Cardiac tissue cinching

Abstract

A torque-delivery tool includes a cable and a distal coupling element. A tissue anchor includes an anchor head, which includes a shaft having a proximal coupling element. The distal and proximal coupling elements are shaped so as to define corresponding interlocking surfaces. An outer tether-securing element of the anchor is shaped so as to define a lateral opening through which a tether is disposed, and at least partially radially surrounds the shaft and a spring. In an unlocked state, a distal spring depressor restrains the spring in an axially-compressed state. In a locked state, the distal and proximal coupling elements are not coupled with one another, the distal spring depressor does not restrain the spring in the axially-compressed state, and the spring is in an axially-expanded state, in which the spring inhibits the sliding of the tether through the lateral opening by pressing the tether against the outer tether-securing element.

Claims

1. Apparatus comprising a tissue-anchor system, which comprises: a torque-delivery tool, which comprises (a) a torque-delivery cable, which comprises a distal torque-delivery head, (b) a distal coupler that is fixed to a distal end of the distal torque-delivery head, and (c) a distal spring depressor; a tether; and a tissue anchor, which comprises (a) a tissue coupler, and (b) an anchor head, which (i) is attached to a proximal portion of the tissue coupler, and (ii) comprises: an axially-stationary shaft, which (a) has a distal portion that is axially fixed with respect to the proximal portion of the tissue coupler, and (b) has a proximal end that comprises a proximal coupler, wherein the distal and the proximal couplers are shaped so as to define corresponding interlocking surfaces; a spring; and an outer tether-securing element, which (a) is shaped so as to define a lateral opening through which the tether is disposed, and (b) at least partially radially surrounds the axially-stationary shaft and the spring, wherein the tissue-anchor system is configured to assume: an unlocked state, in which (a) the distal and the proximal couplers are interlockedly coupled with one other, and (b) the distal spring depressor restrains the spring in an axially-compressed state, in which state the spring does not inhibit sliding of the tether through the lateral opening, and a locked state, in which (a) the distal and the proximal couplers are not coupled with one another, (b) the distal spring depressor does not restrain the spring in the axially-compressed state, and (c) the spring is in an axially-expanded state, in which state the spring inhibits the sliding of the tether through the lateral opening by pressing the tether against the outer tether-securing element.

2. The apparatus according to claim 1, wherein at least a portion of the spring radially surrounds the axially-stationary shaft.

3. The apparatus according to claim 1, wherein at least a portion of the spring is helical.

4. The apparatus according to claim 1, wherein, when the tissue-anchor system is in the locked state, the spring inhibits the sliding of the tether through the lateral opening by pressing the tether against a perimeter of the lateral opening of the outer tether-securing element.

5. The apparatus according to claim 1, wherein the tissue-anchor system further comprises a locking wire, wherein the torque-delivery cable, including the distal torque-delivery head, the distal coupler, the proximal coupler, and the axially-stationary shaft are shaped so as define respective channels therethrough, which are radially aligned with each other and coaxial with the tissue anchor, and wherein, when the tissue-anchor system is in the unlocked state, a portion of the locking wire is disposed in the channels, thereby preventing decoupling of the distal and the proximal couplers from one another.

6. The apparatus according to claim 5, wherein the locking wire has a sharp distal tip.

7. The apparatus according to claim 1, wherein the anchor head further comprises a hammer cap, which covers at least a portion of the spring, including a proximal end of the spring, and wherein, when the tissue-anchor system is in the locked state, the spring presses the tether against the outer tether-securing element by pressing the hammer cap against the outer tether-securing element.

8. The apparatus according to claim 7, wherein, when the tissue-anchor system is in the locked state, the spring presses the hammer cap against a perimeter of the lateral opening of the outer tether-securing element.

9. The apparatus according to claim 7, wherein the hammer cap is fixed to the spring.

10. The apparatus according to claim 1, wherein the outer tether-securing element is rotatable with respect to the tissue coupler and the axially-stationary shaft.

11. The apparatus according to claim 1, wherein the outer tether-securing element is shaped as a partial cylinder.

12. The apparatus according to claim 1, wherein the tissue anchor is a first tissue anchor, and wherein the tissue-anchor system further comprises a second tissue anchor, to which the tether is fixed.

13. The apparatus according to claim 1, wherein the tether is flexible, and wherein, when the tether is tensioned into a straight, untwisted configuration: the tether has a central longitudinal axis, and is shaped so as to define first and second cross sections perpendicular to the central longitudinal axis, at first and second different longitudinal locations, respectively, the first and the second cross sections have respective first and second greatest dimensions, which define respective first and second lines, and if the first and the second cross sections were to be projected onto one another while preserving rotation about the central longitudinal axis, (a) the first and the second lines would intersect at an angle of at least 30 degrees, and (b) the first and the second cross sections would not coincide.

14. The apparatus according to claim 13, wherein the angle is at least 60 degrees.

15. The apparatus according to claim 13, wherein the first and the second greatest dimensions are a first and second greatest major dimensions, wherein the first and the second cross sections have respective first and second greatest minor dimensions, which are measured perpendicular to the first and the second greatest major dimensions, respectively, and wherein the first and the second greatest minor dimensions equal no more than 50% of the first and the second greatest major dimensions, respectively.

16. The apparatus according to claim 13, wherein, when the tether is tensioned into the straight, untwisted configuration: the tether is shaped so as to define a third cross section perpendicular to the central longitudinal axis, at a third longitudinal location, wherein the second longitudinal location is longitudinally between the first and the third longitudinal locations along the central longitudinal axis, the third second cross section has a third greatest dimension, which defines a third line, and if the second and the third cross sections were to be projected onto one another while preserving rotation about the central longitudinal axis, (a) the second and the third lines would intersect at an angle of at least 30 degrees, and (b) the second and the third cross sections would not coincide.

17. The apparatus according to claim 13, wherein the first and the second cross sections have a same shape, which has different rotational orientations about the central longitudinal axis at the first and the second longitudinal locations.

18. The apparatus according to claim 13, wherein the first and the second longitudinal locations are within 10 mm of one another along the central longitudinal axis.

19. A method comprising: providing a torque-delivery tool of a tissue-anchor system, which torque-delivery tool includes (a) a torque-delivery cable, which includes a distal torque-delivery head, (b) a distal coupler that is fixed to a distal end of the distal torque-delivery head, and (c) a distal spring depressor; providing a tether of the tissue-anchor system; and providing a tissue anchor of the tissue-anchor system, which tissue anchor includes (a) a tissue coupler, and (b) an anchor head, which (i) is attached to a proximal portion of the tissue coupler, and (ii) includes: an axially-stationary shaft, which (a) has a distal portion that is axially fixed with respect to the proximal portion of the tissue coupler, and (b) has a proximal end that includes a proximal coupler, wherein the distal and the proximal couplers are shaped so as to define corresponding interlocking surfaces; a spring; and an outer tether-securing element, which (a) is shaped so as to define a lateral opening through which the tether is disposed, and (b) at least partially radially surrounds the axially-stationary shaft and the spring, advancing the tissue-anchor system into a body of a subject, while the tissue-anchor system is in an unlocked state, in which (a) the distal and the proximal couplers are interlockedly coupled with one other, and (b) the distal spring depressor restrains the spring in an axially-compressed state, in which state the spring does not inhibit sliding of the tether through the lateral opening; thereafter, using the torque-delivery cable, implanting the tissue anchor in tissue of the subject; thereafter, applying tension to the tether; and thereafter, transitioning the tissue-anchor system to a locked state, in which (a) the distal and the proximal couplers are not coupled with one another, (b) the distal spring depressor does not restrain the spring in the axially-compressed state, and (c) the spring is in an axially-expanded state, in which state the spring inhibits the sliding of the tether through the lateral opening by pressing the tether against the outer tether-securing element.

20. The method according to claim 19, wherein, when the tissue-anchor system is in the locked state, the spring inhibits the sliding of the tether through the lateral opening by pressing the tether against a perimeter of the lateral opening of the outer tether-securing element.

21. The method according to claim 19, wherein the tissue-anchor system further includes a locking wire, wherein the torque-delivery cable, including the distal torque-delivery head, the distal coupler, the proximal coupler, and the axially-stationary shaft are shaped so as define respective channels therethrough, which are radially aligned with each other and coaxial with the tissue anchor, wherein advancing the tissue-anchor system comprises advancing the tissue-anchor system in the unlocked state while a portion of the locking wire is disposed in the channels, thereby preventing decoupling of the distal and the proximal couplers from one another, and wherein transitioning the tissue-anchor system to the locked state comprises withdrawing the locking wire from the channels.

22. The method according to claim 21, wherein the locking wire has a sharp distal tip.

23. The method according to claim 19, wherein the anchor head further includes a hammer cap, which covers at least a portion of the spring, including a proximal end of the spring, and wherein, when the tissue-anchor system is in the locked state, the spring presses the tether against the outer tether-securing element by pressing the hammer cap against the outer tether-securing element.

24. The method according to claim 23, wherein the hammer cap is fixed to the spring.

25. The method according to claim 19, wherein the tether is flexible, and wherein, when the tether is tensioned into a straight, untwisted configuration (1) the tether has a central longitudinal axis, and is shaped so as to define first and second cross sections perpendicular to the central longitudinal axis, at first and second different longitudinal locations, respectively, (2) the first and the second cross sections have respective first and second greatest dimensions, which define respective first and second lines, and (3) if the first and the second cross sections were to be projected onto one another while preserving rotation about the central longitudinal axis, (a) the first and the second lines would intersect at an angle of at least 30 degrees, and (b) the first and the second cross sections would not coincide.

26. The method according to claim 25, wherein the first and the second longitudinal locations are within 10 mm of one another along the central longitudinal axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1A-F are schematic illustrations of a tissue-anchor system in an unlocked state, in accordance with an application of the present invention;

(2) FIGS. 2A-B are schematic illustrations of the tissue-anchor system of FIGS. 1A-F in a locked state, in accordance with an application of the present invention;

(3) FIG. 3A is a schematic illustration of a tissue anchor, in accordance with an application of the present invention;

(4) FIGS. 3B-C are schematic illustrations of another tissue anchor in unlocked and locked states, respectively, in accordance with an application of the present invention;

(5) FIGS. 3D-E are schematic illustrations of yet another tissue anchor in unlocked and locked states, respectively, in accordance with an application of the present invention;

(6) FIGS. 4A-E are schematic illustrations of friction-enhancing features of a tether of the tissue-anchor system of FIGS. 1A-F and 2A-B, in accordance with respective applications of the present invention;

(7) FIGS. 5A-D are schematic illustrations of a tricuspid valve repair procedure using the tissue-anchor system of FIGS. 1A-F and 2A-B in a right atrium, in accordance with an application of the present invention;

(8) FIGS. 6A-E are schematic illustrations of a tricuspid-mitral valve repair procedure, in accordance with an application of the present invention;

(9) FIG. 7 is a schematic illustration of a heart upon conclusion of the tricuspid-mitral valve repair procedure of FIGS. 6A-E, in accordance with an application of the present invention;

(10) FIG. 8 is a schematic illustration of a multiple tissue-anchor system, in accordance with an application of the present invention;

(11) FIG. 9 is a schematic illustration of the multiple tissue-anchor system of FIG. 8 applied to a tricuspid valve, in accordance with an application of the present invention;

(12) FIGS. 10A-B are schematic illustrations of the multiple tissue-anchor system of FIG. 8 applied to a right ventricle, in accordance with an application of the present invention;

(13) FIGS. 11A-D are schematic illustrations of a cutting tool, in accordance with an application of the present invention;

(14) FIGS. 12A-C are schematic illustrations of a tissue anchor system in an engaged state, in accordance with an application of the present invention;

(15) FIGS. 13A-B and 14A-B are schematic illustrations of the tissue anchor system of FIGS. 12A-C in a disengaged state, in accordance with an application of the present invention;

(16) FIG. 15 is a schematic illustration of another configuration of the tissue anchor system of FIGS. 12A-C, in accordance with an application of the present invention;

(17) FIGS. 16A-C are schematic illustrations of two exemplary deployments of a tissue anchor of the tissue anchor system of FIGS. 12A-14B using a torque-delivery tool of the tissue anchor system of FIGS. 12A-14B, in accordance with respective applications of the present invention;

(18) FIGS. 17A-19 are schematic illustrations of a flexible tether, in accordance with an application of the present invention;

(19) FIGS. 20A-C are schematic illustrations of cross sections of the flexible tether of FIGS. 17A-19, in accordance with an application of the present invention;

(20) FIGS. 21A-C are schematic illustrations of another configuration of the flexible tether of FIGS. 17A-19, in accordance with an application of the present invention;

(21) FIG. 22 is a schematic illustration of one use of the flexible tether of FIGS. 20A-C, in accordance with an application of the present invention;

(22) FIGS. 23A-B are schematic illustrations of one use of the flexible tether of FIGS. 21A-C, in accordance with an application of the present invention; and

(23) FIGS. 24A-C are schematic illustrations of one use of the tether described hereinabove with reference to FIG. 21A-C, in accordance with an application of the present invention.

