Abstract:
A prosthetic heart valve comprises a biological tissue valve and a collapsible and expandable support frame having a longitudinal axis. The frame comprises an outflow circumferential structure defining an outflow end of the frame and consisting essentially row of diamond-shaded expandable cells. The frame also comprises three V-shaped structures spaced apart from the outflow circumferential structure and three struts longitudinally aligned with the longitudinal axis of the frame. The three struts are configured to facilitate mounting the biological tissue valve to the frame and interconnect the outflow circumferential structure to the three V-shaped structures. The frame also includes three undulating structures, each of the three undulating structures interconnecting respective adjacent V-shaped structures of the three V-shaped structures. The prosthetic heart valve is configured to be collapsed for introduction into a patient using; a catheter and to be expanded for deployment at an implantation site.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation-in-part of U.S. Ser. No. 10/412,634 filed on Apr. 10, 2003, which is (1) a continuation-in-part of U.S. Ser. No. 10/130,355 filed on May 17, 2002, which is the U.S. national phase under §371 of International Application No. PCT/FR00/03176, filed on Nov. 15, 2000, which was published in a language other than English and which claimed priority from French Application No. 99/14462 filed on Nov. 17, 1999, now French Patent No. 2,800,984, and (2) also a continuation-in-part of International Application No. PCT/FR01/03258 filed on Oct. 19, 2001, which was published in a language other than English and which claimed priority from French Application No. 00/14028 filed on Oct. 31, 2000, now French Patent No. 2,815,844. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a prosthetic cardiac valve and related deployment system that can be delivered percutaneously through the vasculature, and a method for delivering same. 
       BACKGROUND OF THE INVENTION 
       [0003]    Currently, the replacement of a deficient cardiac valve is often performed by opening the thorax, placing the patient under extracorporeal circulation or peripheral aorto-venous heart assistance, temporarily stopping the heart, surgically opening the heart, excising the deficient valve, and then implanting a prosthetic valve in its place. U.S. Pat. No. 4,106,129 to Carpentier describes a bioprosthetic heart valve with compliant orifice ring for surgical implantation. This procedure generally requires prolonged patient hospitalization, as well as extensive and often painful recovery. It also presents advanced complexities and significant costs. 
         [0004]    To address the risks associated with open heart implantation, devices and methods for replacing a cardiac valve by a less invasive means have been contemplated. For example, French Patent Application No. 99 14462 illustrates a technique and a device for the ablation of a deficient heart valve by percutaneous route, with a peripheral valvular approach. International Application (PCT) Nos. WO 93/01768 and WO 97/28807, as well as U.S. Pat. No. 5,814,097 to Sterman et al., U.S. Pat. No. 5,370,685 to Stevens, and U.S. Pat. No. 5,545,214 to Stevens illustrate techniques that are not very invasive as well as instruments for implementation of these techniques. 
         [0005]    U.S. Pat. No. 3,671,979 to Moulopoulos and U.S. Pat. No. 4,056,854 to Boretos describe a catheter-mounted artificial heart valve for implantation in close proximity to a defective heart valve. Both of these prostheses are temporary in nature and require continued connection to the catheter for subsequent repositioning or removal of the valve prosthesis, or for subsequent valve activation. 
         [0006]    With regard to the positioning of a replacement heart valve, attaching this valve on a support with a structure in the form of a wire or network of wires, currently called a stent, has been proposed. This stent support can be contracted radially in such a way that it can be introduced into the body of the patient percutaneously by means of a catheter, and it can be deployed so as to be radially expanded once it is positioned at the desired target site. U.S. Pat. No. 3,657,744 to Ersek discloses a cylindrical, stent-supported, tri-leaflet, tissue, heart valve that can be delivered through a portion of the vasculature using an elongate tool. The stent is mounted onto the expansion tool prior to delivery to the target location where the stent and valve are expanded into place. More recently, U.S. Pat. No. 5,411,552 to Andersen also illustrates a technique of this type. In the Andersen patent, a stent-supported tissue valve is deliverable percutaneously to the native heart valve site for deployment using a balloon or other expanding device. Efforts have been made to develop a stent-supported valve that is self-expandable, using memory materials such as Nitinol. 
         [0007]    The stent-supported systems designed for the positioning of a heart valve introduce uncertainties of varying degree with regard to minimizing migration from the target valve site. A cardiac valve that is not adequately anchored in place to resist the forces of the constantly changing vessel wall diameter, and turbulent blood flow therethrough, may dislodge itself, or otherwise become ineffective. In particular, the known stents do not appear to be suited to sites in which the cardiac wall widens on either proximally and/or distally of the valve annulus situs. Furthermore, the native cardiac ring remaining after ablation of the native valve can hinder the positioning of these stents. These known systems also in certain cases create problems related to the sealing quality of the replacement valve. In effect, the existing cardiac ring can have a surface that is to varying degrees irregular and calcified, which not only lessens the quality of the support of the stent against this ring but also acts as the source of leaks between the valve and this ring. Also, these systems can no longer be moved at all after deployment of the support, even if their position is not optimal. Furthermore, inflating a balloon on a stented valve as described by Andersen may traumatize the valve, especially if the valve is made from a fragile material as a living or former living tissue. 
         [0008]    Also, the existing techniques are however considered not completely satisfactory and capable of being improved. In particular, some of these techniques have the problem of involving in any case putting the patient under extracorporeal circulation or peripheral aorto-venous heart assistance and temporary stopping of the heart; they are difficult to put into practice; they do not allow precise control of the diameter according to which the natural valve is cut, in view of the later calibration of the prosthetic valve; they lead to risks of diffusion of natural valve fragments, often calcified, into the organism, which can lead to an embolism, as well as to risks of perforation of the aortic or cardiac wall; they moreover induce risks of acute reflux of blood during ablation of the natural valve and risk of obstruction of blood flow during implantation of the device with a balloon expandable stent for example. 
       SUMMARY OF THE INVENTION 
       [0009]    The object of the present invention is to transluminally provide a prosthetic valve assembly that includes features for preventing substantial migration of the prosthetic valve assembly once delivered to a desired location within a body. The present invention aims to remedy these significant problems. Another objective of the invention is to provide a support at the time of positioning of the replacement valve that makes it possible to eliminate the problem caused by the native valve sheets, which are naturally calcified, thickened and indurated, or by the residues of the valve sheets after valve resection. Yet another objective of the invention is to provide a support making possible complete sealing of the replacement valve, even in case of an existing cardiac ring which has a surface which is to varying degrees irregular and/or to varying degrees calcified. Another objective of the invention is to have a device that can adapt itself to the local anatomy (i.e. varying diameters of the ring, the subannular zone, the sino-tubular junction) and maintain a known diameter of the valve prosthesis to optimize function and durability. The invention also has the objective of providing a support whose position can be adapted and/or corrected if necessary at the time of implantation. 
         [0010]    The present invention is a prosthesis comprising a tissue valve supported on a self-expandable stent in the form of a wire or a plurality of wires that can be contracted radially in order to make possible the introduction of the support-valve assembly into the body of the patient by means of a catheter, and which can be deployed in order to allow this structure to engage the wall of the site where the valve is to be deployed. In one embodiment, the valve is supported entirely within a central, self-expandable, band. The prosthetic valve assembly also includes proximal and distal anchors. In one embodiment, the anchors comprise discrete self-expandable bands connected to the cent al band so that the entire assembly expands in unison into place to conform more naturally to the anatomy. 
         [0011]    The valve can be made from a biological material, such as an animal or human valve or tissue, or from a synthetic material, such as a polymer, and includes an annulus, leaflets and commissure points. The valve is attached to the valve support band with, for example, a suture. The suture can be a biologically compatible thread, plastic, metal or adhesive, such as cyanoacrylate. In one embodiment, the valve support band is made from a single wire bent in a zigzag manner to form a cylinder. Alternatively, the valve support band can be made from a plurality of wires interwoven with one another. The wire can be made from stainless steel, silver, tantalum, gold, titanium, or any suitable tissue or biologically compatible plastic, such as ePTFE or Teflon. The valve support band may have a loop at its ends so that the valve support band can be attached to an upper anchor band at its upper end, and a lower anchor band at its lower end. The link can be made from, for example, stainless steel, silver, tantalum, gold, titanium, any suitable plastic material, or suture. 
         [0012]    The prosthetic valve assembly is compressible about its center axis such that its diameter can be decreased from an expanded position to a compressed position. The prosthetic valve assembly may be loaded onto a catheter in its compressed position, and so held in place. Once loaded onto the catheter and secured in the compressed position, the prosthetic valve assembly can be transluminally delivered to a desired location within a body, such as a deficient valve within the heart. Once properly positioned within the body, the catheter can be manipulated to release the prosthetic valve assembly and permit it to into its expanded position. In one embodiment, the catheter includes adjustment hooks such that the prosthetic valve assembly may be partially released and expanded within the body and moved or otherwise adjusted to a final desired location. At the final desired location, the prosthetic valve assembly may be totally released from the catheter and expanded to its fully expanded position. Once the prosthetic valve assembly is fully released from the catheter and expanded, the catheter may be removed from the body. 
         [0013]    Other embodiments are contemplated. In one such alternative embodiment, this structure comprises an axial valve support portion that has a structure in the form of a wire or in the form of a network of wires suitable for receiving the replacement valve mounted on it, and suitable for supporting the cardiac ring remaining after the removal of the deficient native valve. The embodiment may further comprise at least one axial wedging portion, that has a structure in the form of a wire or in the form of a network of wires that is distinct from the structure of said axial valve support portion, and of which at least a part has, when deployed a diameter greater or smaller than that of said deployed axial valve support portion, such that this axial wedging portion or anchor is suitable for supporting the wall bordering said existing cardiac ring. The embodiment preferably further comprises at least one wire for connecting the two portions, the wire or wires being connected at points to these portions in such a way as not to obstruct the deployment of said axial portions according to their respective diameters. The embodiment thus provides a support in the form of at least two axial portions that are individualized with respect to one another with regard to their structure, and that are connected in a localized manner by at least one wire; where this wire or these wires do not obstruct the variable deployment of the axial portion with the valve and of the axial wedging portion(s) or anchors. The anchors may be positioned distally or proximally. 
         [0014]    The presence of a structure in the form of a wire or in the form of a network of wires in the axial valve support portion makes possible a perfect assembly of this valve with this structure, and the shape as well as the diameter of this axial portion can be adapted for supporting the existing cardiac ring under the best conditions. In particular, this axial valve support portion can have a radial force of expansion such that it pushes back (“impacts”) the valve sheets that are naturally calcified or the residues of the valve sheets after valve resection onto or into the underlying tissues, so that these elements do not constitute a hindrance to the positioning of the replacement valve and also allow for a greater orifice area. This structure also makes it possible to support an optional anchoring means and/or optional sealing means for sealing the space between the existing cardiac ring and the replacement valve, as indicated below. 
