Abstract:
A device for treatment of mitral annulus dilation is disclosed, wherein the device comprises two states. In a first of these states the device is insertable into the coronary sinus and has a shape of the coronary sinus. When positioned in the coronary sinus, the device is transferable to the second state assuming a reduced radius of curvature, whereby the radius of curvature of the coronary sinus and the radius of curvature as well as the circumference of the mitral annulus is reduced.

Description:
REFERENCE TO RELATED APPLICATIONS 
   The present application is a continuation-in-part of U.S. patent application Ser. No. 09/775,677, filed Feb. 5, 2001, which is a continuation-in-part of U.S. patent application Ser. No. 09/345,475, filed Jun. 30, 1999, now U.S. Pat. No. 6,210,432. The present application also claims priority of provisional application No. 60/344,121 entitled METHOD AND DEVICE FOR TREATMENT OF MITRAL INSUFFICIENCY, filed Dec. 28, 2001. 

   FIELD OF THE INVENTION 
   The present invention relates to a device for treatment of mitral insufficiency and, more specifically, for treatment of dilation of the mitral annulus. 
   BACKGROUND OF THE INVENTION 
   Mitral insufficiency can result from several causes, such as ischemic disease, degenerative disease of the mitral apparatus, rheumatic fever, endocarditis, congenital heart disease and cardiomyopathy. The four major structural components of the mitral valve are the annulus, the two leaflets, the chordae and the papillary muscles. Any one or all of these in different combinations may be injured and create insufficiency. Annular dilation is a major component in the pathology of mitral insufficiency regardless of cause. Moreover, many patients have a mitral insufficiency primarily or exclusively due to posterior annular dilation, since the annulus of the anterior leaflet does not dilate because it is anchored to the fibrous skeleton of the base of the heart. 
   Studies of the natural history of mitral insufficiency have found that totally asymptomatic patients with severe mitral insufficiency usually progress to severe disability within five years. Currently, the treatment consists of either mitral valve replacements or repair, both methods requiring open heart surgery. Replacement can be performed with either mechanical or biological valves. 
   The mechanical valve carries the risk of thromboembolism and requires anticoagulation, with all its potential hazards, whereas biological prostheses suffer from limited durability. Another hazard with replacement is the risk of endocarditis. These risks and other valve related complications are greatly diminished with valve repair. 
   Mitral valve repair theoretically is possible if an essentially normal anterior leaflet is present. The basic four techniques of repair include the use of an annuloplasty ring, quadrangular segmental resection of diseased posterior leaflet, shortening of elongated chordae, and transposition of posterior leaflet chordae to the anterior leaflet. 
   Annuloplasty rings are needed to achieve a durable reduction of the annular dilation. All the common rings are sutured along the posterior mitral leaflet adjacent to the mitral annulus in the left atrium. The Duran ring encircles the valve completely, whereas the others are open towards the anterior leaflet. The ring can either be rigid, like the original Carpentier ring, or flexible but non-elastic, like the Duran ring or the Cosgrove-Edwards ring. 
   Effective treatment of mitral insufficiency currently requires open-heart surgery, by the use of total cardiopulmonary bypass, aortic cross-clamping and cardioplegic cardiac arrest. To certain groups of patients, this is particularly hazardous. Elderly patients, patients with a poor left ventricular function, renal disease, severe calcification of the aorta, and those having previous cardiac surgery or other concomitant diseases would in particular most likely benefit from a less invasive approach, even if repair is not complete. 
   In view of these drawbacks of previously known treatments, it would be desirable to provide a minimally invasive approach to treat mitral insufficiency, i.e., without the need for cardiopulmonary bypass and without opening of the chest and heart. 
   It also would be desirable to provide a reduction of the mitral annulus using only catheter based technology. 
   It further would be desirable to provide a treatment for mitral insufficiency that minimizes trauma to a patient&#39;s vasculature while using catheter based technology. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, it is an object of the present invention to provide a minimally invasive approach to treat mitral insufficiency, i.e., without the need for cardiopulmonary bypass and without opening of the chest and heart. 
   It is also an object of the present invention to provide a reduction of the mitral annulus using only catheter-based technology. 
   It is another object of the present invention to provide a treatment for mitral insufficiency that minimizes trauma to a patient&#39;s vasculature while using catheter based technology. 
   These and other objects of the present invention are achieved by providing a device for treatment of mitral insufficiency, whereby the circumference of the mitral valve annulus is reduced when the device is deployed and/or actuated in at least a portion of the coronary sinus. 
   The device in accordance with principles of the present invention may comprise one or more components suitable for deployment in the coronary sinus and adjoining coronary veins. The device may be configured to bend in-situ to apply a compressive load to the mitral valve annulus with or without a length change, or may include multiple components that are drawn or contracted towards one another to reduce the circumference of the mitral valve annulus. Any of a number of types of anchors may be used to engage the surrounding vein and tissue, including hooks, barbs, flanges, partial or completely through-wall tee structures, or biological anchoring. Where multiple components are provided, reduction of the mitral valve annulus may be accomplished during initial deployment of the device, or by biological actuation during subsequent in-dwelling of the device. 
