Abstract:
An implant for supplementing, repairing, or replacing a native heart valve leaflet or leaflets provides a scaffold, which defines a pseudo-annulus. The implant further has at least two struts in generally oppositely spaced apart positions on the scaffold. The scaffold can be placed in an elastically loaded condition in a heart with the struts engaging tissue at or near the leaflet commissures of a heart valve annulus, to reshape the annulus for leaflet coaptation. The implant further provides a neoleaflet element coupled to the scaffold within pseudo-annulus, to provide a one-way valve function.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a divisional of co-pending U.S. patent application Ser. No. 10/676,815, filed Oct. 1, 2003, which is a continuation-in-part of U.S. patent application Ser. No. 09/666,617, filed Sep. 20, 2000 and entitled “Heart Valve Annulus Device and Methods of Using Same,” which is incorporated herein by reference. This application is also a continuation-in-part of Patent Cooperation Treaty Application Serial No. PCT/US 02/31376, filed Oct. 1, 2002 and entitled “Systems and Devices for Heart Valve Treatments,” which claimed the benefit of U.S. Provisional Patent Application Ser. No. 60/326,590, filed Oct. 1, 2001, which are incorporated herein by reference. This application also claims the benefit of U.S. Provisional Application Ser. No. 60/429,444, filed Nov. 26, 2002, and entitled “Heart Valve Remodeling Devices;” U.S. Provisional Patent Application Ser. No. 60/429,709, filed Nov. 26, 2002, and entitled “Neo-Leaflet Medical Devices;” and U.S. Provisional Patent Application Ser. No. 60/429,462, filed Nov. 26, 2002, and entitled “Heart Valve Leaflet Retaining Devices,” which are each incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention is directed to devices, systems, and methods for improving the function of a heart valve, e.g., in the treatment of mitral valve regurgitation.  
       BACKGROUND OF THE INVENTION  
       [0000]     I. The Anatomy of a Healthy Heart  
         [0003]     The heart (see  FIG. 1 ) is slightly larger than a clenched fist. It is a double (left and right side), self-adjusting muscular pump, the parts of which work in unison to propel blood to all parts of the body. The right side of the heart receives poorly oxygenated (“venous”) blood from the body from the superior vena cava and inferior vena cava and pumps it through the pulmonary artery to the lungs for oxygenation. The left side receives well-oxygenation (“arterial”) blood from the lungs through the pulmonary veins and pumps it into the aorta for distribution to the body.  
         [0004]     The heart has four chambers, two on each side—the right and left atria, and the right and left ventricles. The atria are the blood-receiving chambers, which pump blood into the ventricles. A wall composed of membranous and muscular parts, called the interatrial septum, separates the right and left atria. The ventricles are the blood-discharging chambers. A wall composed of membranous and muscular parts, called the interventricular septum, separates the right and left ventricles.  
         [0005]     The synchronous pumping actions of the left and right sides of the heart constitute the cardiac cycle. The cycle begins with a period of ventricular relaxation, called ventricular diastole. The cycle ends with a period of ventricular contraction, called ventricular systole.  
         [0006]     The heart has four valves (see  FIGS. 2 and 3 ) that ensure that blood does not flow in the wrong direction during the cardiac cycle; that is, to ensure that the blood does not back flow from the ventricles into the corresponding atria, or back flow from the arteries into the corresponding ventricles. The valve between the left atrium and the left ventricle is the mitral valve. The valve between the right atrium and the right ventricle is the tricuspid valve. The pulmonary valve is at the opening of the pulmonary artery. The aortic valve is at the opening of the aorta.  
         [0007]     At the beginning of ventricular diastole (i.e., ventricular filling)(see  FIG. 2 ), the aortic and pulmonary valves are closed to prevent back flow from the arteries into the ventricles. Shortly thereafter, the tricuspid and mitral valves open (as  FIG. 2  shows), to allow flow from the atria into the corresponding ventricles. Shortly after ventricular systole (i.e., ventricular emptying) begins, the tricuspid and mitral valves close (see  FIG. 3 )—to prevent back flow from the ventricles into the corresponding atria—and the aortic and pulmonary valves open—to permit discharge of blood into the arteries from the corresponding ventricles.  
