Abstract:
Method and apparatus implementing and using techniques for body lumen closure, including use of an implantable medical closure device. The device includes a flexible strand defining an arcuate form. The strand is deformable upon implantation from a large cross-section condition to a small cross-section condition and has at least two anchoring portions disposed along the strand. The anchoring portions are configured to penetrate a wall of a body lumen such that when the strand is deformed to the small cross-section condition, the wall of the body lumen is disposed inwardly.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to body lumen closure.  
         BACKGROUND  
         [0002]    A venous valve functions to prevent retrograde flow of blood and allow only antegrade flow of blood to the heart. Referring to FIG. 1A, a healthy venous valve  12  is illustrated in a vessel  10 . The valve is bicuspid, with opposed cusps  14 . In the closed condition, the cusps  14  are drawn together to prevent retrograde flow (arrow  16 ) of blood. Referring to FIG. 1B, if the valve is incompetent, the cusps  14  do not seal properly and retrograde flow of blood occurs. Incompetence of a venous valve is thought to arise from at least the following two medical conditions: varicose veins and chronic venous insufficiency.  
         SUMMARY  
         [0003]    In a first aspect, the invention features an implantable medical closure device. The device includes a flexible strand defining an arcuate form. The strand is deformable upon implantation from a large cross-section condition to a small cross-section condition and has at least two anchoring portions disposed along the strand. The anchoring portions are configured to penetrate a wall of a body lumen such that when the strand is deformed to the small cross-section condition, the wall of the body lumen is disposed inwardly.  
           [0004]    The strand can also be deformable from a second small cross-section condition to the large cross-section condition, for example, the strand may be deformed to the second small cross-section condition to facilitate delivery of the strand to a treatment site, where it is then deformed to the large cross-section condition upon implementation. The strand can include free ends, which free ends can include the anchoring portions of the strand. The strand can define an arc, a helix or can include linear leg portions. The strand can be a filament-form or a band and may be corrugated. The strand can deform from the large cross-section condition to the small cross-section condition by, for example, elastic recovery forces or thermal shape-memory effect. The strand can be formed of metal, for example, nitinol. The anchoring portions of the strand can include, for example, a loop or a barb.  
           [0005]    In another aspect, the invention features a catheter system, which system includes a catheter for delivery into a lumen. The catheter includes an expander that can be operated between a small cross-section and a large cross-section. The catheter system also includes a closure device positioned about the expander. The closure device is a strand defining an arcuate form and including at least two anchoring portions configured to penetrate a wall of a body lumen. The closure device is deformable by the expander from a first small cross-section condition to a larger cross-section condition to dispose the closure device into engagement with the lumen wall. The closure device is further deformable to a second small cross-section condition, so that the wall of the body lumen is disposed inwardly.  
           [0006]    The expander can take any convenient form, including, for example, an inflatable balloon, a mechanical expander or a leveraging device. The mechanical expander can include a two-part axial member having a first inner part connected to a first coiled spring and a second outer part connected to a second coiled spring. The closure device is mounted on the first and second coiled springs, and the first inner part of the axial member is rotatable to expand the first coiled spring and the second outer part of the axial member is rotatable to expand the second coiled spring. Expansion of the first and second coiled springs expands the closure device. Each coiled spring can include a distal end configured to fit within a groove formed on either end of the closure device.  
           [0007]    The leveraging device can include a two-part axial member including a first outer part and a second inner part. A splayed cuff is connected to the distal end of the first outer part of the two-part axial member, and at least two flexible legs are connected to the distal end of the second inner part of the two-part axial member. The legs are flared outwardly to contact the distal end of the splayed cuff. The second inner part of the two-part axial member is moveable toward the splayed cuff such that the flexible legs and the splayed cuff expand radially. The closure device is positioned about the flexible legs and expansion of the flexible legs expands the closure device from a first small cross-section condition to a larger cross-section condition. The second inner part of the two-part axial member is also moveable away from the splayed cuff such that the flexible legs and the splayed cuff retract.  
