Patent Publication Number: US-9414921-B2

Title: Tissue anchor for annuloplasty device

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 13/504,870 to Miller et al., entitled, “Tissue anchor for annuloplasty device,” filed on Jul. 19, 2012, which published as US 2012/0283757, and which is a US national phase application of PCT/IL2010/000890 to Miller et al., entitled, “Tissue anchor for annuloplasty device,” filed on Oct. 28, 2010, which published as WO 2011/051942, and which claims priority from and is a continuation-in-part of U.S. patent application Ser. No. 12/608,316 to Miller et al., entitled, “Tissue anchor for annuloplasty device,” filed on Oct. 29, 2009, which issued as U.S. Pat. No. 8,277,502. All of these applications and the patent are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     Some applications of the present invention relate in general to tissue anchors. More specifically, some applications of the present invention relate to tissue anchors for repair of an atrioventricular valve of a patient. 
     BACKGROUND OF THE INVENTION 
     Dilation of the annulus of the mitral valve prevents the valve leaflets from fully coapting when the valve is closed. Mitral regurgitation of blood from the left ventricle into the left atrium results in increased total stroke volume and decreased cardiac output, and ultimate weakening of the left ventricle secondary to a volume overload and a pressure overload of the left atrium. 
     US Patent Application 2004/0236419 to Milo describes methods for reconfiguring an atrioventricular heart valve that may use systems comprising a partial or complete annuloplasty rings proportioned to reconfigure a heart valve that has become in some way incompetent, a pair of trigonal sutures or implantable anchors, and a plurality of staples which may have pairs of legs that are sized and shaped for association with the ring at spaced locations along its length. These systems permit relative axial movement between the staples and the ring, whereby a patient&#39;s heart valve can be reconfigured in a manner that does not deter subtle shifting of the native valve components. Shape-memory alloy material staples may have legs with free ends that interlock following implantation. Annuloplasty rings may be complete or partial and may be fenestrated. One alternative method routes a flexible wire, preferably of shape-memory material, through the bights of pre-implanted staples. Other alternative systems use linkers of shape-memory material having hooked ends to interengage with staples or other implanted supports which, following implantation, decrease in effective length and pull the staples or other supports toward one another so as to create desired curvature of the reconfigured valve. These linkers may be separate from the supports or may be integral with them and may have a variety of shapes and forms. Various of these systems may be implanted non-invasively using a delivery catheter. 
     US 2007/0049942 to Hindrichs et al. describes remodeling a soft body tissue structure by shortening the distance between first and second portions of that tissue structure. First and second anchor structures are respectively implanted in the first and second portions of the tissue structure. These anchor structures are linked by a linking structure, the length of which between the anchor structures can be shortened to pull the tissue structure portions toward one another. Each of the anchor structures may include two screw structures that are driven into the associated tissue structure portion transverse to the linking structure and with a spacer between the two screws. The entire prosthesis can be implanted percutaneously if desired. An illustrative use of the prosthesis is to shorten the annulus of a patient&#39;s mitral valve, with at least a portion of the prosthesis implanted in the patient&#39;s coronary sinus. 
     The following patents and patent application publications may be of interest: 
     PCT Publication WO 07/136783 to Cartledge et al. 
     PCT Publication WO 08/068756 to Gross et al. 
     PCT Publication WO 10/004546 to Gross et al. 
     PCT Publication WO 10/073246 to Cabiri et al. 
     U.S. Pat. No. 5,306,296 to Wright et al. 
     U.S. Pat. No. 6,569,198 to Wilson et al. 
     U.S. Pat. No. 6,619,291 to Hlavka et al. 
     U.S. Pat. No. 6,764,510 to Vidlund et al. 
     U.S. Pat. No. 7,004,176 to Lau 
     U.S. Pat. No. 7,101,395 to Tremulis et al. 
     U.S. Pat. No. 7,175,660 to Cartledge et al. 
     US 2003/0050693 to Quijano et al 
     US 2003/0167062 to Gambale et al. 
     US 2004/0024451 to Johnson et al. 
     US 2004/0148021 to Cartledge et al. 
     US 2005/0171601 to Cosgrove et al. 
     US 2005/0288781 to Moaddeb et al. 
     US 2007/0016287 to Cartledge et al. 
     US 2007/0080188 to Spence et al. 
     US 2007/0219558 to Deutsch 
     US 2007/0282375 to Hindrichs et al. 
     US 2008/0262609 to Gross et al. 
     US 2010/0161041 to Maisano et al. 
     US 2010/0161042 to Maisano et al. 
     US 2010/0211166 to Miller et al. 
     The following articles may be of interest: 
     O&#39;Reilly S et al., “Heart valve surgery pushes the envelope,” Medtech Insight 8(3): 73, 99-108 (2006) 
     Dieter RS, “Percutaneous valve repair: Update on mitral regurgitation and endovascular approaches to the mitral valve,” Applications in Imaging, Cardiac Interventions, Supported by an educational grant from Amersham Health pp. 11-14 (2003) 
     SUMMARY OF THE INVENTION 
     In some applications of the present invention, a tissue anchor is provided that is configured for receiving an implant and facilitating implantation of the implant. The anchor comprises a distal tissue coupling element, e.g., a helical anchor, which penetrates tissue of a patient. The anchor also comprises a proximal implant-penetrating element which receives and facilitates coupling of the implant to the tissue anchor. The implant-penetrating element comprises a post, which extends between the proximal tip and the proximal end of the distal tissue coupling element. For some applications, the proximal tip of the implant-penetrating element comprises a barb which punctures and receives the implant. 
     Typically, during an open-heart, minimally-invasive, or transcatheter procedure, a plurality of tissue anchors are implanted along an annulus of an atrioventricular valve of the patient, and are configured to receive and facilitate implantation of a valve-repair implant, e.g., an annuloplasty ring or a prosthetic valve. Each anchor is reversibly coupled to a cord, e.g., a suture or a wire, at a proximal end of the implant-penetrating element. Prior to implantation of the valve-repair implant, each cord is threaded through the implant, and the implant is then slid toward the annulus along the cords. In response to continued pushing of the valve-repair implant, the implant is then punctured at respective locations by the proximal tips of each one of the implant-penetrating elements. The physician continues to push the valve-repair implant so that the implant slides along the implant-penetrating elements and the posts of the anchors. The implant is pushed along the post until the proximal tips of each one of the implant-penetrating elements are exposed from within the lumen of the valve-repair implant and disposed proximally to a proximal surface of the implant. The valve-repair implant is then locked in place at the surface of the implant that faces the lumen of the atrium of the patient. Following the locking in place of the implant, the cords are decoupled from the anchors and removed from within the body of the patient. 
     In some applications of the present invention, a proximal restraining element, e.g., radially-expandable arms, is coupled to a proximal portion of the post of the anchor. This restraining element restrains the implant from separating from the implant-penetrating element. 
     In some applications of the present invention, an elastic portion, e.g., a tension spring, is coupled at a proximal end to the proximal tip of the implant-penetrating element, and at a distal end to the proximal end of the post. 
     There is therefore provided, in accordance with some applications of the present invention, apparatus for use with an implant, the apparatus including:
         a tissue anchor, which includes:
           a distal tissue coupling element, which is configured to penetrate cardiac tissue; and   a proximal implant-penetrating element configured to penetrate the implant, the proximal implant-penetrating element being shaped so as to define a passage therethrough, which passage has at least two openings that are within 1 mm of a proximal end of the implant-penetrating element; and   
           a cord configured to be removably passed through the passage.       

     In some applications of the present invention, the proximal implant-penetrating element includes a post. 
     In some applications of the present invention, the post has a length of between 1 and 7 mm and a greatest cross-sectional area of between 0.03 mm^2 and 0.2 mm^2, which length is at least 4 times the square root of the greatest cross-sectional area. 
     In some applications of the present invention, the length of the post is at least 5 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the length of the post is at least 8 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the length of the post is at least 10 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the length of the post is at least 15 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the apparatus further includes a proximal restraining element, which is configured to be coupleable to the post within 2 mm of a proximal end of the post, and which is configured to restrain the implant from separating from the implant-penetrating element. 
     In some applications of the present invention, the proximal restraining element is shaped so as to define an opening therethrough, through which the cord is configured to pass. 
     In some applications of the present invention, the post defines a protrusion configured to protrude into a plane of the implant and to couple the implant to the tissue anchor. 
     In some applications of the present invention, the protrusion is shaped so as to define a distal shelf that has a transverse cross-sectional length that is larger than a transverse cross-sectional length of the implant-receiving element, the distal shelf being configured to facilitate restricting of proximal motion of the implant along the protrusion. 
     In some applications of the present invention, the proximal restraining element has a greatest cross-sectional area that is at least 1.5 times a greatest cross-sectional area of the post. 
     In some applications of the present invention, the apparatus further includes a lock configured to be advanced toward the anchor and disposed between the implant and the proximal restraining element, the lock including: 
     a distal portion configured to rest against the implant, and 
     an expandable proximal portion having a cross-sectional area during a resting state of the lock that is larger than the greatest cross-sectional area of the post and smaller than the greatest cross-sectional area of the proximal restraining element. 
     In some applications of the present invention, the proximal implant-penetrating element includes a barb configured to restrict proximal movement of the implant along the implant-penetrating element. 
     In some applications of the present invention, the barb includes a proximal restraining element which is configured to restrain the implant from separating from the implant-penetrating element. 
     In some applications of the present invention, the barb includes one or more arms that are radially expandable to rest against an external surface of the implant following coupling of the implant to the implant-penetrating element. 
     In some applications of the present invention, the arms are radially collapsible during at least a portion of the coupling of the implant to the implant-penetrating element. 
     In some applications of the present invention, the proximal implant-penetrating element includes an elastic portion that is configured to assume a first length when relaxed, and a second, greater length when under load. 
     In some applications of the present invention, the elastic portion includes a tension spring. 
     In some applications of the present invention, the proximal implant-penetrating element has a length of between 3 and 5 mm when the elastic portion is relaxed. 
     In some applications of the present invention, the implant-penetrating element includes a proximal restraining element which is coupled to the post, and which is configured to restrain the implant from separating from the implant-penetrating element. 
     In some applications of the present invention, the proximal restraining element is coupled within 2 mm of a proximal end of the post. 
     In some applications of the present invention, the proximal restraining element is shaped so as to define an opening therethrough, through which the cord is configured to pass. 
     In some applications of the present invention, the proximal restraining element includes a protrusion configured to protrude into a plane of the implant and to couple the implant to the tissue anchor. 
     In some applications of the present invention, the protrusion is shaped so as to define a distal shelf that has a transverse cross-sectional length that is larger than a transverse cross-sectional length of the implant-receiving element, the distal shelf being configured to facilitate restricting of proximal motion of the implant along the protrusion. 
     In some applications of the present invention, the proximal restraining element has a greatest cross-sectional area that is at least 1.5 times a greatest cross-sectional area of the post. 
     In some applications of the present invention, the apparatus further includes a lock configured to be advanced toward the anchor and disposed between the implant and the proximal restraining element, the lock including: 
     a distal portion configured to rest against the implant, and 
     an expandable proximal portion having a cross-sectional area during a resting state of the lock that is larger than the greatest cross-sectional area of the post and smaller than the greatest cross-sectional area of the proximal restraining element. 
     I the proximal restraining element includes a barb configured to restrict proximal movement of the implant along the implant-penetrating element. 
     In some applications of the present invention, the barb includes one or more arms that are radially expandable to rest against an external surface of the implant following coupling of the implant to the implant-penetrating element. 
     In some applications of the present invention, the arms are radially collapsible during at least a portion of the coupling of the implant to the implant-penetrating element. 
     In some applications of the present invention, the proximal implant-penetrating element includes an elastic portion that is configured to assume a first length when relaxed, and a second, greater length when under load. 
     In some applications of the present invention, the elastic portion includes a tension spring. 
     In some applications of the present invention, the proximal implant-penetrating element has a length of between 3 and 5 mm when the elastic portion is relaxed. 
     In some applications of the present invention, the coupling element is shaped so as to define a shape selected from the group consisting of: a helix, a spiral, and a screw shaft. 
     In some applications of the present invention, the coupling element is shaped so as to define one or more radially-expandable prongs, the prongs being configured to expand and facilitate anchoring of the coupling element and restrict proximal motion of the tissue anchor. 
     In some applications of the present invention, the apparatus further includes the implant, the post is configured to couple the implant to the anchor. 
     In some applications of the present invention, the implant includes an annuloplasty device. 
     In some applications of the present invention, the annuloplasty device includes: 
     a sleeve having a lumen; 
     a spool coupled to the sleeve; and 
     a flexible contracting member that is coupled to the spool and the sleeve, such that winding the contracting member around the spool tightens the device. 
     In some applications of the present invention, the distal tissue coupling element and the proximal implant-penetrating element include respective elements that are coupled to one another. 
     In some applications of the present invention, the distal tissue coupling element and the proximal implant-penetrating element are fabricated from a single piece. 
     There is additionally provided, in accordance with some applications of the present invention apparatus, including: 
     a tissue-repair implant configured to reside chronically in a heart of a patient; 
     a tissue anchor including:
         a distal tissue coupling element configured to couple the tissue anchor to tissue of the heart of the patient; and   a proximal implant-receiving element configured to receive at least a portion of the tissue-repair implant and facilitate coupling of the tissue-repair implant to the tissue anchor, the proximal implant-receiving element including:   a proximal implant-restraining element coupled to a proximal portion of the implant-receiving element, the proximal implant-restraining element being configured to restrain the implant from separating from the implant-receiving element.       

