Abstract:
A valve prosthesis includes a flexible plug and an annular bearing reinforcement which is embodied such that it is radially rigid and surgically implantable in the area of a heart valve. The valve prosthesis is provided with an interchangeable prosthetic valve, is independent of the bearing reinforcement, endoluminally placeable and includes a tubular support which is radially deformable between a folded setting position and an unfolded position for implanting into a bearing structure and the flexible plug connected to a tubular support. The bearing reinforcement forms an annular support devoid of any plug capable of univocally limiting a blood flow circulation.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a valve prosthesis to be put into place by an endoluminal approach. The prosthesis is the type comprising a flexible shutter and an annular carrier structure that is radially rigid and suitable for being surgically implanted at the location of a heart valve. 
   The heart comprises two atriums and two ventricles which are separated by valves. Valves are also present at the outlets from the right ventricle (pulmonary valve) and from the left ventricle (aortic valve). 
   These valves ensure that blood flows in one direction only, avoiding reflux of blood at the end of ventricular contraction. 
   Valves can suffer diseases. In particular, they can suffer from poor opening, thus reducing the flow of blood, or from being somewhat leaky, thus allowing a reflux or regurgitation of blood back into the ventricle that has just expelled it. 
   These regurgitation problems lead to abnormal expansion of the ventricle thereby producing, in the long run, heart failure. 
   It is known to treat that type of disease surgically, by replacing the diseased valve. Diseased valves, and in particular the aortic valve at the outlet from the left ventricle, are replaced by valves taken from a deceased subject, or by prosthetic valves, commonly referred to as bioprostheses. A prosthetic valve is constituted by a metal ring structure and a flexible shutter made of tissue of animal origin. The shutter is permanently secured to the structure. 
   Such valves are described in particular in documents WO 01/03095 and WO 00/27975. 
   Once implanted, the structure bears against the inside wall of the heart to which it is sutured, in particular at the inlet to the aortic valve coming from the left ventricle. 
   It is found that after such a prosthesis has been implanted for several years, it degenerates and no longer functions efficiently. In particular, the flexible shutter tears and presents holes, or the shutter becomes calcified and thus loses flexibility, thus no longer being capable of deforming to perform its valve function. It is then necessary to put a new prosthesis into place. 
   However, it is not possible to remove the old prosthesis via an endoluminal path, in particular because the carrier structure of the prosthesis is sutured to the wall of the heart, meaning that they cannot be separated without major surgery for complete replacement of the valve. 
   In order to avoid a major surgical operation for removing the old prosthesis and putting a second prosthesis into place, it has been envisaged that a new prosthetic valve could be put into place by an endoluminal approach inside the old prosthesis which is left in place. 
   The new prosthetic valve is formed by a tubular support constituted by a radially deformable lattice fitted with a flexible shutter disposed in the duct defined by the tubular support. The shutter is connected to the tubular support and presents a shape that enables it, by deforming, to allow blood to flow in one direction and to prevent the blood from flowing in the opposite direction. 
   It has been envisaged that the tubular support could be made of interlaced resilient metal wires defining meshes that are generally lozenge-shaped. Such a tubular support is known as a “stent”. The tubular support is deformable between an insertion position, in which its diameter is reduced, and an implantation position in which its diameter is larger and sufficient to enable the support to bear against the inside of the carrier structure of the old prosthesis. 
   In order to be put into place, such prosthetic valves comprising a tubular lattice support are disposed inside a small-diameter catheter. The end of the catheter is brought via the arterial network to the region where the no longer functioning, old prosthesis has been fitted. The new prosthetic valve is pushed out from the catheter using a wire-shaped member engaged in the catheter. Since the tubular support is resilient, it deploys immediately on its own when it is no longer compressed radially by the catheter. It then comes to bear around the inside perimeter of the carrier structure of the old prosthesis. 
   Putting the new valve into place and deploying it are operations that are very difficult, particularly when the old prosthesis is very damaged. 
