Abstract:
A prosthetic mitral valve assembly and method of inserting the same is disclosed. In certain disclosed embodiments, the prosthetic mitral valve assembly includes a stent and valve combination. The stent is designed so that the anchoring portion is positioned above the annulus of the mitral valve and in the left atrium. The stent is radially expandable so that it can expand into position against the walls of the left atrium and accommodate a wide range of anatomies. Contact between the stent and the native tissue in the left atrium reduces paravalvular leakage and prevents migration of the stent once in place.

Description:
FIELD 
       [0001]    The present disclosure concerns a prosthetic mitral heart valve and a method for implanting such a heart valve. 
       BACKGROUND 
       [0002]    Prosthetic cardiac valves have been used for many years to treat cardiac valvular disorders. The native heart valves (such as the aortic, pulmonary, tricuspid and mitral valves) serve critical functions in assuring the forward flow of an adequate supply of blood through the cardiovascular system. These heart valves can be rendered less effective by congenital, inflammatory, infectious conditions or disease. Such damage to the valves can result in serious cardiovascular compromise or death. For many years the definitive treatment for such disorders was the surgical repair or replacement of the valve during open heart surgery, but such surgeries are prone to many complications. More recently a transvascular technique has been developed for introducing and implanting a prosthetic heart valve using a flexible catheter in a manner that is less invasive than open heart surgery. 
         [0003]    In this technique, a prosthetic valve is mounted in a crimped state on the end portion of a flexible catheter and advanced through a blood vessel of the patient until the valve reaches the implantation site. The valve at the catheter tip is then expanded to its functional size at the site of the defective native valve such as by inflating a balloon on which the valve is mounted. 
         [0004]    Another known technique for implanting a prosthetic aortic valve is a transapical approach where a small incision is made in the chest wall of a patient and the catheter is advanced through the apex (i.e., bottom tip) of the heart. Transapical techniques are disclosed in U.S. Patent Application Publication No. 20070112422, which is hereby incorporated by reference. Like the transvascular approach, the transapical approach includes a balloon catheter having a steering mechanism for delivering a balloon-expandable prosthetic heart valve through an introducer to the aortic annulus. The balloon catheter includes a deflecting segment just proximal to the distal balloon to facilitate positioning of the prosthetic heart valve in the proper orientation within the aortic annulus. 
         [0005]    The above techniques and others have provided numerous options for high-risk patients with aortic valve stenosis to avoid the consequences of open heart surgery and cardiopulmonary bypass. While procedures for the aortic valve are well-developed, such procedures are not necessarily applicable to the mitral valve. 
         [0006]    Mitral valve repair has increased in popularity due to its high success rates, and clinical improvements noted after repair. Unfortunately, a significant percentage of patients still receive mitral valve replacement due to stenosis or anatomical limitations. There are a number of technologies aimed at making mitral repair a less invasive procedure. These technologies range from iterations of the Alfieri stitch procedure to coronary sinus-based modifications of mitral anatomy to subvalvular placations or ventricular remodeling devices, which would incidently correct mitral regurgitation. 
         [0007]    However, for mitral valve replacement, few less-invasive options are available. There are approximately 60,000 mitral valve replacements (MVR) each year and it is estimated that another 60,000 patients should receive a MVR due to increased risk of operation and age. The large majority of these replacements are accomplished through open-heart surgery. One potential option for a less invasive mitral valve replacement is disclosed in U.S. Patent Application 2007/0016286 to Herrmann. However, the stent disclosed in that application has a claw structure for attaching the prosthetic valve to the heart. Such a claw structure could have stability issues and limit consistent placement of a transcatheter mitral replacement valve. 
         [0008]    Accordingly, further options are needed for less-invasive mitral valve replacement. 
       SUMMARY 
       [0009]    A prosthetic mitral valve assembly and method of inserting the same is disclosed. 
         [0010]    In certain disclosed embodiments, the prosthetic mitral valve assembly includes a stent and valve combination. The stent is designed so that the anchoring portion is positioned above the annulus of the mitral valve and in the left atrium. The stent is radially expandable and can press against the walls of the left atrium with a pressure or friction fit to accommodate a wide range of anatomies. 
         [0011]    In one embodiment, the entire prosthetic mitral valve assembly is positioned above the native annulus so that the native mitral valve leaflets and chordae are preserved. As a result, the prosthetic mitral valve and the native mitral valve function in series. 
         [0012]    In another embodiment, a majority of the prosthetic mitral valve assembly is implantable in the left atrium. However, a lower portion of the mitral valve assembly extends into the native mitral valve rendering the native mitral valve incompetent. Contact between the stent and the native tissue in the left atrium reduces paravalvular leakage and prevents migration of the stent once in place. 
         [0013]    In another embodiment, a majority of the prosthetic mitral valve assembly is implantable in the left atrium. A lower tapered portion partially extends into the native mitral valve but does not extend into the left ventricle in order to ensure that the chordae tendineae are not contacted by portions of the stent. This embodiment can improve cardiac performance while preserving the function of the chordae tendineae. 
         [0014]    In yet another embodiment, the mitral valve assembly includes additional anchoring with one or more anchoring arms that contact an upper portion of the atrium or the pulmonary veins. The anchoring arms utilize the natural anatomy of the patient&#39;s heart in order to resist against upward migration of the assembly. Other embodiments also use the upper portion of the atrium or the pulmonary veins without using anchoring arms. 
