Patent Publication Number: US-2022218477-A1

Title: Flexible commissure frame

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 17/706,419, filed Mar. 28, 2022, which is a continuation of U.S. patent application Ser. No. 16/112,556, filed Aug. 24, 2018, which is a continuation of U.S. patent application Ser. No. 14/625,344, filed Feb. 18, 2015, now U.S. Pat. No. 10,058,420, which claims the benefit of U.S. Provisional Application No. 61/941,123, filed Feb. 18, 2014. These applications are incorporated by reference herein. 
    
    
     FIELD 
     This disclosure is in the field of prosthetic heart valves, stents for use with prosthetic heart valves, and methods for delivering prosthetic heart valves. 
     BACKGROUND 
     Existing frames for prosthetic heart valves typically comprise rows of angled struts and a plurality of axial frame members spaced apart around the circumference of the frame. The plurality of axial frame members may comprise a plurality of leaflet attachment members (for attaching to the commissures of the supported valvular structure) and a multitude of axially directed struts extending between the rows of angled struts. A frame usually has three or more axially directed struts for every leaflet attachment member, and generally has no more than two angled struts located in between adjacent struts or other axial frame members. Indeed, having a large number of axially directed struts is perceived to be necessary for preserving the structural stability of the stent and/or valve. Unfortunately, having a large number of axial struts can come at the expense of valve flexibility. 
     A need therefore exists for stents and prosthetic valves that can have a high degree of flexibility, without compromising mechanical integrity or function. 
     SUMMARY 
     In one aspect of the disclosure, a prosthetic device for implantation at a cardiac valve annulus has an annular frame with an inflow end, an outflow end, and a plurality of axial frame members bridging two circumferentially extending rows of angled struts, wherein the plurality of axial frame members comprises a plurality of axially extending leaflet attachment members and a plurality of axial struts in a 1:1 ratio. 
     In some embodiments, the device can further comprise a leaflet structure positioned within the frame, the leaflet structure having a plurality of commissures that are secured to the frame at the leaflet attachment members. 
     In some embodiments, at least three angled struts separate adjacent axial frame members along each of the two rows of angled struts. 
     In some embodiments, exactly six angled struts separate adjacent leaflet attachment members along each of the two rows of angled struts, and exactly three angled struts separate adjacent axial frame members along each of the two rows of angled struts, such that each axial strut is positioned halfway between adjacent leaflet attachment members. 
     In some embodiments, each axial frame member extends between locations defined by the convergence of adjacent angled struts. 
     In some embodiments, the device further comprises an inner skirt secured to an interior portion of the annular frame, and an outer skirt secured to an exterior portion of the annular frame. 
     In some embodiments, the frame comprises exactly four rows of angled struts. 
     In some embodiments, the valve member comprises exactly three leaflets arranged in a tricuspid configuration, wherein the frame comprises exactly three axial struts and exactly three leaflet attachment members, and wherein the exactly three angled struts separate adjacent axial frame members along each of the two rows of angled struts. 
     In another aspect of the disclosure, an annular frame for a prosthetic heart valve can comprise an inflow end, an outflow end, and a plurality of axial frame members spaced angularly around the circumference of the frame. The plurality of axial frame members can bridge two circumferentially extending rows of angled struts, wherein each of the two rows comprise at least three angled struts between adjacent axial frame members. 
     In some embodiments, each of the two rows comprises exactly three angled struts between adjacent axial frame members. 
     In some embodiments, the plurality of axial frame members comprises a plurality of axially extending leaflet attachment members, and each of the two rows comprises exactly six angled struts between adjacent leaflet attachment members. 
     In some embodiments, the plurality of axial frame members comprises a plurality of axially extending leaflet attachment members, wherein each of the two rows comprises four angled struts between adjacent axial frame members and eight angled struts between adjacent leaflet attachment members. 
     In some embodiments, the plurality of axial frame members comprises exactly three leaflet attachment members and exactly three axial struts. 
     In some embodiments, the leaflet attachment members extend between locations defined by the convergence of the upper ends of adjacent angled struts of each row of angled struts, and the axial struts extend between locations defined by the convergence of the lower ends of adjacent angled struts of each row of angled struts. 
     In some embodiments, the two rows of angled struts can comprise a first row and a second row, wherein the first row is closer to the outflow end than the second row. 
     In some embodiments, the leaflet attachment members extend from locations defined by the convergence of the upper ends of adjacent angled struts along the first row of angled struts to locations defined by the convergence of the lower ends of adjacent angled struts along the second row of angled struts, and the axial struts extend between locations defined by the convergence of the lower ends of adjacent angled struts along the first row of angled struts to locations defined by the convergence of upper ends of adjacent angled struts along the second row of angled struts. 
