Patent Publication Number: US-2019167421-A1

Title: Prosthetic Valve For Replacing Mitral Valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/299,897, filed Oct. 21, 2016, entitled “Prosthetic Valve for Replacing Mitral Valve,” which is a continuation of U.S. patent application Ser. No. 14/470,621, filed Aug. 27, 2014, entitled “Prosthetic Valve for Replacing Mitral Valve,” now Abandoned, which is a continuation of U.S. patent application Ser. No. 13/356,136, filed Jan. 23, 2012, entitled “Prosthetic Valve for Replacing Mitral Valve,” now Abandoned, which is a continuation of U.S. patent application Ser. No. 12/959,292, filed Dec. 2, 2010, entitled “Prosthetic Valve for Replacing Mitral Valve,” now U.S. Patent No. 8,449,599, which claims priority to and the benefit of U.S. Provisional Application No. 61/266,774, filed Dec. 4, 2009, entitled “Prosthetic Mitral Valve with Subvalvular Anchoring,” and U.S. Provisional Application No. 61/287,099, filed Dec. 16, 2009, entitled “Prosthetic Mitral Valve with Subvalvular Anchoring.” The disclosure of each of the foregoing applications is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     This disclosure pertains generally to prosthetic devices for repairing and/or replacing native heart valves, and in particular to prosthetic valves for replacing defective mitral valves, as well as methods and devices for delivering and implanting the same within a human heart. 
     Prosthetic valves have been used for many years to treat cardiac valvular disorders. The native heart valves (i.e., 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 malformations, inflammatory processes, 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. However, such surgeries are highly invasive and are prone to many complications. Therefore, elderly and frail patients with defective heart valves often go untreated. 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 much less invasive than open heart surgery. 
     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. 
     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. 2007/0112422, which is hereby incorporated by reference Like the transvascular approach, the transapical approach can include 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 can include 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. 
     The above techniques and others have provided numerous options for high operative risk patients with aortic valve disease to avoid the consequences of open heart surgery and cardiopulmonary bypass. While devices and procedures for the aortic valve are well-developed, such catheter-based procedures are not necessarily applicable to the mitral valve due to the distinct differences between the aortic and mitral valve. The mitral valve has complex subvalvular apparatus, i.e., chordae tendinae, which are not present in the aortic valve. 
     Surgical mitral valve repair techniques (e.g., mitral annuloplasty) have increased in popularity due to their high success rates, and clinical improvements noted after repair. In addition to the existing mitral valve repair technologies, there are a number of new technologies aimed at making mitral valve 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 plications or ventricular remodeling devices, which would incidentally correct mitral regurgitation. 
     However, for mitral valve replacement, few less-invasive options are available. There are approximately 25,000 mitral valve replacements (MVR) each year in the United States. However, it is estimated that over 300,000 patients who meet guidelines for treatment are denied treatment based on their age and/or co-morbities. Thus, a need exists for minimally invasive techniques for replacing the mitral valve. 
     SUMMARY 
     Prosthetic mitral valves, components thereof, and methods and devices for implanting the same are described herein. 
     A prosthetic apparatus is described that is configured for implanting at the native mitral valve region of the heart and includes a main body that is radially compressible to a radially compressed state and self-expandable from the compressed state to a radially expanded state. The prosthetic apparatus also comprises at least one ventricular anchor coupled to the main body and disposed outside of the main body such that when the main body is compressed to the compressed state, a leaflet-receiving space between the ventricular anchor and an outer surface of the main body increases to receive a native valve leaflet therebetween. When the main body self-expands to the expanded state in the absence of any substantial external inward forces on the main body or the ventricular anchor, the space decreases to capture the leaflet between the main body and the ventricular anchor. 
     In some embodiments, a prosthetic apparatus, for implanting at the native mitral valve region of the heart, includes a frame having a main body and at least one ventricular anchor coupled to and disposed outside of the main body. The prosthetic apparatus also includes a plurality of leaflets supported by the main body that form a one-way valve for the flow of blood through the main body. The main body is radially compressible to a radially compressed state for delivery into the body and self-expandable from the compressed state to a radially expanded state. The ventricular anchor comprises a base that is fixedly secured to the main body, a free end portion opposite the base, and an intermediate portion defining a leaflet-receiving space between the ventricular anchor and the main body for receiving a leaflet of the native valve. Expansion of the main body from its compressed state to its radially expanded state in the absence of any radial inward forces on the ventricular anchor causes the leaflet-receiving space to decrease. 
     In other embodiments, a prosthetic apparatus for implanting at the native mitral valve region includes a main body, at least one ventricular anchor and at least one atrial anchor. The main body is configured for placement within the native mitral valve and is compressible to a compressed state for delivery into the heart and self-expandable from the compressed state to an expanded state. At least one ventricular anchor is coupled to and disposed outside of the main body such that, in the expanded state, a leaflet-receiving space exists between the ventricular anchor and an outer surface of the main body to receive a free edge portion of a native valve leaflet. The ventricular anchor comprises an engagement portion configured to extend behind the received native leaflet and contact a ventricular surface of the native mitral annulus, the annulus connection portion of the received native leaflet, or both the ventricular surface of the native annulus and the annulus connection portion of the received native leaflet. At least one atrial sealing member is coupled to and disposed outside of the main body and is configured to contact an atrial portion of the native mitral annulus, the annulus connection portion of the received native leaflet, or both the atrial surface of the native annulus and the annulus connection portion of the received native leaflet at a location opposite from the engagement portion of the ventricular anchor for retention of the prosthetic apparatus and/or prevention of paravalvular leakage. 
     Exemplary delivery systems are also described for delivering a prosthetic apparatus into the heart. Some embodiments include an inner sheath having a distal end portion having at least one longitudinal slot extending proximally from a distal end of the inner sheath. The distal end portion of the inner sheath is configured to contain the prosthetic apparatus in a radially compressed state. An outer sheath is positioned concentrically around the inner sheath and at least one of the inner sheath and outer sheath is movable axially relative to the other between a first position in which the outer sheath extends over at least a portion of the longitudinal slot and a second position in which the at least a portion of the longitudinal slot is uncovered by the outer sheath so to allow a portion of the prosthetic apparatus contained within the inner sheath to expand radially outward through the slot. 
     Exemplary methods are also described for implanting a prosthetic apparatus at the native mitral valve region of the heart. One such method includes delivering the prosthetic apparatus into the heart in a radially compressed state; allowing a ventricular anchor to self-expand away from a main body of the frame while the main body is held in the compressed state, thereby increasing a gap between the ventricular anchor and an outer surface of the main body; positioning the main body in the annulus of the native mitral valve and the ventricular anchor adjacent the ventricular side of a native mitral valve leaflet such that the leaflet is disposed in the gap between the ventricular anchor and the outer surface of the main body; and allowing the main body to self-expand to an expanded state such that the gap decreases to capture the leaflet between the outer surface of the main body and the ventricular anchor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view of the human heart. 
         FIG. 2  is another cross sectional view of the human heart showing the mitral valve region. 
         FIG. 3  is a schematic view of the native mitral valve anatomy showing the mitral leaflets attached to the papillary muscles via chordae tendineae. 
         FIG. 4A  is a diagram of native mitral valve showing Carpentier nomenclature. 
         FIG. 4B  shows a native mitral valve with a gap between the leaflets. 
         FIGS. 4C and 4D  show an exemplary prosthetic valve positioned within a native mitral valve. 
         FIG. 5  is a side view of an exemplary embodiment of a prosthetic valve. 
         FIG. 6  shows the prosthetic valve of  FIG. 5  rotated  90  degrees with respect to a longitudinal axis of the value. 
         FIG. 7  is a ventricular (outflow) view of the prosthetic valve shown of  FIG. 5 . 
         FIGS. 8-10  are views corresponding to  FIGS. 5-7 , showing an exemplary embodiment of a frame of the prosthetic valve of  FIGS. 5-7 . 
         FIGS. 11-16  are a series of side views of the frame of  FIGS. 9 , without the atrial sealing member, showing the leaflet-receiving spaces between the ventricular anchors and the main body increasing as the main body is radially compressed. 
         FIGS. 17-22  are a series of end views corresponding to  FIGS. 11-16 , respectively. 
         FIG. 23  is a cross-sectional view of the heart showing the frame of  FIGS. 9  implanted in the mitral valve region, wherein the native mitral valve leaflets are captured between the main body and the ventricular anchors. 
         FIG. 24  shows exemplary dimensions of the atrial sealing member, main body and ventricular anchors of  FIG. 9 . 
         FIG. 25  shows an exemplary embodiment of a frame, with the atrial sealing member excluded, comprising a “T” shaped pushing member extending downward from a ventricular end of the main body. 
         FIG. 26  shows an exemplary embodiment of a frame, with the atrial sealing member excluded, comprising a “V” shaped pushing member extending downward from the ventricular end of the main body. 
         FIGS. 27-29  show an exemplary embodiment of a prosthetic valve having a frame with four ventricular anchors. 
         FIGS. 30-32  show the frame of the prosthetic valve shown in  FIGS. 27-29 . 
         FIG. 33  is a cross-sectional view of the heart showing the frame of  FIGS. 30-32  implanted in the mitral valve region. 
         FIG. 34  is a cross-sectional view of the heart showing an embodiment of a frame, comprising extended ventricular anchors and an atrial sealing member, implanted in the mitral valve region such that the mitral annulus and/or native leaflets are compressed between the ends of the extended ventricular anchors and the atrial sealing member. 
         FIGS. 35 and 36  are side views of an exemplary embodiment of a frame comprising “S” shaped ventricular anchors. 
         FIGS. 37 and 38  are side and top views, respectively, of an exemplary embodiment of a frame, with the atrial sealing member excluded, comprising wider shaped ventricular anchors. 
         FIG. 39  is a cross-sectional view of the heart showing an embodiment of a frame implanted in the mitral valve region, wherein the ventricular anchors remain separated from the body of the frame after expansion and the ventricular anchors contact the lower ends of the mitral leaflets to utilize tension from the chordae tendineae to retain the frame. 
         FIG. 40  shows an exemplary embodiment of a frame comprising a substantially flat atrial sealing member. 
         FIG. 41  shows an exemplary embodiment of a frame comprising an upwardly extending atrial sealing member. 
         FIG. 42  shows an exemplary embodiment of a frame comprising an upwardly extending atrial sealing member and extended ventricular anchors. 
         FIG. 43  shows an exemplary embodiment of a frame, with the atrial sealing member excluded, comprising wide-set ventricular anchors. 
         FIG. 44  depicts a series of side views of an exemplary embodiment of a frame, with the atrial sealing member excluded, having ventricular anchors that flip up into a final configuration. 
         FIG. 45  depicts a series of side views of an exemplary embodiment of a frame, with the atrial sealing member excluded, having ventricular anchors that curl up into a final configuration. 
         FIGS. 46A-46C  show an exemplary embodiment of a frame, with the atrial sealing member excluded, wherein the main body is manufactured separately from the ventricular anchors. 
         FIGS. 47A-47D  show another embodiment of a frame, with the atrial sealing member excluded, wherein the main body is manufactured separately from the ventricular anchors and attached using a sleeve. 
         FIGS. 48A-48C  show another embodiment of a frame, with the atrial sealing member excluded, wherein the main body is manufactured separately from the ventricular anchors and attached using a sleeve with a mechanical lock. 
         FIG. 49  shows an exemplary embodiment of a delivery system for delivering and implanting a prosthetic valve at a native mitral valve region of the heart. 
         FIG. 50  is a detailed view of the distal portion of the delivery system of  FIG. 49 . 
         FIG. 51  is a cross-sectional view of a handle portion of the delivery system of  FIG. 49 , taken along section line  51 - 51 . 
         FIG. 52  is a cross sectional view of the handle portion of the delivery system of  FIG. 49 , taken along section line  52 - 52 . 
         FIG. 53  is a cross sectional view of an insertable portion of the delivery system of  FIG. 49 , taken along section line  53 - 53 . 
         FIG. 54  shows the delivery system of  FIG. 49  with a prosthetic valve loaded within a slotted inner sheath with the ventricular anchors extending outward through slots of the inner sheath. 
         FIG. 55  is a cross-sectional view of the delivery system of  FIG. 49  in a delivery position containing the prosthetic valve within inner and outer sheaths and between a nose cone and a tip of a pusher shaft. 
         FIG. 56  is a cross-sectional view of a distal end portion of the delivery system of  FIG. 49  showing the outer sheath of the delivery system retracted such that ventricular anchors extend outward through slots of the inner sheath. 
         FIG. 57  is a cross-sectional view of the heart showing the ventricular anchors of the prosthetic valve being pre-deployed in the left ventricle using the delivery system of  FIG. 49 . 
         FIG. 58  is a view of the mitral valve region of the heart from the left ventricle showing the ventricular anchors extending from the slots in the delivery system and showing the ventricular anchors positioned between respective mitral leaflets and the ventricular walls. 