         [0015]    The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of an embodiment of a mitral valve assembly that can be inserted into the native mitral valve, but that is anchored above a native annulus. 
           [0017]      FIG. 2  is a perspective view of another embodiment of a mitral valve assembly that can work in series with the native mitral valve. 
           [0018]      FIG. 3  is a perspective view of another embodiment of a mitral valve assembly having outwardly extending prongs for anchoring the assembly. 
           [0019]      FIG. 4  is a perspective view of another embodiment of a mitral valve assembly that can extend partially into the native mitral valve. 
           [0020]      FIG. 5  is a cross-sectional view of a heart with the mitral valve assembly of  FIG. 2  mounted in the left atrium. 
           [0021]      FIG. 6  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with the mitral valve assembly extending to a roof of the atrium. 
           [0022]      FIG. 7  is a cross-sectional view of a heart with another embodiment of the mitral valve assembly mounted in the left atrium and having at least one anchoring arm extending to a roof of the atrium. 
           [0023]      FIG. 8  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending into at least one pulmonary vein. 
           [0024]      FIG. 9  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending to a roof of the atrium. 
           [0025]      FIG. 10  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending into at least one pulmonary vein. 
           [0026]      FIG. 11  is a cross-sectional view of a heart having the mitral valve assembly of  FIG. 1  mounted in the left atrium with a lower portion of the mitral valve assembly positioned in the native mitral valve. 
           [0027]      FIG. 12  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with the mitral valve assembly extending to the roof of the atrium and with a lower portion of the mitral valve assembly positioned in the native mitral valve. 
           [0028]      FIG. 13  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending to a roof of the atrium and with a lower portion of the mitral valve assembly positioned in the native mitral valve. 
           [0029]      FIG. 14  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending into pulmonary veins and with a lower portion of the mitral valve assembly positioned in the native mitral valve. 
           [0030]      FIG. 15  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending to a roof of the atrium and with a lower portion of the mitral valve assembly positioned in the native mitral valve. 
           [0031]      FIG. 16  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending into pulmonary veins and with a lower portion of the mitral valve assembly positioned in the native mitral valve. 
           [0032]      FIG. 17  is a cross-sectional view of a heart having the mitral valve assembly of  FIG. 4  mounted in the left atrium. 
           [0033]      FIG. 18  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with the mitral valve assembly extending to a roof of the atrium. 
           [0034]      FIG. 19  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending to a roof of the atrium and with a lower portion of the mitral valve assembly partially extending into the native mitral valve. 
           [0035]      FIG. 20  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending into pulmonary veins and with a lower portion of the mitral valve assembly partially extending into the native mitral valve. 
           [0036]      FIG. 21  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending to a roof of the atrium and with a lower portion of the mitral valve assembly partially extending into the native mitral valve. 
           [0037]      FIG. 22  is a cross-sectional view of a heart having another embodiment of the mitral valve assembly mounted in the left atrium with at least one anchoring arm extending into pulmonary veins and with a lower portion of the mitral valve assembly partially extending into the native mitral valve. 
           [0038]      FIG. 23A  is a cross-sectional view of the distal end portion of a delivery apparatus that can be used to implant a prosthetic mitral valve in the heart, according to another embodiment. 
           [0039]      FIG. 23B  is an enlarged view of a portion of  FIG. 23A  showing the connection between the valve stent and the distal end of the delivery apparatus. 
           [0040]      FIG. 23C  is a perspective view of the delivery apparatus of  FIG. 23A . 
           [0041]      FIGS. 23D and 23E  illustrate the valve being deployed from the delivery apparatus shown in  FIG. 23A . 
           [0042]      FIG. 24A  is a perspective view of a delivery apparatus for a prosthetic valve shown with the sheath of the delivery apparatus in a retracted position for deploying the valve, according to another embodiment. 
           [0043]      FIG. 24B  is a perspective view of the delivery apparatus of  FIG. 24A  shown with the sheath in a distal position for covering the valve during valve delivery. 
           [0044]      FIG. 24C  is an enlarged, perspective view of an end piece of the delivery apparatus of  FIG. 24A  and three posts of a valve stent that are received within respective recesses in the end piece. 
           [0045]      FIG. 24D  is a cross-sectional view of the end piece shown in  FIG. 24C . 
           [0046]      FIG. 25  is a perspective view of an embodiment of a prosthetic valve assembly having tensioning members coupled to prosthetic leaflets of the valve to simulate chordae tendineae. 
           [0047]      FIG. 26  is a perspective view of a prosthetic valve assembly having tensioning members, according to another embodiment. 
           [0048]      FIG. 27  is a perspective view of a prosthetic valve assembly having tensioning members, according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    As used herein, the singular forms “a,” “an,” and “the” refer to one or more than one, unless the context clearly dictates otherwise. 
         [0050]    As used herein, the term “includes” means “comprises.” For example, a device that includes or comprises A and B contains A and B but can optionally contain C or other components other than A and B. A device that includes or comprises A or B may contain A or B or A and B, and optionally one or more other components such as C. 
