Patent Publication Number: US-2023149167-A1

Title: Systems and methods for reshaping a heart valve

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Application No. 16/287,208, filed Feb. 27, 2019, which is a continuation of U.S. Application. No. 14/774,656, filed Sep. 10, 2015, and issued as U.S. Pat. 10,321,999, on Jun. 18, 2023, which is a U.S. National Stage application under 35 U.S.C. § 371 of PCT/US2014/026333, filed Mar. 13, 2014, which claims benefit of priority under 35 U.S.C. §119 to U.S. Provisional Application No. 61/783,420, filed Mar. 14, 2013, the entire disclosures of which applications are hereby incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present disclosure relates generally to heart treatment devices and methods, and more particularly, to systems and methods for reshaping a heart valve. 
     BACKGROUND 
     The present disclosure addresses heart valve incompetency. For example, heart disease can cause the chambers of the heart to expand and weaken. With specific reference to the mitral valve, as the left ventricle dilates, the papillary muscles are displaced. Consequently, the annulus of the mitral heart valve dilates, excessively. In this state of dilation, valve leaflets no longer effectively close, or coapt, during systolic contraction. Consequently, regurgitation of blood occurs during ventricular contraction and cardiac output is decreased. 
     This condition is typically addressed by open-heart surgical implantation of an annuloplasty ring. A surgeon positions the annuloplasty ring proximate the valve annulus and sutures it in place thereby restoring the valve annulus to approximately its native circumference. The valve leaflets can then function normally again. 
     SUMMARY 
     In one embodiment, the present disclosure includes a device for reshaping a heart valve comprising a central ring about a central axis and a plurality of arms coupled to the central ring, each of the arms coupled to the central ring at a pivot point at a first end of the arm, the arm comprising an attachment feature at a second point along the arm, the pivot point configured to allow movement of the arm about the pivot point through a plane extending radially from the central axis through the arm. In this embodiment, the plurality of arms are contractable and are extendable such that the attachment features extend beyond a dilated heart valve. 
     In another embodiment, the present disclosure includes a method for reshaping a heart valve comprising deploying a device, the device comprising a central ring about a central axis and a plurality of arms coupled to the central ring, each of the arms coupled to the central ring at a pivot point at a first end of the arm, the arm comprising an attachment feature at a second point along the arm, the pivot point configured to allow movement of the arm about the pivot point through a plane extending radially from the central axis through the arm. The method also includes extending the plurality of arms beyond a dilated heart valve and engaging the attachment features into tissue proximate the dilated heart valve. The method additionally includes contracting the plurality of arms to reduce the circumference of the dilated heart valve. 
     In an additional embodiment, the present disclosure includes a system comprising a delivery catheter and a delivery shaft disposed within the delivery catheter. The system also includes a device for delivery by the delivery catheter and removably coupled to the delivery shaft. The device comprises a central ring about a central axis, and a plurality of arms coupled to the central ring, each of the arms coupled to the central ring at a pivot point at a first end of the arm, the arm comprising an attachment feature at a second point along the arm, the pivot point configured to allow movement of the arm about the pivot point through a plane extending radially from the central axis through the arm. In such an embodiment, the plurality of arms are contractable and are extendable such that the attachment features extend beyond a dilated heart valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: 
         FIGS.  1 A through  1 D  illustrate an example of a device for reshaping a heart valve, in accordance with some embodiments of the present disclosure; 
         FIGS.  2 A and  2 B  illustrate an example embodiment of reshaping a heart valve using a device, in accordance with some embodiments of the present disclosure; 
         FIG.  3    illustrates an example of a delivery system for delivery of a device for reshaping a valve, in accordance with some embodiments of the present disclosure; 
         FIGS.  4 A- 4 F  illustrate an example of expanding a device, in accordance with some embodiments of the present disclosure; 
         FIGS.  5 A and  5 B  illustrate an example of utilizing an engaging member, in accordance with some embodiments of the present disclosure; 
         FIGS.  6 A- 6 D  illustrate an example embodiment of a device for reshaping a heart valve; 
         FIGS.  7 A- 7 D  illustrate an example of operation of an example hook, in accordance with some embodiments of the present disclosure; and 
         FIGS.  8 A- 8 D  illustrate an example of operation of another example hook, in accordance with some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure addresses systems and methods for reshaping a heart valve. A device with a plurality of arms coupled to a central ring may be utilized to reshape a heart valve. The device may pivot about one end of the arms, which may be coupled to the central ring. At a second point along a respective arm (for example, the opposite end from the pivot point), there may be a hook or some other attachment feature. An arm may have its pivoting motion limited to the plane extending radially from a central axis of the ring through the arm. The device may also include a slider with linkages between the slider and the arms. Thus, the action of the device may resemble that of a parasol as the slider is slid along the central axis of the central ring to cause the arms of the device to extend or contract. To reshape the heart valve, the device may be deployed proximate the valve annulus. The arms may be extended (for example, like a parasol opening) beyond the annulus or beyond a diseased or dilated heart valve and then the hooks at the end of the arms may be engaged with the tissue, for example, by pulling the device down against the valve with the arms extended. Once the hooks are engaged, the arms may be contracted (for example, like a parasol closing). With the hooks engaged in the tissue, the contracting arms may draw the annular tissue inwards as they are contracted such that the valve leaflets coapt more appropriately by decreasing the circumference of the valve annulus or the area of the valve opening. The device may then be caused to retain its contracted shape. 
