Patent Publication Number: US-2020297489-A1

Title: Method and apparatus for mitral valve chord repair

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     This application a continuation in part of U.S. patent application Ser. No. 16/297,422, filed Mar. 8, 2019, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/641,612 filed Mar. 12, 2018 and is a continuation-in-part of U.S. application Ser. No. 15/858,671, filed Dec. 29, 2017, which is a continuation-in-part of U.S. application Ser. No. 15/638,176, filed Jun. 29, 2017, now U.S. Pat. No. 9,877,833, which claims priority to U.S. Provisional Application 62/441,031, filed on Dec. 30, 2016, the entirety of each of these applications is hereby incorporated by reference herein for all purposes. 
     This application also claims the priority benefit under 35 U.S.C. § 119(e) of U.S Provisional Application No. 62/778,662, filed Dec. 12, 2018, U.S. Provisional Application No. 62/778,624, filed Dec. 12, 2018, U.S. Provisional Application No. 62/875,265, filed Jul. 17, 2019, U.S. Provisional Application No. 62/897,207, filed Sep. 6, 2019, U.S. Provisional Application No. 62/897,809, filed Sep. 9, 2019, and U.S. Provisional Application No. 62/905,267, filed Sep. 24, 2019, the entirety of each of these applications is hereby incorporated by reference herein for all purposes. p Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
    
    
     BACKGROUND 
     The present disclosure relates to mitral valve repair or replacement and more generally to methods and methods and devices for mitral valve reshaping, repair and/or replacement of mitral chords to restore proper functioning of the mitral valve from a state of mitral valve regurgitation. 
     Description of the Related Art 
     The heart includes four heart valves, which allow blood to pass through the four chambers of the heart in one direction. The four valves are the tricuspid, mitral, pulmonary and aortic valves. The four chambers are the right and left atria (upper chambers) and right and left ventricle (lower chambers). 
     The mitral valve is formed by two leaflets, which are known as the anterior leaflet and the posterior leaflet, which open and close in response to pressure placed on the leaflets by the pumping of the heart. There are several problems that can develop or occur with respect to the mitral valve. Such problems include mitral valve regurgitation (MR), in which the mitral valve leaflets do not close properly, which can cause leakage of the mitral valve. Severe mitral regurgitation can adversely affect cardiac function and compromise a patient&#39;s quality of life and life-span. 
     Several techniques have been developed, for correcting mitral valve regurgitation. These include heart transplant, valve replacement or repair, chordae tendinea shortening or replacement and mitral annular repair also known as annuloplasty, depending upon the stage and underlying etiology. 
     As it relates to chordae tendinea replacement or repair, certain surgical and trans apical approaches have been proposed. Despite those efforts, however, there remains a need for a transvascular approach for chordae tendinea replacement or repair, to reduce or eliminate MR. 
     SUMMARY 
     An aspect of the disclosure includes an intravascular deployment catheter for deploying an implantable device, comprising: an elongate, flexible tubular body, having a proximal end, a distal end and a central lumen; a sheath on the distal end of the tubular body, having a side wall defining a cavity for removably receiving the implantable device; at least one radially extending first engagement element on the side wall and exposed to the cavity, for engaging a complementary second engagement element on the implantable device. 
     Another aspect of the disclosure includes a ventricular tissue anchor delivery system, comprising: an elongate, flexible tubular body, having a proximal end, a distal end and a central lumen; a sheath on the distal end of the tubular body, having a side wall defining a cavity; a ventricular tissue anchor removably positioned within the cavity, the tissue anchor comprising a hub and a helical tissue anchor; and at least one radially extending first engagement element on the side wall and exposed to the cavity, for engaging the helical tissue anchor; wherein rotation of the helical tissue anchor relative to the tubular body advances the helical tissue anchor distally out of the cavity. 
     In accordance with another aspect of the disclosure, a method of deploying an implant from a deployment catheter through a delivery catheter, where the implant has an outside diameter that is larger than an outside diameter of the delivery catheter can comprise the steps of: deploying the implant from a collapsible sheath on a distal end of the deployment catheter; proximally retracting the deployment catheter into the delivery catheter; and collapsing the sheath in response to proximally retracting the deployment catheter into the delivery catheter. 
     Another aspect of the disclosure includes an endovascular suture cutter for cutting a suture, comprising: a cutter housing defining a suture path extending therethrough; a cutter head rotatably positioned within the cutter housing, the cutter head including a cutting edge, wherein rotation of the cutter head within the cutter housing causes the cutting edge to cross the suture path to cut the suture extending along the suture path. 
     Another aspect of the disclosure includes a method of cutting a suture, comprising the steps of: advancing a suture through a suture path extending through a cutter housing; and rotating a cutter head within the cutter housing to cause a cutting edge on the cutter head to cross the suture path to cut a suture extending along the suture path. 
     Another aspect of the disclosure includes a leaflet anchor comprising: a pledget having a first end, a second end and a plurality of apertures positioned between the first end to the second end of the pledget; a suture having a distal end and a tail end; the distal end of the suture coupled to and extending from the second end of the pledget; and a radiopaque marker; wherein the tail end of the suture has been extended through the plurality of apertures such that suture extends through pledget openings and the leaflet anchor is enlargeable from a first reduced cross section for advancing through a leaflet, to a second, enlarged cross section for contacting an atrial side of the leaflet as the pledget is compressed against the leaflet as the suture is retracted through the leaflet. 
     Another aspect of the disclosure includes a leaflet anchor deployment assembly comprising; a catheter, a hollow needle positioned within the catheter and configured to be advanced out of the catheter to puncture a leaflet of a mitral valve of a heart; the hollow needle having a leaflet anchor positioned within the needle; the hollow needle comprising a sharpened end for piercing the leaflet and a flexible portion proximal to the sharpened tip; and a leaflet suture coupled to the leaflet anchor extending proximally through the catheter. 
     Another aspect of the disclosure includes a system for deploying a leaflet anchor, the system comprising: a catheter, a needle positioned within the catheter and configured to be advanced out of the catheter to puncture a leaflet of a mitral valve of a heart; a leaflet anchor; a leaflet suture coupled to the leaflet anchor extending proximally through the catheter; and a stored energy device for advancing the needle with sufficient force to puncture the leaflet with the needle. 
     An aspect of the disclosure includes a method of transvascular prosthetic chordae tendinae implantation, comprising the steps of: advancing a catheter into the left atrium, through the mitral valve, and into the left ventricle; deploying a ventricular anchor from the catheter and into a wall of the left ventricle, leaving a ventricular suture attached to the ventricular anchor and extending proximally through the catheter; from an atrium side, advancing a leaflet anchor through a superior surface of a mitral valve leaflet to position a leaflet anchor against the inferior (ventricular) side of the leaflet with a leaflet suture extending proximally through the leaflet, into and through the catheter; and securing the leaflet suture over the top of the leaflet coaptive edge to the ventricular suture to limit a range of travel of the leaflet in the direction of the left atrium. 
     Another aspect of the disclosure is a leaflet anchor deployment system, comprising: a catheter having a proximal end and a distal end; a leaflet anchor positioned on a distal end of the catheter; and a needle advanceable through the leaflet anchor, the needle releasably carrying a radially enlargeable leaflet anchor preloaded therein and having a suture extending proximally through the catheter. 
     In accordance with another aspect of the disclosure there is provided a method of transvascular prosthetic chordae tendinae implantation. The method comprises the steps of advancing a catheter into the left atrium, through the mitral valve, and into the left ventricle; deploying a ventricular anchor from the catheter and into a wall of the left ventricle, leaving a ventricular suture attached to the ventricular anchor and extending proximally through the catheter; from an atrium side, securing a leaflet anchor catheter to a mitral valve leaflet; with the leaflet anchor catheter secured to the leaflet, advancing a leaflet anchor from the catheter through the mitral valve leaflet to secure the mitral valve leaflet to a leaflet suture, with the leaflet suture extending proximally through the catheter; and securing the leaflet suture to the ventricular suture to limit a range of travel of the leaflet in the direction of the left atrium. 
     The step of advancing a leaflet anchor from the catheter through the mitral valve leaflet to secure the mitral valve leaflet to a leaflet suture may comprise advancing a needle preloaded with the leaflet anchor through the superior surface of the mitral valve leaflet. The securing a leaflet anchor catheter to a mitral valve leaflet step may comprise using a leaflet connector. The leaflet connector may comprise a helical anchor or a tissue hook. 
     In accordance with another aspect of the disclosure there is provided a method of securing a leaflet anchor to a mitral valve leaflet. The method comprises the steps of advancing a catheter into the left atrium; from an atrium side, securing a leaflet connector coupled to the catheter to a mitral valve leaflet from an atrial side of the leaflet; and after securing the leaflet connector to the mitral valve leaflet, advancing a leaflet anchor through the mitral valve leaflet to secure the mitral valve leaflet to a leaflet suture. 
     The step of advancing a leaflet anchor through the mitral valve leaflet to secure the mitral valve leaflet to a leaflet suture may comprise advancing a needle preloaded with the leaflet anchor through the mitral valve leaflet from the atrial side. The needle may be advanced through the leaflet connector. The leaflet connector may comprise a helical anchor. 
     In accordance with another aspect of the disclosure there is provided a leaflet anchor deployment system. The system comprises a catheter having a proximal end and a distal end; a leaflet connector positioned on a distal end of the catheter; and a needle advanceable through the leaflet connector, the needle including a radially enlargeable leaflet anchor preloaded therein and having a suture extending proximally through the catheter. The leaflet connector may comprise a helical anchor. 
     In accordance with another aspect of the disclosure there is provided a neo chordae tendinae deployment system. The system comprises a catheter having a proximal end and a distal end; a helical ventricular anchor subassembly extendable through the catheter, having a ventricular suture extending proximally through the catheter; and a leaflet anchor deployment subassembly extendable through the catheter, having a radially enlargeable leaflet anchor within the subassembly and having a leaflet suture extending proximally through the catheter. 
     The radially enlargeable leaflet anchor may comprise a pledget. The pledget may be transformable from an elongate strip configuration to a radially enlarged, axially shortened configuration by proximal retraction of the suture. The radially enlargeable leaflet anchor may comprise the leaflet suture positioned between two sheets of material. The radially enlargeable leaflet anchor may be carried within a needle having a sharpened end for piercing the leaflet. The leaflet anchor deployment subassembly may comprise an elongate tube having a distal end and a central lumen, and a leaflet connector on the distal end. The leaflet connector may comprise a helical leaflet anchor. The needle may be axially movable with respect to the helical leaflet anchor. The system may further comprise a suture locking subassembly, advanceable through the catheter and configured to connect the ventricular suture to the leaflet suture. 
     In accordance with another aspect of the disclosure there is provided a leaflet anchor delivery subsystem. The subsystem comprises an elongate flexible tubular body, having a proximal end, a distal end and a central lumen; a deployment needle axially movably advancable through the central lumen; a leaflet anchor carried within the deployment needle; and a leaflet connector carried by the distal end of the tubular body. The leaflet anchor may comprise a helical element. The deployment needle may be axially extendable through the helical element. 
     In accordance with another aspect of the disclosure there is provided a tissue anchor. The tissue anchor comprises a hub; a suture extending proximally from the hub; a helical anchor extending distally from the hub; a core wire extending concentrically through the helical anchor, and beyond the distal end of the helical anchor. 
     The tissue anchor may further comprise a suture anchor guide extending proximally from the hub. The tissue anchor may further comprise a tubular sleeve having a length of no more than about 10 cm extending proximally from the hub. The tissue anchor may further comprise a radiopaque marker carried by the sleeve. The tissue anchor may further comprise a radiopaque marker axially movably carried by the core wire. The tissue anchor may further comprise a spring carried by the core wire. The tissue anchor may further comprise a tissue piercing point on a distal end of the helical anchor, and a barb on the helical anchor configured to resist rotation of the helical anchor out of engagement with tissue. 
     In accordance with another aspect of the disclosure there is provided a tissue anchor with dynamic depth indicator. The tissue anchor comprises a hub; a tissue anchor extending distally from the hub; a core wire extending distally from the hub; a radiopaque marker movably carried by the hub; and a spring for biasing the radiopaque marker in a distal direction; wherein the radiopaque marker is advanced proximally with respect to the tissue anchor in response to the tissue anchor advancing into tissue. 
     In accordance with another aspect of the disclosure there is provided an endovascular suture lock. The suture lock comprises a body having a suture path extending therethrough; a movable wall in the housing, for reducing a cross sectional dimension of the suture path; a rotatable coupling on the housing; and a drive mechanism for advancing the movable wall in response to rotation of the coupling. 
     The suture lock may additionally comprise a friction enhancing surface exposed to the suture path. The friction enhancing surface may be on the movable wall. The suture lock may comprise a push wedge having an angled surface and axially movable within the housing. Rotation of the coupling may advance the push wedge axially which advances the movable wall laterally to change the cross sectional dimension of the suture path. The movable wall may comprise a suture gripping surface on a first side and a ramp surface on a second side, the ramp surface configured for sliding contact with the angled surface on the push wedge. 
     Accordance with another aspect of the disclosure, a stabilization system for transvascular cardiac repair can include a base a distal docking platform, axially movably carried by the base; a proximal docking platform, axially movably carried by the base; and an intermediate docking platform, axially movably carried by the base. 
     Accordance with another aspect of the disclosure, a suture management system for a transvascular cardiac repair an anchor tension component can include a tension component that includes a clutch for limiting the amount of tension that can be applied to a suture wrapped around the spool. 
     Accordance with another aspect of the disclosure, a transvascular cardiac repair system can include a base; a distal docking platform, carried by the base; an access sheath connected to the distal docking platform; a proximal docking platform, carried by the base; a rotatable spool carried by the proximal docking station; and a first suture extending through the access sheath and from the access sheath to the spool. 
     Accordance with another aspect of the disclosure, the dynamic leaflet management system can include a base; a distal docking platform, carried by the base; an access sheath connected to the distal docking platform; a proximal docking platform, carried by the base; a first suture guide on the proximal docking platform; a first leaflet suture extending proximally out of the access sheath, across the first suture guide; and a weight connected to the first leaflet suture proximally of the first suture guide. 
     A method of synchronizing deployment of a tissue anchor needle with the cardiac cycle, comprising the steps of monitoring a physiological parameter of the cardiac cycle; creating a time signal correlating to the timing of a pressure peak in the left ventricle; initiating a control signal to an actuator in response to the time signal; and deploying a needle during the pressure peak in response to actuation of the actuator. The physiological parameter may comprise pulse, peripheral pulse, an ECG signal, and in particular a QRS wave. The physiological parameter may comprise blood pressure. The physiological parameter may be acquired transdermally, or may be acquired by an intravascular sensor. The sensor may comprises a pressure sensor. 
     The actuator may comprise a force driven anchor driver. Alternatively, the actuator may comprise a lockout which prevents deployment of the needle until actuation of the actuator to disengage the lockout. 
     There is provided in accordance with another aspect of the disclosure, a cardiac synchronous leaflet anchor deployment system. The system comprises a delivery catheter; a needle, axially reciprocally carried by the delivery catheter; a needle driver, configured to advance the needle from a first position within the catheter to a second position extending beyond the catheter; an actuator; a connector for electrical connection to a source of cardiac cycle data; and a control circuit. The control circuit may be configured to activate the actuator in response to detection of a predetermined point in the cardiac cycle. 
     In one implementation, the actuator activates the needle driver, to advance the needle distally. The system may further comprise a lockout which when enabled prevents a clinician from advancing the needle distally, wherein the actuator disables the lockout to enable the clinician to advance the needle distally. 
     The needle driver may be spring loaded, electromagnetically driven, hydraulically driven, pneumatically driven or manually driven by the clinician. In one implementation, the system is provided with a manual control to enable the clinician to manually activate the needle driver. 
     The needle may be provided with at least one retention element, to resist proximal retraction of the needle from target tissue. The retention element may comprise a radially outwardly extending tissue engagement surface to resist proximal retraction of the needle from the leaflet. One particular retention element comprises a helical thread surrounding the needle. The helical thread may comprise a wire wrapped helically around the needle, which may be welded to the outside of the needle. 
     There is provided in accordance with a further aspect of the present disclosure a leaflet anchor deployment system. The system comprises a delivery catheter; a needle, axially reciprocally carried by the delivery catheter; a tissue retention structure carried by the needle; and a tissue anchor carried within the needle. The tissue retention structure may comprise a radially outwardly extending flange, which may be a helical flange, and may comprise a wire, wrapped helically around the needle. The leaflet anchor deployment system may further comprise a deflection zone. The deflection zone may comprise a slotted sidewall of the needle. A pledget may be carried within the needle, such as within the deflection zone. The deflection zone may reside completely within the distal most 6 cm or distal most 4 cm or 2 cm of the needle. 
     An aspect of the present disclosure can include a tissue anchor that comprises a hub, a suture extending proximally from the hub, a helical anchor extending distally from the hub, and a secondary anchor axially movable in a distal direction from a first configuration to a second, deployed configuration to engage tissue an inhibit unscrewing of the helical anchor. 
     Another aspect of the present disclosure can include a neo chordae tendinae deployment system that comprises a catheter having a proximal end and a distal end. A ventricular anchor subassembly is extendable through the catheter and can have a ventricular suture extending proximally through the catheter. The ventricular anchor subassembly comprises a helical tissue anchor and secondary tissue anchor axially movable in a distal direction from a first configuration to a second, deployed configuration to engage tissue and inhibit unscrewing of the helical tissue anchor. A leaflet anchor deployment subassembly is extendable through the catheter and has a radially enlargeable leaflet anchor within the subassembly and having a leaflet suture extending proximally through the catheter. 
     Another aspect of the present disclosure a method of transvascular prosthetic chordae tendinae implantation that can include the steps of advancing a catheter into the left atrium, through the mitral valve, and into the left ventricle, deploying a ventricular anchor from the catheter and into a wall of the left ventricle by rotating a helical tissue anchor into the wall of left ventricle, deploying a secondary tissue anchor into the wall of the left ventricle to inhibit unscrewing of the helical tissue anchor; leaving a ventricular suture attached to the ventricular anchor and extending proximally through the catheter, from an atrium side, securing a leaflet anchor catheter to a mitral valve leaflet, with the leaflet anchor catheter secured to the leaflet, advancing a leaflet anchor from the catheter through the mitral valve leaflet to secure the mitral valve leaflet to a leaflet suture, with the leaflet suture extending proximally through the catheter; and securing the leaflet suture to the ventricular suture to limit a range of travel of the leaflet in the direction of the left atrium. 
     According to a first aspect of the present disclosure, a system for transcatheter mitral chordal repair comprises an anchor configured to couple with ventricular tissue in a left ventricle of a heart; a suture configured to couple with a leaflet of a mitral valve of the heart; a suture lock having a distal aperture and a proximal aperture separated along a longitudinal axis, the suture lock configured to pass the suture through the suture lock between the distal aperture and the proximal aperture; a socket configured to couple with the anchor and to receive the suture lock, the socket configured to retain the suture lock relative to the anchor, with a distal portion of the suture extending through the suture lock in a direction substantially parallel the longitudinal axis of the suture lock and a proximal portion of the suture extending between the socket and the suture lock in a direction substantially parallel the longitudinal axis of the suture lock. In some variations of the first embodiment, the socket is configured to restrain movement of the suture relative to the suture lock. 
     In some variations of the first aspect, the socket is configured to retain the suture lock relative to the anchor so as to enable one-to-one movement or near one-to-one movement of the suture. In some variations of the first aspect, the socket and the suture lock retain the suture between an inner surface of the socket and an outer surface of the suture lock so that a proximal portion of the suture external to the socket can be cut without causing movement of the suture lock greater than 5/1000th of an inch. In some variations of the first aspect, the socket and the suture lock retain the suture between an inner surface of the socket and an outer surface of the suture lock so as to maintain tension on a distal portion of the suture near the leaflet in the absence or reduction of tension on a proximal portion of the suture external to the socket. 
     In some variations of the first aspect, the suture is a first suture coupled to a first leaflet, the system further comprising at least a second suture coupled to the first leaflet, wherein tension of the first suture between the suture lock and the first leaflet is adjustable and the tension of the at least one second suture is also adjustable. In an alternative embodiment, at least one additional suture may be coupled to a second leaflet of the mitral valve without substantially altering tension of the first and at least one second suture between the suture lock and the first leaflet. 
     In some variations of the first aspect, the socket is configured to promote tissue encapsulation or ingrowth. In some variations of the first aspect, the suture lock includes a tapered nose. In some variations of the first aspect, the socket includes a bushing configured to contact the tapered nose when the suture lock is inserted into the socket. In some variations of the first aspect, the socket is formed of a material configured to reduce wear on the suture. In some variations of the first aspect, a proximal portion of the socket presents a tapered surface to facilitate entry of the suture lock into the socket. In some variations of the first aspect, an interior surface of the socket and an exterior surface of the suture lock are configured to exert retaining forces that resist forces exerted on the suture by the leaflet. 
     In some variations of the first aspect, the suture lock is radiopaque, and the socket includes a radiopaque element located near a proximal surface of the suture lock. Alternatively, the socket may be at least partially or completely radiopaque. In some variations of the first aspect, the socket includes a support coil. In some variations of the first aspect, the socket is radially compliant to permit the suture lock to enter the socket while providing constraining forces. In some variations of the first aspect, the suture is configured to create a prosthetic chord that remains functional over at least 400 million cycles. In some variations of the first aspect, the suture is a first suture, and the system includes an anchor suture configured to couple to the anchor and pass through the socket and the suture lock and may facilitate guiding the suture lock into the socket. 
     In some variations of the first aspect, a portion of the socket is configured to retain the suture lock over displacing forces in the range of 0 N to approximately 10 N. In some variations of the first aspect, a portion of the socket is configured to retain the suture lock over displacing forces in the range of 0 N to approximately 6 N. In some variations of the first aspect, a portion of the socket is configured to retain the suture lock over displacing forces in the range of 0 N to approximately 4 N. 
     In some variations of the first aspect, the suture is configured to extend from the proximal opening of the suture lock and wrap around a nose portion of the suture lock when the suture lock is located in the socket, and the nose portion presents a substantially round profile to reduce wear on the suture. 
     In some variations of the first aspect, the socket facilitates maintaining the longitudinal orientation of the suture lock within about 15 degrees or less of a line, or longitudinal orientation, drawn between the suture lock and the leaflet when the suture lock is located in the socket. In some variations of the first aspect, the suture lock is insertable into the socket and is removable from the socket. 
     In a second aspect, a system for creating a prosthetic chord for transcatheter mitral chordal repair comprises a suture lock configured to engage a suture coupled to a leaflet of a mitral valve; and an anchor configured to couple with ventricular tissue, the anchor including a retaining member configured to couple with the suture lock so that the suture lock maintains a positional relationship with the anchor. 
     In some variations of the second aspect, the retaining member is configured to couple with the suture lock to restrict movement of the suture lock relative to the anchor during cardiac cycles. In some variations of the second aspect, the retaining member is configured to couple with an exterior surface of the suture lock located between a proximal end and a distal end of the suture lock. Alternatively, the retaining member may at least partially couple or engage with at least a portion of an interior surface of the suture lock. In some variations of the second aspect, the retaining member includes a socket configured to couple with the suture lock. The socket may be configured to be radially compliant to permit the suture lock to enter the socket and couple with the socket. 
     In some variations of the second aspect, the retaining member is configured to selectively couple and decouple with the suture lock. In some variations of the second aspect, the retaining member is configured to maintain coupling with the suture lock over displacing forces up to approximately 3 N. In some variations of the second aspect, the retaining member is configured to maintain coupling with the suture lock over displacing forces up to approximately 1.5 N. 
     In some variations of the second aspect, the retaining member is configured to couple with the suture lock at least partially via an interference fit. 
     In a third aspect, a system for a prosthetic chord for transcatheter mitral chordal repair comprises: a suture configured to couple with a leaflet of a mitral valve of a heart; a suture lock configured to engage the suture; and an anchor configured to couple with tissue below the mitral valve, the anchor and the suture coupled with the leaflet defining a substantially longitudinal direction and including a restraining member configured to constrain movement of the suture lock relative to the anchor in a direction orthogonal to the longitudinal direction. 
     In some variations of the third aspect, the restraining member is configured to constrain movement of the suture lock relative to the anchor in a plane orthogonal to the longitudinal direction. The restraining member may be further configured to constrain movement of the suture lock relative to the anchor along the longitudinal direction. In some variations of the third aspect, the suture lock defines a longitudinal direction, and the restraining member is configured to substantially align the longitudinal direction defined by the anchor with the longitudinal direction defined by the suture lock. In some variations of the third aspect, the restraining member is configured to contact the suture lock in at least two locations to constrain movement of the suture lock relative to the anchor. In some variations of the third aspect, the restraining member is configured to contact an external surface of the suture lock at three or more points to constrain movement of the suture lock relative to the anchor. 
     In some variations of the third aspect, the restraining member is configured to contact a proximal surface of the suture lock to constrain movement of the suture lock relative to the anchor. 
