Disposable holder for prosthetic heart valve
BACKGROUND OF THE INVENTION 
     A common surgical technique currently available is the complete replacement of a malfunctioning or damaged human heart valve with a prosthetic valve. While the mortality rate for such replacement has improved considerably over the last few years, certain dangers still exist. For example, there is a recognized incidence of failure of these operations due to the trauma occasioned by the replacement operation itself. For most prosthetic heart valves, the suturing of the valve in place requires an extended period of time during which extra-corporeal perfusion and coronary-pulmonary bypass is necessary. 
     Typically, the prosthetic heart valve is provided with a suture ring, generally made from a cloth material or some other biologically compatible material, which is used in suturing the heart valve in position within the heart. The valve is secured by sutures connecting the sewing ring to the tissue surrounding the valvular orifice. The surgeon or an assistant typically holds the prosthesis in position during the suturing operation, by use of a holding device which engages the body of the valve. 
     Once the prosthetic heart valve is in place, it sometimes becomes necessary to rotate or reposition the valve. This is generally accomplished by reattaching the holder to the valve and rotating the holder. 
     Reusable holding devices, although extensively used for holding the heart valve during the suturing procedure, all suffer from several problems. Thus, they require a considerable amount of time for the surgeon both to premount the prosthesis on them, and, if necessary, reattach the holder during the surgical procedure. These holders generally comprise complex mechanisms in which an advancing screw thread causes two or more fingers to spread apart and engage a surface of the prosthetic heart valve. Numerous turns of the screw mechanism are usually required, depending upon the size of the valve being mounted on the holder. The surgeon is also required to position the holder on the heart valve in the proper orientation, whether it be aortic or mitral. If the holder is attached to the valve incorrectly or in the improper orientation, valuable time is lost which increases the risk to the patient. 
     Furthermore, the reusable heart valve holders have to be cleaned and sterilized after each operation, adding to the expense of a very expensive operation. Moreover, after many uses, there is a danger that the holder will malfunction, damage the valve, or even completely fail. A broken-off piece of the holder could cause severe injury to the patient or death. At best, a serious time delay will result with further danger to the patient. 
     Various types of disposable holders are currently available which, because they are prepositioned on the heart valve prior to surgery, overcome many of the disadvantages of the prior art reusable holders. However, no known prior art holder provides the ease of removal and reattachment coupled with the inexpensive manufacturability of valve holders constructed in accordance with this invention. 
     SUMMARY OF THE INVENTION 
     The prosthetic heart valve holder of the present invention overcomes the problems and disadvantages of the prior art by providing a disposable, single-piece holder having arms that are resiliently prepositioned on the valve body. 
     In addition, if reattachment is necessary in order to reorient the valve, this process is greatly facilitated by the ease with which the flexible, resilient arms of the holder are engaged on the valve. The holder has a narrow profile and is not an obstruction to the suturing process. 
     The present holder comprises a base or body portion having means for threadedly receiving a handle. Extending from and integral with the base are two flexible fingers which are biased in opposite directions when engaged within the interior portion of the annular valve ring. The resiliency of the fingers securely holds the heart valve ring in small retainers or detents provided near the distal ends of the fingers. In order to detach the holder from the valve, the surgeon simply manually depresses or squeezes the two fingers together slightly and removes the holder. Preferably, the holder is rotated about the shorter, more rigid finger. The longer, more flexible finger is provided with a tapered leading edge to facilitate reattachment. This longer finger is removed first during removal and is attached last during reattachment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of the heart valve holder of the present invention and a typical prosthetic heart valve on which the holder may be prepositioned; and 
     FIG. 2 is a partial cross-sectional side view of the holder of the present invention, illustrating an attached prosthetic heart valve in phantom. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the heart valve holder 10 of the present invention comes preattached to a prosthetic heart valve 12, FIG. 1 illustrates these elements in exploded position for ease of illustration and description. 
     The prosthetic heart valve 12 shown in FIG. 1 is of a discoid or poppet type, although the present invention can be successfully utilized with any heart valve prosthesis. The discoid valve 12 shown comprises a main body portion or valve ring 14 which is surrounded by an annular suture ring 16 comprised, in this case, of a cloth material. The suture ring 16 is used for the actual attachment of the heart valve 12 to its orifice (not shown). The valve 12 also comprises a pair of opposite hinge members, 18 and 20, which have dual strut supports. The poppet disc 22, which is shown in the open position in FIG. 1, opens and closes in response to blood pressure using the hinge members 18 and 20 as camming surfaces. Discoid valves of similar construction are disclosed and claimed in U.S. Pat. Nos. 3,824,629 issued July 23, 1974, to Donald P. Shiley and 4,057,857 issued Nov. 15, 1977 to Bruce E. Fettel, both being assigned to Shiley, Inc., assignee of the present invention. 
     The heart valve holder 10 of the present invention is illustrated in FIGS. 1 and 2. The holder 10 is a generally U-shaped device comprising a base portion or shoulder 24 with a pair of fingers 26 and 28 extending integrally and generally parallel from opposite ends of the shoulder 24. Located near the distal end of each finger 26 and 28 is a small detent 30 which engages the interior surface 32 of the annular valve ring 14 in order to hold it in position during suturing. The shoulder 24 is provided with a threaded hole 34 to receive a handle 36 for facilitating the holding of the valve 12 during suturing. The handle 36 is not shown in FIG. 1 and is shown partially in phantom in FIG. 2. Each finger 26 and 28 is also provided with a serrated, indented grip 38 which is located proximal of the detents 30 and provides a convenient location for the manual manipulation of the fingers 26 and 28 in order to remove the holder 10 from the valve 12 or reattach it, if necessary. The holder 10 can be constructed from any suitable material and in accordance with any suitable process, preferably by the injection-molding of a polypropylene acetal material. 
