Patent Publication Number: US-2018036123-A1

Title: Delivery devices for implantable medical devices and methods of manufacturing same

Description:
BACKGROUND 
     The disclosure generally relates to, among other things, devices and methods of manufacturing delivery devices for transcatheter delivery of an implantable medical device, such as a prosthetic heart valve. 
     A number of implantable medical devices are available for replacement or repair of a conduit, vessel, or organ structure within a patient. Such devices include homografts, xenografts, bioprostheses such as replacement valves, stents, and the like. Many of such devices are implantable with a delivery device via transcatheter procedures, which are procedures where the delivery device, in which or about which the implantable medical device is disposed, is advanced within a vessel, organ structure or other conduit to a desired location where the implantable medical device is deployed. With certain patients, the configuration delivery device may not be suitable to navigate the unique aspects of the patient&#39;s anatomy, which can jeopardize a successful outcome. 
     The disclosure addresses problems and limitations associated with the related art. 
     SUMMARY 
     Various aspects of the disclosure relate to the use of additive manufacturing, otherwise known as three-dimensional (3D) printing technologies, to manufacture a patient-specific delivery sheath of a delivery device configured to deliver and deploy an implantable medical device, such as a prosthetic heart valve. Prior to manufacture of the delivery sheath, a three-dimensional computed tomography (CT) scan of the pertinent vasculature of the patient is analyzed by a clinician to identify tortuous features of the patient&#39;s anatomy that the delivery device will need to traverse in order to deliver the implantable medical device. Then, a dataset corresponding to a three-dimensional delivery sheath of the delivery device is prepared and sent to a 3D printer, which forms the three-dimensional delivery sheath of the delivery device using three-dimensional printing technology. Three dimensional printers and related technology provide relatively inexpensive manufacture of a delivery sheath having a patient-specific variation of durometers at one or more various locations along a length and/or circumference of the delivery sheath based on the patient&#39;s particular anatomical features so that the delivery sheath can perform specific bend and flex actions as it moves through a patient&#39;s vasculature. Once the delivery sheath is printed, an optional capsule is coupled or otherwise attached to the end of the delivery sheath via a thread, similar coupling or could alternatively be an integrally formed part of the delivery sheath. The delivery sheath and optional capsule form a delivery sheath assembly. The delivery sheath assembly is loaded over an inner shaft assembly of the remainder of a premanufactured delivery device for insertion within the patient along with additional components of the delivery device. The inner shaft assembly is generally flexible and takes the shape formed by the delivery sheath. Alternatively, the delivery sheath can be a separate sheath positioned over both an outer sheath that is attached to a capsule and also the inner shaft assembly. In essence, the delivery sheath is the outermost sheath of the delivery device and components of the delivery device positioned within the delivery sheath are sufficiently flexible to take the shape of the custom manufactured delivery sheath. Patient-specific delivery sheaths disclosed herein are advantageous for achieving proper placement of the implantable medical device in the proper location, which can have many advantages including minimizing the risk of heart block, vascular trauma and/or paravalvular leakage in prosthetic heart valve applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic side view of an embodiment of a prosthetic heart valve in a natural, expanded arrangement. 
         FIG. 1B  is a schematic side view of the prosthetic heart valve of  FIG. 1A  in a compressed or collapsed arrangement. 
         FIG. 2A  is a partially-exploded, perspective view of an embodiment of a delivery device configured to deliver an implantable medical device, such as the prosthetic heart valve of  FIGS. 1A-1B . 
         FIG. 2B  is an assembled, top view of the delivery device of  FIG. 2A . 
         FIG. 3  is a partially-exploded, perspective view of an alternate embodiment of a delivery device configured to deliver an implantable medical device, such as the prosthetic heart valve of  FIGS. 1A-1B . 
         FIG. 4  is a partial, cross-sectional, schematic view of a delivery sheath for use with the delivery device of  FIG. 2A or 3 . 
         FIG. 5  is a partial, cross-sectional, schematic view of an alternate delivery sheath for use with the delivery device of  FIG. 2A or 3 . 
         FIG. 6  is a partial, schematic view of an alternate delivery sheath for use with the delivery device of  FIG. 2A or 3 . 
         FIG. 7  is a partial, cross-sectional, schematic view of an alternate delivery sheath for use with the delivery device of  FIG. 2A or 3 . 
