Patent Publication Number: US-10758351-B2

Title: Devices and methods for transcatheter heart valve delivery

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 14/738,325, filed Jun. 12, 2015, which is a continuation of U.S. patent application Ser. No. 13/788,820, filed Mar. 7, 2013, now U.S. Pat. No. 9,060,860, which claims the benefit of the filing date of U.S. Provisional Patent Application Nos. 61/665,527, filed Jun. 28, 2012, and 61/642,875, filed May 4, 2012, the disclosures of all of which are hereby incorporated herein by reference. The following commonly-owned applications are also hereby incorporated by reference herein: U.S. patent application Ser. No. 13/234,782, filed Sep. 16, 2011, and Ser. No. 13/212,442, filed Aug. 18, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is related to prosthetic heart valve replacement, and more particularly to devices, systems, and methods for transapical and transcatheter delivery of collapsible prosthetic heart valves. 
     Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery. 
     Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size. 
     When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient&#39;s heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn. 
     In conventional delivery systems for self-expanding aortic valves, for example, after the delivery system has been positioned for deployment, the annulus end of the valve is typically unsheathed and expanded first, while the aortic end of the valve remains sheathed. Once the annulus end of the valve has expanded, it may be determined that the valve needs to be repositioned in the patient&#39;s aortic annulus. To accomplish this, a user (such as a surgeon or an interventional cardiologist) typically resheathes the annulus end of the valve, so that the valve can be repositioned while in a collapsed state. After the valve has been repositioned, the user can again release the valve. 
     Once a self-expanding valve has been fully deployed, it expands to a diameter larger than that of the sheath that previously contained the valve in the collapsed condition, making resheathing impossible, or difficult at best. In order for the user to be able to resheathe a partially-deployed valve, a portion of the valve must still be collapsed inside of the sheath. 
     Despite the various improvements that have been made to the collapsible prosthetic heart valve delivery process, conventional delivery devices, systems, and methods suffer from some shortcomings. For example, in conventional delivery devices for self-expanding valves, it is difficult to control how much of the valve remains in the sheath during a partial deployment, and the user may accidentally deploy the valve fully before verifying that the annulus end of the valve is in the optimal position in the patient&#39;s valve annulus, thereby taking away the opportunity to resheathe and reposition the valve. 
     There therefore is a need for further improvements to the devices, systems, and methods for transcatheter delivery of collapsible prosthetic heart valves, and in particular, self-expanding prosthetic heart valves. Among other advantages, the present invention may address one or more of these needs. 
     BRIEF SUMMARY OF THE INVENTION 
     Delivery devices for a collapsible prosthetic heart valve and methods of delivering a collapsible prosthetic heart valve using same are aspects of the invention. In addition, any device having one or more of the following features and used in the transcatheter delivery of a collapsible heart valve are the specific aspects of the invention. 
     A delivery device for a collapsible prosthetic heart valve includes an operating handle and a catheter assembly. The operating handle may include a housing defining a movement space therein, a carriage assembly moveable in a longitudinal direction within the movement space, a deployment actuator coupled to the housing and rotatable relative to the housing, and a coupling assembly rotationally fixed to the deployment actuator. The catheter assembly may include a first shaft around which a compartment is defined and a distal sheath operatively connected to the carriage assembly. 
     The coupling assembly may have an engaged position in which rotation of the deployment actuator moves the carriage assembly in the longitudinal direction, and a disengaged position in which rotation of the deployment actuator does not move the carriage assembly in the longitudinal direction. The first shaft may be operatively connected to the housing. The compartment may be adapted to receive the valve in an assembled condition. The distal sheath may be moveable between a closed condition covering the compartment and an open condition uncovering the compartment for deployment of the valve. Movement of the carriage assembly in the longitudinal direction in the movement space may move the distal sheath between the closed condition and the open condition. 
     The carriage assembly may include a threaded rod extending from a body of the carriage assembly and into threaded engagement with the coupling assembly. Rotation of the deployment actuator in a first direction may move the carriage assembly proximally in the longitudinal direction in the movement space, and rotation of the deployment actuator in a second direction opposite the first direction may move the carriage assembly distally in the longitudinal direction in the movement space. The coupling assembly may include a split nut having a plurality of threaded split nut portions. The split nut portions may each be linearly slideable away from one another and away from the threaded rod. The split nut may have an engaged position in which threads of the split nut portions are engaged with the threaded rod and a disengaged position in which the threads of the split nut portions do not engage the threaded rod. 
     The coupling assembly may include a ring coupled to the split nut portions. The ring may have cam surfaces. The split nut portions may be slideable along the cam surfaces when the split nut portions move between the engaged and disengaged positions. The deployment actuator may be a knob rotatable about a central axis that extends parallel to the longitudinal direction. The carriage assembly may include a toothed rack extending from a body of the carriage assembly and into threaded engagement with the coupling assembly. The deployment actuator may be a knob rotatable about a central axis that extends perpendicular to the longitudinal direction. 
     The operating handle may also include a resheathing lock having a lock position and a release position. The resheathing lock in the lock position may limit movement of the carriage assembly in the longitudinal direction to a stop position in the movement space. The resheathing lock in the release position may permit movement of the carriage assembly beyond the stop position. Movement of the carriage assembly to the stop position may move the distal sheath to a condition between the closed condition and the open condition so that the valve is not fully deployed. The compartment may have a first length and the stop position in the movement space corresponds to a travel distance of the carriage assembly. The travel distance may be less than the first length. 
     The collapsible prosthetic heart valve may have a second length, and the travel distance may be between about 80% and about 90% of the second length. The catheter assembly may also include an outer shaft attached to the distal sheath and operatively connected to the carriage assembly. The outer shaft may at least partially surround the first shaft. The operating handle may also include a mechanism adapted to move the first shaft proximally relative to the housing. The first shaft may be attached to the distal sheath and may be operatively connected to the carriage assembly. The catheter assembly may also include an outer shaft connecting the housing to the compartment and at least partially surrounding the first shaft. 
     The catheter assembly may also include an atraumatic tip having a lumen extending longitudinally therethrough and an insert located within the lumen. The first shaft may have an outwardly flared distal end that is fixed between a distal end of the insert and material forming the atraumatic tip. The insert may have a plurality of ribs. Each rib may extend continuously or discontinuously around a circumference of the insert. The atraumatic tip may have an outer surface that is concavely tapered in a longitudinal direction thereof. 
     A method of delivering a collapsible prosthetic heart valve in a patient includes providing a delivery device having a catheter assembly and an operating handle, the catheter assembly including a compartment adapted to receive the valve in an assembled condition. The operating handle may include a housing defining a movement space therein, a carriage assembly moveable in first and second longitudinal directions within the movement space, a deployment actuator coupled to the housing and rotatable relative to the housing, and a coupling assembly rotationally fixed to the deployment actuator. 
     The method may also include loading the valve into the compartment of the catheter assembly and covering the compartment and the valve with a distal sheath of the catheter assembly, inserting the catheter assembly into the patient so that the valve is positioned at a target location within the patient, partially deploying the valve by moving the carriage assembly of the operating handle in the first longitudinal direction along a first portion of the movement space, and fully deploying the valve by continuing movement of the carriage assembly in the first longitudinal direction along a second portion of the movement space. 
     The operating handle may also include a threaded rod extending from the carriage assembly and into threaded engagement with the coupling assembly. The deployment actuator may be longitudinally constrained relative to the housing. The partially deploying step may include rotating the deployment actuator. The coupling assembly may include a split nut having a plurality of threaded split nut portions. The split nut portions may each be linearly slideable away from one another and away from the threaded rod. The method may also include moving the split nut portions from a disengaged position in which threads of the split nut portions do not engage the threaded rod to an engaged position in which the threads of the split nut portions are engaged with the threaded rod. 