     In a fourth aspect, a system for transcatheter mitral chordal repair comprises an anchor configured to couple with ventricular tissue below a mitral valve, the anchor including a retaining member; and a suture lock configured to effect a prosthetic chord for the mitral valve by coupling a leaflet of the mitral valve to the anchor via a suture, the suture lock configured to couple with the retaining member of the anchor, whereby at least some displacement forces are transferred from the suture lock to the anchor. 
     In some variations of the fourth aspect, the suture lock is configured to transfer displacement forces to the retaining member, the displacement forces ranging up to approximately 3 N. In some aspect of the fourth embodiment, the retaining member is configured to decouple with the suture lock in response to forces exceeding approximately 6 N. In some variations of the fourth aspect, the prosthetic chord remains functional over at least 400 million cycles. 
     In some variations of the fourth aspect, the suture lock extends along a longitudinal direction, the suture lock includes a peripheral surface extending between a distal surface and a proximal surface, and the peripheral surface includes longitudinally extending portions configured to couple with the retaining member. 
     In a fifth aspect, a system for transcatheter mitral chordal repair comprises a suture configured to couple with a leaflet of a mitral valve; an anchor configured to couple with ventricular tissue below the mitral valve; and a suture lock configured to engage the suture and to couple with a retaining member of the anchor so as to constrain angular movement of the suture relative to the suture lock. 
     In some variations of the fifth aspect, the suture lock is configured to couple with the retaining member of the anchor so as to constrain angular movement of the suture relative to a longitudinal direction defined by the suture lock. In some variations of the fifth aspect, the suture is configured to slide relative to the suture lock after the retaining member couples with the suture lock. In some variations of the fifth embodiment, the suture lock includes an internal locking member configured to engage the suture. 
     In some variations of the fifth aspect, the retaining member is configured to engage the suture in combination with the suture lock. The retaining member and the suture lock may be further configured to engage a portion the suture adjacent interfacing surfaces of the retaining member and the suture lock. The anchor may define a longitudinal direction and the portion of the suture between adjacent interfacing surfaces of the retaining member and the suture lock may extend in a direction substantially parallel to the longitudinal direction. 
     In some variations of the fifth aspect, the anchor defines a longitudinal direction and the retaining member is configured to orient the suture lock so that a line extending from the suture lock parallel to the longitudinal direction intersects the leaflet of the mitral valve. In some variations of the fifth aspect, the suture is at least a first suture coupled with a first leaflet of the mitral valve, and the system further comprises at least a second suture configured to couple with a second leaflet of the mitral valve, and the suture lock is configured to engage the second suture and to couple with the retaining member of the anchor so as to constrain angular movement of the second suture relative to the suture lock. The suture lock may be configured to couple with the retaining member of the anchor so as to constrain angular movement of the second suture relative to a longitudinal direction defined by the suture lock. 
     In a sixth aspect, a system for a prosthetic chord for transcatheter mitral chordal repair comprises a suture configured to couple with a mitral valve leaflet; a suture lock configured to engage the suture, the suture lock oriented along a longitudinal direction; and an anchor configured to couple with ventricular tissue below the mitral valve and with the suture lock via an anchor suture, the anchor including a retaining member configured to couple with the suture lock to limit change of an orientation angle of the suture lock relative to the longitudinal direction to less than 90°. 
     In some variations of the sixth aspect, the retaining member is configured to couple with the suture lock so that the angle changes by less than approximately 10° during movement of the suture during cardiac cycles. In some variations of the sixth aspect, the retaining member is configured to couple with the suture lock so that the angle changes by less than approximately 5° during movement of the suture during cardiac cycles. In some variations of the sixth aspect, the retaining member is a socket. 
     In some variations of the sixth aspect, the suture is a first suture and the mitral valve leaflet is a first mitral valve leaflet, the system further comprises a second suture configured to couple with a second mitral valve leaflet, and the retaining member is configured to couple with the suture lock to limit change of an angle formed between the second suture extending from the suture lock towards the second mitral valve leaflet and the suture lock&#39;s longitudinal direction to less than 90°. The retaining member may be configured to couple with the suture lock so that the angle formed by the second suture extending from the suture lock towards the second mitral valve leaflet and the suture lock&#39;s longitudinal direction changes by less than approximately 5° during movement of the second suture during cardiac cycles. 
     In a seventh aspect, a system for a prosthetic chord for transcatheter mitral chordal repair comprises a suture configured to couple with a mitral valve leaflet; a suture lock configured to engage the suture, the suture lock extending along a longitudinal direction; and an anchor configured to couple with tissue below the mitral valve, the anchor including a retaining member configured to couple with the suture lock so that the suture extends from the suture lock towards the mitral valve leaflet at an angle of less than approximately 45° with respect to the suture lock&#39;s longitudinal direction. 
     In some variations of the seventh aspect, the suture extends from the suture lock towards the mitral valve leaflet at an angle of less than approximately 5° with respect to the suture lock&#39;s longitudinal direction. In some variations of the seventh embodiment, during movement of the suture during cardiac cycles, the angle is within a range of 0-45°. In some variations of the seventh aspect, the suture is a first suture and the mitral valve leaflet is a first mitral valve leaflet, the system further comprises a second suture configured to couple with a second mitral valve leaflet, and the retaining member is configured to couple with the suture lock so that the second suture extends from the suture lock towards the second mitral valve leaflet at an angle of less than approximately 45° with respect to the suture lock&#39;s longitudinal direction. The second suture may extend from the suture lock towards the second mitral valve leaflet at an angle of less than approximately 5° with respect to the suture lock&#39;s longitudinal direction. In some variations of the seventh aspect, the prosthetic chord remains functional over at least 400 million cycles. 
     In an eight aspect, a prosthetic chord for transcatheter mitral chordal repair comprises a suture having a distal portion configured to couple with a leaflet of a mitral valve; a suture lock configured to couple with the suture; and a restraining member configured to couple with the suture lock and with an anchor engaging tissue below the mitral valve, the restraining member configured to maintain an orientation of the suture lock relative to the restraining member during forces applied to the prosthetic chord. 
     In some variations of the eighth aspect, the forces applied to the prosthetic chord range up to approximately 2.0 N. In some variations of the eighth aspect, the restraining member is configured maintain an angle between a line defined by the suture lock and a line defined by restraining member within a range of approximately 0° to 5°. 
     In some variations of the eighth aspect, the suture includes a proximal portion located proximal of the suture lock, and the restraining member is configured to maintain the orientation of the suture lock relative to the restraining member during removal of the proximal portion of the suture lock. In some variations of the eighth aspect, the suture includes a proximal portion located proximal of the suture lock, and the restraining member is configured to maintain the orientation of the suture lock relative to the restraining member during tension changes in the proximal portion of the suture lock. In some variations of the eighth aspect, the suture includes a proximal portion located proximal of the suture lock, and the restraining member is configured to maintain the orientation of the suture lock relative to the restraining member in the absence of tension in the proximal portion of the suture. 
     In some variations of the eighth aspect, the restraining member is configured to maintain an orientation of at least a portion of the suture relative to the restraining member. In some variations of the eighth aspect, the restraining member is configured to maintain an angle formed between a portion of the suture and a longitudinal line defined by the restraining member within a range of 0° to approximately 15°. The portion of the suture may be located proximal to a distal surface of the suture lock, and the angle may be substantially 0°. The portion of the suture may be located distal of a distal surface of the suture lock. In some variations of the eighth aspect, the restraining member is configured to maintain a substantially co-axial relationship between the suture lock and the restraining member. 
     In a ninth aspect, a system for transcatheter mitral chordal repair comprises a first suture configured to couple with a first leaflet of a mitral valve; a second suture configured to couple with either the first leaflet or a second leaflet of the mitral valve; a suture lock configured to couple with the first suture and the second suture; and an anchor configured to couple with tissue below the mitral valve and to restrict movement of the suture lock relative to the anchor. 
     In some variations of the ninth aspect, the anchor includes a restraining member configured to restrict rotational and positional movement of the suture lock relative to the anchor. In some variations of the ninth embodiment, the anchor is configured to restrict movement of the suture lock relative to the anchor over forces between approximately 0 N and 4 N. In some variations of the ninth aspect, the anchor is configured to restrict rotational movement of the suture lock relative to the anchor over forces between approximately 0 N and 10 N. In some variations of the ninth aspect, the anchor is configured to restrict movement of the suture lock relative to the anchor over forces between approximately 0 N and 6 N. 
     In some variations of the ninth aspect, the first suture includes a distal portion configured to couple with the first leaflet and a proximal portion located proximal of the suture lock, and the anchor is configured restrict rotational movement of the suture lock relative to the anchor during removal of the proximal portion of the first suture In some variations of the ninth aspect, the second suture includes a distal portion configured to couple with the second leaflet and a proximal portion located proximal of the suture lock, the anchor is configured to restrict rotational movement of the suture lock relative to the anchor during removal of the proximal portion of the second suture. 
     In a tenth aspect, a prosthetic chord for transcatheter mitral chordal repair comprises a suture configured to couple with a leaflet of a mitral valve; a suture lock configured to couple with the suture; and a restraining member configured to couple with the suture lock and with an anchor engaging tissue below the mitral valve, the restraining member configured to limit changes in a length of the prosthetic chord over changes in forces applied to the prosthetic chord. In some variations of the tenth embodiment, the restraining member is configured to limit changes in the length of the prosthetic chord to less than approximately 0.5 mm over changes in forces applied to the prosthetic chord. 
     In some variations of the tenth aspect, the restraining member is configured to limit changes in the length of the prosthetic chord to less than approximately 0.1 mm over changes in forces applied to the prosthetic chord. In some variations of the tenth aspect, the suture includes a distal portion configured to couple with the leaflet and a proximal portion configured to couple to a catheter for adjustment of the distal portion of the suture, the restraining member is configured to limit changes in the length of the prosthetic chord over forces applied via the catheter. 
     In an eleventh aspect, a system for transcatheter mitral chordal repair comprises a suture configured to couple with a leaflet of a mitral valve; a suture lock configured to advance along the suture and to selectively engage the suture; and an anchor configured to couple with tissue below the mitral valve, the anchor including a retaining member configured to align the suture lock and the anchor. 
     In some variations of the eleventh aspect, the retaining member is configured to maintain alignment of the suture lock relative to the anchor over rotational forces exerted on the suture lock by the suture. In some variations of the eleventh aspect, the retaining member is configured to maintain alignment of the suture lock relative to the anchor over rotational forces exerted on the suture lock by the suture after the suture lock selectively engages the suture. In some variations of the eleventh embodiment, the anchor defines a longitudinal line and the suture lock defines a longitudinal line, and the retaining member is configured to align the suture lock with the anchor so that the longitudinal line of the anchor is substantially parallel to the longitudinal line of the suture lock. 
     In some variations of the eleventh aspect, the suture lock defines a longitudinal line and the retaining member is configured to align the suture lock with the anchor so that the longitudinal line defined by the suture lock extends to the leaflet. 
     In a twelfth aspect, a system for transcatheter mitral cordial repair comprises a suture with a distal portion for coupling with a leaflet of a mitral valve and a proximal portion for adjustment of the suture with respect to the leaflet; a suture lock configured advance along the suture; and an anchor configured to couple with tissue below the mitral valve, the anchor including a retaining member configured to selectively couple with the suture lock to restrict movement of the suture lock. 
     In some variations of the twelfth emb aspect odiment, the retaining member is configured to selectively couple with the suture lock, with the suture lock providing a pivot point for the suture that remains substantially stationary relative to the anchor. 
     In some variations of the twelfth aspect, the suture is a first suture, the system further comprising a second suture with a distal portion for coupling with a leaflet of the mitral valve and a proximal portion for adjustment of the second suture; and the suture lock is configured to advance along the first suture and the second suture. The suture lock may provide a pivot point for the first and second sutures that remains substantially stationary relative to the anchor. The distal portion of the first suture may be configured to couple to a first leaflet of the mitral valve and the distal portion of the second suture may be configured to couple to a second leaflet of the mitral valve. In some aspect of the twelfth embodiment, the retaining member is a socket. 
     In a thirteenth aspect, a system for establishing a plurality of prosthetic chords for transcatheter mitral cordial repair comprises a first suture with a distal portion for coupling with a leaflet of a mitral valve and a proximal portion for adjustment of the first suture; a second suture with a distal portion for coupling with a leaflet of the mitral valve and a proximal portion for adjustment of the second suture; a suture lock configured to advance along the first suture and the second suture; and an anchor configured to couple with tissue below the mitral valve, the anchor including a retaining member configured to selectively couple with the suture lock so as to maintain tension on the distal portion of the first suture during adjustment of the second suture. 
     In some variations of the thirteenth aspect, adjustment of the second suture includes adjustment of the distal portion of the second suture using the proximal portion of the second suture. In some variations of the thirteenth aspect, the retaining member is configured to selectively couple with the suture lock so as to substantially maintain a tension of the distal portion of the second suture during adjustment of the first suture. Adjustment of the first suture may include adjustment of the distal portion of the first suture using the proximal portion of the first suture. 
     In some variations of the thirteenth aspect, the retaining member is a socket. The socket may be configured to engage a portion of the first suture located adjacent to an external surface of the suture lock. The socket may also be configured to engage a portion of the second suture located adjacent to the external surface of the suture lock. An internal surface of the socket and an external surface of the suture lock may be configured to restrain a portion of the first suture and a portion of the second suture. An internal surface of the socket may include a material whose crystalline structure is oriented in a direction that corresponds to an orientation of material of the first suture and an orientation of material of the second suture. In some variations of the thirteenth embodiment, the distal portion of the first suture and the distal portion of the second suture are configured to couple with a first leaflet of the mitral valve. 
     In a fourteenth aspect, a system for transcatheter mitral chordal repair comprises an anchor configured to couple with ventricular tissue; a suture configured to couple with a mitral valve leaflet; a suture lock configured to selectively engage the suture; and a retaining element configured to couple the suture lock to the anchor, at least one of the suture lock and the retaining element including a tapered surface to facilitate coupling the suture lock to the anchor. 
     In some variations of the fourteenth aspect, the suture lock includes a proximal portion having the tapered surface, and the tapered surface is cone shaped. In some variations of the fourteenth embodiment, the retaining element includes a distal portion having the tapered surface, and the tapered surface is funnel shaped. In some variations of the fourteenth aspect, the suture lock includes a proximal portion having the tapered surface, and the retaining element includes a distal portion whose surface has a profile that corresponds to a profile of the tapered surface of the suture lock. In some variations of the fourteenth aspect, the retaining element is permanently attached to the anchor. In some variations of the fourteenth aspect, the retaining element is permanently attached to the suture lock. In some variations of the fourteenth aspect, the retaining element includes a distal portion incorporating radiopaque material. The retaining element may include a non-radiopaque portion located proximally of the radiopaque material of the distal portion. The suture lock may be radiopaque. In some variations of the fourteenth aspect, an anchor suture is coupled to the anchor to guide the suture lock to the retaining member. The suture lock may be configured to selectively engage the anchor suture. 
     In a fifteenth aspect, a system for transcatheter mitral chordal repair comprises an anchor configured to couple with ventricular tissue; a suture configured to couple with a mitral valve leaflet; a suture lock configured to selectively engage the suture, the suture lock extending along a longitudinal line; and a retaining member configured to secure the suture lock to the anchor, the retaining member configured to exert retaining forces on the suture lock in a direction orthogonal to the longitudinal line of the suture lock. 
     In some variations of the fifteenth aspect, the retaining member is configured to promote tissue encapsulation or ingrowth. In some variations of the fifteenth aspect, the retaining member includes a bushing configured to contact the suture lock when the suture lock is inserted into the retaining member. In some variations of the fifteenth aspect, the retaining member includes a coil configured to resist buckling of the retaining member during insertion of the suture lock into the retaining member. In some variations of the fifteenth aspect, the retaining member is formed of a material configured to reduce wear on the suture. 
     In some variations of the fifteenth aspect, the suture is configured to extend from a proximal opening of the suture lock and wrap around a nose portion of the suture lock when the suture lock is secured by the retaining member, and the nose portion presents a substantially round profile. In some variations of the fifteenth aspect, the retaining member is a socket. In some variations of the fifteenth aspect, the retaining member includes a pin. In some variations of the fifteenth aspect, the retaining member includes an anchor suture configured to exert retaining forces on the suture lock in a direction substantially parallel to the longitudinal line of the suture lock. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are not to be considered limiting on scope. 
         FIG. 1  illustrates placement of a ventricular anchor via transceptal approach to the mitral valve. 
         FIGS. 2A and 2B  illustrate a ventricular anchor. 
         FIG. 2C  is a perspective view of a ventricular anchor on the distal end of a ventricular anchor deployment tool. 
         FIG. 2D  is a perspective view of the proximal end of a ventricular anchor deployment tool. 
         FIG. 2E  is a partially exploded perspective view of a ventricular anchor and the distal end of a ventricular anchor deployment tool. 
         FIG. 2F  illustrates a ventricular anchor with a secondary anchor in a first configuration. 
         FIG. 2G  illustrates the ventricular anchor of  FIG. 2F  with the secondary anchor in a second, deployed configuration. 
         FIG. 3  illustrates the deployment end of a catheter positioned to engage a leaflet of the mitral valve. 
         FIG. 4  illustrates the leaflet captured by the helical leaflet anchor, and a needle crossing through the leaflet from the atrium to the ventricle. 
         FIG. 5  illustrates a pledget type leaflet anchor deployed from the needle and into the ventricle. 
         FIG. 6A  illustrates proximal traction on a leaflet suture to collapse the pledget against the ventricular side of the leaflet. 
         FIGS. 6B-6D  illustrate details of a pledget type leaflet anchor. 
         FIG. 7  illustrates a deployed leaflet anchor and suture and a deployed ventricular anchor and suture ready for tensioning and attachment of a suture lock. 
         FIG. 8  illustrates a perspective view of a distal end of the leaflet anchor delivery subsystem. 
         FIG. 9  illustrates a perspective view of a proximal end of the leaflet anchor delivery subsystem. 
         FIG. 10  illustrates an exploded view of the distal end of the leaflet anchor delivery subsystem. 
         FIG. 11  depicts advancing a suture lock via a suture lock delivery subsystem over the leaflet anchor suture and ventricular anchor suture to connect the leaflet anchor to the ventricular anchor. 
         FIG. 12  depicts the suture lock in a locked position after the tension has been adjusted and the suture tails having been severed. 
         FIG. 13  depicts a perspective view of a distal end of the suture lock delivery subsystem. 
         FIG. 14  depicts a perspective view of a proximal end of the suture lock delivery subsystem. 
         FIG. 15  depicts a partially exploded view of the distal end of the suture lock delivery subsystem. 
         FIG. 16  depicts a perspective view of a distal end of a suture cutting assembly. 
         FIG. 17  depicts a side view of a cutting assembly portion of the suture lock delivery subsystem in a configuration where the cutting head is not yet advanced for holding the sutures prior to being severed. 
         FIG. 18  depicts a side view of the cutting assembly portion of the suture lock delivery subsystem in a configuration where the cutting head has been advanced for severing the sutures. 
         FIG. 19  depicts a side view of a suture lock and a distal end of a torque driver configured to engage the suture lock. 
         FIG. 20  depicts a proximal end view of a suture lock. 
         FIG. 21  depicts a distal end of view of a suture lock. 
         FIG. 22A  is a side view of a ventricular anchor delivery subsystem according to aspects of the disclosure. 
         FIG. 22B  is a side view of a proximal portion of the ventricular anchor delivery subsystem shown in  FIG. 22A . 
         FIG. 22C  is a side view of an intermediate portion of the ventricular anchor delivery subsystem shown in  FIG. 22A   
         FIG. 22D  is a side view of a distal portion of the ventricular anchor delivery subsystem shown in  FIG. 22A   
         FIG. 22E  is a longitudinal cross-sectional view taken through a portion of  FIG. 22D . 
         FIG. 22F  is longitudinal cross-sectional view taken through a mandrel that can be used to form the distal portion of the ventricular anchor delivery subsystem shown in  FIG. 22A . 
         FIG. 23A  is a top view of an embodiment of a cutter catheter according to aspects of the disclosure. 
         FIG. 23B  is a side and partial cross-sectional view of the cutter catheter of  FIG. 23A . 
         FIG. 23C  is a cross-sectional view taken along line  23 C- 23 C of  FIG. 23A . 
         FIG. 24A  is a front view of a cutter housing of the cutter catheter of  FIG. 23A  according to aspects of the disclosure. 
         FIG. 24B  is a side view of the cutter housing of  FIG. 23A . 
         FIG. 24C  is a cross-sectional side view of the cutter housing of  FIG. 23B . 
         FIG. 24D  is a view of the cutter housing taken from line  24 D- 24 D of  FIG. 24C . 
         FIG. 25A  is front view of an embodiment of a cutter head. 
         FIG. 25B  is a side view of the cutter head of  FIG. 25A . 
         FIG. 26  is perspective side view of the cutter head positioned with the cutter housing with the cutter housing shown in phantom. 
         FIG. 27  is a cross-sectional side view of a handle of an embodiment of the cutter catheter. 
         FIG. 28  is a top view of an embodiment of a suture and pledget that can form an embodiment of a leaflet anchor. 
         FIG. 29  is a cross-sectional view taken through line B-B of  FIG. 28 . 
         FIG. 30  is a top view of an embodiment of a suture and pledget with apertures that can form an embodiment of a leaflet anchor. 
         FIG. 31  illustrates an embodiment of the leaflet anchor of  FIG. 30  with the suture extending through the apertures  31   
         FIG. 32  is a side perspective view of needle according to certain aspects of the disclosure. 
         FIG. 33  is a perspective view of a pledget delivery handle according to certain aspects of the disclosure. 
         FIG. 34A  is a top rear perspective view of a stabilization system and a suture management system in accordance with certain aspects of the present disclosure. 
         FIG. 34B  is a top side perspective view of the stabilization system and the suture management system of  FIG. 34A . 
         FIG. 35  is aside view of the stabilization system and the suture management system of  FIG. 34A . 
         FIG. 36  is a top view of the stabilization system and the suture management system of  FIG. 34A . 
         FIG. 37  is a closer top view of the rear portion of the stabilization system and the suture management system of  FIG. 34A . 
         FIG. 38  is a closer review view of the stabilization system and the suture management system of  FIG. 34A . 
         FIG. 39  is a distal end perspective view of an alternate leaflet anchor deployment needle. 
         FIG. 40  is a schematic block diagram of a system to provide a synchronized control signal based upon detection of a preselected point in the cardiac cycle. 
         FIG. 41  is a schematic block diagram of a trigger generator used in the system shown in  FIG. 23 . 
         FIG. 42  is a schematic block diagram of an actuator firing circuit used in the system shown in  FIG. 40 . 
         FIG. 43  is a schematic block diagram of an actuator unit used in the system shown in  FIG. 40 . 
         FIG. 44  illustrates an ECG signal, marker pulse, trigger pulse and firing pulse waveforms occurring in the system depicted in  FIG. 40 . 
         FIG. 45  illustrates a touch sensitive monitor which may be used in the device depicted in  FIG. 40 . 
         FIG. 46  is a schematic side perspective view of a heart with a transcatheter mitral chordal repair system in accordance with aspects of the present disclosure. 
         FIG. 47  is a cut-away side perspective view of a suture cutter mechanism in accordance with aspects of the present disclosure. 
         FIG. 48  depicts motion of a pledget suture and a suture lock in certain transcatheter mitral chordal repair systems, according to aspects of the present disclosure. 
         FIGS. 49 and 50  illustrate movement of sutures and a suture lock, according to aspects of the present disclosure. 
         FIG. 51  illustrates an anchor, retaining member, and suture lock of a transcatheter mitral chordal repair system in which an upper portion of the anchor extends along a portion of the outer surface of the retaining member, according to aspects of the present disclosure. 
         FIG. 52  illustrates a cut-away view of the transcatheter mitral chordal repair system of  FIG. 51 , with the suture lock located within the retaining member. 
         FIG. 53  illustrates an orientation of a suture lock, retaining member, and anchor according to aspects of the present disclosure. 
         FIG. 54  illustrates an orientation of a suture lock and suture, according to embodiments of the present disclosure. 
         FIG. 55  illustrates an anchor, retaining member, and suture lock of a transcatheter mitral chordal repair system in which the anchor extends over an anchor hub, according to embodiments of the present disclosure. 
         FIGS. 56, 57 and 58  illustrate an anchor, retaining member, and suture lock of a transcatheter mitral chordal repair system in which the anchor is advanced out of the retaining member and into adjacent tissue. 
         FIGS. 59 and 60  illustrate an anchor, retaining member, and suture lock of a transcatheter mitral chordal repair system in which an anchor pledget is located between the suture lock and the anchor hub, according to aspects of the present disclosure. 
         FIG. 61  illustrates a side cutaway view of a retaining member, according to aspects of the present disclosure. 
         FIG. 62  illustrates a side cutaway view of an upper portion of a retaining member, according to aspects of the present disclosure. 
         FIG. 63  illustrates a retaining member including a densified portion that secures an anchor hub, aspects to embodiments of the present disclosure. 
         FIG. 64  illustrates a cutaway view of the socket of  FIG. 63 . 
         FIG. 65A  illustrates a side perspective view of a socket, according to aspects of the present disclosure. 
         FIG. 65B  illustrates a top cutaway view of the socket of  FIG. 65A . 
