Abstract:
A method and apparatus for providing safe and efficient transcatheter correction of the shape of heart chambers, valves, or other body members. The apparatus generally performs this correction by securing a tether to body surfaces. The attachment device includes an anchor comprising a wire braid and at least one clamp affixed to and constraining a portion of the wire braid, the clamp having threading for temporarily coupling the anchor to a delivery member and an internal lumen through which the tether can pass. The device also includes a locking member cooperating with the lumen to lock the tether to the clamp at a preselected position along the length of the tether.

Description:
I. FIELD OF THE INVENTION  
       [0001]     The present invention relates to devices and methods for improving the function of a diseased heart. Such devices and methods are particularly useful for non-invasively treating structural conditions of the diseased heart that can lead to morbidity and early death.  
       II. BACKGROUND OF THE INVENTION  
       [0002]     The human heart is a complex pumping system of contracting chambers and valves that causes blood to flow through the vascular system of the body. The healthy human heart beats on average more than 40 million times a year. Over time, disease and injury can cause damage to the heart. In a diseased heart, the chambers can become swollen and distended leading to cardiac inefficiency and heart failure. Such swelling can lead to damage to the electrical conduction paths in the heart that control its rhythm. Likewise, the annulus of the mitral valve of the heart can become distended such that the leaflets do not fully close permitting blood to regurgitate (i.e., flow in the wrong direction through the valve). Such regurgitation can result in inefficient pumping by the heart to a degree that is detrimental to patient health.  
         [0003]     In the past, various medical, electrophysiological and surgical techniques have been used to treat such cardiac conditions. Such medical techniques have typically involved treatment using pharmaceuticals. Such pharmaceuticals do not really remedy the condition, but instead can help control the effects of the condition or prevent a worsening of the condition. For example, diuretics are available to relieve accumulation of fluids in the lungs or legs that can accompany heart failure or mitral valve regurgitation. Antibiotics are used to prevent endocarditis which can also result from such conditions. High blood pressure can exacerbate mitral valve regurgitation so drugs to treat high blood pressure have also been used.  
         [0004]     Electrophysiologic treatments typically involve the use of a pulse generator (i.e. a pacemaker, cardioverter or defibrillator) and lead system to deliver pulse to the heart to control its rhythm.  
         [0005]     Surgical treatments have been used to both reshape the chambers of the heart and repair or replace the valves. For example, chambers of the heart have been surgically shaped through resection of the heart tissue or by applying a patch, cuff or sleeve to the outside of the heart to constrain distended heart tissue. See, for example, U.S. Pat. No. 6,808,488 to Mortier et al. Valves have been surgically repaired through the use of annuloplasty rings, through quadrangular segmental resection of the leaflets of the valve, through shortening of the elongated cordae of the valve, or through transposition of the posterior leaflet cordae to the anterior leaflet. Human heart valves have been surgically replaced with either tissue valves from pigs or artificial mechanical valves. Heart surgery typically entails great trauma to the patient and long recovery periods. Such surgery, and particularly open heart surgery, is typically performed under general anesthesia through an incision that extends the entire length of the breastbone. The ribs are spread to expose the heart and the patient is attached to a heart-lung machine which serves as a temporary replacement for the heart during surgery. The heart must be stopped, repaired surgically, and then restarted. The risk of death during surgery is significant particularly because heart disease has often weakened the body, and particularly the heart, before such surgery is even attempted. Substantial efforts have been undertaken to find ways to treat cardiac conditions that will reduce such trauma and recovery periods.  
         [0006]     In recent years, a variety of highly traumatic surgical procedures have been replaced with procedures that involve the use of a catheter advanced through the vascular system of the body to gain access to the heart. Balloon catheters have been used to perform angioplasty procedures as a replacement for a surgical heart bypass. Leads for cardiac rhythm management devices are now placed in the heart through the vasculature of the body rather than surgically sewn or attached to the outside of the heart. A variety of stents have been deployed via a catheter.  
         [0007]     A variety of transcatheter deliverable devices have been developed by the assignee of the present invention to close holes in the heart. Such holes include atrial septal defects, ventricular septal defects, patent ductus arteriosus and patent foramen ovale. Recovery periods when these devices are implanted are virtually non-extent as compared to the weeks and months of recovery most patients experienced when surgical repairs were performed.  
         [0008]     In recent years, various transcatheter approaches for non-surgical repair of heart valves and distended heart chambers have been disclosed. For example, U.S. Patent Publication No. 2001/0018611 (Solem et al) and U.S. Patent Publication No. 2005/0149182 (Alferness et al) each describe devices advanced via a catheter into the coronary sinus and deployed there to change the radius of curvature of the coronary sinus and the adjacent mitral valve annulus. In theory, changing the shape of the annulus can enable the leaflets to better close the orifice surrounded by the annulus.  
         [0009]     While the above-referenced patent applications disclose theoretical concepts for changing the size and shape of the annulus, those skilled in the art will recognize issues that make these proposed solutions impractical for general use. First, the geometry of every heart is different. Therefore, what affect changing the radius of curvature of the coronary sinus will have on the annulus of the mitral valve cannot be accurately predicted or easily controlled. Second, even if the effect on the annulus were predictable, alignment of the biasing member in the coronary sinus would have to be precise. There is no teaching in these patent publications of how such precise alignment could be achieved. Third, the coronary sinus only surrounds about half of the mitral valve. Application of the devices shown in these patent publications may, therefore, change the shape of the annulus in a way that exacerbates mitral valve regurgitation rather than solving the problem. Fourth, the devices shown could very well lead to significant occlusion of the coronary sinus which is an essential conduit for carrying blood.  