           [0008]    In another aspect, the invention features a method of treating a body lumen. The method includes delivering a closure device into a lumen and positioning the strand about the lumen such that a portion of the strand penetrates the wall of the lumen. The method further includes deforming the strand to a smaller cross-section condition such that the wall of the lumen is disposed inwardly. The strand can be positioned about the lumen such that an end of the strand extends through the wall of the lumen. The strand can be disposed on a catheter, which catheter is then delivered into the lumen. The catheter can include an expansion member.  
           [0009]    Embodiments may have one or more of the following advantages. Closure of a body lumen can be achieved in a minimally invasive manner by delivery of a closure device to a treatment site using a catheter. The closure device may be partially installed within the lumen but configured to minimize profile and thus reduce impedance to the flow of body fluids through the lumen. The amount of lumen closure can be controlled by selecting the size and/or recovery force of the closure device.  
           [0010]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0011]    [0011]FIG. 1A is a cross-sectional schematic of a vessel including a competent venous valve while FIG. 1B is a schematic of a vessel including an in competent venous valve.  
         [0012]    [0012]FIG. 2A is a longitudinal cross section of a vessel including a closure device, while FIG. 2B is a radial cross section of the vessel including the closure device.  
         [0013]    [0013]FIGS. 3A and 3B are longitudinal and radial cross-sectional views, respectively, illustrating delivery of a closure device using a catheter.  
         [0014]    [0014]FIGS. 4A, 4B and  4 C are radial cross-sectional views illustrating implantation of a closure device from within a vessel.  
         [0015]    [0015]FIG. 5 is a schematic view of an embodiment of a closure device.  
         [0016]    [0016]FIG. 6 is a schematic view of an embodiment of a closure device.  
         [0017]    [0017]FIG. 7 is a schematic view of an embodiment of a closure device.  
         [0018]    [0018]FIGS. 8A, 8B and  8 C are radial cross-sectional views illustrating implantation of a closure device from within a vessel.  
         [0019]    [0019]FIG. 9 is a schematic view of an embodiment of a closure device.  
         [0020]    [0020]FIG. 10 is a schematic view of an embodiment of a closure device.  
         [0021]    [0021]FIG. 11 is a schematic view of an embodiment of a closure device.  
         [0022]    [0022]FIGS. 12A, 12B, and  12 D are longitudinal cross-sectional schematic views and FIG. 12C is a radial cross-sectional schematic view illustrating implantation of a closure device from within a vessel.  
         [0023]    [0023]FIGS. 13A, 13B,  13 C,  13 D and  13 E are longitudinal cross-sectional schematic views illustrating implantation of a closure device from within a vessel.  
         [0024]    [0024]FIGS. 14A, 14B and  14 C are longitudinal cross-sectional schematic views illustrating implantation of a closure device from within a vessel.  
         [0025]    [0025]FIGS. 15A, 15B and  15 C are schematic views of an embodiment of a medical device.  
         [0026]    [0026]FIGS. 16A, 16B and  16 C are longitudinal cross-sectional schematic views illustrating implantation of a closure device from within a vessel. 
     
    
       [0027]    Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0028]    Referring to FIGS. 2A and 2B, a valve closure device  20  is illustrated in position about a vessel  22  at the location of a valve  24  including cusps  26 . The closure device  20  is an arcuate, open-ended, filament-form defining an arc that includes a body  28  which is located in the lumen of the vessel and two anchoring portions  30  which extend into the walls  32  of the vessel. The device  20  provides a force (arrows  34 ) that draws the vessel walls inward, enhancing the function of the valve  24 . As evident, the closure device  20  does not substantially impede the flow of blood through the vessel. The body portion  30  is thin and conforms closely to the vessel wall, outside of central portions of the vessel, where flow volume and rate is greatest.  