     In some applications of the present invention, the proximal restraining element includes a protrusion configured to protrude into a plane of the implant and to couple the implant to the tissue anchor. 
     In some applications of the present invention, the protrusion is shaped so as to define a distal shelf that has a transverse cross-sectional length that is larger than a transverse cross-sectional length of the implant-receiving element, the distal shelf being configured to facilitate restricting of proximal motion of the implant along the protrusion. 
     In some applications of the present invention, the apparatus further includes a cord removably couplable to the tissue anchor, the cord being configured to facilitate passage of the implant therealong and toward the tissue anchor. 
     In some applications of the present invention, the cord passes through a portion of the implant-receiving element. 
     In some applications of the present invention, the proximal implant-receiving element includes a post. 
     In some applications of the present invention, the post has a length of between 1 and 7 mm and a greatest cross-sectional area of between 0.03 mm^2 and 0.2 mm^2, which length is at least 4 times the square root of the greatest cross-sectional area. 
     In some applications of the present invention, the length of the post is at least 5 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the length of the post is at least 8 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the length of the post is at least 10 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the length of the post is at least 15 times the square root of the greatest cross-sectional area of the post. 
     In some applications of the present invention, the proximal implant-restraining element is coupled to the post within 2 mm of a proximal end of the post. 
     In some applications of the present invention, the proximal implant-restraining element is shaped so as to define an opening therethrough, through which the cord is configured to pass. 
     In some applications of the present invention, the proximal implant-restraining element has a greatest cross-sectional area that is at least 1.5 times a greatest cross-sectional area of the post. 
     In some applications of the present invention, the apparatus further includes a lock configured to be advanced toward the anchor and disposed between the implant and the proximal implant-restraining element, the lock including: 
     a distal portion configured to rest against the implant; and 
     an expandable proximal portion having a cross-sectional area during a resting state of the lock that is larger than the greatest cross-sectional area of the post and smaller than the greatest cross-sectional area of the proximal implant-restraining element. 
     In some applications of the present invention, the proximal implant-restraining element includes a barb configured to restrict proximal movement of the implant along the implant-receiving element. 
     In some applications of the present invention, the barb includes one or more arms that are radially expandable to rest against an external surface of the implant following coupling of the implant to the implant-receiving element. 
     In some applications of the present invention, the arms are radially collapsible during at least a portion of the coupling of the implant to the implant-receiving element. 
     In some applications of the present invention, the proximal implant-receiving element includes an elastic portion that is configured to assume a first length when relaxed, and a second, greater length when under load. 
     In some applications of the present invention, the elastic portion includes a tension spring. 
     In some applications of the present invention, the proximal implant-receiving element has a length of between 3 and 5 mm when the elastic portion is relaxed. 
     In some applications of the present invention, the distal tissue coupling element is shaped so as to define a shape selected from the group consisting of: a helix, a spiral, and a screw shaft. 
     In some applications of the present invention, the distal tissue coupling element is shaped so as to define one or more radially-expandable prongs, the prongs being configured to expand and facilitate anchoring of the coupling element and restrict proximal motion of the tissue anchor. 
     In some applications of the present invention, the apparatus further includes the implant, the implant-receiving element is configured to couple the implant to the anchor. 
     In some applications of the present invention, the implant includes an annuloplasty device. 
     In some applications of the present invention, the implant includes: 
     a spool coupled to the tissue-repair implant; and 
     a flexible contracting member that is coupled to the spool and the sleeve, such that winding the contracting member around the spool tightens the contracting member. 
     In some applications of the present invention, the distal tissue coupling element and the proximal implant-receiving element include respective elements that are coupled to one another. 
     In some applications of the present invention, the distal tissue coupling element and the proximal implant-receiving element are fabricated from a single piece. 
     There is also provided, in accordance with some applications of the present invention, the following inventive concepts:
     1. A method comprising:   

     coupling, to cardiac tissue of a patient, a distal tissue coupling element of a tissue anchor, which tissue anchor further includes (a) a proximal implant-penetrating element, which is shaped so as to define a passage therethrough, which passage has at least two openings that are within 1 mm of a proximal end of the implant-penetrating element, and (b) a cord, which is removably passed through the passage; 
     passing the cord through an implant; and 
     advancing the implant over the cord until the implant reaches and is penetrated by the proximal implant-penetrating element.
     2. The method according to inventive concept 1, wherein coupling the distal tissue coupling element comprises:   

     coupling a distal tissue coupling element that comprises one or more radially-expandable prongs configured to expand and facilitate anchoring of the coupling element, and 
     by the coupling, restricting proximal motion of the tissue anchor.
     3. The method according to inventive concept 1, wherein the proximal implant-penetrating element includes a post, and wherein advancing comprises advancing the implant until the implant reaches and is penetrated by the post.   4. The method according to inventive concept 3, further comprising restraining the implant from separating from the implant-penetrating element by coupling a proximal restraining element to the post within 2 mm of the proximal end of the post.   5. The method according to inventive concept 4, wherein restraining the implant comprises advancing a lock along the cord to between the implant and the proximal restraining element, the lock including (a) a distal portion configured to rest against the implant, and (b) an expandable proximal portion having a cross-sectional area at its resting state that is larger than a greatest cross-sectional area of the post and smaller than a greatest cross-sectional area of the proximal restraining element.   6. The method according to inventive concept 1, wherein the proximal implant-penetrating element includes a barb, and wherein the method further comprises restraining the implant from separating from the implant-penetrating element by penetrating the barb through the implant.   7. The method according to inventive concept 6, wherein the barb includes one or more arms that are radially expandable, and wherein the method further comprises:   

     passing the one or more arms through the implant in a compressed state thereof, and 
     restraining the implant from separating from the implant-penetrating element by allowing the one or more arms to expand and rest against an outer surface of the implant following the penetrating of the barb through the implant.
     8. The method according to inventive concept 6, wherein the proximal implant-penetrating element includes an elastic portion that is configured to assume a first length when relaxed, and a second, greater length when under load, and wherein penetrating the barb through the implant comprises pulling the barb through the implant by pulling on the cord.   9. The method according to inventive concept 8, wherein the elastic portion includes a tension spring.   10. The method according to inventive concept 3, wherein the proximal restraining element is coupled within 2 mm of the proximal end of the post, and wherein restraining the implant from separating from the implant-penetrating element comprises restraining the implant from separating from the implant-penetrating element by the proximal restraining element is coupled within 2 mm of the proximal end of the post.   11. The method according to inventive concept 3, further comprising restraining the implant from separating from the implant-penetrating element by a proximal restraining element that is coupled to a proximal end of the post.   12. The method according to inventive concept 11, wherein restraining the implant comprises advancing a lock along the cord to between the implant and the proximal restraining element, the lock including (a) a distal portion configured to rest against the implant, and (b) an expandable proximal portion having a cross-sectional area at its resting state that is larger than a greatest cross-sectional area of the post and smaller than a greatest cross-sectional area of the proximal restraining element.   13. The method according to inventive concept 11, wherein the proximal implant-penetrating element includes a barb, and wherein restraining the implant from separating from the implant-penetrating element comprises penetrating the barb through the implant.   14. The method according to inventive concept 13, wherein the barb includes one or more arms that are radially expandable, and wherein the method further comprises:   

     passing the one or more arms through the implant in a compressed state thereof, and 
     restraining the implant from separating from the implant-penetrating element by allowing the one or more arms to expand and rest against an outer surface of the implant following the penetrating of the barb through the implant.
     15. The method according to inventive concept 13, wherein the proximal implant-penetrating element includes an elastic portion that is configured to assume a first length when relaxed, and a second, greater length when under load, and wherein penetrating the barb through the implant comprises pulling the barb through the implant by pulling on the cord.   16. The method according to inventive concept 15, wherein the elastic portion includes a tension spring.   17. The method according to inventive concept 1, wherein coupling comprises coupling the distal tissue coupling element to the tissue at a site within a heart chamber of the patient, and wherein the method further comprises, after the advancing of the implant over the cord:   