         FIG. 8  is a schematic drawing illustrating the use of the example delivery device of  FIG. 2A-2B or 3  for transcatheter delivery of an implantable medical device, such as the prosthetic heart valve of  FIGS. 1A-1B  (not visible). 
         FIGS. 9A-9B  are example CT scans of a patient&#39;s vasculature. 
         FIG. 10  is flow chart illustrating one embodiment of a method of designing and manufacturing a delivery sheath for a delivery device, such as the delivery devices of  FIG. 2A-2B or 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Implantable medical devices disclosed herein may be expandable from a collapsed or compressed configuration to an expanded configuration and may interact with the interior wall of a vessel, organ structure, or other bioprosthetic or natural conduit, or the like via interference fit when expanded. Examples of expandable implantable medical devices include prosthetic heart valves, stents, grafts and the like. 
     By way of example, one non-limiting example of a prosthetic heart valve  10  useful with devices and methods of the present disclosure is illustrated in  FIGS. 1A-1B . As a point of reference, the prosthetic heart valve  10  is shown in a natural or expanded arrangement in the view of  FIG. 1A .  FIG. 1B  illustrates the prosthetic heart valve  10  in a compressed arrangement (e.g., when compressively retained within a delivery sheath or the like). The prosthetic heart valve  10  includes a stent or stent frame  12  and a valve structure  14 . The stent frame  12  can assume a variety of forms and is generally constructed so as to be self- or otherwise-expandable from the compressed arrangement ( FIG. 1B ) to the natural, expanded arrangement ( FIG. 1A ). The valve structure  14  is assembled to the stent frame  12  and forms or provides two or more (typically three) leaflets  16 . The valve structure  14  can also take a variety of forms and can be assembled to the stent frame  12  in various manners, such as by sewing the valve structure  14  to one or more of the wire segments  18  defined by the stent frame  12 . 
     One acceptable construction of the prosthetic heart valve  10  depicted in  FIGS. 1A and 1B  can be used for repairing a native heart valve. Of course, other shapes and sizes are envisioned to adapt to the specific anatomy of the valve to be repaired (e.g., prosthetic heart valves in accordance with the present disclosure can be shaped and/or sized for replacing a native mitral, aortic, or tricuspid valve). In the depicted embodiment, the valve structure  14  extends less than the entire length of the stent frame  12 . An outflow region  20  of the prosthetic heart valve  10  is generally free of the valve structure  14  material, with the valve structure  14  extending along an inflow region  22  of the prosthetic heart valve  10 . As a point of reference, “inflow” and “outflow” terminology is in reference to an arrangement of the prosthetic heart valve  10  upon final implantation relative to the native valve being repaired. A wide variety of constructions are also acceptable and within the scope of the present disclosure. For example, in other embodiments, the valve structure  14  can extend along an entirety, or a near entirety, of a length of the stent frame  12 . 
     A delivery device  30  for percutaneously delivering the prosthetic heart valve  10  of  FIGS. 1A-1B  or other implantable medical device is shown in simplified form in  FIGS. 2A and 2B . In this illustrative embodiment, the delivery device  30  includes a delivery sheath assembly  32 , an inner shaft assembly  40  and a handle assembly  50 . Details on the various components are provided below. In general terms, however, the delivery device  30  combines with a prosthetic heart valve or other implantable medical device (not shown) to form a system for performing a therapeutic procedure (e.g., on a defective heart valve of a patient). The delivery device  30  provides a loaded or delivery state in which the prosthetic heart valve is loaded over a support shaft  42  of the inner shaft assembly  40  and is compressively retained within a capsule  38  of the delivery sheath assembly  32  include or provide a valve retainer  52  configured to selectively receive a corresponding feature (e.g., posts) provided with the prosthetic heart valve stent frame. The delivery sheath assembly  32  can be manipulated to withdraw the capsule  38  proximally from over the prosthetic heart valve via operation of the handle assembly  50 , permitting the prosthetic heart valve to self-expand and partially release from the support shaft  42 . When the capsule  38  is retracted proximally beyond the valve retainer  52 , the prosthetic heart valve can completely release or deploy from the delivery device  30 . The delivery device  30  can optionally include other components that assist, facilitate or control complete deployment of the implantable medical device. For example, the delivery device  30  can optionally include additional components or features, such as a flush port assembly  54 , a recapture sheath (not shown), ability to steer or articulate etc. 