   SUMMARY OF THE INVENTION 
   An object of the invention is to propose a valve prosthesis that can be put back into condition easily by means of an endoluminal approach. 
   To this end, the invention provides a valve prosthesis of the above-specified type, which comprises: 
   an interchangeable prosthetic valve independent of the carrier structure to be put into place by an endoluminal approach through the annular carrier structure and comprising: a tubular support that is radially deformable relative to a main axis between a folded position for being put into place, and a deployed position implanted in the carrier structure, in which the tubular support bears at its periphery against the carrier structure. 
   The flexible shutter is connected to the tubular support and deformable between an obstruction position in which it is extended transversally and a release position in which it is contracted transversally under the action of the blood flowing through the tubular support. 
   The carrier structure forms an annular support having no shutter suitable for restricting the flow of blood to one direction only. 
   In particular embodiments, the valve prosthesis includes one or more of the following characteristics:
         the tubular support defines a solid cylindrical wall that is liquid-proof;   the tubular support comprises a tubular lattice covered in a stretchable film that is liquid-proof and that forms the solid cylindrical wall;   The prosthesis includes at least one rigid member extending generally along a generator line of the tubular support, which member is connected to the tubular support at least two points that are spaced apart along the axis of the tubular support;   the tubular support presents a generally cylindrical middle trunk and, axially at either end of the trunk, two generally frustoconical collars flaring from the trunk towards the ends of the support;   the tubular support is resilient and is shaped to be urged resiliently from its folded position towards its deployed position;   each member has a projecting end for connection to a prop for holding the prosthetic valve in position;   the tubular support is extended by converging legs forming a tripod, which legs are connected together at a connection point lying substantially on the axis of the tubular support;   the shutter comprises three membranes that are deformable between a closed position in which the free edges of the membranes, over half their length, touch one another in pairs, and an open position for passing blood in which the three membranes are spaced apart from one another;   the carrier structure comprises a rigid ring and a set of rigid pegs each extending from the ring parallel to the axis of the ring; and   the carrier structure includes at its surface a textile sheet making suturing possible.       

   The invention also provides a treatment kit comprising:
         a valve prosthesis as described above; and   a catheter for putting the prosthetic valve into place.       

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better understood upon reading the following description given purely by way of example and made with reference to the drawings, in which: 
       FIG. 1  is a perspective view of the carrier structure on its own of the valve prosthesis that is implanted surgically; 
       FIG. 2  is a perspective view of a valve prosthesis of the invention in its closed state; 
       FIG. 3  is an end view of the  FIG. 2  valve prosthesis; 
       FIG. 4  is a view identical to that of  FIG. 3 , the valve prosthesis being in its open state; 
       FIGS. 5 and 6  are longitudinal section views showing the successive stages in putting a prosthetic valve of a valve prosthesis of the invention into place; and 
       FIGS. 7 and 8  are views identical to those of  FIGS. 5 and 6 , showing successive stages in withdrawing a prosthetic valve from a valve prosthesis of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIGS. 1 and 2 , a valve prosthesis  10  that can be seen in full in  FIG. 2  and only in part in  FIG. 1 . The valve prosthesis is for an aortic valve of the heart. Thus, this prosthesis is placed immediately upstream from the aorta at the location of the natural valve. 
   The valve prosthesis includes a carrier structure  12  that can be seen on its own in  FIG. 1 . This structure essentially comprises a rigid ring  16  carrying three rigid pegs  18 , each extending from the ring parallel to the axis of the ring  16 . This ring is constituted by a rigid metal torus having the three pegs  18  welded thereto. The torus is covered over its entire surface in a woven textile sheet  20  enabling the carrier structure to be secured to the tissue of the heart by suturing the textile sheet to the wall of the heart. The inside diameter of the ring  16  lies in the range 15 millimeters (mm) to 40 mm. 