   In one embodiment comprising multiple components, the device comprises proximal and distal stent sections, wherein the proximal stent section comprises a deployable flange. The stent sections are delivered into the coronary sinus in a contracted state, and then are deployed within the coronary venous vasculature so that the flange engages the coronary sinus ostium. A cinch mechanism, comprising, for example, a plurality of wires and eyelets, is provided to reduce the distance between proximal and distal stent sections, thereby reducing the circumference of the mitral valve annulus. 
   In an alternative embodiment, the distal stent is replaced by or includes a suitably-shaped distal anchor that is disposed within or through the left ventricular myocardium. The distal anchor may be in the form of a Tee-shape or barbed section, and engages the ventricular myocardium, or extends into the left ventricle, to provide a distal fixation point. As in the preceding embodiment, a cinch mechanism is provided to shorten a structure, such as a wire, that extends between the proximal stent and the distal anchor. The distal anchor may be used alone or in conjunction with the proximal flange of the preceding embodiment. 
   In a further alternative embodiment, a balloon catheter is used wherein a balloon in fluid communication with a lumen of the catheter comprises a predetermined deployed shape. A stent, which may be compressed onto the balloon in a contracted state, then is plastically deformed by the balloon within the coronary sinus, and the stent substantially conforms to the predetermined shape of the balloon in a deployed state. The balloon preferably comprises a convex shape, so that the stent will assume the convex shape of the balloon and bend the coronary sinus accordingly. The shape of the stent, convex or otherwise, will be configured to reduce the circumference of the mitral valve annulus when deployed in the coronary sinus. 
   The configuration of cells of the stent also may be varied to encourage the stent to assume a convex shape upon deployment. For example, one side of the stent may be configured to expand a greater amount than the other side, thereby imparting a convex curvature upon the stent. To facilitate proper positioning of the stent within the coronary sinus, an intravascular ultrasound transducer or radiopaque marker bands may be used to align the correct side of the stent adjacent the mitral valve annulus. 
   In a yet further embodiment, the proximal and distal stent sections are directly coupled to one another by a central section, so that expansion of the central section causes the proximal and distal stent sections to be drawn together. In this embodiment, however, the central section includes one or more biodegradable structures, such as biodegradable sutures, that retain the central section in its contracted state until the vessel endothelium has overgrown a portion of the proximal and distal stent sections, thereby providing biological anchoring of the proximal and distal stent sections. After the proximal and distal stent sections have become endothelialized, the biodegradable structure degrades, releasing the central section and enabling it to expand. The central section thereby applies a tensile load to the proximal and distal stent sections, causing a reduction in the circumference of the mitral valve annulus. 
   A yet further alternative embodiment comprises a series of linked segments that are capable of relative rotational and telescoping movement. In a preferred embodiment, each segment includes a ball element that couples to a socket element on an adjacent segment. The ball and socket connections permit the segments of the device to become angled relative to one another so that the device is capable of assuming a three-dimensional curvature. A cinch wire extends through a passage in the segments and permits the device to be cinched rigidly into a predetermined shape. Some segments also may include telescoping joints that permit the overall length of the device to be reduced upon actuation of the cinch wire. The cinch wire may include either a locking mechanism attached to the cinch wire or alternatively may include striations on the contacting ball and socket surfaces that permit the segments to rigidly engage one another when cinched. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which: 
       FIG. 1  is a cross-sectional view of a part of a heart; 
       FIGS. 2–3  are schematic views of a first embodiment according to the present invention; 
       FIGS. 4–6  are schematic views illustrating an instrument that may be used when positioning the device of  FIGS. 2–3  in the coronary sinus; 
       FIG. 7  is a partial, enlarged view of the first embodiment shown in  FIG. 2 ; 
       FIGS. 8–9  are schematic views illustrating the positioning of the device of  FIGS. 2–3  in the coronary sinus; 
       FIGS. 10–11  are schematic views illustrating the positioning of a solid U-shaped wire within the coronary sinus; 
       FIGS. 12A–12D  illustrate an alternative embodiment comprising a deployable flange coupled to the proximal stent section; 
       FIGS. 13A–13B  illustrate deployment and actuation of the device of  FIGS. 12A–12C ; 
       FIGS. 14A–14C  illustrate an alternative embodiment of the device of the present invention having a distal anchor; 
       FIGS. 15A–15B  illustrate deployment and actuation of the device of  FIGS. 14A–14C ; 
       FIGS. 16A–16B  illustrate another alternative embodiment of the device of the present invention comprising a balloon-expandable device that is deployed to a curved shape; 
       FIGS. 17A–17B  illustrate a balloon that deploys to a predetermined curved shape; 
       FIGS. 18A–18C  are perspective and side views of a further alternative embodiment of a device of the present invention; 
       FIGS. 19A–19D  illustrate deployment of the device depicted in  FIGS. 18A–18B ; and 
       FIGS. 20–22  illustrate a still further alternative embodiment of the present invention comprising a plurality of interconnected segments and deployment thereof. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention takes advantage of the position of the coronary sinus being close to the mitral annulus. This makes repair possible by the use of current catheter-guided techniques by deploying one element in the coronary venous vasculature that applies a load to, and reshapes, the adjacent posterior portion of the mitral annulus. 
