Abstract:
A delivery device usable to deliver an inverting implant is provided that includes a positioning mechanism that automatically initiates the inversion process once a predetermined length of the implant has exited a delivery catheter. The positioning mechanism allows the implant to be safely and accurately deployed with reduced operator experience and in a greater variety of target locations.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a Continuation-In-Part of U.S. patent application Ser. No. 13/473,475, filed on May 16, 2012, entitled Inversion Delivery Device and Method for a Prosthesis, which claims priority to U.S. Provisional Application Ser. No. 61/486,682 filed May 16, 2011 entitled Inversion Delivery Device and Method For A Prosthesis, which is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    There has been a significant movement toward developing and performing cardiovascular surgeries using a percutaneous approach. Through the use of one or more catheters that are introduced through, for example, the femoral artery, tools and devices can be delivered to a desired area in the cardiovascular system to perform many number of complicated procedures that normally otherwise require an invasive surgical procedure. Such approaches greatly reduce the trauma endured by the patient and can significantly reduce recovery periods. The percutaneous approach is particularly attractive as an alternative to performing open-heart surgery. 
         [0003]    Valve replacement surgery provides one example of an area where percutaneous solutions are being developed. A number of diseases result in a thickening, and subsequent immobility or reduced mobility, of heart valve leaflets. Such immobility also may lead to a narrowing, or stenosis, of the passageway through the valve. The increased resistance to blood flow that a stenosed valve presents can eventually lead to heart failure and ultimately death. 
         [0004]    Treating valve stenosis or regurgitation has heretofore involved complete removal of the existing native valve through an open-heart procedure followed by the implantation of a prosthetic valve. Naturally, this is a heavily invasive procedure and inflicts great trauma on the body leading usually to great discomfort and considerable recovery time. It is also a sophisticated procedure that requires great expertise and talent to perform. 
         [0005]    Historically, such valve replacement surgery has been performed using traditional open-heart surgery where the chest is opened, the heart stopped, the patient placed on cardiopulmonary bypass, the native valve excised and the replacement valve attached. A proposed percutaneous valve replacement alternative method on the other hand, is disclosed in U.S. Pat. No. 6,168,614 (the entire contents of which are hereby incorporated by reference) issued to Andersen et al. In this patent, the prosthetic valve is mounted on a stent that is collapsed to a size that fits within a catheter. The catheter is then inserted into the patient&#39;s vasculature and moved so as to position the collapsed stent at the location of the native valve. A deployment mechanism is activated that expands the stent containing the replacement valve against the valve cusps. The expanded structure includes a stent configured to have a valve shape with valve leaflet supports begins to take on the function of the native valve. As a result, a full valve replacement has been achieved but at a significantly reduced physical impact to the patient. 
         [0006]    However, this approach has decided shortcomings. One particular drawback with the percutaneous approach disclosed in the Andersen &#39;614 patent is the difficulty in preventing leakage around the perimeter of the new valve after implantation. Since the tissue of the native valve remains within the lumen, there is a strong likelihood that the commissural junctions and fusion points of the valve tissue (as pushed apart and fixed by the stent) will make sealing around the prosthetic valve difficult. In practice, this has often led to severe leakage of blood around the stent apparatus. 
         [0007]    Other drawbacks of the Andersen &#39;614 approach pertain to its reliance on stents as support scaffolding for the prosthetic valve. First, stents can create emboli when they expand. Second, stents are typically not effective at trapping the emboli they dislodge, either during or after deployment. Third, stents do not typically conform to the features of the native lumen in which they are placed, making a prosthetic valve housed within a stent subject to paravalvular leakage. Fourth, stents are subject to a tradeoff between strength and compressibility. Fifth, stents cannot be retrieved once deployed. Sixth, stents have an inherent strength that is not adjustable. 
         [0008]    As to the first drawback, stents usually fall into one of two categories: self-expanding stents and balloon expandable stents. Self-expanding stents are compressed when loaded into a catheter and expand to their original, non-compressed size when released from the catheter. These are typically made of Nitinol. Balloon expandable stents are loaded into a catheter in a compressed but relaxed state. These are typically made from stainless steel or other malleable metals. A balloon is placed within the stent. Upon deployment, the catheter is retracted and the balloon inflated, thereby expanding the stent to a desired size. Both of these stent types exhibit significant force upon expansion. The force is usually strong enough to crack or deform thrombosis, thereby causing pieces of atherosclerotic plaque to dislodge and become emboli. If the stent is being implanted to treat a stenosed vessel, a certain degree of such expansion is desirable. However, if the stent is merely being implanted to displace native valves, less force may be desirable to reduce the chance of creating emboli. An additional concern related to displacing an aortic valve is the risk of conduction disturbances (i.e. left bundle branch block) due to the close proximity of the conduction pathways to the native valve structure. Excessive radial force applied at the native valve site increases the risk of irritation or damage to the conduction pathway and heart block. 
         [0009]    As to the second drawback, if emboli are created, expanded stents usually have members that are too spaced apart to be effective to trap any dislodged material. Often, secondary precautions must be taken including the use of nets and irrigation ports. 
