Patent Publication Number: US-2022211494-A1

Title: Leaflet attachment frame for prosthetic valve

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/702233, filed Mar. 23, 2022, which is a continuation of Ser. No. 16/868,887, filed May 7, 2020, which is a continuation of U.S. patent application Ser. No. 16/568,094, filed Sep. 11, 2019, now U.S. Pat. No. 10,646,336, which is a continuation of U.S. patent application Ser. No. 15/367,092, filed on Dec. 1, 2016, now U.S. Pat. No. 10,413,404, which is continuation of U.S. patent application Ser. No. 12/335,461, filed on Dec. 15, 2008, now U.S. Pat. No. 9,510,942, which claims the benefit of U.S. Provisional Application No. 61/014,007, filed on Dec. 14, 2007, all of which applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates generally to an apparatus and method for the restoration of heart valve function. More particularly, the present disclosure concerns embodiments of an implantable prosthetic valve and methods for making the same. 
     BACKGROUND 
     Prosthetic cardiac valves have been used for many years to treat various cardiac valvular disorders. For many years, the definitive treatment was the surgical repair or replacement of a native valve during open heart surgery. More recently, transvascular techniques have been developed, which reduce or eliminate many of the undesirable complications of open heart surgery. Such transvascular techniques traditionally involve the implantation of a prosthetic valve that can be compressed or folded to a reduced diameter. By compressing or folding the prosthetic valve to a reduced diameter, the prosthetic valve can be delivered through a less invasive penetration to a desired target location within the human anatomy. Thereafter, the compressed valve is traditionally released, expanded, separated from the delivery system, and secured to the desired target location. 
     SUMMARY 
     A valve prosthesis is provided which is suitable for implantation in body channels or ducts. The valve prosthesis includes an implantable structure having a deployable construction adapted to be initially crimped in a narrow configuration suitable for catheterization through the body ducts to a target location and adapted to be deployed by exerting substantially radial forces (or releasing the valve, if the valve is self-expandable) from within by means of a deployment device to a deployed state at the target location. 
     The valve prosthesis desirably includes a two-part foldable frame. The frame is configured to support the flexible leaflets of a unidirectional valve in an optimal manner. The frame has an “upper part” and a “lower part” wherein each part of the frame is shaped with rounded arc portions to support the leaflets. The leaflets are sandwiched between the upper and lower arcs. The frame can have portions, e.g., leaflet receiving portions, that are scalloped shaped to match the shape of the flexible leaflets. 
     The length of the arcs is matched to the total length of the cell struts that create the frame. The geometrical constraint on the length of the cell struts is such that the frame can be evenly crimped. 
     In one aspect of the invention, a cloth is first assembled (sewn) to the leaflets. The leaflets with the cloth are sandwiched between the two arcs and the cloth is wrapped over the arcs and sewn together. This suture line crosses all the fabric layers of the wrapped over cloth as well as the leaflet to create a robust leaflet attachment. 
     In one embodiment, an implantable prosthetic device is provided. The device comprises an upper frame section having a plurality of struts and a first leaflet receiving surface at a lower portion of the upper frame section, a lower frame section having a second leaflet receiving surface at an upper portion of the lower frame section, and at least one flexible leaflet with a first edge portion. The first edge portion is disposed between the first and second leaflet receiving surfaces. In specific implementations, the first and second leaflet receiving surfaces are scalloped shaped. 
     In other specific implementations, the device further comprises one or more cloth portions that are attached to the flexible leaflet at or near the first edge portion and wrapped around at least a portion of one or both of the first and second receiving surfaces to secure the flexible leaflet to the upper and lower frame sections. The cloth portions can be attached to the flexible leaflet so that a first excess cloth portion extends away from the first edge portion on an upper side of the flexible leaflet and a second excess cloth portion extends away from the first edge portion on a lower side of the flexible leaflet. The first and second excess cloth portions can be wrapped around the respective first and second leaflet receiving surface and secured to one another. In other specific implementations, the upper frame section and the lower frame section can be connected via one or more struts. 