     Various features of the components  32 ,  40  and  50  reflected in  FIGS. 2A and 2B  and as described below can be modified or replaced with differing structures and/or mechanisms. Thus, the present disclosure is in no way limited to the delivery sheath assembly  32 , the inner shaft assembly  40 , or the handle assembly  50  as shown and described below. Any construction that generally facilitates loading of an implantable medical device for transcatheter delivery via a patient&#39;s vasculature is acceptable. 
     In some embodiments, the delivery sheath assembly  32  defines proximal and distal ends  60 ,  62 , and includes the capsule  38  and a delivery sheath  34 . The delivery sheath assembly  32  can be akin to a sheath, defining a lumen  64  (referenced generally) that extends from the distal end  62  through the capsule  38  and at least a portion of the delivery sheath  34 . The lumen  64  can be open at the proximal end  60  (e.g., the delivery sheath  34  can be a tube). The capsule  38  extends distally from the delivery sheath  34 , and in some embodiments has a more stiffened construction (as compared to a stiffness of the delivery sheath  34 ) that exhibits sufficient radial or circumferential rigidity to overtly resist the expected expansive forces of the prosthetic heart valve (not shown) when compressed within the capsule  38 . For example, the delivery sheath  34  can be a polymer tube, whereas the capsule  38  includes a laser-cut metal tube that is optionally embedded within a polymer covering. Alternatively, the capsule  38  and the delivery sheath  34  can have a more uniform or even homogenous construction (e.g., a continuous polymer tube). Regardless, the capsule  38  is constructed to compressively retain the prosthetic heart valve at a predetermined diameter when loaded within the capsule  38 , and the delivery sheath  34  serves to connect the capsule  38  with the handle assembly  50 . The delivery sheath  34  (as well as the capsule  38 ) is constructed to be sufficiently flexible for passage through a patient&#39;s vasculature, yet exhibits sufficient longitudinal rigidity to effectuate desired axial movement of the capsule  38 . Proximal retraction of the delivery sheath  34  is directly transferred to the capsule  38  and causes a corresponding proximal retraction of the capsule  38 . In certain embodiments, the delivery sheath  34  is further configured to transmit a rotational force or movement onto the capsule  38 . In this embodiment, the delivery sheath  34  is custom printed to be particularly capable of navigating a patient&#39;s specific vasculature, as will be further discussed below. 
     In some embodiments, the inner shaft assembly  40  includes a proximal shaft or tube  46 , an intermediate shaft or tube  44  and the support shaft  42  that terminates at a tip  48 . The support shaft  42  is sized to be slidably received within the lumen  64  of the delivery sheath assembly  32  and exhibits sufficient structural integrity to support a loaded, compressed implantable medical device (not shown). The tip  48  forms or defines a nose cone having a distally tapering outer surface adapted to promote atraumatic contact with bodily tissue. The tip  48  can be fixed or slidable relative to the support shaft  42 . The intermediate tube  44  is optionally formed of a flexible polymer material (e.g., PEEK) with or without a metal braid, and is sized to be slidably received within the delivery sheath assembly  32 . The intermediate tube  44  in some embodiments is a flexible polymer tubing (e.g., PEEK) having a diameter slightly less than that of the proximal tube  46 . The proximal tube  46  can have a more rigid construction, configured for robust assembly with the handle assembly  50 , such as a metal hypotube. Other constructions are also envisioned. For example, in other embodiments, the intermediate and proximal tubes  44 ,  46  are integrally formed as a single, homogenous tube or shaft. Regardless, the inner shaft assembly  40  forms or defines at least one lumen (not shown) sized, for example, to slidably receive a guide wire (not shown). The inner shaft assembly  40  can also define a continuous lumen (not shown) sized to slidably receive an auxiliary component such as a guide wire (not shown). 
     The handle assembly  50  generally includes a housing  66  and one or more actuator mechanisms  68  (referenced generally). The housing  66  maintains the actuator mechanism(s)  68 , with the handle assembly  50  configured to facilitate sliding movement of the capsule  38  relative to other components (e.g., the inner shaft assembly  40  and its support shaft  42 ). The housing  66  can have any shape or size appropriate for convenient handling by a user. 