     cutting the cord at a site outside of the heart chamber; and 
     withdrawing the cord from the passage.
     18. The method according to inventive concept 1, wherein coupling comprises coupling the distal tissue coupling element to the tissue at a site within a heart chamber of the patient, and wherein the method further comprises, after the advancing of the implant over the cord, withdrawing the cord from the passage.   19. The method according to inventive concept 1, wherein the implant includes an annuloplasty device, and wherein advancing the implant comprises advancing the device over the cord until the device reaches and is penetrated by the proximal implant-penetrating element.   20. The method according to inventive concept 19, wherein coupling the distal tissue coupling element and advancing the device comprise coupling and advancing during a transcatheter procedure.   21. The method according to inventive concept 19, wherein advancing the device comprises advancing the device into an atrium of a heart of the patient in a vicinity of an annulus of an atrioventricular valve.   22. The method according to inventive concept 19, further comprising tightening the annuloplasty device by winding a flexible contracting member of the device around a spool coupled to the device.   23. A method comprising:   

     coupling, to a first portion of cardiac tissue of a patient, a distal tissue coupling element of a tissue anchor, which tissue anchor further includes (a) a proximal implant-receiving element, and (b) a cord, which is removably coupled to the implant-receiving element; 
     passing the cord through a tissue-repair implant; 
     advancing the implant over the cord until the implant reaches and is received at least in part by the proximal implant-receiving element, the proximal implant-receiving element comprising a proximal implant-restraining element; and 
     restraining the implant from separating from the implant-receiving element by the proximal implant-restraining element.
     24. The method according to inventive concept 23, wherein coupling the distal tissue coupling element comprises:   

     coupling a distal tissue coupling element that comprises one or more radially-expandable prongs configured to expand and facilitate anchoring of the coupling element, and 
     by the coupling, restricting proximal motion of the tissue anchor.
     25. The method according to inventive concept 23, wherein the proximal implant-receiving element includes a post, wherein the proximal implant-restraining element is coupled to a proximal portion of the post, and wherein advancing comprises advancing the implant until the implant reaches and is penetrated by the post.   26. The method according to inventive concept 25, wherein the proximal restraining element is coupled within 2 mm of the proximal end of the post, and wherein restraining the implant from separating from the implant-penetrating element comprises restraining the implant from separating from the implant-penetrating element by the proximal restraining element is coupled within 2 mm of the proximal end of the post.   27. The method according to inventive concept 25, wherein restraining the implant comprises advancing a lock along the cord to between the implant and the proximal restraining element, the lock including (a) a distal portion configured to rest against the implant, and (b) an expandable proximal portion having a cross-sectional area at its resting state that is larger than a greatest cross-sectional area of the post and smaller than a greatest cross-sectional area of the proximal implant-restraining element.   28. The method according to inventive concept 23, wherein the proximal implant-restraining element includes a barb, and wherein the method further comprises restraining the implant from separating from the implant-receiving element by penetrating the barb through at least a portion of the implant.   29. The method according to inventive concept 28, wherein the barb includes one or more arms that are radially expandable, and wherein the method further comprises:   

     passing the one or more arms through the implant in a compressed state thereof, and 
     restraining the implant from separating from the implant-receiving element by allowing the one or more arms to expand and rest against an outer surface of the implant following the penetrating of the barb through the implant.
     30. The method according to inventive concept 28, wherein the proximal implant-receiving element includes an elastic portion that is configured to assume a first length when relaxed, and a second, greater length when under load, and wherein penetrating the barb through the implant comprises pulling the barb through the implant by pulling on the cord.   31. The method according to inventive concept 30, wherein the elastic portion includes a tension spring.   32. The method according to inventive concept 23, wherein coupling comprises coupling the distal tissue coupling element to the tissue at a site within a heart chamber of the patient, and wherein the method further comprises, after the advancing of the implant over the cord:   

     cutting the cord at a site outside of the heart chamber; and 
     withdrawing the cord from the passage.
     33. The method according to inventive concept 23, wherein coupling comprises coupling the distal tissue coupling element to the tissue at a site within a heart chamber of the patient, and wherein the method further comprises, after the advancing of the implant over the cord, withdrawing the cord from the tissue anchor.   34. The method according to inventive concept 23, wherein coupling the distal tissue coupling element and advancing the implant comprise coupling and advancing during a transcatheter procedure.   35. The method according to inventive concept 23, wherein advancing the implant comprises advancing the device into an atrium of a heart of the patient in a vicinity of an annulus of an atrioventricular valve.   36. The method according to inventive concept 23, further comprising adjusting a distance between the first portion of cardiac tissue and a second portion of cardiac tissue by winding a flexible contracting member of the device around a spool coupled to the implant.   37. The method according to inventive concept 23, wherein the implant includes an annuloplasty device, and wherein advancing the implant comprises advancing the device over the cord until the device reaches and is penetrated by the proximal implant-receiving element.   38. The method according to inventive concept 37, further comprising tightening the annuloplasty device by winding a flexible contracting member of the device around a spool coupled to the device.   

     The present invention will be more fully understood from the following detailed description of applications thereof, taken together with the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-F  are schematic illustrations of a procedure for implanting a tissue anchor for receiving a valve-repair implant, in accordance with some applications of the present invention; 
         FIGS. 2A-C  are schematic illustrations of the tissue anchor and a delivery tool therefor, in accordance with some applications of the present invention; 
         FIG. 3  is a schematic illustration of a plurality of the tissue anchors of  FIGS. 2A-C  implanted along an annulus of a patient, in accordance with some applications of the present invention; 
         FIG. 4  is a schematic illustration of a valve-repair implant being advanced toward the plurality of anchors of  FIG. 3 , in accordance with some applications of the present invention; 
         FIGS. 5A-B ,  6 A-B, and  7  are schematic illustrations of respective locking mechanisms for each of the tissue anchors of  FIGS. 3-4 , in accordance with some applications of the present invention; 
         FIGS. 8 and 9  are schematic illustrations of examples of valve-repair implants which are received by the tissue anchors of  FIGS. 3-4 , in accordance with respective applications of the present invention; 
         FIG. 10  is a schematic illustration of a tissue anchor for receiving a valve-repair implant, in accordance with another application of the present invention; 
         FIGS. 11A-D  are schematic illustrations of a transcatheter procedure for implanting a plurality of tissue anchors of  FIG. 10 , in accordance with some applications of the present invention; 
         FIGS. 12-14  are schematic illustrations of a manipulator for implanting the tissue anchors or  FIGS. 2A-C  and  10  during a minimally-invasive or open-heart procedure, in accordance with some applications of the present invention; 
         FIGS. 15-18  are schematic illustrations of the implantation and locking of the valve-repair implant during the minimally-invasive or open-heart procedure, in accordance with some applications of the present invention; 
         FIG. 19  is a schematic illustration of the tissue anchor of  FIGS. 2A-C  in accordance with some applications of the present invention; and 
         FIG. 20  is a schematic illustration of the tissue anchor of  FIG. 10 , in accordance with some applications of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF APPLICATIONS 
     Reference is now made to  FIGS. 1A-F ,  2 A-C, and  3 , which are schematic illustrations of a system  20  for implanting a tissue anchor  49 , in accordance with some applications of the present invention.  FIGS. 1A-F  show a transcatheter procedure for implanting tissue anchor  49 .  FIGS. 2A-C  show a transcatheter delivery tool  42  for delivering toward and implanting anchor  49  at an implantation site, e.g., an annulus  25  of a heart  22  of a patient, as shown. Typically, the implantation site includes an annulus of an atrioventricular valve, e.g., a mitral valve or a tricuspid valve. It is to be noted that the implantation site is not limited to a heart valve of the patient, and anchor  49  may be implanted in other tissue of the patient, e.g., a portion of the inner wall of the heart of the patient, in a stomach of a patient, etc. Tissue anchor  49 , as shown in  FIG. 2B  comprises a distal tissue coupling element  50 , e.g., a helical tissue anchor  58 , and a proximal implant-penetrating element  47   a . Proximal implant-penetrating element  47   a  comprises a post  52   a  and a proximal implant-restraining element  53   a  which is configured to puncture and pass through a portion of a valve-repair implant, as will be described hereinbelow. Proximal restraining element  53   a  (i.e., a portion of implant-penetrating element  47   a ) is shaped so as to define a passage  56  therethrough. A cord  54  is removably coupled to anchor  49  by being passed through passage  56 . Cord  54  functions to facilitate guiding of the valve-repair implant toward tissue anchor  49  implanted at annulus  25 . 
     Reference is now made to  FIGS. 1A-F ,  2 A-C, and  3 - 4  which are schematic illustrations of a procedure for implanting a plurality of tissue anchors  49  in order to repair a mitral valve  24  of the patient, in accordance with some applications of the present invention. Mitral valve  24  is shown including leaflets  26  and  28 . The procedure is typically performed with the aid of imaging, such as fluoroscopy, transesophageal echo, and/or echocardiography. 
     The procedure typically begins by advancing a semi-rigid guidewire  32  into a right atrium of the patient, as shown in  FIG. 1A . 
     As show in  FIG. 1B , guidewire  32  provides a guide for the subsequent advancement of a sheath  34  therealong and into the right atrium. Once sheath  34  has entered the right atrium, guidewire  32  is retracted from the patient&#39;s body. Sheath  34  typically comprises a 14-20 F sheath, although the size may be selected as appropriate for a given patient. Sheath  34  is advanced through vasculature into the right atrium using a suitable point of origin typically determined for a given patient. For example:
         sheath  34  may be introduced into the femoral vein of the patient, through an inferior vena cava  30 , into the right atrium, and into a left atrium transseptally, typically through the fossa ovalis;   sheath  34  may be introduced into the basilic vein, through the subclavian vein to the superior vena cava, into the right atrium, and into the left atrium transseptally, typically through the fossa ovalis; or   sheath  34  may be introduced into the external jugular vein, through the subclavian vein to the superior vena cava, into the right atrium, and into the left atrium transseptally, typically through the fossa ovalis.       