         FIG. 66  is a schematic illustration of an anchor, retaining member, and suture lock according to aspects of the present disclosure. 
         FIG. 67  illustrates an orientation of a prosthetic chord, according to aspects of the present disclosure. 
         FIG. 68  is a side perspective view of a suture lock and lock driver mechanism in accordance with embodiments of the present disclosure. 
         FIG. 69  is a side perspective view of a suture lock after tightening and initial dis-engagement of a lock driver mechanism and boot in accordance with aspects of the present disclosure. 
         FIG. 70  is a side perspective view of the configuration of  FIG. 69  upon further dis-engagement of the lock driver and boot in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     U.S. patent application Ser. No. 15/858,671, filed Dec. 29, 2017 (the entirety of which is hereby incorporated by reference herein discloses systems and methods for the transvascular prosthetic chordae tendinae implantation. One aspect involves advancing a catheter into the left atrium, through the mitral valve, and into the left ventricle; deploying a ventricular anchor from the catheter and into a wall of the left ventricle, leaving a ventricular suture attached to the ventricular anchor and extending proximally through the catheter; and advancing a leaflet anchor into a mitral valve leaflet to secure the mitral valve leaflet to a leaflet suture, with the leaflet suture extending proximally through the catheter, and extending the leaflet suture over the top of the coaptive edge and securing the leaflet suture to the ventricular suture to limit a range of travel of the leaflet in the direction of the left atrium. Certain aspects are developed further herein. 
     The approach to the mitral valve can be accomplished through a standard transceptal approach to provide access to the left atrium. With this access, a first step can include securing a leaflet capture catheter to the leaflet of the mitral valve in the location determined to best correct regurgitation. Probing the surface of the leaflet from the superior atrium surface can advantageously provide immediate feedback as to the optimal location to add an additional mitral valve chord. In another implementation of the disclosure, the ventricular anchor is deployed first, followed by deployment of the leaflet anchor. 
     Referring to  FIG. 1 , a ventricular anchor such as a helical anchor  32  has been deployed near the apex  20  of the left ventricle  24 . While the helical anchor  32  is shown positioned near the apex  20  in the following Figures, the anchor  32  can be attached at a point that is offset from the thin tissue of the apex, and can be instead implanted in the generally thicker adjacent wall of the ventricle, such as between the two papillary muscles. This allows the implanted neo chord construct (suture, optional neo papillary muscle, and/or the helical anchor) to be aligned along a longitudinal axis substantially parallel to or concentric with the original path of the native chord. In certain embodiments, the implanted neo chord construct is aligned along a longitudinal axis that is within 5 degrees, 10 degrees, or 15 degrees of being parallel with the original path of the native chord and/or the path of the adjacent native chord. In addition, while a helical anchor is illustrated the anchor can have a different structure for engaging tissue of the heart and thus other tissue anchor structures can be used instead of a helical structure including various piercing, hook or radially expandable structures known for engaging tissue. 
     Referring to  FIGS. 2A and 2B , there is illustrated one implementation of a tissue anchor suitable for use as a ventricular anchor in accordance with an aspect of the present disclosure. The anchor assembly  50  will be described primarily in the context of the present chordae repair application, however the anchor may be utilized in any of a wide variety of other applications where a soft tissue or bone anchor may be desired. 
     The anchor assembly  50  generally comprises a coil  54  which may comprise any of a variety of materials such as stainless steel or Nitinol. The coil  54  extends helically between a proximal end  56  and a distal end  58 . Distal end  58  is provided with a sharpened tip  59 , and also carries a retention barb  61 , configured to resist reverse rotation of the coil and detachment from tissue. The proximal end  56  of the coil  54  is carried by (attached to or formed integrally with) a hub  57  discussed in additional detail below. 
     Extending distally from the hub  57  and within the coil  54  is an elongate core wire  62  having a sharp, tissue piercing distal end  64 . The distal end  64  is positioned distally of the distal end  58  of the coil  54 . This enables the sharp distal end  64  to pierce tissue upon contact, and prior to beginning rotation of the coil  54  to embed the coil  54  within the target tissue. Engaging the tip  64  prior to rotation of the anchor stabilizes the anchor against sideways movement allowing a single placement of the anchor  50  against tissue, and rotation of the coil  54  to engage tissue, without ‘walking’ of the anchor away from the desired target site as will be understood by those of skill in the art. A proximal end of the core wire  62  may be attached to the hub in any of a variety of ways, such as by soldering, brazing, adhesives and / or mechanical interference such as by entering an aperture in a sidewall or other surface of the hub  57 . 
     A radiopaque depth marker  66  is provided with an aperture  68  and is axially movably carried on the core wire  62 . A distal stop  70  such as a radially outwardly extending protrusion or annular ridge is carried by the core wire  62 , and spaced proximally of the sharpened distal end  64  to provide a core wire leading segment  72  on the distal side of the stop  70  so that the marker  66  cannot interfere with the tissue anchoring function of the distal tip  64 . The stop  70  functions to limit distal travel of the marker  66 . The marker  66  may be an annular structure such as a circular disc with a central aperture to receive the core wire  62 . 
     A coil spring  71  is concentrically carried over the core wire  62  and biases the radiopaque marker  66  in the distal direction. The radiopaque marker  66  is thus held in position against a proximal surface of the stop  70 . In use, the marker  66  rides on the surface of tissue at the target attachment site. As the helical coil anchor  54  is rotated and advances distally into tissue, the marker  66  rides proximally on the core wire  62  along with the tissue surface, compressing the coil spring  71  until the marker  66  is retracted proximally to the hub when the tissue anchor is fully embedded. This enables fluoroscopic visualization of the progress of the coil into tissue and of the fully engaged end point of embedding the coil  54  into the target tissue, by observing the changing distance between marker  66  and a reference such as the hub  57  or other radiopaque marker. 
     The hub  57  comprises a proximal connector for engagement with a rotational driver as discussed elsewhere herein. In one implementation, the connector comprises an aperture such as a hexagonal aperture for removably engaging a complementary surface structure on the distal end of the driver. A suture  74  is secured to the anchor assembly  50 , for example secured to the hub  57 , coil  54  or core wire  62 . In the illustrated embodiment, the suture  74  is attached to a cross pin  76  which may be inserted through one or two apertures in the sidewall of the hub and across a central hub lumen. The suture may additionally carry one or two or more radiopaque markers  82  spaced apart from the hub  57 , and may extend proximally through the proximal connector and a central lumen in the rotational driver. 
     A suture lock guide such as a tubular sleeve  78  extends proximally from the hub  57  for at least about 2 mm or 4 mm or 8 mm but generally no more than about 5 cm or 2 cm depending upon desired performance. The guide sleeve  78  may comprise a flexible material such as ePTFE. Preferably a radiopaque marker band  80  is carried by the proximal end of sleeve  78  and spaced axially apart from the marker  82  on suture  74 , to facilitate fluoroscopic visualization of the suture lock as it is advanced distally over the suture  74 . The marker band  80  may be positioned in between an inner layer and an outer layer of ePTFE sleeve, such as may result from placing the band over the sleeve and inverting the sleeve over itself to entrap the ring. 
     The suture lock guide may comprise any of a variety of structures such as a sleeve as illustrated or an alignment pin extending proximally from the hub and received within a lumen in the suture lock, for maintaining the orientation of the suture lock following detachment from the deployment catheter. Since the tension on the suture is optimized while the suture lock is held in place by the deployment catheter, any change in the orientation of the suture lock following release from the catheter would affect tension on the leaflet and potentially negatively affect the therapeutic value of the implant. The suture lock guide helps maintain constant the maximum distance between the ventricular anchor and the leaflet anchor both pre and post deployment from the catheter. In this manner the maximum tension on the leaflet suture (during systole) remains unchanged after the suture lock has been locked, both before and after detachment of the catheter. 
     The helical anchor assembly  50  may be delivered by a ventricular anchor delivery subsystem  300 .  FIGS. 2C-2E  illustrate various views of a ventricular anchor delivery subsystem  300  and its components.  FIG. 2C  depicts a perspective view of a distal end of the subsystem  300 .  FIG. 2D  depicts a perspective view of a proximal end of the subsystem  300 .  FIG. 2E  depicts a partially exploded view of a distal end of the subsystem  300 . 
     The subsystem  300  may be delivered through the delivery catheter  100 . The delivery catheter  100  may access the left atrium through conventional techniques, such as through an atrial trans-septal puncture. The delivery catheter  100  may be maintained in a substantially constant location throughout the procedure as various subsystems are placed and removed from the delivery catheter  100 . For instance, the distal end of the delivery catheter  100  may be positioned in the left atrium. In other implementations, the distal end of the delivery catheter  100  may be positioned in the left ventricle throughout the duration of the procedure. 
     As shown in  FIGS. 2C-2E , the ventricular anchor delivery subsystem  300  may comprise an outer sheath  304 , a driver (comprising shaft  307  and head  306 ), an anchor hub  308 , and an anchor  302 . The anchor may be a helical anchor  302  and the drive head  306  can be configured to rotate the helical anchor  302 . The helical anchor  302  may comprise an inner diameter configured to be received over the outer diameter of an anchor hub  308 . The helical anchor  302  may be securely fixed secured to the anchor hub  308  by an interference fit or other frictional engagement, soldering or other known attachment technique. The anchor hub  308  may be left implanted along with the helical anchor  302 . 
     The anchor hub  308  may comprise a lumen positioned substantially along a central axis of the anchor hub  308  for receiving a suture  74  ( FIG. 2A ) and attaching the suture  74  to the helical anchor  302 . In some embodiments, the suture  74  may comprise an attachment element (e.g. a knot or a washer) with a diameter sized to prevent the suture  74  from being pulled proximally through the anchor hub  308  lumen. For example, the suture  74  may be knotted on a distal side of the lumen. In some embodiments, the suture  74  may be tied to the anchor hub  308  (e.g., passed through the lumen, wrapped around a structure such as the outer surface or a cross pin  76  as shown in  FIG. 2B , and tied to itself). 
     The helical anchor  302  may comprise a distal section of windings and a proximal section of windings. The proximal section of windings may be spaced closer together than the distal section of windings and may be configured for securing the helical anchor  302  to the anchor hub  308 . The distal section of windings may be spaced further apart than the proximal section of windings and may be configured for insertion into the ventricular tissue. The anchor hub  308  may comprise an enlarged cross-section at its proximal end configured to abut the helical anchor  302  and/or prevent the helical anchor  302  from advancing proximally over the proximal end of the anchor hub  308 . Other helical anchors, such as those described elsewhere herein, may be configured to be used with the ventricular anchor delivery subsystem  300  described herein as well. 
     The proximal face of the helical anchor  308  may comprise a recess for receiving an extending portion  306 ′ of the driver head  306 . The recess may be non-circular (e.g., oblong or polygonal such as hexagonal) such that it is configured to transfer torque from the driver to the anchor hub  308  upon rotation of the driver. The recess may be positioned around the central lumen of the anchor hub  308 . 
     In other embodiments, the anchor hub  308  may comprise an extending portion and the driver  306  may have a complementary recess. The driver head  306  may be generally cylindrical, with a distally facing post or aperture with a complementary configuration to rotationally engage the corresponding component on the anchor. The driver head  306  may be fixedly coupled to a drive shaft  307 . The driver may comprise a central lumen through the driver head  306  and drive shaft  307  configured to receive the suture  74 . The central lumen of the driver may be configured to be aligned with the central lumen of the anchor hub  308 . The drive shaft  307  may be received within a guide shaft  305 . The diameter of the driver head  306  may be larger than the inner diameter of the guide shaft  305 . The outer sheath  304  may be sized to receive the guide shaft  305  as well as the driver head  306 , the anchor hub  308 , and the helical anchor  302 . 
     The outer sheath  304  may be delivered into the left ventricle and proximal to the ventricular attachment site via the delivery catheter  100 . In some embodiments, the outer sheath  304  may be delivered without a delivery catheter. In some implementations, the helical anchor  302  may be concealed within the outer sheath  304  until the outer sheath  304  is positioned proximal to the ventricular attachment site then pushed distally through the outer sheath  304  or the outer sheath  304  is proximally retracted so that the helical anchor  302  is exposed. The helical anchor  302  may be placed into contact with the ventricular tissue. Rotation of the drive shaft  307  may cause the driver head  306 , the anchor hub  308 , and the helical anchor  302  to rotate thereby screwing the ventricular anchor  302  into the ventricular tissue. Rotation of the driver  309  may axially advance the driver  309 , anchor hub  308 , and helical screw  302  in a distal direction with respect to the outer sheath  304 . 
     The drive shaft  307  may be rotated manually by a user using a drive handle  312 , as shown in  FIG. 2D . The proximal end of the ventricular anchor delivery subsystem  300 , as illustrated in  FIG. 2D , may comprise first and second hemostasis valves  314 ,  316 . The first hemostasis valve  314  may be positioned distal to the drive handle  312  and may provide access to the guide shaft  305 . The second hemostasis valve  316  may be positioned proximal to the drive handle  312  and may provide access to the central lumen of the driver. The ventricular anchor suture (not shown) may extend through the second hemostasis valve  316 . 
     In some implementations, the inserting portion  306 ′ of the driver head  306  and the recess of the anchor hub  308  may have a frictional engagement that transiently holds the two components together. The frictional engagement may be overcome upon proximal retraction of the driver by a counter force from the ventricular tissue once the helical anchor  302  is inserted. In some implementations, proximal tension on the suture  74  may provide an engagement force between the proximal hub  308  and the driver head  306 , which can be released upon retraction of the driver  309 . The driver head  306  may be proximally withdrawn into the outer sheath  304  before the outer sheath  304  is withdrawn into the delivery catheter  100 . 
     The non-implanted components of the ventricular anchor delivery subsystem  300  may be removed from the delivery catheter  100  and subsequent subsystems may be placed in the delivery catheter  100  for completing implantation of the neo chordae. In a modified embodiment, the ventricular anchor delivery subsystem  300  and subsequent subsystems such as the leaflet anchor delivery subsystem  330  may be positioned within the delivery catheter  100  at the same time and in certain arrangements the tissue and leaflet anchors can both be preloaded into the delivery catheter. In alternative embodiments, the implantation of the ventricular anchor may be performed in a different order (e.g., after the implantation of the leaflet anchor). The ventricular anchor delivery components may be proximally retracted over a proximal end of the suture  74 , which may remain extending through the delivery catheter  100  to the ventricular anchor  302 . 
     In certain implementations of the present disclosure, it may be desirable to provide a secondary anchor to prevent the helical coil  54  of the ventricular anchor  32  from reverse rotation post implantation which can cause the helical coil  54  to become disengaged from the attachment site. In general, the secondary anchor can be advanceable from a first configuration such as for transluminal navigation and attachment of the primary, helical anchor, to a second, deployed configuration for engaging tissue and inhibiting unscrewing of the helical anchor  54  from the attachment site. 
     In certain embodiments, the secondary anchor may be deployed into the second configuration automatically in response to full engagement of the primary helical anchor. Alternatively the secondary anchor may be deployed by manual manipulation of a control or distal advance of a pusher by the attending clinician. The pusher may be in the form of a tubular body axially movably carried over the anchor driver. Alternatively, the pusher may comprise the anchor driver. In such implementations, the anchor driver may be provided with an engagement surface structure such as a ratchet which cooperates with a complementary surface structure on a radially inwardly facing surface of the secondary anchor assembly. The anchor driver may be proximally retracted without affecting the secondary anchor, but subsequent distal advance of the anchor driver deploys the secondary anchor. The pusher may alternatively comprise the suture lock catheter, as discussed further below. 
     Embodiments of the secondary anchor described above and with respect to  FIGS. 2F and 2G  can be used independently and/or in combination with features and aspects of the ventricular anchor  32  described herein and with respect to the embodiments described with respect to  FIGS. 2A-2E . 
       FIGS. 2F and 2G  illustrate an embodiment of the ventricular anchor  32  that can include a secondary anchor  110 . In the illustrated embodiment, the secondary anchor  110  comprises at least a first tine  112  extending between a proximal end  114  and a distal sharpened end  116 . The tine  112  may be carried by a support  118 , such as by connection to proximal end  114 . Support  118  can facilitate axial advancement of the tine  112 . In the illustrated embodiment, the support  118  comprises an annular structure having an aperture  120 , such as a ring  122 . The aperture  120  is configured to axially movably receive the anchor driver (not illustrated), or other tubular structure or component that may be a part of the anchor deployment system. 
     The hub  57  is provided with at least a first tine guide  124 , such as an aperture or lumen, for axially movably receiving the first tine  112  therethrough. The first tine guide  124  may include a deflection surface for deflecting the tine  112  into a launch angle that inclines radially outwardly in the distal direction. The launch angle measured at the exit from the tine guide  124  may be within the range of from about 30 degrees to about 45 degrees, and in some implementations within the range of from about 35 degrees to about 40 degrees from the central longitudinal axis of the anchor. 
     As an alternative or in addition to the deflection surface, the tine may be pre biased radially outwardly, so that it ramps outwardly as it is advanced out of the tine guide  124 . Distal advance of the first tine  112  advances the tine through the first tine guide, distal of which the tine  112  extends radially outwardly in a distal direction to expose a length of tine of at least about 1 mm or 2 mm or 3 mm or 4 mm or more, depending upon the desired performance. Measured perpendicular to the longitudinal axis, the distal tip  116  of the fully deployed tine is at least about 1 mm or 2 mm or 3 mm or 4 mm or more from the outer surface of the helical coil  54 . The distal tip  116  upon full deployment may be spaced laterally from the helical coil by at least about 50% or 75% or 100% or more of the outside diameter of the helical coil. 
     The tine  112  may comprise any of a variety of materials such as stainless steel or Nitinol, having sufficient structural integrity to resist rotation and preferably capable of holding a bias. Tine  112  may comprise a flat ribbon or round wire, and in one implementation, comprises 0.016″ stainless steel round wire. 
     Distal advancement of the first tine  112  may be accomplished by applying distal pressure on the support  118 , such as by a secondary anchor deployment pusher or catheter advanced over the suture  74  and/or anchor driver discussed elsewhere herein. Alternatively, the secondary anchor  110  may be deployed by advancing the suture lock distally over the sutures and into contact with the support  118 , and further to advance the support  118  distally to entrap the support  118  in between the distal end of the suture lock and the hub  57 . In this manner, the suture lock can serve as a secondary anchor lock to preventing or inhibit the secondary anchor from backing away from the deployment site. 
     A second tine  126  may be provided, extending through a second tine guide  128  and connecting to the support ring  122 . Three or four or more tines may be provided, depending upon desired performance of the secondary anchoring system. In the illustrated embodiment, two tines are shown, spaced at approximately 180 degrees apart around the circumference of the helical anchor. In a three tine embodiment, the tines may be equidistantly spaced at approximately 120 degree intervals. 
     As illustrated, the tine guides  124 ,  128  can direct the tines  112 ,  126  through the fabric of the tubular suture anchor guide. The fabric may be provided with an aperture aligned with the path of the tine, or the tine may pierce the fabric during deployment. The exit path of the tines can be moved distally if desired, such that the tines extend axially through the hub and into the helical coil, and exit laterally between two spaced apart adjacent windings of the coil. The tines and/or the support  118  may comprise a radiopaque marker or material to enable fluoroscopic confirmation of full deployment. 
       FIGS. 3-6  depict the deployment of the leaflet anchor. Referring to  FIG. 3 , the ventricular anchor  32  has been deployed and is tethered to the catheter  100  by a ventricular anchor suture  74  and the ventricular anchor subsystem has been removed. The leaflet anchor is carried within a needle  338 , shown aimed at a target site on the atrial side of the leaflet. The needle  338  is axially reciprocally carried within the catheter  100 , such as within a tubular sleeve  332  advanceable through the catheter  100 . Additional details of the needle and needle driver are discussed below. 
     As shown in  FIG. 3 , in the illustrated arrangement, the needle can cross through the leaflet from the atrium to the ventricle and a preloaded suture can then be advanced into the ventricle. The suture can then be used to collapse the pledget against the ventricular side of the leaflet to anchor the suture to the leaflet as shown in  FIG. 4 . Thus the pledget forms a radially enlargeable leaflet anchor. In certain embodiments, other forms of a radially enlargeable leaflet anchor can be used. 
     The leaflet anchor and suture can then be used in combination with a ventricular anchor, suture and suture lock to effectively create a new mitral chord as shown in  FIG. 5 . As noted above, the leaflet anchor and suture can be used in combination with the systems and methods for the transvascular prosthetic chordae tendinae implantation disclosed in the U.S. patent application Ser. No. 15/858,671 (the entirety of which is incorporated by reference herein) and the various embodiments of ventricular anchors, sutures and suture locks disclosed therein. 
     Preferably, the leaflet anchor deployment subassembly is provided with a temporary anchor for capturing and stabilizing the leaflet while the needle tip  338  is advanced therethrough at a target side. As illustrated in  FIG. 3  and  FIG. 4 , a distal end  400  of delivery tube  332  or other system component carries a temporary tissue anchor such as a helical tissue anchor  402 . Anchor  402  may be similar to ventricular anchor  54  except that temporary anchor  402  does not have a distal barb since it is intended to be only momentarily in engagement with the leaflet. The anchor  402  thus comprises a helical element  406  which terminates in a distal tip  408 . 
     In use, the distal tip  408  is positioned at a target site on the surface of the leaflet, and the helical element  406  is rotated about its axis to engage and penetrate the leaflet. The needle tip  338  may be optionally engaged with the leaflet prior to rotation of the helical element  406 , and utilized to stabilize the anchor against moving away from the target site in response to rotation, in a manner similar to that discussed in connection with the ventricular anchor and  FIGS. 2A and 2B . 
     Following engagement of the helical element  406  to capture the leaflet from the atrial side and secure the leaflet to the catheter, the needle may be advanced distally through the central lumen defined by the helical element  406  and completely through the leaflet so that the needle tip  338  exits the ventricular side of the leaflet as seen in  FIG. 4 . An anchor deployment actuator such as a pusher extending through the needle may be utilized to deploy the anchor from the needle and into the ventricle. 
     Referring to  FIG. 5 , the leaflet anchor may be a pledget  340  similar to those described elsewhere herein. The pledget  340  may be coupled or attached to the distal end of a leaflet anchor suture  344 . The pledget may comprise a soft and/or flexible material such as a fabric. The suture  344  may extend through the needle  336 . The pledget  340  may be folded or compressed in a conformation comprising a reduced radial cross section such that it may be disposed within the needle  336  for delivery, as shown in  FIGS. 8 and 10  discussed below. The pledget  340  may expand from a reduced cross section to assume a larger radial cross section upon deployment from the distal end of the needle tip  338 , as shown in  FIG. 5 . In some embodiments, the pledget  340  may be pushed through the needle  336  via a push wire or release wire (not shown). Upon delivery through the needle tip  338 , proximal retraction of the leaflet suture  344  as shown in  FIG. 6  may cause the leaflet anchor to assume an axially collapsed, radially enlarged conformation which prevents the leaflet anchor from being retracted through the puncture in the leaflet and thereby anchors the leaflet suture  344  to the leaflet, as shown in  FIG. 7 . 
       FIGS. 6A-6D  schematically depict a pledget  340  connected to the distal end of a leaflet suture  344 . The pledget  340  may comprise two wings  341 ,  342 , which may be rolled/folded (e.g., both in a clockwise or counterclockwise direction) around a longitudinal axis of the pledget  340  to form a reduced cross section conformation. In some embodiments, the leaflet suture  344  may be integrally formed with the pledget  340 . In order to produce a foldable or collapsible configuration, the suture  344  may extend distally through the pledget, loop around the distal end of the pledget and return proximally and threaded back through one or more apertures (e.g., two apertures, three apertures, four apertures, etc.) formed in the pledget  340 , as shown in  FIG. 6A . In some embodiments, the apertures may be aligned along a center of the pledget  340 . 
     The apertures may extend through the pledget  340  and through the portion of the embedded portion of the suture  344  which is integral with the pledget  340 . The embedded portion of the suture  344  may be at least partially flatted within the pledget  340 . In some embodiments, the apertures may be placed substantially near the center of the pledget (e.g., immediately to the left or right of the embedded suture  344  or alternating between the left and right side of the suture  344 ). When deployed the suture  344  may be effectively joined to a distal end of the pledget  340  (e.g., the suture  344  may loop back to where it inserts between the pledget sheets). 
       FIGS. 6B-6D  schematically depict an example of a pledget as described elsewhere herein.  FIG. 6B  schematically depicts a pledget  340  formed by affixing a distal end (shown in dashed lines) of the suture  344  between two flat sheets, such that the sheets for left and right wings  341 ,  342 .  FIG. 6C  shows a cross-section of the pledget  340  along the axis of B-B illustrated in  FIG. 6B . In some embodiments, the suture  344  may be inserted between two sheets (e.g., substantially down the middle of the sheets) and pressed and/or laminated to join the three components together (e.g., under heat and/or pressure). At least one of the layers may be partially sintered. The suture  344  may be flattened and/or densified to improve resistance to suture tear out. The sheets may be flat polytetrafluoroethylene (PTFE) sheets (e.g., thin uncured expanded PTFE (ePTFE) sheets) or any other suitable material. In some implementations, the leaflet suture  344  may be disposed between the sheets in alternative configurations, such as a zig-zag or s-shaped configuration.  FIG. 6D  shows the pledget  340  of  FIG. 6B  comprising a plurality of apertures  343  through which the proximal tail end of the suture  344  may be threaded through. 