     An alternate delivery device  30 ′ is schematically illustrated in  FIG. 3 . The delivery device  30 ′ is configured and operates similar to the delivery device  30  of  FIGS. 2A-2B  with the exception that the delivery device  30 ′ includes a delivery sheath assembly  32 ′ having both an outer sheath  33  and a delivery sheath  34 ′. As shown in  FIG. 3 , the delivery device  30 ′ includes an inner shaft assembly  40 ′ having an inner shaft  42 ′ over which an implantable medical device (not shown) can be positioned. The outer sheath  33  includes a capsule  38 ′, that is configured to compressively retain the implantable medical device (not shown) and the movement of which is controlled by a handle assembly  50 ′. In this embodiment, the delivery sheath  34 ′ is custom printed to be particularly capable of navigating a patient&#39;s specific vasculature, as will be further discussed below. Once printed, the delivery sheath  34 ′ is then secured over the outer sheath  33  and capsule  38 ′, which are positioned over the inner shaft assembly  40 ′. 
     A mass produced, “one size fits all” delivery device can accommodate many patients, however, some patients can benefit from a custom device better suited for their particular anatomical features. For example, older patients having scoliosis can have a particularly tortuous anatomy. Therefore, the disclosed delivery devices and methods provide a custom produced delivery sheath designed specifically to navigate through the patent&#39;s individual anatomical features. The delivery sheath is designed and manufactured to have a variable durometer or stiffness along its length and/or circumference, which is configured to be aligned with the patient&#39;s anatomical features so that the delivery sheath can bend and flex at certain points during delivery of the implantable medical device. Therefore, the delivery devices disclosed herein are better suited to navigate through the patent&#39;s particular vasculature, thus generally resulting in more successful outcomes. 
       FIG. 4  schematically illustrates one example of how a delivery sheath  34   a , similar to the delivery sheaths  34 ,  34 ′, can be designed to have varying stiffness at one or more areas of the delivery sheath  34   a . In this embodiment, the delivery sheath  34   a  is manufactured to have one or more areas made of a first material  56   a  having an increased stiffness relative to an adjacent area or section  58   a  made of a second material. It is to be understood that the more flexible areas made of the second material  58   a  can be positioned along as many or as few areas along the length of the delivery sheath  34   a , as desired. Moreover, the area of lesser stiffness  58   a  can extend along the entirely of the circumference of the area  58   a , or, alternatively, can be irregular or extend along a portion or less than the entirety of the circumference of the delivery sheath  34   a . The disclosure is not intended to be limited to any specific configuration in which the first and second materials  56   a ,  58   b  can be arranged along the length and/or circumference of the delivery sheath  34   a.    
       FIG. 5  schematically illustrates another example of how a delivery sheath  34   b , similar to delivery sheaths  34 ,  34 ′, can be designed to have varying stiffness at one or more areas of the delivery sheath  34   b . In this embodiment, the delivery sheath  34   b  is manufactured to have one or more areas  56   b  having an increased stiffness relative to an adjacent area or section  58   b  having a lesser stiffness resulting from one or more cuts (generally referenced by  58   b ) extending through a partial thickness of the delivery sheath  34   b . It will be understood that the “cuts”, in this embodiment, are formed by printing as described herein. The number and location of cuts can vary, as desired, to create areas  58   b  having a lesser stiffness or greater flexibility as compared to adjacent areas  56   b  that do not include cuts. As shown, the area of lesser stiffness  58   b  can extend along the entirety of the circumference of the area  58   b , or, alternatively, can be irregular or extend along a portion of the circumference of the delivery sheath  34   b . The disclosure is not intended to be limited to any specific configuration in which the stiffness can vary along the length and/or circumference of the delivery sheath  34   b.    
       FIG. 6  schematically illustrates yet another example of how a delivery sheath  34   c , similar to delivery sheaths  34 ,  34 ′, can be designed to have varying stiffness at one or more areas of the delivery sheath  34   c . In this embodiment, the delivery sheath  34   c  is manufactured to have areas  56   c  having an increased stiffness relative to an adjacent area or section  58   c . The variance in stiffness is a result of one or more spiral cuts (generally referenced by  58   c ) printed into a partial thickness of the delivery sheath  34   c . It will be understood that the “cuts”, in this embodiment, are formed by printing as described herein. The number, length and location of cuts can vary, as desired, to create areas  58   c  having a lesser stiffness or greater flexibility as compared to adjacent areas  56   c  that do not include cuts. As shown, the area of lesser stiffness  58   a  resulting from the cuts can extend along the entirely of the circumference of the area  58   c , or, alternatively, can be irregular or extend along a portion of the circumference of the delivery sheath  34   c . The disclosure is not intended to be limited to any specific configuration in which the stiffness can vary along the length and/or circumference of the delivery sheath  34   c . 
