Abstract:
A connector for coupling a distal sheath to an inner shaft of a medical delivery device includes a wedge defining a lumen for accepting the inner shaft of the medical delivery device and a cylindrical ring sized to mate with the wedge. The wedge may be welded or otherwise fixed to the inner shaft. The wedge and the ring are configured to be pressed together and lock a portion of the distal sheath therebetween.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is related to prosthetic heart valve replacement, and more particularly to devices, systems, and methods for 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 For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.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 resheaths 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 fully 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 resheath 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 some delivery devices for self-expanding valves, inner connections of the delivery device are prone to failure and may be unduly bulky. 
     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 
     A delivery device for a collapsible prosthetic heart valve and a method of delivering a collapsible prosthetic heart valve in a patient are disclosed. 
     In some embodiments, a connector for coupling a distal sheath and an inner shaft of a medical delivery device includes a wedge defining a lumen for accepting the inner shaft of the medical delivery device, at least a portion of the wedge having an outer diameter sized to be received in the distal sheath. The connector further includes a cylindrical ring sized to be disposed over the distal sheath and at least the portion of the wedge. Engagement of the cylindrical ring with the wedge sandwiches the distal sheath between at least the portion of the wedge and the cylindrical ring. 
     In some examples, the wedge may include a cylindrical body and a cone portion. The cone portion of the wedge may include a series of annular steps having increasing diameters. The wedge may include a biocompatible metal. The wedge may include stainless steel. The ring may define an outwardly tapering lumen configured to receive the steps of the wedge. The ring and the wedge may include the same metal. The wedge may be welded to the inner shaft and the wedge and the ring may be welded together. The distal sheath may be inwardly tapered at a portion sandwiched between the wedge and the ring. 
     In some embodiments, a method of coupling a distal sheath and an inner shaft of a delivery device includes providing a connector having a wedge defining a lumen for accepting the inner shaft of the medical delivery device, at least a portion of the wedge having an outer diameter sized to be received in the distal sheath and a cylindrical ring sized to be disposed over the distal sheath and at least the portion of the wedge. A portion of the distal sheath may be positioned between the wedge and the ring of the connector. The wedge may be coupled to the inner shaft and the ring so as to sandwich the distal sheath between at least the portion of the wedge and the cylindrical body. 
     In some examples, the coupling step includes laser welding the wedge to the inner shaft. The coupling step may include laser welding the ring to the wedge. The method may further include thermoforming the portion of the distal sheath prior to positioning the portion of the distal sheath between the wedge and the ring. The thermoforming step may include inwardly tapering the portion using a tipping machine. The method may further include clamping the wedge and the ring together during assembly and the clamping step may include pushing the wedge and the ring together using a pneumatic cylinder. The positioning step may include sliding the wedge into the distal sheath through a non-tapered end of the distal sheath. The method may further include sliding the ring onto the distal sheath after sliding the wedge into the distal sheath. 
    
    
     
       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. 1  is a bottom plan view of an operating handle for a transapical delivery device for a collapsible prosthetic heart valve, shown with a side elevation of the distal portion of a transapical catheter assembly; 
         FIG. 2  is an enlarged cross-sectional view of a conventional distal sheath connection having pins; 
         FIG. 3  is an enlarged perspective view of a distal sheath and inner shaft connector; 
         FIGS. 4A and 4B  are side and cross-sectional views of a wedge of a distal sheath connector; 
         FIGS. 5A-5C  are side and cross-sectional views of two examples of a ring of a distal sheath connector; 
         FIG. 6  is a cross-sectional view of a distal sheath connector in a pneumatic cylinder; and 
         FIG. 7  is a cross-sectional view of an assembled distal sheath connector. 
     
    
    
