Abstract:
The invention relates to a prosthetic valve which is endoluminally placeable and comprises a tubular support radially deformable with respect to a main axis (X-X) from an unfolded implanting position to a folded setting position. A flexible plug connected to the tubular support and deformable between a blocking position in which it is transversally stretched and a releasing position in which it is transversally contracted by the action of a flow circulating through said tubular support. The inventive valve also comprises a rigid chord which extends generally along the generatrix of the tubular support and is connected thereto at least at two points which are remote from each other along the axis thereof.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a prosthetic valve to be put into place by an endoluminal approach, the valve being of the type involving a tubular support that is radially deformable relative to a main axis between a deployed implantation position and a folded positioning position; and a flexible shutter connected to the tubular support and deformable between an obstruction position in which it extends transversally and a release position in which it is contracted transversally under the action of a flow of blood through the tubular support. 
     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 develops 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 proposed 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 from flowing in the opposite direction. 
     It has been proposed 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. 
     The new prosthetic valve is then put into place while the heart is still beating. When treating an aortic valve, the prosthetic valve is brought in against the flow of blood. Thus, while the new prosthetic valve is being deployed, it deploys at the inlet to the aortic artery, thereby obstructing it. During deployment, the new prosthetic valve presents a transverse surface area that is large. Thus, during a contraction of the heart leading to blood being expelled into the aorta, the prosthetic valve runs the risk of being entrained during deployment, and can thus end up being positioned away from the carrier structure of the old valve. The new valve then obstructs the artery without performing its function in a satisfactory manner. 
     The consequences of the new prosthetic valve being wrongly positioned are often very damaging for the patient, since the newly-inserted prosthetic valve cannot be withdrawn other than surgically. 
     In order to avoid that difficulty, it is known to deploy the new prosthetic valve quickly and exactly between two contractions of the heart. However, since that length of time is very short, it is difficult to put the new prosthetic valve into place. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to propose a prosthetic valve that can be put into place by an endoluminal approach without major risk of the valve being wrongly positioned axially, even in the presence of a powerful flow of blood in the region where it is being implanted. 
     To this end, the invention provides an interchangeable prosthetic valve of the above-specified type, characterized in that it comprises at least one rigid member extending generally along a generator line (and along an axial direction) of the tubular support. 
     The member is connected to the tubular support at least two points that are spaced along the axis of the tubular support. 
     In particular embodiments, the prosthetic valve 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;   each member is engaged in alternation in the meshes of the lattice;   the tubular support presents a generally cylindrical middle trunk and, axially at each end of the trunk, two generally frustoconical collars flaring away from the trunk towards the ends of the supports;   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 place;   the tubular support is extended by converging legs forming a tripod, which legs are connected to one another at a connection point lying substantially on the axis of the tubular support; and   the shutter has three membranes that are deformable between a closed position in which the free edges of the membranes touch one another in pairs over half their length, and an open position for passing the flow of blood in which the three membranes are spaced apart from one another.       

     The invention also provides a treatment kit comprising:
         a prosthetic valve as described above;   a catheter for putting the valve into place; and   a prop for holding the prosthetic valve. The prop includes means for interconnecting it in line with the member of the prosthetic valve.       

    
    
