Abstract:
Described is a prosthetic valve assembly comprising: a radially self-expandable stent configured to expand to bear against a wall of a native body lumen; and an implantable prosthetic valve, having a diameter, the valve being mounted inside the stent; wherein the diameter of the stent is greater than the diameter of the prosthetic valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Application No. 61/031,266, filed Feb. 25, 2008, and titled “Infundibular Reducer and Related Devices,” the entire contents of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to the treatment of cardiac valve disease using prosthetic valves, and more particularly to replacement of malfunctioning pulmonary valves using infundibular reducer devices. 
     BACKGROUND OF THE INVENTION 
     Natural heart valves, such as aortic valves, mitral valves, pulmonary valves and tricuspid valves, often become damaged by disease in such a manner that they fail to maintain blood flow in a single direction. A malfunctioning heart valve may be stenotic (i.e., heart leaflets are closed down) or regurgitant (i.e., heart leaflets are wide open). Maintenance of blood flow in a single direction through the heart valve is important for proper flow, pressure and perfusion of blood through the body. Hence, a heart valve that does not function properly may noticeably impair the function of the heart. 
     Cardiac valve prostheses are well known in the treatment of heart disease to replace malfunctioning heart valves. Heart valve replacement generally has been accomplished by major open heart surgery. This is a serious operation that requires general anesthesia, full cardiopulmonary bypass with complete cessation of cardiopulmonary activity, an extended hospitalization stay, and several more weeks to months of recuperation time. For some patients, open heart surgery is not an option because of the critical condition of the patient, advanced age, co-existing infection, or other physical limitations. 
     Recently, there has been increasing interest in minimally invasive and percutaneous replacement of cardiac valves, typically by way of catheterization. In minimally invasive procedures, a catheter is used to insert a mechanical or bioprosthetic valve in a lumen of a blood vessel via percutaneous entry through a distal blood vessel. Typically, such percutaneous prosthetic valve devices comprise an expandable stent segment, a stent anchoring segment and a flow-regulation segment, such as a ball valve or a biological valve. The expandable stent portion is generally expanded using a balloon that is part of a transcatheter delivery system. 
     In the specific context of pulmonary valve replacement, U.S. Patent Application Publication Nos. 2003/0199971 A1 and 2003/0199963 A1, both filed by Tower, et al. and incorporated herein by reference, describe replacing a pulmonary valve with a venous valvular replacement. The replacement pulmonary valve is mounted on a balloon catheter and delivered percutaneously via the vascular system to the location of the failed pulmonary valve and expanded by the balloon to compress the native valve leaflets against the right ventricular outflow tract, anchoring and sealing the replacement valve. As described in the articles:  Percutaneous Insertion of the Pulmonary Valve , Bonhoeffer, et al., Journal of the American College of Cardiology 2002; 39: 1664-1669 and  Transcatheter Replacement of a Bovine Valve in Pulmonary Position , Bonhoeffer, et al., Circulation 2000; 102: 813-816, both incorporated herein by reference in their entireties, the replacement pulmonary valve may be implanted to replace native pulmonary valves or prosthetic pulmonary valves located in valved conduits. Surgical procedures for percutaneous pulmonary valve implantation are described in Khambadkone et al.,  Percutaneous Pulmonary Valve Implantation in Humans , Circulation, 1189-1197 (Aug. 23, 2005). 
     Pulmonary valve replacement using venous valves is not available to all who might benefit from it due to the relatively narrow size range of available valved segments of veins, for example, with typical sizes available only up to a diameter of about 22 mm. 
     Unfortunately, many patients requiring pulmonary valve replacement are adults and children who have right ventricular outflow tracts that are larger than 22 mm in diameter. This could have resulted, for example, from having previously undergone transannular patch repair of tetralogy of Fallot during infancy. There are other causes, however, for an enlarged right ventricular outflow tract. Thus, venous valvular replacements, having an upper limit of 22 mm on their diameters, cannot typically be securely implanted within these patients. 
     Thus, there is a continuing need to improve upon the devices available for heart valve replacement, in particular those including venous valve replacements and pericardial valve replacements, and even more particularly those that may be placed in patients with irregular right ventricular outflow tracts (e.g., right ventricular outflow tracts that are larger than 22 mm in diameter, or irregular in shape). 