         [0008]     The opening and closing of heart valves occur primarily as a result of pressure differences. For example, the opening and closing of the mitral valve occurs as a result of the pressure differences between the left atrium and the left ventricle. During ventricular diastole, when ventricles are relaxed, the venous return of blood from the pulmonary veins into the left atrium causes the pressure in the atrium to exceed that in the ventricle. As a result, the mitral valve opens, allowing blood to enter the ventricle. As the ventricle contracts during ventricular systole, the intraventricular pressure rises above the pressure in the atrium and pushes the mitral valve shut.  
         [0009]      FIG. 4  shows a posterior oblique cutaway view of a healthy human heart  100 . Two of the four heart chambers are shown, the left atrium  170 , and the left ventricle  140  (not shown are the right atrium and right ventricle). The left atrium  170  fills with blood from the pulmonary veins. The blood then passes through the mitral valve (also known as the bicuspid valve, and more generally known as an atrioventricular valve) during ventricular diastole and into the left ventricle  140 . During ventricular systole, the blood is then ejected out of the left ventricle  140  through the aortic valve  150  and into the aorta  160 . At this time, the mitral valve should be shut so that blood is not regurgitated back into the left atrium.  
         [0010]     The mitral valve consists of two leaflets, an anterior leaflet  110 , and a posterior leaflet  115 , attached to chordae tendineae  120  (or chords), which in turn are connected to papillary muscles  130  within the left atrium  140 . Typically, the mitral valve has a D-shaped anterior leaflet  110  oriented toward the aortic valve, with a crescent shaped posterior leaflet  115 . The leaflets intersect with the atrium  170  at the mitral annulus  190 .  
         [0011]     In a healthy heart, these muscles and their chords support the mitral and tricuspid valves, allowing the leaflets to resist the high pressure developed during contractions (pumping) of the left and right ventricles. In a healthy heart, the chords become taut, preventing the leaflets from being forced into the left or right atria and everted. Prolapse is a term used to describe the condition wherein the coaptation edges of each leaflet initially may coapt and close, but then the leaflets rise higher and the edges separate and the valve leaks. This is normally prevented by contraction of the papillary muscles and the normal length of the chords. Contraction of the papillary muscles is simultaneous with the contraction of the ventricle and serves to keep healthy valve leaflets tightly shut at peak contraction pressures exerted by the ventricle.  
         [0000]     II. Characteristics and Causes of Mitral Valve Dysfunction  
         [0012]     Valve malfunction can result from the chords becoming stretched, and in some cases tearing. When a chord tears, the result is a flailed leaflet. Also, a normally structured valve may not function properly because of an enlargement of the valve annulus pulling the leaflets apart. This condition is referred to as a dilation of the annulus and generally results from heart muscle failure. In addition, the valve may be defective at birth or because of an acquired disease, usually infectious or inflammatory.  
         [0013]      FIG. 5  shows a cutaway view of a human heart  200  with a prolapsed mitral valve. The prolapsed valve does not form a tight seal during ventricular systole, and thus allows blood to be regurgitated back into the left atrium during ventricular contraction. The anterior  220  and posterior  225  leaflets are shown rising higher than normal (i.e., prolapsing) into the left atrium. The arrows indicate the direction of regurgitant flow. Among other causes, regurgitation can result from redundant valve leaflet tissue or from stretched chords  210  that are too long to prevent the leaflets from being blown into the atrium. As a result, the leaflets do not form a tight seal, and blood is regurgitated into the atrium.  
         [0014]      FIG. 6  shows a cutaway view of a human heart  300  with a flailing mitral valve  320 . The flailing valve also does not form a tight seal during ventricular systole. Blood thus regurgitates back into the left atrium during ventricular contraction, as indicated by the arrows. Among other causes, regurgitation can also result from torn chords  310 . As an example,  FIG. 7  shows a cutaway view of a human heart where the anterior leaflet  910  has torn chords  920 . As a result, valve flailing and blood regurgitation occur during ventricular systole.  
