Patent Publication Number: US-11654023-B2

Title: Covered prosthetic heart valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. application Ser. No. 16/252,890, filed on Jan. 21, 2019, which is a continuation of PCT Application No. PCT/US2019/014338, filed on Jan. 18, 2019, which is a continuation-in-part of U.S. application Ser. No. 15/876,053, filed on Jan. 19, 2018, and which claims the benefit of U.S. Provisional Application No. 62/703,363, filed on Jul. 25, 2018. U.S. application Ser. No. 15/876,053 claims the benefit of U.S. Provisional Application No. 62/449,320 filed on Jan. 23, 2017, U.S. Provisional Application No. 62/520,703 filed on Jun. 16, 2017, and U.S. Provisional Application No. 62/535,724 filed on Jul. 21, 2017. The present application also claims the benefit of U.S. Provisional Application No. 62/703,363, filed on Jul. 25, 2018. Each of the foregoing applications is incorporated by reference in their entirety herein. 
    
    
     FIELD 
     The present disclosure relates to prosthetic heart valves, and in particular to prosthetic heart valves including a covering. 
     BACKGROUND 
     In a procedure to implant a transcatheter prosthetic heart valve, the prosthetic heart valve can be positioned in the annulus of a native heart valve and expanded or allowed to expand to its functional size. In order to retain the prosthetic heart valve at the desired location, the prosthetic heart valve may be larger than the diameter of the native valve annulus such that it applies force to the surrounding tissue in order to prevent the prosthetic heart valve from becoming dislodged. In other configurations, the prosthetic heart valve may be expanded within a support structure that is located within the native annulus and configured to retain the prosthetic heart valve at a selected position with respect to the annulus. Over time, relative motion of the prosthetic heart valve and tissue of the native heart valve (e.g., native valve leaflets, chordae tendineae, etc.) in contact with the prosthetic heart valve may cause damage to the tissue. Accordingly, there is a need for improvements to prosthetic heart valves. 
     SUMMARY 
     Certain disclosed embodiments concern coverings for prosthetic heart valves and methods of making and using the same. This summary is meant to provide some examples and is not intended to be limiting of the scope of the invention in any way. For example, any feature included in an example of this summary is not required by the claims, unless the claims explicitly recite the features. Also, the features described can be combined in a variety of ways. Various features and steps as described elsewhere in this disclosure can be included in the examples summarized here. 
     In a representative embodiment, a prosthetic heart valve comprises a frame comprising a plurality of strut members, the frame being radially collapsible and expandable between a collapsed configuration and an expanded configuration, the frame having an inflow end and an outflow end, and defining a longitudinal axis. The prosthetic heart valve further comprises a leaflet structure situated at least partially within the frame, and a sealing member disposed around the frame (e.g., around some, a portion, or all of the frame). The sealing member can comprise a first portion extending circumferentially around at least a portion of the frame, the first portion being configured to resiliently stretch in a direction along the longitudinal axis of the frame between a first state corresponding to the expanded configuration of the frame and a second state corresponding to the collapsed configuration of the frame. The sealing member can further comprise a second portion extending circumferentially around at least a portion of the frame, the second portion being configured to resiliently stretch in a circumferential direction between a first state corresponding to the collapsed configuration of the frame and a second state corresponding to the expanded configuration of the frame. 
     In any or all of the disclosed embodiments, the first portion comprises a resiliently stretchable portion that is stretchable in a direction along the longitudinal axis of the frame. 
     In any or all of the disclosed embodiments, the resiliently stretchable portion of the first portion comprises texturized yarns extending in a direction along the longitudinal axis of the frame. 
     In any or all of the disclosed embodiments, the first portion further comprises a first woven portion and a second woven portion spaced apart from the first woven portion in a direction along the longitudinal axis of the frame, and the texturized yarns extend between the first woven portion and the second woven portion and form a floating yarn portion between the first woven portion and the second woven portion. 
     In any or all of the disclosed embodiments, the texturized yarns are configured to provide compressible volume to the floating yarn portion of the sealing member when the frame is in the expanded configuration. 
     In any or all of the disclosed embodiments, the texturized yarns are woven into a leno weave pattern in the first woven portion and in the second woven portion. 
     In any or all of the disclosed embodiments, the first portion of the sealing member comprises a plurality of floating yarn portions spaced apart from each other along the longitudinal axis of the frame. 
     In any or all of the disclosed embodiments, the second portion comprises a resiliently stretchable portion that is stretchable in a circumferential direction around the frame. 
     In any or all of the disclosed embodiments, the resiliently stretchable portion of the second portion comprises texturized yarns extending in a circumferential direction around the frame. 
     In any or all of the disclosed embodiments, the second portion further comprises a first woven portion and a second woven portion spaced apart from the first woven portion in a circumferential direction around the frame, and the texturized yarns extend between the first woven portion and the second woven portion and form a floating yarn portion between the first woven portion and the second woven portion. 
     In any or all of the disclosed embodiments, the second portion is a first circumferentially resilient portion configured to resiliently stretch in a circumferential direction, and the sealing member further comprises a second circumferentially resilient portion on the opposite side of the floating yarn portion from the first circumferentially resilient portion such that the first circumferentially resilient portion and the second circumferentially resilient portion are axially offset from each other along the longitudinal axis of the frame. 
     In any or all of the disclosed embodiments, the second portion comprises a plurality of first strands interwoven with a plurality of second strands, and an angle formed between the first strands and the second strands changes as the frame moves between the collapsed configuration and the expanded configuration. 
     In any or all of the disclosed embodiments, when the frame is in the collapsed configuration, the first strands and the second strands form a first angle and the second portion has a first arc length, and when the frame is in the expanded configuration, the first strands and the second strands form a second angle and the second portion has a second arc length that is greater than the first arc length. 
     In any or all of the disclosed embodiments, the sealing member comprises an axial dimension in a direction along the longitudinal axis of the frame, and the sealing member remains in contact with the frame along substantially its entire axial dimension between the collapsed configuration and the expanded configuration. 
     In any or all of the disclosed embodiments, the first portion of the sealing member is directly secured to the frame, and the second portion of the sealing member is coupled to the first portion but not directly secured to the frame. 
     In another representative embodiment, a prosthetic heart valve comprises a frame comprising a plurality of strut members, the frame being radially collapsible and expandable between a collapsed configuration and an expanded configuration, the frame having an inflow end and an outflow end, and defining a longitudinal axis. The prosthetic heart valve further comprises a leaflet structure situated at least partially within the frame, and a sealing member disposed around the frame. The sealing member comprises a first portion extending circumferentially around at least a portion of the frame, the first portion comprising a plurality of texturized yarns extending along the longitudinal axis of the frame and configured to resiliently lengthen as the frame moves between the expanded configuration and the collapsed configuration. The sealing member further comprises a second portion extending circumferentially around at least a portion of the frame and comprising a plurality of texturized yarns extending in a circumferential direction around the frame, the texturized yarns of the second portion being configured to resiliently lengthen in the circumferential direction as the frame moves between the collapsed and the expanded configurations. 
     In any or all of the disclosed embodiments, the first portion further comprises a first woven portion and a second woven portion spaced apart from the first woven portion in a direction along the longitudinal axis of the frame, and the texturized yarns of the first portion extend between the first woven portion and the second woven portion and form a floating yarn portion between the first woven portion and the second woven portion. 
     In any or all of the disclosed embodiments, the texturized yarns are configured to provide compressible volume to the floating yarn portion when the frame is in the expanded configuration. 
     In any or all of the disclosed embodiments, the texturized yarns can be woven into a leno weave pattern in the first woven portion and in the second woven portion. 
     In any or all of the disclosed embodiments, the second portion further comprises a first woven portion and a second woven portion spaced apart from the first woven portion in a circumferential direction around the frame, and the texturized yarns of the second portion extend between the first woven portion and the second woven portion and form a floating yarn portion between the first woven portion and the second woven portion. 
     In another representative embodiment, a prosthetic heart valve comprises a frame comprising a plurality of strut members, the frame being radially collapsible and expandable between a collapsed configuration and an expanded configuration, the frame having an inflow end and an outflow end, and defining a longitudinal axis. The prosthetic heart valve further comprises a leaflet structure situated at least partially within the frame, and a sealing member disposed around the frame. The sealing member comprises a first portion extending circumferentially around at least a portion of the frame, the first portion comprising a floating yarn portion configured to resiliently lengthen in a direction along the longitudinal axis of the frame as the frame moves between the expanded configuration and the collapsed configuration. The sealing member further comprises a second portion extending circumferentially around at least a portion of the frame and comprising a floating yarn portion configured to resiliently lengthen in the circumferential direction as the frame moves between the collapsed configuration and the expanded configuration. 
     The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows a schematic cross-sectional view of a human heart. 
         FIG.  2    shows a schematic top view of a mitral valve annulus of a heart. 
         FIG.  3    is a perspective view of an embodiment of a prosthetic heart valve. 
         FIG.  4 A  is a cross-sectional side view of a ring anchor or docking device deployed in a mitral position of the heart, with an implanted valve prosthesis, according to one embodiment. 
         FIG.  4 B  illustrates a cross-sectional side view of an example of a coil anchor or docking device deployed in the mitral position of the heart, with an implanted valve prosthesis. 
         FIG.  4 C  is a perspective view of a representative embodiment of an anchor or docking device. 
         FIG.  5    is a perspective view of a prosthetic heart valve including a representative embodiment of a covering. 
         FIG.  6    is a side-elevation view of the prosthetic heart valve of  FIG.  5   . 
         FIG.  7    is a top plan view of the prosthetic heart valve of  FIG.  5   . 
         FIG.  8    is a cross-sectional side elevation view of the prosthetic heart valve of  FIG.  5   . 
         FIG.  9    is a perspective view of a representative embodiment of a cushioning layer including a plush pile. 
         FIG.  10    is a cross-sectional side view of the prosthetic heart valve of  FIG.  5    deployed in the mitral position of the heart. 
         FIG.  11    is a side elevation view of a prosthetic heart valve including an example of a covering. 
         FIG.  12    is a perspective view of a backing layer, a stencil for producing the backing layer, and a cushioning layer, before the backing layer and the cushioning layer are secured together. 
         FIG.  13    is a cross-sectional side elevation view of a prosthetic heart valve including an example of a covering. 
         FIG.  14    is a detail view of an inflow protective portion of the covering of  FIG.  13   . 
         FIG.  15    is a side elevation view of a prosthetic heart valve including an example of a covering comprising a spacer fabric. 
         FIG.  16    is a perspective view of a representative embodiment of a spacer cloth including looped pile yarns. 
         FIG.  17    is a side elevation view of the spacer fabric of  FIG.  16   . 
         FIG.  18    is a top plan view of an embodiment of a backing layer after it is cut using a parallelogram stencil. 
         FIG.  19    is a perspective view of a prosthetic heart valve including an example of a covering. 
         FIG.  20    is a side elevation view of the prosthetic heart valve of  FIG.  19   . 
         FIG.  21    is a plan view of an outflow end of the prosthetic heart valve of  FIG.  19   . 
         FIG.  22    is a cross-sectional side elevation view of the prosthetic heart valve of  FIG.  19   . 
         FIG.  23    is a top plan view of the covering of  FIG.  19    in an unfolded configuration. 
         FIG.  24    is a perspective view illustrating placement of the prosthetic heart valve of  FIG.  19    into the covering after the covering is formed into a cylindrical shape. 
         FIG.  25    is a perspective view of the inflow end of the prosthetic heart valve of  FIG.  19    illustrating attachment of the covering to the strut members of the valve frame. 
         FIG.  26    is a perspective view of the inflow end of the prosthetic heart valve of  FIG.  19    illustrating a strip member of the covering folded over the strut members of the valve frame to form an inflow protective portion. 
         FIG.  27    is a perspective view of a frame for a prosthetic heart valve including an example of a covering. 
         FIG.  28    is a cross-sectional side elevation view of the frame and covering of  FIG.  27   . 
         FIGS.  29 - 31 A  are perspective views illustrating a representative method of making the covering of  FIG.  27   . 
         FIG.  31 B  is a detail view of the electrospun layer of the inflow end portion of the covering of  FIG.  31 A . 
         FIG.  32    is a perspective view of a prosthetic heart valve including a main covering and a second covering extending over the apices of the frame. 
         FIG.  33    is a side elevation view of the prosthetic heart valve of  FIG.  32   . 
         FIG.  34    is a plan view of a portion of the frame of the prosthetic valve of  FIG.  32    in a laid-flat configuration. 
         FIG.  35    is a perspective view of the prosthetic heart valve of  FIG.  32    without the main outer covering. 
         FIG.  36    is a perspective view of the prosthetic heart valve of  FIG.  32    illustrating how the second covering is wrapped around the apices of the frame. 
         FIG.  37    is a perspective view illustrating the frame of the prosthetic valve of  FIG.  32    including the second covering crimped onto a shaft of a delivery apparatus. 
         FIG.  38 A  is a side elevation view of the prosthetic valve of  FIG.  19    including an example of an outer covering. 
         FIG.  38 B  is a detail view of the fabric of the outer covering of  FIG.  38 A . 
         FIG.  39 A  is a plan view illustrating the prosthetic heart valve of  FIG.  38 A  crimped onto a shaft of a delivery device. 
         FIG.  39 B  is a detail view of the outer covering of the prosthetic heart valve in  FIG.  39 A . 
         FIG.  40 A  is a cross-sectional side elevation view of the fabric of the outer covering of  FIG.  38 A  in a relaxed state, 
         FIG.  40 B  is a cross-sectional side elevation view of the fabric of the outer covering of  FIG.  38 A  in a tensioned state. 
         FIG.  41 A  is a plan view of an example of a fabric outer covering for a prosthetic valve in a laid-flat configuration and including an outer surface defined by a pile layer. 
         FIG.  41 B  is a magnified view of the outer covering of  FIG.  41 A . 
         FIG.  42 A  is a plan view of a base layer of the outer covering of  FIG.  41 A . 
         FIG.  42 B  is a magnified view of the base layer of  FIG.  42 A . 
         FIGS.  43 - 45    are a side elevational views of a prosthetic heart valve including various embodiments of an outer covering including openings. 
         FIG.  46    is a plan view of an example of a sealing member or a cover member for a prosthetic heart valve including woven portions and floating portions configured as floating yarn portions. 
         FIG.  47    is a magnified view of a first woven portion of the sealing member or cover member of  FIG.  46   . 
         FIG.  48    is a magnified view of a second woven portion of the sealing member or cover member of  FIG.  46   . 
         FIG.  49    is a magnified view of a floating yarn portion of the sealing member or cover member of  FIG.  46    in a relaxed state. 
         FIG.  50    illustrates the floating yarn portion of  FIG.  49    in a stretched state. 
         FIG.  51    is a plan view of the sealing member or cover member of  FIG.  46    in a stretched state. 
         FIG.  52    is a perspective view illustrating an edge portion of the sealing member or cover member of  FIG.  46   . 
         FIG.  53    is a side elevational view of a prosthetic heart valve having an outer covering including the sealing member or cover member of  FIG.  46   , according to one embodiment. 
         FIG.  54    illustrates the prosthetic heart valve of  FIG.  53    crimped onto a balloon at the distal end of a delivery apparatus. 
         FIGS.  55 A- 55 J  illustrate various examples of leno weave patterns and leno weaving techniques. 
         FIG.  56    is a perspective view of a mechanically-expandable prosthetic heart valve, according to one embodiment. 
         FIG.  57    is a side-elevation view of an example of a mechanically-expandable frame for a prosthetic heart valve. 
         FIG.  58    is a plan view of an example of a sealing member or cover member for a prosthetic heart valve. 
         FIG.  59    is a magnified view of a portion of the sealing member or cover member of  FIG.  58   . 
         FIG.  60    is a side elevation view showing an example of a covering formed from the sealing member or cover member of  FIG.  58    attached to the frame of  FIG.  57    in the radially expanded configuration. 
         FIG.  61    is a perspective view of the inflow end portion of the frame and covering assembly of  FIG.  60   . 
         FIG.  62    is a side elevation view of the frame and covering of  FIG.  60    in the radially collapsed configuration. 
         FIG.  63    is a side elevation view of the frame of  FIG.  58    including another embodiment of a sealing member that includes an axially resilient portion and a circumferentially resilient portion. 
         FIG.  64    is a top plan view of the frame and sealing member of  FIG.  63    in the expanded configuration. 
         FIG.  65    is a side elevation view of the frame and sealing member of  FIG.  63    in the collapsed configuration. 
         FIG.  66    is a top plan view of the frame and sealing member of  FIG.  63    in the collapsed configuration. 
         FIG.  67    is a plan view of another embodiment of a sealing member valve that includes an axially resilient portion and a circumferentially resilient portion. 
         FIG.  68    is a plan view of another embodiment of a sealing member that includes an axially resilient portion and a circumferentially resilient portion in a natural configuration. 
         FIG.  69    is a plan view of the sealing member of  FIG.  68    tensioned in a first direction. 
         FIG.  70    is a plan view of the sealing member of  FIG.  68    tensioned in a second direction. 
         FIG.  71    is a top plan view of the frame of  FIG.  58    including another embodiment of a sealing member including two circumferentially resilient portions. 
         FIG.  72    is a side elevation view of another embodiment of a sealing member attached to the frame of  FIG.  57    in the radially expanded configuration. 
         FIG.  73    is a side elevation view of another embodiment of a sealing member. 
         FIG.  74    is a side elevation view of the sealing member of  FIG.  73    disposed on a prosthetic valve. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure concerns embodiments of implantable prosthetic heart valves and methods of making and using such devices. In one aspect, a prosthetic heart valve includes a covering or outer covering having a backing layer and a main cushioning layer disposed on the backing layer such that the cushioning layer is oriented radially outward about the circumference of the valve. The cushioning layer can be soft and compliant in order to reduce damage to native tissues of the heart valve and/or of the surrounding anatomy at the implantation site due to, for example, relative movement or friction between the prosthetic valve and the tissue as the heart expands and contracts. The covering can also include an inflow protective portion and an outflow protective portion to cushion the surrounding anatomy and prevent the native tissue of the heart valve from contacting the apices of the strut members of the frame, thereby protecting the surrounding tissue. In one embodiment, the covering can include an inflow strip member and an outflow strip member secured to the cushioning layer and folded over the apices of the strut members to form the inflow and outflow protective portions. 
     Embodiments of the disclosed technology can be used in combination with various prosthetic heart valves configured for implantation at various locations within the heart. A representative, non-limiting example is a prosthetic heart valve for replacing the function of the native mitral valve.  FIGS.  1  and  2    illustrate the mitral valve of the human heart. The mitral valve controls the flow of blood between the left atrium and the left ventricle. After the left atrium receives oxygenated blood from the lungs via the pulmonary veins, the mitral valve permits the flow of the oxygenated blood from the left atrium into the left ventricle. When the left ventricle contracts, the oxygenated blood that was held in the left ventricle is delivered through the aortic valve and the aorta to the rest of the body. Meanwhile, the mitral valve closes during ventricular contraction to prevent any blood from flowing back into the left atrium. 