     In some embodiments, the leaflet attachment members extend from locations defined by the convergence of the upper ends of adjacent angled struts along the first row of angled struts to locations defined by the convergence of the upper ends of adjacent angled struts along the second row of angled struts, and the axial struts extend between locations defined by the convergence of the lower ends of adjacent angled struts along the first row of angled struts to locations defined by the convergence of lower ends of adjacent angled struts along the second row of angled struts. 
     In some embodiments, the frame comprises exactly four rows of angled struts. 
     In another aspect of the disclosure, a prosthetic device for implantation at a cardiac valve annulus is provided, comprising an annular frame having an inflow end, an outflow end, at least four rows of circumferentially extending angled struts, and exactly six axial frame members bridging two rows of the four rows of circumferentially extending angled struts. The plurality of axial frame members can comprise exactly three axially extending leaflet attachment members and exactly three axial struts, wherein each of the two rows comprises exactly three angled struts between each adjacent pair of a leaflet attachment member and an axial strut, and exactly six angled struts between adjacent leaflet attachment members. The device can further comprise a tri-leaflet valve member positioned within the frame having commissures that are secured to the frame at the leaflet attachment members. 
     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 
         FIGS. 1 and 2  show side and perspective views of an exemplary embodiment of a prosthetic heart valve. 
         FIGS. 3-5  show side, perspective, and flattened views of an exemplary frame of the prosthetic heart valve of  FIG. 1 . 
         FIG. 6  is a perspective view of another exemplary prosthetic heart valve. 
         FIGS. 7-8  show perspective and flattened views of an exemplary frame of the prosthetic heart valve of  FIG. 6 . 
         FIG. 9  shows a flattened view of another exemplary frame for a prosthetic heart valve. 
         FIG. 10  shows a flattened view of a portion of another exemplary frame for a prosthetic heart valve. 
         FIG. 11  shows a flattened view of a portion of another exemplary frame for a prosthetic heart valve. 
         FIG. 12  shows a flattened view of a portion of another exemplary frame for a prosthetic heart valve. 
         FIG. 13  shows a flattened view of a portion of another exemplary frame for a prosthetic heart valve. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are prosthetic heart valves and stents for use with such valves that are capable of a high degree of flexibility. This flexibility can be useful for delivery to the valve annulus (such as for crimping/expanding a transcatheter heart valve (THV)) and/or for accommodating movement of the valve during cardiac cycling. In particular embodiments, strategically selected locations around the circumference of the frame are without axial struts, resulting in the improved flexibility. In various embodiments, the flexibility of the commissures is enhanced as a result of an increase in the distance between each commissure and the nearest axial frame member (other than any support member located at the commissure such as a commissure support or window frame member). The frame can have one or more circumferentially extending rows of struts with three continuous angled struts between one or more pairs of axial supports. In some embodiments, these one or more rows of struts are located towards an outflow end of the frame. In some embodiments, the frame can have two rows of circumferentially extending struts (towards the outflow end of the valve) having three continuous angled struts between pairs of axial supports. In some embodiments, the frame has three continuous angled struts separating each commissure support (located at each commissure) from the nearest axial support. In another embodiment, there are four such angled struts separating each commissure support from the nearest axial strut. 
     As used herein, an “axial support” is a junction where at least three struts are connected, such as two angled struts connecting to a single axial strut or a junction of two angled struts and another axial member such as a commissure support. As used herein, an “axial frame member” is any axially extending support member that connects two (or more) circumferentially extending rows of angled struts. Thus, an axial frame member can be an axial support member that engages one or more leaflets, such as a commissure support. An axial frame member can also be a simple axial strut or other axial member that does not engage a leaflet. As used herein, a “commissure support” (also referred to as a “leaflet attachment member”) is an axially extending support member configured to support a respective commissure of a prosthetic valve member. A commissure support can be a commissure “window frame member” configured to receive a commissure of a prosthetic valve member through an opening in the frame member, as further described below. A commissure support can also be an axial strut or other axial support member that does not include a window or other opening sized to receive a commissure. As such, a commissure can be supported by a leaflet attachment member using various techniques or mechanisms, such as by securing commissures to respective leaflet attachment members with sutures extending through suture openings in the leaflet attachment members. 
