Patent Publication Number: US-8992604-B2

Title: Techniques for percutaneous mitral valve replacement and sealing

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. Ser. No. 12/840,463 to Hacohen, filed Jul. 21, 2010, entitled “Guide wires with commissural anchors to advance a prosthetic valve,” which published as US 2012/0022639, and which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     Embodiments of the present invention relate in general to valve replacement. More specifically, embodiments of the present invention relate to prosthetic valves for replacement of an atrioventricular valve. 
     BACKGROUND 
     Ischemic heart disease causes regurgitation of a heart valve by the combination of ischemic dysfunction of the papillary muscles, and the dilatation of the ventricle that is present in ischemic heart disease, with the subsequent displacement of the papillary muscles and the dilatation of the valve annulus. 
     Dilation of the annulus of the valve prevents the valve leaflets from fully coapting when the valve is closed. Regurgitation of blood from the ventricle into the atrium results in increased total stroke volume and decreased cardiac output, and ultimate weakening of the ventricle secondary to a volume overload and a pressure overload of the atrium. 
     SUMMARY 
     For some applications of the present invention, one or more guide members (e.g., wires, sutures, or strings) is configured to be anchored to respective commissures of a native atrioventricular valve of a patient, and each guide member facilitates the advancement therealong of respective commissural anchors. The commissural anchors are shaped so as to define a plurality of barbs or prongs which are expandable to restrict proximal movement of the anchors following their deployment. The guide members facilitate advancement of a collapsible prosthetic valve support (e.g., a skirt) which serves as a base for and receives a collapsible prosthetic mitral valve which is subsequently coupled to the support. The support comprises a proximal annular element, or ring, and a distal cylindrical element. The cylindrical element is configured to push aside and press against the native leaflets of the native valve, and the proximal annular element is shaped so as to define one or more holes for sliding the valve support along the one or more guide members. The proximal annular element is configured to be positioned along the annulus of the native valve. 
     The collapsible prosthetic valve is configured for implantation in and/or at least partial replacement (e.g., full replacement) of the native atrioventricular valve of the patient, such as a native mitral valve or a native tricuspid valve. The valve support and the prosthetic valve are configured to assume collapsed states for minimally-invasive delivery to the diseased native valve, such as by percutaneous or transluminal delivery using one or more catheters. For some applications, the valve support and the prosthetic valve are implanted during an open-heart procedure. 
     The prosthetic valve support is shaped so as to define a downstream skirt. The downstream skirt is configured to be placed at native valve, such that the downstream skirt passes through the orifice of the native valve and extends toward, and, typically partially into, a ventricle. The downstream skirt typically additionally pushes aside and presses against the native leaflets of the native valve, which are left in place during and after implantation of the prosthetic valve support and/or the prosthetic valve. 
     The proximal annular element has upper and lower surfaces. For some applications of the present invention, one or more, e.g., a plurality of, tissue anchors are coupled to the lower surface and facilitate anchoring of the proximal annular element to the annulus of the native valve. For some applications, the one or more anchors comprise at least first and second commissural anchors that are configured to be implanted at or in the vicinity of the commissures of the native valve. 
     The cylindrical element of the valve support has first and second ends and a cylindrical body disposed between the first and second ends. The first end of the cylindrical element is coupled to the annular element while the second end defines a free end of the cylindrical element. For some applications of the present invention, the cylindrical element of the valve support is invertible such that (1) during a first period, the second end and the cylindrical body of the cylindrical element are disposed above the annular element (e.g., in the atrium of the heart), and (2) during a second period, the second end and the cylindrical body of the cylindrical element are disposed below the annular element (e.g., in the ventricle of the heart). 
     For some applications, techniques are applied to facilitate sealing of the interface between the valve support and the native valve, and/or the interface between the prosthetic valve and the native valve. For example, a sealing balloon may be placed on a valve-facing, lower side of the annular element of the valve support, the sealing balloon being configured to be inflated such that the balloon seals the interface between the valve support and the native valve. Alternatively or additionally, commissural helices are wrapped around chordae tendineae of the patient in order to facilitate sealing of the valve commissures around the valve support and/or around the valve. Further alternatively or additionally, the valve commissures are grasped by grasping elements that act in order to facilitate sealing of the commissures around the valve support and/or around the valve. For some applications, one or more of the aforementioned sealing elements facilitates anchoring of the prosthetic valve to the native valve in addition to facilitating sealing. 
     For some applications, the prosthetic valve comprises a wire frame, and a sealing material (such as latex) is disposed on the outer surface of the wire frame so as to form webbing between at least some of the struts of the wire frame, and to provide sealing between the wire frame and the native valve. 
     For some applications, an invertible prosthetic valve support is used to support a prosthetic valve. Typically, a sealing element is disposed circumferentially around a surface of the invertible prosthetic valve support that is initially an inner surface of the invertible prosthetic valve support. The invertible prosthetic valve support is anchored to the native valve, and is subsequently inverted. Subsequent to the inversion of the invertible prosthetic valve support, the sealing element is disposed on the outer surface of the invertible prosthetic valve support and acts to seal the interface between the outer surface and the native valve. 
     There is therefore provided, in accordance with some applications of the present invention, apparatus, including: 
     one or more valve support guide members configured to be delivered to one or more commissures of a native atrioventricular valve of a patient; 
     a prosthetic valve support configured to be advanced toward the native valve along the one or more valve support guide members and placed at the native valve; 
     a prosthetic valve configured to be coupled to the valve support; and 
     one or more sealing elements configured to facilitate sealing of an interface between the prosthetic valve support and the native valve. 
     For some applications, the sealing element includes a balloon disposed circumferentially around an outer surface of the prosthetic valve support. 
     For some applications, the sealing element includes one or more helices that are configured to facilitate sealing of commissures of the native valve with respect to the valve support by being wrapped around chordae tendineae of the native valve. 
     For some applications, the sealing element includes grasping elements that are configured to facilitate sealing of commissures of the native valve with respect to the valve support by grasping the commissures. 
     For some applications, the sealing element is configured to facilitate anchoring of the support to the native valve. 
     For some applications, the valve support is collapsible for transcatheter delivery and expandable to contact the native atrioventricular valve. 
     For some applications, the prosthetic valve includes two or more prosthetic leaflets. 
     For some applications, the native atrioventricular valve includes a mitral valve, and the prosthetic valve includes three prosthetic leaflets. 
     For some applications, the valve support guide members are removable from the patient following coupling of the prosthetic valve to the valve support. 
     For some applications, the valve support is shaped so as to define a distal portion which is configured to push aside, at least in part, native leaflets of the valve of the patient. 
     For some applications, the valve support is shaped so as to define one or more holes, the one or more holes being configured to facilitate slidable passage therethrough of a respective one of the one or more valve support guide members. 
     For some applications, the one or more valve support guide members includes one valve support guide member that is looped through first and second commissures of the atrioventricular valve in a manner in which a looped portion of the valve support guide member is disposed in a ventricle of the patient and first and second free ends of the valve support guide member are accessible from a site outside a body of the patient. 
     For some applications, the apparatus further includes: 
     a guide wire configured to be advanced, via the native atrioventricular valve, into a ventricle of the patient, and coupled to an inner wall of the patient&#39;s ventricle; and 
     a valve support guide member tube coupled to the guide wire, 
     and a distal portion of the valve support guide member is configured to loop through the valve support guide member tube, such that, in response to the valve support guide member being pushed distally, portions of the valve support guide member are pushed to respective commissures of the native valve. 
     For some applications, the prosthetic valve is shaped so as to define one or more protrusions configured to ensnare one or more native leaflets of the native valve of the patient. 
     For some applications, the protrusions are disposed in a sinusoidal configuration such that the protrusions conform with a saddle shape of the patient&#39;s native annulus. 
     For some applications, the protrusions are configured to prevent the native leaflets from interfering with a left ventricular outflow tract of the patient, by sandwiching the leaflets between the protrusions and the prosthetic valve support. 
     For some applications, the valve support includes: 
     a first end that is configured to be placed on an atrial side of a native atrioventricular valve of a patient; and 
     a second end that is configured, during a first period, to be disposed inside the patient&#39;s atrium, above the first end of the valve support, 
     the valve support being at least partially invertible in a manner in which, during a second period, the second end of the valve support is disposed at least partially inside a ventricle of the patient, below the first end of the valve support. 
     For some applications, the valve support includes an annular element and a generally cylindrical element coupled to the annular element, the generally cylindrical element being configured to push aside native leaflets of the native valve, and the cylindrical element has first and second ends and a cylindrical body that is disposed between the first and second ends. 
