Patent Publication Number: US-10758352-B2

Title: Transcatheter delivery system with two modes of actuation

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of the filing date of U.S. Provisional Patent Application No. 62/429,361 filed Dec. 2, 2016, the disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to a delivery system for heart valve replacement and, in particular, for replacement of collapsible prosthetic heart valves. More particularly, the present disclosure relates to delivery systems for collapsible prosthetic heart valves that may be repositioned during the deployment procedure. 
     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 For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.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 retained the valve in the collapsed condition, making resheathing difficult. In order for the user to be able to more readily resheathe a valve, it is preferable that the valve be only partially deployed, with a portion of the valve still 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 some 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. Moreover, it is difficult during prosthetic heart valve delivery to determine whether a valve assembly will function as intended without full deployment of the heart valve. Due to anatomical variations between patients, a fully deployed heart valve may need to be removed from the patient if it appears that the valve is not functioning properly. Removing a fully deployed heart valve increases the length of the procedure and increases the risk of infection and/or damage to heart tissue. 
     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 disclosure may address one or more of these needs. 
     SUMMARY OF THE INVENTION 
     In some embodiments, a delivery device for a collapsible prosthetic heart valve, the delivery device includes an inner shaft, a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve, the inner shaft and the distal sheath being slidable relative to one another, and a handle including a frame, a deployment actuator, a lever, and a hub, each of the deployment actuator, the lever, and the hub being independently capable of opening and closing the compartment, a resheathing lock configured to alert a user of a position of the distal sheath relative to the inner shaft and to impede movement of the distal sheath relative to the frame, and an indicator disposed on the frame and capable of showing an extent of deployment of the prosthetic heart valve. 
     In some embodiments, a delivery device for a collapsible prosthetic heart valve, the delivery device includes an inner shaft, a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve, the inner shaft and the distal sheath being movable relative to one another, and a handle including a frame, a deployment actuator, a lever, and a hub, each of the deployment actuator, the lever, and the hub being independently capable of opening and closing the compartment. 
     In some embodiments, a delivery device for a collapsible prosthetic heart valve, the delivery device includes an inner shaft, a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, the compartment being adapted to receive the prosthetic heart valve, the inner shaft and the distal sheath being slidable relative to one another, and a handle including a frame, a deployment actuator, a lever, and a visual indicator disposed on the frame and capable of showing an extent of deployment of the prosthetic heart valve, the visual indicator being responsive to actuation of the deployment actuator and being responsive to actuation of the lever. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present delivery system are disclosed herein with reference to the drawings, wherein: 
         FIG. 1  is a side elevational view of a prior art collapsible prosthetic heart valve, showing the valve assembly attached to the stent; 
         FIG. 2A  is a highly schematic side elevational view showing partial deployment of a collapsible prosthetic heart valve with high placement according to the prior art; 
         FIG. 2B  is a highly schematic side elevational view showing partial deployment of a collapsible prosthetic heart valve with low placement according to the prior art; 
         FIG. 3A  is side view of an operating handle for a transfemoral delivery device for a collapsible prosthetic heart valve, shown with a side elevational view of the distal portion of a transfemoral catheter assembly; 
         FIGS. 3B-D  are side, bottom and top views of the operating handle of  FIG. 3A ; 
         FIG. 3E  is side view of the operating handle of  FIG. 3A  showing the lever in the use position; 
         FIG. 4  is an enlarged perspective view of the carriage assembly of the handle of  FIG. 3A ; 
         FIG. 5A  is an enlarged schematic representation of a portion of the threaded rod of the carriage assembly of the operating handle; 
         FIG. 5B  is an enlarged schematic representation of a coupling mechanism between a lever and a threaded rod; 
         FIG. 6  shows a deployment indicator for use with the operating handle; and 
         FIGS. 7A-B  are schematic illustrations showing the use of the operating handle. 
     
    
    
     Various embodiments of the present disclosure will now be described with reference to the appended drawings. It is to be appreciated that these drawings depict only some embodiments of the disclosure and are therefore not to be considered limiting of its scope. 
     DETAILED DESCRIPTION 
     As used herein in connection with prosthetic heart valves, the term “proximal” refers to the end of the heart valve closest to the heart when the heart valve is implanted in a patient, whereas the term “distal” refers to the end of the heart valve farthest from the heart when the heart valve is implanted in a patient. When used in connection with devices for delivering a prosthetic heart valve into a patient, the terms “proximal” and “distal” are to be taken as relative to the user of the 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. 
       FIG. 1  shows a collapsible prosthetic heart valve  200  according to the prior art. The prosthetic heart valve  200  is designed to replace the function of a native aortic valve of a patient. Examples of collapsible prosthetic heart valves are described in International Patent Application Publication No. WO/2009/042196; and U.S. Pat. Nos. 7,018,406 and 7,329,278, the disclosures of all of which are hereby incorporated herein by reference. As discussed in detail below, the prosthetic heart valve has an expanded condition and a collapsed condition. Although the delivery system is described herein in connection with its use to deliver a prosthetic heart valve for replacing a native aortic valve, the delivery system is not so limited, and may be used to deliver prosthetic valves for replacing other types of native or prosthetic cardiac valves. 