         [0051]      FIG. 1  is a perspective view of a mitral valve assembly  8  that can be used as a mitral valve replacement. The mitral valve assembly  8  includes a radially compressible and expandable stent  10  having an upper portion  12  with an enlarged end, a tapered middle portion  14  and a lower portion  16  with a circumference that is less than that of the upper portion  12 . The stent can be an inverted bell shape, but other shapes can be used. Additionally, although only the middle portion  14  is shown as tapered, the stent  10  can have a continuous taper from the upper portion  12  to the lower portion  16 . An upper edge  18  of the stent  10  can be a sawtoothed or scalloped pattern to maximize a surface area with which the stent connects to the native tissue. Alternatively, the upper edge can be a straight edge, or some other pattern. 
         [0052]    The stent  10  can have a self-expanding frame  20  formed from a shape memory material, such as, for example, Nitinol. The illustrated embodiment shows that the stent frame  20  can include metal strips or struts arranged in a lattice pattern, but other patterns can be used. In certain embodiments the stent frame  20  can be made of stainless steel or any other suitable materials. The tapered middle portion  14  can have certain of the metal strips intentionally disconnected from the upper portion  12  in order to create prongs  22  extending outwardly from the stent  10  that assist in holding the prosthetic mitral valve assembly to the native tissue. Alternatively, barbs (not shown) can be separately attached to the stent in order to create the prongs. One advantage of the illustrated embodiment is that the prongs  22  are formed from the frame itself or integral with the frame, rather than being separately added. In other embodiments (not shown), the disconnected metal strips can be connected, if the prongs  22  are not desired. In such a case, each cell of the tapered portion  14  can be connected to the upper portion  12 . A biocompatible sheet or fabric material  24  can be connected to the inner surface of the frame  20  to form an inner layer or envelope covering the open portions of the stent to reduce paravalular leakage. The sheet or fabric  24  can be made from synthetic materials, such as a polyester material or a biocompatible polymer. One example of a polyester material is polyethylene terephthalate (PET). Alternative materials can be used. For example, the sheet or fabric can be made from biological matter, such as natural tissue, pericardial tissue (e.g., bovine, porcine or equine pericadium) or other biological tissue. The sheet or fabric  24  can be connected to the frame  20  by sutures, such as shown at  26 . 
         [0053]    As shown in dashed lines, the mitral valve assembly  8  includes a valve  28  positioned in the lower portion  16  of the stent  10 . The valve  28  can have a leafed-valve configuration, such as a bicuspid valve or tricuspid valve configuration. The valve  28  can be connected to the frame  20  using, for example, sutures  26  or other suitable connection techniques well-known in the art. Alternatively, the valve  18  can be a mechanical type valve, rather than a leafed type valve. Still further, the valve  18  can be made from biological matter, such as natural tissue, pericardial tissue (e.g., bovine, porcine or equine pericadium), a harvested natural valve, or other biological tissue. Alternatively, the valve can be made from biocompatible synthetic materials (e.g., biocompatible polymers), which are well known in the art. Blood flow through the valve proceeds in a direction from the upper portion  12  to the lower portion  16 . Those skilled in the art will recognize that the particular type of valve used is not of importance and a wide variety of valves can be used. 
         [0054]    The features of  FIG. 1  can be used in any of the embodiments herein described. Thus, for each of the embodiments below, the materials that can be used for the valve, the biocompatible sheet, and the frame will not be repeated and should be assumed to be at least those described in  FIG. 1 . Additionally, the prongs and barbs of  FIG. 1  can be used in any of the embodiments described herein. 
         [0055]      FIG. 2  is a perspective view of another embodiment of a mitral valve assembly  38  sized for atrial implantation and designed to work in series with the native mitral valve, as further described below. The mitral valve assembly  38  includes a stent  40  having a frame  42  supporting a biocompatible sheet or fabric  44 , both of which are similar to those already described. The stent supports a valve (not visible in  FIG. 2 ) attached to and sized to be compatible with the frame  42 . Any of the valves already described can be used. However, because of the location of the stent  40  in the atrium, the valve can be larger than that of  FIG. 1 . 
         [0056]      FIG. 3  is a perspective view of another embodiment of a mitral valve assembly, which is the same as  FIG. 2 , but with prongs  45  added. More particularly, cells of the frame&#39;s lattice structure are left intentionally disconnected from adjacent cells and are bent outwardly to create the prongs  45 .  FIG. 3  is illustrative that prongs can be added to any of the embodiments described herein. Alternatively, the prongs can be removed from any of the embodiments simply by leaving the lattice structure fully connected. Furthermore, in any of the embodiments herein described, barbs (not shown) can be separately attached to the stent in order to create the prongs. 
         [0057]      FIG. 4  shows another embodiment  46  of a mitral valve assembly having an upper portion and a lower tapered portion  47 . The mitral valve assembly includes a frame  48  having a lattice structure with certain cells of the lattice left intentionally disconnected to create outwardly extending prongs  49 , similar to those described in relation to  FIG. 1  (the prongs can be eliminated or separate barbs added, as already described above). The lower tapered portion  47  partially extends into the native mitral valve, but does not extend into the left ventricle, which can improve cardiac performance and ensure that the chordae tendineae are not damaged by the assembly. 