     For some applications, the sealing element includes a balloon disposed underneath the annular element and configured to facilitate sealing of an interface between the annular element and the native valve. 
     For some applications, the apparatus further includes one or more prosthetic valve guide members, the prosthetic valve guide members being configured to facilitate advancement of the prosthetic valve therealong and toward the valve support. 
     For some applications: 
     the first end of the cylindrical element is coupled to the annular element, 
     during a first period, the second end of the cylindrical element is disposed above the annular element in a manner in which the body of the cylindrical element is disposed above the annular element, and 
     the cylindrical element is invertible in a manner in which, during a second period, the second end of the cylindrical element is disposed below the annular element and the body of the cylindrical element is disposed below the annular element. 
     For some applications: 
     during the first period, the second end of the cylindrical element is disposed in an atrium of a heart of the patient and the annular element is positioned along an annulus of the native valve, 
     the prosthetic valve is advanceable along the one or more prosthetic valve guide members into a ventricle of the heart of the patient, and 
     in response to advancement of the prosthetic valve into the ventricle, the one or more prosthetic valve guide members are pulled into the ventricle and pull the second end and the body of the cylindrical element into the ventricle to invert the cylindrical element. 
     There is further provided, in accordance with some applications of the present invention, apparatus, including: 
     a prosthetic valve support configured to be advanced toward a native atrioventricular valve of a patient and placed at the native valve; 
     a prosthetic valve configured to be coupled to the valve support, the prosthetic valve being shaped so as to define first and second sets of one or more protrusions, each set of protrusions configured to ensnare a respective native leaflet of the native valve of the patient, the first set of protrusions being disposed within a first circumferential arc with respect to a longitudinal axis of the prosthetic valve, on a first side of a distal end of the prosthetic valve, the second set of protrusions being disposed within a second circumferential arc with respect to the longitudinal axis of the prosthetic valve, on a second side of the distal end of the prosthetic valve, the first and second sets being disposed so as to provide first and second gaps therebetween at the distal end of the prosthetic valve, at least one of the gaps having a circumferential arc of at least 20 degrees; and 
     one or more valve guide members configured to be delivered to one or more commissures of the native valve, and to guide the valve such that the first and second circumferential arcs are aligned with respective leaflets of the native valve and such that the first and second gaps are aligned with respective commissures of the native valve. 
     For some applications, the at least one of the gaps has a circumferential arc of at least 60 degrees. 
     For some applications, the first circumferential arc defines an angle of between 25 degrees and 90 degrees about the longitudinal axis of the prosthetic valve. 
     For some applications, the second circumferential arc defines an angle of between 25 degrees and 90 degrees about the longitudinal axis of the prosthetic valve. 
     For some applications, the first circumferential arc defines an angle of between 45 degrees and 75 degrees about the longitudinal axis of the prosthetic valve. 
     For some applications, the second circumferential arc defines an angle of between 45 degrees and 75 degrees about the longitudinal axis of the prosthetic valve. 
     There is additionally provided, in accordance with some applications of the present invention, a method, including: 
     determining an area defined by an annulus of a native atrioventricular valve of a patient; 
     selecting a prosthetic valve to be placed in the native valve by determining that the valve defines a cross-sectional area that is less than 90% of the area defined by the annulus; and 
     deploying the prosthetic valve at the native valve, 
     the selecting of the prosthetic valve facilitating sealing of the native valve with respect to the prosthetic valve by facilitating closing of leaflets of the native valve around the prosthetic valve, upon deployment of the prosthetic valve. 
     For some applications, selecting the prosthetic valve includes selecting a prosthetic valve having a material disposed on an outer surface thereof. 
     For some applications, selecting the prosthetic valve includes selecting a prosthetic valve having a material that prevents tissue growth disposed on an outer surface thereof. 
     For some applications, selecting the prosthetic valve includes selecting a prosthetic valve having a material that promotes tissue growth disposed on an outer surface thereof. 
     For some applications, selecting the prosthetic valve to be placed in the native valve includes determining that the valve defines a cross-sectional area that is less than 80% of the area defined by the annulus. 
     For some applications, selecting the prosthetic valve to be placed in the native valve includes determining that the valve defines a cross-sectional area that is less than 60% of the area defined by the annulus. 
     There is further provided, in accordance with some applications of the present invention, apparatus including: 
     a valve support for receiving a prosthetic valve, the valve support including:
         a first end that is configured to be placed on an atrial side of a native atrioventricular valve of a patient; and   a second end that is configured, during a first period, to be disposed inside the patient&#39;s atrium, above the first end of the valve support,   the valve support being at least partially invertible in a manner in which, during a second period, the second end of the cylindrical element is disposed at least partially inside a ventricle of the patient, below the first end of the valve support.       

     For some applications, the valve support includes a flexible wireframe covered by a fabric. 
     For some applications, the valve support is collapsible for transcatheter delivery and expandable to contact the native atrioventricular valve. 
     For some applications, the valve support defines a surface that is an inner surface of the valve support during the first period, and an outer surface of the valve support during the second period, and the apparatus further includes a sealing material that is disposed on the surface, such that during the second period the sealing material facilitates sealing between the valve support and the native valve. 
     For some applications, the first end includes a coupling element configured to couple the valve support to tissue of the native valve on the atrial side of the native valve. 
     For some applications, the first end is shaped to define barbs that are configured to couple the valve support to tissue of the native valve on the atrial side of the native valve 
     For some applications, the valve support includes: 
     an annular element configured to be positioned along a native annulus of the native atrioventricular valve; and 
     a flexible generally cylindrical element configured to be positioned in the native atrioventricular valve of the patient and to push aside native leaflets of the native valve, the first end of the cylindrical element defining the first end of the valve support, and the first end of the cylindrical element being coupled to the annular element. 
     For some applications, the apparatus further includes one or more valve support guide members configured to be delivered to one or more commissures of the native atrioventricular valve of the patient, and the one or more valve support guide members are configured to facilitate advancement of the valve support toward the native valve. 
     For some applications, the valve support is shaped so as to define one or more holes, the one or more holes configured to facilitate slidable passage therethrough of a respective one of the one or more valve support guide members. 
     For some applications, the one or more valve support guide members includes one valve support guide member that is looped through first and second commissures of the atrioventricular valve in a manner in which a looped portion of the valve support guide member is disposed in a ventricle of the patient and first and second free ends of the valve support guide member are accessible from a site outside a body of the patient. 
     For some applications, the apparatus further includes: 
     a guide wire configured to be advanced, via the native atrioventricular valve, into a ventricle of the patient, and coupled to an inner wall of the patient&#39;s ventricle; and 
     a valve support guide member tube coupled to the guide wire, 
     and a distal portion of the valve support guide member is configured to loop through the valve support guide member tube, such that, in response to the valve support guide member being pushed distally, portions of the valve support guide member are pushed to respective commissures of the native valve. 
     For some applications, the apparatus further includes one or more prosthetic valve guide members reversibly couplable to the cylindrical element in a vicinity of the second end of the cylindrical element, the prosthetic valve guide members being configured to facilitate advancement of the prosthetic valve therealong and toward the valve support. 
     For some applications, the apparatus further includes the prosthetic valve, and the prosthetic valve is couplable to the valve support. 
     For some applications: 
     during the first period, the second end of the cylindrical element is disposed in an atrium of a heart of the patient and the annular element is positioned along an annulus of the native valve, 
     the prosthetic valve is advanceable along the one or more prosthetic valve guide members into a ventricle of the heart of the patient, and 
     in response to advancement of the prosthetic valve into the ventricle, the one or more prosthetic valve guide members are pulled into the ventricle and pull the second end of the cylindrical element into the ventricle to invert the cylindrical element. 
     For some applications, the apparatus further includes one or more sealing elements configured to facilitate sealing of an interface between the prosthetic valve support and the native valve. 
     For some applications, the sealing element includes a balloon disposed circumferentially around a surface of the prosthetic valve support. 
     For some applications, the sealing element includes one or more helices that are configured to facilitate sealing of commissures of the native valve with respect to the valve support by being wrapped around chordae tendineae of the native valve. 
     For some applications, the sealing element includes grasping elements that are configured to facilitate sealing of commissures of the native valve with respect to the valve support by grasping the commissures. 
     For some applications, the sealing element is configured to facilitate anchoring of the support to the native valve. 