         [0010]    The third drawback is due to the relative inflexibility of stents. Stents typically rely on the elastic nature of the native vessel to conform around the stent. Stents used to open a restricted vessel do not require a seal between the vessel and the stent. However, when using a stent to displace native valves and house a prosthetic valve, a seal between the stent and the vessel is necessary to prevent paravalvular leakage. Due to the non-conforming nature of stents, this seal is hard to achieve, especially when displacing stenosed valve leaflets. 
         [0011]    The fourth drawback is the tradeoff between compressibility and strength. Stents are made stronger or larger by manufacturing them with thicker members. Stronger stents are thus not as compressible as weaker stents. Most stents suitable for use in a valve are not compressible enough to be placed in a thin catheter, such as a 18Fr catheter. Larger delivery catheters are more difficult to maneuver to a target area and also result in more trauma to the patient. 
         [0012]    The fifth drawback of stents is that they are not easily retrievable. Once deployed, a stent may not be recompressed and drawn back into the catheter for repositioning due to the non-elastic deformation (stainless steel) or the radial force required to maintain the stent in place (Nitinol). Thus, if a physician is unsatisfied with the deployed location or orientation of a stent, there is little he or she can do to correct the problem. 
         [0013]    The sixth drawback listed above is that stents have an inherent strength and are thus not adjustable. As previously stated, stronger stents are made with stronger members. Once a stent is selected and deployed, there is little a physician can do if the stent proves to be too strong or too weak. 
         [0014]    Various embodiments of devices that solve these problems are introduced in U.S. Patent Publication No. 2006/0271166 to Thill et al., entitled “Stentless Support Structure,” the contents of which is incorporated herein in their entirety. This publication teaches a braided mesh tube that is capable of folding back and forth into itself to build, in situ, a support structure that is strong enough to hold back the leaflets of a native valve sufficiently to successfully deploy a replacement valve, thus obviating the need for excision of the native valve. Advantageously, because of the inverting nature of these devices, the braided mesh, in an elongated delivery configuration, does not need to possess the strength to accomplish native valve displacement until the inversion process occurs. This allows the mesh tube to be constructed such that, in the elongated delivery state, the tube can be compressed into a very small catheter, such as a 18Fr or smaller catheter. Such a small catheter significantly reduces patient trauma and allows for easy percutaneous, intraluminal navigation through the blood vessels. It is to be understood that terms like transluminal and percutaneous, as used herein, are expressly defined as navigation to a target location through and axially along the lumen of a blood vessel or blood vessels as opposed to surgically cutting the target vessel or heart open and installing the device manually. It is further to be understood that the term “mesh” as used herein describes a material constructed of one or more braided or woven strands. 
         [0015]    In order to accomplish the folding back and forth feature of this device, there are preformed, circumferential folds in the device. One embodiment has two circumferential folds that are longitudinally spaced apart in the extended configuration. One of these folds is preformed to fold inwardly, and the other is preformed to fold outwardly. These preformed folds, when released out of a catheter, tend to return to a folded configuration that has a z-like cross-section. This cross-section design results not only because the inward pre-formed fold folds inwardly and the outward pre-formed fold folds outwardly, but because these folds reverse longitudinal positions once folded. If the inward preformed fold is distal of the outward preformed fold in the extended position, in the folded position the inward preformed fold will be proximal of the outward preformed fold. This design allows a valve on a distal end of the device to be drawn into the device when folded, without requiring the valve itself to be inverted or everted. In one embodiment having two preformed folds, the inversion process thus results in a three-layered configuration that could be significantly shorter than the extended length, depending on the spacing of the folds. 
         [0016]    In the development of the devices described in the aforementioned publication, U.S. Pat. Pub. 2006/0271166, it was found that, occasionally, it was advantageous to use an additional device to hold the outermost layer of the implant axially in place while inversion of a layer was being effected. This gave rise to the delivery tool shown and described in U.S. Patent Publication 2008/0082165 to Wilson et al., entitled “Delivery Tool For Percutaneous Delivery Of A Prosthesis.” This delivery tool includes an expandable mesh region that, when axially compressed, flares outwardly to form a bulbous or rounded structure of increased radius. Further axial compression creates a flat, disc-like surface. In use, the device is extended through an implant prior to releasing the implant from the delivery catheter. The device is then expanded to the disc-like configuration and pulled proximally to act as a backstop at a desired target location, against which the implant is delivered. Thus, the disc-like device prevents axial migration of the implant in a distal direction if and when distal force is placed on the implant during inversion of the second or subsequent layers into the first layer. 
         [0017]    It has been found, however, that in some cases, depending on target location and patient anatomy, there is insufficient space in a distal axial direction beyond the target location to efficiently use this delivery device. For example, some patients may have limited left ventricular space, which may prohibit the use of the backstop device. 
         [0018]    There is thus a need for a device that is able to prevent axial migration of the aforementioned braided implant devices during inversion, but does not require significant space distally beyond the target location. 
       BRIEF SUMMARY OF THE INVENTION 
       [0019]    The present invention meets the identified need by providing a delivery device that holds a braided implant in a desired location during inversion of a subsequent layer into a first layer. More specifically, the present invention provides a delivery device that releasably attaches at or near a first fold location, hereinafter referred to as the “aortic flare,” which is a hinge point around which the inversion of the implant used with the present invention occurs. 