     In some embodiments, one or more apertures  343  may be formed through the pledget, in various configurations, to form a collapsible structure, as described elsewhere herein, which is configured to anchor the suture  344  against the mitral leaflet.  FIG. 6D  shows apertures  343  alternating around opposing sides of the suture  344 . In some embodiments, the apertures  343  may be formed on the same side of the suture  344  (e.g., in wing  341  or wing  342 ). In some embodiments, the apertures  343  may be formed through the suture  344 . The apertures  343  may be aligned along a center of the pledget  340 . The apertures  343  may be aligned along the length of the suture  344  (e.g., may form a straight line). The suture  344  may be at least partially flattened between the two opposing sheets, which may facilitate the placement of apertures  343  through the suture  344 . Various combinations of apertures  343 , including the positioning described above, may be used. 
     The pledget  340  may be formed such that the wings  341 ,  342  are approximately the same size or they may be formed to be different sizes. Upon proximal retraction of the leaflet suture  344 , the pledget  340  may be folded to assume an accordion-like conformation, as depicted in  FIG. 6A . The pledget  340  may assume a conformation comprising a substantially planar proximal surface which is approximately perpendicular to the longitudinal axis of the leaflet suture  344 . This conformation may facilitate anchoring the suture  344  in the leaflet. Upon anchoring the leaflet suture  344  in the leaflet, the leaflet anchor delivery subsystem  340  may be withdrawn from the delivery catheter  100 . The leaflet anchor delivery components may be proximally retracted over a proximal end of the suture  344 , which may remain extending through the delivery catheter  100  to the leaflet anchor  340 , alongside the ventricular anchor suture  74 . 
       FIGS. 8-10  illustrate various views of the leaflet anchor delivery subsystem  330  and its components.  FIG. 8  depicts a perspective view of a distal end of the subsystem  330 .  FIG. 9  depicts a perspective view of a proximal end of the subsystem  330 .  FIG. 10  depicts an exploded view of the distal end of the subsystem  330 . 
     As shown in  FIGS. 8 and 10 , the leaflet anchor delivery subsystem  330  may comprise an outer delivery tube  332 . The tube  332  may optionally include a deflection zone and may be configured to be steerable by an operator such as by proximal retraction of one or two or more pull wires (not shown) along various sides of the flex tube  332 . The operator may control the flexion of the flex tube via a knob  352  or lever or other actuation mechanism positioned on a handle  350  at the proximal end of the leaflet anchor delivery subsystem  330 , as shown in  FIG. 9 . 
     An internal tubular shaft or needle  336  terminating at a distal end with a needle point  338  may extend through the delivery tube  332 . The internal needle  336  may comprise a hypotube, extrusion or braided tube or catheter which is flexible enough to conform to the shape of the optional flex tube  332 . A needle tip  338  may be coupled to the distal end of the internal flexible shaft  336 . A flexible jacket  333  may surround the flex tube  332  and a delivery shaft  334 . 
     The proximal end of the internal tubular shaft  336  may be connected to a needle handle  354 , as shown in  FIG. 9 . The needle handle  354  may comprise a hemostasis valve  356 . The leaflet suture  344  may be inserted through valve  356 . Valve  356  may be a tuohy-borst valve. The needle handle  354  may include additional ports  358  for accessing the lumen of the internal flexible shaft  336 . The needle handle  354  may be positioned proximally to the handle  350  such that the internal flexible shaft  336  extends through the handle  350  and into the lumen of the delivery shaft  334 . The handle  350  may comprise a hemostasis valve for receiving the internal flexible shaft  336  and sealing the internal components of the handle, including the opening to the delivery shaft  334 , from the ambient environment. 
     The needle tip  338  may be extendable and retractable by extending the needle handle  354  toward the handle  350  or retracting the needle handle  354  from the handle  350 , respectively. Distal advance of the needle  336  may be accomplished by manually advancing the handle  354 . Alternatively, the distal advance of the needle may be assisted by a mechanical or electromechanical mechanism to produce a relatively high velocity, low stroke length distal advance. 
     Exertion of pressure on the leaflet when the needle tip  338  is extended distally beyond the tube  332  may cause the needle tip  338  to puncture the leaflet such that the needle tip  338  may extend through to the opposite side (e.g., the atrial side) of the leaflet, as shown in  FIG. 4 . This pressure may be exerted by extending the needle tip  338  and/or retracting the entire delivery device  330  in a proximal direction with the needle tip  338  in an extended position. 
     The ventricular anchor suture  74  and the leaflet anchor suture  344  may be coupled together in a tensioned fashion to form the neo chordae implant or to join two sections of the neo chordae implant together, such that the neo chordae extends between the ventricular anchor  302  and the leaflet anchor  340  across the atrial side of the coaptive edge of the leaflet. The overall length of the neo chordae may be adjusted by proximal traction of one or both sutures  74 ,  344  prior to engaging the suture lock  376  such that an appropriate tension is applied to the leaflet, with the tension subsequently maintained by the ventricular anchor  302 . The sutures  74 ,  344  may remain extending proximally through the delivery catheter  100  to a location outside the body. In some embodiments, the proximal ends of the suture  74 ,  344  may be fed into a handle or proximal portion of a suture lock delivery system  370  to facilitate placement of the suture lock and cutting of the sutures  74 ,  344 . In some embodiments, the proximal ends may remain free or coupled or secured by other means. 
       FIG. 11  depicts the advancement of suture lock  376  over the ventricular anchor suture  74  and the leaflet suture  344 . The suture lock delivery subsystem  370  may be advanced through the delivery catheter  100  and a tubular pusher catheter  372  may push a suture lock  376  along the distal direction of the sutures  74 ,  344 . Once the suture lock  376  has reached the ventricle, it can continue to be pushed along the ventricle suture  74  with proximal traction on the suture  74  and while allowing the leaflet suture  344  to feed distally through the catheter if needed for the suture lock  376  to advance distally to the ventricular anchor. As discussed further below,  FIG. 12  illustrates the final construct with the leaflet anchor and ventricular anchors tethered together to form an artificial chordae. The proximal tails of the two sutures has been severed and catheter proximally retracted from the ventricle through the mitral valve. 
       FIGS. 13-14  illustrate various views of the suture lock delivery subsystem  370  and its components.  FIG. 13  depicts a perspective view of a distal end of the subsystem  370 .  FIG. 14  depicts a perspective view of a proximal end of the subsystem  370 .  FIG. 15  depicts a partially exploded view of the distal end of the subsystem  370 .  FIG. 16  depicts a perspective view of a distal end of a cutting assembly.  FIGS. 17 and 18  depict side views of a cutting assembly portion of the subsystem  370 .  FIG. 19  depicts a side view of a suture lock  376  and a distal end of a torque driver  388  configured to engage the suture lock  376 .  FIGS. 20 and 21  depict a proximal end view and a distal end view, respectively, of the suture lock  376 . 
     The suture lock delivery subsystem  370  may be configured to advance (e.g., slide) a suture lock  376  over both the sutures  74 ,  344  (or even three or four or additional sutures) securing them together. The sutures  74 ,  344  may each be proximally retracted relative to the suture lock  376  to tension the sutures  74 ,  344  and modulate the length of each suture  74 ,  344  between the suture lock  376  and the respective tissue anchors  302 ,  340 . Once the tension and length of the neo chordae implant is optimized, the suture lock  376  may be locked to fix the length of the sutures  74 ,  344  such that the sutures  74 ,  344  can no longer move with respect to the suture lock  376 . The sutures  74 ,  344  may then be severed at a point proximal to the suture lock  376 . The suture  74 ,  344  may be cut by the same suture lock delivery subsystem  370  which delivered the suture lock  376 . In other embodiments, a separate cutting device may be inserted into the delivery catheter  100  after the suture lock has been locked in place. 
     The suture lock allows one or two or more sutures to be advanced therethrough and adjusted, and then locked with sufficient clamping efficiency that an ePTFE suture can be prevented from slipping from the suture lock under normal use conditions (e.g., withstand tension of at least about 60% or 80% or more of the suture breaking strength, without slipping). The lock may be reopened to permit readjustment of the tension on the mitral leaflet, and retightened, until a desired result has been achieved. The tightening tool may then be removed, leaving the suture lock behind. 
     The suture lock  376  may be advanced along the sutures by a retainer catheter  373 . The distal end of the retainer catheter  373  may be coupled to a retainer element  377  ( FIG. 15 ). The retainer element may comprise a flange  371  or other mechanical feature configured to engage the suture lock  376 . For example, the flange  371  may be inserted into a recess at a proximal end of the suture lock  376 . In some embodiments, rotation of the retainer catheter  373  and/or translation substantially perpendicular to the axial direction of the retainer catheter  373  may be used to disengage the retainer catheter  373  from the suture lock  376 . 
     The sutures  74 ,  344  may extend from their respective tissue anchors to pass through the suture lock  376 , entering from a distal opening  395  in a distal face of the suture lock  376 , shown in  FIG. 21 , and exiting at a proximal opening  394  to the suture path in a proximal face of the suture lock  376 , shown in  FIG. 20 . The sutures  74 ,  344  may extend through a channel in a cutter head  375  proximal to the suture lock  376  and along the outside of the retainer catheter  373  and through the delivery catheter  100 . The cutter head  375  may be coupled to the distal end of a cutter catheter  372 . The retainer catheter  373  may extend through an internal lumen of the cutter catheter  372  such that the two catheters  372 ,  373  may be extendable or retractable relative to one another. 
     Once the sutures  74 ,  344  are locked (fixedly secured) within the suture lock  376 , the proximal ends of the suture  74 ,  344  may be cut adjacent to the proximal face of the suture lock. The sutures  74 ,  344  may be cut by advancing the cutter catheter  372  coupled to the cutter head  375  toward the proximal face of the suture lock  376 . As schematically illustrated in  FIGS. 17-18 , as the cutter head  375  advances along the retainer catheter  373  toward the retainer element  377 , the cutter head brings the sutures  74 ,  344  into close proximity to a cutting blade  379  positioned on the retainer element  377 . The cutter head  375  is configured to advance over the retainer element  377  in such a fashion that the channel in the cutter head  375  retaining the sutures  74 ,  344  becomes increasingly spatially occupied by the blade  379 . As the blade  379  is forced into the channel of the cutter head  375 , the blade  379  shears the sutures  74 ,  344 . Application of proximal tension to the sutures  74 ,  344  may facilitate the cutting of the sutures  74 ,  344 . In other embodiments, different actuations (e.g., rotation of a cutting catheter) can be configured to sever the sutures  74 ,  344 . 
     In some implementations, more than two sutures may be employed and may be locked within the suture lock  376  and severed by the suture lock delivery subsystem  370  in the same fashion. In some embodiments, advancement of the cutter head  375  over the retainer element  377  may facilitate the disengagement of the retainer catheter  373  from the suture lock  376 . For example, the cutter head  375  may advance to a distal position where it is configured to stabilize the suture lock  376 , allowing the retainer catheter  373  to be axially and/or rotationally disengaged from the suture lock  376 . 
       FIG. 19  illustrates a side view of an example of a suture lock  376  (shown with its outer casing/shell removed). The sutures may pass through the suture lock  376  from a distal end to a proximal end as described elsewhere herein. The suture lock  376  may comprise a screw  382  configured to distally advance or proximally retract a push wedge  384 , depending on the direction of rotation of the screw. The screw  382  may be rotated by a torque shaft  388 . The torque shaft  388  may comprise a driver head configured to mate with recess  381  (e.g., a polygonal recess or other non-circular shaped recess, as shown in  FIG. 20 ) positioned at the proximal end of the suture lock  376  such that rotation of the torque shaft  388  causes rotation of the screw  382 . The torque shaft  388  may extend through an internal lumen of the retainer catheter  373 . The torque shaft  388  may be rotated at its proximal end by a knob  398  or other actuation mechanism positioned at a proximal end of the subsystem handle  396 . The handle  396  may include a hemostasis valve  397 . In some implementations, the sutures  311 ,  344  may pass through the hemostasis valve  397 . 
     Advancement of the push wedge  384  by the torque shaft  388  may cause a ramp or angled surface  386  to gradually compress one or more springs, such as spring pins  388 . The springs bias the clamp upward to open the suture path until forced closure by rotation of the torque shaft  388 . Compression of the one or more springs  388  may force a clamp  390  downward on the sutures  311 ,  344 , compressing the sutures  311 ,  344  between two opposing surfaces. In some embodiments, the clamp  390  and the opposing surface  392  may have notched surfaces configured to mate with each other at discrete increments. The mated notched surfaces may provide enhanced friction and in some implementations mechanical interference for retention of the sutures  311 ,  344  between the opposing surfaces such that they cannot be withdrawn, either proximally or distally, from the suture lock  376 . In some embodiments, the tightening may be reversible by rotating the torque shaft in an opposite direction. 
     Once the suture lock is properly positioned over the sutures  74 ,  344  and locked into place, the sutures  74 ,  344  may be severed as described elsewhere herein.  FIG. 12  depicts the retraction of the suture lock delivery subsystem  370  after the sutures  74 ,  344  have been cut. Once the suture lock delivery subsystem  370  has been removed from the delivery catheter  100 , the delivery catheter  100  may be withdrawn from the body. 
     Collapsible Anchor Delivery Sheath 
     Depending on the configuration of the anchor assembly  50 , coil  54  and/or tubular sleeve  78 , in certain embodiments, the outer profile of the deployed anchor assembly  50  may be larger than the inner diameter of the delivery catheter  100  and/or introducer sheath. Thus, in certain embodiments, the ventricular anchor delivery subsystem  300  described above can be modified as shown in  FIGS. 22A-E  such that a ventricular anchor delivery subsystem  400  includes a collapsible anchor delivery sheath  404  that can provide protection and support for the anchor assembly  50 , coil  54  and/or tubular sleeve  78  during delivery while also being collapsible to fit through the inner diameter of the delivery catheter  100 . In this manner, the collapsible anchor delivery sheath  404  can be collapsed to a smaller diameter while the sheath  404  is withdrawn into the delivery catheter  100 . Such a collapsible delivery sheath  404  can also be configured to secure the anchor assembly  50  during delivery such that the anchor assembly  50  will not be stripped out of the delivery sheath  404  by, for example, the beating ventricle or other motion or geometries encountered during introduction and placement. The delivery sheath  404  may also in certain embodiments be sufficiently kink resistant to resist movement of the beating ventricle once the coil  54  of the anchor assembly  50  is engaged with the heart wall. As will be described below, the sheath  404  can include a radiopaque tip for detection. The delivery sheath  404  in certain embodiments can have a sufficient inner diameter to retain the coil  54  and tubular sleeve  78  but small enough in outer diameter to fit within the delivery catheter  100  or introducer sheath. In certain embodiments, the anchor delivery sheath  404  is collapsible such that when the anchor assembly  50  is delivered, the sheath  404  may be drawn through the narrower constriction of the delivery catheter  100  without excessive force and without tearing. In certain embodiments, the anchor delivery sheath  404  is adapted to transition in diameter from the size inner diameter of the delivery catheter  100  (for example, in some embodiments, about 9 Fr) to a second, larger, size required to fit the anchor assembly  50  (for example, in some embodiments, about 19 Fr) 
     In one specific non-limiting, exemplary embodiment of the collapsible anchor sheath  404 , the sheath comprises an approximately 0.005″ wall thermoplastic elastomer material (such as, for example, Pebax) configured into tubes of three different diameters. For example, two relatively shorter pieces can be used to transition the diameter from a smaller diameter catheter (9 French in an embodiment) to the a larger diameter for accommodating the anchor assembly  50  (19 French diameter in an embodiment). The third tube can form the collapsible portion of the sheath itself. All three pieces can be formed over a tapered mandrel using a thermal bonding or other suitable forming process. In a further embodiment, a radiopaque marker, such as a polymer radiopaque marker band made from, for example, a thermoplastic elastomer with 60% wt Tungsten that be incorporated with the sheath and thermally or otherwise suitably bonded to the sheath. 
       FIGS. 22A-F  illustrate the ventricular anchor delivery subsystem  400  with the collapsible sheath  404 . The ventricular anchor delivery subsystem  400  can be used in the methods and steps described above and with the drive shaft  307 , driver head  306  and other components described above for rotating and delivering the anchor assembly  50 . The ventricular anchor delivery subsystem  400  can include a sheath  405  having a proximal portion  410 , an intermediate portion  412  and a distal portion  414  that can include the collapsible sheath  404 . The proximal portion  410  can include a hemostasis valve  416  with a side port  418 . In the illustrated embodiment the proximal portion  410  and the intermediate portion  412  of the sheath  405  can be formed from a tube such as a stainless steel hypotube which can have an outer diameter of  9  French. The collapsible sheath  404  can be formed form a separate material that is bonded or otherwise attached to the smaller diameter tube. 
     As seen in  FIGS. 22D and 22E , a distal end of the collapsible sheath  404  can have an larger diameter than the intermediate portion  412 .  FIG. 22E  is a longitudinal cross-sectional view of  FIG. 22D . Threads  422  can be formed on the inner surface of the distal end of the collapsible sheath  404  to retain the anchor assembly  50  within collapsible sheath  404 . Thus, in one arrangement, the coil  54  of the anchor assembly  50  can engage the threads  422  in the collapsible sheath  404  such that the anchor assembly  50  is retained within the sheath  404 . Rotation of the anchor assembly  50  can drive the anchor assembly  50  forward through the sheath  404 . In this manner, the sheath  404  can support the anchor assembly  50  during delivery such that the anchor assembly  50  will not be stripped out of the delivery sheath  404  during delivery. The distal larger diameter end of the sheath  404  is also collapsible to fit through the inner diameter of the delivery catheter  100  such that the collapsible anchor delivery sheath  404  can be withdrawn into the delivery catheter  100 . In modified arrangements, the sheath  404  can include grooves, protrusions or other elements for engaging the anchor assembly  50 . 
     In general, the sheath  404  may be provided with any of a variety of interference elements which releasably engage an implantable device such as a helical tissue anchor and resist axial pull out of the helical anchor once positioned within the sheath. Rotation of the anchor in a first direction relative to the sheath causes the anchor to move axially distally as the helix unthreads from the sheath. The interference element may be a helical (radially outwardly extending) channel or (radially inwardly extending) ridge, extending at least about one or two or four or more complete revolutions about the inner circumference of the sheath. 
     Alternatively, at least about one or two or six or more radially inwardly extending tabs may be provided, each extending less than a full revolution around the circumference of the sheath. Engagement tabs may have a length in the circumferential direction of no more than about 90 degrees, and in some implementations no more than about 45 degrees or 20 degrees or 10 degrees or less around the inside surface of the sheath. Depending upon the desired performance, the implant can be disengaged from the catheter by a plurality of complete rotations, or by a rotation through, for example, less than a full rotation such as less than about a half or a quarter turn relative to the catheter. 
     Either the catheter side wall, the rotational anchor driver or both may be provided with torque transmission elements such as a spiral wound or braided side wall to facilitate rotation of the driver and inhibit rotation of the deployment catheter. 
     The sheath extends between a distal open end and a proximal end attached to the catheter shaft. The proximal end may have an angled engagement surface, for slidably engaging the distal opening on a delivery catheter so that the sheath is transformable from the radially enlarged configuration to the radially reduced configuration in response to proximal retraction into the delivery catheter. 
     The sheath may have an axial length that corresponds to the intended implant, generally less than about 15 cm and in many implementations no more than about 10 cm or 5 cm or 3 cm or less. 
     The rotational interlock feature described above can be implemented on the inside surface of a flexible (collapsible) sidewall as described above, or on a fixed (non collapsible) sidewall catheter, in an embodiment where the OD of the device is smaller than the ID of the lumen in the deployment catheter. In a collapsible sheath implementation, the sheath may be collapsed following deployment of the device, by proximal retraction into the delivery catheter, which may have an ID which is smaller than the OD of the sheath when in the radially enlarged configuration for containing the implantable device. 
       FIG. 22F  illustrates a method of forming the collapsible sheath  404 . A mandrel  426  having a first diameter  430  and a second smaller diameter  432  can be provided.  FIG. 22F  is a longitudinal cross-sectional view of the mandrel similar to the cross-section view of  FIG. 2E . The small diameter portion  432  of the mandrel  426  can be positioned within distal end of the intermediate portion  412 . The mandrel  426  can include a transition zone  427  between the first and second portions  430  and  432  of the mandrel  426 . A coil  450  can be positioned on an outer surface of the larger diameter portion  430  of the mandrel  426 . A sheath  452  which will form the collapsible sheath  404  can be positioned over the mandrel  426  and the distal end of the tube intermediate portion  412 . In an embodiment, the sheath  452  can comprise an approximately 0.005″ wall thermoplastic elastomer (such as Pebax). The sheath  452  can be heat treated while on the mandrel  426  such that the proximal end of the sheath  452  is reduced in diameter and bonded to intermediate portion  412  and the distal end of the sheath  452  takes on the form of the coil  450  to form internal threads on the sheath  404 . As noted above, the sheath  404  can include a radiopaque marker, such as a polymer radiopaque marker band made from, for example, a thermoplastic elastomer with 60% wt Tungsten that be incorporated with the sheath and thermally or otherwise suitably bonded to the sheath  404 . In an embodiment, the marker is positioned on a distal end of the sheath. 
     Rotational Suture Cutter 
       FIGS. 23A-C ,  24 A-D,  25 A-B and  26  illustrate another embodiment of a cutter catheter  500  that can be used to cut sutures  74 ,  344  in one more of the procedures and systems described above. For example, once the sutures  74 ,  344  are locked (fixedly secured) within the suture lock  376 , the proximal ends of the sutures  74 ,  344  may be cut adjacent to the proximal face of the suture lock  376  with an embodiment of the suture cutter catheter  500  described herein. 
     With initial reference to  FIGS. 23A and 23B , the cutter catheter (also referred to as a endovascular suture cutter)  500  can include an outer sheath  504  extending through the delivery catheter  502  and an inner shaft  506  extending through the outer sheath  504 . A proximal end of the outer sheath  504  can be coupled to a luer lock  503 . With reference to  FIG. 24 , the outer sheath  504  is coupled to a cutter housing  510  at the distal end of the outer sheath  504 . The cutter housing  510  can be in the shape of a barrel that forms cylindrical chamber. The distal end of the cutter housing  510  can have opening  512  through which sutures can extend from the opening  512  and then through a window  514  formed on a side of the cutter housing  510  to define a suture path extending through the cutter housing  510 . In this manner, sutures  74 ,  344  can be advanced through the cutter housing  510  as shown in  FIG. 23C . 
     With reference to  FIGS. 25A, 25B and 26 , a cutter head  520  can be rotationally positioned within the cutter housing  510 . The cutter head  520  can have a hollow half-barrel or partial barrel shape that includes a cutting edge  522 . The cutting edge  522  can have a helical path or curved shape as the edge  522  extends from the distal end to the proximal end of the cutter head  520 . The cutting edge  522  can extend along a side surface of the cutter head  520  as shown in  FIG. 26 . Sutures extending through the distal opening  512  and the side window  514  can be cut by rotating the cutter head  520  within the cutter housing  510 . Rotation will cause the sutures to be compressed between the cutting edge  522  and the inside surface of the cutter housing  510 . Because of the profile of the cutting edge  522 , the sutures can be sliced which can produce a more efficient and reliable cutting motion as compared to compressing or chopping motions. 
     Advantageously, when the endovascular suture cutter  500  is advanced into the heart the cutting edge  522  of the cutter head  520  is not exposed and covered by the surfaces of cutter housing  510 . For example, as shown in  FIG. 26 , the cutting edge  522  is covered by the inside surfaces of the cutter housing  510 . In the illustrated embodiment, the cutter catheter  500  also includes a lock  540  at the distal end of the endovascular suture cutter  500  to prevent rotation between the cutter head  520  and the cutter housing  510 . In the illustrated embodiment, the lock  540  can comprise a protrusion  550  on the cutter head  520  that engages a corresponding recess  552  in the cutter housing  510 . When engaged, the protrusion  550  and the recess  552  prevent rotation between the cutter head  520  and the cutter housing  510 . In this manner, the cutting edges  522  can remain in a position in which they are not exposed and are covered by the inner surfaces of the cutter housing  510 . The protrusion  520  and the recess  522  can be disengaged by axially advancing the rotational housing  520  with respect to the cutter housing  510 . In the disengaged position, the cutter head  520  can be rotated with respect to the cutter housing  510  to cut sutures as described above. The protrusion  520  and the recess  522  can be reversed in other arrangements and/or positioned on other portions of the cutter housing  510  and cutter head  520 . 