       FIGS. 1-2  show a prosthetic heart valve  100 , according to one embodiment in side view and in perspective, respectively. The illustrated prosthetic valve is adapted to be implanted in the native aortic annulus, although in other embodiments it can be adapted to be implanted in the other native annuluses of the heart (i.e., the native mitral, pulmonary, and tricuspid valves) or in other tubular passageways in the body. The valve  100  can have four main components: a stent or frame  102 , a valvular structure  104 , an inner skirt  106 , and an outer skirt  108 . The frame  102  can have an inflow end  103  and an outflow end  105 . 
     The valvular structure  104  can comprise three leaflets  110 , collectively forming a leaflet structure, which can be arranged to collapse in a tricuspid arrangement. The leaflets  110  can be secured to one another at their adjacent sides to form commissures. The leaflets  110  can be formed of pericardial tissue (e.g., bovine pericardial tissue), biocompatible synthetic materials, or various other suitable natural or synthetic materials as known in the art and described in U.S. Pat. No. 6,730,118, which is incorporated by reference herein. 
     The bare frame  102  is shown in  FIGS. 3-5  in a side view, a perspective view, and an unrolled and flattened configuration, respectively. The frame  102  can be formed with a plurality of circumferentially spaced slots, or commissure windows  120  (three in the illustrated embodiment), that are adapted to mount the commissures of the valvular structure  104  to the frame, as described in greater detail below. The frame  102  can be made of any of various suitable plastically-expandable materials (e.g., stainless steel, etc.) or self-expanding materials (e.g., nitinol) as known in the art. 
     Suitable plastically-expandable materials that can be used to form the frame  102  can include, without limitation, stainless steel, a nickel based alloy (e.g., a cobalt-chromium or a nickel-cobalt-chromium alloy), polymers, or combinations thereof. In particular embodiments, the frame  102  can be made of a nickel-cobalt-chromium-molybdenum alloy, such as MP35N® alloy (SPS Technologies), which is equivalent to UNS R30035 alloy (covered by ASTM F562-02). MP35N®/UNS R30035 alloy comprises 35% nickel, 35% cobalt, 20% chromium, and 10% molybdenum, by weight. It has been found that the use of MP35N® alloy to form the frame  102  can provide superior structural results over stainless steel. In particular, when MP35N® alloy is used as the frame material, less material is needed to achieve the same or better performance in radial and crush force resistance, fatigue resistances, and corrosion resistance. Moreover, since less material is required, the crimped profile of the frame  102  can be reduced, thereby providing a lower profile valve assembly for percutaneous delivery to the treatment location in the body. 
     When constructed of a plastically-expandable material, the frame  102  (and thus the valve  10 ) can be crimped to a radially compressed state on a delivery catheter and then expanded inside a patient by an inflatable balloon or equivalent expansion mechanism. When constructed of a self-expandable material, the frame  102  (and thus the valve  100 ) can be crimped to a radially compressed state and restrained in the compressed state by insertion into a sheath or equivalent mechanism of a delivery catheter. Once inside the body, the valve can be advanced from the delivery sheath, which allows the valve to expand to its functional size. 
     Referring to  FIG. 5 , the frame  102  (shown in a flattened configuration) in the illustrated embodiment comprises a first, lower row I of angled struts  112  arranged end-to-end and extending circumferentially at the inflow end of the frame; a second row II of circumferentially extending, angled struts  114 ; a third row III of circumferentially extending, angled struts  116 ; a fourth row IV of circumferentially extending, angled struts  118 ; and a fifth row V of circumferentially extending, angled struts  122  at the outflow end  105 . A plurality of substantially straight, axially extending struts  124  can be used to interconnect the struts  112  of the first row I with the struts  114  of the second row II. The fifth row V of angled struts  122  are connected to the fourth row IV of angled struts  118  by a plurality of axially extending window frame portions  130  (which define the commissure windows  120 ) and a plurality of axially extending struts  132 . 
     Each commissure window frame portion  130  mounts a respective commissure of the valvular structure  104 . As can be seen, each window frame portion  130  is secured at its upper and lower ends to the adjacent rows of angled struts to provide a robust configuration that enhances fatigue resistance under cyclic loading of the valve compared with known frames using cantilevered struts for supporting the commissures of the leaflet structure. This configuration enables a reduction in the frame wall thickness to achieve a smaller crimped diameter of the valve. In particular embodiments, the thickness of the frame  12  as measured between the inner diameter and outer diameter is about 0.48 mm or less. 