     The coupling assembly may include a ring coupled to the split nut portions. The ring may have cam surfaces. The step of moving the split nut portions may include sliding the split nut portions along the cam surfaces from the disengaged position to the engaged position. The deployment actuator may be a knob rotatable about a central axis that extends parallel to the first and second longitudinal directions. The operating handle may also include a toothed rack extending from the carriage assembly and into engagement with the coupling assembly. The deployment actuator may be longitudinally constrained relative to the housing. The partially deploying step may include rotating the deployment actuator. The deployment actuator may be a knob rotatable about a central axis that extends perpendicular to the first and second longitudinal directions. 
     The catheter assembly may also include a first shaft around which the compartment is defined and an outer shaft connecting the carriage assembly to the distal sheath and at least partially surrounding the first shaft. The first shaft may be fixedly connected to the housing. The distal sheath may be operatively connected to the carriage assembly. The steps of partially deploying the valve and fully deploying the valve may each include moving the outer shaft proximally relative to the housing. The catheter assembly may also include a first shaft around which the compartment is defined and an outer shaft connecting the housing to the compartment and at least partially surrounding the first shaft. The first shaft and the distal sheath may be operatively connected to the carriage assembly. The steps of partially deploying the valve and fully deploying the valve may each include moving the first shaft distally relative to the housing. 
     The operating handle may also include a resheathing lock having a lock position and a release position. The resheathing lock in the lock position may limit movement of the carriage assembly in the first longitudinal direction to a stop position in the movement space. The resheathing lock in the release position may permit movement of the carriage assembly in the first longitudinal direction beyond the stop position. The method may also include resheathing the valve by moving the carriage assembly in the second longitudinal direction opposite the first longitudinal direction. The target location may be the native aortic annulus of the patient. The inserting step may include inserting the distal sheath of the catheter assembly through a femoral artery of the patient. The inserting step may include inserting the distal sheath of the catheter assembly through the apex of the heart of the patient. 
     A delivery device for a collapsible prosthetic heart valve may include a first shaft around which a compartment is defined, an outer shaft surrounding at least a longitudinal portion of the first shaft, a distal sheath attached to one of the first shaft and the outer shaft and surrounding a longitudinal portion of the first shaft, and an atraumatic tip attached to a distal end of the first shaft. The first shaft may extend in a longitudinal direction and may have an outwardly flared portion at the distal end thereof. The compartment may be adapted to receive the valve in an assembled condition. 
     The outer shaft may be slidable relative to the first shaft in the longitudinal direction. The distal sheath may be moveable in the longitudinal direction between a closed condition covering the compartment and an open condition uncovering the compartment for deployment of the valve. The atraumatic tip may have a lumen extending longitudinally therethrough and an insert located within the lumen. The outwardly flared portion of the first shaft may be fixed between a distal end of the insert and material forming the atraumatic tip. The insert may have a plurality of ribs. Each rib may extend continuously or discontinuously around a circumference of the insert. The atraumatic tip may have an outer surface that is concavely tapered in the longitudinal direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present invention will now be described with reference to the appended drawings. It is to be appreciated that these drawings depict only some embodiments of the invention and are therefore not to be considered limiting of its scope. 
         FIG. 1A  is a top plan view of a portion of an operating handle for a transfemoral delivery device for a collapsible prosthetic heart valve, shown with a partial longitudinal cross-section of the distal portion of a transfemoral catheter assembly; 
         FIG. 1B  is a side view of the handle of  FIG. 1A ; 
         FIG. 1C  is an exploded perspective view of the handle of  FIG. 1A ; 
         FIG. 2A  is an exploded perspective view of the deployment actuator assembly of  FIG. 1C ; 
         FIG. 2B  is an enlarged perspective view of a portion of the deployment actuator assembly of  FIG. 1C ; 
         FIG. 2C  is a longitudinal cross-section of the deployment actuator assembly of  FIG. 1C , with the deployment actuator shown in threaded engagement with the carriage assembly; 
         FIG. 2D  is a longitudinal cross-section of the deployment actuator assembly of  FIG. 1C , with the deployment actuator shown disengaged from the threads of the carriage assembly; 
         FIG. 3A  is a partially transparent side perspective view of a portion of the operating handle of  FIG. 1A , showing the carriage assembly in an intermediate position; 
         FIG. 3B  is an enlarged partially transparent side perspective view of a portion of the operating handle of  FIG. 1A , showing the carriage assembly in another intermediate position; 
         FIG. 3C  is an enlarged partially transparent side perspective view of a portion of the operating handle of  FIG. 1A , showing the carriage assembly in contact with the deployment lock; 
         FIG. 3D  is a partially transparent side view of a portion of the operating handle of  FIG. 1A , showing the deployment lock in an actuated position; 
         FIG. 4A  is a partially transparent top view of a portion of the operating handle of  FIG. 1A , showing the arms of the deployment lock contacting the reset lever; 
         FIG. 4B  is a partially transparent top perspective view of a portion of the operating handle of  FIG. 1A , showing the arms of the deployment lock overlying the reset lever; 
         FIG. 5A  is a top view of another embodiment of an operating handle for a transfemoral delivery device for a collapsible prosthetic heart valve, shown with a portion of the housing removed; 
         FIG. 5B  is a top view of the operating handle of  FIG. 5A , shown with the entire housing; 
         FIG. 6A  is a top perspective view of an operating handle for a transapical delivery device for a collapsible prosthetic heart valve, shown with a top view of the distal portion of a transapical catheter assembly; 
         FIG. 6B  is a top perspective view of a delivery device including the operating handle of  FIG. 6A , shown with the compartment unsheathed; 
         FIGS. 6C and 6D  are enlarged perspective views of portions of the delivery device of  FIG. 6B ; 
         FIG. 7A  is a side view of another embodiment of an operating handle for a transfemoral delivery device for a collapsible prosthetic heart valve; 
         FIG. 7B  is a top plan view of the handle of  FIG. 7A ; 
         FIG. 7C  is a bottom perspective view of the handle of  FIG. 7A ; 
         FIG. 8A  is a side view of the rack assembly of the operating handle of  FIG. 7A ; 
         FIG. 8B  is a top view of the rack assembly of  FIG. 8A ; 
         FIG. 8C  is a longitudinal cross-section showing a portion of the rack assembly of  FIG. 8A  with a portion of the handle of  FIG. 7A ; 
         FIG. 8D  is a longitudinal cross-section showing a portion of the rack assembly of  FIG. 8A  engaged with an opening in a portion of the handle of  FIG. 7A ; 
         FIG. 9A  is a side view of the motion transfer assembly of the operating handle of  FIG. 7A , shown in partial cross-section with the pinion engaged with the rack; 
         FIG. 9B  is a cross-sectional view of the motion transfer assembly and rack of  FIG. 9A ; 
         FIG. 10A  is a side view of the motion transfer assembly of the operating handle of  FIG. 7A , shown in partial cross-section with the pinion disengaged from the rack; 
         FIG. 10B  is a cross-sectional view of the motion transfer assembly and rack of  FIG. 10A ; 
         FIG. 11A  is a side view showing a portion of the handle of  FIG. 7A  with the proximal end of the rack assembly engaged with the housing, and a side elevation of the distal portion of a transfemoral catheter assembly in a first condition; 
         FIG. 11B  is a side view showing a portion of the handle of  FIG. 7A  with the proximal end of the rack assembly disengaged from the housing, and a side elevation of the distal portion of the transfemoral catheter assembly in a second condition; 
         FIG. 12A  is a longitudinal cross-section of one embodiment of an atraumatic tip; and 
         FIG. 12B  is a longitudinal cross-section of an alternative embodiment of an atraumatic tip. 