         [0010]     U.S. Patent Publication No. 2005/0065550 (Starksen et al) apparently attempts to overcome the problems with the coronary sinus approach for reshaping the annulus. As an alternative, that publication discloses a device that includes a plurality of hook type anchors that penetrate the annulus of the valve and cooperate with a biasing member that draws the anchors together circumferentially to tighten (i.e., reduce the size of) the valve annulus. The theory behind this concept is similar to the theory used by orthodontists to straighten teeth or correct an overbite. While in theory, the system disclosed in the Starksen et al application might work, the system is impractical given the difficulty in aligning the device, setting the hook type anchors and applying proper tension between the anchors with the biasing means to achieve the proper shape all through a catheter. There are risks of infection, damage to the muscle and thrombus formation between the various components that could lead to stroke or death.  
         [0011]     Others have disclosed concepts for reshaping the annulus using a tether stretched across the valve and anchored at its two ends to opposing walls of the heart. Similar approaches have been disclosed for reshaping or relieving stress on the walls of a heart chamber. International Patent Publication No. WO2004/112585 (Huynh et al) shows such a device for reducing the annulus of a heart valve. One of the anchors is a stent located in the coronary sinus. The other anchor is selected from “a coil barbed anchor, a hooked anchor, and a harpoon barbed anchor”. This anchor punctures another wall of the heart. The two anchors are joined by a tension member that passes through a puncture in the wall of the coronary sinus and pulls the tissue in the location of the anchors (and, in theory, opposing sides of the valve annulus) together.  
         [0012]     The system shown in the Huynh et al is not practical for several reasons. First, it would be extremely difficult to safely position the harpoon anchor in the coronary sinus, use it to puncture the coronary sinus, advance it across the atrium, and then securely and permanently fix it to the opposing heart wall. Even if this could be accomplished, it would be difficult to ensure that the spot where this anchor is coupled to the wall and the point where it penetrates the coronary sinus will result in tension being supplied in a manner that corrects the shape of the annulus of the valve. The risk of a tear in the coronary sinus that could lead to emergency open heart surgery cannot be overlooked. Likewise, the risk that the anchor could be pulled from the heart wall is significant.  
         [0013]     Similar problems are inherent in the disclosure contained in U.S. Patent Publication No. 2005/0222488 (Change et al). Again, an anchor is placed in the great cardiac vein and the tether must be passed through the wall of the main vein of the heart. Also, the tether runs from a point along the great vein or coronary sinus to the fossa ovalis in the atrial septum. There is no guaranteeing that applying tension along that vector will result in proper reshaping of the annulus of the mitral valve. Chang et al does have the advantage of disclosing an anchor (modeled after applicant&#39;s septal defect occluders) that will spread the forces better and likely be more secure than the harpoon, coiled barb or hook type anchors of Huynh et al.  
         [0014]     U.S. Pat. No. 6,764,510 to Vidlund et al discusses the need to properly align one or more tensioning members to achieve the desired effect on the valve.  FIGS. 7   a  and  7   b  of this patent show a rigid elongated member  130  extending along the line of leaflet coaptation of the mitral valve. More specifically, the elongated member is positioned slightly above or slightly below the valve annulus so as to appropriately affect the valve leaflets and move them into the desired position. However, the device shown is not implanted using a catheter. Instead, the patent describes the elongated member being inserted (twice) through the wall of the left atrium and then coupled to pads  132  that rest against the outside of the heart wall. Thus, implantation requires surgical approach through the chest wall. There is nothing to suggest that either the rigid elongated member  130  or the pads  122  could be implanted using a transcatheter approach.  
       SUMMARY OF THE INVENTION  
       [0015]     A first object of the present invention is to provide methods and devices for safe and effective transcatheter correction of the shape of heart chambers and/or valves for improved performance of the heart.  
         [0016]     A second object of the invention is to provide a tether and anchoring apparatus that can be implanted through a catheter of a relatively small diameter.  
         [0017]     A third object of the invention is to provide such an anchor that can spread forces applied to the tissue by the anchor over a suitably large area to prevent the anchor from becoming dislodged or damaging the tissue contacted by the anchor.  
         [0018]     A fourth object of the invention is to provide such an anchor that does not rub against or cause undue irritation to the tissue.  
         [0019]     A fifth object of the invention is to provide a method for determining and permitting transcatheter placement of anchors at appropriate locations for achieving the desired affect on the shape of a heart chamber or valve annulus.  
         [0020]     A sixth object of the invention is to provide a method for measuring and transcatheter adjustment of the length of a tether between two properly positioned anchors to achieve the desired affect on the shape of a heart chamber or valve annulus.  
         [0021]     A seventh object of the invention is to provide a method for measuring and transcatheter adjustment of the forces supplied by the anchors and tether of a device to the tissue to which the device is attached.  
         [0022]     An eighth object of the invention is to provide an anchoring and tethering device that will not detrimentally occlude a chamber or vessel.  
