Abstract:
The invention provides devices, systems and methods for tissue approximation and repair at treatment sites. The devices, systems and methods of the invention will find use in a variety of therapeutic procedures, including endovascular, minimally-invasive, and open surgical procedures, and can be used in various anatomical regions, including the abdomen, thorax, cardiovascular system, heart, intestinal tract, stomach, urinary tract, bladder, lung, and other organs, vessels, and tissues. The invention is particularly useful in those procedures requiring minimally-invasive or endovascular access to remote tissue locations, where the instruments utilized must negotiate long, narrow, and tortuous pathways to the treatment site. In addition, many of the devices and systems of the invention are adapted to be reversible and removable from the patient at any point without interference with or trauma to internal tissues.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application a divisional of U.S. patent application Ser. No. 13/231,572, filed Sep. 13, 2011, the full disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to medical methods, devices, and systems. In particular, the present invention relates to methods, devices, and systems for the endovascular, percutaneous or minimally invasive surgical treatment of bodily tissues, such as tissue approximation or valve repair. More particularly, the present invention relates to repair of valves of the heart and venous valves. 
         [0004]    Mitral valve regurgitation is characterized by retrograde flow from the left ventricle of a heart through an incompetent mitral valve into the left atrium. During a normal cycle of heart contraction (systole), the mitral valve acts as a check valve to prevent flow of oxygenated blood back into the left atrium. In this way, the oxygenated blood is pumped into the aorta through the aortic valve. Regurgitation of the valve can significantly decrease the pumping efficiency of the heart, placing the patient at risk of severe, progressive heart failure. 
         [0005]    Mitral valve regurgitation can result from a number of different mechanical defects in the mitral valve or the left ventricular wall. The valve leaflets, the valve chordae which connect the leaflets to the papillary muscles, the papillary muscles or the left ventricular wall may be damaged or otherwise dysfunctional. Commonly, the valve annulus may be damaged, dilated, or weakened limiting the ability of the mitral valve to close adequately against the high pressures of the left ventricle. 
         [0006]    The most common treatments for mitral valve regurgitation rely on valve replacement or repair including leaflet and annulus remodeling, the latter generally referred to as valve annuloplasty. A recent technique for mitral valve repair which relies on suturing adjacent segments of the opposed valve leaflets together is referred to as the “bow-tie” or “edge-to-edge” technique. While all these techniques can be very effective, they usually rely on open heart surgery where the patient&#39;s chest is opened, typically via a sternotomy, and the patient placed on cardiopulmonary bypass. The need to both open the chest and place the patient on bypass is traumatic and has associated high mortality and morbidity. More recently, minimially invasive catheter based procedures have been developed to deliver implantable clips to the incompetent valve. These clips are used to fasten a portion of the valve leaflets together, thereby reducing the regurgitation. While the clips appear to be promising, delivery and deployment of the clip can be challenging. In some situations, it may be challenging to visualize the clip and valve leaflets using techniques such as fluoroscopy and echocardiography. Therefore, improved attachment mechanisms and attachment evaluation methods would be desirable. 
         [0007]    For these reasons, it would be desirable to provide improved methods, devices, and systems for performing the repair of mitral and other cardiac valves. Such methods, devices, and systems should preferably not require open chest access and be capable of being performed either endovascularly, i.e., using devices which are advanced to the heart from a point in the patient&#39;s vasculature remote from the heart or by a minimally invasive approach. Further, such devices and systems should provide features which allow easier delivery of fixation devices, as well as repositioning and optional removal of the fixation device prior to fixation to ensure optimal placement. Still more preferably, the methods, devices, and systems would be useful for repair of tissues in the body other than heart valves. At least some of these objectives will be met by the inventions described hereinbelow. 
         [0008]    2. Description of the Related Art 
         [0009]    Minimally invasive and percutaneous techniques for coapting and modifying mitral valve leaflets to treat mitral valve regurgitation are described in PCT Publication Nos. WO 98/35638; WO 99/00059; WO 99/01377; and WO 00/03759. 
         [0010]    Maisano et al. (1998)  Eur. J. Cardiothorac. Surg.  13:240-246; Fucci et al. (1995)  Eur. J. Cardiothorac. Surg.  9:621-627; and Umana et al. (1998)  Ann. Thorac. Surg.  66:1640-1646, describe open surgical procedures for performing “edge-to-edge” or “bow-tie” mitral valve repair where edges of the opposed valve leaflets are sutured together to lessen regurgitation. Dec and Fuster (1994)  N. Engl. J. Med.  331:1564-1575 and Alvarez et al. (1996)  J. Thorac. Cardiovasc. Surg.  112:238-247 are review articles discussing the nature of and treatments for dilated cardiomyopathy. 
         [0011]    Mitral valve annuloplasty is described in the following publications. Bach and Bolling (1996)  Am. J. Cardiol.  78:966-969; Kameda et al. (1996)  Ann. Thorac. Surg.  61:1829-1832; Bach and Bolling (1995)  Am. Heart J.  129:1165-1170; and Bolling et al. (1995) 109:676-683. Linear segmental annuloplasty for mitral valve repair is described in Ricchi et al. (1997)  Ann. Thorac. Surg.  63:1805-1806. Tricuspid valve annuloplasty is described in McCarthy and Cosgrove ( 1997 )  Ann. Thorac. Surg.  64:267-268; Tager et al. (1998)  Am. J. Cardiol.  81:1013-1016; and Abe et al. (1989)  Ann. Thorac. Surg.  48:670-676. 
         [0012]    Percutaneous transluminal cardiac repair procedures are described in Park et al. (1978)  Circulation  58:600-608; Uchida et al. (1991)  Am. Heart J.  121: 1221-1224; and Ali Khan et al. (1991)  Cathet. Cardiovasc. Diagn.  23:257-262. 
         [0013]    Endovascular cardiac valve replacement is described in U.S. Pat. Nos. 5,840,081; 5,411,552; 5,554,185; 5,332,402; 4,994,077; and 4,056,854. See also U.S. Pat. No. 3,671,979 which describes a catheter for temporary placement of an artificial heart valve. 
         [0014]    Other percutaneous and endovascular cardiac repair procedures are described in U.S. Pat. Nos. 4,917,089; 4,484,579; and 3,874,338; and PCT Publication No. WO 91/01689. 
         [0015]    Thoracoscopic and other minimally invasive heart valve repair and replacement procedures are described in U.S. Pat. Nos. 5,855,614; 5,829,447; 5,823,956; 5,797,960; 5,769,812; and 5,718,725. 
       SUMMARY OF THE INVENTION 
       [0016]    Exemplary embodiments of the present invention overcome the above disadvantages and other disadvantages not described above. Also, the present invention is not required to overcome the disadvantages described above, and an exemplary embodiment of the present invention may not overcome any of the problems described above. Aspects of the invention provide devices, systems and methods for tissue approximation and repair at treatment sites. The devices, systems and methods of the invention will find use in a variety of therapeutic procedures, including endovascular, minimally-invasive, and open surgical procedures, and can be used in various anatomical regions, including the abdomen, thorax, cardiovascular system, heart, intestinal tract, stomach, urinary tract, bladder, lung, and other organs, vessels, and tissues. The invention is particularly useful in those procedures requiring minimally-invasive or endovascular access to remote tissue locations, where the instruments utilized must negotiate long, narrow, and tortuous pathways to the treatment site. In addition, many of the devices and systems of the invention are adapted to be reversible and removable from the patient at any point without interference with or trauma to internal tissues. 
         [0017]    According to certain aspects of the invention, the devices, systems and methods are adapted for fixation of tissue at a treatment site. Exemplary tissue fixation applications include cardiac valve repair, septal defect repair, vascular ligation and clamping, laceration repair and wound closure, but the invention may find use in a wide variety of tissue approximation and repair procedures. In one embodiment, the devices, systems and methods of the invention are adapted for repair of cardiac valves, and particularly the mitral valve, as a therapy for regurgitation. The invention enables two or more valve leaflets to be coapted using an “edge-to-edge” or “bow-tie” technique to reduce regurgitation, yet does not require open heart surgery through the chest and heart wall as in conventional approaches. Using the devices, systems and methods of the invention, the mitral valve can be accessed from a remote surgical or vascular access point and the two valve leaflets may be coapted using endovascular or minimally invasive approaches. In some circumstances the invention may also find application in open surgical approaches as well. According certain aspects of the invention, the mitral valve may be approached either from the atrial side (antegrade approach) or the ventricular side (retrograde approach), and either through blood vessels or through the heart wall. 
         [0018]    The devices, systems and methods of the invention are centered on variety of devices which may be used individually or in a variety of combinations to form interventional systems. In preferred embodiments, the interventional system includes a multi-catheter guiding system, a delivery catheter and an interventional device. Each of these components will be discussed herein. 
         [0019]    According to one aspect of the invention, a fixation system for engaging tissue comprises an implantable fixation device comprising a pair of fixation elements each having a first end, a free end opposite the first end, and an engagement surface therebetween for engaging the tissue. The first ends are movably coupled together such that the fixation elements are moveable between a closed position, wherein the engagement surfaces face each other, to a first open position wherein the engagement surfaces are positioned away from each other. The fixation system also comprises an actuation mechanism coupled to the fixation elements adapted to move the fixation elements between the closed position and the first open position and a pair of gripping elements comprising a first gripping element and a second gripping element. Each of the gripping elements is moveable with respect to one of the fixation elements and configured to be moved in opposition to one of the engagement surfaces so as to capture tissue therebetween. The fixation system also comprises a first gripper actuator releasably coupled to the implantable fixation device and configured to individually actuate the gripping elements. The free ends of the fixation elements are moveably coupled to move between a closed position where the engagement surfaces face each other and a closed position where the engagement surfaces face away from one another. The fixation elements may each have a concave portion for receiving a corresponding one of the pair of gripping elements when the gripping elements are moved into opposition to one of the engagement surfaces. 
         [0020]    The first gripping actuator may be releasably coupled to the implantation fixation device and actuatable between a first configuration and a second configuration that moves the first gripping element toward a first fixation element of the pair of fixation elements. The first gripper actuator may also be actuatable between the second configuration and a third configuration that moves the second gripping element toward a second fixation element of the pair of fixation elements independently of the movement of the first gripping element. 
         [0021]    The elongate delivery shaft may comprise a proximal portion and a distal portion, wherein the distal portion is releasably coupled to the proximal portion of the implantable fixation device. The gripper actuator may comprise a proximal end and a distal end, the distal end being releasably coupled to at least one of the proximal end of the implantable fixation device or the distal end of the elongate delivery shaft. The gripper actuator may further comprise a gripper line that extends from the proximal end of the delivery shaft and which is coupled to each of the first gripping element and the second gripping element at portions of the gripper line between the proximal end of the delivery shaft and releasably coupled to at least one of the proximal end of the implantable fixation device or the distal end of the elongate delivery shaft. 
         [0022]    According to another aspect, the gripper line may be actuated by tension on the gripper line and configured to apply a different resultant force the each of the first gripping element and the second gripping element to induce the individual activation of the gripping elements at different levels of tension. The gripper actuator may be configured to be released from the implantable fixation device when the elongate delivery shaft is decoupled from the implantable fixation device. 
         [0023]    According to another aspect, a fixation system for engaging tissue may comprise an implantable fixation device comprising a pair of fixation elements including a first fixation element and a second fixation element, each having a first end, a free end opposite the first end, and an engagement surface therebetween for engaging the tissue. The first ends may be movably coupled together such that the fixation elements are moveable between a closed position, wherein the engagement surfaces face each other, to a first open position wherein the engagement surfaces are positioned away from each other. An actuation mechanism may be coupled to the fixation elements and adapted to move the fixation elements between the closed position and the first open position. The fixation system may also include a pair of gripping elements comprising a first gripping element and a second gripping element, each of the gripping elements configured to be moveable with respect to one of the fixation elements and configured to be moved in opposition to one of the engagement surfaces so as to capture tissue therebetween. The fixation system may comprise a first gripper actuator releasably coupled to the implantable fixation device and configured to actuate the first gripping element, the first gripper actuator having a first configuration and a second configuration, wherein actuating the first gripper actuator between the first configuration and the second configuration moves the first gripping element with respect to the first fixation element. A second gripper actuator may also be releasably coupled to the implantable fixation device and configured to actuate the second gripping element, the second gripper actuator having first configuration and a second configuration, wherein actuating second gripper actuator between the first configuration and the second configuration moves the first gripping element with respect to the first fixation element. The first gripper actuator and the second gripper actuator may be actuatable between the first configuration and the second configuration independently of each other. 
         [0024]    The first gripper actuator may comprise a first gripper line having a proximal end and a distal end, and the second gripper actuator may comprise a second gripper line having a proximal end and a distal end. The distal portions of the first gripper line and the second gripper line may be releasably coupled to the implantable fixation device. 
