Disclosure of Invention
According to one embodiment of the present invention, a reinforcement device is described that includes a plurality of commissural (commissural) supports, a plurality of intercommissural (intercommissural) supports, and a base. Each commissure support is configured to stabilize a valve wall of the biological valve at a commissure of the biological valve. Each intercommissural support is configured to stabilize the valve wall at a position circumferentially between two of the commissures. The base is attached to the plurality of commissural supports and the plurality of intercommissural supports and is configured to receive a biological valve mounted on the base at an inflow region of the biological valve. In one aspect of this embodiment, the commissural supports are configured to stand substantially within the valve wall. In the previous aspect, the intercommissural support may also be configured to stand substantially upright within the valve wall. In another aspect, the commissural supports are configured to stand outside the valve wall. In the previous aspect, the commissural supports can be configured to be sutured to the valve wall. In another aspect, the base is continuous around the valve wall in the inflow region of the biological valve. In another aspect, the commissural supports and the intercommissural supports are discontinuous around the valve wall in the outflow region of the biological valve. In yet another aspect, the commissural supports and the intercommissural supports are disposed at separate locations of the valve wall in the outflow region of the biological valve. In another aspect, the commissural supports and intercommissural supports comprise metal wires. The metal line may comprise titanium. In another aspect, each of the commissural supports includes a first straight portion and a second straight portion. The first and second straight portions may be separated by a distance sufficient to avoid damaging a marking zone (marking zone) located near the commissure when the commissure support is attached to the valve wall. The first and second straight portions may be substantially parallel. In addition, the first straight portion and the second straight portion may be connected together by a curved portion. The curved portion may have a constant radius of curvature equal to half the distance between the first straight portion and the second straight portion. The first and second straight portions may be configured to stand within a wall of the biological valve. The curved portion may be configured to stand at least partially outside a wall of the biological valve. In another aspect of this embodiment, each of the intercommissural supports comprises first and second substantially parallel straight portions. The first straight portion and the second straight portion may be connected together by a curved portion. In yet another embodiment, the plurality of commissure supports includes 3 commissure supports disposed substantially symmetrically about the base. In another aspect, the plurality of commissure supports includes 3 commissure supports asymmetrically arranged about the base. In the previous aspect, the plurality of commissural supports may include 3 commissural supports, each of the commissural supports being disposed between a pair of commissural supports. Each intercommissural support may be disposed approximately midway between each pair of commissural supports. In another aspect, a base includes a ring and a cover. In the previous aspect, the ring may be as thick or thicker than the valve wall. In another aspect, the base includes a first plurality of apertures configured to closely receive the commissural supports and a second plurality of apertures configured to closely receive the intercommissural supports. For each commissural support, the first plurality may include 5 holes to adjustably position the commissural support relative to the base. In another aspect, the reinforcement device includes a constraining wall (crimping wall) configured to secure the commissural supports and the intercommissural supports to the base when the constraining wall is pressed against the supports. In another aspect, the base comprises a metal. The metal may comprise titanium. In these and other aspects, the biological valve may be an aortic valve or a mitral valve.
In another embodiment, a reinforced prosthetic valve is described. The reinforced prosthetic valve includes a biological valve mounted on a base, a plurality of commissural supports extending from the base, and a plurality of intercommissural supports extending from the base. The biological valve has leaflets attached to the outer wall at commissures and has an inflow region and an outflow region. Each commissure support is configured to stabilize the outer wall at one of the commissures. Each intercommissural support is configured to stabilize the outer wall in a position circumferentially between two of the commissures. In one aspect of this embodiment, the commissural supports and the intercommissural supports do not continuously surround the valve in the outflow region. In another aspect, the commissural supports and the intercommissural supports are disposed substantially within the outer wall. In another aspect, the commissural supports and the intercommissural supports are disposed outside of the outer wall. In the previous aspect, the commissural supports and intercommissural supports are secured to the outer wall by sutures.