         [0023]     A ninth object of the invention is to provide anchors which over a relatively short period of time will become endothelialized.  
         [0024]     A tenth object of the invention is to provide anchoring and tethering devices that will not unduly increase the risk of embolism or stroke.  
         [0025]     An eleventh object of the invention is to provide a method for placement of an anchoring and tethering device that does not interfere with valve operation, permits suitable blood flow past the tether, reduces the risk of nerve damage, reduces the risk of damage to electrical conducting tissues, and reduces the risk of undesirable clotting, thrombosis and infection.  
         [0026]     A twelfth object of the invention is to provide a transcatheter technique for positioning two anchors joined together by a tether so that the tether extends along the desired vector to ensure not only improved but acceptable cardiac performance.  
         [0027]     A thirteenth object of the invention is to provide an attachment between an anchor and the tether that permits adjustment of the length of the tether in situ.  
         [0028]     A fourteenth object of the invention is to provide a tether and anchors that are sufficiently flexible to be advanced and positioned using a catheter and are durable enough for permanent implantation.  
         [0029]     Another object of the invention is to provide such an anchoring and tethering device that can be safely used to treat other medical conditions such as obesity, incontinence, hernias, and wounds.  
         [0030]     These and other objectives are met and important advantages are achieved by providing a device that includes one or more anchors preferably made of either a shape memory or super-elastic metal alloy (such as nitinol) having a first configuration for deployment through a catheter to an anchoring site comprising a hole through a wall and a second configuration for coupling the anchor to the wall at the anchoring site. More specifically, the anchor preferably comprises a braid made of at least one wire which, when in the second configuration, has a first expanded diameter portion on one side of the wall, a second expanded diameter portion on the other side of the wall, and a narrow waist that extends through the hole in the wall. The anchor further includes one or more clamps used to secure the braid. At least one of the clamps preferably has a lumen through which the tether can pass. The anchor also includes a member used to fix the tether to the anchor. This member has a first orientation which permits the tether to move longitudinally through the lumen of the clamp and a second position wherein the member grips the tether preventing such movement of the tether.  
         [0031]     Ideally, one of the clamps will have a threaded portion which permits it to be secured to a reciprocally threaded portion at the distal end of a delivery member.  
         [0032]     The delivery member is used to advance the anchor through the catheter to the anchoring site. The delivery member preferably has a lumen extending its entire length from its threaded portion at its distal end to its proximal end such that the tether can pass through the clamp and delivery member and out the proximal end of the delivery member. Alternating, the lumen in the delivery member extends through the threaded portion of the distal end of the delivery member and then a short distance toward the proximal end to an opening in the side wall of the delivery member. This permits the tether to pass through the clamp and lumen of the delivery member and exit the opening in the side wall of the delivery member.  
         [0033]     When this arrangement is used, the tether exits the hole and then runs parallel to the delivery member to the proximal end of the catheter, i.e., the delivery member and a substantial portion of the tether are side by side in the catheter. This alternative embodiment makes it easier to thread the flexible tether through the lumen.  
         [0034]     The methods of the present invention involve the following steps in different combinations:  
         [0035]     a. determining the desired anchoring sites for the distal and proximal anchors;  
         [0036]     b. advancing a catheter to the anchoring site for the proximal anchor;  
         [0037]     c. advancing a puncturing tool through the catheter and puncturing a hole through the wall at the proximal anchoring site;  
         [0038]     d. further advancing the catheter through the hole at the proximal anchoring site to the distal anchoring site;  
         [0039]     e. advancing the puncturing tool through the catheter to the distal anchoring site, puncturing a hole through the wall at the distal anchoring site, and then withdrawing the puncturing tool from the catheter;  
         [0040]     f. attaching tether and the delivery member to the distal anchor;  
         [0041]     g. passing the tether through the lumen of the delivery member;  
         [0042]     h. advancing the distal anchor through the catheter and deploying it in the hole formed at the distal anchor site;  
         [0043]     i. releasing the delivery member from the distal anchor and withdrawing it from the catheter;  
         [0044]     j. retracting the distal end of the catheter back to the proximal anchor site;  
         [0045]     k. attaching the delivery member to the proximal anchor and feeding the proximal end of the tether through the proximal anchor and lumen of the delivery member;  
         [0046]     l. advancing the proximal anchor through the catheter and deploying it in the hole formed at the proximal anchor site;  
         [0047]     m. releasing the proximal anchor from the delivery member and withdrawing the delivery member;  
         [0048]     n. applying tension to the tether to draw the proximal and distal anchors toward each other while monitoring the performance of the heart;  
         [0049]     o. coupling the tether to the proximal anchor at the proper position along the length of the tether so that proper tension is supplied to satisfactorily improve performance of the heart; and  
         [0050]     p. trimming the excess length of the tether and withdrawing the excess length of the tether and the catheter from the body. Additional steps may also be performed without deviating from the invention.  
         [0051]     Of course, the method described above can be modified depending on the anatomy of the patient if, for example, the great vein or some already present opening in the septal wall provides an acceptable location for anchoring. Also, additional anchors and tethers can be deployed to correct chamber and valve shape and maximize cardiac performance. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0052]      FIG. 1  is a cross-sectional view of a human heart showing a preferred embodiment of the present invention supplying tension between the left atrial wall and the atrial septum.  
