Abstract:
A kit for implanting in a duct, which includes a tubular endoprosthesis and a prosthetic valve is disclosed. The prosthetic valve includes a carrier frame that is radially deformable in elastic manner relative to a central axis of the tubular endoprosthesis between a deployed, implanted position, and a folded, implanting position. The carrier frame is urged elastically towards its deployed position. A flexible shutter is connected to the carrier frame. The shutter is deformable between an obstruction position in which it is extended transversely, and a release position in which it is contracted transversely under to allow a fluid to flow through the carrier frame. The carrier frame also includes an integrated centripetal compressing mechanism for centripetally compressing the carrier frame towards folded position.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a kit for implanting in a duct, the kit being of the type comprising:
         a tubular endoprosthesis; and   a prosthetic valve.       

     The heart comprises two atria and two ventricles which are separated by valves. Valves are also present at the outlet from the right ventricle (pulmonary valve) and from the left ventricle (aortic valve). 
     These valves ensure that blood flows in one direction only, preventing a backflow of blood at the end of ventricular contraction. 
     Valves can suffer from diseases. In particular, they can suffer from poor opening, thereby reducing blood flow, or from not being fully leaktight, thus allowing backflow or regurgitation towards the ventricle that expels the blood flow. 
     These problems of regurgitation lead to abnormal dilation of the ventricle which can lead in the long run to heart failure. 
     2. Description of the Related Art 
     It is known to treat this type of disease surgically, by replacing the diseased valve. Diseased valves, and in particular the pulmonary valve at the outlet from the right ventricle, are replaced by a valve taken from a deceased donor, or by a bioprosthesis constituted by a metal frame and a shutter made of a tissue of animal origin. The shutter is permanently secured to the frame. 
     Prosthetic valves are also known. These are constituted by a metal frame supporting a polymer shutter. Such valves are described in particular in documents WO 01/154625 and WO 01/28459. 
     In such prostheses, the frame is elastically deformable to a small extent only, and the shutter is constituted by a pouch. The elastically deformable frame bears against the inside wall of an organic duct, in particular the pulmonary artery coming from the right ventricle. 
     It has been found that, after such a prosthesis has been implanted for several years, it degrades and no longer operates effectively. It is then necessary to put a new prosthesis into place. 
     However, it is not possible to withdraw the old prosthesis in an endoluminar manner, in particular because the carrier frame of the prosthesis has become secured to the heart wall, meaning that they cannot be separated without major surgical intervention for replacing the valve. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to propose a kit comprising a prosthetic valve that can be replaced without excessive difficulty, and without requiring major surgical intervention. 
     To this end, the invention provides a kit of the type specified, in which the prosthetic valve is for implanting removably in the tubular endoprosthesis. The prosthetic valve comprises: firstly, a carrier frame that is radially deformable in elastic manner relative to a main axis between a deployed implanted position and a folded, implanting position, which carrier frame is urged resiliently towards its deployed position; and secondly, a flexible shutter connected to the carrier frame and deformable between an obstruction position in which it is extended transversely, and a release position in which it is contracted transversely under the action of the flow passing through the carrier frame; and an integrated centripetal compression means for compressing the carrier frame towards its folded position against the elastic action. 
     In particular embodiments, the kit includes one or more of the following characteristics:
         the shutter comprises a pouch;   the pouch includes an evacuation orifice formed in its end wall;   the end wall of the kit is generally hemispherical;   the centripetal compression means comprises a clamp having at least two branches connected together in a common region, each branch being connected to the shutter by a connection segment, each of the branches presenting a drive segment suitable for co-operating with a complementary clamping member for centripetally compressing the carrier frame towards its folded position;   the branches are welded together in their common region, and the carrier frame is fork-shaped, each branch being elastically deformable, the drive segments and the connection segments for connecting the branches to the shutter both being situated on the same side of the weld;   the carrier frame has two branches;   the carrier frame has three branches;   the valve includes threads connecting the end wall of the pouch to each of the branches; and   the carrier frame comprises a resilient wire mesh and the centripetal compression means comprises a constriction strand engaged around the resilient wire mesh.       

