve. At a certain diameter of the stent, the slack 152 tightens and limits further expansion (to one or more valve sizes).

[0055] FIG. 11 shows a radial cross section of the valve 130 with potential locations of placement of the expansion-limiting loops described above. The valve 130 includes an internal stent with an inner band 160 and an outer band 162, and a wireform 164. The outer edges 166 of the leaflets 132 are secured between the upper end of the fabric-covered composite bands 160, 162 and wireform 164. The sewing ring 136 is shown attached at its inner surface to the outer band 162 and includes a suture-permeable insert 168, such as silicone rubber. The locations of possible placement of the expansion-limiting loops are given at 170a-170e. Depending on the placement, a length of slack may be included in the loop, such as shown at 152 in FIG. 10.

[0056] The specific locations shown are: on the outer edge of the sewing ring 136 at 170a, on an outer edge of the stent (composite bands 160, 162) at 170b, to the inside of the stent at 170c, at an inflow end of the stent at 170d (inside the stent), and at the underside of the sewing ring 136 at 170e. Each of these locations has a fabric covering such as at 134, and so the loop of suture material can either be stitched in and out of the fabric or supplemental stitches added to hold it in place.

[0057] Again, this particular expansion-limiting solution can be implemented across various expandable surgical valve designs, since it is independent of and therefore avoids modification to the internal structure of the valve. This approach also could allow tailored amount of expansion that could be independent of the design of the internal structure of the valve

[0058] While certain principles have been described with reference to particular embodiments, it will understood that various changes and additional variations may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or device to the teachings without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed herein, but will include all embodiments falling within the scope of the appended claims.