         [0015]    The configuration of each anchor portion can be adapted for supporting the cardiac wall situated at the approach to the existing cardiac ring under the best conditions. In particular, this anchor portion can have a tubular shape with a constant diameter greater than that of the axial valve support portion, or the form of a truncated cone whose diameter increases with distance from the axial valve support portion. By attaching at least one anchor portion to the axial valve support portion, the prosthetic valve assembly assumes a non-cylindrical or toroidal configuration. This non-cylindrical configuration provides an increased radial expansion force and increased diameter at both ends of the prosthetic valve assembly that may tighten the fit between the valve assembly and surrounding tissue structures. The tighter ft from a non-cylindrical configuration can favorably increase the anchoring and sealing characteristics of the prosthesis. The axial valve support portion itself may be non-cylindrical as well. 
         [0016]    Preferably, the tubular support has an axial valve support portion in the form of at least two parts, of which at least one is suitable for supporting the valve and of which at least another is suitable for pushing back the native valve sheets or the residues of the native valve sheets after valve resection, into or onto the adjacent tissue in order to make this region able to receive the tubular support. This axial valve support portion eliminates the problem generated by these valve or cardiac ring elements at the time of positioning of the replacement valve. The radial force of this axial valve support portion, by impacting all or part of the valvular tissue or in the wall or its vicinity in effect ensures a more regular surface more capable of receiving the valve support axis. It also ensures a better connection with the wall while reducing the risk of peri-prosthetic leakage. Furthermore, such a structure permits the valve to maintain a diameter within a preset range to ensure substantial coaptivity and avoid significant leakage. 
         [0017]    The particular method of maintaining the valve diameter within a preset range described above relates to the general concept of controlling the expanded diameter of the prosthesis. The diameter attained by a portion of the prosthesis is a function of the radial inward forces and the radial expansion forces acting upon that portion of the prosthesis. A portion of the prosthesis will reach its final diameter when the net sum of these forces is equal to zero. Thus, controlling the diameter of the prosthesis can be addressed by addressing the radial expansion force, the radial inward forces, or a combination of both. Changes to the radial expansion force generally occur in a diameter-dependent manner and can occur extrinsically or intrinsically. Resisting further expansion can occur extrinsically by using structural restraints that oppose the intrinsic radial expansion force of the prosthesis, or intrinsically by changing the expansion force so that it does not expand beyond a preset diameter. The first way, referred to previously, relates to controlling expansion extrinsically to a preset diameter to ensure coaptivity. In one embodiment configured to control diameter, a maximum diameter of at least a portion of the support structure may be ensured by a radial restraint provided along at least a portion of circumference of the support structure. The radial restraint may comprise a wire, thread or cuff engaging the support structure. The restraint may be attached to the support structure by knots, sutures or adhesives, or may be integrally formed with the support structure. The radial restraints may also be integrally formed with the support structure during the manufacturing of the support structure. The configuration of the radial restraint would depend upon the restraining forces necessary and the particular stent structure used for the prosthesis. A radial restraint comprising a mechanical stop system is also contemplated. A mechanical stop system uses the inverse relationship between the circumference of the support structure and the length of the support structure. As the support structure radially expands, the longitudinal length of the support structure will generally contract or compress as the wires of the support structure having a generally longitudinal orientation change to a circumferential orientation during radial expansion. By limiting the distance by which the support structure can compress in a longitudinal direction, or the angle to which the support structure wires reorient, radial expansion in turn can be limited to a maximum diameter. The radial restraint may comprise a plurality of protrusions on the support structure where the protrusions abut or form a mechanical stop against another portion of the support structure when the support structure is expanded to the desired diameter. 
         [0018]    In an embodiment configured to control the expanded diameter intrinsically for a portion of the support, the radial expansion force of the valve support may be configured to apply up to a preset diameter. This can be achieved by the use of the shape memory effect of certain metal alloys like nickel titanium or Nitinol. When Nitinol material is exposed to body heat, it will expand from a compressed diameter to its original diameter. As the Nitinol prosthesis expands, it will exert a radial expansion force that decreases as the prosthesis expands closer to its original diameter, reaching a zero radial expansion force when its original diameter is reached. Thus, use of a shape memory alloy such as Nitinol is one way to provide an intrinsic radial restraint. A non-shape memory material that is elastically deformed during compression will also exhibit diameter-related expansion forces when allowed to return to its original shape. 
         [0019]    Although both shape memory and non-shape memory based material may provide diameter-dependent expansion forces that reach zero upon attaining their original shapes, the degree of force exerted can be further modified by altering the thickness of the wire or structure used to configure the support or prosthesis. The prosthesis may be configured with thicker wires to provide a greater expansion force to resist, for example, greater radial inward forces located at the native valve site, but the greater expansion force will still reduce to zero upon the prosthesis attaining its preset diameter. Changes to the wire thickness need not occur uniformly throughout a support or a prosthesis. Wire thickness can vary between different circumferences of a support or prosthesis, or between straight portions and bends of the wire structure. 
         [0020]    The other way of controlling diameter previously mentioned is to alter or resist the radial inward or recoil forces acting upon the support or prosthesis. Recoil forces refer to any radially inward force acting upon the valve assembly that prevents the valve support from maintaining a desired expanded diameter. Recoil forces include but are not limited to radially inward forces exerted by the surrounding tissue and forces caused by elastic deformation of the valve support. Opposing or reducing recoil forces help to ensure deployment of the support structure to the desired diameter. 
         [0021]    Means for substantially minimizing recoil are also contemplated. Such means may include a feature, such as a mechanical stop, integral with the support structure to limit recoil. By forming an interference fit between the mechanical stop and another portion of the support structure when the support structure is expanded to its preset diameter, the support structure can resist collapse to a smaller diameter and resist further expansion beyond the preset diameter. The interference fit may comprise an intercalating teeth configuration or a latch mechanism. Alternatively, a separate stent may be applied to the lumen of the cardiac ring to further push aside the native valve leaflets or valve remnants by plastically deforming a portion of the prosthesis. This separate stent may be placed in addition to the support structure and may overlap at least a portion of the support structure. By overlapping a portion of the support structure, the separate stent can reduce any recoil force acting on the support structure. It is also contemplated that this separate stent might be applied to the native lumen before the introduction of the valve prosthesis described herein. Another alternative is to plastically deform the valve assembly diameter beyond its yield point so that the prosthesis does not return to its previous diameter. 
         [0022]    At portions of the prosthesis where the control of the expansion force against surrounding tissue is desired, the various methods for controlling diameter can be adapted to provide the desired control of expansion force. Portions of the prosthesis may include areas used for anchoring and sealing such as the axial wedging portions previously described. 
         [0023]    Specifically, in order to support the valve, the axial valve support portion can have a part in the form of an undulating wire with large-amplitude undulations, and a part in the form of an undulating wire with small-amplitude undulations, adjacent to said part with large amplitude undulations, having a relatively greater radial force in order to make it possible to push said valvular tissue against or into the wall of the passage. Preferably, the support according to one embodiment of the present invention has two axial wedging portions, one connected to an axial end of said valve support portion and the other to the other axial end of this same valve support portion. These two axial wedging portions thus make it possible to wedge the support on both sides of the existing cardiac ring, and consequently make possible complete wedging of the support in two opposite directions with respect to the treated site. If necessary, for example, in the case in which the passage with the valve has an aneurysm, the support according to the invention has: an axial holding portion, suitable for supporting in the deployed state the wall of the passage, and connecting wires such as the aforementioned connecting wires, connecting said axial valve support portion and said axial holding portion, these wires having a length such that the axial holding portion is situated after implantation a distance away from the axial valve support portion. This distance allows said axial holding portion to rest against a region of the wall of the passage not related to a possible defect which may be present at the approach to the valve, particularly an aneurysm. The length of the connecting wires can also be calculated in order to prevent the axial holding portion from coming into contact with the ostia of the coronary arteries. The aforementioned axial portions (valve support, wedging, holding portions) can have a structure in the form of an undulating wire, in zigzag form, or preferably a structure in diamond-shaped mesh form, the mesh parts being juxtaposed in the direction of the circumference of these portions. This last structure allows a suitable radial force making it possible to ensure complete resting of said portions against the wall that receives them. 
         [0024]    As previously mentioned, the support according to the invention can be produced from a metal that can be plastically deformed. The instrument for positioning of the support then includes a balloon which has an axial portion with a predetermined diameter, adapted for realizing the deployment of said axial valve support portion, and at least one axial portion shaped so as to have, in the inflated state, a greater cross section than that of the passage to be treated, in such a way as to produce the expansion of the axial wedging portion placed on it until this axial wedging portion encounters the wall which it is intended to engage. The support according to this embodiment of the present invention can also be produced from a material that can be elastically deformed or even a material with shape memory, such as Nitinol, which can be contracted radially at a temperature different from that of the body of the patient and which regains its original shape when its temperature approaches or reaches that of the body of the patient. 
         [0025]    Alternatively, the support may be made from a shape memory material that can be plastically deformed, or may be partially made from a shape memory material and partially made from a material that can be plastically deformed. With this embodiment, the support can be brought, by shape memory or plastic deformation, from a state of contraction to a stable intermediate state of deployment between the state of contraction and the state of total deployment, and then by plastic deformation or shape memory respectively, from said intermediate state of deployment to said state of total deployment. In said intermediate state of deployment, the support is preferably configured such that it remains mobile with respect to the site to be treated. The support may thus be brought to the site to be treated and then deployed to its intermediate state; its position can then possibly be adapted and/or corrected, and then the support be brought to its state of total deployment. One example of a shape memory material that can be plastically deformed may be a nickel-titanium alloy of the type called “martensitic Nitinol” that can undergo plastic deformation by means of a balloon. By using a balloon to expand and stress the alloy beyond its yield point, plastic deformation can occur. Plastic deformation by a balloon of a portion of the prosthesis that has already undergone self-expansion can also be used to compensate for any recoil that occurs. 
         [0026]    Advantageously, the support according to the invention has some anchoring means suitable for insertion into the wall of the site to be treated, and is shaped in such a way as to be mobile between an inactive position, in which it does not obstruct the introduction of the support into the body of the patient, and an active position, in which it is inserted into the wall of the site to be treated. Substantially complete immobilization of the support at the site is thus obtained. In particular, this anchoring means can be in the form of needles and can be mounted on the support between retracted positions and radially projected positions. Advantageously, the axial valve support portion has, at the site of its exterior surface, a sealing means shaped in such a way as to absorb the surface irregularities that, might exist at or near the existing cardiac ring. This sealing means can consist of a peripheral shell made from a compressible material such as polyester or tissue identical to the valve or a peripheral shell delimiting a chamber and having a radially expandable structure, this chamber being capable of receiving an inflating fluid suitable for solidifying after a predetermined delay following the introduction into said chamber. This sealing means can also include a material that can be applied between the existing cardiac ring and the axial valve support portion, this material being capable of solidifying after a predetermined delay following this application. Specifically, in this case, this material is capable of heat activation, for example, by means of a laser, through the balloon, or capable of activation by emission of light of predetermined frequency, for example, by means of an ultraviolet laser, through the balloon. Said sealing means can also be present in the form of an inflatable insert with a spool-shaped cross section in the inflated state, which can be inserted between the existing cardiac ring and the axial valve support portion. Said spool shape allows this insert to conform to the best extent possible to the adjacent irregular structures and to provide a better seal. 