         [0020]    Through attachment to the aortic flare, the delivery device of the present invention enables precise positioning and inversion by limiting advancement of a portion of the implant while continuing to advance the remainder of the device. Hence, inversion is effected at a location selected by the user, independent of patient anatomy or geometric interference. One embodiment of the invention achieves this precise positioning through attachment to a distal end of the device. 
         [0021]    Two aspects of the present invention provide reliable performance of the delivery device of the present invention. A first aspect is an attachment mechanism that can be mounted to a braided device without requiring significant modification to the function of the braided device. This attachment mechanism provides device stabilization during the support structure inversion process. This attachment mechanism provides both attachment to the device and a release capability in some embodiments. A second aspect of the present invention includes positioning mechanisms that prevent movement of the device in the target location during the inversion process. 
         [0022]    Another aspect of the present invention provides freedom of motion to the support structure anchors as the device is being deployed, but automatically actuates anchor locking mechanisms when the device has been advanced to the appropriate position for the inversion process. This automatic actuation reduces the need for physician involvement or judgment in the tensioning and setting of the anchor mechanisms. The nature of the mechanism also accounts for manufacturing and use tolerances, precisely tuning the anchor locking mechanism to the selected valve and delivery system. 
         [0023]    Yet another aspect of the invention provides a deployment device that allows the positioning, implantation and deployment of a prosthetic valve such that the valve achieves complete function prior to releasing the valve. The valve may be observed and verified that it is functioning normally prior to release. If the valve is not functioning as intended, the entire device may be quickly pulled back into the delivery device. In some circumstances, the valve is able to be relocated and redeployed. 
         [0024]    Still another aspect of the invention provides a delivery device that includes a limiter that may be set prior to or during the procedure. The limiter ensures that the braided implant does not exit the delivery device more than a desired amount, prior to inverting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a partial cross-sectional view of an embodiment of a delivery device of the present invention with an implant loaded in a distal end thereof; 
           [0026]      FIG. 2   a  is a perspective view of a distal end of an embodiment of a pusher catheter of the present invention; 
           [0027]      FIG. 2   b  is a perspective view of a distal end of an alternative embodiment to that of  FIG. 2   a;    
           [0028]      FIG. 3  is a perspective view of an embodiment of a distal end of a release mechanism of the present invention in an open configuration; 
           [0029]      FIG. 4  is a perspective view of the mechanism of  FIG. 3  in a closed configuration; 
           [0030]      FIG. 5  is a plan cross-sectional view of an embodiment of a delivery device of the present invention, just prior to an inversion process of an implant; 
           [0031]      FIG. 6  is a plan cross-sectional view of an embodiment of a delivery device as shown in  FIG. 1 , just after the implant has been inverted; 
           [0032]      FIG. 7-10  are perspective views of a pusher catheter of an embodiment of a delivery device; 
           [0033]      FIG. 11  is a plan view of an embodiment of a handle assembly of the invention; 
           [0034]      FIG. 12  is an exploded view of an embodiment of a valve retention cable control of the invention; 
           [0035]      FIG. 13  is a perspective view of an embodiment of a valve retention cable control of the invention in a closed position; 
           [0036]      FIG. 14  is a perspective view of an embodiment of a valve retention cable control of the invention in an open position; 
           [0037]      FIG. 15  is a partial perspective view of an embodiment of a handle assembly of the invention showing an embodiment of a pusher catheter control; 
           [0038]      FIG. 16  is a partial perspective view of an embodiment of a handle assembly of the invention showing an embodiment of a drive mechanism; 
           [0039]      FIG. 17  is a perspective view of an embodiment of a tether release controller of the invention in a closed position; 
           [0040]      FIG. 18  is a perspective view of an embodiment of a tether release controller of the invention in an open position; 
           [0041]      FIG. 19  is an exploded view of an embodiment of a tether positioning mechanism of the invention; 
           [0042]      FIG. 20  is a perspective view of an embodiment of a tether positioning mechanism of the invention in a locked position; 
           [0043]      FIG. 21  is a perspective view of an embodiment of a tether positioning mechanism of the invention in an unlocked position; 
           [0044]      FIG. 22  is a side view of an embodiment of a delivery device of the present invention in a vessel of a patient; 
           [0045]      FIG. 23  is a side view of an embodiment of a delivery device as shown in  FIG. 22 , just after crossing a heart valve; 
           [0046]      FIG. 24  is a side view of an embodiment of a delivery device as shown in  FIG. 22 , in which an implant is partially deployed; 
           [0047]      FIG. 25  is a side view of an embodiment of a delivery device as shown in  FIG. 22 , in which the tethers are tightened; 
           [0048]      FIG. 26  is a side view of an embodiment of a delivery device as shown in  FIG. 22 , just after the implant has been inverted; 
           [0049]      FIG. 27  is a side view of an embodiment of a delivery device as shown in  FIG. 22 , just after releasing and withdrawing the tethers from the implant; 
           [0050]      FIG. 28  is a side view of an embodiment of a delivery device as shown in  FIG. 22 , just prior to releasing the attachment cables; and, 
           [0051]      FIG. 29  is a side view of an embodiment of the implant, just after release of the attachment cables. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0052]    Referring now to the Figures and first to  FIG. 1 , there is shown a distal end of a delivery device  10  of the present invention. The delivery device generally includes a delivery catheter  20 , and a pusher catheter  30  slidably contained within the delivery catheter  20 . The pusher catheter  30  is preferably a multi-lumen catheter containing lumens for slidably containing and maintaining alignment of three attachment cables  40  (hereinafter “valve retention cables”) (see  FIG. 3 ), each of which has a releasable grasping mechanism  50  at a distal end thereof. The delivery device  10  also includes at least one positioning mechanism  60  used to aid the tool or implant  1  in achieving a folded, deployed configuration from an extended, unfolded, navigation configuration. In one embodiment, the at least one positioning mechanism  60  is attached to a distal end of the delivery catheter  20 . In another embodiment, the at least one positioning mechanism  60  is slidably contained within the delivery catheter  20 , similar to the valve retention cables  40 . 