     For some applications, the apparatus further includes the prosthetic valve, and the prosthetic valve is couplable to the valve support. 
     For some applications, the prosthetic valve is collapsible for transcatheter delivery and expandable when exposed from within a delivery catheter. 
     For some applications, the prosthetic valve includes two or more prosthetic leaflets. 
     For some applications, the native atrioventricular valve includes a mitral valve, and the prosthetic valve includes three prosthetic leaflets. 
     For some applications, the prosthetic valve is shaped so as to define one or more protrusions configured to ensnare one or more native leaflets of the native valve of the patient. 
     For some applications, the protrusions are disposed in a sinusoidal configuration such that the protrusions conform with a saddle shape of the patient&#39;s native annulus. 
     For some applications, the protrusions are configured to prevent the native leaflets from interfering with a left ventricular outflow tract of the patient, by sandwiching the leaflets between the protrusions and the prosthetic valve support. 
     There is further provided, in accordance with some applications of the present invention, apparatus, including: 
     a guide wire configured to be advanced into a patient&#39;s ventricle via a native atrioventricular valve of the patient, and coupled to an inner wall of the patient&#39;s ventricle; 
     a valve support guide member tube coupled to the guide wire; 
     a valve support guide member, a distal portion of the valve support guide member looping through the valve support guide member tube, such that, in response to the valve support guide member being pushed distally, portions of the valve support guide member are pushed to respective commissures of the native valve; 
     a prosthetic valve support configured to be advanced toward the commissures of the native valve along the valve support guide member portions; and 
     a prosthetic valve configured to be coupled to the valve support. 
     For some applications, first and second free ends of the valve support guide member are accessible from a site outside a body of the patient. 
     For some applications, the valve support includes: 
     an annular element configured to be positioned along a native annulus of the native atrioventricular valve; and 
     a generally cylindrical element configured to be positioned in the native atrioventricular valve of the patient and to push aside native leaflets of the native valve, the cylindrical element being coupled to the annular element, at a first end of the cylindrical element. 
     For some applications, the valve support is shaped so as to define one or more holes, the one or more holes configured to facilitate slidable passage therethrough of respective portions of the portions of the valve support guide member. 
     For some applications, the guide member is configured to facilitate advancement of the prosthetic valve therealong and toward the valve support. 
     For some applications, the prosthetic valve is collapsible for transcatheter delivery and expandable when exposed from within a delivery catheter. 
     For some applications, the prosthetic valve includes two or more prosthetic leaflets. 
     For some applications, the native atrioventricular valve includes a mitral valve, and the prosthetic valve includes three prosthetic leaflets. 
     For some applications, the guide member is removable from the patient following the coupling of the prosthetic valve to the valve support. 
     For some applications, the prosthetic valve is shaped so as to define one or more protrusions configured to ensnare one or more native leaflets of the native valve of the patient. 
     For some applications, the protrusions are disposed in a sinusoidal configuration such that the protrusions conform with a saddle shape of the patient&#39;s native annulus. 
     For some applications, the protrusions are configured to prevent the native leaflets from interfering with a left ventricular outflow tract of the patient, by sandwiching the leaflets between the protrusions and the prosthetic valve support. 
     For some applications, the apparatus further includes one or more sealing elements configured to facilitate sealing of an interface between the prosthetic valve support and the native valve. 
     For some applications, the sealing element includes a balloon disposed circumferentially around a surface of the prosthetic valve support. 
     For some applications, the sealing element includes one or more helices that are configured to facilitate sealing of commissures of the native valve with respect to the valve support by being wrapped around chordae tendineae of the native valve. 
     For some applications, the sealing element includes grasping elements that are configured to facilitate sealing of commissures of the native valve with respect to the valve support by grasping the commissures. 
     For some applications, the sealing element is configured to facilitate anchoring of the support to the native valve. 
     There is additionally provided, in accordance with some applications of the present invention, apparatus, including: 
     one or more valve guide members configured to be delivered to one or more commissures of a native atrioventricular valve of a patient; 
     a prosthetic valve configured to be advanced to be advanced toward the native valve along the one or more valve guide members and placed at the native valve at least the one or more commissures; and 
     one or more proximally-facing grasping elements that are configured to facilitate sealing of commissures of the native valve with respect to the valve by:
         being inserted into a ventricle of the patient; and   being pulled proximally and being closed around tissue in a vicinity of the commissures.       

     For some applications, the grasping elements include two surfaces that are hingedly coupled to one another, and that are configured to facilitate the sealing of the commissures of the native valve with respect to the prosthetic valve by being closed about the hinge with respect to one another. 
     There is further provided, in accordance with some applications of the present invention, a method, including: 
     advancing one or more valve support guide members toward one or more commissures of a native atrioventricular valve of a patient; 
     placing a prosthetic valve support at the native atrioventricular valve by advancing the valve support along the one or more valve support guide members; 
     coupling a prosthetic valve to the prosthetic valve support; and 
     facilitating sealing of an interface between the prosthetic valve support and the native valve by deploying a sealing element in a vicinity of the interface. 
     There is additionally provided, in accordance with some applications of the present invention, a method including: 
     placing a first end of a prosthetic valve support on an atrial side of a native atrioventricular valve of a patient, such that a second end of the valve support is disposed, during a first period, inside the patient&#39;s atrium, above the first end of the valve support; and 
     subsequent to the placing of the valve support, inverting at least a portion of the valve support such that, during a second period, the second end of the valve support is disposed at least partially inside a ventricle of the patient, below the first end of the valve support. 
     There is additionally provided, in accordance with some applications of the present invention, a method, including: 
     advancing a guide wire, via a native atrioventricular valve, into a ventricle of the patient, a valve support guide member tube being coupled to the guide wire; 
     coupling a distal end of the guide wire to an inner wall of the patient&#39;s ventricle; and 
     causing portions of a valve support guide member to be pushed to respective commissures of the native valve, by pushing the guide member distally, a distal portion of the valve support guide member looping through the valve support guide member tube; 
     advancing a prosthetic valve support toward the commissures of the native valve along the valve support guide member portions; and 
     coupling a prosthetic valve to the valve support. 
     There is further provided, in accordance with some applications of the present invention, a method, including: 
     advancing one or more valve guide members toward one or more commissures of a native atrioventricular valve of a patient; 
     placing a prosthetic valve at the native atrioventricular valve by advancing the valve along the one or more valve guide members; and 
     facilitating sealing of commissures of the native valve with respect to the valve by:
         inserting into a ventricle of the patient one or more grasping elements that are coupled to the prosthetic valve;   pulling the grasping elements proximally; and   closing the grasping elements around tissue in a vicinity of the commissures.       

     The present invention will be more fully understood from the following detailed description of embodiments thereof, taken together with the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-B  are schematic illustrations of advancement of one or more guide members toward respective commissures of a mitral valve, in accordance with some applications of the present invention; 
         FIGS. 1C-D  are schematic illustrations of the advancement and deployment of commissural anchors via the guide members, in accordance with some applications of the present invention; 
         FIGS. 2A-D  are schematic illustrations of the advancement of a prosthetic valve support toward a native atrioventricular valve of a patient, in accordance with some applications of the present invention; 
         FIGS. 2E-F  are schematic illustrations of locking of the prosthetic valve support at the native valve, in accordance with some applications of the present invention; 
         FIGS. 2G-K  are schematic illustrations of the advancement of a prosthetic valve and the coupling of the prosthetic valve to the valve support, in accordance with some applications of the present invention; 
         FIGS. 3A-B  are schematic illustrations of the advancement of a prosthetic valve support toward a native atrioventricular valve of a patient, the valve support including a sealing balloon, in accordance with some applications of the present invention; 
         FIGS. 3C-D  are schematic illustrations of locking of the prosthetic valve support at the native valve, the valve support including the sealing balloon, in accordance with some applications of the present invention; 
         FIGS. 4A-C  are schematic illustrations of a valve support being used with commissural helices that facilitate anchoring and/or sealing of the valve support, in accordance with some applications of the present invention; 
         FIGS. 5A-D  are schematic illustrations of grasping elements being used to anchor and/or provide sealing of a prosthetic valve, in accordance with some applications of the present invention; 
         FIGS. 6A-B  are schematic illustrations of a prosthetic valve that includes a sealing material, in accordance with some applications of the present invention; 
         FIGS. 7A-F  are schematic illustrations of a guide wire delivery system, in accordance with some applications of the present invention; 
         FIGS. 8A-C  are schematic illustrations of a valve support that has a cylindrical element that is invertible, in accordance with some applications of the present invention; 
         FIGS. 9A-D  are schematic illustrations of the advancement of an invertible prosthetic valve support toward a native atrioventricular valve of a patient, in accordance with some applications of the present invention; 
         FIG. 9E  is a schematic illustration of inversion of the invertible prosthetic valve support at the native valve, in accordance with some applications of the present invention; 
         FIGS. 9F-H  are schematic illustrations of the advancement of a prosthetic valve and the coupling of the prosthetic valve to the invertible valve support, in accordance with some applications of the present invention; 
         FIG. 10  is a schematic illustration of a prosthetic valve, the cross-sectional area of which is smaller than the area defined by the patient&#39;s native valve annulus, in accordance with some applications of the present invention; 
         FIGS. 11A-D  are schematic illustrations of a prosthetic valve that defines protrusions from portions of the distal end of the valve, in accordance with some applications of the present invention; and 
         FIGS. 12A-C  are schematic illustrations of a prosthetic valve that defines distal protrusions that are disposed sinusoidally around the circumference of the valve, in accordance with some applications of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference is now made to  FIGS. 1A-B , which are schematic illustrations of a system  20  for replacing an atrioventricular valve  5  of a patient comprising one or more guide members  21   a  and  21   b  which are advanced toward first and second commissures  8  and  10  of valve  5  of a heart  2  of the patient, in accordance with some applications of the present invention. For some applications, guide members  21   a  and  21   b  comprise distinct guide members. Alternatively (as shown in  FIGS. 8A-F ), only one guide member is looped through commissures  8  and  10  in a manner in which the guide member defines a looped portion between commissures  8  and  10  (i.e., a portion of the guide member that is disposed in a ventricle  6  of heart  2 ), and first and second free ends which are disposed and accessible at a site outside the body of the patient. For such applications, the guide member defines portions  21   a  and  21   b.    