         [0053]      FIG. 2  is a cross-section of the heart showing the heart valves.  
         [0054]      FIG. 3  is a side view of a first embodiment of an anchor of the present invention.  
         [0055]      FIG. 4  is a side view of a second embodiment of an anchor if the present invention.  
         [0056]      FIG. 5  is a side view showing a pair of anchors of a third embodiment and a tether in its relaxed state.  
         [0057]      FIG. 6  shows a delivery tool used to deploy the anchors and tether.  
         [0058]      FIG. 7  illustrates in cross-section a first embodiment of a securement mechanism used to fix at an appropriate point along its length, a tether to an anchor;  
         [0059]      FIG. 8  illustrates in cross-section a second embodiment of a securement mechanism used to fix, at an appropriate point along its length, a tether to an anchor;  
         [0060]      FIG. 9  illustrates a third embodiment of a securement mechanism;  
         [0061]      FIGS. 10   a - 10   c  are cross-sectional views of alternative securement mechanisms of the type shown in  FIG. 9  taken along line A-A in  FIG. 9 .  
         [0062]      FIGS. 11   a - 11   d  illustrate a fourth securement mechanism used to fix, at an appropriate point along its length, a tether to an anchor;  
         [0063]      FIG. 12  shows a reinforcement mechanism for reinforcing an anchor;  
         [0064]      FIG. 13  illustrates how the reinforcement mechanism of  FIG. 12  is deployed;  
         [0065]      FIGS. 14   a - 14   e  show how the tether can be fixed to an anchor using any of a variety of securement mechanisms. 
     
    
     DETAILED DESCRIPTION  
       [0066]     The human heart  1  includes four chambers, the right atrium  2 , the left atrium  3 , the right ventricle  4  and the left ventricle  5 . The atrial septum  6  separates the right and left atria. The ventricular septum  7  separates the ventricles. The mitral valve  8  separates the left atrium  3  from the left ventricle  5 . The tricuspid valve  9  separates the right atrium  2  from the right ventricle  4 .  
         [0067]     As shown in  FIG. 2 , the mitral valve  8 , sometimes referred to as the bicuspid valve, is made up of two leaflets  10  and  11  partially surrounded by an annulus  12 , a diaphanous incomplete ring around the valve. During left ventricular diastole, after pressure drops in the left ventricle  5  due to relaxation of the ventricular myocardium, the mitral valve  8  opens and blood travels from the left atrium  3  into the left ventricle  5 . In a healthy heart, the mitral valve  8  closes completely and the aortic valve  13  opens so that blood is forced by contraction of the walls of the left ventricle  5  out through the aorta rather than back through the mitral valve  8  and into the left atrium  3 . In a diseased heart, the atrium and ventricles can swell causing the annulus  12  of the mitral valve  8  to become distended. This, in turn, prevents the leaflets  10  and  11  from fully closing resulting in retrograde flow through the mitral valve  8  and inefficient pumping by the heart.  
         [0068]     A solution for correcting swelling of the left atrium  3  and annulus  12  to provide improved closure of the mitral valve leaflets  10  and  11  is represented in  FIG. 1 . As shown, this solution involves locating a pair of anchors, one in the outer wall  14  of the left atrium and one in the atrial septum  6 . The anchor in the atrial wall  14  is referred to herein as the distal anchor  20  and the anchor in the septum  6  is referred to as the proximal anchor  30 . A tether  50  extends between and is connected to the anchors  20  and  30  to provide tension which pulls the exterior wall  14  toward the septum  6 . If the requisite tension is applied by tether  50  along the correct line, the shape of the annulus  12  of the mitral valve  8  will be corrected causing the leaflets  10  and  11  to close in a satisfactory manner.  
         [0069]      FIG. 3  shows the general construction of the anchor  30  when in its relaxed, deployed position. The anchor  20  may have either the same structure or a modified structure. As shown in  FIG. 3 , the anchor  30  is comprised of a wire mesh. The material used in forming the wire used in the mesh is ideally either a super-elastic or shape memory alloy. This allows the mesh to be stretched into an elongated shape for delivery via a catheter and return to the shape shown in  FIG. 3  automatically when deployed from the catheter and unconstrained by the inside wall of the catheter. Portions of the anchor may also be constructed of a bioabsorbable material such as magnesium or a polymer such as PLA/GLA. Also, the bioabsorbable material will be absorbed by the body over time.  
         [0070]     As is also shown in  FIG. 3 , the anchor  30  has a first expanded diameter portion  32  and a second expanded diameter portion  34  separated by a neck  36  of an appropriate length. The anchor  30  is intended to be passed through a naturally occurring or physician-created opening in the septal wall  16 . When in use, the first expanded diameter portion  32  resides on one side of the wall and the second expanded diameter portion  34  resides on the opposite side of the wall. The neck  36  is located in the hole through the wall. Given this configuration, the anchor  30  not only provides a firm connection to the septal wall  6 , but also occludes the opening through the septum  6 . Anchor  20  similarly provides both of these functions with respect to the outer wall  14  and a hole through the outer wall.  