         [0015]     As a result of regurgitation, “extra” blood back flows into the left atrium. During subsequent ventricular diastole (when the heart relaxes), this “extra” blood returns to the left ventricle, creating a volume overload, i.e., too much blood in the left ventricle. During subsequent ventricular systole (when the heart contracts), there is more blood in the ventricle than expected. This means that: (1) the heart must pump harder to move the extra blood; (2) too little blood may move from the heart to the rest of the body; and (3) over time, the left ventricle may begin to stretch and enlarge to accommodate the larger volume of blood, and the left ventricle may become weaker.  
         [0016]     Although mild cases of mitral valve regurgitation result in few problems, more severe and chronic cases eventually weaken the heart and can result in heart failure. Mitral valve regurgitation can be an acute or chronic condition. It is sometimes called mitral insufficiency.  
         [0000]     III. Prior Treatment Modalities  
         [0017]     In the treatment of mitral valve regurgitation, diuretics and/or vasodilators can be used to help reduce the amount of blood flowing back into the left atrium. An intra-aortic balloon counterpulsation device is used if the condition is not stabilized with medications. For chronic or acute mitral valve regurgitation, surgery to repair or replace the mitral valve is often necessary.  
         [0018]     To date, invasive, open heart surgical approaches have been used to repair or replace the mitral valve with either a mechanical valve or biological tissue (bioprosthetic) taken from pigs, cows, or horses.  
         [0019]     The need remains for simple, cost-effective, and less invasive devices, systems, and methods for treating dysfunction of a heart valve, e.g., in the treatment of mitral valve regurgitation.  
       SUMMARY OF THE INVENTION  
       [0020]     The invention provides devices, systems and methods that supplement, repair, or replace a native heart valve leaflet. The devices, systems, and methods include an implant that, in use, rests adjacent a valve annulus. The implant defines a pseudo-annulus. The implant includes a neoleaflet element that occupies the space of at least a portion of one native valve leaflet. The implant allows the native leaflets to coexist with the implant, or if desired or indicated, one or more native leaflets can be removed and replaced by the implant. The neoleaflet element of the implant is shaped and compressed to mimic the one-way valve function of a native leaflet. The implant includes spaced-apart struts that are sized and configured to contact tissue near or within the heart valve annulus to brace the implant against migration within the annulus during the one-way valve function.  
         [0021]     According to one aspect of the invention, the implant includes a scaffold, which defines a pseudo-annulus. The implant further includes at least two struts in generally oppositely spaced apart positions on the scaffold. The scaffold can be placed in an elastically loaded condition in a heart with the struts engaging tissue at or near the leaflet commissures of a heart valve annulus, to reshape the annulus for leaflet coaptation. The implant further provides a neoleaflet element coupled to the scaffold within pseudo-annulus, to provide a one-way valve function.  
         [0022]     Other features and advantages of the invention shall be apparent based upon the accompanying description, drawings, and claims. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is a perspective, anterior anatomic view of the interior of a healthy heart.  
         [0024]      FIG. 2  is a superior anatomic view of the interior of a healthy heart, with the atria removed, showing the condition of the heart valves during ventricular diastole.  
         [0025]      FIG. 3  is a superior anatomic view of the interior of a healthy heart, with the atria removed, showing the condition of the heart valves during ventricular systole.  
         [0026]      FIG. 4  is a posterior oblique cutaway view of a portion of a human heart, showing a healthy mitral valve during ventricular systole, with the leaflets properly coapting.  
         [0027]      FIG. 5  is a posterior oblique cutaway view of a portion of a human heart, showing a dysfunctional prolapsing mitral valve during ventricular systole, with the leaflets not properly coapting, causing regurgitation.  
         [0028]      FIG. 6  is a posterior oblique cutaway view of a portion of a human heart, showing a dysfunctional mitral valve during ventricular systole, with the leaflets flailing, causing regurgitation.  
         [0029]      FIG. 7  is a posterior oblique cutaway view of a portion of a human heart, showing a dysfunctional mitral valve during ventricular systole, caused by torn chords, that leads to regurgitation.  
         [0030]      FIG. 8  is a perspective view of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being sized and configured to extend about a heart valve annulus and including a neoleaflet element that occupies the space of at least one native valve leaflet.  
         [0031]      FIG. 9A  is a perspective, anatomic view of the implant shown in  FIG. 8 , with the neoleaflet element installed over an anterior leaflet of a mitral valve to restore normal function.  
