Abstract:
A synthetic blood vessel graft (e.g., for use with a prosthetic heart valve) includes a mounting cuff adjacent at least one end for facilitating attachment of the graft to another structure (e.g., a sewing cuff of a heart valve). The mounting cuff may be sized and shaped to provide good conformance to the target structure to which it may be attached (e.g., the heart valve sewing cuff). The graft is preferably preclotted. Especially for use with a tissue valve (which must be supplied in a packaging solution that would react with a preclotting agent), the graft is preferably supplied separately from the valve.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to synthetic blood vessel grafts. Although the invention also has other possible uses, the invention is particularly useful in conjunction with artificial heart valves. 
   The use of a composite valved graft is an established treatment for patients with aortic valve disease and ascending aortic aneurysms. It is preferred to have the graft part of the composite device supplied “preclotted” or pre-sealed. Having a pre-sealed graft not only eliminates the need for preclotting during surgery, it also tends to reduce the possibility of post-implantation bleeding, because the manufacturing process for pre-sealing can be carried out more consistently to reliably provide an adequate seal. The material used to seal the graft is hydrolysable, so that after implantation the sealant will be degraded and removed to allow the host tissue to grow into the graft to stabilize it and to cover the graft to form an ideal blood-contacting surface. 
   Because of the benefits of a preclotted graft, most mechanical valved grafts that are commercially available today are supplied with the graft pre-sealed. However, for a composite device that includes a valve made of tissue, the graft is not preclotted because the valve needs to be stored in a solution to prevent the tissue from dehydration. The material that would be used to preseal the graft portion of the device would react undesirably with the packaging solution. Therefore, for a Bentall procedure (replacement of aortic valve and adjacent section of the aorta) using a tissue valve, the surgeon has to either seal the graft portion of a composite device using the patient&#39;s blood, or construct a composite device using a tissue valve and a preclotted graft that are supplied separately. For the latter case, the available preclotted grafts are basically straight tubes that need to be carefully attached to the tissue valve to provide a structurally stable interface and adequately prevent blood leakage. 
   In view of the foregoing, it is an object of this invention to provide improved preclotted synthetic grafts, especially for use in conjunction with artificial heart valves, and most especially with tissue heart valves. 
   SUMMARY OF THE INVENTION 
   This and other objects of the invention are accomplished in accordance with the invention by providing a preclotted graft with a mounting cuff on at least one end of the graft. The mounting cuff can be used to more easily attach the graft to an artificial heart valve (e.g., a tissue valve) to form a leak-tight interface. The mounting cuff can also include features to facilitate quicker and more reliable attachment to an artificial heart valve, especially when the graft is to be used with a specific valve. Such a graft can be used with a tissue valve to more easily form a composite device for a Bentall procedure. Or the graft can be used with a mechanical valve when a composite device with the desired mechanical valve is not available. The mounting cuff(s) on the graft can also be designed for other applications where there is a need to attach the graft to another device, component, or portion of the patient&#39;s anatomy to ease the attachment process and enhance the attachment integrity. 
   Further features of the invention, its nature and various advantages, will be more apparent form the accompanying drawings and the following detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a simplified elevational view of an illustrative prosthetic, artificial heart valve that can be used with a synthetic graft in accordance with the invention. 
       FIG. 2  is another view of the valve shown in  FIG. 1 . 
       FIG. 3  is a simplified perspective view of an illustrative embodiment of a synthetic graft in accordance with the invention. 
       FIG. 4  is similar to  FIG. 3 , but shows the graft associated with an illustrative prosthetic heart valve in accordance with the invention. 
       FIG. 5  is a simplified perspective view of another illustrative embodiment of a synthetic graft in accordance with the invention. 
       FIG. 6  is similar to  FIG. 5 , but shows the graft associated with an illustrative prosthetic heart valve in accordance with the invention. 
       FIG. 7  is a simplified depiction of the  FIG. 3  graft in an illustrative storage container in accordance with the invention. 
       FIG. 8  is a simplified depiction of the  FIG. 5  graft in an illustrative storage container in accordance with the invention. 
       FIG. 9  is a simplified elevational view showing an illustrative implant that includes multiple synthetic grafts in accordance with the invention. 
   

   DETAILED DESCRIPTION 
   An illustrative prosthetic, artificial heart valve  10  that can be used with a synthetic graft in accordance with the invention is shown in  FIGS. 1 and 2 . Valve  10  is a tissue valve with a sewing cuff  20  around the outside of the valve. Sewing cuff  20  extends radially outward from the remainder of the valve, and it also extends annularly all the way around the valve. Unlike most of the remainder of the valve, sewing cuff  20  is typically made of synthetic material rather than tissue. For example, sewing cuff  20  may include an outer layer of knitted or woven dacron fabric or other similar material. The remaining radially outer surface of valve  10  may also be covered with such fabric. But the inner, actually operating portions of valve  10  are tissue. Sewing cuff  20  is used for suturing the valve into the patient. For example, sutures (not shown) are typically passed through sewing cuff  20  into adjacent living tissue of the patient (e.g., the annulus of the patient&#39;s heart valve that remains after the native heart valve leaflets have been excised). 