     In other specific implementations, the upper and lower frame sections can be configured to be expanded from a first configuration to a second configuration. The lengths of the first and second leaflet receiving surfaces can be substantially the same in both the first and second configurations. In other specific implementations, the first leaflet receiving surface comprises an arc section. The arc section can be defined as a portion of the leaflet receiving surface that is located between one or more struts that extend away from the first leaflet receiving surface. The length of the arc section can be substantially equal to the combined length of one or more struts on the upper frame section. 
     In another embodiment, an implantable prosthetic device comprises a frame comprising a plurality of frame sections. Each frame section can have a lower portion with a scalloped shape. A flexible membrane can comprise a plurality of flexible leaflets, with each flexible leaflet having a lower portion with a scalloped shape. The lower portion of each flexible leaflet can be attached to the lower portion of each frame section. 
     In specific implementations, the lower portion of each frame section comprises a first part and a second part, the first and second parts being spaced apart to receive the lower portion of the flexible leaflets in an opening formed therebetween. In other specific implementations, one or more cloth portions are attached to each flexible leaflet, and the cloth portions are wrapped around at least a portion of the first and second parts to secure the flexible leaflets to the frame. 
     In other specific implementations, the frame further comprises first and second vertical posts at an upper area between two frame sections. The two vertical posts can be spaced apart so that they define an opening for receiving a first portion of a first flexible leaflet and a second portion of a second flexible leaflet. Both the first and second portions can be attached to a first and second cloth portion, respectively. The first and second cloth portions can be wrapped around at least a portion of the first and second vertical posts, respectively, to attach the flexible leaflets to the frame. In other specific implementations, a third cloth portion can be positioned radially outside of the frame. The first and second leaflets can be secured to the frame by attaching the first and second cloth portions to the third cloth portion. 
     In another embodiment, a method is provided for assembling an implantable prosthetic valve comprising a flexible membrane and crimpable frame with an upper and lower part. The method comprises partially crimping the frame to have a diameter that is less than the diameter of the frame when the valve is expanded to its functional size, positioning an edge of the flexible membrane between the upper and lower part of the frame, and securing the edge of the flexible membrane to both the upper and lower part of the frame. 
     In specific implementations, the method further comprises attaching a cloth portion to the edge of the flexible leaflet so that a first excess cloth portion extends away from the edge on an upper side of the flexible membrane and a second excess cloth portion extends away from the edge on a lower side of the flexible membrane. The first excess cloth portion can be wrapped around at least a portion of the upper part of the frame and the second excess cloth portion can be wrapped around at least a portion of the lower part of the frame. The first and second excess cloth portions can be secured to each other at an area radially outside of the frame. 
     The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one embodiment of a prosthetic valve; 
         FIG. 2  is a schematic illustration of one embodiment of a prosthetic valve mounted to a balloon and deployed within a patient; 
         FIG. 3  is a flattened view of one embodiment of a frame of a prosthetic valve; 
         FIG. 4  is a perspective view of one embodiment of a prosthetic valve; 
         FIG. 5  is a flattened view of one embodiment showing a portion of a frame of a prosthetic valve; 
         FIG. 6  is a cross-section view taken along line  5 - 5  in  FIG. 5 , with a leaflet attachment portion included; 
         FIG. 7  is a perspective view of an embodiment of a flexible leaflet with one or more cloth portions sewn to the leaflet; 
         FIG. 8  is a simplified sectional side view of a portion of the flexible leaflet and cloth shown in  FIG. 7 ; 
         FIG. 9A  is a flattened view of one embodiment showing a portion of a frame of a prosthetic valve; 
         FIG. 9B  is a cross-section view taken along line  9 B- 9 B in  FIG. 9A , with two leaflet attachment portions included; 
         FIG. 10  is a cross-section view showing another embodiment of a portion of a prosthetic valve having two leaflet attachment portions attached to a portion of a frame; 
         FIG. 11  is an embodiment of another portion of a frames of a prosthetic valve; 
         FIG. 12  is an embodiment of another portion of a frames of a prosthetic valve; 
         FIG. 13  is an embodiment of another portion of a frames of a prosthetic valve; 
         FIG. 14  is a cross-section view taken along line  14 - 14  in  FIG. 11 ; 
         FIG. 15  is a view of an embodiment of a frame, with the frame shown in a crimped or partially crimped configuration; 
         FIG. 16  is a view of the frame shown in  FIG. 15  in an expanded (or uncrimped) configuration; and 
         FIG. 17  is a view of another embodiment of a frame, with the frame shown in a crimped or partially crimped configuration. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Various changes to the described embodiment may be made in the function and arrangement of the elements described herein without departing from the scope of the invention. 