     SUMMARY OF THE INVENTION 
     The present invention provides infundibular reducer devices used for replacing a malfunctioning heart valve, and in particular, a pulmonary heart valve. The infundibular reducer devices may be delivered through percutaneous transcatheter implantation to an anatomic site within or near the heart. The devices are at least partially self-expandable, and have modularity, such that segments of the devices are independently expandable with respect to other segments of the devices. Preferably, the infundibular reducer devices include a pericardial heart valve or a valved segment of bovine jugular vein, for example, and are implanted in the right ventricular outflow tract, for example. In addition, however, it is contemplated that the present inventive devices may include other collapsible valves and may be implanted in other anatomical sites in the body. 
     A benefit of some embodiments of the present invention is that the devices may be delivered through a catheter to a desired anatomic site and may expand without a need for a balloon to expand the devices. Delivery of devices without a balloon minimizes the bulkiness of the delivery system, which can allow for easier insertion and removal of the devices. 
     Another benefit of the present invention is that modularity of the devices allows different segments of the devices to expand and move independently. Thus, the devices are able to conform more closely to an irregular implanted site. Certain segments of the devices may rotate with respect to other segments, and the devices may shorten and lengthen. The devices are also able to move within the implanted site during the cardiac cycle, and still conform to the implanted site. As a result, the devices are more effective. 
     Another benefit of the devices is that the devices may be collapsed and repositioned after partial deployment or partial expansion. This is beneficial if it is determined during early stages of delivery of one of the devices that the device is not being placed correctly. The device may then be re-compressed and moved to a correct location. 
     Yet another benefit of the devise of the present invention is that the devices are easily explantable. The stent portion may be peeled from the wall of the implanted site, collapsed, and the valve and stent may then be removed from the body. 
     A further benefit of the present invention is that drastic failure of the devices due to fracture of one wire or a few wires is eliminated. Since the stent portions of the devices are comprised of a plurality of wires that are independently connected in a plurality of locations to the fabric frame, fracture of one wire or a few wires does not cause the whole device to fail. 
     A still further benefit of some embodiments of the invention is that the devices may include features that allow the devices to be located using fluoroscopy, for example. Fluoroscopy may be helpful in placement of the devices as well as for later identification purposes. 
     An additional benefit of some embodiments of the devices is that the devices may include materials that are antimicrobial, prevent thrombosis, and either increase or reduce tissue ingrowth. Such materials allow the devices to be better secured in a vessel, and decrease the chance of rejection of the devices. 
     Another benefit of the present invention is that the stent portion may later serve as a landing zone or site for implantation of a later-needed prosthetic valve. Another valve may be delivered percutaneously to the inner lumen of the device that is already implanted. 
     A first aspect of the present invention is a prosthetic valve assembly. One embodiment comprises: a radially self-expandable stent configured to expand to bear against a wall of a native body lumen; and an implantable prosthetic valve, having a diameter, the valve being mounted inside the stent; wherein the diameter of the stent is greater than the diameter of the prosthetic valve. The stent may comprise a plurality of wires. The plurality of wires may comprise a material having shape memory, or the plurality of wires may comprise a plurality of different materials. The plurality of wires may be circular in shape and include a plurality of sinusoidal bends. The sinusoidal bends in the wires may have different sizes. At least some of the plurality of wires are in a nested configuration. At least some of the plurality of wires are in a point-to-point configuration. The stent may comprise a middle portion having a smaller diameter than at end portions thereof, and the valve may be mounted in the middle portion. The stent may comprise a middle portion having a diameter and end portions thereof may have tapered diameters in directions toward the middle portion, and the valve may be mounted in the middle portion. The middle portion may be cylindrical in shape. The stent may comprise a plurality of wires attached to at least one piece of fabric. The middle portion and each end portion articulate with respect to each other. 
     A second embodiment of the invention is a prosthetic valve assembly comprising: a radially self-expandable stent comprising a middle portion having a smaller diameter than end portions thereof, with the end portions configured to expand to bear against a wall of a native body lumen; and an implantable prosthetic valve mounted inside the middle portion of the stent. The stent may comprise a plurality of wires. The plurality of wires may comprise a plurality of different materials. The plurality of wires may be circular in shape and include a plurality of bends. The bends in the wires may be sinusoidal in shape. The plurality of wires may comprise a material having shape memory. The end portions may have tapered diameters in directions toward the middle portion. The middle portion may be cylindrical in shape. The stent may comprise a plurality of wires attached to at least one piece of fabric. The middle portion and each end portion articulate with respect to each other. At least some of the plurality of wires are in a nested configuration. At least some of the plurality of wires are in a point-to-point configuration. 