         [0029]    Referring to FIGS. 3A and 3B, the closure device  20  can be positioned at a treatment site in vessel  22  using a catheter  36 , which may be delivered into the vessel percutaneously. The catheter  36  includes a long, flexible body adapted for delivery through the vessel and has near its distal end an expander  38 , such as an inflatable balloon. Suitable balloon catheters include angioplasty balloon catheters and balloon catheters adapted for delivering stents. An example utilizing a coextruded balloon is described in Hamilton et al., U.S. Pat. No. 5,797,877, the entire contents of which is incorporated herein by reference. The catheter may be delivered over a guidewire (not shown). The device  20  may be friction fit over the catheter. A retractable sheath may be used to cover the device and balloon during delivery.  
         [0030]    The closure device  20 , in a radially compacted form, is positioned over the expander  38  in a deflated condition for delivery to the treatment site. Referring as well to FIGS.  4 A- 4 C, the closure device  20  is installed at the treatment site by expanding the expander  38 , i.e. by inflating the balloon. (In FIGS.  4 A- 4 C, the expander and valve cusps are omitted to more clearly illustrate the installation of the closure device  32 ). Referring particularly to FIG. 4A, the closure device  20  is in a compacted condition as it is carried to the treatment site on the catheter, with the expander in the unexpanded condition. The closure device  20  is sized such that it is smaller than the cross-section of the vessel. In the embodiment illustrated, the closure device  20  defines an arc that is generally concentric with the arc defined by the vessel wall. In this condition, the anchoring portions  30  terminate in ends  21  which are oriented along a line  40 , substantially parallel to the center line  44  through the cross-section of the vessel and generally parallel to a tangent  42 , on the blood vessel wall  32 . Referring particularly to FIG. 4B, as the closure device  20  is expanded, the device can both stretch axially (arrow  45 ) and deform radially (arrow  46 ) as well as be displaced upwardly (arrow  47 ). The axial stretching does not fully accommodate the expansion. As a result, the ends of the filament are deflected such that they are oriented along line  40 , and come into contact with the vessel wall  32 , such that the ends become embedded in the wall. The initial penetration of the ends can be enhanced by rotating the catheter slightly about the catheter axis. Referring to FIG. 4C, as the expander is contracted (i.e. deflated) device  30  begins to contract. The ends  21  further penetrate the wall  32 . As shown the ends may pierce the entire thickness of the wall, and deflect inwardly (arrow  49 ) to contract the vessel. The closure device can be deployed near the base of cusps of an incompetent venous valve, where the cusps meet the wall of the blood vessel. The deployment may be upstream of the cusps. Alternatively, the deployment site can be downstream of the cusps. The catheter is withdrawn through the blood vessel in the same manner the catheter was initially inserted.  
         [0031]    The closure device may be made of a thin elongate, filament form, such as a metal wire. The metal may be selected such that the device is elastically expandable from the compacted condition for delivery into a lumen to an expanded condition for implantation. Once implanted, elastic recovery of the wire contracts the device and the vessel wall. Suitable metals include elastic steels and superelastic alloy materials such as nitinol. The filament may also be a composite material, such as a composite wire. Superelastic metals and composite wires are described in Heath, U.S. Pat. No. 5,725,570, and Mayer, U.S. Pat. No. 5,800,511, the entire contents of both of which are incorporated herein by reference. The metal may also be a temperature-effect shape memory superelastic alloy that conforms to an implanted condition upon exposure to a controlled temperature, e.g. body temperature. Suitable shape memory alloys such as nitinol are discussed in Schetsky MacDonald “Shape Memory Alloys,” Encyclopedia of Chemical Technology (3 rd  ed) John Wiley and Sons, 1982, vol. 20, p. 726-736. The temperature of the device may be controlled, for example, by heating the expander or by heating the balloon inflation fluid. The wire may also be selected such that the device is plastically deformed from the compacted condition to an expanded condition for embedding the anchoring elements into the vessel wall, with some elastic recovery after the expansion to contract the wall. Alternatively, a mechanical gripper can be used to draw the anchoring portions inward. The filament may also be made of a flexible polymer. The device may be coated with a lubricious polymer or a drug. For example, the anchoring portions may include a tissue sealant to minimize bleeding and enhance vessel wall integrity in the penetration regions.  
