Abstract:
Holders for releasably holding annuloplasty rings prior to and during the implantation of the rings employ any of a variety of features relating to such things as holder shape, handle attachment structures, securement of a ring to the holder, and release of the ring from the holder.

Description:
BACKGROUND OF THE INVENTION 
     This application claims the benefit of U.S. provisional patent application No. 60/571,020, filed May 14, 2004, which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     This invention relates generally to holding devices for implantable medical prostheses or devices, and more specifically to holding devices for securing and supporting annuloplasty rings to be implanted adjacent to mitral or tricuspid valves. 
     Annuloplasty rings are useful in a variety of medical procedures, such as strengthening the base annulus of mitral and tricuspid valves in the heart. Heart disease may result in disorders of the cardiac valves characterized by weakening or loosening of the heart muscle tissue forming and surrounding the heart valves. The mitral and tricuspid valves respectively allow blood to flow from the heart&#39;s left and right atria into the heart&#39;s left and right ventricles. Weakening of heart tissues may cause these valves to function improperly. In particular, these valves may no longer close completely, allowing blood to be regurgitated back through the valve during ventricle contraction. An annuloplasty ring may be used to provide support to the base annulus of a cardiac valve, restoring the ability of the valve to close and seal itself adequately. The ring prevents the base annulus of the valve from deforming, thereby reducing or eliminating regurgitation through the valve. 
     The implantation of an annuloplasty ring on a cardiac valve may require open-heart or less invasive surgery. During surgery, the implanted ring is mounted on a specially designed holder which is used to secure and maintain the shape of the ring while the ring is placed into the heart and is sutured to the valve annulus. The holder may also be used to secure and support the ring during storing, transportation, and other manipulations surrounding the implantation procedure. The holder is typically detached from the ring during the ring implantation procedure, and is removed from the implantation site. 
     U.S. Pat. Nos. 5,041,130, 5,011,481, and 6,001,127 show and describe annular and C-shaped annuloplasty ring holders. 
     SUMMARY OF THE INVENTION 
     The present invention provides apparatus and methods for securing and supporting annuloplasty rings during implantation of the rings and during related procedures. The apparatus may include a specially designed holder to which the ring can be releasably secured. 
     The holder may be planar or saddle-shaped, and may be shaped so as to approximate the shape of the implanted ring. The holder may also be flexible or semi-flexible. The holder may include holes or be structured so as to increase the visibility of the valve and surrounding area through or around the holder. A connector may be mounted on the holder to allow the holder to be manipulated by the physician. The connector may be placed, shaped, or recessed so as to increase visibility of the operative area, to improve access to the area, or to suit other objectives. 
     The ring may be secured to the holder using a variety of means and methods. Suture threads may be used to tie the ring to the holder. Threads may be stitched through, or looped or wrapped around either or both of the ring and holder. Suture threads may be released using cutting blocks indicating locations for or guiding the cutting of the threads. Cutting blocks may be located or recessed at various locations on the holder, may be shaped to suit a variety of objectives, and may incorporate knot tying posts where suture thread may be tied. Suture threads may also be released using other methods. The ring may also be secured to the holder using internal tension or clamping means. A variety of holders functioning on these principles are presented. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features of the invention, its nature, and various advantages will be more apparent from the following detailed description and the accompanying drawings, in which: 
         FIG. 1  is a side view of an illustrative planar annuloplasty ring holder in accordance with the invention. 
         FIG. 2  is a top view of a planar annuloplasty ring holder similar to that shown in  FIG. 1 . 
         FIG. 3  is a side view of an illustrative saddle-shaped annuloplasty ring holder in accordance with the invention. 
         FIG. 4  is a top view of a saddle-shaped annuloplasty ring holder similar to that shown in  FIG. 3 . 
         FIG. 5  is a top view of another illustrative annuloplasty ring holder in accordance with the invention. 
         FIG. 6  is a top view an illustrative annuloplasty ring holder attached to an annuloplasty ring, in accordance with the invention. 
         FIG. 7  is a side view of an illustrative planar annuloplasty ring holder with a shortened connector stub, recessed connector base and recessed cutting blocks, in accordance with the invention. 
         FIG. 8  is a side view of an illustrative saddle-shaped annuloplasty ring holder with a recessed connector base, in accordance with the invention. 