     In some applications of the present invention, sheath  34  is advanced through an inferior vena cava  30  of the patient (as shown) and into the right atrium using a suitable point of origin typically determined for a given patient. 
     (In this context, in the specification and in the claims, “proximal” means closer to the orifice through which system  20  is originally placed into the body of the patient, and “distal” means further from this orifice.) 
     Sheath  34  is advanced distally until the sheath reaches the interatrial septum, as shown in  FIG. 1C . 
     As shown in  FIG. 1D , a resilient needle  38  coupled to en elongate wire  36  and a dilator (not shown) are advanced through sheath  34  and into heart  22 . In order to advance sheath  34  trans septally into the left atrium, the dilator is advanced to the septum, and needle  38  is pushed from within the dilator and is allowed to puncture the septum to create an opening that facilitates passage of the dilator and subsequently sheath  34  therethrough and into the left atrium. The dilator is passed through the hole in the septum created by the needle. Typically, the dilator is shaped to define a hollow tube shaft for passage along needle  38 , and the hollow tube shaft is shaped to define a tapered distal end. This tapered distal end is first advanced through the hole created by needle  38 . The hole is enlarged when the gradually increasing diameter of the distal end of the dilator is pushed through the hole in the septum. 
     The advancement of sheath  34  through the septum and into the left atrium is followed by the extraction of the dilator and needle  38  from within sheath  34 , as shown in  FIG. 1E . 
     Subsequently, as shown in  FIG. 1F , delivery tool  42  is advanced within an advancement catheter  40  and through sheath  34 . Delivery tool  42  comprises an elongate tube shaft that is coupled at a distal end thereof to a manipulator  44 . Manipulator  44  reversibly engages anchor  49  and facilitates the delivery of anchor  49  to the left atrium and the subsequent implantation of anchor  49  in tissue of annulus  25  of the patient. Delivery tool  42  is described hereinbelow with reference to  FIGS. 2A-C . 
       FIG. 2A  shows delivery tool  42  disposed within advancement catheter  40 , which slides through sheath  34  and toward annulus  25  of heart  22 . Delivery tool  42 , manipulator  44 , and anchor  49  are shown in cross-section. 
       FIG. 2B  shows the relative spatial configurations of delivery tool  42 , manipulator  44 , and anchor  49 . Anchor  49  comprises a distal tissue coupling element  50  having a pointed distal tip  51  configured for puncturing tissue of the patient. Distal tissue coupling element  50  comprises a helical tissue anchor  58 , by way of illustration and not limitation, e.g., tissue coupling element  50  may comprise any suitable tissue anchor known in the art (e.g., as is shown hereinbelow in  FIGS. 19 and 20 ). For example, distal tissue coupling element  50  may comprise any suitable tissue anchor known in the art (e.g., a spiral or a screw shaft) or any tissue anchor as described in PCT Patent Application PCT/IL2009/000593 to Gross et al., entitled, “Annuloplasty devices and methods of delivery therefor,” filed Jun. 15, 2009, which published as WO 10/004546, and which is incorporated herein by reference. 
     Reference is now made to  FIGS. 2A-B . The helical coils of helical tissue anchor  58  form a generally-cylindrical coil surrounding a lumen of helical tissue anchor  58 . Helical tissue anchor  58  is shaped to provide a bar  55  which projects into the lumen of helical tissue anchor  58 . A distal portion  57  of implant-penetrating element  47   a  is coupled, e.g., welded, to bar  55 . 
     Reference is again made to  FIG. 2B . Anchor  49 , comprising distal tissue coupling element  50  and implant-penetrating element  47   a , has a length L 1  of 6-18, e.g., 6-12 mm, e.g., 10 mm. In some applications of the present invention, distal tissue coupling element  50  and implant-penetrating element  47   a  are separate pieces that are coupled, e.g., welded, to one another. Alternatively, distal tissue coupling element  50  and implant-penetrating element  47   a  are fabricated from a single piece. Implant-penetrating element  47   a  has a length L 2  of 4-10 mm, e.g., 5.5 mm. Distal tissue coupling element  50  has a length L 3  of 2-8 mm, e.g., 4 mm. Implant-penetrating element  47   a  comprises a post  52   a  and proximal restraining element  53   a . Post  52   a  has a length of between 1 and 7 mm, e.g., 5.5 mm and a greatest cross-sectional area (measured at a plane that is perpendicular to the axis along which the length of post  52   a  is measured) of between 0.03 and 0.2 mm^2, e.g., 0.13 mm^2, which length is at least 4 times (e.g., 5, 8, or 10 times) the square root of the greatest cross-sectional area. Post  52   a  has a longest dimension at its cross-section of between 0.2 mm and 0.5 mm (e.g., 0.4 mm). That is, for example, post  52   a  has a length of 5.5 mm and a longest cross-sectional dimension (measured at the plane that is perpendicular to the axis along with the length of post  52   a  is measured) of 0.4 mm. In such an example, the ratio of the length to the longest cross-sectional dimension is around 13.75:1. For some applications, this ratio is between 5:1 and 14:1, and the ratio varies depending on the size of the implant that is anchored to the tissue of the patient via anchor  49 . 
     It is to be noted that anchors  49  may be used to implant any implant of any suitable size to any tissue of the patient, and that the ratio of length to the longest cross-sectional dimension of post  52   a  of between 5:1 and 14:1 varies depending on the size of the implant that is anchored to the patient. 
     Proximal restraining element  53   a , is coupleable or coupled to post  52   a  within 2 mm of the proximal end of post  52   a . For some applications, as recited above, implant-penetrating element  47   a  comprises proximal restraining element  53   a . Proximal restraining element  53   a  has a longest dimension at its cross-section (measured at a plane that is perpendicular to the axis along which the length L 1  is measured) of between 0.3 mm and 0.75 mm, e.g., 0.6 mm. Proximal restraining element  53   a  has a greatest cross-sectional area of between 0.07 and 0.44 mm^2, (e.g., 0.28 mm^2) that is at least 1.5 times a greatest cross-sectional area of post  52   a . Following the subsequent implantation of the valve-repair implant, as will be described hereinbelow, proximal restraining element  53   a  restrains the implant from sliding proximally along post  52   a  and separating from implant-penetrating element  47   a . Implant-penetrating element  47   a  is thus shaped to provide an elongate penetration having a sufficient length-to-width ratio for penetrating the implant and for passing through the lumen of the implant such that proximal restraining element  53   a  is disposed proximally to the outer surface of the implant. In this configuration, proximal restraining element  53   a  restrains the implant from separating from implant-penetrating element  47   a , as is described hereinbelow. 
     Proximal restraining element  53   a  is shaped so as to define a passage  56  therethrough, which passage has at least two openings that are within 1 mm, e.g., such as 0.5 mm, of a proximal end of implant-penetrating element  47   a . Cord  54  is looped through passage  56  and is thereby removably coupled to anchor  49 . As shown in  FIG. 2C , the two portions of cord  54  that project away from passage  56  of proximal restraining element  53   a , are joined, e.g., welded, together at site proximal to tissue anchor  49 , e.g., at a site outside the body of the patient, in order to form a single proximal end portion  59  of cord  54 . End portion  59  of cord  54  is ultimately threaded through the implant outside the body of the patient in order for the implant to be slid along cord  54  and toward tissue anchor  49  at annulus  25 . Once the implant is implanted at the annulus of the patient, cord  54  is cut distally to single proximal end portion  59  so as to sever the loop created by the joining of the two portions of cord  54  at end portion  59 . Once cord  54  is cut, the physician extracts cord  54  from within the body of the patient as he or she pulls on proximal end portion  59  until cord  54  is pulled from within passage  56  of proximal restraining element  53   a  and is decoupled from anchor  49 . 
     Reference is again made to  FIG. 2A . As shown in the cross-sectional illustration, delivery tool  42  and manipulator  44  are each shaped so as to define a central lumen for cord  54  that is coupled to proximal restraining element  53   a  of implant-penetrating element  47   a . Cord  54  comprises a wire, a ribbon, a rope, or a band, which typically comprises a flexible and/or superelastic material, e.g., nitinol, ePTFE, PTFE, polyester, stainless steel, or cobalt chrome. In some applications of the present invention, cord  54  comprises a braided polyester suture (e.g., Ticron). In some applications of the present invention, cord  54  is coated with polytetrafluoroethylene (PTFE). In some applications of the present invention, cord  54  comprises a plurality of wires that are intertwined to form a rope structure. 
     Manipulator  44  is disposed at the distal end of the tube shaft of delivery tool  42  and is shaped to provide a distal applicator portion  46  which has a smaller outer diameter than an outer diameter of a proximal portion of manipulator  44 . As shown in the cross-sectional illustration of manipulator  44  and anchor  49  in  FIG. 2A , distal applicator portion  46  is shaped so as to fit within a lumen of distal tissue coupling element  50  (i.e., the outer diameter of portion  46  is smaller than an inner diameter of distal tissue coupling element  50 ). Manipulator  44  is shaped so as to define a slit  48  which bisects the distal end portion of manipulator  44  into two lateral walled portions. Slit  48  functions as a housing for housing and reversibly coupling implant-penetrating element  47   a  to delivery tool  42  (as shown in  FIG. 2A ). Slit  48  holds in place anchor  49  as it is advanced toward annulus  25 . Delivery tool  42  then functions to implant distal tissue coupling element  50  of anchor  49  in tissue of annulus  25 . First, torque is delivered toward manipulator  44  in response to rotation of the tube shaft of delivery tool  42 . Responsively to the torque, the lateral walled portions at the distal portion of manipulator  44  and distal applicator portion  46  function as a screw-driving tool by applying annular force to implant-penetrating element  47   a  and helical tissue anchor  58 . 
     As shown in  FIG. 2A , bar  55  of distal tissue coupling element  50  functions to couple anchor  49  to manipulator  44  when bar  55  is received and disposed within slit  48  and surrounded by the lateral wall portions of manipulator  44 . 
       FIG. 3  shows a plurality of anchors  49  implanted in respective portions of tissue of annulus  25  around a perimeter thereof. Each anchor  49  is implanted such that a central longitudinal axis therethrough forms an angle of between about 45 and 90 degrees with a surface of the tissue of annulus  25 , such as between about 75 and 90 degrees, e.g., about 90 degrees. The physician uses delivery tool  42 , as described hereinabove to systematically advance each anchor  49  through sheath  34  and toward annulus  25 . A first anchor  49  is coupled to manipulator  44  of delivery tool  42 , as follows: (a) cord  45  is fed through the lumen of the tube shaft of delivery tool  42  and through the lumen of manipulator  44 , and (b) distal applicator portion  46  of manipulator  44  is advanced within the lumen of helical tissue anchor  58 , while (c) bar  55  of helical tissue anchor  58  is advanced in place within slit  48  of manipulator  44 . The relative spatial configurations anchor  49  and manipulator  44  when anchor  49  is coupled to manipulator  44  is shown hereinabove with reference to  FIG. 2A . 