     As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the term “coupled” generally means electrically, electromagnetically, and/or physically (e.g., mechanically or chemically) coupled or linked and does not exclude the presence of intermediate elements between the coupled items. 
     As used herein, the “expanded” or “deployed” state of a valve assembly or frame refers to the state of the valve assembly/frame when radially expanded to its functional size. The “crimped”, “compressed” or “folded” state of a valve assembly or frame refers to the state of the valve assembly/frame when radially compressed or collapsed to a diameter suitable for delivering the valve assembly through a patient&#39;s vasculature on a catheter or equivalent mechanism. A valve assembly/frame that is “partially crimped” or “partially compressed” has a diameter that is less than the diameter of the valve assembly/frame in the expanded state and greater than the diameter of the valve assembly/frame in the compressed state. 
     Although the operations of exemplary embodiments of the disclosed method may be described in a particular, sequential order for convenient presentation, it should be understood that disclosed embodiments can encompass an order of operations other than the particular, sequential order disclosed. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Further, descriptions and disclosures provided in association with one particular embodiment are not limited to that embodiment, and may be applied to any embodiment disclosed. 
     Moreover, for the sake of simplicity, the attached figures may not show the various ways (readily discernable, based on this disclosure, by one of ordinary skill in the art) in which the disclosed system, method, and apparatus can be used in combination with other systems, methods, and apparatuses. Additionally, the description sometimes uses terms such as “produce” and “provide” to describe the disclosed method. These terms are high-level abstractions of the actual operations that can be performed. The actual operations that correspond to these terms can vary depending on the particular implementation and are, based on this disclosure, readily discernible by one of ordinary skill in the art. 
       FIG. 1  shows a perspective view of an implantable prosthetic valve  100  (hereinafter “valve  100 ”), suitable for percutaneous deployment and configured to replace a diseased native valve in a patient. As discussed in more detail below, valve  100  can include a generally cylindrical support frame, such as a stent, which is compressible and/or foldable to a smaller delivery diameter, and a plurality of flexible leaflets releasably attached to the support element. 
     The valve  100  in the illustrated embodiment comprises a flexible membrane, or leaflet assembly,  102  mounted on an expandable, annular support stent, or frame,  104 . As discussed in more detail below, frame  104  can comprise one or more scalloped portions  166  to which the flexible membrane is attached. 
     Valve  100  is desirably adapted to be radially collapsed or compressed to facilitate navigation through the narrow passages of a patient&#39;s vasculature to the treatment site within the patient&#39;s body. After valve  100  reaches the treatment site (e.g., the aortic valve annulus), valve  100  can be expanded within the orifice. To achieve the radial compression of the valve  100 , frame  104  desirably comprises a collapsible and/or compressible support structure. 
     Flexible membrane  102  can be attached to frame  104  so that the flexible membrane  102  permits fluid flow through the valve  100  in one direction along a structural axis of the frame  104  and resists fluid flow in the opposite direction. In particular, the implantable structure supports flexible leaflets that allow a forward flow through the valve prosthesis and prevent a reverse flow as the flexible leaflets collapse inwardly to block the reverse flow. To provide for such fluid flow, flexible membrane  102  can comprise a collapsible pliant material formed as flexible leaflets  106  that are arranged to collapse in a tricuspid arrangement. Alternatively, the flexible membrane can be formed into other configurations, including, for example, a mono cusp or bicuspid configuration. Flexible leaflets  106  can comprise three pieces of pliant material that are connected to each other at seams (also referred to as commissure tabs) to form the flexible membrane. 
     The flexible membrane  102  can be made from biological matter, such as natural tissue, pericardial tissue (such as bovine, porcine or equine pericardium), a harvested natural valve or other biological tissue. Alternatively, the valve member  102  can be made from biocompatible polymers or similar materials. Various flexible leaflet configurations and materials for constructing such leaflets are described in U.S. Pat. Nos. 6,730,118, 6,767,362, and 6,908,481, each of which is incorporated by reference herein. 