     When the left ventricle contracts, the blood pressure in the left ventricle increases substantially, which urges the mitral valve closed. Due to the large pressure differential between the left ventricle and the left atrium during this time, a possibility of prolapse, or eversion of the leaflets of the mitral valve back into the atrium, arises. A series of chordae tendineae therefore connect the leaflets of the mitral valve to papillary muscles located on the walls of the left ventricle, where both the chordae tendineae and the papillary muscles are tensioned during ventricular contraction to hold the leaflets in the closed position and to prevent them from extending back towards the left atrium. This generally prevents backflow of oxygenated blood back into the left atrium. The chordae tendineae are schematically illustrated in both the heart cross-section of  FIG.  1    and the top view of the mitral valve of  FIG.  2   . 
     A general shape of the mitral valve and its leaflets as viewed from the left atrium is shown in  FIG.  2   . Various complications of the mitral valve can potentially cause fatal heart failure. One form of valvular heart disease is mitral valve leak or mitral regurgitation, characterized by abnormal leaking of blood from the left ventricle through the mitral valve back into the left atrium. This can be caused by, for example, dilation of the left ventricle, which can cause incomplete coaptation of the native mitral leaflets resulting in leakage through the valve. Mitral valve regurgitation can also be caused by damage to the native leaflets. In these circumstances, it may be desirable to repair the mitral valve, or to replace the functionality of the mitral valve with that of a prosthetic heart valve, such as a transcatheter heart valve. 
     Some transcatheter heart valves are designed to be radially crimped or compressed to facilitate endovascular delivery to an implant site at a patient&#39;s heart. Once positioned at a native valve annulus, the replacement valve is then expanded to an operational state, for example, by an expansion balloon, such that a leaflet structure of the prosthetic heart valve regulates blood flow through the native valve annulus. In other cases, the prosthetic valve can be mechanically expanded or radially self-expand from a compressed delivery state to the operational state under its own resiliency when released from a delivery sheath. One embodiment of a prosthetic heart valve is illustrated in  FIG.  3   . A transcatheter heart valve with a valve profile similar to the prosthetic valve shown in  FIG.  3    is the Edwards Lifesciences SAPIEN XT™ valve. The prosthetic valve  1  in  FIG.  3    has an inflow end  2  and an outflow end  3 , includes a frame or stent  10 , and a leaflet structure  20  supported inside the frame  10 . In some embodiments, a skirt  30  is attached to an inner surface of the frame  10  to form a more suitable attachment surface for the valve leaflets of the leaflet structure  20 . 
     The frame  10  can be made of any body-compatible expandable material that permits both crimping to a radially collapsed state and expansion back to the expanded functional state illustrated in  FIG.  3   . For example, in embodiments where the prosthetic valve is a self-expandable prosthetic valve that expands to its functional size under its own resiliency, the frame  10  can be made of Nitinol or another self-expanding material. In some embodiments, the prosthetic valve can be a plastically expandable valve that is expanded to its functional size by a balloon or another expansion device, in which case the frame can be made of a plastically expandable material, such as stainless steel or a cobalt chromium alloy. Other suitable materials or combinations of materials can also be used. 
     The frame  10  can comprise an annular structure having a plurality of vertically extending commissure attachment posts  11 , which attach and help shape the leaflet structure  20  therein. Additional vertical posts or strut members  12 , along with circumferentially extending strut members  13 , help form the rest of the frame  10 . The strut members  13  of the frame  10  zig-zag and form edged crown portions or apices  14  at the inflow and outflow ends  2 ,  3  of the valve  1 . Furthermore, the attachment posts  11  can also form edges at one or both ends of the frame  10 . 
     In prosthetic valve  1 , the skirt  30  can be attached to an inner surface of the valve frame  10  via one or more threads  40 , which generally wrap around to the outside of various struts  11 ,  12 ,  13  of the frame  10 , as needed. The skirt  30  provides a more substantive attachment surface for portions of the leaflet structure  20  positioned closer to the inflow end  2  of the valve  1 . 
       FIGS.  4 A and  4 B  show side cross-sectional views of embodiments of different anchors that can be used to facilitate implantation of the valve  1  at a native valve, such as at the mitral valve position or tricuspid valve position of a an animal or patient. As shown, for example, in  FIGS.  4 A and  4 B , a left side of a heart  80  includes a left atrium  82 , a left ventricle  84 , and a mitral valve  86  connecting the left atrium  82  and the left ventricle  84 . The mitral valve  86  includes anterior and posterior leaflets  88  that are connected to an inner wall of the left ventricle  84  via chordae tendineae  90  and papillary muscles  92 . 
     In  FIG.  4 A , a first anchoring device includes a flexible ring or halo  60  that surrounds the native leaflets  88  of the native valve  86  and/or the chordae tendineae  90 . The ring  60  pinches or urges portions of the leaflets inwards, in order to form a more circular opening at the native valve, for more effective implantation of the prosthetic valve  1 . The valve prosthesis  1  is retained at the native valve  86  by the ring anchor  60  (which acts as a docking device), and can be delivered to the position shown, for example, by positioning the valve  1  in the native valve  86  while the prosthetic valve  1  is delivered and expanded once it is positioned as shown in  FIG.  4 A . Once expanded, the prosthetic valve  1  pushes outwardly against the ring anchor  60  to secure the positions of both the valve  1  and the ring anchor  60 . In some embodiments, an undersized ring anchor  60  with an inner diameter that is slightly smaller than the diameter of the prosthetic valve  1  in its expanded state can be used, to provide stronger friction between the parts, leading to more secure attachment. As can be seen in  FIG.  4 A , at least a portion of the native valve leaflets  88  and/or a portion of the chordae tendineae  90  are pinched or sandwiched between the valve  1  and the ring anchor  60  to secure the components to the native anatomy. 
       FIG.  4 B  is similar to  FIG.  4 A , except instead of a ring anchor  60 , a helical or coiled anchor or docking device  70  is utilized instead. The helical anchor  70  can include more coils or turns than the ring anchor  60 , and can extend both upstream and downstream of the native valve  86 . The helical anchor  70  in some situations can provide a greater and more secure attachment area against which the prosthetic valve  1  can abut. Similar to the ring anchor  60  in  FIG.  4 A , at least a portion of the native valve leaflets  88  and/or the chordae  90  are pinched between the valve  1  and the helical anchor  70 . Methods and devices for implanting anchors/docking devices and prosthetic valves, which can be used with the inventions in this disclosure, are described in U.S. application Ser. No. 15/682,287, filed on Aug. 21, 2017 and published as US 2018/0055628, U.S. application Ser. No. 15/684,836, filed on Aug. 23, 2017 and published as US 2018/0055630, and U.S. application Ser. No. 15/984,661, filed on May 21, 2018 and published as US 2018/0318079, which are each incorporated herein by reference. 
       FIG.  4 C  illustrates another representative embodiment of an anchor or docking device  300  that can be used in combination with any of the prosthetic valves described herein. The anchor  300  has a functional coil/turn region or central region  302  and an encircling turn or lower region  304 . The anchor  300  can also, optionally, have an upper region  306 . The lower region  304  includes one or more turns that can be configured to encircle or capture the chordae tendineae and/or the leaflets of a native valve, such as the mitral valve or tricuspid valve. The central region  302  includes a plurality of turns configured to retain the prosthetic valve at the native valve. The upper region  306  can include one or more turns, and can be configured to keep the anchor from being dislodged from the valve annulus prior to implantation of the prosthetic valve. In some embodiments, the upper region  306  can be positioned over the floor of the atrium, and can be configured to keep the turns of the central region  302  positioned high within the native valve apparatus. 
     The anchor  300  can, optionally, also include an extension portion  308  positioned between the central region  302  and the upper region  306 . In some embodiments, the extension portion  308  can instead be positioned, for example, wholly in the central region  302  (e.g., at an upper portion of the central region) or wholly in the upper region  306 . The extension portion  308  includes a part of the coil that extends substantially parallel to a central axis of the anchor. In some embodiments, the extension portion  308  can be angled relative to the central axis of the anchor. In some embodiments, the extension portions  308  can be longer or shorter than that shown and can have a larger or smaller angle relative to region  302  and/or region  306 . The extension portion  308  can serve to space the central region  302  and the upper region  306  apart from one another in a direction along the central axis so that a gap is formed between the atrial side and the ventricular side of the anchor. 
     The extension portion  308  of the anchor can be configured to be positioned through, near, and/or around the native valve annulus, in order to reduce the amount of the anchor that passes through, pushes, or rests against the native annulus and/or the native leaflets when the anchor is implanted. This can reduce the force applied by the anchor on the native valve and reduce abrasion of the native leaflets. In one arrangement, the extension portion  308  is positioned at and passes through one of the commissures of the native valve. In this manner, the extension portion  308  can space the upper region  306  apart from the native leaflets of the native valve to prevent the upper region  306  from interacting with the native leaflets from the atrial side. The extension portion  308  also elevates the upper region  306  such that the upper region contacts the atrial wall above the native valve, which can reduce the stress on and around the native valve, as well as provide for better retention of the anchor. 
     As shown in  FIG.  4 C , the anchor  300  can further include one or more openings configured as through holes  310  at or near one or both of the proximal and distal ends of the anchor. The through holes  310  can serve, for example, as suturing holes for attaching a cover layer over the coil of the anchor, and/or as an attachment site or tethering holes for delivery tools such as a pull wire, retention member, retention suture, etc. In some embodiments, a width or thickness of the coil of the anchor  300  can also be varied along the length of the anchor. For example, a central portion of the anchor and/or extension  308  can be made thinner than end portions of the anchor. This can allow the central portion and/or extension  308  to exhibit greater flexibility, while the end portions can be stronger or more robust. In certain examples, making the end portions of the coil relatively thicker can also provide more surface area for suturing or otherwise attaching a cover layer to the coil of the anchor. 
     In certain embodiments, the anchor or docking device  300  can be configured for insertion through the native valve annulus in a counter-clockwise direction. For example, the anchor can be advanced through commissure A3P3, commissure A1P1, or through another part of the native mitral valve. The counter-clockwise direction of the coil of the anchor  300  can also allow for bending of the distal end of the delivery catheter in a similar counter-clockwise direction, which can be easier to achieve than to bend the delivery catheter in the clockwise direction. However, it should be understood that the anchor can be configured for either clockwise or counter-clockwise insertion through the valve, as desired. 
     Returning to the prosthetic valve example of  FIG.  3   , the prosthetic valve  1  generally includes a metal frame  10  that forms a number of edges. In addition, many frames  10  are constructed with edged crowns or apices  14  and protruding commissure attachment posts  11 , as well as threads  40  that can be exposed along an outer surface of the frame  10 . These features can cause damage to the native tissue, such as tissue lodged between the prosthetic valve  1  and the anchor  60 ,  70 , for example, by movement or friction between the native tissue and the various abrasive surfaces of the prosthetic valve  1 . In addition, other native tissue in close proximity to the prosthetic valve  1 , such as the chordae tendineae, can also potentially be damaged. 
       FIGS.  5 - 7    illustrate a representative embodiment of a prosthetic heart valve  100  similar to the Edwards Lifesciences SAPIEN™ 3 valve, which is described in detail in U.S. Pat. No. 9,393,110, which is incorporated herein by reference. The prosthetic valve  100  includes a frame  102  formed by a plurality of angled strut members  104 , and having an inflow end  106  and an outflow end  108 . The prosthetic valve  100  also includes a leaflet structure comprising three leaflets  110  situated at least partially within the frame  102  and configured to collapse in a tricuspid arrangement similar to the aortic valve, although the prosthetic valve can also include two leaflets configured to collapse in a bicuspid arrangement in the manner of the mitral valve, or more than three leaflets, as desired. The strut members  104  can form a plurality of apices  124  arranged around the inflow and outflow ends of the frame. 
     The prosthetic heart valve can include a covering or outer covering  112  configured to cushion (protect) native tissue in contact with the prosthetic valve after implantation, and to reduce damage to the tissue due to movement or friction between the tissue and surfaces of the valve. The covering  112  can also reduce paravalvular leakage. In the embodiment of  FIG.  5   , the covering  112  includes a first layer configured as a backing layer  114  (see, e.g.,  FIG.  8   ), and a second layer configured as a cushioning layer  116 . The cushioning layer  116  can be disposed on the backing layer  114 , and can comprise a soft, plush surface  118  oriented radially outward so as to protect tissue or objects in contact with the cushioning layer. In the illustrated configuration, the covering  112  also includes an atraumatic inflow protective portion  120  extending circumferentially around the inflow end  106  of the frame, and an atraumatic outflow protective portion  122  extending circumferentially around the outflow end  108  of the frame. The portion of the cushioning layer  116  between the inflow and outflow protective portions  120 ,  122  can define a main cushioning portion  136 . The first layer  114  and the second layer  116  can together form a sealing member or cover member that can be placed around the frame to form the covering  112 . The sealing member/cover member can also comprise the protective portions  120 ,  122 . 
       FIG.  8    is a cross-sectional view schematically illustrating the prosthetic valve  100  with the leaflet structure removed for purposes of illustration. The covering  112  extends around the exterior of the frame  102 , such that an interior surface of the backing layer  114  is adjacent or against the exterior surfaces of the strut members  104 . As illustrated in  FIG.  8   , the cushioning layer  116  can have a length that is greater than the length of the frame as measured along a longitudinal axis  126  of the frame. Thus, the covering  112  can be situated such that the cushioning layer  116  extends distally (e.g., in the upstream direction) beyond the apices  124  of the strut members at the inflow end  106  of the frame, with the portion of the cushioning layer extending beyond the apices being referred to herein as distal end portion  128 . At the opposite end of the valve, the cushioning layer  116  can extend proximally (e.g., in the downstream direction) beyond the apices  124  of the strut members, with the portion located beyond the apices being referred to as proximal end portion  130 . The distances by which the proximal and distal end portions  128 ,  130  of the cushioning layer  116  extend beyond the apices at the respective end of the valve can be the same or different depending upon, for example, the dimensions of the valve, the particular application, etc. 
     The backing layer  114  can have sufficient length in the axial direction such that a proximal end portion or flap  132  of the backing layer  114  can be folded over the proximal end portion  130  of the cushioning layer  116  in the manner of a cuff to form the outflow protective portion  122 . Meanwhile, a distal end portion or flap  134  of the backing layer  114  can be folded over the distal end portion  128  of the cushioning layer  116  to form the inflow protective portion  120 . The proximal and distal flaps  132 ,  134  of the backing layer  116  can be secured to the underlying section of the backing layer by attachment means, for example, sutures  136 , adhesive, clips, etc. In this manner, the inflow and outflow protective portions  120 ,  122  are constructed such that the proximal and distal end portions  130 ,  128  of the cushioning layer  116  are at least partially enclosed by the flaps  132 ,  134  of the backing layer  116 . This construction provides sufficient strength and resistance to bending to the inflow and outflow protective portions  120 ,  122  so that they extend along the longitudinal axis  126  of the valve without bending or otherwise protruding into the inner diameter of the valve (e.g., by bending under their own weight, by blood flow, or by blood pressure). In this manner, the inflow and outflow protective portions  120 ,  122  minimally impact flow through the prosthetic valve and avoid interfering with the prosthetic valve leaflets, reducing flow disturbances, and potentially reducing the risk of thrombus. 
     In the illustrated configuration, the inflow protective portion  120  can extend beyond the apices  124  of the strut members at the inflow end of the frame by a distance d 1 , and the outflow protective portion  122  can extend beyond the apices  124  of the strut members at the outflow end of the frame by a distance d 2 . The distances d 1  and d 2  can be the same or different, depending upon the type of prosthetic valve, the treatment location, etc. For example, for a 29 mm prosthetic valve, the distances d 1  and d 2  can be from about 0.5 mm to about 3 mm. In a representative embodiment, the distances d 1  and d 2  can be from about 1 mm to about 2 mm. Because the inflow and outflow protective portions  120 ,  122  extend beyond the apices  124  of the respective ends of the frame, the inflow and outflow protective portions can shield adjacent tissue and/or another implant adjacent the prosthetic valve from contacting the apices  124  of the frame. 
     For example,  FIG.  10    illustrates the prosthetic valve  100  implanted within an anchor or docking device  70  in the native valve  86 , similar to  FIGS.  4 A and  4 B  above. In the illustrated example, the inflow end portion of the prosthetic valve is shown positioned above the superior surface of the native valve annulus and spaced from surrounding tissue. However, in other implementations, depending on the axial positioning of the prosthetic valve, which can be varied, the inflow protective portion  120  can contact the native leaflets  88  and prevent them from directly contacting the apices  124  at the inflow end of the frame. Depending on the diameter of the prosthetic valve at the inflow end, the inflow protective portion  120  can serve to prevent the atrium wall from directly contacting the apices  124  at the inflow end of the frame. 
     As shown in  FIG.  10   , the anchor  70  can also rest against the compliant inflow protective portion  120 . Meanwhile, the portions of the native leaflets  88  captured between the anchor  70  and the prosthetic valve  100  can be cushioned by the plush surface  118  of the main cushioning portion  136 . In certain embodiments, the soft, compliant nature and texture of the cushioning layer  116  can increase friction between the native leaflets and the prosthetic valve. This can reduce relative movement of the native leaflets and the prosthetic valve as the left ventricle expands and contracts, reducing the likelihood of damage to the native leaflets and the surrounding tissue. The cushioning layer  116  can also provide increased retention forces between the anchor  70  and the prosthetic valve  100 . The plush, compressible nature of the cushioning layer  116  can also reduce penetration of the covering  112  through the openings in the frame  102  caused by application of pressure to the covering, thereby reducing interference with the hemodynamics of the valve. Additionally, the outflow cushioning portion  122  can protect the chordae tendineae  90  from contacting the strut members of the frame, and in particular the apices  124  at the outflow end of the frame, thereby reducing the risk of injury or rupture of the chordae. 
     The backing layer  114  can comprise, for example, any of various woven fabrics, such as gauze, polyethylene terephthalate (PET) fabric (e.g., Dacron), polyester fabric, polyamide fabric, or any of various non-woven fabrics, such as felt. In certain embodiments, the backing layer  114  can also comprise a film including any of a variety of crystalline or semi-crystalline polymeric materials, such as polytetrafluorethylene (PTFE), PET, polypropylene, polyamide, polyetheretherketone (PEEK), etc. In this manner, the backing layer  114  can be relatively thin and yet strong enough to allow the covering  112  to be sutured to the frame, and to allow the prosthetic valve to be crimped, without tearing. 