In another embodiment, a method of reinforcing a biological valve is described. The biological valve has leaflets attached to the outer wall at commissures. The method includes securing a commissural support to the outer wall at or near each commissure and coupling the commissural support to the base. The method also includes securing the intercommissural supports to the outer wall between each pair of commissural supports and coupling the intercommissural supports to the base. In one aspect of this embodiment, securing the commissural supports to the outer wall includes inserting the commissural supports into the outer wall in a generally longitudinal direction. In another aspect, securing the commissure supports to the outer wall includes suturing the commissure supports to the outer wall. In another aspect of this embodiment, the method further comprises the step of adjusting the tension in the biological valve by adjusting the position of the commissural supports relative to the base. In yet another embodiment, the base is provided with a first plurality of apertures configured to receive the commissural supports and a second plurality of apertures configured to receive the intercommissural supports. The first plurality of holes may include 5 holes configured to allow adjustable placement of the commissural supports. Coupling the commissural supports and the intercommissural supports to the base may comprise constraining the commissural supports and the intercommissural supports to the base.
In another embodiment, a method of making a reinforced biological valve is described. The biological valve has a valve wall and a plurality of commissures. Biological valves comprise biological tissue that has been fixed in a physically unconstrained state. The method includes securing commissure supports to the valve wall adjacent each commissure and securing an intercommissure support to the valve wall between each pair of commissure supports. In one aspect of this embodiment, the method further comprises providing a base configured to couple with the commissural supports and the intercommissural supports, and adjusting the tension in the biological valve by adjusting the position of the commissural supports relative to the base. The biological valve may have an inflow region and an outflow region, with the commissural supports and the intercommissural supports being discontinuous about the valve in the outflow region. The commissural supports can be secured to the valve wall by longitudinally inserting the commissural supports into the valve wall.
Yet another embodiment is a method of making a reinforced biological valve. The biological valve has a valve wall, a plurality of commissures, an inflow region, and an outflow region. The method includes securing biological tissue in a physically unconstrained state, forming a biological valve from the biological tissue, attaching commissure supports to the valve wall adjacent each commissure, and attaching an intercommissure support to the valve wall between each pair of commissure supports. In one aspect of this embodiment, the commissural supports and the intercommissural supports do not continuously surround the biological valve at the outflow region. The commissural supports can be attached to the valve wall by placing the commissural supports substantially within the valve wall.
Yet another embodiment is a method of replacing a dysfunctional valve in an individual. The method includes removing the dysfunctional valve from the subject, providing a reinforced biological valve including a plurality of commissural supports and a plurality of intercommissural supports, and implanting the reinforced biological valve into the subject to replace the dysfunctional valve. Each commissural support is configured to stabilize a commissure of the biological valve, and each intercommissural support is configured to stabilize a wall of the valve between each pair of commissural supports. The commissural supports and the intercommissural supports are disposed at separate locations around an outflow region of the biological valve.
In another embodiment, a prosthetic biological valve includes a frame and a cross-linked biological valve. The frame includes 3 attachment points forming a first triangle and 3 attachment points forming a second triangle, and the frame has a first diameter. The cross-linked biological valve has a second diameter when the valve is not attached to the frame, the second diameter being less than the first diameter. The cross-linked biological valve is attached to the attachment point under tension such that a diameter of the cross-linked biological valve substantially stretches to the first diameter. In one aspect of this embodiment, the attachment point of the first trigone is attached to a commissure of the biological valve. In another aspect, the attachment point of the second trigone is attached between the commissures of the biological valve. In another aspect, the biological valve is attached to the attachment point by at least one in-wall support. In another aspect, the frame includes a means for adjusting tension in the valve wall. In another aspect, the frame includes a means for adjusting tension in the valve wall.
In another embodiment, a method of making a bioprosthetic valve is provided. The method includes providing a biological valve, and providing a frame comprising first and second trigones, each trigone comprising 3 attachment points, the frame having a diameter greater than a diameter of the biological valve. The method also includes attaching the biological valve to the frame at the first trigone, adjusting tension in the biological valve, and attaching the biological valve to the frame at the second trigone. In one aspect of this embodiment, attaching the biological valve to the frame at the first trigone comprises attaching commissures of the valve to attachment points of the first trigone. In another aspect, attaching the commissures to the attachment points of the first trigone comprises inserting the intramural support in the commissures of the valve. In another aspect, attaching the commissures to the attachment points of the first trigone comprises suturing the commissures of the valve to the commissure supports. In another embodiment, attaching the biological valve to the frame at the second triangle includes attaching a wall of the valve to an attachment point of the second triangle. In another aspect, the biological valve has been secured in a physically unconstrained state. In another aspect, the step of adjusting the tension includes applying tension to the biological valve such that the biological valve has substantially the same diameter as the frame.