DETAILED DESCRIPTION OF APPLICATIONS

(24) FIGS. 1A-F are schematic illustrations of a tissue-anchor system 10 in an unlocked state, in accordance with an application of the present invention. FIGS. 2A-B are schematic illustrations of tissue-anchor system 10 in a locked state, in accordance with an application of the present invention. Tissue-anchor system 10 comprises a torque-delivery tool 20, a tether 22, and a tissue anchor 24. Torque-delivery tool 20 is configured to implant tissue anchor 24 in cardiac tissue, and to thereafter lock tether 22 to tissue anchor 24, such that sliding of tether 22 with respect to tissue anchor 24 is inhibited. Typically, tether 22 is tensioned after tissue anchor 24 has been implanted in the cardiac tissue, and after the tether has been tensioned, tether 22 is locked to tissue anchor 24.

(25) Torque-delivery tool 20 comprises (a) a torque-delivery cable 28, which comprises a distal torque-delivery head 30, (b) a distal coupling element 32 that is fixed to a distal end 34 of distal torque-delivery head 30, and (c) a distal spring depressor 36.

(26) Tissue anchor 24 comprises (a) a tissue-coupling element 50, and (b) a proximal anchor head 52, which is attached to a proximal portion 54 of tissue-coupling element 50. For some applications, tissue-coupling element 50 comprises a helical tissue-coupling element, which punctures and screws into cardiac tissue. For some applications, tissue-coupling element 50 implements features of one or more of the tissue-coupling elements described in PCT Application PCT/IL2014/050027, filed Jan. 9, 2014, which published as PCT Publication WO 2014/108903 and is incorporated herein by reference.

(27) Anchor head 52 comprises an axially-stationary shaft 56 and a tether-locking mechanism 68. Axially-stationary shaft 56 (which can best be seen in FIGS. 1D-F) has (a) a distal portion 58 that is axially fixed with respect to proximal portion 54 of tissue-coupling element 50, and (b) a proximal end 60 that comprises a proximal coupling element 62. Distal and proximal coupling elements 32 and 62 are shaped so as to define corresponding interlocking surfaces, which facilitate coupling of distal torque-delivery head 30 to axially-stationary shaft 56.

(28) Tether-locking mechanism 68 comprises: a spring 70 (which can best be seen in FIG. 1D) (for clarity of illustration of other elements, spring 70 is not shown in FIGS. 1E-F; the spring is actually present); and an outer tether-securing element 80, which (a) is shaped so as to define a lateral opening 82 through which tether 22 is disposed, and (b) at least partially radially surrounds axially-stationary shaft 56 and spring 70 (and hammer cap 100, if provided, as described below). For some applications, as shown in the figures, outer tether-securing element 80 is shaped as a partial cylinder.

(29) For some applications, at least a portion of spring 70 radially surrounds axially-stationary shaft 56, such as shown in FIG. 1D. For some applications, at least a portion of spring 70 is helical, such as shown in FIGS. 1D, 2A-B, and 3A (e.g., the entire spring is helical, such as shown in FIGS. 1D and 2A-B), while for other applications, spring 70 is not helical, such as described hereinbelow with reference to FIGS. 3B-E.

(30) Tissue-anchor system 10 is configured to assume: an unlocked state, as shown in FIGS. 1A-F, in which (a) distal and proximal coupling elements 32 and 62 are interlockedly coupled with one other, and (b) distal spring depressor 36 restrains spring 70 in an axially-compressed state, in which state spring 70 does not inhibit sliding of tether 22 through lateral opening 82, and a locked state, as shown in FIGS. 2A-B, in which (a) distal and proximal coupling elements 32 and 62 are not coupled with one another, (b) distal spring depressor 36 does not restrain spring 70 in the axially-compressed state, and (c) spring 70 is in an axially-expanded state, in which state spring 70 inhibits the sliding of tether 22 through lateral opening 82 by pressing tether 22 against outer tether-securing element 80, such as against a perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80.

(31) When tissue-anchor system 10 is in the unlocked state, tether-locking mechanism 68 is also in an unlocked state, in which state spring 70 does not inhibit sliding of tether 22 through lateral opening 82. When tissue-anchor system 10 is in the locked state, tether-locking mechanism 68 is also in a locked state, in which state spring 70 inhibits the sliding of tether 22 through lateral opening 82 by pressing tether 22 against outer tether-securing element 80, such as against perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80.

(32) Tissue-anchor system 10 is advanced into the heart in the unlocked state. Tissue anchor 24 is implanted in cardiac tissue, using torque-delivery cable 28 while tissue-anchor system 10 is in the unlocked state. After tissue anchor 24 is implanted, tension is applied to tether 22. Thereafter, torque-delivery cable 28 (including distal torque-delivery head 30) is decoupled from axially-stationary shaft 56 of tissue anchor 24, thereby allowing spring 70 to expand and press tether 22 against outer tether-securing element 80. This pressing locks tether 22 with respect to tissue anchor 24, and maintains the distance and tension between tissue anchor 24 and one or more other implanted tissue anchors, such as described hereinbelow with reference to FIGS. 5C and 6E. Alternatively, tissue-anchor system 10 is used to implant tissue anchor 24 in non-cardiac tissue of a subject, in which case tissue-anchor system 10 is advanced into another location in the subject's body.

(33) Torque-delivery cable 28 (including distal torque-delivery head 30) thus serves two functions: implanting tissue anchor 24 in cardiac tissue, by applying a rotational force to tissue anchor 24; and maintaining tissue-anchor system 10 in the unlocked state, in which state tether 22 can slide with respect to tissue anchor 24, allowing tension to be applied to the tether (and adjusted as necessary).

(34) Similarly, decoupling of torque-delivery cable 28 (including distal torque-delivery head 30) from axially-stationary shaft 56 of anchor head 52 of tissue anchor 24 simultaneously (1) releases tissue anchor 24 and (2) transitions tissue-anchor system to the locked state.

(35) For some applications, as can be seen in FIGS. 1A-C and FIGS. 2A-B, anchor head 52 further comprises a hammer cap 100, which is fixed to spring 70, and covers at least a portion 102 of spring 70, including a proximal end 104 of spring 70. (For clarity of illustration of other elements, hammer cap 100 is not shown in FIGS. 1D-F; the hammer cap is optionally present.) When tissue-anchor system 10 is in the locked state, spring 70 presses tether 22 against outer tether-securing element 80 by pressing hammer cap 100 against outer tether-securing element 80, such as perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80. Hammer cap 100 may prevent entanglement of tether 22 with spring 70. In addition, providing hammer cap 100 may obviate the need to weld a distal end of spring 70 to anchor head 52, because the hammer cap surrounds at least a portion of the spring and thereby couples the spring to the anchor head. For some applications, tether 22 prevents hammer cap 100 from proximally exiting outer tether-securing element 80. Alternatively or additionally, for some applications, one or more small pins 108 (shown in FIG. 2A) are provided that extend radially inward from an inner surface of outer tether-securing element 80; the pins prevent the hammer cap from proximally exiting the outer tether-securing element.

(36) For some applications, tissue-anchor system 10 further comprises a locking wire 110. Torque-delivery cable 28 (including distal torque-delivery head 30), distal coupling element 32, proximal coupling element 62, and axially-stationary shaft 56 are shaped so as define respective channels 72, 74, 76, and 78 therethrough, which are radially aligned with each other and coaxial with tissue anchor 24. When tissue-anchor system 10 is in the unlocked state, a portion of locking wire 110 is disposed in the channels, thereby preventing decoupling of distal and proximal coupling elements 32 and 62 from one another. Proximal withdrawal and removal of the portion of locking wire 110 from the channels allows the decoupling of distal and proximal coupling elements 32 and 62 from one another.

(37) For some applications, locking wire 110 is shaped so as to define a sharp distal tip 727. For these applications, tissue-coupling element 50 typically is helical, and locking wire 110 is initially removably positioned within a channel defined by the helix. As tissue-coupling element 50 is screwed into tissue, locking wire 110 penetrates and advances into the tissue along with the anchor to a certain depth in the tissue. For some applications, when the locking wire penetrates to the certain depth, the locking wire is withdrawn slightly. Typically, after tissue-coupling element 50 has been fully implanted, locking wire 110 is withdrawn entirely from the tissue, and removed from the subject's body. Optionally, sharp distal tip 727 of locking wire 110 is inserted into the tissue slightly, even before insertion of tissue-coupling element 50, in order to inhibit sliding of the tissue-coupling element on the surface of the tissue before commencement of insertion of the tissue-coupling element into the tissue.

(38) For some applications, outer tether-securing element 80 is rotatable with respect to tissue-coupling element 50 and axially-stationary shaft 56, in order to provide rotational freedom of movement to tether 22 after implantation of tissue anchor 24, particularly during tensioning of tether 22. This rotational freedom of movement avoids twisting of the tether around the anchor head, and facilitates ideal orientation of the tether with another tissue anchor.

(39) For some applications, outer tether-securing element 80 has an outer diameter of at least 1 mm, no more than 6 mm, and/or between 1 and 6 mm. For some applications, tissue anchor 24 has an outer diameter of at least 2 mm, no more than 8 mm, and/or between 2 and 8 mm.

(40) Reference is now made to FIG. 3A, which is a schematic illustration of a tissue anchor 124, in accordance with an application of the present invention. Except as described below, tissue anchor 124 is generally similar to tissue anchor 24, and may be used in tissue-anchor system 10 instead of tissue anchor 24 in any of the applications described herein. Tissue anchor 124 comprises a spring 126, which is shaped to provide a proximal surface 128 that presses tether 22 against outer tether-securing element 80, such as against perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80, when tissue-anchor system 10 is in the locked state, such as shown in FIG. 3A. Typically, at least a portion of spring 126 that does not provide proximal surface 128 is helical. For some applications, proximal surface 128 is circular. Proximal surface 128 may serve as a hammer head that presses tether 22 against outer tether-securing element 80 when tissue-anchor system 10 is in the locked state.

(41) Reference is now made to FIGS. 3B-C, which are schematic illustrations of a tissue anchor 134 in unlocked and locked states, respectively, in accordance with an application of the present invention. Except as described below, tissue anchor 134 is generally similar to tissue anchor 24, and may be used in tissue-anchor system 10 instead of tissue anchor 24 in any of the applications described herein. Tissue anchor 134 comprises (a) a spring 136, which comprises an elastic band 138, and (b) a hammer element 140. Hammer element 140 is shaped to provide a proximal surface 142 that presses tether 22 against outer tether-securing element 80, such as against perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80, when tissue-anchor system 10 is in the locked state, as shown in FIG. 3C. Elastic band 138 of spring 136 and hammer element 140 are arranged such that elastic band 138 applies a proximal force on a distal end of hammer element 140. For some applications, proximal surface 142 is circular. Proximal surface 142 may serve as a hammer head that presses tether 22 against outer tether-securing element 80 when tissue-anchor system 10 is in the locked state.

(42) Reference is now made to FIGS. 3D-E, which are schematic illustrations of a tissue anchor 144 in unlocked and locked states, respectively, in accordance with an application of the present invention. Except as described below, tissue anchor 144 is generally similar to tissue anchor 24, and may be used in tissue-anchor system 10 instead of tissue anchor 24 in any of the applications described herein. Tissue anchor 144 comprises (a) a spring 146, which comprises an expandable material 148, and (b) a hammer element 150. For example, expandable material 148 may comprise an expandable elastomeric material, a foam (e.g., foamed silicone), or a sponge, as is known in the materials arts. Hammer element 150 is shaped to provide a proximal surface 152 that presses tether 22 against outer tether-securing element 80, such as against perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80, when tissue-anchor system 10 is in the locked state, as shown in FIG. 3E. Expandable material 148 of spring 146 and hammer element 150 are arranged such that expandable material 148 applies a proximal force on a distal end of hammer element 150. For some applications, proximal surface 142 is circular. Proximal surface 152 may serve as a hammer head that presses tether 22 against outer tether-securing element 80 when tissue-anchor system 10 is in the locked state.

(43) Reference is now made to FIGS. 4A-E, which are schematic illustrations of friction-enhancing features of tether 22, in accordance with respective applications of the present invention. These features may be used with tether 22 in any of the configurations described herein. The friction-enhancing features enhance friction between the tether and outer tether-securing element 80, when tissue-anchor system 10 is in the locked state (and tether-locking mechanism 68 is in the locked state). For some applications, these friction-enhancing features enable one-way ratcheting of tether 22 through lateral opening 82 of outer tether-securing element 80.