         [0058]      FIG. 5  shows a cross-sectional view of a heart with the prosthetic mitral-valve assembly  38  inserted into a patient&#39;s heart. For purposes of background, the four-chambered heart is explained further. On the left side of the heart, the native mitral valve  50  is located between the left atrium  52  and left ventricle  54 . The mitral valve  50  generally comprises two leaflets, an anterior leaflet  56  and a posterior leaflet  58  that are attached to the left ventricle by chordae tendineae  59 , which prevent eversion of the leaflets into the left atrium. The mitral valve leaflets are attached to a mitral valve annulus  60 , which is defined as the portion of tissue surrounding the mitral valve orifice. More specifically, the mitral annulus constitutes the anatomical junction between the ventricle and the left atrium, and serves an insertion site for the leaflet tissue. The left atrium  52  receives oxygenated blood from the pulmonary veins  61  (only two of four pulmonary veins are shown for simplicity). The oxygenated blood that is collected in the left atrium  52  enters the left ventricle  54  through the mitral valve  50 . Contraction of the left ventricle  54  forces blood through the left ventricular outflow tract and into the aorta (not shown). As used herein, the left ventricular outflow tract (LVOT) is intended to generally include the portion of the heart through which blood is channeled from the left ventricle to the aorta. On the right side of the heart, the tricuspid valve  66  is located between the right atrium  68  and the right ventricle  70 . The right atrium  68  receives blood from the superior vena cava  72  and the inferior vena cava (not shown). The superior vena cava  72  returns de-oxygenated blood from the upper part of the body and the inferior vena cava returns de-oxygenated blood from the lower part of the body. The right atrium  68  also receives blood from the heart muscle itself via the coronary sinus. The blood in the right atrium  68  enters into the right ventricle  70  through the tricuspid valve  66 . Contraction of the right ventricle forces blood through the right ventricle outflow tract and into the pulmonary arteries. The left and right sides of the heart are separated by a wall generally referred to as the septum  78 . The portion of the septum that separates the two upper chambers (the right and left atria) of the heart is termed the artial (or interatrial) septum while the portion of the septum that lies between the two lower chambers (the right and left ventricles) of the heart is called the ventricular (or interventricular) septum. A healthy heart has a generally conical shape that tapers from a base to an apex  80 . 
         [0059]    The mitral valve assembly  38  is shown as positioned above the annulus  60  of the native mitral valve  50  and entirely within the left atrium. As already described, the stent  40  is radially expandable and is anchored in the atrium through a pressure or friction fit with the surrounding tissue. Through radial expansion, the frame  42  adapts to the natural anatomy of the patient&#39;s atrium. For purposes of illustration, a valve  90  is shown as visible through the biocompatible sheet  44 . As shown, the native mitral valve  50  is competent and works in series with the prosthetic mitral valve assembly  38 . Any regurgitant volume that passes back through the native valve in the left atrium is immediately blocked by the secondary prosthetic mitral valve assembly  38 . The native valve absorbs the majority of the systolic pressure, while the prosthetic mitral valve assembly  38  receives only a fraction of the systolic pressure imparted by the regurgitant volume. As a result, the prosthetic mitral valve assembly can have improved durability and reduced risk of valve migration. Such an ability to work in series with the native mitral valve is also true of the embodiments described in  FIGS. 6-10 . 
         [0060]      FIG. 6  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  100  inserted into the atrium. In this embodiment, a stent  102  has a self-expanding frame similar to stent  40  described above. The mitral valve assembly  100  has a dome-shaped upper portion  104  that can expand to fit the natural anatomical geometry of a roof of the atrium. As a result, the mitral valve assembly  100  can expand in two dimensions, such as a horizontal direction and a vertical direction. By expanding horizontally, the mitral-valve assembly uses side walls of the atrium to anchor the assembly. By expanding vertically, the assembly expands between the annulus of the mitral valve and the roof of the atrium in order to anchor the assembly in the atrium. Thus, the roof of the atrium can exert a downward pressure on the assembly in order to prevent upward migration. A biocompatible sheet  106  extends from a bottom edge of the stent to some point below the pulmonary veins  61  so that blood flow through the pulmonary veins remains unobstructed. A valve (not shown) can be positioned at a lower end of the assembly and works in series with the native mitral valve, similar to the embodiments already described. 
         [0061]      FIG. 7  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  120  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . The assembly  120  includes a radially-expandable stent  122  that is anchored in the atrium through a pressure or friction fit. Through radial expansion, the frame of the stent adapts to the natural anatomy of the patient&#39;s atrium. A valve  124  is shown as visible through a biocompatible sheet  126 . As shown, the native mitral valve  50  is competent and works in series with the prosthetic mitral valve assembly  120 . Any regurgitant volume that passes by the native valve is blocked by the secondary prosthetic valve assembly. As already described, the result is an assembly with improved durability and reduced risk of valve migration. As in the other embodiments, the biocompatible sheet  126  is attached to the stent  122  in order to prevent paravalvular leakage. Four anchoring arms  128  are coupled to the stent frame  122  and are equally spaced around the frame&#39;s circumference. The opposite ends of the anchoring arms  128  are coupled together adjacent the roof of the atrium to create an open-ended dome. The anchoring arms  128  allow the mitral valve assembly  120  to expand in two dimensions, such as a horizontal direction and a vertical direction. By expanding horizontally, the mitral-valve assembly uses side walls of the atrium to anchor the assembly. By expanding vertically, the assembly expands between the annulus of the mitral valve and the roof of the atrium in order to anchor the assembly in the atrium. Thus, the roof of the atrium can exert a downward pressure on the assembly in order to prevent upward migration. Although four anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, 5, 6, etc.) Additionally, the anchoring arms  128  can be made of a flexible metal (similar or identical to the stent) or polymer. 