Features, aspects, and advantages of the present invention will now be described with reference to the accompanying drawings of several embodiments that fall within the scope of the invention disclosed herein. These and other embodiments will be apparent to those skilled in the art from the following detailed description of the embodiments, which proceeds with reference to the accompanying drawings, and the invention is not limited to any particular embodiments disclosed.
It has been mentioned in the background section that stented valves include an outer frame (stent) on which the biological tissue valve is mounted. The stent continuously surrounds and supports the outflow region of the valve (the region outside the leaflet plane in the flow direction) to hold the valve wall in the open configuration. While stented valves provide relative ease of implantation and stability of the configuration after implantation, the stented design also adds size to the replacement valve device. The stenting design results in a significant reduction in ventricular outflow tract diameter (on the order of about 3-8 mm), thereby artificially increasing the pressure gradient across the valve. Stenting designs can also reduce the Effective Open Area (EOA) of the valve. Thus, a stented design may provide relatively poor hemodynamics compared to a non-stented design.
Because stentless valves introduce little or no increased size, the pressure gradient in the replacement valve is more like a native valve. The unsupported design may also provide increased flexibility relative to the stented design. Thus, the design without a stent provides hemodynamic advantages. However, conventional stentless designs are more difficult to orient during implantation and require more complex sutures to maintain the post-implantation valve configuration. This undesirably results in longer procedure times and increased risk and expense of the procedure. In addition, complex intraoperative sutures can alter the desired geometric configuration of the valve.
Another drawback of conventional biological replacement valve designs is that they require some artificial external stress (axial, radial, and/or circumferential) on the leaflets during the cross-linking (fixation) process in order to establish a root geometric configuration. This can undesirably affect the biomechanics of the leaflet tissue and the anatomical configuration of the leaflets relative to each other because the tissue is effectively fixed in a slightly pre-stressed state. This reduces the ability of the leaflets to function properly and negatively impacts the performance characteristics of the valve. Conventional methods also compensate for the contraction of tissue (which tends to occur during fixation) by starting with an oversized valve (pre-fixation). Post-fixation results in additional tissue mass, reducing the EOA of the traditional reinforced valve.
Various embodiments of the present invention advantageously provide devices and methods for supporting and stabilizing a biological heart valve without adding significant mass or reducing the working diameter of the valve. Thus, embodiments allow for replacement of a native valve with a prosthesis having optimal dimensions. In addition, embodiments of the present invention also provide a reinforced prosthetic valve that can be prepared and installed in a relatively quick and simple manner prior to surgery without the need for complex suturing during implantation. Certain reinforced prosthetic valves are described in U.S. patent application Ser. No. 10/550,297, entitled "Intra-mural Aortic Valve Reinforcement Device and reinforced Aortic Valve" and PCT application No. PCT/IB2005/000573, entitled "reinforced Intra-mural Device for a Biological Heart Prosthesis and reinforced Biological Heart Prosthesis", the disclosures of which are incorporated herein by reference in their entirety.
In addition, the commissural supports and intercommissural supports used in these and other embodiments may provide a reference point for the surgeon to assist the surgeon in marking the correct orientation of the prosthesis and facilitating implantation of the prosthesis. These and other embodiments, therefore, combine the advantages of both conventional stented and stentless valves while reducing or eliminating their associated disadvantages.
Embodiments also desirably allow for the reconstruction of the native heart valve root configuration (further described below as a "double trigonal" geometry) without the need for mechanical, hydrostatic, or other external stabilization devices during the cross-linking process. In contrast, biological tissue can be fixed in a zero stress environment without affecting the morphology of the collagen or elastin of the tissue, thereby fixing the tissue in a natural, unstressed state. The root geometry can thus be reconstructed (and manipulated if necessary) after fixation using a support disposed near or inside the valve wall at the commissures and in the intercommissure spaces. Stabilizing the valve wall at the discrete locations around the outflow region strengthens the geometric configuration of the roots while allowing some flexibility of the non-reinforced portion of the valve wall during operation of the valve.