     For some applications, guide members  21   a  and  21   b  comprise guide wires having a diameter of 0.035 inches. 
     The transcatheter procedure typically begins with the advancing of a semi-rigid guide wire into a right atrium  4  of the patient. The semi-rigid guide wire provides a guide for the subsequent advancement of a sheath  25  therealong and into the right atrium. Once sheath  25  has entered the right atrium, the semi-rigid guide wire is retracted from the patient&#39;s body. Sheath  25  typically comprises a 13-20 F sheath, although the size may be selected as appropriate for a given patient. Sheath  25  is advanced through vasculature into the right atrium using a suitable point of origin typically determined for a given patient. For example:
         sheath  25  may be introduced into the femoral vein of the patient, through an inferior vena cava, into the right atrium, and into the left atrium transseptally, typically through the fossa ovalis;   sheath  25  may be introduced into the basilic vein, through the subclavian vein to the superior vena cava, into the right atrium, and into the left atrium transseptally, typically through the fossa ovalis; or   sheath  25  may be introduced into the external jugular vein, through the subclavian vein to the superior vena cava, into the right atrium, and into the left atrium transseptally, typically through the fossa ovalis.       

     In some applications of the present invention, sheath is advanced through the inferior vena cava of the patient and into the right atrium using a suitable point of origin typically determined for a given patient. 
     Sheath  25  is advanced distally until sheath  25  reaches the interatrial septum. For some applications, a resilient needle and a dilator (not shown) are advanced through the sheath and into the heart. In order to advance the sheath transseptally into the left atrium, the dilator is advanced to the septum, and the needle is pushed from within the dilator and is allowed to puncture the septum to create an opening that facilitates passage of the dilator and subsequently the sheath therethrough and into the left atrium. The dilator is passed through the hole in the septum created by the needle. Typically, the dilator is shaped to define a hollow shaft for passage along the needle, and the hollow shaft is shaped to define a tapered distal end. This tapered distal end is first advanced through the hole created by the needle. The hole is enlarged when the gradually increasing diameter of the distal end of the dilator is pushed through the hole in the septum. 
     The advancement of sheath  25  through the septum and into the left atrium is followed by the extraction of the dilator and the needle from within sheath  25 . 
       FIGS. 1C-D  and  2 A-B show advancement of one or more tissue anchors  30   a  and  30   b  along guide members  21   a  and  21   b , respectively. Anchors  30   a  and  30   b  comprise a flexible, biocompatible material (e.g., nitinol) and comprise one or more (e.g., a plurality of) radially-expandable prongs  32  (e.g., barbs). Each anchor  30   a  and  30   b  is reversibly coupled to a respective delivery lumen  27   a  and  27   b . Each delivery lumen  27  slides around a respective guide member  21 . A respective surrounding sheath  26   a  and  26   b  surrounds each delivery lumen  27   a  and  27   b  and around anchors  30   a  and  30   b  at least in part in order to compress and prevent expansion of prongs  32  of tissue anchors  30   a  and  30   b.    
     As shown in  FIG. 1D , the distal ends of lumens  27   a  and  27   b  are reversibly coupled to ribbed crimping structures  34 . As described hereinbelow, anchors  30   a  and  30   b  are anchored to ventricular surfaces of commissures  8  and  10 . Following the anchoring, ribbed crimping structures  34  extend from anchors  30   a  and  30   b  through commissures  8  and  10 , respectively, and toward the atrial surfaces of commissures  8  and  10 . Ribbed crimping structures  34  are configured to facilitate anchoring of a valve support (described hereinbelow) to the atrial surfaces of commissures  8  and  10 . 
     Anchors  30   a  and  30   b , ribbed crimping structures  34 , and the distal ends of surrounding sheaths  26   a  and  26   b  are advanced into ventricle  6 . Subsequently, anchors  30   a  and  30   b  are pushed distally from within sheaths  26   a  and  26   b , (or sheaths  26   a  and  26   b  are pulled proximally with respect to anchors  30   a  and  30   b ) to expose anchors  30   a  and  30   b . As anchors  30   a  and  30   b  are exposed from within sheaths  26   a  and  26   b , prongs  32  are free to expand, as shown in  FIG. 1D . Prongs  32  expand such that anchors  30   a  and  30   b  assume a flower shape. Prongs  32 , collectively in their expanded state, create a larger surface area to engage tissue than in their compressed states. Following the exposing of anchors  30   a  and  30   b , sheaths  26   a  and  26   b  are extracted. 
     As shown in  FIG. 2B , lumens  27   a  and  27   b  are pulled proximally so that prongs  32  of anchors  30   a  and  30   b  engage respective ventricular surface of commissures  8  and  10 . Prongs  32  create a large surface area which restricts proximal motion of anchors  30   a  and  30   b  from commissures  8  and  10 , respectively. 
     For some applications, following the anchoring of anchors  30   a  and  30   b  to commissures  8  and  10 , respectively, guide members  21   a  and  21   b  are removed from the body of the patient. 
     Reference is now made to  FIGS. 2C-F , which are schematic illustrations of the advancement of a prosthetic valve support  40  along lumens  27   a  and  27   b , in accordance with some applications of the present invention. In such a manner, lumens  27   a  and  27   b  function as valve support guide members. Support  40  comprises a collapsible skirt having a proximal annular element  44  and a distal cylindrical element  42 . Support  40  is configured to assume a collapsed state (e.g., surrounded by a sheath or overtube  50  shown in  FIG. 2C ) for minimally-invasive delivery to the diseased native valve, such as by percutaneous or transluminal delivery using one or more catheters.  FIG. 20  and the other figures show support  40  in an expanded state after delivery in right atrium  4  and advancement toward the native valve. As shown in  FIG. 2D , support  40  is shaped so as to define one or more (e.g., two, as shown in View A) holes  46   a  and  46   b  for slidable advancement of support  40  along lumens  27   a  and  27   b , respectively. That is, prior to introduction of support  40  into the body of the patient, lumens  27   a  and  27   b  are threaded through holes  46   a  and  46   b , respectively, and support  40  is slid along lumens  27   a  and  27   b . Support  40  is slid by pushing elements  52   a  and  52   b  which surround delivery lumens  27   a  and  27   b , respectively. 
     It is to be noted that support  40  is slid along lumens  27   a  and  27   b  by way of illustration and not limitation. That is, for some applications, following the anchoring of anchors  30   a  and  30   b  to commissures  8  and  10 , respectively, guide members  21   a  and  21   b  are not removed from the body of the patient, but rather lumens  27   a  and  27   b  are removed (e.g., by being decoupled from crimping structures  34 ) leaving behind anchors  30   a  and  30   b  and guide members  21   a  and  21   b . Guide members  21   a  and  21   b  may then be threaded through holes  46   a  and  46   b , respectively, and support  40  is slid along guide members  21   a  and  21   b . In such a manner, guide members  21   a  and  21   b  function as valve support guide members. 
