Patent Publication Number: US-2007123934-A1

Title: Delivery system for patent foramen ovale closure device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims benefits from U.S. Provisional Patent Application, Ser. No. 60/720,911, filed on Sep. 26, 2005, entitled “DELIVERY SYSTEM FOR PFO CLOSURE DEVICE”, the disclosure of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. The Field of the Invention  
      The present invention relates generally to implanting medical devices within a patient. More particularly, the present invention relates to the field of patent foramen ovale (“PFO”) closure devices and delivery devices therefore.  
      2. The Relevant Technology  
       FIGS. 1A-1C  depict various views of a heart. Heart  10  is shown in a cross-section view in  FIG. 1A . In a normal heart, the right atrium  30  receives systemic venous blood from the superior vena cava  15  and the inferior vena cava  25  and then delivers the blood via the tricuspid valve  35  to the right ventricle  60 . However, in heart  10 , there is a septal defect between right atrium  30  and left atrium  40  of a patient&#39;s heart which is referred to as a patent foramen ovale (“PFO”). PFO is a birth defect that occurs when an opening between the upper two chambers of the heart fail to close after birth to a lesser or greater degree. This birth defect is sometimes also known as a “hole in the heart.” 
      Other problems with this condition are that a blood clot may travel freely between the left or right atria of the heart, and end up on the arterial side. This could allow the clot to travel to the brain, or other organs, and cause embolization, or even a heart attack. These and other similar defects (septal or otherwise), where some tissue needs to be closed to function properly include the general categories of atrial septal defects (“ASDs”), ventricular septal defects (“VSCs”) and patent ductus arterosus (“PDA”), and so forth.  
      The PFO, which is an open flap on the septum between the heart&#39;s right and left atria, is generally identified at  50 . In a normal heart, left atrium  40  receives oxygenated blood from the lungs via pulmonary arteries  75  and then delivers the blood to the left ventricle  80  via the bicuspid valve  45 . However, in heart  10  some systemic venous blood also passes from right atrium  30  through PFO  50 , mixes with the oxygenated blood in left atrium  40  and then is routed to the body from left ventricle  80  via aorta  85 .  
      During fetal development of the heart, the interventricular septum  70  divides right ventricle  60  and left ventricle  80 . In contrast, the atrium is only partially partitioned into right and left chambers during normal fetal development as there is a foramen ovale. When the septum primum  52  incompletely fuses with the septum secundum  54  of the atrial wall, the result is a PFO, such as the PFO  50  shown in  FIGS. 1A-1C , or an atrial septal defect referred to as an ASD.  
       FIG. 1C  provides a view of the crescent-shaped, overhanging configuration of the typical septum secundum  54  from within right atrium  30 . Septum secundum  54  is defined by its inferior aspect  55 , corresponding with the solid line in  FIG. 1C , and its superior aspect  53 , which is its attachment location to septum primum  52  as represented by the phantom line. Septum secundum  54  and septum primum  52  blend together at the ends of septum secundum  54 ; these anterior and posterior ends are referred to herein as “merger points” and are respectively identified at  56   a  and  56   p . The length of the overhang of septum secundum  54 , the distance between superior aspect  53  and inferior aspect  55 , increases towards the center portion of the septum secundum  54  as shown.  
      A tunnel  58  is defined by portions of septum primum  52  and septum secundum  54  between the merger points  56   a  and  56   p  which have failed to fuse. The tunnel  58  is often at the apex of the septum secundum  54  as shown. When viewed within right atrium  30 , the portion of septum secundum  54  to the left of tunnel  58 , which is referred to herein as the posterior portion  57   p  of the septum secundum  54 , is longer than the portion of the septum secundum  54  to the right of tunnel  58 , which is referred to herein as the anterior portion  57   a  of the septum secundum  54 . In addition to being typically longer, the left portion also typically has a more gradual taper than the right portion, as shown. The area defined by the overhang of the anterior portion  57   a  of septum secundum  54  and the septum primum  52  and extending from the anterior merger point  56   a  toward tunnel  58  is an anterior pocket  59   a . Similarly, the area defined by the overhang of the posterior portion  57   p  of septum secundum  54  and the septum primum  52  and extending from the posterior merger point  56   p  toward tunnel  58  is a posterior pocket  59   p.    
      Conventional treatments for PFO (and related conditions), have generally involved invasive surgery, which presents a different, new set of risks to a patient. Although there are some less invasive treatments for PFO, these have typically been less efficient at closing the PFO opening than techniques involving invasive surgery. Accordingly, there is a continuing need for improved methods and devices for closing the PFO opening. In particular, there is a need for improved methods and devices for deploying PFO closure anchors in a patient.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
       FIG. 1A  is a cross-sectional view of a heart;  
       FIG. 1B  is an enlarged cross-section view of the septum primum and the septum secundum and a PFO tunnel between the septum primum and the septum secundum;  
       FIG. 1C  is a perspective view of the septum secundum with the tunnel and the septum primum shown in phantom;  
       FIG. 2  is a perspective view of a medical system including a PFO closure device and a delivery device therefore;  
       FIG. 3A  is a partial break-away, perspective view of the delivery device of  FIG. 2 ;  
       FIG. 3B  is a partial break-away, perspective view of a portion of the medical system of  FIG. 2 ;  
       FIG. 4A  is a partial cross-sectional view of the delivery device of  FIG. 2 ;  
       FIG. 4B  is a partial cross-sectional view of the delivery device of  FIG. 4  in a linked orientation;  
       FIG. 5A  is a cross-sectional view of the medical system of  FIG. 2  as it is being positioned in a PFO;  
       FIG. 5B  is a cross-sectional view of the medical system of  FIG. 2  as left anchor is deployed;  
       FIG. 5C  is a cross-sectional view of the medical system of  FIG. 2  illustrating deployment of left and right anchors;  
       FIG. 5D  is a perspective view of left anchors as viewed from the left atrium;  
       FIG. 6A  is a cross-sectional view of the PFO closure device as positioned in the PFO; and  
       FIG. 6B  is a perspective view of the right anchor as viewed from the right atrium.  