   The coronary veins drain blood from the myocardium to the right atrium. The smaller veins drain blood directly into the atrial cavity, and the larger veins accompany the major arteries and run into the coronary sinus which substantially encircles the mitral orifice and annulus. The coronary sinus runs in the posterior atrioventricular groove, lying in the fatty tissue between the left atrial wall and the ventricular myocardium, before draining into the right atrium between the atrial septum and the post-Eustachian sinus. 
     FIG. 1  is a cross-sectional view through the heart area of posterior atrioventricular groove  1 , which is filled with fatty tissue. It shows posterior leaflet  2  of the mitral valve and adjoining parts  3 ,  4  of the atrial myocardium and the ventricular myocardium. Coronary sinus  5  is shown close to mitral annulus  6  and behind attachment  7  of posterior leaflet  2 . Since coronary sinus  5  substantially encircles mitral annulus  6 , a reduction of the radius of curvature of bent coronary sinus  5  also will result in a diameter and circumference reduction of mitral annulus  6 . 
   In an adult, the course of coronary sinus  5  may approach within 5–15 mm of the medial attachment of posterior leaflet  2  of the mitral valve. Preliminary measurements performed at autopsies of adults of normal weight show similar results, with a distance of 5.3±0.6 mm at the medial attachment and about 10 mm at the lateral aspect of posterior leaflet  2 . The circumference of coronary sinus  5  was 18.3±2.9 mm at its ostium (giving a sinus diameter of the septal aspect of the posterior leaflet of 5.8±0.9 mm) and 9.7±0.6 mm along the lateral aspect of posterior leaflet  2  (corresponding to a sinus diameter of 3.1±0.2 mm). 
   In accordance with the principles of the present invention, devices and methods for treating mitral insufficiency are provided, wherein the circumference of the mitral valve annulus is reduced when the device is deployed and/or actuated in at least a portion of the coronary sinus. 
   Devices constructed in accordance with principles of the present invention may comprise one or more components suitable for deployment in the coronary sinus and adjoining coronary veins. The device may be configured to bend in-situ to apply a compressive load to the mitral valve annulus with or without a length change, or may include multiple components that are drawn or contracted towards one another to reduce the circumference of the mitral valve annulus. Any of a number of types of anchors may be used to engage the surrounding vein and tissue, including hooks, barbs, flanges, partial or completely through-wall tee structures, or biological anchoring. Where multiple components are provided, reduction of the mitral valve annulus may be accomplished during initial deployment of the device, or by biological actuation during subsequent in-dwelling of the device. 
   With respect to  FIGS. 2 and 3 , a device that experiences shortening during deployment is described as comprising an elongate body  8  made of memory metal, e.g. Nitinol, or other similar material which has a memory of an original shape, illustrated in  FIG. 3 , and which can be temporarily forced into another shape, illustrated in  FIG. 2 . Elongate body  8  comprises one, two or more memory metal strings  9  of helical or other shape so as to fit together and be able of to permit the movements described below. Along elongate body  8 , plurality of hooks  10  are fastened so as to extend radially out therefrom. Hooks  10  are covered by a cover sheath  11  in  FIG. 2 . 
   Elongate body  8  is forced into a stretched or extended state by means of stabilizing instrument  12  shown in  FIG. 4 . Instrument  12  has two arms  13  at distal end  14  of rod  15  and locking means  16  at proximal end of rod  15 . The distance between the ends of rod  15  corresponds to the desired length of elongate body  8  when being inserted into coronary sinus  5 . 
   Arms  13  are free to move between the position shown in  FIG. 4  and a position in alignment with rod  15 , as shown in  FIG. 6 . Locking means  16  has two locking knobs  17 , which are pressed radially outwards from rod  15  by two spring blades  18 . Thus, elongated body  8  can be pushed over rod  15  of stabilizing instrument  12 , then stretched between arms  13  and knobs  17 , and finally locked in its stretched state on stabilizing instrument  12  between arms  13  and knobs  17 , as illustrated in  FIG. 5 . 
   Rod  15  may be a metal wire which is relatively stiff between distal end  14  and locking means  16  but still so bendable that it will follow the shape of coronary sinus  5 . Proximally of locking means  16  the metal wire of stabilizing instrument  11  is more pliable to be able to easily follow the bends of the veins. 