     Support  40  comprises a collapsible flexible support frame  48 , which is at least partially covered by a covering  49 . Support  40  is configured to be placed at native valve  5 , such that cylindrical element  42  passes through the orifice of the native valve and extends towards, and, typically partially into, ventricle  6  (as shown in  FIG. 2E ). Cylindrical element  42  typically pushes aside and presses against native leaflets of native valve  5  at least in part, which are left in place during and after implantation of the prosthetic valve. Annular element  44  is configured to be placed around a native annulus  11  of the native valve, and to extend at least partially into an atrium  4  such that annular element  44  rests against the native annulus. Annular element  44  is typically too large to pass through the annulus, and may, for example, have an outer diameter of between 30 and 60 mm. 
     For some applications, collapsible support frame  48  comprises a stent, which comprises a plurality of struts. The struts may comprise, for example, a metal such as nitinol or stainless steel. For some applications, frame comprises a flexible metal, e.g., nitinol, which facilitates compression of support  40  within a delivery sheath or overtube  50 . For some applications, covering  49  comprises a fabric, such as a woven fabric, e.g., Dacron. Covering  49  is typically configured to cover at least a portion of cylindrical element  42 , and at least a portion of annular element  44 . The covering may comprise a single piece, or a plurality of pieces sewn together. 
     As shown in  FIG. 2D , pushing elements  52   a  and  52   b  are each coupled to locking crimping elements  64   a  and  64   b , respectively. Locking crimping elements  64   a  and  64   b  are disposed adjacently, proximally to holes  46   a  and  46   b  respectively of valve support  40 . These techniques enable the surgeon to readily bring crimping elements  64   a  and  64   b  to the appropriate sites along annular element  44 , without the need for excessive imaging, such as fluoroscopy. 
       FIG. 2E  shows valve support  40  prior to implantation at annulus  11 . As shown, ribbed crimping structures  34  project away from anchors  30   a  and  30   b , through commissures  8  and  10 , and toward atrium  4 . Valve support  40  is advanced along lumens  27   a  and  27   b  toward structures  34  by being pushed by pushing elements  52   a  and  52   b  and locking crimping elements  64   a  and  64   b.    
     In  FIG. 2F , valve support  40  is further pushed by pushing elements  52   a  and  52   b  and locking crimping elements  64   a  and  64   b  such holes  46   a  and  46   b  of support  40  advance around ribbed crimping structures  34 . As holes  46   a  and  46   b  are advanced around ribbed crimping structures  34 , locking crimping elements  64   a  and  64   b  advance over and surround ribbed crimping elements  34  to lock in place valve support  40  from an atrial surface of valve  5 . 
     Responsively to the placement of valve support  40  at native valve  5 , cylindrical element  42  is positioned partially within ventricle  6  and native leaflets  12  and  14  of native valve  5  are pushed aside. 
     As shown in section A-A, ribbed crimping structures  34  are shaped so as to define a plurality of male couplings. Locking crimping elements  64   a  and  64   b  each comprise a cylindrical element having an inner lumen that is shaped so as to surround a respective ribbed crimping structure  34 . Each inner lumen of locking crimping elements  64   a  and  64   b  is shaped so as to define female couplings to receive the male couplings of ribbed crimping structure  34 . The female couplings of locking crimping element  64  are directioned such that they facilitate distal advancement of locking crimping element  64  while restricting proximal advancement of locking crimping element  64 . When the female couplings of locking crimping element  64  receive the male couplings of ribbed crimping structure  34 , valve support  40  is locked in place from an atrial surface of valve  5 . It is to be noted that for some applications, ribbed crimping elements  34  comprise female couplings, and locking crimping elements  64  comprise male couplings. 
     Reference is now made to  FIGS. 2G-K  which are schematic illustrations of the coupling of a prosthetic atrioventricular valve  80  to valve support  40 , in accordance with some applications of the present invention. Support  40  receives the prosthetic valve and functions as a docking station. Thus, the docking station is a coupling element that provides coupling between two other elements (in this case, between annulus  11  and the prosthetic valve.) 
     Following the placement of support  40  at annulus  11 , pushing elements  52   a  and  52   b  and sheath or overtube  50  are removed from the body of the patient, leaving behind lumens  27   a  and  27   b , as shown in  FIG. 2G . 
     As shown in  FIG. 2G , a guide wire  72  is advanced toward ventricle  6  and facilitates the advancement of an overtube  70  through sheath  25  and the positioning of a distal end of overtube  70  within ventricle  6 . Overtube  70  facilitates the advancement of prosthetic valve  80  in a compressed state, toward valve support  40 . 
       FIG. 2H  shows partial deployment of valve  80  within ventricle  6  of heart  2 . Valve  80  is shown comprising a flexible wire frame comprising a plurality of stent struts by way of illustration and not limitation. The wireframe of valve  80  comprises a flexible metal, e.g., nitinol or stainless steel. It is to be noted that the wireframe of valve  80  is covered by a covering (not shown for clarity of illustration) comprising a braided mesh or in a fabric such as a woven fabric, e.g., Dacron. The covering is typically configured to cover at least a portion of the frame. The covering may comprise a single piece, or a plurality of pieces sewn together. 
     Following the partial deployment of valve  80  in ventricle  6 , overtube  70  is pulled proximally to pull valve  80  proximally such that cylindrical element  42  of valve support  40  surrounds a proximal portion of prosthetic valve  80 . Valve  80  has a tendency to expand such that valve  80  is held in place with respect to valve support  40  responsively to radial forces acted upon valve support  40  by prosthetic valve  80 . 
     Valve  80  comprises a plurality of distal protrusions (e.g., snares). When valve  80  is pulled proximally, as described hereinabove, protrusions  84  ensnare and engage the native leaflets of the atrioventricular valve. By the ensnaring of the native leaflets, protrusions  84  sandwich the native valve between protrusions  84  and prosthetic valve support  40 . Such ensnaring helps further anchor prosthetic valve  80  to the native atrioventricular valve. The scope of the present invention includes using any sort of protrusions (e.g., hooks) that protrude from the distal end of the main frame of prosthetic valve  80  and that are configured such that the native valve is sandwiched between the protrusions and valve support  40 . Typically, the protrusions cause sandwiching of the native valve leaflets, such that the leaflets do not interfere with the left ventricular outflow tract (LVOT). 
     For some applications, during the procedure, the prosthetic valve is pulled back proximally with respect to valve support, as described hereinabove. The prosthetic valve is pulled back to a position with respect to valve support that is such that protrusions  84  prevent the native leaflets from interfering with the LVOT, by sandwiching the native leaflets between the protrusions and the valve support. The prosthetic valve is then deployed at this position. 
     For some applications, protrusions are disposed on the valve on the sides of the valve that are adjacent to the anterior and posterior leaflets of the native valve, and the valve does not includes protrusions on the portions of the valve that are adjacent to the commissures of the native valve, as described with reference to  FIGS. 11A-D . For some applications, the protrusions are disposed in a sinusoidal configuration in order to conform with the saddle shape of the native valve, as described hereinbelow with reference to  FIGS. 12A-C . 
     Additionally, as shown in  FIG. 2J , valve  80  comprises one or more (e.g., a plurality, as shown) coupling elements  81  at the proximal end of valve  80 . Overtube  70 , which facilitates the advancement of prosthetic valve  80 , is reversibly coupled to valve  80 , via coupling elements  81 . 
     Prosthetic valve  80  is configured for implantation in and/or at least partial replacement of a native atrioventricular valve  5  of the patient, such as a native mitral valve or a native tricuspid valve. Prosthetic valve  80  is configured to assume a collapsed state for minimally-invasive delivery to the diseased native valve, such as by percutaneous or transluminal delivery using one or more catheters.  FIG. 2J  shows prosthetic valve  80  in an expanded state after delivery to the native valve. 
     Reference is now made to  FIG. 2K  which shows a bird&#39;s-eye view of valve  80 . Prosthetic valve  80  further comprises a plurality of valve leaflets  82 , which may be artificial or tissue-based. The leaflets are typically coupled to an inner surface of the valve prosthesis. Leaflets  82  are coupled, e.g., sewn, to the frame and/or to the covering. For applications in which the prosthetic valve is configured to be implanted at the native mitral valve, the prosthetic valve typically comprises three leaflets  82   a ,  82   b , and  82   c , as shown in  FIG. 2K . 