     Prosthetic heart valve  200  includes an expandable stent  202  which may be formed from any biocompatible material, such as metals, synthetic polymers or biopolymers capable of functioning as a stent. Stent  202  extends from a proximal or annulus end  230  to a distal or aortic end  232 , and includes an annulus section  240  adjacent the proximal end and an aortic section  242  adjacent the distal end. The annulus section  240  has a relatively small cross-section in the expanded condition, while the aortic section  242  has a relatively large cross-section in the expanded condition. Preferably, annulus section  240  is in the form of a cylinder having a substantially constant diameter along its length. A transition section  241  may taper outwardly from the annulus section  240  to the aortic section  242 . Each of the sections of the stent  202  includes a plurality of cells  212  connected to one another in one or more annular rows around the stent. For example, as shown in  FIG. 1 , the annulus section  240  may have two annular rows of complete cells  212  and the aortic section  242  and transition section  241  may each have one or more annular rows of partial cells  212 . The cells  212  in the aortic section  242  may be larger than the cells  212  in the annulus section  240 . The larger cells in the aortic section  242  better enable the prosthetic valve  200  to be positioned without the stent structure interfering with blood flow to the coronary arteries. 
     Stent  202  may include one or more retaining elements  218  at the distal end  232  thereof, the retaining elements being sized and shaped to cooperate with female retaining structures provided on the deployment device. The engagement of retaining elements  218  with the female retaining structures on the deployment device helps maintain prosthetic heart valve  200  in assembled relationship with the deployment device, minimizes longitudinal movement of the prosthetic heart valve relative to the deployment device during unsheathing or resheathing procedures, and helps prevent rotation of the prosthetic heart valve relative to the deployment device as the deployment device is advanced to the target location and during deployment. 
     The prosthetic heart valve  200  includes a valve assembly  204  positioned in the annulus section  240 . Valve assembly  204  includes a cuff  206  and a plurality of leaflets  208  which collectively function as a one-way valve. The commissure between adjacent leaflets  208  may be connected to commissure features  216  on stent  202 .  FIG. 1  illustrates a prosthetic heart valve for replacing a native tricuspid valve, such as the aortic valve. Accordingly, prosthetic heart valve  200  is shown in  FIG. 1  with three leaflets  208 , as well as three commissure features  216 . As can be seen in  FIG. 1 , the commissure features  216  may lie at the intersection of four cells  212 , two of the cells being adjacent one another in the same annular row, and the other two cells being in different annular rows and lying in end-to-end relationship. Preferably, commissure features  216  are positioned entirely within annulus section  240  or at the juncture of annulus section  240  and transition section  241 . Commissure features  216  may include one or more eyelets which facilitate the suturing of the leaflet commissure to the stent. However, it will be appreciated that the prosthetic heart valves may have a greater or lesser number of leaflets and commissure features. Additionally, although cuff  206  is shown in  FIG. 1  as being disposed on the luminal surface of annulus section  240 , it is contemplated that the cuff may be disposed on the abluminal surface of annulus section  240 , or may cover all or part of either or both of the luminal and abluminal surfaces of annulus section  240 . Both the cuff  206  and the leaflets  208  may be wholly or partly formed of any suitable biological material or polymer. 
     In operation, a prosthetic heart valve, including the prosthetic heart valve described above, may be used to replace a native heart valve, such as the aortic valve, a surgical heart valve or a heart valve that has undergone a surgical procedure. The prosthetic heart valve may be delivered to the desired site (e.g., near a native aortic annulus) using any suitable delivery device, including the delivery devices described in detail below. During delivery, the prosthetic heart valve is disposed inside the delivery device in the collapsed condition. The delivery device may be introduced into a patient using a transfemoral, transapical or transseptal approach. Once the delivery device has reached the target site, the user may deploy the prosthetic heart valve. Upon deployment, the prosthetic heart valve expands into secure engagement within the native aortic annulus. When the prosthetic heart valve is properly positioned inside the heart, it works as a one-way valve, allowing blood to flow in one direction and preventing blood from flowing in the opposite direction. 