     As discussed above, frame  104  can comprise, for example, stent that has a generally cylindrical framework that can be expanded at a treatment site to secure valve  100  within or adjacent to the defective valve annulus. Frame  104  can also provide stability to the valve  100  and prevent the valve  100  from migrating after it has been implanted. Frame  104  can be a self-expanding frame or it can be expandable by a balloon member or other mechanical means. Frame  104  can be made from any of various suitable expandable and/or elastic materials and is typically made of a metal, such as stainless steel, CoCr alloys, titanium, or other biocompatible metals. Frame  104  also can be made from self expandable shape memory alloys, such as nickel titanium (NiTi) shape memory alloys, as marketed, for example, under the trade name Nitinol. 
       FIG. 2  is a schematic illustration of a flexible membrane  102  coupled to a frame  104  that is mounted on an inflatable balloon  110  of a balloon catheter for delivery and deployment of valve  100 . Valve  100  can be initially crimped to a smaller radial profile on balloon  110  so that is presents a narrower cross-sectional profile to facilitate percutaneous delivery of the valve  100  to the treatment site.  FIG. 2  illustrates the valve  100  being deployed in the aorta A at the aortic annulus  116  to replace a diseased or damaged native aortic valve. However, it should be understood that the prosthetic valves described herein can be implanted in other channels or orifices in the body using the same techniques as the one used for the implantation of the aortic valve prosthesis. Such an implantation may, for example, include the implantation of: valves in the veins (for instance a cardiac valve), valves in the esophagus and/or at the stomach, valves in the ureter and/or the vesica, valves in the biliary passages, valves in the lymphatic system, and valves in the intestines. 
     In one embodiment, a delivery catheter can advance valve  100  (mounted on balloon  110 ) through an introducer sheath and into the vasculature of a patient. The delivery catheter can then be advanced over a guidewire to move valve  100  to a target location in a body duct, such as the aortic annulus  116  of aorta A ( FIG. 2 ). After the valve  100  is properly positioned at the treatment site, balloon  110  can be inflated to expand frame  104  radially to the desired size, securing valve  100  at the treatment site. It should be understood that valve  100  can also be deployed using a non-inflatable, mechanical embodiment of the delivery catheter or, alternatively, valve  100  can be a self-expanding valve. 
     In one embodiment, frame  104  can comprise one or more scalloped portions  166  at a lower portion of frame  104 .  FIG. 3  illustrates, for convenience, a flattened schematic view of a frame  104  that comprises a plurality of frame sections  150 ,  152 ,  154 , which each have a respective scalloped portion  166  at a lower portion of frame  104 . Frame sections  150 ,  152 ,  154  can comprise a plurality of struts (or strut sections)  160 ,  210 . Adjacent scalloped portions  166  can be connected together by struts  160 . Because the frame is shown in a flattened view, the two end strut sections  160  of  FIG. 3  appear to be disconnected; however, the two end strut sections  160  are desirably connected to one another, in the same manner of the other strut sections  160  shown in  FIG. 3 . 
     Referring again to  FIG. 1 , if desired, an expansion restriction member  162  can be secured between two adjacent strut sections  160 . Expansion restriction member  162  can be, for example, a suture or thread that is secured to adjacent strut sections  160  to prevent the valve  100  from being over-expanded during deployment. 
       FIG. 4  illustrates a valve  100  with a frame  104  that has a plurality of scalloped portions  166 . Frame  104  comprises a collapsible frame with a flexible membrane  102  attached thereto. As noted above, strut sections  160  desirably extend from a portion of the scalloped frame to provide structural strength to the frame  104 . The number of strut sections  160  between adjacent scalloped portions  166  can vary. For example,  FIG. 3  shows two strut sections  160  (forming one cell) between adjacent scalloped portions  166 , while  FIG. 4  shows four strut sections  160  between adjacent scalloped portions  166  (arranged to form three cells between adjacent scalloped portions). Strut sections  160  can also extend radially outward from the frame  104 , as shown in  FIG. 4 , to help anchor the valve  100  in the body and to help prevent migration or movement of the valve after it has been deployed within the body. Other portions of the frame  104  can also be configured to extend radially outward to help anchor the valve in place. For example, certain cell struts, such as cell struts  270  ( FIG. 4 ), can be configured to extend radially outwards from the frame  104  to provide additional valve anchoring means. 