         FIG. 9  is a side view of an illustrative saddle-shaped annuloplasty ring holder with a recessed connector base, in accordance with the invention. 
         FIG. 10  is a top view of an illustrative planar annuloplasty ring holder indicating the location (at line  11 - 11 ) of the cross-sectional view shown in  FIG. 11 , in accordance with the invention. 
         FIG. 11  is an oblique, cross-sectional view of a planar annuloplasty ring holder taken along the line  11 - 11  in  FIG. 10 , in accordance with the invention. 
         FIGS. 12   a - 12   c  are a series of three cut-away views of an illustrative annuloplasty ring holder including knot tying posts in accordance with the invention. 
         FIGS. 13   a - 13   c  show three illustrative suture thread wrapping methods in accordance with the invention. 
         FIGS. 14   a  and  14   b  show an illustrative annuloplasty ring holder with releasable suture threads in accordance with the invention. 
         FIG. 15  is a schematic depiction of an illustrative internal tension annuloplasty ring holder in accordance with the invention. 
         FIGS. 16   a  and  16   b  are two views of an illustrative internal clamping annuloplasty ring holder in accordance with the invention. 
         FIGS. 17   a  and  17   b  are two views of an illustrative internal clamping annuloplasty ring holder in accordance with the invention. 
         FIG. 18  is a schematic depiction of serrated clamps that may be included in an annuloplasty ring holder in accordance with the invention. 
         FIGS. 19   a  and  19   b  show an illustrative end-clamping annuloplasty ring holder in accordance with the invention. 
         FIGS. 20   a  and  20   b  show an illustrative internal tension annuloplasty ring holder with retractable pins in accordance with the invention. 
         FIG. 21  is a schematic depiction of illustrative clamping brackets that may be included in an annuloplasty ring holder in accordance with the invention. 
         FIGS. 22   a  and  22   b  show an illustrative clamping annuloplasty ring holder in accordance with the invention. 
         FIGS. 23   a  and  23   b  respectively show schematic depictions of an illustrative clamping annuloplasty ring holder and an illustrative non-thread holder in accordance with the invention. 
         FIG. 24  is a schematic depiction of an illustrative sheath holder in accordance with the invention. 
         FIGS. 25   a  and  25   b  show an illustrative annuloplasty holder and ring with pre-stitched sutures in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     This invention describes embodiments of a holder for an annuloplasty ring. An annuloplasty ring may be used by a surgeon to assist in strengthening or reshaping a heart valve. An annuloplasty ring may be sutured to the heart adjacent to, for example, the mitral valve to reshape the valve. This procedure may be used to treat and limit valve regurgitation, or any other valve malfunction. Before and during implantation of the annuloplasty ring into the patient, the ring is mounted on a holder which is used to secure and support the ring as it is placed and sutured into the heart. The holder may be stiff or flexible, and may alternatively be used during open-heart or minimally invasive surgery. A flexible holder may be especially well suited for minimally invasive surgery, during which the holder and ring may have to be inserted into the patient&#39;s heart through a catheter. The holder may also be used to support the ring during storage, manipulation or other procedures surrounding annuloplasty ring implantation and preparation. In a preferred embodiment, the holder is not implanted into the patient. Instead, the holder is detached from the ring during the implantation procedure and is removed from the implant site. The ring holder may be manipulated by the surgeon using a handle or other grasping device that attaches to a connector included on the ring holder. 
     The following specification describes various novel features that may be incorporated into a ring holder. These features may include, for example, alternate holder structures, connector structures, cutting blocks and suture tying posts, suture and non-suture methods of attaching the ring to the holder, as well as pre-stitched sutures. Such features are described in the associated titled sections of the following description. 
     Those skilled in the art will appreciate that while the invention is described with regard to holders specifically designed for annuloplasty rings, the invention may be used in the more general context of designing mounting brackets for a variety of medical and other applications. 
     A. Holder Structure 
       FIGS. 2 ,  4 , and  5  show top views of illustrative annuloplasty ring holders  10 ,  30 , and  50 . The upper surface of each holder is visible in these top-down views. The three holders  10 ,  30 , and  50  include outer oval  11  or D-shaped  31  and  51  bracket structures which can support annuloplasty rings mounted on the holders. The shape of the bracket may be designed to approximate the shape of an associated annuloplasty ring. The bracket may also be shaped according to other criteria. The bracket may also be made of flexible or semi-flexible material, and may adapt its shape to that of the ring it is supporting. The holders  10 ,  30 , and  50  also include other features visible on their upper surface, including cutting blocks  17 ,  37 , and  57 , suture threading holes  19 ,  39 , and  59 , and connectors  15 ,  35 , and  55 . Each of these features will be discussed in more detail in following sections of this description. 