         FIG. 59  is a cross-sectional view of the heart showing the prosthetic valve being implanted in the mitral valve region using the delivery system of  FIG. 49  with the native leaflets positioned between the ventricular anchors and the inner sheath. 
         FIG. 60  is a cross-sectional view of the delivery system of  FIG. 49  showing the slotted inner sheath retracted to a point where the ventricular anchors of the prosthetic valve contact a notched retaining band around the slotted inner sheath. 
         FIG. 61  is a cross-sectional view of the delivery system of  FIG. 49  showing the slotted inner sheath fully retracted after the band has been broken, and the prosthetic valve in an expanded state after being fully deployed from the sheath. 
         FIG. 62  is a view of the mitral valve region of the heart from the left ventricle showing an exemplary embodiment of a prosthetic valve fully implanted with the mitral leaflets captured between a main body and ventricular anchors. 
         FIG. 63  shows an exemplary embodiment of a prosthetic valve within a catheter sheath for delivering to a native valve region of the heart, according to another embodiment. 
         FIG. 64  shows the prosthetic valve of  FIG. 63  with the catheter sheath pulled back such that the ventricular anchors are free to expand but the main body remains compressed. 
         FIG. 65  shows the prosthetic valve of  FIG. 63  with the outer sheath recapturing the main body such that only the ventricular anchors are exposed. 
         FIG. 66  is a cross-sectional view of the heart showing the prosthetic valve of  FIG. 65  being implanted in the native mitral valve region using a transatrial approach. 
         FIG. 67  is a cross-sectional view of the heart showing the prosthetic valve of  FIGS. 65  being implanted in the native mitral valve region using a transeptal approach. 
         FIG. 68  is a view of the mitral valve region from the left ventricle showing an embodiment of an atrially delivered prosthetic valve having ventricular anchors extending free of a sheath and positioned between the native mitral valve leaflets and the ventricular walls. 
         FIG. 69  is a view of the mitral valve region from the left ventricle showing the prosthetic valve of  FIG. 68  fully expanded and anchored to the native mitral valve leaflets. 
         FIG. 70  is a cross-sectional view of the heart showing an embodiment of a docking frame that is secured to the native tissue of mitral valve region and a separately deployed prosthetic valve that is secured to the docking frame within the lumen of the docking frame. 
         FIG. 71  a perspective view of an embodiment of a prosthetic apparatus for implanting at the native mitral valve region to treat mitral regurgitation. 
         FIG. 72  is a side view of the prosthetic apparatus of  FIG. 71 . 
         FIG. 73  is another side view of the prosthetic apparatus of  FIG. 71 . 
         FIG. 74  is an end view of the prosthetic apparatus of  FIG. 71 . 
         FIGS. 75-79  are cross-sectional views of the heart showing a transeptal delivery of the prosthetic apparatus of  FIG. 71 . 
         FIG. 80  is a side view of an alternative embodiment of a prosthetic apparatus of  FIG. 71 , comprising prosthetic valve. 
         FIG. 81  is a partial side view of an alternative embodiment of a prosthetic apparatus of  FIG. 71 , comprising a Z-cut frame body. 
         FIG. 82  is a partial side view of an alternative embodiment of a prosthetic apparatus of  FIG. 71 , comprising a lattice frame body and a prosthetic valve. 
         FIG. 83  is a partial side view of an alternative embodiment of a prosthetic apparatus of  FIG. 71  comprising a helical frame body. 
         FIGS. 84 and 85  show an exemplary method for implanting an exemplary prosthetic apparatus having “L” shaped ventricular anchors. 
         FIGS. 86 and 87  show another exemplary method for implanting another prosthetic apparatus having “L” shaped ventricular anchors. 
         FIG. 88  is ventricular view of the native mitral valve region. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein are embodiments of prosthetic valves and components thereof that are primarily intended to be implanted at the mitral valve region of a human heart, as well as apparatus and methods for implanting the same. The prosthetic valves can be used to help restore and/or replace the functionality of a defective native valve. 
     The Human Heart 
     Relevant portions of the human heart are shown in  FIGS. 1 and 2 . A healthy heart has a generally conical shape that tapers to a lower apex  38 . The heart is four-chambered and comprises the left atrium  4 , right atrium  26 , left ventricle  6 , and right ventricle  28 . The left and right sides of the heart are separated by a wall generally referred to as the septum  30 . The native mitral valve  2  of the human heart connects the left atrium  4  to the left ventricle  6 . The mitral valve  2  has a very different anatomy than other native heart valves, such as the aortic valve  14 . 
     The mitral valve  2  includes an annulus portion  8 , which is an annular portion of the native valve tissue surrounding the mitral valve orifice, and a pair of cusps, or leaflets,  10 ,  12  extending downward from the annulus  8  into the left ventricle  6 . The mitral valve annulus  8  can form a “D” shaped, oval, or otherwise out-of-round cross-sectional shape having major and minor axes. The anterior leaflet  10  can be larger than the posterior leaflet  12 , as shown schematically in  FIG. 4A , forming a generally “C” shaped boundary between the abutting free edges of the leaflets when they are closed together.  FIG. 4B  shows the native mitral valve  2  with a slight gap  3  between the leaflets  10 ,  12 , such as with a defective native mitral valve that fails to completely close, which can lead to mitral regurgitation and/or other undesirable conditions. 
     When operating properly, the anterior leaflet  10  and the posterior leaflet  12  function together as a one-way valve to allow blood to flow only from the left atrium  4  to the left ventricle  6 . The left atrium  4  receives oxygenated blood from the pulmonary veins  32 . When the muscles of the left atrium  4  contract and the left ventricle dilates, the oxygenated blood that is collected in the left atrium  4  flows into the left ventricle  6 . When the muscles of the left atrium  4  relax and the muscles of the left ventricle  6  contract, the increased blood pressure in the left ventricle urges the two leaflets together, thereby closing the one-way mitral valve so that blood cannot flow back to the left atrium and is instead expelled out of the left ventricle through the aortic valve  14 . 
     To prevent the two leaflets  10 ,  12  from prolapsing under pressure and folding back through the mitral annulus  8  toward the left atrium  4 , a plurality of fibrous cords called chordae tendineae  16  tether the leaflets  10 ,  12  to papillary muscles in the left ventricle  6 . Referring to  FIGS. 3 and 4 , chordae  16  are attached to and extend between the postero-medial papillary muscle  22  and the postero-medial margins of both the anterior leaflet  10  and the posterior leaflet  12  (A 1  and P 1  areas, respectively, as identified by Carpentier nomenclature). Similarly, chordae  16  are attached to and extend between the antero-lateral papillary muscle  24  and the antero-lateral margins of both the anterior leaflet  10  and the posterior leaflet  12  (A 3  and P 3  areas, respectively, as identified by Carpentier nomenclature). The A 2  and P 2  areas are relatively free of chordae attachment points and provide a region where a prosthetic mitral valve can be anchored (see  FIG. 3 ). In addition, the organization of the chordae provides an approach path to deliver a prosthetic mitral valve with minimal risk of chordae entanglement. 
     Prosthetic Valve 
     When the native mitral valve fails to function properly, a prosthetic valve replacement can help restore the proper functionality. Compared to the aortic valve  14 , however, which has a relatively round and firm annulus (especially in the case of aortic stenosis), the mitral valve annulus  8  can be relatively less firm and more unstable. Consequently, it may not be possible to secure a prosthetic valve that is designed primarily for the aortic valve within the native mitral valve annulus  8  by relying solely on friction from the radial force of an outer surface of a prosthetic valve pressed against the native mitral annulus  8 . Accordingly, the prosthetic valves described herein can rely on ventricular anchors instead of, or in addition to, radial friction forces, to secure the prosthetic valve within the native mitral valve annulus  8  (see  FIG. 23 , for example). 
     In addition to providing an anchoring means for the prosthetic valve, the ventricular anchors can also remodel the left ventricle  6  to help treat an underlying cause of mitral regurgitation—left ventricle enlargement/dilation. The ventricular anchors can pull the native mitral valve leaflets  10 ,  12  closer together and toward the left atrium and, via the chordae  16 , thereby pull the papillary muscles  22 ,  24  closer together, which can positively remodel the ventricle acutely and prevent the left ventricle from further enlarging. Thus, the ventricular anchors can also be referred to as tensioning members or reshaping members. 
       FIGS. 5-7  illustrate an exemplary prosthetic valve  100 , according to one embodiment, that can be implanted in the native mitral valve region of the heart to replace the functionality of the native mitral valve  2 . The prosthetic valve  100  comprises a frame  102  and a valve structure  104  supported by and/or within the frame. The valve structure  104  can include a plurality of prosthetic leaflets  106  (three in the illustrated embodiment) and/or other components for regulating the flow of blood in one direction through the prosthetic valve  100 . In  FIGS. 5 and 6 , for example, valve structure  104  is oriented within the frame  102  such that an upper end  110  of the valve structure is the inflow end and a lower end  112  of the valve structure is the outflow end. The valve structure  104  can comprise any of various suitable materials, such as natural tissue (e.g., bovine pericardial tissue) or synthetic materials. The valve structure  104  can be mounted to the frame  102  using suitable techniques and mechanisms. In the illustrated embodiment, for example, the leaflets  106  are sutured to the frame  102  in a tricuspid arrangement, as shown in  FIG. 7 . 
     Additional details regarding components and assembly of prosthetic valves (including techniques for mounting leaflets to the frame) are described, for example, in U.S. Patent Application Publication No. 2009/0276040 A1 and U.S. patent application Ser. No. 12/393,010, which are incorporated by reference herein. 
     As shown in  FIGS. 8-10 , the frame  102  can comprise a tubular main body  122 , one or more ventricular anchors  126  extending from a ventricular end  130  of the main body and optionally an atrial sealing member  124  extending radially outward from an atrial end  132  of the main body. When the frame  102  is implanted in the native mitral valve region of the heart, as shown in  FIG. 23 , the main body  122  is positioned within the native mitral valve annulus  8  with the ventricular end  130  of the main body  122  being a lower outlet end, the atrial end  132  of the main body  132  being an upper inlet end, the ventricular anchors  126  being located in the left ventricle  6 , and the atrial sealing member  124  being located in the left atrium  4 . 
     The frame  102  can be made of a wire mesh and can be radially collapsible and expandable between a radially expanded state and a radially compressed state (as shown schematically in a series of successive stages in  FIGS. 11-16 and 17-22 ) to enable delivery and implantation at the mitral valve region of the heart (or within another native heart valve). The embodiments of the frame  102  shown in  FIGS. 11-22  do not include an atrial sealing member  124 , though other embodiments of the frame  102  do include an atrial sealing member  124 . The wire mesh can include metal wires or struts arranged in a lattice pattern, such as the sawtooth or zig-zag pattern shown in  FIGS. 8-10  for example, but other patterns may also be used. The frame  102  can comprise a shape-memory material, such as Nitinol for example, to enable self-expansion from the radially compressed state to the expanded state. In alternative embodiments, the frame  102  can be plastically expandable from a radially compressed state to an expanded state by an expansion device, such as an inflatable balloon (not shown) for example. Such plastically expanding frames can comprise stainless steel, chromium alloys, and/or other suitable materials. 
     In an expanded state, as shown in  FIGS. 8-10 , the main body  122  of the frame  102  can form an open-ended tube. The valve structure  104  can be coupled to an inner surface of the frame  102 , such as via a material layer  142  on the inner surface of the frame, as discussed below, and can be retained within the lumen formed by the main body  122 , as shown in  FIG. 7 . An outer surface of the main body  122  can have dimensions similar to that of the mitral orifice, i.e., the inner surface of the mitral annulus  8 , but not necessarily. In some embodiments, for example, the outer surface of the main body  122  can have diametrical dimensions that are smaller than the diametrical dimensions of the native mitral orifice, such that the main body  122  can fit within the mitral orifice in the expanded state without substantially stretching the native mitral annulus  8 , such as in  FIG. 23 . In such embodiments, the frame  102  need not rely on a pressure fit, or friction fit, between the outer surface of the main body  122  and the inner surface of the mitral annulus  8  for prosthetic valve retention. Instead, the frame  102  can rely on the ventricular anchors  126  and/or the atrial sealing member  124  for retention, as further described below. In other embodiments, however, the main body  122  can be configured to expand to an equal or greater size than the native mitral orifice and thereby create a pressure fit when implanted. 
     In embodiments wherein the main body  122  comprises diametrical dimensions that are smaller than the diametrical dimensions of the native mitral orifice, the main body can sit loosely, or “float,” between the native leaflets  10 ,  12 . As shown in  FIG. 4C , this loose fit can create gaps  37  between the leaflets  10 ,  12  and the main body  122  of the frame. To prevent blood flow between the outside of the prosthetic valve  100  and the native valve tissue, such as through the gaps  37 , the annular atrial sealing member  124  can create a fully annular contact area, or seal, with the native tissue on the atrial side of the mitral annulus  8 . Accordingly, as shown in  FIG. 4D , the atrial sealing member  124  can be sized to fully cover the gaps  37 . 