         [0032]    The anchoring portions can also take a number of different forms that permit the ends of the closure device to penetrate the wall of the blood vessel, and restrain the ends from re-entering the vessel. In the embodiment illustrated above, the device  20  is formed of an open-ended strand in the shape of an arc. This shape facilitates deflection of the ends of the strand so that they can be embedded in the vessel wall and also provides a small profile within the vessel, so that blood flow is not substantially impeded. As illustrated above, the body of the device, within the vessel, closely conforms to the inner wall of the lumen.  
         [0033]    Referring to FIG. 5, in another embodiment, the closure device  61  can be an open strand defining an arc, which includes ends  64  with anchoring elements  62 , which define loops. Once the anchoring elements  62  are positioned on the exterior of the blood vessel, the loops defined by the elements  62  prevent the ends  64  of the closure device  61  from reentering the blood vessel and secure the closure device  61  to the wall. The loops can be pressed into the vessel wall on implantation. Alternatively, the ends can be formed of a temperature effect shape memory metal, such that the ends are in a substantially straight condition for implantation but subsequently revert to a loop shape after being embedded in the vessel wall.  
         [0034]    Referring to FIG. 6, the closure device  66  can alternatively include ends  68  with anchoring elements  69  configured with barbs, such that the ends  68  can penetrate the wall of the blood vessel and be prevented from reentering the blood vessel by the barbs of the fish hook-like anchoring elements  69 .  
         [0035]    Referring to FIG. 7, the closure device can be an open strand  120  having flared ends  122  that terminate in barb elements  123 . The ends  122  can penetrate the wall of the blood vessel and secure the strand  120  to the wall by the curvature of the flared ends  122 . The barb elements are easily pushed into the vessel wall as the device is extended, but resist withdrawal from the wall as the device deflects inwardly.  
         [0036]    As shown in FIGS.  8 A- 8 C, the closure device  70  can be a spiraled open strand to form a loop and a half or more, so that the ends  72  are positioned opposite one another, and include fish hook-like anchoring elements  71 . Referring particularly to FIG. 8A, the closure device  70  is shown in a compacted condition, with the anchoring elements  71  oriented along a tangent line  73 , which is substantially parallel to the center line  75  through the cross-section of the blood vessel, and parallel to a tangent  74 , on the blood vessel wall. Referring particularly to FIG. 8B, as the closure device  70  is expanded by the expansion device (not shown), the strand can both stretch axially (arrow  78 ) and deform radially (arrow  79 ). The axial stretch does not fully accommodate the expansion. As a result, the free ends  72  of the strand are deflected such that the tangent line  73  defines an angle θ with respect to the tangent  74  on the vessel wall and thus penetrates the vessel wall. Referring to FIG. 8C, as the device  70  begins to contract, the ends  72  of the strand further penetrate the wall and deflect inwardly to contract the wall.  
         [0037]    Referring to FIG. 9, the closure device  76  can be a spiraled open strand to form a loop and a half, so that the ends  72  are positioned opposite one another, and include anchoring elements  77  defining loops. Implantation of this device would be similar to implantation of the device shown in FIG. 8, as described above.  
         [0038]    Referring to FIG. 10, the closure device  80  can be a strand in the shape of a thin, flat slotted band including three (or more) anchoring elements  60 . The slotted band  80  can include an upper band  65 , middle band  63  and lower band  67 , where the upper band  65  and lower band  67  each include an anchoring element  60  on their distal ends on an opposite side of the band  80  from an anchoring element  60  formed at the distal end of the middle band  63 . Expansion of the closure device  80  by an expansion device causes the anchoring elements  60  to penetrate the vessel wall. Upon contracting the expansion device, the band  80  attempts to contract to the smaller condition and, because the band  80  is secured to the vessel wall, contracts the cross-section of the vessel.  