       FIGS.  1 A and  1 B  illustrate an example of a device  100  for reshaping a heart valve, in accordance with some embodiments of the present disclosure.  FIG.  1 A  illustrates a perspective view and  FIG.  1 B  illustrates a top-down view of device  100 . Device  100  may include a central ring  110  with a plurality of arms  120  coupled to central ring  110 . For reference, a central axis  130  may pass through the center of central ring  110  and be perpendicular to the plane of central ring  110 . Device  100  may further include a slider  140 , which is slidable along central axis  130  and linkages  150 , which are coupled to slider  140  and to arms  120 . Device  100  may be made of any suitable biocompatible metal or high strength polymer such as stainless steel, cobalt chromium, nitinol, titanium, platinum, platinum/iridium, high molecular weight polyethylene or polyurethane, or any other biocompatible material as is known in the art. 
     Each arm  120  may be coupled to central ring  110  at a pivot point  160 . Device  100  may be expanded or contracted by extending or contracting arms  120  about their respective pivot points  160 . In some embodiments, the motion of arms  120  may be limited to essentially motion along the plane extending radially from central axis  130  to a particular arm  120 . For example, the coupling between a given arm  120  and central ring  110  may limit this motion as the coupling may be a hinge, an eye socket on arm  120  at pivot point  160 , or some other mechanism as known in the art to facilitate motion limited about a pivot point. The motion of each arm may be independent, or some or all of the arms may be moved simultaneously. 
     The motion of extending or contracting arms  120  about pivot point  160  may be facilitated using slider  140  and linkages  150 . By way of example, when slider  140  is at a position away from central ring  110 , arms  120  may be in a more contracted position. When slider  140  is slid along central axis  130  from an initial position away from central ring  110  and towards central ring  110 , linkages  150  may push arms  120  radially outward from central axis  130 , extending arms  120  of device  100 . In the reverse, when slider  140  is slid along central axis  130  from a position proximate central ring  110  away from central ring  110 , linkages  150  may pull arms  120  in towards central axis  130 , contracting arms  120  of device  100 . By way of example and in no way meant to be limiting, this motion using slider  140  and linkages  150  may be similar conceptually to that observed in a parasol in which a slider may be used to open and close the parasol. In some embodiments, linkages  150  may comprise more than one piece. For example, linkages  150  may include two components that are coupled by a hinge j oint, or two components that slide past each other. 
       FIGS.  1 C and  1 D  illustrate an example perspective view ( FIG.  1 C ) and top-down view ( FIG.  1 D ) of device  100  when its arms  120  are extended. As shown in  FIGS.  1 C and  1 D , as slider  140  is moved closer to central ring  110 , linkages  150  may force arms  120  to extend radially outward from central ring  110 . 
     In some embodiments, linkages  150  may include a hinge joint at each end. In other words, linkage may have a hinge at both slider  140  and arm  120 . Linkages  150  may also simply rely on the flexion of a rigid body to accomplish the parasol-like motion of arms  120 . For example, if linkages  150  are fixed to slider  140  and unattached to arms  120 , as slider  140  is moved closer to central ring  110 , linkages  150  may force arms  120  to extend. If arms  120  were biased towards a closed position (for example using springs or a memory shaped material) or if arms  120  are coupled to linkage  150  with a hinge joint, when slider  140  is moved away from central ring  110 , arms  120  would contract. It will be appreciated that these are merely examples of implementations of the parasol-like motion, and any similar expansion or contraction supported by a slider and linkages would be within the scope of the present disclosure. 