         [0032]      FIG. 9B  is a perspective, anatomic view of the implant of the type shown in  FIG. 8 , with the neoleaflet element installed over a posterior leaflet of a mitral valve to restore normal function to the native valve leaflet.  
         [0033]      FIG. 10  is a perspective view of another illustrative embodiment of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being shown installed on a mitral valve annulus and having a neoleaflet element that occupies the space of at least one native valve leaflet, the implant also including a framework that rises above the neoleaflet element in the atrium to help fix and stabilize the implant.  
         [0034]      FIG. 11  is a perspective view of another illustrative embodiment of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being sized and configured to extend about a heart valve annulus and including two neoleaflet elements that occupy the space of two native valve leaflets.  
         [0035]      FIG. 12  is a perspective view of the implant shown in  FIG. 11 , with the two neoleaflet elements in a valve opened condition, as would exist during ventricular diastole.  
         [0036]      FIG. 13  is a perspective view of another illustrative embodiment of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being sized and configured to extend about a heart valve annulus and including a neoleaflet element formed by a membrane.  
         [0037]      FIG. 14  is a perspective view of another illustrative embodiment of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being sized and configured to extend about a heart valve annulus and including a neoleaf let element formed by a membrane, the implant also including a framework that rises above the neoleaflet element in the atrium to help fix and stabilize the implant.  
         [0038]      FIG. 15  is a perspective view of another illustrative embodiment of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being sized and configured to extend about a heart valve annulus and including two neoleaflet elements to form a duckbill valve, the valve being shown in an opened condition as would exist during ventricular diastole.  
         [0039]      FIG. 16  is a perspective view of the implant shown in  FIG. 15 , the duckbill valve being shown in a closed condition as would exist during ventricular systole.  
         [0040]      FIGS. 17 and 18  are side views of the implant shown, respectively, in  FIGS. 15 and 16 , with the duckbill valve, respectively, in an opened and a closed condition.  
         [0041]      FIG. 19  is a perspective view of another illustrative embodiment of an implant that supplements, repairs, or replaces a native heart valve leaflet, the implant being sized and configured to extend about a heart valve annulus and including two neoleaflet elements formed by a duckbill valve, the valve being shown in an opened condition as would exist during ventricular diastole, the implant also including a framework that rises above the neoleaflet elements in the atrium to help fix and stabilize the implant.  
         [0042]      FIG. 20  is a perspective view of the implant shown in  FIG. 19 , the duckbill valve being shown in a closed condition as would exist during ventricular systole.  
         [0043]      FIGS. 21A  to  21 C diagrammatically show a method of gaining intravascular access to the left atrium for the purpose of deploying a delivery catheter to place an. implant in a valve annulus to supplement, repair, or replace a native heart valve leaflet 
     
    
     DETAILED DESCRIPTION  
       [0044]     Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.  
         [0045]      FIGS. 8 and 9  show an implant  400  sized and configured to supplement, repair, or replace a dysfunctional native heart valve leaflet or leaflets. In use (see, in particular,  FIG. 9 ), the implant  400  defines a pseudo-annulus that rests adjacent the native valve annulus and includes a neoleaflet element that occupies the space of at least a portion of one native valve leaflet. The implant  400  allows the native leaflets to coexist with the implant  400 . If desired or indicated, one or more native leaflets can be removed and replaced by the implant  400 .  
         [0046]     In its most basic form, the implant  400  is made—e.g., by machining, bending, shaping, joining, molding, or extrusion—from a biocompatible metallic or polymer material, or a metallic or polymer material that is suitably coated, impregnated, or otherwise treated with a material to impart biocompatibility, or a combination of such materials. The material is also desirably radio-opaque to facilitate fluoroscopic visualization.  
         [0047]     As  FIG. 8  shows, the implant  400  includes a base or scaffold  420  that, in the illustrated embodiment, is sized and configured to rest adjacent the mitral annulus. At least a portion of the base  420  forms an annular body that approximates the shape of the native annulus. For this reason, the base  420  will also be referred to as a “pseudo-annulus.” 
