Abstract:
A delivery/recovery system to allow an operator to deploy and recover a medical implant, such as an occluder for closing a patent foramen ovale (PFO). In one embodiment, the system includes a delivery mandrel for preventing the occluder from moving in the proximal direction, a delivery wire for securing the occluder to the delivery mandrel and preventing unwanted movement in the distal direction, and a sheath for enveloping the delivery wire, mandrel and occluder. By moving the sheath relative to the occluder in a series of steps, the occluder opens first on a distal side and then on a proximal side, in a manner that holds the occluder in place.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 13/007,660 filed Jan. 16, 2011, now issued as U.S. Pat. No. 8,568,431; which is a continuation application of U.S. application Ser. No. 11/070,027, now issued as U.S. Pat. No. 7,871,419; which claims the benefit under 35 USC §119(e) to U.S. Application Ser. No. 60/569,422 filed May 7, 2004 and U.S. Application Ser. No. 60/549,741 filed Mar. 3, 2004, both now expired. The disclosure of each of the prior applications is considered part of and is incorporated by reference in the disclosure of this application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to an occlusion device for the closure of physical anomalies like septal apertures, such as patent foramen ovale and other septal and vascular defects. 
         [0004]    2. Background Information 
         [0005]    A patent foramen ovale (PFO), illustrated in  FIG. 1 , is a persistent, one-way, usually flap-like opening in the wall between the right atrium  11  and left atrium  13  of the heart  10 . Because left atrial (LA) pressure is normally higher than right atrial (RA) pressure, the flap usually stays closed. Under certain conditions, however, right atrial pressure can exceed left atrial pressure, creating the possibility that blood could pass from the right atrium  11  to the left atrium  13  and blood clots could enter the systemic circulation. It is desirable that this circumstance be eliminated. 
         [0006]    The foramen ovale serves a desired purpose when a fetus is gestating. Because blood is oxygenated through the umbilical cord, and not through the developing lungs, the circulatory system of a heart in a fetus allows the blood to flow through the foramen ovale as a physiologic conduit for right-to-left shunting. After birth, with the establishment of pulmonary circulation, the increased left atrial blood flow and pressure results in functional closure of the foramen ovale. This functional closure is subsequently followed by anatomical closure of the two over-lapping layers of tissue: septum primum  14  and septum secundum  16 . However, a PFO has been shown to persist in a number of adults. 
       SUMMARY OF THE INVENTION 
       [0007]    Embodiments of a delivery/recovery system allow an operator to deploy and, in many cases, recover a medical implant, such as an occluder for closing a PFO. In one embodiment, the system includes a delivery mandrel for preventing the occluder from moving in the proximal direction, a delivery wire for securing the occluder to the delivery mandrel and preventing unwanted movement in the distal direction, and a sheath for enveloping the delivery wire, mandrel and occluder. By moving the sheath relative to the occluder in a series of steps, the occluder opens first on a distal side and then on a proximal side, in a manner that locks the occluder in place. 
         [0008]    In this embodiment, the system preferably further includes a recovery catheter with claws that can be controlled to grasp a partially deployed occluder and withdrawing the occluder back into the sheath for repositioning or removal. 
         [0009]    A handle can be provided for assisting the operator with manipulations to deliver and/or recover an occluder. The handle can include springs for biasing the mandrel and sheath, with knobs for holding these components in desired positions. 
         [0010]    The system can be used with a PFO occluder, such as an occluder with a center joint for passing through the PFO tunnel, and closure components on the distal (left atrial) side and on the proximal (right atrial) side. The closure components can include loops, open ended struts, or struts that double back from the center joint to an end of the occluder. The occluder preferably also has a catching structure for holding the components in place. The occluder can be made of a polymer, nitinol, stainless steel, or other suitable material, and can include a fabric for promoting tissue growth. 
         [0011]    The delivery/recovery system in the preferred embodiment provides a convenient mechanism for delivering the occluder or other device, and for recovering the device as needed. Other features and advantages will become apparent from the following detailed description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a human heart with anatomical structures relevant to this description. 
           [0013]      FIG. 2  is a cross-section of a clover leaf occluder and a delivery/recovery system in its “stowed” configuration. 
           [0014]      FIGS. 3 ,  4 ,  5 A,  5 B and  5 C are cross-sectional views that illustrate a sequence of events for using the recovery/delivery system to deploy the clover leaf occluder within the PFO. 
           [0015]      FIGS. 6 ,  7 ,  8 ,  9 ,  10  and  11  are cross-sectional views that illustrate a sequence of events for using the delivery/recovery system to recover a deployed occluder. 
           [0016]      FIG. 12  shows an occluder deployed as described herein. 
           [0017]      FIGS. 13 and 14  show an occluder with a locking member having a third stop between the end stops. 