         [0025]    The fixation system may also comprise an elongate delivery shaft having a proximal portion and a distal portion, wherein the distal portion of the elongate delivery shaft is releasably coupled to a proximal portion of the fixation device. The first gripper actuator may comprise a first gripper line having a proximal end and a distal end, and the second gripper actuator may comprise a second gripper line having a proximal end and a distal end, wherein the distal portions of the first gripper line and the second gripper line are releasably coupled to at least one of the proximal end of the implantable fixation device or the distal end of the elongate delivery shaft. The first gripper actuator and the second gripper actuator may be configured to be released from the at least one of the proximal end of the implantable fixation device or the distal end of the elongate delivery shaft when the elongate delivery shaft is decoupled from the implantable fixation device. 
         [0026]    The fixation system may also comprise a gripper pusher releasably coupled to the implantable fixation device adjacent the pair of gripping elements, the gripper pusher having an expanded configuration and a collapsed configuration. Also, when in the expanded configuration the gripper pusher may be configured to engage the pair of gripping elements and advances the pair of gripping elements toward the engagement surfaces of the fixation elements. On the other hand, when in the collapsed configuration the gripper pusher has a reduced radial profile relative to the gripper pusher radial profile in the expanded configuration thereby allowing the pair of gripping elements to move away from the engagement surfaces of the fixation elements. The first gripping actuator may be releasably coupled to the implantation fixation device and be actuatable between a first configuration and a second configuration that moves the first gripping element toward a first fixation element of the pair of fixation elements. The first gripper actuator may also be actuatable between the second configuration and a third configuration that moves the second gripping element toward a second fixation element of the pair of fixation elements independently of the movement of the first gripping element. 
         [0027]    According to another aspect, a distal portion of the gripper pusher may be releasably attached to the implantable fixation device. The gripper pusher may comprise a pair of elongate flexible arms and a shaft of the implantable fixation device includes apertures for releasably engaging a distal end of each of the pair of elongate flexible arms. Also, a proximal portion of the implantable fixation device may comprise a pair of apertures, wherein the distal portion of the elongate delivery shaft comprises a pair of L-shaped ends resiliently biased to fit into the pair of apertures, and wherein the distal ends of the pair of elongate flexible arms are releasably coupled to the implantable fixation device by being fitted into the apertures and with the pair of L-shaped ends. The fixation system may also comprise an actuation rod configured to extend through the elongate delivery shaft and into the implantable fixation device to actuate the pair of fixation elements, wherein the fixation system is configured such that withdrawal of the actuation rod from the implantable fixation device releases the L-shaped ends and the distal ends of the pair of elongate flexible arms from the implantable fixation device. 
         [0028]    According to another aspect, the first gripper actuator and the second gripper actuator each comprise distal ends, wherein placing the distal ends of the first gripper actuator and the second gripper actuator adjacent the distal portion of the elongate deliver shaft and coupling the distal portion of the elongate delivery shaft to the proximal portion of the fixation device locks the distal ends of the first gripper actuator and the second gripper actuator in position. The distal ends of the first gripper actuator and the second gripper actuator may comprise a narrow portion and a wide portion, and the elongate delivery shaft and the fixation device may be shaped to form hollow portions that when coupled together hold the wide portion of the first gripper actuator and the second gripper actuator in position. 
         [0029]    According to another aspect, the distal ends of the first gripper actuator and the second gripper actuator may comprise a narrow portion and a wide portion and the elongate delivery shaft may comprise open slots having a width narrower than the wide portion of the first and second gripper actuators. The fixation device may be configured to closes the open slots when coupled to the elongate delivery shaft to hold the first gripper actuator and the second gripper actuator in position. 
         [0030]    According to another aspect, the fixation system may comprise a covering assembly coupled to and disposed over the distal portion of the elongate delivery shaft. The covering assembly may comprise an outer slideable section and an inner section having a T-shaped opening such that the first gripper actuator is releasably coupled to the fixation device by sliding a T-shaped distal end of the first gripper actuator into the T-shaped opening of the inner section of the covering assembly and sliding the outer slideable section to cover the T-shaped openings. 
         [0031]    According to another aspect, the fixation system may comprise an actuator rod that extends through the delivery shaft and into the implantable fixation device to actuate the pair of fixation elements. The delivery shaft may comprise opening portions and liners disposed inside of the delivery shaft configured to occlude the opening portions. The pair of gripper actuators may be disposed in a corresponding one of the opening portions and fixed by the liners when the actuator rod is extended into the implantable fixation device and released by the liners when the actuator rod is withdraw from the implantable fixation device. The liner may be hingedly attached to the delivery shaft. 
         [0032]    The fixation system may further comprise an actuator rod that extends through the delivery shaft and into the implantable fixation device to actuate the pair of fixation elements. The delivery shaft may comprise opening portions and spring members disposed on the exterior of the delivery shaft having bent portions that extend into the opening portions, each spring member having a notched end and the notched ends of the spring members being configured to abut to form an opening sized to releasably engage the first gripper actuator. The actuator rod may have a taper shape configured to press the bent portions when the actuator rod is withdrawn from the implantable fixation device to release the first gripper actuator by causing the notched ends to separate. 
         [0033]    According to another aspect, a method for fixing tissue is provided. The method comprises providing an implantable fixation device comprising a pair of fixation elements each having a first end, a free end opposite the first end, and an engagement surface therebetween for engaging the tissue, the first ends being movably coupled together such that the fixation elements are moveable between a closed position wherein the engagement surfaces face each other to a first open position wherein the engagement surfaces are positioned away from each other; an actuation mechanism coupled to the fixation elements adapted to move the fixation elements between the closed position and the first open position; and a pair of gripping elements comprising a first gripping element and a second gripping element, each of the gripping elements moveable with respect to one of the fixation elements and configured to be moved in opposition to one of the engagement surfaces so as to capture tissue therebetween. The method also comprises positioning the fixation elements so that tissue is disposed between the pair of gripping elements and the engagement surfaces of the pair of fixation element; and activating a first gripper actuator to individually actuate the first gripping elements to grasp tissue between the first gripping element and one of the fixation elements. 
         [0034]    Other aspects of the nature and advantages of the invention are set forth in the detailed description set forth below, taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The above and other aspects and features of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0036]      FIG. 1  illustrates the left ventricle and left atrium of the heart during systole. 
           [0037]      FIG. 2A  illustrates free edges of leaflets in normal coaptation, and  FIG. 2B  illustrates the free edges in regurgitative coaptation. 
           [0038]      FIGS. 3A-3C  illustrate grasping of the leaflets with a fixation device, inversion of the distal elements of the fixation device and removal of the fixation device, respectively. 
           [0039]      FIG. 4  illustrates the position of the fixation device in a desired orientation relative to the leaflets. 
           [0040]      FIGS. 5A-5B  and  6 A- 6 B illustrate exemplary embodiments of coupling mechanisms of the instant application. 
           [0041]      FIGS. 7A-7B  and  8 A- 8 B illustrate the movement of fixation elements of an embodiment of the fixation device of the present invention. 
           [0042]      FIG. 9  illustrates another embodiment of the fixation device. 
           [0043]      FIGS. 10A-10B ,  11 A- 11 B,  12 A- 12 B,  13 A- 13 B and  14 - 16  illustrate the fixation device of  FIG. 7  in various possible positions during introduction and placement of the device within the body to perform a therapeutic procedure. 
           [0044]      FIGS. 17A-17C  illustrate the fixation device in various positions. 
           [0045]      FIGS. 18-19  illustrate an embodiment of the fixation device including proximal elements and a locking mechanism. 
           [0046]      FIGS. 20-21  provide a cross-sectional view of the locking mechanism in the unlocked and locked positions respectively. 
           [0047]      FIGS. 22-27  illustrate another embodiment of fixation device having a covering and independent actuation. 
           [0048]      FIG. 28  illustrates another embodiment of a fixation device including a gripper pusher. 
           [0049]      FIG. 29  illustrates an embodiment of a fixation device having independent proximal element actuation. 
           [0050]      FIG. 30  illustrates another embodiment of a fixation device having independent proximal element actuation. 
           [0051]      FIG. 31  illustrates another embodiment of a fixation device having independent proximal element actuation. 
           [0052]      FIG. 32  illustrates another embodiment of a fixation device having independent proximal element actuation. 
           [0053]      FIG. 33  illustrates another embodiment of a fixation device having independent proximal element actuation. 
           [0054]      FIGS. 34-35  illustrates another embodiment of a fixation device having independent proximal element actuation with a single actuator. 
           [0055]      FIGS. 36-40  illustrate the fixation device of  FIG. 9  with a gripper pusher. 
           [0056]      FIGS. 41-46  illustrate another embodiment of a fixation device of with a gripper pusher and independent actuation. 
           [0057]      FIG. 47  illustrates another embodiment of a fixation device having a gripper pusher and independent actuation. 
           [0058]      FIG. 48  illustrates another embodiment of a fixation device having a gripper pusher and independent actuation with a single actuator. 
           [0059]      FIGS. 49A-49C ,  50 A- 50 E,  51 A- 51 B and  52 A- 52 G illustrate various embodiments of coupling a proximal element line to a proximal element of a fixation device. 
           [0060]      FIGS. 53 ,  54 A-D,  55 A-C and  56 A-B illustrate an actuator rod and related components according an another embodiment of the fixation device. 
           [0061]      FIGS. 57 and 58  illustrate an embodiment for releasably coupling a gripper pusher to a fixation device. 
           [0062]      FIGS. 59A and 59B  illustrate the configuration of a proximal element actuator. 
           [0063]      FIGS. 60A and 60B  illustrate another configuration of a proximal element actuator. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0064]    I. Cardiac Physiology 
         [0065]    The left ventricle LV of a normal heart H in systole is illustrated in  FIG. 1 . The left ventricle LV is contracting and blood flows outwardly through the tricuspid (aortic) valve AV in the direction of the arrows. Back flow of blood or “regurgitation” through the mitral valve MV is prevented since the mitral valve is configured as a “check valve” which prevents back flow when pressure in the left ventricle is higher than that in the left atrium LA. The mitral valve MV comprises a pair of leaflets having free edges FE which meet evenly to close, as illustrated in  FIG. 1 . The opposite ends of the leaflets LF are attached to the surrounding heart structure along an annular region referred to as the annulus AN. The free edges FE of the leaflets LF are secured to the lower portions of the left ventricle LV through chordae tendinae CT (referred to hereinafter as the chordae) which include a plurality of branching tendons secured over the lower surfaces of each of the valve leaflets LF. The chordae CT in turn, are attached to the papillary muscles PM which extend upwardly from the lower portions of the left ventricle and intraventricular septum IVS. 
         [0066]    A number of structural defects in the heart can cause mitral valve regurgitation. Regurgitation occurs when the valve leaflets do not close properly allowing leakage from the ventricle into the atrium. As shown in  FIG. 2A , the free edges of the anterior and posterior leaflets normally meet along a line of coaptation C. An example of a defect causing regurgitation is shown in  FIG. 2B . Here an enlargement of the heart causes the mitral annulus to become enlarged, making it impossible for the free edges FE to meet during systole. This results in a gap G which allows blood to leak through the valve during ventricular systole. Ruptured or elongated chordae can also cause a valve leaflet to prolapse since inadequate tension is transmitted to the leaflet via the chordae. While the other leaflet maintains a normal profile, the two valve leaflets do not properly meet and leakage from the left ventricle into the left atrium will occur. Such regurgitation can also occur in patients who have suffered ischemic heart disease where the left ventricle does not contract sufficiently to effect proper closure. 
         [0067]    II. General Overview 
         [0068]    Aspects of the present invention provides methods and devices for grasping, approximating and fixating tissues such as valve leaflets to treat cardiac valve regurgitation, particularly mitral valve regurgitation. The present invention also provides features that allow repositioning and removal of the device if so desired, particularly in areas where removal may be hindered by anatomical features such as chordae CT. Such removal would allow the surgeon to reapproach the valve in a new manner if so desired. 
         [0069]    Grasping will preferably be atraumatic providing a number of benefits. By atraumatic, it is meant that the devices and methods of the invention may be applied to the valve leaflets and then removed without causing any significant clinical impairment of leaflet structure or function. The leaflets and valve continue to function substantially the same as before the invention was applied. Thus, some minor penetration or denting of the leaflets may occur using the invention while still meeting the definition of “atraumatic”. This enables the devices of the invention to be applied to a diseased valve and, if desired, removed or repositioned without having negatively affected valve function. In addition, it will be understood that in some cases it may be necessary or desirable to pierce or otherwise permanently affect the leaflets during either grasping, fixing or both. In some of these cases, grasping and fixation may be accomplished by a single device. Although a number of embodiments are provided to achieve these results, a general overview of the basic features will be presented herein. Such features are not intended to limit the scope of the invention and are presented with the aim of providing a basis for descriptions of individual embodiments presented later in the application. 
         [0070]    The devices and methods of the invention rely upon the use of an interventional tool that is positioned near a desired treatment site and used to grasp the target tissue. In endovascular applications, the interventional tool is typically an interventional catheter. In surgical applications, the interventional tool is typically an interventional instrument. In preferred embodiments, fixation of the grasped tissue is accomplished by maintaining grasping with a portion of the interventional tool which is left behind as an implant. While the invention may have a variety of applications for tissue approximation and fixation throughout the body, it is particularly well adapted for the repair of valves, especially cardiac valves such as the mitral valve. Referring to  FIG. 3A , an interventional tool  10 , having a delivery device, such as a shaft  12 , and a fixation device  14 , is illustrated having approached the mitral valve MV from the atrial side and grasped the leaflets LF. The mitral valve may be accessed either surgically or by using endovascular techniques, and either by a retrograde approach through the ventricle or by an antegrade approach through the atrium, as described above. For illustration purposes, an antegrade approach is described. 