     As best shown in  FIGS. 3-4 , the struts and frame portions of the frame collectively define a plurality of open cells of the frame. At the inflow end of the frame  102 , struts  112 , struts  114 , and struts  124  define a lower row of cells defining openings  136 . The second, third, and fourth rows of struts  114 ,  116 , and  118  define two intermediate rows of cells defining openings  138 . The fourth and fifth rows of struts  118  and  122 , along with window frame portions  130  and struts  132 , define an upper row of cells defining openings  140 . The openings  140  are relatively large and are sized to allow portions of the valvular structure  104  to protrude, or bulge, into and/or through the openings  140  when the frame  102  is crimped in order to minimize the crimping profile. 
     In some embodiments, there are fewer than three axially extending struts  132  between adjacent window frame portions  130 , along the length of the rows, such as only two axially extending struts  132  or only one axially extending strut  132 . In some embodiments, there is only one axially extending strut  132  in between adjacent window frame portions  130 , which can be located halfway in between the window frame portions  130 . Thus, in various embodiments, the frame can be specifically constructed to integrate window frame portions  130  and axially extending struts  132  in a 1:1 ratio. 
     In one embodiment illustrated in  FIGS. 3-5 , there are exactly three window frame portions  130  and exactly three axial struts  132 . Minimizing or reducing the number of axially extending struts  132  between window frame portions  130  promotes more compact crimping of the prosthetic valve. This also maximizes or increases the size of openings  140 , which, for example, is advantageous in cases where the outflow end  105  of the prosthetic valve extends higher than the level of the coronary ostia. In such cases, the larger openings  140  can provide access to the coronary arteries for future procedures, such as procedures requiring catheterization of the coronary arteries. 
     Each window frame portion  130  and/or each axially extending strut  132  can each extend between locations  142  characterized by the convergence of the lower ends of two angled struts  122  (of row V, at the outflow end  105 ) to locations or nodes  144  defined by the convergence of the upper ends of two angled struts  118  (of row IV). There can be two angled struts  122  along row V from one location  142  to the next location  142 , and two angled struts  118  along row IV from one location  144  to the next location  144 . 
     The frame  102  can comprise an axially extending frame member (i.e., a frame portion  130  or a strut  132 ) at every other such pair of such locations  142 ,  144  along the rows V and VI, respectively. The frame  102  can have a window frame portion  130  every four such locations, and spaced equally apart around the circumference of the frame  102 , which can provide for a total of three window frame portions  130  (corresponding to the three commissures in a tri-leaflet valve). Thus, the frame  102  can comprise, in sequence along the row V, a window frame portion  130  extending between a pair of such locations  142 ,  144  followed next by a second pair of locations  142 ,  144  lacking an axially extending strut or frame member extending therebetween, followed then by an axially extending strut  132  extending between a third pair of locations  142 ,  144 , followed then by a fourth pair of locations  142 ,  144  again lacking an axially extending strut or frame member, followed by another window frame portion  130  extending between a pair of such locations  142 ,  144  (and thus re-starting the sequence of struts and frame portions). With two angled struts (along each of rows IV and V) between each set of locations  142 ,  144 , this embodiment can thus have sets of eight angled struts between adjacent window frame portions  130 , along each row, with four continuous angled struts between each window frame portion  130  and its adjacent axial struts  132  (i.e., no other axial frame members in between). 
     After the prosthetic heart valve  100  is properly implanted at the valve annulus, the prosthetic valve  100  can cycle between open and closed states to permit or restrict the flow of blood. In various embodiments, the frame  102  of the prosthetic heart valve  100  provides a measure of damping during valve closure by bending inwards during diastole, which relieves stress on the leaflets. For example, forces that pull the commissures of the leaflets  110  radially inwards (such as during valve closure) can also pull areas of the frame immediately adjacent the commissures (such as the window frame portions  130 ) radially inward, while the axial struts  132  can be urged radially outward. In various embodiments, this damping effect (including pulling of the frame portions  130  radially inward and pushing of the axial struts  132  radially outward) is enhanced by reducing the number of axial struts present along the top rungs (between rows IV and V in valve  100 ) as disclosed herein, relative to frames having a greater number of axial frame members (e.g., greater number of axial struts). 
     The main functions of the inner skirt  106  are to assist in securing the valvular structure  104  to the frame  102  and to assist in forming a good seal between the valve  100  and the native annulus by blocking the flow of blood through the open cells of the frame  102  below the lower edge of the leaflets  110 . The inner skirt  106  desirably comprises a tough, tear resistant material such as polyethylene terephthalate (PET), although various other synthetic or natural materials can be used. The inner skirt  106  can be secured to the inside of the frame  102  via sutures. The valvular structure  104  can be attached to the inner skirt  106  with the assistance of one or more thin PET reinforcing strips (which collectively can form a sleeve, not pictured), which can enable secure suturing and protect the pericardial tissue of the leaflet structure from tearing. The valvular structure  104  can be sandwiched between the inner skirt  106  and the thin PET strips. 