       FIG. 7  schematically illustrates one example of how a delivery sheath  34   d , similar to delivery sheaths  34 ,  34 ′, can be custom designed to have varying stiffness at one or more areas of the delivery sheath  34   d . In this embodiment, the delivery sheath  34   d  is designed and manufactured to have areas made of a single material, the areas including an area of increased stiffness  56   d  relative to an adjacent area or section  58   d . In this embodiment, the variance in stiffness between areas  56   d ,  58   d  is a result of the delivery sheath  34   d  having a variance in a wall thickness. It is to be understood that the areas having a lesser stiffness  58   d  can be positioned along as many or as few areas along the length of the delivery sheath  34   d , as desired. Moreover, the area of lesser stiffness  58   d  can be irregular or extend along the entirely of the circumference of the delivery sheath  34   d , or, alternatively, can extend along a portion of the circumference of the delivery sheath  34   d . The disclosure is not intended to be limited to any specific configuration in which the stiffness can vary along the length and/or circumference of the delivery sheath  34   d.    
     A prosthetic heart valve, such as that depicted in  FIGS. 1A-B , or other implantable medical device, may be implanted via a transcatheter procedure. Part of one such procedure is schematically reflected in  FIG. 8  in which the delivery device  30  is employed to repair a defective aortic valve  72 . As shown, the delivery device  30  (in the loaded state having a loaded prosthetic valve, which is not visible) is introduced into the patient&#39;s vasculature  70  (referenced generally) via an introducer device  24 . The introducer device  24  provides a port or access to a femoral artery  74 . From the femoral artery  74 , the delivery device  30  (that compressively retains the implantable medical device) is advanced via a retrograde approach through an aortic arch  76  (e.g., via iliac arteries).  FIG. 8  depicts the delivery sheath assembly  32  having the delivery sheath  34  extending along a substantial length of delivery sheath assembly  32 , with a distal end of the delivery sheath  34  being fairly proximate to the capsule  38  retaining the prosthetic heart valve. Deployment of the prosthetic heart valve from the delivery device  30  can be accomplished via proximal retraction of the delivery sheath  34 , and, in this particular embodiment, the capsule  38 . 
     In various embodiments described herein, one or more characteristics or dimensions of a vessel, organ structure or other bioprosthetic or natural conduit is assessed, measured or determined. As used hereinafter, “vasculature” will be used to collectively refer to a natural conduit, vessel, or organ structure into which an expandable, implantable medical device may be implanted via transcatheter procedure. In various embodiments described herein, one or more maximum and minimum characteristics or dimensions such as diameters, perimeters, lengths, areas, including cross-sectional area or surface area, etc., of a conduit are determined by imaging a portion of the conduit into which the device is to be implanted at appropriate points in the cardiac cycle (or other appropriate cycle, such as the respiratory cycle, etc.). As used herein, “dimensional characteristic” or “anatomical features” will be used to refer collectively to perimeter, diameter (including perimeter derived diameter, area derived diameter, average diameter, major diameter, minor diameter, etc.), area (such as cross-sectional area, surface area, etc.), length, aspect ratio, shape and the like. For example, the dimensional characteristics of the patient&#39;s vasculature within the portion of interest may be evaluated and compared to various delivery sheath configurations. 
     To design and manufacture one of the many delivery sheath embodiments disclosed herein, a three-dimensional computed tomography scan (CT scan) of the patient&#39;s vasculature  70  or natural conduit through which the delivery device must travel is obtained. As an example,  FIGS. 9A-9B  illustrate, in two dimensions, an example CT scan of a patient&#39;s vasculature pertinent for transcatheter prosthetic heart valve implantation procedure. The CT scans of  FIGS. 9A-9B  are annotated to generally identify five areas of interest including the patient&#39;s femoral tortuosity  80 , length of the descending aorta  82 , length, angulation and curvature of the aortic arch  84 , length of the ascending aorta  86  and angulation of the aortic annulus  88 . From the CT scan, one or more three-dimensional tortuosities or other anatomical features can be identified in the delivery path. A centerline tortuosity can be used to identify the delivery path and the areas of greatest curvature can correlate to the desired areas of greatest flexibility on the delivery sheath. In certain embodiments, the delivery sheath will be designed to be more flexible on an inner surface (with respect to the patient) of the delivery sheath to traverse the aortic arch. After identifying anatomical features that would prove challenging for delivery of the implantable medical device, a patient-specific delivery sheath can be designed including one or more of variances in stiffness (durometer) along the length and/or circumference of the delivery sheath. In this way, the patient-specific delivery device and implantable medical device delivered therewith, can more easily navigate the patient&#39;s particular vasculature. 