     The ends of the frame  102  can have a sawtoothed or zig-zag pattern, as shown in  FIGS. 8-10 , comprising a series of side-by-side “V” shaped portions connected together at their upper ends, for example. This pattern can facilitate compression and can help maximize a surface area with which the frame connects to the native tissue. Alternatively, the ends of the frame  102  can have a straight edge, or some other pattern. 
     In some embodiments, the main body  122  can comprise at least one extension member, or pushing member, that extends downward from the ventricular end  130  of the main body  122 . The frame  202  shown in  FIG. 25 , for example, comprises an extension member in the form of a prong  204  that extends from the lower vertex of one of the “V” shaped portions of a main body  222 . The prong  204  can have an upside-down “T” shape comprising a lower pushing surface  206 . In another embodiment, the frame  302  shown in  FIG. 26  comprises a “V” shaped pushing member  304  that extends from two adjacent lower vertices of a main body  322  and comprises a pushing surface  306 . The pushing surfaces  206  and  306  can comprise the lowermost points on the frames  202  and  302 , respectively, and can provide a pushing surface for the frame to be expelled out of a delivery device without contacting the ventricular anchors  226 ,  326 , as described in more detail below. 
     With reference again to the embodiment shown in  FIGS. 8-10 , the atrial sealing member  124  of the frame  102  can be integral with the main body  122  and can be comprised of the same wire mesh lattice as the main body  122  such that the atrial sealing member  124  can also be radially collapsible and expandable. In the expanded state, the atrial sealing member  124  can be generally frustoconical and extend from the atrial end  132  of main body  122  both radially outward and axially downward toward the ventricular end  130  of the main body  122 . An outer rim  140  of the atrial sealing member  124  can be sized and shaped to contact the atrial side of the mitral annulus and tissue of the left atrium  8  when the frame  102  is implanted, as shown in  FIG. 23 . The end view profile of the outer rim  140 , as shown in  FIG. 10 , can have a generally circular, oval, or other shape that generally corresponds to the native geometry of the atrial walls  18  and the mitral annulus  8 . The contact between the atrial sealing member  124  and the tissue of the atrial walls  18  and/or the mitral annulus  8  can promote tissue ingrowth with the frame, which can improve retention and reduce paravalvular leakage. 
     The atrial sealing member  124  desirably is sized such that when the prosthetic valve  100  is implanted in the native mitral valve, as shown in  FIG. 23 , the outer rim  140  contacts the native annulus  8  around the entire native valve and therefore completely covers the opening between the native leaflets  10 ,  12 . The atrial sealing member  124  desirably includes a sealing layer  142  that is impervious to the flow of blood. In this manner, the atrial sealing member  124  is able to block blood from flowing back into the left atrium between the outer surfaces of the prosthetic valve  100  and the native valve tissue. The atrial sealing member also ensures that all, or substantially all, of the blood passes through the one-way valve as it flows from the left atrium to the left ventricle. 
     As shown in  FIGS. 5-7 , at least one biocompatible sheet or layer  142  can be connected to the inner and/or outer surfaces of the main body  122  and the atrial sealing member  124  to form at least one layer or envelope covering the openings in the wire mesh. The layer  142  can be connected to the frame  102  by sutures, for example. The layer  142  can form a fluid-occluding and/or sealing member that can at least partially block the flow of blood through the wire mesh to reduce paravalvular leakage and can promote tissue ingrowth with the frame  102 . The layer  142  can provide a mounting surface, or scaffold, to which the portions of the valve structure  104 , such as the leaflets  106 , can be secured. For example, the dashed line  108  in  FIGS. 5 and 6  represents where the inlet ends of the leaflets  106  can be sewn, sutured, or otherwise secured to the layer  142 . This seam between the inlet ends of the leaflets  106  and the layer  142  can form a seal that is continuous around the inner perimeter of the layer  142  and can block blood flow between the inner surface of the layer  142  and the outer surface of the leaflets  106 . This seal can allow the prosthetic valve  100  to direct blood to flow between the plurality of leaflets  106 . 
     The same layer  142  and/or one or more separate cuffs  144  can also wrap around, or cover, the end edges of the frame  102 , such as the ventricular end  130  of the main body  122  and/or the outer rim  140  of the atrial sealing member  124 . Such a cuff  144  can cover and protect sharp edges at the ends of the frame  102 . For example, in the embodiment shown in  FIG. 5 , the layer  142  extends from the outer rim  140  across the upper surface of the atrial sealing member  124  and downward along the inner surface of the main body  122  and comprises a cuff  144  that wraps around and covers a ventricular end portion of the main body  122 . The layer  142  can be sutured to the outer rim  140  and to the inner surface of the main body  122 . 
     [The layer  142  can comprise a semi-porous fabric that blocks blood flow but can allow for tissue ingrowth. The layer  142  can comprise synthetic materials, such as polyester material or a biocompatible polymer. One example of a polyester material is polyethylene terephthalate (PET). Alternative materials can be used. For example, the layer can comprise biological matter, such as natural tissue, pericardial tissue (e.g., bovine, porcine, or equine pericardium) or other biological tissue. 
     [With reference to  FIGS. 8 and 9 , one or more ventricular anchors  126  can extend from the main body  122  of the frame  102 , such as from the ventricular end  130  of the main body. The ventricular anchors  126  can function to retain the frame  102 , with or without the valve structure  104 , within a native valve region of the heart. In the embodiment shown in  FIGS. 8 and 9 , the frame  102  comprises two diametrically opposed ventricular anchors  126  that can function to secure the frame  102  to the anterior and posterior mitral leaflets  10 ,  12 , respectively, when the frame  102  is implanted in the mitral valve region, as shown in  FIG. 23 . In alternate embodiments, the frame  102  can have three or more ventricular anchors  126 , which can be angularly spaced around the main body  122  of the frame. 
     When the frame  102  is in an expanded state, as in  FIG. 9 , the geometry of the frame can cause the ventricular anchors  126  to be urged against the outer surface of the main body  122 . Alternatively, the ventricular anchors  126  can be configured to be spaced apart from the outer surface of the main body  122  when the frame  102  is in the expanded state (see  FIG. 39 , for example). In any case, when the frame  102  is radially compressed to the compressed state, the space or gap between the ventricular anchors  126  and the outer surface of the main body  122  can increase, as shown in  FIGS. 11-16 . 
     While the main body  122  and the atrial sealing member  124  are in the compressed state, the frame  102  can be inserted into the mitral valve orifice such that the spaced apart ventricular anchors  126  wrap around the leaflets  10 ,  12  and extend upward between the leaflets and the ventricular walls  20  (see  FIG. 59 , for example). With reference to  FIG. 23 , an anterior ventricular anchor  146  can be located behind the anterior leaflet  10  and a posterior ventricular anchor  148  can be located behind the posterior leaflet  12 . With reference to  FIGS. 3 and 4 , the two ventricular anchors are desirably located behind the respective leaflets near the middle portions of the leaflets A 2 , P 2  about midway between the commissures  36  where the two leaflets meet. These middle portions A 2 , P 2  of the leaflets  10 , 12  are desirable ventricular anchor locations because the chordae tendineae  16  attachments to the leaflets are sparser in these locations compared to locations nearer to the commissures  36 . 
     When the main body  122  is subsequently expanded or allowed to self-expand to the expanded state, as shown in  FIGS. 11-16  in reverse order, the ventricular anchors are configured to pivot radially inward relative to the main body  122 , without external compressive forces on the ventricular anchors. This causes the gaps between the ventricular anchors  126  and the outer surface of the main body  122  to decrease, thereby enabling the capture of the leaflets  10 ,  12  between the ventricular anchors and the main body. Conversely, compressing the main body  122  causes the ventricular anchors  126  to pivot away from the main body to increase the gaps between the outer surface of the main body and the ventricular anchors. In some embodiments, the free ends, or apexes,  162  of the ventricular anchors  126  can remain substantially the same distance apart from one another as the main body  122  is radially compressed or expanded free of external forces on the ventricular anchors. In some embodiments, such as the embodiment shown in  FIG. 23 , the frame is configured to compress the native mitral leaflets  10 ,  12  between the main body and the ventricular anchors when the frame expands to the expanded state. In other embodiments, such as the embodiment shown in  FIG. 39 , the ventricular anchors do not compress or clamp the native leaflets against the main body but still prevent the prosthetic valve from migrating toward the left atrium by the hooking of the ventricular anchors around the native leaflets  10 ,  12 . In such embodiments, the prosthetic valve  100  can be retained in place against migration toward the left ventricle by the atrial sealing member  124  as further described below. 
     With reference to the embodiment shown in  FIGS. 8-10 , each ventricular anchor  126  can comprise a flexible, elongate member, or wire,  150  comprised of a shape memory material, such as, for example, Nitinol. In some embodiments, as shown in  FIG. 8 , each wire  150  can comprise a first end portion  152  coupled to a first attachment location  156  of the main body  122 , and a second end portion  154  coupled to a second attachment location  158  of the main body. The first and second end portions  152 ,  154  form a base of the ventricular anchor. The first and second attachment locations  152 ,  154  of the main body can be at, or adjacent to, the ventricular end  130  of the main body  122 . The two end portions  152 ,  154  of each wire  150  can be extensions of the wires or struts that make up the lattice mesh of the main body  122 . Each wire  150  further comprises an intermediate portion  160  extending in a direction lengthwise of the main body between the end portions  152 ,  154 . The intermediate portion  160  includes a bend  162  that forms the free end portion, or apex, of the ventricular anchor. 
     The wire  150  can have a circular or non-circular cross-sectional profile perpendicular to a length of the wire, such as a polygonal cross-sectional profile. With reference to  FIG. 8A , the wire  150  can comprise a rectangular cross-sectional shape having a length “L” and a relatively narrower width “W” such that when the two end portions  152 ,  154  of the ventricular anchor  126  attached to the frame  102  are moved toward each other, such as when the frame is compressed, the wire  150  bends primarily in the width direction. This promotes bending of the ventricular anchor  126  in a direction radially outward away from the main body  122 , widening the gap between the ventricular anchor  126  and the main body  122 . This feature can help to capture a leaflet between the ventricular anchor  126  and the main body  122  during implantation. 
     Ventricular anchors can comprise various shapes or configurations. Some frame embodiments, such as the frame  102  shown in  FIG. 8 , comprise generally “U” or “V” shaped ventricular anchors  126  that connect to the main body  122  at two attachment locations  156 ,  158 . The upper apex  162  of the ventricular anchors  126  can function like a wedge to facilitate moving the ventricular anchors behind respective leaflets while minimizing the risk of chordae entanglement. The end portions  152 ,  154  of each wire  150  can extend downward from attachment locations  156 ,  158 , respectively, at the ventricular end  130  of the main body  122 . The wire  150  can then curve back upward from each end portion  152 ,  154  toward the apex  162 . 
     The wires  150  can be covered by biocompatible materials, such as in the embodiment shown in  FIGS. 5-7 . A first material  164  can be wrapped around, or coat, at least some portion of the wire  150 . A second material  166  can span across two portions of the wire  150  to form a web, which can improve tissue ingrowth. The first and second materials  164 ,  166  can comprise the same material or different materials, such as a biocompatible semi-porous fabric, for example. The covering materials  164 ,  166  can increase tissue ingrowth with the ventricular anchor  126  to improve retention. Furthermore, the covering materials can decrease the frictional properties of the ventricular anchors  126  to facilitate implantation and/or increase the frictional properties of the ventricular anchors to improve retention. 
       FIG. 24  shows exemplary dimensions of the embodiment of the frame  102  shown in  FIG. 9 . The diameter “Dmax” of the outer rim  140  of the atrial sealing member  124  can range from about 50 mm to about 70 mm, and is about 50 mm in one example. The diameter “Dbody” of the outer surface of the main body  122  can range from about 23 mm to about 50 mm, and is about 29 mm in one example. The distance “W 1 ” between the two attachment points  156 ,  158  for one ventricular anchor  126  can range from about 8 mm to about 50 mm, and is about 25 mm in one example. The overall axial height “Hmax” of the frame  102  can range from about 20 mm to about 40 mm, and is about 30 mm in one example. The axial height “H 1 ” from the outer rim  140  to the lowermost portion  168  of the ventricular anchors  126  can range from about 10 mm to about 40 mm, and is about 23 mm in one example. The axial distance “H 2 ” from the apex  162  of the ventricular anchor  126  to the lowermost portion  168  of the ventricular anchor  126  can range from about 10 mm to about 40 mm, and is about 18 mm in one example. The axial distance “H 3 ” from the lower end  130  of the main body  122  to the lowermost portion  168  of the ventricular anchor  126  can range from about 0 mm to about 10 mm, and is about 5 mm in one example. 