   The above-described elongate body  8  is positioned in the coronary sinus  5  in the following way: 
   An introduction sheath (not shown) of synthetic material may be used to get access to the venous system. Having reached access to the venous system, a long guiding wire (not shown) of metal is advanced through the introduction sheath and via the venous system to coronary sinus  5 . This guiding wire is provided with X-ray distance markers so that the position of the guiding wire in coronary sinus  5  may be monitored. 
   Elongate body  8  is locked onto stabilizing instrument  12 , as shown in  FIG. 5 , and introduced into long cover sheath  11  of synthetic material. This aggregate is then pushed through the introduction sheath and the venous system to coronary sinus  5  riding on the guiding wire. After exact positioning of elongate body  8  in coronary sinus  5 , as illustrated in  FIG. 8  where mitral valve  19  is shown having central gap  20 , cover sheath  11  is retracted to expose elongate body  8  within coronary sinus  5 . This maneuver allows hooks  10  on elongate body  8  to dig into the walls of coronary sinus  5  and into the heart. Elongate body  8  is still locked on to stabilizing instrument  12  such that hooks  10  engage the walls of coronary sinus  5  in the stretched or extended state of elongate body  8 . 
   Catheter  12 , shown in  FIG. 6 , is pushed forward on the guiding wire and rod  15 , to release elongate body  8  from locking means  16  by pressing spring blades  18  toward rod  15 . This movement releases knobs  17  as well as arms  13  from engagement with elongate body  8 , which contracts elongate body  8  as illustrated in  FIG. 9 , thereby shortening the radius of curvature of coronary sinus  5 . As a result, mitral valve annulus  6  shrinks moving the posterior part thereof forward (shown by arrows in  FIG. 9 ). This movement reduces the circumference of mitral valve annulus  6  and thereby closes central gap  20 . 
     FIG. 7  illustrates a part of an arrangement of wires  9  and hooks  10  along a peripheral part of elongate body  8 , whereby elongate body  8  will be asymmetrically contracted resulting in a bending thereof when interconnecting parts  13  of at least some of hooks  10  are shortened to an original shape. 
     FIGS. 10 and 11  illustrate an alternative embodiment of an elongate body  8 ′ which does not experience shortening during deployment. Elongate body  8 ′ comprises a solid wire in the shape of an open U-shaped ring that will engage the wall of coronary sinus  5  most adjacent to mitral valve annulus  6  when inserted into coronary sinus  5 . Elongate body  8 ′ consists of a memory metal material which when reverting to its original shape will bend as illustrated in  FIG. 11 . The return of open ring  8 ′ to its original shape may be initiated in several ways, as is obvious to one skilled in the art. 
   Further embodiments comprising two or more stent sections that are coupled by a system of wires and eyelets are described in co-pending U.S. patent application Ser. No. 09/775,677 (“the &#39;677 application”), filed Feb. 5, 2001, U.S. Patent Application Publication No. 2001/0018611, which is incorporated herein by reference. In the embodiments described therein, individual proximal and distal stents are first deployed in the coronary sinus, and a cinch mechanism, illustratively comprising a wire and eyelets, is used to draw the proximal and distal stent sections towards one another, thereby reducing the circumference of the mitral valve annulus. 
   Referring now to  FIG. 12 , a further alternative embodiment is described, wherein the proximal stent section includes a flange that can be deployed to abut against the coronary ostium. Apparatus  56  comprises device  58  disposed within delivery sheath  60 . Device  58  comprises proximal stent section  62  joined to distal stent section  64  via wire  66  and cinch mechanism  67 . Proximal and distal stent sections  62  and  64  illustratively are self-expanding stents, but alternatively may comprise balloon expandable stents, coiled-sheet stents, or other type of stent. 
   Stents  62  and  64  are disposed within delivery sheath  60  with a distal end of push tube  68  contacting the proximal end of proximal stent section  62 . Proximal stent section  62  comprises deployable flange  69 . Deployable flange  69  is initially constrained within delivery sheath  60 , as shown in  FIG. 12A , and preferably comprises a shape memory material, e.g., Nitinol, so that flange  69  self-deploys to a predetermined shape upon retraction of delivery sheath  60 . 
   Wire  66  and cinch mechanism  67  may comprise a combination of wires and eyelets as described in accordance with any of the embodiments in the &#39;677 application, or any other arrangement that permits the wire to be tightened and locked into position, as will be apparent to one of ordinary skill. Wire  66  includes a proximal portion that remains outside of the patient&#39;s vessel for manipulation by a physician, and is configured to reduce the distance between proximal and distal stent sections  62  and  64 . 
   Apparatus  56  is navigated through the patient&#39;s vasculature with stents  62  and  64  in the contracted state and into coronary sinus C. The distal end of sheath  60  is disposed, under fluoroscopic guidance, at a suitable position within the coronary sinus, great cardiac vein, or adjacent vein. Push tube  68  is then urged distally to eject distal stent section  64  from within delivery sheath  60 , thereby permitting distal stent section  64  to self-expand into engagement with the vessel wall, as shown in  FIG. 12B . 