         [0071]    The fixation device  14  is releasably attached to the shaft  12  of the interventional tool  10  at its distal end. When describing the devices of the invention herein, “proximal” shall mean the direction toward the end of the device to be manipulated by the user outside the patient&#39;s body, and “distal” shall mean the direction toward the working end of the device that is positioned at the treatment site and away from the user. With respect to the mitral valve, proximal shall refer to the atrial or upstream side of the valve leaflets and distal shall refer to the ventricular or downstream side of the valve leaflets. 
         [0072]    The fixation device  14  typically comprises proximal elements  16  (or gripping elements) and distal elements  18  (or fixation elements) which protrude radially outward and are positionable on opposite sides of the leaflets LF as shown so as to capture or retain the leaflets therebetween. The proximal elements  16  are preferably comprised of cobalt chromium, nitinol or stainless steel, and the distal elements  18  are preferably comprised of cobalt chromium or stainless steel, however any suitable materials may be used. The fixation device  14  is coupleable to the shaft  12  by a coupling mechanism  17 . The coupling mechanism  17  allows the fixation device  14  to detach and be left behind as an implant to hold the leaflets together in the coapted position. 
         [0073]    In some situations, it may be desired to reposition or remove the fixation device  14  after the proximal elements  16 , distal elements  18 , or both have been deployed to capture the leaflets LF. Such repositioning or removal may be desired for a variety of reasons, such as to reapproach the valve in an attempt to achieve better valve function, more optimal positioning of the device  14  on the leaflets, better purchase on the leaflets, to detangle the device  14  from surrounding tissue such as chordae, to exchange the device  14  with one having a different design, or to abort the fixation procedure, to name a few. To facilitate repositioning or removal of the fixation device  14  the distal elements  18  are releasable and optionally invertible to a configuration suitable for withdrawal of the device  14  from the valve without tangling or interfering with or damaging the chordae, leaflets or other tissue.  FIG. 3B  illustrates inversion wherein the distal elements  18  are moveable in the direction of arrows  40  to an inverted position. Likewise, the proximal elements  16  may be raised, if desired. In the inverted position, the device  14  may be repositioned to a desired orientation wherein the distal elements may then be reverted to a grasping position against the leaflets as in  FIG. 3A . Alternatively, the fixation device  14  may be withdrawn (indicated by arrow  42 ) from the leaflets as shown in  FIG. 3C . Such inversion reduces trauma to the leaflets and minimizes any entanglement of the device with surrounding tissues. Once the device  14  has been withdrawn through the valve leaflets, the proximal and distal elements may be moved to a closed position or configuration suitable for removal from the body or for reinsertion through the mitral valve. 
         [0074]      FIG. 4  illustrates the position of the fixation device  14  in a desired orientation in relation to the leaflets LF. This is a short-axis view of the mitral valve MV from the atrial side, therefore, the proximal elements  16  are shown in solid line and the distal elements  18  are shown in dashed line. The proximal and distal elements  16 ,  18  are positioned to be substantially perpendicular to the line of coaptation C. The device  14  may be moved roughly along the line of coaptation to the location of regurgitation. The leaflets LF are held in place so that during diastole, as shown in  FIG. 4 , the leaflets LF remain in position between the elements  16 ,  18  surrounded by openings O which result from the diastolic pressure gradient. Advantageously, leaflets LF are coapted such that their proximal or upstream surfaces are facing each other in a vertical orientation, parallel to the direction of blood flow through mitral valve MV. The upstream surfaces may be brought together so as to be in contact with one another or may be held slightly apart, but will preferably be maintained in the vertical orientation in which the upstream surfaces face each other at the point of coaptation. This simulates the double orifice geometry of a standard surgical bow-tie repair. Color Doppler echo will show if the regurgitation of the valve has been reduced. If the resulting mitral flow pattern is satisfactory, the leaflets may be fixed together in this orientation. If the resulting color Doppler image shows insufficient improvement in mitral regurgitation, the interventional tool  10  may be repositioned. This may be repeated until an optimal result is produced wherein the leaflets LF are held in place. 
         [0075]    Once the leaflets are coapted in the desired arrangement, the fixation device  14  is then detached from the shaft  12  and left behind as an implant to hold the leaflets together in the coapted position. As mentioned previously, the fixation device  14  is coupled to the shaft  12  by a coupling mechanism  17 .  FIGS. 5A-5B ,  6 A- 6 B illustrate exemplary embodiments of such coupling mechanisms.  FIG. 5A  shows an upper shaft  20  and a detachable lower shaft  22  which are interlocked at a joining line or mating surface  24 . The mating surface  24  may have any shape or curvature which will allow or facilitate interlocking and later detachment. A snuggly fitting outer sheath  26  is positioned over the shafts  20 ,  22  to cover the mating surface  24  as shown.  FIG. 5B  illustrates detachment of the lower shaft  22  from the upper shaft  20 . This is achieved by retracting the outer sheath  26 , so that the mating surface  24  is exposed, which allows the shafts  20 ,  22  to separate. 
         [0076]    Similarly,  FIG. 6A  illustrates a tubular upper shaft  28  and a detachable tubular lower shaft  30  which are interlocked at a mating surface  32 . Again, the mating surface  32  may have any shape or curvature which will allow or facilitate interlocking and later detachment. The tubular upper shaft  28  and tubular lower shaft  30  form an outer member having an axial channel. A snuggly fitting rod  34  or inner member is inserted through the tubular shafts  28 ,  30  to bridge the mating surface  32  as shown.  FIG. 6B  illustrates detachment of the lower shaft  30  from the upper shaft  28 . This is achieved by retracting the rod  34  to a position above the mating surface  32  which in turn allows the shafts  28 ,  30  to separate. Other examples of coupling mechanisms are described and illustrated in copending U.S. patent application Ser. No. 09/894,493), incorporated herein by reference for all purposes. 
         [0077]    Similarly,  FIG. 6A  illustrates a tubular upper shaft  28  and a detachable tubular lower shaft  30  which are interlocked at a mating surface  32 . Again, the mating surface  32  may have any shape or curvature which will allow or facilitate interlocking and later detachment. The tubular upper shaft  28  and tubular lower shaft  30  form an outer member having an axial channel. A snuggly fitting rod  34  or inner member is inserted through the tubular shafts  28 ,  30  to bridge the mating surface  32  as shown.  FIG. 6B  illustrates detachment of the lower shaft  30  from the upper shaft  28 . This is achieved by retracting the rod  34  to a position above the mating surface  32  which in turn allows the shafts  28 ,  30  to separate. Other examples of coupling mechanisms are described and illustrated in copending U.S. patent application Ser. No. 09/894,493, incorporated herein by reference for all purposes. 
         [0078]    III. Fixation Device 
         [0079]    A. Introduction and Placement 
         [0080]    The fixation device  14  is delivered to the valve or the desired tissues with the use of a delivery device. The delivery device may be rigid or flexible depending on the application. For endovascular applications, the delivery device comprises a flexible delivery catheter which will be described in later sections. Typically, however, such a catheter comprises a shaft, having a proximal end and a distal end, and a fixation device releasably attached to its distal end. The shaft is usually elongate and flexible, suitable for intravascular introduction. Alternatively, the delivery device may comprise a shorter and less flexible interventional instrument which may be used for trans-thoracic surgical introduction through the wall of the heart, although some flexibility and a minimal profile will generally be desirable. A fixation device is releasably coupleable with the delivery device as illustrated in  FIG. 3A . The fixation device may have a variety of forms, a few embodiments of which will be described herein. 
         [0081]      FIGS. 7A-8B  illustrate an embodiment of a fixation device  14  in various positions or configurations.  FIG. 7A  illustrates the fixation device  14  in a closed configuration for delivery through the patient&#39;s vasculature and, in this example, through the mitral valve. The fixation device  14  includes a coupling member  19  which allows detachment of the fixation device  14  for implantation. In this example, the coupling member  19  is shown to include the lower shaft  22  and mating surface  24  of  FIGS. 5A-5B , and therefore the coupling member  19  would function similarly as described above. The fixation device  14  also includes a pair of opposed distal elements  18 , each distal element  18  having an engagement surface  50  facing inwardly toward the opposed distal element  18  in the closed configuration. Distal elements  18  preferably comprise elongate arms  53 , each arm having a proximal end  52  rotatably connected to the coupling member  19  and a free end  54 . Suitable connections for arms  53  to coupling member  19  include pins, living hinges, or other known rotational connection mechanisms. In the closed configuration of  FIG. 7A , free ends  54  point in a first direction such that the arms  53  and engagement surfaces  50  are nearly parallel to each other and to an axis  21 , and preferably are angled slightly inwardly toward each other. In a preferred embodiment, when tissue is not present between arms  53 , the arms  53  may be closed until free ends  54  either touch each other or engage shaft  12  when fixation device  14  is attached thereto, thereby minimizing the profile of the fixation device  14  for passage through a delivery device. 
         [0082]      FIGS. 7B-8A  illustrate the fixation device  14  in an open position wherein the engagement surfaces  50  are disposed at a separation angle  56  apart, wherein the separation angle  56  is typically up to approximately 180 degrees, preferably up to 90-180 degrees, and arms  53  are disposed generally symmetrically relative to axis  21 . The arms  53  may be moveable to the open position by a variety of actuation mechanisms. For example, a plunger or actuator rod may be advanced through the coupling member  19 , as indicated by arrow  62 , so as to engage a spring or spring loaded actuation mechanism  58  which is attached to the distal elements  18 . By exerting a force against the actuation mechanism  58 , the distal elements  18  are rotated relative to coupling member  19 . The distal elements  18  may be held in this open position by the actuator rod against the resistance provided by the spring of the actuation mechanism  58  which biases the distal elements  18  toward the closed position of  FIG. 7A  when the distal elements  18  are less than 180 degrees apart. The spring loading of the actuation mechanism  58  resists outward movement of the actuation mechanism  58  and urges the device  14  towards the closed position. 
         [0083]    In this embodiment, proximal elements  16  comprise resilient loop-shaped wire forms biased outwardly and attached to the coupling member  19  so as to be biased to an open position shown in  FIG. 8A  but moveable rotationally inwardly when arms  53  are closed. The wire forms may be flexible enough to be rigidly attached to coupling member  19  and resiliently deflectable inwardly, or they may be attached by a rotational coupling such as a pin or living hinge. In use, leaflets LF are positioned between the proximal elements  16  and distal elements  18 . Once, the leaflets LF are positioned between the proximal and distal elements  16 ,  18 , the distal elements  18  may be closed, compressing the leaflets between engagement surfaces  50  and proximal elements  18 . Depending upon the thickness of the leaflets, the arrangements of the leaflets, the position of the fixation device on the leaflets and other factors, the arms  53  may be maintained in the open position of  FIG. 7B , moved to the fully closed position of  FIG. 7A , or placed in any of various positions in between so as to coapt the leaflets LF and hold them in the desired position with the desired degree of force. In any case, the fixation device  14  will remain in place as an implant following detachment from the delivery catheter. 
         [0084]    In some situations, as previously mentioned, it may be desirable to reopen the fixation device  14  following initial placement. To reopen the device  14 , the actuator rod may be readvanced or reinserted through the coupling member  19  and readvanced to press against the actuation mechanism  58 , as previously indicated by arrow  62  in  FIG. 7B . Again, such advancement applies a force against the actuation mechanism  58  in the manner described above thus moving arms  53  outwardly to release force against leaflets and move engagement surfaces  50  away from proximal elements  16 . The leaflets are then free to move relative to fixation device  14 . The fixation device  14  may then be repositioned as desired and the actuator rod retracted to reclose the distal elements  18  to coapt the leaflets. 
         [0085]    Under some circumstances, it may be further desirable to withdraw the fixation device  14  back through the valve or completely from the patient following initial insertion through the valve. Should this be attempted with the clip in the closed or open positions illustrated in  FIGS. 7A-8A , there may be a risk that arms  53  could interfere or become entangled with the chordae, leaflets or other tissues. To avoid this, the fixation element  14  is preferably adapted for inversion of arms  53  so that free ends  54  point in a second direction, opposite to the first direction in which the free ends  54  pointed in the closed position, each arm  53  forming an obtuse angle relative to axis  21  as illustrated in  FIG. 8B . The arms  53  may be rotated so that the engagement surfaces  50  are disposed at a separation angle  56  of up to 360 degrees, and preferably at least up to 270 degrees. This may be accomplished by exerting a force against actuation mechanism  58  with a push rod or plunger extending through coupling member  19  as described above. In this embodiment, once the distal elements  18  have rotated beyond 180 degrees apart, the spring loading of the actuation mechanism  58  biases the distal elements  18  toward the inverted position. The spring loading of the actuation mechanism  58  resists outward movement of the actuation mechanism  58  and urges the device  14  towards the inverted position. 