     
    
    
     DETAILED DESCRIPTION 
     As used herein, the terms “proximal” and “distal” are to be taken as relative to a user using the disclosed delivery devices. “Proximal” is to be understood as relatively close to the user and “distal” is to be understood as relatively farther away from the user. 
     Referring now to  FIGS. 1A-1C  to illustrate the structure and function of the present invention, an exemplary transfemoral delivery device  10  for a collapsible prosthetic heart valve (or other types of self-expanding collapsible stents) has a catheter assembly  16  for delivering the heart valve to and deploying the heart valve at a target location, and an operating handle  20  for controlling deployment of the valve from the catheter assembly. The delivery device  10  extends from a proximal end  12  ( FIG. 1B ) to an atraumatic tip  14  at the distal end of catheter assembly  16 . The catheter assembly  16  is adapted to receive a collapsible prosthetic heart valve (not shown) in a compartment  23  defined around an inner shaft  26  and covered by a distal sheath  24 . 
     The inner shaft  26  may extend through the operating handle  20  to the atraumatic tip  14  of the delivery device, and includes a retainer  25  affixed thereto at a spaced distance from tip  14  and adapted to hold a collapsible prosthetic valve in the compartment  23 . The inner shaft  26  may be made of a flexible material such as braided polyimide or polyetheretherketone (PEEK), for example. Using a material such as PEEK may improve the resistance of the inner shaft  26  to kinking while the catheter assembly  16  is tracking through the vasculature of a patient. The retainer  25  may have recesses  80  therein that are adapted to hold corresponding retention members of the valve. 
     The distal sheath  24  surrounds the inner shaft  26  and is slidable relative to the inner shaft such that it can selectively cover or uncover the compartment  23 . The distal sheath  24  is affixed at its proximal end to an outer shaft  22 , the proximal end of which is connected to the operating handle  20  in a manner to be described. The distal end  27  of the distal sheath  24  abuts the atraumatic tip  14  when the distal sheath is fully covering the compartment  23 , and is spaced apart from the atraumatic tip when the compartment  23  is at least partially uncovered. 
     The operating handle  20  is adapted to control deployment of a prosthetic valve located in the compartment  23  by permitting a user to selectively slide the outer shaft  22  proximally or distally relative to the inner shaft  26 , thereby respectively uncovering or covering the compartment with the distal sheath  24 . The outer shaft  22  may be made of a flexible material such as nylon 11 or nylon 12, and it may have a round braid construction (i.e., round cross-section fibers braided together) or flat braid construction (i.e., rectangular cross-section fibers braided together), for example. The proximal end of the inner shaft  26  may be connected in substantially fixed relationship to an outer housing  30  of the operating handle  20  (the longitudinal position of the inner shaft relative to the housing may be movable in some embodiments, for example, as described below with reference to  FIGS. 11A and 11B ), and the proximal end of the outer shaft  22  is affixed to a carriage assembly  40  that is slidable along a longitudinal axis of the handle housing, such that a user can selectively slide the outer shaft relative to the inner shaft by sliding the carriage assembly relative to the housing. A hemostasis valve  28  includes an internal gasket adapted to create a seal between the inner shaft  26  and the proximal end of the outer shaft  22 . 
     The handle housing  30  includes a top portion  30   a  and a bottom portion  30   b . The top and bottom portions  30   a  and  30   b  may be individual pieces joined to one another as shown in  FIG. 1C . Collectively, the top and bottom portions  30   a  and  30   b  define an elongated space  34  in the housing  30  in which the carriage assembly  40  may travel. The elongated space  34  preferably permits the carriage assembly  40  to travel a distance that is at least as long as the anticipated length of the prosthetic valve to be delivered (e.g., at least about 50 mm), such that the distal sheath  24  can be fully retracted from around the prosthetic valve. A pair of slots  31  may be formed on opposite sides of the housing  30 , contiguous with the elongated space  34 . The length of the slots  31 , minus the width of the carriage grip shafts  43  (described below), determines the maximum distance that the carriage assembly  40  can travel within the space  34 . 
     The carriage assembly  40  has a body portion  41  with a threaded rod  36  extending proximally therefrom along the longitudinal axis of the housing  30 . A series of ribs  29  in the handle housing  30  collectively define an enlarged bore  35  ( FIG. 1C ) that is sized to freely and slidingly receive a threaded rod  36 . The enlarged bore  35  has an inner diameter slightly larger than the outer diameter of the threaded rod  36 . The threaded rod  36  preferably is longer than the anticipated maximum travel distance of the carriage assembly  40  within the elongated space  34  (e.g., at least about 50 mm), such that the threaded rod  36  does not fully disengage from the deployment actuator  21  (described below) during sheathing or resheathing of the prosthetic valve. 
     The carriage assembly  40  further includes a pair of carriage grips  42  each attached to the body portion  41  by a respective carriage grip shaft  43 . Although the carriage assembly  40  is shown in  FIGS. 1A and 1C  as having two carriage grips  42 , that need not be the case. For example, the embodiment shown in  FIG. 6A  has a single carriage grip. As shown in  FIG. 1C , the lateral sides  44  of the carriage grips  42  may include a plurality of parallel ridges  45  to facilitate grasping and moving of the carriage grips. 
     The handle housing  30  further defines a pocket  37  that extends through the top portion  30   a  and bottom portion  30   b  for receiving a deployment actuator  21 . Deployment actuator  21  is internally threaded for selective engagement with the threaded rod  36 . The pocket  37  is sized and shaped to receive the deployment actuator  21  with minimal clearance, such that the location of the deployment actuator remains substantially fixed relative to the housing  30  as it is rotated about the threaded rod  36 . That is, when the deployment actuator  21  is in threaded engagement with the threaded rod  36 , rotation of the deployment actuator in one direction (either clockwise or counterclockwise depending on the orientation of the threads on the threaded rod) causes the threaded rod to move proximally within the bore  35 , at the same time pulling the body portion  41  of the carriage assembly  40  proximally through the elongated space  34 . Similarly, when the deployment actuator  21  is in threaded engagement with the threaded rod  36 , rotation of the deployment actuator in the opposite direction causes the threaded rod to move distally within the bore  35 , at the same time pushing the body portion  41  of the carriage assembly  40  distally through the elongated space  34 . 
     The deployment actuator  21  may be selectively placed in threaded engagement with the threaded rod  36  by a coupling assembly  60 , the details of which are shown in  FIGS. 2A-2D . The coupling assembly  60  may include a split nut  64  mounted within the deployment actuator  21  through an open side thereof. The split nut  64  has first and second nut portions  64   a  and  64   b  that are internally threaded to mate with the threaded rod  36 . Each nut portion  64   a  and  64   b  has a pair of spaced tabs projecting therefrom, with each tab having an aperture  65  sized to receive a pin  76 . 
     A nut ramp  66  may be mounted within the deployment actuator  21  adjacent the split nut  64 . The nut ramp  66  has an annular body  66   a  with a pair of cam arms  67  projecting distally therefrom and slidably positioned between the spaced tabs on respective nut portions  64   a  and  64   b . Each cam arm  67  has an elongated cam slot  68  sized to slidably receive the pin  76  therein. 
     A retention ring  74  may be press fit into the open side of the deployment actuator  21 . A plurality of ribs on the outer periphery of the retention ring  74  may mate with a plurality of recesses formed on the inner surface of the deployment actuator  21  to prevent the retention ring from rotating relative to the deployment actuator. The retention ring  74  may include a pair of spaced flanges  74   a  that cooperate with similar spaced flanges formed on the interior of the deployment actuator  21  to sandwich the generally rectangular outer periphery of the split nut  64  in an assembled position. A large central aperture  74   b  in the retention ring  74  is sized to slidably receive the annular body  66   a  of the nut ramp  66  therethrough. The retention ring  74  further includes a pair of diametrically opposed slots  74   c  that are sized and positioned to receive the cam arms  67  of the nut ramp  66  as the annular body  66   a  thereof travels through the aperture  74   b  in the retention ring. 