     Delivery tool  42  is then fed within advancement catheter  40 , and catheter  40  is advanced within sheath  34  toward annulus  25  until a distal end of catheter  40  emerges from within the distal end of sheath  34  and into the left atrium of the patient. Advancement catheter  40  is advanced toward a given location along annulus  25 . Subsequently, the tube shaft of delivery tool  42  is pushed such that distal tip  51  of helical tissue anchor  58  abuts the surface of tissue of the annulus. Torque is then delivered to manipulator  44  when the physician rotates the tube shaft of delivery tool  42  about a central axis of tool  42 . Such rotation of tool  42  rotates manipulator  44  in a manner in which the distal walled portions of the distal end of manipulator  44  apply an annular force to helical tissue anchor  58 . Responsively to the continued application of the annular force to helical tissue anchor  58 , distal tip  51  punctures the tissue of annulus  25  and continues along a helical path until helical tissue anchor  58  is corkscrewed sufficiently into tissue of annulus  25  at the given location. For applications in which distal tissue coupling element  50  comprises any other tissue coupling anchor, delivery tool  42  or any other delivery tool facilitates coupling of anchor  49  to annulus  25  by advancing distal tissue coupling element  50  into the tissue of annulus  25 . 
     Following the corkscrewing of helical tissue anchor  58  into tissue of the annulus, the physician pulls slightly on the tube shaft of delivery tool  42 . Upon applying the pulling force to tool  42 , the tissue of the annulus responsively pulls on the corkscrewed distal tissue coupling element  50 , thereby pulling implant-penetrating element  47   a  from within slit  48  of manipulator  44  and disengaging anchor  49  from tool  42 . As implant-penetrating element  47   a  is pulled from and slides distally within slit  48 , it frees anchor  49  from manipulator  44 . Delivery tool  42 , freed from anchor  49 , is then retracted within catheter  40 , and catheter  40  is extracted from within the body through sheath  34  which remains in place for the subsequent advancements of the remaining anchors  49 . As delivery tool  42  and catheter  40  are extracted, cord  45  remains looped within passage  56  of proximal restraining element  53   a  and is left disposed within sheath  34  such that proximal end portion  59  of cord  54  is disposed and accessible outside the body of the patient. 
     Once outside the body of the patient, delivery tool  42  is then coupled to a second anchor  49  (as described hereinabove with reference to the coupling of anchor  49  to manipulator  44 ), and tool  42  is fed into advancement catheter  40  which is then reintroduced into sheath  34 . The second anchor  49  is implanted, as described hereinabove. These steps are repeated until all of the anchors have been implanted around annulus  25 , as shown in  FIG. 3 . As shown, cords  45  reversibly coupled to each anchor  49  are disposed within sheath  34  and are accessible at their respective proximal portions  59  at a site outside the body of the patient. It is to be noted that although eight anchors  49  are implanted around annulus  25  by way of illustration and not limitation, any suitable number of anchors  49  may be implanted along annulus  25  according to the needs of a given patient, e.g., depending on the level of distention and relaxation of the annulus of a given patient. 
     Reference is now made to  FIG. 4 , which is a schematic illustration of a tissue-repair implant  60  being advanced along cords  54  toward annulus  25  of the mitral valve of the patient. As shown, repair implant  60  comprises a non-continuous, open, partial annuloplasty ring, by way of illustration and not limitation. It is to be noted that any valve-repair device, or implant (e.g., a full annuloplasty ring, a partial annuloplasty ring, a prosthetic valve, or a docking station for a prosthetic valve such as an annular valve support member) may be advanceable along cords  54 . The partial, open ring of repair implant  60  may be implemented using any one of the techniques described in U.S. patent application Ser. No. 12/341,960 to Cabiri, which issued as U.S. Pat. No. 8,241,351, and which is incorporated herein by reference. Typically, these techniques describe a full or partial ring comprising a sleeve, a spool coupled to the sleeve, and a flexible contracting member that is coupled to the spool and the sleeve, such that (1) winding the contracting member around the spool tightens the ring, and (2) unwinding the contracting member from around the spool relaxes and expands the ring. As shown, implant  60  comprises a penetrable sleeve comprising a braided fabric mesh. Implant  60  may also comprise a coiled implant in addition to or independently of the sleeve. 
     Reference is made to  FIGS. 2C and 4 . Prior to the advancing of implant  60 , a respective proximal end portion  59  of each cord  54  is threaded through the material of repair implant  60 . For example, end portion  59  is threaded (a) through a first surface of implant  60 , (b) through the lumen of implant  60  such that portion  59  passes orthogonal to the longitudinal axis defined by the lumen of implant  60 , and then (c) through an opposing surface of implant  60  such that it emerges proximal to the outer surface of implant  60 . A pushing tool (not shown for clarity of illustration) is used to advance implant  60  through advancement catheter  40  (which is advanced through sheath  34 ) and along each cord  54  toward annulus  25 . Once implant  60  emerges from within catheter  40 , the pushing tool is retracted and extracted from the body. Subsequently, implant  60  is locked in place along annulus  25  via anchors  49 , as is described hereinbelow. 
       FIGS. 5A-B  show a locking mechanism  74  that comprises a lock  80  having an annular distal portion  82  that is coupled to a plurality of radially-collapsible prongs  84 , in accordance with some applications of the present invention. Annular distal portion  82  has a diameter of between 1.5 mm and 3 mm, e.g., 2.2 mm. Following the advancement of mechanism  74  through the vasculature of the patient, lock  80  is ultimately positioned at a proximal portion of post  52   a  of implant-penetrating element  47   a  at a site distal to implant-restraining element  53   a  ( FIG. 5B ), as described hereinbelow. 
     It is to be noted that lock  80  also functions as a proximal restraining element to restrain implant  60  from sliding proximally away from anchor  49  and annulus  25 . 
     Locking mechanism  74  is coupled to a distal end of an advancement tube  72  and is advanced toward annulus  25  of the patient while surrounded by an overtube  70 . Locking mechanism  74  comprises a lock holder  73  which has radially-expandable arms  75  and  77 . Each of arms  75  and  77  is shaped to define a respective slot  81  and  83  which each cup and receive respective portions of annular distal portion  82  of lock  80 , as shown in the enlarged image of  FIG. 5A . A distal portion of overtube  70  surrounds arms  75  and  77  during the advancement of locking mechanism  74  toward annulus  25  of the patient. Overtube  70  thus prevents arms  75  and  77  from radially expanding, and this maintains coupling between holder  73  and lock  80 . As shown, locking mechanism  74 , advancement tube  72 , and overtube  70  are advanced toward implant  60 , along cord  54 . 
     The distal ends of advancement tube  72  and overtube  70  are advanced until they contact a proximal surface of a portion of implant  60 . In response to continued pushing of tubes  70  and  72 , tubes  70  and  72  push the portion of implant  60  distally such that implant  60  is penetrated by implant-penetrating element  47   a  (i.e., first by proximal restraining element  53   a  and then by post  52   a ). For some applications, proximal restraining element  53   a  is shaped to define a pointed tip, e.g., a barb, configure to puncture and penetrate a portion of implant  60 . Once implant  60  is fully pushed, a distal surface of implant  60  contacts tissue of annulus  25  and the proximal surface of implant  60  is disposed distally to a distal end of proximal restraining element  53   a . Post  52   a  couples implant  60  to anchor  49  by extending through a lumen of implant  60 . 
     It is to be noted that implant-penetrating element  47   a  may penetrate the implant by penetrating a braided mesh surrounding the implant, may penetrate the implant by passing between coils of a coiled implant, and/or may penetrate the implant in any other penetrating manner. 
       FIG. 5B  shows the disengaging of lock  80  from mechanism  74  following the locking in place of implant  60  to anchor  49  via lock  80 . As described hereinbelow, once lock  80  is coupled to anchor  49 , overtube  70  is slid proximally with respect to advancement tube  72  such that arms  75  and  77  of lock holder  73  are exposed from within the distal portion of overtube  70 . Once arms  75  and  77  are exposed, they expand radially (as is their natural tendency), and respective portions of annular distal portion  82  of lock  80  are freed from within slots  81  and  83  of arms  75  and  77 , respectively. Once lock  80  is freed from locking mechanism  74 , advancement tube  72 , locking mechanism  74 , and overtube  70  are retracted from within the body of the patient. In conjunction with the retracting, cord  54  is clipped and pulled such that it is no longer looped within passage  56  of proximal restraining element  53   a . The physician continues to pull cord  54  until cord  54  is extracted from within the body of the patient. 
       FIGS. 6A-B  and  7  show the method for locking repair implant  60  to annulus  25  via anchor  49 , in accordance with some applications of the present invention. As shown, post  52   a  of anchor  49  extends through the lumen of implant  60  from a distal surface of implant  60  (i.e., the surface in contact with annulus  25 ) to an opposing surface at the proximal surface of implant  60  (i.e., the surface in communication with the atrium of the patient). Post  52   a  extends through the lumen of implant  60  in a manner in which a distal end of proximal restraining element  53   a  is disposed proximally to the proximal surface of implant  60 . 
     Overtube  70  (and advancement tube  72 , locking mechanism  74 , and lock  80  disposed in overtube  70 ) is advanced along cord  54  and toward anchor  49  implanted at a given location along annulus  25 . The distal end of overtube  70  approaches the proximal surface of repair implant  60 . Overtube  70  and advancement tube  72  are pushed so that locking mechanism  74  and lock  80  engage implant-penetrating element  47   a  of anchor  49 . As tubes  70  and  72  are pushed, locking mechanism  74  is pushed toward implant  60 , and mechanism  74  in turn, pushes on annular distal portion  82  of lock  80  in order to slide lock  80  distally and around proximal restraining element  53   a . As annular distal portion  82  is pushed, prongs  84  slide along proximal restraining element  53   a  ( FIG. 6A ). 
     Typically, in their resting state, the proximal portions of prongs  84  are aligned in a manner in which they form a circle at their cross-section having a longest dimension measured at a cross-section (measured at a plane that is perpendicular to the longitudinal axis along which length L 1  of implant  60  is measured) of between 0.25 mm and 0.6 mm, (e.g., 0.45 mm) and a greatest cross-sectional area of between 0.05 mm^2 and 0.28 mm^2, e.g., 0.16 mm^2. It is to be noted that the proximal portions of prongs  84  are aligned in a manner in which they form a circle by way of illustration and not limitation, and that proximal portions of prongs  84  may be shaped so as to assume any given shape at their cross-section having a greatest cross-sectional area during the resting state of between 0.05 mm^2 and 0.28 mm^2, e.g., 0.16 mm^2. Since proximal restraining element  53   a  has a longest dimension at its cross-section of between 0.3 mm and 0.75 mm, as prongs  84  are advanced distally over proximal restraining element  53   a  proximal restraining element  53   a  pushes the proximal portions of prongs  84  radially such that the proximal portions of prongs  84  expand from their resting state to assume a greatest cross-sectional area of between 0.33 and 0.64 mm^2, i.e., a longest dimension at the cross-section of between 0.65 mm and 0.9 mm. As the proximal portions of prongs  84  are radially pushed, their collective cross-sectional area is larger than the greatest cross-sectional area of proximal restraining element  53   a.    