     BRIEF SUMMARY OF THE DISCLOSURE  
      The invention relates to a medical system for use in reducing the size of an internal tissue opening, such as a PFO. In one embodiment, the medical system can include a PFO closure device and a delivery device therefore. The PFO closure device can include left and right anchors connected by a stem. The proximal end of the stem can include a set of internal threads for use in selectively connecting and disconnecting the delivery device to the PFO closure device. The delivery device can enable a practitioner to efficiently secure the PFO closure device in an internal tissue opening. Furthermore, the delivery device can enable a practitioner to adjust and reposition the PFO closure device after left and right anchors are deployed by selectively retracting the right anchor. The ability to reposition the PFO closure device provides practitioners with the added ability of more effectively reducing the size of an internal tissue opening by being able to adjust the PFO closure device during insertion to achieve the best position.  
      In one embodiment, the delivery device can include a tether shaft for removably coupling the delivery device to the PFO closure device. The tether shaft can include a first rigid portion and a second flexible portion, wherein the flexible second portion can be coupled to the stem of the PFO closure device through a threaded arrangement. Furthermore, one or more filaments can be coupled to a movable filament operating shaft and looped around one or more arms of the right anchor. Movement of the filament operating shaft can cause movement of the right anchor between a deployed and retracted position. Thus, a practitioner can move the filament operating shaft with respect to the PFO closure device to selectively deploy and/or retract the right anchor of the PFO closure device.  
      To facilitate disconnecting the delivery device and the PFO closure device, the tether shaft can be selectively linked to the filament operating shaft. In one embodiment, the tether shaft can be rotatably coupled to a shuttle block and the filament operating shaft can be coupled to a filament drive rod. The filament drive rod can be linked to the shuttle block by two rod pins, each positioned in the filament drive rod on opposing side of the shuttle block. As the filament drive rod moves in a distal direction, one of the rod pins contacts and engages the shuttle block, thus causing the shuttle block to move within a housing. However, prior to the rod pin contacting and engaging the shuttle block, movement of the filament drive rod in the distal direction can cause the one or more filaments to slacken, thus deploying the right anchors.  
      Linking of the tether shaft to the filament operating shaft can be facilitated by the configuration of the housing. The housing can be configured such that as the shuttle block moves in the distal direction, a pin, which can be located in an aperture or opening in the shuttle block, can be forced into a recess in the filament drive rod. As such, movement of the pin into the recess of the filament drive rod links the tether shaft to the filament operating shaft via the shuttle block. In this manner, a practitioner can safely move the tether shaft and the filament operating shaft in concert without concern that the right anchor will be inadvertently retracted by the delivery device.  
      These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention extends to systems, methods, and apparatus for deploying a device that can be suitable for reducing the size of an internal tissue opening. By way of explanation, the devices disclosed herein can be used for any internal tissue opening, although frequent reference is made herein to closing a PFO opening of a heart tissue using right atrial anchors and left atrial anchors for purposes of simplicity. Accordingly, it will be understood that references to PFO openings are not limiting of the invention.  
      In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be obvious, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known aspects of PFO closure devices or medical devices in general have not been described in particular detail in order to avoid unnecessarily obscuring the present invention. In addition, it is understood that the drawings are diagrammatic and schematic representations of certain embodiments of the invention, and are not limiting of the present invention nor are they necessarily drawn to scale.  
      The invention extends to systems, methods, and apparatus for deploying a device that can be suitable for reducing the size of an internal tissue opening. An apparatus for reducing the size of an internal tissue opening, such as a PFO closure device, can include a left atrial anchor and a right atrial anchor. The PFO closure device can be deployed by use of a delivery device. In one embodiment, the delivery device can be removably coupled to the PFO closure device by a threaded arrangement. In addition to being selectively removable from the PFO closure device, the delivery device can be configured to enable a practitioner to adjust and selectively manipulate the right anchor of the PFO closure device.  
      In one embodiment, the delivery device can include a tether shaft for removably coupling the delivery device to the PFO closure device and a housing enclosing at least a portion of the tether shaft. The tether shaft can include a first rigid portion and a second flexible portion, wherein the flexible second portion can be coupled to the stem of the PFO closure device through a threaded arrangement. However, the tether shaft can also be configured to have substantially the same rigidity along its length. Furthermore, the delivery device can be connected to the PFO closure device by one or more filaments. The filaments can be linked to the right and/or left anchor(s) such that movement of the filaments can cause movement of the respective anchor. In this manner, the anchor(s) of the PFO closure device can be selectively deployed and thereafter adjusted by a practitioner.  
      In one embodiment, the tether shaft can be selectively linked to the filaments to facilitate disconnecting the delivery device from the PFO closure device. For example, the tether shaft can be coupled to a movable member, such as a shuttle block, which in turn can be linked to a filament member, such as a filament drive rod or a filament operating shaft. The filament member can be coupled to the housing and can be linked to the shuttle block by a movable pin within the shuttle block. In one embodiment, the pin can move into an aperture or recess in the filament member, thus linking the filament member to the shuttle block. In this manner, the tether shaft can be linked to the filaments, such that movement of the filament member in a distal direction causes movement of the tether shaft in the distal direction.  