     The center of the annuloplasty ring holder  10 ,  30 , or  50  may include one or multiple large open areas  13 ,  33 , or  53 . The open area may be formed by multiple holes  13  pierced through the upper surface of the holder, or by a single large central hole  33  or  53 . The center of the holder is pierced so as to increase the visibility of the heart valve region through the ring holder, enabling the surgeon to more accurately place and suture the annuloplasty ring at the implant site. 
     The center of the holder may contain at least one connector  15 ,  35 , or  55 . The connector is represented by a hexagonal stub in the accompanying figures. The connector may be used to attach the holder to a handle or other grasping device used by the surgeon to grasp and manipulate the holder. The connector is typically located along the bracket  31  or  51 , or in the central portion of the bracket  11  with support arms connecting it to the outer bracket. The connector may also be located elsewhere on the ring holder. In a preferred embodiment, the location of the connector is determined so as to be accessible to the surgeon, and to provide easy and skillful manipulation of the ring and holder when a handle or other device is attached to the connector. The location of the connector may also be determined so as to increase the visibility of the heart valve area to the physician, and to decrease the cluttering of the operating area. Other requirements may also influence the location of the connector on the annuloplasty ring holder. In the illustrative embodiments shown in  FIGS. 2 ,  4 , and  5 , the connector  15 ,  35 , or  55  is alternately located in the middle of the bracket  11 , or placed along the edge of the bracket  31  or  51  so as to provide a continuous open area  33  or  53  in the center of the bracket. The connector may be centered along the central axis of the bracket  10  or  30 , located at another location on the bracket  50 . The connector may also be located along the edge of bracket  11 , in the center of brackets  31  or  51 , or at any other location on holders  10 ,  30 , and  50 . 
       FIGS. 1 and 3  show side views of annuloplasty ring holders  10  and  30 . The holder  10  may be planar, as shown in  FIG. 1 . A planar holder may have an essentially flat bracket  11 . The holder  30  may alternatively be saddle-shaped, to more closely follow and support the shape of a saddle-shaped ring. A saddle-shaped ring holder may have a non-planar bracket  31 , and may be used to secure and support essentially saddled-shaped annuloplasty rings. Saddle-shaped rings may more closely follow the natural shape of the base of the heart valve (e.g., the mitral valve), and may thus further improve the functioning of the valve after implantation of the ring. The saddle of the ring holder may be symmetrical on the posterior and anterior section of the holder. The saddle may have varying height, typically in the range of 2 mm to 10 mm from the lowest to highest points on the holder (corresponding to an Annular Height to Commissure Width Ratio (AHCWR) in the range from about 5% to about 25%). 
     The ring holder may incorporate other features to aid the physician during the ring implantation procedure.  FIG. 6  shows a ring holder  60  with indicator tabs  66 . An annuloplasty ring  62  is shown attached to the ring holder  60 . The indicator tabs  66  indicate the trigone locations, and help the physician to align the ring on the heart valve with ease and precision. The indicator tabs may be printed, molded, or other visual indications placed on the ring or ring holder, which help align the ring and holder on the heart valve. Indicator tabs may also assume other forms. 
     The annuloplasty ring  62  shown in  FIG. 6  may be a full circular ring (as shown), a circular ring with a gap (a gapped ring), or a C-shaped prosthesis, among others. For simplicity, the term ‘ring’ is used herein to refer to any annuloplasty ring embodiment. Note that while either full circular or C-shaped rings are alternatively shown in the accompanying figures, the holders, features and embodiments described herein may be used with any type of ring, except in those cases where it is specified otherwise. 