     On the opposite end of arms  120  from pivot point  160  may be one or more hooks  170 . Hooks  170  may be designed and shaped to pierce and engage annular tissue. In some embodiments, hooks  170  may be a tapered point of arm  120 . Hooks  170  may also be an angled and tapered point of arm  120 . For example, hooks  170  may be angled at between approximately forty-five degrees and ninety degrees relative to the annular tissue when arms  120  are fully extended, although these are merely examples and any angle that facilitates hooks  170  piercing and engaging the annular tissue would be within the present disclosure. The angled orientation of hooks  170  to the annular heart tissue may reduce the force needed to pierce the annular tissue. 
     As will be appreciated, as device  100  is contracted by contracting arms  112 , the orientation of hooks  170  may also change. As their orientation changes, hooks  170  may transition from perpendicular to the annular tissue to facilitate piercing the tissue, to an angled orientation for scooping tissue or drawing tissue towards central axis  130 . This inward orientation may be angled such that it opposes the forces and movement of the surrounding annular tissue and heart structures. In some embodiments, hooks  170  may be oriented differently with respect to each other such that, overall, they are resisting forces, in multiple vectors, that might tend to extract or dislodge hooks  170 . This may be beneficial due to the continuous beating of the heart, generating diverse directions of forces on device  100 , which might otherwise dislodge device  100 . 
       FIGS.  2 A and  2 B  illustrate an example embodiment of reshaping a heart valve using a device, in accordance with some embodiments of the present disclosure.  FIGS.  2 A and  2 B  will be described with reference to device  100  of  FIGS.  1 A- 1 D . Once device  100  has been deployed to a desired location, for example, a left atrium with a dilated valve, device  100  may be expanded by extending arms  120  of device  100 . As described above and by way of non-limiting example, this motion may be analogous to a parasol opening. Once extended beyond the dilated valve annulus, a force may be applied to engage hooks  170  with the annular tissue. For example, as shown in  FIG.  2 A , device  100  has hooks  170  which have been engaged in annular tissue. 
     With hooks  170  engaged in annular tissue, device  100  may be contracted such that hooks  170  draw the annular tissue with them to reduce the circumference or area of the valve opening. This may, for example, reduce or lessen mitral regurgitation. As described above and by way of non-limiting example, this motion may be analogous to a parasol closing. For example, as shown in  FIG.  2 B , hooks  170  are engaged with the tissue and arms  120  have contracted, drawing the valve leaflets closer together. The action of hooks  170  when contracting arms  120  may also be described as gathering or pushing the heart tissue surrounding the valve inwardly. The circumference of the annulus or valve area may thus be reduced such that the valve leaflets coapt normally and regurgitation is reduced. In some embodiments, regurgitation may be completely eliminated. 
       FIG.  3    illustrates an example of a delivery system for delivery of a device for reshaping a valve. As shown in  FIG.  3   , a delivery system  300  may include a delivery catheter  310 , a delivery shaft  320 , and a device  100  for reshaping a valve. 
     Delivery catheter  310  may be any catheter with sufficient circumference to carry device  100  and delivery shaft  320 . Delivery catheter  310  may be introduced using any known method or route to arrive at the desired chamber of the heart. For example, delivery catheter  310  may be routed transapically, transseptally from the right atrium, or through the femoral artery over the aortic arch and through the left ventricle. Still another entry may be directed through the left atrium. 
     Delivery shaft  320  may be removably coupled to device  100 . For example, after deployment in the heart tissue and retraction of device  100 , delivery shaft  320  may be decoupled from device  100 , for example, by disengaging or unthreading, leaving device  100  behind as a permanent implant. Device  100  thus may also include corresponding threads, couplings, sockets, or other connecting features to allow device  100  to be removably coupled with delivery shaft  320 . 