     Some frame embodiments comprise more than two ventricular anchors. For example, a frame can have two or more ventricular anchors configured to attach to multiple locations along a single leaflet of a native valve. In some such embodiments (not shown), the frame can comprise two ventricular anchors that attach to the anterior mitral leaflet  10  and/or two ventricular anchors that attach to the posterior mitral leaflet  12 . Ventricular anchors can also attach to other regions of the leaflets instead of, or in addition to, the A 2  and P 2  regions. 
     Some prosthetic valve embodiments comprise four ventricular anchors spaced evenly apart around a main body.  FIGS. 27-32  show one such prosthetic valve embodiment  400  comprising a frame  402  that comprises a pair of ventricular anchors  426  on diametrically opposed sides of a main body  422  and a pair of diametrically opposed commissure anchors  428  located about midway between the ventricular anchors  426 . The ventricular anchors  426  extend downward from attachment points  456  and  458  and comprise a neck portion  450  (see  FIG. 31 ). These ventricular anchors  426  can function similarly to the ventricular anchors  126  of the frame  102  to capture leaflets and retain the frame  402  within the mitral orifice, as shown in  FIG. 33 . The commissure anchors  428  can extend upward from the same attachment locations  456 ,  458  on the main body  422  (see  FIG. 30 ). While the ventricular anchors  426  can clip the mitral leaflets  10 ,  12  at the A 2  and P 2  regions, respectively, the commissure anchors  428  can hook around and extend upward behind the mitral commissures  36 , not compressing the leaflets. The apexes  464  of the commissure anchors  428  can extend upward to abut the ventricular side of the mitral annulus  8  and compress the mitral annulus  8  between the outer rim  440  of the atrial sealing member  424  and the apexes  464  of the commissure anchors  428 . 
     This compression of the mitral annulus  8  can provide additional retention against both atrial and ventricular movement. 
     Other frame embodiments can comprise more than four ventricular anchors. For example, a frame can comprise six or more ventricular anchors that can engage multiple locations on the leaflets  10 ,  12  and/or the commissures  36 . 
       FIG. 34  shows a frame embodiment  502  that comprises extended ventricular anchors  526  that are configured to extend around the ends of the leaflets  10 ,  12  and extend upward behind the leaflets to locations proximate the outer rim  540  of a downwardly extending frustoconical atrial sealing member  524 . The upper apexes  562  of the extended ventricular anchors  526  contact the ventricular surface of the mitral annulus  8  and/or portions of the native leaflets  10 ,  12  adjacent to the annulus, or annulus connection portions of the leaflets, while the outer rim  540  of the atrial sealing member  524  contacts the atrial surface of the mitral annulus and/or the annulus connection portions of the leaflets. The extended ventricular anchors  526  and the atrial sealing member  524  can be configured to oppose one another and desirably compress the mitral annulus  8  and/or annulus connection portions of the leaflets  10 ,  12  to retain the frame  502  from movement in both the atrial and ventricular directions. Thus, in this embodiment, the ventricular anchors  526  need not compress the native leaflets  10 ,  12  against the outer surface of the main body  522  of the frame. Instead, as shown in  FIG. 34 , the leaflets  10 ,  12  can be captured loosely between the extended ventricular anchors  526  and the outer surface of the main body  522 . 
       FIGS. 35 and 36  show a frame embodiment  602  comprising necked, “S” shaped ventricular anchors  626 . From the side view of  FIG. 35 , the “S” shape of the ventricular anchors  626  is apparent. Starting from one attachment point A on the ventricular end  630  of the main body  622 , the ventricular anchor wire  650  extends downward and radially outward from the main body to a point B, then curves upward and outward to a point C, then curves upward and inward to a point D, and then curves upward and back outward to an uppermost point, or apex, E. The ventricular anchor wire  650  then continues to extend back to the second attachment point following a similar, but mirrored path. From the frontal view of  FIG. 36 , the ventricular anchor wire  650  forms a necked shape that is symmetrical about a longitudinal center axis  690  extending through the center of the main body  622 , forming two mirrored halves. Each half of ventricular anchor wire  650  begins at an attachment point A on the ventricular end  630  of the main body  622 , curves downward and inward (toward the other half) to point B, then curves upward and inward to a necked portion at point C, then curves upward and outward (away from the other half) to a point D, then curves upward and inward again to an uppermost point, or apex, E where the two halves join together. Referring to  FIG. 35 , the radial distances from a longitudinal center axis  690  of the main body  622  to points C and E are both greater than the radial distances from the axis  690  to points D. Furthermore, the distance between the two points C is less than the distance between the two points D. The “S” shaped ventricular anchor  626  can help distribute stresses more evenly along the wire  650  and reduce stress concentrations at certain locations, such as the attachment points A. 
       FIGS. 37 and 38  show a frame embodiment  702  that comprises two wider shaped ventricular anchors  726 . Each wider shaped ventricular anchors  726  comprises a necked mid portion  780  and a broad upper portion  782 . The upper portion  782  can extend generally parallel to the inflow opening of the frame  702  and can be curved around the outer surface of a main body  722 . This wider shape can increase surface contact with the native leaflet and/or other cardiac tissue to reduce pressure and thereby reduce abrasion. In some embodiments, the broad upper portion  782  of the wider shaped ventricular anchors  726  can have a curvature that corresponds to the curvature of the outer surface of the main body  722  (see  FIG. 38 ) to further improve tissue contact. The wider shaped ventricular anchor can have a longer surface contact with the atrial sealing member; thereby increasing retention performance and reducing paravalvular leak. 
       FIG. 39  shows a frame embodiment  802  comprising ventricular anchors  826  that are configured to define a separation, or gap, between the anchors and the main body  822  even after the frame  802  expands (although the anchors  826  can otherwise function similar to ventricular anchors  126 , such that the gaps between the anchors  826  and the frame main body  822  can increase and decrease upon compression and expansion of the main body, respectively, to facilitate placement of the anchors  826  behind the native leaflets). The gap can be sized to facilitate capturing the native leaflets  10 ,  12  with little or no compression of the native leaflets. Since little or no leaflet compression occurs, this frame embodiment  802  can minimize trauma to the native leaflets. Instead of compressing the leaflets  10 ,  12  for valve retention, the ventricular anchors  826  can hook the ventricular edges  40 ,  42  of the leaflets  10 ,  12 , respectively, while an atrial sealing member  824  of the frame presses downwardly on the atrial side of the mitral valve annulus  8 . The contact between the atrial sealing member  824  and the annulus  8  causes the main body  822  to shift slightly upwardly pulling the ventricular anchors  826  upwardly against the ventricular edges of the leaflets  10 ,  12 . The upward force of the ventricular anchors in conjunction with downward tension on the leaflets from the chordae tendineae  16  restrain the implant from moving upward toward the left atrium  4 . 
       FIG. 40  shows a frame embodiment  902  that comprises a main body  922 , ventricular anchors  926  and a disk-like atrial sealing member  924  that extends radially outward from the upper end  932  of the main body  922 . In this embodiment, the atrial sealing member  924  extends substantially perpendicular to the frame opening defined by the upper and  932  rather than downwardly toward the frame&#39;s lower end  930 . The disk-like atrial sealing member  924  can be positioned flat across the top surface of the mitral annulus  8  and provide increased surface area contact for tissue ingrowth. 
       FIGS. 41 and 42  show frame embodiments  1002  and  1012 , respectively, that comprise an atrial sealing member  1024  having a generally frustoconical portion  1028  that extends from the upper end  1032  of a main body  1022  both radially outward and axially upward away from the main body. The atrial sealing member  1024  can also include a generally cylindrical upper, or inlet, portion  1029  that extends further upward from the frustoconical portion  1028  opposite the upper end  1032  of the main body  1022 . The atrial sealing member  1024  can generally correspond to the shape of the atrial walls  18  adjacent to the mitral annulus  8  and provide for increased contact area between the atrial wall tissue and the atrial sealing member  1024 . The frame  1002  includes ventricular anchors  1026  that extend from a ventricular end  1030  of the main body  1022  and along the majority of the length of the main body. 
     The frame  1012  shown in  FIG. 42  comprises extended ventricular anchors  1050 . The extended anchors  1050  can extend from the ventricular end  1030  of the main body  1022  along the outer surface of the main body and bend radially outward to form upper portions  1060  that extend along the lower surface of the frustoconical portion  1028 . This configuration can allow the extended ventricular anchors  1050  to trap more of the leaflets  10 ,  12  and/or the mitral annulus  8  against the frame, thereby reducing paravalvular leakage and improving tissue ingrowth and retention. 
       FIG. 43  shows a frame embodiment  1102  having ventricular anchors  1126  that have shorter moment arms D 2  compared to the ventricular anchors  126  of the frame  102  shown in  FIG. 9 . The shorter moment arms D 2  can result in reduced torque at the ventricular anchor attachment points  1156 ,  1158 . The distance D 2  can be reduced by increasing the distance D 1  between the attachment points  1158  and  1156  on the main body  1122  of neighboring ventricular anchors  1126 . The distance D 1  between the ventricular anchors  1126  of the frame  1102  is greater than the distance D 1  between the attachment points  158  and  156  of frame  102  (see  FIG. 9 ), thus shortening the moment arm D 2  of the force F relative to the attachment point  1156 . The reduced torque at the attachment points  1156  and  1158  can reduce fatigue and thus improve the durability of the frame  1102 . 
     Some embodiments of ventricular anchors can optionally also comprise one or more barbs (not shown) that can protrude radially from a ventricular anchor toward the ventricular walls  20  or toward the leaflets  10 ,  12 . Such barbs can help retain a frame, particularly against movement towards the left ventricle  6 . 
       FIGS. 44A-44D  illustrate a frame embodiment  1202  comprising “flip-up” ventricular anchors  1226 . Each ventricular anchor  1226  can be finger-like and can extend from only one attachment point on the lower end  1230  of the main body  1222 . Alternatively, each ventricular anchor can comprise a wire or similar element that extends from two attachment points on the main body  1222 . In the illustrated embodiment, the ventricular anchors  1226  can be pre-formed to extend along the outer side of the main body  1222  in the functional, deployed state, as shown in  FIG. 44D . During delivery, the ventricular anchors  1226  can be partially or completely straightened, as shown in  FIG. 44A , and retained in that state by a delivery device, such as a sheath. As the frame  1202  is advanced from the sheath, for example, the ventricular anchors  1226  spring back to their pre-formed shape, as shown in  FIGS. 44B-44D , capturing the leaflets  10 ,  12  between the ventricular anchors  1226  and the main body  1222 . 
       FIGS. 45A-45E  represent a frame embodiment  1302  comprising “curl-up” ventricular anchors  1326 . As with the ventricular anchors  1226  of  FIG. 44 , each ventricular anchor  1326  can be finger-like and can extend from two or more points on lower end  1330  of the main body  1322 . The ventricular anchors  1326  can be pre-formed in a curved shape, as shown in  FIG. 45E , that extends along the side of the main body  1322  in the deployed state. During delivery, the ventricular anchors  1326  can be partially or completely straightened, as shown  FIG. 45A , and retained in that state by a delivery device, such as a sheath. As the frame  1302  is advanced from the sheath, for example, the ventricular anchors  1326  are allowed to spring back to their pre-formed curved shape, as shown in  FIGS. 45B-45E , capturing the leaflets  10 ,  12  between the ventricular anchors  1326  and the main body  1322 . 
     In some frame embodiments, one or more ventricular anchor components can be formed separately from the main body and later assembled together to form a frame. In one such frame embodiment  1402 , as shown in  FIGS. 46A-46C , a main body  1422  is formed separately from at least one ventricular anchor portion  1424 . The ventricular anchor portions  1424  can comprise one or more ventricular anchors  1426  extending from an at least partially annular base  1432 , which can comprise side-by-side “V” shaped strut portions connected together at their upper ends. The lower ends of the ventricular anchors  1426  in the illustrated embodiment are connected to the base  1432  at the lower vertexes of the “V” shaped portions. After the main body and the ventricular anchor portions are separately formed, the ventricular anchor portions  1424  can be attached to the lower portion  1430  of the main body  1422 . For example, the bases  1432  can be placed on opposite sides of the outer surface of the main body  1422  and then sewn, welded, or otherwise attached to the lower portion  1430  of the main body  1422  in a suitable manner, such as by using a locking mechanism. The bases  1432  can be attached to the main body  1422  such that the “V” shaped portions of the bases overlap with corresponding “V” shaped portions of the lower end  1430  of the main body  1422 . In some embodiments, the ventricular anchor portion  1424  can comprise a complete ring having all of the ventricular anchors  1426  extending from one annular base such that the ventricular anchors are pre-spaced relative to one another. The annular base can then be attached around the lower end  1430  of the main body  1422 . In other embodiments, multiple ventricular anchor portions  1424 , each having one or more ventricular anchors  1426  extending from a respective base  1432  comprising a partial ring, are secured to the main body  1422 . 