         [0048]     The base  420  supports a bridge  430  that extends into the valve. The bridge  430  is sized and configured (see  FIG. 9A ) to overlay the space of at least a portion of one native valve leaflet. In  FIG. 9A , the bridge  430  overlays an anterior leaflet. However, as  FIG. 9B  shows, the bridge  430  could be oriented to overlay a posterior leaflet. As will be described later (see  FIG. 11 ), two bridges can be formed to overlay both leaflets.  
         [0049]     As  FIG. 8  shows, the implant  400  includes a material  410  that covers or spans the bridge  430 . The spanning material  410  may be attached to the implant  400  with one or more attachment means  440 . For example, the spanning materials  410  may be sewn, glued, or welded to the implant  400 , or it may be attached to itself when wrapped around the implant  400 . The spanning material  410  may be made from a synthetic material (for example, thin Nitinol, polyester fabric, polytetrafluoroethylene or PTFE, silicone, or polyurethane) or a biological material (for example, human or animal pericardium).  
         [0050]     Together, the bridge  430  and the spanning material  410  comprise a neoleaflet element  470  coupled to the base  420 . The neoleaflet element  470  may be rigid, semi-rigid, or flexible. The neoleaflet element  470  is coupled to the base  420  in a manner that exerts a mechanical, one-way force to provide a valve function that responds to differential pressure conditions across the neoleaflet element. In response to one prescribed differential pressure condition, the neoleaflet element  470  will deflect and, with a native leaflet, assume a valve opened condition. In response to another prescribed pressure condition, the neoleaflet element  470  will resist deflection and, by coaptation with a native leaflet (or a companion neoleaflet element) at, above, or below the annulus plane, maintain a valve closed condition.  
         [0051]     In the context of the illustrated embodiment (when installed in a mitral valve annulus), the neoleaflet element resists being moved in the cranial (superior) direction (into the atrium), when the pressure in the ventricle exceeds the pressure in the atrium—as it would during ventricular systole. The neoleaflet element  470  may move, however, in the caudal (inferior) direction (into the ventricle), when the pressure in the ventricle is less than the pressure in the atrium—as it would during ventricular diastole. The neoleaflet element  470  thereby mimics the one-way valve function of a native leaflet, to prevent retrograde flow.  
         [0052]     The implant  400  is sized and shaped so that, in use adjacent the valve annulus of the mitral valve, it keeps the native valve leaflet closed during ventricular systole (as shown in  FIGS. 9A and 9B ), to prevent flailing and/or prolapse of the native valve leaflet it overlays during ventricular systole. The implant  400  thus restores to the heart valve leaflet or leaflets a normal resistance to the high pressure developed during ventricular contractions, resisting valve leaflet eversion and/or prolapse and the resulting back flow of blood from the ventricle into the atrium during ventricular systole. The pressure difference serves to keep valve leaflets tightly shut during ventricular systole. The implant  400 , however, does not interfere with opening of the native valve leaflet or leaflets during ventricular diastole (see, e.g.,  FIG. 12 ). The implant  400  allows the leaflet or leaflets to open during ventricular diastole, so that blood flow occurs from the atrium into the ventricle. The implant  400  thereby restores normal one-way function to the valve, to prevent retrograde flow.  
         [0053]     The functional characteristics of the implant  400  just described can be imparted to the neoleaflet element  470  in various ways. For example, hinges and springs (mechanical or plastic) can be used to couple the bridge to the base. Desirably, the implant  400  is made from materials that provide it with spring-like characteristics.  
         [0054]     As shown in  FIG. 8 , in the illustrated embodiment, the base  420  and bridge  430  are shaped from a length of wire-formed material. The shape and material properties of the implant determine its physical spring-like characteristics as well as its ability to open in one direction only. The spring-like characteristics of the implant  400  allow it to respond dynamically to changing differential pressure conditions within the heart.  
         [0055]     More particularly, in the illustrated mitral valve embodiment, when greater pressure exists superior to the bridge  430  than inferior to the bridge (i.e., during ventricular diastole), the shape and material properties of the bridge  430  accommodate its deflection into the ventricle—i.e., an opened valve condition (as  FIG. 12  shows in another illustrative embodiment). When greater pressure exists inferior to the bridge  430  than superior to the bridge (i.e., during ventricular systole), the shape and material properties of the bridge  430  enable it to resist superior movement of the leaflet into the atrium, and otherwise resist eversion and/or prolapse of the valve leaflet into the atrium (as  FIGS. 9A and 9B  also show).  