         [0053]    The delivery catheter  20  is an external sheath defining a single lumen for housing the pusher catheter  30 , the tool or implant  1 , the valve retention cables  40 , and the positioning mechanisms  60 . The delivery catheter  20 , when loaded, houses a tool or implant  1  near its distal end  22 . The implant  1  is preferably an implant similar to those taught and described in U.S. Patent Publication No. 2006/0271166. The delivery catheter  20  may be formed with a preset curve at its distal end. Positive results have been achieved with a 180 degree preset curve. 
         [0054]    The pusher catheter  30  may include up to seven lumens. Three lumens slidably house the three valve retention cables  40 . In an embodiment used over-the-wire, a fourth lumen accommodates a guidewire. In yet another embodiment, three additional lumens slidably house three positioning mechanisms, described below. 
         [0055]      FIGS. 2   a  and  2   b  show two similar embodiments of the pusher catheter  30  of the present invention defining seven lumens. The pusher catheter  30  includes a central guidewire lumen  32 , and three lumens  34  that contain either the valve retention cables  40  or the positioning mechanisms described below. The remaining three lumens  36  house the remaining valve retention cables or positioning mechanisms. In order to save on space, the lumens  36  may be formed as external indentations, thereby relying on the inner wall of the delivery catheter  20  to complete the lumen and contain the remaining valve retention cables or positioning mechanisms. In a preferred embodiment, the lumens  34  contain the valve retention cables  40  and the lumens  36  contain the positioning mechanisms  60 . In this embodiment, the pusher catheter  30  may continue to be advanced even if the positioning mechanisms  60  can no longer be advanced. 
         [0056]    In one embodiment, the positioning mechanisms are small enough to fit three valve retention mechanisms, and an associated containment sheath, in a single lumen  36 , leaving two other lumens  36  unused or available for use as irrigation channels. 
         [0057]    The releasable grasping mechanisms  50  may be similar to those shown and described in U.S. Pat. Pub. 2008/0082165 (at  FIGS. 5-8 ). Another embodiment of releasable grasping mechanisms is shown in  FIGS. 3 and 4 . The grasping mechanisms  50  are attached to commissural points on an implant  1  when the device  10  is loaded. The grasping mechanism  50  provide the ability to retract the implant back into the device  10  in the event that the physician feels doing so is appropriate. 
         [0058]      FIG. 3  shows a grasping mechanism  50  in an open configuration. The grasping mechanism  50  includes a hook  52  that slides within a mouth  54 . The hook  52  defines a recess  56  sized to accommodate a component, such as a commissural point or a braid, of the tool or implant  1 . The mouth  54  defines a slot  58  that is also sized to accommodate the component.  FIG. 4  shows that when the grasping mechanism  50  is in a closed configuration, the recess  56  and the slot  58  together define a passage  59  that traps the component therein. 
         [0059]    The grasping mechanism  50  is attached to a distal end of an valve retention cable  40 . The valve retention cable  40  includes a wire  42  attached to the hook  52  and an elastomeric sheath  44  that is attached to the mouth  54 . The wire  42  and the hook  52  are slidably contained within the sheath  44  and the mouth  54 . The sheath  44  is elastomeric such that it is capable of being compressed longitudinally. This feature prevents accidental release of a tool or component contained within the passage  59 . For example, when pulling a tool or implant back into the delivery sheath  20  during a retrieval, a load is placed on the wire  42 , causing the wire to stretch. If the sheath  44  were not compressed, the wire  42  could stretch enough to cause the hook  52  to exit the mouth  54 , thereby assuming the open configuration of  FIG. 3 . However, because the sheath  44  is compressed when the hook  52  is drawn into the mouth  54  during closing, the sheath  44  elongates when the wire  42  is stretched, thereby maintaining the closed configuration of  FIG. 4 . 
         [0060]    The positioning mechanisms  60  aid in inverting the tool or component  1 . In one embodiment, shown in  FIGS. 1 ,  5  and  6 , the positioning mechanisms  60  connect the delivery catheter  20  with a first inversion pre-fold point (also referred to herein as an “aortic flare”) on the implant  1 . 