       FIGS. 47A-47D  and  FIGS. 48A-48C  show alternative frame embodiments wherein one or more ventricular anchor components are formed separately from a main body and later assembled together to form a frame. In these frame embodiments, the main body can comprise attachment portions to which anchor portions can be attached using sleeves. For example,  FIGS. 47A-47D  show an exemplary frame  1500  comprising a main body  1502  having at least two ventricular anchor attachment portions  1508  and at least one ventricular anchor  1504  having two attachment portions  1510  connected to respective attachment portions  1508  with respective sleeves  1506 . Similarly,  FIG. 48A-48C  show an exemplary frame  1600  comprising a main body  1602  having at least two ventricular anchor attachment portions  1608  and at least one ventricular anchor  1604  having two attachment portions  1610  connected to respective attachment portions  1608  with respective sleeves  1606 . The sleeves can comprise, for example, a metal material, such as Nitinol, having superelastic and/or shape-memory characteristics. In some embodiments, the sleeves can comprise metal of an anneal state suitable for a crimping process. The sleeves can be attached to the anchor portions and to the attachment portions of the main body by any suitable attachment means, such as by welding. As shown in  FIGS. 48A-48C , the attachment portion  1610  of the anchors  1604  and the attachment portions  1608  of the main body  1602  can comprise geometric features, such as narrow regions, or cut-outs, which allow the sleeves  1606  to integrate the anchor portions  1604  to the main body  1602 , such as by forming a mechanical lock. 
     Multi-part construction of a frame, as shown in  FIG. 46-48 , can reduce strain and fatigue at the ventricular anchor attachment locations compared to a unibody, or one-piece, construction. By contrast, in some embodiments comprising a unibody construction, the ventricular anchors are initially laser cut and expanded such that they extend downward from the lower end of the main body, and are then formed, or bent, to a desired configuration adjacent to the outside of the main body of the frame. Such bending can strain and weaken the bent portion. 
     To avoid strain caused by plastic deformation of the ventricular anchors, the ventricular anchors can be pre-formed in a desired implantation (deployed) shape without plastically bending the ventricular anchors. The ventricular anchors can then be elastically deformed, such as straightened and/or compressed, to fit into a delivery device for delivery through the body to the mitral valve region of the heart. The deformed ventricular anchors can resiliently regain their pre-formed shape once freed from the axial constraint of a delivery device to facilitate capturing the leaflets  10 ,  12  between the ventricular anchors and the main body of the frame. 
     Any of the various embodiments of frames described above can be combined with a fluid-occluding member, such as valve structure  104 , to form a fully assembled prosthetic valve that can be implanted within the native mitral valve. In other embodiments, any of the frames described above can be provided without a fluid-occluding member and can be used as a scaffolding or docking structure for receiving a separate prosthetic valve in a two-stage delivery process. With reference to the exemplary embodiment shown in  FIG. 70 , a docking frame  103  (which can have a construction similar to the frame  102 ) can be deployed first, for example by any of the anchoring techniques discussed above. Then, a separate prosthetic valve  114  can be delivered and deployed within the lumen formed by the previously deployed docking frame  103 . The separate prosthetic valve  114  desirably comprises a radially compressible and expandable frame  116  that mounts a fluid-occluding member (not shown in  FIG. 70 ), such as the valve structure  104  (see  FIG. 7 ) having a plurality of leaflets  106 . When expanded inside the docking frame  103 , the frame  116  of the prosthetic valve  114  engages the inside surface of the docking frame  103  so as to retain, such by friction or mechanical locking feature, the prosthetic valve  114  within the docking frame  103 . Examples of prosthetic valves that can be used in such a two-stage process are disclosed in U.S. Pat. No. 7,510,575, which is incorporate herein by reference. In particular embodiments, the prosthetic valve can comprise any of various transcatheter heart valves, such as the Sapien valve, available from Edwards Lifesciences LLC (Irvine, Calif.). 
     The technique of capturing the leaflets  10 ,  12  between a ventricular anchor and the main body of a frame, such as shown in  FIG. 23 , can provide several advantages. First, this can allow for anchoring onto the native leaflets  10 ,  12  for retention within the mitral valve region. Second, this technique can utilize the native chordae  16  for retention. Third, this technique can prevent the anterior leaflet  10  from being “pulled” toward the aortic valve  14  when the left ventricle  6  contracts and blood rushes out through the aortic valve (systolic anterior motion). Fourth, this technique tends to force the native leaflets  10 ,  12  to collapse around the main body of the frame, which can reduce leakage between the outside of the prosthetic valve  100  and the native mitral valve  2 . Fifth, this technique allows for implantation from either the left atrium  4  or from the left ventricle  6 , as described in detail below. 
     As described above, various frame embodiments can utilize one or more anchoring techniques other than compressing the leaflets  10 ,  12  to retain the prosthetic valve  100  in a desired position within the mitral valve orifice. These anchoring techniques can include, for example, utilizing tension of the native chordae  16 , extending the ventricular anchor length such that the apex of the ventricular anchor is pressed up against the mitral annulus  8  so as to form a stop, and compressing the mitral annulus  8  and/or atrial tissue between the apex of an ventricular anchor and the outer rim of an atrial sealing member of the frame. 
     Delivery Approaches 
     The various methods and apparatus described hereinafter for delivery and implantation at the native mitral valve region are described with respect to the prosthetic valve  100 , though it should be understood that similar methods and apparatus can be used to deliver and/or implant a component of the prosthetic valve  100 , such as the frame  102  without the valve structure  104 , or other prosthetic apparatus. 
     The prosthetic valve  100  can be delivered to the mitral valve region from the left ventricle  6  or from the left atrium  4 . Because of the anatomy of the native mitral valve  2 , different techniques and/or equipment can be used depending on the direction the prosthetic valve  100  is delivered. 
     Delivery from the ventricular side of the mitral annulus  8  can be accomplished in various manners. For example, the prosthetic valve  100  can be delivered via a transapical approach in which access is made to the left ventricle  6  via the heart apex  38 , as shown in  FIG. 57 . 
     Delivery from the atrial side of the mitral annulus  8  can also be accomplished in various manners. For example, a transatrial approach can be made through an atrial wall  18 , as shown in  FIG. 66 , for example by an incision through the chest. An atrial delivery can also be made from a pulmonary vein  32  (see  FIG. 1 ). In addition, atrial delivery can be made via a transeptal approach, as shown in  FIG. 67 , wherein an incision is made in the atrial portion of the septum  30  to allow access from the right atrium  26 , such as via the inferior or superior vena cava  34 . 
     Ventricular Approaches 
     One technique for delivering a compressed prosthetic apparatus, such as the prosthetic valve  100 , to the mitral valve region includes accessing the native mitral valve region from the left ventricle  6 , one example being the transapical approach. Alternatively, access to the left ventricle  6  can be made through the aortic valve  14 . In the transapical approach, access to the left ventricle  6  can be made through an incision in the chest and an incision at the heart apex  38 , as shown in  FIG. 57 . A transapical delivery system can be used with the transapical approach. 
       FIGS. 49-53  show an exemplary transapical delivery system, or delivery tool,  2000  that is configured to deliver and implant the prosthetic valve  100 . The delivery system  2000  can comprise a series of concentric shafts and sheaths aligned about a central axis and slidable relative to one another in the axial directions. The delivery system  2000  can comprise a proximal handle portion  2002  for physician manipulation outside of the body while a distal end portion, or insertion portion,  2004  is inserted into the body. 
     The delivery system  2000  can comprise an inner shaft  2006  that runs the length of the delivery system and comprises a lumen  2008  through which a guidewire (not shown) can pass. The inner shaft  2006  can be positioned within a lumen of a pusher shaft  2010  and can have a length that extends proximally beyond the proximal end of the pusher shaft and distally beyond the distal end of the pusher shaft. The delivery system  2000  can comprise an annular space  2012  between the outer surface of the inner shaft  2006  and the inner surface of the pusher shaft  2010 . This annular space can be used for flushing with saline or for allowing blood to be expelled distally. 
     The delivery system  2000  further comprises an inner sheath  2014  positioned concentrically around at least a distal portion of the pusher shaft  2010 . The inner sheath  2014  is axially slidable relative to the pusher shaft  2010  between a delivery position (see  FIG. 55 ) and a retracted position (see  FIG. 50 ). In the delivery position, a distal end portion  2016  of the inner sheath  2014  is positioned distal to a distal end, or pusher tip  2018 , of the pusher shaft  2010 . In the delivery position, the distal end portion  2016  of the inner sheath  2014  forms an inner cavity that can contain a compressed prosthetic valve  100 . In the retracted position (see  FIG. 50 ), the distal end  2017  of the inner sheath  2014  is positioned proximal to or aligned axially with the pusher tip  2018 . As the inner sheath  2014  moves from the delivery position toward the retracted position (either by retracting the inner sheath  2014  proximally relative to the pusher shaft  2010  or advancing the pusher shaft distally relative to the inner sheath), the pusher tip  2018  can force the prosthetic valve  100  out of the distal end portion  2016  of the inner sheath. 
     As shown in  FIG. 50 , the inner sheath  2014  comprises one or more longitudinally disposed slots  2028  extending proximally from a distal end  2017  of the inner sheath. These slots  2028  can allow ventricular anchors  126  of a prosthetic valve  100  contained within the inner sheath  2014  to extend radially outward from the compressed main body of the prosthetic valve while the main body is retained in the compressed state within the inner sheath. In the embodiment shown in  FIG. 50 , two slots  2028  are shown oriented on diametrically opposed sides of a longitudinal central axis of the inner sheath  2014 . This embodiment corresponds to the prosthetic valve  100 , which comprises two opposed ventricular anchors  126 . In other embodiments, the inner sheath  2014  can comprise a different number of slots  2028 , for example four slots, that correspond to the number and location of ventricular anchors on a selected prosthetic valve. In some embodiments, such as shown in  FIG. 50 , the proximal end portion  2020  of the each slot  2028  comprises a rounded opening that has a greater angular width than the rest of the slot. 
     A break-away, or frangible, retaining band  2022  can be positioned around the distal end portion  2016  of the inner sheath  2014 , as shown in  FIG. 50 . The band  2022  can help retain the distal end portion  2016  of the inner sheath  2014  from splaying apart from the force of a compressed prosthetic valve  100  contained within the inner sheath  2014 . The band  2022  comprises a proximal edge  2024  that can comprise at least one notch  2026  located over a slot  2028  in the inner sheath  2014 . The band  2022  can comprise a frangible material and can be configured to tear or break apart at the notch location when a sufficient axial force is applied at the notch  2026 . In use, the band  2022  is configured to break at notches  2026  under the force of the ventricular anchors  126  of the valve  100  as it is deployed from the inner sheath  2014 , as further described below. 
     An outer sheath  2036  is positioned concentrically around a portion of the inner sheath  2014  and is slidable axially relative to the inner sheath. The outer sheath  2036  can be positioned to cover at least a portion of the distal end portion  2016  of the inner sheath  2014 . In such a covered position, such as shown in  FIG. 55 , the ventricular anchors can be contained between the inner and outer sheath. The outer sheath  2036  is in this covered position while the loaded delivery system  2000  is inserted through the body and into the left ventricle  6 . The outer sheath  2036  can be retracted proximally relative to the sheath  2014  to uncover the slots  2028  and allow the ventricular anchors  126  to spring outward through the slots in the inner sheath  2014  during deployment. Alternatively, the inner sheath  2014  can be advanced distally relative to the outer sheath  2036  to uncover the slots  2028 . 
     With reference to  FIG. 51 , the handle portion  2002  of the delivery system  2000  can comprise components that facilitate sliding the inner sheath  2014  and the outer sheath  2036  back and forth along their respective ranges of axial movement to load, deliver, and deploy the prosthetic valve  100 . An outer sheath grip  2052  can be attached to the proximal end of the outer sheath  2036 . A physician can grasp the outer sheath grip  2052  and push or pull the outer sheath  2036  proximally or distally relative to the rest of the delivery system  2000 . The outer sheath can also be mounted on a lead screw (not shown). The handle portion  2002  of the delivery system  2000  can further comprise a housing  2054  that provides a hand grip or handle for the physician to hold the delivery system  2000  steady while she uses the other hand to actuate the sheaths. A sliding lead screw  2056  can be fixed (e.g., bonded, mechanically locked, etc.) to a proximal end portion  2058  of the inner sheath  2014  and be positioned within the housing  2054 . The lead screw  2056  can be fixed rotationally relative to the housing  2054  and can be constrained to an axial sliding range within the housing. A rotatable sleeve  2060  can be positioned concentrically between the outer housing  2054  and the inner lead screw  2056  and can comprise a proximal knob portion  2062  that extends free of the housing  2054  to provide a hand grip for the physician to rotate the rotatable sleeve  2060 . The rotatable sleeve  2060  can be free to rotate relative to the housing  2054 , but be fixed axially relative to the housing. The lead screw  2056  can comprise an outer helical groove  2064  that interacts with inwardly projecting ridges  2066  on the rotatable sleeve  2060  such that when the knob  2062  is rotated relative to the lead screw  2056  and the housing  2054 , the ridges  2066  cause the lead screw  2056  to slide axially, thereby causing the inner sheath  2014  to also slide axially. Thus, the physician can move the inner sheath  2014  proximally by rotating the knob  2062  one direction relative to the housing  2054  and distally by rotating the knob the opposite direction relative to the housing. The housing  2054  can be fixed relative to the pusher shaft  2010  such that when the knob  2062  is rotated relative to the housing, the lead screw  2056  and the inner sheath  2014  slide axially together relative to the pusher shaft  2010  and the housing  2054 . 