     B. Connector Structure 
     The connector  15 ,  35 , or  55 , is a part of the holder which can be used to attach the holder to a handle or other grasping instrument (not shown). The physician may attach a handle or grasping instrument to the connector in order to manipulate the holder and ring assembly, and to place them at an implant or other appropriate site. The connector may include features allowing it to be grasped using fingers, forceps, or other means, or secured using a snap fit, screw thread, twist pin or other means of connecting a handle. The connector may also include permanent attachments, in cases in which the holder and handle or grasping instrument are a single entity. In the figures, the connector is illustratively represented as a hexagonal stub. This does not preclude use of a different non-hexagonal connector. 
     As noted above, and as illustrated in  FIGS. 2 ,  4 , and  5 , the location of the connector on the holder may be varied to suit a variety of objectives. The connector may be placed in such a way as to maximize the physician&#39;s visibility of the implanted ring, of the heart valve, and of the operative area surrounding these structures. The connector may also be placed in such a way as to maximize the physician&#39;s ability to place and otherwise manipulate the ring and holder with accuracy, to maximize the physician&#39;s access to the operative area, and to minimize cluttering of the operative region with the handle or grasping device used to manipulate the holder. Other objectives may also influence the positioning of the connector on the holder. 
     The position of the connector in the holder&#39;s horizontal plane was discussed above in the context of  FIGS. 2 ,  4 , and  5 . The following paragraphs describe varying the position and height of the holder in the vertical direction. 
       FIG. 1  shows a planar ring holder  10  with a connector  15  whose bottom surface is flush with the lower surface  14  of the holder. The connector stub  15  protrudes above the upper surface  12  of the holder, while the base of the connector is flush with the lower surface  14  of the holder. The planar ring holder  70  shown in  FIG. 7  shows a recessed connector base  78  whose lower surface is lower than the lower surface  74  of the holder. The recessed connector base  78  may jut down below the holder bracket  71 , jutting down into the valve orifice when the holder and ring are place at the implant site. The ring holder  70  may also employ a shortened connector stub  75  which is shorter than a full-length connector structure  15  and protrudes less from the holder. In another embodiment, the connector base  78  may be further recessed into the holder  70 , or the connector stub  75  further shortened, so as to reduce the protrusion of the connector structure from the ring holder  70 . The shortening of the connector stub  75  and the lowering of the connector base  78  provide better access and visibility along the upper portion of the holder. By reducing or eliminating the protrusion of the connector stub  75  above the bracket  71 , the physician may have more space to tie the implanting suture knots, or to perform other manipulations along the periphery of the ring. The reduced protrusion of the stub  75  may also improve the physician&#39;s view of the periphery of the ring and other adjoining structures. 
       FIGS. 8 and 9  show similarly recessed and shortened connectors  85  and  95  in the context of saddle-shaped ring holders. In a first embodiment  30  of a saddle-shaped holder shown in  FIG. 3 , the connector base  38  is approximately level with the highest point reached by the lower surface  34  of the holder bracket  31 . The connector stub  35  protrudes above the highest point reached by the upper surface  32  of the bracket. In a second embodiment  80 , the connector base  88  is lower than in the first embodiment  30 . This causes the connector stub  85  to protrude less above the upper surface  82  of holder bracket  81 , increasing visibility above the holder  80 . Similarly, in a third embodiment  90 , connector base  98  is further recessed. Connector stub  95  protrudes less above the upper surface  92  of bracket  91 . In fact, in third embodiment  90 , the connector stub  95  is almost flush with the upper surface  92  of the bracket  91 . In both the second and third embodiments, the recessed connector stub bases  88  and  98  may jut down to varying degrees into the heart valve tissue and orifice found below the implantation site of the ring. In these second and third embodiments, the visibility of the operative area above the holders  80  and  90  is improved along the top of the holder by reducing the protrusion of connector stubs  85  and  95  above the holder brackets  81  and  91 . Note that while shortened connector stubs such as stub  75  are not shown in  FIGS. 3 ,  8 , and  9 , shortened connector stubs may be used in combination with saddle-shaped holders to reduce protrusion of the stub above the bracket. Shortened stubs may also be used to reduce the jutting out of connector bases  88  and  98  into the heart valve tissue below the bracket  81  and  91 . 
     C. Cutting Blocks 
     Before and during the implantation procedure, the annuloplasty ring may be secured to the holder. The holder may be used to hold and manipulate the ring as it is placed at the implant site, and to support the ring during handling and while the ring is sutured into place. The holder may be detached from the ring during the implantation procedure, because the holder is typically not implanted with the annuloplasty ring into the heart. The ring may be secured to the holder using a variety of means. The ring may be attached to the holder using suture thread, or other thread-like structures. Alternatively, the ring may be attached to the holder using other releasable means. Various methods that may be used to secure the ring to the holder are described in more detail later in this specification. 