   It will be noted that sewing cuff  20  is scalloped, i.e., it rises adjacent each of the three commissure posts of the valve (radially inside the dark marks  12  on valve  10 ), and it falls between each adjacent pair of commissures. This may be done so that the cuff  20  will more closely follow the patient&#39;s native valve annulus, which is also typically scalloped in this same general way. 
     FIG. 3  shows a first illustrative embodiment of a synthetic graft  100  in accordance with the invention. Graft  100  is basically a hollow tube  110  with a first mounting cuff  120  at one end and a second mounting cuff  130  at the other end. Graft  100  may basically be made of woven or knitted, biocompatible fabric such as dacron. Each of cuffs  120  and  130  may also include such fabric. Each cuff may be given additional bulk by forming a roll of the fabric, by enclosing another body such as a biocompatible string in an outer layer of the fabric, or by any other suitable means. Each mounting cuff  120  and  130  preferably extends annularly all the way around the adjacent end of the tube  110 , and each cuff  120  and  130  also preferably extends radially outward from the adjacent portion of the tube. 
   Graft  100  is intended for use with valve  10 . Accordingly, the end of graft  100  adjacent to mounting cuff  120  is sized and shaped to fit around the outside of the portion of valve  10  that is above sewing cuff  20  in  FIGS. 1 and 2 .  FIG. 4  shows valve  10  and graft  100  after they have been put together in this way. Mounting cuff  120  is scalloped in the same way that sewing cuff  20  is scalloped. Accordingly, mounting cuff  120  closely follows sewing cuff  20  all the way around combined structures  10  and  100 . The two cuffs  20  and  120  may be similar in size, i.e., they may be at similar radial distance from a longitudinal axis which passes centrally through assembled elements  10  and  100 . In addition, cuffs  20  and  120  may have the same basic scalloped shape (i.e., the same number and size of scallops in the same general locations) so that when cuffs  20  and  120  are put together as shown in  FIG. 4 , they are congruent to one another or abut one another all the way around the assembly of elements  10  and  100 . 
   If desired, elements  10  and  100  can be sutured together in the condition shown in  FIG. 4  to produce a composite device. This can be done, for example, with sutures that are passed through and between both of cuffs  20  and  120 . The resulting composite device can then be sutured into a patient, e.g., by passing more sutures through cuffs  20  and  120  and adjacent tissue of the patient. Alternatively, valve  10  can first be sutured into the patient separately, e.g., by passing sutures through sewing cuff  20  and adjacent tissue of the patient. Thereafter, graft  100  can be added, e.g., by passing additional sutures through cuff  120  and at least cuff  20 . In either case, the other end of graft  100  is ultimately attached to another portion of the patient&#39;s anatomy (e.g., healthy aorta tissue) using cuff  130  (e.g., by passing additional sutures through cuff  130  and adjacent native tissue). In whatever way that elements  10  and  100  are used together, the congruency of cuffs  20  and  120  facilitates putting them together in a secure and blood-tight implant. 
     FIG. 5  shows another illustrative embodiment of a synthetic graft  200  in accordance with the invention. Once again, graft  200  is basically a hollow tube  210 . In this embodiment, however, the graft has a mounting cuff  220  at only one of its ends. The other end is basically straight, i.e., without a cuff. Closely adjacent to cuff  220 , graft  200  bulges radially outwardly as shown at  250 . 
   In the embodiment shown in  FIG. 5  mounting cuff  220  is basically straight (i.e., it is not scalloped like mounting cuff  120  in  FIGS. 3 and 4 ). Accordingly, graft  200  is adapted for use with a valve that has a straight cuff.  FIG. 6  shows how graft  200  may be put together with a valve  60  having a straight cuff  70 .  FIG. 6  is generally similar to  FIG. 4 , except that in  FIG. 6  cuffs  70  are  220  are both straight. Again, because both cuffs  70  and  220  have the same basic size and shape, they are congruent to one another when elements  60  and  200  are put together as shown in  FIG. 6 . This basic congruency of cuffs  70  and  220  means that they closely follow one another all the way around an assembly of elements  60  and  200 . Once again, this facilitates secure and blood-tight implantation of elements  60  and  200  together. As in the case of the earlier embodiment, elements  60  and  200  can first be put together as a composite device, which is then implanted. Or valve  60  can first be implanted, and then element  200  can be added over the implanted valve. With either approach, the other (uncuffed) end of graft  200  (remote from cuff  220 ) is ultimately connected to other tissue of the patient (e.g., healthy aorta tissue). 