     As shown in  FIG. 51 , the inner shaft  2006  passes all the way through the handle portion  2002  of the delivery system  2000  and the pusher shaft  2010  can terminate at or near a proximal end cap  2068  of the handle portion  2002 . The annular space  2012  between the outer surface of the inner shaft  2006  and the inner surface of the pusher shaft  2010  (see  FIGS. 52 and 53 ) can be fluidly connected to at least one flushing port  2070  in the end cap  2068  of the handle portion  2002 . The flushing port  2070  can provide access to inject fluid into the annular space  2012  and/or allow fluid to escape from the annular space. 
     As shown in  FIG. 49 , a nose cone  2030  can be attached to the distal end of the inner shaft  2006 . The nose cone  2030  can be tapered from a proximal base  2034  to a distal apex  2032 . The base  2034  can have a diameter about equal to the diameter of the outer sheath  2036 . The nose cone  2030  can be retracted proximally, by sliding the inner shaft  2006  proximally relative to the rest of the delivery system  2000 , to mate against the distal end of the outer sheath  2036  and/or the inner sheath  2014  to further contain the compressed prosthetic valve  100 , as shown in  FIG. 55 . The nose cone  2030  can also be moved distally away from the sheaths to provide space for the prosthetic valve  100  to be loaded and/or deployed. During insertion of the delivery system  2000  through the body, the tapered nose cone  2030  can act as a wedge to guide the insertion portion  2004  of the delivery system  2000  into the body and provides an atraumatic tip to minimize trauma to surrounding tissue as the delivery system is advanced through the body. 
     To load the prosthetic valve  100  into the delivery system  2000 , the nose cone  2030  must be moved distally away from the sheaths and the inner sheath  2014  must be advanced distally to the delivery position, as shown in  FIG. 54  (without retaining band  2022 ). The outer sheath  2036  can be retracted to expose the slots  2028  in the inner sheath  2014 . The prosthetic valve  100  is then positioned between the nose cone  2030  and the inner sheath  2014  and around the inner shaft  2006 . The prosthetic valve  100  is then compressed to the compressed state and slid into the inner sheath  2014  such that the proximal, or lower, end of the prosthetic valve is adjacent to or contacting the pusher tip, as shown in  FIG. 56 . A loading cone or equivalent mechanism can be used to insert the valve  100  into the inner sheath  2014 . In embodiments of the prosthetic valve  100  comprising a pusher member  204 , such as in  FIG. 25 , the bottom end  206  of the pusher member  204  can contact the pusher tip  2018 , as shown in  FIG. 56 . The ventricular anchors  126  can be allowed to extend out through the rounded proximal end portions  2020  of the respective slots  2028 , as shown in  FIG. 54 . The proximal end portion  2020  of each slot can have sufficient angular width to allow the two end portions of the ventricular anchor  126  to reside side-by-side within the slot, which can cause the intermediate portion of the ventricular anchor to assume a desired shape for implanting behind the leaflets  10 ,  12 . The break-away retaining band  2022  can be placed around the distal end portion of the inner sheath  2014  such that each notch  2026  in the band  2022  is located over a respective slot, as shown in  FIG. 50 . The outer sheath  2036  is then advanced distally to cover the slots  2028 , as shown in  FIG. 55 , thereby compressing the ventricular anchors  126  and constraining the ventricular anchors within the outer sheath  2036 . Alternatively, the prosthetic valve can be inserted into the inner sheath  2014  while the outer sheath  2036  is covering the slots  2028 , such that the ventricular anchors  126  are positioned in the slots, but cannot extend out of the slots. The ventricular anchors  126  can also be constrained between the outer surface of the inner sheath  2014  and inner surface of the outer sheath  2036 . In any case, the ventricular anchors  126  are free to spring radially outward once the outer sheath  2036  is retracted. After the prosthetic valve  100  is within the inner sheath  2014 , the inner shaft  2006  can be retracted to pull the nose cone  2030  against the distal end of the inner sheath  2014  and/or the outer sheath  2036 , as shown in  FIG. 55 . With the prosthetic valve  100  within the inner shaft  2006 , the nose cone  2030  retracted and the outer sheath  2036  constraining the ventricular anchors  126 , the delivery system  2000  is in the loaded configuration and ready for insertion into the body. 
     In the loaded configuration shown in  FIG. 55 , the loaded delivery system  2000  can be inserted, nose cone  2030  first, through heart apex  38  into the left ventricle  6  and positioned near the mitral valve region for deployment. An introducer sheath (not shown) can be initially inserted through an incision in the heart to provide a port for introducing the delivery system  2000  into the heart. In addition, the delivery system  2000  can be advanced over a conventional guide wire (not shown) that is advanced into the heart ahead of the delivery system  2000 . The grip  2052  can then be moved proximally relative to the rest of the delivery system to retract the outer sheath  2036  relative to the inner sheath  2014  and allow the ventricular anchors  126  to spring outwardly away from the inner sheath  2014 , as shown in  FIGS. 56 and 57 , such that the ventricular anchors extend through the rounded proximal end portion  2020  of the slots  2028 . The delivery system desirably is oriented rotationally such that each ventricular anchor  126  is positioned between sets of chordate tendineae  16  attached to one of the native mitral valve leaflets  10 ,  12 . Next, the delivery system  2000  can be advanced atrially such that the nose cone  2030  enters the native mitral valve orifice and the protruding ventricular anchors  126  move between respective leaflets  10 ,  12  and the ventricular walls  20 , as shown in  FIG. 58 . Then, while holding a housing  2054  of the delivery system  2000  steady, the physician can rotate the knob  2062  of the rotatable sleeve  2060  relative to the housing to retract the inner sheath  2014  proximally. The pusher tip  2018  remains stationary while the inner sheath  2014  retracts, thereby leaving the compressed prosthetic valve  100  in the same axial location as it is uncovered and deployed from the inner sheath  2014 . Alternatively, the inner sheath  2014  can be held stationary while the pusher tip  2060  is moved distally to push the valve  100  out of the inner sheath  2014 . While the inner sheath  2014  is being retracted relative to the pusher tip  2018 , the pusher tip can exert an axial force in the distal direction upon the proximal, or lowermost, surface of the prosthetic valve  100 . In embodiments of the prosthetic valve having a pusher member  204 , the pusher member  204  can direct this axial force directly to the main body  122  and prevent direct contact between the pusher tip  2018  and the ventricular anchor  126  to reduce the risk of damage to the ventricular anchors. 
     When the inner sheath  2014  is retracted relative to the prosthetic valve  100 , the distal, or upper, portion of the prosthetic valve comprising the downwardly folded atrial sealing member  124  is uncovered first. With reference to  FIGS. 59 and 60 , when the inner sheath  2014  has been retracted beyond the outer rim of the atrial sealing member  124  of the prosthetic valve  100 , the atrial sealing member can spring radially outward away from the main body  122 , pivoting about the distal end of the main body. 
     As the inner sheath  2014  is retracted relative to the prosthetic valve  100 , the end portions of the ventricular anchors  126  passing through the rounded proximal end portion  2020  of the slots  2028  are forced through the narrower distal portions of the slots  2028  toward the retaining band  2022 , as shown in  FIGS. 59 and 60 . The end portions of the ventricular anchors are initially side-by-side in the wider proximal end portion  2020  of the slot. When forced into the narrower portion of a slot  2028 , the two end portions of each ventricular anchor  126  can be radially overlapping, or oriented one on top of the other, as opposed to side-by-side. In other embodiments, the slots  2028  can be wider such that the two end portions of the ventricular anchor  126  can move about the slots  2028  side-by-side. As the ventricular anchor  126  moves toward the distal end of a slot  2028 , the ventricular anchor can contact the notch  2026  in the retaining band  2022 , as shown in  FIG. 60 , and can cut the band  2022  or otherwise cause the band to tear or split apart at the notched location, as shown in  FIG. 61 . When the inner sheath  2014  is retracted beyond the proximal, or lower, end of the prosthetic valve  100 , the compressed body of the prosthetic valve can resiliently self-expand to the expanded state, as shown in  FIG. 61 . As the prosthetic valve expands, the gaps between the ventricular anchors  126  and the outer surface of the main body  122  decreases, capturing the leaflets  10 ,  12  between the ventricular anchors  126  and the main body  122 , as shown in  FIGS. 23 and 62 . The expansion of the main body  122  of the prosthetic valve  100  can force open the native mitral leaflets  10 ,  12 , holding the native mitral valve  2  in an open position. The prosthetic valve  100  can then replace the functionality of the native mitral valve  2 . After the prosthetic valve  100  is expanded, the inner shaft  2006  of the delivery system can be retracted, pulling the nose cone  2030  back through the prosthetic valve, and the whole delivery system  2000  can be retracted out of the body. 
     In some embodiments, the delivery system  2000  can be guided in and/or out of the body using a guide wire (not shown). The guide wire can be inserted into the heart and through the native mitral orifice, and then a proximal end of the guidewire can be threaded through the lumen  2008  of the inner shaft  2006 . The delivery system  2000  can then be inserted through the body using the guidewire to direct the path of the delivery system. 
     Atrial Approaches 
     The prosthetic valve  100  can alternatively be delivered to the native mitral valve region from the left atrium  4 . Referring to  FIGS. 63-67 , one approach for delivering the prosthetic valve from the atrial side of the mitral valve region utilizes a delivery catheter  2100 . The prosthetic valve  100  is first crimped from the expanded state to the radially compressed state and loaded into a primary sheath  2102 , and optionally also a secondary sheath, at the distal end portion of the delivery catheter  2100 , as shown in  FIG. 63 . The delivery catheter  2100  is used to guide the prosthetic valve  100  through the body and into the left atrium  4 . The prosthetic valve  100  is oriented within the sheath  2102  such that the outflow end  112  of the prosthetic valve  100  (the end supporting the ventricular anchors  126 ) is closest to the distal end of the sheath and thus enters the left atrium  4  first and the inflow end  110  (the atrial sealing member  124 ) of the prosthetic valve enters last. The sheath  2102  can then be inserted into the left atrium  4  in various manners, one example being the transatrial approach shown in  FIG. 66 , and another example being the transeptal approach shown in  FIG. 67 . When the delivery catheter  2100  is used to access the heart via the patient&#39;s vasculature, such as shown in  FIG. 67 , the catheter  2100  can comprise a flexible, steerable catheter. 
     Once in the left atrium  4 , the distal end  2104  of the primary sheath  2102  can be moved across the mitral annulus  8  such that the ventricular anchors  126  are positioned beyond the mitral leaflets  10 ,  12  prior to deploying the ventricular anchors from the sheath. 
     The prosthetic valve  100  can then be partially expelled from of the distal end  2104  of the primary sheath  2102  using a rigid pusher shaft  2106  (see  FIG. 64 ) that is positioned within the sheath  2102  and can slide axially relative to the sheath. When the sheath  2102  is retracted proximally relative to the pusher shaft  2106  and the prosthetic valve  100 , the pusher shaft  2106  urges the prosthetic valve distally out of the sheath  2102 , as shown in  FIG. 64 . Alternatively, the pusher shaft  2106  can be moved distally while the sheath  2102  is held in place, thereby pushing the prosthetic valve  100  distally out of the sheath. 
     When the primary sheath  2102  is inserted across the mitral annulus  8  and past the lower ends of the leaflets  10 ,  12 , the prosthetic valve  100  can be partially expelled to free the ventricular anchors  126 , as shown in  FIG. 64 . The freed ventricular anchors  126  can spring outwardly when they are freed from the sheath  2102 . Optionally, the sheath  2102  can then be slid back over the exposed portion of the main body  122 , such that only the ventricular anchors are showing, as shown in  FIG. 65 . To accomplish this step, the atrial end of the frame can comprise features (not shown), such as mechanical locking features, for releasably attaching the prosthetic valve  100  to the pusher shaft  2106 , such that the pusher shaft can pull the prosthetic valve back into the sheath  2102 . The sheath  2102  and the prosthetic valve  100  are then retracted atrially, proximally, such that the outwardly protruding ventricular anchors  126  move between respective leaflets  10 ,  12 , and the ventricular walls  20 , as shown in  FIGS. 66-68 . In other embodiments, such as those shown in  FIGS. 44 and 45 , the ventricular anchors can elastically deflect upward or bend around respective leaflets  10 ,  12  when the ventricular anchors are freed from the sheath  2102 . 