     In embodiments of this invention in which annuloplasty rings are secured to the ring holder by suture threads or other means amenable to cutting, cutting blocks may be included on the holder. Cutting blocks are guides used to facilitate the cutting of suture threads or other means of attaching an implanted annuloplasty ring to a holder. Cutting blocks may be used to help the physician locate the appropriate suture threads to cut, to ensure that the physician cuts the proper threads, and to prevent the physician from cutting tissue or sutures other than those passing through the cutting block. 
     Cutting blocks may include visual or other guides indicating to the physician the preferred location or locations where a suture thread used to attach the ring to the holder may be cut. In this way, cutting blocks may be used to identify those sutures that should or can be cut to release the ring from the holder. Cutting blocks may include painted, molded, or other visual indications highlighting the locations of preferred cutting locations. Cutting blocks may also include physical guides that direct or steer in other ways the physician to a preferred cutting location. In a preferred embodiment, the cutting blocks may include slots or other guiding means used to direct the physician&#39;s scalpel blade and ensure that the appropriate suture thread is cut. 
     Cutting blocks may be located at a variety of locations on the ring holder. In the particular embodiment shown in  FIG. 10 , four cutting blocks  107  are placed at various location on the holding bracket  101 . In the embodiment shown in  FIG. 4 , three cutting blocks  37  are located on bracket  31 . Holders with more or fewer cutting blocks, or cutting blocks placed at different locations on the bracket or on the holder, may also be used. As in the case of connector locations, cutting blocks may be placed in the center of the bracket, if appropriate, with support structures holding the cutting block in place with respect to the bracket. 
     The location of cutting blocks may also be varied in the vertical holder plane. Cutting blocks, which include cutting slots, have non-negligible depths. Such cutting blocks may be thicker than the holder brackets  11 ,  31 , or  71 , and may protrude above or below the upper and lower surfaces of the brackets, respectively. As in the case of connectors, the vertical position of the cutting blocks may be varied to increase access and visibility around the upper edge of the holder, or to satisfy other objectives.  FIG. 1  holder  10  shows cutting blocks  17  protruding above the upper surface  12  of bracket  11 . The cutting block may be recessed, as shown in  FIG. 7 . In the holder embodiment of  FIG. 7 , cutting blocks  77  do not protrude above the upper surface  72  of bracket  71 . Instead, cutting blocks  77  protrude below the lower surface  74  of bracket  71 . Recessed cutting blocks  77  may protrude into the valve tissue and valve orifice found below the ring implantation site. However, recessed cutting blocks  77  provide better visibility along the upper surface  72  of holder  70 , giving the physician an unobstructed view of the implanted ring and structures adjacent to the implant site. While recessed cutting blocks  77  are shown in  FIG. 7  in the particular context of planar holder  70 , recessed cutting blocks may be included on saddle-shaped holders, or other types of implant device holders. 
       FIGS. 10 and 11  show two views of an illustrative annuloplasty ring holder that includes cutting blocks.  FIG. 10  shows a top-down view of a holder  100 , showing the plane of section  11 - 11  illustrated in the cross-sectional view of  FIG. 11 . The cross-sectional view of  FIG. 11  shows a cut-away view through a cutting block. As seen in  FIG. 11 , each cutting block  107  may include a slit into which a scalpel blade may be introduced, and two holes  109  through which suture thread may pass. The axis of the holes intersects the axis of the cutting slit, so that a thread passing through the holes crosses the cutting slit. The thread may cross at approximately half the slot depth. When a scalpel is passed through the cutting slit, the suture thread is cut, releasing at least one section of the ring from the holder. 
     The cutting slit shown in cross-sectional view  11 - 11  of cutting block  107  may have an asymmetrical half-moon shape. The cutting slit may be shaped to match the shape of the scalpel blade, in order to increase cutting efficiency. The shape of the slit may also be designed to guide cutting in a preferred direction, or to permit cutting in both directions. The shape may also be adjusted to draw the cutting action upward and away from the tissue, minimizing the risk of damaging structures surrounding the implant site. In the particular example shown in  FIG. 11 , the cutting slit may match the shape of a #15 scalpel blade. Slits may be shaped to match other standard scalpel blades. 