     A ring  62  may be positioned adjacent the retention ring  74  and may be coupled to the nut ramp  66  by a flanged fastening ring  70  that fits through the ring  62  and snaps into the nut ramp with an interference fit. The connection between the fastening ring  70  and the nut ramp  66  is such that the ring  62  has some freedom of movement between the annular body  66   a  of the nut ramp and the flange of the fastening ring. An aperture  70   a  extending longitudinally through the fastening ring  70  has a diameter that is larger than the diameter of the threaded rod  36  so that the threaded rod can slide smoothly and freely therethrough. A compression spring  72 , the purpose of which will be described below, may be mounted in the annular space between the fastening ring  70  and the ring  62  and may be constrained longitudinally between the annular body  66   a  of the nut ramp  66  and an annular flange formed on the ring  62 . 
     A pair of buttons  61  positioned on opposite lateral sides of the ring  62  may be slidably received in longitudinal openings  38  formed on opposite lateral sides of the housing  30 . Movement of the buttons  61  to a proximal position in the openings  38  will cause the ring  62  and, hence, the nut ramp  66  to move proximally relative to the split nut  64 , and movement of the buttons  61  to a distal position in the openings  38  will cause the ring  62  and the nut ring  66  to move distally relative to the split nut. 
     The ring  62  further includes an arm  63  that extends distally from an outer periphery of the ring. The arm  63  is sized to reside between a pair of posts  33  that project upwardly from the housing portion  30   b . The free end of the arm  63  includes a pair of nubs  63   a  that project therefrom in opposite lateral directions. When the buttons  61  are moved to a distalmost position in the opening  31 , the nubs  63   a  will be positioned on the distal side of the posts  33 , locking the ring  32  in this position. When the buttons  61  are moved to a proximalmost position in the openings  38 , the nubs  63   a  will be positioned on the proximal side of the posts  33 , locking the ring in this position. As the buttons  61  are moved between the proximalmost and distalmost positions, the nubs  63   a  will deflect the posts  33  slightly outward as they move between the posts. The engagement of a rib  33   a  extending longitudinally in the housing portion  30   b  in a longitudinal slot  63   b  on the back of the arm  63  maintains the alignment of the ring  62  as it slides between the proximalmost and distalmost positions. 
     The first and second nut portions  64   a  and  64   b  have freedom of motion to slide in a substantially perpendicular direction towards or away from the threaded rod  36 , but they are constrained from longitudinal movement relative to the threaded rod by the sandwiching effect of the inner flanges of the deployment actuator  21  and the retention ring flanges  74   a . Thus, in the assembly described above, the cam slots  68  are adapted to translate movement of the nut ramp  66  along the longitudinal axis into lateral movement of the first and second nut portions  64   a  and  64   b  towards or away from the threaded rod  36 . 
     For example, when the buttons  61  are moved to the proximal ends of the respective openings  38 , the pins  76  will be disposed at the distal ends of the cam slots  68 , which are located closest to the threaded rod  36  in a direction perpendicular to the longitudinal axis. In this position, the nut portions  64   a  and  64   b  will be in threaded engagement with the threaded rod  36 . When the buttons  61  are moved to the distal ends of the respective openings  38 , the pins  76  will be disposed at the proximal ends of the cam slots  68 , which are located farthest from the threaded rod  36  in the direction perpendicular to the longitudinal axis. In this position, the nut portions  64   a  and  64   b  will be disengaged from the threaded rod  36 . Therefore, when a user slides the buttons  61  proximally, rotation of the deployment actuator  21  translates the threaded rod  36 , and when the user slides the buttons distally, the deployment actuator becomes decoupled from the threaded rod. 
     When the user slides the buttons  61  proximally to move the nut portions  64   a  and  64   b  toward the threaded rod  36 , interference between the threads on the nut portions and the threads on the threaded rod may prevent complete threaded engagement between the split nut  64  and the threaded rod. Nonetheless, the ring  62  will move to its proximalmost position so that the nubs  63   a  snap into place on the proximal side of the posts  33 . With the aforementioned interference preventing the nut portions  64   a  and  64   b  from continuing into full threaded engagement with the threaded rod  36 , and thus preventing the nut ramp  66  from further movement proximally, the last portion of the movement of the ring  62  in the proximal direction will cause the spring  72  to compress. This compression will add an extra lateral force to the nut ramp  66 . Accordingly, as the deployment actuator  21  is rotated, the threads of the nut portions  64   a  and  64   b  will properly align with the threads of threaded rod  36  and the biasing force exerted by the spring  72  on the nut ramp  66  will assure that the nut portions become fully engaged with the threaded rod. 
     The ability of the coupling assembly  60  to translate rotation of the deployment actuator  21  into translation of the carriage assembly  40  relative to the housing  30  may provide the user with the ability to carefully control movement of the carriage assembly both proximally within the space  34  during a valve deployment operation, and distally within the space  34  during a resheathing operation, as described more fully below. The ability of the coupling assembly  60  to decouple the deployment actuator  21  from the carriage assembly  40  so that the carriage assembly can freely move longitudinally relative to the housing  30  enables gross movement of the carriage assembly proximally or distally within the space  34  without the mechanical advantage provided by the deployment actuator. Such movement is not easily controllable, but rather is subject to the “touch and feel” of the user. 
     Referring now to  FIGS. 3A-3D , the carriage assembly  40  may include a resheathing lock adapted to limit the longitudinal movement of the carriage assembly proximally within the handle housing  30 , thereby preventing the user from completing the deployment of a prosthetic valve when unintended. One embodiment of a resheathing lock may include a control member  50  that is pivotable relative to the housing  30  between a lock position (shown in  FIG. 3A ) and a release position (shown in  FIG. 3D ). 
     The control member  50  includes a pair of spaced arms  52  that extend distally into the space  34  in the housing  30 . Each arm  52  terminates in a notch  54  that is adapted to interfere with a respective carriage grip shaft  43  when the control member  50  is in the lock position, thereby preventing the carriage assembly  40  from continued proximal movement, as shown in  FIG. 3C . A pin  51  projects laterally from each arm  52  (only one such pin  51  is shown in the drawings) and is pivotally engaged in respective apertures  39  formed on opposite sides of the housing  30 . The pins  51  are not positioned in the center of arms  52 , but rather are positioned much closer to the proximal end of the control member  50 . As a result, a much greater weight of the control member  50  resides between the pins  51  and the notches  54  than between the pins  51  and the proximal end of the control member, such that the weight differential biases the control member to the lock position. 
     With the control member  50  in its lock position (shown in  FIG. 3A ), a button  53  on the proximal end of the control member projects through an opening  32  in the housing  30 , where it is available to be pressed by the user. Depressing the button  53  overcomes the weight-based biasing force and pivots the control member  50  about the pins  51 , causing the notched end of each arm  52  to move up and out of engagement with the respective carriage grip shaft  43 . This action thus frees the carriage assembly  40  for further proximal movement relative to the housing  30 , as shown in  FIG. 3D , thereby permitting full deployment of a prosthetic valve from the catheter assembly  16 . 
     The initial distance that the carriage assembly  40  can travel before being limited by the control member  50  may depend on the structure of the particular prosthetic valve to be deployed. Preferably, the initial travel distance of the carriage assembly  40  is about 3 mm to about 5 mm less than the crimped valve length. Alternatively, the initial travel distance of the carriage assembly  40  may be about 40 mm to about 45 mm, which is about 80% to about 90% of the length of an exemplary 50 mm valve. The initial distance that the carriage assembly  40  can travel may be determined as a percentage of the length of the prosthetic valve and/or the compartment  23 , including, for example, 50%, 60%, 70%, 75%, 85%, or 95%. 