Furthermore, as described above, the fixation process may cause a certain amount of shrinkage in the biological tissue. According to an embodiment of the invention, providing a zero stress fixation allows optimizing the size of the valve tissue with the reinforcement means, since after fixation the slightly contracted (fixed) tissue may stretch back substantially to its original size. This reduces or eliminates undesirable increased tissue mass, thereby increasing the EOA of the valve over conventional configurations. Providing zero-stress fixation also minimizes undesirable artificial stresses introduced on the leaflets during operation of the valve. Thus, embodiments require less work to open the leaflets, thereby minimizing energy loss across the reinforced valve.
Reinforced valve
Referring now to fig. 1, an embodiment of a reinforced biological valve 50 is illustrated. The reinforced valve 50 includes a biological valve reinforcement device 10 having commissure supports 14(a) -14(c) and intercommissural supports 16(a) -16(c) (valve leaflets not shown in fig. 1) disposed mostly within the outer wall 24 of the biological valve 20. Alternatively, the device 10 may include commissural supports and intercommissural supports that are disposed just outside the valve 20 and secured to the valve tissue, such as by sutures. As better illustrated in fig. 3, the biological valve 20 includes 3 leaflets 22(a) -26(c) attached laterally to an outer wall 24 at 3 commissures 26(a) -26 (c). At the intersection of each of the commissures 26(a) -26(c) with the wall 24 there is a "marker region" with a complex reinforced anatomical structure (formality). The marked area 36(c) corresponding to the commissure 26(c) is illustrated in dashed lines. The native channel 30 in which the reinforced valve 50 may be implanted is also illustrated in dashed lines. For example, the native channel 30 may be an aortic channel. The flow direction through the valve 20 is indicated by arrows 32 (inflow) and 34 (outflow).
Reinforcing device
In the embodiment shown in fig. 1, the device 10 generally includes a base 12 (to which a biological valve 20 may be mounted), a plurality of commissural supports 14(a) -14(c) (shown in mostly dashed lines), and a plurality of intercommissural supports 16(a) -16(c) (also shown in mostly dashed lines). The commissural supports 14(a) -14(c) may be generally placed at the commissures of the valve 20, and the intercommissural supports 16(a) -16(c) may be placed in or near the valve wall 24. In some embodiments, the intercommissural supports 16(a) -16(c) may be positioned approximately midway between each pair of commissures. However, it is understood that the intercommissural support can be positioned at any location consistent with its intended function. The commissural supports 14(a) -14(c) and intercommissural supports 16(a) -16(c) may be attached to the base 12.
Base seat
With continued reference to fig. 1, the base 12 may have an inner diameter substantially equal to the inner diameter of the biological valve 20. Thus, as shown, the inflow region of the valve 20 (the region forward of the leaflet plane moving in the flow direction) can be mounted directly on top of the base 12 with the inner walls of the valve 20 substantially flush with the inner surface of the base 12. The base 12 may also have a thickness that may preferably be substantially equal to the thickness of the wall 24 of the biological valve 20. Thus, the base 12 may have an outer diameter that may preferably be substantially equal to the outer diameter of the wall 24 of the biological valve 20. The thickness of the base 12 may also be greater or less than the thickness of the biological valve 20. For example, for a smaller size valve, the base 12 may have a thickness that is slightly greater than the thickness of the valve wall.
As shown in fig. 2, the base 12 may be provided with a plurality of holes 13. The hole 13 may be disposed on the top surface of the base 12, midway between the inner and outer walls of the base 12 (as shown in fig. 2) or at the outer edge of the top surface of the base (see fig. 7). The holes 13 may be arranged in any other position consistent with their intended use. The holes 13 can be configured to receive the commissures and the intercommissural supports 14(a) -14(c) and 16(a) -16(c) (described in more detail below).
As better illustrated in fig. 5A-5B, one or more holes 13(a) may be provided for each commissural support 14(a) -14(c) to allow adjustable placement of the commissural supports 14(a) -14(c) around the base 12. For example, if the legs of the supports 14(a) -14(c) are spaced 4mm apart, then 5 holes may be provided and spaced 2mm apart so that the supports may fit in the first and third holes, the second and fourth holes, or the third and fifth holes. The holes 13(a) or groups of holes 13(a) may be arranged in a slightly asymmetrical manner around the base 12; for example, in some embodiments, the apertures 13(a) or groups of apertures 13(a) may be spaced from each other by about 120 °, 105 °, and 135 °. Alternatively, the apertures 13(a) or groups of apertures 13(a) may be arranged in a generally symmetrical manner about the base 12, depending on the needs of a particular application.