     Annuloplasty ring holders may include knot tying posts on which suture threads used to hold the ring to the holder may be knotted. The knot tying posts may be placed next to cutting blocks, as the suture thread may pass through both structures. As shown in  FIGS. 12   a - 12   c , the thread  123  may pass through the annuloplasty ring and the cutting block&#39;s suture channels  129 , and have at least one of its ends knotted  124  to a knot tying post  128 . Both ends of the thread may also be knotted  124  to each other and to the knot tying post  128 , as shown in  FIGS. 12   a - 12   c . The knot tying post may be used to hide sutures used to hold the ring to the holder underneath the holder&#39;s upper surface. As such, knot tying posts may be located on the lower side of the holder, so as to reduce visual distractions on the holder&#39;s upper surface. The knot tying post may also be used to ensure the suture thread does not remain attached to the implanted annuloplasty ring after the ring is released from the holder. To this end, both ends of the suture thread may be tied to a knot tying post, thereby ensuring that both portions of the cut thread remain attached to the holder when the holder is removed from the implant site. Knots  124  may be tied on each side of the post, as shown on knot tying post  128 , to retain suture after it is cut. 
     D. Fixation of the Annuloplasty Ring to the Holder 
     Various methods may be used to secure the annuloplasty ring to the ring holder. Methods involving suture thread, or other thread-like implements, may be used to tie the ring to the holder. Alternatively, other retaining means may be used to secure the ring to the holder. These may include clamping devices or other restraining devices incorporated into the holder. Such devices are described in further detail in the following two sections of this description. 
     1. Suture Methods—Attachment to Holder 
     The annuloplasty ring may be attached to the ring holder using suture thread, or similar thread-like implements. The suture thread may pass through the holder, may be looped around the holder, or may be attached to the holder in other ways.  FIG. 6  shows an exemplary arrangement in which the thread  63  passes through suture channels  69  on the holder bracket  61 . The suture channels  69  may be located at various locations on the holder  60 , in order to ensure that the ring  62  can be held firmly against the holder bracket  61 . In the particular embodiment shown in  FIG. 6 , a single length of suture thread  63  may be looped multiple times through the holder  60  and around the ring  62 . By looping the thread around the ring and holder assembly multiple times, fewer threads may be needed to hold the ring attached to the holder, because each length of thread secures the ring on the holder in multiple locations. In such an embodiment, fewer cutting blocks may be required because each length of thread need only be cut in one location. In the particular embodiment of  FIG. 6 , the ring  62  is retained by the thread  63  using forces pulling inward in the radial direction. The overhang of the holder bracket may therefore be reduced, improving access to the ring periphery and to the surgeon&#39;s suturing positions on the ring. 
     The suture thread may also be looped around the holder, with or without passing through suture channels on the holder. Such an embodiment is shown for example in  FIGS. 14   a  and  14   b . In this embodiment, the suture thread  143  may not pass through the holder bracket  141 . Instead, the threads may be held taut against the edges of the bracket. Different means of wrapping the suture thread around the holder and bracket may be used. For example, means similar to those used to secure the ring described in the following section may also be used to secure the suture thread to the holder. 
     2. Suture Methods—Attachment to Annuloplasty Ring 
     In embodiments in which suture thread is used to secure the ring to the holder, the suture thread may be secured to the annuloplasty ring by passing through the ring, by looping around the ring, or by holding the ring to the holder in other ways. In one illustrative embodiment shown in  FIG. 13   a , the thread  133  may be passed one or more times through the ring  131  in a through stitch. The same thread may also pass through or wrap around the ring holder  132 , as described in previous sections of this description. 