      The configuration the housing can facilitate linking of the tether shaft to the filament operating shaft. The housing can be configured such that as the shuttle block moves in the distal direction, a pin, which can be located in an aperture or opening in the shuttle block, can be forced into a recess in the filament drive rod. In this manner, the filament drive rod links the tether shaft to the filaments via the filament operating shaft, the pin and the shuttle block. In this manner, a practitioner can safely move the tether shaft and the filament operating shaft in concert with a reduced concern that the right anchor will be inadvertently retracted by the delivery device.  
      With reference now to  FIG. 2 , illustrated is a medical system  100  for use in reducing the size of an internal tissue opening such as a PFO, for example. In the illustrated embodiment, medical system  100  can include a PFO closure device  200  and a delivery device  300  for delivering and positioning PFO closure device  200 . Delivery device  300  enables a practitioner to position a PFO closure device  200 . For example, delivery device  300  can be configured to enable a practitioner to adjust and reposition PFO closure device  200  after PFO closure device  200  is positioned in a PFO, as will be described more fully hereinafter. Also, delivery device  300  can be configured to facilitate an unobstructed view of PFO closure device  200  when positioned in an opening, while maintaining connection with PFO closure device  200  in the event that repositioning is needed. Furthermore, delivery device  300  enables a practitioner to position PFO closure device  200  by utilizing conveniently positioned controls.  
      In the illustrated embodiment, PFO closure device  200  can include a stem  210 , a right anchor  220  linked to stem  210  via a right anchor hub  222 , and a left anchor  230  linked to stem  210  via a left anchor hub  232 . Right and left anchors  220 ,  230  may include one or more arms  220   a, b  and  230   a, b  configured to engage the tissues of the heart  10 . It will be understood that left anchor  230  and right anchor  220  can include more than the two arms and may have any of a variety of shapes known in the art. For example, U.S. patent application Ser. No. 11/102,095, filed Apr. 8, 2005 and incorporated herein by reference, discloses various compatible shapes and configurations for left and right anchors.  
      As further illustrated in  FIG. 2 , delivery device  300  can include a filament control system  310  connected to a handle  380 . Filament control system  310  can be configured to facilitate the positioning of PFO closure device  200  in a patient. Likewise, handle  350  can be configured to work in conjunction with filament control system  310  to enable positioning and securement of PFO closure device  200  in an internal tissue opening. Filament control system  310  and handle  380  contain mechanisms which facilitate deployment and retraction of left and right anchors  230 ,  220 . In the illustrated embodiment, delivery device  300  can be connected to PFO closure device  200 , at least in part, by pusher catheter  332  via associated pusher catheter shaft  334  and by one or more filaments  322 . It should be understood in light of the disclosure provided herein that for each arm of right anchor there can be a filament associated therewith, such that all arms of right anchor can be selectively retracted and deployed.  
       FIG. 3A  is a perspective partial break-away view of filament control system  310  and handle  380  of delivery device  300 . Handle  380  and filament control system  310  operate in conjunction to enable a practitioner to position PFO closure device  200  by controlling the deployment of left and right anchors  230 ,  220 . The ability to control the position of left and right anchors  230 ,  220  enables a practitioner the ability to adjust and reposition PFO closure device  200 .  
      Filament control system  310  facilitates selective deployment of right anchor  220  and selective repositioning of right anchor  220  after right anchor  220  has been deployed. As such, filament control system  310  enables right anchor  220  to be selectively deployed and selectively retracted by a practitioner using delivery device  300 . Likewise, handle  380  can work in conjunction with filament control system  310  to enable a practitioner to position PFO closure device  200  inside an internal tissue opening and to remove delivery device  300  when PFO closure device  200  is appropriately positioned.  
      As shown in the illustrated embodiment, a tether shaft  320  can extend through handle  380  in an arrangement such that tether shaft  320  is capable of rotational movement within handle  380 . A filament drive rod  316  couples to handle  380  and terminates at the proximal end within handle  380  such that a filament cutting shaft  340  can be exposed therefrom within handle  380 . Coupled to handle  380  adjacent a proximal end of filament cutting shaft  340  is a filament cutting handle  348 . Filament cutting handle  348  can be pivotally coupled to handle  380  such that movement of a handle portion  348   a  about a pivot point  348   c  in a direction away from filament drive rod  316  causes a portion of filament cutting handle  348  to rotate. Rotation of filament cutting handle  348  in this manner causes an engagement portion  348   b  to contact filament cutting shaft  340 . Continued rotation of filament cutting handle  348  in this direction will cause filament cutting shaft  340  to translate and move distally through filament drive rod  316 .  
      While handle  380  is illustrated as being substantially hollow in construction, it will be appreciated that handle  380  can be constructed to be substantially solid with recesses of sufficient size and configuration so as to allow filament cutting handle  348  and filament cutting shaft  340  to operate as described herein. Furthermore, a pin can be implemented at pivot point  348   c  so as to pivotally couple filament cutting handle  348  to handle  380  and to enable filament cutting handle  348  to pivot about pivot point  348   c . Furthermore, it will be appreciated by one of ordinary skill in the art in view of the disclosure provided herein that filament cutting handle  348  may alternatively be positioned in housing  312 , or may be integrally coupled into filament cutting shaft  340  such that filament cutting shaft  340  and filament cutting handle  348  form a single piece.  
      In the illustrated embodiment, filament control system  310  can include a housing  312 , a shuttle block  314  positioned in housing  312  and moveable along at least a part of the length of housing  312 , filament drive rod  316  and a filament operating shaft  318  coupled to filament drive rod  316 . In one embodiment, housing  312  can include a cylindrical tube having an elongate hollow portion extending at least partially along the length of housing  312  and configured to house various elements of filament control system  310 .  
      In the illustrated embodiment, filament drive rod  316  and tether shaft  320  connect housing  312  to handle  380 . Tether shaft  320  extends through handle  380  and can be capable of rotational movement therein. Filament drive rod  316  can be fixed to handle  380  such that movement of handle  380  causes movement of filament drive rod  316 . Collars  322   a, b  are coupled to tether shaft  320 , each on opposite sides of shuttle block  314  such that movement of tether shaft  320  causes movement of shuttle block  314 .  