In addition, one or more apertures 13(b) may be provided for each of the intercommissural supports 16(a) -16 (c). As shown in fig. 5B, each hole 13(B) or group of holes 13(B) may be disposed approximately midway between each group of commissure support holes 13 (a). Of course, the commissure support holes 13(a) and the intercommissural support holes 13(b) may be arranged in any other configuration consistent with their intended use. For example, the base 12 may be provided with evenly spaced apertures 13 to allow maximum adjustability or may be provided with apertures 13 in separate locations to ensure accurate positioning of the supports 14(a) -14(c) and 16(a) -16 (c).
Referring now to fig. 5A-5D and 6A-6B, in some embodiments, the base 12 may include a ring 60 and a cover 70. The ring 60 may be provided with a plurality of holes 13 as described above. As shown in fig. 5C-5D, the ring 60 may have an inner wall 62, a constraining wall 64, and an outer lip 66. The constraining wall 64 may be configured to provide a friction constraint (friction crimp) against a support 14, 16 inserted in one of the holes 13 when the wall 64 is pressed against said support 14, 16. As shown in fig. 6A-6B, the cap 70 may have an inner lip 72 configured to mate with the inner wall 62 of the ring 60 and an outer wall 76 configured to mate with the outer wall 66 of the ring 60. The outer wall 76 may be provided with a chamfer 73, the chamfer 73 being configured to allow the cover 70 to slide over the constraining surface of the constraining wall 64 of the ring 60. The outer wall 76 may also be provided with an annular groove 75, the annular groove 75 being configured to be secured to the constraining surface of the constraining wall 64. In alternative embodiments, the base 12 may have any other configuration that allows it to secure the supports 14, 16 and support a biological valve mounted thereon.
The base 12 may comprise a suitable material for receiving and/or securing the supports 14(a) -14(c) and 16(a) -16 (c). For example, the base 12 may be formed of a metal such as titanium. Alternatively, the base 12 may be formed from a rigid, semi-rigid, or flexible polymer.
Commissural support
Referring again to the embodiment shown in FIG. 2, commissure supports 14(a) -14(c) may be disposed at each of the commissures 26 and connected to the base 12. The commissural supports 14(a) -14(c) may each include two legs connected by a curved portion at the end of the support distal from the base 12. The two legs may be generally straight and generally parallel (as shown) or may be slightly curved apart or slightly angled apart. The two legs may also be spaced apart a distance sufficient to avoid damage to the biological tissue in the marked regions 36(a) -36(c) of the biological valve 20 (the marked region 36(c) is shown in fig. 3), thereby maintaining the structural integrity of the biological valve 20. For example, the legs may be separated by a distance of 4mm or 3mm (especially in the case of smaller sized valves). The legs may also be separated by any distance appropriate to the intended use of the valve. In some embodiments, the curved portion may have a constant bend radius, which may be equal to half the distance between the parallel legs.
In the embodiment of fig. 1, the commissural supports 14(a) -14(c) may be configured to stand mostly within the outer wall 24 of the biological valve 20. Alternative embodiments may include a commissural support having any configuration capable of providing sufficient support to the commissures during exposure to physiologic fluid pressures and flow rates. For example, the embodiment shown in fig. 7 has commissure supports 84(a) -84(c) disposed outside of the valve wall 24 around the outer circumference of the base 82, the valve 20 being disposed on top of the base 82 and the inner wall of the valve 20 being substantially flush with the inner circumference of the base 82. The external commissure supports may comprise a single straight rod, T-shaped rod, curved wire, or narrow sheet or plate that may be sutured or otherwise attached to the biological valve tissue at the valve commissures (see fig. 7). As described above in connection with fig. 5A-5B, depending on the geometric configuration of the biological valve 20, the commissure supports can be disposed somewhat asymmetrically around the base. The commissural supports may also be disposed about the base in any other configuration consistent with its intended use.