     The thread may also wrap around the annuloplasty ring  131 , with or without being stitched through the ring.  FIG. 13   b  shows a thread  134  looping a single time around the ring  131  in one embodiment, and  FIG. 13   c  shows a thread  135  wrapped multiple times around the ring  131  in a second embodiment. By wrapping the thread  135  multiple times around the ring and holder, a single length of thread can be used to secure a wider section of the ring against the holder than a single loop  134  of thread can secure. Wrapping the thread  135  multiple times around the ring and holder may reduce the total number of threads, cutting blocks, tying posts and other holder structures that may be used to hold the ring attached to the holder. By looping or wrapping the thread around the ring, the thread may pull the ring radially inward against the holder bracket. In such an embodiment, the holder bracket can have minimal overhang above and below the ring, supplying instead an inner support structure against which the ring is held. This may improve access to the ring&#39;s outer periphery, improving the physician&#39;s view and access to the ring periphery. Alternatively, the looping or wrapping of the thread around the ring can be used to pull the ring upward against a holder bracket placed substantially around the ring&#39;s upper surface. Such a holder may have fewer bracket structures in its center, providing the physician with an unobstructed view of the heart valve region through the center of the holder. 
     In embodiments in which suture methods are used to secure the ring to the holder, the thread or threads used to secure the ring may be cut to release the ring from the holder. The cutting may be performed using a scalpel, cutting blocks, or other appropriate cutting methods. Other methods may also be used to release the ring from the holder.  FIGS. 14   a  and  14   b  show a push-button release method for disengaging the thread  143  and releasing the ring  142 . The push-button  144  may be used to release one or multiple threads concurrently. Releasing of the ring may require one or multiple push-buttons to be pressed. 
     3. Non-Suture Methods 
     Other methods may be used to secure the ring to the holder. These methods may use internal tension, clamping, or other means to hold the ring. 
       FIGS. 15 through 20  show a series of illustrative holders that use internal tension or internal clamping to hold the ring. These holders may have braces that can extend or retract in the radial direction. When the braces are extended outwards, friction or internal tension forces between the brace and the ring may secure the ring to the holder. Alternatively, or in addition to internal tension, brace structures may be used to hold the ring. 
       FIG. 15  shows a basic internal tension holder  152  holding ring  151 . Holder  152  may be stiff or elastic, and may include central structures to maintain its shape and elasticity, or to attach a connector. A flexible or semi-flexible holder  152  may be used to support D-shaped rings. In such a case, the natural shape adopted by the holder and ring assembly when internal tension is applied may be a saddle-shape. In general, ring  151  may be a complete annuloplasty ring. Ring  151  may also be a C-shaped (as shown) or gapped ring, which may require a stiff or elastic suture thread  153  to be tied between the ends of the ring. Suture thread  153  may serve to maintain the ring&#39;s shape, and to keep the ring on the holder. Holder  152  may be an flexible holder. 
       FIGS. 16 and 17  show holders with C-shaped braces  161  and  171 . The beveled edges of the braces may serve to support the ring, and to keep it from slipping out of the holder when the braces are extended radially outward. Serrated, high friction, or clipping brackets may also be used to further secure the ring in the brackets.  FIG. 18  shows one schematic embodiment of serrated clip brackets  182  holding ring  181 . The clip brackets may have hinged jaws that can alternately clamp and hold the ring, or open and release the ring from the holder. 
     The holders may also have a release mechanism used to disengage the braces securing the ring. The release mechanisms may include a push-button or other type of mechanism which may be used to draw the braces inward, releasing the ring from the holder.  FIGS. 16 and 17  show two exemplary release mechanisms in which a push-button or lever placed at or near the center of the holder is used to retract the braces. The release mechanisms shown in these figures are exemplary, and other known types of release mechanisms may be used in these holders. The braces may be retracted by moving upper and lower sets of radial bracket support arms  162  and  172  in substantially opposite directions. The upper set of support arms  162  or  172  may move substantially in an upwards direction, while the lower set of support arms  162  or  172  may move substantially in a downward direction. Movement of the support arms in different directions may act to draw retaining braces  161  and  171  radially inward, and to release the ring from the holder. 
       FIGS. 19   a  and  19   b  show an exemplary holder that uses end-clamps  192  to hold a C-shaped prosthesis (“ring”) to the holder. The end-clamps  192  latch onto the ring  191 , while beveled edges on the bracket may assist in securing the ring. The end-clamps may be disengaged as shown at  193  when the ring is released from the holder. A C-shaped holder may fold onto itself, as shown in  FIG. 19   b , to release the ring  191  from its outer brackets  194 . 