         [0027]    In one embodiment of the invention, a drug-eluting component is contemplated. This component comprises a surface coating or matrix bonding to at least a portion of support structure. Drug elution is well known to those in the art. Potential drugs may include but are not limited to antibiotics, cellular anti-proliferative and anti-thrombogenic drugs. 
         [0028]    An assembly and method for removing the native valve is also contemplated. In particular, the invention has the objective of providing a device that gives complete satisfaction with regard to the exeresis and replacement of the valve, while allowing one to operate without opening of the thorax, stopping of the heart and/or opening of the heart, and preventing any diffusion into the circulatory system of fragments of the removed valve. In one embodiment, the assembly comprises: (a) an elongated support element; (b) a first set of elongated blades arranged around the circumference of said elongated element and connected in a pivoting manner to the elongated element at the site of their proximal longitudinal ends, each blade having a sharp edge at the site of its distal longitudinal end and configured to pivot with respect to the elongated element between a folded up (retracted) position, in which they are near the wall of the elongated element in such a way that they do not stand in the way of the introduction and sliding of the device in the body channel in which the valve is located, in particular in the aorta, and an opened out (protracted) position, in which these blades are spread out in the form of a corolla in such a way that their sharp edges are placed in extension of one another and thus constitute a sharp circular edge; (c) a second set of blades arranged consecutively to said first series of blades in the distal direction; the blades of this second set have a structure identical to that of the blades of said first set, wherein the blades of this second series are connected to the elongated element by their distal longitudinal ends and wherein each has a sharp edge at the site of its proximal longitudinal end; (d) means making it possible to bring the blades of said first and second set from their retracted position to their protracted position; (e) means for permitting axial movement of the sets of blades axially relative to one another between a spaced position in which one set of blades can be placed axially on one side of the natural valve while the other set of blades is placed axially on the other side of this valve, and a proximate position in which the sharp circular edges of the two sets of blades may be brought into mutual contact for excising the natural valve. 
         [0029]    A method of using this assembly comprises the steps of introducing the assembly percutaneously into said body channel and delivering the assembly to a position where the first and second sets of blades are spaced on opposite sides of the natural valve using the means of identification. The method may further comprise putting in place a system of peripheral aorto-venous heart assistance, extracorporeal circulation or a blood pump through the center of the delivery system for pumping blood, in the case of an aortic valve replacement, from the left ventricle (proximal to the aortic valve) to the aorta (distal to the aortic valve) in order to facilitate the flow of the blood, for the purpose of preventing stagnation of the blood in the heart. One embodiment of a blood flow pump is described further below. After the assembly is positioned in place, the method further comprises spreading the blades of the two sets of blades out; then bringing the two sets closer together to excise the valve. The configuration of these blades makes it possible to execute this cutting in a single operation, minimizing the generation of fragments that can be diffused into the circulatory system. This configuration moreover makes possible precise control of the diameter according to which the natural valve is cut, in view of later calibration of the prosthetic valve. The blades may then be retracted for placement of the prosthetic valve. 
         [0030]    The prosthetic valve may be deployed discretely from the assembly, in which case the method may comprise removing the assembly and then separately deploying the prosthetic valve. Preferably however, the assembly comprises a proximal prosthetic valve having an expandable support structure that may occupy a contracted position near the wall of said elongated element for transmission through the body channel, and an expanded position to replace the natural cardiac valve. 
         [0031]    After excising the natural valve, the method further comprises sliding the assembly axially in the distal direction in order to bring the prosthetic valve to the desired site in the channel, and then expanding the prosthetic valve support into place. The assembly may then be withdrawn, recovering the excised natural valve. 
         [0032]    Preferably, the elongated support element is a tubular catheter permitting blood to flow through it during the excision of the natural valve. The cross section of the channel of this catheter can be sufficient to allow the blood to flow through this channel with or without the help of a pump. Continued blood flow during the excision procedure may limit or eliminate the need for placing the patient under extracorporeal circulation or peripheral aorto-venous heart assistance. The catheter has a lateral distal opening in order to allow the blood to rejoin the body channel, for example the ascending aorta, this opening being arranged in such a way that the length of catheter passed through the blood is as short as possible. Alternatively, the catheter may have a small diameter to facilitate the introduction and delivery of the assembly in the body channel, but a small diameter might require the provision of peripheral circulation by an external assistance system such as an extracorporeal circulation system or peripheral aorto-venous heart assistance. 
         [0033]    Preferably, the assembly for excising the native valve includes a distal inflatable balloon, placed at the site of the exterior surface of said elongated element; wherein the balloon is configured so as to occupy a deflated position, in which it has a cross section such that it does not stand hinder introduction and advancement of the assembly within the body channel, and an expanded position. The balloon may be inflated after the positioning of the sets of blades on both sides of the natural valve in order to prevent reflux of the blood during the ablation of the natural valve. If the elongated element is a catheter, this balloon moreover makes it possible to cause blood to flow only through the catheter. Once the prosthetic valve is positioned, the balloon is deflated to re-establish the blood flow through the body channel. 
         [0034]    The assembly for excising the native valve may optionally include a distal filter made of flexible material placed on the exterior surface of the elongated element. The filter is configured so that it can occupy a retracted position or a contracted position. This filter serves to capture possible fragments generated by the excision of the natural valve, for removal from the blood circulation. The assembly may include means for moving the sets of blades in the axial direction relative to the balloon and/or from said filter. 
         [0035]    The balloon and optional filter may be separate from the assembly, being mounted on an elongated support element specific to them. In case of operation on a mitral valve, this balloon or filter may be introduced into the aorta by a peripheral artery route, and the assembly is itself introduced into the heart by the peripheral venous system, up to the right atrium and then into the left atrium through the interatrial septum, up to the site of the mitral valve. The prosthetic valve can advantageously have a frame made of a material with a shape memory, particularly a nickel-titanium alloy known as “Nitinol.” This same valve can have valve leaflets made of biological material (preserved animal or human valves) or synthetic material such as a polymer. When replacing an aortic valve the assembly may be alternatively introduced in a retrograde manner through a peripheral artery (femoral artery) or through a venous approach and transseptally (antegrade). 
         [0036]    One embodiment of a system for deploying a prosthetic valve may comprise a blood pump insertable into the lumen of a catheter to facilitate blood flow across the native valve and implantation sites during the implantation procedure. When the catheter is positioned across the implantation site, a proximal opening of the delivery catheter is on one side of the implantation site and the lateral distal opening is on another side of the implantation site. By inserting the blood pump into the catheter lumen between the proximal and lateral distal openings, blood flow across the native valve and implantation sites is maintained during the procedure. One embodiment of the blood pump comprises a rotating impeller attached to a reversible motor by a shaft. When the impeller is rotated, blood flow can be created in either direction along the longitudinal axis of the catheter between the proximal and lateral distal openings to provide blood flow across the implantation site. The pump may be used during the native valve excision step if so carried out. 
         [0037]    In one application of the present invention, the prosthetic valve may be implanted by first passing a guidewire inserted peripherally, for instance, through a vein access; transseptally from the right atrium to the left atrium and then snaring the distal end of the guidewire and externalizing the distal end out of the body through the arterial circulation. This placement of the guidewire provides access to the implantation site from both venous and arterial routes. By providing venous access to the native valve, massive valvular regurgitation during the implantation procedure may be avoided by first implanting the replacement valve and then radially pushing aside the native valve leaflets through the venous access route. 
         [0038]    The above embodiments and methods of use are explained in more detail below. 
     
    
     
       BRIEF DESCRIPTION 
         [0039]      FIG. 1  is a cross-sectional side view of one embodiment of an assembly of the present invention for removing and replacing a native heart valve percutaneously; 
           [0040]      FIG. 2  is a cross-section axial view of the assembly of  FIG. 1  taken at line II-II, shown in a closed condition; 
           [0041]      FIG. 3  is a cross-section axial view of the assembly of  FIG. 1  taken at line II-II, shown in an opened condition; 
           [0042]      FIG. 4  is a perspective schematic view of one embodiment of a prosthetic valve of the present invention; 
           [0043]      FIGS. 5 to 9  are schematic views of the assembly of the present invention positioned in a heart, at the site of the valve that is to be treated, during the various successive operations by means of which this valve is cut out and the prosthetic valve shown in  FIG. 4  deployed; 
           [0044]      FIG. 10  is a schematic view of the prosthetic valve shown of  FIG. 4  shown in a deployed state; 
           [0045]      FIG. 11  is a schematic view of an alternative embodiment of the assembly of the present invention shown treating a mitral valve; 
           [0046]      FIG. 12  is a cross-sectional view of a section of a blade used in excising the native valve. 
           [0047]      FIG. 13  is a schematic view of one embodiment of the support structure of the prosthesis assembly of the present invention; 
           [0048]      FIG. 14  is a cross-sectional view of the support of  FIG. 13  showing a heart valve supported by the central portion of the support; 
           [0049]      FIG. 15  is an end view of the support of  FIGS. 13 and 14  in the deployed state; 
           [0050]      FIG. 16  is an end view of the support of  FIGS. 13 and 14  in the contracted state; 
           [0051]      FIG. 17  is a schematic view of a heart with an embodiment of the present inventive prosthesis shown deployed in place; 
           [0052]      FIG. 18  is a schematic view of an alternative embodiment of the present invention; 
           [0053]      FIG. 19  is schematic view of an alternative embodiment of the present invention; 
           [0054]      FIG. 20  is a detail view of a part of the support structure of one embodiment of the present invention; 
           [0055]      FIG. 21  is a schematic view of the support of  FIG. 19  shown in a deployed state; 
           [0056]      FIG. 22  is schematic view of an alternative embodiment of the present invention; 
           [0057]      FIG. 23  is a detail view of the support of  FIG. 22  shown in the contracted state; 
           [0058]      FIG. 24  is a detail view of the support of  FIG. 23  taken along line  23 - 23 ; 
           [0059]      FIG. 25  is a detail view of the support of  FIG. 22  shown in the expanded state; 
           [0060]      FIG. 26  is a detail view of the support of  FIG. 25  taken along line  25 - 25 ; 
           [0061]      FIG. 27  is a schematic view of an alternative embodiment of the present invention; 
           [0062]      FIG. 28  is a detailed cross section view of the support of  FIG. 27 ; 
           [0063]      FIG. 29  is a partial schematic view in longitudinal section of the support of the present invention and of a calcified cardiac ring; 
           [0064]      FIG. 30  is a schematic view of an alternative to the support of  FIG. 29 ; 
           [0065]      FIG. 31  is a schematic view of an alternative to the support of  FIG. 29 ; 
           [0066]      FIGS. 32 and 33  are schematic views of an alternative to the support of  FIG. 29 ; 
           [0067]      FIG. 34  is a schematic cross-sectional view of a balloon corresponding to the support structure of  FIGS. 19 to 21 ; 
           [0068]      FIG. 35  is a schematic longitudinal sectional view of an alternative embodiment of the balloon of  FIG. 34 ; 
           [0069]      FIG. 36  is a schematic view of a heart with an embodiment of the present inventive prosthesis shown deployed in place; 
           [0070]      FIG. 37  is a perspective view of one embodiment of a prosthetic valve assembly of the present, invention; 
           [0071]      FIG. 38  is a side view of the prosthetic valve assembly of  FIG. 37 ; 
           [0072]      FIG. 39  is a perspective view of one embodiment of the prosthetic valve assembly of  FIG. 37 ; 
           [0073]      FIG. 40  is a perspective view of an alternative embodiment of the prosthetic valve assembly with a sheath around the valve; 
           [0074]      FIG. 41A  is a perspective view of a distal portion of a catheter assembly for use in deploying the prosthetic valve assembly described herein; 
           [0075]      FIG. 41B  is a perspective view of a proximal portion of the catheter assembly of  FIG. 41A ; 
           [0076]      FIG. 42  is a perspective view of the distal portion of the catheter assembly of  FIG. 41A ; 
           [0077]      FIGS. 43 through 45  are perspective views of the catheter assembly of  FIG. 41A  showing deployment of a prosthesis assembly in sequence; 
           [0078]      FIGS. 46 and 47  are perspective views of the catheter assembly of  FIG. 41A  showing deployment of an alternative prosthesis assembly; 
           [0079]      FIG. 48  is a perspective view of the alternative prosthesis assembly shown in  FIGS. 46 and 47 . 