      As shown in the illustrated embodiment, shuttle block  314  includes an aperture or opening  324  in which a pin  326  is received. Pin  326  can be utilized to link tether shaft  320  to one or more filaments  322 . Filament drive rod  316  can include a first rod pin  330   a  and a second rod pin  330   b  positioned in and extending through the sidewalls of filament drive rod  330 . Rod pins  330   a, b  are utilized in connection with safety features of delivery device  300 , as will be discussed hereinafter.  
       FIG. 3B  is a perspective view of the distal end of the delivery device  300 . Further shown are partial cutouts illustrating the connection between delivery device  300  and PFO closure device  200 , as well as the distal end of filament operating shaft  318 . As shown in the illustrated embodiment, tether shaft  320  and filament operating shaft  318  are housed within a pusher catheter  332 . Pusher catheter  332  can be coupled at its proximal end to the distal end of housing  312  and can be configured to facilitate positioning of PFO closure device  200 . Furthermore, pusher catheter  332  can be configured to house tether shaft  320  and filament operating shaft  318 .  
      In one embodiment, pusher catheter  332  can be a double-lumen catheter with tether shaft  320  being housed in a first lumen of pusher catheter  332  and filament operating shaft  318  being housed in a second lumen of pusher catheter  332 . Tether shaft  320  can be capable of rotational and translational movement within pusher catheter  332 . Likewise, filament operating shaft  318  can be capable of translational movement within pusher catheter  332 . In this manner, a user of delivery device  300  can rotate tether shaft  320  about its central axis relative to pusher catheter  332 . Also, a practitioner can move the distal end of filament operating shaft  318  closer to or further away from PFO closure device  200 . The ability to move the distal end of filament operating shaft  318  closer or further away from PFO closure device  200  enables the practitioner to selectively control deployment of an atrial anchor, such as right anchor  220 , of PFO closure device  200 .  
      In the illustrated embodiment, pusher catheter  332  can be coupled to the distal end of housing  312  and can extend to substantially the distal end of delivery device  300 . Pusher catheter  332  can include a pusher catheter extending shaft  334  and a pusher catheter tip  336  at the distal end of pusher catheter extending shaft  334 . Pusher catheter extending shaft  334  can be configured to provide some degree of rigidity to a flexible second portion  320   b  of tether shaft  320  to facilitate placement of PFO closure device  200 . Pusher catheter extending shaft  334  can extend from the distal end of filament operating shaft  318  and can terminate at pusher catheter tip  336 .  
      Pusher catheter tip  336  can be configured to engage a proximal end of stem  210  of PFO closure device  200 . Furthermore, pusher catheter tip  336  can be configured to be repositionable over stem  210  after pusher catheter tip  336  has been disengaged from stem  210 . This can be done by a user moving tether shaft  320  in the proximal direction with respect to housing  312 . With the pusher catheter  332  coupled to housing  312  and pusher catheter tip  336  coupled to pusher catheter  332 , movement of tether shaft  320  in this manner would force the proximal end of stem  210  back into pusher catheter tip  336 .  
      As shown in the illustrated embodiment, tether shaft  320  can include a first portion  320   a  and a second portion  320   b  coupled thereto. First portion  320   a  can include a resilient rod configured to be rotatable and provide enough stiffness to delivery device  300  so as to substantially prevent bucking of delivery device  300  as it is being used to deliver a PFO closure device  200 . First portion  320   a  of tether shaft  320  further can include a threaded portion at the distal end which can be configured to be received within and engage internal threads of the second portion  320   b  of tether shaft  320 . While the illustrated embodiment demonstrates that first and second portions  320   a,b  may be coupled through use of threads, it will be understood that a variety of types of connection means may be employed to connect first portion  320   a  to second portion  320   b.    
      Second portion  320   b  can include a flexible rod comprising a shape memory material such as a shape memory alloy, a shape memory polymer, or the like. In one embodiment, the shape memory material can be NITINOL. Furthermore, coupled to the distal end of second portion  320   b  can be a threaded portion  320   c . Threaded portion  320   c  can be configured to correspond to a set of internal threads  212  at the proximal end of stem  210 . As will be appreciated, rotation of tether shaft  320  with respect to PFO closure device  200  will cause threaded portion  320   c  of tether shaft  320  to disengage from the internal threads  212  of stem  210 . In this manner, delivery device  300  can be disengaged from PFO closure device  200  subject to connection by one or more filaments  322 .  
      Furthermore, it will be understood by one of ordinary skill in the art in view of the disclosure provided herein that a variety of types of connection means may be employed to selectively couple tether shaft  320  to PFO closure device  200 . For example, in an alternative embodiment, tether shaft  320  can be coupled to PFO closure device  200  by a hook and latch. Furthermore, it will be understood by one of ordinary skill in the art that a securing agent, such as an adhesive, can be applied between first portion  320   a  and second portion  320   b  of tether shaft  320  such that rotation of tether shaft  320  can cause disengagement of PFO closure device  200  from tether shaft  320  rather than disengagement of first portion  320   a  from second portion  320   b . Alternatively, reverse threads can be utilized in one of the two coupling arrangements.  
      As shown in the illustrated embodiment, filament operating shaft  318  can be connected to arm  220   b  of right anchor  220  by filament  322   b . In this manner, movement of filament operating shaft  318  causes movement of right anchor  220 , specifically arm  220   b , when filament  322   b  is taut. Filament operating shaft  318  can include openings  318   a, b  through which one or more filaments  322  pass.  