         [0071]     Anchor  30  is shown as having two clamps  36  and  38 . The functions performed by these clamps can, of course, be performed by a single clamp if desired. The functions of the clamps include (1) preventing the braid from unraveling; (2) providing a channel in the anchor through which the tether can pass; (3) providing one portion of a threaded connection to which a delivery member can be attached; and (4) providing sturdy engagement for the tether. Further details related to the structure of these clamps are provided below.  
         [0072]      FIG. 4  shows an alternative anchor  31 . In this embodiment, the anchor is again formed of a braided wire mesh made preferably of a super-elastic or shape memory material. The anchor has a first elongated shape permitting it to pass through a catheter and the deployed shape shown in  FIG. 4 . In the deployed shape, the anchor  31  has an expanded diameter portion  33  having a wall engagement surface  35  and a neck that resides in the hole in the exterior or septal wall in which anchor  33  is deployed. Anchor  31  again has a pair of clamps  36  and  38 .  
         [0073]     A further embodiment of the invention is shown in  FIG. 5 . The embodiment includes a first anchor  40  and a second anchor  41 . Anchors  40  and  41  each comprise a braided wire mesh  42  having a tissue engaging surface  43  and a clamp  44 . In  FIG. 4 , the tether  50  is shown as a braided cable. Use of a braided cable adds strength while maintaining the flexibility required for transcatheter delivery of the device. As discussed below, the tether may also include a central lumen  51  extending its entire length. As shown, the distal end  52  of the tether  50  is fixed to clamp  44  of the anchor  40  and passes through and is in slidable engagement with the clamp  44  of anchor  41 . This slidable engagement is a temporary condition necessary for the tether  50  to be pulled tight between the two anchors  40  and  41  and so that the anchors  40  and  41  and tether  50  can cooperate to draw together the two walls to which the anchors are respectively coupled.  
         [0074]      FIG. 6  shows a mechanism for delivery and implantation of the anchors. The deliver system includes a catheter  60  and a delivery mechanism  62  coupled at its proximal end to a handle  64  and at its distal end to a threaded fitting  66 . The catheter  60  has a central lumen. This lumen is used for a variety of purposes. During an implantation procedure an introducer (not shown) will be used to gain access to the vasculature of the body. A guidewire (also not shown) is then passed through the introducer and vasculature to the treatment site (e.g., the right atrium of the heart). The lumen of the catheter  60  is then used to slide the catheter over the guidewire to the treatment site. The guidewire is then pulled out of the lumen.  
         [0075]     Various tools can then be advanced through the lumen to the treatment site. Such tools could include, for example, a fiber optic cable for visualizing the treatment site or a puncturing tool for piercing the septum or other heart wall at the anchoring location. The lumen is also used for delivery of the anchors and tether, any tools needed to lock the tether to the anchors, and any tools needed to trim and withdraw excess portions of the tether.  
         [0076]     The delivery member  62  also has a central lumen  68  that, as shown, extends the entire length of the delivery member  62 . As explained below, the tether  50  (and perhaps one or more other elements) is passed through this lumen  68  during implantation of the device.  
         [0077]     As shown in  FIGS. 1 and 5 , the distal end  52  of tether  50  must be fixed to the distal anchor  20 / 40 . Various options for fixing the distal end  52  of tether  50  to the distal anchor will now be discussed with reference to  FIG. 3 .  
         [0078]     First, the tether  50  can be clamped along with the ends of the wire(s) of the braid using either clamp  36  or  38 . If clamp  38  is used for this purpose, the clamp  36 , in addition to having threads  37 , should have an internal lumen through which the tether  50  is passed. During manufacture, the distal end of tether  50  can then be fixed to clamp  38  along with the wires of the braid.  
         [0079]     Second, both clamps  36  and  38  can have lumens extending therethrough. The distal end  52  of the tether  50  can be attached to a cap sized to seat on or in the distal end of clamp  38 . The tether  50  can then be threaded through the lumens of clamps  36  and  38  and pulled until the cap seats on or in the distal end of clamp  38 .  
         [0080]     Third, it may be desirable to have the cap reside within the wire mesh. In this case, the tether is threaded through the lumen in clamp  36  and pulled until the cap seats against the distal end of clamp  36 .  
         [0081]     Fourth, the cap on the distal end of the tether  50  can be provided with threads that cooperate with matching threads on one of clamps  36  or  38 . If the threads for joining the tether  59  are on clamp  36 , clamp  36  will have two sets of threads, one for permanently joining the tether  50  to the clamp  36  and the other for temporarily joining the delivery member to clamp  36 . The two sets of threads on clamp  36  can be provided coaxially such that one set is on the inside of the clamp and the other is on the outside of the clamp. If the threads for joining the tether  50  are on the clamp  38 , the tether  50  passes through a lumen in clamp  36  so that the tether can be attached at its distal end to clamp  38 .  
         [0082]     Various other arrangements for securing the distal end of the tether  50  to a distal anchor (including those discussed for fixing the tether  50  to the proximal anchor  30 / 40 ) can be employed without deviating from the invention. Generally speaking, the tether  50  will be coupled to the distal clamp either at the time of manufacture or at some other time prior to insertion of the distal anchor into the body. Thus, any number of arrangements can successfully be used.  