           [0080]      FIG. 49  is a perspective view of an alternative embodiment of the prosthetic valve assembly of  FIG. 37  showing a distal anchor; 
           [0081]      FIG. 50  is side view of an impeller and impeller housing of one embodiment of the blood pump; 
           [0082]      FIG. 51  is a side view of a catheter with catheter openings that allow blood flow by the impeller; 
           [0083]      FIG. 52  is a side view of the catheter with the impeller in place and blood flow depicted by arrows; 
           [0084]      FIG. 53  depicts another embodiment of the invention with a separate blood pump catheter relative to the prosthesis delivery system; 
           [0085]      FIG. 54  illustrates the embodiment shown in  FIG. 16  with the blood pump in place and blood flow shown by arrows; 
           [0086]      FIG. 55  depicts one embodiment of the present invention comprising loop elements released from a delivery catheter after withdrawal of an outer sheath; 
           [0087]      FIGS. 56A and 56B  represent one embodiment of the radial restraint comprising a wire interwoven into the support structure; 
           [0088]      FIG. 57  depicts another embodiment of the invention wherein two radial restraints of different size are attached to different portions of the support structure; 
           [0089]      FIG. 58  represents one embodiment of the radial restraint comprising a cuff-type restraint; 
           [0090]      FIG. 59  is a schematic view of a wire bend with a symmetrically reduced diameter; 
           [0091]      FIG. 60  is a schematic view of an alternative embodiment of a wire bend with an asymmetrically reduced diameter; 
           [0092]      FIG. 61  is a schematic view of one embodiment of the implantation procedure for the prosthetic valve where the distal end of a transseptally placed guidewire has been externalized from the arterial circulation; 
           [0093]      FIG. 62  is a schematic view of a balloon catheter passed over the guidewire of  FIG. 61  to dilate the native valve; 
           [0094]      FIG. 63  is a schematic view showing the deployment of a prosthetic valve by an arterial approach over the guidewire of  FIG. 62 ; 
           [0095]      FIG. 64  is a schematic view showing a balloon catheter passed over the guidewire of  FIG. 63  from a venous approach and placed opposite the stented native valve for additional ablation and/or securing of the lower portion of the stent; 
           [0096]      FIG. 65  is a schematic view showing how the stent of  FIG. 64  remains attached to the delivery system by braces to allow full positioning of the stent; 
           [0097]      FIG. 66  depicts a schematic view of another embodiment of the implantation procedure for the prosthetic valve where a guidewire is inserted into the axillary artery and passed to the left ventricle; 
           [0098]      FIG. 67  depicts a schematic view of a blood pump passed over the guidewire of  FIG. 66 ; 
           [0099]      FIG. 68  depicts a schematic view of a valve prosthesis passed over the blood pump of  FIG. 67 ; 
           [0100]      FIGS. 69 and 70  depict schematic views of the deployment and attachment of the prosthesis of  FIG. 68  to the vessel wall. 
           [0101]      FIG. 71  is a photograph of a valve assembly with radial restraints integrally formed by laser cutting; 
           [0102]      FIGS. 72A through 72C  are schematic views of a portion of a valve assembly with different radial restraints formed by laser cutting; 
           [0103]      FIGS. 73A through 73E  are schematic views of another embodiment of a laser cut anti-recoil feature, in various states of expansion; 
           [0104]      FIGS. 74A and 74B  are schematic views of an angular mechanical stop for controlling diameter; and 
           [0105]      FIGS. 75A and 75B  are schematic views of an angular mechanical stop with a latch for resisting recoil. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0106]    Reference is now made to the figures wherein like parts are designated with like numerals throughout.  FIGS. 1 to 3  represent a device  1  for replacing a heart valve by a percutaneous route. This device comprises a tubular catheter  2  formed from three tubes  5 ,  6 ,  7  engaged one inside the other and on which there are placed, from the proximal end to the distal end (considered with respect to the flow of blood, that is to say from right to left in  FIG. 1 ), a prosthetic valve  10 , two series of blades  11 ,  12 , a balloon  13  and a filter  14 . The three tubes  5 ,  6 ,  7  are mounted so that they can slide one inside the other. The interior tube  5  delimits a passage  15 , the cross section of which is large enough to allow blood to flow through it. At the proximal end, the intermediate tube  6  forms a bell housing  6   a  delimiting, with the interior tube  5 , an annular cavity  17  in which the prosthetic valve  10  is contained in the furled condition. 
         [0107]      FIG. 4  shows that this valve  10  comprises an armature  20  and valve leaflets  21  mounted so that they are functionally mobile on this armature  20 . The armature comprises a collection of wires  22 ,  23 ,  24  made of shape memory material, particularly of nickel-titanium alloy known by the name of “NITINOL;” namely, (i) a proximal end wire  22  which, when the valve  10  is in the deployed state, has a roughly circular shape; (ii) a distal end wire  23  forming three corrugations in the axial direction, these corrugations being distributed uniformly around the circumference of the valve  10 , and (iii) an intermediate wire  24  forming longitudinal corrugations between the wires  22  and  23 , this wire  24  being connected to the latter ones via the ends of each of these corrugations. The valve leaflets  21  for their part are made of biological material (preserved human or animal valve leaflets) or of synthetic material, such as a polymer. The armature  20  may, when its material is cooled, be radially contracted so that the valve  10  can enter the cavity  17 . When this material is heated to body temperature, this armature  20  returns to its original shape, depicted in  FIG. 4 , in which it has a diameter matched to that of a bodily vessel, particularly the aorta, in which the native valve that is to be treated lies. This diameter of the armature  20  is such that the valve  10  bears against the wall of the bodily vessel and is immobilized in the axial direction with respect to that vessel. 
         [0108]    Each series of blades  11 ,  12  comprises metal elongate blades  30  and an inflatable balloon  31  situated between the catheter  2  and these blades  30 . The blades  30  have a curved profile and are arranged on the circumference of the catheter  2 , as shown in  FIGS. 2 ,  3  and  3 A. The blades  30  of the proximal series  11  are connected pivotably to the tube  6  by their proximal ends and comprise a cutting distal edge  30   a , while the blades  30  of the distal series  12  are connected pivotably to the exterior tube  7  by their distal ends and comprise a cutting proximal edge  30   b . The connection between the blades  30  and the respective tubes  6  and  7  is achieved by welding the ends of the blades  30  together to form a ring, this ring being fixed axially to the corresponding tube  6 ,  7  by crimping this ring onto this tube  6 ,  7 , the pivoting of the blades  30  being achieved by simple elastic deformation of these blades  30 . This pivoting can take place between a position in which the blades  30  are furled, radially internally with respect to the catheter  2  and shown in  FIGS. 1 and 2 , and a position in which these blades  30  are unfurled, radially externally with respect to this catheter  2  and shown in  FIG. 3 . In the furled position, the blades  30  lie close to the wall of the tube  6  and partially overlap each other so that they do not impede the introduction and the sliding of the device  1  into and in the bodily vessel in which the native valve that is to be treated lies; in said unfurled position, the blades  30  are deployed in a corolla so that their cutting edges  30   a ,  30   b  are placed in the continuation of one another and thus constitute a circular cutting edge visible in  FIG. 3 . 
         [0109]    Each balloon  31 , placed between the tube  3  and the blades  30 , may be inflated from the end of the catheter  2  which emerges from the patient, via a passage  32  formed in the tube  6 . It thus, when inflated, allows the blades  30  to be brought from their furled position into their unfurled position, and performs the reverse effect when deflated. The axial sliding of the tube  6  with respect to the tube  7  allows the series of blades  11 ,  12  to be moved axially toward one another, between a spaced-apart position shown in  FIG. 1 , and a close-together position. In the former of these positions, one series of blades  11  may be placed axially on one side of the native valve while the other series of blades  12  is placed axially on the other side of this valve, whereas in the latter of these positions, the circular cutting edges of these two series of blades  11 ,  12  are brought into mutual contact and thus cut through the native valve in such a way as to detach it from said bodily vessel. The tubes  5  to  7  further comprise marks (not visible in the figures) in barium sulfate allowing the axial position of the device  1  with respect to the native valve to be identified percutaneously so that, each of the two series of blades  11 ,  12  can be placed on one axial side of this valve. These tubes  5  to  7  also comprise lateral distal openings (not depicted) to allow the blood to reach the bodily vessel, these openings being formed in such a way that the length of catheter  2  through which the blood flows is as short as possible, that is to say immediately after the filter  14 , in the distal direction. 
         [0110]    The balloon  13  is placed on the exterior face of the tube  7 , distally with respect to the series  12 . This balloon  13  has an annular shape and is shaped to be able to occupy a furled position in which it has a cross section such that it does not impede the introduction and sliding of the device  1  into and in said bodily vessel, and an unfurled position, in which it occupies all of the space between the exterior face of the tube  7  and the wall of said bodily vessel and, via a peripheral edge  13   a  which it comprises, bears against this wall. 
         [0111]    The filter  14  is placed distally with respect to the balloon  13 , on the tube  7 , to which it is axially fixed. This filter  14  is made of flexible material, for example polyester netting, and is shaped to be able to occupy a furled position in which it has a cross section such that it does not impede the introduction and sliding of the device  1  into and in said bodily vessel, and an unfurled position in which it occupies all of the space between the exterior face of the catheter  2  and the wall of this vessel and, via a peripheral edge  14   a  which it comprises, bears against this wall. 