     A third embodiment of the present invention is a prosthetic valve assembly comprising: a radially self-expandable stent configured to expand to bear against a wall of a native body lumen, the stent comprising: a plurality of wires; and at least one piece of fabric to which the plurality of wires are attached; and an implantable prosthetic valve mounted inside the stent; wherein the plurality of wires of the stent are individually expandable and compressible providing the assembly with modularity. The plurality of wires comprise circular wires having a plurality of bends around the circumference of the circular wires. The plurality of wires may be in a nested configuration or a point-to-point configuration or a combination thereof. The plurality of wires may comprise a material having shape memory. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein: 
         FIG. 1  is a perspective view of an infundibular reducer device, in accordance with the present invention; 
         FIG. 2  is a side view of the infundibular reducer device of  FIG. 1 ; 
         FIG. 3  is an end view of the infundibular device of  FIGS. 1 and 2 ; 
         FIG. 4  is a side view of an infundibular reducer device, in accordance with the present invention; 
         FIG. 5  is a side view of an infundibular reducer device, in accordance with the present invention; 
         FIG. 6  is a perspective view of an infundibular device, in accordance with the present invention; 
         FIG. 7  is a side view of the infundibular device of  FIG. 6 ; and 
         FIG. 8  is an end view of the infundibular device of  FIGS. 6 and 7 . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to the accompanying figures, wherein like components are labeled with like numerals throughout the figures, illustrative infundibular reducer and related devices are disclosed, taught and suggested by the multiple embodiments. Although the devices are called “infundibular reducer” devices, the devices may be used in anatomic locations other than the infundibulum, such as the right ventricular outflow tract and other locations in or near the heart. In particular, the devices allow for prosthetic heart valves to be implanted in the right ventricular outflow tract or the infundibulum. The purpose of such devices is to allow replacement valves, such as pericardial heart valves, for example, having a smaller diameter than the diameter of the implanted site (e.g., the right ventricular outflow tract) to be implanted. However, the devices generally disclosed and shown may be used for other purposes as well. 
     The devices disclosed are beneficially configured such that the devices fit well in irregularly-shaped anatomy. The infundibular reducer devices of the present invention are preferably at least partially self-expandable. In addition, the devices are modular, which means that different segments of the devices are somewhat independent in their ability to expand and move. Thus, the devices are able to conform more closely to an irregularly shaped implant site. In addition, the modularity of the devices allows different segments of the devices to move with respect to one another in order to accommodate the movement of different segments of the implant site during a cardiac cycle, for example. The feature of the devices that allows for the modularity is the plurality of wires that comprise the device. These wires are preferably independently connected to one piece of fabric, for example. The configuration of and the material that comprises each of the plurality of wires may vary in order to provide additional modularity of the devices. As a result of the modularity, in particular, some segments of the devices may expand to greater diameters than other segments. Segments may rotate with respect to other segments. Also, the devices may be able to shorten and lengthen. Thus, the modularity also allows the devices to better fit in an irregularly shaped implant site and move within the site during a cardiac cycle, for example. Thus, the devices are more stable in the implant site, and are more effective. The better contact that the device has with the wall of the implant site, the more stable the device is in the site, which prevents paravalvular leaks around the device. 
     The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention. 
     Referring now to  FIGS. 1-3 , an infundibular reducer device  100 , in accordance with the present invention, is shown. The infundibular reducer device  100  comprises a self-expandable stent portion  105  and a replacement valve portion  102  (visible in  FIG. 3 ). 
     The infundibular reducer device  100  is preferably compressible to be inserted via catheter and expandable to fit a desired body lumen, such as the infundibulum or the right ventricular outflow tract. The device  100  is preferably self-expandable from a first reduced diameter to a second enlarged diameter. The device  100  is also preferably modular in expandability, meaning that different segments of the device  100  may independently expand from a first reduced diameter to a second enlarged diameter, and such different segments may rotate with respect to each other and/or cause the device  100  to shorten and lengthen. Such modularity of expandability of the device  100  allows the device  100  to fit in an irregularly shaped implantation site (e.g., the right ventricular outflow tract). 