     The invention also provides an implanted prosthesis made from a kit as defined above, the endoprosthesis being placed against the inside surface of a duct, and the prosthetic valve being placed in tubular endoprosthesis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood from the following description given purely by way of example and made with reference to the drawings, in which: 
         FIG. 1  is a longitudinal section view of a prosthesis implanted in an organic duct, comprising a prosthetic valve in its closed state; 
         FIG. 2  is a cross-section of the prosthesis illustrated in  FIG. 1  along on line II-II; 
         FIGS. 3 and 4  are views identical to  FIGS. 1 and 2 , with the prosthetic valve being in its open state; 
         FIGS. 5 and 6  are views identical to that of  FIG. 1  showing successive stages in withdrawing a prosthetic valve of the invention; 
         FIG. 7  is a view identical to that of  FIG. 1  showing a variant embodiment of a prosthetic valve of the invention; and 
         FIG. 8  is a view identical to that of  FIG. 1  showing another embodiment of a prosthesis comprising a prosthetic valve. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     prosthesis of the invention that is adapted to be implanted in a pulmonary artery  12  connected at its end  12 A to the outlet from the right ventricle of the heart, in particular of a human being, and at its end  12 B to the lungs. 
       FIG. 1  shows a prosthesis of the invention that is adapted to be implanted in a pulmonary artery  12  connected at its end  12 A to the outlet from the right ventricle of the heart, in particular of a human being, and at its end  12 B to the lungs. 
     In the invention, the prosthesis comprises an outer tubular endoprosthesis  14  having disposed therein a removable and replaceable prosthetic valve  16 . 
     By way of example, the endoprosthesis  14  is constituted by a tubular mesh  14 A embedded in a stretchable film  14 B that is liquid-proof, such as an elastomer. The mesh  14 A is made of stainless steel wire having spring properties, such that the endoprosthesis  14  is self-expanding. Such an endoprosthesis is commonly referred to as a “stent”. 
     The endoprosthesis  14  is capable of deforming spontaneously from a compressed state in which it has a small diameter, to a dilated state in which it has a larger diameter, the dilated state constituting its rest state. 
     In its implanted state, as shown in the figures, and because of its own elasticity, the endoprosthesis  14  bears against the inside surface of the duct  12 , thus forming an inside sheath for the duct. 
     An interchangeable prosthetic valve  16  comprises a carrier frame  22  and a deformable shutter  24  supported by the frame  22  and secured thereto. The valve is generally symmetrical about the axis X-X. 
     The carrier frame has means integrated therein to compress it centripetally. More precisely, the frame  22  is constituted by two branches  26 A,  26 B connected together at a first end  28  so as to form a clamp that is elastically deformable between a deployed position in which the two branches are spaced apart from the middle (central) axis X-X, and a folded position in which the two branches are moved towards the middle axis X-X. 
     The two branches  26 A,  26 B are generally symmetrical about the middle axis X-X that coincides with the axis of the duct once the prosthesis has been implanted. 
     The length of the branches measured along the axis X-X lies in the range 2 centimeters (cm) to 4 cm, and is preferably equal to 3 cm. 
     Each branch  26 A,  26 B has a bearing segment  30 A,  30 B for bearing against the endoprosthesis  14 . Each bearing segment is constituted by a rectilinear segment extending generally along a generator line of the endoprosthesis  14  when the frame is deployed. 
     The length of the bearing segments lies in the range 1 cm to 3 cm, and is preferably about 2 cm. 
     The bearing segments  30 A,  30 B are extended by drive segments  32 A,  32 B that converge towards each other onto the connection point  28 . These segments are generally inclined relative to the middle axis X-X. 
     The drive segments  32 A,  32 B are generally curved and present a center of curvature lying outside the space defined between the two branches. Thus, the segments  32 A and  32 B bulge towards the inside of the clamp. 
     The shutter  24  is constituted by a flexible pouch  34  having a generally circular opening  35  on the axis X-X when the pouch is inflated. 
     The pouch  34  has a generally cylindrical skirt  36  extended by a generally hemispherical end wall  38 . The end wall  38  has an orifice  40  of a diameter that is small relative to the section of the opening  35 . 
     By way of example, the pouch  34  is made of polyurethane or out of a biological material (bovine pericardium). 
     By way of example, the height of the skirt  36  is equal to 4 millimeters (mm) or 5 mm, and it preferably lies in the range 2 mm to 5 mm. 
     The pouch  34  is connected to the two bearing segments  30 A,  30 B by adhesive or by any other appropriate means along the length of the generator lines of the skirt  36 . 
     Advantageously, the pouch  34  is connected to the two branches  26 A,  26 B in such a manner that the two half-skirts defined on either side are of lengths that are slightly different. 
     Finally, the end wall  38  is connected by threads  42  to the drive segments  32 A,  32 B of the two branches of the carrier frame so as to prevent the pouch from being turned inside out by invagination. 
     When implanted, such a prosthetic valve operates as follows. At the end of expulsion from the right ventricle, when the ventricle increases in volume, the blood flow is sucked into the duct  12  from the end  12 B towards the end  12 A. The blood then fills the pouch  34  which presses against the endoprosthesis  14 , as shown in  FIGS. 1 and 2 , thereby closing off the organic duct  12  in a substantially leaktight manner. 