         [0061]    The positioning mechanisms  60  may comprise a plurality of tethers  62  and connectors  64 . The tethers  62  may be any resilient strand-like material, flexible enough to invert from a navigation configuration to a deployment configuration. In the navigation configuration, as shown in  FIG. 1 , the tethers extend proximally from the distal end of the delivery catheter  20 , to the connectors  64 . In the deployment configuration, shown in  FIGS. 5 and 6 , the tethers  62  extend distally from the distal end of the delivery catheter  20  to the connectors  64 . In one embodiment, the connectors  64  are able to grasp any individual braid or strand of an implant  1 . In another embodiment, the connectors  64  are designed to grasp the intersection of two braids or strands. In yet another embodiment, the connectors  64  are able to grasp discrete attachment points (e.g. wire loops, sutures, etc.), that have been integrated into the mesh implant or tool  1 . The length of the tethers  62  are at least the length of the material of the implant  1  that extends distally of the connectors  64  when the implant  1  is loaded into the delivery catheter  20 . This way, the implant  1  remains completely within the delivery catheter  20  in the navigation configuration. 
         [0062]    In another embodiment, the positioning mechanisms  60  are similar in construction to the valve retention cables  40  and releasable grasping mechanism  50 . However, because the strength requirements of the positioning mechanisms  60  are less than those of the valve retention cables  40  and their releasable grasping mechanisms  50 , the positioning mechanisms  60  may be smaller in diameter, thereby allowing a smaller overall delivery device  10 . Rather than being attached to the distal end of the delivery catheter  20 , as described above, the positioning mechanisms  60  of this embodiment are slidably contained within the lumens  36  of the pusher catheter  30  shown in  FIG. 2 . 
         [0063]    Referring to  FIGS. 5 and 6 , the device  10  is designed to be able to pass over a guidewire  70  during navigation. A conical or otherwise tapered dilator tip  80  abuts against the distal end  22  of the delivery catheter  20  and is flush therewith. The dilator  80  allows the device  10  to be passed through the vasculature with minimal trauma. The dilator  80  is not physically attached to the delivery catheter  20 , such that it is easily moved distally during delivery of the implant  1  to avoid interference with the deployment of the implant  1 . 
         [0064]    Having described the various components of the present invention, the various steps and configurations that occur during navigation and deployment of an implant can now be explained.  FIG. 1  shows the navigation configuration of the device  10 . In the navigation configuration, the implant  1  is loaded into the distal end of the delivery catheter  20  such that the implant  1  is in an elongated, non-folded state. The pusher catheter  30  is positioned within the delivery catheter  20  with its distal end  22  proximal of the implant  1 . The valve retention cables  40  extend distally from the pusher catheter  30  and are connected to commissural points of the implant  1  with the releasable grasping mechanisms  50 . The conical dilator  80  abuts against the distal end  22  of the delivery catheter  20 . During navigation, the entire device  10  and implant  1  travel over a guidewire  70  to the target location. 
         [0065]      FIG. 5  shows the initial stages of deployment of the implant  1 . The target location has been reached and the delivery catheter  20  is retracted while the pusher catheter  30  and valve retention cables ( 40 ) remain stationary relative to the target location. Retracting the delivery catheter  20  causes the pusher catheter  30  to push the implant  1  out of the distal end  22  of the delivery catheter. As the implant  1  exits the delivery catheter  20  the implant  1  expands and the positioning mechanisms  60  are advanced through the delivery catheter  20  until the tethers  62  become taut, or in the case of the positioning mechanisms that are slidably contained within the lumens of the pusher catheter  30 , the positioning mechanisms  60  can no longer be advanced. 
         [0066]    As seen in  FIG. 6 , further advancement of the pusher catheter  30  causes implant material that is proximal of the connectors  64  to invert into the implant material that is distal of the connector  64 . This is because the positioning mechanisms  60  are taut and do not allow further distal advancement of the implant  1 . As such, the inversion of the implant  1  is urged by the preformed fold in the implant, the expansion of the memory metal making up the implant  1 , and the restraint provided by the positioning mechanisms  60 . Notably, the transition of the implant from initial advancement to inversion happens automatically and is dictated by the length of the tethers  64 . As such, operator experience is not required to initiate inversion. Nor is there any reliance on anatomical structure to provide friction against the implant to initiate inversion. 
         [0067]    Once the implant  1  has been fully deployed, the implant  1  is fully functional prior to release. This allows verification of proper operation of the implant  1  via one or more imaging modalities prior to full release of the implant  1 . If proper operation is not achieved, the grasping mechanisms  50  can be used to pull the implant  1  back into the delivery catheter  20  such that the implant may be either removed or redeployed. If proper operation is verified, the connectors  64  are actuated to release the braids or strands of the implant  1 . The pusher catheter  30  and the delivery catheter  20  are withdrawn slightly while maintaining connection with the implant  1  and the device  10  via the releasable grasping mechanism. Subsequently, the grasping mechanisms  50  are actuated to release the commissural points of the implant  1 . The pusher catheter  30  is retracted into the delivery catheter  20  and the delivery catheter  20  and the guidewire  70  are withdrawn from the patient. 
         [0068]      FIGS. 7-21  illustrate another embodiment of a delivery device  100  that is generally similar to the previously described delivery device  10 , especially where noted with similar element numbers. However, the delivery device  100  includes a positioning tether assembly  110 , the distal end of which is seen best in  FIGS. 7-10 , having a sliding release mechanism for releasing a connection to the implant  1 . 