           [0018]      FIGS. 15 ,  16  and  17  show an occluder with a locking member as in  FIG. 13 , in three stages of deployment. 
           [0019]      FIGS. 18A and 18B  show another embodiment of the mandrel tip. 
           [0020]      FIGS. 19A and 19B  show several alternative embodiments of the mandrel tip. 
           [0021]      FIG. 19C  shows another alternative embodiment of the mandrel tip. 
           [0022]      FIGS. 19D ,  19 E and  19 F show several embodiments of the distal end of the wire for use with the mandrel tip of  FIG. 19C . 
           [0023]      FIG. 19G  shows a mandrel with a soft segment added near its distal end. 
           [0024]      FIG. 20  shows a handle for use with the occluder delivery/recovery system of  FIG. 2 . 
           [0025]      FIGS. 21 ,  22 ,  23 ,  24  and  25  show stages of a delivery sequence using the handle of  FIG. 20 . 
           [0026]      FIGS. 26 ,  27 ,  28 ,  29  and  30  show stages of a recovery sequence using the handle of  FIG. 20 . 
           [0027]      FIGS. 31A and 31B  show another embodiment of an occluder that may be used with some of the delivery systems herein. 
           [0028]      FIGS. 32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38  and  39  show several views of another occluder. 
           [0029]      FIGS. 40 ,  41 ,  42 ,  43 ,  44  and  45  show several further embodiments of occluders. 
           [0030]      FIGS. 46 ,  47  and  48  show still further embodiments of occluders, these with an end cap lock stop. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    The described embodiment is a delivery/recovery system for deploying and/or removing a device for occluding an aperture within body tissue. In particular and as described in detail below, an occluder may be used for closing a PFO in the atrial septum of a heart. Application Ser. No. 10/890,784, filed Jul. 14, 2004, which is incorporated herein by reference, provides a more detailed description of an occluder that the described embodiment manipulates. This occluder has a center joint, opposite ends, and loops extending from the center joint to the ends such that the loops are generally parallel to the PFO tunnel. Because of its shape, the occluder is referred to as a “clover leaf” occluder. 
         [0032]    Although the embodiments described herein refer to a PFO in particular, the devices and methods of these embodiments may be used to treat other anatomical conditions, such as an atrial septal defect (ASD) or ventricular septal defect (VSD). As such, the invention should not be considered limited to any particular anatomical condition. Similarly, although the embodiments described herein refer to a clover leaf occluder in particular, the devices and methods of these embodiments may be used to deploy other occluders, and other implants in general. As such, the invention should not be considered limited to any particular deployable implants. For example, an occluder can include struts that extend out in a manner like an umbrella, or can have struts that double back from a center joint to ends, with loops that are perpendicular to the PFO tunnel. As used herein, the term “operator” means the person operating the delivery/recovery system to insert an occluder into the body of a patient. 
         [0033]      FIG. 1  illustrates a human heart  10 , having a right atrium  11  and a left atrium  13 . The atrial septum  12  includes septum primum  14 , septum secundum  16 , and a passage  18  between the right atrium  11  and left atrium  13 . The anatomy of the septum varies widely within the population. In some people, septum primum  14  extends to and overlaps with septum secundum  16 . The septum primum  14  may be quite thin. When a PFO is present, there is a chance that blood could travel through the passage  18  between septum primum  14  and septum secundum  16  (referred to as “the PFO tunnel”).  FIG. 1  further shows an outline of the delivery/recovery system  100 , described herein, being inserted into the right atrium  11  through the inferior vena cava  20 . 
         [0034]    As shown in  FIG. 2 , a clover leaf occluder delivery/recovery system  100  includes a clover leaf occluder  102 , a delivery wire  104 , a mandrel tip  106 , a mandrel  108 , a recovery catheter  110 , recovery claws  112 , a delivery/recovery sheath  114 , and a catch member  116  of the clover leaf occluder. The delivery/recovery system also includes a handle (not shown) that enables the operator to repeatably and efficiently perform the steps described herein. The handle is described in more detail in the sections to follow. The occluder  102  and all components of the delivery/recovery system  100  may be advanced into the sheath  114  after the sheath  114  has crossed the PFO  18 , and the guide wire has been removed from the sheath  114 . 
         [0035]      FIG. 2  shows the clover leaf occluder delivery/recovery system  100  in its “stowed” configuration, i.e., as it is arranged when it is ready to be inserted into a patient. The delivery wire  104 , the mandrel  108 , the recovery catheter  110 , and the delivery/recovery sheath  114  are all disposed in a coaxial arrangement about a longitudinal central axis, with the mandrel  108  disposed about the delivery wire  104 , the recovery catheter  110  disposed about the mandrel  108 , and the delivery/recovery sheath  114  disposed about the recovery catheter  110 . The mandrel tip  106  refers to the distal end of the mandrel  108 . The mandrel  108  extends through the occluder  102  so that the mandrel tip  106  is disposed at the distal end of the catch member  116 . The delivery wire extends through the mandrel and out of the mandrel tip  106 , and is bent at its distal end to form a hook. The bent end of the delivery wire rests against the distal end of the locking member and provides a restraining force for preventing the catch member  116  from moving in the distal direction. 