     As best shown in  FIG. 5 , a frame  104  can be comprised of a first or “upper” part  202  and a second or “lower” part  204 . First part  202  can include a plurality of struts or strut sections  210  and a first arc section  206 . Second part  204  includes a second arc section  208 . Both arc sections  206 ,  208  desirably have an arc length  280  that is substantially the same. First part  202  and second part  204  are desirably separate elements that are not connected to each other by any strut members of the frame  104 . Accordingly, as shown in  FIG. 5 , when first part  202  is positioned adjacent second part  204 , a gap (or opening)  282  is defined between the two parts. A flexible membrane  102  or portions thereof can be received into gap  282  to facilitate attachment of the flexible membrane  102  to the frame  104 . The two surfaces facing gap  282  include a first leaflet receiving surface (e.g., the lower surface of upper part  202 ) and a second leaflet receiving surface (e.g., the upper surface of lower part  204 ). If desired, the first part  202  and second part  204  can be connected via one or more connecting struts  268  ( FIG. 17 ) to provide additional structural strength to the frame  104 . 
     In one embodiment, the flexible leaflets  106  of the flexible membrane  102  can be received in the gap  282  and the first and second arc sections  206  and  208  can help secure the flexible leaflets to the frame  104  and/or provide a point of attachment. Referring to  FIGS. 7 and 8 , a cloth member  304  is desirably attached to a flexible leaflet  106 .  FIG. 7  is a perspective view of a leaflet sub-assembly  302  in which one or more portions of cloth  304  are attached to selected portions of flexible leaflet  106 . Leaflet sub-assembly  302  can be formed by attaching cloth  304  to flexible leaflet  106  by sewing (suturing) or other suitable attachment means. The cloth  304  can be any fabric or other material made from any of various suitable biocompatible synthetic materials, such as woven polyester, polyethylene terephthalate (PET), or polytetrafluoroethylene (PTFE). 
     To attach cloth  304  to the leaflet  106 , a cloth portion  304  can be folded over a lower edge portion  308  ( FIG. 8 ) of leaflet  106 , and cloth  304  and leaflet  106  can be sewn together along a leaflet-cloth suture line  330  (hereinafter “suture line  330 ”). In this manner, leaflet edge  308  is captured between two layers of cloth  304  to form a leaflet attachment portion  314  ( FIG. 6 ). Excess portions  310  of cloth  304  extend along both sides of flexible leaflet  106  away from suture line  330  and away from edge  308 . As described in more detail below, excess cloth portions  310  can be used to secure the flexible leaflets  106  to the frame  104 . If desired, a plurality of separate cloth portions  304  (as shown in  FIG. 7 ) can be attached to the leaflet  106 . In this manner, when the leaflet is secured to the frame between the first and second arc sections  206 ,  208 , the separate cloth portions  304  can extend between the struts that extend from the first arc section  206 . 
     Referring now to  FIG. 6 , a method of attaching leaflet sub-assembly  302  to frame  104  is described.  FIG. 6  is a simplified cross-sectional view of a leaflet sub-assembly attached to a frame. In particular, leaflet sub-assembly  302  extends radially between and is “sandwiched” or otherwise captured between first arc section  206  (of the first part  202  of the frame) and second arc section  208  (of the second part  204  of the frame). As shown in  FIG. 6 , leaflet sub-assembly  302  can be positioned between the two arc sections so that suture-line  330  is substantially captured between the two arcs. Additionally, an edge portion  314  comprised of two layers of cloth and a portion of the leaflet desirably extends radially outwards from between the first and second arc sections  206  and  208 . 
     As illustrated in  FIG. 6 , excess cloth portions  310  of cloth  304  can be wrapped over and around first arc section  206  and second arc section  208 . In this embodiment, excess portions  310  of cloth  304  can be sewn together within an attachment area  316 . Attachment area  316  is desirably located outside of (e.g., radially external to) frame  104 . For example, a sandwiching suture line  320  can pass through the two ends of excess cloth portions  310  and also through the edge portion  314  that extends out from between first and second arc sections  206  and  208 . Thus, by securing the flexible leaflet to the cloth and then securing portions of the cloth to itself, the flexible leaflet  106  can be securely attached to the frame  104  without requiring additional sutures passing through the flexible leaflet  106 . If desired, leaflet  106  can be positioned so that suture line  320  passes through the excess cloth portions  310  and through the leaflet  106 . 