       FIG. 27  illustrates a proximal handle  570  which can be formed around the luer lock  503 . The handle  570  can be used to control the movement of the cutter head  520  and cutter housing  510 . In this arrangement, the cutter head  510  can be fixed with respect to a handle  570 . The cutter head  520  can be rotationally linked and coupled to a suture cutter handle  572  such that rotation of the suture cutter handle  572  will cause the cutter head  520  to rotate with respect to the cutter housing  510 . As shown, the suture cutter handle  572  is positioned in retracted position with respect to the handle  570  in which the protrusion  550  and the recess  552  would be engaged to prevent rotation between the cutter head  520  and the cutter housing  510 . A lock  578  can be provided on the handle  570 . Releasing the lock  578 , allows the cutter head handle  572  to move axially (e.g., distally in the illustrated embodiment) with respect to the handle  570 . In this manner, the protrusion  550  and the recess  552  can be disengaged and the suture cutter handle  572  can be rotated with respect to the handle  570  to cut sutures. 
     Pledget with Radiopaque Marker 
       FIGS. 28-31  illustrate an embodiment of a leaflet anchor  641  that can include a pledget  640  and can be use used with and in the systems and methods described herein.  FIGS. 28 and 29  schematically depict an embodiment the pledget  640  that formed by affixing a distal end a suture  644  between two flat sheets  645   a ,  645   b.    FIG. 29  shows a cross-section of the pledget  640  along the axis of B-B illustrated in  FIG. 28 . In some embodiments, the suture  644  may be inserted between the two sheets  645   a ,  645   b  (e.g., substantially down the middle of the sheets) and pressed and/or laminated to join the three components together (e.g., under heat and/or pressure). At least one of the layers may be partially sintered. The suture  644  may be flattened and/or densified to improve resistance to suture tear out. The sheets may be flat polytetrafluoroethylene (PTFE) sheets (e.g., thin uncured expanded PTFE (ePTFE) sheets) or any other suitable material. In some implementations, the leaflet suture  644  may be disposed between the sheets in alternative configurations, such as a zig-zag or s-shaped configuration.  FIG. 30  shows the pledget  640  of  FIG. 28  comprising a plurality of apertures  643  through which a proximal tail end  660  of the suture  644  may be threaded through. In some embodiments, one or more apertures  643  may be formed through the pledget, in various configurations, to form a collapsible structure, as described elsewhere herein, which is configured to anchor the suture  644  against the mitral leaflet.  FIG. 30  shows apertures  643  extending through the center of the pledget through the suture  644 . In some embodiments, the apertures  643  can be alternating around opposing sides of the suture  644 . In some embodiments, the apertures  643  may be formed on the same side of the suture  644  (e.g., in wing  641  or wing  642 ). In the illustrated arrangement, the apertures  643  can be formed through the suture  644 . The apertures  643  can be aligned along a center of the pledget  640 . The apertures  643  may be aligned along the length of the suture  644  (e.g., may form a straight line). The apertures  643  can extend from a first or proximal end to a distal or second end of the pledget  640 . The suture  644  may be at least partially flattened between the two opposing sheets, which may facilitate the placement of apertures  643  through the suture  644 . Various combinations of apertures  643 , including the positioning described above, may be used. 
     A radiopaque marker may be added to the pledget  640 . For example, in the illustrated embodiment of  FIGS. 28-31 , a marker band  660   a  can be positioned about the suture adjacent the second or distal end of the pledget  640 . The marker band  660 a can be crimped to the suture  644  in this position. The proximal end  660  of the suture  644  can then be threaded through the apertures  643  formed in the pledget  640  starting with an aperture  643  closest to the marker band  660   a  as shown in  FIG. 31  thereby positioning the marker band  660   a  at the distal end of the pledget  640  when deployed. The pledget  640  may be transformable from an elongate strip configuration to a radially enlarged, axially shortened configuration by proximal retraction of the suture  644 . 
     Flexible Pledget Delivery Needle 
     As noted above, in certain embodiments, a radially enlargeable leaflet anchor may be carried within a hollow needle having a sharpened end for piercing the leaflet. The radially enlargeable leaflet anchor may comprise a pledget. The pledget may be transformable from an elongate strip configuration to a radially enlarged, axially shortened configuration by proximal retraction of the suture. 
     In some embodiments, the hollow needle comprises an exterior surface having one or more helical grooves. In other embodiments, the hollow needle may comprise one or more raised helical coils, for example, a thin coil that is attached to the exterior of the hollow needle.  FIG. 32  shows an embodiment wherein the hollow needle  1204  has a helical coil  1205  attached to an outer surface of the needle  1204 . Since the leaflet may be in motion before, during and after the puncture process, the leaflet may have enough range of motion that a hollow needle without grooves or the raised helical coil may slip off of the leaflet. The grooved surface or raised helical coil can present several benefits. First, in the event that the hollow needle does not completely puncture the leaflet, i.e., the distal portion of the hollow needle does not allow delivery of the pledget or if the physician determines that the hollow needle may prematurely slip off of the leaflet during the procedure, the physician can provide a force onto the catheter or a mechanism within the catheter that transfers a rotational force to the needle, thereby screwing the hollow needle in further to the leaflet tissue and securing leaflet so that it does not move off of the needle. Secondly, once the pledget has been delivered, the physician can provide a force to the catheter or a mechanism within the catheter that transfers a rotation force to the hollow needle, thereby allowing the physician to remove the needle by unscrewing the hollow needle from the leaflet. 
     According to the catheter system used, the hollow needle can be directed to puncture the needle from the left atrial side of the heart to the left ventricular side. In other embodiments, the hollow needle can be directed to puncture the leaflet from the left ventricular side of the heart to the left atrial side. Since the entry points from the exterior of the patient to the heart can vary, it can be desirable that at least a portion of the hollow needle is flexible. Utilizing a flexible hollow needle can allow the hollow needle to travel around all of the curvature in order to access the leaflet and can allow the physician the ability to fine tune placement of the needle prior to puncturing the leaflet.  FIG. 32  shows cut portions  1203  of the hollow needle which allow the hollow needle to flex as needed. In some embodiments, the cut portions  1203 , of the hollow needle can be laser cut, can be machined, or other known methods can be used. 
     The system can also comprise a hollow needle wherein the hollow needle punctures the leaflet via the release of a stored energy source. For example, the stored energy can be in the form of a spring, a liquid under pressure, a gas under pressure, an electrically activated piston or other known method. In some embodiments, the stored energy device is a spring. In still further embodiments, the spring is located in the pledget delivery handle  1202 , shown in  FIG. 33 . 
     The amount of stored energy should provide enough force to the hollow needle in order to puncture the leaflet a sufficient distance or depth. As used herein, “sufficient distance or depth” can mean one or more of the following: wherein the distal end of the hollow needle completely punctures the leaflet without causing the hollow needle to contact or puncture any other structures within the heart; allows the needle to stay engaged with the leaflet while the leaflet is moving; and allows the physician to deliver the pledget. If the needle did not puncture through the leaflet a sufficient distance or depth, the physician can rotate the hollow needle in order to drive the hollow needle further through the leaflet tissue. If the needle did not puncture the leaflet in the correct location, the physician can rotate the hollow needle in an opposite direction thereby removing the hollow needle from the leaflet tissue. The system can then be re-armed, that is, re-energized with the stored energy, repositioned and actuated in order to properly place the hollow needle for delivery of the pledget. In some embodiments, the system comprises a control device wherein the physician is able to position the catheter (containing the retracted hollow needle) on or near the leaflet, check the positioning of the catheter relative to the leaflet to be sure that the catheter is in the correct location and actuate the release of the stored energy to puncture the leaflet. At least a portion of the distal end of the catheter, of the hollow needle or both may be radiopaque or include other visualization aids in order to allow the physician to check that the position of the puncture is correct prior to delivering the pledget, via the release of the stored energy. 
     Component Stabilization and Suture Management System 
     An aspect of the present disclosure that can be used alone or in combination with aspects of the disclosure described above is a stabilization system for a transvascular cardiac repair that can be used to stabilize and/or adjust the position of a proximal portion (e.g., a handle) of one or more of the subassembly components described (e.g., the delivery catheter  100  and/or one or more of the various subsystems that can be advanced into the delivery catheter). The stabilization system can also include a suture management system for adjusting the length and/or the tension on one or both of the ventricular anchor suture and at least one leaflet suture. 
     In certain aspects, the suture management system for transvascular cardiac repair can assist in maintaining a substantially fixed force, or tension, on the sutures while the physician is adjusting the suture lengths and setting the tension of the suture lock. It should be understood by one of skill in the art that the term “substantially fixed force” may include allowing for some small changes in tension to occur. For example, in one aspect a 10% change in tension can occur. 
     An advantage of using such a suture management system is that the leaflet can be allowed to continue moving during the repair procedure in its “natural” state in response to the beating of the heart, but each pledget can be maintained substantially in contact with the leaflet through application of substantially constant tension on the sutures. Additionally, suture tangling can be prevented or minimized through use of the apparatus. A further advantage is that the physician can individually adjust each suture for decreasing or increasing tension to tailor the final movement of the leaflet, as appropriate. The suture management system can be located in the operating room near the physician during surgery. After the anchor and leaflet sutures are deployed in the patient, the ends of the sutures that pass through the delivery catheter can be attached to the suture management system and held in the aforementioned substantially constant tension. 
     In certain aspects of the disclosure, aspects of the stabilization system can have advantages and be used independently and without aspects of the suture management system or device. In a similar manner, in certain aspects of the suture management system can have advantages and can be used independently and without aspects of the stabilization system. Nevertheless, as described herein, certain advantages can be achieved system utilizing combinations and sub-combinations various aspects of the stabilization and suture management systems described herein. 
       FIGS. 34A and 34B  illustrate an embodiment of a stabilization system (also referred to herein as “system”)  1500 . The system  1500  can comprises a base, or tray,  1502  which can be mounted to a stand or table (not shown) to avoid movement of the apparatus during a procedure. As shown in  FIG. 35 , the base can comprise an upper or top plate  1504  and a lower or bottom plate  1506 . The upper and lower plates (also referred to herein as top and bottom plates)  1504 ,  1506  can be movably connected to each other through an adjustable positioning mechanism  1510  (also referred to herein as “adjustment mechanism”), which in the illustrated embodiment can comprise a lower threaded boss  1512  that is coupled to a the lower plate  1506  and an upper threaded boss  1514  that is coupled to the upper plate  1504 . A screw  1516  can extend through the lower and upper threaded bosses  1512 ,  1514 . Axial motion of the screw  1516  (see  FIG. 35 ) with respect to the lower plate  1506  can be limited such that rotation of a screw handle  1518  can cause the upper plate  1504  to move with respect to the lower plate  1506 . In this manner, the adjustment mechanism  1510  can re-position in the upper plate  1504  (and components coupled thereto) with respect the direction of arrow  1520  to the lower plate  1506 , which can be attached to the stand or table, as needed. The adjustment mechanism 1510  can include a lock to prevent movement between the upper and lower plates  1504 ,  1506 . In several embodiments, other mechanisms can be used to similarly move the upper and lower plates reciprocally in axial direction with respect to each other such as sliding plates, complimentary rail and second channel or rollers. 
     A stabilization portion  1550  of the system  1500  can include several components that can be used to hold or stabilize components of the mitral valve chord repair devices described above. In particular, as will be described in detail below, the device can be used to hold or stabilize a proximal portion (e.g., a handle) of an introducer sheath, a delivery catheter  100 , ventricular anchor delivery subsystem  300 , a suture lock delivery subsystem  370 , a pledget delivery subsystem or handle  1202 , and/or proximal end or handle of a suture cutter catheter  500  and such components can be configured in accordance with the embodiments and aspects describe herein. 
     For example, the system can include a first docking platform  1600  that can be positioned on a distal portion of the system  1500  and can be referred to herein as the “distal docking platform  1600 ”. The distal docking platform  1600  can be configured to hold or stabilize a handle or proximal portion of an introducer catheter through which various components of the delivery subsystems described herein can be advanced. With reference to  FIG. 35 , the distal docking platform  1600  can include a first stabilization device  1602  which can be in the form of a clamp  1602 . The first stabilization device  1602  can be configured to clamp around a tubular portion of catheter such as an introducer or access sheath. In the illustrated embodiment, the clamp  1602  comprise pair of clamp plates,  1604 ,  1606  that can be moved towards and away from each other by a threaded post  1608  coupled to a handle  1610 . Accordingly, in the illustrated arrangement manipulation of a control such as rotation of the handle  1610  can bring the plates  1604 ,  1606  together to clamp the introducer sheath (not shown) to the system  1500 . In several embodiments, other mechanisms can be used in the first stabilization device  1600  to stabilize a catheter or introducer sheath such as friction fit devices, collets, or devices that positively connect to engagement features on a handle of the introducer sheath. 
     As shown in  FIGS. 34A, 34B and 35 , the clamp can be coupled to the upper plate  1504  base  1502  by an arm  1620 . The arm  1620  can have an “L-shape” that positions the clamp  1602  above and forward along the axial the axial direction of the upper plate  1504 . The arm  1620  can be coupled to the upper plate such that movement of the upper plate  1504  with respect to the lower plate  1506  causes axial movement of the clamp  1602 . 
     As best seen in  FIG. 36 , distal docking platform  1600  can include a second stabilization device  1650 . In the illustrated embodiment, the second stabilization device  1650  can also be in the form of a clamp and can be provided on the on the arm  1620 . In the illustrated embodiment, the second stabilization device  1650  can be positioned on an elbow of the arm  1620 . The second stabilization device  1650  can be used to stabilize another component of the mitral valve repair system descried herein. For example, the second stabilization device  1650  can be used to stabilize the proximal end (or handle) of the suture lock delivery subsystem (see e.g.  FIG. 14 ). 
     The illustrated second stabilization device  1650  can include a clamp  1652  for holding components. See  FIG. 34A . In the illustrated embodiment, the clamp  1652  comprises pair of plates that can be moved towards and away from each other by a control such as a screw similar to the first stabilization device. Accordingly, in the illustrated arrangement rotation of the screw can bring the plates together to clamp a portion of the suture lock delivery subsystem (not shown) to the system  1500 . In several embodiments, other mechanisms can be used in the forward mount to stabilize the suture lock delivery subsystem such as friction fit devices, or devices that positively connect to engagement features on the suture lock delivery subsystem. As shown in  FIG. 36 , the arm may include a platform  1660  that can used to support a portion of the handle or other portion of the suture lock delivery subsystem. In one arrangement, the second stabilization device  1650  can be used to secure the front portion of the suture lock delivery subsystem while the rear or back portion of a handle suture lock delivery subsystem rests on the platform  1660 . 
     With continued reference to  FIGS. 35 and 36 , the system  1500  can include a second docking platform  1700 , which in the illustrated embodiment can be positioned proximal to the first docking platform  1600  and can also be referred to herein as the proximal docking platform  1700 . The proximal or second docking platform  1700  can be supported above the base  1502  by an arm  1702  that extends from the top plate  1504 . The proximal docking platform  1700  can be generally at the same elevation as the stabilization devices described above. The proximal docking platform  1700  can include components of a suture management system, which will be described in more detail below. The proximal docking platform  1700  can include a third stabilization device  1710 . The device  1710  can include an elongate concave support surface such as a U-shaped channel extending in the axial direction that can be used to support components such as a handle of the ventricular anchor delivery subsystem according to embodiments described herein. The second docking platform  1700  can be coupled to the top plate  1504  through the arm  1702  such that movement of the top plate  1504  causes the platform  1700  to move. Accordingly, in the illustrated arrangement, proximal docking platform  1700  and the distal platform  1600  can both carried by the upper plate and in several embodiments can be fixedly carried by the upper plate. 
     With continued reference to  FIGS. 35 and 36 , the system  1500  can include a third docking platform  1800 . The third docking platform  1800  can be positioned between, in an axially direction of instruments being mounted thereto, the first and second docking platforms  1600 ,  1700  which as described above can be positioned in distally and proximally with respect to each other. The third docking platform  1800  can also be referred to herein as the intermediate docking platform  1800 . The intermediate docking platform  1800  can include a fourth stabilization device  1802 , which can be in the form of a vice or clamp. The intermediate docking platform  1800  can be positioned can be positioned between the first and second docking platforms  1600 ,  1700 . The intermediate docking platform  1800  can include an adjustment mechanism  1810 , which in the illustrated embodiment can comprise a threaded engagement between the stabilization device  1802  and a lower rail  1812 . The lower rail  1812  can be fixed with respect to the upper plate  1505 . A screw  1816  can be rotated to move the stabilization device  1802  with respect to the rail  1812  and upper plate  1504 . In this manner, the adjustment mechanism  1810  can re-position in the fourth stabilization device (and components coupled thereto) to the lower plate  1506  , which can be attached to the stand or table, as needed. The adjustment mechanism  1810  can include a lock to prevent movement. The intermediate docking platform can be carried by the upper plate  1504 . The adjustment mechanism  1810  can also re-position in the fourth stabilization device (and components coupled thereto) to the upper plate  1504  and components that are carried by or fixedly carried by the upper plate such as the distal and proximal docking platforms (and components coupled thereto). 
     In one embodiment of use, the fourth stabilization device can be used to stabilize the delivery catheter such as according to the delivery catheter  100  described above. In certain embodiments, the first stabilization device  1650  can be used to stabilize an introducer catheter while the fourth stabilization  1802  device can used to stabilize the delivery catheter  100  which is inserted through the introducer catheter. In this manner, rotation of the screw  1816  can allow fine movement of the delivery catheter with respect the introducer catheter. That is movement of the intermediate docking platform can move the delivery catheter with respect to the distal docking platform and the introducer catheter mounted thereto. 
     With reference to  FIGS. 37 and 38 , a suture management system  1700  can include at least one, two, three or more tensioning components that can be used to hold each suture and assist to keep the sutures under tension at all times, thus avoiding slack which could result in the pledgets being pulled into the left atrium or the left ventricle from the force created with each heartbeat, or additionally to avoid slack sutures binding up in the left atrium or left ventricle, or even slack sutures binding up with other chordae in the left ventricle. 
     For example, in one embodiment, the anchor suture may be attached to an anchor tension component  1720 . The anchor tension component  1720  can comprise a rotatable spool  1712  equipped with a torque limiting fixture such as a clutch to limit the amount of tension that can be applied to a suture (for example a suture coupled to the ventricular anchor) wrapped around the spool. The anchor tension component  1720  can advantageously avoid or reduce the risk of the anchor being pulled out of the heart wall if too much tension is applied to the anchor suture. In another embodiment, the anchor tension component  1720  may comprise a spring loaded post configuration to impart tension to the sutures. In one embodiment, a proximal end of a suture coupled to the ventricle anchor  302  of the ventricular anchor delivery subsystem  300  can be wrapped around the anchor tension component  1720  after the ventricle anchor is deployed. In this manner, a constant tension can be applied to the suture and the torque clutch limiting fixture can prevent or limit excessive tension from being applied to the ventricle anchor. In one embodiment, the torque limit of the clutch is between about 0.2 N to about 5 N. 
     With continued reference to  FIGS. 37 and 38 , at least one, two, three or more suture adjustment fingers  1770  can be provided allow adjustment of the pledget suture tension on the leaflet. In use, a suture that is coupled to a pledget can be attached to a tensioning force, such as a weight  1750  to provide the desired tension. In certain embodiments, the weight can be within the range from about 2 to about 8 grams. In the illustrated embodiment, the weights  1750  can be stored on the proximal platform  1700  by providing weight mounts such as a plurality of holes, recesses or sockets that can receive the weights  1750 . The suture (e.g., a leaflet suture) can be placed in a suture guide  1760  which can be notch or groove formed on the platform  1700 . The guide  1760  can be configured to allow the suture to axially slide while providing some constraint in lateral movement. The proximal docking platform  1700  can include at least one, two, three, or more suture guides  1760 . By hanging the end of the suture (for example a leaflet suture) attached to a weight  1750  over the edge of a platform  1700  a constant tension can be applied to the pledget sutures which can be useful in limiting or preventing suture tangling. As noted above, the platform  1700  can be provided with more than one guide  1760  so that more than one suture can be hung over the edge of the platform  1700 . 
     As shown in  FIGS. 37 and 38 , the platform  1700  can also include the suture adjustment features or fingers  1770  that can be positioned near or adjacent the notches or grooves  1760 . The suture adjustment features  1770  can comprise rotatable spools. Each spool can include a slot  1774  through which a suture can extend. The rotatable spools  1770  can then be rotated to adjust the tension on the suture. 
     The suture management system can provide a dynamic leaflet management system. An advantage of using such a system is that the leaflet can be allowed to continue moving during the repair procedure in its “natural” state in response to the beating of the heart, but each pledget can be maintained substantially in contact with the leaflet through application of substantially constant tension on the sutures. Additionally, suture tangling can be prevented or minimized through use of the system. A further advantage can include providing the physician with the ability to individually adjust each suture for decreasing or increasing tension to tailor the final movement of the leaflet, as appropriate. For example, in an embodiment of use, after the advancing the suture lock (embodiments described above), into the patient and before locking and cutting the sutures, the tensions on the sutures can be adjusted to while viewing valve competency. This can be done by rotating the spools to increase or decrease the slack in the wire and the corresponding tension. Once the desired tension is achieved, the suture lock can be activated as described above. 
     A plurality of sutures can be fixed to the suture management apparatus, including for example up to 4, and multiple suture management apparatuses may be used, as needed. The apparatus components may comprise any suitable sterilizable materials which meet the apparatus performance requirements, including non-limiting examples such as stainless steel, acetal resin such as polyoxymethylene, PTFE, aluminum, 3D printed resin materials, and the like. 
     Leaflet Tissue Anchor Deployment System 
     In accordance with a further aspect of the present disclosure, there is provided an alternative leaflet tissue anchor deployment system. Referring to  FIG. 39 , a needle deployment catheter  332  axially reciprocally carries a needle  336 . A radio opaque marker band  1900  is provided at the distal end of the needle deployment catheter  332 , so that positioning of the marker band  1900  can be visualized in relationship to the mitral valve leaflet while the needle  336  is proximal retracted within the catheter  332 . 
     In  FIG. 39 , the needle  336  is illustrated in the distally advanced configuration. Needle  336  comprises a tubular body  1902  having a sidewall  1904  and at least one flexibility enhancing feature such as a slot pattern. In the illustrated embodiment at least one serpentine slot  1906  extends through the side wall. The serpentine slot  1906  may be formed in any variety of ways known in the art, such as by laser etching a hypo tube. The serpentine slot  1906  enhances the lateral flexibility of the needle  336  along a deflection zone, to facilitate aiming at the appropriate location on the mitral valve leaflet. The deflection zone is typically less than about 4 cm or less than about 2 cm in length, but long enough to contain the entire length of the pledget. 
     The needle  336  terminates distally in a sharpened tip  1908  separated from the tubular side wall  1904  by an inclined face  1910 . The inclination angle of the face  1910  will generally be within the range of from about 30 degrees and 85 degrees, preferably within the range of from about 70 degrees and 80 degrees, and in one implementation is about 75 degrees. 
     At least one tissue retention element  1912  is provided, to permit rapid, forcible powered advance of the needle  336  distally through tissue, but resist proximal retraction of the needle  336  from the target tissue. Retention element  1912  may comprise any of a variety of structures which extend radially outwardly from the tubular sidewall  1904 , such as at least one or two or five or 10 or more barbs, annular rings or tabs. In the illustrated embodiment, the retention element comprises annular rings in the form of a continuous helix  1914  which may be formed from a polymeric strand or metal wire wrapped into a helix around the tubular body  1902 . In one implementation, a helical wire such as a 0.008 inch wire is welded or otherwise secured to the tubular body  1902 . 
     Distal advance of the needle  336  from the diploma catheter  332  at a sufficient velocity enables the needle  336  to penetrate the leaflet, without the need for the leaflet stabilization anchor such as  406  disclosed in  FIG. 3 . Retention elements  1912  provide sufficient retention to retain the leaflet on the needle, until following deployment of the pledget. Thereafter, the needle may be proximally retracted without rotation, or may be rotated, to unscrew and remove the needle from the leaflet. 
     If additional leaflet stabilization is desired, stabilization may be achieved by the temporary leaflet anchor disclosed previously herein, or by alternative mechanical techniques of grasping or pinching the leaflet or by suction or freeze-grabbing with a cryo-catheter. These techniques would include a cryo-catheter of the type used in ablation procedures to freeze a target tissue. These cryoablation-catheters used for atrial fibrillation often attach themselves to the mitral leaflets accidentally and need to be deactivated to release the attached leaflets. This same cryo attachment can be used to locate and isolate the leaflet in question for stabilization during deployment of the leaflet anchor deployment needle. The cryo catheter uses a gaseous exchange (NO or Argon) to drop the temperature of the tip of the catheter, and can reach temperatures as low as minus 75 degrees Celsius. 
     Actuator Control System 
     Deployment of the mitral leaflet anchor described herein is accomplished by piercing the leaflet from the atrial side of the valve. In order to avoid the need for a grasping structure to capture and support the leaflet during leaflet puncture, and use a needle such as that shown in  FIG. 39 , the distal ejection of the leaflet anchor deployment needle can be timed to correspond with peak (systolic) pressure in the ventricle which occurs at about the QRS wave. This synchronizes piercing of the leaflet with mitral valve closure so that systolic pressure within the ventricle provides the necessary back up support during penetration of the leaflet from the atrium. 