     Optionally, the delivery catheter  2100  can also include a secondary sheath (not shown) within the outer sheath  2102  and can contain the pusher shaft  2106 , the atrial sealing member  124  and the main body  122  of the frame, but not the anchors  126 . In the position shown in  FIG. 63 , the distal end of the secondary sheath can be positioned between the anchors  126  and the main body  122 . As the outer primary sheath  2102  is retracted, as in  FIG. 64 , the secondary sheath can remain in a position compressing the main body  122  of the frame while the anchors  126  are freed to extend outward. Because the secondary sheath remains covering and compressing the main body  122 , there is no need recover the main body with the primary sheath  2102 , as in  FIG. 65 . Instead, the prosthetic valve  100  is moved proximally by moving the secondary sheath and pusher shaft proximally in unison. Then, to expel the prosthetic valve  100  from the secondary sheath, the secondary sheath is retracted proximally relative to the pusher shaft  2106 . 
     After the ventricular anchors  126  are positioned behind the leaflets  10 ,  12  and the remaining portion of the prosthetic valve  100  is expelled from the primary sheath  2102 , the prosthetic valve  100  can expand to its functional size, as shown in  FIGS. 62 and 69 , thereby capturing the leaflets  10 ,  12  between the ventricular anchors  126  and the main body  122 . Once the prosthetic valve  100  is implanted, the delivery catheter  2100  can be retracted back out of the body. 
     In alternative prosthetic valve embodiments, the main body and the atrial sealing member of the frame can be plastically expandable and can be expanded by a balloon of a balloon catheter (not shown) when the prosthetic valve is positioned at the desired location. The ventricular anchors in such an embodiment can exhibit a desired amount of elasticity to assist in positioning the leaflets  10 ,  12  between the ventricular anchors and the main body during deployment. Once the prosthetic valve is fully expanded, the balloon can be retracted through the expanded prosthetic valve and out of the body. 
     Mitral Regurgitation Reduction 
     Mitral regurgitation (MR) occurs when the native mitral valve fails to close properly and blood flows into the left atrium from the left ventricle during the systole phase of heart contraction. MR is the most common form of valvular heart disease. MR has different causes, such as leaflet prolapse, dysfunctional papillary muscles and/or stretching of the mitral valve annulus resulting from dilation of the left ventricle. MR at a central portion of the leaflets can be referred to as central jet MR and MR nearer to one commissure of the leaflets can be referred to as eccentric jet MR. 
     Rather than completely replacing the native mitral valve, another way to treat MR is by positioning a prosthetic spacer between the leaflets that decreases the regurgitant orifice area, allowing the mitral valve to function with little or no regurgitation, while minimizing impact to the native valve and left ventricle function and to the surrounding tissue. Additional information regarding treatment of MR can be found in U.S. Pat. No. 7,704,277 and U.S. Publication No. 2006/0241745 A1, both of which are incorporated by reference herein. 
       FIG. 71  shows an exemplary prosthetic spacer embodiment  3000  with which a spacer, or other body, can be suspended or “floated” between the leaflets using anchoring concepts described herein. The prosthetic spacer  3000  can comprise a frame  3002  and spacer body  3004 . The spacer body  3004  can comprise polyurethane, foam, and/or other suitable material(s) and can optionally be coated with Teflon and/or other suitable material(s). The spacer body  3004  can comprise a crescent shape that conforms to the crescent shaped juncture between the anterior leaflet  10  and the posterior leaflet  12  (see  FIGS. 4A and 4B ), or the spacer body can comprise other suitable shapes, such as an ellipse, circle, hourglass, etc. Depending on the shape of the spacer body  3004  and the positioning of the spacer body relative to the native structure, embodiments of the prosthetic spacer  3000  can help treat central jet MR, eccentric jet MR, or both. 
     Furthermore, the spacer body  3004  can comprise a minimal transverse cross sectional area and tapered edges. This shape can reduce diastolic forces from blood flowing through the mitral valve from the left atrium to the left ventricle. This shape can also reduce systolic forces on the spacer body  3004  when the native valve is closed around the spacer body and naturally place a larger portion of the systolic forces on the native leaflets and chordae. The shape of the spacer body  3004  can therefore reduce the forces transferred to the native valve tissue at anchor engagement locations, which can reduce the likelihood of perforation and erosion at the engagement locations and rupture of the native chordae that support the leaflets. The overall minimal size of the prosthetic spacer  3000  can further provide an opportunity to decrease the required cross-sectional size of a delivery system, allowing for delivery via narrower vasculature and/or less invasive incisions in the body and heart. 
     The frame  3002  can be made of a strong, flexible material, such as Nitinol. As shown in  FIG. 71 , the frame  3002  can comprise a frame body  3006 , an anterior ventricular anchor  3008 , a posterior ventricular anchor  3010 , an anterior atrial anchor  3012  and a posterior atrial anchor  3014 . The frame body  3006  can comprise a generally longitudinal column extending through the spacer body  3004 . Various embodiments of the frame body  3006  are described in detail below. 
     The frame  3002  can further comprise one or more spacer expanders  3024  extending laterally from the frame body  3006  through the spacer body  3004 . The expanders  3024  can resiliently expand away from the frame body and assist in the expansion of the spacer body  3004  during deployment. In some embodiments, the spacer expanders  3024  can be rectangular cut-out portions of a cylindrical frame body  3006 , as shown in  FIG. 71 , that are bent radially away from the frame body. 
     The anterior ventricular anchor  3008  is configured to extend from the ventricular end of the frame body  3006 , around the A 2  edge of the anterior leaflet  10  and extend upward behind the leaflet to a location on the ventricular surface of the mitral annulus  8  and/or the annulus connection portion of the anterior leaflet, while the anterior atrial anchor  3012  is configured to extend radially from the atrial end of the frame body  3006  to a location on the atrial surface of the mitral annulus  8  opposite the anterior ventricular anchor  3008 . Similarly, the posterior ventricular anchor  3010  is configured to extend from the ventricular end of the frame body  3006 , around the P 2  edge of the posterior leaflet  12  and extend upward behind the leaflet to a location on the ventricular surface of the mitral annulus  8  and/or the annulus connection portion of the posterior leaflet, while the posterior atrial anchor  3014  is configured to extend radially from the atrial end of the frame body  3006  to a location on the atrial surface of the mitral annulus  8  opposite the posterior ventricular anchor  3010 . 
     The ventricular anchors  3008 ,  3010  and the atrial anchors  3012 ,  3014  can comprise broad engagement portions  3016 ,  3018 ,  3020  and  3022 , respectively, that can be configured to compress the mitral annulus  8  and/or annulus connection portions of the leaflets  10 ,  12  to retain the prosthetic spacer  3000  from movement in both the atrial and ventricular directions. The broad engagement portions can provide a greater area of contact between the anchors and the native tissue to distribute the load and reduce the likelihood of damaging the native tissue, such as perforation or erosion at the engagement location. The ventricular anchors  3008 ,  3010  in the illustrated configuration loop around the native leaflets  10 ,  12  and do not compress the native leaflets against the outer surface of the spacer body  3004 , allowing the native leaflets to naturally open and close around the spacer body  3004 . 
     As shown in  FIG. 74 , the mitral annulus  8  is generally kidney shaped such that the anterior-posterior dimension is referred to as the minor dimension of the annulus. Because the prosthetic spacer  3000  can anchor at the anterior and posterior regions of the native mitral valve  2 , the prosthetic spacer can be sized according to the minor dimension of the annulus  8 . Echo and CT measuring of the minor dimension of the mitral annulus  8  are exemplary methods of sizing the prosthetic spacer  3000 . 
       FIGS. 75-79  illustrate an exemplary method for delivering the prosthetic spacer  3000  to the native mitral valve region of the heart. The prosthetic spacer  3000  can be delivered into the heart using a delivery system comprising an outer sheath  3030  and inner torque shaft  3032 . The prosthetic spacer  3000  is compressed and loaded into a distal end of the outer sheath  3030  with the atrial anchors  3012 ,  3014  loaded first. As shown in  FIG. 75 , the atrial anchors are resiliently extended proximally and the ventricular anchors  3008 ,  3010  are resiliently extended distally such that the prosthetic spacer  3000  assumes a sufficiently narrow cross-sectional area to fit within the lumen of the outer sheath  3030 . Within the outer sheath  3030 , the prosthetic spacer  3000  is positioned such that the atrial end of the frame body  3006  abuts the distal end of the torque shaft  3032 , the atrial anchors  3012 ,  3014  are between the torque shaft and the inner wall of the outer shaft, the compressed spacer  3004  abuts the inner wall of the outer sheath, and the distal ends of the ventricular anchors  3008 ,  3010  are adjacent to the distal opening of the outer sheath. The torque shaft  3032  can be releasably coupled to the atrial end of the prosthetic spacer  3000 , such as at the proximal end of the frame body  3006 . 
     Once loaded, the delivery system can be introduced into the left atrium  4 , such as via the atrial septum  30 , and the distal end of the outer sheath  3030  can be passed through the native mitral valve  2  and into the left ventricle  6 , as shown in  FIG. 75 . 
     Next, the outer sheath  3030  can be retracted relative to the torque shaft  3032  to expel the ventricular anchors  3008 ,  3010  from the distal opening of the outer sheath. At this point, the torque shaft  3032  can be rotated to rotate the prosthetic spacer  3000  within the outer sheath  3030  (or optionally, the torque shaft and the outer sheath can both be rotated) as needed to align the ventricular anchors with the A 2 /P 2  aspects of the native valve  2 . The releasable attachment between the torque shaft  3032  and the prosthetic spacer  3000  can be sufficient to transfer torque from the torque shaft to the prosthetic in order to rotate the prosthetic as needed. The ventricular anchors  3008 ,  3010  can be pre-formed such that, as they are gradually expelled from the outer sheath  3030 , they begin to curl apart from each other and around the A 2 /P 2  regions of the leaflets. This curling movement can be desirable to avoid entanglement with the ventricular walls. When the outer sheath  3030  is retracted to the ventricular end of the frame body  3006 , as shown in  FIG. 76 , the ventricular anchors  3008 ,  3010  are fully expelled from the outer sheath and positioned behind the leaflets. The entire delivery system and prosthetic can them be moved proximally until the engagement portions  3016 ,  3018  of the ventricular anchors abut the ventricular side of the mitral annulus  8  and/or the annulus connection portions of the leaflets  10 ,  12 . 
     Next, the outer sheath  3030  can be further retracted to relative to the torque shaft  3032  such that the distal end of the outer sheath is even with the atrial end of the frame body  3006 , as shown in  FIG. 77 , which allows the compressed spacer expanders  3024  and the compressed spacer body, or other body,  3004  to resiliently self-expand radially outward to the fully expanded, functional state. Note that the spacer body  3004  expands mostly in a direction perpendicular to the minor dimension of the annulus, or toward the commissures  36  (see  FIG. 74 ). In some embodiments, the spacer body  3004  can unfold or unfurl from the compressed state to the expanded state and in some embodiments the spacer body can be inflated, such as with saline or with an epoxy that hardens over time. 
     Once the spacer body is expanded within the valve, as shown in  FIG. 77 , hemodynamic evaluation of the spacer can be performed to assess the effectiveness of the prosthetic spacer  3000  in reducing MR. Depending on the result of the evaluation, deployment can continue or the prosthetic spacer  3000  can be recovered, retracted and/or repositioned for deployment. 
     From the position shown in  FIG. 77 , the outer sheath  3030  can be advanced back over the spacer body  3004  (by advancing the outer sheath  3030  relative to the torque shaft  3032 ), causing the spacer body to re-compress, as shown in  FIG. 76 . In some embodiments, the ventricular anchors are not recoverable, though in some embodiments the ventricular anchors can be sufficiently pliable to be re-straightened and recovered, in which case then entire delivery process can be reversed and restarted. From the position shown in  FIG. 76 , the delivery system can be repositioned and the spacer body  3004  can be redeployed and reassessed. 
     Once the ventricular anchors  3008 ,  3010  and the spacer body  3004  are acceptably deployed, the outer sheath  3030  can be further retracted relative to the prosthetic spacer  3000  and the torque shaft  3032  to expel the atrial anchors  3012 ,  3014  from the outer sheath, as shown in  FIG. 78 . Once fully expelled, the atrial anchors resiliently curl into their final deployment position shown in  FIG. 78  with their engagement portions  3020 ,  3022  pressed against the atrial side of the annulus  8  and/or the annulus connection portions of the leaflets  10 ,  12  opposite the engagement portions  3016 ,  3018 , respectively, of the ventricular anchors, thereby compressing the annulus and/or the annulus connection portions of the leaflets at the A 2  and P 2  regions to retain the prosthetic spacer  3000  within the native mitral valve region  2 . 
     Once the atrial anchors  3012 ,  3014  are deployed, the torque shaft  3032  can be released from the atrial end of the frame body  3006 . The delivery system can then be retracted back out of the body, leaving the prosthetic spacer  3000  implanted, as shown in  FIG. 79 . 