     Referring now to  FIGS. 4A and 4B , each arm  52  of the control member  50  may also include one or more protrusions  56  that project laterally towards the longitudinal axis of the housing  30 , and each carriage grip shaft  43  may include a reset lever  46  extending proximally therefrom. During proximal movement of the carriage assembly  40 , as the carriage grip shafts  43  approach the ends of the arms  52 , the reset levers  46  will contact the protrusions  56  and will be deflected laterally inward towards the longitudinal axis of the housing  30 . The reset levers  46  will continue to be deflected laterally inward as the carriage assembly  40  continues to move proximally until the notches  54  at the ends of the arms  52  engage the carriage grip shafts  43 . 
     At this juncture, to continue deployment, the button  53  may be depressed to pivot the ends of the arms  52  up and away from the carriage grip shafts  43 . As the arms  52  pivot upwardly, the protrusions  56  will also move upwardly until they are positioned above the reset levers  46 , which then return to their straight or undeflected condition. The protrusions  56  will thereafter rest on the upper surfaces of the reset levers  46 , thereby holding the control member  50  in the release position, even after the button  53  has been released by the user. The fact that the control member  50  remains in the release position even after the button  53  has been released frees the user to again operate the deployment actuator  21 , thus enabling one-handed operation of the device  10 . 
     When the carriage assembly  40  is moved distally to resheathe the compartment  23  with distal sheath  24 , the protrusions  56  will ride along the top of reset levers  46 , with the control member  50  in the release position, until the carriage grip shafts  43  have moved just distally of the notches  54 . At this point, the protrusions  56  will clear the reset levers  46  and the weight of the arms  52  will bias control member  50  back to the lock position. 
     The operation of the present invention to deploy a prosthetic valve will now be described. To load the delivery device  10  with a collapsible prosthetic valve, the user may place the buttons  61  in the distalmost position within the openings  38  to disengage the split nut  64  from the threaded rod  36 . The carriage grips  42  may then be slid proximally relative to the slots  31  to move the carriage assembly  40  proximally and thereby retract the distal sheath  24  and expose the compartment  23 . During this retraction, the button  53  may be depressed to place the control member  50  in its release position to enable the carriage assembly  40  to move fully to its proximalmost position and thereby fully expose the compartment  23 . A compressed or crimped valve may then be loaded around the inner shaft  26 , and the proximal end of the valve may be coupled to the retainer  25 . The carriage grips  42  may then be slid in the opposite or distal direction relative to the slots  31  to move the carriage assembly  40  distally and cover the compartment  23  with the distal sheath  24  to hold the valve in the compressed state. The buttons  61  may then be placed in the starting condition of the delivery device  10 . In this starting condition, the handle  20  will be in an initial state with the carriage assembly  40  at its distalmost position within the handle housing  30 , the control member  50  of the resheathing lock will be in its lock position to prevent full deployment, and the buttons  61  will each be at the proximalmost position within the respective openings  38 , such that the deployment actuator  21  is threadedly engaged with the threaded rod  36 . 
     To use the operating handle  20  to deploy a prosthetic valve that has been loaded into the compartment  23  and covered by the distal sheath  24 , the user may rotate the deployment actuator  21 , causing the carriage assembly  40  to slide proximally within the elongated space  34  in the housing  30 . Because the distal sheath  24  is affixed to the outer shaft  22 , which in turn is affixed to the carriage assembly  40 , and because the inner shaft  26  is fixed to the housing  30 , sliding the carriage assembly proximally relative to the housing will retract the distal sheath proximally from the compartment  23 , thereby exposing and initiating deployment of the valve located therein. 
     It will be appreciated that the user may initiate the deployment process without use of the deployment actuator  21  by simply sliding the buttons  61  of the coupling assembly  60  distally, thereby decoupling the split nut  64  from the threaded rod  36 , and pulling the carriage assembly  40  proximally within the housing  30 . Such action may require significant pulling force in order to overcome the frictional forces acting on the outer shaft  22  and the distal sheath  24 . For that reason, the use of the deployment actuator  21  to begin retracting the distal sheath  24  is preferred since such use provides the user with a mechanical advantage to overcome the aforementioned frictional forces, thereby providing the user with much greater control of the deployment process. 
     After the distal sheath  24  has been partially retracted from the compartment  23  and a portion of the prosthetic valve has been exposed, the frictional forces acting between the valve and the distal sheath may be greatly reduced. At this point, the user may continue the deployment process with or without use of the deployment actuator  21 . If the user prefers to continue the deployment process without use of the deployment actuator  21 , the user can slide the buttons  61  of the coupling assembly  60  distally to disengage the split nut  64  from the threaded rod  36  and can pull the carriage assembly  40  proximally within the housing  30  by exerting a pulling force on carriage grips  42 . Although the user will not have a mechanical advantage without using the deployment actuator  21  to move the carriage assembly  40  proximally, continuing the deployment process while the deployment actuator is decoupled from the carriage assembly may allow such process to be completed more quickly. 
     In any event, since the control member  50  of the resheathing lock is in the lock position, movement of the carriage assembly  40  proximally may continue only until the carriage grip shafts  43  contact the notches  54  at the ends of the arms  52 . At this point, the distal sheath  24  will not be fully withdrawn from the compartment  23 , and the prosthetic valve will not be fully deployed. 
     When the deployment procedure has reached this juncture, the user can evaluate the position of the valve relative to the patient&#39;s aortic annulus and may be able to determine whether the valve is functioning properly. If repositioning or removal is desired, with the buttons  61  positioned to engage the split nut  64  with the threaded rod  36 , the user may resheathe the valve by rotating the deployment actuator  21  in the direction opposite that used for deployment. Such rotation will cause the threaded rod  36  to progress distally through the deployment actuator  21  until the carriage assembly  40  has reached the starting position shown in  FIG. 1B , thereby recollapsing the expanded part of the valve as the distal sheath  24  is moved distally over the compartment  23  and the partially deployed valve. With the valve resheathed, the user can reposition the delivery device  10  and can commence the deployment procedure once again or can simply remove the valve from the patient. 
     It will be appreciated that the user may partially or fully resheathe the valve without use of the deployment actuator  21  by simply sliding the buttons  61  of the coupling assembly  60  distally, thereby decoupling the deployment actuator from the carriage assembly  40 , and pushing the carriage assembly distally within the housing  30 . Such action may require significant pushing force in order to overcome the frictional forces acting on the outer shaft  22  and the distal sheath  24 , as well as the resilient forces which expand the stent portion of the valve. For that reason, a user may choose to use the deployment actuator  21  to replace the distal sheath  24  over the compartment  23  since such use provides the user with a mechanical advantage to overcome the aforementioned forces. 
     Once the proper positioning of the valve relative to the aortic annulus has been assured, the user may complete the deployment process. To do so, the user may depress the button  53  of the control member  50  of the resheathing lock, thereby causing the control member to pivot from the lock position to the release position and the arms  52  to pivot upward out of the path of the carriage grip shafts  43  so that the carriage assembly  40  is free to continue its movement proximally. The user can continue to slide the carriage assembly  40  proximally to complete the deployment of the valve by rotating the deployment actuator  21  or by sliding the buttons  61  of the coupling assembly  60  distally to decouple the deployment actuator from the carriage assembly  40 , and pulling the carriage assembly proximally within the housing  30 . When the valve has been completely unsheathed, the stent portion of the valve self-expands and disengages from the retainer  25 , thereby releasing the valve from the catheter assembly  16 . 