         [0112]    An inflatable balloon  35  is placed between the tube  7  and the filter  14  so as, depending on whether it is inflated or deflated, to bring the filter  14  into its respective unfurled and furled positions. In practice, as shown by  FIGS. 5 to 9 , the device  1  is introduced into said bodily vessel  50  by a percutaneous route and is slid along inside this vessel  50  until each of the series  11 ,  12  of blades is placed on one side of the native valve  55  that is to be treated ( FIG. 5 ). This position is identified using the aforementioned marks. When the device is in this position, the proximal part of the catheter  2  is situated in the heart, preferably in the left ventricle, while the aforementioned distal lateral openings are placed in a peripheral arterial vessel, preferably in the ascending aorta. The balloons  13  and  35  are inflated in such a way as to cause blood to flow only through the passage  15  and prevent blood reflux during the ablation of the valve  55 . A peripheral perfusion system is set in place to facilitate this flow, as further described below in connection with  FIGS. 50 through 52 . The blades  30  of the two series  11 ,  12  are then deployed ( FIG. 6 ) by inflating the balloons  31 , then these two series  11 ,  12  are moved closer together by sliding the tube  6  with respect to the tube  7 , until the valve  55  is cut through ( FIG. 7 ). The blades  30  are then returned to their furled position by deflating the balloons  31  while at the same time remaining in their close-together position, which allows the cut-out valve  55  to be held between them. The device  1  is then slid axially in the distal direction so as to bring the bell housing  6   a  to the appropriate position in the vessel  50  ( FIG. 8 ), after which the valve  10  is deployed by sliding the tube  6  with respect to the tube  5  ( FIG. 9 ). The balloons  13  and  35  are deflated then the device  1  is withdrawn and the cut-out valve  55  is recovered ( FIG. 10 ). 
         [0113]      FIG. 11  shows a second embodiment of the device  1 , allowing operation on a mitral valve  56 . The same reference numerals are used to denote the same elements or parts as the aforementioned, as long as these elements or parts are identical or similar in both embodiments. In this case, the tubular catheter is replaced by a support wire  2 , on which one of the series of blades is mounted and by a tube engaged over and able to slide along this wire, on which tube the other series of blades is mounted; the passages for inflating the balloons  31  run along this support wire and this tube; the balloon  13  and the filter  14  are separate from the device  1  and are introduced into the aorta via a peripheral arterial route, by means of a support wire  40  along which the passages for inflating the balloons  13  and  35  run. The device  1 , devoid of balloon  13  and the filter  14 , is for its part introduced into the heart through the peripheral venous system, as far as the right atrium then into the left atrium through the inter-auricular septum, as far as the valve  56 . For the remainder, the device  1  operates in the same way as was mentioned earlier. The invention thus provides a device for replacing a heart valve by a percutaneous route, making it possible to overcome the drawbacks of the prior techniques. Indeed the device  1  is entirely satisfactory as regards the cutting-away of the valve  55 ,  56 , making it possible to operate without stopping the heart and making it possible, by virtue of the filter  14 , to prevent tiny dispersion of valve fragments  55 ,  56  into the circulatory system. 
         [0114]    The above device may comprise a fourth tube, engaged on and able to slide along the tube  7 , this fourth tube comprising the balloon and the filter mounted on it and allowing said series of blades to be moved in the axial direction independently of said balloon and/or of said filter; the blades may be straight as depicted in the drawing or may be curved toward the axis of the device at their end which has the cutting edge, so as to eliminate any risk of lesion in the wall of the bodily vessel, as shown in  FIG. 12 ; the filter  14  may be of the self-expanding type and normally kept in the contracted position by a sliding tube, which covers it, making the balloon  35  unnecessary. 
         [0115]      FIGS. 13 to 16  represent tubular support  101  for positioning, by percutaneous route, of replacement heart valve  102 . The support structure  101  includes median portion  103 , which contains valve  102 , two extreme wedging portions  104  and wires  105  for connecting these portions  103  and  104 . Median portion  103  also includes peripheral shell  106  provided with anchoring needles  107  and shell  108  made of compressible material. As is particularly apparent from  FIG. 12 , each of portions  103  and  104  is formed with an undulating wire, and wires  105  connect pointwise the ends of the undulations of portion  103  to the end of an adjacent wave of portion  104 . Portions  104 , seen in expanded form, have lengths greater than the length of portion  103 , so that when the ends of the wires respectively forming portions  103  and  104  are connected in order to form the tubular support structure  101 , the diameter of portion  103  is smaller than the diameter of portions  104 . 
         [0116]    The diameter of portion  103  is such that portion  103  can, as shown by  FIG. 17 , support cardiac ring  110  that remains after removal of the deficient native valve, while portions  104  support walls  111  bordering ring  110 . These respective diameters are preferably such that said supporting operations take place with slight radial restraint of ring  110  and walls  111 . Portion  103  presents in the deployed state a constant diameter. Portions  104  can have a constant diameter in the form of a truncated cone whose diameter increases away from portion  103 . The entire support structure  101  can be made from a material with shape memory, such as the nickel-titanium alloy known as “Nitinol.” This material allows the structure to be contracted radially, as shown in  FIG. 16 , at a temperature different from that of the body of the patient and to regain the original shape shown in  FIGS. 14 and 15  when its temperature approaches or reaches that of the body of the patient. The entire support structure  101  can also be made from a material that can be expanded using a balloon, such as from medical stainless steel (steel 316 L). Valve  102  can be made of biological or synthetic tissue. It is connected to portion  103  by sutures or by any other appropriate means of attachment. It can also be molded on portion  103 . Shell  106  may be made of “Nitinol.” It is connected to the undulations of portion  103  at mid-amplitude, and has needles  107  at the sire of its regions connected to these undulations. Needles  107  consist of strands of metallic wire pointed at their free ends, which project radially towards the exterior of shell  106 . 
         [0117]    This shell can take on the undulating form that can be seen in  FIG. 16  in the contacted state of support  101  and the circular form which can be seen in  FIG. 4  in the deployed state of this support  101 . In its undulating form, shell  106  forms undulations  106   a  projecting radially on the outside of support  101 , beyond needles  107 , so that these needles  107 , in the retracted position, do not obstruct the introduction of support  101  in a catheter or, once support  101  has been introduced into the heart using this catheter, do not obstruct the deployment out of this support  1 . The return of shell  106  to its circular form brings needles  107  to a position of deployment, allowing them to be inserted in ring  110  in order to complete the anchoring of support  101 . Shell  108  is attached on shell  106 . Its compressible material allows it to absorb the surface irregularities that might exist at or near ring  110  and thus to ensure complex sealing of valve  102 . 
         [0118]      FIG. 18  shows a support structure  101  having a single portion  104  connected to portion  103  by wires  105 . This portion  104  is formed by two undulating wires  114  connected together by wires  115 .  FIG. 19  shows a support structure  101  that has portion  103  and portion  104  connected by connecting wires  105 . These portions  103  and  104  have diamond-shaped mesh structures, these mesh parts being juxtaposed in the direction of the circumference of these portions and connected together at the site of two of their opposite angles in the direction of the circumference of these portions  103  and  104 . Wires  105  are connected to these structures at the site of the region of junction of two consecutive mesh parts. These mesh parts also have anchoring hooks  107  extending through them from one of their angles situated in the longitudinal direction of support  101 . 
         [0119]      FIG. 20  illustrates, in an enlarged scale, the structure of this portion  104  and of a part of wires  105 , as cut, for example, with a laser from a cylinder of stainless steel, and after bending of sharp ends  107   a  of hooks  107 . These hooks, in a profile view, can have the shape as shown in  FIG. 24  or  26 . The structure represented in  FIG. 19  also has axial holding portion  120 , which has a structure identical to that of portion  104  but with a coarser mesh size, and three wires  105  of significant length connecting this portion  120  to portion  103 . Those wises  105 , on the side of portion  120 , have a single link  105   a  and on the side of portion  103 , a double link  105   b . Their number corresponds to the three junctions formed by the three valves of valve  102 , which facilitates mounting of valve  102  on support  101  thus formed. The support according to  FIG. 19  is intended to be used, as appears in  FIG. 21 , when the body passage with the valve to be replaced, in particular the aorta, has a variation in diameter at the approach to the valve. The length of wires  105  connecting portions  103  and  120  is provided so that after implantation, portion  120  is situated in a non-dilated region of said body passage, and this portion  120  is provided so as to engage the wall of the passage. 
         [0120]      FIG. 22  shows a structure similar to that of  FIG. 19  but unexpanded, except that the three wires  105  have a single wire structure but have an undulating wire  121  ensuring additional support near portion  103 . This wire  121  is designed to support valve  102  with three valve leaflets.  FIGS. 23 to 26  show an embodiment variant of the structure of portions  103 ,  104  or  120 , when this structure is equipped with hooks  107 . In this case, the structure has a zigzagged form, and each hook  107  has two arms  107   b ; each of these arms  107   b  is connected to the other arm  107   b  at one end and to an arm of structure  101  at its other end. The region of junction of the two arms  107   b  has bent hooking pin  107   a.    
         [0121]      FIG. 27  shows portion  103  that has two undulating wires  125 ,  126  extending in the vicinity of one another and secondary undulating wire  127 . As represented in  FIG. 28 , wires  125 ,  126  can be used to execute the insertion of valve  102  made of biological material between them and the attachment of this valve  102  to them by means of sutures  127 .  FIG. 29  shows a part of support  101  according to  FIGS. 13 to 17  and the way in which the compressible material constituting shell  108  can absorb the surface irregularities possibly existing at or near ring  110 , which result from calcifications.  FIG. 30  shows support  101  whose shell  106  has no compressible shell. A material can then be applied, by means of an appropriate cannula (not represented), between ring  110  and this shell  106 , this material being able to solidify after a predetermined delay following application. 
         [0122]      FIG. 31  shows support  101  whose shell  106  has a cross section in the form of a broken line, delimiting, on the exterior radial side, a lower shoulder. Housed in the step formed by this shoulder and the adjacent circumferential wall is peripheral shell  108  which can be inflated by means of a catheter (not represented). This shell  108  delimits a chamber and has a radially expandable structure, such that it has in cross section, in the inflated state, two widened ends projecting on both sides of shell  106 . This chamber can receive an inflating fluid that can solidify in a predetermined delay following its introduction into said chamber. Once this material has solidified, the inflating catheter is cut off. 
         [0123]      FIGS. 32 and 33  show support  101  whose shell  106  receives inflatable insert  108  which has a spool-shaped cross section in the inflated state; this insert  108  can be inflated by means of catheter  129 . Insert  108  is positioned in the uninflated state ( FIG. 32 ) at the sites in which a space exists between shell  106  and existing cardiac ring  110 . Its spool shape allows this insert (cf.  FIG. 33 ) to conform as much as possible to the adjacent irregular structures and to ensure a better seal. 
         [0124]      FIG. 34  shows balloon  130  making it possible to deploy support  101  according to  FIGS. 19 to 21 . This balloon  130  has cylindrical portion  131  whose diameter in the inflated state makes possible the expansion of holding portion  120 , a cylindrical portion  132  of lesser diameter, suitable for producing the expansion of portion  103 , and portion  133  in the form of a truncated cone, makes possible the expansion of portion  104 . As shown by  FIG. 35 , portion  132  can be limited to what is strictly necessary for deploying portion  103 , which makes it possible to produce balloon  130  in two parts instead of a single part, thus limiting the volume of this balloon  130 . 