     In order to be self-expandable and modular, the stent  105  is preferably formed from a plurality of wires  115  that are shaped in order for the stent portion  105  (and specifically different segments of the stent  105 ) to have a desired expanded configuration. The plurality of wires  115  should allow the stent portion  105  to be compressed to a particular shape and size, and also allows the stent to regain the desired expanded configuration upon release from compression. The wires  115  preferably include a series of sinusoidal bends around their circumference, as shown in  FIGS. 1-3 , which allow for the compression and expansion of the stent  105  with minimal force. The shapes of the wires  115  may include sinusoidal bends that resemble a sine wave with rounded apices, or the wires  115  have a zig-zag design that resembles more of a triangular wave form and with sharper apices having a smaller interior angle. The angles of the wires  115  may depend upon the diameter of the wires  115  and the material comprising the wires  115 . Other shapes of the wires  115 , beside those shown, having, for example, different shapes, angles and numbers of apices, are also contemplated by the present invention. 
     Each of the plurality of wires  115  is preferably circular in shape, without free ends. However, other shapes are contemplated. The ends of each of the plurality of wires  115  are preferably joined using a crimped hypotube  116 , as shown in  FIG. 1 , that surrounds the ends and joins them. However, it is contemplated that the ends of the wires  115  may be joined using any other possible means for attachment (e.g., gluing or melting ends of wires  115  together). 
     The wires  115  preferably include sinusoidal bends around their circumference. Each of the sinusoidal bends (or other shapes, as discussed above) of the wires  115  includes an apex, and as shown, the apices of each wire  115  may each contact an apex of an adjacent wire  115  (i.e., a point-to-point configuration). Alternatively, the sinusoidal bends may line up, follow, or “nest” together and will not contact each other at apices (i.e., a nesting configuration). It is also contemplated, however, that adjacent wires within a single device may have different numbers of sinusoidal bends and apices, and therefore, less than all of the apices of adjacent wires may have either a point-to-point configuration or a nesting configuration, and it is possible to have a combination of both configurations in one device. The different configurations of the wires  115 , such as the point-to-point configuration and the nesting configuration may result in different load distribution to the anatomy at the implanted site. For example, separate joints will distribute the load more than those that are connected, such as in a point-to-point configuration. The different configurations of the wires  115  may also allow different movement of the device. For example, if a sufficient amount of the wires  125  are in a nesting configuration, the device may be able to shorten and lengthen. 
     Preferably, the plurality of wires  115  comprise a material or materials that have shape memory characteristics, such as a nickel-titanium alloy (Nitinol™), or other similar inert biocompatible metal or combination of metals. In one embodiment, the material from which the stents are made includes approximately 54.5 percent to 57 percent nickel, and a majority of the balance of the material comprises titanium, as such percentages are known in the field of medical devices and surgical implants (see ASTM designation: F 2063-00, for example). In the prosthetic valve  100  shown, the stent portion  105  is preferably formed into a desired shape and made from a framework that comprises a plurality of wires  115  made of Nitinol™. 
     It is possible for device  100  to include a plurality of wires  115 , with different wires  115  comprising different materials. In particular, the different materials may have different strengths and may contribute to modularity of the device. For example, different strengths of the wires  115  may result in some wires  115  expanding to a larger or a smaller diameter than other wires  115 . For example, one embodiment may include a more stiff or rigid wire material for the wires surrounding the valve portion of the device, in order to stabilize the valve. Meanwhile, the end portions of the device may include wires made of a more flexible material, in order for the end portions to conform more closely to the anatomy of the implantation site. 
     The plurality of wires  115  of device  100  may also have different configurations. For example, the wires  115  may have different numbers of sinusoidal bends or the amplitudes of such bends may differ. The varying configurations of the wires  115  also contributes to the modularity of the device  100 . For example, wires  115  with sinusoidal bends that have a smaller amplitude may be stiffer than those with bends having larger amplitudes. Thus, the configuration of the wires  115 , as well as the number of wires  115 , and the material comprising the wires  115  may all be varied in order to contribute to a desired modularity of device  100  for a given application. 
     The wires  115  of the stent portion  105  are preferably shaped, configured and aligned such that a central lumen  101  runs through the center of the stent  105  along its length. Such a central lumen  101  accommodates a replacement valve portion  102  ( FIG. 3 ), such as a bovine jugular vein, a pericardial heart valve, or other collapsible valve, for example. Other biological or prosthetic valves may also be used in the stent portion  105 , having a size and shape that accommodates the patient&#39;s anatomy. Although only  FIG. 3  illustrates the inclusion of the replacement valve portion  102 , it is contemplated that any of the devices shown or described herein preferably includes such a replacement valve portion  102 . 