         [0056]     The implant  400  may be delivered percutaneously, thoracoscopically through the chest, or using open heart surgical techniques. If delivered percutaneously, the implant  400  may be made from a superelastic material (for example superelastic Nitinol alloy) enabling it to be folded and collapsed such that it can be delivered in a catheter, and will subsequently self-expand into the desired shape and tension when released from the catheter.  
         [0057]     For example, percutaneous vascular access can be achieved by conventional methods into the femoral or jugular vein. As  FIG. 21A  shows, under image guidance (e.g., fluoroscopic, ultrasonic, magnetic resonance, computed tomography, or combinations thereof), a catheter  52  is steered through the vasculature into the right atrium. A needle cannula  54  carried on the distal end of the catheter is deployed to pierce the septum between the right and left atrium. As  FIG. 21B  shows, a guide wire  56  is advanced trans-septally through the needle catheter  52  into the left atrium. The first catheter  52  is withdrawn, and (as  FIG. 21C  shows) under image guidance, an implant delivery catheter  58  is advanced over the guide wire  56  into the left atrium into proximity with the mitral valve. Alternatively, the implant delivery catheter  58  can be deployed trans-septally by means of surgical access through the right atrium.  
         [0058]     The distal end of the catheter  58  encloses an implant  400 , like that shown in  FIG. 8 , which is constrained in a collapsed condition. A flexible push rod in the catheter  58  can be used to expel the implant  400  from the catheter  58 . Free of the catheter, the implant  400  will self-expand to its preordained configuration, e.g., like that shown in  FIGS. 9A  or  9 B.  
         [0059]     The implant  400  may be fixed to the annulus in various ways. For example, the implant  400  may be secured to the annulus with sutures or other attachment means (i.e. barbs, hooks, staples, etc.) Also, the implant  400  may be secured with struts or tabs  450  (see  FIGS. 8 and 9 A), that extend from the base  420  above or below the plane of the annulus. The struts  450  are preferably configured with narrow connecting members that extend through the valve orifice so that they will not interfere with the opening and closing of the valve.  
         [0060]     In this arrangement, the struts  450  are desirably sized and configured to contact tissue near or within the heart valve annulus to brace the base  420  against migration within the annulus during the one-way valve function of the neoleaflet element. In this arrangement, it is also desirable that the base  420  be “elastic,” i.e., the material of the base  420  is selected to possess a desired spring constant. This means that the base  420  is sized and configured to possess a normal, unloaded, shape or condition (shown in  FIG. 8 ), in which the base  420  is not in net compression, and the struts  450  are spaced apart farther than the longest cross-annulus distance between the tissue that the struts  450  are intended to contact. In the illustrated embodiment, the base  420  is shown resting along the major (i.e., longest) axis of the valve annulus, with the struts  450  contacting tissue at or near the leaflet commissures. However, other orientations are possible. The struts  450  need not rest at or near the leaflet commissures, but may be significantly removed from the commissures, so as to gain padding from the leaflets. The spring constant imparts to the base  420  the ability to be elastically compressed out of its normal, unloaded condition, in response to external compression forces applied at the struts  450 . The base  420  is sized and configured to assume an elastically loaded, in net compression condition, during which the struts  450  are spaced apart a sufficiently shorter distance to rest in engagement with tissue at or near the leaflet commissures (or wherever tissue contact with the struts  450  is intended to occur) (see  FIGS. 9A  or  9 B). When in its elastically loaded, net compressed condition (see  FIGS. 9A and 9B ), the base  450  can exert forces to the tissues through the struts  450 . These forces hold the base  420  against migration within the annulus. Furthermore, when the struts  450  are positioned at or near the commissures, they tend to outwardly displace tissue and separate tissue along the major axis of the annulus, which also typically stretches the leaflet commissures, shortens the minor axis, and/or reshapes surrounding anatomic structures. The base  450  can also thereby reshape the valve annulus toward a shape more conducive to leaflet coaptation. It should be appreciated that, in order to be therapeutic, the implant may only need to reshape the annulus during a portion of the heart cycle, such as during ventricular systolic contraction. For example, the implant may be sized to produce small or negligible outward displacement of tissue during ventricular diastole when the tissue is relaxed, but restrict the inward movement of tissue during ventricular systolic contraction.  