         [0062]      FIG. 8  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  140  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . This embodiment also includes anchoring arms  142 , similar to  FIG. 7 , except the anchoring arms  142  are coupled to a stent frame  144  at one end and to one or more pulmonary veins  61  at an opposite end. To couple the anchoring arms  142  to the pulmonary veins  61 , pulmonary vein stents  146  are mounted into the pulmonary veins and are coupled to one end of the anchoring arms  142 . The pulmonary vein stents  146  can be made from the same material as other stents described above and can be radially expandable. Additionally, the anchoring arms  142  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although two anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). As in the other embodiments, a biocompatible sheet  150  can be attached to the stent in order to prevent paravalvular leakage. 
         [0063]      FIG. 9  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  160  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . The embodiment of  FIG. 9  is similar to the embodiment of  FIG. 7 , but with one or more anchoring arms  162 , each coupled at one end to a stent  164  and left uncoupled at an opposing end. The anchoring arms  162  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although three anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). The anchoring arms press against the roof of the atrium to provide a pressure on the stent  164  in a direction of the mitral valve to prevent upward migration of the stent. As in the other embodiments, a biocompatible sheet  170  can be attached to the stent in order to prevent paravalvular leakage. 
         [0064]      FIG. 10  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  180  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . This embodiment is similar to the embodiment of  FIG. 8 , except anchoring arms  182  are coupled to a stent frame  184  at one end and to one or more pulmonary veins  61  at an opposite end using threaded pulmonary vein screws  186 . The threaded screws  186  are mounted into the pulmonary veins and secure the anchoring arms in place. The anchoring arms can therefore provide a downward pressure on the stent frame  184  in order to resist upward migration of the stent. The pulmonary vein screws  186  can be hollow to allow blood to flow therethrough. Additionally, the anchoring arms  182  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although two anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). As in the other embodiments, a biocompatible sheet  190  can be attached to the stent in order to prevent paravalvular leakage. 
         [0065]      FIG. 11  shows a cross-sectional view of a heart with the prosthetic mitral-valve assembly  8  from  FIG. 1  inserted into a patient&#39;s heart. As shown, the lower portion  16  can displace the native mitral valve leaflets  56 ,  58 . The upper portion  12  allows for anchoring the stent  10  in the atrium. More particularly, the stent is secured in place using contact between the radially expanding upper portion  12  and the atrium walls. The lower portion  16  may or may not contact the native mitral valve leaflets  56 ,  58  as indicated by gaps  200  between the lower portion  16  and the mitral valve  50 . A valve  202  is positioned in the lower portion  16  of the stent  10  so that the portion of the stent  10  for supporting the valve  202  is independent from the portion of the stent  10  for anchoring the stent in the heart. As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0066]      FIG. 12  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  220  inserted into the atrium. In this embodiment, a stent  222  has a self-expanding frame similar to stents described above. The mitral valve assembly  222  has a dome-shaped upper portion  224  that can expand to fit the natural anatomical geometry of a roof of the atrium. As a result, the mitral valve assembly  220  can expand in two dimensions, such as a horizontal direction and a vertical direction, as indicated by the arrows. By expanding horizontally, the mitral-valve assembly uses side walls of the atrium to anchor the assembly. By expanding vertically, the assembly expands between the annulus of the mitral valve and the roof of the atrium in order to anchor the assembly in the atrium. Thus, the roof of the atrium can exert a downward pressure on the assembly in order to prevent upward migration. A valve  226  is positioned in the lower portion  230  of the stent so that the portion of the stent for supporting the valve  226  is independent from the portion of the stent for anchoring the stent in the heart. As in the other embodiments, a biocompatible sheet (not shown) is attached to the stent in order to prevent paravalvular leakage. However, the biocompatible sheet is desirably not be positioned so as to obstruct blood flow through the pulmonary veins. 
         [0067]      FIG. 13  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  250  inserted into the atrium. As in the other embodiments, a biocompatible sheet  252  is attached to a stent frame  254  in order to prevent paravalvular leakage. Four anchoring arms  256  are coupled to the stent frame  254  so that they are equally spaced around the frame&#39;s circumference. The opposite ends of the anchoring arms  256  are coupled together adjacent the roof of the atrium to create an open-ended dome. The anchoring arms  256  allow the mitral valve assembly  250  to expand in two dimensions, such as a horizontal direction and a vertical direction. By expanding horizontally, the mitral-valve assembly uses side walls of the atrium to anchor the assembly. By expanding vertically, the assembly expands between the annulus of the mitral valve and the roof of the atrium in order to anchor the assembly in the atrium. Thus, the roof of the atrium can exert a downward pressure on the assembly in order to prevent upward migration. Although four anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, 5, 6, etc.) Additionally, the anchoring arms  256  can be made of a flexible metal (similar or identical to the stent) or polymer. 