     As stated above, the cushioning layer  116  can comprise at least one soft, plush surface  118 . In certain examples, the cushioning layer  116  can be made from any of a variety of woven or knitted fabrics wherein the surface  116  is the surface of a plush nap or pile of the fabric. Exemplary fabrics having a pile include velour, velvet, velveteen, corduroy, terrycloth, fleece, etc.  FIG.  9    illustrates a representative embodiment of the cushioning layer  116  in greater detail. In the embodiment of  FIG.  9   , the cushioning layer  116  can have a base layer  162  (a first layer) from which the pile  158  (a second layer) extends. The base layer  162  can comprise warp and weft strands (e.g., yarns, etc.) woven or knitted into a mesh-like structure. For example, in a representative configuration, the strands/yarns of the base layer  162  can be flat strands/yarns with a denier range of from about 7 dtex to about 100 dtex, and can be knitted with a density of from about 20 to about 100 wales per inch and from about 30 to about 110 courses per inch. The strands/yarns can be made from, for example, biocompatible thermoplastic polymers such as PET, Nylon, ePTFE, etc., other suitable natural or synthetic fibers, or soft monolithic materials. 
     The pile  158  can comprise pile strands or pile yarns  164  woven or knitted into loops. In certain configurations, the pile strands or pile yarns  164  can be the warp strands/yarns or the weft strands/yarns of the base layer  162  woven or knitted to form the loops. The pile strands or pile yarns  164  can also be separate strands/yarns incorporated into the base layer, depending upon the particular characteristics desired. In certain embodiments, the loops can be cut such that the pile  158  is a cut pile in the manner of, for example, a velour fabric.  FIGS.  5 - 8    illustrate a representative embodiment of the cushioning layer  116  configured as a velour fabric. In some embodiments, the loops can be left intact to form a looped pile in the manner of, for example, terrycloth.  FIG.  9    illustrates a representative embodiment of the cushioning layer  116  in which the pile strands or pile yarns  164  are knitted to form loops  166 .  FIG.  11    illustrates an embodiment of the covering  112  incorporating the cushioning layer  116  of  FIG.  9   . 
     In some configurations, the pile strands or pile yarns  164  are texturized or textured strands/yarns having an increased surface area due to, for example, a wavy or undulating structure. In configurations such as the looped pile embodiment of  FIG.  11   , the loop structure and the increased surface area provided by the textured strands or textured yarn of the loops  166  can allow the loops to act as a scaffold for tissue growth into and around the loops of the pile. Promoting tissue growth into the pile  158  can increase retention of the valve at the implant site and contribute to long-term stability of the valve. 
     The cushioning layer embodiments described herein can also contribute to improved compressibility and shape memory properties of the covering  112  over known valve coverings and skirts. For example, the pile  158  can be compliant such that it compresses under load (e.g., when in contact with tissue, implants, or the like), and returns to its original size and shape when the load is relieved. This can help to improve sealing between the cushioning layer  116  and, for example, support structures or other devices such as the helical anchor  70  in which the prosthetic valve is deployed, or between the cushioning layer and the walls of the native annulus. The compressibility provided by the pile  158  of the cushioning layer  116  is also beneficial in reducing the crimp profile of the prosthetic valve. Additionally, the covering  112  can prevent the leaflets  110  or portions thereof from extending through spaces between the strut members  104  as the prosthetic valve is crimped, thereby reducing damage to the prosthetic leaflets due to pinching of the leaflets between struts. 
     In some embodiments, the cushioning layer  116  is made of non-woven fabric such as felt, or fibers such as non-woven cotton fibers. The cushioning layer  116  can also be made of porous or spongey materials such as, for example, any of a variety of compliant polymeric foam materials, or woven or knitted fabrics, such as woven or knitted PET. In some embodiments, the proximal and distal end portions of the cushioning layer  116  of the embodiment of  FIG.  11    are free of loops  166 , and the inflow and outflow protective portions  120 ,  122  are formed by folding the base layer  162  back on itself to form cuffs at the inflow and outflow ends of the valve. 
     In a representative example illustrated in  FIG.  12   , the covering  112  of  FIGS.  5 - 8    is made, at least in part, by cutting a fabric material (e.g., a PET fabric) with a stencil  138  to form the backing layer  114 . In the illustrated embodiment, the stencil  138  is shaped like a parallelogram, although other configurations and shapes are possible. The angles of the corners of the stencil  138  can be shaped such that the fabric material is cut at about a 45 degree angle relative to the direction of the fibers of the fabric. This can improve the crimpability of the resulting backing layer  114  by, for example, allowing the backing layer to stretch along a direction diagonal to the warp and weft strands/yarns.  FIG.  18    illustrates a plan view of a representative example of the backing layer  114  after being cut using the parallelogram stencil  138 . 
     The cushioning layer  116  can be attached (e.g., by sutures, adhesive, etc.) to the backing layer  114 . In  FIG.  12   , the location of the proximal and distal ends of the frame  102  when the covering is attached to the frame are represented as dashed lines  140 ,  141  on the backing layer  114 . Meanwhile, dashed lines  142 ,  144  represent the location of the proximal and distal edges of the cushioning layer  116  once the cushioning layer is secured to the backing layer. For example, the cushioning layer  116  can be sutured to the backing layer  114  along the proximal and distal edges at or near lines  142 ,  144 . As shown in  FIG.  12   , line  142  representing the proximal edge of the cushioning layer  116  can be offset from the proximal edge  146  of the backing layer  114  by a distance d 3  to create the proximal flap  132 . Meanwhile, line  144  representing the distal edge of the cushioning layer  116  can be offset from the distal edge  148  of the backing layer  114  by a distance d 4  to create the distal flap  134 . The distances d 3  and d 4  can be the same or different, as desired. For example, depending upon the size of the valve and the size of the inflow and outflow cushioning portions, the distances d 3  and d 4  can be, for example, about 3-5 mm. In some embodiments, the distances d 3  and d 4  can be about 3.5 mm. 
     Once the cushioning layer  116  is secured to the backing layer  114 , the resulting swatch can be folded and sutured into a cylindrical shape. The flaps  132 ,  134  of the backing layer  114  can be folded over the edges of the cushioning layer  116  and sutured to form the inflow and outflow protective portions  120 ,  122 . The resulting covering  112  can then be secured to the frame  102  by attachment means, for example, suturing, clipping, adhering, etc. it to the strut members  104 . 
       FIGS.  13  and  14    illustrate an example of the covering  112  in which the inflow and outflow protective portions  120 ,  122  are formed with separate pieces of material that wrap around the ends of the cushioning layer  116  at the inflow and outflow ends of the valve. For example, the proximal end portion  130  of the cushioning layer  116  can be covered by a member configured as a strip  150  of material that wraps around the cushioning layer from the interior surface  170  (e.g., the surface adjacent the frame) of the cushioning layer  116 , over the circumferential edge of the proximal end portion  130 , and onto the exterior surface  118  of the cushioning layer to form the outflow protective portion  122 . Likewise, a material strip member  152  can extend from the interior surface  170  of the cushioning layer, over the circumferential edge of the distal end portion  128 , and onto the exterior surface of the cushioning layer to form the inflow protective portion  120 . The strip members  150 ,  152  can be sutured to the cushioning layer  116  along the proximal and distal edge portions  130 ,  128  of the cushioning layer at suture lines  154 ,  156 , respectively. 
     In certain configurations, the strip members  150 ,  152  can be made from any of various natural materials and/or tissues, such as pericardial tissue (e.g., bovine pericardial tissue). The strip members  150 ,  152  can also be made of any of various synthetic materials, such as PET and/or expanded polytetrafluoroethylene (ePTFE). In some configurations, making the strip members  150 ,  152  from natural tissues such as pericardial tissue can provide desirable properties such as strength, durability, fatigue resistance, and compliance, and cushioning and reduced friction with materials or tissues surrounding the implant. 
       FIG.  15    illustrates a prosthetic valve  200  including an example of an outer cover or covering  202  comprising a cushioning layer  204  made of a spacer fabric. In the illustrated embodiment, the outer covering  202  is shown without inflow and outflow protective portions, and with the cushioning layer  204  extending along the full length of the frame from the inflow end to the outflow end of the valve. However, the outer covering  202  may also include inflow and/or outflow protective portions, as described elsewhere herein. The cushioning layer  204  can be or form a sealing member or cover member, which can be attached to the frame to form the covering  202 . 
     Referring to  FIGS.  16  and  17   , the spacer fabric cushioning layer or sealing member/cover member can comprise a first layer  206 , a second layer  208 , and a spacer layer  210  extending between the first and second layers to create a three-dimensional fabric. The first and second layers  206 ,  208  can be woven fabric or mesh layers. In certain configurations, one or more of the first and second layers  206 ,  208  can be woven such that they define a plurality of openings  212 . In some examples, openings such as the openings  212  can promote tissue growth into the covering  202 . In some embodiments, the layers  206 ,  208  need not define openings, but can be porous, as desired. 
     The spacer layer  210  can comprise a plurality of pile strands or pile yarns  214 . The pile strands or pile yarns  214  can be, for example, monofilament strands/yarns arranged to form a scaffold-like structure between the first and second layers  206 ,  208 . For example,  FIGS.  16  and  17    illustrate an embodiment in which the pile strands or pile yarns  214  extend between the first and second layers  206 ,  208  in a sinusoidal or looping pattern. 
     In certain examples, the pile strands or pile yarns  214  can have a rigidity that is greater than the rigidity of the fabric of the first and second layers  206 ,  208  such that the pile strands or pile yarns  214  can extend between the first and second layers  206 ,  208  without collapsing under the weight of the second layer  208 . The pile strands or pile yarns  214  can also be sufficiently resilient such that the pile strands or pile yarns can bend or give when subjected to a load, allowing the fabric to compress, and return to their non-deflected state when the load is removed. 
     The spacer fabric can be warp-knitted, or weft-knitted, as desired. Some configurations of the spacer cloth can be made on a double-bar knitting machine. In a representative example, the strands/yarns of the first and second layers  206 ,  208  can have a denier range of from about 10 dtex to about 70 dtex, and the strands/yarns of the monofilament pile strands/yarns  214  can have a denier range of from about 2 mil to about 10 mil. The pile strands or pile yarns  214  can have a knitting density of from about 20 to about 100 wales per inch, and from about 30 to about 110 courses per inch. Additionally, in some configurations (e.g., warp-knitted spacer fabrics) materials with different flexibility properties may be incorporated into the spacer cloth to improve the overall flexibility of the spacer cloth. 
       FIGS.  19 - 21    illustrate an example of a prosthetic heart valve  400  including an outer covering with inflow and outflow protective portions that encapsulate the apices of the strut members. For example, the prosthetic valve can include a frame  402  formed by a plurality of strut members  404  defining apices  420  ( FIGS.  22  and  24   ), and can have an inflow end  406  and an outflow end  408 . A plurality of leaflets  410  can be situated at least partially within the frame  402 . 
     The prosthetic valve can include a covering or outer covering  412  situated about the frame  402 . The outer covering  412  can include a main layer or main cushioning layer  414  including a plush exterior surface  432  (e.g., a first surface), similar to the cushioning layer  116  of  FIG.  13    above. The covering  412  can also include an inflow protective portion  416  extending circumferentially around the inflow end  406  of the valve, and an outflow protective portion  418  extending circumferentially around the outflow end  408  of the valve. The inflow and outflow protective portions  416 ,  418  can be formed with separate pieces of material that are folded around the circumferential ends of the cushioning layer  414  at the inflow and outflow ends of the valve such that the protective portions encapsulate the apices  420  of the strut members. The layer  414  alone or together with protective portions  416 ,  418  can form a sealing member or cover member that can be placed around the frame to form the covering  412 . 
     For example, with reference to  FIG.  22   , the inflow protective portion  416  can comprise a member configured as a strip  424  of material including a first circumferential edge portion  426  and a second circumferential edge portion  428 . The strip member  424  of material can be folded such that the first circumferential edge portion  426  is adjacent (e.g., contacting) an inner skirt  430  disposed within the frame  402 . The first circumferential edge portion  426  thereby forms a first or inner layer of the inflow protective portion  416 . The strip member  424  can extend over the apices  420  of the strut members, and over an inflow end portion  422  of the cushioning layer  414  such that the second circumferential edge portion  428  is disposed on the exterior surface  432  of the cushioning layer  414 . In this manner, the inflow end portion  422  of the cushioning layer  414  can form a second layer of the inflow protective portion  414 , and the second circumferential edge portion  428  can form a third or outer layer of the inflow protective portion. The first and second circumferential edge portions  426 ,  428  of the strip member  424  can be secured to the strut members  404  (e.g., the rung of struts nearest the inflow end  406 ) with attachment means, such as sutures  434 ,  435 , adhesive, etc. Thus, the strip member  424  can encapsulate the apices  420 , along with the inflow end portion  422  of the cushioning layer  414 , between the first and second circumferential edge portions  426 ,  428 . 
     In the illustrated configuration, the inflow protective portion  416  extends beyond the apices  420  of the frame, similar to the embodiments above. In particular, the inflow end portion  422  of the cushioning layer  414  can extend beyond the apices  420  of the frame and into the inflow protective portion  416  within the folded strip  424 . In this manner, the inflow end portion  422  of the cushioning layer  414 , together with the strip member  424 , can impart a resilient, cushioning quality to the inflow protective portion  416 . This can also allow the inflow protective portion  416  to resiliently deform to accommodate and protect, for example, native tissue, other implants, etc., that come in contact with the inflow protective portion. 
     Optionally, one or more additional materials or layers can be included under and/or to form any of the protective portions (e.g.,  120 ,  122 ,  416 ,  418 ,  518 ,  520 , etc.) to provide added cushioning and/or protection at the apices of the frame. 
     In the illustrated embodiment, the inflow end portion  422  can extend beyond the apices  420  by a distance d 1 . The distance d 1  can be configured such the inflow end portion  422  can extend over or cover the apices  420  when the inflow protective portion  416  comes in contact with, for example, native tissue at the treatment site. The strip member  424  can also form a dome over the edge of the of the inflow end portion  422  such that the edge of the inflow end portion  422  is spaced apart from the domed portion of the strip member  424 . In some embodiments, the strip member  424  is folded such that it contacts the edge of the inflow edge portion  422 , similar to the embodiment of  FIG.  13   . 
     The outflow protective portion  418  can include a member configured as a strip  436  of material folded such that a first circumferential edge portion  438  is adjacent (e.g., contacting) inner surfaces  440  of the strut members, and a second circumferential edge portion  442  is disposed on the exterior surface  432  of the cushioning layer  414 , similar to the inflow protective portion  416 . An outflow end portion  444  of the cushioning layer  414  can extend beyond the apices  420  by a distance d 2 , and can be encapsulated by the strip member  436  together with the apices  420  between the first and second circumferential edge portions  438 ,  442 . The distance d 2  can be the same as distance d 1  or different, as desired. The strip member  436  can be secured to the strut members  404  with attachment means, such as sutures  446 ,  447 , adhesive, etc. The strip member  436  can also form a domed shape similar to the strip member  424 . 
     In certain configurations, the cushioning layer  414  can be a fabric including a plush pile, such as a velour fabric, or any other type of plush knitted, woven, or non-woven material, as described above. In some embodiments, the cushioning layer  414  may also comprise a relatively low thickness woven fabric without a plush pile. In certain configurations, the strip members  424 ,  436  can be made of resilient natural tissue materials such as pericardium. Optionally, the strip members can also be made from fabric or polymeric materials such as PTFE or ePTFE. 
       FIGS.  23 - 26    illustrate a representative method of making the covering or outer covering  412  and attaching the covering to the prosthetic valve  400  to form the inflow and outflow protective portions  416 ,  418 .  FIG.  23    illustrates the outer covering  412  in an unfolded configuration prior to securing the covering to the frame  402 . As illustrated in  FIG.  23   , the second circumferential edge portion  428  of the strip member  424  can be sutured to the plush surface  432  (e.g., the first surface) of the cushioning layer  414  at the inflow end portion  422  of the cushioning layer. The second circumferential edge portion  442  of the strip member  436  can be sutured to the plush surface  432  of the cushioning layer  414  at the outflow end portion  444  of the cushioning layer. 
     In the illustrated configuration, the cushioning layer  414  and the strip members  424 ,  436  can have a length dimension L corresponding to a circumference of the frame  402 . In a representative example, the length dimension L can be about 93 mm. The strip members  424 ,  436  can also have respective width dimensions W 1 , W 2 . Referring to width dimension W 1  for purposes of illustration, the width dimension W 1  can be configured such that the strip member  424  extends from the interior of the valve to the exterior of the valve without contacting the apices  420  of the strut members, as shown in  FIG.  22   . For example, the width dimension W 1  can be configured such that the strip member  424  extends from adjacent the rung of strut members  404  at the inflow end  406  of the frame to the exterior of the valve adjacent the same rung of strut members and forms a domed shape over the apices  420 . In certain configurations, the width dimension W 1  can be about 6 mm. The width dimension W 2  can be the same as W 1  or different, as desired. 
     Referring to  FIG.  24   , the outer covering  412  can be folded and sutured into a cylindrical shape. The outer covering  412  can then be situated around the frame  402  such that a second or interior surface  454  of the cushioning layer  414  is oriented toward the frame. In certain configurations, the frame  402  can already include the inner skirt  430  and the leaflet structure  410 , as shown in  FIG.  24   . 
     Referring to  FIGS.  25  and  26   , the outer covering  412  can then be sutured to the frame. For example, as illustrated in  FIG.  25   , the strip member  424  can be aligned with an adjacent rung of strut members  404  (e.g., the rung of strut members nearest the inflow end of the frame). The cushioning layer  414  and/or the strip member  424  can then be sutured to the strut members  404  at suture line  434 . The strip member  424  can then be folded over the apices  420  at the inflow end of the frame, and the first and second circumferential edge portions  426 ,  428  can be sutured to each other at suture line  435  to form the inflow protective portion  416 . In some embodiments, the strip member  424  is folded and sutured to form the inflow protective portion  416  before the outer covering  412  is sutured to the frame. 
     The outflow protective portion  418  can be formed in a similar manner. For example, the strip member  426  can be aligned with the rung of strut members  404  adjacent the outflow end  408  of the frame, and the strip member  426  and/or the cushioning layer  414  can be sutured to the strut members. The strip member  436  can then be folded over the apices  420  and the cushioning layer  414  at the outflow end of the frame, and the first and second circumferential edge portions  438 ,  442  can be sutured together, and to the rung of strut members  404  adjacent the outflow end of the frame, to form the outflow protective portion  418 . The covering  412  can also be sutured to the frame at one or more additional locations, such as at suture lines  448  and  450 , as shown in  FIG.  22   . 