     In response to continued pushing of lock  80  by locking mechanism  74 , lock  80  slides distally until the respective proximal ends of each prong  84  are disposed distally to the distal end of proximal restraining element  53   a  (shown in  FIG. 6B ). Since the greatest cross-sectional area of post  52   a  (i.e., between 0.03 mm^2 and 0.2 mm^2) is smaller than the greatest cross-sectional area of proximal restraining element  53   a  (i.e., between 0.07 mm^2 and 0.44 mm^2), the proximal portions of prongs  84  radially collapse around post  52   a  to assume a greatest cross-sectional area that is smaller than the greatest cross-sectional area of proximal restraining element  53   a . Since the greatest cross-sectional area of proximal restraining element  53   a  is larger than the greatest collective cross-sectional area of the proximal portions of prongs  84  in their resting state and as they surround post  52   a , prongs  84  are restricted from moving proximally because they have collapsed around post  52   a . That is, when lock  80  moves proximally along post  52   a , the proximal end portions of prongs  84  abut against the distal end of proximal restraining element  53   a . In such a manner, proximal restraining element  53   a , restrains prongs  84  of lock  80  from sliding proximally, and thereby proximal restraining element  53   a , together with lock  80 , restrain implant  60  from sliding proximally away from anchor  49  and from annulus  25 . In such a manner, post  52   a  functions as a protrusion which protrudes into a plane defined by implant  60 , and the distal portion of proximal restraining element  53   a  functions as a shelf which facilitates restricting of proximal potion of the implant along the protrusion. As described herein above with reference to the cross-sectional area of proximal restraining element  53   a  (measured at a plane that is perpendicular to the longitudinal axis along which length L 1  of implant  60  is measured), the shelf has a transverse cross-sectional length (i.e., the cross-sectional area, as described hereinabove), that is larger than a transverse cross-sectional length of implant-penetrating element  47   a.    
     Additionally, as lock  80  is pushed distally, annular distal portion  82  pushes against a portion of implant  60 . Responsively, implant  60  pushes against annular distal portion  82  so as to (1) create pressure between the proximal portions of prongs  84  and the distal end of proximal restraining element  53   a , and (2) lock lock  80  in place with respect to proximal restraining element  53   a  in order to restrain implant  60  from sliding proximally. 
       FIG. 7  shows the decoupling of lock holder  73  from lock  80  and from anchor  49 . Overtube  70  is retracted proximally in order to expose arms  75  and  77  of lock holder  73 . Once arms  75  and  77  are exposed from within overtube  70 , they expand radially, as shown, and respective portions of annular distal portion  82  of lock  80  are freed from within slots  81  and  83  of arms  75  and  77 , respectively. Overtube  70 , advancement tube  72 , and lock holder  73  are then retracted through sheath  34  along cord  54 . 
     Reference is now made to  FIGS. 2C and 7 . Once lock  80  is locked in place between implant  60  and proximal restraining element  53   a  of anchor  49 , cord  54  is clipped distally to proximal end portion  59  thereof so as to create free ends of cord  54 . A first free end of cord  54  is then pulled so that the second free end is pulled through advancement tube  72  and toward anchor  49 . In response to continued pulling of the first free end of cord  54 , the second end of cord  54  is pulled through passage  56  of proximal restraining element  53   a  until cord  54  is decoupled from anchor  49 . The physician continues to pull on the first free end of cord  54  until the second free end is once again exposed from within tube  72 , and thereby cord  54  is extracted from within the body of the patient. 
       FIG. 7  shows the decoupling of lock holder  73  of locking mechanism  74  from one of the eight anchors  49  around annulus  25 . It is to be noted that the method for the locking in place of implant  60  via anchors  49  and locks  80  (as described hereinabove with reference to  FIGS. 5A-B ,  6 A-B, and  7 ) is applied to every anchor  49  implanted along annulus  25 .  FIG. 7  shows implant  60  comprising a partial, open, non-continuous ring as described in U.S. patent application Ser. No. 12/341,960 to Cabiri (which is incorporated herein by reference), by way of illustration and not limitation. For example, any suitable tissue repair device known in the art may be anchored to any tissue of the patient via anchor(s)  49 . For example, anchors  49  may be implanted in a stomach of the patient and may be used to anchor a gastric bypass ring to the stomach of the patient, in a manner as described hereinabove. 
       FIGS. 8 and 9  are schematic illustrations of examples of the types of implants  60  that are anchored to annulus  25  via anchors  49 , in accordance with respective applications of the present invention.  FIG. 8  shows implant  60  comprising a partial, open, non-continuous annuloplasty ring by way of illustration and not limitation.  FIG. 9  shows a system  110  in which implant  60  comprises a full annuloplasty ring by way of illustration and not limitation. As described hereinabove implants  60 , as shown in  FIGS. 8 and 9 , are shown by way of illustration and not limitation and that any suitable tissue-remodeling device or implant may be anchored to tissue of the patient using anchor(s)  49 . 
     Reference is now made to  FIG. 10 , which is a schematic illustration of a system  120  comprising a tissue anchor  121  comprising a distal tissue coupling element  50  and a proximal implant-penetrating element  47   b , in accordance with some applications of the present invention. Implant-penetrating element  47   b  comprises a proximal elastic portion comprising a tension spring  122  and a proximal restraining element  53   b  comprising radially-expandable anchor arms  128 . Implant-penetrating element  47   b  comprises a proximal portion  124  shaped to define a pointed tip  126  for penetrating an implant (e.g., a tissue-repair implant  60 ) and facilitating passage of the implant over implant-penetrating element  47   b . Typically, proximal portion  124 , pointed tip  126 , and arms  128  together form and function as a barb  153 . A proximal elastic portion comprises a tension spring  122  (i.e., implant-penetrating element  47   b ), as shown by way of illustration and not limitation, and has a length L 4  of between 3 mm and 5 mm, e.g., 4 mm, when spring  122  is relaxed. Radially-expandable arms  128  are compressible and expandable along a longitudinal axis  130  of anchor  121 . Distal tissue coupling element  50  comprises a distal tissue-penetrating tip  51  and is shaped to define helical tissue anchor  58  by way of illustration and not limitation, e.g., tissue coupling element  50  may comprise any suitable tissue anchor known in the art (e.g., as is shown hereinbelow in  FIGS. 19 and 20 ). 
     It is to be noted that proximal implant-penetrating element  47   b  of anchor  121  is similar in function to proximal implant-penetrating element  47   a  of anchor  49  in that both proximal implant-penetrating elements  47   a  and  47   b  function to receive and facilitate coupling of the implant to the tissue anchor. It is to be further noted that proximal restraining element  53   b  of anchor  121  is similar in function to proximal restraining element  53   a  of anchor  49  in that both proximal restraining elements  53   a  and  53   b  function to restrain the implant from sliding proximally and separating from respective implant-penetrating elements  47   a  and  47   b.    
     As described hereinabove, distal tissue coupling element  50  has length L 3  of 2-8 mm, e.g., 4 mm. Thus, for some applications, anchor  121  has a total length L 5  of 5-13 mm. 
     The elastic portion is shown in  FIG. 10  when spring  122  is in its relaxed, resting state. In this relaxed state of spring  122 , the elastic portion has a length of between 3 and 5 mm. Spring  122  is configured to be pulled during one stage of implantation of the tissue-repair device. During such pulling, spring  122  is under load and assumes a greater length when under load than when in its relaxed state. 
     The proximal portion of implant-penetrating element  47   b  is shaped so as to define one or more passages  56  therethrough. It is to be noted that only one opening of one passage  56  is shown in the configuration as shown in  FIG. 10 , and that cord  54  passes through passage  56  on the sides of proximal portion  124 . Cord  54  is removably coupled to anchor  121  by being passed through passage  56  (as described hereinabove with reference to anchor  49 ) and functions to facilitate guiding of the valve-repair implant toward tissue anchor  121  implanted at annulus  25 . As described hereinabove, passage  56  has at least two openings that are within 1 mm, e.g., 0.5 mm, of a proximal end of implant-penetrating element  47   b.    
     The distal portion of implant-penetrating element  47   b  comprises a post  52   b    10  which couples distal tissue coupling element  50  to the elastic portion. Post  52   b  in such an application has a height of between 0.2 mm and 0.4 mm. Anchor  121 , comprising distal tissue coupling element  50  and implant-penetrating element  47   b , has a length measured along axis  130  of 6-12 mm, e.g., 10 mm. Implant-penetrating element  47   b  has a length measured along axis  130  of 4-10 mm, e.g., 5.5 mm. Distal tissue coupling element  50  has a length measured along axis  130  of 2-8 mm, e.g., 4 mm. For some applications, post  52   b  includes spring  122 , and in such an application, post  52   b  has a length of between 1 and 7 mm. 
       FIG. 11A  shows a plurality of tissue anchors  121  implanted along annulus  25 , in accordance with some applications of the present invention. Each anchor  121  is reversibly coupled to an elongate delivery tool (not shown for clarity of illustration) and is transcatheterally advanced via the tool toward annulus  25 . The delivery tool facilitates corkscrewing of helical tissue anchor  58  into tissue of the annulus. For applications in distal tissue coupling element  50  comprises any other tissue coupling anchor, the delivery tool facilitates coupling of anchor  121  to annulus  25  by advancing distal tissue coupling element  50  into the tissue of annulus  25 . 
     Each anchor  121  is implanted in a manner in which a proximal end of tissue coupling element  50  is disposed within tissue of annulus  25  and a distal end portion of spring  122  is disposed proximally to the surface of annulus  25 , as shown in the enlarged image of tissue anchor  121  of  FIG. 11A . For some applications of the present invention, delivery tool  42 , as described hereinabove with reference to  FIGS. 2A-C  may be reversibly coupled to each anchor  121  and facilitate implantation of each anchor  121 . In such an application, arms  128  of implant-penetrating element  47   b  are compressed within slit  48  of manipulator  44  of tool  42 . 
     Once tissue anchor  121  is implanted, cord  54  remains coupled to anchor  121 , as described hereinabove with reference to the cord  54  coupled to tissue anchor  49 . It is to be noted that although eight anchors  121  are implanted around annulus  25  by way of illustration and not limitation, any suitable number of anchors  121  may be implanted along annulus  25  according to the needs of a given patient, e.g., depending on the level of distention and relaxation of the annulus of a given patient. 
     Reference is now made to  FIG. 11B , which is a schematic illustration of a tissue-repair implant  60  being advanced along cords  54  toward annulus  25  of the mitral valve of the patient. As shown, repair implant  60  comprises a non-continuous, open, partial annuloplasty ring, by way of illustration and not limitation. It is to be noted that any valve repair implant, e.g., a full annuloplasty ring, a partial annuloplasty ring, or a prosthetic valve, may be advanceable along cords  54 . The partial, open ring of repair implant  60  may be implemented using any one of the techniques described in U.S. patent application Ser. No. 12/341,960 to Cabiri, which is incorporated herein by reference. 