     Reference is now made to  FIGS. 3A-D , which are schematic illustrations of the advancement of prosthetic valve support  40  toward native atrioventricular valve  5  of a patient, the valve support including a sealing balloon  90 , in accordance with some applications of the present invention. The steps shown in  FIGS. 3A-C  are generally similar to those shown in  FIGS. 2C-F . For some applications, sealing balloon  40  is disposed on the valve-facing, lower side of annular element  44  of the prosthetic valve support.  FIG. 3D  shows valve support  40 , the valve support having been implanted at annulus  11 . Typically, at this stage, balloon  40  is inflated, as shown in the transition from  FIG. 3C  to  FIG. 3D . The balloon is inflated via an inflation lumen  92 , shown in  FIG. 3C , for example. For some applications, the balloon seals the interface between the prosthetic valve support and native annulus  11 , thereby reducing retrograde blood flow from ventricle  6  into atrium  4 , relative to retrograde blood flow in the absence of a sealing balloon. For some applications, the balloon is inflated prior to the placement of the prosthetic support at annulus  11 . 
     Reference is now made to  FIGS. 4A-C , which are schematic illustrations of prosthetic valve support  40  being used with commissural helices  100   a  and  100   b  that facilitate anchoring and/or sealing of the valve support, in accordance with some applications of the present invention. For some applications, commissural helices are used as an alternative or in addition to anchors  30   a  and  30   b  and/or other anchoring elements described herein, in order to facilitate the anchoring of valve support  40 . 
     Commissural helices  100   a  and  100   b  are typically placed at commissures  8  and  10  in a generally similar technique to that described with reference to anchors  30   a  and  30   b . Typically, each helix  30   a  and  30   b  is reversibly coupled to a respective delivery lumen  27   a  and  27   b . As described above, each delivery lumen  27  slides around a respective guide member  21 , and a respective surrounding sheath  26   a  and  26   b  surrounds each delivery lumen  27   a  and  27   b.    
     Commissural helices  100   a  and  100   b  (optionally, ribbed crimping structures  34 ), and the distal ends of surrounding sheaths  26   a  and  26   b  are advanced into ventricle  6 . The helices are pushed out of the distal ends of surrounding sheaths  26   a  and  26   b . Subsequently, the helices are rotated proximally such that the helices wrap around at least some chordae tendineae  102  of the patient. Following the advancement of the helices out of sheaths  26   a  and  26   b , the sheaths are extracted. For some applications the helices are conical helices (as shown), and the wider end of the conical helix is disposed at the proximal end of the helix. 
     Subsequent to the placement of commissural helices  100   a  and  100   b  around the chordae tendineae, prosthetic valve support  40  is placed at annulus  11 , in accordance with the techniques described hereinabove, and as shown in  FIG. 4B . Subsequently, prosthetic valve  80  is coupled to the prosthetic valve support, in accordance with the techniques described hereinabove, and as shown in  FIG. 4C . 
     Typically, commissural helices  100   a  and  100   b  facilitate sealing of native commissures  8  and  10 , thereby reducing retrograde blood flow via the commissures, relative to retrograde blood flow in the absence of the helices. Further typically, the sealing of the native commissures facilitates anchoring of the prosthetic valve support to native valve  5 . 
     Reference is now made to  FIGS. 5A-D , which are schematic illustrations of grasping elements  106   a  and  106   b  being used to anchor prosthetic valve  80 , in accordance with some applications of the present invention. For some applications, guide members  21   a  and  21   b  are advanced toward first and second commissures  8  and  10  of valve  5  of the patient, as described hereinabove. Grasping elements  106   a  and  106   b  are reversibly coupled to distal ends of delivery lumen  27   a  and  27   b , the delivery lumens being advanced over respective guide members, as described hereinabove. For some applications, the guiding members and the grasping elements are advanced toward the patient&#39;s commissures via surrounding sheaths  26   a  and  26   b , the surrounding sheaths being generally as described hereinabove. The grasping elements are typically placed distally to the commissures in a proximally-facing configuration, as shown in  FIG. 5A . For example, as shown, the grasping elements may be configured to be proximally facing due to the coupling of the grasping elements to the guide members. 
     Subsequent to the placement of grasping elements  106   a  and  106   b  distally to native commissures  8  and  10 , prosthetic valve  80  is advanced toward native valve  5 , as shown in  FIG. 5B . For example, the prosthetic valve may be advanced over delivery lumens  27   a  and  27   b , as shown. The prosthetic valve is placed at the native valve and, subsequently, the grasping elements are retracted proximally toward commissures  8  and  10 , as shown in the transition from  FIG. 5B  to  FIG. 5C . For some applications, the grasping elements are coupled to valve  80  via coupling tubes  107   a  and  107   b , the coupling tubes being coupled to the sides of the valve, as shown. The grasping elements are closed such that the native commissures are grasped and sealed by the grasping elements, as shown in  FIG. 5D . Typically, the grasping elements define two surfaces that are hingedly coupled to each other. For example, the grasping elements may include forceps, as shown. The grasping elements are closed by closing the surfaces about the hinge, with respect to one another. 
     Typically, grasping elements  106   a  and  106   b  facilitate sealing of native commissures  8  and  10 , thereby reducing retrograde blood flow via the commissures, relative to retrograde blood flow in the absence of the grasping elements. Further typically, the sealing of the native commissures facilitates anchoring of the prosthetic valve to native valve  5 . 
     Although not shown, for some applications, prosthetic valve support  40  is used in addition to grasping elements  106   a  and  106   b , in order to anchor prosthetic valve  80  to native valve  5 . For some applications, the grasping elements are used to anchor and/or provide sealing for prosthetic valve support  40  (instead of, or in addition to, being used to anchor prosthetic valve  80 , as shown). For such applications, generally similar techniques are used to those described with respect to the use of the grasping elements for anchoring the prosthetic valve, mutatis mutandis. 
     Reference is now made to  FIGS. 6A-B , which are schematic illustrations of prosthetic valve  80 , the prosthetic valve comprising a sealing material  110  on an outer surface of the valve, in accordance with some applications of the present invention. For some applications, prosthetic valve  80  is used in conjunction with prosthetic valve support  40 , as described hereinabove. The techniques for implanting prosthetic valve  80  as shown in  FIGS. 6A-B  are generally similar to those described hereinabove. Typically, sealing material  110  seals the interface between the prosthetic valve and native valve  5 . The sealing material reduces retrograde blood flow from ventricle  6  into atrium  4 , relative to retrograde blood flow in the absence of the sealing material. Typically, the sealing material is composed of latex, dacron, and/or any other suitable biocompatible material. The sealing material is typically placed around at least a portion of the wire frame of the prosthetic valve so as to form a webbing between struts of the wire frame. 
     Reference is now made to  FIGS. 7A-F , which are schematic illustrations of a guide wire delivery system, in accordance with some applications of the present invention. As described hereinabove (e.g., with reference to  FIGS. 2C-F ), for some applications, guide members  21   a  and  21   b , function as valve support guide members, by support  40  being slid along guide members  21   a  and  21   b . For some applications, only one guide member  21  is looped through commissures  8  and  10  in a manner in which the guide member defines a looped portion between commissures  8  and  10  (i.e., a portion of the guide member that is disposed in a ventricle  6  of heart  2 ), and first and second free ends, which are disposed and accessible at a site outside the body of the patient. For such applications, the guide member defines portions  21   a  and  21   b.    
     For some applications, an anchor  302  is advanced toward the vicinity of apex  304  of heart  2 , via sheath  25 , and is anchored to the vicinity of the apex, as shown in  FIG. 7A . A guidewire  306  extends proximally from anchor. Guide member  21  passes through a guide member tube  320 , the guide member tube being coupled to guidewire  306 . Guide member  21  is pushed distally. Guide member tube  320  is unable to advance distally over guidewire  306 , due to the coupling of the guide member tube to the guidewire. Therefore, the pushing of guide member  21  distally, causes portions  21   a  and  21   b  to spread apart from one another and to be pushed against commissures  8  and  10  of native valve  5 . Portions  21   a  and  21   b  are then used to guide valve support  40  to the commissures, as shown in  FIGS. 7B-F , using generally similar techniques to those described hereinabove, except for the differences described hereinbelow. 