Referring again to the embodiment shown in FIG. 1, the commissural supports 14(a) -14(c) may be arranged in a direction substantially parallel to the flow direction 32 through the valve 20. The legs of the commissural supports 14(a) -14(c) may be disposed entirely within the tissue of the wall 24, while the curved portions of the commissural supports 14(a) -14(c) may extend partially or entirely outside the tissue at an end distal from the base 12. For example, the commissure supports 14(a) -14(c) may each comprise a continuous wire, such as a titanium wire. Alternatively, the commissural supports 14(a) -14(c) may comprise rigid, semi-rigid, or flexible polymers.
Referring now to the embodiment shown in fig. 4, which illustrates a bottom view of the device 10 incorporated into a reinforced biological valve 50, the commissural supports 14(a) -14(c) may collectively define a commissural triangle 44 (shown in dashed lines).
Intercommissural support
Referring again to the embodiment shown in fig. 1, intercommissural supports 16(a) -16(c) (shown largely in phantom) may be disposed in the intercommissural space, preferably in each pair of commissural supports 14(a), 14 (b); 14(b), 14 (c); and approximately halfway between 14(c) and 14 (a). Intercommissural supports 16(a) -16(c) may also be attached to base 12. In the embodiment of fig. 1, the intercommissural supports 16(a) -16(c) may be configured to stand mostly within the outer wall 24 of the biological valve 20. Alternative embodiments may include an intercommissure support disposed outside of the biological valve tissue that may be sutured or otherwise attached to the valve tissue in the intercommissure space (see fig. 7).
Referring again to the embodiment shown in FIG. 2, each of the intercommissural supports 16(a) -16(c) may include two legs connected by a curved portion at the end of the support distal from the base 12. The two legs may be generally straight and generally parallel (as shown) or may be slightly curved apart or slightly angled apart. The curved portion may have a constant bend radius equal to half the distance between the parallel legs. Alternatively, since the intercommissural space does not include particularly vulnerable marker regions, the intercommissural supports may each comprise a single straight rod, T-shaped rod, or narrow sheet or plate. Embodiments may include intercommissural supports having other shapes, such as a spiral shape, that may assist in inserting the support into valve tissue.
In the embodiment shown in fig. 1, the intercommissural supports 16(a) -16(c) may be arranged in a direction substantially parallel to the flow direction 32. The legs of the intercommissural supports 16(a) -16(c) may be disposed entirely within the tissue of the wall 24, while the curved portions of the intercommissural supports 16(a) -16(c) may extend partially or entirely outside the tissue at an end distal from the base 12. In the embodiment shown in FIG. 2, the intercommissural supports 16(a) -16(c) may be shorter than the intercommissural supports 14(a) -14(c) because the wall 24 is typically cut shorter in the intercommissural space than in the vicinity of the commissures 26. For example, the intercommissural supports 16(a) -16(c) may each comprise a continuous wire, such as a titanium wire. Alternatively, the intercommissural supports 16(a) -16(c) may comprise a rigid, semi-rigid, or flexible polymer.
Referring again to FIG. 4, the intercommissural supports 16(a) -16(c) may collectively define an intercommissural triangle 46 (shown in dashed lines). The commissure trigone configuration 46 may be used to resist radial forces acting on the commissure spaces when the leaflets 22 are closed. Thus, the commissural supports 14(a) -14(c) and the intercommissural supports 16(a) -16(c) together define a double-trigonal geometric configuration (see lines 44, 46) that closely resembles the native geometric configuration of the biological valve 20.
Referring now to fig. 3, a reinforced biological valve 50 may be provided with a sewing ring 52, the sewing ring 52 may comprise flexible synthetic fibers. The entire periphery of the valve 50 may also be covered with synthetic fibers 54.
Preparation of reinforced devices and reinforced valves
Methods of reinforcing a biological valve are also provided. The method can include placing a commissural support at or near each commissure of the biological valve and securing the commissural support to valve tissue. The method may further comprise positioning the commissural supports approximately midway between each pair of commissural supports and securing the commissural supports to the valve tissue. The method can further include attaching the commissural supports and the intercommissural supports to a base, which can be positioned under the biological valve.