     Preferably, the wires  115  of the invention are formed in their desired circular shape and also preferably including their desired sinusoidal wave pattern. This method of manufacture is preferred because if wires fracture they generally return to their earlier configuration. Thus, if a wire is formed in a flat configuration, it will generally return to that flat configuration. The straightening of a wire in a device may result in failure of the device. Therefore, an advantage of embodiments of the invention is that because the wire  115  are preferably formed in their shaped configurations, if fracture of one wire does occur, the fracture will not result in failure of the device as a whole. 
     The stent portion  105  of the device  100 , of the construction and configuration as herein described, preferably has extremely good flexibility, dimensional stability, very smooth surfaces, a low profile when collapsed and an immunity to fatigue and corrosion. The length of the stent portion  105  can be adjusted or designed by varying the number of wires  115  that are utilized, by varying the arrangement of wires  115 , and/or by varying other features of the wires  115  and arrangement of wires  115  as discussed above. The working range of the stent  105  between its collapsed condition/configuration and its expanded condition/configuration can also be adjusted by choosing or designing a certain number of curves, zig-zags or bends in each wire  115 . In this way, a stent may be tailored for insertion into a particular body site to provide for the most effective implantation of the replacement valve  102  that is attached to the stent  105 . 
     The shape of the self-expandable stent  105 , as shown in  FIG. 2  is one exemplary shape, which can be described as a generally hourglass shape. Such an hourglass shape (which is achieved when the stent  105  is in an expanded or partially-expanded configuration) includes a middle portion  125  that is generally cylindrical in shape. This middle portion  125  has a diameter that is preferably at least slightly smaller than the diameter of end portions  130 . One advantage of the middle portion  125  having a smaller diameter than the end portions  130  is to allow at least a portion of the middle portion  125  of the stent  105  to hold or retain a replacement valve portion (not visible) (e.g., a valved segment of bovine jugular vein) in its central lumen, when such a replacement valve portion  102  has a smaller diameter than the lumen in which the prosthetic valve  100  is to be placed. The larger diameter of the end portions  130  allows the prosthetic valve  100  to be secured in place in such a tubular organ, or a valved anatomic site, having a diameter larger than that of the replacement valve but smaller than the diameter of the end portions  130 . The end portions  130  are also shown to be flared, such that they increase in diameter from where the end portions  130  extend from the middle portion  125 . The angle at which these flared end portions  130  extend from the middle portion  125  can vary depending on the desired maximum diameter and desired length of the stent  105 , along with other factors. 
     It is also possible to vary the number, configuration and material of the wires  115  in the middle portion  125  in order to allow the stent  105  to be more rigid in that area, for example. Increased rigidity in the middle portion  125  may assist in better retaining and supporting a replacement valve  102  in the device  100 . 
     The areas of the ends portions  130  that result from bends in the wire  115  on the outer edge of the end portions  130  are referred to as crowns  132  of the device  100 . The number, spacing, and amplitude of the crowns  132  can vary the modularity and also the stability of the device  100  in an implanted site. The more spaced out the crowns  132  are, for example, the more flexible are the end portions  130  of the device  100 . The invention contemplates many different configurations, numbers and spacings of the crowns  132 . 
     The crowns  132  on at least one of the end portions  130  preferably comprise attachment loops  133 . The purpose of the attachment loops  133  is to attach the device  100  to a delivery system. The loops  133  preferably do not impede blood flow through the device  100 , and may be located such that the loops  133  are attached to or formed on the outer surface of the crowns  132 . The attachment loops  133  may preferably resemble belt loops, however, other shapes are contemplated. The attachment lops  133  may be made from the same material as fabric  120 , or the loops  133  may comprise suture material, for example. Other materials for the attachment loops  133  are also contemplated by the present invention, however. 
     In particular, the attachment loops  13  are threaded onto another component (e.g., a wire in a circular shape with free ends) of the delivery system, which allows the end portion  132  of the device  100  to be compressed and attached to the delivery system. Such a compressed configuration preferably allows the device  100  to be inserted percutaneously. Alternatively, both end portions  130  may include the attachment loops  133  on crowns  132 . One example of a delivery system that the device  100  may be attached to by using such attachment lops  133  is described in co-pending patent application Ser. No. 12/358,388 filed on Jan. 23, 2009, titled “Infundibular Reducer Device Delivery System and Related Methods.” 