         [0083]     The range of available options is more limited for fixing the tether  50  to the proximal anchor  30 . This is because the anchor  30  will not generally be fixed to the tether  50  at a specific point along its length prior to implant, but only after the proximal anchor  30  is implanted. Of course, if the physician implanting the device knew prior to implant exactly what the length of the tether  50  between anchors  20  and  30  should be, any of the securement mechanisms described above with respect to the distal anchor could also be used in securing the proximal end of the tether  50  to the proximal anchor.  
         [0084]     Since the exact length is likely not known prior to implant, the securement arrangement used to fix the tether  50  and proximal anchor  30  together must first permit the tether  50  to be pulled through the proximal anchor  30  to take up any slack and supply the correct amount of tension, and second lock the tether  50  to the proximal anchor  30  at the desired point along the tether&#39;s length.  
         [0085]     Preferably, the clamp(s) of the proximal anchor  30  will have lumens through which the tether  50  can slidably pass and a securement mechanism that cooperates with at least one clamp of anchor  30  to secure the tether  50  to the proximal anchor  30  at the desired point along the tether&#39;s length. If the proximal anchor  30  has two clamps  36  and  38 , the most proximal clamp  36  will generally be used for this purpose.  
         [0086]     Various securement mechanisms can be employed that meet the need to fix the proximal anchor  30  to the tether  50 . For example, at least one of the clamps can be formed as a compression fitting having one or more gripping members that are biased toward a closed, gripping position. When the delivery member is attached to the fitting, the gripping members are spread permitting the tether to slide. However, as the delivery member is released, the gripping members close clamping the tether in place. Another is the use of a quick-setting cement. Still another is a cap that can slide over the tether through the catheter and cooperate with the clamp to secure the tether in place. Still another technique is to form a fitting made of a shape memory or super-elastic material that can slide over (or through) the tether and down the catheter to the location of clamp  36  which, upon warming or release from a constraint, changes shape to fix the tether  50  to the anchor  30 .  
         [0087]      FIGS. 7-12  show in greater detail various alternative arrangements that may be used to secure the tether  50  to the proximal anchor  30 . As shown in  FIG. 7 , the anchor  30  has a distal clamp  38  and a proximal clamp  36 . Both clamps prevent the wire braid from coming apart. Both also have a central lumen  35  through which the tether  50  can pass. Clamp  36  has a threaded section  37  which cooperates with the threaded fitting  66  of the delivery member  62  to temporarily secure the anchor to the delivery member. The tether is also shown as passing through the lumen  68  of the delivery member  62 .  
         [0088]     An important feature of the embodiment shown in  FIG. 7  is the set of barbs  39  located within the lumen  35  of clamp  36 . The barbs  39  are angled and positioned so that the tether  50  can only be pulled in the proximal direction. The barbs  39  seat against the tether  50  preventing movement in the distal direction. More specifically, the barbs  39  must be pointed in the direction that the tether  50  is drawn to increase tension between the two anchors. While the barbs  39  could be placed in the lumen  35  of either or both clamps  36  and  38 , it is typically advantageous to place barbs  39  only in clamp  36  so that tension supplied by tether  50  flattens the corresponding expanding diameter portion  32  against the septal wall  6 . If the tether  50  were locked to the distal clamp  38 , the tension supplied by tether  50  could pull the anchor  30  back through the hole in the wall  6 .  
         [0089]      FIG. 8  shows an alternative locking arrangement. Cooperating with the clamp  36  of anchor  30  is a wedge  80  having a lumen  81  through which the tether  50  can pass. The wedge  80  has a cylindrical section  82 , a locking section  84 , and a tapered section  86  having a first engagement wall  87 . An engagement member  88  having a second wall  89  and a third wall  90  has been added to the lumen  35  of clamp  30 . When in the locking position, the first engagement wall  87  of the wedge  80  is in face-to-face registration with the second engagement wall  89  of the clamp  36 . This prevents the wedge  80  from moving proximally relative to the anchor  30 . Also, the locking section  84  of the wedge  80  engages the third wall  90  of the clamp  36  to close the lumen  81  of the wedge  80  against the tether  50  thus locking the tether  50  to the anchor.  
         [0090]     The arrangement shown in  FIG. 8  offers several advantages. First, the tension supplied by the tether  50  can be easily adjusted and the results of differing amounts of tension supplied can be evaluated prior to inserting the wedge  80  into the lumen  35  of clamp  36 . Also, if there is a problem, the wedge  80  can be removed to permit readjustment of the tension. The wedge  80  can be made of any of a variety of polymer or metal materials.  
         [0091]      FIG. 9  shows a modification to the wedge  80  shown in  FIG. 8 . In this embodiment, the wedge  80  has a cylindrical section and a tapered locking section  84 . The wedge shown in  FIG. 9  can be used with a clamp that does not have an engagement member  88  thus making the clamp easier to machine.  
         [0092]      FIGS. 10   a - 10   c  show a cross-section of differing locking sections  84  of wedge  80 . A lumen  81  is shown in each case. Compression cutouts  83  are also shown. The compression cutouts  83  have wall segments  85  and  87  that move toward each other as the tapered section  86  is advanced into the lumen  35  of the clamp  36 . This serves to close the lumen  81  securely against the tether  50  to lock the tether  50  to the anchor.  