     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 to  FIG. 1 , 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 a distal tip  114 . 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  121  and covered by a distal sheath  124 . 
     The support shaft  121  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  121  and between the retainers  125  and  127  in the compartment  123 . 
     The distal sheath  124  surrounds the support shaft  121  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 distal tip  114 , and its proximal end  129  abuts the retainer  127  when the distal sheath is fully covering the compartment  123 , as shown in  FIG. 1 . 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 connected to the operating handle  120 , and the distal end of which is connected to the retainer  127 . An inner shaft  126  extends through the operating handle  120  and the support shaft  121  to the distal tip  114 . The connection of the distal sheath  124  to the distal 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  121 , thereby respectively uncovering or covering the compartment with the distal sheath. The operating handle  120  may include a resheathing lock mechanism for preventing the user from accidentally completing the deployment of a valve located in the compartment  123 . Details of the operating handle is described in U.S. Provisional Patent Ser. No. 61/665,527, filed Jun. 28, 2012, the content of which is hereby incorporated by reference in its entirety. 
       FIG. 2  is a cross-sectional view of a conventional distal sheath connection having pins. Distal sheath  124  may be attached to nosecone insert  140  through one or more radially extending pins  190 . Nosecone insert  140  may be attached to inner shaft  126  by laser welds  142 . Pins  190  create a low strength connection between distal sheath  124  and nosecone insert  140  and are difficult to manufacture. In addition, pins  190  may unnecessarily increase the outer diameter of the distal end of the device. Such pins  190  may be trimmed so as to form a flush surface with the distal sheath  124 . Pins  190  may further require the use of adhesive  195  to protect the patient from sharp edges. 
       FIG. 3  is an enlarged perspective view of a distal sheath  124  and inner shaft  126  of the delivery device of  FIG. 1  attached to one another using a connector  200 . For the sake of clarity, tip  114  is shown in phantom lines to expose the connector. Distal sheath connector  200  forms a durable attachment between distal sheath  124  and inner shaft  126 , while maintaining a small diameter and eliminating the need for adhesive to protect the patient from sharp edges as shown in  FIG. 2 . The components of distal sheath connector  200  will be described in more detail with reference to  FIGS. 4A, 4B and 5A -C. 
       FIGS. 4A and 4B  are side and cross-sectional views of a wedge  300  of a distal sheath connector  200 . Wedge  300  may be formed of stainless steel or any other suitable metal such as Titanium, Nitinol, platinum, tantalum, gold, silver, cobalt-chromium. Alternatively, wedge  300  may be formed of any suitable biocompatible material including certain plastics and polymers. 
     Wedge  300  forms the first component of distal sheath connector  200  and sits inside a ring as will be described in further detail below. Wedge  300  may be formed of a substantially cylindrical body having a cone portion  340 , and a lumen  330  extending therethrough between a first end  310  and a second end  320 . Lumen  330  may be sized to receive inner shaft  126 . As seen in  FIG. 4A , cone portion  340  may include a series of annular steps  350  such that the outer diameter of the wedge  300  increases from the first end  310  to the second end  320 . Annular steps may allow for better attachment to distal sheath  124 . 
       FIGS. 5A and 5B  are side and cross-sectional views of a ring  400  of distal sheath connector  200 . Ring  400  may be formed of stainless steel or other suitable metals such as those used for wedge  300 . Ring  400  and wedge  300  may be formed of the same material. Ring  400  includes a first end  410 , a second end  420  and a lumen  430  extending therethrough. Lumen  430  widens to form a taper  450  near second end  420  to complement steps  350  of wedge  300  as will be appreciated from the assembled connector. As shown in  FIG. 5C , instead of a taper  450 , ring  400  may include a series of concentric recesses  455  sized and shaped to complement annular steps  350  of wedge  300 . 
       FIG. 6  is a cross-sectional view of the distal sheath, inner shaft and distal sheath connector disposed in a pneumatic cylinder during assembly. Wedge  300  may be first mounted on inner shaft  126  and welded to the inner shaft at position W 1 . This welding may be accomplished using a laser welder. In addition, an end portion T of distal sheath  124  may be thermoformed or tapered inwardly as seen in  FIG. 6  using a tipping machine (not shown). 
     Wedge  300  and inner shaft  126  may be slid into distal sheath  124  through the non-tapered end of the sheath until the steps  350  of the wedge contact the tapered portion T of the sheath. Ring  400  may then be assembled over wedge  300  with tapered portion T of distal sheath  124  disposed therebetween. A pneumatic cylinder may be used to clamp wedge  300 , ring  400  and distal sheath  124  together. An exemplary embodiment of pneumatic cylinder  500  includes a first plate P 1  and a second plate P 2  that apply force to the assembly in the directions shown by arrows A. Plates P 1  and P 2  move toward one another forcing wedge  300  into and through ring  400  so that the annular steps  350  engage with at least one of concentric recesses  455  of ring  400  and distal sheath  124 . Thus, plates P 1  and P 2  may hold wedge  300  and ring  400  of the connector in place, with the distal sheath partially sandwiched in between. A final weld W 2  may be circumferentially made between wedge  300  and ring  400  to permanently fix the two together. In some examples, welds W 1  and W 2  may be laser welds. Though the preceding example illustrates joining the wedge and ring using welds, it will be understood that any suitable technique for joining the two components may be used including for example, heat staking, impulse sealing, ultrasonic welding, snap fit, press fit, friction welding, vibration welding, hot plate welding and adhesive bonding and may depend on the materials for the wedge and/or ring. 
       FIG. 7  is a cross-sectional view of an assembled distal sheath connector  200  showing distal sheath  124  sandwiched between wedge  300  and ring  400 . Using distal sheath connector  200 , distal sheath  124  will more reliably attached to inner shaft  126  and be less prone to failure. 
     In operation, handle  120  may be used to deploy a prosthetic valve from the compartment  123 . Specifically, the user can rotate the deployment actuator  121  to push the distal sheath  124  distally relative to the compartment  123  and expose and initiate deployment of the valve located therein. Once the valve has been properly positioned, the deployment operation may be completed to release the valve from compartment  123 . 
     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 frame while the lock is in a locked position. Moreover, the operating handle may include a resheathing lock, or a number of resheathing locks, with or without a deployment lock, resulting in any number of stages in the deployment process. For example, there may be two, three, four, five, six or more resheathing locks, which thus enable the deployment procedure to be controlled incrementally. Such deployment locks and resheathing locks may have a structure similar to those shown and described in co-pending U.S. patent application Ser. No. 13/212,442, filed on Aug. 18, 2011, the content of which is hereby incorporated by reference herein in its entirety. 
     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.