     A typical delivery process may include using a guidewire to navigate the body as described above to the desired chamber of the heart, for example, the left atrium. Delivery catheter  310  may then be fed down the guidewire to the desired chamber. Delivery shaft  320  may then be guided down delivery catheter  310  and into the desired chamber either passively by the guidewire or actively by steering means from outside the patient via control handle. The controls may include push-pull wire mechanism and or rotational controls or the catheters or sheaths for accurate delivery. At this point, delivery catheter  310  may be partially withdrawn or delivery shaft  320  may be extended beyond delivery catheter  310  such that device  100  is no longer constrained within delivery catheter  310 . 
       FIGS.  4 A- 4 C  illustrate a side view of an example of expanding a device, and  FIGS.  4 D- 4 F  illustrate corresponding top views of an example of expanding a device, in accordance with some embodiments of the present disclosure. With reference to  FIGS.  4 A- 4 F , once no longer constrained within delivery catheter  310  shown in  FIG.  3   , device  100  may be expanded by extending arms  120  of device  100 . This may be accomplished, for example, by sliding slider  140  along central axis  130  from a location at its maximum distance from central ring  110  (for example as shown in  FIGS.  4 A and  4 D ) to a position proximate central ring  110  (for example progressing from the positions shown in  FIGS.  4 A and  4 D  to that shown in  FIGS.  4 B and  4 E  and ultimately to that shown in  FIGS.  4 C and  4 F ). Slider  140  may be configured to slide along delivery shaft  320 . This may be done by a tool within delivery catheter  310  able to move relative to delivery shaft  320  to force slider  140  along delivery shaft  320 . As described above and by way of non-limiting example, this motion may be analogous to a parasol opening. 
     Once expanded beyond a dilated valve annulus, a force may be applied via the delivery shaft  320  to engage hooks  170  with the annular tissue. Once engaged, device  100  may be contracted, hooks  170  drawing the annular tissue with them to reduce the circumference of the valve. This may be accomplished, for example, by sliding slider  140  along central axis  130  from a location proximate central ring  110  (for example, as shown in  FIGS.  4 C and  4 F ) to a location further away from central ring  110  (for example, that shown in  FIGS.  4 B and  4 E ). This may be done by sliding slider  140  along delivery shaft  320 . As described above and by way of non-limiting example, this motion may be analogous to a parasol closing. 
     Depending on the delivery path, delivery catheter  310  may be approaching the valve from above the valve (e.g. from within the atrium) or may be approaching the valve from beneath the valve (e.g. from within the ventricle, through the valve and into the atrium). When approaching from above the valve, a force may be generated to engage hooks  170  with the annular tissue by pushing on delivery shaft  320 . This may then be pushing device  100  and thus hooks  170  into the annular tissue. When approaching from below the valve, a force may be generated to engage hooks  170  with the annular tissue by pulling on delivery shaft  320 . This may then pull device  100  and thus hooks  170  into the annular tissue. 
       FIGS.  5 A and  5 B  illustrate an example of utilizing an engaging member, m accordance with some embodiments of the present disclosure. For example,  FIG.  5 A  illustrates device  100  with hooks  170  engaged with annular tissue. Further, as shown in  FIG.  5 A , arms  120  are contracted down a certain amount such that the circumference of the valve has been reduced. In some embodiments of the present disclosure, an engaging member may be utilized to prevent arms  120  from extending beyond a desired size. The present disclosure contemplates any mechanism employed or component coupled to device  100  to maintain arms  120  in a contracted state. One non-limiting, illustrative example of such an engaging member is a ring like that illustrated in  FIG.  5 B . 
       FIG.  5 B  illustrates a ring  510  that may be slid over the top of device  100  to engage arms  120  to maintain device  100  in the contracted state. By maintaining arms  120  of device  100  in a contracted state, the dilated valve may also be maintained in a reduced circumference. Placing ring  510  over the top of device  100  and sliding it down arms  120  of device  100  may further contract arms  120  by applying a force to the outside of arms  120 , where slider  140  and linkages  150  of  FIGS.  1 A- 1 D  applied a force to the inside of arms  120 . In some embodiments, arms  120  may have a groove or notch on the outside for ring  510  to settle in once ring  510  has been slid down the outside of arms  120  a desired distance. Ring  510  may be made of any biocompatible material, for example, metal, metal alloy, plastic, elastomer, or other biocompatible materials as known in the art. In addition to ring  510 , other engaging members may be used to maintain arms  120  of device  100  in a contracted state. 