     In a prosthetic heart valve, the valve assembly may be spaced from the distal or aortic end of the stent by a distance that enables deployment of the heart valve by an amount sufficient for the valve leaflets of the prosthetic valve to operate as intended, while the distal end of the stent remains captured by the delivery device. More particularly, as will be explained further below, the annulus end of the prosthetic heart valve may be deployed first, while the aortic end of the prosthetic heart valve remains at least partially covered by a distal sheath of the delivery device. The annulus portion of the prosthetic heart valve may be deployed so that the entirety of the valve leaflets, up to and including the commissures, is deployed and fully operational. By deploying the prosthetic heart valve in this manner, the user can determine whether the valve leaflets are properly positioned relative to the native valve annulus, and whether the valve is functioning properly. If the user determines that the positioning and operation of the valve are acceptable, the remainder of the valve may be deployed. However, if it is determined that the leaflet position is improper or that the valve is not functioning properly, the user may resheathe the valve and either reposition it for redeployment, or remove it entirely from the patient. This can be particularly important in very high risk patients who would typically be recipients of these types of valves, because of the nature of their condition and the impact that may have on the shape and/or condition of the native valve and valve annulus. 
     As is shown in  FIG. 1 , in one embodiment the entirety of valve assembly  204 , including the leaflet commissures, is positioned in the annulus section  240  of stent  202 . When opened, the leaflets may extend further into the transition section  241  or may be designed such that they remain substantially completely within the annulus section. That is, substantially the entirety of valve assembly  204  is positioned between the proximal end  230  of stent  202  and the commissure features  216 , and none of the valve assembly  204  is positioned between commissure features  216  and the distal end  232  of the stent. Indeed, in some embodiments, the valve can be designed such that, upon partial deployment, the commissure features are fully exposed, oriented generally parallel to the direction of blood flow, and at or near their actual radially expanded position (but not necessarily their eventual position relative to the annulus), such that the leaflets can operate substantially as they would when the valve is fully deployed, even though enough of the stent is still retained within the delivery device or sheath to permit resheathing. 
     In a preferred arrangement, the distance between commissure features  216  and the distal end  232  of stent  202  will be about two-thirds of the length of the stent from the proximal end  230  to the distal end. This structural arrangement provides advantages in the deployment of prosthetic valve  200  as will be discussed in more detail with reference to  FIGS. 2A and 2B . By having the entirety of valve assembly  204  positioned within annulus section  240 , and by having a sufficient distance between commissure features  216  and the distal end  232  of stent  202 , the valve assembly and commissures will not impede blood flow into the coronary arteries and will not interfere with access thereto during cardiac intervention, such as angiography, annuloplasty or stent placement. 
     Further, it is possible to partially deploy prosthetic valve  200  so that the valve assembly  204  thereof is able to fully function in its intended position in the native valve annulus, while a sufficient amount of the aortic section  242  is retained within the delivery device should resheathing become necessary. In other words, as will be explained in more detail below, the user may withdraw the distal sheath of the delivery device to gradually expose prosthetic valve  200 , beginning at the proximal end  230 . Continued withdrawal of the distal sheath will expose a greater extent of the prosthetic valve until the entire annulus section  240  and valve assembly  204  have been exposed. Upon exposure, these portions of the prosthetic valve will expand into engagement with the native valve annulus, entrapping the native valves, except for a small portion immediately adjacent the free end of the distal sheath which will be constrained by the distal sheath from fully expanding. 
     However, once the distal sheath has been withdrawn to expose a sufficient portion of the aortic section  242 , the annulus section  240  will be able to fully expand and valve assembly  204  will be able to function in the same manner as if the entirety of prosthetic valve  200  had been deployed. At this juncture, it will be possible for the user to ascertain whether annulus section  240  and valve assembly  204  have been properly positioned relative to the native valve annulus, and whether the valve assembly is functioning properly. 
     If the position and operation of valve assembly  204  are acceptable, the distal sheath may be withdrawn further to deploy the remainder of prosthetic valve  200 . On the other hand, if the positioning or operation of valve assembly  204  are unacceptable, the user may advance the distal sheath to resheathe the prosthetic valve, reposition the valve and initiate the deployment procedure anew. And if it is determined that the valve is not functioning properly, it can be withdrawn from the patient and a new valve introduced. 
     It will be appreciated from the foregoing that the position of the leaflets  208  within the stent  202  can affect the valve functioning during partial deployment.  FIG. 2A  illustrates a valve assembly  204  with high placement, while  FIG. 2B  illustrates a valve assembly with low placement. As used herein, the phrase “high placement” of a valve assembly refers to locating the valve assembly within the transition section  241  of the stent  202 , or within the portion of the annulus section  240  closest to the transition section. The phrase “low placement” of a valve assembly refers to locating the valve assembly closer to the proximal end  230  of the stent  202  and entirely within the annulus section  240  thereof, such that the leaflets  208  are substantially disposed within the annulus section  208 . 
