Abstract:
A holding device for a tricuspid prosthetic tissue heart valve which permits the commissure support struts to be drawn toward one another by increasing the tension on the threads which attach the holder to the valve. The resulting tapered valve configuration facilitates valve insertion and reduces the possibility of damaging the valve tissue during implantation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to prosthetic heart valves and more particularly to a device for holding and positioning the heart valve during surgical implantation. 
     2. Description of Prior Art 
     Natural heart valves taken from animals, particularly porcine heart valves, have been widely used for several years in the replacement of diseased valves in humans. The porcine valve suitably treated with gluteraldehyde or other fixative solution is mounted on a cloth covered stent or supporting framework prior to implantation. The stent is typically an open cylindrical device having a gently scalloped base curve and three axially extending commissure support struts adapted to support the margins of the valve cusps as illustrated in U.S. Pat. No. 3,570,014. The stent is constructed of metal or plastic, covered with a cloth material, and provided with a circumferential sewing cushion extending outward from the base. 
     To facilitate handling of the valve during implantation, valve manufacturers have provided various valve holding devices which attach to the valve and allow the surgeon to more easily place the mounting sutures and position the valve in the original valve annulus. Once the valve and sutures are in position, the valve holder is detached from the valve and the surgical implantation procedure is completed. 
     Valve holders of the prior art consist in general of a support member sutured to the sewing cushion of the valve and an elongated handle which attaches to the support member by screw threads or other suitable means. The valve holder is separated from the valve by cutting the attaching sutures and withdrawing the handle and support member from the operating area. The handle may optionally include an elbow or other means to permit the valve to be angled relative to the main axis of the handle. 
     In mitral and tricuspid valve replacement, the prosthetic valve is inserted into position with the cusps directed away from the surgeon. In this position the cusps of the valve are subject to damage from snagging in the surrounding anatomical profile as the valve is moved into position and difficulty is sometimes encountered in inserting the valve into the original valve annulus. The mounting sutures are also suseptible to looping over the commissure posts as the valve is moved into position. Even with the aid of a valve holder, placing the valve in position is a sensitive and delicate procedure. 
     It is accordingly an object of the present invention to provide a valve holder for natural tissue prosthetic heart valves. It is a further object of this invention to provide a holder for mitral and tricuspid valves which facilitates the positioning of the valve within the original valve annulus. It is a yet further object of the present invention to provide a valve holder which permits the commissure support struts of the valve stent to be drawn toward one another prior to placement of the valve, thereby reducing the diameter of the leading portion of the valve and the possibility of snagging the valve cusps and damaging the delicate valve tissue. These and other objects of the invention will be apparent from the ensuing description and claims. 
     SUMMARY 
     The valve holder of the present invention consists of a central support member having three spaced valve support legs extending radially therefrom. A foot at the distal end of each leg is provided with thread guiding and attaching means. The central support member is provided with thread collecting means. 
     The valve holder is positioned on the sewing cushion of the valve stent with the legs of the holder in registry with the commissure support struts. The foot of each support leg is secured to the sewing cushion by means of retention threads which are placed through the valve holder and valve stent as follows. 
     The free end of one thread which is preferably a size 4-0 braided polyester suture is secured to the thread collection means of the central support member and passed through the guide means in the foot of one valve support leg and on through the underlying sewing cushion of the stent. The thread proceeds through the fabric cover at the tip of the proximate commissure support strut, across the valve orifice area to the tip of an adjacent commissure support strut, through the fabric cover at the tip of said strut and thence through the sewing cushion and overlying foot of the corresponding adjacent valve support leg. The end of the suture is thereupon attached to the foot of that support leg. The procedure is repeated with two additional sutures which are attached respectively to the remaining two suture legs. 
     When all of the sutures have been placed as described above, the valve holder may be drawn tightly against the sewing cushion of the stent by activating the thread collecting means to take up any slack in the sutures. Further activation of the thread collecting means will result in increased tension on the sutures with the tips of the commissure support struts being drawn inward to impart a tapered configuration to the valve. This taper permits the valve to be guided-into the original valve annulus more easily and with minimum danger of snagging or damaging the delicate valve cusp tissue. The retention threads extending across the valve orifice area between commissure support struts also reduce the possibility of the mounting sutures looping over the struts. 
     Once the valve is positioned in the annulus of the patient and the surgeon is ready to remove the valve holder, each retention thread is cut at the point between the foot of the valve support leg and the central support area. As the threads are cut, the commissure support struts are released from the restraints imposed by the threads and return to their normal configuration. The valve holder and handle are then separated from the valve with the loose ends of each thread remaining attached to the valve holder and being withdrawn from the valve as the holder is removed. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view in perspective of the valve holder of the present invention attached to a mitral heart valve stent. 
         FIG. 2  is a plan top view in partial section of the valve holder of  FIG. 1 . 
         FIG. 3  is a side elevation view in cross section through the valve holder of  FIG. 2  taken on line  3 — 3 . 
         FIG. 4  is a top plan view of the thread collecting means utilized in the valve holder of  FIG. 1 . 
         FIG. 5  is a side elevation view in cross section of the thread collecting means of  FIG. 4  taken through line  5 — 5 . 