       FIGS.  27  and  28    illustrates an example of a prosthetic heart valve  500  including a frame  502  formed by a plurality of strut members  504  defining apices  506  ( FIG.  28   ), similar to the frame 102 described above and in U.S. Pat. No. 9,393,110. The prosthetic valve  500  can have an inflow end  508  and an outflow end  510 , and can include a leaflet structure (not shown) situated at least partially within the frame. 
     The prosthetic valve can include an outer covering  514  situated about the frame  502 . The covering or outer covering  514  can include a main cushioning layer  516  (also referred to as a main layer) having a cylindrical shape, and made from a woven, knitted, or braided fabric (e.g., a PET fabric, an ultra-high molecular weight polyethylene (UHMWPE) fabric, a PTFE fabric, etc.). In some embodiments, the fabric of the main cushioning layer  516  can include a plush pile. In some embodiments, the fabric of the main cushioning layer  516  can comprise texturized strands (e.g., texturized yarns, etc.) in which the constituent fibers of the strands/yarns have been bulked by, for example, being twisted, heat set, and untwisted such that the fibers retain their deformed, twisted shape and create a voluminous fabric. The volume contributed by the texturized strands/yarns can improve the cushioning properties of the covering, as well as increase friction between the fabric and the surrounding anatomy and/or an anchoring device into which the valve is deployed. The layer  516  alone or together with protective portions  518 ,  520  and/or layers  530 ,  534  can form a sealing member or cover member that can be placed around the frame to form the covering  514 . 
     The outer covering  514  can include an inflow protective portion  518  extending circumferentially around the inflow end  508  of the frame, and an outflow protective portion  520  extending circumferentially around the outflow end  510  of the frame. In certain embodiments, the inflow and outflow protective portions  518  and  520  can be formed on the fabric of the main cushioning layer  516  such that the outer covering  514  is a one-piece, unitary construction, as described further below. 
     Referring to  FIG.  28   , the main cushioning layer  516  can include a first circumferential edge portion  522  (also referred to as an inflow edge portion) located adjacent the inflow end  508  of the valve, which can form a part of the inflow protective portion  518 . The cushioning layer  516  can further include a second circumferential edge portion  524  (also referred to as an outflow edge portion) located adjacent the outflow end  510  of the valve, and which can form a part of the outflow protective portion  520 . Referring still to  FIG.  28   , the first circumferential edge portion  522  can comprise an edge  526 , and the second circumferential edge portion  524  can comprise an edge  528 . The first circumferential edge portion  522  can be folded or wrapped over the apices  506  of the strut members  504  such that the edge  526  is disposed on the inside of the frame  502 . The second circumferential edge portion  524  can be folded around the apices  506  at the outflow end  510  of the frame in a similar fashion such that the edge  528  is also disposed on the inside of the frame opposite the edge  522 . 
     In the illustrated configuration, the inflow protective portion  518  can include a second or outer layer configured as a lubricious layer  530  of material disposed on an outer surface  532  of the main cushioning layer  516 . The outflow protective portion  520  can also include a second or outer lubricious layer  534  of material disposed on the outer surface  532  of the main cushioning layer  516 . In some embodiments, the layers  530  and  534  can be smooth, low-thickness coatings comprising a low-friction or lubricious material. For example, in certain configurations one or both of the layers  530 ,  534  can comprise PTFE or ePTFE. 
     In the illustrated configuration, the lubricious layer  530  can have a first circumferential edge  536  ( FIG.  27   ) and a second circumferential edge  538  ( FIG.  28   ). The lubricious layer  530  can extend from the outer surface  532  of the main cushioning layer  516  and over the apices  506  such that the first circumferential edge  536  is disposed on the outside of the frame and the second circumferential edge  538  is disposed on the inside of the frame. The lubricious layer  534  can be configured similarly, such that a first circumferential edge  540  ( FIG.  27   ) is disposed outside the frame, the layer  534  extends over the apices  506  of the outflow end  510  of the frame, and a second circumferential edge  542  ( FIG.  28   ) is disposed inside the frame. Once implanted in a native heart valve, the protection portions  518  and  520  can prevent direct contact between the apices  506  and the surrounding anatomy. The lubricious material of the layers  530  and  534  can also reduce friction with tissue of the native valve (e.g., chordae) in contact with the inflow and outflow ends of the prosthetic valve, thereby preventing damage to the tissue. In some embodiments, the entire outer surface  532  of the main cushioning layer  516 , or a portion thereof, is covered with a lubricious coating such as ePTFE in addition to the inflow and outflow protective portions  518  and  520  such that the lubricious coating extends axially from the inflow end to the outflow end of the covering. In some embodiments, the cushioning layer  516  is formed from woven, knitted, braided, or electrospun fibers of lubricious material, such as PTFE, ePTFE, etc., and can form the inflow and outflow protective portions. 
       FIGS.  29 - 31 B  illustrate a representative method of making the covering  514 .  FIG.  29    illustrates the main cushioning layer  516  formed into a cylindrical, tubular body. Referring to  FIG.  30   , the first circumferential edge portion  522  of the cushioning layer  516  can then be folded over (e.g., inward toward the interior surface of the tubular body) in the direction of arrows  544  such that the lower edge  526  is inside the tubular body and disposed against the interior surface of the tubular body. The edge portion  524  can be folded in a similar manner as indicated by arrows  546  such that the top edge  528  is inside the tubular body and disposed against the interior surface. 
     Referring to  FIGS.  31 A and  31 B , the lubricious layers  530 ,  534  can then be applied to the main layer  516  to form the inflow and outflow protection portions  518  and  520 . In certain embodiments, the lubricious layers  530 ,  534  can be formed by electrospinning a low-friction material (e.g., PTFE, ePTFE, etc.) onto the first and second circumferential edge portions  522  and  524 . In certain embodiments, forming the layers  530 , and  534  by electrospinning can provide a smooth, uniform surface, and keep the thickness of the layers within strictly prescribed specifications. 
     For example, the layers  530  and  534  can be made relatively thin, which can reduce the overall crimp profile of the valve. In certain embodiments, a thickness of the layers  530  and  534  can be from about 10 μm to about 500 μm, about 100 μm to about 500 μm, about 200 μm to about 300 μm, about 200 μm, or about 300 μm. They layers  530  and  534  can be made and/or modified in a variety of ways. In some embodiments, the layer  530  and/or  534  is made by dip-coating, spray-coating, or any other suitable method for applying a thin layer of lubricious material to the main cushioning layer  516 . The finished covering or outer covering  514  can then be situated about and secured to the frame  502  using attachment means, for example, sutures, adhesive, ultrasonic welding, or any other suitable attachment method or means. In some embodiments, the main cushioning layer  516  is situated about the frame  502  before the edges are folded, and/or before the lubricious layers  530  and  534  are applied. In some embodiments, one or both of the lubricious layers  530  and/or  534  can be omitted from the first and second circumferential edge portions  522  and  524 . In some embodiments, one or both of the first and second circumferential edge portions  522 ,  524  need not be folded inside the frame, but can extend to the respective inflow or outflow end of the frame, or beyond the ends of the frame on the exterior of the frame, as desired. 
     In addition to covering the frame  502  and the apices  506 , the outer covering  514  can provide a number of other significant advantages. For example, the covering  514  can be relatively thin, allowing the prosthetic valve to achieve a low crimp profile (e.g., 23 Fr or below). The one-piece, unitary construction of the outer covering  514  and the protective portions  518  and  520  can also significantly reduce the time required to produce the covering and secure it to the frame, and can increase production yield. 
     In some embodiments, one or both of the inflow and outflow protection portions can be configured as separate coverings or covers that are spaced apart from the main layer or main cushioning layer, and may or may not be coupled to the main layer or main cushioning layer. For example,  FIGS.  32 - 36    illustrate an example of a prosthetic heart valve  600  including a frame  602  formed by a plurality of strut members  604  defining apices  606 , similar to the frame 102 described above and in U.S. Pat. No. 9,393,110. The prosthetic valve  600  can have an inflow end  608  and an outflow end  610 , and can include a plurality of leaflets  612  situated at least partially within the frame. 
       FIG.  34    illustrates a portion of the frame  602  in a laid-flat configuration for purposes of illustration. The strut members  604  can be arranged end-to-end to form a plurality of rows or rungs of strut members that extend circumferentially around the frame  602 . For example, with reference to  FIG.  34   , the frame  602  can comprise a first or lower row I of angled strut members forming the inflow end  608  of the frame; a second row II of strut members above the first row; a third row III of strut members above the second row; a fourth row IV of strut members above the third row, and a fifth row V of strut members above the fourth row and forming the outflow end  610  of the frame. At the outflow end  610  of the frame, the strut members  604  of the fifth row V can be arranged at alternating angles in a zig-zag pattern. The strut members  604  of the fifth row V can be joined together at their distal ends (relative to the direction of implantation, for example, in the mitral valve) to form the apices  606 , and joined together at their proximal ends at junctions  630 , which may form part of the commissure windows  638 . Additional structure and characteristics of the rows I-V of strut members  604  are described in greater detail in U.S. Pat. No. 9,393,110, incorporated by reference above. 
     Returning to  FIGS.  32  and  33   , the prosthetic valve can include a first covering or first layer  614  (also referred to as a main covering or main layer) situated about the frame  602 . The valve can also include an outflow protective portion configured as a second covering or cover  616  disposed about the strut members  604  and the apices  606  of the fifth row V of strut members at the outflow end  610  of the frame. The first covering or layer  614  can comprise a woven or knitted fabric made from, for example, PET, UHMWPE, PTFE, etc. Referring to  FIG.  33   , the first covering or layer  614  can include an inflow end portion  618  located at the inflow end  608  of the valve, and an outflow end portion  620  located at the outflow end  610  of the valve. In the illustrated embodiment, the outflow end portion  620  of the first covering or layer  614  can be offset toward the inflow end of the frame (e.g., in the upstream direction) from the fifth row V of strut members  604 . Stated differently, the strut members  604  of the fifth row V can extend beyond an uppermost circumferential edge  622  of the first covering or layer  614  (e.g., distally beyond the edge  622  when the prosthetic valve is implanted in the native valve). A lowermost circumferential edge  624  of the main covering or layer  614  can be disposed adjacent the first row I of strut members  604  at the inflow end  608  of the valve. In some embodiments, the first covering or layer  614  can extend over and cover the apices  606  at the inflow end  608  of the frame. 
       FIG.  35    illustrates the frame  602  including the second covering or cover  616  and an inner skirt  640 , and without the first covering or layer  614  for purposes of illustration. In certain embodiments, the second covering or cover  616  can be configured as a wrapping that extends around the circumference of the frame  602  and surrounds the fifth row V of strut members  604 . For example, with reference to  FIG.  36   , the covering or cover  616  can be configured as one or more straps or strips  626  of material that are helically wrapped around the struts  604  and the apices  606  of the fifth row V of strut members at the outflow end  610  of the frame in the direction such as indicated by arrow  632 . In certain configurations, second covering or cover  616  is made of a lubricious or low-friction polymeric material, such as PTFE, ePTFE, UHMWPE, polyurethane, etc. In this manner, the second covering or cover  616  can reduce friction between the second covering or cover and native tissue that is in contact with the outflow end  610  of the valve. The covering or cover  616  can also prevent injury to native tissue by preventing it from directly contacting the apices  606 . 
     In some embodiments, the strip  626  can be relatively thick to improve the cushioning characteristics of the second covering or cover  616 . For example, in some embodiments, the strip  626  can be a PTFE strip having a thickness of from about 0.1 mm to about 0.5 mm, and a width of from about 3 mm to about 10 mm. In a representative embodiment, the strip  626  can have a thickness of about 0.25 mm, and a width of about 6 mm. The second covering or cover  616  can also include one or multiple layers. For example, the second covering or cover  616  can include a single layer (e.g., a single strip  626 ) wrapped around a row of struts of the frame. The second covering or cover may also include two layers, three layers, or more of strips wrapped around a row of struts of the frame. In some embodiments, the second covering or cover  616  can comprise multiple layers made of different materials. In certain configurations, the second covering or cover  616  can also be porous, and can have a pore size and pore density configured to promote tissue ingrowth into the material of the second covering/cover. 
     In some embodiments, the first covering or layer  614  and/or the second covering or cover  616  can be secured to the frame by attachment means, for example, suturing, adhesive, etc. In some embodiments, the first and second coverings  614 ,  616  can also be secured to each other with attachment means. For example, with reference to  FIGS.  32  and  33   , the first covering or layer  614  can include one or more sutures  628  extending circumferentially around the outflow end portion  620  of the first covering in, for example, a running stitch. At or near the junctions  630  ( FIG.  34   ) of the fifth row V of strut members  604 , the suture  628  can extend out of the stitch line (e.g., from the radially outward surface of the covering  614 ), and loop over the second covering/cover  616 . The suture  628  can then reenter the covering  614  (e.g., on the radially inward surface of the covering/layer  614 ) and resume the running stitch. In the illustrated embodiment, the suture  628  can loop over the second covering/cover  616  at the junctions  630 . The loops of suture  628  thereby rest in “valleys” between the apices  606 , and can serve to hold the second covering/cover  616  in place on the strut members  602 . The suture  628  can also hold the first covering  614  in place while the valve is being crimped. 
     Still referring to  FIGS.  32  and  33   , the circumferential edge  622  of the first covering/layer  614  can be relatively straight, while the second covering/cover  616  can conform to the angled or zig-zag pattern of the fifth row V of strut members  604 . In this manner, the first and second coverings  614  and  616  can define a plurality of gaps or openings  634  through the frame  602  between the first and second coverings. In the illustrated embodiment, the openings  634  have a triangular shape, with the base of the triangle being defined by the edge  622  of the first covering  614 , and the sides being defined by the second covering/cover  616 . The openings  634  can be configured such that after the valve  600  is implanted, blood can flow in and/or out of the frame  602  through the openings. In this manner, the space between the interior of the frame  602  and the ventricular surfaces  638  of the leaflets  612  can be flushed or washed by blood flowing into and out of the openings  634  during operation of the prosthetic valve. This may potentially reduce the risk of thrombus formation and left ventricular outflow tract obstruction. 
       FIG.  37    illustrates the frame  602  including the second covering/cover  616  in a radially collapsed or crimped delivery configuration on a shaft  636  of a delivery apparatus. As shown in  FIG.  37   , the second covering/cover  616  can conform to the closely-packed, serpentine shape of the strut members  604  as they move to the radially collapsed configuration. In certain configurations, the second covering/cover  616  can closely mimic the shape and direction of the strut members  604  without bulging, pleating, creasing, or bunching to maintain a low crimp profile. In some embodiments, the inflow end of the frame includes a separate covering similar to the covering/cover  616 . 
       FIGS.  38 A,  38 B,  39 A, and  39 B  illustrate the prosthetic valve  400  of  FIGS.  19 - 26    including an example covering or outer covering  700 . The outer covering  700  can include a main layer or main cushioning layer  702  having a plush exterior surface  704 . The covering  700  can also include an inflow protection portion  706  extending circumferentially around the inflow end  406  of the valve, and an outflow protection portion  708  extending circumferentially around the outflow end  408  of the valve. As in the embodiment of  FIGS.  19 - 26   , the inflow and outflow protection portions  706 ,  708  can be formed with separate pieces of material that are folded around the circumferential ends of the main layer  702  such that the cushioning portions encapsulate the apices  420  of the strut members at the inflow and outflow ends of the valve. For example, the inflow and outflow protection portions  706 ,  708  can be constructed from strips of material (e.g., polymeric materials such as PTFE, ePTFE, etc., or natural tissues such as pericardium, etc.) folded such that one circumferential edge of the strips is disposed against the interior of the frame  402  (or an inner skirt within the frame), and the other circumferential edge is disposed against the outer surface of the main layer  702 . The outer covering  700  can be secured to the frame  402  using attachment means, for example, sutures, ultrasonic welding, or any other suitable attachment method or means. The layer  702  alone or together with protective portions  706 ,  708  can form a sealing member or cover member that can be placed around the frame to form the covering  700 . 
     The main layer  702  of the outer covering  700  can comprise a woven or knitted fabric. The fabric of the main layer  702  can be resiliently stretchable between a first, natural, or relaxed configuration ( FIGS.  38 A and  38 B ), and a second, elongated, or tensioned configuration ( FIGS.  39 A and  39 B ). When disposed on the frame  402 , the relaxed configuration can correspond to the radially expanded, functional configuration of the prosthetic valve, and the elongated configuration can correspond to the radially collapsed delivery configuration of the valve. Thus, with reference to  FIG.  38 A , the outer covering  700  can have a first length L 1  when the prosthetic valve is in the expanded configuration, and a second length L 2  ( FIG.  39 A ) that is longer than L 1  when the valve is crimped to the delivery configuration, as described in greater detail below. 
     The fabric can comprise a plurality of circumferentially extending warp strands/yarns  712  and a plurality of axially extending weft strands/yarns  714 . In some embodiments, the warp strands/yarns  712  can have a denier of from about 1 D to about 300 D, about 10 D to about 200 D, or about 10 D to about 100 D. In some embodiments, the warp strands/yarns  712  can have a thickness t 1  ( FIG.  40 A ) of from about 0.01 mm to about 0.5 mm, about 0.02 mm to about 0.3 mm, or about 0.03 mm to about 0.1 mm. In some embodiments, the warp strands/yarns  712  can have a thickness t 1  of about 0.03 mm, about 0.04 mm, about 0.05 mm, about 0.06 mm, about 0.07 mm, about 0.08 mm, about 0.09 mm, or about 0.1 mm. In a representative embodiment, the warp strands/yarns  712  can have a thickness of about 0.06 mm. 
     The weft strands/yarns  714  can be texturized strands/yarns comprising a plurality of texturized filaments  716 . For example, the filaments  716  of the weft strands/yarns  714  can be bulked, wherein, for example, the filaments  716  are twisted, heat set, and untwisted such that the filaments retain their deformed, twisted shape in the relaxed, non-stretched configuration. The filaments  716  can also be texturized by crimping, coiling, etc. When the weft strands/yarns  714  are in a relaxed, non-tensioned state, the filaments  716  can be loosely packed and can provide compressible volume or bulk to the fabric, as well as a plush surface. In some embodiments, the weft strands/yarns  714  can have a denier of from about 1 D to about 500 D, about 10 D to about 400 D, about 20 D to about 350 D, about 20 D to about 300 D, or about 40 D to about 200 D. In certain embodiments, the weft strands/yarns  714  can have a denier of about 150 D. In some embodiments, a filament count of the weft strands/yarns  714  can be from 2 filaments per strand/yarn to 200 filaments per strand/yarn, 10 filaments per strand/yarn to 100 filaments per strand/yarn, 20 filaments per strand/yarn to 80 filaments per strand/yarn, or about 30 filaments per strand/yarn to 60 filaments per yarn. Additionally, although the axially-extending textured strands/yarns  714  are referred to as weft strands/yarns in the illustrated configuration, the fabric may also be manufactured such that the axially-extending textured strands/yarns are warp strands/yarns and the circumferentially-extending strands/yarns are weft strands/yarns. 