     As seen in  FIG. 2A , during partial deployment the annulus end of the heart valve  200  is unsheathed and allowed to expand. The distal end  232 , including the aortic section  242 , remains partially sheathed and coupled to the delivery device. Operation of the delivery device is described below in more detail with reference to  FIGS. 3A-7B . Turning back to  FIG. 2A , it will be appreciated that high placement of valve assembly  204  will cause the valve assembly to not be fully deployed when heart valve  200  is only partially deployed, thereby affecting leaflet function. Specifically, since the commissure features  216  are located closer to or within the transition section  241 , they do not reach their fully expanded positions. As such, the leaflets  208  remain partially closed at this stage of deployment. Because of the location of the commissure features  216  and the leaflets  208 , the valve assembly  204  cannot be tested during partial deployment. Instead, the user must unsheathe a portion of the aortic section  242  as well, which may pose problems if the valve assembly  204  is to be resheathed and redeployed. 
     In contrast to the prosthetic heart valve of  FIG. 2A , the heart valve  200  of  FIG. 2B  exhibits low placement of the valve assembly  204  within the annulus section  240 . Low placement of the valve assembly  204  enables the valve assembly to fully deploy when heart valve  200  is only partially deployed. As such, leaflets  208  reach their fully expanded and open positions during partial deployment and are able to function near normally, enabling a better assessment of the valve&#39;s functioning and final placement within the actual anatomy. Thus, if it appears that the valve needs to be moved, the heart valve  200  may be easily resheathed and repositioned. This concept is beneficial when dealing with less than ideal anatomical configurations. 
     The shape of the stent  202  during partial deployment will also affect the valve  204 . If the stent shape is such that, while still partially retained by the sheath, it cannot open sufficiently to allow operation of the valve, it may not be possible to fully assess the operation of the valve in its intended placement position. Moreover, the height of the valve commissure features  216  relative to the proximal end  230  of the valve will affect the valve function. The lower the commissure features  216 , meaning the closer to the proximal end  230 , the more they will expand outwardly and the valve leaflets will be able to open during partial deployment, creating a flow passageway through the leaflets which approaches that of a fully deployed valve. 
     A transfemoral or transapical delivery device may be used to partially deploy the prosthetic heart valve such that an assessment may be made regarding flow through the valve and adequacy of coaptation. If, after the annulus section is unsheathed and the valve is tested, it is found that the valve needs to be repositioned, the annulus section may be resheathed and the valve redeployed as necessary. 
     Turning now to  FIGS. 3A-E , an exemplary transfemoral delivery device  1010  for a collapsible prosthetic heart valve (or other types of self-expanding collapsible stents) has a catheter assembly  1016  for delivering the heart valve to and deploying the heart valve at a target location, and an operating handle  1020  for controlling deployment of the valve from the catheter assembly. The delivery device  1010  extends from a proximal end  1012  to a distal tip  1014 . The catheter assembly  1016  is adapted to receive a collapsible prosthetic heart valve (not shown) in a compartment  1023  defined around an inner shaft  1026  and covered by a distal sheath  1024 . The inner shaft  1026  extends through the operating handle  1020  to the distal tip  1014  of the delivery device, and includes a retainer  1025  affixed thereto at a spaced distance from distal tip  1014  and adapted to hold a collapsible prosthetic valve in the compartment  1023 . 
     The distal sheath  1024  surrounds the inner shaft  1026  and is slidable relative to the inner shaft such that it can selectively cover or uncover the compartment  1023 . The distal sheath  1024  is affixed at its proximal end to an outer shaft  1022 , the proximal end of which is connected to the operating handle  1020  in a manner to be described. The distal end  1027  of the distal sheath  1024  abuts the distal tip  1014  when the distal sheath fully covers the compartment  1023 , and is spaced apart from the distal tip  1014  when the compartment  1023  is at least partially uncovered. 
     The operating handle  1020  is adapted to control deployment of a prosthetic valve located in the compartment  1023  by permitting a user to selectively slide the outer shaft  1022  proximally or distally relative to the inner shaft  1026 , or to slide the inner shaft  1026  relative to the outer shaft  1022 , thereby respectively uncovering or covering the compartment with the distal sheath  1024 . Operating handle  1020  includes frame  1030  which extends from a proximal end  1031  to a distal end  1035  and includes a top frame portion  1030   a  and a bottom frame portion  1030   b . The proximal end of the inner shaft  1026  is coupled to a hub  1100 , that, unless moved manually by a user has a fixed position relative to frame  1030 , and the proximal end of the outer shaft  1022  is affixed to a carriage assembly  1040  ( FIG. 4 ) that is slidable within the operating handle along a longitudinal axis of the frame  1030 , such that a user can selectively slide the outer shaft relative to the inner shaft by sliding the carriage assembly relative to the frame. Alternatively, hub  110  may be used to withdraw inner shaft  1026  distally out from the distal sheath to uncover the compartment or proximally into distal sheath  1024  to cover the compartment, as will be discussed in greater detail below. 
     A first mechanism for covering and uncovering the compartment  1023  will be referred to a “fine” technique as covering and uncovering occurs slowly with a high degree of precision. To allow for this technique, frame  1030  defines an elongated space  1035  in which carriage assembly  1040  may travel ( FIG. 5A ). The elongated space preferably permits the carriage assembly  1040  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  1024  can be fully retracted off of the prosthetic valve. 