         FIG. 6  is a partial side elevation view in cross section of the valve holder and stent of  FIG. 1  taken through one leg thereof. 
         FIG. 7  is a schematic view in perspective of the suture configuration securing the valve holder to the valve stent as illustrated in  FIG. 1 . 
         FIG. 8  is an enlarged top plan view of an alternate foot configuration for a valve support leg. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , there is illustrated valve holder  10  attached to the sewing cushion  11  of valve stent  12 . For clarity of illustration, the porcine tissue valve ordinarily mounted within the confines of the stent has been omitted from the drawings. Handle  13 ′ shown in part is attachable to the valve holder by means of screw threads  14 . 
     Valve holder  10  consists of a central support member  15  and three valve support legs  16  (two visible in  FIG. 1 ) extending radially outward from the central support member. Each leg terminates in a foot  17  which includes thread guide and attachment means  25  in the form of a circular opening. Central support member  15  consists of a cylindrical structure having one open end facing stent  12  and terminating at the other end in coaxial hub  18  extending outward from annular flange  19 . Positioned within the confines of the central support member is thread collecting disc  20  which includes stub axle  28  extending into hub  18  as illustrated in detail in  FIGS. 4-6 . 
     With further reference to  FIG. 1 , threads  22  are secured at one end to the thread collecting disc housed within the confines of the central support member and pass outward through windows  21  in the wall of member  15 . Each thread passes through a guide means  25  in foot  17  of each respective valve support leg and thence through the underlying sewing cushion of the valve stent. Each thread continues to the tip or apex of the proximate commissure support strut where it passes briefly through cloth cover  23  and thereafter across the valley between commissure support struts to the next adjacent strut. The thread passes through the cloth cover at the tip of the adjacent commissure support strut and thence through the sewing cushion and foot portion of the overlying valve support leg, whereupon it is secured to the foot of said leg at thread attaching means  25 . 
     Thread guide and attaching means  25  in the foot of each valve support leg is more clearly illustrated in  FIG. 2  which is a top plan view of the valve holder of  FIG. 1 , and  FIG. 3  which is a cross section of  FIG. 2 . In the illustrated embodiment, openings  25  extend into outwardly facing channels (or angled slot)  26  in the leg portion immediately adjacent the foot, and such channels  26  are effective to guide the threads over the knee of the leg. 
     The inner wall of central support cylinder  15  preferably includes a ratchet surface as illustrated in  FIG. 2  which, in cooperation with a pawl on the thread collection means, permits rotation of the collection means in only one direction. This construction is most clearly illustrated in  FIGS. 2 and 3  where the ratchet surface is indicated at  24 . 
     Referring now to  FIGS. 4 and 5 , thread collecting means  20  is illustrated in detail and consists of a base plate  27  having stub axle  28  extending from one side thereof. Base plate  27  is further provided with pawl  33  which in the assembled valve holder engages ratchet teeth  24  to restrict rotation of the thread collection device. Base plate  27  is further provided with drill holes  32  as means for attaching one end of threads  22 . 
     Also illustrated in  FIGS. 2 and 3  are circumferential cleats  37  extending from the inner wall of hub  18 , which in cooperation with a circumferential groove in the stub axle of the thread collecting disc, provide a snap fit to restrain the disc against axial displacement while permitting free rotation. The circumferential groove of the axle  28  is indicated at  29  in  FIG. 5  which is a cross section through the center of the thread collecting device. Axle  28  is further provided with threaded drill hole  31  adapted to receive the screw threads of handle  13  as illustrated in  FIG. 1 . 
     The assembled valve holder is illustrated in cross section in  FIG. 6  which further illustrates the path of threads  22  proceeding from the central support area through the thread guide means in the foot of each leg of the valve holder and thence through the sewing cushion and cloth covering at the tip of the commissure support struts. The two threads illustrated in  FIG. 6  are, as explained above, two of three individual threads used to attach the valve holder to the valve stent. The configuration of the three threads in the assembled device is illustrated schematically in  FIG. 7  where X indicates the end of the thread tied to the foot of the valve support leg and indicates the end of the thread attached to the thread collection device. 
     The thread guide and attaching means in the foot of each valve support leg may be a simple drill hole as illustrated in  FIG. 2  or a channelled opening as illustrated at  34  in  FIG. 8 . 
     The retention thread configuration as described and illustrated above results in the tips of the stent commissure support struts being drawn together as the thread collection device is rotated to wind one end of each thread around stub axle  28 . By thus reducing the spread of the commissure support struts, placement of the valve in a confined area is facilitated and the possibility of damaging the delicate tissue of the valve mounted within the confutes of the stent is reduced. To release the valve after it is positioned within the valve annulus, each thread is cut at a convenient spot over the valve support leg. As the thread tension is released the commissure support struts return to their normal spread. The threads passing through the valve stent remain securely attached to the valve support legs and the cut ends are withdrawn from the stent as the holder is removed from the area. 
     The preceding description and drawings are to a specific preferred embodiment of the present invention and are not for purposes of limitation. The key element of the present invention resides in the combination of the valve holder and the attaching threads which permit the threads to be collected by the valve holder in order to draw the tips of the commissure support struts toward each other and provide a tapered valve configuration.