   Delivery sheath  60  is then withdrawn proximally, under fluoroscopic guidance, until proximal stent  62  is situated extending from the coronary sinus. Push tube  68  is then held stationary while sheath  60  is further retracted, thus releasing proximal stent section  62 . Once released from delivery sheath  60 , proximal stent section  62  expands into engagement with the wall of the coronary sinus, and flange  69  abuts against the coronary ostium O, as shown in  FIG. 12C . 
   Delivery sheath  60  (and or push tube  68 ) may then be positioned against flange  69  of proximal stent section  62 , and wire  66  retracted in the proximal direction to draw distal stent section  64  towards proximal stent section  62 . As will of course be understood, distal stent section  64  is drawn towards proximal stent section  62  under fluoroscopic or other type of guidance, so that the degree of reduction in the mitral valve annulus may be assessed. As wire  66  is drawn proximally, cinch mechanism  67  prevents distal slipping of the wire. For example, wire  66  may include a series of grooves along its length that are successively captured in a V-shaped groove, a pall and ratchet mechanism, or other well-known mechanism that permits one-way motion. Catheter  60  and push tube  68  then may be removed, as shown in  FIG. 12D . 
   Flange  69  may comprise a substantially circular shape-memory member, as illustrated, a plurality of wire members, e.g., manufactured using Nitinol, that self-deploy upon removal of sheath  60  and abut ostium O when proximally retracted, or other suitable shape. 
   Referring to  FIG. 13 , a preferred method for using apparatus  56  of  FIG. 12  to close a central gap  72  of mitral valve  70  is described. In  FIG. 13A , proximal and distal stent sections  62  and  64  are deployed in the coronary sinus so that flange  69  of proximal stent section  62  engages coronary ostium O. Distal stent section  64  is disposed at such a distance apart from proximal stent section  62  that the two stent sections apply a compressive force upon mitral valve  70  when wire  66  and cinch  67  are actuated. 
   In  FIG. 13B , cinch  67  is actuated from the proximal end to reduce the distance between proximal and distal stent section  62  and  64 , e.g., as described hereinabove. When wire  66  and cinch mechanism  67  are actuated, distal stent section  64  is pulled in a proximal direction and proximal stent section  62  is pulled in a distal direction until flange  69  abuts coronary ostium O. The reduction in distance between proximal and distal stent sections  62  and  64  reduces the circumference of mitral valve annulus  71  and thereby closes gap  72 . Flange  69  provides a secure anchor point that prevents further distally-directed movement of proximal stent section  62 , and reduces shear stresses applied to the proximal portion of the coronary sinus. 
   Referring now to  FIG. 14 , a further aspect of the present invention is described, in which the distal stent section of the embodiment of  FIG. 12  is replaced with an anchor that is disposed within or through the myocardium. As will be appreciated, this feature of the device of the present invention may be used either separately or in conjunction with the flange feature described hereinabove. Device  90  comprises proximal stent section  92  coupled by wire  94  and cinch mechanism  95  to distal anchor  96 . Proximal stent section  92  may include flange  93 . Optional coil section  98  extends distally from proximal stent section  92  to distal anchor  96 , and serves to distribute compressive forces created by wire  94  to a larger area of the venous vessel wall. 
   Device  90  is loaded into delivery apparatus  100  comprising curved stylet  102 , push wire  104  and delivery sheath  106 . Curved stylet  102  preferably comprises a shape memory alloy capable of being straightened, but adopting a curved shape when extended beyond a distal end of delivery sheath  106 . Curved stylet  102  includes sharpened distal tip  101  capable of piercing the left ventricular myocardium, and is disposed in lumen  105  of delivery sheath. Push wire  104  is slidably disposed in lumen  103  of curved stylet  102 , and may be advanced distally to eject distal anchor  96  into the left ventricular myocardium or the left ventricle. 
   As depicted in  FIG. 14A , distal anchor comprises a Tee-shaped bar to which wire  94  is coupled. Optional coil section  98  also may be coupled to distal anchor  96 , and is contracted around curved stylet  102  when device  90  is loaded into delivery sheath  106 . Distal anchor  96  is disposed within lumen  103  of curved stylet so that wire  94  and coil section  98  exit through lateral slot  107  in the stylet. Push wire  104  is disposed in lumen  103  of stylet  102  abutting against the proximal face of distal anchor  96 . 
   In  FIG. 14A , device  90  is shown loaded into delivery apparatus  100 . Delivery apparatus  100  has been disposed in the coronary sinus using conventional guidance and visualization techniques. The distal end of delivery apparatus  100  is advanced into the coronary venous vasculature to a desired location, and then stylet  102  is advanced distally beyond the end of delivery sheath  106 , thereby causing the stylet to regain its curved shape. Further advancement of stylet  102  causes the distal end of the stylet to pierce the coronary vein and extend into the left ventricular myocardium. Push rod  104  is then advanced distally to eject distal anchor  96  into the myocardium, or within the left ventricle, as shown in  FIG. 14B . 