         [0036]    In one embodiment, the mandrel  108  includes a portion at the distal end that has a smaller outside diameter, creating a shoulder at the transition. The smaller outside diameter portion fits through the catch member  116 , and the shoulder provides a stop against which the proximal end of the catch member  116  rests. The shoulder therefore prevents movement of the catch member  116  in the proximal direction. In an alternative embodiment, the mandrel  108  has an outside diameter slightly less than the inside diameter of the locking member, and includes a region having an extended outside diameter for providing a stop (i.e., a bump) against which the proximal end of the locking member  116  rests, to prevent movement of the catch member in the proximal direction. 
         [0037]    The recovery claws  112  are attached to the distal end of the recovery catheter  110 , and are spring loaded to tend toward opening, i.e., expansion away from the central axis. The distal end of the catch member  116  is fixedly attached to the distal end of the occluder  102 . 
         [0038]      FIGS. 3 ,  4 ,  5 A,  5 B and  5 C illustrate a sequence of events for using the recovery/delivery system  100  to deploy the clover leaf occluder  102  within the PFO tunnel  18 .  FIG. 3  shows a sheath  114  inserted into the PFO tunnel, with the occluder  102  partially deployed on the left atrial side of the PFO tunnel  18 . The operator causes the occluder  102  to exit the sheath  114  by moving the sheath relative to the occluder, preferably by pulling the sheath  114  away from the distal end, while maintaining the mandrel  108  and delivery wire  104  relatively fixed. Once the sheath  114  uncovers approximately one half of the occluder  102 , the clover petals of the occluder  102  are free to expand away from the central axis on the left atrial side of the PFO  18 . The operator pushes the sheath relative to the mandrel  108  and the wire  104 , further forcing the clover petals open to extend outwardly in a radial direction (an example in partially deployed form is shown in  FIG. 15 , with full deployment in  FIG. 17 ). This movement also pushes a central portion  136  of the occluder  102  over the larger diameter proximal end  130  of the locking member. 
         [0039]    Referring to  FIG. 4 , the operator again moves the sheath  114  relative to the mandrel  108  and the wire  104 , preferably by pulling back on the sheath  114 , thereby uncovering the proximal petals of the occluder  102  in the right atrium  11  and allowing these petals to expand away from the central axis. The operator then pushes the sheath  114  relative  20  to the mandrel  108  and wire  104  further forcing those clover petals to extend outwardly in a radial direction on the right atrial  11  side of the PFO  18 . The operator continues to push the sheath relative to the mandrel  108  and wire  104 , forcing the proximal end of the occluder over the proximal end of the catch member  116 , thereby holding the occluder  102  in its deployed position. 
         [0040]    At this time the operator pulls the sheath  114  relative to the mandrel  108 , away from the deployed occluder  102 , as shown in  FIG. 5A . Withdrawing the sheath  114  from the occluder  102  provides the flexibility necessary to pivot the occluder  102  via the mandrel  108  to a desired position. The operator can then determine whether the occluder  102  is properly deployed with respect to the PFO tunnel  18 , using techniques such as transesophageal or intracardiac echo, and/or fluoroscopy. If the operator deems the occluder  102  to be properly deployed, the operator pulls on the delivery wire  104  while holding the mandrel  108  in a fixed position. If the operator pulls the delivery wire  104  with sufficient force, the bend at the distal end of the delivery wire  104  straightens against the mandrel tip  106 , and the wire  104  withdraws into the mandrel  108  ( FIG. 5B ). Once the bend in the distal end of the wire  104  is gone, there is no longer a restraining force preventing the catch mechanism  116  from moving in the distal direction, and the operator disengages the mandrel  108  from the catch member  116  ( FIG. 5C ). Alternatively, the operator could straighten the bend in the wire  104  by holding the delivery wire  104  in a fixed position and pushing on the mandrel  108 , or by a combination of pulling on the wire  104  and pushing on the mandrel  108 . 
         [0041]    If, after withdrawing the sheath  114  and manipulating the occluder  102  as described above ( FIG. 5A ), the operator decides the occluder  102  is not properly deployed, the operator can perform a recovery and/or repositioning procedure.  FIGS. 6 through 11  illustrate a sequence of steps described in detail below. From the position shown in  FIG. 5A , the operator pushes longitudinally on the recovery catheter  110  with respect to the sheath  114 . Doing so causes the sheath  114  to uncover the recovery claws  112 , removing a restricting force from the spring-loaded recovery claws  112 , and allowing the claws  112  to expand away from the central axis, as shown in  FIG. 6 . The operator continues to push the recovery catheter  110  relative to the sheath until the claws  112  surround the proximal end of the occluder  102 . The operator then pushes the sheath  114  longitudinally relative to the recovery catheter  110  until the sheath covers the claws  112 , thereby closing the claws  112  on the proximal end of the occluder  102 , as shown in  FIG. 7 . 