         [0068]      FIG. 14  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  270  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . This embodiment also includes anchoring arms  272 , similar to  FIG. 13 , except the anchoring arms  272  are coupled to a stent frame  274  at one end and to one or more pulmonary veins  61  at an opposite end. To couple the anchoring arms  272  to the pulmonary veins  61 , pulmonary vein stents  276  are mounted into the pulmonary veins and are coupled to one end of the anchoring arms  272 . The pulmonary vein stents  276  can be made from the same material as other stents described herein. Additionally, the anchoring arms  272  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although two anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0069]      FIG. 15  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  290  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . The embodiment of  FIG. 15  is similar to the embodiment of  FIG. 13 , but with one or more anchoring arms  292 , each coupled at one end to a stent  294  and left uncoupled at an opposing end. The anchoring arms  292  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although three anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). The anchoring arms use the roof of the atrium to provide a pressure on the stent  294  in a direction of the mitral valve to prevent upward migration of the stent. As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0070]      FIG. 16  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  300  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . This embodiment is similar to the embodiment of  FIG. 14 , except anchoring arms  302  are coupled to a stent frame  304  at one end and to one or more pulmonary veins  61  at an opposite end using threaded pulmonary vein screws  306 . The threaded screws  306  are mounted into the pulmonary veins and secure the anchoring arms in place. The anchoring arms can therefore provide a downward pressure on the stent frame  304  in order to resist upward migration of the stent. The pulmonary vein screws  306  can be hollow to allow blood to flow therethrough. Additionally, the anchoring arms  302  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although two anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0071]      FIG. 17  shows a cross-sectional view of a heart with the prosthetic mitral-valve assembly from  FIG. 4  inserted into a patient&#39;s heart. As shown, the lower tapered portion  47  can partially displace the native mitral valve leaflets  56 ,  58 . The upper portion allows for anchoring the stent in the atrium. More particularly, the stent is secured in place using contact between the radially expanding upper portion and the atrium walls. The lower portion  47  only partially engages the native mitral valve leaflets  56 ,  58 , but is sized so as not to extend into the left ventricle. As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0072]      FIG. 18  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  30  inserted into the atrium. In this embodiment, a stent has a self-expanding frame  312  similar to stents described above. The mitral valve assembly  310  has a dome-shaped upper portion  314  that can expand to fit the natural anatomical geometry of a roof of the atrium. As a result, the mitral valve assembly can expand in two dimensions, such as a horizontal direction and a vertical direction. By expanding horizontally, the mitral-valve assembly uses side walls of the atrium to anchor the assembly. By expanding vertically, the assembly expands between the annulus of the mitral valve and the roof of the atrium in order to anchor the assembly in the atrium. Thus, the roof of the atrium can exert a downward pressure on the assembly in order to prevent upward migration. A valve  316  is positioned in the lower portion of the stent so that the portion of the stent for supporting the valve can be independent from the portion of the stent for anchoring the assembly in the heart. As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. However, the sheet should be sized so as not to obstruct blood flow in the pulmonary veins. 
         [0073]      FIG. 19  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  350  inserted into the atrium. This embodiment has characteristics of the mitral valve assembly of  FIG. 4 , but with additional atrial anchoring. As in the other embodiments, a biocompatible sheet (not shown) can be attached to a stent frame  354  in order to prevent paravalvular leakage. Four anchoring arms  356  are coupled to the stent frame  354  so that they are equally spaced around the frame&#39;s circumference. The opposite ends of the anchoring arms  356  are coupled together adjacent the roof of the atrium to create an open-ended dome. The anchoring arms  356  allow the mitral valve assembly  350  to expand in two dimensions, such as a horizontal direction and a vertical direction. By expanding horizontally, the mitral-valve assembly uses side walls of the atrium to anchor the assembly. By expanding vertically, the assembly expands between the annulus of the mitral valve and the roof of the atrium in order to anchor the assembly in the atrium. Thus, the roof of the atrium can exert a downward pressure on the assembly in order to prevent upward migration. Although four anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, 5, 6, etc.) Additionally, the anchoring arms  356  can be made of a flexible metal (similar or identical to the stent) or polymer. A lower tapered portion  360  of the mitral valve assembly  350  partially extends into the native mitral valve, but can remain distant enough from the left ventricle so as not to damage the chordae tendineae. 
         [0074]      FIG. 20  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  400  inserted into the atrium and a majority thereof positioned above the annulus  60  of the native mitral valve  50 . This embodiment also includes anchoring arms  402 , similar to  FIG. 8  with the anchoring arms  402  coupled to a stent frame  404  at one end and to one or more pulmonary veins  61  at an opposite end. To couple the anchoring arms  402  to the pulmonary veins  61 , pulmonary vein stents  406  are mounted into the pulmonary veins and are coupled to one end of the anchoring arms  402 . The pulmonary vein stents  406  can be made from the same material as other stents described herein. Additionally, the anchoring arms  402  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although two anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0075]      FIG. 21  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  420  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . The embodiment of  FIG. 21  is similar to the embodiment of  FIG. 15 , with one or more anchoring arms  422 , each coupled at one end to a stent  424  and left uncoupled at an opposing end. The anchoring arms  422  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although three anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). The anchoring arms use the roof of the atrium to provide a pressure on the stent  424  in a direction of the mitral valve to prevent upward migration of the stent. As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0076]      FIG. 22  shows a cross-sectional view of a heart with another embodiment of a prosthetic mitral-valve assembly  450  inserted into the atrium and positioned above the annulus  60  of the native mitral valve  50 . This embodiment is similar to the embodiment of  FIG. 16  with anchoring arms  452  coupled to a stent frame  454  at one end and to one or more pulmonary veins  61  at an opposite end using threaded pulmonary vein screws  456 . The threaded screws  456  are mounted into the pulmonary veins and secure the anchoring arms in place. The anchoring arms can therefore provide a downward pressure on the stent frame  454  in order to resist upward migration of the stent. The pulmonary vein screws  456  can be hollow to allow blood to flow therethrough. Additionally, the anchoring arms  452  can be made of a flexible metal (similar or identical to the stent) or polymer. Furthermore, although two anchoring arms are shown, any number of anchoring arms can be used (e.g., 1, 2, 3, or 4). As in the other embodiments, a biocompatible sheet (not shown) can be attached to the stent in order to prevent paravalvular leakage. 