       FIGS.  40 A and  40 B  illustrate a cross-sectional view of the main layer  702  in which the weft strands/yarns  712  extend into the plane of the page. With reference to  FIG.  40 A , the fabric of the main layer  702  can have a thickness t 2  of from about 0.1 mm to about 10 mm, about 1 mm to about 8 mm, about 1 mm to about 5 mm, about 1 mm to about 3 mm, about 0.5 mm, about 1 mm, about 1.5 mm, about 2 mm, about 2.5 mm, or about 3 mm when in a relaxed state and secured to a frame. In some embodiments, the main layer  702  can have a thickness of about 0.1 mm, about 0.2 mm, about 0.3 mm, about 0.4 mm, or about 0.5 mm as measured in a relaxed state with a weighted drop gauge having a presser foot. In a representative example, the main layer  702  can have a thickness of about 1.5 mm when secured to a prosthetic valve frame in the relaxed state. This can allow the fabric of the main layer  702  to cushion the leaflets between the valve body and an anchor or ring into which the valve is implanted, as well as to occupy voids or space in the anatomy. The texturized, loosely packed filaments  716  of the weft strands/yarns  714  in the relaxed state can also promote tissue growth into the main layer  702 . 
     When the fabric is in the relaxed state, the textured filaments  716  of the weft strands/yarns  714  can be widely dispersed such that individual weft strands/yarns are not readily discerned, as in  FIGS.  38 A and  38 B . When tensioned, the filaments  716  of the weft strands/yarns  714  can be drawn together as the weft strands/yarns elongate and the kinks, twists, etc., of the filaments are pulled straight such that the fabric is stretched and the thickness decreases. In certain embodiments, when sufficient tension is applied to the fabric in the axial (e.g., weft) direction, such as when the prosthetic valve is crimped onto a delivery shaft, the textured fibers  716  can be pulled together such that individual weft strands/yarns  714  become discernable, as best shown in  FIGS.  39 B and  40 B . 
     Thus, for example, when fully stretched, the main layer  702  can have a second thickness t 3 , as shown in  FIG.  40 B  that is less than the thickness t 2 . In certain embodiments, the thickness of the tensioned weft strands/yarns  714  may be the same or nearly the same as the thickness t 1  of the warp strands/yarns  712 . Thus, in certain examples, when stretched the fabric can have a thickness t 3  that is the same or nearly the same as three times the thickness t 1  of the warp strands/yarns  712  depending upon, for example, the amount of flattening of the weft strands/yarns  714 . Accordingly, in the example above in which the warp strands/yarns  712  have a thickness of about 0.06 mm, the thickness of the main layer  702  can vary between about 0.2 mm and about 1.5 mm as the fabric stretches and relaxes. Stated differently, the thickness of the fabric can vary by 750% or more as the fabric stretches and relaxes. 
     Additionally, as shown in  FIG.  40 A , the warp strands/yarns  712  can be spaced apart from each other in the fabric by a distance y 1  when the outer covering is in a relaxed state. As shown in  FIGS.  39 B and  40 B , when tension is applied to the fabric in the direction perpendicular to the warp strands/yarns  712  and parallel to the weft strands/yarns  714 , the distance between the warp strands/yarns  712  can increase as the weft strands/yarns  714  lengthen. In the example illustrated in  FIG.  40 B , in which the fabric has been stretched such that the weft strands/yarns  714  have lengthened and narrowed to approximately the diameter of the warp strands/yarns  712 , the distance between the warp strands/yarns  712  can increase to a new distance y 2  that is greater than the distance y 1 . 
     In certain embodiments, the distance y 1  can be, for example, about 1 mm to about 10 mm, about 2 mm to about 8 mm, or about 3 mm to about 5 mm. In a representative example, the distance y 1  can be about 3 mm. In some embodiments, when the fabric is stretched as in  FIGS.  39 B and  40 B , the distance y 2  can be about 6 mm to about 10 mm. Thus, in certain embodiments, the length of the outer covering  700  can vary by 100% or more between the relaxed length L 1  and the fully stretched length (e.g., L 2 ). The fabric&#39;s ability to lengthen in this manner can allow the prosthetic valve to be crimped to diameters of, for example, 23 Fr, without being limited by the outer covering&#39;s ability to stretch. Thus, the outer covering  700  can be soft and voluminous when the prosthetic valve is expanded to its functional size, and relatively thin when the prosthetic valve is crimped to minimize the overall crimp profile of the prosthetic valve. 
       FIGS.  41 A,  41 B,  42 A, and  42 B  show an example of a sealing member or cover member  800  for a prosthetic heart valve (e.g., such as the prosthetic heart valve  400 ). The sealing member  800  can be a dual-layer fabric comprising a base layer  802  and a pile layer  804 .  FIG.  41 A  shows the outer surface of the sealing member  800  defined by the pile layer  804 .  FIG.  42 A  shows the inner surface of the sealing member  800  defined by the base layer  802 . The base layer  802  in the illustrated configuration comprises a mesh weave having circumferentially extending rows or stripes  806  of higher-density mesh portions interspersed with rows or stripes  808  of lower-density mesh portions. The sealing member/cover member  800  can be used to cover or form a covering on a stent frame (e.g. on some, a portion, or all of a stent frame). 
     In some embodiments, the strand/yarn count of strands/yarns extending in the circumferential direction (side-to-side or horizontally in  FIGS.  42 A and  42 B ) is greater in the higher-density rows  806  than in the lower-density rows  808 . In some embodiments, the strand/yarn count of strands/yarns extending in the circumferential direction and the strand/yarn count of strands/yarns extending in the axial direction (vertically in  FIGS.  42 A and  42 B ) is greater in the higher-density rows  806  than in the lower-density rows  808 . 
     The pile layer  804  can be formed from strands/yarns woven into the base layer  802 . For example, the pile layer  804  can comprise a velour weave formed from strands/yarns incorporated in the base layer  802 . Referring to  FIG.  41 B , the pile layer  804  can comprise circumferentially extending rows or stripes  810  of pile formed at axially-spaced locations along the height of the sealing member  800  such that there are axial extending gaps between adjacent rows  810 . In this manner, the density of the pile layer varies along the height of the sealing member. In some embodiments, the pile layer  804  can be formed without gaps between adjacent rows of pile, but the pile layer can comprise circumferentially extending rows or stripes of higher-density pile interspersed with rows or stripes of lower-density pile. 
     In some embodiments, the base layer  802  can comprise a uniform mesh weave (the density of the weave pattern is uniform) and the pile layer  804  has a varying density. 
     In some embodiments, the density of the sealing member  800  can vary along the circumference of the sealing member. For example, the pile layer  804  can comprise a plurality of axially-extending, circumferentially-spaced, rows of pile yarns, or can comprise alternating axially-extending rows of higher-density pile interspersed with axially-extending rows of lower-density pile. Similarly, the base layer  802  can comprise a plurality axially-extending rows of higher-density mesh interspersed with rows of lower-density mesh. 
     In some embodiments, the sealing member  800  includes a base layer  802  and/or a pile layer  804  that varies in density along the circumference of the sealing member and along the height of the sealing member. 
     Varying the density of the pile layer  804  and/or the base layer  802  along the height and/or the circumference of the sealing member  800  is advantageous in that it reduces the bulkiness of the sealing member in the radially collapsed state and therefore reduces the overall crimp profile of the prosthetic heart valve. 
     In certain embodiments, the outer covering  800  can include inflow and/or outflow protective portions similar to the protective portions  416  and  418  above. However, in some embodiments, the outer covering  800  need not include protective portions and can extend between the top and bottom row of strut members of a frame, or between intermediate rows of strut members, depending upon the particular application. 
       FIGS.  43  and  44    illustrate a prosthetic heart valve  900  including an example of a covering or outer covering  902  situated around a frame  904 , and including a plurality of leaflets  922  ( FIG.  44   ) situated at least partially within the frame  904 . The frame  904  can include a plurality of struts  920 , and can be configured as the frame of the Edwards Lifesciences SAPIEN® 3 prosthetic heart valve, similar to the frame  402  of  FIG.  19   . The outer covering  902  can include a main cushioning layer or sealing member/cover member  906  (also referred to as a main layer) having a cylindrical shape, and made from a woven, knitted, or braided fabric (e.g., a PET fabric, an ultra-high molecular weight polyethylene (UHMWPE) fabric, a PTFE fabric, etc.), a non-woven fabric such as felt, or an extruded polymer film (e.g., an ePTFE or UHMWPE membrane). The outer covering  902  can also include an inflow protection portion  908  extending circumferentially around the inflow end  910  of the frame, and an outflow protection portion  912  extending circumferentially around the outflow end  914  of the frame. In the embodiment of  FIGS.  43  and  44   , the inflow and outflow protection portions  908  and  912  are configured as separate pieces of material folded around the circumferential ends of the main layer  906  similar to the embodiment of  FIGS.  19 - 26   , but may also comprise lubricous layers formed on the circumferential edge portions of the main layer  906  by other means, such as by electrospinning, as in the embodiment of  FIG.  31 A . 
     Referring to  FIG.  43   , the layer  906  of the outer covering  902  can comprise a woven or knitted fabric. The layer  906  can comprise a plurality of holes or openings  916  circumferentially spaced apart from each other around the frame  904 , and aligned with or overlying openings defined between the frame struts. For example, in the illustrated embodiment the openings  916  can be located at the level of openings  918  defined between the frame struts  920  of the fourth row IV and the fifth row V of struts (see also  FIG.  34   ) near the outflow end  914  of the frame. The openings  916  can be relatively small, as in the embodiment of  FIG.  43   , or larger, depending upon the particular characteristics desired. 
     For example, with reference to  FIG.  44   , in certain embodiments the openings  916  can be the same size and shape, or nearly the same size and shape, as the frame openings  918 . Thus, in the embodiment of  FIG.  44   , the openings  916  can comprise the polygonal (e.g., hexagonal) shape of the frame openings  918 , and can be of the same size or area as the frame openings  918 . In this configuration, relatively narrow strips  930  of the main layer  906  can extend along axially-oriented struts  920 A between the fourth row IV and the fifth row V of struts, and over the commissure windows and the commissure tabs  932  of the leaflets  922 . Thus, in certain configurations, the openings  916  of the covering  902  can be aligned with the frame openings  918 , and yet the covering  902  can cover the entire outer surface of the frame  904 . In other words, the covering  902  can cover the outer surfaces of all of the strut members  920 . 
     The openings  916  can be formed in a variety of ways. In certain embodiments, the openings  916  are cut (e.g., using a laser) from the fabric of the main layer  906  before the covering is assembled on the frame  904 . In some embodiments, the covering  902  comprises two separate outer or main layers spaced apart axially from each other on the frame  904 , with one layer extending between, for example, the first row I of struts  920  and the fourth row IV of struts, and the other layer extending along the fifth row V such that the frame openings  918  are uncovered. The openings  916  of the main layer  906  can have any size or shape, can be located at any location along the axis of the prosthetic valve, and/or at different axial locations. The openings  916  can also have any suitable circumferential spacing. 
       FIG.  45    illustrates an example of the prosthetic valve  900  in which the main layer  906  (which can form part or all of a sealing member or cover member) of the outer covering  902  comprises a first portion  924  including a plush (e.g., knitted) pile layer  928  similar to the covering  414  of  FIG.  19   , and a second portion  926  without a pile. Additional portions are also possible. The plush pile layer  928  of the first portion  924  can extend circumferentially around the frame  904 , and axially along the frame  904  from the inflow end portion  910  to the level of the fourth row IV of struts  920 . The second portion  926  can define a plurality of round openings  916  positioned over the frame openings  918 , and having an area smaller than the frame openings  918 , although the openings  916  can have any size, shape, location, and/or spacing. The pile layer  928  can be configured to extend along any portion of the axis of the prosthetic valve. 
     In certain embodiments, the first portion  924  and the second portion  926  comprise different pieces of material. For example, in some embodiments, the first portion  924  is a knitted fabric comprising the plush pile layer  928  described above, and the second portion  926  is a knitted fabric without a pile layer. The first and second portions  924 ,  926  can be configured to overlap each other (e.g., a portion of the first portion  924  may extend over the second portion  926  where the two pieces of fabric meet). The second portion  926  can also have a different knit pattern than the first portion  924 , and can also comprise strands (e.g., yarns, etc.) having different properties (e.g., denier, material, surface characteristics such as texturing, number of filaments, number of plies, number of twists, etc.) from the strands/yarns of the first portion  924 . In some embodiments the first portion  924  and/or the second portion  926  comprise knit patterns formed using a two bar system, a three bar system, a four bar system, etc., or as many as an eight bar system. The first portion  924  and/or the second portion  926  can be knitted in a variety of ways, e.g., using a circular technique, a crochet technique, a tricot technique, a raschel technique, other techniques, or combinations thereof. The properties of the second portion  926  can be optimized to allow the openings  916  to be created more easily (e.g., by laser cutting), and to ensure that the fabric retains its structural integrity. For example, cloth or fabric made of certain types of woven strands or woven yarns may be more likely to fall apart and/or fray if openings are cut therein, so the second portion  926  could be made of a bias cloth or bias fabric that is less likely to fall apart or fray when openings are cut therein. Optionally, the first and second portions  924 ,  926  can comprise a single piece of fabric. In some embodiments, the first portion  924  and/or the second portion  926  comprise a non-woven material (e.g., foam, felt, etc.). 
     Including openings such as the openings  916  in the outer covering  902  may promote blood flow through the covering from the interior of the prosthetic valve to the exterior such that the struts  920  and the radially-outward surfaces of the leaflets  922  are bathed or washed by blood flowing through the prosthetic valve during valve operation. This may help to reduce blood stasis around the strut members  920 , and between the struts  920  and the leaflets  922 , which may potentially reduce the risk of thrombosis. 
       FIGS.  46 - 51    show an example of a main cushioning layer or sealing member/cover member  1000 . The sealing member  1000  can comprise a fabric body having a plurality of different portions working together, such as a plurality first portions (e.g., woven portions, multiple sets of woven portions, etc.) and a plurality of second portions (e.g., elastic, stretchable portions configured as floating portions, such as floating yarn portions), which can be incorporated into any of the prosthetic valve outer coverings described herein.  FIG.  46    illustrates the sealing member/cover member  1000  in a laid-flat configuration where the x-axis corresponds to the circumferential direction and the y-axis corresponds to the axial direction when the sealing member is attached to a frame of a prosthetic valve. The sealing member  1000  can comprise a plurality of first portions (such as first woven portions  1002  configured as woven strips or stripes extending along the x-axis), a plurality of second portions (such as second woven portions  1004  configured as woven strips or stripes extending along the x-axis), a plurality of third portions (e.g., floating portions or floating yarn portions, strips, or stripes  1006  extending along the x-axis), and/or optionally additional portions. The various woven and floating portions/floating yarn portions can be spaced apart from each other along the y-axis. In the illustrated configuration, the first woven portions  1002  comprise a weave pattern that is different from the weave pattern of the second woven portions  1004 , as described in greater detail below. 
     In one example configuration, as illustrated, the sealing member/cover member  1000  comprises a first woven portion  1002 A, which can be at the lower or inflow edge of the sealing member/cover member. Moving in a direction along the positive y-axis, the sealing member/cover member  1000  can further comprise a second woven portion  1004 A, a floating portion/floating yarn portion  1006 A, a second woven portion  1004 B, a floating portion/floating yarn portion  1006 B, a second woven portion  1004 C, a floating portion/floating yarn portion  1006 C, a second woven portion  1004 D, a floating portion/floating yarn portion  1006 D, a second woven portion  1004 E, a first woven portion  1002 B, a second woven portion  1004 F, a floating portion/floating yarn portion  1006 E, a second woven portion  1004 G, and a first woven portion  1002 C at the opposite end of the sealing member/cover member from the first woven portion  1002 A. In other words, the first woven portion  1002 B and each of the floating portions/floating yarn portions  1006 A- 1006 E can be located between two second woven portions  1004  such that the first woven portion  1002 B and each of the floating portion/floating yarn portions  1006 A- 1006 E are bounded or edged in a direction along the x-axis by respective second woven portions  1004 . 
     Referring to  FIGS.  47  and  48   , the main layer or sealing member/cover member  1000  can comprise a plurality of first strands  1008  (e.g., yarns, etc.) oriented generally along the x-axis and a plurality of second yarns  1010  oriented generally along the y-axis. In certain configurations, the first strands/yarns  1008  are warp strands/yarns, meaning that during the weaving process the strands/yarns  1008  are held by the loom, while the second strands/yarns  1010  are weft strands/yarns, which are interwoven with the warp strands/yarns by a moving shuttle or weft-carrying mechanism during the weaving process. However, in some embodiments the first strands/yarns  1008  can be weft strands/yarns and the second strands/yarns  1010  can be warp strands/yarns. 
     Each of the first strands/yarns  1008  and the second strands/yarns  1010  can comprise a plurality of constituent filaments  1012  that are spun, wound, twisted, intermingled, interlaced, etc., together to form the respective strands/yarns. Exemplary individual filaments  1012  of the second strands/yarns  1010  can be seen in  FIGS.  48 - 50   . In some embodiments, the first strands/yarns  1008  have a denier of from about 1 D to about 200 D, about 10 D to about 100 D, about 10 D to about 80 D, about 10 D to about 60 D, or about 10 D to about 50 D. In some embodiments, the first strands/yarns  1008  have a filament count of 1 to about 600 filaments per strand/yarn, about 10 to about 300 filaments per strand/yarn, about 10 to about 100 filaments per strand/yarn, about 10 to about 60 filaments per strand/yarn, about 10 to about 50 filaments per strand/yarn, or about 10 to about 30 filaments per yarn. In some embodiments, the first strands/yarns  1008  have a denier of about 40 D and a filament count of 24 filaments per yarn. The first strands/yarns  1008  can also be twisted strands/yarns or non-twisted strands/yarns. In the illustrated embodiment, the filaments  1012  of the first strands/yarns  1008  are not texturized. However, in some embodiments, the first strands/yarns  1008  can comprise texturized filaments. 
     The second strands/yarns  1010  can be texturized strands/yarns comprising a plurality of texturized filaments  1012 . For example, the filaments  1012  of the second strands/yarns  1010  can be texturized, for example, by twisting the filaments, heat-setting them, and untwisting the filaments as described above. In some embodiments, the second strands/yarns  1010  have a denier of from about 1 D to about 200 D, about 10 D to about 100 D, about 10 D to about 80 D, or about 10 D to about 70 D. In some embodiments, a filament count of the second strands/yarns  1010  is between 1 filament per strand/yarn to about 100 filaments per strand/yarn, about 10 to about 80 filaments per strand/yarn, about 10 to about 60 filaments per strand/yarn, or about 10 to about 50 filaments per yarn. In some embodiments, the second strands/yarns  1010  have a denier of about 68 D and a filament count of about 36 filaments per yarn. 