(44) In these configurations, tether 22 typically defines a plurality of securement protrusions 160 spaced at intervals (I) along tether 22, which protrusions serve as the friction-enhancing features. For some applications, an average interval of securement protrusions 160 along tether 22 is at least 1 mm, no more than 18 mm, and/or between 1 and 18 mm, e.g., at least 3 mm, no more than 18 mm, and/or between 3 and 18 mm. For some applications, securement protrusions 160 have an outer diameter of at least 0.3 mm (e.g., at least 0.4 mm, such as at least 1 mm), no more than 6 mm (such as no more than 1.25 mm), and/or between 0.3 mm and 6 mm, such as between 0.4 mm and 1.25 mm. The outer diameter is typically less than the greatest dimension of lateral opening 82. For some applications, tether 22 comprises between 2 and 20 securement protrusions 160.

(45) For some applications, protrusions 160 comprise respective cylinders 168 on tether 22, such as shown in FIG. 4A. For some applications, protrusions 160 are defined by respective knots 170 in tether 22, such as shown in FIG. 4B. For some applications, protrusions 160 comprise respective cones 172 on tether 22, such as shown in FIG. 4C; this configuration may restrict retrograde movement of the tether through outer tether-securing element 80, while allowing antegrade movement. For some applications, protrusions 160 comprise respective scales 174 on tether 22, such as shown in FIG. 4D. For some applications, protrusions 160 comprise respective beads 176 on tether 22, such as shown in FIG. 4E. For some of the applications described with reference to FIGS. 4A, 4C, 4D, and 4E, the elements the protrusions comprise are crimped to an outer surface of the tether. For some of the applications described with reference to FIGS. 4A, 4C, 4D, and 4E, protrusions 160 comprise a radiopaque material, which enhances fluoroscopy feedback to the user, particularly as the protrusions 160 are advanced through lateral opening 82 during application of tension to tether 22.

(46) Reference is now made to FIGS. 5A-D, which are schematic illustrations of a tricuspid valve repair procedure using tissue-anchor system 10 in a right atrium 200, in accordance with an application of the present invention. The procedure is performed using a valve-tensioning implant system 202. Valve-tensioning implant system 202 comprises tissue-anchor system 10, including torque-delivery tool 20, tether 22, and tissue anchor 24, as described hereinabove with reference to FIGS. 1A-4E. In this procedure, tissue anchor 24 serves as a second tissue anchor 24. Valve-tensioning implant system 202 further comprises a first tissue anchor 204, which typically comprises a helical tissue-coupling element, which punctures and screws into cardiac muscle tissue. For some applications, first tissue anchor 204 implements techniques of one or more of the tissue anchors described in International Application PCT/IL2014/050027, filed Jan. 9, 2014, which published as PCT Publication WO 2014/108903 and is incorporated herein by reference. Alternatively, first tissue anchor 204 comprises a clip, jaws, or a clamp which grips and squeezes a portion of cardiac muscle tissue and does not puncture the cardiac muscle tissue. For some applications, a head 208 of first tissue anchor 204 comprises an interface 210 that is configured to rotate with respect to a helical tissue-coupling element 212 of tissue anchor 204, in order to provide rotational freedom of movement to tether 22 after implantation of the tissue anchor. Tether 22 is typically fixed to interface 210, such that tether 22 cannot slide with respect to interface 210.

(47) Valve-tensioning implant system 202 further comprises a catheter 206 and a tool for delivering first tissue anchor 204. For some applications, the tool implements techniques described with reference to FIGS. 21 and 22A-D of PCT Publication WO 2013/011502, which is incorporated herein by reference, mutatis mutandis. For some applications, catheter 206 comprises a steering mechanism, as is known in the catheter art.

(48) Valve-tensioning implant system 202 is typically introduced transcatheterly and endovascularly (typically percutaneously), via catheter 206, with the aid of a guidewire, through vasculature of the subject, such as (a) via the femoral vein, through inferior vena cava 274, and into right atrium 200, (b) via the basilic vein, through the subclavian vein through superior vena cava 276, and into right atrium 200, or (c) via the external jugular vein, through the subclavian vein through superior vena cava 276, and into right atrium 200. The procedure is typically performed with the aid of imaging, such as fluoroscopy, transesophageal, transthoratic echocardiography, ICE, and/or echocardiography. The procedure may be performed using techniques described in US Patent Application Publication 2012/0035712, which is assigned to the assignee of the present application and is incorporated herein by reference, with reference to FIGS. 1A-D thereof, mutatis mutandis.

(49) As shown in FIG. 5A, first tissue anchor 204 is implanted at a first atrial site 292. Typically, first atrial site 292 is selected from the group of sites consisting of: an annulus 283 of a tricuspid valve 207, and a wall of right atrium 200 above annulus 283 of tricuspid valve 207. For some applications, first atrial site 292 is located within 1 cm of a site on annulus 283 that circumferentially corresponds to a location that is (a) at or counterclockwise to a point on the annulus that is 1 cm septal (i.e., clockwise) to a posteroseptal commissure 217, and (b) at or clockwise to a point on the annulus that is 1 cm anterior (i.e., counterclockwise) to an anteroposterior commissure (APC) 324, as viewed from the right atrium. For some applications, the location is (a) at posteroseptal commissure 217, (b) at anteroposterior commissure 324, or (c) along posterior leaflet 284; in other words, the location is (a) at or counterclockwise to posteroseptal commissure 217, and (b) at or clockwise to anteroposterior commissure 324, as viewed from the right atrium. For example, the location may be at: a circumferential middle 219 of posterior leaflet 284 of a tricuspid valve 207, as shown in FIG. 5A, posteroseptal commissure 217 (configuration not shown), or anteroposterior commissure 324 (configuration not shown).

(50) The direction of the 1 cm from the described anatomical sites may be either circumferentially around the annulus, up the wall of right atrium 200 above annulus 283, or a combination of circumferentially around the annulus and up the wall of the atrium.

(51) Alternatively, for some applications, first tissue anchor 204 is implanted at a ventricular site below the level of the valve, typically up to 3 cm below the level of the valve. In this case, tether 22 may pass through tricuspid valve 207, such as through a commissure of the valve.

(52) After first tissue anchor 204 has been implanted at first atrial site 292, the implantation tool is removed from the subject's body, typically leaving catheter 206 in situ.

(53) Outside the subject's body, the physician threads a free end 213 of tether 22 through lateral opening 82 of outer tether-securing element 80 of second tissue anchor 24, and then through a lumen of a delivery tube 214 of tissue-anchor system 10 (shown in FIG. 5B). Tether 22 thus connects first and second tissue anchors 204 and 24. Valve-tensioning implant system 202 enables this remote coupling of the anchors to one another via catheter 206.

(54) As shown in FIG. 5B, second tissue anchor 24 is implanted at a second atrial site 293 using torque-delivery cable 28 of torque-delivery tool 20. Tissue-anchor system 10, including second tissue anchor 24 and torque-delivery cable 28, is introduced over tether 22 and through delivery tube 214, which itself is advanced through catheter 206. Tissue-anchor system 10 is introduced in the unlocked state (tether-locking mechanism 68 is also in the unlocked state), as described hereinabove with reference to FIGS. 1A-F. Second atrial site 293 is selected from the group of sites consisting of: annulus 283, and a wall of right atrium 200 above annulus 283. For some applications, second atrial site 293 is located within 1 cm of a site on annulus 283 that circumferentially corresponds to a location that is (a) at or clockwise to a point on the annulus 1 cm septal (i.e., counterclockwise) to a septoanterior commissure (SAC) 290, and (b) at or counterclockwise to a point on the annulus 1 cm posterior (i.e., clockwise) to anteroposterior commissure (APC) 324, as viewed from the right atrium. For some applications, the location is (a) at septoanterior commissure (SAC) 290, (b) at anteroposterior commissure (APC) 324, or (c) along anterior leaflet 286; in other words, the location is (a) at or clockwise to septoanterior commissure (SAC) 290, and (b) at or counterclockwise to anteroposterior commissure (APC) 324, as viewed from the right atrium. For example, the location may be at: a circumferential middle 221 of anterior leaflet 286 shown in FIG. 5B, septoanterior commissure 290 (configuration not shown), or anteroposterior commissure 324 (configuration not shown).

(55) The direction of the 1 cm from the described anatomical sites may be either circumferentially around the annulus, up the wall of right atrium 200 above annulus 283, or a combination of circumferentially around the annulus and up the wall of the atrium.

(56) The locations of first and second atrial sites 292 and 293 may be inverted, such as when an approach from superior vena cava 276 is used.

(57) Second tissue anchor 24 is implanted at second atrial site 293 by rotating torque-delivery cable 28 (including distal torque-delivery head 30).

(58) The size of the tricuspid valve orifice is reduced by tensioning tether 22, so as to reduce regurgitation. Such tensioning may be performed by proximally pulling on free end 213 tether 22, such that a portion of tether 22 is pulled through lateral opening 82 of outer tether-securing element 80 of second tissue anchor 24. Tissue-anchor system 10 enables this tension to be applied remotely, i.e., via catheter 206.

(59) As shown in FIG. 5C, once the tension has been applied, torque-delivery cable 28 (including distal torque-delivery head 30) is decoupled from axially-stationary shaft 56 of second tissue anchor 24, such as by removing locking wire 110. As a result, spring 70 expands and presses tether 22 against outer tether-securing element 80. This pressing transitions tissue-anchor system 10 to the locked state (and tether-locking mechanism 68 to the locked state), by locking tether 22 with respect to tissue anchor 24. Such locking maintains the distance and tension between second tissue anchor 24 and first tissue anchor 204.

(60) As shown in FIG. 5D, after tether 22 has been tensioned, an excess portion 294 of tether 22 remains free in right atrium 200. It is generally undesirable to leave this excess portion free to move around in the atrium. For some applications, excess portion 294 of tether 22 is cut and removed from the atrium, using a cutting tool 498, such as thoracoscopic scissors, as known in the art. Alternatively, the excess portion is cut using cutting tool 600, described hereinbelow with reference to FIGS. 11A-D. Further alternatively, for some applications, excess portion 294 is secured in a desired disposition in the vasculature of right atrium 200, such as in inferior vena cava 274, superior vena cava 276, or a coronary sinus.

(61) Valve-tensioning implant system 202 allows first and second anchors 204 and 24 to be delivered separately and connected afterwards in situ. This simplifies the procedure for the operator, and allows an approach from two or more different blood vessels such as transfemoral, transjugular, transradial or transapical approaches, which may provide simpler access to the anchoring point.

(62) Although valve-tensioning implant system 202 and tissue-anchor system 10 have been described hereinabove as being used to remodel the tricuspid valve, they may also be used to remodel the mitral valve, mutatis mutandis, such as using multiple tissue-anchor system 400, described hereinbelow with reference to FIG. 8 (for example, with a plurality of tissue anchors implanted along the posterior annulus).

(63) Reference is now made to FIGS. 6A-E, which are schematic illustrations of a tricuspid-mitral valve repair procedure, in accordance with an application of the present invention. In this procedure, both the tricuspid and the mitral valves are repaired by simultaneously applying tension across both valves using a tether that passes through the atrial septum.

(64) For some applications, the procedure is performed using valve-tensioning implant system 202, described hereinabove with reference to FIGS. 5A-D. Alternatively, other tissue-anchoring and/or tether tensioning techniques may be used. For applications in which valve-tensioning implant system 202 is used, tissue anchor 24 serves as a second tissue anchor 24, and valve-tensioning implant system 202 further comprises first tissue anchor 204, as described hereinabove with reference to FIGS. 5A-D. Alternatively, tissue anchor 724, described hereinbelow with reference to FIGS. 12A-14B, or another tissue anchor, may be used as the first tissue anchor. Valve-tensioning implant system 202 is typically introduced transcatheterly and endovascularly (typically percutaneously), via catheter 206, with the aid of a guidewire, through vasculature of the subject, such as (a) via the femoral vein, through the inferior vena cava, and into right atrium 200, (b) via the basilic vein, through the subclavian vein through the superior vena cava, and into right atrium 200, or (c) via the external jugular vein, through the subclavian vein through the superior vena cava, and into right atrium 200. The procedure is typically performed with the aid of imaging, such as fluoroscopy, transesophageal, transthoratic echocardiography, ICE, and/or echocardiography. The procedure may be performed using techniques described in above-mentioned US Patent Application Publication 2012/0035712, with reference to FIGS. 1A-D thereof, mutatis mutandis.

(65) After catheter 206 has been introduced into right atrium 200, an opening 300 is made through an atrial septum 302 at a septal site 304, which is typically at least 5 mm from the fossa ovalis, such as at least 10 mm from the fossa ovalis (shown in FIG. 7).