       FIGS.  6 A- 6 D  illustrate an example embodiment of a device  600  for reshaping a heart valve. As shown in  FIG.  6 A , in some embodiments, device  600  may include a central ring  610 , arms  620  coupled to central ring  610 , and hooks  670  at the end of arms  620 . For reference, a central axis  630  may pass through the center of central ring  610  and be perpendicular to the plane of central ring  610 . In the embodiment shown in  FIGS.  6 A- 6 D , an alternative mechanism is used to extend and contract arms  620  of device  600  when compared with the mechanism described with respect to  FIGS.  1 A- 1 D . While arms  620  follow a similar path of motion as that described with respect to device  100  of  FIGS.  1 A- 1 D , device  600  does not use a slider or linkage system similar to that illustrated in  FIGS.  1 A- 1 D . For example, the motion of arms  620  may be limited to essentially motion along the plane extending radially from central axis  630  to a particular arm  620 . 
     In some embodiments, the force to contract arms  620  may be derived by using a shape memory material, for example nitinol. For example, device  600  may have a memory configuration of a contracted state such that device  600  may be deployed or deformed to a particular state and, at body temperature, will transform back to the contracted state. This may be a completely contracted state, for example one in which arms  620  are substantially parallel with central axis  630 , or may be only partially contracted, for example one in which arms  620  are at some acute angle (for example between zero and sixty degrees) with central axis  630 . 
     To provide the expansive force to extend arms  620  of device  600 , a delivery catheter  650  may utilize a balloon  652 . For example, when deploying device  600 , balloon  652  may be disposed between arms  620  and delivery shaft  650 . When device  600  has been disposed within the desired location (e.g. the left atrium), balloon  652  may be inflated to cause arms  620  to extend outward against the inwardly biased memory shape of device  600 . For example, when comparing  FIG.  6 A  to  FIG.  6 B , balloon  655  is inflated causing arms  620  to be extended. 
     In some embodiments, the expansion caused by inflation of balloon  655  may not be only about the point where arms  620  couple with central ring  610 . For example, a portion of the displacement of arms  620  caused by balloon  655  may be bowing or bending of arms  620 . 
     In some embodiments, a cap  680  may be used to limit the expansion of arms  620  based on the inflation of balloon  652 . For example, cap  680  may prevent arms  620  from extending beyond approximately perpendicular to central axis  630 . Cap  680  may be part of device  600  or may be a separate component that may be deployed with delivery shaft  650  and removed upon contraction of arms  620 . 
     With this embodiment in mind, as shown in  FIG.  6 B , balloon  655  may be inflated to extend arms  620  beyond their shape memory state. In this extended state, a force may be applied to cause hooks  670  to engage the annular tissue. As shown in  FIG.  6 C , once the hooks have engaged the annular tissue, balloon  655  may be deflated. As balloon  655  is deflated the shape memory characteristics of device  600  cause arms  620  to contract back to their shape memory state. As this occurs, hooks  670 , which are engaged in the annular tissue, draw the annular tissue along with them causing a decrease in the circumference of the valve. Stated another way, as arms  620  contract back to their shape memory state, hooks  670  gather or push the heart tissue surrounding the annulus or valve area inwardly. 
     Once balloon  655  has been sufficiently deflated, delivery shaft  650  and balloon  655  may be withdrawn such that device  600  remains as a permanent implant to maintain the reduced circumference of the heart valve. In embodiments where cap  680  is a separate component, it may also be retrieved and withdrawn at the same time that delivery shaft  650  and balloon  655  are withdrawn. This may leave device  600  in a final configuration as a permanent implant, for example, as shown in  FIG.  6 D . 
     In some embodiments, central ring  610  and arms  620  may be a unitary body of shape memory material. Alternatively, arms  620  may be shape memory material and coupled to central ring  610  as a separate component. In some embodiments, multiple arms  620  may be a unitary body coupled to central ring  610 . 
     The embodiments shown in  FIGS.  6 A- 6 D  may also use an engaging member to provide assistance to device  600  in returning to its contracted memory shape and/or in retaining its contracted shape. For example, a ring may be placed over the top of device  600  and slid down arms  620 , providing additional force to contract arms  620 . 