         [0042]    With the claws  112  immobilizing the occluder  102  relative to the recovery catheter  110 , the operator pushes the mandrel  108  longitudinally relative to the recovery catheter  110 , forcing the proximal stop  130  of the catch member  116  through the proximal end of the occluder  102  in a distal direction, as shown in  FIG. 8 . As the operator continues to push the mandrel  108  relative to the recovery catheter  110 , the mandrel  108  pushes the proximal stop  130  of the catch member  116  through the occluder center joint  136 , and the occluder elongates, so that the clover petals of the occluder retract toward the central axis, as shown in  FIGS. 9 and 10 . The operator pulls the recovery catheter  110  longitudinally relative to the sheath  114 , so that the claws  112  pull the elongated occluder  102  back into the sheath  114 . Once the sheath  114  covers the occluder  102 , as shown in  FIG. 11 , the operator can remove the delivery/recovery system  100  from the patient. 
         [0043]    During this process, such as at points shown in  FIG. 9 ,  FIG. 10  or  FIG. 11 , the operator can reverse course and deploy again as in the manner described in conjunction with  FIGS. 3 ,  4   5 A,  5 B and  5 C. 
         [0044]      FIG. 12  shows an occluder  102  deployed as described above. The catch member  116  in this embodiment includes a proximal stop  130  and a distal stop  132 . The diameter A of the proximal stop  130  is greater than the inside diameter D of the occluder  102 , and the diameter B of the distal stop  132  is greater than the diameter A of the proximal stop  130 . As described herein, distal stop  132  should be fixedly connected to the rest of the occluder and thus should not be movable with respect to the end of the occluder at any time, while the portions of the occluder move over the proximal end to lock the occluder in place. 
         [0045]    Referring to  FIGS. 13 and 14 , in another embodiment, the catch member  116   a  has a third stop  134  between the proximal stop  130  and the distal stop  132 . The third stop  134  provides an intermediate stop for the center joint  136  of the occluder  102 . The diameter A of the proximal stop  130  is greater than the inside diameter D of the occluder  102 , the diameter B of the distal stop  132  is greater than the diameter A of the proximal stop  130 , and the diameter C of the intermediate stop  134  is approximately equal to the proximal stop  130 . The third stop  134  allows the distal petals  138  of the occluder  102  to maintain their form prior to the engagement of the proximal stop  130 , and in the event the proximal stop  130  fails. 
         [0046]      FIGS. 15 ,  16  and  17  show a clover leaf occluder  102  in three stages of deployment with a three stop catch member  116   a .  FIG. 15  shows the occluder  102  with the distal end against the distal stop  132 ,  FIG. 16  shows the occluder  102  with the center joint locked with the intermediate stop  134 , and  FIG. 17  shows the occluder  102  completely deployed with the distal end locked against the distal stop  132 , the center joint  136  held against the intermediate stop  134 , and the proximal end held against the proximal stop  130 . 
         [0047]    One embodiment includes a self-locking mandrel tip  106   a  as shown in  FIGS. 18A and 18B . This mandrel tip  106   a  eliminates the need for a bend at the end of the delivery wire  104  by including an L-shaped extension  140  that is preferably biased toward the center axis AX. When biased as shown in  FIG. 18A , the mandrel tip  106   a  can pass relatively unimpeded through the axial passage in the catch member  116 . When a straight delivery wire  104   a  is inserted through the mandrel  106   a  as shown in  FIG. 18B , the wire  104   a  forces the L-shaped extension  140  away from the center axis and beyond the inside diameter envelope of the catch member. In this position, the L-shaped extension  140  impedes passage through the catch member  116 , and performs the same function that the bent wire  104  provided in the earlier-described embodiment. Removing the wire  104   a  allows the L-shaped extension  140  to return to its former biased position, again allowing relatively unimpeded passage through the locking member  116 . 
         [0048]    Other alternative shapes for the mandrel tip  106   a  are shown in  FIGS. 19A and 19B . All of these examples allow easier passage through the locking member  116  without a delivery wire  104   a  inserted than with a delivery wire  104   a  inserted, and all of these examples operate without requiring a bend in the distal end of the delivery wire and the associated force required to remove it. 