     Referring now to  FIG. 5A , an operating handle  20   a  is shown having an alternate resheathing lock design than that shown in  FIGS. 1A through 4B . The resheathing lock of the operating handle  20   a  includes a control member  50   a  that is rotatable between first and second positions relative to the housing  30   a  and the carriage assembly  40 . The control member  50   a  includes a generally cylindrical body  57  disposed between the housing  30   a  and the threaded rod  36 , such that the threaded rod extends through a generally cylindrical opening extending through the control member along the longitudinal direction of the housing  30 . 
     The cylindrical body  57  of the control member  50   a  has a distal end  59  and a slot  58  extending proximally from the distal end in the longitudinal direction of the housing  30 . The distal end  59  is adapted to interfere with a protrusion  47  on the body  41  of the carriage assembly  40  when the control member  50   a  is in the lock position shown in  FIGS. 5A and 5B , thereby preventing the carriage assembly from continued proximal movement. 
     With the control member  50   a  in its lock position, a button  53   a  on the proximal end of the control member projects through an opening  32   a  in the housing  30 , where it is available to be moved by the user. Sliding the button  53   a  from the lock position adjacent a first end  32   b  of the opening  32   a  to a second opposite end  32   c  of the opening slightly rotates the control member  50   a  about the threaded rod  36 , causing the slot  58  to rotate into alignment with the protrusion  47 . As the slot  58  is sized to receive the protrusion  47  therein, this action frees the carriage assembly  40  for further proximal movement relative to the housing  30 , thereby permitting full deployment of a prosthetic valve from the catheter assembly  16 . 
     Referring now to  FIG. 6A , an exemplary transapical delivery device  110  for a collapsible prosthetic heart valve (or other types of self-expanding collapsible stents) has a catheter assembly  116  for delivering the heart valve to and deploying the heart valve at a target location, and an operating handle  120  for controlling deployment of the valve from the catheter assembly. The delivery device  110  extends from a proximal end  112  to an atraumatic tip  114  at the distal end of the catheter assembly  116 . The atraumatic tip  114  may be formed from or may include a radiopaque material to enable the tip to be visible under fluoroscopy during a deployment procedure. The catheter assembly  116  is adapted to receive a collapsible prosthetic heart valve (not shown) in a compartment  123  defined around a tubular support shaft  119  and covered by a distal sheath  124 . 
     The support shaft  119  extends between a pair of spaced retainers  125  and  127  affixed thereto and defining the ends of the compartment  123 . A collapsible prosthetic valve may be assembled around the support shaft  119  and between the retainers  125  and  127  in the compartment  123 . 
     The distal sheath  124  surrounds the support shaft  119  and is slidable relative to the support shaft such that it can selectively cover or uncover the compartment  123 . The distal sheath  124  is affixed at its distal end to the atraumatic tip  114 , and its proximal end  129  terminates at or near the retainer  127  when the distal sheath is fully covering the compartment  123 , as shown in  FIG. 6A . The proximal end  129  of the distal sheath  124  is spaced apart from the retainer  127  when the compartment  123  is at least partially uncovered. 
     The delivery device further includes an outer shaft  122 , the proximal end of which is fixedly connected to the operating handle  120 , and the distal end of which terminates at or near the retainer  127 , and preferably abuts the proximal end  129  of the distal sheath  124  when the distal sheath is in the proximalmost position. An inner shaft  126  extends through the operating handle  120  and the support shaft  119  to the atraumatic tip  114 . The connection of the distal sheath  124  to the atraumatic tip  114  thus enables the inner shaft  126  to control the movement of the distal sheath both proximally and distally. 
     The operating handle  120  is adapted to control deployment of a prosthetic valve located in the compartment  123  by permitting a user to selectively slide the inner shaft  126  and the attached distal sheath  124  distally or proximally relative to the support shaft  119 , thereby respectively uncovering or covering the compartment with the distal sheath. The proximal end of the outer shaft  122  is connected in substantially fixed relationship to an outer housing  130  of the operating handle  120 , and a location near the proximal end of the inner shaft  126  is connected to a carriage assembly (similar to the carriage assembly  40  described above) that is slidable along a longitudinal axis of the handle housing, such that a user can selectively slide the inner shaft relative to the outer shaft by sliding the carriage assembly relative to the housing. As shown in  FIG. 6A , the inner shaft  126  may extend through the carriage assembly, and the proximal end of the inner shaft may extend through the housing  130  beyond the proximal end  112  thereof. A hemostasis valve  128  attached to the proximal end of the inner shaft  126  may permit removal of air from the device  110  through the inner shaft before deployment of the valve. 
     The handle housing  130  includes a top portion  130   a  and a bottom portion (not shown in the figures). The top portion  130   a  and bottom portion may be similar to the top and bottom portion  30   a  and  30   b  described above. Collectively, the top portion  130   a  and bottom portion define an elongated space  134  in the housing  130  in which the carriage assembly may travel. 
     The housing  130  also includes a slot  131  contiguous with the elongated space  134 . The length of the slot  131 , minus the width of the carriage grip shaft (not visible in the figures, but similar to the carriage grip shafts  43  described above) that attaches the carriage grip  142  to the body portion  141  of the carriage assembly, determines the maximum distance that the carriage assembly can travel within the space  134 . Although only one slot  131  is shown in  FIG. 6A , a second slot  131  and a second carriage grip  142  may be provided on the opposite side of the housing  130 , similar to the configuration shown in  FIG. 1A . As shown, the slot  131  extends through the top portion  130   a  of the housing  130 . An enlarged bore  135  defined by the housing  130  is sized to freely and slidingly receive a threaded rod  136  that extends proximally from the body portion  141  of the carriage assembly, as described below. 
     The device  110  may include a coupling assembly to convert rotational motion of a deployment actuator  121  into linear motion of the carriage assembly. The coupling assembly may be configured in much the same manner as the coupling assembly  60  described above with reference to  FIGS. 1C through 2D , and the pair of buttons  161  engaged in respective openings  138  can have a structure and function similar to those of the buttons  61  of the device  10  described above. 
     The deployment actuator  121  may be located within a pocket  137  extending transversely through the housing  130 , and it may selectively be placed in threaded engagement with the threaded rod  136 . When the deployment actuator  121  is in threaded engagement with the threaded rod  136 , rotation of the deployment actuator in one direction (either clockwise or counterclockwise depending on the orientation of the threads on the threaded rod) causes the threaded rod to move proximally within the bore  135 , at the same time pulling the carriage assembly proximally through the elongated space  134 . Similarly, when the deployment actuator  121  is in threaded engagement with the threaded rod  136 , rotation of the deployment actuator in the opposite direction causes the threaded rod to move distally within the bore  135 , at the same time pushing the body portion  141  of the carriage assembly distally through the elongated space  134 . The deployment actuator  121  may be selectively placed in threaded engagement with the threaded rod  136  by a coupling assembly similar to the coupling assembly  60  described above with respect to the device  10 . 
     The operating handle  120  may also include a resheathing lock mechanism for preventing the user from accidentally completing the deployment of a valve located in the compartment  123 . Although such a resheathing lock is not shown in  FIG. 6A , the resheathing lock may be similar to those described above with reference to  FIGS. 1A through 5B . As with device  10 , such a sheath lock may limit the longitudinal movement of the carriage assembly within the handle housing  130 . 
     Referring to  FIGS. 6B-6D , the delivery device  110  may include measurement markings  180  thereon to assist the user in determining the location or depth of portions of the device with respect to the aortic annulus or the apex of the heart. One or more of the markings  180  also may be located on the distal sheath  124 , so that the user can determine how far the distal sheath has moved during deployment of a valve relative to its initial position. One or more of the markings  180  may be located on the support shaft  119  at the anticipated location of the leaflets of the prosthetic aortic valve, so that the user can know where the leaflets are relative to the native aortic annulus during deployment of the valve. 