         [0069]    More specifically, the positioning tether assembly  110  includes a plurality of tethers  104  that are each arranged in a generally closed loop. These looped tethers  104  pass through portions of the implant  1  and therefore can maintain the implant  1  in a desired position during a procedure (e.g., can prevent distal movement of the implant  1 ). The tethers can be disconnected from the implant  1  by releasing one end of each of the tethers  104 , effectively opening the loop shape. In this respect, withdrawal of the positioning tether assembly  110  also pulls the tethers  104  out of and away from the implant  1 . 
         [0070]    The release mechanism of the positioning tether assembly  110  is triggered by advancing a sliding member  114  to the position seen in  FIGS. 8 and 10  from the retracted position seen in  FIGS. 7 and 9 . Note that the tethers  104  are connected to a distal end  114 B of the sliding member  114  (e.g., either fixed in place or pass through the member  114  back to the proximal end of the positioning tether assembly  110 ), but for illustrative purposes are not shown as such in  FIGS. 9 and 10 . Initially, the free ends  104 B of the tethers  104  are located within a depression  114 A of the sliding member  114  and are captured by a first slot  112 A of an outer tether sheath  112 . When the sliding member  114  is advanced, the depression  114 A is positioned beneath a wider, second slot  112 B, which allows the free ends  104 B of the tethers  104  to be released. 
         [0071]    As best seen in  FIG. 9 , the free ends  104 B of the tethers  104  have a generally larger size or diameter than the remaining portion of the tether  104  and can have a variety of different shapes, such as rounded, spherical or even square. The first slot  112 A has a width that is large enough to accommodate the diameter of the tether  104  but is smaller than the diameter of the free ends  104 B, thereby allowing the tether  104  to laterally slide within the slot  112 A without the free ends  104 B from traversing through. 
         [0072]    The second slot  1128  is positioned distal to the first slot  112 A and has a width that is larger than the free ends  104 B. In this respect, once the depression  114 A aligns under this second slot  112 B, as seen in  FIG. 10 , the free ends  104 B are released, thereby allowing the tethers  104  to assume a generally linear configuration, similar to that in  FIG. 8 . 
         [0073]    While two slots are shown, a single slot may alternately be used in another embodiment. Specifically, the single slot may be similar in size to slot  112 A, but extends to the distal end of the tether sheath  112 . In this respect, the free ends  1048  are released when the depression  114 A is advanced outside of the tether sheath  112 . 
         [0074]    The positioning tether assembly  110  may be constructed with an overall outside diameter that is small enough to be slidingly contained in one of the lumens  34  or  36  of the pusher catheter  30  shown in  FIG. 2   a  or  2   b.    
         [0075]      FIGS. 11-22  show the proximal end or handle assembly  200  of the delivery device  100 . The handle assembly generally includes valve retention cable control group  210 , a pusher catheter control  250 , a drive mechanism  260 , irrigation ports  280 , and a tether control assembly  300 . 
         [0076]    The valve retention cable control group  210  includes a plurality of valve retention cable controls  212 , housed in a recess  214  of the handle  200 , and a locking pin  216 . The individual valve retention cable controls  212  are best seen in  FIGS. 12-14 . 
         [0077]      FIG. 12  shows an exploded view of an individual valve retention cable control  212 . The control  212  includes a housing  218 , to which is attached a proximal end of the elastomeric sheath  44  of the retention cable  40  (see  FIG. 3 ). Slidingly contained within the housing  218  is a thumb slide  220 , which is connected to the wire  42  of the retention cable  40 . Behind the thumb slide  220  is a spring-loaded catch  222 . In operation, pulling the thumb slide rearward toward the catch  222  pulls the wire  42  relative to the sheath  44 , thereby retracting the hook  52  into the mouth  54  at the distal end of the cable  40 . The catch  222  maintains the retention cable  40  in a closed position. The hook  52  can be quickly released from the mouth  54  by depressing the catch  222 . 
         [0078]      FIG. 14  shows the thumb slide  220  in the forward, open position. The corresponding open position of the distal end of the cable  40  is also shown.  FIG. 15  shows the thumb slide  220  in the rearward, closed position. The corresponding closed position of the distal end of the cable  40  is also shown. Furthermore, a locking pin  216  has been inserted through the housing  218  and the thumb slide  220  to prevent accidental release of the implant  1  held in the mouth  54  of the retention cable  40 . 
         [0079]    Referring back to  FIG. 11 , it is shown that there are three controls  212  arranged in the handle  200 . It can also be seen that a single locking pin  216  passes through the handle  200  and all three controls  212 . This locking pin  216  is a precautionary feature that ensures none of the controls  212  are inadvertently opened. Once the valve position and operation have been verified, the physician is then able to unlock all three controls  212  by removing the single pin  216 . 
         [0080]      FIG. 15  is a partial view of the handle  200  of the device  100 .  FIG. 15  shows the pusher catheter control  250 , which is shown as a sliding ring  250  that slides over the handle  200 . The ring  250  is connected through a slot  252  in the side of the handle  200  to the pusher catheter  30 . When the ring  250  is advanced to its most distal position, it may be rotated to lock the pusher catheter relative to the valve retention cables  40 . 