         [0049]      FIG. 19C  shows another embodiment of a self-catching mandrel tip  106   c  having an aperture  150  in the side wall of the mandrel. The delivery wire  104  passes through this aperture  150  rather than extending out through the distal end of the mandrel as in the previously-described embodiments. The distal end  152  of the delivery wire in this embodiment has a hook that restricts the distal stop  132  of the catch member  116 , and/or the distal end of the occluder  102 , from movement in the distal direction. Other possible shapes for the distal end  152  of the delivery wire  104  may also be used, for example those shown in  FIGS. 19D ,  19 E and  19 F. The shape shown in  FIG. 19F  uses a wire that is thinner than the other embodiments shown, so that a pair of wires passes through the mandrel. When pulling the delivery wire to release the implant from the system  100 , the force required to “unbend” the hook is isolated to the rim of the aperture  150 . Since the mandrel is preferably made of stainless steel or another similarly hard material, the rim of the aperture  150  can withstand that force without significant deformation. 
         [0050]      FIG. 19G  shows a mandrel with a soft segment  156  added near the distal end of the mandrel to improve pivoting between the delivery system and the implant. In this embodiment, the soft segment is made of a martensitic or R-phase tube segment  156  attached to the proximal portion  158  of the mandrel and the distal portion  160  of the mandrel via any of several appropriate techniques known in the art. For example, a titanium sleeve  162  may be used to attach the segment  156  via welding or crimping to the proximal portion  158  and the distal portion  160  of the mandrel, as shown in  FIG. 19G . The proximal portion  158  and the distal portion  160  of the mandrel may be made of stainless steel to provide a more cost effective system than having the entire mandrel made of a martensitic or R-phase material (e.g., nitinol). Other metals and/or polymers may alternatively be used to achieve similar results. 
         [0051]    In contrast to occlusion devices made of materials such as nitinol, polymers typically produce recovery forces that are low and can be insufficient to bring an implant device (e.g., an occluder) to its desired shape upon delivery without some assistance from the operator. The operator might have to manipulate several elements of the delivery/recovery system. A handle  200  for this embodiment of an occluder delivery/recovery system  100  performs many of these manipulations with minimal input from the operator, so that a polymer may be deployed almost as easily as, and in some cases easier than, a metal device. By carefully controlling and regulating the applied forces, the handle  200  also protects the implant devices from overstressing that can occur with manual manipulations. Elements of the handle also have general applicability to metal implant devices. 
         [0052]      FIG. 20  shows a handle  200  for use with the occluder delivery/recovery system  100  described herein. The general procedure for inserting and/or removing an implant is similar to that described in connection with  FIGS. 3 ,  4 ,  5 A,  5 B,  5 C,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12 ,  13  and  14 , above. The handle  200  includes a delivery knob  202  attached to the sheath  114 , and operates between two primary positions, as further described herein. A separator  204  separates recovery and delivery springs, and provides a small amount of compression to the springs in their most extended configuration. A recovery knob  206  attaches to the recovery catheter  110  and operates between two primary positions as further described herein. A mandrel knob  208  attaches to the mandrel  108  and operates between two primary positions, as further described herein. A delivery wire knob  210  attaches to the delivery wire  104  and the mandrel  108 . A delivery spring  212  compresses between the delivery knob  202  and the separator  204 , so that withdrawal of the delivery knob  202  away from the occluder  202  compresses the delivery spring  212 . A recovery spring  214  is disposed between the recovery knob  206  and the separator  204 , so that advancing the recovery knob  206  toward the occluder  102  compresses the recovery spring  214 . 
         [0053]    A handle housing  216  provides a casing for the other handle components and restricts their movements to within predetermined ranges. The casing may have an ergonomic design so that the various components are easily accessible to the operator, and the required manipulations can be performed in an efficient and repeatable manner. 
         [0054]    A detachment screw  218  mates with the delivery wire knob  210 , and is fixedly attached to the delivery wire  104 . Rotating the detachment screw  218  incrementally pulls on the delivery wire  104  with significant force, but in a controlled manner, pulling the bend in the distal end of the delivery wire  104  against the mandrel tip  106 , thereby straightening the bend and releasing the implant from the delivery/recovery system  100 . 
         [0055]    The delivery sequence for deploying an occluder  102  using the handle  200  begins with the distal end of the delivery/recovery system  100  inserted through the PFO tunnel  18  from the right atrial side and extended partially into the left atrium  13 . As used herein, the term “retract” means to pull away, longitudinally, from the distal end of the delivery/recovery system  100 . The term “advance” means to push, longitudinally, toward the distal end of the delivery/recovery system  100 . The operator begins the delivery sequence by retracting the delivery knob  202  from position Ito position II, which compresses the delivery spring  212  and uncovers the distal half of the occluder  102 , as shown in  FIG. 21 . This allows the occluder clover petals to relax and partially expand away from the central axis. The operator then releases the delivery knob  202 , and the delivery spring  212  forces the delivery knob  202  back to position I. The movement of the sheath  114  presses against the clover petals, causing them to fully expand on the left atrial side of the PFO, as illustrated in  FIG. 22 . 