     In some embodiments, the spacer body  3004  can comprise a valve structure  3040 , such the embodiments shown in  FIGS. 80 and 82 . The valve structure  3040  can function in conjunction with the native mitral valve  2  to regulate blood flow between the left atrium  4  and the left ventricle  6 . For example, the valve structure  3040  can be positioned between the native leaflets such that the native leaflets close around the outside of the valve structure such that some blood flows through the valve structure while other blood flows between the outside of the valve structure and the native leaflets. The valve structure  3040  can comprise a three-leaflet configuration, such as is described herein with reference to the valve structure  104  and shown in  FIGS. 5-7 . 
     In some embodiments, the frame body  3006  can comprise a cylinder, which can optionally comprise solid-walled tube, such as in  FIGS. 71-74 , a mesh-like wire lattice  3046 , such as in  FIG. 82 , or other cylindrical configurations. With reference to  FIGS. 71-75 , the frame body  3006  and optionally one or more of the anchors can be formed from a solid-walled tube, such as of Nitinol, wherein the atrial anchors are formed, such as by laser cutting, from one portion of the tube and the ventricular anchors are formed from a second portion of the tube and the frame body is formed from a portion of the tube between the first and second portions. The anchors can then be formed, such as by heat treatment, to a desired implantation configuration. In such embodiments, the anchors and the frame body can be a unibody, or monolithic, structure. 
     In other embodiments, the frame body  3006  can comprise a spring-like helically coiled wire column  3050 , as shown in  FIG. 83 . Such a coiled column  3050  can be made from wire having a round or rectangular cross-section and can comprise a resiliently flexible material, such as Nitinol, providing lateral flexibility for conforming to the native valve structure while maintaining longitudinal column stiffness for delivery. In some of these embodiments, the frame body  3006  can comprise a quadrahelical coil of four wires having four atrial ends that extend to form the atrial anchors  3012 ,  3014  and four ventricular ends that extend to form the four ventricular anchors  3008 ,  3010 . 
     In other embodiments, the frame body  3006  can comprise a plurality of longitudinal members (not shown). In one such example, the frame body  3006  can comprise four longitudinal members: two longitudinal members that extend to form the anterior anchors  3012 ,  3014  and two longitudinal members that extend to from the posterior anchors  3008 ,  3010 . 
     In other embodiments, the frame body  3006  can comprise a zig-zag cut pattern  3050  along the longitudinal direction of the body, as shown in  FIG. 81 , that can also provide lateral flexibility while maintaining column strength. 
     In some embodiments, the prosthetic spacer  3000  can have additional anchors. In some embodiment (not shown), the prosthetic spacer  3000  can have three pairs of anchors: one pair of anchors centered around the posterior leaflet  12 , such as the posterior anchors  3010  and  3014  described above, and one pair of anchors at each commissure  36  between the native leaflets  10 ,  12 . These commissure anchors pairs can similarly comprise a ventricular anchor and an atrial anchor and can similarly compress the native annulus  8 . In other embodiments, the anterior anchors  3008  and  3012  can also be included as a fourth pair of anchors. Other embodiments can comprise other combinations of these four pairs of anchors and/or additional anchors. 
     In addition to filling the regurgitant orifice area and blocking blood from flowing toward the left atrium, the prosthetic spacer  3000  can also add tension to the chordae tendinae to prevent further enlargement of the left ventricle and prevent further dilation of the mitral valve annulus. 
     Anchoring Beneath the Mitral Valve Commissures 
     Some embodiments of prosthetic devices comprising ventricular anchors, including both prosthetic valves and prosthetic spacers, can be configured such that the ventricular anchors anchor beneath the commissures  36  of the native mitral valve  2  instead of, or in addition to, anchoring behind the A 2 /P 2  regions of the native mitral leaflets  10 ,  12 .  FIGS. 84-87  show exemplary prosthetic device embodiments that comprise ventricular anchors that anchor beneath the two commissures  36  of the native mitral valve  2 , and related delivery methods. These commissure-anchoring concepts are primarily for use with prosthetic valves, but can be used with other prosthetic devices, including prosthetic spacers. 
     As shown in  FIGS. 3, 4 and 88 , the commissures  36  are the areas of the native mitral valve  2  where the anterior leaflet  10  and the posterior leaflet  12  are joined. Portions  39  of the native mitral annulus  8  adjacent to each commissure  36 , as shown in  FIG. 88 , can be relatively thicker and/or stronger than the portions of the mitral annulus  8  adjacent to the intermediate portions of the leaflets A 2 /P 2 , providing a rigid, stable location to anchor a prosthetic apparatus. These annulus regions  39  can comprise tough, fibrous tissue that can take a greater load than the native leaflet tissue, and can form a natural concave surface, or cavity. 
       FIGS. 84 and 85  show an exemplary prosthetic apparatus  4000  being implanted at the native mitral valve region  2  by positioning a ventricular anchor  4002  at one of the cavities  39 . The prosthetic apparatus  4000  can be a prosthetic valve having a leaflet structure or a spacer device having a spacer body  3004  for reducing MR. The chordae tendinae  16  attach to the leaflets  10 ,  12  adjacent to the commissures  36 , which can present an obstacle in positioning ventricular anchors in the cavities  39  behind the chordae. It is possible, however, to deliver anchors, such as anchor  4002 , around the chordae  16  to reach the cavities  39 . Positioning engagement portions, such as the engagement portion  4004 , of the ventricular anchors behind the chordae  16  in these natural cavities  39  can be desirable for retaining a prosthetic apparatus at the native mitral valve region  2 . However, to avoid entanglement with and/or damage to the native chordae  16 , it can be desirable to first guide the engagement portions of the anchors vertically behind the leaflets  10 ,  12  at the A 2 /P 2  regions, between the chordae  16  from the postero-medial papillary muscle  22  and the chordae  16  from the antero-lateral papillary muscle  24 , as shown in  FIG. 84 , an then move or rotate the engagement portions of the anchors horizontally around behind the chordae  16  toward the commissure cavities  39 , as shown in  FIG. 85 . 
     In some such methods, the ventricular anchors are first deployed behind the A 2 /P 2  regions of the leaflets and then the entire prosthetic apparatus is rotated or twisted to move the engagement portions of the anchors horizontally toward the cavities  39 , as shown in  FIGS. 84 and 85 . For example, a first anchor deployed behind the anterior leaflet  10  can move toward one of the cavities  39  while a second anchor deployed behind the posterior leaflet  12  can move toward the other cavity  39 . This method can also be referred to as a “screw method” because the entire prosthetic is rotated to engage the anchors with the native tissue. 
     As shown in  FIGS. 84 and 85 , a prosthetic apparatus  4000  comprising bent, curved, hooked, or generally “L” shaped, anchors  4002  can be used with the screw method. The “L” shaped anchors  4002  can comprise a leg portion  4006  the extends vertically upward from the body of the apparatus  4000 , a knee portion  4008 , and a foot portion  4010  extending horizontally from the knee portion and terminating in the engagement portion  4004 . In some of these embodiments, the “L” shaped anchor  4002  can comprise a looped wire that attaches to the body of the apparatus  4000  at two locations, such that the wire forms a pair of leg portions  4006 , a pair of knee portions  4008  and a pair of foot portions  4010 . In other embodiments, the anchor  4002  can have other similar shapes, such as a more arced shape, rather than the right angle shape shown in  FIG. 84 . During delivery into the heart, the foot portion  4010  can be curled or wrapped around the outer surface of the body of the apparatus  4000 . 
     As shown in  FIG. 84 , in order to move the foot portion  4010  vertically behind the leaflet  10  without entanglement with the chordae, the leg portion  4006  can be positioned slightly off center from the A 2  region, closer to the chordae opposite the cavity  39  of desired delivery. As shown in  FIG. 84 , the leg portion  4006  is positioned to the right such that the foot portion  4010  can pass between the chordae  16 . 
     After the foot portion  4010  clears the chordae  16  and is positioned behind the leaflet, the apparatus  4000  can be rotated to move the engagement portion  4004  horizontally into the cavity  39 , as shown in  FIG. 85 . Note that in  FIG. 85  the leg portion  4006  can end up positioned at the A 2 /P 2  region between the chordae  16  to avoid interference with the chordae. 
     While  FIGS. 84 and 85  show a single anchor  4002 , both an anterior and a posterior anchor can be delivery in symmetrical manners on opposite sides of the native valve  2 , one being anchored at each cavity  39 . The feet  4010  of the two anchors  4002  can point in opposite directions, such that the twisting motion shown in  FIG. 85  can move them simultaneously to the two cavities  39 . During delivery of two anchor embodiments, the two foot portions  4010  can wrap around the outer surface of the body of the apparatus  4000  such that the two foot portions  4010  overlap one another. 
     In similar embodiments, the anchors  4002  can comprise a paddle shape (see  FIG. 37  for example) having two foot portions  4010  extending in opposite directions. While more difficult to move between the chordae, these paddle shaped anchors can allow the apparatus  4000  to be rotated in either direction to engage one of the foot portions  4010  at a cavity  39 . In some embodiments, the paddle shaped anchors can be wide enough such that one foot portion  4010  can be positioned at one cavity  39  while the other foot portion is positioned at the other cavity. 
     Because the anchors  4002  each attach to the body of the apparatus  4000  at two locations, the anchors can spread apart from the main body of the apparatus when the main body is compressed, forming a gap to receive a leaflet, as described in detail above with reference to  FIGS. 11-22 . In some embodiments, the anchors can separate from the main body when the main body is compressed and either remain separated from the main body, such that the leaflets are not pinched or compressed between the anchors and the main body of the apparatus, or close against the main body during expansion to engage the leaflets. In some embodiments, the main body can move toward the anchors to reduce the gap when then main body expands while maintaining the distance between the foot portions  4010  of the opposing anchors. 
       FIGS. 86 and 87  shown another exemplary prosthetic apparatus  5000  being implanted at the native mitral valve region  2  by positioning ventricular anchors  5002  at the cavities  39  and a corresponding method for do so. In this embodiment, the apparatus  5000  can comprise a pair of “L” shaped anchors  5002  on each side (only one pair is visible in  FIGS. 86 and 87 ), with each pair comprising one anchor for positioning in one of the cavities  39  and another anchor for positioning in the other cavity. Each of the anchors can comprise a leg portion  5006  extending vertically from the body of the apparatus  5000  to a knee portion  5008 , and a foot portion  5010  extending horizontally from the knee portion  5008  to an engagement portion  5004 . In other embodiments, the anchors  5002  can have other similar shapes, such as a more arced shape, rather than the angled shape shown in  FIG. 86 . 
     Each pair of anchors  5002  can comprise a resiliently flexible material, such as Nitinol, such that they can be pre-flexed and constrained in a cocked position for delivery behind the leaflets, as shown in  FIG. 86 , and then released to resiliently spring apart to move the engagement portions  5004  in opposite directions toward the two cavities  39 , as shown in  FIG. 87 . Any suitable constrainment and release mechanisms can be used, such as a releasable mechanical lock mechanism. Once released, one anterior anchor and one posterior anchor can be positioned at one cavity  39  from opposite directions, and a second anterior anchor and a second posterior anchor can be positioned at the other cavity from opposite directions. Some embodiments can include only one anchor on each side of the apparatus  5000  that move in opposite directions toward opposite cavities  39  when released. 
     Because each pair of anchors  5002  are initially constrained together, as shown in  FIG. 86 , each pair of anchors can act like a single anchor having two attachment points to the main body of the apparatus  5000 . Thus, the anchor pairs can separate, or expand away, from the main body when the main body is compressed and either remain spaced from the main body, such that the leaflets are not pinched or compressed between the anchors and the main body of the apparatus, or close against the main body during expansion to engage the leaflets. In some embodiments, the main body can move toward the anchor pairs to reduce the gap when then main body expands while maintaining the distance between the foot portions  5010  of the opposing anchor pairs. 
     In the embodiments shown in  FIGS. 84-87 , the prosthetic apparatus  4000  or  5000  can have a main frame body similar to the embodiments shown in  FIG. 5 , from which the ventricular anchors  4002 ,  5002  can extend, and can further comprise one or more atrial anchors, such as an atrial sealing member similar to the atrial sealing member  124  shown in  FIG. 5  or a plurality of atrial anchors similar to the atrial anchors  3012  and  3014  shown in  FIG. 71 , for example. The atrial anchors can extend radially outward from an atrial end of the prosthetic apparatus and contact the native tissue opposite the cavities  39  and thereby compress the tissue between the atrial anchors and the engagement portions  4004 ,  5004  of the ventricular anchors  4002 ,  5002  to retain the prosthetic apparatus at the native mitral valve region. The atrial anchors and the ventricular anchors can comprise a broad contact area to distribute the load over a wider area and reduce the likelihood of damaging the native tissue. 
     In view of the many possible embodiments to which the principles disclosed herein may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the disclosure. Rather, the scope is defined by the following claims. We therefore claim all that comes within the scope and spirit of these claims.