         [0081]    The drive mechanism  260  is shown in  FIG. 16 . The drive mechanism  260  includes a lead-screw  262  and a threaded nut combination  264 . The threaded nut combination  264  includes a nut  266  contained within a knob  268  and a quick release  270 . Rotation of the knob  268  causes the nut  266  to act against the lead-screw  262 . The knob  268  is axially fixed relative to the handle  200 . The lead-screw  262  is slidingly contained within the handle  200 . As such, when the nut  266  acts against the lead-screw  262 , the lead-screw  262  advances or retracts in the handle  200 . The lead-screw  262  is connected at its distal end to the delivery catheter  20 . The rotatable threaded nut combination  264  thus allows precise control over the relative motion between the pusher catheter  30  and the delivery catheter  20 . The quick release  270  may be in the form of a button or lever that disengages the nut  266  from the threads of the lead-screw  262  to allow the pusher catheter  30  and valve retention cables  40  to be quickly retracted into the delivery catheter  20 . 
         [0082]    It has been found that retracting an implant back into the delivery catheter  20  is more successful when done quickly. A slow retraction increases the risk that the catheter may buckle. As such, the handle  200  has been designed to effect a quick retraction of an implant back into the device  100  when necessary. This is accomplished by ensuring the ring  250  is rotated into the locked position so that when the handle is retracted relative to the delivery catheter , the pusher catheter  30  and the valve retention cables  40  are fixed relative to each other and thus retracted simultaneously. Depressing the quick release  270  while pulling on the knob  268  while holding the delivery catheter  20  stable causes the implant to be quickly drawn back into the delivery catheter  20 . 
         [0083]    The various components of the tether control assembly  300  are shown in  FIGS. 17-21 . The tether control assembly  300  generally includes a tether release controller  310  and a tether positioning mechanism  340 . 
         [0084]    The tether release controller  310  is shown in  FIGS. 17 and 18  and includes a housing  312  and a control knob  314 . The housing  312  is fixed to the proximal end of the outer tether sheath  112  (See  FIGS. 9 and 10 ) of the positioning tether assembly  110 . The control knob  314  is able to slide axially, relative to the housing  312 , and is attached to the proximal end of sliding member  114  ( FIGS. 9 and 10 ). Thus, when the control knob  314  is in the forward position shown in  FIG. 18 , the tethers are released. When the control knob  314  is in the rearward position shown in  FIG. 17 , the tethers ends are trapped in the first slot  112 A of the outer tether sheath  112 . In the embodiment shown in the Figures, the control knob  314  can be turned in the closed position, thereby locking it closed. Also includes is a clip  320  which may be used to prevent the control knob  314  from advancing to the open position in the event it is accidentally actuated. The clip  320  is easily removed when it is desired to release the tethers. 
         [0085]      FIGS. 19-21  show the tether positioning mechanism  340 . The tether positioning mechanism is a slide-lock that includes a housing  342 , a lever  344 , and a clamp block  346 . The housing  342  passes over the outer tether sheath  112  and keeps the tether sheath positioned between the lever  344  and the clamp block  346 . When the lever  344  is lowered to the closed position, shown in  FIG. 20 , the outer tether sheath  112 , and the tethers contained therein, are clamped between the lever  344  and the block  346 , and cannot slide. Thus the tether positioning mechanism  340  is fixed relative to the outer tether sheath  112 . When the lever  344  is in the open position, the tether positioning mechanism  340  is able to slide over the outer tether sheath  112 . 
         [0086]      FIGS. 22-29  illustrate how the delivery device  100  can be used to deliver an implant  1  according to the present invention. First, an implant  1  is loaded into the delivery device  100 . After the selected valve is rinsed, each of the three valve retention cables  40  are individually attached to each of three wire form eyelets on the implant. This is accomplished by opening the valve retention cable control  212 , pushing the thumb slide  220  forward to expose the hook  52  from the mouth  54 . The hook  52  is placed through the wire form eyelet and the thumb slide  220  is retracted rearwardly until it engaged the catch  222 . Doing so locks the slide  220  and closes the hook  52  into the mouth  54 . It also compresses the outer elastomeric sheath  44  of the valve retention cable  40  to maintain interference between the hook  52  and the mouth  54 , even if a pulling force is placed on the cable sufficient to stretch the cable, thereby preventing accidental release during a retrieval procedure. 
         [0087]    After all three valve retention cables  40  are attached, the position tethers  104  are attached to the implant  1 . (Alternatively, the position tethers  104  may be attached prior to the valve retention cables  40 ). This is accomplished by threading each of the three tethers  104  through the center of the implant and through a ventricular loop of the implant&#39;s support structure at 120 degree intervals from the inside to the outside of the implant. Once all three tethers  104  have been threaded, they are passed back up through the valve and the three tethers  104  are locked within the slot  112 A of the outer tether sheath  112 . Locking is accomplished by pulling the control knob  314  and rotating it to the locked position shown in  FIG. 17 . 
         [0088]    Next the pusher catheter  30  is pushed forward to capture the valve retention cables  40 . At the distal-most position of the pusher catheter control ring  250 , the ring  250  is rotated to lock the position of the pusher catheter  30  relative to the valve retention cables  40 . 