     In some embodiments the devices for reshaping a heart valve of the present disclosure may also be covered in Dacron, polyester, or some other biocompatible material. It may be that only a portion of the device may be covered, for example, any one or combination of the arms, central ring, linkages, hooks, and slider may be covered. 
       FIGS.  7 A- 7 D  illustrate an example of operation of an example hook, in accordance with some embodiments of the present disclosure. As shown in  FIG.  7 A  and as described above, at the end of arm  120  is a hook  770 . As shown in  FIG.  7 A , the profile of hook  770  may be a tapered point of arm  120 . Additionally, as shown in  FIG.  7 B , hook  770  may be angled such that it is positioned to more effectively pierce, penetrate, or otherwise engage annular tissue. For example, as described above, hook  770  may form an angle of between approximately forty-five and ninety degrees with the annular tissue. 
     As illustrated between  FIGS.  7 B and  7 C , a force may be applied to cause hook  770  to pierce, penetrate, or otherwise engage the annular tissue. Once that has occurred, arm  120  may be contracted, as described herein. As illustrated in  FIG.  7 D , as arm  120  is contracted, hook  770  gathers and draws annular tissue inward with it as arm  120  contracts. Additionally, because of the orientation of hook  770 , it may resist withdrawal from the annular tissue, with the resistance increasing the further arm  120  is contracted. 
       FIGS.  8 A- 8 D  illustrate an example of operation of another example hook, m accordance with some embodiments of the present disclosure. As shown in  FIG.  8 A , at the end of arm  120  is a hook  870 . As shown in  FIG.  8 A , the profile of hook  870  may include a point but may also include scoops on either side of the point. In other words, hook  870  may have a scooped profile. These scoops may be shaped such that hook  870  may still be able to adequately puncture, pierce, or otherwise engage annular tissue. For example, hook  870  may be flat but with the profile shown in  FIG.  870   . In this way, for example as shown in  FIGS.  8 B and  8 C , arm  120  may be extended and then hook  870  may be forced into the annular tissue. As shown in comparison of  FIGS.  8 C to  8 D , as arm  120  is contracted, hook  870  is able to draw annular tissue inwards with it. When compared to the profile of hook  770  illustrated in  FIG.  7 A , the profile of hook  870  of  FIG.  8 A  may have an increased surface area to catch and draw more annular tissue inwards as arm  120  contracts. This may be because of the scoops on either side of the point of hook  870 . 
     While two examples of hooks are shown in  FIGS.  7 A- 7 D  and  FIGS.  8 A- 8 D , it will be appreciated that the hooks of the present disclosure could take any of a variety of profiles or shapes and are within the scope of the present disclosure. For example, as the surface area of a hook is increased, it will resist contraction of the arm more but will draw more annular tissue inwards with it. An increase in surface area may also make it more difficult for the hook to pierce the annular tissue. As the surface area decreases, or in other words, as the point becomes more pointed, it may become easier to pierce the annular tissue. However, this may come at a cost that the hook may not draw as much annular tissue with it when the hook’s arm contracts. 
     Additionally, the hooks of the present disclosure may include features to resist withdrawal from the annular tissue. For example, they may include barbs, protrusions, or other projections that prevent or resist withdrawal of the hooks out of the annular tissue. In some embodiments, a portion of the hooks may be sharpened or otherwise configured to more readily pierce or engage with the annular tissue. 
     In addition to the profiles of hooks shown in  FIGS.  7 A- 7 D  and  FIGS.  8 A- 8 D , other attachment feature may be used to engage the arms with the tissue. By way of non-limiting example, this may include staples, sutures, or barbs to engage the tissue proximate the heart valve. 
     While hooks  170 , hooks  770  and hooks  870  are all shown at an end of the plurality of arms, it is envisioned that an attachment feature, including said hooks, could be placed at any point along a respective arm. For example, the feature may be placed near the end opposite the pivot point, but not all the way to the end. As another example, the attachment feature may be located approximately half way down the arm. In some embodiments, more than one hook or other attachment feature may be included on an arm, and may be at more than one location. 
     This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. For example, various embodiments may perform all, some, or none of the steps described above. Various embodiments may also perform the functions described in various orders. 
     Although the present invention has been described above in connection with several embodiments; changes, substitutions, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, substitutions, variations, alterations, transformations, and modifications as fall within the spirit and scope of the appended claims.