     The carriage assembly  1040  includes a main body  1041  and a threaded rod  1036  extending proximally therefrom in a direction parallel to the longitudinal axis of the frame  1030 . The threaded rod  1036  preferably is longer than the anticipated maximum travel distance of the carriage assembly  1040  within the elongated space  1035  (e.g., at least about 50 mm), such that the threaded rod does not fully withdraw from the elongated space  1035  during deployment of the prosthetic valve. 
     A deployment actuator  1021 , shown in  FIGS. 3A-D  as a wheel whose central axis of rotation is parallel to the longitudinal axis of frame  1030 , protrudes through apertures  1032   a  and  1032   b  from the top and bottom of frame  1030  is fixedly coupled to a first gear  1038  so that rotation of actuator  1021  causes a corresponding rotation of gear  1038  ( FIG. 5A ). Gear  1038 , in turn, is threadedly engaged with threaded rod  1036 . Thus, gear  1038  convert rotation of deployment actuator  1021  into longitudinal translation of threaded rod  1036  in the direction of arrows T 1  and T 2  and a corresponding translation of main body  1041 . Apertures  1032   a  and  1032   b , however, captures actuator  1021  and maintain it in a fixed longitudinal position relative to frame  1030 . Hence, rotation of actuator  1021  in one direction (either clockwise or counterclockwise depending on the orientation of the threads on the threaded rod  1036 ) causes the carriage assembly  1040  to translate proximally within the elongated space  1035 . 
     As outer shaft  1022  is fixedly connected to carriage assembly  1040 , translation of the carriage assembly results in a longitudinal translation of outer shaft  1022  and with it distal sheath  1024 . Thus, deployment actuator  1021  is configured to provide for fine movement of distal sheath  1024  for deployment and recapture of the prosthetic heart valve. The coarseness of the threads in threaded rod  1036  as well as their pitch will determine how fine this movement will be, i.e., how far the threaded rod will travel longitudinally with each rotation of actuator  1021 . As deployment actuator  1021  protrudes from the top and bottom of frame  1030  approximately halfway between the proximal and distal ends of the handle  1020 , a user may readily rotate the actuator with his or her thumb and/or index finger ( FIG. 7A ). 
     Optionally, handle  1020  further includes a resheathing lock  1043  adapted to prevent any longitudinal translation of main body  1041  within the frame  1030 , thereby preventing a user from accidentally initiating deployment of the prosthetic valve ( FIG. 3D ). Resheathing lock  1043  may be coupled to main body  1041  so as to move along the elongated space  1035  with the carriage assembly  1040 . The resheathing lock  1043  may include a pin  1044  which extends laterally from main body  1041  toward frame  1030 . Pin  1044  may be hollow and a spring  1045  may be assembled therein. In an unlocked condition of resheathing lock  1043 , pin  1044  will be in a compressed condition with its free end contacting an interior surface of frame  1030  and spring  1045  compressed against main body  1041 . As the user rotates deployment actuator  1021 , outer shaft  1022  is pulled back and with it distal sheath  1024  to uncover a portion of compartment  1023 . As this process proceeds, carriage assembly  1040  will move proximally within frame  1030 , with free end of pin  1044  sliding along the inner surface of the frame in a compressed condition. This process may continue until a predetermined position past which resheathing is no longer possible. When this predetermined position is reached, pin  1044  will be aligned with the aperture in the frame and the biasing force will put the pin outwardly through the aperture until the pin protrudes from frame  1030  ( FIG. 5A ), providing a visual indicator to the user that resheathing is no longer possible past this predetermined position. When this occurs, this engagement of pin  1044  through frame  1030  will prevent further retraction of distal sheath  1024  and will provide a visual indicator to the user to check the position and function of the prosthetic heart valve before full deployment occurs. In order to further translate the carriage assembly  1040 , the user must press pin  1044  inwardly until the free end of the pin slides inside the frame to confirm that further uncovering of compartment  1023  is desired (i.e., that the user wishes to fully deploy the prosthetic heart valve in its current position). 
     The initial distance that the carriage assembly  1040  can travel before actuating resheathing lock  1043  may depend on the structure of the particular prosthetic valve to be deployed. Preferably, the initial travel distance of the carriage assembly  1040  is about 3 mm to about 5 mm less than the crimped valve length (e.g., about 3 mm to 5 mm of the valve may remain covered to permit resheathing). Alternatively, the initial travel distance of the carriage assembly  1040  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. In other arrangements, the initial distance that the carriage assembly  1040  can travel can be determined as a percentage of the length of the prosthetic valve and/or of the compartment  1023 , including, for example, 50%, 60%, 70%, 75%, 85%, or 95%. Thus, resheathing lock  1043  may allow uncovering of compartment  1023  up to a maximum distance or percentage, and allow further uncovering only after the user has pressed on laterally projecting pin  1044  to confirm that additional release (e.g., full release of the prosthetic heart valve) is desired. 