     Implant  60  is advanced along cords  54 , in a manner as described hereinabove with reference to  FIGS. 2C and 4 . A pushing tool (not shown for clarity of illustration) is used to push implant  60  through catheter  40  and toward annulus  25 . Implant  60  is pushed until respective portions of a distal surface of implant  60  contact each pointed tip  126  of proximal portion  124  of implant-penetrating element  47   b.    
       FIG. 11C  shows a pushing tool  140 , as described hereinabove with reference to  FIG. 11B , that pushes respective portions of implant  60  such that they are engaged by each implant-penetrating element  47   b  of anchors  121 , in accordance with some applications of the present invention. Pushing tool  140  is advanced along a respective cord  54 , as shown, and toward a portion of implant  60 . The physician uses pushing tool  140  to push on the proximal surface of implant  60  such that the distal surface of implant  60  is punctured by pointed tip  126  of implant-penetrating element  47   b . Continued pushing of pushing tool  140 : (1) advances a portion of implant  60  around arms  128  and along the elastic portion and spring  122  of implant-penetrating element  47   b , and thereby (2) facilitates coupling of the portion of implant  60  to anchor  121 . As implant  60  is pushed, spring  122  compresses along axis  130  and provides flexibility to system  120 , as implant  60  is anchored to annulus  25 . 
     Following the puncturing of the distal surface of the portion of implant  60  by pointed proximal tip  126  of implant-penetrating element  47   b , an opening is created at the distal surface of implant  60  for passage therethrough of a proximal portion of implant-penetrating element  47   b . As implant  60  is pushed along implant-penetrating element  47   b , the proximal portion is disposed within the lumen of implant  60 , as shown in the enlarged image of  FIG. 11C . The opening at the distal surface of implant  60  that is created by puncturing the material of implant  60  closes around and radially compresses radially-expandable arms  128  as the proximal portion of implant-penetrating element  47   b  passes through implant  60  in conjunction with the pushing of implant  60  (as shown in the enlarged cross-sectional images of implant  60  being coupled to anchor  121 ). Radially-expandable arms  128  are compressed such that they align alongside spring  122  as the portion of implant  60  is pushed along implant-penetrating element  47   b . Responsively to continued pushing of the portion of implant  60  by tool  140 , pointed proximal tip  126  of implant-penetrating element  47   b  punctures a proximal surface of the portion of implant  60  from within the lumen of implant  60 , and proximal tip  126  emerges proximally to the proximal surface of implant  60 . 
     Reference is now made to  FIG. 11D , which is a schematic illustration of the locking in place of the portion of implant  60  at a given location along annulus  25  via arms  128  of anchor  121 , in accordance with some applications of the present invention. As described hereinabove, responsively to continued pushing of the portion of implant  60  by tool  140 , pointed tip  126  of implant-penetrating element  47   b  punctures and creates an opening at the proximal surface of implant  60  and emerges from within the lumen of implant  60  proximally to the upper surface of implant  60 . Responsively to continued pushing of the portion of implant  60  by tool  140 , implant  60  slides along implant-penetrating element  47   b  such that respective distal ends of arms  128  emerge from within the lumen of implant  60  and through the opening at the proximal surface of the portion of implant  60 . Once arms  128  are freed from within the lumen of the portion of implant  60  (i.e., are no longer radially compressed by the lumen of the portion of implant  60  and/or the respective openings at the proximal and distal surfaces of the portion of implant  60 ), arms  128  expand radially, as shown in the enlarged images of  FIG. 11D . Arms  128  are configured to radially compress and expand between 0 and 30 degrees with respect to axis  130  of anchor  121 . Arms  128  expand such that (1) the proximal ends thereof collectively form a perimeter that is larger than the perimeter of the external surface of implant  60 , and (2) arms  128  lock in place around implant  60  to restrict proximal movement of implant  60 . 
     Reference is now made to  FIGS. 11C-D . Arms  128  expand around the external surface of implant  60  and thus function as proximal restraining element  53   b  to restrain proximal sliding of implant  60  along implant-penetrating element  47   b  and decoupling of implant  60  from anchor  121  ( FIG. 11D ). Once arms  128  expand and lock in place the portion of implant  60  to annulus  25  via anchor  121 , pushing tool  140  is extracted from the body of the patient through catheter  40 . Spring  122  is thus no longer compressed responsively to the pushing force of implant  60  applied by tool  140 , and spring  122  relaxes and returns to its resting state ( FIG. 11D ). As shown in  FIG. 11C , following the coupling of respective portions of implant  60  to anchors  121 , each cord  54  coupled to the respective anchor  121  is cut, as described hereinabove with reference to  FIG. 2B , and decoupled from the respective anchor  121 . Typically, but not necessarily, each cord  54  is decoupled from anchor  121  immediately following the coupling of the respective portion of implant  60  to each anchor  121  (as shown in  FIG. 11C ). Alternatively, cords  54  remain coupled to respective anchors  121  until the entire implant  60  is coupled to annulus  25  via anchors  121 . 
     In some embodiments, in conjunction with the pushing of implant  60  by tool  140 , cord  54  is pulled taut so as to apply load to spring  122  such that it expands to a length greater than its length during the resting state of spring  122 . The pulling of spring  122  helps pull arms  128  through the lumen of implant  60  such that they emerge from within the lumen of implant  60 . Once arms  128  emerge from within the lumen of implant  60 , cord  54  is no longer pulled, and spring  122  returns to its resting state in order to allow arms  128  to rest against an external proximal surface of implant  60  and restrict proximal movement of implant  60  along implant-penetrating element  47   b . Thus, arms  128  function as proximal restraining element  53   b , and arms  128  together with portion  124  and tip  126  function as barb  153   b.    
     Reference is again made to  FIG. 11C , which shows, by way of illustration and not limitation, implant  60  being coupled to anchors  121  in a systematic order beginning from the left-most anchor  121 , (i.e., disposed at 10 o&#39;clock) and moving clockwise in series from anchor to anchor. It is to be noted that implant  60  may be coupled to anchors  121  in any suitable order (i.e., not in series from anchor to anchor), in accordance with the protocol of the operating physician. 
     Reference is now made to  FIGS. 12-14 , which are schematic illustrations of a system  200  for implanting anchors  49  and  121  described hereinabove in an open-heart or minimally-invasive procedure, in accordance with some applications of the present invention. System  200  comprises a tool body  202  and proximal handle portions  204  and  206 . Tool body  202  comprises an outer tube shaft  210  and an inner tube shaft  212  ( FIG. 14 ). Inner tube shaft  212  functions similarly to the elongate tube shaft of delivery tool  42 , as described hereinabove with reference to  FIGS. 2A-C . The distal end of tube shaft  212  is coupled to manipulator  44  that is described hereinabove with reference to  FIGS. 2A-C . Manipulator  44  is reversibly coupled to anchor  49 , as described hereinabove. It is to be noted that although  FIGS. 12-14  show manipulator  44  coupled to anchor  49 , manipulator  44  may also be coupled to anchor  121 , in a manner as described hereinabove with reference to  FIG. 11A . The proximal end of inner tube shaft  212  is coupled to handle portion  206  of tool body  202 . For some applications, handle portion  206  is rotatable along an axis  230  of tool body  202  in order to (1) rotate inner tube shaft  212  and, thereby, rotate manipulator  44 , and thereby (2) facilitate corkscrewing of distal tissue coupling element  50  of anchor  49  into tissue of annulus  25 . Alternatively, the entire tool body  202  is rotated about axis  230  of tool body  202  in order to rotate distal tissue coupling element  50  of anchor  49  and facilitate corkscrewing of distal tissue coupling element  50  of anchor  49  into tissue of annulus  25 . In either application, following the corkscrewing of distal tissue coupling element  50  into tissue of annulus  25 , anchor  49  is decoupled from manipulator  44 , as described hereinabove with reference to  FIG. 2B , and thereby decoupled from tool body  202 . 
     As shown in  FIG. 14 , inner tube shaft  212  is housed within a lumen of outer tube shaft  210 . Inner tube shaft  212  and handle portions  204  and  206  are each shaped to provide a lumen for passage therethrough of cord  54  coupled to anchor  49 . Tool body  202  is shaped so as to provide (1) a proximal opening  214  for passage therethrough of cord  54 , and (2) a distal opening  216  for passage therethrough of anchor  49 . Once distal tissue coupling element  50  of anchor  49  is corkscrewed into tissue of annulus  25  and anchor  49  is decoupled from manipulator  44 , tool body  202  is slid proximally along cord  54  leaving anchor  49  and a portion of cord  54  in heart  22  of the patient. 
       FIG. 15  shows system  200  being used to implant anchor  49  in heart  22  of the patient, in accordance with some applications of the present invention during an open-heart or minimally-invasive procedure. In these procedures, an incision is created in heart  22  at the left atrium to provide a passage for the distal end portion of tool body  202  to access an atrial surface of the mitral valve. As shown, tool body  202  (or tube shaft  212 ) is rotated in order to facilitate corkscrewing of distal tissue coupling element  50  of anchor  49  into tissue of annulus  25 . As described hereinabove, pointed distal tip  51  punctures tissue of annulus  25  in order to facilitate corkscrewing of distal tissue coupling element  50  into tissue of annulus  25 . 
       FIG. 16  shows a plurality of anchors  49  implanted along annulus  25  following the corkscrewing of distal tissue coupling element  50  of each anchor  49  into tissue of annulus  25 , as facilitated by tool body  202  of system  200  described hereinabove with reference to  FIGS. 12-14 , in accordance with some applications of the present invention. It is to be noted that anchors  121 , as described hereinabove with reference to  FIGS. 10 and 11A -D, may be implanted along annulus  25  using tool body  202  of system  200 . Following the implantation of each anchor  49  via tool body  202 , respective cords  54  remain coupled to each anchor  49 . The proximal end portions of each cord  54  are accessible outside the body of the patient. 
     As shown, each distal tissue coupling element  50  is disposed within tissue of annulus  25 , and each proximal restraining element  53   a  and post  52   a  of each anchor  49  extend proximally from the proximal surface of annulus  25 . Each implant-penetrating element  47   a  comprising proximal restraining element  53   a  and post  52   a  is thus accessible by any tissue-repair implant  60  advanced theretoward along cord  54  reversibly coupled to proximal restraining element  53   a.    