     
       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 a surgically-implanted prosthetic valve that is damaged; 
         FIG. 2  is a perspective view of a prosthetic valve of the invention in its closed state, the valve being in the process of being implanted through an old prosthetic valve that is damaged; 
         FIG. 3  is an end view of the  FIG. 2  prosthetic valve; 
         FIG. 4  is a view identical to that of  FIG. 3 , the prosthetic valve being in its open state; 
         FIGS. 5 and 6  are longitudinal section views showing the successive stages of putting a prosthetic valve of the invention into place; and 
         FIGS. 7 and 8  are views identical to those of  FIGS. 5 and 6 , showing the successive stages of removing a prosthetic valve of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a prosthetic valve  10  that is damaged and needs to be treated. The prosthetic valve is assumed to have been implanted surgically, e.g. to replace an aortic valve of the heart. Thus, this valve is placed immediately upstream from the aorta at the location of the natural valve. 
     Such a prosthetic valve is known per se, and essentially comprises a carrier structure  12  and a flexible shutter  14 . 
     The carrier structure  12  essentially comprises a rigid ring  16  carrying three rigid pegs  18  each extending parallel to the axis of the ring  16 . The ring is constituted by a rigid metal torus to which the three pegs  18  are welded. The torus is covered over its entire surface in a woven sheet enabling the prosthetic valve to become secured to heart tissue by suturing between the woven sheet and 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  is connected at one end to the ring  16  and all of the pegs project from the same side thereof. The pegs are regularly distributed 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 flexible shutter  14  is permanently secured simultaneously to the pegs  18  and to the ring  16 . In the embodiment shown, the flexible shutter is made up of three membranes  26  of generally rectangular shape. Along a base-forming long side  28 , each membrane  26  is connected to the carrier structure between two successive (adjacent) studs  18 . Thus, along the base, the membrane describes a circular arc along the ring  16 . The two side edges of the membrane are connected lengthwise along the pegs  18 . 
     In a known manner, the three membranes  26  forming the flexible shutter are normally deformable between a closed position in which the three edges of the membranes touch one another, the membranes externally defining three pouches for accumulating blood by being deformed towards the axis of the prosthetic valve, and an open position in which the three membranes are spaced apart from one another, extending generally axially from the ring, the three membranes then together defining a generally cylindrical passage allowing the blood stream to flow. 
     As shown in  FIG. 1 , the prosthetic valve  10  is damaged by holes  32  formed in the membranes  26 , these holes causing the valve to seal poorly. 
       FIG. 2  shows a prosthetic valve  50  of the invention put into place by an endoluminal approach inside the damaged prosthetic valve  10  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 damaged valve  10 . 
     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 has a small diameter to a dilated (expanded) state in which it has a diameter that is greater, the dilated (expanded) 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 damaged valve  10 , holding the three membranes  26  pressed against the outside surface of the support  52 . 
     At each of its axial ends, the support  52  extends axially beyond the carrier structure of the damaged valve  10  by two diverging collars that are generally truncated in shape, flaring towards the axial ends of the support. 
     More precisely, the support  52  presents a middle trunk  62  that is generally cylindrical, having a length corresponding to the height of the carrier structure of the damaged valve, this height being measured along the axis of the valve. The height of the trunk lies in the range 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 second end, the support has a second flared collar  68  extending the trunk  62 . This 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 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 . Thus, 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 tubular shape within the carrier structure  12  of the damaged prosthetic valve. 
     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 second 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 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 stiffener member  90  extending generally along a generator line of the tubular support  52  (along an axial direction of the tubular support  52 , as illustrated in  FIG. 2 ). This stiffener 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 member  90  is formed along one generator line of the trunk  62 . By way of example, this stiffener member  90  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 stiffener member  90  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 stiffener member  90 , and in particular its second 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 stiffener 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 arranged like the shutter  14  of the prosthetic valve  10 . Thus, each membrane  94 A,  94 B, and  94 C is 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. 
     In order to treat the damaged prosthetic valve, the new prosthetic valve is put into place in the space defined by the carrier structure  12  of the damaged valve, as shown in  FIGS. 5 and 6 . 
     For this purpose, a treatment kit  100  shown in these figures is used. It comprises a new prosthetic valve  50  contained in a catheter  102  of outside diameter that is 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 a folded insertion position. 
     In addition, the prop  93  extends lengthwise along the catheter  102  being connected at its end to the end of the axial stiffener member  90 . The prop  93  presents 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 the 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 old prosthetic valve  10  that is damaged, by means of the rigid prop  93  which holds the stiffener member  90  in line therewith. Thus, the presence of the prop  93  cooperating with the stiffener 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 the 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.