(66) As shown in FIG. 6A, first tissue anchor 204 is endovascularly advanced to a left-atrial site 306 of a left atrium 308, the site selected from the group of sites consisting of: a mitral annular site 307 on an annulus of a mitral valve 310, and a wall of left atrium 308 above the mitral annular site. Typically, in order to advance first tissue anchor 204 into left atrium 308, catheter 206 is advanced through opening 300. An inner tube 305 may be advanced through catheter 206, and a delivery tool may be advanced through inner tube 305.

(67) As shown in FIG. 6B, first tissue anchor 204 is implanted at left-atrial site 306. For some applications, mitral annular site 307 circumferentially corresponds to a posterior leaflet 312 of the mitral valve. For example, mitral annular site 307 may circumferentially correspond to an annular site of the mitral valve within 1 cm of a lateral scallop (P1) 313 and/or within 1 cm of a middle scallop (P2) 314 of posterior leaflet 312. Alternatively, first tissue anchor 204 is implanted at any site on the lateral wall of the left side of the heart, atrium, annulus, papillary or any other structure of the left side of the heart or valve that can be used as an anchoring site to move the left lateral wall of the heart septally.

(68) Inner tube 305, if used, is removed from catheter 206, and catheter 206 is withdrawn to right atrium 200. Outside of the subject's body, the physician threads free end 213 of tether 22 through lateral opening 82 of outer tether-securing element 80 of second tissue anchor 24, and then through a lumen of a delivery tube 214 of tissue-anchor system 10 (shown in FIG. 5B), as described hereinabove. Tether 22 thus connects first and second tissue anchors 204 and 24. Valve-tensioning implant system 202 enables this remote coupling of the anchors to one another via catheter 206.

(69) As shown in FIG. 6C, tissue-anchor system 10, including second tissue anchor 24 and torque-delivery cable 28, is endovascularly introduced over tether 22 and through delivery tube 214, which itself is advanced through catheter 206. Tissue-anchor system 10 is introduced in the unlocked state (tether-locking mechanism 68 is also in the unlocked state), as described hereinabove with reference to FIGS. 1A-F. The distal end of delivery tube 214, and second tissue anchor 24, are steered to a right-atrial site 320 of right atrium 200 selected from the group of sites consisting of: a tricuspid annular site 322 on an annulus of tricuspid valve 207, and a wall of right atrium 200 above tricuspid annular site 322. For some applications, tricuspid annular site 322 circumferentially corresponds to an annular site of the tricuspid valve that is (a) at or clockwise to a point on the tricuspid annulus 2 cm anterior (i.e., counterclockwise) to anteroposterior commissure (APC) 324 of tricuspid valve 207, and (b) at or 1 cm counterclockwise to posteroseptal commissure 217 of tricuspid valve 207, as viewed from the right atrium. Alternatively, the annular site is (a) at or clockwise to septoanterior commissure (SAC) 290, and (b) at or counterclockwise to posteroseptal commissure 217. Alternatively, second tissue anchor 24 is implanted at any site on the lateral wall of the right side of the heart, atrium, annulus, papillary or any other structure of the right side of the heart or valve that can be used as an anchoring site to move the right lateral wall of the heart septally.

(70) As shown in FIG. 6D, second tissue anchor 24 is implanted at tricuspid annular site 322 by rotating torque-delivery cable 28 (including distal torque-delivery head 30).

(71) The size of the tricuspid valve orifice and the size of the mitral valve orifice are reduced by approximating left-atrial site 306 and right-atrial site 320 by tensioning tether 22, so as to reduce regurgitation. Such tensioning may be performed by proximally pulling on free end 213 of tether 22, such that a portion of tether 22 is pulled through lateral opening 82 of outer tether-securing element 80 of second tissue anchor 24, as indicated by the arrow in FIG. 6D. Tissue-anchor system 10 enables this tension to be applied remotely, i.e., via catheter 206.

(72) As shown in FIG. 6E, once the tension has been applied, torque-delivery cable 28 (including distal torque-delivery head 30) is decoupled from axially-stationary shaft 56 of second tissue anchor 24, such as by removing locking wire 110. As a result, spring 70 expands and press tether 22 against outer tether-securing element 80. This pressing transitions tissue-anchor system 10 to the locked state (and tether-locking mechanism 68 to the locked state), by locking tether 22 with respect to second tissue anchor 24. Such locking maintains the distance and tension between second tissue anchor 24 and first tissue anchor 204.

(73) As described hereinabove with reference to FIG. 5D, after tether 22 has been tensioned, an excess portion 294 of tether 22 remains free in right atrium 200. It is generally undesirable to leave this excess portion free to move around in the atrium. For some applications, excess portion 294 of tether 22 is cut and removed from the atrium, using a cutting tool 498, such as thoracoscopic scissors, as known in the art. Alternatively, the excess portion is cut using cutting tool 600, described hereinbelow with reference to FIGS. 11A-D. Further alternatively, for some applications, excess portion is secured in a desired disposition in the vasculature of right atrium 200, such as in inferior vena cava 274, superior vena cava 276, or a coronary sinus.

(74) For some applications, as described above with reference to FIGS. 6A-E, second tissue anchor 24 is endovascularly advanced to right-atrial site 320 after first tissue anchor 204 has been implanted. Alternatively, for some applications, first tissue anchor 204 is endovascularly advanced to left-atrial site 306 after second tissue anchor 24 has been implanted. For example, a multiple-anchor delivery tool may be used with tether 22 pre-threaded through second tissue anchor 24.

(75) Reference is made to FIG. 7, which is a schematic illustration of a heart upon conclusion of the tricuspid-mitral valve repair procedure of FIGS. 6A-E (after implantation of tether 22 across both atria), in accordance with an application of the present invention. As can be seen, tether 22 passes through opening 300 through atrial septum 302 at septal site 304. Typically, septal site 304 is typically at least 5 mm from a fossa ovalis 330, such as at least 10 mm from fossa ovalis 330. Typically, septal site 304 is anterior to, and/or apical to, and/or toward the aorta from, fossa ovalis 330 as shown in FIG. 7, such as near or at the septum secundum and/or septum primum. As used in the present application, including in the claims, apical to means in a direction towards the apex of the heart.

(76) Typically, septal site 304 is at least 3 mm, no more than 20 mm, and/or between 3 and 20 mm (e.g., 10 mm) superior and anterior to a coronary sinus orifice, and/or at least 3 mm, no more than 15 mm, and/or between 3 and 15 mm (e.g., 5 mm) posterior to an aorta.

(77) Reference is made to FIGS. 6E and 7. The location of opening 300 is selected such that, after the tissue anchors are implanted and tether 22 has been tensioned, an angle of tether 22 at opening 300 of atrial septum 302 is ideally as close as possible to 180 degrees. In practice, the angle should be at least 120 degrees to avoid excessive force on the atrial septum, such as at least 135 degrees, or at least 150 degrees, and/or less than 180 degrees (in other words, the tether is not straight as it passes through opening 300), such as less than 170 degrees, e.g., no more than 150 degrees, such as between 140 and 150 degrees. Thus, the location of opening 300 should not be too superior and posterior on atrial septum 302, for example, should not be at fossa ovalis 330. A vertex 350 of the angle of tether 22 at opening 300 typically points at least partially in a posterior direction (as can be seen in FIG. 6E), at least partially in a superior direction, and/or in at least partially an away-from-apical direction (as can be seen in FIG. 7).

(78) For some applications, if tensioned tether 22 were to be projected onto a transverse plane 352 of the heart (as shown schematically in FIG. 7), the angle as projected (labeled (alpha) in FIGS. 6E and 7), would be at least 120 degrees, such as at least 135 degrees, or at least 140 degrees. Ideally, the angle as projected is as close as possible to 180 degrees, but in practice the angle as projected is typically less than 180 degrees (i.e., tether 22 is not straight), such as no more than 170 degrees, generally between 140 and 150 degrees.

(79) For some applications, if tensioned tether 22 were to be projected onto a coronal plane 354 of the heart (as shown schematically in FIG. 7), the angle as projected (labeled (beta) in FIG. 7), would be at least 120 degrees, such as at least 135 degrees, e.g., at least 140 degrees. Ideally, the angle as projected is as close as possible to 180 degrees, but in practice the angle as projected is typically less 180 degrees (i.e., tether 22 is not straight), such as no more than 170 degrees, generally between 150 and 170 degrees.

(80) For some applications, as shown in FIG. 7, (a) a portion 342 of tensioned tether 22 in left atrium 308 between opening 300 of atrial septum 302 (apex 340) and first tissue anchor 204 and (b) a plane 344 defined by the annulus of mitral valve 310, form an angle (gamma) of less than 30 degrees. Similarly, for some applications, as shown in FIG. 7, (a) a portion 346 of tensioned tether 22 in right atrium 200 between opening 300 of atrial septum 302 (apex 340) and second tissue anchor 24 and (b) a plane 348 defined by the annulus of tricuspid valve 207, form an angle (delta) of less than 30 degrees.

(81) For some applications, the procedure described with reference to FIGS. 6A-E further comprises placing, in opening 300 of atrial septum 302, an annular reinforcement element 360 that is shaped so as to define an opening therethrough. Reinforcement element 360 is typically delivered and placed after implanting first tissue anchor 204, and before implanting second tissue anchor 24. For example, reinforcement element 360 may be delivered using a balloon-expandable device, or reinforcement element 360 may be self-expanding. Tether 22 passes through the opening of reinforcement element 360. Reinforcement element 360 is typically annular.

(82) Reinforcement element 360 distributes the force of tether 22 against opening 300 of atrial septum 302, which may prevent damage to the atrial septum, such as caused by cutting by the tether. For some applications, reinforcement element 360 is stiffer in one direction, and is placed in opening 300 of atrial septum 302 with the stiffer direction facing away from vertex 350, i.e., in the direction in which tether 22 applies the greatest force to opening 300 of atrial septum 302. Reinforcement element 360 may optionally also be configured to close opening 300 of atrial septum 302, and/or to reduce a size of opening 300 upon withdrawal of catheter 206 from the opening. For example, a radially inner surface of reinforcement element 360 may comprise a material configured to promote tissue growth.

(83) For some applications, annular reinforcement element 360 comprises a locking mechanism, which is configured to inhibit sliding of tether 22 through annular reinforcement element 360 when in a locked state. The locking mechanism is transitioned from an unlocked state to the locked state after tether 22 has been tensioned, as described above. This locking has the effect of fixing the respective distances between opening 300 of atrial septum 302 and the first and the second tissue anchors, and preventing dilation of the annulus of one of the atrioventricular valves and the corresponding reduction in size of the other atrioventricular valve. Typically, at least 75% of the load in tether 22 is borne by the first and the second tissue anchors, and no more than 25% of the load is borne by locked annular reinforcement element 360, thereby reducing the likelihood that annular reinforcement element 360 might tear or otherwise damage atrial septum 302.

(84) Although this tricuspid-mitral valve repair procedure has been described with reference to FIGS. 6A-B as being performed using valve-tensioning implant system 202, alternatively other tissue-anchoring and/or tether tensioning techniques may be used. For example, tissue anchors and/or tensioning techniques may be used that are described in one or more of the patent applications listed and incorporated by reference hereinbelow.

(85) Reference is now made to FIG. 8, which is a schematic illustration of a multiple tissue-anchor system 400, in accordance with an application of the present invention. Multiple tissue-anchor system 400 comprises three or more tissue anchors, which are coupled together by tether 22 and cinched together in situ. For example, such as shown in FIG. 8, multiple tissue-anchor system 400 may comprise first, second, and third tissue anchors 420, 422, and 424, arranged such that second tissue anchor 422 is positioned along tether 22 between first and third tissue anchors 420 and 424.

(86) For some applications, an end portion 430 of tether 22 is fixed to a head 432 of first tissue anchor 420, and first tissue anchor 420 does not comprise tether-locking mechanism 68, described hereinabove with reference to FIGS. 1A-F, 2A-B, and 3A-E. First tissue anchor 420 may, for example, implement any of the features of (a) tissue anchor 204, described hereinabove with reference to FIG. 5A-D (configuration not shown in FIG. 8), or (b) tissue anchor 724, described hereinbelow with reference to FIGS. 12A-14B (configuration shown in FIG. 8). Second tissue anchor 422 comprises a tissue anchor 24 (including tether-locking mechanism 68), described hereinabove with reference to FIGS. 1A-F, 2A-B, and 3A-E, and/or third tissue anchor 424 comprises a tissue anchor 24 (including tether-locking mechanism 68), described hereinabove with reference to FIGS. 1A-F, 2A-B, and 3A-E.

(87) Typically, each of the tissue anchors is delivered using a separate, respective delivery tool. The tissue anchor(s) that comprise tether-locking mechanism 68 may be delivered using torque-delivery tool 20, described hereinabove with reference to FIGS. 1A-F, 2A-B, and 5B-C, and the tissue anchor(s) that do not comprise tether-locking mechanism 68 may be delivered using a tool 440, which implements the features of the tool described hereinabove with reference to FIG. 5A.