   Because the grafts (e.g.,  100 ,  200 ) of this invention can be supplied separately from valves (e.g.,  10 ,  60 ) with which they may be used, the grafts of this invention can be supplied preclotted regardless of the type of valve with which they may be used. Any suitable preclotting substance (e.g., collagen or gelatin) can be used. The preclotting can be part of the process of manufacturing the graft. In this way very high-quality (i.e., gap- and defect-free) preclotting can be achieved. Then the preclotted graft can be packaged and stored for later use. For example, typical packaging for such a preclotted graft is sterile and dry, so that there is nothing to react with and degrade the preclotting agent during what may be a prolonged period of storage prior to use. When it is desired to use the graft (e.g., with a tissue valve), the graft is removed from its packaging and for the first time associated with the valve. Just prior to such association, the valve has typically been removed from its separate packaging. Thus the valve (assumed in this example to be a tissue valve) can be stored wet in a packaging solution. Because the graft is not associated with the valve until the valve is out of its packaging solution, this avoids any possible adverse effect of the valve packaging solution on the graft (especially the preclotting of the graft). 
   Although the example immediately above assumes use of a graft of this invention with a tissue valve, the grafts of this invention are equally usable with mechanical valves. For example, when a composite device with a desired mechanical valve is not available, an initially separate graft in accordance with this invention can be put together with that desired mechanical valve. Similarly, the mounting cuffs (e.g.,  120 ,  130 ,  220 ) on grafts in accordance with the invention can be designed (e.g., shaped and/or sized) for other applications and placed on the graft at any location where there is a need to attach the graft to another device, component, or portion of the patient&#39;s anatomy. Among the benefits of such a purpose-designed mounting cuff is that it eases the attachment process and enhances the attachment integrity. 
     FIGS. 7 and 8  illustrate the point that the grafts of this invention (e.g.,  100 ,  200 ) may be stored and supplied to a surgeon for use in storage containers or packages  300  or  400 . Containers  300 / 400  preferably enclose the graft and keep it sterile until it is ready to be used by a surgeon. Then the surgeon opens the container  300 / 400 , removes the graft (e.g.,  100  or  200 ), and uses it (e.g., in association with a prosthetic heart valve) as described earlier in this specification. The graft is preferably already preclotted when it is initially placed in the container as part of the graft manufacturing process. The environment in the container is preferably such as to have no adverse effect on the preclotting or the preclotting agent during what may be relatively long storage time. Note that no valve is present in the storage container ( 300  or  400 ) with the graft. Any valve is preferably supplied separately (e.g., in a separate container, which can hold the valve in a different environment than is used for the graft). 
     FIG. 9  shows an example of use of instances of synthetic blood vessel grafts in accordance with the invention. In  FIG. 9  a first synthetic graft  510  has mounting cuffs  512  and  514  adjacent its respective opposite axial ends. Synthetic graft  520  has mounting cuffs  522  and  524  adjacent its respective opposite axial ends. Synthetic graft  530  has mounting cuff  532  adjacent at least one of its axial ends. 
   The assembly shown in  FIG. 9  is an apico-aortic conduit that connects the apex of the heart to the descending aorta. In use, the surgeon cuts a hole in the apex of the heart and connects the proximal end  512  of the valved graft to the opening. The distal end of the device (not shown) can be either cuffed or uncuffed and is attached to healthy aorta tissue. 
   Graft  510  is attached to heart  500  using mounting cuff  512 . Prosthetic valve  540  (e.g., similar to any of the previously described prosthetic valves and having sewing cuff  542 ) is connected between grafts  510  and  520 . In particular, the sewing cuff  542  of valve  540  is sandwiched between the mounting cuffs  514  and  522  of grafts  510  and  520 , respectively. The actual operating (leaflet) portion of valve  540  is inside graft  520  near mounting cuff  522 . Graft  530  is attached to the end of graft  520  that is remote from valve  540 . In particular, mounting cuffs  524  and  532  are used to make this attachment. As has already been said, the distal end of graft  530 , which is not shown and which can be either cuffed or uncuffed, is attached to healthy aorta tissue of the patient. The valved graft assembly shown in  FIG. 9  provides a low-resistance bypass for the blood in the ventricle to go out to supply the body. 
     FIG. 9  further illustrates the point that a synthetic graft in accordance with the invention can be intended for use in a specific anatomical location in a patient. For that purpose the graft can be sized and shaped to mate with features of the patient&#39;s anatomy at or adjacent to that location. For example, one or both mounting cuffs of the graft can be sized and shaped for congruence with anatomical features of the patient. As just one illustration of this in the context of  FIG. 9 , mounting cuff  512  can be sized and shaped for congruence with heart tissue. 
   It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. For example, the particular type of tissue valve  10  shown in  FIGS. 1 and 2  is only one of many different types of tissue and mechanical valves with which the grafts of this invention can be used. References herein to artificial heart valves or to prosthetic heart valves are not intended to limit the structures thus mentioned to valves that are necessarily used in the heart. Some such valves may be used adjacent to the heart or otherwise in aid of the functioning of the heart. For example,  FIG. 9  shows such a valve  540  at a location that is somewhat spaced from heart  500  per se. As another example of modifications within the scope of the invention, alternatives to the suturing mentioned herein are well known and can be used if desired. Examples of such alternatives are staples, hooks, and the like. The invention is not limited to straight grafts. Rather, the invention can be applied to grafts having many different configurations such as Y-shaped grafts and grafts with a central portion from which one or more side branches extend. A mounting cuff in accordance with this invention can be provided adjacent an otherwise free end of any one or more tubular portions of such non-straight grafts.