         [0039]    Referring to FIG. 11, in another embodiment, the closure device can be a closed, corrugated band  82 . The band  82  includes anchoring elements  83  projecting from the exterior surface of the band. As the band  82  is expanded, the anchoring elements  83  penetrate the wall of the blood vessel. The anchoring elements  83  can be configured such that they lie flat while being transported through the vessel, and are caused to protrude from the band  82  by the expansion of the band  82  using an expansion device. When the expansion device is contracted, the band  82  attempts to contract to a smaller condition, and the anchoring elements  83  cause the cross-section of the vessel to contract.  
         [0040]    Referring to FIGS.  12 A- 12 D, the closure device can be a helical winding  85  having two or more anchoring portions  86  and having any number of helical turns, for example three turns as shown. Referring to FIG. 12A, the helical winding  85  can be transported to the treatment site within a vessel  31  using a catheter  88  having an expander  87  on the distal end. The treatment site is in close proximity to an incompetent venous valve  24 . The helical winding  85  is mounted to the exterior of the expander  87  and can be held in place by any convenient manner, including, for example, a friction fit. Optionally, a protective sheath  89  can cover the expander  87  and helical winding  85  during transport and be removed once the treatment site is reached. Referring to FIG. 12B, the expander  87  is expanded and thereby expands the helical winding  85  from a small condition to a larger condition. The expander  87  is expanded until the anchoring portions  86  of the helical winding  85  penetrate the wall  44  of the vessel  31  and secure the helical winding  85  to the interior of the vessel  31 . The helical winding  85  can have three anchoring portions  86  as shown in FIG. 12C, or more or less anchoring portions. The expander  87  is then contracted and the catheter  88  removed from the vessel  31 , for example, in the same manner the catheter  88  was deployed. Referring to FIG. 12D, with the expander  87  no longer exerting pressure on the helical winding  85 , the helical winding  85  tends to contract to the small condition, for example, due to elastic restoring forces or temperature-effect shape memory effect, thereby pulling the sides of the wall  44  inwardly and contracting the cross-sectional area of the vessel  31 . With the helical winding  85  in place within the vessel  31 , the cusps  38  of the valve  24  are pulled together so that the valve  24  can function competently to prevent antegrade flow within the vessel  31 .  
         [0041]    Referring to FIGS.  13 A- 13 E, the closure device can be a helical winding  94  that is positioned about the exterior of a vessel  31  in the vicinity of an incompetent venous valve  24 . Referring to FIG. 13A, a catheter  90  having an expander  93  on the distal end is transported to a treatment site with the expander  93  in a contracted state. The treatment site is at or near the incompetent venous valve  24 . The catheter  90  includes a lumen  91  having an opening  92  at or near the base of the expander  93 . Referring to FIG. 13B, at the treatment site the expander  93  is expanded to at least the interior dimension of the vessel  31 . The helical winding  94  is formed of a shape-memory material and is passed through the catheter lumen  91  in a substantially straight position, as shown in FIG. 13C. The helical winding  94  is pushed through the opening  92 , which opening  92  is configured such that the winding  94  is directed toward the wall  44  of the vessel  31 . The winding  94  penetrates and is pushed through the wall  44 . The shape-memory effect causes the winding  94  to revert to a helix as the winding is pushed from the catheter lumen  91 , and rides along the outside of the vessel  31 . Once the helical winding  94  has completely exited the catheter lumen  91  and is situated about the exterior of the vessel  31 , the expander  93  is contracted and the catheter  90  is withdrawn from the vessel. The helical winding  94  is configured so that when the shape-memory effect causes the winding to revert to a helix, the helical winding  94  pulls the wall  44  of the vessel  31  inwardly, causing the cusps  38  to pull together so that the valve can function competently. The winding  94  can be held in place by friction.  