         [0086]    With arms  53  in the inverted position, engagement surfaces  50  provide an atraumatic surface deflect tissues as the fixation device is withdrawn. This allows the device to be retracted back through the valve annulus without risk of injury to valvular and other tissues. In some cases, once the fixation device  14  has been pulled back through the valve, it will be desirable to return the device to the closed position for withdrawal of the device from the body (either through the vasculature or through a surgical opening). 
         [0087]    The embodiment illustrated in  FIGS. 7A-8B  is assembled from separate components composed of biocompatible materials. The components may be formed from the same or different materials, including but not limited to stainless steel or other metals, Elgiloy®, nitinol, titanium, tantalum, metal alloys or polymers. Additionally, some or all of these components may be made of bioabsorbable materials that will be absorbed by surrounding tissues or will dissolve into the bloodstream following implantation. It has been found that in mitral valve repair applications the fixation devices of the invention are completely surrounded by tissue within a few months of implantation, after which the devices could dissolve or be absorbed without negative impact to the repair. 
         [0088]      FIG. 9  illustrates another embodiment of a fixation device  14 . Here, the fixation device  14  is shown coupled to a shaft  12  to form an interventional tool  10 . The fixation device  14  includes a coupling member  19  and a pair of opposed distal elements  18 . The distal elements  18  comprise elongate arms  53 , each arm having a proximal end  52  rotatably connected to the coupling member  19  and a free end  54 . The free ends  54  have a rounded shape to minimize interference with and trauma to surrounding tissue structures. Preferably, each free end  54  defines a curvature about two axes, one being an axis  66  perpendicular to longitudinal axis of arms  53 . Thus, the engagement surfaces  50  have a cupped or concave shape to surface area in contact with tissue and to assist in grasping and holding the valve leaflets. This further allows arms  53  to nest around the shaft  12  in the closed position to minimize the profile of the device. Preferably, arms  53  are at least partially cupped or curved inwardly about their longitudinal axes  66 . Also, preferably, each free end  54  defines a curvature about an axis  67  perpendicular to axis  66  or the longitudinal axis of arms  53 . This curvature is a reverse curvature along the most distal portion of the free end  54 . Likewise, the longitudinal edges of the free ends  54  may flare outwardly. Both the reverse curvature and flaring minimize trauma to the tissue engaged therewith. 
         [0089]    In an embodiment suitable for mitral valve repair, the transverse width across engagement surfaces  50  (which determines the width of tissue engaged) is at least about 2 mm, usually 3-10 mm, and preferably about 4-6 mm. In some situations, a wider engagement is desired wherein the engagement surfaces  50  are larger, for example about 2 cm, or multiple fixation devices are used adjacent to each other. Arms  53  and engagement surfaces  50  are configured to engage a length of tissue of about 4-10 mm, and preferably about 6-8 mm along the longitudinal axis of arms  53 . Arms  53  further include a plurality of openings to enhance grip and to promote tissue ingrowth following implantation. 
         [0090]    The valve leaflets are grasped between the distal elements  18  and proximal elements  16 . In some embodiments, the proximal elements  16  are flexible, resilient, and cantilevered from coupling member  19 . The proximal elements are preferably resiliently biased toward the distal elements. Each proximal element  16  is shaped and positioned to be at least partially recessed within the concavity of the distal element  18  when no tissue is present. When the fixation device  14  is in the open position, the proximal elements  16  are shaped such that each proximal element  16  is separated from the engagement surface  50  near the proximal end  52  of arm  53  and slopes toward the engagement surface  50  near the free end  54  with the free end of the proximal element contacting engagement surface  50 , as illustrated in  FIG. 9 . This shape of the proximal elements  16  accommodates valve leaflets or other tissues of varying thicknesses. 
         [0091]    Proximal elements  16  include a plurality of openings  63  and scalloped side edges  61  to increase grip on tissue. The proximal elements  16  optionally include frictional accessories, frictional features or grip-enhancing elements to assist in grasping and/or holding the leaflets. In preferred embodiments, the frictional accessories comprise barbs  60  having tapering pointed tips extending toward engagement surfaces  50 . It may be appreciated that any suitable frictional accessories may be used, such as prongs, windings, bands, barbs, grooves, channels, bumps, surface roughening, sintering, high-friction pads, coverings, coatings or a combination of these. Optionally, magnets may be present in the proximal and/or distal elements. It may be appreciated that the mating surfaces will be made from or will include material of opposite magnetic charge to cause attraction by magnetic force. For example, the proximal elements and distal elements may each include magnetic material of opposite charge so that tissue is held under constant compression between the proximal and distal elements to facilitate faster healing and ingrowth of tissue. Also, the magnetic force may be used to draw the proximal elements  16  toward the distal elements  18 , in addition to or alternatively to biasing of the proximal elements toward the distal elements. This may assist in deployment of the proximal elements  16 . In another example, the distal elements  18  each include magnetic material of opposite charge so that tissue positioned between the distal elements  18  is held therebetween by magnetic force. 
         [0092]    The proximal elements  16  may be covered with a fabric or other flexible material as described below to enhance grip and tissue ingrowth following implantation. Preferably, when fabrics or coverings are used in combination with barbs or other frictional features, such features will protrude through such fabric or other covering so as to contact any tissue engaged by proximal elements  16 . 
         [0093]    In an exemplary embodiment, proximal elements  16  are formed from metallic sheet of a spring-like material using a stamping operation which creates openings  63 , scalloped edges  61  and barbs  60 . Alternatively, proximal elements  16  could be comprised of a spring-like material or molded from a biocompatible polymer. It should be noted that while some types of frictional accessories that can be used in the present invention may permanently alter or cause some trauma to the tissue engaged thereby, in a preferred embodiment, the frictional accessories will be atraumatic and will not injure or otherwise affect the tissue in a clinically significant way. For example, in the case of barbs  60 , it has been demonstrated that following engagement of mitral valve leaflets by fixation device  14 , should the device later be removed during the procedure barbs  60  leave no significant permanent scarring or other impairment of the leaflet tissue and are thus considered atraumatic. 
         [0094]    The fixation device  14  also includes an actuation mechanism  58 . In this embodiment, the actuation mechanism  58  comprises two link members or legs  68 , each leg  68  having a first end  70  which is rotatably joined with one of the distal elements  18  at a riveted joint  76  and a second end  72  which is rotatably joined with a stud  74 . The legs  68  are preferably comprised of a rigid or semi-rigid metal or polymer such as Elgiloy®, cobalt chromium or stainless steel, however any suitable material may be used. While in the embodiment illustrated both legs  68  are pinned to stud  74  by a single rivet  78 , it may be appreciated, however, that each leg  68  may be individually attached to the stud  74  by a separate rivet or pin. The stud  74  is joinable with an actuator rod  64  (not shown) which extends through the shaft  12  and is axially extendable and retractable to move the stud  74  and therefore the legs  68  which rotate the distal elements  18  between closed, open and inverted positions. Likewise, immobilization of the stud  74  holds the legs  68  in place and therefore holds the distal elements  18  in a desired position. The stud  74  may also be locked in place by a locking feature which will be further described in later sections. 
         [0095]    In any of the embodiments of fixation device  14  disclosed herein, it may be desirable to provide some mobility or flexibility in distal elements  18  and/or proximal elements  16  in the closed position to enable these elements to move or flex with the opening or closing of the valve leaflets. This provides shock absorption and thereby reduces force on the leaflets and minimizes the possibility for tearing or other trauma to the leaflets. Such mobility or flexibility may be provided by using a flexible, resilient metal or polymer of appropriate thickness to construct the distal elements  18 . Also, the locking mechanism of the fixation device (described below) may be constructed of flexible materials to allow some slight movement of the proximal and distal elements even when locked. Further, the distal elements  18  can be connected to the coupling mechanism  19  or to actuation mechanism  58  by a mechanism that biases the distal element into the closed position (inwardly) but permits the arms to open slightly in response to forces exerted by the leaflets. For example, rather than being pinned at a single point, these components may be pinned through a slot that allowed a small amount of translation of the pin in response to forces against the arms. A spring is used to bias the pinned component toward one end of the slot. 
         [0096]      FIGS. 10A-10B ,  11 A- 11 B,  12 A- 12 B,  13 A- 13 B, and  FIGS. 14-16  illustrate embodiments of the fixation device  14  of  FIG. 9  in various possible positions during introduction and placement of the device  14  within the body to perform a therapeutic procedure.  FIG. 10A  illustrates an embodiment of an interventional tool  10  delivered through a catheter  86 . It may be appreciated that the interventional tool  10  may take the form of a catheter, and likewise, the catheter  86  may take the form of a guide catheter or sheath. However, in this example the terms interventional tool  10  and catheter  86  will be used. The interventional tool  10  comprises a fixation device  14  coupled to a shaft  12  and the fixation device  14  is shown in the closed position.  FIG. 10B  illustrates a similar embodiment of the fixation device of  FIG. 10A  in a larger view. In the closed position, the opposed pair of distal elements  18  are positioned so that the engagement surfaces  50  face each other. Each distal element  18  comprises an elongate arm  53  having a cupped or concave shape so that together the arms  53  surround the shaft  12  and optionally contact each other on opposite sides of the shaft. This provides a low profile for the fixation device  14  which is readily passable through the catheter  86  and through any anatomical structures, such as the mitral valve. In addition,  FIG. 10B  further includes an actuation mechanism  58 . In this embodiment, the actuation mechanism  58  comprises two legs  68  which are each movably coupled to a base  69 . The base  69  is joined with an actuator rod  64  which extends through the shaft  12  and is used to manipulate the fixation device  14 . In some embodiments, the actuator rod  64  attaches directly to the actuation mechanism  58 , particularly the base  69 . However, the actuator rod  64  may alternatively attach to a stud  74  which in turn is attached to the base  69 . In some embodiments, the stud  74  is threaded so that the actuator rod  64  attaches to the stud  74  by a screw-type action. However, the rod  64  and stud  74  may be joined by any mechanism which is releasable to allow the fixation device  14  to be detached from shaft  12 . 
         [0097]      FIGS. 11A-11B  illustrate the fixation device  14  in the open position. In the open position, the distal elements  18  are rotated so that the engagement surfaces  50  face a first direction. Distal advancement of the stud  74  relative to coupling member  19  by action of the actuator rod  64  applies force to the distal elements  18  which begin to rotate around joints  76  due to freedom of movement in this direction. Such rotation and movement of the distal elements  18  radially outward causes rotation of the legs  68  about joints  80  so that the legs  68  are directly slightly outwards. The stud  74  may be advanced to any desired distance correlating to a desired separation of the distal elements  18 . In the open position, engagement surfaces  50  are disposed at an acute angle relative to shaft  12 , and are preferably at an angle of between 90 and 180 degrees relative to each other. In one embodiment, in the open position the free ends  54  of arms  53  have a span therebetween of about 10-20 mm, usually about 12-18 mm, and preferably about 14-16 mm. 
         [0098]    Proximal elements  16  are typically biased outwardly toward arms  53 . The proximal elements  16  may be moved inwardly toward the shaft  12  and held against the shaft  12  with the aid of proximal element lines  90  which can be in the form of sutures, wires, nitinol wire, rods, cables, polymeric lines, or other suitable structures. The proximal element lines  90  may be connected with the proximal elements  16  by threading the lines  90  in a variety of ways. When the proximal elements  16  have a loop shape, as shown in  FIG. 11A , the line  90  may pass through the loop and double back. When the proximal elements  16  have an elongate solid shape, as shown in  FIG. 11B , the line  90  may pass through one or more of the openings  63  in the element  16 . Further, a line loop  48  may be present on a proximal element  16 , also illustrated in  FIG. 11B , through which a proximal element line  90  may pass and double back. Such a line loop  48  may be useful to reduce friction on proximal element line  90  or when the proximal elements  16  are solid or devoid of other loops or openings through which the proximal element lines  90  may attach. A proximal element line  90  may attach to the proximal elements  16  by detachable means which would allow a single line  90  to be attached to a proximal element  16  without doubling back and would allow the single line  90  to be detached directly from the proximal element  16  when desired. Examples of such detachable means include hooks, snares, clips or breakable couplings, to name a few. By applying sufficient tension to the proximal element line  90 , the detachable means may be detached from the proximal element  16  such as by breakage of the coupling. Other mechanisms for detachment may also be used. Similarly, a lock line  92  may be attached and detached from a locking mechanism by similar detachable means. 
         [0099]    In the open position, the fixation device  14  can engage the tissue which is to be approximated or treated. The embodiment illustrated in  FIGS. 9-11  is adapted for repair of the mitral valve using an antegrade approach from the left atrium. The interventional tool  10  is advanced through the mitral valve from the left atrium to the left ventricle. The distal elements  18  are oriented to be perpendicular to the line of coaptation and then positioned so that the engagement surfaces  50  contact the ventricular surface of the valve leaflets, thereby grasping the leaflets. The proximal elements  16  remain on the atrial side of the valve leaflets so that the leaflets lie between the proximal and distal elements. In this embodiment, the proximal elements  16  have frictional accessories, such as barbs  60  which are directed toward the distal elements  18 . However, neither the proximal elements  16  nor the barbs  60  contact the leaflets at this time. 