       FIG. 10  is a flow chart showing an embodiment of an example method of forming one of the delivery sheaths disclosed herein. The methods as described with respect to  FIG. 10  include methods for making a delivery sheath using “three-dimensional printing” (3D printing) or “additive manufacturing” or “rapid prototyping”. The term “three-dimensional printing” or “additive manufacturing” or “rapid prototyping” refers to a process of making a three-dimensional solid object of virtually any shape from a dataset. 3D printing is achieved using an additive process, where successive layers of material are laid down in different shapes. Any type of 3D printing machine that can print the materials described herein may be used. 
     One initial step in the method is to obtain a CT scan of at least a portion of the pertinent vasculature of the patient  100 . As also discussed above with respect to  FIGS. 9A-9B , the CT scan is reviewed by a clinician to identify tortious anatomical features of the patent&#39;s anatomy within the vasculature that will have been traversed by the delivery device  102 . Then, a delivery sheath design is prepared  104 . The delivery sheath is designed to have a varying durometer about at least one area of the delivery sheath&#39;s circumference and/or along the length of the delivery sheath so that the delivery sheath can appropriately bend and flex as it moves through the patient&#39;s vasculature to deliver the implantable medical device. A dataset is then prepared corresponding to the three-dimensional delivery sheath  106 . 
     For example, and not by way of limitation, the dataset may be a 3D printable file such as an STL file. STL (STereoLithography) is a file format native to the stereolithography CAD software created by 3D Systems. STL is also known as Standard Tessellation Language. This file format is supported by many software packages for use in 3D printing. The dataset is sent to a 3D printer that subsequently forms or “prints” the delivery sheath as specified by the dataset  108 . In step  110 , the 3D printing machine lays down successive layers of a powder or other form of the desired materials to build the delivery sheath from a series of cross sections. The materials used to form the delivery sheath include the material desired for the finished delivery sheath (also referred to as a “structural material”). 
     Examples of structural materials which may be 3D printed to form the delivery sheath include any biocompatible material, for example, stainless steel (such as “SS316L”), cobalt-chromium alloys, nickel titanium alloys such as Nitinol, magnesium and magnesium alloys, or combinations thereof. The term “cobalt-chromium” alloys as used herein includes alloys with cobalt and chromium. Generally, materials such as, but not limited to, cobalt-nickel-chromium alloys (“MP35N”, “MP20N”, and “MP35NLT”) and chromium-nickel-tungsten-cobalt alloys (“L605”) and cobalt-chromium-nickel-molybdenum alloys (“ELGILOY”) are the types of materials included in the term “cobalt-chromium alloys” as used herein. Polymers may also be used as structural materials to form the delivery sheath. Polymers which may be used to form the delivery sheath include, but are not limited to, polylactide, poylglycolide, polysaccharides, proteins, polyesters, polyhydroxyalkanoates, polyalkelene esters, polyamides, polycaprolactone, polyvinyl esters, polyamide esters, polyvinyl alcohols, modified derivatives of caprolactonepolymers, polytrimethylene carbonate, polyacrylates, polyethylene glycol, hydrogels, photo-curable hydrogels, terminal diols, and combinations thereof. 
     Once the custom delivery sheath is formed via the 3D printer, the delivery sheath can be assembled to the delivery device, over the inner shaft assembly. As also discussed above, the implantable medical device is positioned on the support shaft in a compressed arrangement so that the delivery sheath can be positioned over the implantable medical device and the inner shaft assembly. In some embodiments, the delivery sheath will compressively retain the implantable medical device onto the support shaft and in alternate embodiments, the capsule will be secured to the distal end of the delivery sheath and will compressively retain the implantable medical device over the support shaft. The capsule can be secured to the delivery sheath via a thread (not shown) or similar coupling or could alternatively, in some embodiments, be an integral part of the delivery sheath. In even further alternate embodiments, as discussed above with respect to  FIG. 3 , the delivery sheath can be positioned over an outer sheath, wherein the outer sheath is connected to the capsule and positioned over the inner shaft. The delivery device can be sterilized as per normal manufacturing processes or alternatively the delivery device can be sterilized through in hospital methods (autoclave etc.). In other words, after printing the delivery sheath in the hospital, the delivery device can be sterilized and assembled in the hospital, as opposed to a manufacturing facility. 
     Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present disclosure.