       FIGS. 20   a  and  20   b  show an exemplary holder  200  that has retractable rods or pins  202  sticking radially out of a central holder structure  203 . The rods or pins may be made of stiff or flexible materials, and may be made of shape memory alloy or nitinol. When engaged, the rods  202  extend radially outward from the central structure  203  and exert pressure at multiple points on the ring&#39;s inner surface. When disengaged, the rods  202  retract inward and release the ring  201  from the holder  200 . The rods may be disengaged by rotating a central hub  203  into which the rods  202  are inserted. Other disengagement mechanisms may also be used. 
       FIGS. 21 and 22  show clamping or clamshell holders. These holders may include one or more central braces  212  or  222 , as well as one or more retractable outer supports  213  or  223 . The central and outer braces may be used to substantially clamp or restrain the ring  211  or  221  in one or more locations around the ring. The braces may have beveled edges or protrusions to inhibit the ring from slipping out of the clamp. The clamping brace may release the ring by moving the inner and outer clamping braces apart. In one embodiment shown in  FIGS. 22   a  and  22   b , the outer braces  223  may be released, while the inner braces  222  may remain substantially stationary. In another embodiment, the outer braces may remain substantially stationary while the inner braces retract. Alternatively, both the inner and outer braces may move. The holder may release the ring using a push-button mechanism, or other mechanisms. In the particular embodiment shown in  FIGS. 22   a  and  22   b , the ring is released from the holder by applying a twisting action of a central portion of the holder, and disengaging the outer clamping or clamshell structures  223 . The outer clamping or clamshell structures  223 , once disengaged, may move freely and release the ring  221 . Other known release and clamping mechanisms may also be used. 
     Clamping and other methods used to secure the ring into the holder may be combined with other retaining means.  FIG. 23   a  shows ring  231  secured to holder  232  using clamp-like structures  233 . Clamp-like structures  233  may comprise a variety of materials including thread, cloth, metallic, and/or plastic, among others. The clamp-like structure  233  may be held in place by suture thread  234 . Clamp-like structure  233  may be released by cutting suture thread  234 .  FIG. 23   b  shows ring  231  secured to holder  232  using a non-thread wrap  235 . Non-thread wrap  235  may be of any of a variety of materials, and may be wrapped around either or both of ring  231  and holder  232 . As previously described in the context of suture thread holders, non-thread wrap  235  may be wrapped a single time around ring  231  and/or holder  232 , or looped multiple times around either or both structures. 
     Other holder architectures may also be used.  FIG. 24  shows a sheath holder including a tube structure  242  which fits around annuloplasty ring  241 , and which can slide on and off of annuloplasty ring  241 . The sheath holder may be used with either a C-shaped ring or a gapped full-ring, a gap being required to allow the sheath holder to be removed from the ring. Tube structure  242  may be rigid, to help maintain the shape of the ring. Alternatively, tube structure  242  may be flexible or unshaped. Such a flexible holder may be especially useful in minimally invasive surgery, in which the annuloplasty ring and holder may have to be implanted through an implantation catheter. A flexible holder may permit the physician to collapse the ring and holder into the implantation catheter, in order to bring them to the implantation site. The ring and holder assembly may regain its shape once withdrawn from the implantation catheter at or near the implantation site. During implantation of a ring mounted in a sheath holder, the ring may have to be withdrawn from the holder before suturing the ring at its implant site. The suturing may be done after removal of the holder. The suturing may also be done as the sheath holder is withdrawn, so as to keep un-sutured portions of the ring secured and supported in the holder while sutures are tied to exposed portions of the ring. 
     E. Pre-Stitched Sutures 
     Annuloplasty rings mounted on holders such as the holders described herein may be mounted with pre-stitched sutures.  FIG. 25   a  shows ring  251  attached to holder  250 , with pre-stitched suture threads  252  extending from suture needles  253  through ring  251 . The use of pre-stitched sutures  252  and needles  253  may facilitate and accelerate the suturing of the ring at the implant site. Their use may also allow for better alignment and spacing of the sutures, ensuring better placement of the ring. Anti-entanglement features may be incorporated with the pre-stitched sutures. Suture threads  252  may pass through holder  250 , or may be used to secure or hold ring  251  to holder  250 . Suture threads  252  may also not pass through holder  250 , and may not be used to secure ring  251  to holder  250 .  FIG. 25   b  shows ring  251  sutured at the implant site by sutures  253 . Sutures  253  may be tied while ring  251  is still attached to holder  250 , or after the holder is removed from the ring.