     During circulation of the blood, the orifice  40  allows a constant small flow of blood to pass through the pouch  34 , thus preventing a blood clot from forming at the bottom of the pouch  34  as a result of possible stagnation of the blood. 
     In contrast, during contraction of the right ventricle, blood flows from the end  12 A towards the end  12 B. As shown in  FIGS. 3 and 4 , the pouch  34  is urged outwards from its end wall  38 , thereby causing the pouch to flatten. The blood is thus free to flow along the duct on either side of the pouch. 
     The difference in length between the two portions of the skirt disposed on either side of the two arms ensures that in the position shown in  FIGS. 3 and 4 , the two half-skirts do not press against each other and do not become pressed together definitively against the endoprosthesis  14 . 
     In order to implant the prosthesis in the duct  12 , a kit of the invention comprising the endoprosthesis  14  and the prosthetic valve  16  is used. 
     Initially, the endoprosthesis  14  is implanted in the duct  12  by an endoluminal technique. 
     Thereafter, the valve  16  is implanted by the endoluminal technique inside the endoprosthesis  14 . 
     After such a prosthesis has been implanted, the wall of the organic duct bonds progressively with the endoprosthesis  14 . However, the endoprosthesis  14  constitutes a sheath which acts as a screen between the prosthetic valve  16  and the wall of the duct  12 , thus avoiding agglomeration of the organic duct and the prosthetic valve. This means that it is possible to withdraw the prosthetic valve. 
     In particular, since the prosthetic valve is fitted with centripetal compression means, it can be returned to its compressed state and removed in transluminal manner. 
     More precisely, and as shown in  FIG. 5 , in order to withdraw the prosthetic valve, a catheter  60  is inserted via the right atrium and the right ventricle and is placed in register with the end  28  of the clamp-forming carrier frame. 
     A traction tool  62  is conveyed along the catheter  60 . At its end, the tool has a jaw  64  suitable for taking hold of the end  28  of the clamp. When the open end, referenced  66 , of the catheter comes into contact with the drive segments  32 A,  32 B, the carrier frame is pulled progressively into the duct  60 . By a camming effect, the two arms  26 A,  26 B are moved towards each other and the prosthetic valve is brought progressively into its compact state and is inserted into the catheter  60 , as shown in  FIG. 6 . The catheter  60  containing the prosthetic valve is then extracted from the human body. 
     A new catheter containing a new prosthetic valve is then inserted into the human body and the valve is released by performing the above-described operations in reverse order. In particular, the prosthetic valve is extracted progressively from the catheter  60  by being pushed from its end  28 . Under the resilient action of the clamp constituted by the carrier frame  22 , the prosthetic valve is deployed and bears radially against the tubular endoprosthesis  14 . 
       FIG. 7  shows a variant embodiment of the prosthetic valve of the invention. 
     In this embodiment, the carrier frame, referenced  122 , is constituted by a clamp comprising three arms  126 A,  126 B,  126 C, each in the form of an arm  26 A,  26 B. These arms are regularly distributed around the longitudinal axis X-X of the prosthesis. 
     As before, these arms are suitable for bearing against the endoprosthesis  14 , and they are connected together at a connection end  128 . 
     In yet another variant, as shown in  FIG. 8 , the prosthetic valve  216  comprises a resilient tubular wire mesh  222  and a shutter-forming pouch  224  identical to the pouch  34 . The pouch  224  is connected around its open periphery to the tubular mesh at two or three points. 
     The prosthetic valve also includes a constriction strand  226  permanently engaged in the various loops defined by the endoprosthesis  216  and extending around its circumference. This strand forms a closed loop. It is long enough to allow the valve to expand. This strand forms the centripetal compression means. Applying traction to the strand, e.g. by means of a clamp, causes the carrier frame  222  to be constricted, thus enabling the prosthetic valve to be withdrawn after it has been engaged in a catheter. 
     In another variant, the kit is implanted in a prosthetic duct  12 , in particular a flexible tube, which has previously been implanted in an organic duct or used as a replacement therefor. 
     The endoprosthesis  12  is then placed by the endoluminal technique so as to bear against the inside wall of the flexible tube. 
     In another variant, the kit comprises an endoprosthesis  12  constituted by a rigid ring. The length of the ring is substantially equal to the length of the bearing segments  30 A,  30 B of the prosthetic valve  16 . 
     This type of kit is used when replacing internal heart valves, in particular the tricuspid valves and the mitral valves. 
     In order to implant the kit in the heart, the ring already fitted with the prosthetic valve  16  is implanted initially by the surgical technique in the heart, to replace a defective heart valve. 
     When the prosthetic valve  16  becomes defective, it can also be replaced by the endoluminal technique, as described above.