     The shorter finger 26 of the holder 10 has a forked end 40 which is inserted between the dual struts of the smaller hinge member 20. The central groove 42 forming the fork in the end 40 is for engagement with heart valves having single-strut hinge members (not shown) and is for use in connection with valves of that construction. Thus, regardless of the strut configuration of the valve, the forked-end finger 26 provides snug engagement with the valve ring in the event that rotation of the valve is necessary after implantation. The longer finger 28 advantageously is provided with a sloped and tapered leading edge 44 in order to facilitate reattachment as described in more detail below. 
     The heart valve holder 10 of the present invention is sized to fit the heart valve in order to provide a narrow profile such that the shoulder and legs do not extend beyond the outer diameter of the prosthetic valve, thus facilitating attachment of the valve in its orifice. Furthermore, the holder 10 itself is of a narrow width (indicated in FIG. 1 as the dimension W) so as to not significantly obstruct the suturing process and to avoid the entanglement of sutures. Advantageously the width W decreases as the size of the holder 10 decreases. Moreover, the holder 10 is preferably constructed from a clear polymer material so that it also does not create a visual obstruction to suturing. Preferably, the width W ranges from 0.300 in. to 0.460 in. depending on the size of the holder 10, while maintaining the desired degree of flexibility in the fingers 26 and 28. 
     In its relaxed state, shown in FIG. 1, the holder 10 is sized such that the distance D separating the detents 30 is greater than the inner diameter of the valve ring 14. In addition, the fingers 26 and 28 are sufficiently flexible so that when engaged with the valve ring 14, as shown in FIG. 2, the fingers 26 and 28 exert a resilient force and are biased in opposite directions against the valve ring 14 in order to hold it securely in the detents 30. 
     After the prosthetic valve has been sutured in place, the holder 10 is preferably removed by a rotational movement using the detent 30 of the smaller finger 26 as the axis of rotation. In other words, the longer finger 28 is depressed slightly at an approximate force of 11/2 pounds so that it slips freely within the inner surface of the valve ring 14. The entire holder 10 is then rotated about the detent 30 of the small finger 26 so that the tapered end 44 of the larger finger 28 clears the valve ring 14. The shorter finger 26 can then be removed from the valve 12. Although removal and reattachment can also be accomplished by simultaneously depressing both fingers 26 and 28 slightly until they slip freely within the inner surface of the valve 12, the rotational removal movement described above avoids any serious trauma to the patient in whom the valve 12 has just been implanted. Reattachment of the holder 10, if necessary, in order to reposition the valve 12, is accomplished by a reverse process. The detent 30 of the smaller finger 26 is attached first to the valve 12 followed by the rotation of the holder 10 until the detent 30 of the longer finger 28 locks or snaps into place on the valve ring 14. Thus, the smaller finger 26 serves as a hinge or pivot for the snapping engagement of the longer finger 28 on the valve ring 14. 
     In order to facilitate removal and reattachment, the longer finger 28 is provided with a gently sloping, tapered leading edge 44. Thus, during removal, even if the force on the upper finger 28 is relaxed so that the tapered portion 44 engages the ring 14, it will still slip free of the ring 14 with very little friction. The tapered portion 44 is smooth and does not have any sharp or abrupt edges which could catch on the valve ring 14. Similarly, during reattachment, the tapered leading edge 44 of the longer finger 28 will permit it to slip into position within the valve ring 14 even if sufficient force has not been applied to depress the finger 28. 
     In order to facilitate removal and reattachment of the present holder in accordance with the rotational movement described above, the longer finger 28 is also advantageously constructed to be more flexible than the shorter finger 26 about which rotation is accomplished. Such enhanced flexibility is accomplished, in part, by the additional length of the longer finger 28 which makes it inherently more flexible. In addition, the distance X from the center line of the holder 10 to the longer finger 28 is slightly greater than the distance Y from the center line to the shorter finger 26, as illustrated in FIG. 2. This additional distance increases the flexibility of the longer finger 28. Of course, the amount by which the distance X exceeds the distance Y will depend upon the size of the valve for which the holder is constructed. However, generally X will exceed Y by a distance in the range of one to fifteen percent (1-15%) of the total distance (X plus Y) separating the two fingers 26 and 28. Moreover, increased flexibility is further achieved by a longer finger 28 which is slightly thinner than the shorter finger 26 in the plane shown in FIG. 2. 
     As described above, a significant advantage of the present invention is that the holder 10 comes preattached to the valve 12 in the correct position for implantation. In FIG. 2, the valve 12 is shown in phantom in the aortic position; however, the holder 10 of the present invention can advantageously also hold the valve 12 in the reverse or mitral position. Thus, there is no time wasted while the surgeon attaches the holder to the valve. Furthermore, the surgeon is not relieved upon to attach the holder in the correct position, either aortic or mitral. If reattachment becomes necessary, this is quickly and easily accomplished by the flexible finger construction of the present holder. Furthermore, the holder of the present invention is inexpensive to manufacture and is disposable, eliminating any risk of failure due to reuse.