     Timing of leaflet needle launch with the cardiac cycle can be accomplished manually by the clinician, or can be partially or fully automated depending upon the desired implementation. For example, a visual or audio signal or fluoro image may alert the clinician to the timing of the QRS complex, allowing the clinician to press the launch trigger or other control to deploy the needle. Since clinician reaction times can vary, it may be desirable to partially or fully automate the needle launch procedure. 
     For example, a needle  338  may be provided with an automated needle driver, such as a solenoid carried by the proximal end of the catheter. The solenoid is activated to distally project the needle in response to an activation signal that corresponds in time to a target time in the cardiac cycle, such as during closure of the mitral valve. 
     Alternatively, the activation signal may be in the form of a visual, tactile or auditory signal to the clinician, in response to which the clinician pushes a control such as a button or slider to manually advance the needle, or pushes a control that activates an electromechanical or mechanical needle driver. 
     In another implementation of the disclosore, needle deployment can be accomplished manually by the clinician, but only after disengagement of a lock out. In this implementation, a removable mechanical interference may be created at or linked to a proximal portion of the needle shaft. A distally facing interference surface may be carried by a radially outwardly extending tab or annular flange coupled to the needle, or a distal surface of an aperture extending through the needle. For the present purpose, ‘needle’ refers to the needle itself, as well as any proximally extending structure (e.g., extension tube or rod) that is mechanically linked to and moves with the needle as will be understood by those of skill in the art. 
     A proximally facing interference surface is configured to be movable between an engaged configuration in which it engages in an interference fit with the distally facing interference surface on the needle, and a disengaged configuration in which the distally facing interference surface and associated structure is free to advance distally to eject the needle. The proximally facing interference surface may be carried on a stop such as an axially movable pin or a pivotable or sliding lever which is movably carried by the proximal handpiece. A stop driver such as a solenoid is configured to move the stop between the engaged and disengaged configurations. 
     The stop may be initially engaged, to prevent deployment of the needle. In response to an activation signal indicating the target time (e.g., during or about at the QRS complex), the stop is retracted into the disengaged configuration. This prevents the clinician from prematurely deploying the needle, but allows manual deployment of the needle at the desired target time. The stop may be automatically returned to the engaged configuration following a preset time window following the activation signal, to prevent late deployment of the needle and create a narrow window in which the clinician is allowed to launch the needle. If the clinician failed to timely deploy the needle within the window, the opportunity to launch the needle will reappear with subsequent QRS complex occurances. 
     A variety of techniques have been developed to detect the QRS complex directly, or a proxy for that point in the cardiac cycle. Direct detection techniques include power spectrum analysis, bandpass filtering, differentiation, template matching, and waveform feature-dependent real-time techniques. Proxies include blood pressure such as measured intravascularly in the arterial or venous side or within an atrium or ventricle of the hears, or measured noninvasively such as peripheral blood pressure. Venous side measurements can serve as a proxy for the timing of the QRS complex since the aortic valve is open when the mitral valve is closed, leaving a fingerprint on the cyclic venous pressure curve. The data from any of the foregoing sources may desirably be adjusted to take into account any time delay from the true QRS complex, depending upon the desired time sensitivity. Preferably, the ECG signal will be obtained from a conventional ECG monitor which will normally already be present and in operation in the surgical suite. 
     A typical ECG waveform consists of a P wave indicating atrial depolarization, a QRS complex indicating ventricular depolarization, a T wave indicating ventricular repolarization, and a possible U wave in some cases indicating the extension of the repolarization. The dominant activity of an ECG usually relates to identification of the QRS complex in real time, for various monitoring and diagnostic purposes. The QRS complex or wave normally lasts about 80 to 120 ms in duration and corresponds to the commencement of ventricular contraction and ejection of blood via the aortic valve. This also corresponds to pressure responsive closure of the mitral valve, which is significant for the purpose of the present disclosure. 
       FIGS. 40-45  depict a system which provides control of an actuator in synchrony with heart  10 . As used herein, actuator refers to anything that is activated in response to a control signal triggered by an event in the cardiac cycle, such as a visual, audio or tactile feedback to the clinician, an automated needle firing mechanism, or a lockout mechanism in a manually operated needle deployment embodiment, that prevents the clinician from deploying the needle until the actuator unlocks the firing mechanism. 
     An overview of such a system is shown in  FIG. 40  and is seen to comprise a component to sense the cardiac cycle  212 , a component to generate a trigger pulse for the actuator in response to the sensed cardiac cycle  218 , a component to position the leading edge of the trigger pulse at a specified time within the cardiac cycle  232 , a component to define the width of the trigger pulse to occur during the cardiac cycle  234 , and a component to control the firing of the actuator in response to the trigger pulse and for a period in response to the defined width  222 . 
     In particular, electrocardiogram (ECG) unit  212  electrically connects to heart  10  of a patient so as to sense the cardiac cycle and provide ECG signal  216 . ECG unit  212  may be connected to the heart in any known manner for sensing cardiac signals including surface mounted electrodes typically adhesively mounted to the patient&#39;s chest, as well as internal or intracavitary electrodes. As an alternative, the sensing connection may further be incorporated integrally with the catheter  332 , such as through the provision of one or more electrical leads extending through the catheter  332  to conduct electrical signals or operate a sensor (e.g., pressure sensor) or electrode at the distal end of the catheter  332 . Electrodes may be either of unipolar design, in which case a surface contact may be used or bipolar design. The electrical lead may extend proximally through catheter  332  and end in a standard electrical connector which may then be removably connected to the ECG unit  212  and communicate sensed signals  216  thereto. 
     Signal  216  is delivered to trigger generator  218 . Trigger generator  218  provides a trigger pulse  220  to actuator firing circuit  222 . Actuator firing circuit  222  energizes actuator  224  such as to fire the needle or remove a barrier that inhibited the clinician from prematurely firing the needle as has been discussed. 
     The position of trigger pulse  220  in the heartbeat cycle of ECG signal  216  is determined by pulse positioning circuit  232 . The width of the pulse  220  and its duration during the heartbeat cycle is determined by pulse width circuit  234 . Trigger generator  218 , as well as pulse positioning circuit  232  and pulse width circuit  234 , may be included as an additional board in a PC or a microprocessor  236 , in which case the system can be controlled through a computer keyboard and suitable software. PC  236  and ECG  212  may have separate monitors, or they may have a single monitor  238  which displays both the ECG and information about the trigger pulse  220 . 
     Trigger generator  218  may include a marker pulse circuit  250  which provides marker pulse  252  and trigger pulse circuit  254  which responds to marker pulse  252  to create trigger pulse  220 . Alternatively, marker pulse circuit  250  is included in the ECG itself in some cases. 
     This can be better understood with reference to  FIG. 44 , where ECG signal  216  may be seen as consisting of a series of heartbeat cycles  256   a ,  256   b ,  256   c  each of which contains the waveforms Q, R, S and T. Where waveform R crosses preselected threshold  258 , marker pulses  252   a ,  252   b ,  252   c  are created. Trigger pulses  220   a ,  220   b ,  220   c  are then created by trigger pulse circuit  254 . The position of the leading edge  260  and the overall width  262  of each trigger pulse  220  is determined respectively by pulse positioning circuit  232  and pulse width circuit  234 . In response to trigger pulse  220 , a firing pulse  264  indicated as  264   a ,  264   b  and  264   c ,  FIG. 24 , is created to energize actuator  224 . 
     In  FIG. 42 , actuator firing circuit  222  is shown to include gate  270  which generally inhibits the delivery of trigger circuit  220  to actuator laser power supply  272  (when relevant) in actuator unit  224 . The inhibiting effect of gate  270  can be overcome when the operator activates a switch  274 . Trigger pulse  220  is still inhibited, however, by arming circuit  276  which in turn can have its inhibiting effect overcome by the operation of arming switch  278 . This double lock on the delivery of trigger pulse  220  to actuator power supply  272  ensures that the firing of the actuator is truly desired and not accidental. Thus the operator must first arm the system by operating arming switch  278  to enable arming circuit  276 . Then and only then is he able to pass the next occurring trigger pulse  220  through gate  270  to the actuator power supply  272  by actuating switch  274 . Further details of a suitable design for synchronizing a trigger signal with the QRS wave can be found in U.S. Pat. No. 5,674,217 to Wahlstrom, et al, filed Nov. 16, 1993, the disclosure of which is hereby incorporated in its entirety by reference herein. 
     Meltable Suture 
     The disclosed system can, in certain embodiments, utilize polytetrafluoroethylene (PTFE) or expanded polytetrafluoroethylene (ePTFE) sutures due to their desirable tensile strength and relatively low creep. However, PTFE and ePTFE sutures are not easily severable by cutting or by melting. 
     In order to overcome this challenge, some embodiments of the present disclosure relate to sutures wherein at least a portion of the suture is meltable. In some embodiments, the suture can be a bi-component suture, wherein a distal end of the suture comprises a meltable suture material and the proximal end of the suture is a non-meltable suture material. In some embodiments, the distal portion of the suture comprises less than 50% of the total length of the suture. In other embodiments, the proximal end of the suture comprises greater than or equal to the total length of the suture. In another embodiment, the bi-component suture may comprise one portion of a meltable suture, wherein the meltable portion is a relatively small meltable zone with non-meltable suture material on either side of the meltable zone. The meltable zone should be located at a position on the suture so that it does not impact the tensile strength or creep resistance of the implanted prosthetic chordae. When a bi-component suture is used, the junction between the meltable portion and the non-meltable portion should be placed proximate to the location of the suture lock or the point at which the suture will be tied or knotted so as not to affect the strength of the suture. None or a relatively small portion of the meltable suture should be under tension during the normal functioning of the heart after implantation of the prosthetic chordae. The bi-component suture should have enough tensile strength over the entire length of the suture, and especially at any interface of a meltable portion with a non-meltable portion, so that the physician can provide enough tension on the suture during the tensioning step so that the suture does not break when tension is applied to correct the mitral valve regurgitation. 
       FIG. 46  illustrates one embodiment of a schematic side view of a heart, wherein the left atrium  3301  and the left ventricle  3302  are shown separated by the posterior and anterior mitral valves (not labeled). In this embodiment, a pledget  3303  is secured to the ventricular side of the leaflet with one portion of non-meltable suture  3304  extending from the pledget into the left atrium  3301  passing to the left ventricle  3302  between the two leaflets. In the left ventricle  3302 , a tissue anchor  3305  is secured to the heart tissue using a helical anchor  3306 . Non-meltable suture  3308  is joined to non-meltable suture  3304  with knot  3307 . Meltable suture  3309  shows only a portion of the suture after having been cut with the remaining distal end of the meltable suture having been retracted through the catheter (not shown). In this embodiment, all of the tension of the beating heart is on sutures  3304  and  3308  with substantially no tension on meltable suture  3309 . The length of the distal ends of the sutures should be as small as possible. Note that only one distal end of sutures  3304  and  3308  are shown. 
     The system can further comprises a suture cutter. Once the tension is set in the one or more sutures and the mitral valve regurgitation is corrected or minimized, the suture cutter can be advanced through the catheter placed over the distal ends of one or more of the sutures in order to melt the meltable suture, thereby severing the suture. The distal end of the meltable suture can be retracted through the catheter to be removed from the patient. Each of the one or more sutures can be cut one at a time or two or more sutures can be melted at one time. The suture cutter comprises a heat source, for example, a coil that can be energized in order to heat the coil so that the temperature proximate to the coil rises above the melting temperature of the meltable suture. 
       FIG. 47  illustrates an embodiment wherein a suture cutter  3310  is advanced through the catheter (not shown) over the distal ends  3311  of the sutures and to the suture lock  3312 . The suture connected to the leaflet pledget  3303  and the suture connected to the anchor  3306  having been tensioned to minimize or correct mitral valve regurgitation are clamped in the suture lock  3312  so that sutures are not able to move through the suture lock  3312  as tension is applied to the sutures during the normal functioning of the heart. The suture cutter  3310  can comprise a heating source, for example, a heater coil  3315 , a short tube comprising a heater housing  3316  that is coaxial to the heater coil  3315 , which may serve to insulate the heart structure from the heat, and has a larger inside diameter than the outside diameter of the heater coil, a hypotube  3317 , which may serve to prevent blood from entering the catheter, and an insulated conductor  3318  which provides electrical energy to the heater coils to provide a temperature above the melting point of the meltable suture. The transmission of the electrical energy to the heater coil is actuated by the physician when the suture cutter has been moved into position and can be deactivated by the physician following the cutting of the sutures. In  FIG. 47 , the non-meltable suture (not labeled) extends just past the suture lock (toward the direction of the suture cutter) and the meltable portion of the suture is located coaxial with and inside the inner diameter of the coils of the suture cutter. In this way, once the distal portion of the suture or sutures has been removed, only a relatively short portion of suture ends, or tails, extend beyond the suture lock, and the remaining suture portions that extend to the leaflet and to the ventricular anchor are non-meltable sutures and remain securely clamped in the suture lock. 
     The meltable suture component(s) can include, but are not limited to, suitable melting compositions including polyolefin, polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyester, polyamide, polyglycolide/L-lactide, polyethylene terephthalate, silicone, collagen or other amino acid protein and a combination thereof. In some embodiments, a portion of the suture is meltable using any one of the previously described polymers as the meltable portion of the suture or meltable zone. The non-meltable portion of the suture can be PTFE or ePTFE. 
     Suture Lock Guide 
     The embodiments discussed above can provide effective mechanisms for transcatheter mitral chordal repair, e.g., implanting and effecting prosthetic chords. Embodiments discussed below build on many of these concepts to provide additional advantages. For example, the normal cardiac functions of the heart can cause mitral chordal repair systems to undergo cyclic motion and loading. In particular, a suture lock or other components (e.g., the suture) can oscillate or otherwise move within the ventricle as a result of the heart&#39;s normal compression cycles. This motion is generally shown in  FIG. 48 , where the arrows  4180 ,  4182  generally indicate motion of a suture and motion of a suture lock, respectively. 
     The oscillatory motion of the sutures and the suture lock can contribute to excessive wear on the suture, particularly at their junctures with the suture lock. The resulting wear could eventually result in the premature deterioration and failure of the prosthetic chord. In particular, in some systems the sutures pass through the suture lock, e.g., along its longitudinal direction. The sutures connecting the mitral leaflet and the anchor extend from the one end of the suture. The weight of the suture lock will pull the other end of the suture lock down slightly relative to the true orthogonal, and this angular movement can force the sutures against the suture lock. If the suture lock includes relatively sharp angles, those angles can introduce shearing forces that can cause the sutures to prematurely break. For example,  FIG. 49  illustrates a suture lock  4206  whose orientation results in the suture  4211  located against a sharp angle on the suture lock  4206 . During movement of the suture  4211  and suture lock  4206 , the sharp angle introduces shearing forces on the suture  4211 . Suture  4244  can be subjected to similar shearing forces. These shearing forces can be amplified by rotational movement of the suture lock  4206 , as represented by arrow  4207 . 
     Furthermore, increasing tension on the sutures tends to rotate the suture lock into an orientation that is somewhat orthogonal to the sutures, as shown in, e.g., FIG.  50 . This movement, in addition to the mass and resulting inertia of the suture lock during other movements, can add a high-impulse force to the sutures, e.g., as part of a “whipping” motion. In some situations, this could cause suture materials to shatter due to their visco-elastic characteristics. Accordingly, movement of the suture lock (e.g., relative to the anchor) can be an additional source of potential failure for mitral chordal repair systems. 
     Furthermore, the changing tension on the sutures can alter the length of the prosthetic chord, which can negatively impact the effectiveness of the prosthetic chord, e.g., at resolving MR. For example, and as shown in  FIGS. 49 and 50  the suture lock  4206  assumes a particular orientation relative to the sutures  4211 ,  4244  when tension on the sutures is lowered or removed. In this situation, the prosthetic chord has a particular length, e.g., as measured between the leaflet (where the suture  4244  is coupled to the leaflet) and the ventricular tissue (where the suture  4211  is secured to the anchor  4202 ). In effect, part of the suture (e.g., suture  4211 ) is wound around the suture lock  4206  and does not contribute to the overall length of the prosthetic chord. However, when tension is applied to the sutures, that tension will rotate the suture lock  4206 , as shown in  FIG. 50 . As a result, the portion of the suture  4211  previously wound around the suture lock  4206  is pulled away from the suture lock  4206 , resulting in a corresponding increase in the length of the prosthetic chord. In some situations, this increase is around 0.10 mm to 0.30 mm, though in some cases it can be as much as 0.50 mm. In some embodiments, the amount of change will depend on the width of the suture lock  4206  and the angle of rotation of the suture lock  4206 . In some situations, these changes in length with reduce the efficacy of the prosthetic chord, causing the physician to readjust the prosthetic chord or necessitating reinstallation of the prosthetic chord. 
     Embodiments of the present disclosure are designed to mitigate the effects of some or all of these issues, as well as providing additional advantages that improve the efficacy of the prosthetic chord and/or increase ease of implementation. For example, some embodiments include a transcatheter mitral chordal repair system designed to reduce or eliminate suture movement relative to the suture lock and other system components. Certain embodiments further serve to decrease the amount of unrestrained suture within the ventricle. Some embodiments provide for a prosthetic chord that incorporates a prosthetic papillary muscle, which can reduce the whipping effect. 
     Certain embodiments are designed to limit or eliminate movement of the suture lock relative to the anchor. These embodiments can also limit or eliminate movement of the sutures relative to the anchor, at least at a location near the anchor. As a result, these embodiments reduce wear on the sutures and promote longer lifetime for the mitral chordal repair system. 
     In some embodiments, the transcatheter mitral chordal repair system creates a prosthetic papillary construct using a retaining member also referred to herein as a suture lock guide (e.g., a socket or sleeve) that constrains motion of the suture lock. An example of such a suture lock guide was described above with reference to  FIGS. 2A and 2B  and was in the form of a tubular sleeve  78 . Motion of the sutures relative to the suture lock can also constrained near the suture lock, which reduces the wear on the sutures. In some embodiments, the transcatheter mitral chordal repair system includes an suture lock guide also referred to herein as an anchor socket that restricts motion of the suture lock, relative to the anchor, as well as motion of the sutures relative to the suture lock. 
     Embodiments discussed herein can provide prosthetic systems designed to maintain integrity through about 800 million cycles, or about 20 years. Disclosed are arrangements prosthetic chords that can remain for a minimum of 400 million cycles, or about 10 years. These prosthetic chords will perform under the range of typical situations and environments without excessive structural damage and/or functional impairment after 400 million cycles, i.e., without exhibiting holes, tears, gross delamination, severing, fraying, incomplete leaflet coaptation, excessive regurgitation, and the like. 
       FIGS. 51 and 52  illustrate components of a transcatheter mitral chordal repair system  4300 , according to some embodiments of the present disclosure. That system  300  provides one or more prosthetic chords using one or more sutures or tethers deployed into a beating heart without extracorporeal circulation using a transcatheter delivery system. These embodiments can reduce wear on anchoring sutures or tethers over time by using a retaining member or restraining member, which in some embodiments includes a stent-like or stent graft-like socket anchored to a securing device or anchor located on the epicardium. The delivery systems and techniques discussed above and/or in PCT/US2017/069046 and PCT/US2019/021480, which are incorporated by reference herein, may be employed to deliver the components of system  4300 . 
       FIGS. 51 and 52  illustrate an anchor  4302 , a retaining member  4304 , and a suture lock  3406 . In several of the embodiments illustrated herein, the retaining member  4304  is a socket or sleeve which can be, in certain aspects of the disclosure, similar to the sleeve or socket  78  descried above with respect to  FIGS. 2A and 2B . In other embodiments, the retaining member may be a pin, a hook, a clasp, a claw, a catch, a buckle, a suture, or the like. The anchor  4302  may be—in part or in full—any of the anchors disclosed above and/or in PCT/US2017/069046 or PCT/US2019/021480. Also shown in  FIGS. 51 and 52  are sutures  4308  and an anchor suture  4310 . While two sutures  4308  are shown in  FIGS. 51 and 52 , only one suture or more than two sutures may be used. The sutures  4308  can be coupled to one or more leaflets of the mitral valve, e.g., using pledgets for example using the systems or techniques described above and/or in PCT/US2017/069046 or PCT/US2019/021480. Accordingly, the sutures  4308  may be referred to as pledget sutures. The anchor  4302  can engage the ventricular tissue, and the retaining member  4304  can receive and secure the suture lock  4306  and the sutures  4308 ,  4310 . 
     The suture lock guide or retaining member  4304 , in some embodiments, restricts motion of the sutures  4308  and/or the suture lock  4306  while facilitating installation, adjustment, and eventually operation of the sutures  4308  as part of a prosthetic chord. For example, in some embodiments, the retaining member (also referred to herein as suture lock guide)  4304  is configured to selectively couple and decouple with the suture lock  4306 . When coupled to the suture lock  4306 , the retaining member  4304  may provide securing forces strong enough to prevent slippage during cardiac cycles (e.g., with non-limiting forces ranging up to approximately 1 N, 1.5 N, 2.0 N, 2.5 N, or 3 N) yet still enable a physician to pull on the sutures  4308  to tighten or loosen the sutures  4308  without displacing the suture lock  4306 . In other embodiments, the retaining member  4304  is designed to secure the sutures  4308  and the suture lock  4306 , such that any adjustment to the sutures will require the physician to remove the suture lock  4306  from the retaining member  4304 , adjust the sutures  4308 , and then re-insert the suture lock  4306  back into the retaining member  4304 . Removing the suture lock from the retaining member  4304  may in certain instances requires larger forces, e.g., forces above approximately 6 N to approximately 9 N, or even in excess of 10 N in some embodiments. In other words, in some non-limiting embodiments the retaining member  4304  is configured to exert retaining forces on the suture lock that resist forces between approximately 4 N to at least 10 N, including forces of approximately 4.5 N, 5 N. 5.5 N, 6 N, 6.5 N, 7 N, 7.5 N, 8 N, 8.5 N, 9N, 9.5 N, 10 N, 10.5 N, or 11 N. 
     As a result of the retaining member  4304 , the suture lock  4306  can maintain a positional relationship with the anchor  4302 . For example, as the heart tissue moves during cardiac cycles, the retaining member  4304  will resist displacing forces exerted on the suture lock  4306  (e.g., via the sutures  4308 ). In some embodiments, the retaining member  4304  transfers forces exerted on the suture lock  4306  to the anchor  4302 . The displacing forces may range up to approximately 1 N, though in some situations those forces may be around 1.5 N or up to approximately 3 N. 
     In some embodiments, a retaining member  4304  is a socket formed by inverting a vascular graft tube. The retaining member  4304  is designed to be radially compliable to permit the suture lock  4306  to enter the retaining member  4304  while providing constraining forces. The retaining member  4304  can also be also axially stiff and wear resistant. Axial stiffness enables the suture lock  4306  to enter the retaining member  4304  without buckling. Wear resistance can be minimized with a PTFE-PTFE interaction. 
     For example, in the embodiments shown in  FIGS. 51 and 52 , the retaining member  4304  includes an interior surface  4330  defining a chamber that receives and secures the suture lock  4306  and/or the sutures  4308 . In some embodiments, the retaining member  4304  is made of a material that is flexible enough to accommodate the suture lock  4306  and even permit adjustment of the sutures  4308  relative to suture lock  4306  after the suture lock  4306  is inserted into the retaining member  4304 . In some embodiments, the retaining member  4304  is radially compliable to permit the suture lock  4306  to enter and couple with the retaining member  4304 . The retaining member  4304  may couple with the suture lock  4306  using an interference fit or the like. 
     In some embodiments, the retaining member  4304  couples with an exterior surface of the suture lock  4306 , e.g., a portion of the exterior surface located between a proximal end and a distal end of the suture lock  4306 . For example, the retaining member  4304  contacts opposite sides of the suture lock  4306  to couple with the suture lock  4306 . In other embodiments, the retaining member  4304  contacts the suture lock  4306  at three or more points to constrain movement of the suture lock  4306  relative to the anchor  4302 . In  FIGS. 51 and 52 , the retaining member  4304  and the suture lock  4306  are both cylindrically shaped, and the retaining member  4304  engages the suture lock  4306  about its circumferential perimeter. In  FIGS. 51 and 52  the engaging contact between the retaining member  4304  and the suture lock  4304  extend longitudinally along the circumferential surface of the suture lock. In some embodiments, the engaging contact can extend over half of the longitudinal extent of the suture lock. In other embodiments, the engaging contact can extend over a percentage of the longitudinal extent of the suture lock ranging from approximately 20% to approximately 98%. In other embodiments, that range may be more limited, e.g., approximately 40% to approximately 80%, approximately 50% to approximately 70%, or combinations of the ranges discussed herein (as well as any subranges with the ranges explicitly mentioned as examples). 