In some embodiments, after the initial harvest of the biological material to be used to replace the valve, it can be stored in a preservative solution. The biomaterial may then be subjected to one or more pre-fixation treatments, such as a decellularization treatment, to reduce the risk of post-transplant mineralization. At 5,595,571; 5,720,777, respectively; and 5,843,181, the pre-fixation process is more fully described; the disclosures of these documents are incorporated herein by reference in their entirety.
The biomaterial may then be used in a fixation (cross-linking) process to maintain the structural integrity of the biological valve. Such immobilization may include exposing the biological material to glutaraldehyde. This fixation can occur without any mechanical, hydrostatic, or other external stresses acting on the leaflets. Fixing biological tissue in a "relaxed" state allows some contraction of the material without affecting the orientation of collagen or elastin in the tissue and, therefore, without affecting the biomechanical properties of the tissue. The tissue can then be segmented and synthesized into synthetic biological valves according to known practices. Embodiments of the present invention may also use non-invasive biological valves.
Next, the commissural supports may be inserted into the wall of the biological valve. Each commissure support may comprise two legs, each leg may be provided with a sharpened tip to penetrate the wall of the tissue valve on either side of the commissure marker region. The legs may have different lengths to facilitate insertion. The legs can enter the valve wall at the outflow region of the valve and be pushed through the wall in a direction generally parallel to the central axis of the valve until the legs exit the tissue at the inflow region of the valve. Alternatively, the commissure supports can be disposed outside the valve wall at each commissure and secured to the valve tissue in any suitable manner, such as by sutures.
Once each commissural support is inserted through (or otherwise attached to) the valve wall, these supports may be attached to the base. The commissural supports may first be removably attached to the bases to allow the practitioner to select between bases of different sizes, if necessary. The commissural supports may also be adjustably positioned on the base, taking into account the size of the biological tissue, to allow the practitioner to adjust the height of the support and adjust the tension between the leaflets, if necessary. As mentioned above, the valve tissue may have contracted to some extent (on the order of about one valve size (i.e., about 2mm in diameter)) during zero-stress fixation. Thus, the process of attaching the commissural supports to the base may include stretching the valve tissue slightly to reconstruct the original valve dimensions.
After the proper size and positioning is determined, the commissural supports can be more permanently affixed to the base to create the commissural trigones. The commissural supports may be secured by constraining the walls of the base to the legs of the support. The support may be fixed by using a friction constraint, allowing the height of the support to be adjusted, or may be fixed by using a fixing constraint such that the support is more securely positioned relative to the base. Alternatively, the commissural supports may be secured by any other means consistent with the intended use of the valve. Once the commissural supports are secured to the base, the supports may be bent at an angle of about 90 ° (tangential to the base) and trimmed.
After the commissural trigones are established, the intercommissural supports may be inserted into the valve wall. Each intercommissural support may comprise one or more legs, each of which may be provided with a sharpened tip to penetrate the wall of the tissue valve. The legs can enter the valve wall at the outflow region of the valve and be pushed through the wall until the legs exit the tissue wall at the inflow region of the valve. Alternatively, as with the commissural supports, the commissural supports may be placed outside the valve wall in each of the commissural spaces and secured to the valve tissue in any suitable manner, such as by suturing. The intercommissural support may then be attached to the base and trimmed in a manner similar to the commissural supports. When a base comprising a ring and a cover is used, the cover may be placed over the ring and secured to the ring.
Finally, the reinforced valve may be covered or partially covered with flexible synthetic fibers. The reinforced valve may also be surrounded by a sewing ring, such as a flexible fibrous ring, which may be used to facilitate implantation of the device.
In some embodiments, reconstructing the aortic root geometry of a biological valve used to make a prosthetic biological valve comprises altering a previously cross-linked biological valve by creating two overlapping trigones, the apices of which are located at three commissures and at approximately the mid-point between the commissures, respectively, the valve having been removed from a donor prior to the cross-linking process.
As mentioned above, the traditional method of preparing a bioprosthetic valve compensates for the contraction of tissue that occurs during fixation by starting with an oversized valve (pre-fixation). However, in embodiments of the present invention, a biological valve having dimensions (before fixation) that are approximately the same as the desired diameter of the prosthetic biological valve is used. The biological valve is allowed to contract during the cross-linking process and then expanded back to the desired diameter during formation of the prosthetic biological valve. In some embodiments, a first trigone is created at the commissure, followed by a second trigone approximately midway between each pair of commissures. The creation of each triangle includes applying some tension to the valve wall at these points or regions to pull the apex of the triangle to the size of the desired final valve diameter. Accordingly, embodiments of the present invention include rigid or semi-rigid structures to maintain the apex height and/or inter-apex distance of the trigones after they are built.