   Stylet  102  and push wire  104  are then withdrawn, and delivery sheath  106  is retracted until the proximal stent section is disposed extending out of the coronary ostium. By selection of the length of wire  94  fed through cinch mechanism  95 , proximal stent section  92  may be deployed simply by retracting delivery sheath  106 , because distal anchor  96  and wire  94  will prevent further proximal movement of proximal stent section  92 . In any event, when proximal stent section  92  is released from delivery sheath  106 , it self-expands to engage the vessel wall while flange  93  contacts the coronary ostium, as shown in  FIG. 14C . 
   The proximal end of proximal wire  94  extends through lumen  105  of delivery sheath  106  and may be manipulated by a physician. As in the previous embodiment, once the proximal stent section is deployed, wire  94  may be pulled proximally, with cinch mechanism  95  taking up any slack. The distance between distal anchor  96  and proximal stent section  92  may therefore be reduced a desired amount, causing a corresponding reduction in the circumference of the mitral valve annulus. Optional coil section  98 , if present, assists in redistributing the compressive forces applied by wire  94  to the interior surface of the venous vessel. 
   Referring to  FIGS. 15A and 15B , device  90  of  FIG. 14  is illustrated in a deployed state to treat mitral insufficiency. Flange  93  is deployed abutting coronary ostium O, e.g., within right atrium A. Proximal stent section  92  and optional coil section  98  are deployed within the coronary sinus and great cardiac vein C. Distal anchor  96  is disposed within myocardium M, or alternatively, may extend into the left ventricle or another suitable region, as will be obvious to those skilled in the art. It should further be appreciated to those skilled in the art that while anchor  96  is illustrated as a cylindrical bar, it may comprise square, circular or other configurations, e.g., a plurality of barbs. 
   The proximal end of wire  94  extends through cinch mechanism  95  and is manipulated to impose tension on wire  94 , thereby reducing the distance between proximal stent section  92  and distal anchor  96 . This in turn reduces the circumference of coronary sinus C accordingly, as shown in  FIG. 15B . Upon completion of the procedure, i.e., when gap  72  is sufficiently closed, apparatus  100  is removed from the patient&#39;s vessel. 
   Advantageously, the use of distal anchor  96  is expected to reduce the shear stress imposed on coronary sinus C relative to the use of a proximal stent section alone as described for the embodiment of  FIGS. 12 and 13 . 
   Referring now to  FIGS. 16 and 17 , another embodiment of a device suitable for repairing mitral valve insufficiency is described. In this embodiment, device  110  comprises a balloon expandable stent  112 , which may be tapered along its length. Stent  112  is disposed on balloon  114  at the distal region of balloon catheter  113 . Balloon  114  is capable of assuming a curved shape when inflated. As depicted in  FIG. 16A , stent  112  and balloon catheter  113  are disposed in the patient&#39;s coronary sinus through the coronary ostium. 
   Once the position of stent  112  is determined, for example, by fluoroscopy, balloon  114  is inflated via to expand balloon  114  to its predetermined curved shape. Inflation of balloon  114  causes stent  112  to be plastically deformed in accordance with the predetermined shape of balloon  114 . As will be of course be appreciated, the degree of mitral valve regurgitation may be monitored during the step of inflating balloon  114 , so that stent  112  applies only so much compressive load on the mitral valve annulus as is required to reduce the regurgitation to a clinically acceptable level. Catheter  113  is removed from the patient&#39;s vessel upon completion of the stenting procedure. 
   Referring to  FIGS. 17A and 17B , the distal region of a balloon catheter suitable for use in the embodiment of  FIG. 16  is described. Balloon catheter  113  has proximal and distal ends, and comprises balloon  114 , and inflation lumen and guidewire lumens, as is per se known. In accordance with the principles of the present invention, balloon  114  includes an anchor element  116 , such as a strand of wire, affixed to its interior surface, so that when the balloon is inflated, it adopts a predetermined shape, as shown in  FIG. 17B . Anchor element  116  may comprise a radiopaque material or radiopaque coating to facilitate proper positioning of stent  112  within coronary sinus C. When balloon  114  is deflated, the balloon assumes a straight configuration, shown in  FIG. 17A , thus permitting stent  112  to be crimped to its outer surface. 
   In an alternative embodiment of the device of  FIGS. 16–17 , anchor element  116  may be omitted and balloon  114  may be pre-shrunk on one side, thereby causing the balloon to deploy to the shape depicted in  FIG. 17B . In yet another embodiment, the configuration of cells  117  of stent  112  may be varied to encourage the stent to assume a convex shape upon deployment. For example, the side of the stent adjacent mitral valve annulus  71  may expand less than the side of the stent opposing the mitral valve annulus, thereby imparting a convex curvature upon the stent, as shown in  FIG. 16B . 