      Openings  318   a, b  in filament operating shaft  318  can be configured to facilitate severing of filaments  322  in preparation of removal of delivery device  300  from a patient. Openings  318   a, b  can be sized and configured to allow one or more filaments  322  to be positioned therethrough. Openings  318   a, b  can be positioned and located at the distal end of filament operating shaft  318 . At the distal end of filament operating shaft  318  and adjacent to openings  318   a, b , is a rounded portion that provides a rounded surface for filaments  322 , such that when tension is induced on filaments  322 , filaments  322  are not severed by a sharp outside edge of openings  318   a, b.    
      Filament  322   b  can be coupled on one end to filament operating shaft  318  then pass through openings  318   a, b , loop around arm  320   b  and then can be fixed to the delivery device  300 . In this manner, as filament operating shaft  318  is moved in the distal direction with respect to housing  312 , at least one end of filament  322   b  moves towards PFO closure device  200 , thus enabling arm  220   b  to deploy. Likewise, as filament operating shaft  318  is moved in the proximal direction with respect to housing  312 , at least one end of filament  322   b  moves away from PFO closure device  200 , thus retracting arm  220   b  of right anchor  220  toward pusher catheter shaft  334 .  
      Filament cutting shaft  340  can be housed within filament operating shaft  318  and can be capable of translational and/or rotational movement therein. In the illustrated embodiment, a filament cutting shaft can include a filament cutting portion  338  at the distal end of filament cutting shaft  340 . Filament cutting portion  338  may be a sharp tip on the terminating distal end of filament cutting shaft  340  or may be a separate piece connected to the distal end of filament cutting shaft  340 . Filament cutting portion  338  can be configured to sever filaments  320 , which are positioned in openings  318   a, b . In the illustrated embodiment, filament cutting portion  338  can include a substantially cylindrical member whose outer diameter substantially corresponds with the inner diameter of filament operating shaft  318 . In this manner, as filament cutting portion  338  moves past openings  318   a, b , filaments  322  are severed by a sharp leading edge of filament cutting portion  338 .  
      It will be understood by one of ordinary skill in the art in view of the disclosure provided herein that filaments  322  can be actuated and/or severed by a variety of different configurations. For example, in one embodiment, filaments  322  can be coupled to filament cutting shaft  340 , wherein filament cutting shaft can be rotated thus causing filaments  322  to be wound around filament cutting shaft  340 . In this embodiment, an atrial anchor, such as a right anchor, which is looped by a filament, can be selectively moved between the deployed and retracted orientation by rotating filament cutting shaft. In an alternative embodiment, filaments  322  can be fixed to filament operating shaft  318 , wherein filament operating shaft  318  can be rotated in a similar manner, thus causing filaments  322  to wind around filament operating shaft  318 .  
      In an alternative embodiment, filaments  322  can selectively be disconnected from PFO closure device  200  by rotating filament cutting shaft  340 . In this alternative embodiment, filament cutting shaft  340  can include an aperture through which one end of a filament  322  is received. Filament  322  can then be wrapped around filament cutting shaft  340  so as to secure the end of filament  322 . After PFO closure device  200  has been placed, a practitioner could disconnect filament  322  from right anchor  220  by unwrapping filament  322  from filament cutting shaft  340 . Filament  322  can be unwrapped by rotating filament cutting shaft  340 . The atrial anchors can be manipulated and the filaments can be severed by a variety of different mechanisms and/or configurations as will be appreciated by one of ordinary skill in the art in view of the disclosure provided herein.  
       FIG. 4  is a cutaway side view of filament control system  310  and handle  380 . Filament drive rod  316  can be received within shuttle block  314  and can be configured to be able to translate and/or rotate therein. Shuttle block  314  and filament drive rod  316  are configured to link tether shaft  320  to filaments  322 . Filament drive rod  316  can include a recess  341  and a rod pin ramp  342  defining a portion of recess  341 , and first and second rod pins  330   a, b . Recess  341  can be configured to receive a portion of pin  326  therein, thus linking tether shaft  320  to one or more filaments  322 . Recess  341  can be positioned in filament drive rod  316  to enable pin  326  to be forced therein as shuttle block  314  and filament drive rod  316  move in the distal direction with respect to housing  312 . More specifically, recess  341  can be positioned along the length of filament drive rod  316  with respect to first rod pin  330   a  so as to correspond with opening  328  of shuttle block  314  when first rod pin  330   a  is in contact with and engages a first side  314   a  of shuttle block  314 .  
      Rod pin ramp  342  can be configured to force pin  326  out of recess  341  to enable a user to retract right anchors  220  as will be discussed more fully herein. Rod pin ramp  342  defines a distal portion of recess  341  and can be of sufficient pitch so as to cause pin  326  to move upward toward a first top surface  312   a  of housing  312  when filament drive rod  316  is moved in the proximal direction with respect to shuttle block  314 .  
      Filament drive rod  316  can be coupled to handle  380  such that movement of handle  380  causes movement of filament drive rod  316 . In one embodiment, filament drive rod  316  can include a hollow substantially rigid shaft. First rod pin  330   a  can be configured and positioned in filament drive rod  316  so as to cause filament drive rod  316  to engage shuttle block  314  as filament drive rod  316  is moved in the distal direction with respect to housing  312 . Furthermore, first rod pin  330   a  can be configured to facilitate placement of pin  326  in recess  341 .  
      First rod pin  330   a  can be positioned in and can extend through the sidewalls of filament drive rod  316 . First rod pin  330   a  can be of sufficient length such that as filament drive rod  316  is advanced through shuttle block  314 , first rod pin  330   a  can contact first side  314   a  of shuttle block  314 . First rod pin  330   a  can be positioned along the length of filament drive rod  316 , such that as first rod pin  330   a  contacts first side  314   a  of shuttle block  314 , opening  328  substantially aligns with recess  341  as illustrated. In this manner, as filament drive rod  316  moves in the distal direction with respect to housing  312 , the top portion of pin  326  can contact a housing pin ramp  344 , thus forcing pin  326  into recess  341  of filament drive rod  316 .  