         [0077]    Many of the embodiments described herein show one or more optional extension arms  500  that are used to assist in the delivery of the disclosed embodiments to the heart of a patient, as further described below. The extension arms  500  are generally shown as T-shaped extensions, but can be circular or other geometric shapes. Likewise, the extension arms  500  can be made of metal or a suture material. 
         [0078]      FIGS. 23A-23E  illustrate a delivery apparatus  700 . The delivery apparatus  700  comprises an outer catheter shaft  702  and an inner catheter shaft  704  extending through the outer shaft. The distal end portion of the outer shaft  702  comprises a sheath that extends over a prosthetic, self-expanding stented valve  706  (shown schematically) and retains it in a compressed state during delivery through the patient&#39;s vasculature. The distal end portion of the inner shaft  704  is shaped to cooperate with one or more mating extension arms, or posts,  708  that extend from the stent of the valve  706  to form a releasable connection between the valve and the delivery apparatus. For example, in the illustrated embodiment each post  708  comprises a straight portion terminating at a circular ring portion and the distal end portion of the shaft  704  has a correspondingly shaped recesses  710  that receive respective posts  708 . Each recess  710  can include a radially extending projection  712  that is shaped to extend into an opening  714  in a respective post  708 . As best shown in  FIG. 23B , each recess  710  and projection  712  can be sized to provide a small gap between the surfaces of the post  708  and the adjacent surfaces within the recess to facilitate insertion and removal of the post from the recess in the radial direction (i.e., perpendicular to the axis of the shaft  704 ). 
         [0079]    When the valve  706  is loaded into the delivery apparatus  700 , as depicted in  FIG. 23A , such that each post  708  of the valve is disposed in a recess  710 , the valve is retained against axial movement relative to the shaft  704  (in the proximal and distal directions) by virtue of the shape of the posts and the corresponding recesses. Referring to  FIG. 23D , as the outer shaft  702  is retracted to deploy the valve  706 , the valve is allowed to expand but is retained against “jumping” from the distal end of the sheath by the connection formed by the posts and the corresponding recesses for controlled delivery of the valve. At this stage the partially deployed valve is still retained by the shaft  704  and can be retracted back into the outer sheath  702  by retracting the shaft  704  relative to the outer sheath  702 . Referring to  FIG. 23E , when the outer sheath is retracted in the proximal direction past the posts  708 , the expansion force of the valve stent causes the posts to expand radially outwardly from the recesses  710 , thereby fully releasing the valve from the shaft  704 . 
         [0080]    While three posts  708  and corresponding recesses  710  are shown in the illustrated embodiment, any number of posts and recesses can be used. Furthermore, the posts and recesses can have various other shapes, such as square, oval, rectangular, triangular, or various combinations thereof. The posts can be formed from the same material that is used to form the valve stent (e.g., stainless steel or Nitinol). Alternatively, the posts can be loops formed from less rigid material, such as suture material. The loops are secured to the valve stent and are sized to be received in the recesses  710 . 
         [0081]      FIGS. 24A-24D  illustrate a delivery apparatus  800  that is similar to the delivery apparatus shown in  FIGS. 23A-23E . The delivery apparatus  800  includes a handle portion  802  having a rotatable knob  804 , an outer catheter shaft  806  extending from the handle portion  802 , and an inner catheter shaft  808  extending from the handle portion and through the outer catheter shaft  806 . The distal end of the inner catheter shaft  808  includes an end piece  810  that is formed with an annular recess  812  and a plurality of axially extending, angularly spaced recesses  814 . The recesses  812 ,  814  are sized and shaped to receive T-shaped posts  816  extending from the stent of a valve (not shown in  FIGS. 24A-24D ). Each post  816  has an axially extending portion  816   a  that is received in a corresponding recess  814  and a transverse end portion  816   b  that is received in the annular recess  812 . The outer shaft  806  includes a sheath  818  that is sized and shaped to extend over the end piece  812  and the valve during delivery of the valve. 
         [0082]    The outer shaft  806  is operatively connected to the knob  804  to effect longitudinal movement of the outer shaft  806  and the sheath  818  relative to the inner shaft  808  upon rotation of the knob  804 . In use, the valve is mounted for delivery by placing the posts  816  of the valve in the recesses  812 ,  814  and moving the sheath distally to extend over the valve to maintain the valve in a compressed state. At or near the target site for implanting the valve, the knob  804  is rotated to retract the sheath  818  relative to the valve. As the sheath is retracted to deploy the valve, the valve is allowed to expand but is retained against “jumping” from the distal end of the sheath by the connection formed by the posts and the corresponding recesses for controlled delivery of the valve. At this stage the partially deployed valve is still retained by the end piece  810  and can be retracted back into the sheath by moving the shaft  806  distally relative to the valve. When the sheath is retracted in the proximal direction past the posts  816 , the expansion force of the valve stent causes the posts to expand radially outwardly from the recesses  812 ,  814 , thereby fully releasing the valve from the end piece  810 . 