   Each peg  18  has one end secured to ring  16 , and all of them project from the same side of the ring. They are regularly distributed (evenly spaced) angularly around the axis of the carrier structure  12 . The total height of the pegs  18 , including the ring  16 , lies in the range 10 mm to 30 mm. 
   The carrier structure  12  does not have any flexible shutter deformable in the space defined by the structure between a closed position and an open position. 
     FIG. 2  shows a valve prosthesis  10  of the invention after it has been implanted. The valve prosthesis comprises, in addition to the carrier structure  12 , a prosthetic valve  50  that is interchangeable by an endoluminal approach. In the implanted state, the prosthetic valve extends inside the carrier structure  12  that has previously been implanted surgically. 
   The prosthetic valve  50  comprises a lattice tubular support  52  of axis X-X and a flexible shutter  54  connected to the tubular support  52  and placed inside it. 
   The valve  50  is replaceable and is normally removable relative to the carrier structure  12 . 
   The tubular support  52  is constituted, for example, by a tubular lattice  52 A embedded in a stretchable film  52 B that is liquid-proof, such as an elastomer. Since the film  52 B covers the lattice, it defines, over the entire height of the support  52 , a cylindrical wall that is solid and liquid-proof. The lattice  52 A is made of stainless steel having elastic properties, such that the support  52  is self-expanding. Such a support, when used on its own, is commonly referred to as a “stent”. 
   As is known, the support  52  can deform spontaneously from a compressed state in which it presents a small diameter to a dilated state in which it presents a diameter that is greater, the dilated state constituting its rest state. 
   In its implanted state, as shown in  FIGS. 2 to 4  and because of its resilience, the support  52  bears against the ring  16  and the pegs  18  of the valve prosthesis  10 , holding the three pegs  18  pressed against the outside surface of the support  52 . 
   At each of its axial ends, the support  52  extends axially beyond the carrier structure by two diverging collars that are generally truncated in shape, flaring towards the axial ends of the support. 
   More precisely, the support  52  has a middle trunk  62  that is generally cylindrical, of a length corresponding to the height of the carrier structure, this height being measured along the axis of the valve. The height of the trunk lies in the range of 10 mm to 30 mm. 
   The lattice defining the trunk  62  is made up of interlaced metal wires. Thus, two families of wires cross over one another. The wires in the first family define helixes oriented in the same direction and extending generally parallel to one another. The wires of the second family define helixes oriented in the opposite direction and extending parallel to one another. The wires of the first and second families are engaged successively over and under one another, such that these families of wires define lozenge-shaped meshes, with one diagonal of each mesh extending along the axis of the support, and with its other diagonal extending generally perpendicularly. 
   At a first end of the support, the trunk  62  is extended by a first flared collar  64  constituted by a set of lobes  66  going away from the axis of the support towards their curved ends. These lobes are formed by loops made at the ends of the wires of the first and second families, and they are integral therewith. 
   Similarly, at its other end, the support has a second flared collar  68  extending the trunk  62 . This second collar is likewise defined by outwardly-deformed lobes  70 . 
   At rest, the free ends of the collars, i.e. the most highly-flared end sections of the collars, define an outline of diameter equal to the diameter of the trunk  62  plus 5 mm to 15 mm. 
   Similarly, and advantageously, the height of the collars  64 ,  68 , measured along the axis of the tubular support  52  lies in the range of 5 mm to 15 mm, and for example is equal to 10 mm. 
   The film  52 B in which the tubular lattice  52 A is embedded extends over the lobes forming the collars  64  and  68 . 
   In a first embodiment, the tubular support  52  has over its entire height while at rest, i.e. when it is not compressed in a structure  12 , a diameter that is greater than the diameter of the structure  12 , such that the collars  64  and  68  take up a flared shape merely because of the natural resilience of the tubular support while the trunk is kept confined in a tubular shape within the carrier structure  12 . 