      Linking of tether shaft  320  to filaments  322  in this manner provides safety benefits. Specifically, linking of tether shaft  320  to filaments  322  enables pusher catheter tip  336  to be disengaged from stem  210  without concern that filaments  322  are manipulating the position of right anchor  220 , namely inadvertently deploying and/or retracting right anchor  220 .  
      Second rod pin  330   b  can be positioned in filament drive rod  316  and configured to reduce the risk that filaments  322  are prematurely severed due to a user pulling handle  380  in the proximal direction. Second pin rod  330   b  can be positioned in and extend through the sidewalls of filament drive rod  316 . Second pin rod  330   b  can be positioned in filament drive rod  316  such that as filament drive rod  316  is advanced through shuttle block  314  in the proximal direction with respect to shuttle block  314 , second rod pin contacts a second side  314   b  of shuttle block  314 .  
      Second pin rod  330   b  can be positioned along the length of filament drive rod  316  so as to substantially prevent a user from inducing tension in filaments  322  sufficient to break filaments  322 . For example, when right anchor  220  is completely retracted due to the tension in filaments  322 , second rod pin  330   b  can be in contact with and engage second side  314   b  of shuttle block  314 . In this manner, movement of filament drive rod  316  in a proximal direction with respect to housing  312  corresponds with movement of tether shaft  320  in the proximal direction with respect to housing  312 , thus preventing filaments  322  from being stretched to failure.  
      In the illustrated embodiment, housing  312  can include a first top surface  312   a , a second top surface  312   b , a bottom surface  312   c  and a housing pin ramp  344  connecting first top surface  312   a  to second top surface  312   b . First top surface  312   a  can be a surface on which pin  326  can slide when pin  326  is not within recess  341  of filament drive rod  316 . Second top surface  312   b  can be positioned below first top surface  312   a  and can provide a surface on which shuttle block  314  can slide. Bottom surface  312   c  provides a surface on which a bottom surface of shuttle block  314  can slide. The distance between second top surface  312   b  and bottom surface  312   c  can correspond to the height of shuttle block  314 , such that as pin  326  is received within recess  341  of filament drive rod  316 , second top surface  312   b  helps to maintain pin  326  within recess  341  as shuttle block  314  moves in housing  312 .  
      Housing pin ramp  344  can be configured to position pin  326  in recess  341  as filament drive rod  316  is advanced in the distal direction with respect to housing  312 . Housing pin ramp  344  can be positioned in housing  312  so as to facilitate the linking of tether shaft  320  to one or more filaments  322  after right anchor  220  has been deployed in preparation for removal of delivery device  300  from a patient. The linking of tether shaft  320  to filaments  322  can be advantageous for safety concerns. For example, linking in this manner reduces risks to patients because the only connection between PFO closure device  200  and delivery device  300  are flexible portion  320   b  of tether shaft  320  and filaments  322 .  
      It will be understood by one of ordinary skill in the art in view of the disclosure provide herein that a variety of configurations of filament control system  310  may be utilized without departing from the scope and spirit of the invention. For example, in one embodiment, tether shaft  320  can be linked to filament drive rod  316  by a linkage positioned outside of housing  312  which couples tether shaft  320  to filament drive rod  316 . Alternatively, a linking assembly can be utilized so as to selectively couple tether shaft  320  to filament drive rod  316  when filament drive rod  316  and tether shaft  320  are in a particular orientation with respect to each other. Furthermore, in an alternative embodiment, filament drive rod  316  and filament operating shaft  318  comprise a single element.  
      Filament operating shaft  318  can be configured to facilitate movement of one or more filaments  322  to selectively deploy and retract right anchor  220 . Filament operating shaft  318  can be coupled to filament drive rod  316 , such that movement of filament drive rod  316  causes movement of filament operating shaft  318 . In this manner, handle  380  can be linked to filament operating shaft  318 , such that movement of handle  380  results in movement of filament operating shaft  318 . In one embodiment, filament operating shaft  318  can include a hollow shaft extending from filament drive rod  316  to the distal portion of delivery device  300 . In the illustrated embodiment, filament operating shaft  318  can be at least partially housed by filament drive rod  316  and can extend to handle  380 . As a matter of clarification, in the illustrated embodiment, filament operating shaft  318  is cross-sectioned with respect to handle  380 , but is not shown in cross-section with respect to filament control system  310 .  
      Collars  324   a, b  are configured to link tether shaft  320  to shuttle block  314 . Collars  324   a, b  are located on opposite sides of shuttle block  314  and are fixed to tether shaft  320 . In one embodiment, collars  324   a, b  are compressed onto tether shaft  320  in an interference fit type arrangement. In an alternative embodiment, collars  324   a, b  are fixed to tether shaft  320  by an adhesive, or alternatively, by screws positioned through collars  324   a, b , respectively, to tether shaft  320 . Collar  324   a  can be positioned on the first side  314   a  of shuttle block  314  and collar  324   b  can be positioned on second side  314   b  of shuttle block  314 . In this manner, tether shaft  320  can be capable of rotating within shuttle block  314 , but translation of tether shaft  320  with respect to shuttle block  314  can be substantially prohibited.  
      Handle  380  can be configured to facilitate placement of PFO closure device  200 . Handle  380  can be of sufficient size and shape to allow a practitioner to hold and move handle  380 . Handle  380  can be connected to filament control system  310  via tether shaft  320  and filament drive rod  316 . Handle  380  can be configured to enable tether shaft  320  to rotate therein and translate at least partially therethrough. Tether shaft  320  can be prevented from pulling through handle  380 , at least in part, by knob  346 . Knob  346  can be coupled to the proximal end of tether shaft  320 . Knob  346  can be configured to facilitate removal of tether shaft  320  from PFO closure device  200 . Knob  346  can be coupled to the proximal end of first portion  320   a  of tether shaft  320 . Rotation of knob  346  causes rotation of tether shaft  320 .  