         [0100]    The interventional tool  10  may be repeatedly manipulated to reposition the fixation device  14  so that the leaflets are properly contacted or grasped at a desired location. Repositioning is achieved with the fixation device in the open position. In some instances, regurgitation may also be checked while the device  14  is in the open position. If regurgitation is not satisfactorily reduced, the device may be repositioned and regurgitation checked again until the desired results are achieved. 
         [0101]    It may also be desired to invert the fixation device  14  to aid in repositioning or removal of the fixation device  14 .  FIGS. 12A-12B  illustrate the fixation device  14  in the inverted position. By further advancement of stud  74  relative to coupling member  19 , the distal elements  18  are further rotated so that the engagement surfaces  50  face outwardly and free ends  54  point distally, with each arm  53  forming an obtuse angle relative to shaft  12 . The angle between arms  53  is preferably in the range of about 270 to 360 degrees. Further advancement of the stud  74  further rotates the distal elements  18  around joints  76 . This rotation and movement of the distal elements  18  radially outward causes rotation of the legs  68  about joints  80  so that the legs  68  are returned toward their initial position, generally parallel to each other. The stud  74  may be advanced to any desired distance correlating to a desired inversion of the distal elements  18 . Preferably, in the fully inverted position, the span between free ends  54  is no more than about 20 mm, usually less than about 16 mm, and preferably about 12-14 mm. In this illustration, the proximal elements  16  remain positioned against the shaft  12  by exerting tension on the proximal element lines  90 . Thus, a relatively large space may be created between the elements  16 ,  18  for repositioning. In addition, the inverted position allows withdrawal of the fixation device  14  through the valve while minimizing trauma to the leaflets. Engagement surfaces  50  provide an atraumatic surface for deflecting tissue as the fixation device is retracted proximally. It should be further noted that barbs  60  are angled slightly in the distal direction (away from the free ends of the proximal elements  16 ), reducing the risk that the barbs will catch on or lacerate tissue as the fixation device is withdrawn. 
         [0102]    Once the fixation device  14  has been positioned in a desired location against the valve leaflets, the leaflets may then be captured between the proximal elements  16  and the distal elements  18 .  FIGS. 13A-13B  illustrate the fixation device  14  in such a position. Here, the proximal elements  16  are lowered toward the engagement surfaces  50  so that the leaflets are held therebetween. In  FIG. 13B , the proximal elements  16  are shown to include barbs  60  which may be used to provide atraumatic gripping of the leaflets. Alternatively, larger, more sharply pointed barbs or other penetration structures may be used to pierce the leaflets to more actively assist in holding them in place. This position is similar to the open position of  FIGS. 11A-11B , however the proximal elements  16  are now lowered toward arms  53  by releasing tension on proximal element lines  90  to compress the leaflet tissue therebetween. At any time, the proximal elements  16  may be raised and the distal elements  18  adjusted or inverted to reposition the fixation device  14 , if regurgitation is not sufficiently reduced. 
         [0103]    After the leaflets have been captured between the proximal and distal elements  16 ,  18  in a desired arrangement, the distal elements  18  may be locked to hold the leaflets in this position or the fixation device  14  may be returned to or toward a closed position. Such locking will be described in a later section.  FIG. 14  illustrates the fixation device  14  in the closed position wherein the leaflets (not shown) are captured and coapted. This is achieved by retraction of the stud  74  proximally relative to coupling member  19  so that the legs  68  of the actuation mechanism  58  apply an upwards force to the distal elements  18  which in turn rotate the distal elements  18  so that the engagement surfaces  50  again face one another. The released proximal elements  16  which are biased outwardly toward distal elements  18  are concurrently urged inwardly by the distal elements  18 . The fixation device  14  may then be locked to hold the leaflets in this closed position as described below. 
         [0104]    As shown in  FIG. 15 , the fixation device  14  may then be released from the shaft  12 . As mentioned, the fixation device  14  is releasably coupleable to the shaft  12  by coupling member  19 .  FIG. 15  illustrates the coupling structure, a portion of the shaft  12  to which the coupling member  19  of the fixation device  14  attaches. As shown, the proximal element lines  90  may remain attached to the proximal elements  16  following detachment from shaft  12  to function as a tether to keep the fixation device  14  connected with the catheter  86 . Optionally, a separate tether coupled between shaft  12  and fixation device  14  may be used expressly for this purpose while the proximal element lines  90  are removed. In any case, the repair of the leaflets or tissue may be observed by non-invasive visualization techniques, such as echocardiography, to ensure the desired outcome. If the repair is not desired, the fixation device  14  may be retrieved with the use of the tether or proximal element lines  90  so as to reconnect coupling member  19  with shaft  12 . 
         [0105]    In an exemplary embodiment, proximal element lines  90  are elongated flexible threads, wire, cable, sutures or lines extending through shaft  12 , looped through proximal elements  16 , and extending back through shaft  12  to its proximal end. When detachment is desired, one end of each line may be released at the proximal end of the shaft  12  and the other end pulled to draw the free end of the line distally through shaft  12  and through proximal element  16  thereby releasing the fixation device. 
         [0106]      FIG. 16  illustrates a released fixation device  14  in a closed position. As shown, the coupling member  19  remains separated from the shaft  12  of the interventional tool  10  and the proximal elements  16  are deployed so that tissue (not shown) may reside between the proximal elements  16  and distal elements  18 . 
         [0107]      FIGS. 17A-17C  illustrate a covering  100  on the fixation device  14  wherein the device  14  is in various positions.  FIG. 17A  shows the covering  100  encapsulating the distal elements  18  and the actuation mechanism  58  while the device  14  is in the open position. Thus, the engagement surfaces  50  are covered by the covering  100  which helps to minimize trauma on tissues and provides additional friction to assist in grasping and retaining tissues.  FIG. 17B  shows the device  14  of  FIG. 17A  in the inverted position. The covering  100  is loosely fitted and/or is flexible or elastic such that the device  14  can freely move to various positions and the covering  100  conforms to the contours of the device  14  and remains securely attached in all positions.  FIG. 17C  shows the device  14  in the closed position. Thus, when the fixation device  14  is left behind as an implant in the closed position, the exposed surfaces of the device  14  are substantially covered by the covering  100 . It may be appreciated that the covering  100  may cover specific parts of the fixation device  14  while leaving other parts exposed. For example, the covering  100  may comprise sleeves that fit over the distal elements  18  and not the actuation mechanism  58 , caps that fit over the distal ends  54  of the distal elements  18  or pads that cover the engagement surfaces  50 , to name a few. It may be appreciated that, the covering  100  may allow any frictional accessories, such as barbs, to be exposed. Also, the covering  100  may cover the proximal elements  16  and/or any other surfaces of the fixation device  14 . In any case, the covering  100  should be durable to withstand multiple introduction cycles and, when implanted within a heart, a lifetime of cardiac cycles. 
         [0108]    The covering  100  may alternatively be comprised of a polymer or other suitable materials dipped, sprayed, coated or otherwise adhered to the surfaces of the fixation device  14 . Optionally, the polymer coating may include pores or contours to assist in grasping the tissue and/or to promote tissue ingrowth. 
         [0109]    Any of the coverings  100  may optionally include drugs, antibiotics, anti-thrombosis agents, or anti-platelet agents such as heparin, COUMADIN® (Warfarin Sodium), to name a few. These agents may, for example, be impregnated in or coated on the coverings  100 . These agents may then be delivered to the grasped tissues surrounding tissues and/or bloodstream for therapeutic effects 
         [0110]    C. Fixation Device Locking Mechanisms 
         [0111]    As mentioned previously, the fixation device  14  optionally includes a locking mechanism for locking the device  14  in a particular position, such as an open, closed or inverted position or any position therebetween. It may be appreciated that the locking mechanism includes an unlocking mechanism which allows the device to be both locked and unlocked.  FIGS. 18-21  illustrate an embodiment of a locking mechanism  106 . Referring to  FIG. 18 , in this embodiment, the locking mechanism  106  is disposed between the coupling member  19  and the base  69  of the actuation mechanism  58 . The base  69  is fixedly attached to the stud  74  which extends through the locking mechanism  106 . The stud  74  is releasably attached to the actuator rod  64  which passes through the coupling member  19  and the shaft  12  of the interventional tool  10 . The base  69  is also connected to the legs  68  of the actuation mechanism  58  which are in turn connected to the distal elements  18 . 
         [0112]      FIG. 18  also illustrates the proximal elements  16 , which in this embodiment straddle the locking mechanism and join beneath the locking mechanism  106 . The proximal elements  16  are shown supported by proximal element lines  90 . The proximal elements  16  are raised and lowered by manipulation of the proximal element lines  90 . In addition, lock lines  92  are shown connected with a release harness  108  of the locking mechanism  106 . The lock lines  92  are used to lock and unlock the locking mechanism  106  as will be described below. The proximal element lines  90  and lock lines  92  may be comprised of any suitable material, typically wire, nitinol wire, cable, suture or thread, to name a few. In addition, the proximal element lines  90  and/or lock lines  92  may include a coating, such as parylene. Parylene is a vapor deposited pinhole free protective film which is conformal and biocompatible. It is inert and protects against moisture, chemicals, and electrical charge. 
         [0113]      FIG. 19  provides a front view of the locking mechanism  106  of  FIG. 18 . However, here the proximal elements  16  are supported by a single proximal element line  90  which is through both of the proximal elements  16 . In this arrangement both of the elements are raised and lowered simultaneously by action of a single proximal element line  90 . Whether the proximal elements  16  are manipulated individually by separate proximal element lines  90  or jointly by a single proximal element line  90 , the proximal element lines  90  may extend directly through openings in the proximal elements and/or through a layer or portion of a covering  100  on the proximal elements, or through a suture loop above or below a covering  100 . 
         [0114]      FIGS. 20-21  illustrate the locking mechanism  106  showing the locking mechanism  106  in the unlocked and locked positions respectively. Referring to  FIG. 20 , the locking mechanism  106  includes one or more wedging elements, such as rolling elements. In this embodiment, the rolling elements comprise a pair of barbells  110  disposed on opposite sides of the stud  74 , each barbell having a pair of generally cylindrical caps and a shaft therebetween. The barbells  110  and the stud  74  are preferably comprised of cobalt chromium or stainless steel, however any suitable material may be used. The barbells  110  are manipulated by hooked ends  112  of the release harness  108 . When an upwards force is applied to the harness  108  by the lock line  92  (illustrated in  FIG. 18 ), the hooked ends  112  raise the barbells  110  against a spring  114 , as shown in  FIG. 20 . This draws the barbells  110  up along a sidewall or sloping surface  116  which unwedges the barbells  110  from against the stud  74 . In this position, the stud  74  is free to move. Thus, when the lock line  92  raises or lifts the harness  108 , the locking mechanism  106  is in an unlocked position wherein the stud  74  is free to move the actuation mechanism  58  and therefore the distal elements  18  to any desired position. Release of the harness  108  by the lock line  92  transitions the locking mechanism  106  to a locked position, illustrated in  FIG. 21 . By releasing the upwards force on the barbells  110  by the hooked ends  112 , the spring  114  forces the barbells  110  downwards and wedges the barbells  110  between the sloping surface  116  and the stud  74 . This restricts motion of the stud  74 , which in turn locks the actuation mechanism  58  and therefore distal elements  18  in place. In addition, the stud  74  may include one or more grooves  82  or indentations which receive the barbells  110 . This may provide more rapid and positive locking by causing the barbells  110  to settle in a definite position, increase the stability of the locking feature by further preventing movement of the barbells  110 , as well as tangible indication to the user that the barbell has reached a locking position. In addition, the grooves  82  may be used to indicate the relative position of the distal elements  18 , particularly the distance between the distal elements  18 . For example, each groove  82  may be positioned to correspond with a 0.5 or 1.0 mm decrease in distance between the distal elements  18 . As the stud  74  is moved, the barbells  110  will contact the grooves  82 ; by counting the number of grooves  82  that are felt as the stud  74  is moved, the user can determine the distance between the distal elements  18  and can provide the desired degree of coaptation based upon leaflet thickness, geometry, spacing, blood flow dynamics and other factors. Thus, the grooves  82  may provide tactile feedback to the user. 
         [0115]    The locking mechanism  106  allows the fixation device  14  to remain in an unlocked position when attached to the interventional tool  10  during grasping and repositioning and then maintain a locked position when left behind as an implant. It may be appreciated, however, that the locking mechanism  106  may be repeatedly locked and unlocked throughout the placement of the fixation device  14  if desired. Once the final placement is determined, the lock line  92  and proximal element lines  90  are removed and the fixation device is left behind. 
         [0116]    While the above described embodiments of the invention utilize a push-to-open, pull-to-close mechanism for opening and closing distal elements  18 , it should be understood that a pull-to-open, push-to-close mechanism is equally possible. For example, distal elements  18  may be coupled at their proximal ends to stud  74  rather than to coupling member  19 , and legs  68  may be coupled at their proximal ends to coupling member  19  rather than to stud  74 . In this example, when stud  74  is pushed distally relative to coupling member  19 , distal elements  18  would close, while pulling on stud  74  proximally toward coupling member  19  would open distal elements  18 . 