         [0125]      FIG. 36  shows support  101  whose median portion  103  is in two parts  103   a ,  103   b . Part  103   a  is made of undulating wire with large-amplitude undulations, in order to support valve  102 , and part  103   b , adjacent to said part  103   a  and connected to it by bridges  135 , is made of undulating wire with small-amplitude undulations. Due to its structure, this part  103   b  presents a relatively high radial force of expansion and is intended to be placed opposite ring  110  in order to push back the native valve sheets which are naturally calcified, thickened and indurated, or the residues of the valve sheets after valve resection against or into the wall of the passage. This axial portion  103   a ,  103   b  thus eliminates the problem induced by these sheets or residual sheets at the time of positioning of valve  102 . 
         [0126]    It is apparent from the preceding that one embodiment of the invention provides a tubular support for positioning, by percutaneous route, of a replacement heart valve, which provides, due to its portions  103  and  104 , complete certitude as to its maintenance of position after implantation. This support also makes possible a complete sealing of the replacement valve, even in case of a cardiac ring with a surface that is to varying degrees irregular and/or calcified, and its position can be adapted and/or corrected as necessary at the time of implantation. 
         [0127]    Referring to  FIGS. 37 and 38 , the present invention also comprises an alternative prosthetic valve assembly  310 , which further comprises a prosthetic valve  312 , a valve support band  314 , distal anchor  316 , and a proximal anchor  318 . Valve  312  can be made from a biological material, such as one originating from an animal or human, or from a synthetic material, such as a polymer. Depending upon the native valve to be replaced, the prosthetic valve  312  comprises an annulus  322 , a plurality of leaflets  324  and a plurality of commissure points  326 . The leaflets  324  permit the flow of blood through the valve  312  in only one direction. In the preferred embodiment, the valve annulus  322  and the commissure points  326  are all entirely supported within the central support band  314 . Valve  312  is attached to the valve support band  314  with a plurality of sutures  328 , which can be a biologically compatible thread. The valve could also be supported on band  314  with adhesive, such as cyanoacrylate. 
         [0128]    In one embodiment, valve  312  can be attached to, or may integral with, a sleeve or sheath  313 . The sheath is secured to the valve support band  314  such that the outer surface of the sheath is substantially in contact with the inner surface of the valve support band  314 . In such embodiment, the sheath can be attached to the valve support band  314  with sutures  328 .  FIG. 40  is a schematic of the concept of this alternative embodiment. If desired, the sheath  313  can be secured to the outside of valve support band  314  (not shown). 
         [0129]    Referring to  FIGS. 37 and 38 , in one embodiment, valve support band  314  is made from a single wire  342  configured in a zigzag manner to form a cylinder. Alternatively, valve support band  314  can be made from a plurality of wires  342  attached to one another. In either case, the band may comprise one or more tiers, each of which may comprise one or more wires arranged in a zigzag manner, for structural stability or manufacturing ease, or as anatomical constraints may dictate. If desired, even where the central valve support  314  is manufactured having more than one tier, the entire valve support  314  may comprise a single wire. Wire  342  can be made from, for example, stainless steel, silver, tantalum, gold, titanium or any suitable plastic material. Valve support band  314  may comprise a plurality of loops  344  at opposing ends to permit attachment to valve support band  314  of anchors  316  and/or  318  with a link. Loops  344  can be formed by twisting or bending the wire  342  into a circular shape. Alternatively, valve support band  314  and loops  344  can be formed from a single wire  342  bent in a zigzag manner, and twisted or bent into a circular shape at each bend. The links can be made from, for example, stainless steel, silver, tantalum, gold, titanium, any suitable plastic material, solder, thread, or suture. The ends of wire  342  can be joined together by any suitable method, including welding, gluing or crimping. 
         [0130]    Still referring to  FIGS. 37 and 38 , in one embodiment, distal anchor  316  and proximal anchor  318  each comprise a discrete expandable band made from one or more wires  342  bent in a zigzag manner similar to the central band. Distal anchor band  316  and proximal anchor band  318  may comprise a plurality of loops  344  located at an end of wire  342  so that distal anchor band  316  and proximal anchor band  318  can each be attached to valve support band  314  with a link. Loop  344  can be formed by twisting or bending the wire  342  into a circular shape. As desired, distal and/or proximal anchors  316 ,  318  may comprise one or more tiers, as explained before with the valve support  314 . Likewise, each anchor may comprise one or more wires, regardless of the number of tiers. As explained above in regard to other embodiments, the distal anchor may be attached to the central valve support band  314  directly, as in  FIG. 37 , or spaced distally from the distal end of the valve support  314 , as shown above schematically in  FIGS. 18 ,  19 ,  21  and  22 . In the later instance, one or more struts may be used to link the distal anchor band to the valve support band, as described above. 
         [0131]    Distal anchor band  316  has a first end  350  attached to the central valve band  314 , and a second end  352 . Similarly, proximal anchor band  318  has first attached end  354  and a second end  356 . The unattached ends  352 ,  356  of the anchors  316 ,  318 , respectively are free to expand in a flared manner to conform to the local anatomy. In such embodiment, the distal and proximal anchor bands  316 ,  318  are configured to exert sufficient radial force against the inside wall of a vessel in which it can be inserted. Applying such radial forces provides mechanical fixation of the prosthetic valve assembly  310 , reducing migration of the prosthetic valve assembly  310  once deployed. It is contemplated, however, that the radial forces exerted by the valve support  314  may be sufficient to resist more than a minimal amount of migration, thus avoiding the need for any type of anchor. 
         [0132]    In an alternative embodiment, distal and proximal anchors may comprise a fixation device, including barbs, hooks, or pins (not shown). Such devices may alternatively or in addition be placed on the valve support  314 . If so desired, the prosthetic valve assembly  310  may comprise an adhesive on the exterior thereof to adhere to the internal anatomical lumen. 
         [0133]    Prosthetic valve assembly  310  is compressible about its center axis such that its diameter may be decreased from an expanded position to a compressed position. When placed into the compressed position, valve assembly  310  may be loaded onto a catheter and transluminally delivered to a desired location within a body, such as a blood vessel, or a detective, native heart valve. Once properly positioned within the body the valve assembly  310  can be deployed from the compressed position to the expanded position.  FIG. 39  is a schematic of one embodiment of the prosthetic valve assembly described with both distal and proximal anchor bands  316 ,  318  while  FIG. 49  is a schematic showing only a distal anchor  316 . 
         [0134]    In the preferred embodiment, the prosthetic valve assembly  310  is made of self-expanding material, such as Nitinol. In an alternative embodiment, the valve assembly  310  requires active expansion to deploy it into place. Active expansion may be provided by an expansion device such as a balloon. 
         [0135]    As referred to above in association with other embodiments, the prosthetic valve assembly of the present invention is intended to be percutaneously inserted and deployed using a catheter assembly. Referring to  FIG. 41A , the catheter assembly  510  comprises an outer sheath  512 , an elongate pusher tube  514 , and a central tube  518 , each of which are concentrically aligned and permit relative movement with respect to each other. At a distal end of the pusher tube  514  is a pusher tip  520  and one or more deployment hooks  522  for retaining the prosthesis assembly (not shown). The pusher tip  520  is sufficiently large so that a contracted prosthesis assembly engages the pusher tip  520  in a frictional fit arrangement. Advancement of the pusher tube  514  (within the outer sheath  512 ) in a distal direction serves to advance the prosthesis relative to the outer sheath  512  for deployment purposes. 
         [0136]    At a distal end of the central tube  518  is an atraumatic tip  524  for facilitating the advancement of the catheter assembly  510  through the patient&#39;s skin and vasculature. The central tube  518  comprises a central lumen (shown in phantom) that can accommodate a guide wire  528 . In one embodiment, the central lumen is sufficiently large to accommodate a guide wire  528  that is 0.038 inch in diameter. The guide wire can slide through the total length of the catheter form tip to handle (‘over the wire’ catheter) or the outer sheath  512  can be conformed so as to allow for the guide wire to leave the catheter before reaching its proximal end (‘rapid exchange’ catheter). The space between the pusher tube  514  and the outer sheath  512  forms a space within which a prosthetic valve assembly may be mounted. 
         [0137]    Hooks  522  on the distal end of the pusher tube  514  may be configured in any desired arrangement, depending upon the specific features of the prosthetic assembly. With regard to the prosthesis assembly of  FIGS. 37 and 38 , the hooks  522  preferably comprise an L-shaped arrangement to retain the prosthesis assembly axially, but not radially. With a self-expanding assembly, as the prosthesis assembly is advanced distally beyond the distal end of the outer sheath  512 , the exposed portions of the prosthesis assembly expand while the hooks  522  still retain the portion of the prosthesis still housed within the outer sheath  512 . When the entire prosthesis assembly is advanced beyond the distal end of the outer sheath, the entire prosthesis assembly is permitted to expand, releasing the assembly from the hooks.  FIGS. 42 through 45  show the distal end of one embodiment of the catheter assembly, three of which show sequenced deployment of a valve prosthesis. 
         [0138]      FIG. 48  shows an alternative embodiment of the valve prosthesis, where loop elements extend axially from one end of the prosthesis and are retained by the hooks  522  on pusher tube  514  during deployment.  FIGS. 46 and 47  show a catheter assembly used for deploying the alternative prosthesis assembly of  FIG. 48 . By adding loop elements to the prosthesis, the prosthesis may be positioned with its support and anchors fully expanded in place while permitting axial adjustment into final placement before releasing the prosthesis entirely from the catheter. Referring to  FIG. 55 , an alternative embodiment of a self-expanding valve prosthesis and delivery system comprises loop elements  694  on prosthetic assembly  310  retained by disks  696  on pusher tube  514  by outer sheath  512 . When outer sheath  512  is pulled back to expose disks  696 , self-expanding loop elements  694  are then released from pusher tube  514 . 
         [0139]      FIG. 41B  shows the proximal end of the catheter assembly  510  that, to a greater extent, has many conventional features. At the distal end of the pusher tube  514  is a plunger  530  for advancing and retreating the pusher tube  514  as deployment of the prosthesis assembly is desired. As desired, valves and flush ports proximal and distal to the valve prosthesis may be provided to permit effective and safe utilization of the catheter assembly  510  to deploy a prosthesis assembly. 
         [0140]    In one embodiment, prosthetic valve assembly  310  (not shown) is mounted onto catheter  510  so that the valve assembly  310  may be delivered to a desired location inside of a body. In such embodiment, prosthetic valve assembly  310  is placed around pusher tip  520  and compressed radially around the tip  520 . The distal end of prosthetic valve assembly  310  is positioned on the hooks  522 . While in the compressed position, outer sheath  512  is slid toward the atraumatic tip  524  until it substantially covers prosthetic valve assembly  310 . 