     In the device  100  shown in the Figures, the end portions  130  can be particularly articulable with respect to the middle portion  125  when the wires  115  used for the framework of the middle portion  125  and end portions  130  are not attached to each other. For example, the end portions  130  may be able to rotate with respect to one another and/or with respect to the middle portion  125 . However, it would also be possible for the wires  115  of the middle portion  125  to be attached to the wires  115  of one or both end portions  130 , thereby limiting movement. 
     The replacement valve  102  preferably included in device  100  is a pericardial heart valve or a preserved bovine jugular vein of the type described in the above-cited Bonhoeffer, et al. and Tower, et al. references. Other vessels or donor species may, however, alternatively be employed. Preferably, any collapsible valve may be used. 
     Such replacement valves  102  (example seen in  FIG. 3 ) may be formed from a variety of materials including biological materials and polymers. Exemplary biological materials include homograft, allograft or xenograft, with xenograft being common and well accepted and usually from bovine, ovine, swine or porcine pericardium, or a combination thereof. For example, polymers include expanded TEFLON™ polymers, high density polyethylene, polyurethane, and combinations thereof. Some examples of replacement valves  102  used in the present invention are described in U.S. Pat. Nos. 6,719,789 and 5,480,424, issued to Cox (which are incorporated herein by reference). 
     The replacement valve portion  102  is attached to (i.e., affixed to, held by, retained by, etc.) the central lumen of the stent portion  105 , and is sutured or otherwise attached within the stent  105 . The valve portion  102  may be sutured to the wires  115  and/or the fabric  120  of the stent  105 . Other means and method for attaching the replacement valve portion  102  to the stent portion  105  are also contemplated, however. As discussed above, the replacement valve portion  102  is preferably positioned within the middle portion  125  of the device and in the central lumen  101 . 
     Also, in  FIG. 1 , the stent portion  105  includes one piece of fabric  120  (i.e., cloth, material, etc.) to which the wires  115  are attached or through which the wires  115  are woven. The fabric  120  used for the stent can be a polyester knit, for example, or may instead be an ultra high molecular weight polyethylene (UHMWPE), cotton, or the like. The fabric  120  should be biocompatible and may include a number of different fabrics in different areas of the stent and/or in layers, if desired. It is also contemplated that the device  100  may include more than one piece of fabric  120 . 
     The fabric portion  120  of the present invention provides connection and support for the individual wires  115 . The wires  115  are attached to the fabric portion  120 , and may be woven through the material or otherwise attached. A benefit to attaching the wires  115  to the fabric  120 , and with such regularity (e.g., every 1 to 2 mm along the wires  115 ), is that if a single wire fails or fractures, the whole device  100  is not rendered defective or a failure. The wires  115  preferably hold open the fabric portion  120 . The movement of each wire  115  is independent in the fabric  120  and also limited by the flexibility of the wire  115  itself and by the fabric to some extent. The fabric  120  may comprise stretchable material, such as a knit for example. Alternatively, the fabric  120  may be a non-stretchable woven material, which would restrict the movement of the wires  115  more than a knit material, for example. Thus, the movement of the wires  115  is dependent upon the choice of fabric  120  material as well as the material choice and shape of the wires  115  themselves. 
     The configuration of the plurality of wires  115  also affects the flexibility and movement of the stent  105 . For example, the wires  115  may be nested, as in the embodiment in  FIGS. 1-3 , or aligned point-to-point, as in the embodiment shown in  FIG. 4  (discussed below). The nested configuration allows for more flexibility of the stent  105  than the point-to-point configuration. The nested configuration may also allow the device  100  to be shortened and lengthened. The amount of bends in the wires  115 , creating the points, can also affect the flexibility and motion of the wires  115  of the stent  105 . This nested configuration of the wires  115  also aids in the retractability of the device  100  and the stability of the device  100  longitudinally. 
     A point-to-point configuration, in which the apices may be connected together, for example by sutures, may decrease the flexibility of the device  100 . Therefore, in order to have a device  100  flexible enough to apply to the right ventricular outflow tract, which is quite irregular, it may be desired to include more nesting of wires  115  than point-to-point connections. Flexibility of the device  100  may be, for example, preferred in order to allow the device  100  to better follow the variations in the right ventricular outflow tract that occur throughout the cardiac cycle. Such flexibility in the device  100  would allow for shortening and lengthening of the device  100  without straining the device  100  throughout the cardiac cycle. However, it is contemplated that for different applications, different amounts of flexibility may be desired. The devices, therefore, may be configured with any combination of wire types, materials and configurations, in order to provide the desired amount of flexibility. 