     The upper edge portion of the inner skirt  106  can be formed with a plurality of projections that define an undulating shape that generally follows the shape of the fourth row of struts  118  (row IV) immediately adjacent the lower ends of axial struts  132 . In this manner, as best shown in  FIG. 1 , the upper edge of inner skirt  106  can be tightly secured to struts  118  with suture  146 . The inner skirt  106  can also be secured to the first, second, and/or third rows of struts  112 ,  114 , and  116  (rows I-III), respectively, with suture  146 . 
     The inner skirt  106  can be sutured to the frame  102  at locations away from the suture line attaching the lower edges of the leaflets  110  to the inner skirt  106 , which both reduces concentration of stress at the leaflet-suture-line and increases pliability to the skirt in that area. 
     As shown in  FIGS. 1-2 , a plurality of flexible connectors  125  can be used to interconnect each pair of adjacent edges of the leaflets  110  and to mount the leaflets  110  to the commissure window frame portions  130 . The flexible connectors  125  can be made from a piece of woven PET fabric, although other synthetic and/or natural materials can be used. Each commissure can comprise two tab portions of two adjacent leaflets. Each commissure can be secured to the frame, for example, by inserting the tab portions through the commissure windows  120  of the window frame portions  130 , and suturing the tab portions to a connector  125  outside of the frame  102 . 
     The outer skirt  108  can be laser cut or otherwise formed from a strong, durable piece of material, such as woven PET, although other synthetic or natural materials can be used. The outer skirt  108  can have a substantially straight lower edge and an upper edge defining a plurality of alternating projections  150  and notches  152 . The lower edge of the outer skirt  108  can be sutured to the lower edge of the inner skirt  106  at the inflow end of the valve  100 . In other embodiments, the inner skirt  106  and outer skirt  108  are integrally manufactured as a single component. As shown in  FIGS. 1-2 , each projection  150  can be affixed to the second rung II of struts  114  of the frame  102  with sutures  154 . 
     Additional details relevant to the securing of the valve member  104 , inner skirt  106  and outer skirt  108  to the frame  102  are provided in U.S. Patent Publication 2011/0123529, which is incorporated by reference in its entirety. 
     In various embodiments, a frame can be constructed to have greater or fewer rows of angled struts than in frame  102 , such as four or six rows of angled struts. In various other frame embodiments, each window frame portion and/or each axially extending strut can extend between two locations each defined by the convergence of the upper ends of angled struts. In various embodiments, each window frame portion and/or each axially extending strut can extend between two locations each defined by the convergence of the lower ends of angled struts. 
       FIG. 6  shows a perspective view of another exemplary prosthetic valve  200  with an inner skirt  206 , an outer skirt  208 , and a valve member  204  mounted within a stent  202 . The valve member  204  can have a set of three leaflets  210 . A plurality of flexible connectors  225  can be used to interconnect pairs of adjacent edges of the leaflets  210  and to mount the leaflets  210  to the commissure window frame portions  230 . 
       FIGS. 7-8  show perspective and flattened, unrolled views of the bare stent  202  having an inflow end  203 , an outflow end  205 , and four rows (I-IV) of struts  214 ,  216 ,  218 ,  222  (instead of five rows as shown in  FIGS. 1-5 ). The fourth row IV of angled struts  222  can be connected to the third row IV of angled struts  218  by a plurality of axially extending window frame portions  230  (which define commissure windows  220 ) and a plurality of axially extending struts  232 . 
     Thus, each window frame portion  230  and each axially extending strut  232  can extend between the two rows of angled struts that are closest to the outflow end  205 . In particular, each window frame portion  230  can extend between a location  242  defined by the convergence of the upper ends of two angled struts  222  and a location  244  defined by the convergence of the upper ends of two angled struts  218 . Each axially extending strut  232  can extend between another location  246  defined by the convergence of the lower ends of two angled struts  222  and another location  248  defined by the convergence of the lower ends of two angled struts  218 . 