         [0141]    To deliver prosthetic valve assembly  310  to a desired location within the body, a guide wire  528  is inserted into a suitable lumen of the body, such as the femoral artery or vein to the right atrium, then to the left atrium through a transseptal approach, and maneuvered, utilizing conventional techniques, until the distal end of the guide wire  528  reaches the desired location. The catheter assembly  510  is inserted into the body over the guide wire  528  to the desired position. Atraumatic tip  524  facilitates advancement of the catheter assembly  510  into the body. Once the desired location is reached, the outer sheath  512  is retracted permitting the valve prosthesis to be released from within the outer sheath  512 , and expand to conform to the anatomy. In this partially released state, the position of prosthetic valve  310  may be axially adjusted by moving catheter assembly  510  in the proximal or distal direction. 
         [0142]    It is apparent that the invention advantageously contemplates a prosthesis that may have a non-cylindrical shape, as shown in several earlier described embodiments including but not limited to  FIGS. 21 ,  37 - 40 ,  49  and  59 . This non-cylindrical shape results from controlling the diameters at some portions of prosthetic valve assembly  310 . Referring to  FIG. 56A , yet another non-cylindrical prosthesis is shown. Central support band  314  comprises a diameter-restrained portion of valve assembly  310  attached to distal and proximal anchors  316 ,  318 , that comprise discrete self-expandable bands capable of expanding to a flared or frusta-conical configuration. Anchors  316 ,  318  further accentuate the non-cylindrical shape of central support band  314 .  FIG. 56A  shows one embodiment of the invention for limiting the diameter of portions of the valve assembly  310  from excessive expansion, whereby valve assembly  310  further comprises a radial restraint  690  to limit the diameter of central support band  314 . Radial restraint, as used herein, shall mean any feature or process for providing a desired diameter or range of diameters, including but not limited to the selection of materials or configurations for valve assembly  310  such that it does not expand beyond a preset diameter. Controlling radial expansion to a preset diameter at central support band  314  helps maintain the coaptivity of valve  312  and also preserves the patency of the coronary ostia by preventing central support band  314  from fully expanding to the lumen or chamber wall to cause occlusion. Restraint  690  may be sufficiently flexible such that restraint  690  may contract radially with valve assembly  310 , yet in the expanded state resists stretching beyond a set limit by the radial expansion forces exerted by a self-expanding valve assembly  310  or from a balloon catheter applied to valve assembly  310 . Referring to  FIGS. 56A and 56B , restraint  690  may take any of a variety of forms, including wires  700  of a specified length that join portions of central support band  314 , Threads may also be used for radial restraint  690 . The slack or bends in the wires allow a limited radial expansion to a maximum diameter. Once the slack is eliminated or the bends are straightened, further radial expansion is resisted by tension created in wires  700 . These wires may be soldered, welded or interwoven to valve assembly  310 . By changing the length of wire joining portions of valve assembly  310 , radial restraints of different maximum diameters are created. For example, by using short wires to form the radial restraint, the valve support structure may expand a shorter distance before tension forms in the short wires. If longer wires are used, the support structure may expand farther before tension develops in the longer wires. 
         [0143]      FIG. 57  depicts central support band  314  with a radial restraint  700  of a smaller diameter and another portion of the same valve assembly  310  with longer lengths of wire  701  and allowing a larger maximum diameter. The portion of valve assembly  310  with the larger diameter can be advantageously used to allow greater dilation around cardiac ring  110  and native valve sheets. The degree of resistance to expansion or recollapse can be altered by changing the diameter of the radial restraint or by changing the configuration of the restraint. For example, a cross-linked radial restraint will have a greater resistance to both expansion and recollapse. Referring to  FIG. 58 , restraint  690  may alternatively comprise a cuff  691  encompassing a circumference of central support band  314  that resists expansion of central support band  314  beyond the circumference formed by cuff  691 . Cuff  691  may be made of ePTFE or any other biocompatible and flexible polymer or material as is known to those skilled in the art. Cuff  691  may be attached to valve assembly  310  by sutures  692  or adhesives. 
         [0144]      FIG. 71  illustrates one embodiment of the invention where radial restraints are integrally formed as part of valve assembly  310  by using a laser cutting manufacturing process, herein incorporated by reference.  FIG. 72A  depicts a schematic view of a laser-cut portion of valve assembly  310  in the unexpanded state with several radial restraints  706 ,  708 ,  710 . Each end of radial restraints  706 ,  708 ,  710  is integrally formed and attached to valve assembly  310 . An integrally formed radial restraint may be stronger and may have a lower failure rate compared to radial restraints that are sutured, welded or soldered to valve assembly  310 .  FIG. 72B  depicts a shorter radial restraint  706  along one circumference of valve assembly  310 .  FIG. 72C  depicts another portion of valve assembly  310  with a longer radial restraint  70 S and a cross-linked radial restraint  710  positioned along the same circumference. Thus, the segments of a radial restraint along a given circumference need not have the same characteristics or size. 
         [0145]    Another embodiment of the radial restraint comprises at least one protrusion extending from valve assembly  310  to provide a mechanical stop arrangement. The mechanical stop arrangement restricts radial expansion of valve assembly  310  by using the inverse relationship between the circumference of valve assembly  310  and the length of valve assembly  310 . As valve assembly  310  radially expands, the longitudinal length of valve assembly  310  may contract or compress as the diameter of valve assembly  310  increases, depending upon the particular structure or configuration used for valve assembly  310 . For example,  FIGS. 37 ,  38 ,  56 A,  57  and  71  depict embodiments of the invention wherein valve assembly  310  comprises a diamond-shaped mesh. The segments of the mesh have a generally longitudinal alignment that reorient to a more circumferential alignment during radial expansion of valve assembly  310 . By limiting the distance to which valve assembly  310  can compress in a longitudinal direction, or by restricting the amount of angular reorientation of the wires of valve assembly  310 , radial expansion in turn may be controlled to a pre-set diameter.  FIG. 74A  shows one embodiment of the mechanical stop arrangement comprising an angular stop  730  and an abutting surface  732  on the wire structure of valve assembly  310 . A plurality of stops  730  and abutting surfaces  732  may be used along a circumference of valve assembly  310  to limit expansion to a preset diameter. Angular stop  730  may be located between two adjoining portions of valve assembly  310  forming an angle that reduces with radial expansion. As shown in  FIG. 74B , as valve assembly  310  radially expands, angular stop  730  will come in closer proximity to surface  732  and eventually abut against surface  732  to prevent further diameter expansion of valve assembly  310 . The angular size  734  of stop  730  can be changed to provide different expansion limits. The radial size  736  of stop  730  can also be changed to alter the strength of stop  730 . One skilled in the art will understand that many other configurations may be used for valve assembly  310  besides a diamond-shape configuration. For example,  FIGS. 15 and 16  depict support  101  with an undulating wire stent configuration that exhibits minimal longitudinal shortening when expanding. The mechanical stop arrangements described above may be adapted by those skilled in the art to the undulating wire stent configuration, or any other stent configuration, for controlling the diameter of the support structure or valve assembly  310 . 
         [0146]    The particular method of maintaining the valve diameter within a preset range described previously relates to the general concept of controlling the expanded diameter of the prosthesis. The diameter attained by a portion of the prosthesis is a function of the radial inward forces and the radial expansion forces acting upon that portion of the prosthesis. A portion of the prosthesis will reach its final diameter when the net sum of these forces is equal to zero. Thus, controlling the diameter of the prosthesis can be addressed by changing the radial expansion force, changing the radial inward forces, or a combination of both. Changes to the radial expansion force generally occur in a diameter-related manner and can occur extrinsically or intrinsically. Radial restraint  690 , cuff  691  and mechanical stop  730  of  FIGS. 56A ,  58  and  74 A, respectively, are examples of extrinsic radial restraints that can limit or resist diameter changes of prosthetic valve assembly  310  once a preset diameter is reached. 
         [0147]    Other ways to control diameter may act intrinsically by controlling the expansion force so that it does not expand beyond a preset diameter. This can be achieved by the use of the shape memory effect of certain metal alloys like Nitinol. As previously mentioned, when a Nitinol prosthesis is exposed to body heat, it will expand from a compressed diameter to its original diameter. As the Nitinol prosthesis expands, it will exert a radial expansion force that decreases as the prosthesis expands closer to its original diameter, reaching a zero radial expansion force when its original diameter is reached. Thus, use of a shape memory alloy such as Nitinol is one way to provide an intrinsic radial restraint. A non-shape memory material that is elastically deformed during compression will exhibit similar diameter-dependent expansion forces when returning to its original shape. 
         [0148]    The other way of controlling diameter mentioned previously is to alter the radial inward or recoil forces acting upon the support or prosthesis. Recoil forces refer to any radially inward force acting upon the valve assembly that prevents the valve support from maintaining a desired expanded diameter. Recoil forces include but are not limited to radially inward forces exerted by the surrounding tissue and forces caused by elastic deformation of prosthetic valve assembly  310 . Countering or reducing recoil forces help to ensure deployment of prosthetic valve assembly  310  to the desired diameter or diameter range, particularly at the native valve. For example, when the prosthetic valve assembly  310  of  FIGS. 37 ,  38 ,  56 A,  57  and  58  is deployed, some recoil or diameter reduction may occur that can prevent portions of valve assembly  310  from achieving it pre-set or desired diameter. This recoil can be reduced by applying an expansion force, such as with a balloon, that stresses the material of valve assembly  310  beyond its yield point to cause plastic or permanent deformation, rather than elastic or transient deformation. Similarly, balloon expansion can be used to further expand a self-expanded portion of valve assembly  310  where radially inward anatomical forces have reduced the desired diameter of that portion. Balloon expansion of a self-expanded portion of valve assembly  310  beyond its yield point provides plastic deformation to a larger diameter. 
         [0149]    In addition to the use of a balloon catheter to deform valve assembly  310  beyond its yield point, other means for reducing recoil are contemplated. In the preferred embodiment of the invention, a separate stent may be expanded against cardiac ring  110  in addition or in place of valve assembly  310 . The separate stent may further push back the native valve sheets or residues of the resected valve and reduce the recoil force of these structures on valve assembly  310 . If the separate stent is deployed against cardiac ring  110  prior to deployment of valve assembly  310 , a higher radial force of expansion is exerted against ring  110  without adversely affecting the restrained radial force of expansion desired for the central support band  314  supporting valve  312 . Alternatively, the separate stent may be deployed after valve assembly  310  and advantageously used to reduce the recoil of valve assembly  310  caused by the elastic deformation of the material used to form valve assembly  310 . The separate stent may be self-expanding or balloon-expandable, or a combination thereof. 