       FIG. 17  shows tissue-repair implant  60 , as described hereinabove, coupled to annulus  25  via anchor  49 , in accordance with some applications of the present invention. As described hereinabove, implant  60  is advanced along cords  54  toward tissue of annulus  25 . A tool may be used to advance respective portions of implant  60  along each cord  54 . Alternatively, during an open-heart procedure, the physician uses his or her fingers to push respective portions of implant  60  along each cord  54 . As shown in the enlarged image of  FIG. 17 , a portion of implant  60  is coupled to anchor  49  in a manner in which: (1) the distal surface of the portion of implant  60  contacts the proximal surface of annulus  25 , (2) a distal portion of post  52   a  is disposed within the lumen of implant  60 , and (3) a distal end of proximal restraining element  53   a  is disposed proximally to a proximal surface of the portion of implant  60 . As shown, cords  54  remain coupled to anchors  49  following the coupling of the respective portions of implant  60  to implant-penetrating element  47   a  of each anchor  49 . 
       FIG. 18  shows a tool system  220  for coupling a respective lock  80  to a portion of implant-penetrating element  47   a  that is distal to proximal restraining element  53   a  of each anchor  49 , in accordance with some applications of the present invention. Tool system  220  comprises an outer tube shaft  228  which is shaped to provide a lumen for slidable movement of an inner tube shaft  226 . As shown in the enlarged cross-sectional image of  FIG. 18 , tube shaft  226  is shaped so as to provide a lumen for passage therethrough of cord  54  in order to facilitate sliding of tool system  220  along cord  54  and toward anchor  49 . 
     A distal end of inner tube shaft  226  is coupled to locking mechanism  74  comprising lock holder  73 , as described hereinabove with reference to  FIGS. 5A-B . Thus, inner tube shaft  226  functions similarly to advancement tube  72  (as described hereinabove with reference to  FIGS. 5A-B ) in order to advance locking mechanism distally through outer tube shaft  228 . Outer tube shaft  228  functions similarly to overtube  70  (as described hereinabove with reference to  FIGS. 5A-B ) in order to surround radially-expandable arms  75  and  77  of locking mechanism  74  and maintain arms  75  and  77  in a compressed state within a distal portion of shaft  228  during a resting state of system  220 . As described hereinabove, lock holder  73  of locking mechanism  74  is reversibly coupled to a lock  80  which locks in place a portion of implant  60  to annulus  25  via anchor  49 . 
     A proximal portion of inner tube shaft  226  is coupled to a first engageable element  222 , while a proximal end of outer tube shaft  228  is coupled to a second engageable element  224 . First and second engageable elements  222  and  224  are engageable by the hand of the operating physician. Tool system  220  is spring-loaded so as to facilitate controlled displacement of second engageable element  224  from first engageable element  222 . Responsively to pulling of second engageable element  224  away from first engageable element  222 , outer tube shaft  228  slides proximally along inner tube shaft  226 . 
     Prior to the pulling of second engageable element  224 , the operating physician pushes the entire tool system  220  (i.e., without pulling second engageable element  224  away from first engageable element  222 ) such that (1) the distal end of outer tube shaft  228  contacts the proximal surface of implant  60 , and (2) lock  80  is pushed along proximal restraining element  53   a  and engages post  52   a , in a manner as described hereinabove with reference to  FIGS. 5A-B ,  6 A-B, and  7 . The physician then pulls second engageable element  224  away from first engageable element  222 . In response to the pulling of engageable element  224  (i.e., a pulled state of system  220 ), tube shaft  228  is pulled and a distal portion of lock holder  73  is exposed distally to the distal end of outer tube shaft  228 . Arms  75  and  77  are freed from within a distal end portion of outer tube shaft  228  and radially expand. Annular distal portion  82  of lock  80  is then freed from within slots  81  and  83  of arms  75  and  77 , respectively, and lock  80  is decoupled from locking mechanism  74  and tool system  220 . Once lock  80  is locked in place between implant  60  and proximal restraining element  53   a , cord  54  is clipped distally to proximal end portion  59  thereof so as to create free ends of cord  54 , and cord  54  is extracted from within the body of the patient, as described hereinabove with reference to  FIGS. 2C and 7 . 
     As shown in the enlarged cross-sectional images of  FIG. 18 , a distal portion of post  52   a  couples implant  60  to anchor  49  by being disposed within the lumen of implant  60  between a first opening of implant  60  at a distal surface thereof and a second opening of implant  60  at a proximal surface thereof. 
     Reference is now made to  FIG. 19 , which is a schematic illustration of a system  320  comprising a tissue anchor  321  that is similar to tissue anchor  49 , as described hereinabove, with the exception that distal tissue coupling element  50  comprises an expandable tissue anchor  322  which comprises one or more, e.g., a plurality, of radially-expandable prongs  326 , in accordance with some applications of the present invention. Prongs  326  comprise flexible metal, e.g., nitinol or stainless steel, and have a tendency to expand radially, as shown in the left-most image in  FIG. 19 . Anchors  322  facilitate coupling of tissue anchor  321  to annulus  25  of the native valve, such as the mitral valve or the tricuspid valve, or to any other valve or tissue. Tissue anchor  322  is shaped so as to define a pointed distal tip  324  configured to puncture tissue of annulus  25 . As described hereinabove, distal tissue coupling element  50 , which, for this application of the present invention comprises tissue anchor  322 , has length L 3  of 2-8 mm, e.g., 4 mm. 
     Tissue anchor  322  is coupled to (e.g., welded or otherwise coupled to) post  52   a  of implant-penetrating element  47   a , as described hereinabove. Implant-penetrating element  47   a  has length L 2  of 4-10 mm, e.g., 5.5 mm. Taken together, tissue anchor  321  has length L 1  of 6-18 mm, e.g., 10 mm. 
     In the right-side images of  FIG. 19 , tissue anchor  322  is shown being implanted into tissue of annulus  25 . Pointed distal tip  324  punctures tissue of annulus  25 . In response to distal pushing of anchor  321 , tissue anchor  322  is pushed within tissue of annulus  25 . As anchor  321  is pushed, the force of the tissue of annulus  25  pushes against prongs  326  and compresses prongs  326  inwardly (as shown in the upper-right image). Following the pushing of anchor  321  distally, anchor  321  is pulled slightly proximally (e.g., by pulling on cord  54 ) in order to enable prongs  326  to expand radially to assume a flower shape and a larger surface area, to restrict proximal motion of anchor  321  in tissue of annulus  25 . 
     Following the implanting of anchor  322  within tissue of annulus  25 , post  52   a  remains disposed proximally to a surface of annulus  25 , so that it can puncture and receive the implant, as described hereinabove. 
       FIG. 20  shows a system  420  comprising a tissue anchor  421  that is similar to tissue anchor  121 , as described hereinabove, with the exception that distal tissue coupling element  50  comprises an expandable tissue anchor  322 , as described hereinabove with reference to  FIG. 19 , in accordance with some applications of the present invention. As described hereinabove, distal tissue coupling element  50 , which, for this application of the present invention comprises tissue anchor  322 , has length L 3  of 2-8 mm, e.g., 4 mm. Also, as described hereinabove, anchor  421  comprises a proximal elastic portion which comprises tension spring  122 , as shown by way of illustration and not limitation. Implant-penetrating element  47   b  has a length L 4  of between 3 mm and 5 mm, e.g., 4 mm, when spring  122  is relaxed. Thus, for some applications, anchor  421  has a total length L 5  of 5-13 mm. 
     Tissue anchor  421  comprises distal tissue coupling element  50  and proximal implant-penetrating element  47   b . As described hereinabove, implant-penetrating element  47   b  comprises the proximal elastic portion comprising tension spring  122  and proximal restraining element  53   b  comprising radially-expandable anchor arms  128 . Implant-penetrating element  47   b  comprises a proximal portion  124  shaped to define a pointed tip  126  for penetrating an implant (e.g., a tissue-repair implant  60 ) and facilitating passage of the implant over implant-penetrating element  47   b . Typically, proximal portion  124 , pointed tip  126 , and arms  128  together form and function as a barb  153 . 
     Reference is now made to  FIGS. 19 and 20 . For some applications of the present invention, during the delivery of anchors  321  and  421  toward annulus  25 , a sheath (not shown) surrounds prongs  326  so as to keep them in a closed state and facilitate atraumatic advancement of prongs  326  toward tissue at annulus  25 . 
     Reference is now made to  FIGS. 1A-F ,  2 A-C,  3 - 4 ,  5 A-B,  6 A-B,  7 - 10 ,  11 A-D, and  12 - 20 . It is to be noted that systems, methods, and anchors  49 ,  121 ,  321 , and  421  described herein may be used at any atrioventricular valve, e.g., the mitral valve or the tricuspid valve. It is to be further noted that systems, methods, and anchors  49 ,  121 ,  321 , and  421  described herein may be implanted at any suitable tissue site (e.g., tissue of a stomach of the patient) in order to facilitate implantation of any suitable implant. 
     For some applications of the present invention, techniques described herein are practiced in combination with techniques described in one or more of the references cited in the Background section of the present patent application. 
     Additionally, the scope of the present invention includes applications described in one or more of the following:
         PCT Publication WO 06/097931 to Gross et al., entitled, “Mitral Valve treatment techniques,” filed Mar. 15, 2006;   U.S. Provisional Patent Application 60/873,075 to Gross et al., entitled, “Mitral valve closure techniques,” filed Dec. 5, 2006;   U.S. Provisional Patent Application 60/902,146 to Gross et al., entitled, “Mitral valve closure techniques,” filed Feb. 16, 2007;   U.S. Provisional Patent Application 61/001,013 to Gross et al., entitled, “Segmented ring placement,” filed Oct. 29, 2007;   PCT Publication WO 08/068756 to Gross et al., entitled, “Segmented ring placement,” filed Dec. 5, 2007;   U.S. patent application Ser. No. 11/950,930 to Gross et al., entitled, “Segmented ring placement,” filed Dec. 5, 2007, which published as U.S. 2008/0262609 and which issued as U.S. Pat. No. 8,926,695;   U.S. patent application Ser. No. 12/435,291 to Maisano et al., entitled, “Adjustable repair chords and spool mechanism therefor,” filed on May 4, 2009, which published as US 2010/0161041, and which issued as U.S. Pat. No. 8,147,542;   U.S. patent application Ser. No. 12/437,103 to Zipory et al., entitled, “Annuloplasty ring with intra-ring anchoring,” filed on May 7, 2009 which issued as U.S. Pat. No. 8,715,342;   PCT Publication WO 10/004546 to Gross et al., entitled, “Annuloplasty devices and methods of delivery therefor,” filed on Jun. 15, 2009;   U.S. patent application Ser. No. 12/548,991 to Maisano et al., entitled, “Implantation of repair chords in the heart,” filed on Sep. 21, 2009, which published as US 2010/0161042, and which issued as U.S. Pat. No. 8,808,368;   PCT Publication WO 10/073246 to Cabiri et al., entitled, “Adjustable annuloplasty devices and mechanisms therefor,” filed Dec. 22, 2009;   U.S. patent application Ser. No. 12/706,868 to Miller et al., entitled, “Actively-engageable movement-restriction mechanism for use with an annuloplasty structure,” filed Feb. 17, 2010, which published as US 2010/0211166, and which issued as U.S. Pat. No. 8,353,956;   PCT Patent Application PCT/IL2010/000357 to Maisano et al., entitled, “Implantation of repair chords in the heart,” filed May 4, 2010, which published as WO 10/128502; and/or   PCT Patent Application PCT/IL2010/000358 to Zipory et al., entitled, “Deployment techniques for annuloplasty ring and over-wire rotation tool,” filed May 4, 2010, which published as WO 10/128503.       

     All of these applications are incorporated herein by reference. Techniques described herein can be practiced in combination with techniques described in one or more of these applications. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.