       FIG. 4  shows another embodiment of the present invention. Infundibular reducer device  400  is shown and includes a valve portion (not visible) and a stent portion  405  that comprises a plurality of wires  415  and fabric  420 . The shape and configuration of device  400  is different from that of device  100  ( FIGS. 1-3 ), including a different number, shape, and arrangement of wires  415 . The discussion above with regard to the components of device  100 , however, also applies to the corresponding components of device  400 . For example, device  400  also includes a middle portion  425  with a generally cylindrical shape and flared end portions  430  that include a generally angled portion and a generally straight portion that forms a cylinder with a diameter that is larger than that of the middle portion  425 . 
       FIG. 5  shows another exemplary infundibular reducer device  600  of the present invention. Again, the shape and configuration of a stent portion  605  is different from that of the stent portions  105 ,  405  of the earlier described embodiments, including a different number, shape and arrangement of wires  615 . However, the description above of the corresponding components of the other stent portions is also applicable to the components of stent  605 . Stent  605 , however, does not include end portions  630  that have a diameter that is greater than that of the middle portion  625 . In this embodiment, the inner lumen (not visible) may be configured such that a valve having a smaller diameter than device  600  may be secured in the inner lumen. The embodiment in  FIG. 5  illustrates one of a plurality of configurations that are contemplated by the present invention. 
     Another preferred embodiment of the present invention is device  700  shown in  FIGS. 6-8 . Device  700  includes a stent portion  705  with a middle portion  725  and two end portions  730 ,  740 . As shown, the end portions  730 ,  740  are different in device  700 . End portion  730  has a larger diameter, and the wires  715  in the end portion  730  are in a nested configuration. End portion  740 , on the other hand, is smaller in diameter than end portion  730  and the wires  715  are in a point-to-point configuration. Device  700  may be arranged in an implantation site such that end portion  730  or end portion  740  is located more distal, or vice versa. Device  700  also illustrates that a plurality of different configurations of devices are contemplated by the present invention. 
     The prosthetic valve or infundibular reducer device of the present invention may be part of a delivery system. One exemplary such delivery system is described in co-pending non-provisional patent application Ser. No. 12/358,388 titled “Infundibular Reducer Device Delivery System and Related Methods,”filed on Jan. 23, 2009, and incorporated herein by reference in its entirety. The infundibular reducer devices of the present invention may be fastened to such a delivery system using a fastening means. A plurality of loops  133  provided on or near the proximal end (for example, on the crowns of at least one of the end portions) of the infundibular reducer device is one example of such a fastening means. Such loops  133  may be formed from, for example, sutures or from the fabric used to form part of the stent  105 . Preferably, the attachment loops  133  resemble belt loops, and do not maintain a significant profile so as to not impede blood flow. Other fastening means besides loops  133  are also contemplated by the present invention. 
     Below is a description of additional or optional features that can be included with any of the infundibular reducer devices described above and or other stent-based devices that can be used in the same or different parts of the body. 
     Another feature that can be included in the device of the present invention is to include silver in the stent portion. Silver can be applied to or included in the stent portion in various ways. For example, silver may be applied by using thread impregnated with silver in the stent portion. The silver thread could be applied near where a replacement valve is attached to the stent portion. The silver thread could help prevent excessive tissue ingrowth, which could negatively affect the function of the valve. Distance between the valve portion and a concentration of silver would depend upon a margin of inhibition necessary as well as a duration needed as the device is accepted by the body. It is likely that full ingrowth would be desired for areas contacting the patient&#39;s anatomy, but inhibition of growth could be desired. The silver may also be used as an antimicrobial agent, which helps prevent infection. Thus, a stent portion of a device of the present invention can include such silver impregnated thread in locations where infections are likely to develop. 
     Another purpose for using silver thread is that silver may be viewed under fluoroscopy. Thus, the silver may act as a marker when seeking to locate the valve under fluoroscopy for monitoring and/or subsequent location for deployment or during other procedures. 
     Yet another possible feature of the device of the present invention is inclusion of a pattern of radiopaque markers. An example may be including a radiopaque marker or markers in the shape or pattern of a ring located circumferentially around the ends of the valve portion of the device. Such a ring could be applied directly, with ink, or thread, or tape or other means. In particular, such a ring could allow for easy identification and location of the valve portion of the device of the present invention under fluoroscopy for monitoring and/or subsequent deployment procedures. It is also possible to have a plurality of bands or radiopaque material generally equally spaced along the length of the valve portion. The purpose of the markers would be to locate the valve, especially during subsequent deployment of future prosthetic valves. Another possibility would be to add radiopaque thread markers on the stent portion at various locations. One particular material that can be used as a radiopaque marker is a platinum strand or cable. 