         [0083]      FIG. 25  shows an embodiment comprising a prosthetic mitral valve assembly  952  having leaflets  954 . Each leaflet  954  can be connected to a respective tension member  960 , the lower ends of which can be connected at a suitable location on the heart. For example, the lower end portions of tension members  960  can extend through the apex  962  and can be secured in placed at a common location outside the heart. Tension members may be attached to or through the papillary muscles. The lower ends of tension members can be connected to an enlarged head portion, or anchor,  964 , which secures the tension members to the apex. Tension members  960  can extend through a tensioning block  966 . The tensioning block  966  can be configured to slide upwardly and downwardly relative to tension members  960  to adjust the tension in the tensioning members. For example, sliding the tensioning block  966  upwardly is effective to draw the upper portions of the tension members closer together, thereby increasing the tension in the tension members. The tensioning block  966  desirably is configured to be retained in place along the length of the tension members, such as by crimping the tensioning block against the tension members, once the desired tension is achieved. The tension members can be made of any suitable biocompatible material, such as traditional suture material, GORE-TEX®, or an elastomeric material, such as polyurethane. The tension members  960  further assist in securing the valve assembly in place by resisting upward movement of the valve assembly and prevent the leaflets  954  from everting so as to minimize or prevent regurgitation through the valve assembly. As such, the tethering de-stresses the moveable leaflets. 
         [0084]      FIG. 26  shows another embodiment of a mitral valve assembly  1052  having prosthetic chordae tendineae. The prosthetic chordae tendineae comprise first and second tension members  1053  connected to a respective leaflet  1054  of the valve assembly. As shown, the lower end portions  1056  of each tension member  1053  can be connected at spaced apart locations to the inner walls of the left ventricle, using, for example, anchor members  1060 . A slidable tensioning block  1076  can be placed over each tension member  1053  for adjusting the tension in the corresponding tension member. In certain embodiments, each tension member  1053  can comprise a suture line that extends through a corresponding leaflet  1054  and has its opposite ends secured to the ventricle walls using anchor members  1060 . 
         [0085]    In particular embodiments, the anchor member  1060  can have a plurality of prongs that can grab, penetrate, and/or engage surrounding tissue to secure the device in place. The prongs of the anchor member  1060  can be formed from a shape memory material to allow the anchor member to be inserted into the heart in a radially compressed state (e.g., via an introducer) and expanded when deployed inside the heart. The anchor member can be formed to have an expanded configuration that conforms to the contours of the particular surface area of the heart where the anchor member is to be deployed, such as described in co-pending application Ser. No. 11/750,272, published as US 2007-0270943 A1, which is incorporated herein by reference. Further details of the structure and use of the anchor member are also disclosed in co-pending application Ser. No. 11/695,583 to Rowe, filed Apr. 2, 2007, which is incorporated herein by reference. 
         [0086]    Alternative attachment locations in the heart are possible, such as attachment to the papillary muscle (not shown). In addition, various attachment mechanisms can be used to attach tension members to the heart, such as a barbed or screw-type anchor member. Moreover, any desired number of tension members can be attached to each leaflet (e.g., 1, 2, 3 . . . etc.). Further, it should be understood that tension members can be used on any of the embodiments disclosed herein. 
         [0087]      FIGS. 25-26  show the use of tension members that can mimic the function of chordae. The tethers can have several functions including preventing the valve from migrating into the left atrium, distressing the leaflets by preventing eversion, and preserving ventricular function by maintaining the shape of the left ventricle. In particular, the left ventricle can lose its shape over time as the natural chordae become stretched or break. The artificial chordae can help to maintain the shape. Although  FIGS. 25 and 26  show a tricuspid valve, a bicuspid valve can be used instead. 
         [0088]      FIG. 27  shows another embodiment of a mitral valve assembly  1090  including a valve  1092  and a stent  1094  (shown partially cut-away to expose a portion of the valve). Tension members, shown generally at  1096 , can be connected between leaflets of the valve  1092  and the stent itself. Only two leaflets are shown, but additional tension members can be used for a third leaflet in a tricuspid valve. In the illustrated embodiment, the tension members  1096  can include groups  2002 ,  2004  of three tension members each. The three tension members  1096  of group  2002  can be attached, at one end, to one of the leaflets at spaced intervals and converge to attach at an opposite end to a bottom of the stent  1094 . Group  2004  can be similarly connected between another of the leaflets and the bottom of the stent  1094 . The tension members  1096  can be made of any suitable biocompatible material, such as traditional suture material, GORE-TEX®, or an elastomeric material, such as polyurethane. The tension members can prevent the leaflets from everting so as to minimize or prevent regurgitation through the valve assembly. As such, the tension members de-stress the moveable portions of the leaflets when the leaflets close during systole without the need to connect the tension members to the inner or outer wall of the heart. 
         [0089]    Although groups of three tension members are illustrated, other connection schemes can be used. For example, each group can include any desired number of tension members (e.g., 1, 2, 3, . . . etc.). Additionally, the tension members can connect to any portion of the stent and at spaced intervals, if desired. Likewise, the tension members can connect to the leaflets at a point of convergence, rather than at spaced intervals. Further, the tension members can be used on bicuspid or tricuspid valves. Still further, it should be understood that tension members extending between the stent and the leaflets can be used on any of the embodiments disclosed herein. 
         [0090]    One skilled in the art will recognize that the tethering shown in  FIGS. 25-27  can be used with any of the embodiments described herein. 
         [0091]    In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope of these claims.