     Conventional frames typically require suturing the flexible membranes at the commisures directly to vertical posts. However, the suture line applies local stress and abrasion on the leaflet which may lead to early leaflet failure. Accordingly, this approach causes very high stresses on the commissures when the flexible leaflets move between open and closed positions. 
       FIGS. 9A and 9B  illustrate a method of attaching flexible leaflets to a frame without suturing the flexible valves directly to vertical posts.  FIG. 9A  illustrates an upper portion  402  of frame  104  where two leaflets come together in the valve (e.g., the commissure). At the commissure, first frame part  202  has a first vertical strut  404  and a second vertical strut  406 . First strut  404  and second strut  406  are spaced apart and define an opening  420  therebetween for receiving at least a portion of two adjacent flexible leaflets  106 . 
       FIG. 9B  is a cross-section view taken along line  9 B- 9 B in  FIG. 9A , with flexible leaflets and cloth portions shown positioned between the first and second struts  404 ,  406 . As shown in  FIG. 9B , two flexible leaflets  106   a  and  106   b  can be inserted and captured between first and second struts  404  and  406 . Flexible leaflet  106   a,    106   b  can be attached to a respective cloth  304 , creating an area  408  where the leaflet  106   a  is attached to the cloth  304  and an area where the leaflet  106   a  is not attached to the cloth  304 . Leaflet  106   a  can be wrapped around at least a portion of first strut  404  so that the unattached portion of the leaflet  106   a  extends radially inwards into the interior of the frame. The unattached portion of cloth  304  can form an excess cloth portion  430  that extends radially inward into the frame and wraps back around the strut  404 . 
     Similarly, leaflet  106   b  can be attached to a cloth  304 , creating an area  410  where the leaflet  106   b  is attached to the cloth  304  and an area where the leaflet  106   b  is not attached to the cloth  304 . Leaflet  106   b  can be wrapped around second strut  406  so that the unattached portion of the leaflet  106   b  extends radially inwards into the interior of the frame. The unattached portion of cloth  304  can form an excess cloth portion  432  that extends inward into the frame and wraps back around the strut  406 . 
     To secure the leaflets  106   a,    106   b  to the frame, another piece of cloth  440  can be placed radially outside of the frame and positioned over the portion of flexible leaflets  106   a,    106   b  that extend radially outside of the frame (e.g., the portions of  408 ,  410  that are external to struts  404 ,  406 ). The second piece of cloth  440  can be sewn to the leaflet  106   a  at an attachment area  350  to secure the leaflets to first strut  404 . Thus, the second piece of cloth  440  can be sewn (or otherwise attached) to leaflet  106   a,  the portion of cloth  304  attached to leaflet  106   a,  and to the excess cloth portion  430  that has been wrapped around first strut  404 . The second piece of cloth  440  can similarly be sewn to the leaflet  106   b,  the portion of cloth  304  attached to leaflet  106   b,  and to the excess cloth portion  432  (which has been wrapped around second strut  406 ) at an attachment area  360  to secure the leaflets to second strut  406 . 
     Operationally, when flexible leaflets  106  are closed, load F is applied to the leaflets to move them radially inward as shown in  FIG. 9B . Folding flexible leaflets  106  around stent struts  404  and  406  can reduce stresses on the leaflets by creating a friction attachment at leaflet-strut contact areas  412 , which reduces the stresses at suture lines  340 . Furthermore, as discussed in more detail below, by securing the leaflets  106   a,    106   b  at attachment areas  350 ,  360  on the outer side of frame  104 , relative movement at the leaflet/frame interface can be reduced or eliminated, which further reduces stresses and strains on the leaflets during expansion and/or compression of the valve  100 . 