     Yet another possible feature of the device of the present invention is to embed materials into the fabric used in the stent portion. These materials can be used to enhance tissue ingrowth. The purpose of tissue ingrowth is to secure the device as well as help close any paravalvular leaks. Some exemplary materials that can be embedded include, but are not limited to, collagen, hydrophilic materials, gelatins, albumen, or other proteins. The material could be put into solution and the fabric of the stent portion could be soaked in the solution. The stent portion could then be stored in saline and post-sterilized to prevent destruction of the material in glutaraldehyde or other storage chemical sterilant. 
     A further possible feature of the device of the present invention is the addition of a felt edge on the device. The felt edge would preferably be located on the crowns of at least one of the two end portions. The purpose of adding felt to the edge is to control tissue ingrowth and thrombosis. The felt can facilitate rapid ingrowth of tissue due to its porous nature. Other areas of the stent may be made of a knit or weave where the maximum amount of ingrowth is not necessarily desired. Rapid, healthy tissue ingrowth on the edges of the stent portion, where the stent portion contacts the body, will aid in fixation of the stent to help prevent migration as well as provide strain relief from the remainder to the stent and vessel. 
     Further embodiments of the present invention are possible by varying the permeability or porosity of the fabric used in the device. A semi-permeable material may, for example, be desired to enhance tissue ingrowth of the endothelium into the device. In other cases, the fabric may not be desired to be permeable. It is contemplated that all levels of permeability and porosity are possible for the fabric material of the devices of the present invention. 
     Another possible feature of the present inventive device is adding a hydrophobic material to the stent portion. A hydrophobic material, such as Ultra High Molecular Weight Polyethylene (UHMWPE), polypropylene, etc. could be applied in a variety of ways including using thread made entirely or in part from one of these hydrophobic materials. The material would not need to be applied to all thread, however. For example, hydrophobic thread could be applied at the margin of the implanted valve portion to help prevent excessive tissue ingrowth which could affect the function of the valve. The distance from the valve and the concentration of material would depend upon the margin of inhibition necessary as well as the duration needed as the device is accepted by the body. It is likely that full ingrowth would be desired for the areas contacting the patient anatomy and inhibition of growth within the valve portion. The purpose of using a hydrophobic material may include reducing tissue ingrowth as well as reducing thrombosis. 
     Another optional feature of the present invention can be seen in the embodiment shown in  FIG. 4 . The wires  415  in the end portions  430  can be seen to have a point to point configuration of the bends. The purpose of such a configuration is to keep excess fabric from being in the path of blood flow through the device  400 . Particularly, this configuration is desired at the in-flow end of the device  400 . 
     A further optional feature of the present invention is to add a weave or braid of structural thread to the stent portion in the area where it contacts the valve portion. The angle of the braid or weave is based upon providing a firm fit for the valve portion in the stent portion, but allows for expansion at the rate of subsequent valved stents. 
     In some embodiments, the stent of the present invention may be completely self-expanding based upon the choice of materials and configuration of the wires. In other embodiments, the stent may be moderately self-expanding and may use a balloon to assure complete expansion. In such an embodiment, the wires may comprise MP35N, for example. For example, it may be desired to have the end portions of the device self-expandable while the middle portion, including the valve, is balloon-expandable. 
     It is contemplated that the device of the present invention may not be removed once the replacement valve portion of the device no longer functions, such as after a significant period of time has passed since implantation. The device may then serve as a landing zone or location where a replacement valve may be implanted or docked. One exemplary valve that may be implanted within the present inventive device is the Melody™ Transcatheter Pulmonary Valve, made by Medtronic, Inc., Minneapolis, Minn., U.S.A., which is a bovine jugular vein valve. It is contemplated, however, that other similar devices may also be implanted within the present inventive device. The device of the present invention preferably includes a stent portion that is able to expand to surround the replacement device. 
     The present invention has now been described with reference to several embodiments thereof. The entire disclosure of any patents, patent applications, publications and journal articles identified herein is hereby incorporated by reference. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the structures described herein, but only by the structures described by the language of the claims and the equivalents of those structures.