     The frame  202  can comprise three window frame portions  230  spaced equally apart around the circumference of the frame  202 . As shown, the frame  202  can be constructed to have six angled struts (along each of rows III and IV) between the window frame portions  230  along each row. The frame can be constructed to have three angled struts between each window frame portion  230  and the adjacent axial struts  232 . Thus, each axial strut  232  can be located halfway between adjacent window frame portions  230 , and the frame  200  can be constructed to integrate window frame portions and axially extending struts in a 1:1 ratio. In the illustrated embodiment, there are exactly three window frame portions  230  and exactly three axial struts  232 . 
     In particular, the frame  202  can comprise, in sequence along the rows III and IV, a window frame portion  230  extending between a pair of locations  242 ,  244 , followed by a pair of locations  246 ,  248  lacking an axially extending member, followed by a pair of locations  242 ,  244  lacking an axially extending member, followed by an axially extending strut  232  extending between a pair of locations  246 ,  248 , followed by a pair of locations  242 ,  244  lacking an axially extending member, followed by a pair of locations  246 ,  248  lacking an axially extending member, followed by another window frame portion  230  extending between a pair of locations  242 ,  244  (and thus re-starting the sequence of window frame portions  230  and axially extending struts  232 ). 
     Once the prosthetic heart valve  200  is properly installed at the valve annulus, the valve  200  can cycle between open and closed states to permit or restrict the flow of blood. As discussed with respect to prosthetic valve  100 , forces that pull the commissures radially inwards during cycling can also pull the window frame portions  230  radially inward to relieve stress on the leaflets during valve closure. Meanwhile, the axial struts  232  can be urged radially outward. 
     The frame  200  can be capable of assuming a collapsed configuration (such as for delivery on or within a catheter) and an expanded configuration (i.e., functional configuration at the valve annulus). In various embodiments, in the collapsed configuration, the plurality of axial struts is positioned radially outwards relative to the leaflet attachment members and/or commissures. In one embodiment, in the process of transitioning from an expanded configuration to a collapsed configuration and/or from an collapsed configuration to an expanded configuration, the valve  200  can assume an intermediate configuration in which only those struts  222  of row IV that are adjacent to an axially extending strut  232  are brought together to extend axially (side-by-side and in substantial axial alignment with struts  232 ). 
     In another embodiment, as shown in  FIG. 9 , a frame  302  can have axial window frame members  330  extending between locations  342  defined by the convergence of the upper ends of two angled struts  322  and locations  344  defined by the convergence of the lower ends of two angled struts  318 . The frame  302  can have axially extending struts  332  extending between locations  346  defined by the convergence of the lower ends of two angled struts  322  and locations  348  defined by the convergence of the upper ends of two angled struts  318 . 
     Frame  302  is similar to frame  202  except that the first three rows of angled struts (rows I, II, and III) are shifted 20 degrees relative to the same rows of frame  202 . Thus, each window frame member  330  is axially aligned with a location  344  defined by the convergence of the lower ends of two angled struts  318  of row III. Each window frame member  330  can comprise a lower strut portion  334  below the level of the commissure window  320  (towards the inflow end of the stent  302 ). This lower strut portion  334  extends from the lower end of a window frame member  330  to a location  344  defined by the convergence of the lower ends of two angled struts  318 . The lower strut portion  334  provides added length to the window frame member  330  and allows the frame member  330  to effectively bridge the larger distance between locations  342 ,  344  in this embodiment. Other features and components of frame  302  can be similar to as described above for frame  202 . 
       FIG. 10  shows a portion of a frame  402 , according to another embodiment. In  FIG. 10 , only one-third of the circumference of the two upper rows of angled struts (the rows closest to the outflow end) is shown. The frame  402  can have axial window frame members  430  extending between locations  442  defined by the convergence of the lower ends of two angled struts  422  and locations  444  defined by the convergence of the lower ends of two angled struts  418 . The frame  402  can have axially extending struts  432  extending between locations  446  defined by the convergence of the upper ends of two angled struts  422  and locations  448  defined by the convergence of the upper ends of two angled struts  418 . 
     The two upper rows of angled struts includes a total of three axial window frame members  430  and a total of three axially extending struts  432  located equidistant between the window frame members  430  with three angled struts  418  and three angled struts  422  extending between a window frame member  430  and an adjacent axially extending strut  432 . The frame  402  can also include three additional rows of angled struts located at the inflow end of the frame (not shown in  FIG. 10 ), similar to embodiments discussed above. The lower end of each window frame member  430  can be connected to the upper ends of two angled struts of an adjacent row (the third row from the outflow end of the frame) at a location  444 . Thus, in this embodiment, the lower end of each axially extending strut  432  is not connected to any struts of the adjacent row. 