     Operating handle  1020  may be configured to provide a second “fine technique” for covering or recapturing the heart prosthetic heart valve. As shown in  FIGS. 3A-E , operating handle  1020  may include an elongated lever  1400  disposed on bottom frame portion  1030   b  between proximal end  1031  and deployment actuator  1021 . Lever  1400  may include a series of lateral ribs  1401  to increase a user&#39;s grip. Lever  1400  may be hingedly connected to one end of frame  1030  and configured to pivot between an inactive position in which lever  1400  is substantially parallel with frame  1030  and docked flush therewith ( FIG. 3A ), and a use position in which lever  1400  is angled with respect to frame  1030  ( FIG. 3E ). For example, lever  1400  may form an angle “a” of approximately 10 to 45 degrees with respect to the longitudinal axis of frame  1030 . Handle  1020  may include a release mechanism  1402  which allows lever  1400  to move from the inactive position to the use position. In one simple example, release mechanism  1402  includes a clip  1402   a  on lever  1400  that mates with groove  1402   b  on the frame, clip  1402   a  being engaged with groove  1402   b  in the inactive position of lever  1400 . Pushing clip  1402   a  while pivoting lever  1400  away from frame  1030  may release clip  1402   a  from groove  1402   b  and place the lever in the use position. It will be understood that other configurations and examples are possible to release lever  1400  and allow it to transition to the use position from the inactive position. 
     Lever  1400  may be coupled to one or more curved rails  1403  having teeth  1404  along its length. Teeth  1404  may in turn be engaged with pinion gear  1410  supported by plate  1412 , ( FIG. 5B ). Pinion gear  1410  may in turn be engaged with teeth of rack  1411  extending parallel to longitudinal axis of frame  1030 . Rack  1411  may be connected to threaded rod  1036 . Squeezing of lever  1400  from the use position toward frame  1030  results in rotation of pinion gear  1410  in the distal direction, which in turn results in translation of rack  1411 . Movement of rack  1411  results in translation of threaded rod  1036  and main body  1041  to cover a prosthetic heart valve. Teeth  1404  and pinion gear  1410  may be provided with a ratchet-type action such that multiple squeezes of lever  1400  result in further advancement of threaded rod  1036 . Thus, squeezing of lever  1400  against frame  1030  causes movement of carriage assembly  1040  in one direction only—in this case, distally to advance distal sheath  1024  and cover the prosthetic heart valve. 
     Optionally, plate  1412  may include a boss  1413  that protrudes through an aperture in frame  1030 . Plate  1412  may be mounted to frame  1030  so as to be slidable in a direction transverse to the longitudinal axis of the frame. Depressing boss  1413  will cause plate  1412  to slide transversely to the longitudinal axis of frame  1030  until pinion gear  1410  is disengaged from the teeth of rack  1411 . Additionally, handle  1020  may include a split nut mechanism that decouples deployment actuator  1021  from threaded rod  1036 . One example of a split nut mechanism is described in U.S. patent application Ser. No. 13/788,820, filed Mar. 7, 2013, the disclosure of which is hereby incorporated herein by reference as if fully set forth herein. Using such a mechanism a user may toggle a switch on the handle between a first position, located near the proximal end of the device where lever  1400  is engaged and a second position, located toward the distal end of the device where deployment actuator  1021  engages threaded rod  1036 . In one example, only one of lever  1400  and deployment actuator  1021  is in a working state at a time. Thus, deployment actuator  1021  becomes ineffective when lever  1400  is used and vice versa. Moreover, returning lever  1400  from the use position back to the inactive position recouples deployment actuator  1021  with gear  1038  so that the use of deployment actuator is again possible. 
     Additionally, a “coarse technique,” may be used to cover and uncover compartment  1023  more quickly and with less precision than the fine technique described above. Specifically, hub  1100  may be coupled to the proximal end of inner shaft  1026  and may be capable of moving the inner shaft relative to frame  1030  to facilitate opening and closing of the compartment  1023 . This coarse movement may be used when no prosthetic heart valve is present in the compartment, such as, for example, when the compartment is to be opened prior to loading the prosthetic heart valve therein, and when the compartment is to be closed after the valve has been fully deployed. A mechanical lock  1110  may couple hub  1100  to frame  1030  to prevent accidental movement of inner shaft  1026  while a prosthetic heart valve is loaded in compartment  1023 . For example, hub  1100  and a portion of frame  1030  may be threadedly engaged such that a small rotation of the hub relative to the frame is required to release the hub from the frame. After lock  1110  has been disengaged, hub  1100  may be used to quickly cover or uncover the compartment. Movement of inner shaft  1026  relative to outer shaft  1022  may open and close the compartment. Thus, pushing hub  1100  moves inner shaft  1026  distally relative to outer shaft  1022  to open the compartment, and pulling hub  1100  proximally relative to outer shaft  1022  to closes the compartment. 