         [0117]    D. Individual Actuation of Proximal Elements 
         [0118]    In another embodiment, with reference to  FIG. 9 , actuation of the proximal elements  16  may be accomplished by using one or more proximal element lines or actuators  90 . Such actuation can be achieved in various ways. For example, as shown in  FIG. 22A , the proximal element actuators  90 A and  90 B could be threaded through line loops  48 A and  48 B, which are disposed on the radially outward and proximal sides of the proximal elements  16 A and  16 B, respectively. The distal ends of proximal element actuators  90 A and  90 B may comprise closed loops  95 A and  95 B, which encircle the shaft  12  and the coupling member  19  shown in  FIG. 22A  as coupled together. As discussed above, the shaft  12  and the coupling member  19  can be releasably coupled together. To have the closed loops  95 A and  95 B surround shaft  12  and the coupling member  19 , the closed loops  95 A and  95 B are placed over the shaft  12  and/or the coupling member  19  prior to the coupling shaft  12  and the coupling member  19  together. When the closed loops  95 A and  95 B encircle the shaft  12  and the coupling member  19 , the closed loops  95 A and  95 B hold the distal ends of the proximal element actuators  90 A and  90 B in place relative to the shaft  12  and the coupling member  19  and restrict the degree to which the proximal element actuators  90 A and  90 B can be retracted. By being threaded through the line loops  48 A and  48 B, the proximal element actuators  90 A and  90 B are mechanically linked to the proximal elements  16 A and  16 B, respectively. Thus, as shown in  FIG. 23 , when the proximal element actuators  90 A and  90 B are retracted proximally in a direction  96 , they move the proximal elements  16 A and  16 B away from the distal elements  18 A and  18 B, respectively. Similarly, pushing the proximal element actuators  90 A and  90 B distally moves the proximal elements  16 A and  16 B toward the distal elements  18 A and  18 B. 
         [0119]    In another embodiment, to enable the proximal element actuators  90 A and  90 B to pull the proximal elements  16 A and  16 B proximally, as well as push the proximal elements  16 A and  16 B distally, each of the proximal element actuators  90 A and  90 B may be configured with a thin wire portion  90 D and a thick wire portion  90 E. The thin wire portions  90 D extend from the loops  48 A and  48 B to the thick wire portions  90 E. This thin wire portions  90 D enable the proximal element actuators  90 A and  90 B to be retracted through the line loops  48 A and  48 B when the proximal element actuators are pulled proximally. On the other hand, the thick wire portions  90 E have a stiffness that prevents these portions of the proximal element actuators  90 A and  90 B from passing through the loops  48 A and  48 B as the stiffer sections cannot easily bend to make the turn required to extend through the loops  48 A and  48 B toward the shaft  12 . Thus, when the proximal element actuators  90 A and  90 B are pushed to the point where the thick wire portions  90 E reach the loops  48 A and  48 B, the proximal element actuators  90 A and  90 B function to push the proximal elements  16 A and  16 B toward the distal elements  18 A and  18 B, respectively. 
         [0120]      FIGS. 59A and 59B  show an embodiment in which thick wire portions  90 E are formed by rolling an end of a round thin wire portion  90 D. In particular, the rolling of the round portion of the wire results in a cross section having a thick portion T3 formed as a result of rolling to reduce the round section thickness T1 to a thickness T2. This results in a substantially rectangular shaped cross section having the dimensions T2 and T3. Notably, T3 is greater than T1 and T2 is less than T1. As a result of this flattening of the end of the proximal element actuators  90 A and  90 B, the bending characteristics of the end portion is changed. That is, under a compressive load, the bending will tend to occur along the plane of the  FIG. 59A  and not in the plane of  FIG. 59B . The round portion (thin) may have a diameter in the range of 0.009 to 0.012 inches whereas the thick portion may have a width ranging from 0.013 to 0.02 inches. Also, as shown in  FIGS. 60A and 60B , the proximal element actuators  90 A and  90 B may be formed with multiple thick portions that thicken toward the distal end of the actuators. As shown in  FIG. 60B , TA&lt;TB&lt;TC&lt;TD. 
         [0121]    In another embodiment as shown in  FIG. 22B , as an alternative to using a thick/thin wire combination, the proximal element actuators  90 A and  90 B may comprise a thin wire contained within an outer tube  90 G. In this embodiment, instead of relying on a stiffer thick wire portion, the proximal element actuators include an outer tube  90 G to push the proximal elements  16 A and  16 B distally. The outer tube  90 G may comprise, for example, a braided polyamide tube. 
         [0122]    By using a thick wire portion or an outer tube, the proximal elements  16 A and  16 B can be pushed or position distally toward the distal elements with more force. In contrast, when configured such the proximal elements  16 A and  16 B are biased to extend distally in combination with only thin wire proximal element actuators  90 A and  90 B, the engaging force between the proximal elements  16 A and  16 B and the distal elements  18 A and  18 B decreases as the distal elements are moved distally, i.e., such as 120-180 degrees as shown in  FIG. 3B . However, when either a thick wire portion or an outer tube is introduced in the proximal elements  16 A and  16 B, the proximal elements may be pushed distally with more force. This provides more control and better positioning for capturing leaflets during the coapting of the leaflets. Further, when there is a relatively large gap between the leaflets, having the distal elements extending in a 180 degree alignment a shown in  FIG. 3B , enables the system to more easily capture the leaflets over this gap or separation. Moreover, the ability to push the proximal elements  16 A and  16 B over this range (120-180 degrees or more) to engage the distal elements  18 A and  18 B provides an response as well as improved geometry for leaflet grasping. 
         [0123]    The proximal element actuators  90 A and  90 B may be moved so that the proximal elements  16 A and  16 B are moved at a variety of angles and distances from the distal elements  18 A and  18 B. And, the degree to which the proximal element actuators  90 A and  90 B are pushed or pulled can be maintained to keep the positions of the proximal elements  16 A and  16 B have relative to the distal elements  18 . For example, as shown in  FIG. 24 , the proximal element actuators  90 A and  90 B are pulled proximally and maintained in the position shown so as to maintain the proximal elements  16 A and  16 B in an intermediate position relative to the distal elements  18 . This intermediate position is between a position in which the proximal elements  16 A and  16 B are biased toward and that in which the proximal elements  16 A and  16 B are fully retracted as in  FIG. 23 . As shown in  FIG. 27 , once the proximal elements  16 A and  16 B are in a desired position, the shaft  12  and the coupling member  19  can be decoupled so that proximal retraction of the proximal element actuators  90 A and/or  90 B decouples the proximal element lines from the proximal elements  16 . Thus, the fixation device  14  can be left in place while the shaft  12 , the proximal element actuators  90 A and  90 B, and other parts can be removed from a site of operation. As shown in  FIGS. 22 through 28 , the fixation device  14  typically includes a covering  100  substantially the same as discussed in  FIGS. 16A-16C  below. 
         [0124]    It may be desirable to provide for independent actuation of the proximal elements  16 A and  16 B. For example, as shown in  FIG. 25 , the proximal element actuator  90 A is proximally retracted and rotates the proximal element  16 A away from the distal element  18 A, while the proximal element actuator  90 B is pushed distally and rotates the proximal element  16 B toward the distal element  18 B. Similarly, as shown in  FIG. 26 , the proximal element actuator  90 A is left alone, allowing the proximal element  16 A to maintain the position it is biased toward, while the proximal element actuator  90 B is proximally retracted, moving the proximal element  16 B away from the distal element  18 B. Providing for the independent actuation of the proximal elements  16 A and  16 B allows leaflets to be independently grasped by the proximal elements  16 A and  16 B and the distal elements  18 A and  18 B. Thus, the fixation device  14  can coapt leaflets more easily and at more optimal locations. For example, as opposed to grasping two leaflets simultaneously, a first leaflet can be grasped at a desired position and the fixation device  14  can then be repositioned so that a second leaflet can be grasped at a more optimal position. Alternatively, leaflets may be still be simultaneously grasped if desired as the independently actuatable proximal element actuators can still be moved simultaneously. Also, after leaflets are grasped, they can be released and the leaflets can be grasped again, for example, if the leaflets are malcoapted at the first grasp. The embodiments described about may be utilized with either the s-lock or the 1-lock configurations described herein. 
         [0125]    Embodiments of the fixation device similar to the devices described above may include both a gripper pusher  81  and independently actuatable proximal elements  16 A and  16 B, as shown for example in  FIG. 28 . Having both a gripper pusher  81  and independently actuatable proximal elements  16 A and  16 B may allow the fixation device to have many of the advantages described above such as to more accurately and more strongly grasp leaflets. 
         [0126]    In another embodiment, the proximal element actuators  90 A and  90 B may each comprise a continuous loop that enters and exits the nose  318  of the shaft  302  as shown in  FIG. 18 . However, as shown in  FIGS. 29-33 , the proximal element actuators  90 A and  90 B may be coupled with the release harness  108  so that the lock lines  92  may be eliminated. 
         [0127]      FIG. 29  illustrates a configuration in which the proximal element actuator  90 A is looped through the end of proximal element  16 A and the release harness  108 . The other proximal element actuator  90 B is looped only through the proximal element  16 B. Thus, manipulation of the proximal element actuator  90 A in this embodiment will actuate the proximal element  16 A either proximally or distally to engage or disengage with tissue. After the tissue engagement is completed and the leaflets are properly coapted, the proximal element actuator  90 A may be further actuated to release the release harness  108  of the locking mechanism  106 . On the other hand, if it determined that the fixation device  14  requires repositioning, applying tension on the proximal element actuator  90 A will unlock the locking mechanism. Further actuation of the proximal element actuator  90 A may then cause the proximal element  16 A to disengage from the leaflet so that repositioning can be performed. 
         [0128]    In another embodiment, as illustrated in  FIG. 30 , the proximal element actuators  90 A and  90 B may be configured to cross the shaft  12  to provide better leverage for actuation. Again, in this configuration the proximal element actuator  90 A is looped through the end of proximal element  16 A and the release harness  108 . The other proximal element actuator  90 B is looped only through the proximal element  16 B. However, crossing the shaft in this manner changes the angular relationship between the point where the proximal element actuators  90 A and  90 B exit the nose  318  of the shaft  302  and where they connect to a corresponding proximal element  16 A and  16 B. As such, the resultant force of actuation on the proximal elements  16 A and  16 B is increased for a given amount of tension on the proximal element actuators  90 A and  90 B as shown in the configuration of  FIG. 29 . This arrangement also allows for elimination of the lock lines  92 . As illustrated in  FIG. 29 , each of the proximal element actuators  90 A and  90 B may straddle the shaft  12 . However, the lines may also be routed to cross on the same side of the shaft  12 . 
         [0129]      FIG. 31  shows another configuration of routing the proximal element actuators  90 A and  90 B. In this configuration, the proximal element actuator  90 A and proximal element actuator  90 B are each coupled with the one of the proximal elements  16 A and  16 B and the release harness  108 . While the embodiment shown in  FIG. 30  locks the fixation device  14  only after the proximal element  16 A is moved into an engagement position with a leaflet, the configuration of  FIG. 31  permits the operator to control the sequence of leaftlet engagement between proximal elements  16 A and  16 B. In other words, the proximal element actuator  90 A need not be actuated after locking the fixation device  14  in the event an operator merely elects to actuate proximal element  16 B. 
         [0130]      FIGS. 32 and 33  illustrate another possible configuration for the proximal element actuators  90 A and  90 B. Each proximal element actuator comprises a loop that exits from and returns to the nose  318 . However, in this case, the proximal element actuators  90 A and  90 B are each double threaded through the end of a corresponding one of the proximal elements  16 A and  16 B and then looped around the release harness  108 . In  FIG. 32  the proximal element actuator  90 A exits the nose  318  on a side of the nose  318  adjacent to the proximal element  16 A and the proximal element actuator  90 B exits the nose  318  on a side of the nose  318  adjacent to the proximal element  16 B. In an alternative configuration, the proximal element actuator  90 A exits the nose  318  on a side of the nose  318  opposite to the proximal element  16 A and the proximal element actuator  90 B exits the nose  318  on a side of the nose  318  opposite to the proximal element  16 B. Crossing the shaft in this manner changes the angular relationship between the point where the proximal element actuators  90 A and  90 B exit the nose  318  of the shaft  302  and where they connect to a corresponding proximal element  16 A and  16 B. As such, the resultant force of actuation on the proximal elements  16 A and  16 B is increased for a given amount of tension on the proximal element actuators  90 A and  90 B. 
         [0131]    In each of the embodiments of  FIGS. 29-33 , each of the proximal element actuators  90 A and  90 B may be formed of a single line, which may be formed of a single or multiple filaments, that extends from and returns to the nose  318  of the shaft  302 . However, in the embodiments of  FIGS. 32 and 33 , the proximal element actuators  90 A and  90 B may only extend from the nose  318  and then terminate at the coupling shaft  12  or the coupling member  19  as shown in  FIG. 24 . 