         [0042]    Referring to FIGS.  14 A- 14 C, the closure device  100  can be an angular hinge-form with at least two linear legs  102 . The closure device  100  can be transported in a compressed condition to a deployment site in the blood vessel by a delivery catheter  103  having a housing  105  for containing the closure device  100  in the compressed condition until the deployment site is reached. The device  100  can be pushed out of the housing  105  by the distal end of the catheter, which can be temporarily connected to the device  100 , for example, by a threaded connection. Referring particularly to FIG. 14B, the device  100  will naturally expand upon being released from the confines of the housing  105 . An expansion device  106 , such as an inflatable balloon, on the distal end of the catheter  103  can be inflated to further expand the closure device  100  by spreading the legs  102  until the anchoring elements  104  penetrate the wall  44  of the blood vessel  41 . The device  100  is then pulled in the direction of the catheter by the distal end of the catheter, which is still connected to the device  100 . This movement causes the anchoring elements  104  to fully penetrate the wall of the blood vessel, and secure the device  100  to the vessel. The catheter is disconnected from the device  100  and removed from the vessel. The device  100  attempts to contract to a smaller condition, thus causing the cross section of the blood vessel to contract.  
         [0043]    Referring to FIGS.  15 A- 15 C, the expander can be a mechanical expander  135  including at least two coiled springs  128 ,  129  and having a two-part axial member including an outer tube  133  and an inner rod  134 . The inner rod  134  is affixed to a first coil  129  and can rotate independently of the outer tube  133 , which is affixed to a second coil  128 . The mechanical expander  135  is used in conjunction with a closure device  125  configured to mount about the coils  128 ,  129 . Each coil  128 ,  129  has an end  130 ,  131  configured to fit within a groove  127  formed on either end of the closure device  125 . In this manner, the coils  128 ,  129  and closure device  125  are held together while the expansion device is transported to a treatment site. At the treatment site, the mechanical expander  135  is expanded to expand the closure device  125 , thereby causing the anchoring portions  126  of the closure device  125  to penetrate a vessel wall, in a similar manner as described above.  
         [0044]    The mechanical expander  135  expands by rotating the inner rod  134  to expand the first coil  129  and rotating the outer tube  133  to expand the second coil  128 . The coils  128 ,  129  expand radially in opposite directions, exerting a radial force on the closure device  125 , causing the anchoring portions  126  to penetrate a vessel wall. Once the closure device  125  is secured to the vessel wall, the mechanical expander  135  can be disengaged from the closure device  125  by sliding the mechanical expander  135  axially away from the closure device  125 . The mechanical expander  135  is contracted by rotating the inner rod and outer tube in the opposite directions used for expansion, and is withdrawn from the vessel. Optionally, a retractable sheath can enclose the mechanical expander  135  and closure device  125  while positioning the assembly at the treatment site, which sheath is then retracted.  
         [0045]    Referring to FIGS.  16 A- 16 B, the expander can be a leveraging device  112  having at least two flexible legs  114 , an axial member  115  and a splayed cuff  116 . A closure device  117  can be mounted onto the exterior of the legs  114 . At a deployment site, the axial member  115  can be pulled causing the legs  114  to press against the cuff  116 . The force of the flexible legs  114  against the splayed cuff  116  causes the flexible legs  114  to expand outwardly and the splayed cuff  116  to fan out. The expansion of the circumference around the flexible legs  114  causes the closure device  117  to expand and anchor to the wall of the blood vessel  31 , as described above. Once the closure device  117  is secured to the wall, the axial member  115  is pushed to release the pressure on the flexible legs  114 , causing them to revert back to the original compressed condition. Similarly, with the force on the splayed cuff  116  removed, the cuff  116  recovers to the original state. The expansion device can then be retracted from the vessel.  
         [0046]    Other embodiments are within the scope of the following claims. For example, a closure device may be used to treat vascular vessels at locations without a valve to constrict the vessel at a desired location and other body lumens outside the vascular system.