         [0061]     As the preceding disclosure demonstrates, different forms of heart valve treatment can be performed using a single implant.  
         [0062]     Implants having one or more of the technical features just described, to thereby function in situ as a neo-leaflet, may be sized and configured in various ways. Various illustrative embodiments will now be described.  
         [0063]     In  FIG. 10 , an implant  600  (like implant  400 ) includes a base  620  that defines a pseudo-annulus, with a bridge  630  carrying a spanning material  640  together comprising a neoleaflet element  650  appended to the base  620  within the pseudo-annulus. The neoleaflet element  650  overlays an anterior native leaflet with the same purpose and function described for the implant  400 . Alternatively, the neoleaflet element  650  could overlay a posterior native leaflet, as  FIG. 9B  shows. The implant  600  also includes struts  670 , which desirably contact and exert force against tissue near or within the annulus (in the manner previously described) to brace the base  420  against migration within the annulus.  
         [0064]     In addition, the implant  600  includes an orientation and stabilization framework  610  that may extend from the annulus to the atrial dome. In  FIG. 10 , the framework  610  rises from the base  620  with two substantially parallel arched wires, which connect to form a semicircular hoop above the base  620 . The framework  610  helps to accurately position the implant  600  within the atrium, and also helps to secure the implant  600  within the atrium.  
         [0065]     Preferably the framework  610  does not interfere with atrial contractions, but instead is compliant enough to contract with the atrium. As such, the implant  600  may have nonuniform flexibility to improve its function within the heart.  
         [0066]      FIGS. 11 and 12  show another illustrative embodiment of an implant  700 . In  FIGS. 11 and 12 , the implant  700  contains two neo-leaflet elements. The implant  700  includes an anterior bridge  730  spanned by an anterior bridge material  710 , and a posterior bridge  735  spanned by a posterior bridge material  720 . The bridges and materials together comprise anterior and posterior neoleaflet elements  780 A and  780 P. The implant  700  also includes an orientation and stabilization framework  770 , shown having a configuration different than the framework  610  in  FIG. 9 , but having the same function and serving the same purpose as previously described for the framework  610 .  
         [0067]     In  FIGS. 11 and 12 , the base  760  includes structures like the anchoring clips  740  that, in use, protrude above the plane formed by the annulus of the valve. Additionally, the implant  700  may be secured with struts  750  that extend from the base  760  on narrow connecting members and below the plane of the annulus into the ventricular chamber. The anchoring clips  740  and struts  750  desirably contact and exert force against tissue near or within the annulus (in the manner previously described) to brace the base  760  against migration within the annulus.  FIG. 11  shows the dual neo-leaflets  780 A and  780 B (i.e., the covered anterior and posterior bridges  730  and  735 ) in a closed valve position.  FIG. 12  shows the dual neo-leaflets  780 A and  780 B in an open valve position.  
         [0068]      FIG. 13  shows another illustrative embodiment of an implant  1000  having a full sewing ring  1030  with a membrane  1010  that serves as a neo-leaflet. The device  1000  has an opening  1020  though the sewing ring  1030  opposite the membrane  1010  for blood flow. Alternatively, this embodiment could have two neo-leaflets. This embodiment could be surgically attached to the valve annulus and/or combined with a framework for anchoring the device within the atrium using catheter based intraluminal techniques. Additionally, the device may be secured with struts  1040  that extend from the base on narrow connecting members and below the plane of the annulus into the ventricular chamber. The struts  1040 , which desirably contact and exert force against tissue near or within the annulus (in the manner previously described) to brace the base  420  against migration within the annulus.  
         [0069]     As can be seen, a given implant may carry various structures or mechanisms to enhance the anchorage and stabilization of the implant in the heart valve annulus. The mechanisms may be located below the plane of the annulus, to engage infra-annular heart tissue adjoining the annulus in the ventricle, and/or be located at or above the plane of the annulus, to engage tissue on the annulus or in the atrium. These mechanisms increase the surface area of contact between the implant and tissue. A given implant can also include tissue in-growth surfaces, to provide an environment that encourages the in-growth of neighboring tissue on the implant. Once in-growth occurs, the implant becomes resistant to migration or dislodgment from the annulus. Conventional in-growth materials such as polyester fabric can be used.  