       FIG. 11  shows a portion of a frame  502 , according to another embodiment. In  FIG. 11 , only one-third of the circumference two upper rows of angled struts (the rows closest to the outflow end) are shown. The frame  502  can have axial window frame members  530  extending between locations  542  defined by the convergence of the lower ends of two angled struts  552  and locations  554  defined by the convergence of the upper ends of two angled struts  518 . The frame  502  can have axially extending struts  532  extending between locations  546  defined by the convergence of the upper ends of two angled struts  522  and locations  548  defined by the convergence of the lower ends of two angled struts  518 . The axially extending struts  532  in this embodiment can be longer than the window frame members  530  to account for the greater distance between locations  546 ,  548  compared to the distance between locations  542 ,  544 . 
     The two upper rows of angled struts includes a total of three axial window frame members  530  and a total of three axially extending struts  532  located equidistant between the window frame members  530  with three angled struts  518  and three angled struts  522  extending between a window frame member  530  and an adjacent axially extending strut  532 . The frame  502  can also include three additional rows of angled struts located at the inflow end of the frame (not shown in  FIG. 11 ), similar to embodiments discussed above. The lower end of each axially extending strut  532  can be connected to the upper ends of two angled struts of an adjacent row (the third row from the outflow end of the frame) at a location  548 . Thus, in this embodiment, the lower end of each window frame member  530  is not connected to any angled struts of the adjacent row. 
       FIG. 12  shows a portion of a frame  602 , according to another embodiment. In  FIG. 12 , only one-third of the circumference of the two upper rows of angled struts (the rows closest to the outflow end) is shown. The frame  602  can have axial window frame members  630  extending between locations  642  defined by the convergence of the upper ends of two angled struts  622  and locations  644  defined by the convergence of the upper ends of two angled struts  618 . The frame  602  can have axially extending struts  632  extending between locations  646  defined by the convergence of the lower ends of two angled struts  622  and locations  648  defined by the convergence of the lower ends of two angled struts  618 . 
     In the embodiment of  FIG. 12 , there are two such axially extending struts  632  spaced between each pair of window frame members  630 . In particular, for each pair of window frame members, there are three angles struts  618  and three angles struts  622  between each window frame member  630  and the closest axially extending strut  632 , and two angles struts  618  and two angles struts  622  between the two axially extending struts  632 . Thus, for the entire frame  602 , the two upper rows of angled struts includes a total of three axial window frame members  630  and a total of six axially extending struts  632 . 
     The frame  602  can also include three additional rows of angled struts located at the inflow end of the frame (not shown in  FIG. 12 ), similar to embodiments discussed above. The lower end of each axially extending strut  632  can be connected to the upper ends of two angled struts of an adjacent row (the third row from the outflow end of the frame) at a location  648 . Thus, in this embodiment, the lower end of each window frame member  630  is not connected to any struts of the adjacent row. 
       FIG. 13  shows a portion of a frame  702 , according to another embodiment. In  FIG. 13 , only one-third of the circumference of the two upper rows of angled struts (the rows closest to the outflow end) is shown. The frame  702  can have axial window frame members  730  extending between locations  742  defined by the convergence of the lower ends of two angled struts  722  and locations  744  defined by the convergence of the upper ends of two angled struts  718 . The frame  702  can have axially extending struts  732  extending between locations  746  defined by the convergence of the upper ends of two angled struts  722  and locations  748  defined by the convergence of the lower ends of two angled struts  718 . 
     In the embodiment of  FIG. 13 , there are two such axially extending struts  732  spaced between each pair of window frame members  730 . In particular, for each pair of window frame members, there are three angles struts  718  and three angles struts  722  between each window frame member  730  and the closest axially extending strut  732 , and two angles struts  718  and two angles struts  722  between the two axially extending struts  732 . Thus, for the entire frame  702 , the two upper rows of angled struts includes a total of three axial window frame members  730  and a total of six axially extending struts  732 . Also, struts  732  can be longer than window frame members  730  to account for the greater distance between locations  746 ,  748  compared to the distance between locations  742 ,  744 . 
     The frame  702  can also include three additional rows of angled struts located at the inflow end of the frame (not shown in  FIG. 13 ), similar to embodiments discussed above. The lower end of each axially extending strut  732  can be connected to the upper ends of two angled struts of an adjacent row (the third row from the outflow end of the frame) at a location  748 . Thus, in this embodiment, the lower end of each window frame member  730  is not connected to any struts of the adjacent row. 