     Optionally, an indicator window  1500  ( FIG. 6 ) may be disposed on top of frame  1030  and include a series of increments  1510  showing a percent or extent of deployment of the prosthetic heart valve. A scrolling bar  1520  may move along window  1500  past the series of increments  1510  as deployment continues to illustrate to the user the extent to which the prosthetic heart valve has been deployed. As illustrated, scrolling bar  1520  indicates that a prosthetic heart valve is approximately 37.5% deployed. Indicator window  1500  further includes a critical indicator  1530  showing the position past which resheathing is no longer possible. Resheathing lock  1043  may be activated as scrolling bar  1520 , which is coupled to main body  1041 , reaches position  1530 . 
     The operation of the delivery device  1010  to deploy a prosthetic valve will now be described. Device  1010  may be shipped with outer shaft  1022  in its proximal-most position. Hub  1100  may also be initially shipped in a proximal-most position, the hub being spaced away from the proximal end of frame  1030  as shown in  FIG. 3A . To load the delivery device  1010  with a collapsible prosthetic valve, a user can push hub  1100  toward the proximal end  1031  of frame  1030  (and advance inner shaft  1022 ) to expose the compartment  1023  ( FIG. 7B ), thread the inner shaft  1026  through the valve, couple the valve to the retainer  1025 , and slide the distal sheath back over compartment to compress or crimp the valve by rotating deployment actuator  1021  ( FIG. 7A ) or using lever  1400 , until the valve is fully covered in its compressed state by the distal sheath and the compartment is closed. In this starting condition, the handle  1020  will be in an initial state with the carriage assembly  1040  at its distalmost position within the frame  1030 , the resheathing lock  1043  is in an unlocked state with pin  1044  disposed within frame  1030 , the hub  1100  is against the proximal end  1031  of frame  1030 , and the deployment indicator will show 0% deployment. 
     To use the operating handle  1020  to deploy the prosthetic valve, the user can rotate the deployment actuator  1021  ( FIG. 7A ), causing the carriage assembly  1040  to slide proximally within the elongated space  1035  in frame  1030 . Because the distal sheath  1024  is affixed to the outer shaft  1022 , which in turn is affixed to the carriage assembly  1040 , sliding the carriage assembly proximally relative to the frame will cause the distal sheath to move proximally. Since the inner shaft  1026  is at this point fixed to frame  1030 , it will not move. Hence, the proximal movement of distal sheath  1024  relative to inner shaft  1026  will uncover the compartment  1023 , thereby exposing and initiating deployment of the valve located therein. 
     Movement of the carriage assembly  1040  proximally may continue only until the resheathing lock  1043  is actuated and pin  1044  protrudes from frame  1030 . At this point, the distal sheath  1024  will not be fully withdrawn from the compartment  1023 , and the prosthetic valve will not be fully deployed. Moreover, indicator window  1500  will show that scrolling bar  1520  has reached critical indicator  1530  and that any further uncovering of the compartment will fully deploy the prosthetic heart valve and prevent its resheathing. 
     When the deployment procedure has reached this juncture, the user can evaluate the position of the valve and determine whether the annulus end of the valve is properly aligned relative to the patient&#39;s native valve annulus. If repositioning is desired, the user may resheathe the valve by using deployment actuator  1021  to slide the carriage assembly  1040  distally within the frame  1030 , thereby moving the distal sheath  1024  distally over the compartment  1023  and over the partially deployed valve to recollapse the expanded portion of the valve. 
     Alternatively, if the user prefers the use of lever  1400  to deployment actuator  1021  to resheathe the prosthetic heart valve, the user may actuate release mechanism  1402  by decoupling clip  1402   a  from groove  1402   b  to pivot the lever  1400  from the inactive position in which it is flush with the frame to the use position in which it is angled with respect to the frame ( FIG. 7B ). In some examples, such as those using a split nut mechanism, the user may place lever  1400  in its use position and use a switch to suspend the function of deployment actuator  1021  by decoupling the deployment actuator from threaded rod  1036 . The user may then repeatedly squeeze lever  1400  against frame  1030  to incrementally actuate threaded rod  1036  and push distal sheath distally to cover the prosthetic heart valve. In some examples, multiple squeezes (e.g., four or five) may be required to completely cover prosthetic heart valve. Alternatively, lever  1400  may be configured so that one squeeze completely covers the prosthetic heart valve. Once the valve has been completely covered (i.e., compartment  1023  is closed), the user may return lever  1400  to is inactive position by coupling clip  1402   a  with groove  1402   b . If the function of deployment actuator  1021  has been suspended, a switch may again be used to engage the split nut mechanism and couple actuator  1021  to the threaded rod so that use of deployment actuator  1021  is possible. With the valve resheathed, the user can reposition the catheter assembly  1016  and commence the deployment procedure once again using deployment actuator  1021 . 