     The first strands/yarns  1008  and the second strands/yarns  1010  can be woven together to form the woven portions of the sealing member/cover member, as noted above. For example, in the first woven portions  1002 A- 1002 C, the first and second strands/yarns  1008 ,  1010  can be woven together in a plain weave pattern in which the second strands/yarns  1010  (e.g., the weft strands/yarns) pass over a first strand/yarn  1008  (e.g., a warp yarn) and then under the next first strand/yarn in a repeating pattern. This weave pattern is illustrated in detail in  FIG.  47   . In some embodiments, the density of the first strands/yarns  1008  is from about 10 strands/yarns per inch to about 200 strands/yarns per inch, about 50 strands/yarns per inch to about 200 strands/yarns per inch, or about 100 strands/yarns per inch to about 200 strands/yarns per inch. In certain embodiments, the first woven portion  1002 A and the first woven portion  1002 C can be configured as selvedge (selvage) portions, and can have a lower strand/yarn density than the first woven portion  1002 B to facilitate assembly on a valve frame. Other weave patterns can also be used, such as over two under two, over two under one, etc. The first woven portions can also be woven in plain weave derivative patterns such as twill, satin, or combinations of any of these. 
     In the second woven portions  1004 A- 1004 G, the first and second strands/yarns  1008 ,  1010  can be interwoven in another pattern that is different from the weave pattern of the first woven portions  1002 A- 1002 C. For example, in the illustrated embodiment, the first and second strands/yarns  1008 ,  1010  are woven together in a leno weave pattern in the second woven portions  1004 A- 1004 G.  FIG.  48    illustrates the leno weave of the second woven portion  1004 B in greater detail. With reference to  FIG.  48   , the leno weave can comprise one or more leno strands/yarns or “leno ends”  1014 , and four first strands/yarns  1008 A,  1008 B,  1008 C, and  1008 D, also referred to as “warp ends.” The pattern illustrated in  FIG.  48    includes a single leno strand/yarn  1014  in the manner of a half-leno weave. However, in some embodiments, the leno weave pattern can be a full-leno weave comprising two intertwining leno strands/yarns  1014 , or other leno-derived weaves. Examples of half-leno weaves, full-leno weaves, and associated weaving techniques are illustrated in  FIGS.  55 A- 55 J . 
     In the half-leno weave illustrated in  FIG.  48   , the first strands/yarns  1008 A- 1008 D can extend parallel to the x-axis, and the second strands/yarns  1010  can be interwoven with the first strands/yarns  1008 A- 1008 D in, for example, a plain weave. The leno strand/yarn  1014  can weave around the first strands/yarns  1008 A- 1008 D such that the leno strand/yarn  1014  crosses over, or on top of, the first strands/yarns  1008 A- 1008 D with each pass in the positive y-direction, crosses beneath or behind the next second yarn  1010  in the x-direction, and extends back over the first strands/yarns  1008 A- 1008 D in the negative y-direction. This pattern can be repeated along the length of the second woven portion  1004 B. In this manner, the second woven portions  1004  can be relatively narrow, strong woven portions spaced axially from each other along the frame when the sealing element is mounted to a frame. The leno strand/yarn  1014  can serve to keep the first strands/yarns  1008 A- 1008 D and the second strands/yarns  1010  in place with respect to each other as the prosthetic valve is crimped and expanded, and can impart strength to the second woven portions  1004  while minimizing width. 
     In certain embodiments, each of the second woven portions  1004 A- 1004 G comprise the leno weave pattern described above. In some embodiments, one or more of the second woven portions  1004 A- 1004 G is configured differently, such as by incorporating more or fewer first strands/yarns  1008  in the leno weave, having multiple leno ends woven around multiple groupings of strands/yarns  1008 , etc. In some embodiments, a chemical locking method is used where the leno weave and/or a plain weave includes warp strands/yarns having core-sheath construction filaments. The sheath of the individual filaments can be made of low-melt temperature polymers such as biocompatible polypropylene, and the core of the filaments be made of another biocompatible polymer such as polyester. After the weaving process, the heat setting process described below can enable the softening and/or melting of the sheath. Upon cooling, the softened sheath polymer can bond the core polyester filaments together. This can create a bonded body enabling locking of the woven structure. 
     Referring again to  FIG.  46   , the floating portions or floating yarn portions  1006  can comprise strands/yarns extending in only one axis between respective second woven portions  1004  that are spaced apart from each other along the y-axis. For example, taking the floating portion/floating yarn portion  1006 A as a representative example, the floating portion/floating yarn portion  1006 A can comprise a plurality of second strands/yarns  1010  that exit the leno weave of the second woven portion  1004 A, extend across the floating portion/floating yarn portion  1006 A, and are incorporated into the leno weave of the second woven portion  1004 B without being interwoven with any other strands/yarns in the floating portion/floating yarn portion. In some embodiments, the density of the second strands/yarns in the floating portion/floating yarn portions  1006  is from about 10 to about 200 strands/yarns per inch, about 50 to about 200 strands/yarns per inch, or about 100 to about 200 strands/yarns per inch. In some embodiments, the density of the second strands/yarns  1010  is about 60-80 strands/yarns per inch. In some embodiments, the floating portions/floating yarn portions include first strands/yarns  1008  disposed under or over, but not interwoven with, the second strands/yarns  1010  such that the second strands/yarns float over the first strands/yarns or vice versa. The floating portions or floating yarn portions can also be configured as any other elastically stretchable structure, such as elastically stretchable woven, knitted, braided, or non-woven fabrics, or polymeric membranes, to name a few, that is elastically stretchable at least in the axial direction of the prosthetic valve. 
     In the illustrated embodiment, each of the woven portions  1002 A- 1002 C and  1004 A- 1004 G, and each of the floating portions  1006 A- 1006 E have width dimensions in the y-axis direction. The widths of the constituent portions can be configured such that the overall length L 1  ( FIG.  46   ) of the sealing member/cover member  1000  generally corresponds to the axial length of a prosthetic heart valve in the expanded configuration. For example, in the illustrated embodiment the first woven portions  1002 A and  1002 C each have a width W 1 . In certain embodiments, the width W 1  is configured such that portions of the first woven portions  1002 A and  1002 C can be folded over the respective inflow and/or outflow ends of the frame of a prosthetic valve. 
     The first woven portion  1002 B can have a width W 2 . With reference to  FIG.  52   , when the sealing member/cover member  1000  is used in combination with the frame of the Edwards Lifesciences SAPIEN® 3 prosthetic heart valve, the width W 2  can be configured to correspond to the axial dimension of the frame openings defined by the strut members between the fourth row IV and the fifth row V of struts, as described in greater detail below. In some embodiments, the width W 2  of the first woven portion  1002 B is about 2 mm to about 20 mm, about 2 mm to about 12 mm, or about 3 mm to about 10 mm. In some embodiments, the width W 2  is about 7 mm. 
     The second woven portions  1004 A- 1004 G can have widths W 3  ( FIG.  48   ). In the illustrated embodiment, all of the second woven portions  1004 A- 1004 G have the width W 3 , but one or more of the second woven portions can also have different widths. In certain embodiments, the width W 3  can be relatively short, such as about 0.1 mm to about 3 mm, about 0.1 mm to about 2 mm, or about 0.1 mm to about 1 mm. In some embodiments, the width W 3  is about 1 mm. 
     With reference to  FIGS.  46  and  49 - 52   , in certain embodiments, the sealing member/cover member  1000 , and in particular the floating portions/floating yarn portions  1006 A- 1006 E, are resiliently stretchable between a first, natural, or relaxed configuration ( FIGS.  46  and  49   ) corresponding to the radially expanded state of the prosthetic valve, and a second, elongated, or tensioned configuration ( FIGS.  50  and  51   ) corresponding to the radially compressed state of the prosthetic valve. Thus, the floating portions  1006 A- 1006 E can have initial widths W 4  when the sealing member  1000  is in the relaxed, unstretched state.  FIG.  49    illustrates a portion of the floating portion  1006 B in the natural, relaxed state. When the fabric is in the relaxed state, the textured filaments  1012  of the second strands/yarns  1010  can be kinked and twisted in many directions such that the floating portion  1006 B has a bulky, billowy, or pillow-like quality, and provides a compressible volume or bulk. When tensioned, the kinks, twists, etc., of the filaments  1012  can be pulled at least partially straight along the y-axis, causing the second strands/yarns  1010  to elongate. With reference to  FIG.  50   , the width of the floating portions  1006  can thus increase to a second width W 5  that is larger than the initial width W 4 . 
     The cumulative effect of the floating portions/floating yarn portions  1006 A- 1006 E increasing in width from the initial width W 4  to the second width W 5  is that the overall axial dimension of the sealing member/cover member  1000  can increase from the initial length L 1  ( FIG.  46   ) to a second overall length L 2  ( FIG.  51   ) that is greater than the first length L 1 .  FIG.  51    illustrates the sealing member  1000  in the stretched configuration with the second strands/yarns  1010  of the floating yarn portions  1006 A- 1006 E straightened under tension such that the overall length of the sealing member increases to the second length L 2 . In certain embodiments, the size, number, spacing, etc., of the floating yarn portions  1006 , and the degree of texturing of the constituent second strands/yarns  1010 , can be selected such that the second length L 2  of the sealing member  1000  corresponds to the length of a frame of a prosthetic valve when the prosthetic valve is crimped for delivery on a delivery apparatus, as described below with reference to  FIGS.  53  and  54   . In some embodiments, the relaxed initial width W 4  of the floating yarn portions  1006  is about 1 mm to about 10 mm, about 1 mm to about 8 mm, or about 1 mm to about 5 mm. In some embodiments, the initial width W 4  is about 4 mm. 
       FIG.  52    illustrates an edge portion of the sealing member/cover member  1000  gripped between a pair of grippers  1050 . In certain embodiments, the bulky, billowy nature of the texturized strands/yarns  1010  in the floating portions/floating yarn portions  1006  results in the floating portions/floating yarn portions  1006  having a thickness t 1  that is greater than a thickness t 2  of the woven portions  1002  and  1004 . For example, in certain embodiments the thickness t 1  of the floating portions  1006  is two times, three times, four times, five times, six times, or even ten times greater than the thickness t 2  of the woven portions  1002  and  1004 , or more, when the sealing member is in the relaxed state. This can allow the floating portions  1006  to cushion the native leaflets between the valve body and/or against an anchor or ring into which the prosthetic valve is implanted. The floating portions  1006  can also occupy voids or space in the anatomy, and/or promote tissue growth into the floating portions, as in the embodiments described above. When tension is applied to stretch the floating portions  1006 , the thickness t 1  can decrease as the texturized second strands/yarns  1010  straighten. In certain embodiments, the thickness t 1  is equal or nearly equal to the thickness t 2  of the woven portions  1002  and  1004  when the sealing member is in the tensioned state. When the tension on the sealing member  1000  is released, such as during expansion of the prosthetic valve, the strands/yarns  1012  can resume their texturized shape and the thickness of the floating portions  1006  can return to the initial thickness t 1 . 
       FIG.  53    illustrates the sealing member  1000  formed into an outer covering  1018  and assembled onto the frame  1020  of a prosthetic valve  1022 . In the illustrated embodiment, the frame  1020  is the frame of the Edwards Lifesciences SAPIEN® 3 prosthetic heart valve similar to the frames described above, although the sealing member  1000  can be configured for use on other prosthetic valves as well, including the frame in  FIG.  56   . The outer covering  1018  can also include an inflow protection portion  1024  and an outflow protection portion  1026  similar to the outer coverings described above, and can be configured for implantation in a native valve, such as the mitral valve, tricuspid valve, aortic valve, pulmonary valve, Eustachian valve, etc., although in some embodiments the outer covering need not include the inflow and/or the outflow protection portions, and can be configured for implantation in other heart valves or body lumens as well. The sealing member  1000  can be oriented such that the second woven portions  1004 A- 1004 G and the floating portions/floating yarn portions  1006 A- 1006 E extend circumferentially around the frame  1020 , and such that the floating portion/floating yarn portion  1006 A is adjacent the inflow protection portion  1024  at the inflow end of the prosthetic valve. In this configuration, the texturized second strands/yarns  1010  extend in a direction along the longitudinal axis  1034  of the prosthetic valve. In the illustrated embodiment, the first woven portion  1002 A and the second woven portion  1004 A can be disposed at least partially beneath the inflow protection portion  1024  and are not visible in the figure. Similarly, the first woven portion  1002 C and the second woven portion  1004 G can be disposed at least partially beneath the outflow protection portion  1026  and are also not visible in the figure. 
     Still referring to  FIG.  53   , the outer covering  1018  can be secured to the frame by attachment means, for example, suturing, adhering, etc., the sealing member  1000  to the frame  1020  along one or more of the second woven portions  1004 A- 1004 G. The first woven portion  1002 B can also comprise a plurality of circumferentially spaced-apart openings  1016 . The openings  1016  can be sized and positioned to overlie corresponding openings defined by the frame struts between the fourth row IV of struts and the fifth row V of struts, similar to the embodiment of  FIG.  43    above. In some embodiments, the sealing member  1000  is incorporated into an outer covering in the state illustrated in  FIG.  46    without openings in the first woven portion  1002 B. 
       FIG.  54    illustrates the prosthetic valve  1022  crimped for delivery on a balloon  1028  at the distal end of a balloon catheter  1030  of a delivery apparatus  1032 . Further details of representative delivery systems that can be used with the prosthetic valves described herein can be found in U.S. Publication No. 2017/0065415 and U.S. Pat. No. 9,339,384, which are incorporated herein by reference. As shown in the example illustrated in  FIG.  53   , the floating portions/floating yarn portions  1006 A- 1006 E are elongated and the texturized second strands/yarns  1010  are at least partially straightened, allowing the sealing member  1000  to lengthen to accommodate the increased length of the crimped frame  1020 . In certain embodiments, the floating portions/floating yarn portions  1006 A- 1006 E are configured such that the sealing member  1000  can elongate by about 10% to about 500%, about 10% to about 300%, about 10% to about 200%, about 10% to about 100%, about 10% to about 80%, or about 10% to about 50%. In some embodiments, the floating portions/floating yarn portions  1006 A- 1006 E are configured to allow the sealing member  1000  to elongate by about 30%, corresponding to the elongation of the frame  1022  between the expanded and crimped configurations. As noted above, the increase in width of the floating portions/floating yarn portions  1006 A- 1006 E can also result in a corresponding decrease in thickness of the floating portions/floating yarn portions, reducing the crimp profile of the prosthetic valve during delivery. 
     In some embodiments, the first and second strands/yarns  1008  and  1010  can comprise any of various biocompatible thermoplastic polymers such as PET, Nylon, ePTFE, UHMWPE, etc., or other suitable natural or synthetic fibers. In certain embodiments, the sealing member  1000  can be woven on a loom, and can then be heat-treated or heat-set to achieve the desired size and configuration. For example, depending upon the material selected, heat-setting can cause the sealing member  1000  to shrink. Heat-setting can also cause a texturizing effect, or increase the amount of texturizing, of the second strands/yarns  1010 . After heat treatment, the openings  1016  can be created in the first woven portion  1002 B (e.g., by laser cutting), and the sealing member can be incorporated into and/or form an outer covering such as the covering  1018  for assembly onto a prosthetic valve. In some embodiments, the openings  1016  can also be created before heat treatment. 
     In certain embodiments, the loops, filaments, floating portions, floating yarn portions, etc., of the prosthetic sealing members described herein can be configured to promote a biological response in order to form a seal between the prosthetic valve and the surrounding anatomy. In certain configurations, the sealing members described herein can be configured to form a seal over a selected period of time. For example, in certain embodiments, the open, porous nature of the loops, filaments, strands/yarns, etc., can allow a selected amount of paravalvular leakage around the prosthetic valve in the time period following implantation. The amount of paravalvular leakage past the seal structure may be gradually reduced over a selected period of time as the biological response to the loops, filaments, strands/yarns, etc., causes blood clotting, tissue ingrowth, etc. In some embodiments, the sealing members, and in particular the loops, filaments, strands/yarns, etc., of the paravalvular sealing structure, are treated with one or more agents that inhibit the biological response to the sealing structures. For example, in certain embodiments, the loops, filaments, strands/yarns, etc., are treated with heparin. In certain embodiments, the amount or concentration of the agent(s) is selected such that the agents are depleted after a selected period of time (e.g., days, weeks, or months) after valve implantation. As the agent(s) are depleted, the biological response to the loops, filaments, strands, yarns, etc., of the sealing structures may increase such that a paravalvular seal forms gradually over a selected period of time. This may be advantageous in patients suffering from heart remodeling, such as left atrial or left ventricular remodeling (e.g., due to mitral regurgitation, etc.), by providing an opportunity for the remodeling to reverse as regurgitation past the prosthetic valve is gradually reduced. 
       FIGS.  55 A- 55 J  illustrate various leno weaves and leno weaving techniques that can be used to produce the sealing member/cover member  1000 , or any of the other sealing members/cover members described herein.  FIG.  55 A  is a cross-sectional view illustrating a shed (e.g., the temporary separation of warp strands/yarns to form upper and lower warp strands/yarns) in which a leno yarn, “leno end,” or “crossing end”  1060  forms the top shed on the left of the figure above a weft strand/yarn  1064  and a standard warp strand/yarn  1062  forms the bottom shed.  FIG.  55 B  illustrates a successive shed in which the leno strand/yarn  1060  forms the top shed on the right of the standard warp strand/yarn  1062 . In  FIGS.  55 A and  55 B , the leno strand/yarn  1060  can cross under the standard strand/yarn  1062  in a pattern known as bottom douping. Alternatively, the leno strand/yarn  1060  can cross over the standard strand/yarn  1062 , known as top douping, as in  FIGS.  55 H and  55 I . 
       FIG.  55 C  illustrates a leno weave interlacing pattern produced when one warp beam is used on a loom, and the distortion or tension of the leno strands/yarns  1060  and the standard strands/yarns  1062  is equal such that both the strands/yarns  1060  and the strands/yarns  1062  curve around the weft strands/yarns  1064 .  FIG.  55 D  illustrates a leno weave lacing pattern produced when multiple warp beams are used, and the leno strands/yarns  1060  are less tensioned than the standard strands/yarns  1062  such that the standard strands/yarns  1062  remain relatively straight in the weave, and perpendicular to the weft strands/yarns  1064 , while the leno strands/yarns  1060  curve around the standard strands/yarns  1062 . 