       FIG. 10  shows another embodiment by which flexible leaflets  106   c,    106   d  can be attached to first and second struts  404  and  406  of a frame  104 . Similar to the embodiment shown in  FIG. 9B  and described above, a first leaflet  106   c  is secured to a cloth  304  by a suture  460  and an excess cloth portion  462  extends inwardly of the frame and wraps back around first strut  404  to extend back outwardly of the frame. A second leaflet  106   d  is secured to a cloth  304  by a suture  464  and an excess cloth portion  466  extends inwardly of the frame and wraps back around second strut  406  to extend back outwardly of the frame. After the excess portions of cloth  462 ,  466  are wrapped back around first and second struts  404 ,  406 , they can be secured to one another by another suture  468  at an area outside of the frame  104 . As shown in  FIG. 10 , suture  468  can pass through both of the excess cloth portions  462 ,  466  and through portions of the leaflets (e.g., leaflet portions  470 ,  472 ) that extend outward from between the first and second struts  404 ,  406 . In addition, if desired, the excess cloth portions and/or flexible leaflets can be folded and/or wrapped around each other so that the suture  468  extends through one or more portions of the excess cloth portions and/or the flexible leaflets. 
       FIGS. 11-13  show additional embodiments of frames  104  that have scalloped portions. In particular,  FIGS. 11-13  illustrate alternative shapes and configurations of struts  210 ,  270 . The shape and number of struts can vary. For example, struts  210  can be configured to be substantially straight ( FIG. 13 ), or they can be rounded or curved ( FIG. 12 ). 
     As described above with regard to  FIG. 4 , the struts or other frame members can also be configured to extend radially outward of the generally cylindrical surface of the expandable framework to improve the ability to anchor the frame to the tissue. For example, as best seen in  FIGS. 4, 11, and 14 , struts  160  and/or  270  may be bent so that they protrude outward from stent struts  210  (i.e., radially outward from the tangential plane P defined on an external surface of the cylindrically shaped frame  104 ). Similarly, in the embodiments illustrated in  FIGS. 12 and 13 , struts  160  and/or  270  can be formed so that one or more of struts  160  and/or  270  extend radially outward from the frame  104 . 
     The use of the scalloped frame  104  together with the methods of attachment described herein beneficially enable the flexible membrane and flexible leaflets to be secured to a frame without introducing needle holes and/or sutures in the area where a leaflet flexes (e.g., leaflet flexing area  318  shown in  FIG. 6 ) or undergoes significant stresses. Leaflets are particularly susceptible to failure at areas where they flex and by reducing and/or eliminating needle holes in the leaflets at these areas, the structural integrity of the flexible leaflets can be improved. Thus, in contrast to traditional methods of attachment where a flexible membrane is simply sutured to a frame, the methods of attachment described herein eliminate and/or reduce needle holes and sutures in the leaflet flexing area  318 , which increases the durability of the valve. 
     In addition, the leaflet can be attached to the frame along the length of the first and second arc sections  206  and  208 . By capturing the entire edge  308  (or substantially the entire edge) of flexible leaflet  106  between the arc sections  206  and  208  and securing the leaflet to the arc sections as described herein, the leaflet stresses can be optimally distributed along the length of the leaflet edge. 
     In addition, the methods described herein are particularly useful to facilitate attaching a flexible membrane to a frame while the valve is in a partially collapsed (partially-crimped) configuration. As described in U.S. Patent Publication  2008 / 0154355 , the entire disclosure of which is incorporated by reference herein, it can be desirable to attach a flexible membrane to a partially collapsed frame, which can allow the frame to be constructed with relatively large angles between adjacent struts to enhance the structural rigidity of the frame. Due to the enhanced structural rigidity, the frame can be constructed with thinner metal struts, which can allow the frame to be crimped to a smaller profile. However, it can be difficult to attach a flexible membrane to a frame in a partially collapsed state because the diameter of the flexible membrane is greater than the diameter of the partially collapsed frame. For instance, in certain implementations, the diameter of the valve member can be twice that of the partially collapsed frame. The valve member therefore cannot easily conform to the shape of the partially collapsed frame, and as a result, assembly of the valve assembly is rendered more difficult. 
     The frames described herein can easily and accurately receive flexible membranes while the frames are in a partially collapsed configuration. In addition, by reducing the relative movement that occurs between the frame and the flexible leaflets during expansion of the valve at the treatment site, the valves produced by the methods describe herein have increased strength and durability. 