     Each of the measurement markings  180  may include a material selected from the group consisting of a polymer, gold, platinum, nitinol, and combinations thereof, or one or more other metallic or polymer materials, and such markings may be radiopaque, i.e., the markings may be visible to the user under fluoroscopy. 
     The operation of the operating handle  120  to deploy a prosthetic valve from the compartment  123  is similar to the operation of the operating handle  20  of the device  10  described above. The user can rotate the deployment actuator  121  to slide the carriage assembly distally within the elongated space  134  in the housing  130 , which thereby pushes the distal sheath  124  distally relative to the compartment  123  and exposes and initiates deployment of the valve located therein. 
     After movement of the distal sheath  124  has partially revealed the compartment  123 , the user may continue the deployment process by continuing to rotate the deployment actuator  121 , or the user may continue the deployment process without use of the deployment actuator by sliding the buttons  161  of the coupling assembly distally, thereby decoupling the deployment actuator from the threaded rod, and pushing the carriage assembly distally within the housing  130 . Similar to the deployment process described above with reference to the operating handle  20 , completing the deployment process while the carriage assembly is decoupled from the deployment actuator  121  may allow such process to be completed more quickly. 
     Although not shown in the figures, it will be appreciated that the device  110  may include a resheathing lock with a control member and reset levers similar to the control member  50  and the reset levers  46  described above in connection with the control handle  20 ; a resheathing lock with a slotted control member, protrusion, and actuator button similar to the control member  50   a , the protrusion  47 , and the actuator button  53   a  described above in connection with the control handle  20   a ; or other structures for limiting the movement of the carriage assembly within the handle housing. However, rather than limiting the movement of the carriage assembly proximally within the handle housing, the resheathing lock of the device  110  will limit the movement of the carriage assembly distally within the housing to prevent the user from completing the deployment of a prosthetic valve unintentionally. 
     If the user desires to resheathe and reposition the valve or remove the valve from the patient before full deployment, the user can do so by rotating the deployment actuator  121  in the direction opposite that used for deployment until the carriage assembly reaches the starting position (with the carriage grip  142  in its proximalmost position in the slot  131 ), thereby recollapsing the expanded part of the valve as the distal sheath  124  is moved proximally over the compartment  123  and the partially deployed valve. With the valve resheathed, the user can reposition the delivery device  110  and commence the deployment procedure once again or can remove the valve from the patient. 
     Once the proper positioning of the valve has been assured, the deployment operation may be completed by continuing to slide the carriage assembly distally by rotating the deployment actuator  121  or by sliding the buttons  161  of the coupling assembly distally to decouple the deployment actuator from the threaded rod, and pushing the carriage assembly distally within the housing  130  until the valve is fully deployed. 
     Referring now to  FIGS. 7A-11B , an exemplary transfemoral delivery device  210  is a variation of the delivery device  10  described above, with a similar function of deploying a collapsible prosthetic heart valve (or other types of self-expanding collapsible stents). However, some of the components of the delivery device  210  have different structures for accomplishing similar functions as the delivery device  10 . 
     Referring to  FIGS. 7A-7C , the device  210  includes a catheter assembly  216  adapted to receive a collapsible prosthetic heart valve in a compartment defined around an inner shaft  226  ( FIG. 11A ) and covered by a distal sheath  224 , and an operating handle  220  for controlling deployment of the valve. The proximal end of the inner shaft  226  is operatively coupled in a fixed manner to an outer housing  230  of the operating handle  220 . 
     The device  210  includes a deployment actuator  221  that may be selectively engaged with a carriage assembly  240  ( FIG. 8A ). When the deployment actuator  221  is engaged with the carriage assembly  240  and is rotated in a first direction relative to the housing  230 , the rotational motion is translated to linear motion of the carriage assembly either proximally or distally relative to the housing, and when the deployment actuator is rotated in an opposite direction relative to the housing, the carriage assembly moves linearly in an opposite direction relative to the housing. When the deployment actuator  221  is disengaged from the carriage assembly  240 , the carriage assembly can be manually moved by a user along the longitudinal axis of the housing  230  without any resulting movement of the deployment actuator  221 . 
     As can be seen in  FIGS. 8A-8D , the carriage assembly  240  is similar to the carriage assembly  40  described above, except that the carriage assembly  240  has a toothed rack  236  adapted to be engaged with the deployment actuator  221 , instead of a threaded rod. Rather than having the carriage grip shafts  243  contact another component to provide a resheathing lock feature, the carriage assembly  240  includes a plug  247  coupled to the body  241  by a leaf spring  248  and adapted to engage with an aperture  239  in the housing  230  to provide a resheathing lock feature. When the carriage assembly  240  is in its initial distalmost position shown in  FIGS. 7A and 7B , the plug  247  lies against an inner surface of the housing  230  as shown in  FIG. 8C , such that the leaf spring  248  is in a bent condition as shown in  FIG. 8A . The leaf spring is displaced from its rest position and therefore causes the plug  247  to exert a force against the inner surface of the housing. 
     During deployment of the valve, when the carriage assembly  240  is moved proximally and reaches the desired deployment lock position (e.g., a distance from the initial position of approximately 80% of the length of the valve as described above), the plug  247  reaches the aperture  239  as shown in  FIG. 8D , and the stored energy in the leaf spring  248  forces the plug into the aperture as the leaf spring attempts to return to a straight or rest condition. When the user desires to continue deployment of the valve, the user can depress the plug  247  to remove it from the aperture  239  while simultaneously rotating the deployment actuator  221 , thereby moving the carriage assembly  240  proximally and the plug proximally beyond the aperture. 
     Referring now to  FIGS. 9A through 10B , the deployment actuator  221  may be selectively placed in engagement with the toothed rack  236  by a coupling assembly  260 . The deployment actuator  221  has a hub portion  262  that includes an annular series of elongated fingers  262   a  that are separated by a plurality of deep channels  262   b . A pinion gear  266  has a hub portion  264  that confronts the hub portion  262  of the deployment actuator  221 . The hub portion  264  has an annular series of elongated fingers  264   a  that are separated by a plurality of deep channels  264   b . The fingers  264   a  are sized and spaced to fit within the channels  262   b  and the fingers  262   a  are sized and spaced to fit within the channels  264   b  when the hub portion  262  is fully engaged with the hub portion  264 . The hub portion  262  of the deployment actuator  221  is kept in engagement with the hub portion  264  of the gear  266  by a compression spring  268  positioned between the gear and an inner surface of the housing  230 . The gear  266  also has a plurality of teeth  270  on its outer periphery that are adapted to engage the teeth of the rack  236 . 
       FIGS. 9A and 9B  show the deployment actuator  221  engaged with the toothed rack  236  through the gear  266 . When the gear  266  is in the engaged position shown in  FIGS. 9A and 9B , the fingers  264   a  of the gear are rotationally aligned with and engaged in the corresponding channels  262   b  in the hub portion  262  of the deployment actuator  221 , so that rotation of the deployment actuator effects rotation of the gear. When the gear  266  is in this engaged position, the teeth  270  of the gear are engaged with the rack  236 , so that rotation of the gear effects linear movement of the rack. Therefore, when the gear  266  is in the engaged position, the rotation of the deployment actuator  221  is transferred into linear movement of the rack  236 , and, in turn, linear movement of the entire carriage assembly  240 . 