(88) Reference is now made to FIG. 9, which is a schematic illustration of multiple tissue-anchor system 400 applied to tricuspid valve 207, in accordance with an application of the present invention. In this exemplary deployment, first tissue anchor 420 is first implanted at a first atrial site 450, such as anteroposterior commissure (APC) 324, or any of the other right-atrial sites described hereinabove.

(89) Thereafter, second tissue anchor 422 is implanted at a second atrial site 452, such as posteroseptal commissure 217 or any of the other right-atrial sites described hereinabove. Tether 22 is tensioned between first and second tissue anchors 420 and 422, thereby pulling APC 324 and posteroseptal commissure 217 toward one another, resulting in at least partial bicuspidization. Tether-locking mechanism 68 of second tissue anchor 422 is locked, as described hereinabove. Optionally, tether 22 comprises another set of friction-enhancing features along the portion of the tether than passes through the head of second tissue anchor 422 (not shown in FIG. 9, but shown in FIG. 8).

(90) Thereafter, third tissue anchor 424 is implanted at a third atrial site 454, such as septoanterior commissure (SAC) 290, or any of the other right-atrial sites described hereinabove. Tether 22 is tensioned between second and third tissue anchors 422 and 424, thereby pulling SAC 290 and posteroseptal commissure 217 (and APC 324 to some extent) toward one another. Tether-locking mechanism 68 of third tissue anchor 424 is locked, as described hereinabove. Excess tether 22 is cut or secured, such as described above.

(91) This tensioning between APC 324 and posteroseptal commissure 217, and between SAC 290 and posteroseptal commissure 217, results in a substantial reduction in tricuspid valve circumference and diameter.

(92) Alternatively, second tissue anchor 422 does not comprise tether-locking mechanism 68, and tension is applied between APC 324 and posteroseptal commissure 217, and between SAC 290 and posteroseptal commissure 217, after third tissue anchor 424 has been implanted, and then tether-locking mechanism 68 of third tissue anchor 424 is locked.

(93) It is noted that the physician may decide during the procedure not to implant third tissue anchor 424, such as if a sufficient reduction in regurgitation is achieved using only the first two anchors. Not implanting third tissue anchor 424 is possible because the tissue anchors are threaded over tether 22 one at a time during the procedure.

(94) In some applications of the present invention, valve-tensioning implant system 202, described hereinabove with reference to FIGS. 5A-D, 6A-E, and 7, is used to remodel a pathologically dilated ventricular chamber, or to reduce future ventricular dilation, by applying tension between first and second tissue anchors 204 and 24 implanted in a left or right ventricle, such as in a papillary muscle or wall of the ventricle. This technique may improve ventricular pumping efficiency and/or reduce tricuspid or mitral regurgitation. When used in the right ventricle, this technique might be considered as creating a second artificial moderator band.

(95) Reference is made to FIGS. 10A-B, which are schematic illustrations of multiple tissue-anchor system 400 applied to a right ventricle 500, in accordance with an application of the present invention. In this application, multiple tissue-anchor system 400 is used to treat dilated right ventricle 500, as shown in FIG. 10A. First tissue anchor 420 is first endovascularly (e.g., percutaneously) advanced to and implanted, from within right ventricle 500, at a first ventricular wall site 510, typically on a posterior or an anterior wall below the level of the papillary muscles. Thereafter, second tissue anchor 422 is endovascularly (e.g., percutaneously) advanced to and implanted, from within right ventricle 500, at a second ventricular wall site 512, typically on the anterior wall above the level of or at the junction of the natural moderator band and the anterior wall, typically no more than 2.5 cm from first ventricular wall site 510, depending on the extent of dilation of the ventricle. Tether 22 is tensioned between first and second tissue anchors 420 and 422, thereby approximating first and second ventricular wall sites 510 and 512, and plicating the wall. Tether-locking mechanism 68 of second tissue anchor 422 is locked, as described hereinabove. Thereafter, third tissue anchor 424 is endovascularly (e.g., percutaneously) advanced to and implanted, from within right ventricle 500, at a third ventricular wall site 514 on an interventricular septum 520, typically between the right ventricular outflow tract (RVOT) and a junction of the natural moderator band and an interventricular septal wall. Tether 22 is tensioned between second and third tissue anchors 422 and 424, thereby approximating (a) plicated (approximated) first and second ventricular wall sites 510 and 512, collectively, and (b) third ventricular wall site 514. Tether-locking mechanism 68 of third tissue anchor 424 is locked, as described hereinabove. Excess tether 22 is cut or secured, such as described above. As a result of this tensioning, tether 22 functions as an artificial moderator band, reducing ventricular dilation, such as by resisting movement of the anterior wall as the ventricle fills during diastole.

(96) Alternatively, second tissue anchor 422 does not comprise tether-locking mechanism 68, and tension is applied between first and second ventricular wall site 510 and 512, and between these sites and third ventricular wall site 514, after third tissue anchor 424 has been implanted, and then tether-locking mechanism 68 of third tissue anchor 424 is locked.

(97) For some applications, tether 22 is electrically conductive, in order to facilitate conduction of natural cardiac electrical signals from the wall of interventricular septum 520 to the anterior wall of right ventricle 500, mimicking one of the natural functions of the natural moderator band. Alternatively or additionally, for some applications, tether 22 is elastic, in order to facilitate diastolic relaxation of the right ventricle. For example, tether 22 may be sufficiently elastic to lengthen by at least 10%, no more than 100%, and/or between 10% and 100% under diastolic loading, compared to under systolic loading.

(98) For some applications, the ventricular treatment method described with reference to FIGS. 10A-B is performed using tissue anchors other than those of multiple tissue-anchor system 400. These other tissue anchors do not comprise tether-locking mechanism 68. Typically, these other tissue anchors comprise respective helical tissue-coupling elements, as is known in the art. For some applications, tissue anchors are used that are described in International Application PCT/IL2014/050027, which published as PCT Publication WO 2014/108903, and/or in one or more of the other patent applications incorporated by reference hereinbelow.

(99) Reference is now made to FIGS. 11A-D, which are schematic illustrations of a cutting tool 600, in accordance with an application of the present invention. Cutting tool 600 is configured to cut an elongate member 610, such as tether 22 described above, or any other elongate member, such as a suture; elongate member 610 is typically flexible. Cutting tool 600 is configured to be used in transcatheter procedures. Cutting tool 600 uses torsion to cut elongate member 610, which places no tension on the implant, such as the implanted anchors described hereinabove, and provides a high degree of control of the cutting.

(100) Cutting tool 600 comprises an outer tube 620 and an inner tube 622 that is nested within outer tube 620. Typically, both the inner and the outer tubes are cylindrical. For some applications, outer tube 620 comprises a braided extruded material, such as a metal (such as stainless steel) and nylon, and/or inner tube 622 comprises a metal (such as stainless steel). For some applications, a proximal end of inner tube 622 is fixed (e.g., welded) to a distal end of a torque cable, which typically comprises a metal (such as stainless steel). Inner tube 622 is shaped so as to define an inner-tube distal end (non-lateral) opening 624 through a distal end 626 of inner tube 622. Inner tube 622 is also shaped so as to define an inner-tube lateral opening 628, typically having a distal-most portion 629 that is within 5 mm of distal end 626, such as within 3 mm of the distal end. Typically, inner-tube lateral opening 628 has an area of between 1 and 10 mm2.

(101) Elongate member 610, before being cut, passes through both inner-tube distal end opening 624 and inner-tube lateral opening 628, such as shown in FIGS. 11A-C.

(102) Outer tube 620 is shaped so as to define an outer-tube distal end (non-lateral) opening 630 through a distal end 632 of outer tube 620. Outer tube 620 is also shaped so as to define an outer-tube lateral opening 634, which extends to distal end 632. Typically, a proximal portion 640 of outer-tube lateral opening 634 has a first width W1 that is greater than (e.g., at least 125% of) a second width W2 of a distal portion 642 of outer-tube lateral opening 634, which distal portion 642 extends to distal end 632. First and second widths W1 and W2 are measured circumferentially around outer tube 620. For example, first width W1 may be at least 1.5 mm, no more than 5 mm, and/or between 1.5 and 5 mm, and second width W2 may be at least 0.5 mm, no more than 1.25 mm, and/or between 0.5 and 1.25. Second width W2 is greater than (e.g., at least 125% of) a diameter D of elongate member 610, in order to allow the elongate member to pass through distal portion 642, as described hereinbelow with reference to FIG. 11B.

(103) Typically, proximal portion 640 of outer-tube lateral opening 634 has a first length L1 of at least 0.5 mm, no more than 2 mm, and/or between 0.5 and 2 mm, and distal portion 642 of outer-tube lateral opening 634 has a second length L2 of at least 0.5 mm, no more than 2 mm, and/or between 0.5 and 2 mm. First and second lengths L1 and L2 are measured parallel to a longitudinal axis 648 of outer tube 620.

(104) Proximal portion 640 of outer-tube lateral opening 634 has first and second edges 650A and 650B, which extend axially along outer tube 620. One or both of the edges (typically both) are shaped so as to define a sharp cutting blade.

(105) Outer tube 620 typically has an inner diameter of at least 0.75 mm, no more than 4 mm, and/or between 0.75 and 4 mm, and inner tube 622 typically has an outer diameter that is as least 90%, no more than 99%, and/or between 90% and 99% of the inner diameter of outer tube 620, and/or at least 0.65 mm, no more than 3.95 mm, and/or between 0.65 and 3.95 mm. Outer tube 620 typically has a length of at least 20 cm, no more than 200 cm, and/or between 20 and 200 cm. Inner tube 622 typically has a length of at least 1 cm, no more than 200 cm, and/or between 1 and 200 cm (for applications in which inner tube is fixed to the distal end of a torque cable, as described above, inner tube 622 typically has a length of at least 1 cm, no more than 5 cm, and/or between 1 and 5 cm; for applications in which inner tube 622 is not coupled to a torque cable, and thus extends out of the body, the length is typically at least 20 cm, no more than 200 cm, and/or between 20 and 200 cm.

(106) During use of cutting tool 600, elongate member 610 is threaded through both inner-tube distal end opening 624 and inner-tube lateral opening 628, as shown in FIG. 11A. This threading is performed by passing a free proximal end of the elongate member through the tool, while the free end and the tool are outside the subject's body. A proximal portion of the elongate member extends proximally generally alongside an outer surface of outer tube 620, to outside the subject's body (typically through a catheter through which cutting tool 600 also passes). Distal end 626 of inner tube 622 is distal to distal end 632 of outer tube 620, such that a distal portion of inner tube 622 extends out of outer-tube distal end opening 630, typically by at least 1 mm, no more than 10 mm, and/or between 1 to 10 mm. This relative axial positioning of the inner and outer tubes allows free sliding of elongate member 610 as cutting tool 600 is advanced to a desired cutting location along the elongate member. At least a portion, such as all, of inner-tube lateral opening 628 is disposed distally to distal end 632 of outer tube 620.

(107) As shown in FIG. 11B, inner tube 622 is moved proximally with respect to outer tube 620, either by proximally withdrawing the inner tube and/or by distally advancing the outer tube. Typically, a portion of elongate member 610 passes through distal portion 642 of outer-tube lateral opening 634 during such relative movement. A distal edge 660 of inner-tube lateral opening 628 (which edge is typically dull) presses elongate member 610 against a proximal edge 662 of outer-tube lateral opening 634 (which edge is typically dull), causing a proximal portion of the elongate member to extend radially outward from cutting tool 600, typically at an angle of between 60 and 90 degrees with respect to an outer surface of outer tube 620. (Such a disposition of the elongate member no longer provides free sliding of the elongate member; for this reason the inner tube is initially disposed distal to the outer tube, to allow such free sliding.)

(108) As shown in FIG. 11C, inner tube 622 is rotated with respect to outer tube 620, either by rotating the inner tube and/or by rotating the outer tube. Such rotation pushes elongate member 610 against one of sharp first and second edges 650A and 650B of proximal portion 640 of outer-tube lateral opening 634. Inner and outer tubes 622 and 620 are torqued in opposite rotational directions to apply shear on elongate member 610 with the sharp blade edge, causing the sharp edge to cut elongate member 610, as shown in FIG. 11D. Thus cutting tool 600 performs the cutting with torsional force, rather than axial force.

(109) Reference is now made to FIGS. 12A-14B, which are schematic illustrations of a tissue-anchor system 710, in accordance with an application of the present invention. FIGS. 12A-C show tissue-anchor system 710 in an engaged state, and FIGS. 13A-B and 14A-B show tissue-anchor system 710 in a disengaged state. Tissue-anchor system 710 comprises a torque-delivery tool 720, a tissue anchor 724, and a locking shaft 726, which is typically shaped so as to define a sharp distal tip 727. Locking shaft 726 is similar in many respects to locking wire 110, described hereinabove with reference to FIGS. 1A-2A.