     Referring again to  FIG. 5 , first and second arc sections  206  and  208  are substantially the same length (e.g., arc length  280 ). The length of the first and second arc sections  206 ,  208  desirably can be selected to correspond to the length of a similarly scalloped shaped edge portion of a leaflet. Thus, as described herein, the accurate assembly of the scalloped-shaped leaflet  106  between the two arc sections  206 ,  208  can be achieved. In addition, the attachment of the leaflet  106  to the arc sections  206 ,  208  can be easily and accurately performed even if the frame  104  is in a crimped (folded) or partially crimped configuration due to the fact that the arc length of sections  206 ,  208  where the leaflet is attached remains constant when the frame is compressed. 
       FIGS. 15 and 16  illustrate a segment of a frame that is configured to expand from a reduced profile ( FIG. 15 ) to an expanded profile ( FIG. 16 ) while maintaining the relationship between first and second arc sections  206 ,  208 . In particular, the length of corresponding portions of first and second arc sections  206 ,  208  are desirably matched to the lengths of related struts SL 1 , SL 2 , and SL 3 . For example, as shown in  FIGS. 15 and 16 , arc section  500  can be defined by the length of arc section  206  between two strut members extending therefrom (e.g., SL 1  and SL 3 ). Arc section  500  can be configured to have substantially the same length as the combined length of one or more struts. In particular, Arc section  500  is configured to be substantially the same length as the combined length of struts SL 2  and SL 3 . 
     After flexible leaflets are attached to the frame, the frame can expand smoothly and evenly from a reduced profile ( FIG. 15 ) to an expanded profile ( FIG. 16 ), causing arc sections  206 ,  208  to also expand evenly. This even expansion from a first profile to a second profile reduces relative movement between the arc sections, which, in turn, reduces stress on the leaflets that are attached to the arc sections. Moreover, because the length of the struts are matched to corresponding lengths of sections of the first and second arc sections  206 ,  208 , relative movement between the frame and flexible leaflets is reduced in all configurations and stages of crimping and/or expansion. Thus, a flexible leaflet can be attached to the frame shown in  FIG. 15  and then, if desired, the frame can be crimped (or folded) to an even smaller profile without causing additional stresses at the leaflet attachment area. 
     In prior art implantable valve devices, during deployment, the dimensions of the complete, implantable structure of the implantable valve vary from its initial first crimped position to its final deployed position. Thus, typically when attaching flexible leaflets to the implantable structure one should take into consideration the dimension changes and leave “slack” or extra leaflet material so that upon deployment of the valve device the flexible leaflets do not tear or deform. By maintaining a constant arc length of the arc sections during deployment of valve  100 , there is no need for “slack” material in the flexible leaflets  106 . Instead, the attachment points of the flexible leaflets  106  remain at a constant distance regardless of the delivery position of valve  100  (crimped or expanded). 
     Referring to  FIG. 17 , another embodiment of a frame  104  is disclosed.  FIG. 17  shows a section of a compressed frame that comprises first arc section  206  and second arc section  208 , with the two arc sections being connected via optional connecting struts  268 . As described above with regard to  FIGS. 15 and 16 , relative movement between the first and second arc sections  206 ,  208  can be avoided by matching arc sections with strut sections so that the first arc section  206  and second arc section  208  remain constant during deployment, providing a stable area for anchoring flexible leaflets  106 . As shown in  FIG. 17 , in this embodiment, the arc length of arc section  510  is matched to the total length SL of cell struts SL 1 , SL 2 , and SL 3 . That is, the total length SL (SL 1 +SL 2 +SL 3 ) of the strut sections is substantially the same as the length of arc section  510 . Because the geometrical constraint on length SL of cell struts  210  is designed such that cell struts  210  may be collapsed and expanded without changing the dimensions of the first and second arc sections  206  and  208 , the frame  104  can be evenly crimped and/or expanded, which allows flexible leaflets  106  to also deploy evenly. 
     In embodiments disclosed above, little or no relative movement exists between the flexible leaflets  106  and attachment points on the first and second arc sections  206  and  208 . As a result, the valve has greater durability and is capable of withstanding the harsh conditions prevailing within the vasculature and especially the millions of cycles of stress applied by the blood pressure. 
     In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.