      Knob  346  can also serve to reduce the likelihood of filaments  322  being damaged. For example, the length of tether shaft  320  can be such that as handle  380  is moved in the proximal direction, knob  346  will contact handle  380  when filaments  322  are taut and right anchor  220  is in a fully retracted orientation. In this manner, knob  346  can serve to substantially prevent filaments  322  from being damaged due to movement of handle  380 .  
      Housed within and coupled to handle  380  can be filament drive rod  316  and filament cutting handle  348 . Housed within filament drive rod  316  can be filament operating shaft  318  and filament cutting shaft  340 . Filament cutting handle  348  can be the actuation mechanism utilized to sever filaments  322  upon disconnecting delivery device  300  from PFO closure device  200 . Filament cutting handle  348  can be rotatably or pivotally coupled to handle  380 . Filament cutting handle  348  can be of a sufficient length to actuate filament cutting shaft  340  when filament cutting handle  348  is rotated or pivoted, as discussed above. As filament cutting handle  348  is rotated in the direction shown, a portion of filament cutting handle  348  contacts filament cutting shaft  340  causing filament cutting shaft  340  to translate through filament operating shaft  318 . As filament cutting shaft  340  is translated through or moves through filament operating shaft  318 , filament cutting portion  338  can move to sever filaments  322  at openings  318   a, b  in filament operating shaft  318 .  
      It will be appreciated by one of ordinary skill in the art in view of the disclosure provided herein that filament cutting shaft  340  can be actuated by alternative configurations. For example, in an alternative embodiment, filament cutting shaft  340  comprises a handle member coupled thereto such that movement of the handle member is the distal direction causes the filament cutting shaft  340  to slide or move within filament operating shaft  318  to sever filaments  322 . In an alternative embodiment, a button or knob can be coupled to filament cutting shaft  340  through filament drive rod  316  and filament operating shaft  318 . In this embodiment, a slot can be formed in filament drive rod  316  and filament operating shaft  318  sufficient to allow movement of the button or knob to in turn move filament cutting shaft  340  to sever filaments  322 .  
       FIG. 4A  illustrates pin  326  in a first position. In this orientation, tether shaft  320  is not directly linked to filaments  322 .  FIG. 4B  illustrated pin  326  in a second position. When pin  326  is in the second position, namely, a portion of pin  326  is received in recess of  340  of filament drive rod  316 , tether shaft  320  is directly linked to filaments  322 . In this manner, movement of tether shaft  320  in either the distal or proximal direction with respect to housing  312  will move at least one end of filament  322  in the same direction. Further illustrated in  FIG. 4B  is the positioning of pin  326  relative to recess  341  of filament drive rod  316  and second top surface  312   b . As illustrated, the configuration of recess  341 , second top surface  312   b  and pin  326  can substantially maintain pin  326  in the second position when opening  328  is positioned under second top surface  312   b  of housing  312 .  
      With reference to  FIG. 5A-6B , one method for delivering PFO closure device  200  to PFO  50  will be described. As illustrated in  FIG. 5A , a delivery sheath  400  is introduced into PFO  50  via a delivery path  99 , as identified in  FIGS. 1A-1C . Delivery sheath  400  is a long, somewhat flexible catheter or sheath introduced into a vein, such as femoral vein, and routed up to the right atrium of a patient&#39;s heart. The delivery sheath  400  may be tracked over a guide wire that has been advanced into the heart by a known methodology. After delivery sheath  400  is introduced into the heart via inferior vena cava  25 , delivery sheath  400  is positioned at right atrium  30  in front of the inter atrial communication or PFO  50 , and then through tunnel  58 .  
      Once the distal end of delivery sheath  400  is positioned at the end of tunnel  58  as illustrated in  FIG. 5A , or extends beyond tunnel  58 , medical system  100  is introduced into delivery sheath  400  as shown in  FIG. 5A . Specifically, PFO closure device  200  and delivery device  300  are coupled by means of stem  210  to tether shaft  320  and pusher catheter tip  336 , and by filaments  322 . PFO closure device  200  is introduced first into delivery sheath  400  with arms of left anchor  230  extended upward or distally and filaments taut causing right anchor  220  to be in a retracted orientation. Medical system  100  is then advanced through delivery sheath  400  until left anchor  230  extends beyond the terminating end of delivery sheath  400 . In this manner, left anchor  230  will be able to return to its memory shape and will thus be deployed as shown in  FIG. 5B .  
      A practitioner is able to utilize housing  312  to advance PFO closure device  200  through delivery sheath  400  by moving housing  312  in the distal direction. As will be appreciated, if a practitioner simply pushes on handle  380  to advance PFO closure device  200  through delivery sheath  400 , pin  326  may contact housing pin ramp  344  and be inadvertently forced into recess  341 .  
       FIG. 5A  provides a cross-sectional view of PFO closure device  200  and delivery device  300  just before left anchor  220  is pushed out of delivery sheath  400  and deployed into left atrium  40 . As illustrated, arms  230   a - 230   c  are extending distally such that as medical system  100  is advanced distally within delivery sheath  400 , left anchors  230  deploy into left atrium  40 . Furthermore, arms  220   a - 220   c  of right anchor  220  extends proximally and are held in this retracted orientation by filaments  322 .  FIG. 5B  illustrates left anchor  220  just after deployment in left atrium  40 .  