       FIGS. 51 and 52  also illustrate a support member  4354  or support coil that can reinforce the material of the retaining member  4304  as the retaining member  4304  secures the suture lock  4306  and the sutures  4308 . In some embodiments, the anchor  4302  and the support member  4354  are two separate structures that may be integrated, while in other embodiments the anchor  4302  and the support member  4354  are unitarily formed of a single material. The support member  4354  may extend along a length of the retaining member  4304  so as to terminate at a location that is substantially aligned with a distal surface of the suture lock  4306  when fully inserted into the socket  4304 . In other embodiments, the support member  4354  may extend along a length of the retaining member  4304  so as to terminate at a location that is substantially aligned with an upper portion of the suture lock  4306  but located below (or proximal of) the distal surface of the suture lock  4306 . The support member  4354  contacts an outer surface of the retaining member  4304 . A bonding material  4362  is placed along the support member  4354  and the exposed outer surface of the retaining member  4304 . This bonding material  4362  may also contact the exposed outer surface of an anchor hub  4338 . 
     In some embodiments, the support member  4354  provides axial rigidity to prevent folding as the suture lock  4306  enters the retaining member  4304 . For example, in  FIGS. 51 and 52 , the support member  4354  is a support coil that resists longitudinal forces exerted on the retaining member  4304 , e.g., by the suture lock  4306  as it is pressed into the retaining member  4304 . This additional rigidity holds the retaining member  4304  steady, thereby increasing ease of installation. In other embodiments, the retaining member  4304  may be formed of other materials and may be formed in other configurations. For example, the support member  4304  may be formed of multiple metal strips longitudinally extending along the outer surface of the retaining member  4304  or may be one or more cylindrical cuffs longitudinally spaced along the other surface of the retaining member  4304 . In some embodiments, the retaining member  4354  is formed of nitinol tines or similar material. 
     The support member  4354 , in some embodiments, provides additional securing forces that maintain the suture lock  4306  and sutures  4308  within the retaining member  4304 . For example, in  FIGS. 51 and 52 , the support member  4354  is a support coil. In some embodiments, as the suture lock  4306  is pressed into the retaining member  4304 , the support coil linearly compresses, and its inner diameter increases to accommodate the suture lock  4306 . The compressive forces of the support coil (e.g., as it recoils back towards its original configuration and smaller inner diameter) increases the frictional forces between the retaining member  4304  and the suture lock  4306 . Furthermore, in some embodiments, the support coil is configured to linearly extend in response to forces pulling the suture lock  4306  from the retaining member  4304 . This will further decrease the inner diameter of the support coil, augmenting the frictional forces between the retaining member  4304  and the suture lock  4306 . 
     In some embodiments, the support member  4354  terminates at an intermediate portion of the retaining member  4304  below a distal portion of the retaining member  4304 . In this manner, the distal portion of the retaining member  304  above the support member  4354  exerts relatively smaller forces on the suture lock  4306  and sutures  4308 , compared to the combination of the retaining member  4304  and support member  4354 . With these relatively smaller forces, the physician can adjust the tension or length of the sutures  4308  without displacing the suture lock  306  from the retaining member  4304 . 
     Stated differently, in some embodiments the retaining member  4304  (alone or in combination with the support member  4354 ) provide sufficient forces to retain the suture lock  4306  during cardiac cycles (e.g., forces from approximately 0 N to approximately 4 N). Forces exerted on the sutures  4308  by the physician (e.g., pulling the proximal ends of the sutures  4308 ) and/or leaflet (e.g., pulling the distal ends of the sutures  4308 ) allow the physician to adjust the sutures  4308  relative to the suture lock  4306 , while the suture lock  4306  remains secure within the retaining member  4304 , in order to adjust the length of the sutures  4308  between the suture lock  4306  and the leaflet. The magnitude of the forces required to move the sutures  4308  in some embodiments range from 1 N to 2 N. Thus, the retaining member  4304  (alone or in combination with the support member  4354 ) secures the suture lock  4306  relative to the anchor  4302  during adjustment of the sutures  4308 . One the suture lock  4306  engages the sutures  4308  (as described below), the retaining member  4304  secures the suture lock  4306 , which secures the sutures  4308  as part of the prosthetic mitral chord. 
     Still referring to the embodiments described with reference to  FIGS. 51 and 52 , the retaining member  4304  is a generally cylindrical structure. The retaining member  4304  may be a stent or stent-graft structure formed (in whole or in part) of ePTFE. The materials forming the retaining member  4304  can promote tissue ingrowth to further secure the anchor  4302  and/or the prosthetic chord. The materials forming the retaining member  4304  can include a film microstructure in which the fibrillar orientation is in a direction substantially parallel the longitudinal axis of the retaining member  4304 . In this manner, any longitudinal motion of sutures  4308 , (e.g., ePTFE sutures) will be in line with the fibrillar orientation to further reduce friction and wear on the sutures. 
     Stated differently, in some embodiments, the retaining member  4304  is made from an ePTFE graft, elastomer, other polymer, or combination of these materials. For example, in some embodiments the retaining member  4304  is constructed from ePTFE stretch graft and may be densified to enhance column strength. The retaining member  4304  in some embodiments is partially or fully bio-resorbable or bio-absorbable and provides temporary fixation until, e.g., biological fibrous adhesion between the tissues and other components. In some embodiments, the retaining member  4304  includes a mesh designed to enhance biocompatibility and fibrosis following implantation. All or part of the surface of the retaining member  4304  may be configured to promote tissue growth onto and/or through its surface. In one example, this growth is achieved by providing a relatively rough and/or porous surface. Another example is to have one or multiple holes drilled through the material of the retaining member  4304 , allowing scar tissue fibrocytes to grow through these holes and thereby add strength to the fixation. Additionally, biological coatings of the types known in the art can be included on the surface of the retaining member  4304  to promote healing and tissue growth. 
     The suture lock  4306  can be secured within the retaining member  4304 , where it is aligned coaxially with the anchor  4302 . This configuration can minimize or eliminate the relative motion of the suture lock  4306  with respect to the sutures  4308 , at least within the retaining member  4304 . This configuration can also minimize or eliminate movement of the sutures  4308  within the retaining member  4304  relative to the suture lock  4306  and the anchor  4302 . 
     In some embodiments, the length of the support member  4354  ranges from approximately 0.5 mm to 3.0 mm. In other embodiments. In some embodiments, the length of the support member  4354  varies from a quarter of the length of the retaining member  4304  up to the full length of the retaining member  4304 . 
     Other embodiments (e.g., embodiments shown in  FIGS. 2A, 2B, 55 ) do not include a support member  4354 . Some of these embodiments provide varying restraining forces through other mechanisms, including by varying the materials and/or surface treatments used to construct different portions of the socket or by varying the size of the socket at different locations. Still other embodiments make use of external tools that expand an upper portion of the socket or otherwise reduce the restraining forces on the suture lock and sutures at that upper portion. 
     As can be seen in  FIG. 52 , the sutures  4308  can be located between an outer surface of the suture lock  4306  and an inner surface of the retaining member  4304 . In some embodiments, these surfaces (in whole or in part) are designed to facilitate securement of the sutures  4308 , for example, providing surfaces with higher coefficients of friction. In other embodiments, these surfaces (in whole or in part) are designed to facilitate easy adjustment of the sutures  4308 , providing surfaces with lower coefficients of friction. One or both of these surfaces may be resilient to help secure the sutures  4308  while enabling adjustment. 
     Securing the sutures  4308  between the suture lock  4306  and the retaining member  4304  can provide additional advantages. For example, the suture lock  4304  and the retaining member  4304  can maintain tension on distal portions of the sutures (e.g., portions extending from the suture lock  4306  towards the leaflets) even when tension on proximal portions of the sutures (e.g., portions extending from the socket  4306  towards the physician or proximal end of the catheter) changes or is eliminated. As a result, once the suture lock  4306  is placed within the retaining member  4304 , thereby securing the sutures  4308 , any tension change in the proximal portions of the sutures (e.g., if the physician accidentally bumps the catheters) will not substantially affect tension in the distal portions of the sutures  4308 . Accordingly, physicians need not maintain each suture  4308  in tension during the operation. Furthermore, in some embodiments, the suture lock  4306  and retaining member  4304  can be used to maintain tension in a distal portion of one suture during adjustment of another suture. 
     As shown in  FIG. 52 , in some embodiments the retaining member  4304  includes an upper enlarged portion  4376  and a lower enlarged portion  4378 . These enlarged portions  4376 ,  4378  can provide additional axial rigidity to prevent folding or buckling as the suture lock  4306  is pushed into the retaining member  4304 . In addition, the enlarged upper portion  4376  could incorporate a band that increases rigidity and provides a radiopaque marker. In some embodiments, the upper enlarged portion  4376  includes an outer surface located further out (e.g., along a radial direction) than a lower portion of the socket. The upper enlarged portion  4376  can include an inner surface that is located further out (e.g., along a radial direction) than a lower portion of the retaining member  4304 . For example, the upper enlarged portion  4376  could form a tapered shape (e.g., a funnel) to assist in receiving the suture lock  4306 . 
     The sutures  4308 ,  4310  may be formed from surgical-grade materials such as biocompatible polymer suture material. Examples of such material include 2-0 ePTFE (polytetrafluoroethylene) or 2-0 polypropylene. In some embodiments the sutures  4308 ,  4310  are inelastic. In other embodiments, the sutures  4308 ,  4310  can be partially or fully elastic. The sutures  4308 ,  4310  in some embodiments are be partially or fully bio-resorbable or bio-absorbable and provide temporary fixation until, e.g., biological fibrous adhesion between the tissues and other components. Thus, the sutures  4308 ,  4310  may be formed from a biocompatible material (e.g., nitinol, ePTFE, PTFE, PET, or polyester, nylon, Silicone, collagen or other amino acid protein , stainless steel, cobalt chrome, combinations of these, or the like). 
       FIGS. 51 and 52  illustrate an anchor hub  4338  that can contact the heart tissue  4352  and can serve as a stopping point for the anchor  4302  as it screws into the heart tissue. The anchor hub  4338  can include an upper surface that, in some embodiments, couples to a bushing  4353  (as discussed below). The anchor  4302  and the anchor hub  4338  may be joined together through mechanical means, such as a frictional fit, by chemical means, or through other means. The anchor hub  4338  can transfer forces exerted on the retaining member  4304  (e.g., via the sutures  4308 ) into the heart tissue  4252  via the anchor  4302 . In this manner, the anchor hub  4338  works with the retaining member  4304  to dampen oscillatory motion created by the heart&#39;s movements. 
     In some embodiments, the proximal surface of the anchor hub  4338  contacts the suture lock  4306  (e.g., the nose portion of the suture lock  4306 ) and the sutures  4308 . The anchor hub  4338  (or at least its proximal surface) may be formed of a material designed to augment frictional forces to secure the sutures  4308  located between the anchor hub  4338  and the suture lock  4306  or may be formed of a material that reduces frictional forces to facilitate adjustment of the sutures  4308  located between the anchor hub  4338  and the suture lock  4306 . The anchor hub  4338  could be formed of PFA, silicone material, PTFE material, ePTFE material, thermoplastics, and the like (or combinations thereof). The anchor hub  4338 , in some embodiments, is partially or fully formed of metal, stainless steel or titanium, or potentially a rigid plastic like PEEK, or other sufficiently rigid materials. The bushing, or proximal surface of the anchor hub  4338  that interacts with the suture lock, could be made from PFA, silicone material, PTFE material, ePTFE material, thermoplastics, and the like (or combinations thereof). 
     In some embodiments, a bushing  4353  is located adjacent the anchor hub  4338  to cushion the suture lock  4306 . This bushing may be formed of PFA or another polymer. The bushing provides a surface that contacts the sutures  4308  and, in combination with the nose portion of the suture lock  4306 , helps to secure the sutures  4308 . In some embodiments, the bushing facilitates suture adjustment due to the interactions of the PFA material of the bushing and the ePTFE material of the sutures  4308 . Bushing may also provide a surface that diminishes wear on the sutures, particularly if the anchor hub  4338  would otherwise present a rougher surface (e.g., due to the materials and/or surfaces of the anchor hub  4338 ) against the sutures  4308 . The bushing  4353 , or the proximal surface of the anchor hub  4338  that interacts with the suture lock, could be made from PFA, silicone material, PTFE material, ePTFE material, thermoplastics, and the like. 
     In some embodiments, the diameter of the hub (e.g., hub  4338 ) corresponds to the minor or inner diameter of the support member  4354 . Depending on how it is attached, the length of the hub  4338  is sufficiently long to allow the support member  4354  to be attached to the hub  4338  and to have a driver engage with the hub  4338 . The geometry where the retaining member  4304  is attached to the hub  4338  is smaller than the minor diameter of the support member  4354 . The outer diameter of the retaining member  4304  is smaller than the major diameter of the support member  4354  in some embodiments. 
     As shown in  FIG. 52 , the anchor suture  4310  can pass through a channel  4336  of the anchor hub  4338  and can be secured near the bottom surface  4340  of the anchor hub  4338 . In some embodiments, the channel  4336  includes a bottleneck portion  4342  that secures the anchor suture  4310  (e.g., by trapping a knot formed at the end of the anchor suture  4310  below the bottleneck portion  4342 ). In other embodiments, the anchor suture  4310  and the anchor hub  4338  be joined together through mechanical means, such as a frictional fit, by chemical means, or through other similar means. 
     The suture lock  4306  may incorporate features of the suture locks disclosed herein and/or PCT/US2017/069046 and PCT/US2019/021480. The suture lock  4306  can include a cylindrical outer surface that corresponds to the cylindrical chamber of the retaining member  4304  to provide a frictional or interference fit. The suture lock  4306  can include a locking mechanism (e.g., an internal locking mechanism) that selectively secures the anchor suture  4310  and the sutures  4308 . The illustrated suture lock  4306  includes a nose portion  4370  that presents a rounded surface on which the sutures are pressed when tensioned. In this manner, the suture lock  4306  can avoid sharp edges that could fray the sutures  4308 . In some embodiments, the nose portion  4370  is formed of, e.g., PFA, or another material designed to reduce wear on the sutures. 
     The suture lock  4306  can travel down the anchor suture  4310  until it enters the cylindrical chamber of the retaining member  4304 . The retaining member  4304  can provide some radial resistance to the suture lock  4306  but can be radially compliant to receive the suture lock  4306 . In some embodiments, the sutures  4308  can be adjusted, even when the suture lock  4306  is bottomed out (i.e., passes down to the end of the socket  4304 , which could include pressing against the bushing  4353 ). For example, the sutures  4308  are most easily adjusted while the suture lock  4306  is outside of the retaining member  4304 . However, even after the suture lock  4306  has entered the retaining member  4304 , the sutures  4308  can still be adjusted. When the suture lock  4306  bottoms out in some embodiments, the sutures  4308  are sandwiched between the PFA bushing  4353  and the PFA nose  4370  of the suture lock  4306 . At this stage, the sutures  4308  can still be adjusted in some embodiments, though with greater resistance. For example, the material of the suture lock nose  4370  and the bushing  4353  may reduce friction for easier adjustment. In other embodiments, the bushing  4353  and the nose  4370  are designed to secure the sutures and prevent further movement. 
     In some of the embodiments discussed above, the anchor  4302  is pre-assembled with the retaining member  4304 . In other words, the anchor  4302  and the retaining member  4304  are coupled together outside of the patient. The suture lock  4306  is then coupled to the retaining member  4304  (e.g., via an interference or frictional fit) inside of the patient. In other embodiments, the retaining member  4304  and suture lock  4306  are coupled together outside the patient. The retaining member  4304  and the anchor  4302  are then coupled together (e.g., via an interference or frictional fit) inside of the patient. 
     In some embodiments, the retaining member  4304  is configured to expand. For example, in some embodiments the retaining member  4304  is formed of a resilient material that expands as the suture lock  4306  is pressed down into the retaining member  4304  and will reseal around the suture lock  4306  to help secure it in place. In other embodiments, the retaining member  4304  has an expanded configuration and a retracted position. The retaining member  4304  can be delivered in its expanded configuration and, once the suture lock  4306  is in place, the retaining member  4304  collapses down to its retracted position to secure the suture lock  4306  in place. 
     In some embodiments, and as shown in  FIG. 53 , an anchor  4402  defines a longitudinal line  4403 , and the retaining member  4404  or restraining member (e.g., socket) constrains movement of the suture lock  4406  relative to the anchor  4402  in a direction orthogonal to the longitudinal line  4403  defined by the anchor  4402 . In some embodiments, the retaining member  4404  constrains movement of the suture lock  4406  relative to the anchor  4402  in a plane orthogonal to the longitudinal line  4403 . In some embodiments, the retaining member or restraining member (e.g., socket  4404 ) constrains movement of the suture lock relative to the anchor along the longitudinal line  4403 . 
     As also seen in  FIG. 53 , the restraining member  4404  substantially aligns a longitudinal line  4403  defined by the anchor  4402  and/or a longitudinal line  4405  defined by the restraining member  4404  with a longitudinal line  4407  defined by the suture lock  4406 . In some embodiments, the retaining member  4404  secures the suture lock  4406  in a co-axial relationship with the anchor  4402  and/or the retaining member  4404 . In some embodiments, the longitudinal lines defined by the anchor  4402 , retaining member  4404 , and/or suture lock  4406  extends to a leaflet of the mitral valve. 
     In some embodiments, and as shown in  FIG. 54 , the retaining member  4504  constrains angular movement of a suture (suture  4511 ) relative to the suture lock  4506 . As discussed above with respect to  FIGS. 49 and 50 , in some embodiments the suture lock rotates in response to forces during the cardiac cycle, such that the angles formed by the portions of the sutures extending from the suture lock and towards the leaflets, relative to a longitudinal line defined by the suture lock, will vary widely. The location of the suture lock above the anchor and closer to the leaflets also contributes to the angular movement. However, as shown in  FIG. 54 , the retaining member  4504 , by securing the suture lock  4506  in a particular orientation, restrains angular movement of the suture  4511 . For example, in some embodiments, the angle  4520  formed between the portion of a suture  4511  extending from the suture lock  4506  towards the leaflet and a longitudinal line  4522  of the suture lock  4506  is less than 45°. In some embodiments, angle  4520  can range from approximately −45° to +45°, which may also be understood as approximately 0° to 45° in two opposite directions. This angle  4520  may be formed in any plane that includes that portion of the suture  4511  and the longitudinal line  4522  of the suture lock. 
     While the suture  4511  will move during cardiac cycles, the retaining member  4504  can constrains angular movement (changes in angle  4520 ) to less than 90°. In some embodiments, the angular change is less than 45°, while in other embodiments the angular change can be less than approximately 40°, 35°, 30°, 25°, 20°, 15°, 10°, 8° or even less than approximately 5°. 
     Method for measuring angular changes between ventricular anchor and suture lock 
     The angular change between the anchor and suture lock can be determined, for example, with the following steps: 
     1. Fixture a ventricular anchor into one side of a tensile test machine. This can be done by simulating ventricular anatomy such as a silicone pad or by clamping into standard tensile test machine clamping jaws. 
     2. Fixture a prosthetic chordae into the other side of the tensile test machine. This can be done by simulating leaflet anatomy such as a silicone pad or by clamping into standard tensile test machine clamping jaws. 
     3. Couple the ventricular anchor and the prosthetic chordae together using a suture lock. 
     4. Load the system with the ventricular anchor, prosthetic chordae, and suture lock in tension to a minimum of 2N. 
     5. Measure the angle between the axis of the suture lock, or any linear feature of the suture lock, and the axis of the ventricular anchor, or any linear feature of the ventricular anchor (Angle 1). 
     6. Unload the system with the ventricular anchor, prosthetic chordae, and suture lock to a load less than 0N or a load equivalent to the hanging static weight of system on the load cell. 
     7. Measure the angle between the axis of the suture lock, or any linear feature of the suture lock, and the axis of the ventricular anchor, or any linear feature of the ventricular anchor (Angle 2). 
     8. Calculate the difference between Angle 1 and Angle 2. 
     During installation of the prosthetic chord, the anchor and retaining member can be delivered (e.g., via a catheter) and the anchor is implanted into the ventricular tissue. An anchor suture extends from the anchor. Sutures (e.g., pledget sutures) are then coupled to one or more of the mitral valve leaflets. A suture lock advances over the anchor suture and the pledget sutures. In some embodiments, the physician can adjust the location of the suture lock relative to the pledget sutures so that length of the pledget sutures between the suture lock and the leaflet(s) can ensure that the prosthetic chord can operate adequately (e.g., to reduce and/or eliminate MR). For example, the physician can pull on a proximal portion of one of the sutures to decrease the amount of suture located between the suture lock and the mitral valve leaflet. 
     However, in certain embodiments the suture lock can be unrestrained. As a result, adjustment of a suture (e.g., pulling on the suture) can move the suture lock upwards, which impacts the tension on the portions of the sutures between the suture lock and the mitral valve. This issue can exacerbated when multiple sutures are used with the suture lock. Adjusting one of the sutures can raise the suture lock, undoing any prior adjustments of another suture. 
     For example, the suture can be attached to a leaflet and passes through a suture lock, which functions as a movable pulley for the suture. Specifically, when a physician pulls on the end portion of the suture located outside of the body, this will move the suture. However, pulling the proximal end portion of the suture can move the suture lock upwards, such that the physician&#39;s movement of the suture external to the body will not have a one-to-one correspondence with the movement of the suture between the suture lock and the leaflet. 
     This issue can be exacerbated when multiple sutures pass through a single suture lock. For example, a physician can adjust a first suture to the correct length. However, once the physician begins to adjust a second suture, such movement will displace the suture lock, which could negatively impact the first suture and require the physician to readjust the first suture. Of course, this could then negatively impact the second suture, leading to additional needed adjustments. 
     Additional complications arise when the physician cuts a suture after engaging the suture lock. Prior to cutting the suture, the physician maintains tension on the suture, which maintains the suture lock in a higher position. Cutting the suture (and/or disconnecting the suture lock from the catheter) will release this tension and the suture lock can move downward, which can impact the effectiveness of the suture as a prosthetic-chord. That the physician should maintain tension on the suture (e.g., on a first suture while adjusting a second suture) creates additional complications. For example, any inadvertent movement of the catheter (e.g., an accidental bump) could cause the suture lock to move and change the length of the suture between the suture lock and the tissue (e.g., the leaflet). 
     Several of the embodiments discussed herein address these issues by securing the suture lock within the retaining member, thereby creating a pivot point for the sutures that is relatively stationary relative to the anchor. This can be particularly beneficial during adjustment of the sutures as the physician creates the prosthetic chord. Securing the suture lock to the anchor (e.g., with the retaining member) can substantially eliminate that upward movement of the suture lock during adjustment. 
     Furthermore, having a stationary pivot point can enable more direct correlations between adjustments of a proximal portion of the suture (i.e., pulling on a portion of the suture located near the physician) and resulting adjustments in the distal portion of the suture (i.e., the portion of the suture between the suture lock and the mitral valve). In particular, many of these embodiments discussed herein enable precise, bi-directional adjustment of the sutures in which movement of the guiding device (e.g., a catheter) directly translates into length change of the suture, e.g., between the leaflet and the suture lock. For example, if the guiding device is moved forward one millimeter, the suture is also moved forward one millimeter. This is referred to as “one to one motion.” As one of skill in the art will readily understand from this disclosure, several embodiments discussed herein can enable one to one motion or near one to one motion under various conditions. In particular, PCT/US2017/069046 and PCT/US2019/021480, which is incorporated by reference herein, disclosed mechanisms to make a suture “pushable,” including by placing a stiff tubular structure (i.e., a coil) over the suture. The stiffness provided by the coil allows the suture to be pushed similar to a cardiac guide wire. In this regard, the motion of the modified suture follows the motion of the guiding device (e.g., the catheter or the coil) in a “one to one” manner. 
     Stated differently, securing the suture lock within the retaining member can create fixed pivot point for the suture, such that the physician&#39;s movement of the suture external to the body will have a one-to-one correspondence with the movement of the suture between the suture lock and the leaflet. As a skilled artisan will readily appreciate, in some situations the one-to-one movement will be a near one-to-one movement due to other changes (e.g., slight elongation of the sutures or minor movement of the suture lock within the socket), which are substantially different in nature and degree from the suture lock movements at issue in, e.g., unconstrained embodiments. For example, the movement ratio could vary from 1:1 to approximately 1:0.95, 1:0.90, 1:0.85, 1:0.80, etc., down to 1:0.50. 
     Creating a fixed pivot point with the suture lock can create additional advantages. For example, when multiple sutures pass through the suture lock, each suture can be independently adjusted without substantially affecting the other sutures. In particular, with the suture lock secured within the retaining member, a first suture can be adjusted to the correct length. The physician can then begin to adjust a second suture without disturbing the adjustment of the first suture, since the suture lock will not move with the second suture. 
     Furthermore, in some embodiments a portion of a first suture is located between the outer surface of the suture lock and the inner surface of the socket. The forces provided by those surfaces will retain that portion of the first suture in place as the physician adjusts the second suture. This configuration provides additional advantages, as the physician does not need to maintain external tension on the first suture. Reducing or eliminating tension on the suture can reduce any elongation or other detrimental effects on the sutures. 
     In addition, the first suture can be cut without changing the location of the suture lock and without changing the length of the suture between the suture lock and the tissue. As a skilled artisan will appreciate, there may be some incremental movement (e.g., less than 5/1000th of an inch or less than 5/100th of an inch), which could be deemed less than a substantial change in location in this context. 
     Furthermore, in some embodiments the suture lock serves as a fixed pivot point located close to a target area of tissue (e.g., near the apex of the heart), which can increase the ease of installation. 