(110) Torque-delivery tool 720 is configured to implant tissue anchor 724 in cardiac tissue, and comprises a torque-delivery cable 728, which comprises a distal torque-delivery head 730, which is fixed to torque-delivery cable 728. Distal torque-delivery head 730 is shaped so as to define a chamber 732, which is shaped so as to define (a) a fenestration 734 through a lateral wall 736 of chamber 732, and (b) proximal and distal chamber end openings 738 and 740. Torque-delivery tool 720 further comprises a coupling element 741, which is (a) not fixed to any elements of tissue-anchor system 710, (b) too large to pass through fenestration 734, (c) too large to pass through distal chamber end opening 740, and, optionally, (d) too large to pass through proximal chamber end opening 738. For some applications, fenestration 734 has a greatest dimension (e.g., a greatest diameter) D.sub.F of at least 0.3 mm, no more than 3 mm, and/or between 0.3 mm and 3 mm, and/or distal chamber end opening 740 has a greatest dimension (e.g., a greatest diameter) D.sub.EO of at least 0.25 mm, no more than 2.9 mm, and/or between 0.25 and 2.9 mm.

(111) Tissue anchor 724 comprises: a helical tissue-coupling element 750, which is shaped so as to define and surrounds a helical tissue-coupling element channel 751 that extends to a distal end 753 of helical tissue-coupling element 750; and a proximal anchor head 752, which (a) is attached to a proximal portion 754 of helical tissue-coupling element 750, and (b) is shaped so as to define a head-coupling channel 756, which has an internal wall 758 (labeled in FIG. 14B). Helical tissue-coupling element 750 is configured to puncture and screw into cardiac tissue.

(112) It is noted that proximal anchor head 752 of tissue anchor 724 is typically shorter than proximal anchor head 52 of tissue anchor 24, described hereinabove with reference to FIGS. 1A-3E. The shorter anchor head allows tissue anchor 724 to be drawn closer to another tissue anchor when tension is applied using a tether, than can be achieved with tissue anchor 24. In addition, when two tissue anchors 724 are used, they can be drawn even closer to one another when tension is applied using a tether, than can be achieved with two tissue anchors 24.

(113) For some applications, helical tissue-coupling element 750 implements features of one or more of the tissue-coupling elements described in PCT Application PCT/IL2014/050027, filed Jan. 9, 2014, which published as PCT Publication WO 2014/108903 and is incorporated herein by reference.

(114) Typically, tissue-anchor system further comprises tether 22, which is coupled (optionally, fixed) to anchor head 752, and which typically is tensioned after tissue anchor 724 has been implanted in cardiac tissue.

(115) Torque-delivery cable 728 and distal torque-delivery head 730 together are shaped so as to define a locking-wire-accepting channel 760 (labeled in FIGS. 13B and 14B). Locking-wire-accepting channel 760 passes through (i) torque-delivery cable 728, (ii) chamber 732 (and, typically, the entire distal torque-delivery head 730), and (iii) proximal and distal chamber end openings 738 and 740. In addition, locking-wire-accepting channel 760 is typically coaxial with helical tissue-coupling element channel 751.

(116) Tissue-anchor system 710 is configured to assume engaged and disengaged states, in which distal torque-delivery head 730 is engaged and not engaged to anchor head 752, respectively. Tissue-anchor system 710 is in: the engaged state when locking shaft 726 is removably disposed in locking-wire-accepting channel 760 and at least partially within helical tissue-coupling element channel 751, with locking shaft 726 constraining coupling element 741 to partially protrude through fenestration 734 out of chamber 732 and against internal wall 758 of head-coupling channel 756, thereby axially locking distal torque-delivery head 730 with respect to head-coupling channel 756, as shown in FIGS. 12A-C, and the disengaged state when locking shaft 726 is not disposed in locking-wire-accepting channel 760 and is not disposed in helical tissue-coupling element channel 751, and does not constrain coupling element 741, as shown in FIGS. 13A-B and 14A-B.

(117) As mentioned above, FIGS. 13A-B and 14A-B show tissue-anchor system 710 in the disengaged state. In FIGS. 13A-B, tissue-anchor system 710 is shown in the disengaged state, while distal torque-delivery head 730 is still in head-coupling channel 756 of anchor head 752. As can be seen, coupling element 741 has fallen away from internal wall 758 of head-coupling channel 756, such that coupling element 741 no longer axially locks distal torque-delivery head 730 with respect to head-coupling channel 756. This allows the removal of distal torque-delivery head 730 from head-coupling channel 756 of anchor head 752, as shown in FIGS. 14A-B. It is noted that, as shown in both FIGS. 13A-B and 14A-B, coupling element 741 is trapped in chamber 732 because the coupling element is too large to pass through fenestration 734 and too large to pass through distal chamber end opening 740, and, typically, proximal chamber end opening 738. Coupling element 741 thus cannot be released into the patient's body.

(118) For some applications, coupling element 741 is spherical (as shown), and may, for example, have a diameter D.sub.CE of at least 0.3 mm, no more than 3 mm, and/or between 0.3 and 3 mm. For some applications, coupling element 741 has a volume of at least 0.3 mm3, no more than 8 mm3, and/or between 0.3 and 8 mm3. For some applications, coupling element 741 comprises a metal. For other applications, coupling element 741 comprises a polymer, such as an elastomer.

(119) Typically, internal wall 758 of head-coupling channel 756 is shaped so as to define a coupling indentation 762. Tissue-anchor system 710 is in the engaged state when locking shaft 726 is removably disposed in locking-wire-accepting channel 760 and at least partially within helical tissue-coupling element channel 751, with locking shaft 726 constraining coupling element 741 to partially protrude through fenestration 734 out of chamber 732 and into coupling indentation 762 of the internal wall 758 of head-coupling channel 756.

(120) For some applications, torque-delivery tool 720 further comprises a depth-finding tool 764, which comprises a radiopaque bead 766 shaped so as to define a hole 768 therethrough (labeled in FIGS. 13B and 14B). Bead 766 is removably positioned within helical tissue-coupling element channel 751. Locking shaft 726 passes through hole 768 of bead 766, such that bead 766 is slidable along locking shaft 726 and along helical tissue-coupling element channel 751, when locking shaft 726 is removably disposed at least partially within helical tissue-coupling element channel 751 when tissue-anchor system 710 is in the engaged state. For some applications, depth-finding tool 764 further comprises a bead-coupling wire 770, which is at least partially removably disposed within helical tissue-coupling element channel 751, and which is fixed to bead 766 and a distal portion 772 of distal torque-delivery head 730 (labeled in FIGS. 13B and 14A), thereby (a) preventing bead 766 from exiting a distal end 774 of helical tissue-coupling element channel 751, and (b) facilitating removal of depth-finding tool 764 from tissue anchor 724 upon removal of distal torque-delivery head 730 from anchor head 752. For some applications, bead-coupling wire 770 is shaped as a helical spring 776, such as shown.

(121) For some applications, depth-finding tool 764 implements techniques described in PCT Publication WO 2014/108903, which is incorporated herein by reference. For example, bead 766 serves as a marker that indicates a depth of penetration of helical tissue-coupling element 750 into soft tissue, such as cardiac tissue. When rotated, helical tissue-coupling element 750 penetrates and is advanced into the tissue. Bead 766 does not penetrate the tissue, and thus remains at the surface of the tissue, in contact therewith. As a result, as the tissue-coupling element advances into the tissue, the bead remains stationary, and moves toward a proximal end of tissue anchor 724 (and toward anchor head 752 and distal torque-delivery head 730). In other words, the proximal end of tissue anchor 742 (and anchor head 752 and distal torque-delivery head 730) move closer to bead 766, as measured along a central longitudinal axis of tissue anchor 742.

(122) Both the bead and more proximal portions of the anchor (such as anchor head 752) are viewed using imaging (e.g., fluoroscopy, computed tomography, echocardiography, sonography, or MRI), and the distance between the bead and the proximal end of the tissue anchor (e.g., the anchor head) is estimated and monitored in real time as the anchor is advanced into the tissue. When the bead reaches a desired distance from the head (such as reaches the head itself), the tissue-coupling element has been fully advanced, e.g., screwed, into and embedded in the tissue, and the physician thus ceases rotating the anchor.

(123) Without using a technique such as this for visualizing the advancement of the anchor into the tissue, it is often difficult to ascertain when the tissue anchor has been fully embedded into the tissue, because the tissue is difficult to see in some images, such as fluoroscopic images. As a result, the tissue anchor may inadvertently be insufficiently advanced into the tissue, resulting in poor anchoring in the tissue, or over-advanced into the tissue, possible tearing or otherwise damaging the tissue.

(124) Bead 766 may have any appropriate shape, such as a sphere (as shown) or a disc (not shown). An outer diameter of the bead is typically slightly greater than the inner diameter of an empty space within helical tissue-coupling element 750, in order to provide some friction between the bead and helical tissue-coupling element 750, and prevent the bead from being free-floating within the helix. For example, the outer diameter of the bead may be at least 0.05 microns less than the inner diameter of the empty space. Alternatively or additionally, the bead comprises a coating which provides some friction between the bead and the helix; the coating may be sheared off as the bead moves proximally through the helix. Further alternatively or additionally, the bead and shaft are configured to provide some friction therebetween. For some applications, the outer diameter of the bead may be between 1 and 5 mm.

(125) FIGS. 13A-B show helical spring 776 axially compressed, with bead 766 as close as possible to anchor head 752 and distal torque-delivery head 730. As mentioned above, such a state is reached when bead 766 pushes against tissue. Although the tissue is not shown in FIGS. 13A-B, FIGS. 13A-B nevertheless show helical spring 776 axially compressed, because the spring is typically in this state upon and after removal of locking shaft 726, which removal is performed after the anchor has been implanted in the tissue and the tissue has pushed the bead up against the anchor head.

(126) For some applications, anchor head 752 is shaped so as to define a tether-securing element 780, which is typically shaped so as to define a lateral opening 782 through which tether 22 is disposed. For some applications, tether-securing element 780 is rotatable with respect to helical tissue-coupling element 750, in order to provide rotational freedom of movement to tether 22 after implantation of tissue anchor 724, particularly during tensioning of tether 22. This rotational freedom of movement avoids twisting of the tether around anchor head 752, and facilitates ideal orientation of the tether with another tissue anchor.

(127) Tissue-anchor system 710 is advanced into the heart in the engaged state. Tissue anchor 724 is implanted in cardiac tissue, using torque-delivery cable 728 while tissue-anchor system 710 is in the engaged state. Typically, as tissue anchor 724 is screwed into the tissue, locking shaft 726, which is disposed within locking-wire-accepting channel 760 and helical tissue-coupling element channel 751, penetrates and advances into the tissue along with the tissue anchor. For some applications, when the locking shaft penetrates to a certain depth, the locking shaft is withdrawn slightly. Optionally, sharp distal tip 727 of locking shaft 726 is inserted into the tissue slightly, even before insertion of tissue anchor 724, in order to prevent sliding of the anchor on the surface of the tissue before commencement of insertion of the anchor into the tissue.

(128) After tissue anchor 724 has been fully implanted, locking shaft 726 is withdrawn entirely from the tissue, from helical tissue-coupling element channel 751, and from locking-wire-accepting channel 760, thereby allowing the disengagement of distal torque-delivery head 730 from anchor head 752, as described hereinabove with reference to FIGS. 13A-B and 14A-B. Because depth-finding tool 764 is fixed to distal torque-delivery head 730, removal of distal torque-delivery head 730 from anchor head 752 removes depth-finding tool 764, including radiopaque bead 766, from tissue anchor 724. Removal of radiopaque bead 766 from the empty space within helical tissue-coupling element 750 allows for greater integration of the helical tissue-coupling element with cardiac tissue. In addition, for applications in which bead-coupling wire 770 is shaped as helical spring 776, as described above, removal of radiopaque bead 766 and helical spring 776 prevents the radiopaque bead and the spring from compressing the tissue in the space within the helical tissue-coupling element on a long-term basis.

(129) Reference is now made to FIG. 15, which is a schematic illustration of another configuration of tissue anchor system 710, in accordance with an application of the present invention. In this configuration, locking shaft 726 is shaped so as to define one or more longitudinally-extending grooves 778, such as exactly one groove 778 as shown in FIG. 15. Alternatively, for some applications, locking shaft 726 is shaped so as to define one or more longitudinally-extending flat surfaces, such as a plurality of longitudinally-extending flat surfaces facing in respective different directions (for example, locking shaft 726 may be polygonal in cross-section, such as hexagonal) (configurations not shown). The groove or flat surface helps better seat and secure coupling element 741, by providing a greater contact surface area between the shaft and the coupling element. The groove or flat surface also allows for the use of a larger coupling element 741, which may also increase the contact surface area between the shaft and the coupling element. The groove or flat surface may also prevent rotation of the shaft with respect to torque-delivery cable and anchor 724.