   In a variant, the trunk  62  of the tubular support, when at rest, and even when not compressed inside a structure  12 , has a diameter that is smaller than the end diameter of the collars  64  and  68 . 
   Furthermore, three pairs of wires coming from the first and second families respectively are connected together in pairs at the collar  68  to form three legs  82 . The legs converge towards one another along the axis X-X of the prosthetic valve in order to meet at a connection point  84  located on the axis. The three legs  82  thus define a tripod. They are regularly distributed (evenly shaped) angularly around the axis X-X, and each of them defines relative to the axis an angle that lies in the range 20° to 40°. For connection purposes, the three legs  82  are, for example, twisted together at the point  84 . A connection loop is made at the end point  84 . 
   In addition, and according to the invention, the tubular support  52  includes at least one rigid member  90  extending generally along a generator line of the tubular support  52 . This member is connected to the support at least at two points  92 A,  92 B that are spaced apart along the axis of the support. These two points are formed along the height of the trunk  62 , in particular in the vicinity of the regions where it connects with the collars  64  and  68 . Connection may be performed by welding or by adhesive bonding. 
   Advantageously, a single rigid member  90  is formed along one generator line of the trunk  62 . By way of example, this member is constituted by a longitudinally rigid metal wire that is engaged through the meshes of the lattice, passing alternately inside and outside the lattice. 
   Advantageously, the ends of the member are disposed inside the tubular support, i.e. beside the axis X-X relative to the liquid-proof film  52 B. 
   At least one projecting end  90 A of the member  90 , and in particular its end adjacent to the legs  82 , is suitable for cooperating with a prop  93  for axial connection therewith, as shown in  FIG. 5  and as explained below. The axial connection between the prop  93  and the member  90  is provided, by way of example, by the connection end  90 A of the member being engaged in a housing provided in the thickness of the prop  93  and opening out in the end thereof. 
   The shutter  54  is connected to the inside surface of the tubular support  52 . This shutter is made up of three flexible membranes  94 A,  94 B, and  94 C, each constituted by a polymer film or a layer of organic film such as calf pericardium. Each membrane is generally rectangular in shape. It is connected to the inside surface of the liquid-proof film  52 B along a base-forming long side  98  around the connection circumference between the trunk  62  and the enlarged collar  64 . 
   The longitudinal edges  99  of the three membranes  94 A,  94 B, and  94 C are connected to the tubular support  52  along three generator lines thereof that are regularly distributed angularly around the axis of the tubular support. Thus, the membranes are connected in pairs along their longitudinal edges to the tubular support. This connection is performed over the entire height of the trunk  62 . 
   The shutter-forming membranes  94 A,  94 B, and  94 C are deformable between a closed position shown in  FIGS. 2 and 3  in which the free edges of the membranes touch one another in pairs along half of their length, and a position for passing blood, as shown in  FIG. 4  in which the three membranes are moved apart from one another. 
   In the closed position, the three membranes cooperate with the tubular wall of the support  52  to define three pouches for retaining the stream of blood. In the open position, the three membranes are pressed against the inside surface of the tubular support, as shown in  FIG. 4 , thus together defining a generally circular duct in which the stream of blood can flow. 
   When the valve prosthesis is put into place initially, the surgeon begins by putting the carrier structure  12  into place by a surgical approach. For this purpose, an incision is made in the patient&#39;s chest to bring the carrier structure  12  to the heart, where it is implanted to take the place of the original valve. The carrier structure  12  is secured to the wall of the heart by sutures engaged in the textile coating  20  of the ring. 
   During initial implanting of the valve prosthesis, the prosthetic valve  50  is put into place manually inside the carrier structure  12 , after which the patient&#39;s chest is sewn back up. 
   The structure  12  is implanted permanently in the patient&#39;s body, while the prosthetic valve  50  is interchangeable. Thus, when the prosthetic valve  50  becomes damaged (in particular, because the membranes have become calcified or torn), the prosthetic valve is extracted by an endoluminal approach as explained below, and the new prosthetic valve is put into place in the space defined by the carrier structure  12 , as explained below. 