         [0150]    Another means for addressing recoil involves providing the radial restraint and mechanical stop arrangements previously described with an additional feature that forms an interference fit when the valve assembly  310  is at its preset diameter. By forming an interference fit, the radial restraint or mechanical stop will resist both further expansion and recollapse from recoil.  FIGS. 73A through 73E  depict an embodiment of a radial restraint with a recoil-resistant configuration integrally formed with valve assembly  310 . In this embodiment, each segment of the radial restraint comprises a pair of protrusions  712  having a proximal end  714  and a distal end  716 . Proximal end  714  is integrally formed and attached to valve, assembly  310  while distal end  716  is unattached. Each pair of protrusions  712  is configured so that distal end  716  of one protrusion  712  is in proximity to the proximal end  714  of other protrusion  712  in the unexpanded state, and where distal ends  716  come close together as valve assembly  310  radially expands. Distal ends  716  comprise a plurality of teeth  718  for providing an interference fit between distal ends  716  upon contact with each other. The interference fit that is formed will resist both further radial expansion and collapse of valve assembly  310 . As mentioned earlier, collapse may result from the inherent elastic properties of the materials used for valve assembly  310  or from radially inward forces exerted by the tissue surrounding valve assembly  310 . The interference fit may be provided over a range of expansion, as depicted in  FIGS. 72B and 72C  from the self-expanded state through the extra-expanded state. This allows the inference fit to act even when a self-expanded valve assembly  310  is further expanded by a balloon catheter to an extra-expanded state as the expansion diameter is further adjusted. The lengths of protrusions  712  will determine the amount of radial restraint provided. Shorter protrusions  712  have distal ends  716  that contact each other after a shorter distance of radial expansion, while longer protrusions  712  will form an interference fit after a longer distance. 
         [0151]      FIGS. 75A and 75B  depict another embodiment of a radial restraint with a recoil resistant feature. Angular stop  730  from  FIGS. 74A and 74B  is provided with a notch  736  that forms an interference fit with a latch  738  protruding from valve assembly  310  adjacent to surface  732 . As valve assembly  310  expands, angular stop  730  will eventually abut against to surface  732  to prevent further expansion. Latch  738  will also move closer to notch  736  as valve assembly  310  expands. When the preset diameter is reached, latch  738  forms an interference fit with notch  736  that resists collapse to a smaller diameter. It is contemplated that a balloon catheter may be used to expand valve assembly  310  to the desired diameter and to engage latch  738  to notch  736 . 
         [0152]    Although both shape memory and non-shape memory based prostheses provide diameter-dependent expansion forces that reach zero upon attaining their original shapes, the degree of force exerted can be further modified by altering the thickness of the wire or structure used to configure the support or prosthesis. A prosthesis can be configured with thicker wires to provide a greater expansion force to resist, for example, greater radial inward forces located at the native valve site, but the greater expansion force will still reduce to zero upon the prosthesis attaining its preset diameter. Changes to wire thickness need not occur uniformly throughout a support or prosthesis. Wire thickness can vary between different circumferences of a support or prosthesis, or between straight portions and bends of the wire structure. As illustrated in  FIG. 59 , the decreased diameter  702  may be generally symmetrical about the longitudinal axis of the wire. Alternatively, as in  FIG. 60 , the decreased diameter  704  may be asymmetrical, where the diameter reduction is greater along the lesser curvature of the wire bend or undulation relative to the longitudinal axis of the wire. At portions of the prosthesis where the exertion of a particular expansion force against surrounding tissue has importance over the actual diameter attained by that portion of the prosthesis, the various methods for controlling diameter can be adapted to provide the desired expansion force. These portions of the prosthesis may include areas used for anchoring and sealing such as the axial wedging portions or anchors previously described. 
         [0153]    Referring to  FIG. 61 , a method for deploying the preferred embodiment of the invention using the separate stent is provided. The method of deployment comprises a guidewire  640  inserted via a venous approach  642  and passed from the right  644  to left atrium  646  through a known transseptal approach, herein incorporated by reference. After transseptal puncture, guidewire  640  is further directed from left atrium  646  past the mitral valve  648  to the left ventricle  650  and through the aortic valve  652 . An introducer (not shown) is inserted via an arterial approach and a snare (not shown), such as the Amplatz GOOSE NECK® snare (Microvena, MN), is inserted through the introducer to grasp the distal end of guidewire  640  and externalize guidewire  640  out of the body through the introducer. With both ends of guidewire  640  external to the body, access to the implantation site is available from both the venous  642  and arterial approaches  654 . In  FIG. 62 , aortic valve  652  is pre-dilated by a balloon catheter  656  using a well-known valvuloplasty procedure, herein incorporated by reference. The prosthesis is then implanted as previously described by passing the delivery system from either the venous or arterial approaches. As illustrated in  FIG. 63 , the prosthesis  658  may be implanted using arterial approach  654  with prosthetic valve  658  implanted above the level of native valve  652 . As shown in  FIG. 64 , a balloon catheter  660  may be passed by venous approach  642  for further displacement of native valve  652  and/or to further secure the Sower stent  662  to the annulus. Hooks  664 , shown in  FIG. 65 , connecting the delivery catheter to prosthetic valve  658  allow full control of prosthetic valve  658  positioning until the operator chooses to fully release and implant prosthetic valve  658 . A separate stent may then be implanted by venous approach  642  at the valvular ring to further push back the native valve or valve remnants and reduce recoil forces from these structures. Passing balloon  660  by the venous approach  642  avoids interference with superiorly located prosthetic valve  658 . Implantation of replacement valve  658  by arterial approach  654  prior to the ablation of the native valve  652  or valve remnants by venous approach  642  may reduce the risks associated with massive aortic regurgitation when native valve  652  is pushed back prior to implantation of replacement valve  658 . Reducing the risks of massive aortic regurgitation may provide the operator with additional time to position replacement valve  658 . 
         [0154]    It is further contemplated that in the preferred embodiment of the invention, valve assembly  310  also comprises a drug-eluting component well known in the art and herein incorporated by reference. The drug-eluting component may be a surface coating or a matrix system bonded to various portions of valve assembly  310 , including but not limited to central support band  314 , anchors  316   318 , valve  312 , loop elements  352  or wires  342 . The surface coating or matrix system may have a diffusion-type, erosive-type or reservoir-based drug release mechanism. Drugs comprising the drug-eluting component may include antibiotics, cellular anti-proliferative and/or anti-thrombogenic drugs. Drugs, as used herein, include but are not limited to any type of biologically therapeutic molecule. Particular drugs may include but are not limited to actinomycin-D, batimistat, c-myc antisense, dexamethasone, heparin, paclitaxel, taxanes, sirolimus, tacrolimus and everolimus. 
         [0155]    As previously mentioned, one embodiment of the system for implanting the prosthesis and/or excising the native valve leaflets contemplates maintaining blood flow across the native valve site during the excision and implantation procedure. By maintaining blood flow across the native valve, use of extracorporeal circulation or peripheral aorto-venous heart assistance and their side effects may be reduced or avoided. Major side effects of extracorporeal circulation and peripheral aorto-venous heart assistance include neurological deficits, increased bleeding and massive air emboli.  FIGS. 50 through 52  depict one embodiment of the invention for maintaining blood perfusion during the procedure. This embodiment comprises a blood pump  600  and an opening  602  positioned in the wall of tubular catheter  2  of the excision system. When the tabular catheter  2  is positioned at the excision site, blood pump  600  allows continued blood flow across the excision site that would otherwise be interrupted during the excision procedure. Blood pump  600  may comprise a motor, a shaft and an impeller. Blood pump  600  is insertable through passage  15  of tubular catheter  2 . The motor is connected to a shaft  604  that in turn is coupled to an impeller  606 . The motor is capable of rotating shaft  604 , resulting in the rotation of impeller  606 . Impeller  606  comprises a proximal end  608 , a distal end  610  and a plurality of fins  612  angled along the longitudinal axis of impeller  606 , such that when impeller  606  is rotated in one direction, fins  612  are capable of moving blood from a proximal to distal direction. When impeller  606  is rotated in the other direction, fins  612  are capable of moving blood in a distal to proximal direction. The ability to rotate impeller  606  in either direction allows but is not limited to the use of the blood pump in both anterograde and retrograde approaches to a heart valve. The blood pump is positioned generally about catheter opening  602 . The blood pump has an external diameter of about 4-mm and the passage of the catheter has a 4-mm internal diameter. Catheter opening  602  has a longitudinal length of about 4-mm. Catheter opening  602  may comprise a plurality of openings located along a circumference of tubular catheter  2 . To reduce interruption of blood flow through tubular catheter  2  during the implantation portion of the procedure, catheter opening  602  should preferably be about 30 mm from the tip of catheter  2  or distal to the bell housing  6   a . This positioning of catheter opening  602  reduces the risk of occlusion of catheter opening  602  by the replacement valve. 
         [0156]      FIG. 50  depicts an optional feature of blood pump  600  further comprising an impeller housing  614  having at least one proximal housing opening  616  and at least one distal housing opening  618 . Housing  614  protects passage  15  of tubular catheter  2  from potential damage by rotating impeller  600 . Proximal  616  and distal housing openings  618  provide inflow and outflow of blood from the impeller, depending on the rotation direction of impeller  600 . 
         [0157]    To reduce interruption of blood flow through catheter  2  during the implantation portion of the procedure, catheter opening  602  should preferably be at least a distance of about 30 mm from the distal tip of the catheter or about distal to the bell housing  6   a  to avoid occlusion of catheter opening  602  by the replacement valve. 
         [0158]      FIGS. 53 and 54  depict an alternative embodiment, where blood pump  620  is located in a second catheter  622  in the prosthesis delivery system. Once blood pump  620  and second catheter  622  are in position, the prosthesis delivery system  624  is slid over the separate catheter  622  to position the prosthesis for implantation, while avoiding blockage of blood flow in separate catheter  622 . In this embodiment, the diameter of the delivery system is preferably about 8 mm. 
         [0159]    One method of using the blood flow pump during the implantation of the prosthesis is now described. This procedure may be performed under fluoroscopy and/or transesophageal echocardiography.  FIG. 66  shows vascular access made through the axillary artery  666 . A guidewire  668  is inserted past the aortic valve  670  and into the left ventricle  672 . In  FIG. 67 , a blood pump  674  is inserted into a hollow catheter passed  676  over guidewire  668  inside the aorta  678  and pushed into left ventricle  672 . Blood pump  674  is started to ensure a steady and sufficient blood flow of about 2.5 L/min from left ventricle  672  downstream during the valve replacement.  FIG. 68  depicts valve prosthesis  680 , retained on the delivery system  682  and positioned by sliding over blood pump catheter  676 . Prosthesis  680  is positioned generally about the valve annulus  684  and the coronary ostia  686 , with the assistance of radiographic markers. As shown in  FIGS. 69 and 70 , the sheath  688  overlying prosthesis  680  is pulled back and prosthesis  680  is deployed as previously described Catheter hooks  690  connecting the delivery catheter to the prosthetic valve allow full control of prosthetic valve positioning until the operator chooses to fully release and implant the prosthetic valve. Optional anchoring hooks, described previously, may be deployed generally about the annulus, the ventricle and the ascending aorta. Deployment of the anchoring hooks may be enhanced by radial expansion of a balloon catheter that further engages the hooks into the surrounding structures. Blood pump  674  is stopped and Hood pump catheter  676  is removed. Other configurations may be adapted for replacing a valve at other site will be familiar to those skilled in the art. 
         [0160]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. For all of the embodiments described above, the steps of the methods need not be performed sequentially. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.