         [0093]     Still other alternative embodiments are shown in  FIGS. 11   a - 11   d . In these embodiments, the tether  50  has a lumen  51  such that an expansion member  100  can be advanced through lumen  51  to the location of the clamp  36  and expanded either inside the lumen  51  where it is coaxial with the lumen  35  of the clamp to fix the tether  50  to the clamp by pinching the wall of the tether  50  against the interior wall of the clamp or, as shown, just proximal to the clamp  36  so that it (and the tether at that location) has a diameter larger than the lumen  35  of the clamp  36 . When the tether  50  is pulled from the distal side of the clamp  36 , the section of tether  50  expanded by the expansion member  100  engages the distal surface of clamp  36  to prevent the tether  50  from being pulled through the lumen  35  toward the distal anchor. With this arrangement, the intersection between the lumen  35  and wall of the anchor  36  that engages the expanded portion of the tether  50  should be tapered so that there are no sharp edges that could cut the tether. The expansion member  100  could be in the form of a balloon that is inflated. The expansion member can also comprise various mechanical arrangements such as, for example, a self-expanding structure made of a super-elastic or shape memory material. The expansion member  100  can also be a permanent structure or simply be used to change the shape of the tether  50  and then deflated and removed as suggested by  FIGS. 11   c  and  11   d.    
         [0094]     From the foregoing, it should be clear that the tension applied by the tether  50  must be less than that required to pull either of the anchors through the hole in the wall to which the anchor is attached. Therefore, in some cases it may be desirable to reinforce the expanded diameter portion on the distal side of wall  14  and the expanded diameter portion on the proximal side of wall  6  after they are in place, but before tension is applied via the tether  50 .  FIGS. 12-13  show how this could be done.  
         [0095]     By way of example,  FIG. 12  shows an annular circumferential ring  110  positioned within the proximal expanded diameter portion  32  of anchor  30 . Once in place, ring  110  prevents the circumference of the expanded diameter portion  32  from contracting. In fact, the ring  110  preferably continually applies an urging force outwardly against the circumference of the expanded diameter portion  32 . The ring  110  is preferably made of nitinol or some other super-elastic or shape memory material. As shown in  FIG. 13 , the ring can be straightened for passage through a lumen (such as the lumen of the delivery member) for deployment into the expanded diameter portion of the anchor. Upon deployment, the ring  110  returns to its ring shape and forces the expanded diameter portion of the anchor outwardly to prevent the expanded diameter portion from being pulled through the hole in the wall of the heart as tension is applied by the tether  50 .  
         [0096]     Use of the devices described above offers many advantages over surgical procedures used today. These advantages relate to ease of use, less trauma to the patient, and reduced recovery time. To better understand these advantages, the procedure for implementing a device made in accordance with the present invention will now be discussed.  
         [0097]     Prior to undertaking the implant procedure, the physician will, of course, carry out various diagnostic procedures to assess whether and how use of the device might help the patient. If mitral valve regurgitation is to be treated, such diagnostic procedures would typically include radiologic study of the patient&#39;s heart to assess the degree of the problem, the geometry of the valve, and the geometry of surrounding heart structures. Such diagnostic procedures would also typically include mapping the conduction paths through the tissue of the heart. The physician will then assess the data to determine where the anchors can be placed so the tether applies appropriate tensioning to correct the problem with valve closure and does not interfere with conduction through the tissue.  
         [0098]     The physician will also take into account the location of other structures to ensure that neither of the anchors nor the tether interferes with the operation of those structures. In the event the patient has naturally occurring, but unnecessary and often undesirable openings through the septum such as an ASD, VSD, PFO or the like, the physician considers whether the location of these openings would be suitable for anchoring.  
         [0099]     After careful planning, the physician is ready to begin the implantation of the device. An introducer is used to gain access to the vasculature of the body. The distal end of a guidewire is inserted through the introducer and vessels until it reaches the superior vena cava at which point it is advanced through the superior vena cava into the right atrium. If the patient has an already existing opening through the septum, the guidewire can be further advanced through that opening into the left atrium. If there is no such naturally occurring opening available, the distal guidewire is left in the right atrium.  
         [0100]     Next, a catheter  60  is advanced over the guidewire until the distal end of catheter  60  reaches the right atrium (or in the case of an already existing opening) through the septum, the left atrium. The guidewire is then removed so that the lumen of catheter  60  can be used to gain access to the heart with other devices.  
         [0101]     One or two holes will need to be punctured to permit implantation of the anchors. Thus, the catheter is used to direct a puncturing tool to the anchor site(s). If there is not already a suitable opening in the septal wall, the desired location for this opening is identified and the puncturing tool is used to create an opening of an appropriate size. The catheter is then advanced through this first opening to the site for the other anchor and a second opening may be punctured through the tissue. The puncturing tool is then pulled back out through the catheter.  