         [0056]    The operator again retracts the delivery knob  202  from position Ito position II, uncovering the proximal half of the occluder  102 , allowing the proximal petals to expand partially away from the central axis, as shown in  FIG. 23 . The operator releases the delivery knob  202 , the delivery spring  212  forces the delivery knob  202  back to position I, and the sheath  114  presses against the proximal occluder petals causing them to fully expand on the right atrial side of the PFO, as illustrated in  FIG. 24 . The sheath  114  pressing against the proximal occluder petals forces the proximal end of the occluder  102  over the proximal stop of the catch member  116 , thereby locking the occluder  102  in its deployed position. The operator then retracts the delivery knob  202  to position II and locks it into place (using a locking slot, a set screw, or some other similar locking mechanism known in the art). This retracts the sheath  114  away from the occluder  102 , as shown in  FIG. 25 . 
         [0057]    If the operator determines that the occluder  102  is in the proper position, the operator removes the bend in the distal end of the delivery wire  104  by turning the detachment screw  218 , which pulls the bend against the mandrel tip  106  and forces the bend to straighten. The operator then pulls the mandrel away from the deployed occluder  102  and removes the delivery/recovery system  100  from the patient. 
         [0058]    If the operator determines that the occluder  102  is not in the proper deployed position, the operator begins the recovery sequence by advancing the recovery knob  206  from position III to position IV, compressing the recovery spring  214  and advancing the claws  212  outside of the sheath  114  and toward the proximal end of the occluder  102 . The operator then releases the delivery knob  202  from the locked position II to position I, which forces the sheath  114  over the claws  112 , clamping the claws onto the proximal end of the occluder  102 , as shown in  FIG. 26 . The operator then advances the mandrel knob  208  from position V to position VI, causing the mandrel  108  to push the proximal stop of the locking member  116  through the proximal end of the occluder  102 , unclamping the proximal part of the occluder  102  and allowing the proximal clover petals to elongate, as shown in  FIG. 27 . Note that once the occluder  102  is unclamped, the spring force of the compressed recovery spring  214  pushes the recovery knob  206  from position IV to position III, which causes the claws  112  to pull the proximal half of the occluder  102  into the sheath, along with the mandrel knob  208  from position VI to position V to completely withdraw the proximal petals of the occluder  102  into the sheath  114 , as shown in  FIG. 28 . The operator then advances the mandrel knob  208  from position V to position VI, which allows the distal petals of the occluder  102  to relax and elongate, as shown in  FIG. 29 . The mandrel knob  208  retracts automatically (via spring force, or in some cases with assistance from the operator) from position VI to position V, withdrawing the occluder completely into the sheath  114 , as shown in  FIG. 30 . The sheath may be left behind to allow for another delivery. The operator may remove the recovered occluder  112  and the delivery/recovery system  100  from the patient, or redeploy it. 
         [0059]    The delivery system can be used with other embodiments that have internal interference catching systems. These systems typically include components that pass through a center joint of an implant along a longitudinal axis. This type of catch member typically has a section or sections with a larger outside diameter (OD) than the inside diameter (ID) of the implant, so the catch member can engage the implant in one of several ways, such as: (a) the section of the catch member with a larger OD compresses during the catching process as the catch member passes through the implant, and/or (b) the implant ID increases during the catching process as the catch member passes through the implant. In either case, a proximal tip of the catch member passes through the implant device, the dimensions of both the device and the implant return to more or less their original state, thereby holding the implant. Another option is that the catch member or part of the implant can deform temporarily to allow the catching member to pass through. 
         [0060]      FIG. 31A  illustrates another embodiment of a septal occluder that may be delivered using a system of the type described herein. In this case, an occluder  520  in a deployed position has a distal (left atrial) side  522  and a proximal side  524 , each with four petals. A catch mechanism  530  has a distal ball  532 , a proximal ball  534 , and a rod  536  connecting balls  532  and  534 . Balls  532 ,  534  and rod  536  can each have a central bore (not shown) to allow catch mechanism  530  to be delivered with occluder  520  over a guide wire, and can allow a bent wire to pass through as in  FIGS. 2 and 3 . Other types of occluders, for example, those with petals having solid or mesh surfaces, or those with tissue scaffolds may also be used. 
         [0061]      FIG. 31B  is a side view showing occluder  520  with left atrial side  522  and a right atrial side  524 , each in contact with septum secundum  516  and septum primum  514 . In this figure, the catch mechanism is shown with a delivery wire  540  and sheath  542  in a connected position before the delivery wire  540  would be detached from ball  534 . 
         [0062]    As described in the incorporated application Ser. No. 10/890,784, a device of this type can be formed by making cuts or slits in a tube and compressing the ends. The tube can be made of a polymer. In this embodiment and others, the device can be made of a polymer that can be bioresorbable or not bioresorbable. 