     In some embodiments multiple sutures are coupled to tissue(s) (e.g., one or more leaflets) and pass through the suture lock. Each suture has a length extending between the suture lock and the tissue(s). When the suture lock is placed into the retaining member, the sutures are held in place. Should a first suture need to be adjusted (e.g., decrease the length of the first suture between the suture lock and the tissue), the suture lock can be removed from the retaining member and the physician can pull on the first suture to reduce its length. However, the location of the suture lock remains relatively static during this adjustment (e.g., the suture lock moves no more than 1 mm.) As a result, the physician does not need to further adjust or readjust the other sutures. In some embodiments, the sutures can be adjusted while the suture lock is within the retaining member. The retaining member secures the suture lock, further reducing or eliminating movement of the suture lock during adjustment of a suture. For example, movement of the suture lock can be less than or equal to approximately 0.5 mm. 
     In some embodiments, the suture lock engaged in the retaining member is loose enough that the force of the leaflet on the suture (e.g., an ePTFE chord) is sufficient to pull the suture through the interface between the suture lock and the retaining member, around the nose of the suture lock, through the open clamping mechanism of the suture lock and back to the stiffened pushable portion of the suture assembly. Operable forces for this situation can vary from 0 N to approximately 2 N. In some embodiments, the forces may range from 0.15 N to 1.50 N. 
     In some embodiments, the physician pulls on the external portions of a suture to decrease the length of that suture between the suture lock and the leaflet. Should the physician wish to increase the length of the suture between the suture lock and the leaflet, the physician can release tension on the external portions of the suture, and the movement of the leaflet during the heart&#39;s natural cardiac cycle will pull on the suture. In some embodiments, the suture lock is placed into a first portion of the retaining member, where the forces acting on the sutures are small enough that the physician and the leaflet can effect changes in the length of the sutures between the suture lock and the leaflet, e.g., forces between 0 N to 2 N. At the same time, the securing forces provided by the retaining member prevent the suture lock from moving during these adjustments or restricts movement of the suture lock to around 0.5 mm. 
     In some embodiments, once the lengths of the sutures between the suture lock and the corresponding tissues are correct (e.g., MR is clinically reduced or eliminated), the suture lock is pressed into a second portion of the retaining member, where the retaining member can apply greater securing forces to the suture lock and the sutures. As a result, the forces provided by the leaflet will not cause the suture to move within the suture lock (or to move only by a small amount, e.g., around 0.5 mm), so that the length of the sutures between the suture lock and the tissues remains constant (or moves only by the amount of stretch provided by the sutures, e.g., approximately 10%). At this point, the physician can take a measured analysis of the placement and tension provided by the prosthetic chords. If satisfactory, the physician can engage the suture lock to clamp down on the sutures. In this configuration, the prosthetic chords can operate for at least 400 million cycles, i.e., about 10 years, or even at 800 million cycles or about 20 years. 
     In some embodiments, the sutures are permanently secured using only the restraining forces provided by the retaining member, either alone or in combination with the external surface of the suture lock. For example, the suture lock may lack any internal clamping or restraining mechanisms, instead providing an outer surface that, along with the inner surface of the retaining member, secures the sutures against further movement from the forces originating from the heart&#39;s natural cycles. 
     In some embodiments, the retaining member enables the suture lock to work with sutures of different sizes. For example, sutures of a larger size and/or thickness may be secured once the suture lock is inserted into a first portion of the retaining member. Sutures of a smaller size can also be secured, e.g., by pressing the suture lock deeper into the retaining member. 
     Embodiments of the present disclosure can provide further advantages that facilitate easy adjustment of the suture. For example, friction can create difficulties in adjusting the sutures, as well as the life and efficacy of the sutures. Some embodiments address this issue by using a suture lock having a tapered nose. For example, and as shown in  FIG. 52 , the distal end of the suture lock  4306  includes a tapered nose  4370 . The outer surface of the suture lock  4306  has a cylindrical shape, and the outer surface of the nose portion  4370  likewise has a cylindrical shape whose radius decreases towards the distal end of the nose  4370 . 
     The front surface of the nose portion  4370  presents an inner aperture surrounded by a ring of the tapered nose. In some embodiments, the diameter of the inner aperture can range from 1 mm to 3 mm. The thickness of the ring can range from 0.5 mm to 2.0 mm. 
     The tapered nose portion  4370  can facilitate insertion of the suture lock  4306  into the retaining member  4304 . In some embodiments, the nose portion  4370  tapers more steeply while in other embodiments the nose portion  4370  tapers less steeply. In addition, or alternatively, the retaining member  4304  may include a proximal portion whose profile tapers outward to guide the suture lock  4306  into interior portions of the retaining member  4304 . For example, the proximal end of the retaining member  4304  may have a larger radius than a middle portion of the retaining member  4304 . As discussed above, an anchor suture  4310  can also be used to guide the suture lock  4306  down into the retaining member  4304 . 
     As shown in  FIG. 52 , the interior surface of the nose portion  4370  can include a proximal portion whose thickness increases along a longitudinal line from the front portion to a middle portion. After that middle portion, the thickness of the nose portion decreases towards a distal portion. The proximal end of the nose portion may be configured to snap fit onto the suture lock body in some embodiments. 
     To facilitate bi-directional adjustment, certain embodiments reduce the frictional forces on the sutures via the suture lock and the retaining member. For example, the profile of the nose provides a rounded surface that facilitates movement of the suture around the nose without creating sharp edges that wear down the suture. In addition, the composition of the nose can include, e.g., PFA or other materials that further reduce friction between sutures and the nose. 
     The nose portion can be configured to accommodate multiple sutures simultaneously. At the same time, the tapered profile enables easier access into the retaining member. To take advantage of both of these features, the size of the aperture in the nose portion can correspond to the number of sutures to be used. For example, the diameter of the nose aperture may be 1 mm when two sutures are used, and the diameter of the nose aperture may be 2 mm when four sutures are used. Generally speaking, the ratio of diameter to number of sutures may be approximately 0.5 mm per suture. In some embodiments, different nose portions (e.g., nose portions with apertures of different sizes) may be interchangeably used with a single suture lock body. In other embodiments, the size of the suture lock (e.g., the diameter of the suture lock) is larger or smaller to accommodate different numbers of sutures. 
     In some embodiments, the retaining member is formed of an ePTFE material in which the fibrillar orientation of the film microstructure is oriented in a direction substantially parallel the longitudinal axis of the retaining member. In this manner, any longitudinal motion of the suture (e.g., an ePTFE suture) will be in line with the fibrillar orientation to further reduce friction and wear on the sutures. For example, in some embodiment, the retaining member (in whole or at least the interior surface) is formed of a substantially monolithic ePTFE covering having a node and fibril microstructure in which the nodes are oriented generally perpendicular to the longitudinal axis of the retaining member and the fibrils are oriented generally parallel to the longitudinal axis of the retaining member. 
     As discussed above, the retaining member engages the sutures and/or the suture lock. In some embodiments it is necessary to disengage the suture lock from the retaining member to allow slack into the sutures. This simplifies maintaining tension in one suture relative to another because it eliminates the length changes created through the catheter. In these embodiments the suture lock can be disengaged from the interference fit with the retaining member to add slack to the sutures. In other words, in some embodiments multiple sutures pass through the suture lock, which is inserted into the retaining member. As a result, the sutures are held in place between the outer surface of the suture lock and the interior surface of the retaining member. Should the physician need to adjust one of the sutures, the suture lock can be removed from the retaining member. At this stage, the suture at issue can be adjusted without significant upward movement of the suture lock. Accordingly, adjustment of that suture does not significantly alter the tension in the other sutures. 
     In some embodiments, the retaining member serves as a prosthetic papillary muscle as part of the prosthetic chord. The materials selected for, e.g., the retaining member and the suture (as well as the anchor and/or suture lock) can be selected to promote tissue encapsulation, tissue ingrowth, and/or particular biological reactions. 
       FIG. 55  illustrates another embodiment of a transcatheter mitral chordal repair system  4600 . This system  4600  includes features similar to those shown in  FIGS. 51 and 52 . However, in this embodiment the retaining member  4604  does not include a support member. Instead, the anchor  4602  extends around the anchor hub  4638  at terminates at the lower surface of the retaining member  4604 . A mechanical bond or joint  4601  secures the retaining member  4604  to the anchor hub  4638 . The anchor  4602  and the anchor hub  4638  can be joined together in a manner as discussed above. In  FIG. 55 , the walls of the retaining member  4604  can be 25% to 100% thicker than the walls of the socket in  FIGS. 51 and 52 . Thicker walls can provide axial support to prevent buckling as the suture lock  4606  enters the retaining member  4604 , while still being compliant enough to permit passage. A mechanical bond or joint secures the anchor hub  4638  to the retaining member  4604 , which extends over the anchor hub  4638 . 
     Some embodiments involve a method for transcatheter mitral chordal repair using a transcatheter mitral chordal repair system. During this process, the anchor and anchor socket are delivered together, e.g., via a delivery catheter.  FIGS. 56-58  illustrate a method of deploying an anchor  4702 , socket  4704 , and suture lock  4706 . In  FIG. 56 , the anchor  4702  is located within the socket  4704 . In this configuration, both anchor  4702  and socket  4704  can be passed through a catheter and into the left ventricle (e.g., via the left atrium). In some embodiments, the anchor  4702  is fully retracted within the socket  4704  to prevent the anchor  4702  from contacting or piercing the catheter or other tissue. Once the socket  4704  is located against the ventricular wall, the anchor  4702  is advanced out of the socket  4704  and into the tissue. A socket attachment device  4755  captures the coil threads as the anchor  4702  emerges from the socket  4704 , until the socket attachment device  4755  ultimately contacts the anchor hub  4738  to lock the anchor  4702  in place. In some embodiments, the socket attachment device  4755  is a suture with a loop or a series of loops through which the coil passes. In other embodiments, the socket attachment device  4753  is an extension of the socket material at the distal end of the socket  4704 , this extension having a hole or series of holes through which the coil passes. In both these examples, extrusion of the coil through the hole or loop advances the coil until the socket attachment device  4753  is secured against the hub  4738 . 
       FIG. 57  illustrates the anchor  4702  and socket  4704  once the anchor  4702  is deployed into the ventricular tissue. A socket attachment device  4755  secures the anchor hub  4738  (and thus the anchor  4702 ) in place relative to the socket  4704 . The suture lock  4706  is then advanced along the anchor suture  4710  into the socket  4704  until it contacts the bushing  4753 , as shown in  FIG. 58 . Once the sutures  4708  are correctly tensioned, the suture lock  4706  can be activated and locks the sutures  4708  and the anchor suture  4710  in place. The suture lock  4706  is coaxially aligned with the anchor  4702 , in parallel with the sutures  4708  that are pinned between the outer surface of the suture lock  4706  and the inner surface of the socket  4704 . The sutures  4708  are also pinned between the curved nose of the suture lock  4708  and the bushing  4753 . 
       FIGS. 59 and 60  illustrate another embodiment of a transcatheter mitral chordal repair system  4800 . This system can include features similar to those shown in  FIGS. 51 and 52 . In this embodiment, an anchor pledget  4860  is incorporated into the anchor suture  4810 . As the suture lock  4806  is advanced into the socket  4804 , the pledget  4860  collapses to create a bushing in between the anchor hub  4838  and suture lock  4806 . The suture lock  4806  can selectively engage the sutures  4808  coupled to leaflets and remaining portions of the anchor suture  4810 . 
       FIG. 61  illustrates a socket formed of densified ePTFE  4850 . In some embodiments the socket is formed of ePTFE. The socket can be formed by folding a tube back on itself, creating two layers. This reinforces the socket to resist axial compression and folding as the suture lock enters the socket. In some embodiments, the retaining member is made from a thick-wall graft material. To increase the axial stiffness, the thick wall graft material can be densified. An example of this is shown in  FIG. 61 , depicting a graft material that has been rolled to obtain the proper thickness and density. Furthermore, the resulting two-layer construct increases densified pliability. 
       FIG. 62  illustrates a “rolled” end  4852  of the PTFE socket. In some embodiments the socket is formed of ePTFE. The marker band  4854  is placed on the exterior surface of the tube before it is rolled, located so that the band is placed between the two rolled layers at the top of the socket. This band can be a radiopaque band. In some embodiments, the retaining member includes an end portion whose radial stiffness is different than other portions. For example, the proximal portion of a retaining member can be formed with an increased radial stiffness. In some embodiments, a marker band is placed between layers of the graft material as it is rolled to form the retaining member, as shown in  FIG. 62 . This marker band increases the radial stiffness and makes this portion of the retaining member radiopaque. In some embodiments, the marker band is retained between the two layers of PTFE or ePTFE and densified into the PTFE or ePTFE structure. 
       FIGS. 63 and 64  illustrate a densified PTFE socket  5004  designed to interface with an anchor hub  5016 . In some embodiments the socket  5004  is formed of ePTFE. The densified PTFE or ePTFE socket  5004  includes a lower extension  5070  designed to fit around a corresponding groove  5072  in the anchor hub  5016 . This secures the socket  5004  to the hub  5072 . A radiopaque band  5074  is located near the top of the socket  5004 . The densified PTFE or ePTFE can be used to keep retention of the anchor. As shown in  FIG. 63 , by pressing the PTFE or ePTFE into a retention ring on the anchor, it will be held in place.  FIG. 64  illustrates an exemplary retaining member in which a marking band has been incorporated into a proximal portion while a distal portion include a densified portion designed to retain an anchor (not shown in  FIG. 64 ). 
       FIG. 65A and 65B  illustrate a socket formed by inverting a vascular graft tube, creating an outside wall and an inside wall. This creates a socket from materials that are biocompatible. This material can be the same as the suture material, thereby minimizing or lessening wear of the sutures where they exist the socket. The direction of the fibrils of the socket surfaces can be oriented to match the direction of the fibrils of the suture to further minimize wear. 
     The various prosthetic chordae tendinae deployment systems discussed above can be used in many different medical applications. These embodiments can reduce or eliminate movement of the sutures relative to the suture lock as well as movement of the suture lock relative to the anchor. For example, in some embodiments an anchor is delivered into heart tissue, e.g., near the apex of the left ventricle or near a papillary muscle. As discussed above, the anchor can be delivered through a trans-septal catheter advanced into the left atrium and through the mitral valve. The anchor is a helical anchor and is coupled to a retaining member. In some embodiments, the anchor is initially delivered within the retaining member and is advanced out of the retaining member and into the heart tissue. An anchor suture is attached to the anchor (e.g., via an anchor hub). A leaflet anchor (e.g., pledget) is then delivered and attached to a leaflet of the mitral valve. In some embodiments, the pledget is located on the ventricle side of the leaflet with a pledget suture extending from the atrium side of the leaflet. In other embodiments, the pledget is located on the atrium side of the leaflet and the pledget suture extends from the ventricular side of the leaflet. Multiple pledgets and sutures may be placed in one or more leaflets. 
     To effect the prosthetic chordae tendinae, in certain embodiments, a suture lock can be advanced over the anchor suture and the sutures. Specifically, the proximal ends of the sutures enter through an aperture in the suture lock and pass through the suture lock. The suture lock is advanced towards the retaining member, guided by the suture anchor. Because the suture lock is radiopaque, and because the retaining member can include a radiopaque band near its proximal surface, the physician can use imaging technology to confirm the location of the suture lock relative to the retaining member. Furthermore, the use of a radiopaque band in the retaining member enables the physician to confirm once the suture lock has been fully inserted into the retaining member. 
     In certain embodiments, once the suture lock reaches the retaining member, the physician can adjust the length of the sutures between the suture lock and the leaflet to effect each new prosthetic chordae tendinea. In some embodiments, some or all of this adjustment is made with the suture lock at or in the retaining member. In certain embodiments, any movement of the sutures can result in one-to-one movement or near one-to-one movement of the suture distal of the suture lock, as the suture lock is maintained in a relatively constant position at the retaining member. For example, the ratio of proximal suture movement to distal suture movement can be from 0.5 to 1.0. 
     In some embodiments, this adjustment is made with the suture lock just outside of the retaining member, with the physician holding the suture lock in place and holding the sutures in tension. In other embodiments, this adjustment is made with the suture lock in the retaining member (either in a proximal portion of the retaining member or into a distal portion of the retaining member adjacent the anchor hub). In these embodiments, the retaining member holds the suture lock in place but enables the sutures to slide through the suture lock. The physician does not need to hold the suture lock in place. 
     Furthermore, in some embodiments the restraining force of the retaining member can be sufficient to hold the sutures in place against the forces exerted by the leaflet, and yet permit the sutures to slide in response to pulling forces from the physician. In these embodiments, the physician does not need to hold the suture lock in place and also does not need to hold each suture in tension. Instead, the retaining member maintains the tension of the distal portion of the pledget suture (i.e., the portion of the pledget suture distal of the retaining member and extending to the leaflet). This allows the physician to individually adjust each pledget suture, and any inadvertent movement of the catheter (e.g., accidental bumping) will not affect the sutures. Of course, the adjustments by the physician in this situation are in one direction (i.e., shortening the length of suture between the suture lock and the pledget). Should the physician need to increase the length of the suture between the suture lock and the pledget, the physical can remove the suture lock from the suture so that movement by the leaflets will again pull the sutures through the suture lock. 
     Once the sutures are appropriately tightened, the physician can lock the sutures in place using the suture lock, e.g., using the techniques described herein and/or in PCT/US2017/069046 and PCT/US2019/021480. In other embodiments, the retaining member locks the sutures in place without the need for an additional locking mechanism within the suture lock. The physician can then cut the excess suture (e.g., the suture located proximally of the retaining member). Because the sutures are not in tension proximal of the retaining member, cutting these sutures will not cause significant movement of the suture lock and/or the sutures located between the suture lock and the leaflets. 
     In other embodiments, the retaining member and the suture lock are integrated and are delivered as a unit. In some embodiments, that unit includes the anchor or is coupled to the anchor during the delivery process. The physician can adjust the length of the sutures extending between the suture lock and the leaflets and can using the suture lock to permanently lock the sutures in place. 
     The resulting prosthetic chordae tendinae in these embodiments cam be more durable than prior prosthetic chordae tendinae. First, movement of the sutures relative to the suture lock is reduced or eliminated, reducing the wear of the sutures. Second, movement of the suture lock relative to the anchor is reduced or eliminated, further reducing the wear of the sutures. The orientation of the sutures relative to the suture lock also reduces suture wear. Additional features discussed above (including, e.g., the nose portion of the suture lock) increases the lifetime of the prosthetic chordae tendinae. 
       FIG. 66  illustrates an anchor, retaining member, and suture lock according to aspects of the present disclosure.  FIG. 67  illustrates an orientation of a prosthetic chord, according to aspects of the present disclosure. 
     Suture Lock Boot 
     In certain aspects described herein, once the tension and length of the neo chordae implant is optimized, the suture lock can locked to fix the length of the sutures such that the sutures no longer move with respect to the suture lock. 
     In further aspects of the disclosure, after tensioning of the sutures by the physician to correct or minimize the mitral valve defect, the sutures can be clamped or pinned or otherwise engaged and locked in the suture lock so that the applied length adjustment and tension of the sutures is retained. With this step and resulting lock engagement, the mitral defect can be corrected or minimized and remains corrected throughout the functional lifetime of the neo chordae (i.e., the prosthetic chord). In order to advance the suture lock through the delivery catheter and to clamp or pin the sutures within the suture lock, the suture lock can be coupled to a lock driver mechanism that allows the physician to provide the necessary force to clamp or otherwise lock the sutures within the suture lock, i.e., a lock driver, such as lock screw driver in one alternative embodiment, for example, a stored energy mechanism, or the like, depending on the tightening requirements of the suture lock. 
     In some aspects, the suture lock may further be coupled to a boot located on or with the lock driver, wherein the boot comprises a retaining mechanism configured to reversibly retain the suture lock to the boot to enhance engaging of the lock driver. According to some embodiments and as shown, for example, in  FIG. 68 , the system comprises delivery catheter  6905 , suture lock  6935  and boot  6915 . Also shown in  FIG. 68 , suture lock  6935  includes screw  6925  which engages with lock driver  6910 , wherein the lock driver can be rotated in order to advance or retract ramp (or push wedge)  6930 , thereby clamping sutures  6945  against an opposing internal surface of the suture lock  6940 . Suture lock  6935  is coupled to boot  6915 . Lock driver  6910  (shown by dotted lines) is engaged with the screw head of screw  6925 . The insertion of lock driver  6910  coaxially through boot  6915  can force suture lock retaining member  6920  (two retaining members  6920  are shown in  FIG. 68 , on opposite sides of boot  6915  from each other) to protrude from the outer surface of boot  6915 . The suture lock retaining member  6920  can provide a frictional fit (not shown) to the suture lock  6935  or can engage one or more indentations (shown in dotted perspective view) in the suture lock  6935 . In an alternative embodiment, a frictional fit between the lock driver and the boot alone may be used, without the requirement for suture lock retaining member(s) or indentation(s). Provided that the lock driver  6910  is positioned at a position that is distal to the suture lock retaining member  6920 , then the suture lock retaining member  6920  of the boot  6915  will couple with the suture lock  6935  to restrict or eliminate movement of the suture lock  6935  relative to the boot  6910 . Once the physician has tensioned the sutures to correct the movement of the mitral valve, the physician can then rotate the lock driver  6910  to clamp or pin the sutures within the suture lock  6935 . It would be apparent to one of skill in the art than alternative suture lock clamping or locking configurations are within the scope of the present disclosure, such as either pushing or pulling components together to engage the locking of the suture lock. 
     Once the sutures have been clamped within the suture lock, the physician can use any known visualization technique in order to confirm that the mitral valve defect has been corrected or minimized. If, for example, further adjustments need to be made, the lock driver  6910  can be rotated in order to lessen the force on the sutures  6945  and adjust the tension as needed and repeat the procedure to clamp the sutures. Upon confirmation that the mitral valve defect has been corrected or minimized, lock driver  6910  can be retracted, thereby disengaging from the screw head of screw  6925 . 
       FIGS. 69 and 70  depict removing the lock driver  6910  and the boot  6915  from the suture lock  6935 . As lock driver  6910  is retracted from the suture lock and past the suture lock retaining member, the suture lock retaining members retracts into the boot, thereby disengaging the boot  6915  from the suture lock. With the suture lock retaining members retracted, the boot  6915  can also disengage from the suture lock. Once the boot  6915  disengages the suture lock retaining member  6920  (not shown) from the suture lock  6935 , the physician can then remove the lock driver  6910  and the boot  6915  from the catheter. 
     In some embodiments, the anchor may further comprise a retaining member configured to couple with the suture lock so that the suture lock maintains a positional relationship with the anchor. In these embodiments, the physician can apply pressure on the lock driver and the boot in order to insert the suture lock into the retaining member. Once the suture lock has been inserted into the retaining member and the sutures have been properly tensioned, then the sutures can be clamped in the suture lock, and the lock driver and the boot can be retracted from the suture lock and from the catheter as was discussed above. 
     The suture lock can further comprise alternative mechanisms configured to actuate the suture retaining mechanism. In some embodiments, the suture retaining mechanism can be a screw wherein the rotation of the screw can reversibly apply or remove pressure on the sutures.  FIGS. 68-70  show embodiments wherein the suture retaining mechanism comprises a screw  6925 , one or more ramps  6930  and a surface of the suture lock  6940 . The ramp and/or the opposing surface of the suture lock can comprise a plurality of notches, each having a height that is advanced to clamp the sutures by the rotation of a screw. The height of each notch may increase or decrease from an innermost notch to an outermost notch. Other suture retaining mechanism such as, for example, a spring or other stored energy mechanism may be used to provide the force that clamps the sutures within the suture lock. The spring can be activated, for example, in any known way whereby stored energy of the spring could be released during the removal of the boot from the suture lock. 
     In certain arrangements, a suture can include a thread, cable, wire, filament, strand, line, yarn, gut, or similar structure, whether natural and/or synthetic, in monofilament, composite filament, or multifilament form (whether braided, woven, twisted, or otherwise held together). 
     Although this disclosure describes certain embodiments and examples, many aspects of the above-described systems and methods may be combined differently and/or modified to form still further embodiments or acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure. Indeed, a wide variety of designs and approaches are possible and are within the scope of this disclosure. 
     Furthermore, certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as a subcombination or variation of a sub combination. 
     The disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with various embodiments can be used in all other embodiments set forth herein. Also, any methods described herein may be practiced using any device suitable for performing the recited steps. 
     Moreover, while components and operations may be depicted in the drawings or described in the specification in a particular arrangement or order, such components and operations need not be arranged and performed in the particular arrangement and order shown, nor in sequential order, nor include all of the components and operations, to achieve desirable results. Other components and operations that are not depicted or described can be incorporated in the embodiments and examples. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations. Further, the operations may be rearranged or reordered in other implementations. Also, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products. 
     In summary, various illustrative embodiments and examples are described herein. Although the systems and methods have been disclosed in the context of those embodiments and examples, this disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and/or other uses of the embodiments, as well as to certain modifications and equivalents thereof. This disclosure expressly contemplates that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another. Accordingly, the scope of this disclosure should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow as well as their full scope of equivalents.