         [0089]    The implant  1  is now ready for loading into the delivery catheter  20 . The delivery catheter  20  is advanced by rotating the drive knob  268  toward the user, and the implant  1  is slowly drawn into the distal end of the delivery catheter  20 . While the implant  1  is being loaded, the position of the implant is noted so an observation can be made as to when the implant has achieved the orientation in which the implant would be exposed enough from the delivery catheter  20  to be able to invert into itself. At this point the tether positioning mechanism  340 , which is in the unlocked position, is slid down the sheath  112  until it contacts the delivery catheter manifold  282  ( FIG. 11 ) and the lever  344  is moved to the locked position. 
         [0090]    Continued loading of the implant into the delivery catheter  20  causes the tethers  104  and the tether sheath  112  to retract and the tether positioning mechanism  340  to move proximally relative to the delivery catheter manifold  282 . The implant is fully loaded whent the dilator tip  80  has been partially retracted into the delivery catheter  20  and there is a smooth transition between the dilator tip and the delivery catheter tip. 
         [0091]    As seen in  FIG. 22 , a guidewire  70  is placed across the native aortic valve of the patient and extends out through the vascular introducer at the femoral artery access site. The proximal end of the guidewire is inserted into the dilator tip  80  of the loaded delivery system and the system is advanced over the guidewire until the guidewire is visible through the proximal end of the delivery system. The proximal end of the guidewire is then held stationary in order to maintain the position of the wire in the left ventricle of the patient and the delivery system is advanced into the vasculature through the introducer and across the native aortic valve  4  (seen best in  FIG. 23 ). The guidewire passes through lumen  32  of the pusher catheter  30 . 
         [0092]    Turning to  FIG. 24 , the delivery sheath  20  is proximally retracted to expose a portion of the implant  1  and the tethers  104 . This is accomplished by rotating the drive knob  268 . As the implant  1  becomes exposed, it self-expands outward against the native valve  4 . During deployment, the operator maintains the implant position within the native valve of the patient. If, however, the implant is pulled too high or pushed too low relative to the native valve, the implant can be recaptured by reversing the direction of the drive knob  268  rotation, which draws the implant back into the sheath  20  for repositioning. 
         [0093]    As shown in  FIG. 25 , next, the implant  1  is folded or inverted on itself by restraining the implant with the tethers  104  and pushing a proximal portion of the implant in a distal direction with the pusher catheter  110 . More specifically , when the first layer of the implant has been deployed, the tether positioning mechanism  340  will have reached the delivery catheter manifold. This freezes the position of the ventricular loops (the distal end) of the implant such that further advancement of the implant will result in a shortening and flaring of the implant in preparation for valve invention. 
         [0094]    This flaring aspect of the valve deployment has been described as the anchoring phase, as the implant has expanded to contact the native valve tissue and the aortic flare of the device provides substantial resistance to migration. Once the anchoring phase has begun, the delivery catheter  20  is advanced through the access site and the patient vasculature. Doing so aligns the distal tip of the delivery catheter coaxial to the native valve with the curve of the delivery catheter  20  filling the outer curvature of the native aortic arch. 
         [0095]    After the catheter  20  has been advanced, continued deployment of the valve using the drive knob is used to produce implant invention. The act of inverting the implant also deploys the tissue valve component of the implant. Once the implant has been inverted the valve begins to function, but that function is somewhat constrained due to the proximity of the tethers and the valve control cables. 
         [0096]    After inversion has been accomplished, the user releases the tethers. First the tether positioning mechanism  340  is released by releasing the lever  344 , separating it from the clamp block  346 . The tether positioning mechanism  340  is free to float along the outer tether sheath  112 . The drive knob  268  is rotated to further back the delivery catheter  20  away from the implant. Once the delivery catheter  20  is fully retracted, the tethers  104  can be removed by rotating and releasing the tension in the control knob  314  of the tether release controller  310 . Gently pulling on the tether release controller  310  will separate the tethers  104  from the implant. 
         [0097]    Once the tethers  104  have been removed, only the valve retention cables  40  remain connected to the implant  1 , as seen in  FIG. 28 . As previously discussed, these cables  40  are attached to a proximal feature on the implant (e.g., the commissural points) and allow the physician to completely retract the implant  1  back into the delivery device  100  if a problem arises during the delivery procedure. Specifically, in order to observe full valve function without releasing the implant, the physician beings by rotating the ring  250  away from the operator and sliding the ring  250  in a proximal direction, retracting the pusher catheter  30 . With the pusher catheter  30  retracted, the prosthetic valve now begins to function fully. The remaining attachment of the delivery system to the implant via the valve retention cables  40  has little effect on the functionality of the implant. 
         [0098]    Once satisfied, the physician next releases the implant by pulling the locking pin  216  at the proximal end of the handle assembly  200 . With the locking pin  216  removed, each of the three valve retention cable controllers  212  can be sequentially released. This is accomplished by depressing the catch  222  and sliding the thumb slide  220  forward, releasing the implant  1 . Each cable can be individually retracted into the delivery catheter after it has been disengaged. When all three cables are released, the valve is fully implanted and the delivery system may be removed from the vascular introducer of the patient. 
         [0099]    Finally, the delivery device  100  and guidewire  70  is removed from the patient, leaving only the functioning valve implant  1 , as seen in  FIG. 29 . 
         [0100]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.