       FIG.  55 E  illustrates an interlacing pattern corresponding to  FIG.  55 C , but in which alternate leno strands/yarns  1060  are point-drafted (e.g., a technique in which the leno strands/yarns are drawn through heddles) such that adjacent leno strands/yarns  1060  have opposite lacing directions.  FIG.  55 F  illustrates an interlacing pattern corresponding to  FIG.  55 D , but in which the leno strands/yarns  1060  are point-drafted such that adjacent leno strands/yarns have opposite lacing directions. 
       FIG.  55 G  is a cross-sectional view of a plain leno weave structure taken through the weft strands/yarns  1064 . 
       FIG.  55 J  illustrates a representative leno weave as viewed from the reverse side of the fabric. 
     The prosthetic valve covering embodiments described herein can also be used on a variety of different types of prosthetic heart valves. For example, the coverings can be adapted, and in some embodiments are adapted, for use on mechanically-expandable prosthetic heart valves, such as the valve  1100  illustrated in  FIG.  56   . The prosthetic valve  1100  can include an annular stent or frame  1102 , and a leaflet structure  1104  situated within and coupled to the frame  1102 . The frame  1102  can include an inflow end  1106  and an outflow end  1108 . The leaflet structure can comprise a plurality of leaflets  1110 , such as three leaflets arranged to collapse in a tricuspid arrangement similar to the aortic valve such that the leaflets form commissures  1132  where respective outflow edge portions  1134  of the leaflets contact each other. Optionally, the prosthetic valve can include two leaflets  1110  configured to collapse in a bicuspid arrangement similar to the mitral valve, or more than three leaflets, depending upon the particular application. 
     With reference to  FIG.  56   , the frame  1102  can include a plurality of interconnected lattice struts  1112  arranged in a lattice-type pattern and forming a plurality of apices  1114  at the outflow end  1108  of the prosthetic valve. The struts  1112  can also form similar apices  1114  at the inflow end  1106  of the prosthetic valve. The lattice struts  1112  can be pivotably coupled to one another by hinges  1116  located where the struts overlap each other, and also at the apices  1114 . The hinges  1116  can allow the struts  1112  to pivot relative to one another as the frame  1102  is expanded or contracted, such as during assembly, preparation, or implantation of the prosthetic valve  1100 . The hinges  1116  can comprise rivets or pins that extend through apertures formed in the struts  1112  at the locations where the struts overlap each other. In the embodiment of  FIG.  56   , the struts  1112  include apertures for five hinges  1116 . However, the struts may include any number of hinges depending upon the particular size of the frame, etc. For example, in some embodiments the struts comprise seven hinges, as in the configuration shown in  FIG.  57   . Additional details regarding the frame  1102  and devices and techniques for radially expanding and collapsing the frame can be found in U.S. Publication No. 2018/0153689, which is incorporated herein by reference. 
     As illustrated in  FIG.  56   , the frame  1102  can comprise a plurality of actuator components  1118  that can also function as release-and-locking units (also referred to as locking assemblies) configured to radially expand and contract the frame. In the illustrated configuration, the frame  1102  comprises three actuator components  1118  configured as posts and coupled to the frame  1102  at circumferentially spaced locations, although the frame can include more or fewer actuator components depending upon the particular application. Each of the actuator components  1118  generally can comprise an inner member  1120 , such as an inner tubular member, and an outer member  1122 , such as an outer tubular member concentrically disposed about the inner member  1120 . The inner members  1120  and the outer members  1122  can be moveable longitudinally relative to each other in a telescoping manner to radially expand and contract the frame  1102 , as further described in U.S. Publication No. 2018/0153689. 
     In the illustrated configuration, the inner members  1120  have distal end portions  1124  coupled to the inflow end  1106  of the frame  1102  (e.g., with a coupling element such as a pin member). In the illustrated embodiment, each of the inner members  1120  are coupled to the frame at respective apices  1114  at the inflow end  1106  of the frame. The outer members  1122  can be coupled to apices  1114  at the outflow end  1108  of the frame  1102  at, for example, a mid-portion of the outer member, as shown in  FIG.  56   , or at a proximal end portion of the outer member, as desired. 
     The inner member  1120  and the outer member  1122  can telescope relative to each other between a fully contracted state (corresponding to a fully radially expanded state of the prosthetic valve) and a fully extended state (corresponding to a fully radially compressed state of the prosthetic valve). In the fully extended state, the inner member  1120  is fully extended from the outer member  1122 . In this manner, the actuator components  1118  allow the prosthetic valve to be fully expanded or partially expanded to different diameters and retain the prosthetic valve in the partially or fully expanded state. 
     In some embodiments, the actuator components  1118  are screw actuators configured to radially expand and compress the frame  1102  by rotation of one of the components of the actuators. For example, the inner members  1120  can be configured as screws having external threads that engage internal threads of corresponding outer components. Further details regarding screw actuators are disclosed in U.S. Publication No. 2018/0153689. 
     The prosthetic valve  1100  can also include a plurality of commissure support elements configured as commissure clasps or clamps  1136 . In the illustrated configuration, the prosthetic valve includes a commissure clamp  1136  positioned at each commissure  1132  and configured to grip the leaflets  1110  of the commissure at a location spaced radially inwardly of the frame  1102 . Further details regarding commissure clamps are disclosed in U.S. Publication No. 2018/0325665, which is incorporated herein by reference. 
       FIG.  57    illustrates an example of a mechanically-expandable frame  1202  with components such as the leaflets, leaflet clamps, and actuator components removed for purposes of illustration. The frame  1202  can be similar to the frame  1102 , except that the struts  1204  include seven apertures  1206  spaced apart along the length of each strut for forming hinges similar to the hinges  1116 . For example, each strut  1204  can include a plurality of round, curved, or circular portions  1212  connected by straight portions or segments  1214 . Each successive segment  1214  can be parallel to, but circumferentially offset from, the preceding segment  1214 , as described in U.S. Publication No. 2018/0153689. Each round portion  1212  can define an aperture  1206 . Thus, taking the strut member  1204 A by way of example, the round portion  1212 A at the inflow end  1208  of the frame  1202  can define an aperture  1206 A. Moving along the strut  1204 A in the direction of the outflow end  1210 , the portion  1212 B can define an aperture  1206 B, the portion  1212 C can define an aperture  1206 C, the portion  1212 D can define an aperture  1206 D, the portion  1212 E can define an aperture  1206 E, the portion  1212 F can define an aperture  1206 F, and the portion  1212 G can define an aperture  1206 G at the outflow end  1210 . The apertures, and the hinges formed therewith, can function substantially as described above to allow the frame to be radially collapsed for delivery and radially expanded at the treatment site. 
     In the illustrated configuration, the struts  1204  are arranged in two sets, with the first set being on the inside of the frame  1202 , offset circumferentially from each other, and angled such that the struts extend helically around the central axis  1216  of the frame. In the embodiment of  FIG.  57   , struts  1204 B and  1204 C are part of the first or inner set of struts. The second set of struts  1204  can be disposed radially outward of the first set of struts. The second set of struts can be angled such that the apertures  1206  align with the apertures  1206  of the inner set of struts, and can be oriented with the opposite helicity as the first set of struts. In the embodiment illustrated in  FIG.  57   , the struts  1204 A and  1204 D are part of the second or outer set of struts. The inner and outer sets of struts  1204  can form inflow apices  1218  of the frame where the respective round portions  1212  align, and can form outflow apices  1220  where the respective round portions at the opposite ends of the struts align. In the expanded configuration, the struts  1204  of the inner and outer sets of struts can also define a plurality of diamond-shaped cells or openings  1222 . 
       FIGS.  58  and  59    illustrate an example of a main cushioning layer, cover member, or sealing member  1300 . The sealing member  1300  can comprise a fabric body having a plurality of woven portions and one or more floating portions (e.g., floating yarn portions, etc.), similar to the embodiment of  FIG.  46   .  FIG.  58    illustrates the sealing member  1300  in a laid-flat configuration where the x-axis corresponds to the circumferential direction and the y-axis corresponds to the axial direction when the sealing member  1300  is attached to a prosthetic valve frame.  FIG.  59    is a magnified view of a portion of the sealing member  1300 . Beginning at the inflow end portion  1310  of the sealing member  1300 , the sealing member can comprise a first woven portion  1302 A. Moving in a direction along the positive y-axis, the sealing member  1300  can further comprise a second woven portion  1304 A, a floating portion/floating yarn portion  1306 , a second woven portion  1304 B, and a first woven portion  1302 B. The first woven portion  1302 B is located at the outflow end portion  1312  on the opposite side of the floating portion/floating yarn portion from the first woven portion  1302 A. 
     Still referring to  FIG.  59   , the sealing member  1300  can comprise strands/yarns  1308  extending in the x-direction (e.g., warp strands/yarns) and strands/yarns  1314  extending in the y-direction (e.g., weft strands/yarns), as in the examples above. In certain embodiments, at least the strands/yarns  1314  can be texturized. The texturized strands/yarns  1314  can be interwoven with the strands/yarns  1308  in the first woven portion  1302 A, and in the second woven portion  1304 A. The texturized strands/yarns  1314  can extend or “float” across to the second woven portion  1304 B to form the floating portions/floating yarn portion  1306 . The strands/yarns  1314  can reenter the weave at the second woven portion  1304 B. 
     As in the embodiment of  FIG.  46   , the first woven portions  1302 A and  1302 B can comprise a plain weave. In some embodiments, the first woven portion  1302 A and/or the first woven portion  1302 B can have a strand/yarn density of from 20 strands/yarns (or ends) per inch to 150 strands/yarns per inch, such as 40 strands/yarns per inch to 120 strands/yarns per inch. In some embodiments, first woven portions  1302 A and  1302 B can be configured as selvedges, and can prevent the fabric from unraveling. 
     The second woven portion  1304 A can extend along the lower edge of the floating portion/floating yarn portion  1306 , and second woven portion  1304 B can extend along the upper edge of the floating portion/floating yarn portion  1306 . In this manner, the floating portion/floating yarn portion  1306  can be bounded or edged in a direction along the x-axis by the second woven portions  1304 A and  1304 B. In some configurations, the widths of the second woven portions  1304 A and  1304 B can be relatively small in comparison to the first woven portions  1302 A and  1302 B, similar to the embodiment of  FIG.  46   . In some embodiments, the second woven portions  1304 A and  1304 B comprises a leno weave pattern, such as any of the leno weave patterns described above. For example, with reference to the example in  FIG.  59   , each of the second woven portions  1304 A and  1304 B comprise two leno ends  1316  intertwined around strands/yarns  1314  and strands/yarns  1308 , and may be top-douped or bottom-douped. In some embodiments, the second woven portions  1304 A and  1304 B comprise one leno end, or more than two leno ends. 
     The sealing member  1300  can be resiliently stretchable between a first, natural width corresponding to a non-tensioned state, and a second width when the sealing member is stretched in the y-direction, similar to the embodiment of  FIG.  46   . As in the previously described embodiments, the texturized strands/yarns  1314  of the floating portion/floating yarn portion  1306  can be configured to be provide a bulky, compressible volume when in the relaxed state. When the sealing member  1300  is tensioned in the y-direction, the texturized strands/yarns  1314  can be pulled straight, causing the sealing member to lengthen in the y-direction. 
       FIG.  60    illustrates the sealing member or cover member  1300  secured to the frame  1202  of  FIG.  57    to form a covering on the frame. In  FIG.  60   , the frame is in the expanded configuration and the covering and the sealing member are in the first, relatively non-tensioned state. In the illustrated embodiment, the first woven portion  1302 A can be secured (e.g., by attachment means, such as suturing, adhesive, etc.) to the inflow end portions of the struts  1204 . For example, with reference to  FIG.  61   , the first woven portion  1302 A can be folded over the inflow apices  1218  so that the free edge  1318  of the fabric is located inside the frame  1202 , and so that the first woven portion  1302 A covers the apices  1218 . 
     Referring to the outer struts  1204 A and  1204 D of  FIG.  60   , the first woven portion  1302 B can be sized so that it extends from approximately the level of the round portions  1212 C to the round portions  1212 D. In certain embodiments, the first woven portion  1302 B can be shaped to match the shape of the cells  1222  ( FIG.  57   ) formed by the struts  1204  when the frame  1202  is in the expanded configuration. For example, the first woven portion  1302 B can be cut or shaped such that it comprises a plurality of extension portions  1320 . The extension portions  1320  can be sized to correspond to portions of the cells  1222  that extend above the second woven portion  1304 B. In the illustrated embodiment, the extension portions  1320  are tapered in the direction of flow through the valve such that they have a trapezoidal shape, such as an isosceles trapezoidal shape. However, the extension portions  1320  can have any other shape, such as a triangular shape, a rectangular shape, etc. The extension portions  1320  can be sutured to the frame  1202  along the strut segments  1214  ( FIG.  57   ) extending between the round portions  1212 C and  1212 D of the struts on the outer diameter of the frame, and to the corresponding segments of the struts  1204  on the inside of the frame. 
     With reference to the outer set of struts  1204 , the floating portion/floating yarn portion  1306  can extend between about the level of the round portions  1212 B to the round portions  1212 C. When the frame  1202  is in the expanded configuration, the floating portion/floating yarn portion  1306  can extend or bulge radially outwardly from the frame to form a voluminous, compressible, pillow-like structure or cushion, which can aid in sealing against the surrounding anatomy. The texturized strands/yarns of the floating portion/floating yarn portion  1306  can also provide a porous environment for tissue ingrowth. 
     Still referring to  FIG.  60   , when the frame  1202  is in the expanded configuration, the frame can have a length L 1 . The covering and the sealing member  1300  can have a corresponding length H 1 , which can be measured from the inflow apices  1218  to the upper or outflow-most edge  1322  of the extension portions  1320 . As illustrated in  FIG.  62   , when the frame  1202  is radially collapsed for delivery, the length of the frame can increase to a second length L 2 . As the frame lengthens, the covering and the sealing member  1300 , and the floating portion/floating yarn portion  1306  in particular, can also stretch such that the covering and the sealing member lengthen to a second length H 2  (e.g., corresponding to a second, tensioned state) to accommodate the increased length of the frame  1202 . In some embodiments, the frame  1202  is configured to lengthen by 10% to 160% or more between the expanded configuration and the collapsed configuration. Thus, the covering and the sealing member  1300  can also be configured to stretch by a similar amount, such as from 10% to 200%, 10% to 180%, 10% to 160%, etc., in order to accommodate the length change of the frame. 
       FIG.  63    illustrates another embodiment of a cover member or sealing member  1400  secured to the frame  1202  of  FIG.  57   . The sealing member  1400  can be configured to resiliently expand and contract axially, as well as radially. For example, the sealing member  1400  can be configured to resiliently lengthen in the axial direction as the frame  1202  is crimped, while also resiliently decreasing in diameter (and circumference). When the frame  1202  is expanded, the sealing member  1400  can shorten as the frame  1202  shortens, and can increase in diameter as the frame radially expands. In certain embodiments, the sealing member  1400  can comprise one or a plurality of axially stretchable or resilient portions, and one or a plurality of circumferentially stretchable or resilient portions. 
     For example, in the illustrated configuration the sealing member  1400  can comprise first portion configured as an axially stretchable or resilient portion  1402 , and a second portion configured as a circumferentially stretchable or resilient portion  1404 . As used herein, “axially stretchable” and “axially resilient” portions refer to portion(s) of a sealing member that are configured to lengthen and shorten primarily in a direction along the longitudinal axis of the frame, although the portions may also lengthen and/or shorten in other directions depending upon the particular characteristics of the material. The portions may be resilient in that the material can lengthen when in a tensioned state, and can return to their initial length or state when the tension is relieved. As used herein, “circumferentially stretchable” and “circumferentially resilient” portions refer to portion(s) of a sealing member that are configured to lengthen and shorten primarily in a circumferential direction around the frame (e.g., such that the sealing member increases in diameter), although the portions may also lengthen and/or shorten in other directions. 
     In the illustrated embodiment, the axially resilient portion  1402  can comprise a plurality of first woven portions  1406  configured as woven strips or stripes extending circumferentially around the frame  1220 , a plurality of second woven portions  1408  configured as woven strips or stripes extending circumferentially around the frame  1220 , and a plurality of floating portions/floating yarn portions  1410  (also referred to as floating strand portions) also extending circumferentially around the frame  1220 , and/or optionally additional portions. The various woven and floating portions/floating yarn portions can be arranged in a sequence or spaced apart along the longitudinal axis  1216  of the frame  1202 . 
     In one example configuration, as illustrated, the axially resilient portion  1402  of the sealing member/cover member  1400  can comprise two spaced-apart first woven portions  1406  with a series of alternating second woven portions and floating portions/floating yarn portions  1410  arranged between the first woven portions. For example, the axially resilient portion  1402  comprises a first woven portion  1406 A, which can be at the lower or inflow edge of the sealing member/cover member. Moving in a direction along the longitudinal axis  1216  toward the outflow end  1210 , the axially resilient portion  1402  can further comprise a second woven portion  1408 A, a floating portion/floating yarn portion  1410 A, a second woven portion  1408 B, a floating portion/floating yarn portion  1410 B, a second woven portion  1408 C, a floating portion/floating yarn portion  1410 C, a second woven portion  1408 D, a floating portion/floating yarn portion  1410 D, a second woven portion  1408 E, and a first woven portion  1406 B at the opposite end of the sealing member/cover member from the first woven portion  1406 A. As in the embodiments above, the floating portions/floating yarn portions  1410 A- 1410 D can be located between two second woven portions  1408  such that the floating portions/floating yarn portions are bounded or edged in the circumferential direction by respective second woven portions  1408 . However, in other embodiments the floating strands/yarns/threads can extend directly from one first woven portion to another first woven portion without second woven portions, depending upon the particular characteristics desired. 
     In the illustrated configuration, the first woven portions  1406  comprise a weave pattern that is different from the weave pattern of the second woven portions  1408 , as in the configurations described above. For example, in certain embodiments, the first woven portions  1406  can comprise yarns, threads, or strands woven together in a plain weave or other types of weaves, or knitted together in any of various knitting patterns. The second woven portions  1408  can comprise a second weave pattern, such as a leno weave. Accordingly, in certain embodiments the second woven portions  1408  can comprise one or more leno strands/yarns/threads or “leno ends” woven together with the yarns/threads/strands of the first woven portions  1406  in any of the leno weave patterns described herein. The second woven portions  1408  can also comprise other weave or knit patterns, such as plain weave patterns, twill weave patterns, and/or satin weave patterns, or their derivatives. 