       FIGS. 10A and 10B  show the deployment actuator  221  disengaged from the toothed rack  236 . When the gear  266  is in the disengaged position shown in  FIGS. 10A and 10B , the fingers  264   a  of the gear are rotationally aligned with and engaged in corresponding shallow notches  265  at the ends of fingers  262   a  of the deployment actuator  221 . Such engagement still causes rotation of the deployment actuator  221  to result in rotation of the gear  266 . However, when the gear  266  is in this disengaged position, the teeth  270  of the gear are disengaged from the rack  236 , so that rotation of the gear is not transferred to the rack. Moreover, the rack  236  is free for sliding movement longitudinally in the housing  230 . Therefore, when the gear  266  is in the disengaged position, the user can manually slide the carriage assembly  240  proximally or distally without interference or resistance from the deployment actuator  221 . 
     To move the gear  266  from the engaged position shown in  FIGS. 9A and 9B  to the disengaged position shown in  FIGS. 10A and 10B , the user can depress and release a button  261  mounted in an aperture  238  through the deployment actuator  221 . The button  261  has an outer end exposed for actuation by the user, and an inner end having a plurality of notches  259  that confront the hub portion  264  of the gear  266 . The button  261  is constrained so as to be able to move linearly along the axis of the aperture  238 , but not be able to rotate about the axis of the aperture with respect to the deployment actuator  221 . 
     When the user depresses the button  261 , the notches  259  at the inner end of the button are brought into contact with the ends of the fingers  264   a  of the gear  266 . Continued depressing of the button  261  displaces the gear  266  laterally until the gear teeth  270  are moved out of engagement with the rack  236 . The fingers  264   a  each have an angled tip  267  that is not aligned with the trough at the bottom of the corresponding notch  259 . Rather, as the button  261  is depressed, each angled tip  267  contacts the angled sidewall of a notch  259 . The spring  268  forces the angled tips  267  into the troughs of the notches  259 , thereby rotating the gear  266  slightly so that the angled tips and the troughs of the notches are rotationally aligned. 
     Following the rotation of the gear  266 , the angled tips  267  of the fingers  264   a  will also be aligned with the shallow notches  265  of the deployment actuator  221 . Therefore, when the user releases the button  261 , the spring  268  forces the angled tips  267  of the fingers  264   a  into the shallow notches  265  at the ends of the fingers  262   a . Since the fingers  264   a  are engaged in the shallow notches  265  rather than in the deep channels  262   b , the gear teeth  270  remain disengaged from the rack  236 , as shown in  FIGS. 10A and 10B . 
     To move the gear  266  from the disengaged position shown in  FIGS. 10A and 10B  back to the engaged position shown in  FIGS. 9A and 9B , the user can depress and release the button  261  again. When the user depresses the button  261 , the notches  259  at the inner end of the button are brought into contact with the ends of fingers  264   a  of the gear  266 . This contact pushes the tips  267  of fingers  264   a  out of engagement with the shallow notches  265 . Once again, the angled tip  267  on each of the fingers  264   a  will not be aligned with the trough at the bottom of the corresponding notch  259 . Rather, as the button  261  is depressed, each angled tip  267  contacts the angled sidewall of a notch  259 . The spring  268  forces the angled tips  267  into the troughs of the notches  259 , thereby rotating the gear  266  slightly so that the angled tips and the troughs of the notches are rotationally aligned. 
     After the rotation of gear  266 , the angled tips  267  of the fingers  264   a  will also be aligned with the deep channels  262   b  of the deployment actuator  221 . As a result, when the user releases the button  261 , the spring  268  forces the angled tips  267  of the fingers  264   a  into the deep channels  262   b . Since the fingers  264   a  are engaged in the deep channels  262   b  rather than in the shallow notches  265 , the gear  266  is able to move laterally until the teeth  270  of the gear engage with the rack  236 , as shown in  FIGS. 9A and 9B . 
     Referring now to  FIGS. 11A and 11B , the device  210  may include a detachable proximal tip  212  to permit the user to more easily resheathe the compartment  223  after deployment of the valve, preferably before the device is removed from the patient. The detachable proximal tip  212  may include a shaft member  290  and a resilient contact arm  292  extending from the shaft member. The contact arm  292  may attach the proximal tip  212  to the housing  230  with a bayonet-type connection. After deployment of the valve has been completed, when the distal sheath  224  has uncovered the compartment  223  that previously stored the valve, the proximal end of the rack  236  may contact the shaft member  290  and push the proximal tip  212  out of the housing  230 . This can serve as a signal to the user that deployment of the valve has been completed. 
     To easily and quickly resheathe the compartment  223  for the purpose of removing the device  210  from the patient, the user may pull the proximal tip  212  proximally. The inner shaft  226  is affixed to the proximal tip  212  such that pulling the proximal tip  212  proximally also pulls the inner shaft proximally. Since the distal sheath  224  is connected to the carriage assembly  240  that cannot move further proximally relative to the housing  230  following full deployment, sliding the inner shaft  226  proximally relative to the housing will resheathe the compartment  223  until the atraumatic tip  214  contacts the distal end  227  of the distal sheath. With the compartment  223  closed, the device  210  may be removed from the patient without the need to further operate the deployment actuator  221 , disengage the gear  266  from the rack  236  or perform any other time-consuming operation. 
     The operating handles described herein may be provided with a deployment locking mechanism. Such a deployment locking mechanism may prevent the accidental initiation of deployment by fixing the carriage assembly to the handle housing while the lock is in a locked position. Such a deployment lock may have a structure similar to the deployment locks shown and described in co-pending U.S. patent application Ser. No. 13/212,442, filed Aug. 18, 2011. 
     Many modifications to the various features of the delivery devices described herein are possible. For example, modifications may be made to the atraumatic tip  14  of the catheter assembly  16 .  FIG. 12A  shows a cross-section of the atraumatic tip  14  of  FIG. 1A . The atraumatic tip  14  may have a lumen  26   a  extending longitudinally therethrough. The distal end of the inner shaft  26  may be inserted partially into the lumen  26   a , and it may be held in place with an adhesive, ultrasonic welding, or other technique. 
       FIG. 12B  shows a cross-section of an atraumatic tip  14   a  according to an alternate embodiment. An insert  15  may be assembled to the distal end of the inner shaft  26   b . The insert  15  may have a plurality of ribs  15   a  that extend continuously or discontinuously around the circumference of the insert. The use of the insert  15  provides a strong connection between the tip  14  and the inner shaft  26   b , and such use enables the inner shaft to extend by a lesser amount into the tip, such that the tip may be flexible along a greater extent of its length. 
     There are many ways that the atraumatic tip  14   a , the insert  15 , and the inner shaft  26   b  may be assembled with one another. In a preferred arrangement, the inner shaft  26   b  has a flared portion  26   c  at its distal end. The diameter of this flared portion preferably is greater than the diameter of a lumen  17  through the insert  15 . The insert  15  may be assembled over the proximal end of the inner shaft  26   b  and slid distally until it contacts the flared portion  26   c . Then, the atraumatic tip  14   a  may be molded around the insert  15  and the distal end of the inner shaft  26   b , thereby locking the insert in place. As a result, the inner shaft  26   b  is prevented from moving proximally by the interference between the flared portion  26   c  and the distal end of the insert  15 , and it is prevented from moving distally by the tip material molded around the flared portion, thus providing a secure attachment of the tip to the inner shaft. 
     The atraumatic tips  14  and  14   a  may be tapered along their lengths. For example, the atraumatic tip  14  may have a straight tapered surface  26   d , and the atraumatic tip  14   a  may have a concavely tapered surface  26   e . The radius of curvature of the tapered surface  26   e  may be about 4.0 to about 5.0 inches, with a radius of curvature of about 4.292 inches being preferred. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. 
     It will be appreciated that the various dependent claims and the features set forth therein can be combined in different ways than presented in the initial claims. It will also be appreciated that the features described in connection with individual embodiments may be shared with others of the described embodiments.