   To ensure proper alignment of stent  112  within the coronary sinus prior to deployment of the stent, an intravascular ultrasound transducer or, alternatively, radiopaque marker bands may be used to align the correct side of the stent adjacent the mitral valve annulus. The use of such imaging modalities are described, for example, in U.S. patent application Ser. No. 09/916,394 (“the &#39;394 application”), which is U.S. Patent Application Publication No. 2002/0019660, hereby incorporated by reference in its entirety. Additionally, further techniques for providing a curved stent in accordance with methods of  FIGS. 16–17  also are described in the &#39;394 application. 
   Referring now to  FIGS. 18A–19C , another alternative embodiment of the present invention is described, in which the device comprises proximal and distal stent sections joined by a central section capable of undergoing foreshortening. Device  120  comprises proximal stent section  122 , distal stent section  124  and central section  126 . Further in accordance with the principles of the present invention, device  120  includes one or more biodegradable structures  128 , such as sutures, disposed on central section  126  to retain that section in the contracted shape for a predetermined period after placement of the device in a patient&#39;s vessel. In  FIG. 18A , device  120  is depicted with its proximal and distal stent sections radially expanded, but with central section  126  restrained in the contracted position.  FIG. 18B  depicts device  120  with all three stent sections contracted as if disposed in a delivery catheter.  FIG. 18C  shows all three stent sections fully expanded. 
   In a preferred embodiment, all three sections are integrally formed from a single shape memory alloy tube, e.g., by laser cutting. The stent sections then are processed, using known techniques, to form a self-expanding unit. Device  120  has a contracted delivery configuration, wherein the device is radially contracted within a delivery sheath, and a deployed expanded configuration, wherein at least the proximal and distal sections self-expand to engage the interior surface of the coronary sinus or adjoining veins. Further in accordance with the present invention, the biodegradable structures may be designed to biodegrade simultaneously or at selected intervals. 
   Unlike the preceding embodiments, which may include either a proximal flange, distal anchor, or both, and which rely upon drawing the proximal and distal stent sections together at the time of deploying the device, this embodiment of the present invention permits the proximal and distal stent sections  122  and  124  to become biologically anchored in the venous vasculature before those sections are drawn together by expansion of central section  126  to impose a compressive load on the mitral valve annulus. 
   In particular, as depicted in  FIGS. 19A–19D , device  120  is loaded into delivery sheath  121  and positioned within the patient&#39;s coronary sinus. The device is then ejected from the delivery sheath, so that the proximal and distal stent sections  122  and  124  radially expand into engagement with the vessel wall. At the time of deployment, central section  126  is retained in a contracted state by biodegradable structures  128 , illustratively biodegradable sutures, e.g., a poly-glycol lactide strand or VICREL suture, offered by Ethicon, Inc., New Brunswick, N.J., USA. 
   Over the course of several weeks to months, the proximal and distal stent sections  122  and  124  will endothelialize, i.e., the vessel endothelium will form a layer E that extends through the apertures in the proximal and distal stent sections and causes those stent sections to become biologically anchored to the vessel wall, as depicted in  FIG. 19C . This phenomenon may be further enhanced by the use of a copper layer on the proximal and distal stent sections, as this element is known to cause an aggressive inflammatory reaction. Other techniques for enhancing an inflammatory reaction, such as coatings or layers, will be apparent to those skilled in the art. 
   Over the course of several weeks to months, and preferably after the proximal and distal stent sections have become anchored in the vessel, biodegradable structures  128  that retain central section  126  in the contracted state will biodegrade. Eventually, the self-expanding force of the central section will cause the biodegradable structures to break, and release central section  126  to expand. Because central section  126  is designed to shorten as it expands radially, it causes the proximal and distal stent sections  122  and  124  of device  120  to be drawn towards one another, as shown in  FIG. 19D . The compressive force created by expansion of central section  126  thereby compressively loads, and thus remodels, the mitral valve annulus, as depicted. 
   As suggested hereinabove, biodegradable structures  128  may be designed to rupture simultaneously, or alternatively, at selected intervals over a prolonged period of several months or more. In this manner, progressive remodeling of the mitral valve annulus may be accomplished over a gradual period, without additional interventional procedures. In addition, because the collateral drainage paths exist for blood entering the coronary sinus, it is expected that the device will accomplish its objective even if it results in gradual total occlusion of the coronary sinus. 