     The floating portions/floating yarn portions  1410  can comprise a plurality of strands/yarns/threads that exit the leno weave of the second woven portions  1408 , extend across the floating portion/floating yarn portions  1410 , and are incorporated into the leno weave of the second woven portion  1408  on the opposite side of the floating portion/floating yarn portions  1410 , as described above. In certain examples, at least the floating strands/yarns/threads (e.g., the strands/yarns/threads oriented along the longitudinal axis  1216  in the weave) can be texturized, as described above. Thus, when the fabric is in the relaxed state, the texturized filaments of the second strands/yarns/threads can be kinked and twisted in many directions such that the floating portions/floating yarn portions  1410  have a bulky, billowy, or pillow-like quality, and provide a compressible volume or bulk. When tensioned, the kinks, twists, etc., of the filaments can be pulled at least partially straight along the longitudinal axis  1216 , causing the floating strands/yarns/threads to elongate, as described above. Accordingly, the floating portions/floating yarn portions  1410  can allow the axially resilient portion  1402  to elongate and shorten along the longitudinal axis  1216  as the frame is collapsed and expanded. In other embodiments, the strands/yarns/threads of the floating portions can be untexturized, and can fold or bend outwardly from the frame as the frame foreshortens in the expanded configuration. In certain embodiments, the floating strands/yarns/threads (oriented longitudinally or circumferentially) can be elastic strands/yarns/threads. 
     In the embodiment of  FIG.  63   , the circumferentially resilient portion  1404  can have a construction similar to the axially resilient portion  1402 , but is rotated 90° such that the woven portions extend axially and the texturized strands/yarns/threads of the floating portions/floating yarn portions extend circumferentially. For example, beginning with the left-hand end of the circumferentially resilient portion  1404  in  FIG.  63    and moving to the right, the circumferentially resilient portion  1404  can comprise a longitudinally extending first woven portion  1406 C, a second woven portion  1408 F, a floating portion/floating yarn portion  1410 E, a second woven portion  1408 G, a floating portion/floating yarn portion  1410 F, a second woven portion  1408 H, a floating portion/floating yarn portion  1410 G, a second woven portion  1408 I, a floating portion/floating yarn portion  1410 H, a second woven portion  1408 J, and a first woven portion  1406 D. 
     In certain embodiments, the circumferentially resilient portion  1404  can be separately formed and secured to the axially resilient portion  1402 . For example, in certain embodiments the circumferentially resilient portion  1404  can be sutured or stitched to the axially resilient portion  1402  (e.g., along the edges of the first woven portions  1406 C and  1406 D), and/or can be attached to the axially resilient portion by other securing means such as adhesive, laces, fasteners such as rivets, hook and loop fasteners, etc. In other embodiments, the circumferentially resilient portion  1404  can be integrally formed or woven with the axially resilient portion  1402 , as in the embodiment of  FIG.  67    described below. 
     In certain embodiments, the sealing member  1400  can be secured to the frame  1202  by, for example, suturing. For example, in certain embodiments the axially resilient portion  1402  can be sutured to the struts of the frame  1202 , or secured by other securing means, such that as the frame collapses and lengthens the axially resilient portion  1402  is pulled into a tensioned state and elongates. In certain embodiments, the circumferentially resilient portion  1404  need not be directly secured to the frame. In the illustrated configuration, the inflow edge (not shown) of the sealing member  1400  comprising the first woven portion  1406 A and a corresponding portion of the circumferentially resilient portion  1404  is folded around the inflow apices of the frame struts and secured inside the frame. The outflow edge  1412  of the sealing member  1400  can be located at a height between the round portions  1212 D and  1212 E ( FIG.  57   ), although the sealing member may be wider or narrower. In certain configurations, the circumferentially resilient portion  1404  can be disposed around a portion of the frame, but need not be secured to the frame. 
       FIG.  63    illustrates the frame  1202  in the expanded configuration. In the expanded configuration, the sealing member  1400  is in a first state in which the floating portions/floating yarn portions  1410 A- 1410 D of the axially resilient portion  1402  are in a relaxed state, and the floating portions/floating yarn portions  1410 E- 1410 H of the circumferentially resilient portion  1404  are in a tensioned state. Thus, in the first state shown in  FIG.  63   , the sealing member  1400  has an axial dimension L 1  as measured along the longitudinal axis  1216  of the frame. With reference to  FIG.  64   , which illustrates a top plan view of the sealing member  1400  disposed on the frame  1202 , the circumferentially resilient portion  1404  can extend along a first angular distance cu such that an exterior surface of the portion  1404  has a first arc length S 1 . 
     As the frame  1202  collapses and elongates, the axially resilient portion  1402  will be pulled into a lengthened, expanded, or tensioned state because it is secured to the frame. Thus, the axial dimension of at least a portion of the sealing member  1400  will increase.  FIG.  65    illustrates the frame  1202  in the collapsed state and the sealing member  1400  in a second state wherein the axially resilient portion  1402  is tensioned and elongated to an axial dimension L 2 . Although the circumferentially resilient portion  1404  is not secured to the frame  1202 , it will still circumferentially shorten as the diameter of the frame is reduced and the tension in the texturized yarns/strands is correspondingly relieved.  FIG.  66    schematically illustrates a top plan view of the frame  1202  in the collapsed state showing a second angular distance α 2  (which may or may not be reduced from α 1 ), and a reduced arc length S 2  of the circumferentially resilient portion  1404 . The sealing member  1400  therefore provides the advantage that it can resiliently lengthen and shorten in both the axial and circumferential directions as the frame expands and contracts. 
     Additionally, in certain embodiments, because the sealing member is resiliently stretchable axially and radially, the sealing member  1400  (e.g., the radially inward surface of the sealing member) can remain in contact with the exterior surfaces of the struts  1204  along the entire height or axial dimension of the sealing member, or substantially the entire height or axial dimension of the sealing member, as the sealing member extends and contracts between L 1  and L 2 . In other words, loose material need not drape or hang away from the frame either in the expanded configuration or in the collapsed configuration. This can help reduce the crimp profile of a prosthetic valve incorporating the sealing member  1400  since neither the axial dimension nor the circumference of the sealing member need include extra material or slack to accommodate the frame when the frame is fully expanded or fully collapsed. An additional advantage of the circumferentially expandable sealing member is that it does not significantly resist expansion of the frame. 
       FIG.  67    illustrates another embodiment of the sealing member  1400  in which the second woven portions  1408 F- 1408 J and the floating portions/floating yarn portions  1410 E- 1410 H of the circumferentially resilient portion  1404  are integrally woven or formed with the axially resilient portion  1402 . In the embodiment of  FIG.  67   , the second woven portions  1408 F and  1408 J delineate the boundary between the axially resilient portion and the circumferentially resilient portion, although the circumferentially resilient portion may also include first woven portions integrally woven with the sealing member. 
     In the embodiments illustrated in  FIGS.  63  and  67   , the axially resilient portion  1402  and the circumferentially resilient portion  1404  each include five second woven portions  1408  and four floating portions/floating yarn portions  1410  between the respective first woven portions  1406 . However, in other embodiments the axially resilient portion and/or the circumferentially resilient portion can comprise any number of second woven portions and floating portions/floating yarn portions, depending upon the particular characteristics desired. For example, in other embodiments, the axially resilient portion  1402  and/or the circumferentially resilient portion  1404  can each comprise a single floating portion/floating yarn portion  1410 , similar to the configuration of  FIG.  58   . The first woven portions, the second woven portions, and the floating portions/floating yarn portions can also have any desired axial dimension. 
     In the embodiments illustrated in  FIGS.  63  and  67   , the sealing member  1400  comprises one axially resilient portion and one circumferentially resilient portion. However, in other embodiments the sealing member  1400  can comprise multiple axially resilient portions and multiple circumferentially resilient portions. For example, the sealing member can comprise alternating axially resilient portions and circumferentially resilient portions such that the circumferentially resilient portions are circumferentially offset from each other around the sealing member by axially resilient portions.  FIG.  71    illustrates a representative embodiment including two circumferentially resilient portions  1404  offset circumferentially from each other by 180°. Other embodiments can include three, four, five, etc., circumferentially resilient portions and/or axially resilient portions. 
       FIG.  68    illustrates another embodiment of a sealing member  1500  in a laid-flat configuration. The sealing member  1500  can comprise an axially resilient portion  1502  (shown separated into halves in  FIG.  68   ) and a circumferentially resilient portion  1504 . The axially resilient portion  1502  can comprise a first woven portion  1506 A, which can comprise a fabric woven in a plain weave as described above. The axially resilient portion can further comprise a second woven portion  1508 A, which can comprise a leno weave, a floating portion/floating yarn portion  1510 , a second woven portion  1508 B, and a first woven portion  1506 B, similar to the embodiment of  FIG.  58   . 
     The circumferentially resilient portion  1504  can comprise a first plurality of yarns, threads, or strands  1512  interwoven with a second plurality of yarns, threads, or strands  1514  at an angle. For example, when the sealing member  1500  is in a first, natural, unstretched state, the strands  1512  and  1514  can form an angle θ 1 . In the unstretched state, the circumferentially resilient portion  1504  can have a first length L 1  (which can be an arc length when disposed around a cylindrical frame such as the frame  1202 ). Referring to  FIG.  69   , when the circumferentially resilient portion  1504  is in the contracted state (corresponding to the radially collapsed state of a prosthetic valve), the angle between the strands  1512  and  1514  can decrease to a second angle θ 2 , causing the length dimension of the circumferentially resilient portion to decrease to a second length L 2 . This can cause the diameter of the sealing member  1500  to decrease when secured to a prosthetic heart valve as the circumferentially resilient portion  1504  shortens in the circumferential direction. 
     Referring to  FIG.  70   , when the circumferentially resilient portion  1504  is in a tensioned state (corresponding to the radially expanded state of a prosthetic valve), the angle between the strands  1512  and  1514  can increase to a third angle θ 3 , causing the length dimension of the circumferentially resilient portion to increase to a third length L 3 . The third length L 3  can be between the natural length L 1  and the second length L 2 , or can be greater than the natural length L 1 , depending upon the dimensions of the particular prosthetic valve system. In certain embodiments, and as shown in  FIGS.  68 - 70   , the circumferentially resilient portion  1504  can be stretchable, resilient, or capable of elongating in both the axial direction and in the circumferential direction due to the orientation of the strands  1512  and  1514  at an angle other than 90°. For example, when the frame is crimped and the axially resilient portion  1502  axially elongates, the circumferentially resilient portion  1504  can both axially elongate and circumferentially shorten, as shown in  FIG.  69   . When the frame is expanded, the circumferentially resilient portion  1504  can foreshorten and circumferentially elongate. 
     In some embodiments, the strands  1512  and  1514  can be woven, knitted, and/or braided together. For example, in certain embodiments the strands  1512  and  1514  can be woven together in a plain weave, or in other weave patterns such as a satin weave and/or a twill weave and their derivatives. In some embodiments, the circumferentially resilient portion  1504  can comprise an elastically resilient or stretchable mesh. In some embodiments, the strands  1512  and  1514  can be braided together in a regular braid pattern, a diamond braid pattern, a Hercules braid pattern, or other types of braids. 
     In some embodiments, the axially resilient portion of any of the embodiments above can also include a plurality of strands woven similarly to the circumferentially resilient portion  1504  such that lengthening and shortening of the axially resilient portion is facilitated by changes in the angle between the strands. 
     In other embodiments, one or both of the axially resilient portion and/or the circumferentially resilient portion can comprise other materials such as elastic fibers, elastic polymeric films or sheets, etc., to facilitate resilient stretching and relaxing of the sealing member. In certain embodiments, the axially resilient portion and the circumferentially resilient portion can be attached to each other with elastic sutures, or any other elastic joint. Elastic strands/yarns/threads that can be used in combination with any of the embodiments described herein can comprise thermoplastic polyurethane, polypropylene, and/or any other natural or polymeric material with elastomeric properties. 
     The coverings  1400  and  1500  can be used in combination with the mechanically-expandable frame of  FIG.  57   , and/or with any other mechanically-expandable, plastically-expandable or self-expanding frame. As noted above, in some embodiments the frame  1202  is configured to lengthen by 10% to 160% or more between the expanded configuration and the collapsed configuration. Thus, the sealing members  1400  and  1500  can also be configured to resiliently stretch by a similar amount, such as from 10% to 200%, 10% to 180%, 10% to 160%, etc., in order to accommodate the length change of the frame. In certain embodiments, the circumference of the frame  1202  can increase by 10% to 600%, 100% to 500%, 200% to 400%, 300% to 400%, etc., between the collapsed configuration and the expanded configuration. Thus, the circumferentially resilient portions of the sealing members can be configured to resiliently stretch such that the circumference of the sealing member increases by a corresponding amount. In particular embodiments, the circumference of the sealing member can be configured to increase by 315% between the crimped state and the expanded state. 
       FIG.  72    illustrates another configuration of the sealing member  1300  including a plurality of circumferentially resilient portions  1330 . For example, in the illustrated embodiment the sealing member can comprise a circumferentially resilient portion  1330 A located on the inflow aspect or edge portion of the sealing member and a circumferentially resilient portion  1330 B located on the outflow aspect or edge portion of the sealing member. In the illustrated configuration, the circumferentially resilient portion  1330 A can extend axially across the width of the first woven portion  1302 A and across the width of the second woven portion  1304 A, although in other embodiments the portion  1330 A can extend across one or the other of the portions  1302 A and  1304 A. The circumferentially resilient portion  1330 A can comprise a plurality of texturized and/or elastic strands, yarns, fibers, or threads extending in the circumferential direction, and configured to allow the circumferentially resilient portion  1330 A, and thereby the sealing member  1300 , to elongate circumferentially as the frame  1202  expands. 
     The circumferentially resilient portion  1330 B can be configured similarly to the portion  1330 A, and can be located on an extension portion  1320 . The resilient portions  1330 A and  1330 B can be circumferentially aligned with each other and axially offset. In the illustrated example, the portions  1330 A and  1330 B can be positioned on opposite sides of the resilient portion  1306 . The circumferentially resilient portion  1330 B can extend across both the second woven portion  1304 B and the first woven portion  1302 B, although in other configurations it may extend across one or the other of the first woven portion  1302 B or the second woven portion  1304 B, or a portion(s) thereof. 
     In certain embodiments, the sealing member  1300  can comprise a plurality of circumferentially resilient portions spaced apart from each other circumferentially around the sealing member. For example, in certain embodiments the sealing member can comprise two, three, four, or more circumferentially resilient portions on the inflow edge portion, the outflow edge portion, or both. The circumferentially resilient portions on the inflow and outflow aspects may be circumferentially aligned with each other, or circumferentially offset, depending upon the particular characteristics desired. 
     In other embodiments, the circumferentially resilient portion  1330 A and/or  1330 B can comprise strands/yarns/threads woven or braided together at an angle such that the resilient portions are configured to axially lengthen and shorten, and configured circumferentially lengthen and shorten, similar to the embodiment of  FIGS.  68 - 70   . 
       FIG.  73    illustrates another embodiment of a sealing member  1600 . The sealing member  1600  can comprise a first woven portion  1602 A, a second woven portion  1604 A, a floating portion/floating yarn portion  1606 A, a second woven portion  1604 B, a floating portion/floating yarn portion  1606 B, a second woven portion  1604 C, and a first woven portion  1602 B. The first woven portions, the second woven portions, and the floating portions/floating yarn portions be configured as described above. The floating portions/floating yarn portions  1606 A and  1606 B can comprise texturized and/or elastic fibers/strands/yarns/threads, and can be configured to lengthen and shorten axially in the manner of the axially resilient portions described above. In certain embodiments, the second woven portion  1604 B dividing the floating portions/floating yarn portions  1606 A and  1606 B can provide structural support to the floating portions/floating yarn portions. In the illustrated embodiment, the two ends of the sealing member may be secured to each other by a seam  1608 . The seam  1608  can comprise yarns, threads, strands, fibers, stitches, or sutures woven or sewn into the fabric of the sealing member in a wave-like shape comprising a plurality of peaks and valleys offset circumferentially and axially from each other. 
       FIG.  74    illustrates the sealing member  1600  disposed on a prosthetic heart valve including the frame  1202  of  FIG.  57    and a set of leaflets  1614 . In the illustrated configuration, the first woven portion  1602 A and at least a portion of the second woven portion  1604 A and/or the floating portion/floating yarn portion  1606 A can be folded around the inflow end  1208  of the frame and disposed on the inside of the frame. The first woven portion  1602 B is secured to the frame at least in part by sutures  1610  attaching the sealing member  1600  to a liner member or skirt  1612  disposed between the frame  1202  and the sealing member  1600 . In certain embodiments, the liner member  1612  can be a woven fabric, or a polymeric film, etc. In other embodiments, the sealing member  1600  can be secured (e.g., sutured) to an inner liner or skirt disposed on the inside of the frame. Each of the portions of the sealing member  1600  can be configured according to any of the configurations and alternatives described herein. 
     Although the prosthetic valve covering embodiments described herein are sometimes presented in the context of mitral valve repair, it should be understood that the disclosed coverings can be used in combination with any of various prosthetic heart valves for implantation at any of the native valves in or around the heart. For example, the prosthetic valve coverings described herein can be used in combination with transcatheter heart valves, surgical heart valves, minimally-invasive heart valves, etc. The covering embodiments herein can be used in prosthetic valves intended for implantation at any of the native valve of an animal or patient (e.g., the aortic, pulmonary, mitral, tricuspid, and Eustachian valve, etc.), and include valves that are intended for implantation within existing prosthetics valves (so called “valve-in-valve” procedures). The covering embodiments can also be used in combination with other types of devices implantable within other body lumens outside of the heart, or heart valves that are implantable within the heart at locations other than the native valves, such as trans-atrial or trans-ventricle septum valves. 
     General Considerations 
     For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatus, and systems should not be construed as being limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatus, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved. 
     Although the operations of some of the disclosed embodiments are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. Additionally, the description sometimes uses terms like “provide” or “achieve” to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms may vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art. 
     As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the terms “coupled” and “associated” generally mean electrically, electromagnetically, and/or physically (e.g., mechanically or chemically) coupled or linked and does not exclude the presence of intermediate elements between the coupled or associated items absent specific contrary language. 
     In the context of the present application, the terms “lower” and “upper” are used interchangeably with the terms “inflow” and “outflow”, respectively. Thus, for example, the lower end of the valve is its inflow end and the upper end of the valve is its outflow end. 
     As used herein, the term “proximal” refers to a position, direction, or portion of a device that is closer to the user and further away from the implantation site. As used herein, the term “distal” refers to a position, direction, or portion of a device that is further away from the user and closer to the implantation site. Thus, for example, proximal motion of a device is motion of the device toward the user, while distal motion of the device is motion of the device away from the user. The terms “longitudinal” and “axial” refer to an axis extending in the proximal and distal directions, unless otherwise expressly defined. 
     In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of the disclosure. Rather, the scope of the disclosure is at least as broad as the following claims.