   To put a new prosthetic valve  50  in place by an endoluminal approach, a treatment kit  100 , shown in  FIGS. 5 and 6 , is used. It comprises a new prosthetic valve  50  contained in a catheter  102  of outside diameter smaller than the inside diameter of the carrier structure  12 . 
   As shown in  FIG. 5 , the prosthetic valve, and in particular the tubular support  52 , is compressed radially inside the tube. 
   In addition, the prop  93  extends lengthwise along the catheter  102  being connected at its end to the end of the axial stiffener (rigid) member  90 . The prop  93  has sufficient axial stiffness to be capable of pushing the prosthetic valve out from the catheter  102 . 
   During installation of the valve, the end of the catheter  102  in which the prosthetic valve is received is inserted in the patient&#39;s aorta, and is then moved progressively along the aorta to the location of the damaged prosthetic valve at the outlet from the heart. The catheter is moved against the normal flow of blood. 
   The catheter is brought into the position shown in  FIG. 5 . In this position, the catheter  102  is then pulled while the new prosthetic valve  50  is held in place by the prop  93 . As the catheter  102  moves, the prosthetic valve  50  becomes uncovered, such that its first end deploys to form the collar  64 , and then the tubular support trunk  62  comes to bear against the pegs  18 , and finally its second end deploys to form the collar  68 . 
   During the progressive baring of the prosthetic valve  50  by moving the catheter  102 , the prosthetic valve is held stationary in an axial direction relative to the ducts of the aorta, and in particular relative to the carrier structure  12  left in place by means of the rigid prop  93  which holds the member  90  in line therewith. Thus, the presence of the prop  93  cooperating with the member  90  reduces the risk of the prosthetic valve moving axially as it is being deployed, even if it is deployed during a heartbeat causing blood to flow through the location of the valve. 
   After deployment, the valve is held axially by the presence of the enlarged collars  64  and  68  bearing respectively on the ring  16  and on the ends of the pegs  18 . 
   After deployment, the prop  93  is withdrawn merely by traction. Thus, the member  90  disengages from the end of the prop  93 . The member  90  remains in position since it is integrated in the tubular support  52 . 
   As shown in  FIGS. 7 and 8 , in order to withdraw a damaged prosthetic valve  50 , a catheter  112  is introduced through the aorta and is placed facing the end of the valve that presents the tripod made up of the legs  82 . 
   A traction tool  114  is conveyed along the catheter  112 . At its end, the tool has a hook  116  suitable for catching the connection point  84  of the tripod. While the open end of the catheter is in contact with the legs  82  of the tripod, the prosthetic valve  50  is progressively introduced into the inside of the catheter  112  by advancing the catheter  112  along the length of the valve  50 . By a camming effect, the legs  82  are pushed towards the axis and the prosthetic valve is progressively moved into its tight state and becomes inserted in the catheter  112 , as shown in  FIG. 8 . The catheter  112  containing the prosthetic valve  50  is then extracted from the human body. 
   A new prosthetic valve  50  is then introduced using a kit  100  for performing treatment in the human body, and the new valve is deployed as explained above. 
   It will be understood that with such a vascular prosthesis, only one major surgical operation is required for putting the carrier structure  12  in place, after which the prosthetic valve can be changed periodically by an endoluminal approach, which constitutes an operation that is relatively minor for the patient. 
   The absence of any shutter-forming element on the carrier structure that has the sole function of providing a rigid bearing surface for the prosthetic valve, makes it possible to have a bearing surface that is satisfactory and clean regardless of the state of the prosthetic valve. 
   In contrast, when a prosthetic valve formed by a stent fitted with a shutter is implanted through a damaged prosthetic valve that comprises a carrier structure and a shutter, then the presence of the often-calcified shutter impedes putting the new prosthetic valve into place.