     As shown in  FIG. 7B , valve support  40  is slid over guide member portions  21   a  and  21   b , by pushing elements  52   a  and  52   b . Since the guide member portions are positioned at commissures  8  and  10 , the guide member portions guide the distal ends of pushing elements  52   a  and  52   b , such that the pushing elements push the valve support against the commissures, as shown in  FIG. 7C . 
     Subsequent to the placement of valve support  40  at the native valve, prosthetic atrioventricular valve  80  is coupled to valve support  40 . For some applications, pushing elements  52   a  and  52   b  continue to push the valve support against the native valve, during the coupling of the prosthetic valve to the valve support. As described hereinabove, overtube  70  is advanced into ventricle  6 , as shown in  FIG. 7D .  FIG. 7E  shows prosthetic valve having been partially deployed in the ventricle. Following the partial deployment of valve  80  in ventricle  6 , overtube  70  is pulled proximally to pull valve  80  proximally such that cylindrical element  42  of valve support  40  surrounds a proximal portion of prosthetic valve  80 . Valve  80  has a tendency to expand such that valve  80  is held in place with respect to valve support  40  responsively to radial forces acted upon valve support  40  by prosthetic valve  80 . During the pulling back of overtube  70 , pushing elements  52   a  and  52   b  push valve support  40  against the valve, thereby providing a counter force against which overtube  70  is pulled back. For some applications, the pushing of the valve support against the commissures is such that it is not necessary to use anchors for anchoring the valve support to the native valve during the coupling of the prosthetic valve to the valve support. Alternatively, in addition to the pushing elements providing a counter force against which the prosthetic valve is pulled, anchors are used to anchor the valve support to the native valve during the coupling of the prosthetic valve to the valve support. 
     As described hereinabove, valve  80  comprises a plurality of distal protrusions  84 . When valve  80  is pulled proximally, as described hereinabove, protrusions  84  ensnare and engage the native leaflets of the atrioventricular valve. By the ensnaring of the native leaflets, protrusions  84  sandwich the native valve between protrusions  84  and prosthetic valve support  40 . Such ensnaring helps further anchor prosthetic valve  80  to the native atrioventricular valve. 
     Subsequent to the placement of the prosthetic valve at the native valve, sheath  25 , overtube  70 , pushing elements  52   a  and  52   b , guide member  21 , anchor  302 , and guidewire  306  are removed from the patient&#39;s body, as shown in  FIG. 7F , which shows the prosthetic valve in its deployed state. For some applications, in order to remove guide member  21  from the patient&#39;s body, guide member portions  21   a  and  21   b  are decoupled from guide member tube  320 . For example, the guide member portions may be coupled to the guide member tube via threading, the guide member portions being decoupled from the guide member tube by unscrewing the guide member portions from the guide member tube. 
     Reference is now made to  FIGS. 8A-C  which are schematic illustrations of a system  120  comprising an invertible valve support  140 , in accordance with some applications of the present invention. Invertible valve support  140  is identical to valve support  40  described herein, with the exception that the cylindrical element of valve support  140  is invertible, as is described hereinbelow. Additionally, the method of advancing toward and implanting valve support  140  at annulus  11  is identical to the methods of advancing toward and implanting valve support  40  at annulus  11 , as described hereinabove. 
     Valve support  140  comprises an annular element  144  (that is identical to annular element  44  described hereinabove) and a cylindrical element  142 . Cylindrical element  142  has a first end  150 , a second end  152 , and a cylindrical body  153  disposed between first and second ends  150  and  152 . Cylindrical element  142  is attached to annular element  144  at first end  150  of cylindrical element  142 . 
     During and following implantation of support  140  at annulus  11 , as shown in  FIG. 8A , cylindrical element  142  is disposed above annular element  144  in a manner in which second end  152  and cylindrical body  153  are disposed above annular element  144  and within atrium  4 . One or more elongate guide members  146   a  and  146   b  are reversibly coupled to cylindrical element  142  in a vicinity of second end  152 . Elongate guide members  146   a  and  146   b  facilitate (a) advancement of prosthetic valve  80  therealong and toward valve support  140 , and (b) inversion of cylindrical element  142  toward ventricle  6  when at least a portion of valve  80  is deployed within ventricle  6  (as shown in  FIG. 8B ). 
     The configuration of valve support  140  as shown in  FIG. 8A  (i.e., the configuration in which cylindrical element  142  is disposed within atrium  4 ) eliminates the obstruction of native valve  5  and of leaflets  12  and  14  by any portion of valve support  140 . In this manner, valve support  140  may be implanted at valve  5  while valve  5  resumes its native function and leaflets  12  and  14  resume their natural function (as shown by the phantom drawing of leaflets  12  and  14  in  FIG. 8A  which indicates their movement). This atrially-inverted configuration of valve support  140  reduces and even eliminates the amount of time the patient is under cardiopulmonary bypass. Only once prosthetic valve  80  is delivered and coupled to valve support  140  and cylindrical element  142  is thereby ventricularly-inverted, native leaflets  12  and  14  are pushed aside ( FIG. 8B ). 
       FIG. 8B  shows the inversion of cylindrical element  142  by the partial positioning and deployment of prosthetic valve  80  within ventricle  6 . Elongate guide members  146   a  and  146   b  are reversibly coupled to prosthetic valve  80  and extend within overtube  70 . Following the full deployment of valve  80  and the coupling of valve  80  to valve support  140 , elongate guide members  146   a  and  146   b  are decoupled from prosthetic valve  80  and from cylindrical element  142 . For example, a cutting tool may be used to decouple elongate members  146   a  and  146   b  from the valve support  140 . Alternatively, elongate members  146   a  and  146   b  may be looped through the cylindrical element  142 , such that both ends of each elongate member  146   a  and  146   b  remain outside of the patient&#39;s body. The operating physician decouples elongate members  146   a  and  146   b  from valve support  140  by releasing one end of each of elongate members  146   a  and  146   b  and pulling on the other end, until elongate members  146   a  and  146   b  are drawn from valve support  140  and removed from within the body of the patient. 
       FIG. 8C  shows prosthetic valve  80  coupled to valve support  140 . Valve  80  is identical to the valve described hereinabove. 
     Reference is now made to  FIGS. 9A-E , which are schematic illustrations of the advancement of an invertible prosthetic valve support  300  toward a native atrioventricular valve of a patient, and inversion of the valve support, in accordance with some applications of the present invention. Prosthetic valve support  300  is used to anchor prosthetic valve  80  to native valve  5  in a generally similar manner to that described with reference to prosthetic valve support  40 . 
     During a typical procedure, anchor  302  is advanced toward the vicinity of apex  304  of heart  2 , via sheath  25 , and is anchored to the vicinity of the apex, as shown in  FIG. 8A . A guidewire  306  extends proximally from anchor. A distal tensioning element  308  (e.g., a plunger) is advanced over guidewire  306  into ventricle  6 , and prosthetic valve support  300  is advanced out of the distal end of sheath  25 , as shown in  FIG. 9B . A first end  310  of prosthetic valve support  300  (which at this stage is the distal end of the prosthetic valve support), comprises barbs  314  (shown in  FIG. 9B ), or other anchoring elements for anchoring the first end of the prosthetic valve support to tissue of native valve  5 . Prosthetic valve support  300  is pushed distally such that the barbs are pushed into the native valve tissue, thereby anchoring the first end of the prosthetic valve support to the native valve, as shown in  FIG. 9C . A plurality of wires  309  pass from distal tensioning element  308  to a proximal tensioning element  311  (shown in  FIG. 9D ), via a second end  312  of valve support  300  (which at this stage is the proximal end of the prosthetic valve support). For some applications, a sealing element  316  is disposed circumferentially around a surface of the invertible prosthetic valve support that is initially an inner surface of the invertible prosthetic valve support (a shown in  FIGS. 8A-D ). For example, the sealing material may be latex, dacron, or another suitable biocompatible sealing material. 
     Subsequent to the anchoring of first end  310  of prosthetic valve support  300  to native valve tissue (as shown in  FIG. 9C ), distal tensioning element  308  is further advanced distally into ventricle  6 , and proximal tensioning element  311  is advanced toward the ventricle. As shown in the transition from  FIG. 9D-F , as the proximal tensioning element passes through the valve support, wires  309  cause valve support  300  to invert, by pulling second end  312  of the valve support through first end  310  of the valve support. Subsequent to the inversion of the valve support, sealing material  316  is disposed circumferentially around the outside of the valve support, thereby providing a seal at the interface between valve support  300  and native valve  5 . 