         [0063]      FIG. 32  shows an occluder with a ball and string for catching and holding a device mechanism. In the extended configuration for delivery (shown in  FIG. 32  within a delivery sheath  1136 ), the distal ball  1130  engages the distal joint  1110 , and the proximal ball  1132  is disposed along the delivery string  1134  between the distal joint  1110  and the center joint  1108 .  FIGS. 33 ,  34 ,  35  and  36  show the delivery sequence for the ball and string mechanism of  FIG. 32 . A shown in  FIG. 33 , the distal portion of the occluder is deployed from the delivery sheath  1136  on the left atrial side of the PFO.  FIG. 34  shows the proximal ball  1132  pulled through the center joint  1108 , thereby locking the distal portion of the occluder.  FIG. 35  shows the proximal portion of the occluder deployed from the delivery sheath  1136  on the right atrial side of the PFO.  FIG. 36  shows the proximal ball  1132  pulled through the proximal joint  1106 , thereby locking the proximal portion of the occluder. Detaching wire  1134  from ball  1132  is the step remaining to complete the delivery of the occluder in the PFO. 
         [0064]      FIGS. 37 ,  38  and  39  show a recovery sequence for removing an occluder, such as that delivered in the manner shown in  FIGS. 33 ,  34 ,  35  and  36 .  FIG. 37  shows the delivery sheath  1136  disposed against the proximal end of the occluder. Wire  1134  has been pulled with sufficient force to pull ball  1130  through the distal joint  1110  thereby allowing the distal side of the occluder to start to return toward a tubular shape.  FIG. 38  shows the distal ball  1130  further pulled through the center joint  1108 , and up against the proximal joint  1106 , so the right atrial side starts to lose its compressive force.  FIG. 39  shows the unlocked occluder after it has been retracted back into the delivery sheath and out of the PFO by advancing the sheath, retracting the device, or some combination of these motions. Another method for recovering the device is using a method similar to that shown in a provisional application entitled “Closure Device With Hinges”, provisional application No. 60/569,203, filed May 7, 2004, which is incorporated herein by reference. In that method, a set of claws is used to grip and pull the device, starting with the proximal joint. 
         [0065]    In the embodiment of  FIGS. 32 ,  33 ,  34 ,  35 ,  36 ,  37 ,  38  and  39  and in other embodiments, the balls need not be preferably spherical, but could be altered, such as having a distal ball with a flattened distal end. As with the delivery system of  FIG. 2 , the balls can have bores, and a bent wire or other mechanism can prevent the occluder from moving in a distal direction when it is desirable to prevent such movement. 
         [0066]    The following embodiments include “two elements” catching systems. The two elements systems operate on the principle that two elements work together such that either one is small enough to pass through an occluder center joint, but the two elements together form a unit that is too big to pass through an occluder center joint. 
         [0067]      FIGS. 40 and 41  show one type of two elements catching system, including multiple pairs of balls distributed along a pair of strings. In  FIG. 40 , a first ball  1360  and a second ball  1362  are fixedly attached to a first string  1364  (or wire or suture). The distal end of the first string  1364  is releasably attached to a ball  1365  that is part of the distal joint  1110 , either held to the distal end by the tension, or fixedly connected to the distal end. The proximal end of the first string  1364  extends out through a center joint  1108  and a proximal joint  1106  to the operator. A third ball  1366  and a fourth ball  1368  are fixedly attached to a second string  1370 . The distal end of the second string  1370  is releasably attached to the ball  1365  at the distal joint  1110 , and the proximal end of the second string  1370  extends out through the center joint  1108  and the proximal joint  1106  to the operator. The length of the first string  1364  from the first ball  1360  to the distal joint is the same as the length of the second string  1370  from the third ball  1366  to the distal joint  1110 . The length of the first string between the first ball  1360  and the second ball  1362  is the same as the length of the second string  1370  from the third ball  1366  to the fourth ball  1368 . These lengths ensure that the first ball  1360  and third ball  1366  will be side by side (i.e., at the same point) along the longitudinal axis of the occluder, and the second ball  1362  and the fourth ball  1368  will be side by side along the longitudinal axis of the occluder. At least one of the strings can be elastic, in this case string  1364 , so that one of the strings may be stretched to stagger the balls along the longitudinal axis, as shown in  FIG. 40 . Each of the strings  1364  and  1370  can include multiple string segments. In each case, the strings can be fixedly connected to the respective balls if a mechanism is provided to cut the strings after delivery. 