(130) Reference is now made to FIGS. 16A-C, which are schematic illustrations of three exemplary deployments of tissue anchor 724 using torque-delivery tool 720, in accordance with respective applications of the present invention. These deployments may be performed using techniques described hereinabove with reference to FIGS. 5A-D mutatis mutandis, and/or described in the patent applications incorporated hereinbelow by reference, mutatis mutandis.

(131) In the deployment illustrated in FIG. 16A, tissue anchor 724, described hereinabove with reference to FIGS. 12A-14B, is shown deployed at a first atrial site 790, and tissue anchor 724, described hereinabove with reference to FIGS. 1A-F, 2A-B, 3A-E, and 5A-D, is shown deployed at a second atrial site 792. Tether 22 is tensed as described hereinabove regarding tissue anchor 724.

(132) In the deployment illustrated in FIG. 16B, two tissue anchors 724, described hereinabove with reference to FIGS. 12A-14B, are shown deployed at first and second atrial sites 790 and 792, respectively. Respective tethers 22 are fixed to heads of tissue anchors 724, and are coupled together in tension by a tether-securing device 794. For example, tether-securing device 794 may comprise (a) tether-securing device 330, described with reference to FIGS. 6A-9 of U.S. application Ser. No. 14/525,668, filed Oct. 28, 2014, which published as US Patent Application Publication 2015/0119936 and is assigned to the assignee of the present application and is incorporated herein by reference, or (b) tether-securing device 30, described with reference to FIGS. 1-3 of the '668 application. Techniques for deploying the tether-securing device may be used that are described in the '668 application. Alternatively, a single tissue anchor 724 is deployed, and a second tissue anchor comprises second tissue anchor 252B fixed to tether-securing device 230, both of which are described with reference to FIGS. 4A-5 of the '668 application.

(133) In the deployment illustrated in FIG. 16C, two tissue anchors 724, described hereinabove with reference to FIGS. 12A-14B, are shown deployed at first and second atrial sites 790 and 792, respectively. Tether 22 is provided with securement protrusions 160, which are described hereinabove with reference to FIGS. 4A-E. Tether 22 is fixed to the head of the tissue anchor 724 at first atrial site 790, and passes through lateral opening 782 of tether-securing element 780 of head 752 of the tissue anchor 724 at second atrial site 792. A tether-locking element 796, typically separate from head 752, is provided. Tether 22 passes through tether-locking element 796. Tether-locking element 796 is configured to allow advancement of securement protrusions 160 through tether-locking element 96 in one direction, and inhibit (typically prevent) advancement of the tether through the tether-locking element in the opposite direction. As a result, as tension is applied to tether 22 by pulling on the tether in a direction indicated by an arrow 798, one or more of securement protrusions 160 pass through tether-locking element 796 in the direction indicated by arrow 798, and are prevented from returning through the tether-locking element in the opposite direction, thereby maintaining the tension applied to the tether. Although securement protrusions 160 are shown in FIG. 16C comprising cylinders 168, the securement protrusions may alternatively comprise the other configuration described hereinabove with reference to FIGS. 4B-E or other configurations.

(134) Reference is now made to FIGS. 17A-19, which are schematic illustrations of a flexible tether 822, in accordance with an application of the present invention. FIG. 17C shows tether 822 straight-on from the side. FIGS. 18A-B are cross-sectional views of tether 822 taken along lines XVIIA-XVIIA and XVIIB-XVIIB, respectively, of FIG. 17A. FIG. 19 shows the cross-sectional views of FIGS. 18A-B superimposed on one another for illustrative purposes. Tether 822 may be used, for example, to apply tension between two or more tissue anchors, such as tissue anchors described herein, and/or in the patent applications incorporated by reference hereinbelow. Typically, tether 822 is sterile when provided, typically in protective packaging.

(135) Tether 822, at least when tensioned into a straight, non-twisted configuration, such as shown in FIGS. 17A-19, has a central longitudinal axis 828, and is shaped so as to define first and second blades 830A and 830B (and, typically, at least several more blades), which are disposed (a) at first and second longitudinal locations 832A and 832B, and (b) within 10 mm of one another along central longitudinal axis 828. By within 10 mm of one another it is meant that respective portions of the blades that are closest to one another along the axis are within 10 mm of one another; within 10 mm does not refer to a distance between respective longitudinal centers of the blades. For some applications, first and second blades 830A and 830B are disposed within 5 mm of one another along central longitudinal axis 828, such as touching one another (as shown in FIGS. 17A-C).

(136) First and second blades 830A and 830B have respective best-fit planes 834A and 834B, which intersect at an angle (theta) of at least 30 degrees, such as at least 60 degrees, e.g., at least 85 degrees, for example 90 degrees (as shown). In other words, adjacent first and second blades 830A and 830B are rotationally offset by at least angle (theta). For example, for applications in which angle (theta) equals 90 degrees, the blades may be considered to have two rotational phases, while for other applications in which angle (theta) is less than 90 degrees, the blades may be considered to have three or more rotational phases. Typically, each of the blades defines two opposing generally flat external surfaces that are generally parallel with the blade's best-fit plane.

(137) As used in the present application, including the claims, a blade of tether 822 is a generally flat thin part or section. A blade does not necessarily define a sharp cutting edge, and, in fact, blades 830 do not generally define any sharp cutting edges.

(138) As used in the present application, including in the claims, a best-fit plane of a given blade is the plane that results in the minimum sum of squares of distances between the plane and all points of the volume of the blade. As used in the present application, including in the claims, an angle between two lines or two planes is the smaller of the two supplementary angles between the two lines or two planes, or equals 90 degrees if the two lines or two planes are perpendicular. As used in the present application, including in the claims, a non-twisted configuration means that the tether is not twisted, i.e., not altered in shape, as by turning the ends in opposite directions, so that parts previously in the same straight line and plane are located in a spiral curve, as might occur if the tether were twisted.

(139) As used in the present application, including in the claims, a central longitudinal axis of an elongate structure is the set of all centroids of transverse cross-sectional sections of the structure along the structure. Thus the cross-sectional sections are locally perpendicular to the central longitudinal axis, which runs along the structure. (If the structure is circular in cross-section, the centroids correspond with the centers of the circular cross-sectional sections.)

(140) For some applications, central longitudinal axis 282 falls in first and second best-fit planes 834A and 834B (as shown). For some other applications, central longitudinal axis 282 is parallel to first and second best-fit planes 834A and 834B (configuration not shown).

(141) For some applications, a plane defined by a longitudinal edge 836 of first blade 830A forms an angle with central longitudinal axis 828 of at least 60 degrees, such as 90 degrees. For some applications, the longitudinal edge includes a flat portion, or is entirely flat. Another edge of first blade 830A, as well edges of the other blades 830, may also have one or more of these properties.

(142) First and second blades 830A and 830B have respective first and second greatest dimensions D.sub.GA and D.sub.GB perpendicular to central longitudinal axis 828. For some applications, each of first and second greatest dimensions D.sub.GA and D.sub.GB is at least 0.25 mm (e.g., at least 0.5 mm), no more than 5 mm, and/or between 0.5 and 5 mm (e.g., between 0.25 and 5 mm).

(143) For some applications, first and second greatest dimensions D.sub.GA and D.sub.GB are first and second greatest major dimensions D.sub.GA and D.sub.GB, and first and second blades 830A and 830B have respective first and second greatest minor dimensions D.sub.MA and D.sub.MB, which are measured perpendicular to (a) first and second greatest major dimensions D.sub.GA and D.sub.GB, respectively, and (b) central longitudinal axis 828. First and second greatest minor dimensions D.sub.MA and D.sub.MB typically equal no less than 10% (e.g., no less than 25%), no more than 90% (e.g., no more than 50%), and/or between 10% and 90%, such as between 25% and 50% of first and second greatest major dimensions D.sub.GA and D.sub.GB, respectively. For some applications, each of first and second greatest minor dimensions D.sub.MA and D.sub.MB is at least 0.05 mm, such as at least 0.1 mm, or no more than 3 mm, such as between 0.05 mm (e.g., 0.1 mm) and 3 mm.

(144) As labeled in FIG. 17C, first and second blades 830A and 830B have first and second lengths L.sub.A and L.sub.B, respectively, which are measured along central longitudinal axis 828. For some applications, each of first and second lengths L.sub.A and L.sub.B is at least 0.25 mm (e.g., at least 0.5 mm), no more than 10 mm (e.g., no more than 5 mm), and/or between 0.25 and 10 mm, such as between 0.5 mm and 5 mm, typically between 1 and 5 mm.

(145) Typically, tether 822 is shaped so as to define at least two, no more than 50, and/or between two and 50 blades 830, such as least 10, no more than 30, and/or between 10 and 30 blades 830. These blades 830 include first and second blades 830A and 830B, and a third blade 830C, which is disposed (a) at a third longitudinal location 832C, and (b) within 10 mm of second blade 830B along central longitudinal axis 828. Second longitudinal location 832B is longitudinally between first and third longitudinal locations 832A and 832C along central longitudinal axis 828. Third blade 830C has a third best-fit plane, which intersects second best-fit plane 834B at an angle of at least 30 degrees, when tether 822 is tensioned into the straight, non-twisted configuration.

(146) For some applications, first blade 830A is shaped so as to define at least one flat planar surface portion 840 having a cross-sectional area of at least 0.25 mm2 (labeled in FIG. 18A). For some applications, first blade 830A is shaped so as to define at least two non-coplanar flat planar surface portions 840 and 842, each of which has the area of at least 0.25 mm2. For some applications, the at least two flat planar surface portions 840 and 842 are parallel to one another (such as shown). For some applications, second blade 830B is shaped so as to define at least one flat planar surface portion 844 having a cross-sectional area of at least 0.25 mm2 (labeled in FIG. 18B).

(147) For some applications, first and second blades 830A and 830B have a same shape, which has different rotational orientations about central longitudinal axis 828 at first and second longitudinal locations 832A and 832B (such as shown). For other applications, first and second blades 830A and 830B have different shapes (configuration not shown).

(148) For some applications, tether 822 comprises a polymer. For some applications, tether 822 comprises a polymer/metal composite material. In some applications, the tether is radiopaque such that it is visible under fluoroscopy. For example, the metal may comprise a precious metal or a heavy metal. The radiopaque material may be encapsulated in the tether or may be an independent layer embedded in the structure, such as a wire running along the central longitudinal axis of the tether. The metal component may also be configured to vary in diameter and/or material from the distal end to the proximal end of the tether. A proximal portion of the tether composite may be constructed to be stiff to allow effective torque delivery, and a distal portion of the tether may be constructed to be more flexible and allow for cutting of the tether in situ, for example using cutting tool 600, described hereinabove with reference to FIGS. 11A-D or another cutting tool.

(149) For some applications, first and second blades 830A and 830B have respective first and second greatest cross-sectional areas, measured perpendicular to central longitudinal axis 828, each of which is at least 0.1 mm2, no more than 20 mm2, and/or between 0.1 and 20 mm2, such as at least 0.5 mm2, no more than 5 mm2, and/or between 0.5 and 5 mm2. For some applications, the first and the second greatest cross-sectional areas are equal. For some applications, first and second blades 830A and 830B have respective first and second volumes, each of which is at least 0.05 mm3, no more than 150 mm3, and/or between 0.05 and 150 mm3, such as at least 0.25 mm3, no more than 15 mm3, and/or between 0.25 and 15 mm3.

(150) For some applications, tether 822 is shaped so as to define at least three blades 830, which include first and second blades 830A and 830B, and which are disposed along a longitudinal portion of tether 822. For some applications, an average cross-sectional area of tether 822 along the longitudinal portion is less than 20 mm2, such as less than 4 mm2, and/or a greatest cross-sectional area of tether 822 along the longitudinal portion is less than 20 mm2.

(151) For some applications, a longitudinal portion of tether 822 includes (a) a bladed sub-portion, which is shaped so as to define blades 830, and (b) a non-bladed sub-portion, which is not shaped so as to define any blades 830. The longitudinal portion has a constant cross-sectional area, measured perpendicular to central longitudinal axis 828. For some applications, tether 822 is manufactured by taking a tether that initially has a circular cross-sectional shape, and shape-setting longitudinal portions of the circular tether so as to form blades 830. For some applications, the shape-setting includes flattening and twisting the circular tether, to produce the shape shown in FIGS. 17A-C, which includes short twisted portions at the interfaces between adjacent blades. For other applications, the shape-setting includes flattening portions of the circular tether, to produce the shape shown in FIGS. 21A-C.

(152) For some applications, blades 830 have a hardness of at least 40 Shore D. For some applications in which the tether includes one or more non-bladed sub-portions, the one or more non-bladed sub-portions have the same hardness as blades 830.