     Reference is now made to  FIGS. 9G-H , which are schematic illustrations of the deployment of prosthetic valve  80  and the coupling of the prosthetic valve to invertible valve support  300 , in accordance with some applications of the present invention. 
     The deployment of prosthetic valve  80  is generally similar to the techniques described hereinabove with reference to  FIGS. 2H-J . The valve is partially deployed in ventricle  6 , via overtube  70 . Following the partial deployment of valve  80  in ventricle  6 , overtube  70  is pulled proximally (as shown in  FIG. 8G ) to pull valve  80  proximally such that valve support  300  surrounds a proximal portion of prosthetic valve  80 , as shown in  FIG. 8H . Valve  80  has a tendency to expand such that valve  80  is held in place with respect to valve support  300  responsively to radial forces acted upon valve support  300  by prosthetic valve  80 . 
     As described hereinabove, for some applications, valve  80  comprises a plurality of distal protrusions  84 . When valve  80  is pulled proximally, protrusions  84  ensnare and engage the native leaflets of the atrioventricular valve. By the ensnaring of the native leaflets, protrusions  84  sandwich the native valve between protrusions  84  and prosthetic valve support  300 . Such ensnaring helps further anchor prosthetic valve  80  to the native atrioventricular valve. 
     Additionally, as shown in  FIG. 9H , and as described hereinabove, valve  80  comprises one or more (e.g., a plurality, as shown) coupling elements  81  at the proximal end of valve  80 . Overtube  70 , which facilitates the advancement of prosthetic valve  80 , is reversibly coupled to valve  80 , via coupling elements  81 . 
     Subsequent to the coupling of valve  80  to valve support  300 , overtube  70 , distal and proximal tensioning elements  308  and  311 , and wires  309  are removed from the patient&#39;s body, via sheath  25 . Typically, wires  309  are cut, in order to facilitate the removal of the wires from the patient&#39;s body. Guidewire  306  and anchor  302  are removed from the patient&#39;s body by detaching the anchor from apex  304 , and withdrawing the anchor and the guidewire, via sheath  25 . 
     Reference is now made to  FIG. 10 , which is a schematic illustration of prosthetic valve  80 , for placing inside atrioventricular valve  5  of the patient, in accordance with some applications of the present invention. The frame of the prosthetic valve has a diameter d, and a corresponding cross-sectional area. Native annulus  11 , which is typically saddle-shaped, defines an area A, as shown. For some applications, area A, which is defined by the native annulus is measured, e.g., using a measuring ring. A prosthetic valve is chosen to be placed in the annulus, the cross-sectional area of the prosthetic valve being less than 90% (e.g., less than 80%, or less than 60%) of area A. For some applications, placing a prosthetic valve inside the native valve with the dimensions of the native valve annulus and the prosthetic valve as described, facilitates sealing of the prosthetic valve with respect to the native valve, by the native valve leaflets closing around the outer surface of the prosthetic valve. 
     For some applications, in order to facilitate the sealing of the native valve around the outer surface of the prosthetic valve, a material is placed on the outer surface of the prosthetic valve in order to provide a sealing interface between the prosthetic valve and the native valve. For example, a smooth material that prevents tissue growth (e.g., polytetrafluoroethylene (PTFE), and/or pericardium) may be placed on the outer surface of the prosthetic valve. Alternatively or additionally, a material that facilitates tissue growth (such as dacron) may be placed on the outer surface of the prosthetic valve, in order to (a) act as a sealing interface between the native valve and the prosthetic valve, and (b) facilitate tissue growth around the prosthetic valve to facilitate anchoring and/or sealing of the prosthetic valve. 
     Reference is now made to  FIGS. 11A-D , which are schematic illustrations of prosthetic valve  80 , in accordance with some applications of the present invention. For some applications, protrusions  84  are disposed on the valve on portions  400  of the valve that are placed adjacent to the anterior and posterior leaflets of the native valve, and the valve does not includes protrusions on portions  402  of the valve that are placed adjacent to the commissures of the native valve. 
       FIGS. 11B-D  show bottom views (i.e., views of the distal ends) of respective configurations of prosthetic valve  80  and protrusions  84 . The protrusions converge from the proximal ends  404  of the protrusion to the distal ends  406  of the protrusions. The protrusions are configured such as to ensnare chordae tendineae, and to pull the chordae tendineae toward each other when the prosthetic valve is pulled proximally, due to the convergence of the snares with respect to each other.  FIG. 11D  shows the prosthetic valve deployed at native valve  5 . As shown, the protrusions ensnare chordae tendineae  102  of the patient. The protrusions facilitate sealing and anchoring of the prosthetic valve with respect to the native valve by pulling the chordae tendinae toward each other, as described. As described hereinabove, for some applications the prosthetic valve does not define protrusions  84  on portions  402  that are placed next to the native commissures, e.g., commissure  8 , shown in  FIG. 11D . 
     For some applications, a first set of protrusions  84  from the distal end of prosthetic valve  80  are disposed the within a first circumferential arc with respect to a longitudinal axis of the prosthetic valve, on a first side of the distal end of the prosthetic valve, the first side of the distal end being configured to be placed adjacent to the anterior leaflet of the native valve. A second set of protrusions are disposed the within a second circumferential arc with respect to a longitudinal axis of the prosthetic valve, on a second side of the distal end of the prosthetic valve, the second side of the distal end being configured to be placed adjacent to the posterior leaflet of the native valve. 
     The first and second sets of protrusions are disposed so as to provide first and second gaps therebetween at the distal end of the prosthetic valve. Typically, at least one of the gaps between the two sets of protrusions has a circumferential arc of at least 20 degrees (e.g., at least 60 degrees, or at least 100 degrees), and/or less than 180 degrees (e.g., less than 140 degrees), e.g., 60-180 degrees, or 100-140 degrees. Further typically, one or both of the first and second circumferential arcs defines an angle of at least 25 degrees (e.g., at least 45 degrees), and/or less than 90 degrees (e.g., less than 75 degrees), e.g., 25-90 degrees, or 45-75 degrees. 
     Valve guide members (e.g., guide members  21   a  and  21   b , and/or delivery lumen  27   a  and  27   b , as described hereinabove) are delivered to commissures of the native valve, and guide the valve such that the first and second circumferential arc are aligned with respective leaflets of the native valve and such that the first and second gaps are aligned with respective commissures of the native valve. 
     Reference is now made to  FIGS. 12A-C , which are schematic illustrations of prosthetic valve  80 , the valve defining distal protrusions  84  that are disposed sinusoidally around the circumference of the valve, in accordance with some applications of the present invention. For some applications the protrusions are shaped sinusoidally, in order to conform with the saddle-shape of native valve annulus  11 , thereby facilitating the sandwiching of the native valve leaflets between the protrusions and valve support  40 . As shown, the peaks of the sinusoid that is defined by the protrusions is disposed on portions  402  that are placed next to the native commissures and the troughs of the sinusoid is placed on portions of the valve that are placed in the vicinity of the centers of the anterior and posterior leaflets of the native valve. As shown in  FIG. 12C , for some applications the distal end of the prosthetic valve defines a sinusoidal shape. 
     Reference is now made to  FIGS. 1A-D ,  2 A-K,  3 A-D,  4 A-C,  5 A-D,  6 A-B,  7 A-F,  8 A-C,  9 A-H,  10 ,  11 A-D, and  12 A-C. It is to be noted that valve support  40  may be invertible as described hereinabove with respect to valve supports  140  and  300 , with reference to  FIGS. 8A-C , and  9 A-H. It is to be further noted that valve supports  140  and  300  may be used in conjunction with one or more of the elements for facilitating sealing of the native valve with respect to a valve support or a valve that is described with reference to  FIGS. 3A-D ,  4 A-C,  5 A-D, and  6 A-B. For example, valve supports  140  and  300  may be used with sealing balloon  90 , commissural anchors  100   a  and  100   b , grasping elements  106   a  and  106   b , and/or sealing material  110 . It is still further noted that valve supports  140  and  300  may be implanted using a guide member that defines a looped portion between commissures  8  and  10 , as described with reference to  FIGS. 7A-F . It is further noted that any of the applications described herein can be used in conjunction with valves having configurations as described with reference to  FIGS. 10-12C . 
     The systems described herein are advanced toward valve in a transcatheter procedure, as shown. It is to be noted, however, that the systems described herein may be advanced using any suitable procedure, e.g., minimally-invasive or open-heart. It is to be further noted that valve supports and prosthetic valves herein may be used to replace native mitral valves or native tricuspid valves. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.