         [0068]    To deploy the occluder, the operator pulls one of the strings in a proximal direction to stagger the first and third balls, and the second and fourth balls. While the balls are staggered, the operator pulls both strings until the first ball  1360  and the third ball  1366  are on the proximal side of the center joint  1108 , and the second ball  1362  and the fourth ball  1368  are on the proximal side of the proximal joint  1106 . The operator then releases the string that is in elastic tension, so as to return the first/third and the second/fourth ball pairs in the side-by-side configuration. When the first/third ball and the second/fourth pairs are in side-by-side configuration, as shown in  FIG. 41 , the pairs cannot pass through the center joints, thereby locking the occluder. The strings are then detached or cut from the device to complete delivery. 
         [0069]    To unlock the occluder before the delivery strings are detached, the operator pulls on one of the strings to once again stagger the balls, thereby allowing the staggered balls to pass through the center joints. 
         [0070]    Other embodiments may stagger the balls via other techniques. For example, the first string  1364  and second string  1370  may be one continuous string that passes through the distal joint and can slide along a fixed or rotatable axle, so that the distal joint  1110  acts as a pulley. The operator pulls on one of the strings to stagger or realign the ball pairs. 
         [0071]      FIGS. 42 and 43  show yet another two element catching system for an occluder. A first ball  1380  and a second ball  1382  are fixedly attached to a string  1384  (or wire, suture, or tube). The distal end of the string  1384  is fixedly attached to a ball  1385  that forms part of the distal joint  1110 , and the proximal end of the string  1384  passes through the center joint  1108  and the proximal joint  1106  and out to the operator. To deploy the occluder, the operator pulls the string  1384  until the occluder stops against a delivery sheath  1386 . The operator continues to pull the string  1384  until the first ball  1380  is on the proximal side of the center joint  1108  and the second ball  1382  is on the proximal side of the proximal joint  1106 . The operator then inserts a rod  1388  through the proximal joint  1106 , the center joint  1108 , and the distal joint  1110 , as shown in  FIG. 43 . The outside diameter of the rod  1388  is large enough to prevent either ball from passing through a center joint while the rod  1388  is disposed within the center joints as shown in  FIG. 43 . Note that the string  1384  may include multiple string segments. The method of using claws, as referred to in conjunction with  FIGS. 37 ,  38  and  39 , could also be used here to recover the device. 
         [0072]      FIGS. 44 and 45  illustrate another embodiment similar to that shown in  FIGS. 42 and 43 . A tube  1389  with an outside diameter slightly smaller than the inside diameter of the center joints includes two apertures in the side wall, each large enough for a first ball  1390  or a second ball  1391  to pass. A string  1392  attaches the first ball  1390  to the second ball  1392 . The operator deploys the occluder within the PFO by moving the distal joint  1110  toward the proximal joint  1106 , using any one of several delivery techniques described herein or known in the art. The operator then inserts the rod  1393 , thereby retaining each ball in its respective aperture. At least a portion of each ball extends beyond the outside diameter of the locking tube  1389  in this position, preventing the proximal joint  1106  from moving in the proximal direction or the distal joint from moving in the distal direction, thereby locking the occluder. 
         [0073]      FIGS. 46 ,  47  and  48  show an embodiment of an end cap catching mechanism, including a catch member  1400  with a proximal ball  1402  fixedly attached to its proximal end, and its distal end fixedly attached to the distal joint  1110 . This embodiment shows the distal end of the catch member  1400  fixedly attached to a ball  1405  having an outside diameter larger than the inside diameter of the distal joint  1110 , although other techniques of securing the distal end of the catch member  1400  to the distal joint may also be used. The outside diameter of the proximal ball  1402  may be slightly less than the inside diameter of the center joint  1108  and the proximal joint  1106 . A detachable delivery wire  1404  (or delivery shaft) attaches to the proximal ball  1402 , and a cap  1406  is disposed about the delivery wire  1404  on the proximal side of the locking ball  1402 . 
         [0074]    The operator engages this catch mechanism by pulling on the delivery wire  1404  so as to pull the distal joint  1110  in a proximal direction toward the proximal joint  1106 . Once the proximal ball  1402  is on the proximal side of the proximal joint  1106 , as shown in  FIG. 47 , the operator pushes the cap  1406  over the ball  1402 . In order to pass through the cap  1406  in the proximal direction, the ball  1402  deforms cap  1406 , expanding the inside diameter of the cap  1406 . Once the ball  1402  is through the cap locking  1406 , the cap  1406  returns to its original shape, resisting the ball  1402  from passing back through the cap  1406  in a distal direction. The delivery wire  1404  is then detached from ball  1402  if releasably attached to it, or is cut to sever the connection to ball  1402 . 
         [0075]    In one embodiment, the cap has threads on its distal side, so that the cap  1406  can be screwed onto mating threads disposed on the outside of the proximal portion of the proximal joint  1106 . In other embodiments, a claw can be used to grip the ball  1402 . 
         [0076]    Having described several embodiments, it should be apparent that modification can be made and be within the scope of the appended claims. For example, other shapes and materials can be used.