     Once the valve has been properly positioned relative to the aortic annulus, the user may complete the deployment process. To do so, the user presses pin  1044  through the aperture in the frame, releasing lock  1043 , which frees carriage assembly  1040  to continue its movement proximally within the frame  1030 . The user can complete the deployment of the valve by continuing to slide the carriage assembly  1040  proximally, for example, by rotating the deployment actuator  1021 . When the valve has been fully unsheathed, the stent portion of the valve self-expands and disengages from the retainer  1025 , thereby releasing the valve from the catheter assembly  1016 . Hub  1100  may once again be used to quickly cover the compartment and the delivery device may be removed from the patient. 
     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. 
     In summary, the disclosure herein recites multiple embodiments to summarize the foregoing. Described herein is a delivery device for a collapsible prosthetic heart valve. The delivery device may include an inner shaft, a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, and a handle including a frame, a deployment actuator, a lever, and a hub. The compartment may be adapted to receive the prosthetic heart valve. The inner shaft and the distal sheath may be slidable relative to one another. Each of the deployment actuator, the lever, and the hub may be independently capable of opening and closing the compartment. The handle may include a resheathing lock configured to alert a user of a position of the distal sheath relative to the inner shaft and to impede movement of the distal sheath relative to the frame. The handle may include and an indicator disposed on the frame and capable of showing an extent of deployment of the prosthetic heart valve; and/or 
     the lever may be pivotable from a first inactive position in which the lever is relatively close to the frame, and a use position in which the lever is spaced apart from the frame; and/or 
     the lever may form an angle of between 10 and 45 degrees with respect to a longitudinal axis of the frame in the use position; and/or 
     the deployment actuator may include a wheel having an axis of rotation disposed parallel to a longitudinal axis of the frame; and/or 
     operation of the deployment actuator may longitudinally translate the distal sheath relative to the inner shaft to cover or uncover the compartment; and/or 
     the hub may be attached to a proximal end of the inner shaft such that movement of the hub longitudinally toward the frame translates the inner shaft to uncover the compartment and movement of the hub longitudinally away from the frame translates the inner shaft to cover the compartment; and/or 
     the delivery device may include a carriage assembly having a threaded rod, the deployment actuator being operatively coupled to the threaded rod so that rotation of the deployment actuator results in translation of the carriage assembly along a longitudinal axis of the frame; and/or 
     the lever may be operatively coupled to the carriage assembly such that movement of the lever relative to the frame results in translation of the carriage assembly in a direction parallel to a longitudinal axis of the frame; and/or 
     the resheathing lock may include a pin having a first position in which the pin is disposed within the frame, and a second position in which the pin protrudes from the frame. 
     Also described herein is another delivery device for a collapsible prosthetic heart valve. The delivery device may include an inner shaft, a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, and a handle including a frame, a deployment actuator, a lever, and a hub. The compartment may be adapted to receive the prosthetic heart valve. The inner shaft and the distal sheath may be movable relative to one another. Each of the deployment actuator, the lever, and the hub may be independently capable of opening and closing the compartment; and/or 
     the delivery device may include a resheathing lock configured to visually alert a user of a predetermined position of the distal sheath relative to the inner shaft and to impede movement of the distal sheath relative to the frame; and/or 
     the resheathing lock may include a pin having a first position in which the pin is disposed within the frame, and a second position in which the pin protrudes from the frame; and/or 
     movement of the resheathing lock may release the distal sheath for movement relative to the frame; and/or 
     the delivery device may include an indicator disposed on the frame and capable of showing an extent of deployment of the prosthetic heart valve; and/or 
     the indicator may include a window in the frame having a series of increments, a critical indicator showing a position past which resheathing of the prosthetic heart valve is no longer possible, and a scrolling bar to illustrate the extent of deployment of the prosthetic heart valve. 
     Also described herein is yet another delivery device for a collapsible prosthetic heart valve. The delivery device may include an inner shaft, a distal sheath disposed about a portion of the inner shaft and forming a compartment with the inner shaft, and a handle including a frame, a deployment actuator, a lever, and a visual indicator. The compartment may be adapted to receive the prosthetic heart valve. The inner shaft and the distal sheath may be slidable relative to one another. The visual indicator may be disposed on the frame and capable of showing an extent of deployment of the prosthetic heart valve. The visual indicator may be responsive to actuation of the deployment actuator and may be responsive to actuation of the lever; and/or 
     the indicator may include a window in the frame having a series of increments, a critical indicator showing a position past which resheathing of the prosthetic heart valve is no longer possible, and a scrolling bar to illustrate the extent of deployment of the prosthetic heart valve; and/or 
     the delivery device may include a resheathing lock configured to alert a user of a predetermined position of the distal sheath relative to the inner shaft and to impede movement of the distal sheath relative to the frame.