During the formation of the valve, the practitioner can adjust the tension between the apices of the first trigones (which may be commissure trigones) to ensure that the first trigones closely mimic the proportional geometric configuration of the original biological valve. Next, the practitioner can create a second trigone (which can be an intercommissure trigone). The resulting prosthetic bioprosthetic valve wall is under some tension and reduces or eliminates additional tissue mass resulting from the use of an oversized bioprosthetic valve. This configuration allows the leaflets to open to the largest possible aperture. Thus, the resulting valve better mimics the hemodynamics of the native valve.
In some embodiments, the trigone may be established and/or reinforced by placing a fixation and/or supportive structure within the wall of the valve at the commissure and the intercommissure region, and attaching the supportive structure to a rigid ring or annulus having a desired diameter; the supportive structure has sufficient mechanical properties to maintain the desired apex height for each triangle. In other embodiments, the biological valve can be placed within a rigid or semi-rigid frame or stent having a diameter and profile suitable for holding the biological valve wall in tension, thereby maintaining the reconstructed root geometric triangle. Tension can be applied to the valve wall, for example, circumferentially and/or longitudinally. In these and other embodiments, the biological valve may be attached directly to a supportive frame or stent, or to a covering applied to the frame or stent, by using suturing techniques or other attachment methods. Such a covering may comprise a fabric such as polyester. The supportive frame can be placed outside the valve wall and can be prepared by machining, shaping, cutting or molding a suitable material to form a contour that accommodates the reconstructed valve geometric configuration. In some embodiments, the supportive frame can be an uncovered or fabric-covered plastic stent, an uncovered or fabric-covered stent formed from wire, or an annular metal or plastic ring with support placed within the wall in the commissure and intercommissural region.
Use of reinforced valves
During aortic valve replacement surgery, the diseased or dysfunctional native valve is removed from the native aortic valve orifice. The aortic valve orifice is then sized and a pre-fabricated reinforced biological valve of the appropriate size is selected for implantation. As previously described, reinforcement to provide a double-trigonal geometric configuration for a biological valve allows for optimal sizing of the replacement valve, thereby maintaining a more natural pressure gradient and reducing or eliminating the need for root enlargement or other such manipulation. The surgeon then sutures the replacement valve within or over the aortic annulus by using the commissure reinforcement points as markers to properly orient the reinforced valve. Since the double-trigonal geometric configuration of the valve is reinforced at spaced locations around the circumference of the valve, no complex sutures are required to solidify the configuration of the valve.
Although the hemodynamic properties of a bioprosthetic heart valve measured in flow testing have not been demonstrated to be commensurate with its in situ clinical performance, there is a general consensus that, for a particular cardiac output expressed as liters of blood flowing through any minute, the extent to which the valve opens and the effort necessary to complete adequate flow during flow testing is most likely related to the clinical outcome. In flow tests, embodiments of the present invention have exhibited improved hemodynamics when compared to the most hemodynamically efficient conventional bioprostheses. For example, flow tests have shown that a 25mm diameter valve constructed according to embodiments of the present invention has approximately 20% to 25% higher EOA than a conventionally stented bioprosthetic valve of the same size. Increased EOA results in greater blood flow per beat and also results in lower total energy loss during valve operation. Thus, to accommodate a given cardiac output, the above-described 25mm valve only needs about half as much work as a conventionally stented prosthetic bioprosthetic valve of the same size. This suggests that for aortic applications, the left ventricle of the heart needs to do less work, resulting in accelerated recovery of normal function.
Although the present invention is described in the context of a prosthetic aortic valve, the present invention may also be used with other prosthetic valves, such as a mitral valve, a tricuspid valve, or any other valve requiring unobstructed reinforcement. It will be understood by those skilled in the art that numerous and various modifications can be made without departing from the spirit of the invention. Accordingly, it is to be expressly understood that the forms of the invention described herein are illustrative only and are not intended as limitations on the scope of the invention.