         [0132]    E. Individual Actuation of Proximal Elements/Single Actuator 
         [0133]    In other embodiments, sequential grasping may be accomplished by use of a single actuator.  FIG. 34  illustrates a configuration wherein a single proximal element actuator  90 , having a proximal end and a distal end, extends from the nose  318  of the shaft  302  to one of the proximal elements  16 A. It may be looped through an eyelet at a distal end of the proximal element  16 A or held by a suture at the same location. The same proximal element actuator  90  then extends across the coupling shaft  12  to the other proximal element  16 B where it is coupled to the distal end of this proximal element  16   b  in a manner similar to proximal element  16 A. The distal end of this proximal element actuator  90  extends to either of the coupling shaft  12  or the coupling member  19  where it is secured. In  FIG. 34  it is secured using a loop. However, the proximal element actuator may be releasable fixed to the fixing device  14  in accord in any of the embodiments disclosed below. 
         [0134]    By virtue of the geometry of this configuration, each proximal element  16 A and  16 B may be independently actuated and the proximal element actuator  90  may be released in tandem with the separation of the coupling member  19 . As illustrated in  FIG. 35 , due to the manner of routing the proximal element actuator  90 , the resultant forces F 1  and F 2  are at different angles. These resultant forces and their directions are based on the tension on the proximal element  90  and the direction (angle) at which the proximal element actuator  90  approaches and extends away from a corresponding proximal element  16  A or  16 B. The force that causes a corresponding proximal element to move is the component of the force that is perpendicular to the length of a corresponding proximal element. This perpendicular component is represented by F N1  and F N2 . A smaller angle (θ 1 , θ 2 ) between the resultant force and the perpendicular component leads to a larger perpendicular component. As illustrated in  FIG. 35 , because the angle θ 1  is smaller than the angle θ 2 , the perpendicular component F N1  will be larger that the perpendicular component F N2 . Accordingly, for a given amount of tension in the proximal element actuator  90 , proximal element  16 A will receive more moving force than proximal element  16 B. That means that proximal element  16 B will remain closed as proximal element  16 A opens, and proximal element  16 B will open after proximal element  16 A is fully opened. This allows for independent actuation of the proximal elements  16 A and  16 B using a single proximal element actuator  90 . 
         [0135]    F. Gripper Pusher to Engage Proximal Elements 
         [0136]    In some situations, the valve leaflets may fully or partially detach from the fixation device due to poor leaflet insertion between the proximal and distal elements. Evaluation of valve leaflet insertion in the fixation device is therefore performed using standard imaging technology such as echocardiography and fluoroscopy. However, depending on the angle and/or position of the proximal and distal elements relative to the delivery catheter, it can be challenging to assess the depth of valve leaflet insertion into the fixation device, or to differentiate between the leaflets and the proximal and distal elements of the fixation device. Visualization is therefore preferably performed with the distal elements in a more open configuration with the distal elements displaced from one another. However, since many current embodiments of the fixation device only permit the proximal elements to open up to an included angle of about 85°, the distal elements therefore must be closed up to an included angle of between about 45° and preferably 60° in order securely grasp the valve leaflets between the proximal and distal elements. While this configuration helps an operator visualize and differentiate between the valve leaflets and the fixation device, it is preferable to further open up the distal elements to an included angle of greater than 90°, and more preferably to 120° or more. Thus, it would be desirable to modify the proximal elements to open up further. 
         [0137]      FIGS. 36-40  illustrate an embodiment of a fixation device similar to the device of  FIGS. 7A-14 , with a major difference being that this embodiment includes a gripper pusher.  FIG. 36  illustrates fixation device  14  that generally takes the same form as fixation device  14  previously described. In addition to the features previously described, fixation device  14  also includes a gripper pusher  81 . The gripper pusher  81  deflects radially outward resulting in a bowed region  83  that expands outward until the bowed region  83  engages a superior surface of the proximal elements  16 . As the bowed region  83  continues to deflect radially outward, it further pushes on the proximal elements  16  such that the proximal elements are deflected and rotated outward toward the engagement surface of the distal elements  18 . Thus, the proximal elements  16  may be deflected outward further than they normally would, and therefore the valve leaflets may be captured between the proximal and distal elements when the distal elements are disposed in a more open position with a larger included angle therebetween. In preferred embodiments, the included angle between the distal elements is greater than about 90°, preferably greater than about 110°, and more preferably greater than about 120°. In the embodiment of  FIG. 36 , the gripper pusher  81  includes two arms formed from a metal, polymer or other wire-like material. Exemplary materials include cobalt chromium alloy, stainless steel, nitinol, and the like. Polymers may also be used to fabricate the gripper pusher. The gripper pusher  81  may be actuated to bow outwards upon application of an axially oriented compressive force that is generally parallel to the longitudinal axis of the gripper pusher arms. During compression, the gripper pusher bows outward forming bowed region  83 . In other embodiments, the gripper pusher may be a spring which is resiliently biased to bow outward forming bowed region  83 . However, when proximal element lines (not illustrated here) are tensioned to lift the proximal elements  16 , the gripper pusher springs will collapse to a reduced profile. 
         [0138]      FIG. 37  illustrates the fixation device  14  having a covering for tissue ingrowth, and with the gripper pusher  81  expanded such that the proximal elements  16  (also referred to as gripping elements) are in engagement with the distal elements  18  (also referred to as fixation elements). The valve leaflets (not shown for convenience) are pinched therebetween.  FIG. 38  illustrates the gripper pusher  81  in the collapsed configuration. The bowed region  83  collapses, allowing the proximal elements  16  to retract towards shaft  12 , allowing the valve leaflets (not shown) to be released from the fixation device  14 . The gripper pusher  83  is offset from the proximal elements  16  so that the proximal elements can retract without interfering with the gripper pusher  81 . 
         [0139]      FIG. 39  highlights the gripper pusher  83  which preferably includes two spring arms  99 . Each arm  99  is formed from wire or machined from a sheet or other stock material and in this embodiment has a rectangular cross-section, although other cross-sections are also contemplated. A distal portion  91  of each arm  99  has a notched region  93  forming a pair of fingers that can engage with a boss or other attachment mechanism on the fixation device. The notch may be released from the boss when the fixation device  14  is detached from the delivery catheter shaft  12 . Additionally, each arm includes two bowed regions, or peaks, including a larger distal bowed region  83 , and a smaller proximal bowed region  95 . The larger bowed region  83  flares outwardly a greater distance so as to engage and push the proximal elements  16  into engagement with the distal elements  18 . When the distal bowed region  83  relaxes and collapses away from the proximal elements  16 , or when collapsed by retraction of the proximal elements, the smaller proximal bowed regions  95  expand radially outward. An attachment ring or coupling collar  97  is adjacent nose  318  (described in greater detail below) and is slidably disposed over the shaft  12  and allows coupling of the gripper arms  99  to the shaft  12 .  FIG. 40  illustrates the distal bowed region  83  in engagement with the proximal elements  16 , and also illustrates engagement of the notch  93  on the distal portion of each arm  99  with a boss  94  on the fixation device  14 . 
         [0140]    As described above, for example, with reference to  FIGS. 10A through 11B , actuation of the proximal elements  16  may be accomplished by using one or more proximal element lines or actuators  90 . In another embodiment, this actuation can be achieved by combination of the proximal element actuators  90  and the gripper pusher  81  as set forth above. For example, as shown in  FIG. 41 , the proximal element actuators  90 A and  90 B could be threaded through line loops  48 A and  48 B, which are disposed on the radially outward and proximal sides of the proximal elements  16 A and  16 B, respectively. The distal ends of proximal element actuators  90 A and  90 B may comprise closed loops  95 A and  95 B, which encircle the shaft  12  and the coupling member  19  shown in  FIG. 41  as coupled together. As discussed above, the shaft  12  and the coupling member  19  can be releasably coupled together. To have the closed loops  95 A and  95 B surround shaft  12  and the coupling member  19 , the closed loops  95 A and  95 B are placed over the shaft  12  and/or the coupling member  19  prior to the coupling shaft  12  and the coupling member  19  together. When the closed loops  95 A and  95 B encircle the shaft  12  and the coupling member  19 , the closed loops  95 A and  95 B hold the distal ends of the proximal element actuators  90 A and  90 B in place relative to the shaft  12  and the coupling member  19  and restrict the degree to which the proximal element actuators  90 A and  90 B can be retracted. By being threaded through the line loops  48 A and  48 B, the proximal element actuators  90 A and  90 B are mechanically linked to the proximal elements  16 A and  16 B, respectively. Thus, as shown in  FIG. 42 , when the proximal element actuators  90 A and  90 B are retracted proximally in a direction  96 , they move the proximal elements  16 A and  16 B away from the distal elements  18 A and  18 B, respectively. 
         [0141]    However, in combination with the proximal element actuators  90 A and  90 B, which permit independent actuation of the proximal elements  16 A and  16 B, the gripper pusher  81  may also be included in the fixation device. Thus, the proximal elements  16 A and  16 B may be deflected outward further than they normally would, and therefore the valve leaflets may be captured between the proximal and distal elements when the distal elements are disposed in a more open position with a larger included angle therebetween. In preferred embodiments, the included angle between the distal elements is greater than about 90°, preferably greater than about 110°, and more preferably greater than about 120°. Thus, in this embodiment, the fixation device is capable for independent actuation as well as a wide range of proximal element  16 A and  16 B movement. 
         [0142]    The proximal element actuators  90 A and  90 B may be moved so that the proximal elements  16 A and  16 B are moved at a variety of angles and distances from the distal elements  18 A and  18 B. And, the degree to which the proximal element actuators  90 A and  90 B are pushed or pulled can be maintained to keep the positions the proximal elements  16 A and  16 B have relative to the distal elements  18 . For example, as shown in  FIG. 43 , the proximal element actuators  90 A and  90 B are pulled proximally and maintained in the position shown so as to maintain the proximal elements  16 A and  16 B in an intermediate position relative to the distal elements  18 . This intermediate position is between the position in which the proximal elements  16 A and  16 B are biased toward and that in which the proximal elements  16 A and  16 B are fully retracted as in  FIG. 42 . As shown in  FIG. 46 , once the proximal elements  16 A and  16 B are in a desired position, the shaft  12  and the coupling member  19  can be decoupled so that proximal retraction of the proximal element actuators  90 A and/or  90 B decouples the proximal element lines from the proximal elements  16 . Thus, the fixation device  14  can be left in place while the shaft  12 , the proximal element actuators  90 A and  90 B, and other parts can be removed from a site of operation. As shown in  FIGS. 41 through 47 , the fixation device  14  typically includes a covering  100 . 
         [0143]    It may be desirable to provide for independent actuation of the proximal elements  16 A and  16 B. For example, as shown in  FIG. 44 , the proximal element actuator  90 A is proximally retracted and rotates the proximal element  16 A away from the distal element  18 A, while the proximal element actuator  90 B is pushed distally and rotates the proximal element  16 B toward the distal element  18 B. Similarly, as shown in  FIG. 45 , the proximal element actuator  90 A is left alone, allowing the proximal element  16 A to maintain the position it is biased toward, while the proximal element actuator  90 B is proximally retracted, moving the proximal element  16 B away from the distal element  18 B. 
         [0144]    In another embodiment as illustrated in  FIG. 47 , the independent actuation of the proximal elements  16 A and  16 B is performed in a manner similar to the embodiment depicted in  FIG. 46 . However, as shown in  FIG. 47 , the proximal element actuators  90 A and  90 B are formed of a double loop configuration. The each proximal element actuator  90 A and  90 B exits the and returns through the nose  318  of the shaft  302  after being routed through the distal end of a corresponding one of the proximal elements  16 A and  16 B, and looped around the shaft  12  or coupling mechanism  19 . This configuration provides the similar operational flexibility as the embodiment illustrated in  FIG. 46 , but permits removal of the proximal element actuators  90 A and  90 B before the coupling mechanism  19  is released from the shaft  12 . 
         [0145]    In another embodiment as illustrated in  FIG. 48 , a single proximal element actuator  90  is configured to perform sequential grasping in a similar manner to the embodiment depicted in  FIG. 34 . However, this embodiment also utilizes the gripper pusher  81  to provide for an extended range of movement in the open direction of the distal elements  18 A and  18 B. By virtue of the geometry of this configuration, each proximal element  16 A and  16 B may be independently actuated and the proximal element actuator  90  may be released in tandem with the separation of the coupling member  19 . As illustrated in  FIG. 35 , due to the manner of routing the proximal element actuator  90 , the resultant forces F 1  and F 2  are at different angles. These resultant forces and their directions are based on the tension on the proximal element  90  and the direction (angle) at which the proximal element actuator  90  approaches and extends away from a corresponding proximal element  16  A or  16 B. Again, the force that causes a corresponding proximal element to move is the component of the force that is perpendicular to the length of a corresponding proximal element. This perpendicular component is represented by F N1  and F N2 . Accordingly, for a given amount of tension in the proximal element actuator  90 , proximal element  16 A will receive more moving force than proximal element  16 B. That means that proximal element  16 B will remain closed as proximal element  16 A opens, and proximal element  16 B will open after proximal element  16 A is fully opened. This allows for independent actuation of the proximal elements  16 A and  16 B using a single proximal element actuator  90 . Additionally, however, in this embodiment, the included angle between the distal elements may greater than about 90°, preferably greater than about 110°, and more preferably greater than about 120°. Thus, in this embodiment, the fixation device is capable for independent actuation as well as a wide range of proximal element movement. 