       FIG. 5C  shows left anchor  220  being pulled proximally and positioned adjacent PFO  50 . A practitioner positions PFO closure device  200  in this manner by moving housing  312  and/or handle  380  in the proximal direction. As such, a user can move left anchor  230  in the illustrated position by manipulating housing  312  and/or handle  380 . Once left anchor  230  is in position, a user would move handle  380  in the distal direction with respect to housing  312 , such that filament drive rod  316  and thus filament operating shaft  318  move distally with respect to housing  312 . In this manner, the ends of filaments  322 , which are coupled to filament operating shaft  318 , are moved toward PFO closure device  200 . This movement causes arms of right anchor  220  to deploy so as to extend perpendicularly from the central axis of stem  210 .  
      In the event that the user or practitioner wishes to reposition PFO closure device  200 , a user would simply move the handle  380  in the proximal direction with respect to housing  312  so as to move filament operating shaft  318  in the proximal direction. Movement in this manner causes filaments  322  to pull on arms of right anchor  220 , thus moving the ends of arms of right anchor  220  in the proximal direction. In this manner, the user would be able to reposition and move the PFO closure device  200  and then again deploy right anchor  220  by moving handle  380  in the distal direction until the practitioner is satisfied with the location of PFO closure device  200 .  
      Once right and left anchors  220 ,  230  are deployed and PFO closure device  200  is in a satisfactory position, the practitioner can disengage pusher catheter tip  336  from the proximal end of stem  210 . This is done by moving the handle  380  in the distal direction with respect to housing  312  until pin  326  moves from the first to the second position, as shown in  FIG. 4B . As will be appreciated in light of the disclosure, pin  326  is forced into recess  341  of filament drive rod  316  as filament drive rod  316  advances distally through housing  312 . Furthermore, with shuttle block  314  now linking tether shaft  320  to filament drive rod  316 , as handle  380  is further advanced toward housing  312 , tether shaft  320  is advanced through pusher catheter  332 . As tether shaft  320  is advanced distally through pusher catheter  332 , it will be appreciated that tether shaft  320  will force stem  210  away from pusher catheter tip  336 , thus causing disengagement. With pusher catheter tip  336  disengaged from stem  210 , a practitioner is better able to view placement of PFO closure device  200  in tunnel  58 .  
       FIG. 5C  further depicts pusher catheter tip  336  being disengaged from the proximal end of stem  210 , in preparation of removal of delivery device  300  from the patient. In this manner, the only connection between PFO closure device  200  and delivery device  300  are flexible filaments  320  and flexible second portion  320   b  of tether shaft  320 . In this manner, a practitioner is able to use known methodologies to observe the positioning of PFO closure device  200  in relation to PFO  50 .  
      Furthermore, should PFO closure device  200  require repositioning, a user would have the option of repositioning PFO closure device  200 . Repositioning can be effectuated by reengaging pusher catheter tip  336  with the proximal end portion of stem  210  and inducing tension in filaments  322  by moving proximally filament operating shaft  318 . Pusher catheter tip  336  can be reengaged with stem  210  by a user grasping knob  346  and moving tether shaft  320  in the proximal direction with respect to housing until pusher catheter tip  336  moves over and mates with the outer surface of stem  210 . Furthermore, right anchors  220  can be retracted by a user moving handle  380  in the proximal direction with respect to housing  312 , thus causing filament operating shaft  318  to translate proximally.  
      A user can disengage pusher catheter tip  336  from stem  210  by observing the following procedure. Once PFO closure device  200  is in position and filaments  322  are slackened, a user moves handle  380  toward housing  312  until first rod pin  330   a  contacts and engages first side  314   a  of shuttle block  314 . As a user continues to move handle  380  toward housing  312 , first rod pin  330   a  causes shuttle block  314  to move in the distal direction. As shuttle block  314  moves in the distal direction, the top portion of pin  326  will contact housing pin ramp  344 , thus forcing pin  326  into recess  341  of filament drive  316 . Once pin  316  is in recess  341 , tether shaft  320  is linked to filaments  322  by filament drive rod  316  and filament operating shaft  318 . A user would then continue to move handle  380  toward housing  312 , and at the same time move housing  312  and handle  380  in the proximal direction so as to prevent right anchor  220  from being pushed into left atrium  40 .  
       FIG. 5D  illustrates the position of left anchor  230  as viewed from left atrium  40 . In the illustrated embodiment, two arms of left anchor  230  are in contact with septum secundum  54  and two arms of left anchor  230  are in contact with septum primum  52 .  
       FIG. 6A  illustrates PFO closure device  200  in PFO  50  after delivery device  300  has been disconnected from PFO closure device  200 . To disconnect delivery device  300  from PFO closure device  200 , a user simply needs to disengage pusher catheter tip  336  from stem  210  and remove tension from filaments  322  as discussed above and then observe the following procedures. A user would rotate knob  346  so as to disengage threaded portion  320   c  from internal threads  212  of stem  210 . Next, a user would actuate filament cutting shaft  340  by rotating filament cutting lever  348  in the direction indicated in  FIG. 4A . In this manner, filament cutting portion  338  would sever filaments  322 . With filaments  322  severed and threaded portion  320   c  of tether shaft  320  disengaged from internal threads  212  of stem  210 , delivery device  300  is disconnected from PFO closure device  200 . As such, delivery device  300  can then be removed from delivery sheath  400 , delivery sheath  400  can then be removed from the patient, and the PFO closure device  200  is completely installed, as shown in  FIGS. 6A-6B .  FIG. 6B  illustrates PFO closure device  200  in PFO  50  as viewed from right atrium  30 .  
      The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. Exemplary claims have been included herein to illustrate embodiments of the invention. Although exemplary claims are presented, the invention is not limited to these claims, and the applicant reserves the right to present different or other claims in the future in view of the embodiments of the invention described herein.