     The prosthetic valve embodiments disclosed herein can be surgically implanted and/or can be delivered using a delivery apparatus, such as a catheter. The prosthetic valve can be mounted in a crimped state on or adjacent an inflatable balloon or equivalent expansion mechanism of the delivery apparatus. The delivery apparatus and crimped prosthetic valve can be inserted into the patient&#39;s vasculature and advanced through the patient&#39;s body using known techniques. 
     In one implementation, the prosthetic valve is delivered in a transfemoral procedure in which the delivery apparatus is inserted into a femoral artery and advanced through the aorta to the native aortic valve (or another native valve of the heart). In another implementation, the prosthetic valve can be delivered in a transventricular procedure in which the delivery apparatus is inserted through a small surgical opening in the chest and another surgical opening in the wall of the heart, such as the wall of the left ventricle. In another implementation, the prosthetic valve can be delivered in a transaortic procedure in which the delivery apparatus is inserted through a small surgical opening in the chest and another surgical opening in the ascending aorta, at a location above the aortic valve. In another implementation, the prosthetic valve is a replacement venous valve for implantation in a vein, or a replacement for another valve with a lower flow rate relative to the aortic valve. 
     When the prosthetic valve is positioned at the desired deployment location (e.g., within the native aortic valve), the balloon of the delivery apparatus can be inflated to radially expand the prosthetic valve. In some embodiments, upon full expansion of the prosthetic valve, the outer skirt of the prosthetic valve can be forced into contact with the surrounding tissue of the native valve, establishing a seal between the outer surface of the frame and the surrounding tissue. The frame of the prosthetic valve, when in the radially compressed, mounted configuration, can comprise an inflow end portion that has an outer diameter that is smaller than the outer diameter of the outflow end portion of the frame. 
     When constructed of a self-expanding material, the prosthetic valve can be crimped to a radially compressed state and restrained in the compressed state by insertion into a sheath or equivalent mechanism of a delivery catheter. After the delivery apparatus is inserted into the body and advanced to position the prosthetic valve at the desired deployment location, the prosthetic valve can be advanced from the delivery sheath. As the prosthetic valve is deployed from the delivery sheath, the prosthetic valve can radially self-expand to its functional size. 
     The prosthetic heart valve can comprise commissure portions of the leaflets extending radially outwardly through corresponding window frame portions to locations outside of the frame and sutured to the side struts of the commissure window frame. To minimize the crimp profile of the prosthetic valve, the window frame portions can be depressed radially inwardly relative to the surrounding portions of the frame, such as the frame portions extending between adjacent commissure windows, when the prosthetic valve is radially compressed to the collapsed configuration on a catheter. 
     For example, the commissure windows of the frame can be depressed inwardly a radial distance, such as between 0.2 mm and 1.0 mm, relative to the portions of the frame extending between adjacent commissure windows when the prosthetic valve is radially collapsed. In this way, the outer diameter of the outflow end portion the prosthetic valve comprising the commissure portions can be generally consistent, as opposed to the commissure portions jutting outward from the surrounding portions of the prosthetic valve, which could hinder delivery of the prosthetic valve into the body. Even with the radially depressed commissure window frames, the outer diameter of the inflow end portion of the frame can still be smaller than, or about equal to, the outer diameter of the outflow end portion of the frame when the prosthetic valve is radially collapsed on the catheter, allowing for a minimal or reduced maximum overall diameter of the prosthetic valve. By minimizing or reducing the diameter of the prosthetic valve when mounted on the delivery catheter, the diameter of a delivery catheter through which the prosthetic valve is advanced can also be minimized or reduced. This allows the prosthetic valve to be delivered through smaller vessels in the body, making the delivery procedure less invasive, in general. 
     Additional details relevant to delivery of the prosthetic heart valves disclosed herein are provided in U.S. Patent Publication 2011/0123529, which is incorporated herein by reference. 
     General Considerations 
     For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatuses, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatuses, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved. 
     Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached drawings may not show the various ways in which the disclosed methods can be used in conjunction with other methods. As used herein, the terms “a”, “an”, and “at least one” encompass one or more of the specified element. That is, if two of a particular element are present, one of these elements is also present and thus “an” element is present. The terms “a plurality of” and “plural” mean two or more of the specified element. 
     As used herein, the term “and/or” used between the last two of a list of elements means any one or more of the listed elements. For example, the phrase “A, B, and/or C” means “A”, “B”, “C”, “A and B”, “A and C”, “B and C”, or “A, B, and C”. 
     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. I therefore claim as my invention all that comes within the scope and spirit of these claims.