(153) Reference is now made to FIGS. 20A-C, which are schematic illustrations of cross sections of tether 822, in accordance with an application of the present invention. For some applications, when tether 822 is tensioned into a straight (typically non-twisted) configuration, tether 822 has central longitudinal axis 828, and is shaped so as to define first and second cross sections 850A and 850B perpendicular to central longitudinal axis 828, at first and second different longitudinal locations 832A and 832B that are within 10 mm of one another along central longitudinal axis 828. First and second cross sections 850A and 850B have respective first and second greatest dimensions D.sub.GA and D.sub.GB, which define respective first and second lines 852A and 852B. If first and second cross sections 850A and 850B were to be projected onto one another while preserving rotation about central longitudinal axis 828, as shown in FIG. 20C, (a) first and second lines 852A and 852B would intersect at an angle (epsilon) of at least 30 degrees, such as at least 60 degrees, e.g., at least 85 degrees, for example 90 degrees (as shown), and (b) first and second cross sections 850A and 850B would not coincide.

(154) For some applications, when tensioned into the straight, non-twisted configuration, tether 822 is shaped so as to define a third cross section perpendicular to central longitudinal axis 828 at third longitudinal location 832C. The third second cross section has a third greatest dimension, which defines a third line. If second cross section 850B and the third cross section were to be projected onto one another while preserving rotation about central longitudinal axis 828, (a) the second and the third lines would intersect at an angle of at least 30 degrees, and (b) the second and the third cross sections would not coincide.

(155) For some applications, a first perimeter 860A of first cross section 850A is shaped so as to define at least one straight line segment 862 having a length of at least 0.5 mm. For some applications, first perimeter 860A is shaped so as to define at least two non-coaxial straight line segments 862 and 864, each of which has the length of at least 0.5 mm. For some applications, the at least two non-coaxial straight line segments 862 and 864 are parallel to one another (such as shown). For some applications, a second perimeter 860B of second cross section 850B is shaped so as to define at least one straight line segment 866 having a length of at least 0.5 mm.

(156) For some applications, first and second cross sections 850A and 850B have a same shape, which has different rotational orientations about central longitudinal axis 828 at first and second longitudinal locations 832A and 832B.

(157) For some applications, when tensioned into the straight, non-twisted configuration, tether 822 is shaped so as to define a first longitudinal segment 870A (labeled in FIG. 17C) that includes first longitudinal location 832A and has a first length L.sub.A of at least 0.25 mm (e.g., at least 0.5 mm), no more than 10 mm (e.g., no more than 5 mm), and/or between 0.25 and 10 mm, such as between 0.5 mm and 5 mm, typically between 1 and 5 mm. First length L.sub.A is measured along central longitudinal axis 828, and corresponds to first length L.sub.A described hereinabove regarding first blade 830A. First longitudinal segment 870A, at every longitudinal location therealong, has first cross sections, which (a) include first cross section 850A, and (b) have respective first greatest dimensions, which define respective first lines, which include the first line 852A. If the first cross sections were to be projected onto second cross section 850B while preserving rotation about central longitudinal axis 828: (a) the first lines would intersect second line 852B at respective angles, each of at least 30 degrees, and (b) the first cross sections would not coincide with second cross section 850B. For some applications, the first cross sections have a same shape. For some applications, the shape has a same rotational orientation about central longitudinal axis 828 along first longitudinal segment 870A. Alternatively, for some applications, the shape has different rotational orientations about central longitudinal axis 828 at at least two longitudinal locations along first longitudinal segment 870A.

(158) For some applications, when tensioned into the straight, non-twisted configuration, tether 822 is shaped so as to define a second longitudinal segment 870B (labeled in FIG. 17C) that includes second longitudinal location 832B and has a second length L.sub.B of at least 0.25 mm (e.g., at least 0.5 mm), no more than 10 mm (e.g., no more than 5 mm), and/or between 0.25 and 10 mm, such as between 0.5 mm and 5 mm, typically between 1 and 5 mm. Second length L.sub.B is measured along central longitudinal axis 828, and corresponds to second length L.sub.B described hereinabove regarding second blade 830B. Second longitudinal segment 870B, at every longitudinal location therealong, has second cross sections, which (a) include second cross section 850B, and (b) have respective second greatest dimensions, which define respective second lines, which include second line 852B. If the second cross sections were to be projected onto first cross section 850A while preserving rotation about central longitudinal axis 828: (a) the second lines would intersect first line 852A at respective angles, each of at least 30 degrees, and (b) the second cross sections would not coincide with first cross section 850A.

(159) For some applications, first and second cross sections 850A and 850B have first and second areas, respectively, each of which is at least 0.05 mm2, no more than 15 mm2, and/or between 0.05 and 15 mm2.

(160) Reference is now made to FIGS. 21A-C, which are schematic illustrations of another configuration of flexible tether 822, in accordance with an application of the present invention. FIG. 21B shows tether 822 straight-on from the side. FIG. 21C is a cross-sectional view of tether 822 taken along line XXIC-XXIC of FIG. 21A. In this configuration, first and second blades 830A and 830B are separated by a blade-free longitudinal gap 874, which has a length of at least 0.25 mm. Tether 822 is thus narrower along the gap, because no blades are disposed in the gap. For some applications, tether 822 along gap 874 is circular in cross-section. Gaps 874 may be provided between all or a portion of longitudinally-adjacent blades 830 of tether 822. This configuration may be particularly suitable for practicing the techniques described hereinbelow with reference to FIGS. 23A-B.

(161) Reference is now made to FIG. 22, which is a schematic illustration of one use of tether 822, in accordance with an application of the present invention. In FIG. 22, tether 822 is shown passing through lateral opening 82 of tissue anchor 24, while tissue anchor system 10 is in the locked state. Tissue anchor system 10 and tissue anchor 24 are described hereinabove with reference to FIGS. 1A-3E. When tissue-anchor system 10 (and tether-locking mechanism 68 thereof) is in the locked state, spring 70 (and, optionally, hammer cap 100) inhibits the sliding of tether 822 through lateral opening 82 by pressing tether 822 against outer tether-securing element 80, such as against perimeter 84 of lateral opening 82, and/or an inner surface of outer tether-securing element 80.

(162) When anchor system 10 transitions from the unlocked state to the locked state, tether 822, at some longitudinal location therealong, is pressed between perimeter 84 of lateral opening 82 (or the inner surface of outer tether-securing element 80) and spring 70 (or hammer cap 100). Spring 70 (or hammer cap 100) impinges on tether 822 and causes the tether to rotate such that the opposing generally flat surfaces of the blade 830 at the longitudinal location (e.g., blade 830A) respectively contact (a) perimeter 84 of lateral opening 82 (or the inner surface of outer tether-securing element 80) and (b) spring 70 (or hammer cap 100). As a result of this rotational alignment, the two adjacent blades 830 (e.g., blades 830A and 830B) are aligned with respect to one another about central longitudinal axis 828 at angle (theta), described hereinabove with reference to FIGS. 17A-19, e.g., at least 30 degrees.

(163) When tension is applied to tether 822 in the direction indicated by an arrow 880, the adjacent blade 830 that is opposite the direction of tension (e.g., blade 830B) is pulled against (a) perimeter 84 of lateral opening 82 (or the inner surface of outer tether-securing element 80) and (b) spring 70 (or hammer cap 100). The rotationally-offset orientation of this adjacent blade inhibits passage of this adjacent blade (e.g., blade 830B) through the narrow space between perimeter 84 of lateral opening 82 (or the inner surface of outer tether-securing element 80) and spring 70 (or hammer cap 100).

(164) Reference is now made to FIGS. 23A-B, which are schematic illustrations of another use of tether 822, in accordance with an application of the present invention. In FIGS. 23A-B, tether 822, in the configuration described hereinabove with reference to FIG. 21A-C, is shown passing through lateral opening 782 of tissue anchor 724. Lateral opening 782 is fairly narrow, such that the angled orientation of the adjacent blade 830 that is opposite the direction of tension (e.g., blade 830B) inhibits passage of this adjacent blade (e.g., blade 830B) through the opening. The blade-free longitudinal gap 874 between adjacent blades 830 allows for full passage of one blade 830 before the adjacent blade (e.g., blade 830B) contacts the perimeter of the opening.

(165) In order to advance tether 822 with respect to opening 782, either in the direction of arrow 880 or the opposite direction, the physician (a) pulls tether 822, until one of gaps 874 is in opening 782, (b) rotates tether 822, as indicated by an arrow 890, and (c) pulls the tether in the desired direction of advancement. For example, FIG. 23B shows tether 822 after it has been advanced in the direction indicated by arrow 880. As can be seen, the angled orientation of the next adjacent blade 830 that is opposite the direction of tension (e.g., blade 830C) inhibits passage of this adjacent blade (e.g., blade 830C) through the opening. Tether 822 is sufficiently rigid to transmit torque, at least from a longitudinal location of a rotation tool to opening 782.

(166) Reference is now made to FIGS. 24A-C, which are schematic illustrations of one use of tether 822 in the configuration described hereinabove with reference to FIG. 21A-C, in accordance with an application of the present invention. FIGS. 24B-C are cross-sectional views taken along the line XXIVB-XXIVB of FIG. 24A. In FIG. 24A-C, tether 822 is shown passing through lateral opening 82 of tissue anchor 24. FIGS. 24A-B show tissue anchor system 10 is in the unlocked state, and FIG. 24C shows tissue anchor system in the locked state. Tissue anchor system 10 and tissue anchor 24 are described hereinabove with reference to FIGS. 1A-3E, except that in the present configuration, lateral opening 82 is oriented vertically, i.e., has a long axis that is parallel to the axis of the anchor. Lateral opening 82 is typically shaped as a vertical slot.

(167) When anchor system 10 is the unlocked state, lateral opening 82 is not obstructed by spring 70 (or hammer cap 100), and thus allows for passage of tether 822. Tether 822 can only advance through lateral opening 82 when the blade 830 at the opening has the same orientation as the opening. Tether 822 is advanced through the opening to a desired level of tension, as described hereinabove with reference to FIGS. 23A-B. The blade-free longitudinal gap 874 between adjacent blades 830 allows for full passage of one blade 830 before the adjacent blade contacts the perimeter of lateral opening 82.

(168) When anchor system 10 transitions from the unlocked state to the locked state, tether 822, at some longitudinal location therealong, is pressed between the perimeter of lateral opening 82 (or the inner surface of outer tether-securing element 80) and spring 70 (or hammer cap 100). Spring 70 (or hammer cap 100) impinges on tether 822 and causes the tether rotate such that both of the blades adjacent to opening 82 (e.g., blades 830A and 830B in FIG. 24C) become substantially parallel to one another. Blade 830B thus become oriented perpendicular to the long axis of opening 82, and inhibits motion in the direction indicated by arrow 880, when tension is applied to tether 822 in the direction indicated by arrow 880.

(169) The scope of the present invention includes embodiments described in the following applications, which are assigned to the assignee of the present application and are incorporated herein by reference. In an embodiment, techniques and apparatus described in one or more of the following applications are combined with techniques and apparatus described herein: U.S. application Ser. No. 12/692,061, filed Jan. 22, 2010, which issued as U.S. Pat. No. 8,475,525; U.S. application Ser. No. 13/188,175, filed Jul. 21, 2011, which issued as U.S. Pat. No. 8,961,596; U.S. application Ser. No. 13/485,145, filed May 31, 2012, which issued as U.S. Pat. No. 8,961,594; U.S. application Ser. No. 13/553,081, filed Jul. 19, 2012, which published as US Patent Application Publication 2013/0018459; U.S. application Ser. No. 13/574,088, filed Oct. 19, 2012, which published as US Patent Application Publication 2013/0046380; U.S. application Ser. No. 14/143,355, filed Dec. 30, 2013, which published as US Patent Application Publication 2014/0114390; U.S. application Ser. No. 14/525,668, filed Oct. 28, 2014, which published as US Patent Application Publication 2015/0119936; International Application PCT/IL2011/000064, filed Jan. 20, 2011, which published as PCT Publication WO 2011/089601; International Application PCT/IL2012/000282, filed Jul. 19, 2012, which published as PCT Publication WO 2013/011502; International Application PCT/IL2013/050470, filed May 30, 2013, which published as PCT Publication WO 2013/179295; International Application PCT/IL2014/050027, filed Jan. 9, 2014, which published as PCT Publication WO 2014/108903; International Application PCT/IL2014/050233, filed Mar. 9, 2014, which published as PCT Publication WO 2014/141239; International Application PCT/IB2014/002351, filed Oct. 28, 2014, which published as PCT Publication WO 2015/063580; U.S. Provisional Application 61/897,491, filed Oct. 30, 2013; U.S. Provisional Application 61/897,509, filed Oct. 30, 2013; and U.S. Provisional Application 62/014,397, filed Jun. 19, 2014.

(170) 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.