         [0070]      FIG. 14  shows another illustrative embodiment of an implant  1100  having a framework  1120  and struts or tabs  1110 . This implant  1100  includes a membrane  1130 , that serves as a neo-leaflet, attached to the base  1140  of the device with an attachment means  1150 .  
         [0071]      FIG. 15  shows another illustrative embodiment of an implant  1200 . In this embodiment, the implant  1200  includes a base  1220  that defines a pseudo-annulus and that, in use, is rests adjacent all or a portion of a native valve annulus. The base  1240  supports a duckbill valve  1210 , which forms a neoleaflet element. Peripherally supported on the base  1240 , the duckbill valve  1210  rests in the pseudo-annulus. Struts  1230  (which also carry additional tab structures to increase the surface area of tissue contact) help brace the base  1240  to tissue near or within the heart valve annulus.  
         [0072]     In this embodiment, the duckbill valve  1210  replaces the native anterior and posterior leaflets. The duckbill valve  1210  serves as dual neo-leaflets, which mutually open and close in response to changes in pressure, replacing the function of the native leaflets.  FIG. 15  shows the duckbill valve  1210  in the open valve position. In  FIG. 15 , the arrow shows the direction of blood flow through the opened valve.  FIG. 16  shows the duckbill valve in the closed valve position. When closed, the duckbill valve  1210  resists eversion and regurgitation.  
         [0073]     When the implant  1200  is used to replace a mitral valve (see  FIGS. 17 and 18 ), the duckbill valve  1210  extends from the plane of the valve annulus and into the ventricle. The duckbill valve  1210  is shown to have a more rigid or thick composition emerging from the base member, and gradually becoming less rigid or thick away from the base member. This variation in mechanical properties ensures a valve that responds dynamically to pressure changes, but that is also rigid enough to not become everted.  FIG. 17  shows the valve  1210  in an opened valve condition. In  FIG. 17 , the arrow shows the direction of blood flow through the opened valve.  FIG. 18  shows the duckbill valve in the closed valve position, without eversion and regurgitation.  
         [0074]      FIGS. 19 and 20  show another illustrative embodiment of an implant  1600  of the type shown in  FIGS. 15 and 16 . Like the implant  1200 , the implant  1600  includes base  1620  defining a pseudo-annulus to which a duckbill valve  1630  is appended, which serves as a neoleaflet element to replace the native anterior and posterior leaflets and serves as dual neo-leaflets.  FIG. 19  shows the duckbill valve  1630  in the open valve position, allowing forward flow of blood through the opened valve.  FIG. 20  shows the duckbill valve  1630  in the closed valve position, resisting eversion and regurgitation.  
         [0075]     In  FIGS. 19 and 20 , the implant  1600  includes an orientation and stabilization framework  1610 . The framework  1610  rises from the base  1620  as two arches extending from opposite sides of the base  1620 . The dual arch framework  1610  possesses compliance to contract with the atrium. As before explained, the framework  1610  helps to accurately position the implant  1600  within the atrium, and also helps to secure the implant  600  within the atrium. The implant  1600  also includes struts  1640 , which desirably contact and exert force against tissue near or within the annulus (in the manner previously described) to brace the base  1620  against migration within the annulus.  
         [0076]     While the new devices and methods have been more specifically described in the context of the treatment of a mitral heart valve, it should be understood that other heart valve types can be treated in the same or equivalent fashion. By way of example, and not by limitation, the present systems and methods could be used to prevent or resist retrograde flow in any heart valve annulus, including the tricuspid valve, the pulmonary valve, or the aortic valve. In addition, other embodiments and uses of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification and examples should be considered exemplary and merely descriptive of key technical features and principles, and are not meant to be limiting. The true scope and spirit of the invention are defined by the following claims. As will be easily understood by those of ordinary skill in the art, variations and modifications of each of the disclosed embodiments can be easily made within the scope of this invention as defined by the following claims.