         [0102]     The next step is to implant the distal anchor  20  with the tether  50  secured to it. This is done via the catheter  60  using the delivery member  62 . The tether  50  is pulled through the lumen  68  of the delivery member  62  and the delivery member  62  is then coupled to the distal anchor  20  using the threads of clamp  36  of the anchor and the threaded fitting  66  of the delivery member. The anchor  20  is then passed through the lumen of catheter  60  by pushing on the delivery member until it reaches the second hole. Preferably, the distal end of the catheter  60  is advanced a short distance through and past the second hole. The distal expanded diameter portion  34  is then deployed from the catheter on the distal side of the wall. The catheter is then retracted back through the hole where the rest of anchor  20  is deployed. When fully deployed, opposing surfaces of expanded diameter portions  32  and  34  contact opposite sides of the wall. Also, the neck  36  expands to engage the tissue surrounding the opening cut through the wall. The anchor  20  thus occludes the opening preventing blood from flowing out the opening cut in the wall. The anchor  20  also secures the distal end of the tether  50  in place. If desired, a reinforcing member  100  is passed through the lumen  68  of the delivery member  62  and into the distal expanded diameter portion  34  of anchor  20  where it assumes a ring shape and provides an outward force against the circumference of expanded diameter portion  34 . The delivery member is then unscrewed from the anchor  20  and fully retracted from the catheter as the catheter is left in place.  
         [0103]     Next, the proximal anchor  30  is implanted. To do so, the delivery member  62  is attached to clamp  36  of anchor  30 . The proximal end of tether  50  is then inserted through the lumens in clamps of the anchor  30  and through the lumen in the delivery member. The anchor  30  is advanced through the lumen of catheter  60  to the distal end of the catheter  60  which still preferably resides in the left atrium. The distal portion  34  of anchor  30  is pushed out of the catheter and permitted to expand and deploy. The assembly is pulled back until the wall contacting surface of expanded diameter portion  34  engages the distal side of the septal wall  6 . The catheter  60  is retracted further permitting the proximal expanded diameter portion  36  to deploy in the right atrium and the neck  36  to move outwardly into contact with the tissue surrounding the opening in the septal wall. In this way, the anchor  30  occludes the opening in the septal wall preventing blood flow through the opening. If desired, a reinforcing ring  110  can be deployed in expanded diameter portion  36  of anchor  30  via the lumen  68  of the delivery member  62 .  
         [0104]     At this point, the physician is ready to apply tension to the tether  50  to relieve any slack in the tether between the two anchors and also to pull tissue to which the distal anchor  20  is attached toward the proximal anchor  30 . Radiological visualization and other assessment tools can be used at this point to determine what amount of tension will provide the greatest benefit in terms of proper valve closure and maximum cardiac efficiency. The tether can be temporarily clamped in place outside the body while such assessments are made.  
         [0105]     Once the assessments are completed and the tether is in the desired position with respect to proximal anchor  30 , the permanent securement mechanism is deployed, and the delivery member is detached from the anchor  30  and retracted. Of course, the permanent securement mechanism may also be deployed after the delivery member has been detached. A tether cutting tool is advanced through the catheter into the right atrium to cut the tether proximally of the clamp  36  and permanent securement mechanism. The cutting tool, excess tether material and catheter are then removed essentially completing the procedure.  
         [0106]      FIGS. 14   a - 14   f  are provided to help explain how the tether  50  is fixed to the anchor  30  at the correct point along the length of tether  50  to supply the correct amount of tension between the two anchors.  
         [0107]     In  FIG. 14   a , the distal anchor (not shown) is already implanted with the tether  50  extending proximally through and out the proximal end of the delivery catheter  60 . As shown, the proximal end of the tether  50  has been threaded through the anchor  30  and through the lumen  68  of the delivery member  62 . The threaded connection between the threads  37  of proximal clamp  36  of the anchor  30  and fitting  66  of the delivery member  62  is used to temporarily join the anchor  30  to the end of the delivery member  62 . The delivery member is then used to push the anchor  30  through the catheter  60  to the hole in the septum  6  where the anchor is deployed.  
         [0108]      FIG. 14   b  shows the anchor  30  positioned in the hole through the septum  6 . Also shown is a wedge  80  and a pusher  85  having a lumen through which the tether  50  has been threaded. The distal end of the pusher  85  engages the wedge  80  to advance the wedge  80  through the lumen  68  of the delivery member  62  toward the anchor  30 . At this point, the physician can still adjust the tension supplied by the tether  50  because the tether  50  is not yet locked to the anchor  30 . When the physician has determined the desired point along the tether&#39;s length, the physician temporarily clamps the tether  50  to the delivery member  62  outside of the body of the patient to restrict movement between the tether  50  and the delivery member  62 . The physician then can pull slightly on the delivery member  62  while pushing on the pusher  85  to further advance the wedge  80  and to force the wedge  80  into the lumen of clamp  36  and thus lock the tether  50  to the clamp  36  at the desired point along its length.  
         [0109]     Next, the delivery member  62  is decoupled from the anchor  30  and removed from the patient as shown in FIG.  14   c . After removal of the delivery member  62 , the proximal end of the tether  50  is passed through an elongated tool  150  having a cutting head  152  at its distal end. See  FIG. 14   d . The elongated cutting tool is then advanced through the delivery catheter  60  (not shown) until it reaches the clamp  36  of anchor  30 . The cutting tool is then actuated to cut the tether  50 . The unused portion of the tether  50 , the cutting tool  150  and the delivery catheter  60  are then removed from the patient as indicated in  FIG. 14   e.    
         [0110]     Within the first few weeks following the procedure, the anchors will endothelialize further enhancing occlusion and anchoring and further reducing the risk of thrombosis. The risk of thrombosis can be further reduced by forming the components out of or coating the components with a non-thrombogenic material.  
         [0111]     The foregoing discussion is not intended to be limiting. Instead, the following claims define the scope of this invention.