         [0146]    Coupling of Proximal Element Actuator 
         [0147]    In many of the embodiments described above, the proximal element actuator  90  or proximal element actuators  90 A and  90 B includes an end that may be releasable coupled to the fixation device  14 . Describe below are multiple embodiments showing various methods and structures for releasably coupling the proximal element actuators that may be applied to any of the embodiments described above. 
         [0148]    In many embodiments, the shaft  12  and the coupling member  19  are releaseably coupled together via an L-locking mechanism. For example, as shown in  FIG. 49A , the proximal element actuator  90  may comprise a round T-shaped end  90 T distal of the flat section  90 F and the shaft  12  may comprise L-shaped ends  12 L. As shown in the perspective view of  FIG. 49B , the proximal element actuator  90  is releaseably coupled to the coupling member  19  when it and shaft  12  are placed into the channel  19 C of the coupling member  19 . As the shaft  12  is placed through the channel  19 C, the L-shaped ends  12 L are forced inwardly until they reach apertures  19 A. At that point, the L-shaped ends  12 L expand outwardly to fit into the apertures  19 A, thereby locking the shaft  12  in place relative to the coupling member  19 , as shown in cross-sectional view of  FIG. 49C . The round T-shaped distal end  90 T will typically be placed in the space  19 CA prior to the shaft  12  being placed in the channel  19 C. As shown in  FIG. 49C , the round T-shaped distal end  90 T then becomes trapped in the space or pocket  19 CA between the channel  19 C and a wider portion of the shaft  12  when the shaft is placed therein. Other L-locking or other locking mechanisms are described in commonly assigned U.S. patent application Ser. No. 12/393,452 entitled “Detachment Mechanism for Implantable Fixation Devices” and filed Feb. 26, 2009, the full contents of which are incorporated herein by reference. 
         [0149]    The round T-shaped end  90 T of the proximal element actuator  90  may also be used to facilitate releaseably coupling the proximal element line  90  to the shaft  12  and coupling member  19  is many other ways. For example, as shown in  FIG. 50A , the L-shaped end  12 L of the shaft  12  may comprise at least one proximal element line slot  12 S. As shown in  FIGS. 50C and 50D , the T-shape end  90 T of the proximal element actuator  90  is slid into the proximal element line slot  12 S. Then, the shaft  12  is placed into the coupling member  19 , thereby also locking the proximal element line  90  in place. As shown in  FIG. 50E , removing the shaft  12  from the coupling member  19  allows the proximal element line  90  to be slid out of the proximal element line slot  12 S of L-shaped end  12 L, thereby decoupling the proximal element actuator  90  from both the shaft  12  and the coupling device  19 . 
         [0150]    As shown in  FIG. 51A , the proximal element actuator  90  may comprise a flat T-shaped end  90 TF. The shaft  12  may further comprise an inner distal covering  1511  surrounding a distal portion of the shaft  12  and an outer distal covering  1521  surrounding the inner distal covering. The inner distal covering  1511  will typically be in a fixed position relative to the shaft  12  while the outer distal covering will be moveable relative to the shaft  12  at a range determined by tabs  1515  of inner distal covering  1511  placed through side channels  1525  of the outer distal covering  1521 . To releaseably couple the proximal element actuator  90  to the shaft  12  and coupling line  19 , the T-shaped end  90 TF is fit into a T-shaped cutout  1513  of inner distal covering  1511 , and when the shaft  12  is placed into the coupling device  19 , the coupling device  19  pushes the outer distal covering  1521  over the inner distal covering  1511  to cover the T-shaped cutout  1513  as well as the T-shaped end  90 TF, as shown in  FIG. 51B . This compresses a coil spring  1522  placed between the inner distal covering  1511  and the outer distal covering  1521 . When the fixation device  14  is released from the shaft  12 , the outer distal covering  1521  moves distally due to the action of the coil spring  1522  to expose the T-shape cutout  1513  to release the proximal element actuator. In some embodiments, the outer distal covering  1521  may be spring loaded against the inner distal cover  1523  so that tend to maintain their relative positions shown in  FIG. 51B . 
         [0151]    Proximal element actuators  90  may be releaseably coupled to the fixation device  14  in a variety of ways using variations of inner and outer distal collars over the distal portion of shaft  12 , for example, as shown in  FIGS. 52A to 52G . FIG.  15 AB 1  shows an inner distal collar  1511 A having a pair of T-shaped cutouts  1513  and a tab  1514 .  FIG. 52C  shows an outer distal collar  1521 A having a channel  1524 . The channel  1524  guides the inner distal collar  1511 A via its tab  1514  as the inner distal collar  1511 A is slid into the outer distal collar  1521 A, for example as shown in  FIGS. 52C through 52E . As in the embodiment shown in  FIGS. 51A and 51B , to releaseably couple the proximal element actuators  90  to the shaft  12  and coupling member  19 , the T-shaped end  90 TF is fit into a T-shaped cutout  1513  of inner distal collar  1511 S. When the shaft  12  is placed into the coupling device  19 , the coupling member  19  pushes the outer distal collar  1521 S over the inner distal collar  1511 S to cover the T-shaped cutout  1513  as well as the T-shaped end  90 TF, as shown in  FIGS. 52F and 52G . This compresses the coil spring  1522 A shown in  FIG. 52C . When the fixation device  14  is released from the shaft  12 , the outer distal covering  1521 A moves distally due to the action of the coil spring  1522 A to expose the T-shape cutout  1513 A to release the proximal element actuator  90 . 
         [0152]    In other embodiments, the proximal element actuators  90  may be releasably engaged with structures that are activated by removal of the actuator rod  64  that passed through the coupling member  19  and the shaft  12 . As illustrated in  FIG. 53  a stud  74  is releasably attached to the actuator rod  64  which passes through the coupling member  19  and the shaft  12  of the interventional tool  10 . In this way, the actuator rod  64  is connectable with the fixation device and acts to manipulate the fixation device, typically opening and closing the distal elements. After the leaflets have been coapted, the actuator rod  64  is removed proximally from the stud  74  to release the coupling member  19 , or alternatively, the L-lock mechanism described above. In the following embodiments, this action of the actuator rod  64  may be utilized to release the proximal element actuators  90 . 
         [0153]    In one embodiment, as illustrated in  FIGS. 54A through 54D  and  55 A through  55 , spring members  331  are utilized in combination with the actuator rod  64  to hold and release the proximal element actuators  90 . As shown in  FIG. 54A , a portion of the shaft extending from the nose  318  has two windows  333  formed therein. Two spring members are positioned on the periphery of the shaft  12  adjacent a corresponding window so that a bent portion  335  extends into the actuator rod pathway formed within the shaft  12 . A proximal side of these bent portions  335  may be fixed to the nose  318  or an external portion of the shaft  12 . A distal side of each bent portion  335  is attached to a “C” shaped portion having a notch  339  formed at each end of the “C” shape. The corresponding end portions of one “C” shape portions on one spring are configured to abut the end portions of another spring so that the corresponding notches  339  can restrict the movement of a ball  337  at the end of either one of the proximal element actuators.  FIG. 54C  illustrates a position in which the “C” shaped portions are in contact to form a notch that prevents distal movement of the ball  337 . 
         [0154]    As illustrated in  FIG. 55A , the actuator rod  64  is configured to have a tapered profile having a narrow portion and a wide portion. As the actuator rod  64  is moved proximally in  FIG. 55B , a wide portion of the actuator rod  64  contacts the bent portions  335  to separate the corresponding “C” shaped portions of the adjacent spring members  331 . This opens the notches  339  so that the ball  337  of the proximal actuator  90  is released as shown in  FIG. 55C . 
         [0155]    In another embodiment as illustrated in  FIGS. 56A and 56B , the proximal element actuator  90  or proximal element actuators  90 A and  90 B may be releasably attached to the shaft  12  by using one or a set of liners  65  hingedly attached to the shaft  12 . In this configuration, a pair of windows  33  (only one window is required in the case of a single proximal element actuator) is formed in the shaft  12 . A liner is hingedly attached to the inside of the shaft  12  on a proximal side of each of the windows  33 . As shown in  FIG. 56A , when the actuator rod  64  is withdrawn proximally, the liners  65  move inwardly such that the proximal element actuators  90  are free to move. When the actuator rod  64  is in this position, the proximal element actuators  90  may be inserted into, or withdraw from, the windows  33 . On the other hand, when the actuator rod  64  is moved distally as shown in  FIG. 56B , the liners  65  are pressed outwardly against the inside surface of the shaft  12  to trap or pinch the proximal element actuators. This secures the proximal element actuators so that the proximal elements  16  can be moved independently. The proximal element actuators  90  are fixed to the shaft  12  until the actuator rod  64  is again moved proximally to the position shown in  FIG. 56A . 
         [0156]    While the methods and structures of releasably fixing the proximal element actuators  90  are shown above with either one or two proximal element actuators, it is possible to utilize or modify those structures for use with either a single or multiple proximal element actuators  90 . 
         [0157]    Releasably Fixing the Gripper Pushers 
         [0158]    As set forth above,  FIG. 39  highlights the gripper pusher  83  which preferably includes two spring arms  99 . Each arm  99  is formed from wire or machined from a sheet or other stock material and in this embodiment has a rectangular cross-section, although other cross-sections are also contemplated. In the embodiment of  FIG. 39 , a distal portion  91  of each arm  99  has a notched region  93  forming a pair of fingers that can engage with a boss or other attachment mechanism on the fixation device. The notch may be released from the boss when the fixation device  14  is detached from the delivery catheter shaft  12 .  FIGS. 57 and 58  show an alternative embodiment for releasably securing the arms  99  of the gripper pusher  83  in combination with an L-lock configuration. 
         [0159]      FIGS. 57 and 58  illustrate an alternate embodiment to the mating surface  32  illustrated in  FIG. 6A . Here, upper shaft  500  is releasably coupled with lower shaft  506  with a detent mechanism  504 ,  508 . The upper and lower shafts in this embodiment are generally tubular shaped although one of skill in the art will appreciate that other configurations are possible. The detent mechanism in this exemplary embodiment includes one or more spring arms  502  integrally formed on tubular upper shaft  500  and one or more receptacles  508  sized to receive the spring arms  502 . Tubular upper shaft  500  is integrally formed with one or more spring arms  502  having a flange-like engagement surface  504  at a distal end thereof. The spring arms  502  are preferably biased inwardly, i.e., toward the interior of the shaft  500 . Detachable tubular lower shaft  506  features one or more receptacles, here apertures  508  are configured to receive and mate with the engagement surface  504  of the spring arm  502  and an engagement surface of the arm  99  of the gripper pusher  83 . The apertures  508  may extend all the way through the wall of the lower shaft  506  and are sized to snuggly fit both the engagement surface  504  of the spring arms  502  and the engagement surface  101  at the distal end  91  of the arms  99 . To releasably couple the arms  99  to the tubular lower shaft  506 , the engagement surfaces  101  of the arms  99  are fitted into a corresponding aperture  508 . Then, a snuggly fitting rod  34  (such as actuator rod  64 ) is inserted through the tubular shafts  500 ,  506  outwardly deflecting the inwardly biased spring arm(s)  502  such that the engagement surface  504  is pushed into engagement with a corresponding receptacle  508  and arm  99  thereby coupling the gripper pusher  83  and the upper shaft  500  to the lower shaft  506 . 
         [0160]      FIG. 58  illustrates detachment of the lower shaft  506  from the upper shaft  500 . This is achieved by retracting the rod  34  to a position above the spring arm(s)  502  which allows the inwardly biased engagement surface  504  to disengage from the receptacle  508  allowing the arms  99  of the gripper pusher  83  to separate along with the shafts  500 ,  506 . 
         [0161]    While the foregoing is a complete description of the preferred embodiments of the invention, various alternatives, substitutions, additions, modifications, and equivalents are possible without departing from the scope of the invention. For example, in many of the above-described embodiments, the invention is described in the context of approaching a valve structure from the upstream side—that is, the atrial side in the case of a mitral valve. It should be understood that any of the foregoing embodiments may be utilized in other approaches as well, including from the ventricular or downstream side of the valve, as well as using surgical approaches through a wall of the heart. Moreover, the invention may be used in the treatment of a variety of other tissue structures besides heart valves, and will find usefulness in a variety of tissue approximation, attachment, closure, clamping and ligation applications, some endovascular, some endoscopic, and some open surgical. 
         [0162]    Again, although the foregoing invention has been described in some detail by way of illustration and example, for purposes of clarity of understanding, it will be obvious that various alternatives, modifications and equivalents may be used and the above description should not be taken as limiting in scope of the invention which is defined by the appended claims.