   Referring now to  FIGS. 20A–20B , another alternative embodiment of the present invention is described. In  FIG. 20A , apparatus  180  comprises a plurality of interlocking segments  181 . Each interlocking segment  181  preferably comprises a proximal section having socket  184 , a distal section having ball  182 , and a central section  183  extending therebetween. Each interlocking segment  181  further comprises lumen  185  configured to permit cinch wire  187  to pass through lumen  185 . Cinch wire  187  having proximal and distal ends preferably comprises ball  188  affixed to the distal end so that ball  188  engages a distalmost interlocking segment  181  when retracted proximally. The retraction of cinch wire  187  enables a ball  182  to interlock with a socket  184  of an adjacent segment  181 . 
   Apparatus  180  of  FIG. 20A  preferably is used in combination with apparatus  190  of  FIG. 20B . A preferred use of apparatus  180  and  190  in combination is described in  FIG. 22  hereinbelow. Apparatus  190  comprises proximal ball segment  202 , distal ball segment  200 , and connecting segment  204  having a plurality of sockets  205  separated by humps  209 . Proximal ball segment  202  comprises proximal and distal ball segments  212  and  210 , respectively, each having lumens extending therethrough, and hollow rod  211  extending therebetween. Similarly, distal ball segment  200  comprises proximal and distal balls  208  and  206 , respectively, each having lumens extending therethrough, and hollow rod  207  extending therebetween. Distal ball  210  of proximal segment  202  initially is configured to engage the most proximal socket  205  within connecting segment  204 , while proximal ball  208  of distal segment  200  initially is configured to engage a distalmost socket  205 . 
   Proximal and distal ball segments  202  and  200  are capable of relative rotational and telescoping movement. Such movement may be achieved using a cinch wire configured to pass through each segment  200  and  202 , as shown in  FIG. 21A . In  FIG. 21A , cinch wire  218  comprises distal ball  220  that is larger than a lumen of hollow rod  207  and is configured to abut distal ball  206  when a proximal end of cinch wire  218  is retracted proximally. Cinch wire  218  preferably is used in combination with push tube  216  that may stabilize or distally advance proximal segment  202 . 
   By varying the maneuvers of push tube  216  and cinch wire  218 , a range of telescoping and rotational motions between proximal and distal segments  202  and  200  may be achieved, as shown in  FIG. 21B . In  FIG. 21B , a push force applied to ball  212  allows ball  210  to overcome the resistive forces provided by hump  209 . As illustrated, the push force applied to ball  212  has advanced proximal segment  202  by two sockets relative to distal segment  200 . Also, as shown in  FIG. 21B , distal segment  200  has been retracted by one socket with respect to proximal segment  202 , e.g., by proximally retracting cinch wire  218 . Ball  208  also has been rotated at an angle, which in turn rotates distal segment  200  with respect to proximal segment  202 . 
   Referring to  FIG. 21C , an alternative method for providing relative telescoping and rotational motion for apparatus  190  of  FIG. 20B  is described. Apparatus  190  further comprises push tube  216  and wire loop  225 . Wire loop  225  extends through a lumen within proximal and distal segments  202  and  200 , then loops around the distal end of distal segment  200  and back into opening  227  of push tube  216 . A physician then may manipulate a proximal portion of wire loop  225  to provide a range of telescoping or rotational motions between proximal and distal segments  202  and  200 . At least one hook or eyelet  231  may be coupled to an exterior surface of connecting segment  204  to serve as a guide for wire  225 , and to facilitate controlled actuation of proximal and distal segments  202  and  200 . 
   Referring now to  FIG. 22 , a combination of apparatus  180  and apparatus  190  are used to provide a range of motion within vessel V, e.g., the coronary sinus. As described hereinabove, the present invention aims to treat mitral insufficiency by shortening the radius of curvature of the coronary sinus, which in turn applies a compressive force upon the mitral valve. In  FIG. 22 , the combination of apparatus  180  and apparatus  190  first may engage a wall of vessel V, e.g., via barbs or hooks (not shown) affixed to apparatus  180  and  190 , and then the relative telescoping or rotational motion of segments may be used to bend vessel V to apply a compressive load on the mitral valve annulus. 
   In a preferred embodiment, mitral insufficiency apparatus  179  comprises a proximal and distal section comprising apparatus  180 , and a plurality of sections comprising apparatus  190  disposed therebetween. Cinch wire  218  and push tube  216  of  FIG. 21  preferably are used to manipulate relative rotational and telescopic motion of all of the components. In a first preferred step, the balls of apparatus  180  are coupled to their respective sockets, e.g., by proximally retracting cinch wire  218 . Then, in a next step, balls  240  and  250  which connect apparatus  180  to apparatus  190  are rotated within sockets of connective segment  204  to allow apparatus  180  to be angled relative to apparatus  190  by angles α and β, as illustrated in  FIG. 22 . This in turn applies a desired compressive load on the mitral valve annulus. Then, in a final step, the balls of apparatus  190  may be advanced incrementally in a longitudinal direction within sockets  205  of connective segments  204  to reduce distance X. When vessel V is the coronary sinus, reducing the distance X will apply a compressive force to the mitral valve to treat mitral insufficiency. 
   While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.