Patent Publication Number: US-2021177591-A1

Title: Bowed Runners and Corresponding Valve Assemblies for Paravalvular Leak Protection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/299,969 filed Mar. 12, 2019, which is a continuation of U.S. patent application Ser. No. 15/921,106, filed Mar. 14, 2018 (now U.S. Pat. No. 10,271,946), which is a continuation of U.S. patent application Ser. No. 15/118,991 (now U.S. Pat. No. 9,949,825), filed Aug. 15, 2016, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/US2015/015533 filed Feb. 12, 2015, published in English, which claims priority from U.S. Provisional Patent Application No. 61/941,012, filed Feb. 18, 2014, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present disclosure relates in general to heart valve replacement and, in particular, to collapsible prosthetic heart valves. More particularly, the present disclosure relates to devices and methods for positioning and sealing collapsible prosthetic heart valves within a native valve annulus. 
     Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery. 
     Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two common types of stents on which the valve structures are mounted: a self-expanding stent or a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size. 
     When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient&#39;s heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn. 
     SUMMARY OF THE INVENTION 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a stent extending between a proximal end and a distal end and including a plurality of struts forming cells, the stent having a collapsed condition and an expanded condition. At least one runner is coupled to a cell, the at least one runner being configured to transition from a first configuration to a second configuration when the stent moves from the collapsed condition to the expanded condition, the at least one runner projecting radially outwardly from the cell in the second configuration. A valve assembly is disposed within the stent, the valve assembly including a plurality of leaflets, a cuff at least partially disposed on a luminal surface of the stent and a covering material disposed on an abluminal surface of the stent and covering the at least one runner in the second configuration. 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a stent extending between a proximal end and a distal end and including a plurality of struts forming cells and a plurality of runners, the stent having a collapsed condition and an expanded condition, the struts defining a first diameter and the runners defining a second diameter, the second diameter being greater than the first diameter. A valve assembly is disposed within the stent, the valve assembly including a plurality of leaflets and a cuff at least partially disposed on a luminal surface of the stent and partially disposed on an abluminal surface of the stent to cover the runner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments in accordance with the present disclosure will now be described with reference to the appended drawings. It is to be appreciated that these drawings depict only some embodiments and are therefore not to be considered limiting of its scope. 
         FIG. 1  is a side elevational view of a conventional prosthetic heart valve; 
         FIG. 2  is a highly schematic cross-sectional view taken along line A-A of  FIG. 1  and showing the prosthetic heart valve disposed within a native valve annulus; 
         FIG. 3A  is a highly schematic side view of one embodiment of a heart valve having bowed runners intended to fill irregularities between the heart valve and the native valve annulus; 
         FIG. 3B  is a developed view of the stent of the heart valve of  FIG. 3A  in the collapsed configuration; 
         FIGS. 3C and 3D  are enlarged highly schematic partial views of a stent cell having a runner in the collapsed configuration and bowed configuration, respectively; 
         FIGS. 4A-D  are highly schematic side views of one method of delivering and deploying the heart valve of  FIG. 3A  within the native valve annulus; 
         FIGS. 5A-10B  are enlarged highly schematic partial side views of several variations of collapsed stent cells having runners and their respective shapes in the bowed configuration; 
         FIGS. 11A-C  are enlarged highly schematic side views of heart valves having bowed runners at various longitudinal positions; and 
         FIG. 12  is a highly schematic cross-sectional view of a heart valve having bowed runners disposed within a native valve annulus; 
         FIGS. 13-15  are highly schematic developed views of portions of heart valves including cuffs having folding flaps for covering runners in a first row; 
         FIGS. 16A and 16B  are highly schematic partial views of another method of folding a cuff over runners in a first row; 
         FIG. 17  is a highly schematic developed view of a portion of a heart valve having a cuff and individual panels attached over runners in a first row; 
         FIGS. 18-20  are highly schematic developed views of portions of heart valves including cuffs having folding flaps attached over runners in a second row; 
         FIG. 21  is a highly schematic developed view of a portion of a heart valve including a cuff and a covering disposed over runners in a second row; and 
         FIGS. 22A-24  are highly schematic developed views of portions of heart valves including cuffs having various folding flaps and panels for covering runners in a third row. 
     
    
    
     DETAILED DESCRIPTION 
     Despite various improvements that have been made to the collapsible prosthetic heart valve delivery process, conventional devices suffer from some shortcomings. For example, with conventional self-expanding valves, the clinical success of the valve is dependent on accurate deployment and anchoring. Inaccurate deployment and anchoring of the valve increases risks, such as those associated with valve migration, which may cause complications due to the obstruction of the left ventricular outflow tract. Inaccurate deployment and anchoring may also result in the leakage of blood between the implanted heart valve and the native valve annulus, commonly referred to as paravalvular leakage (also known as “perivalvular leakage”). In aortic valves, this leakage enables blood to flow from the aorta back into the left ventricle, reducing cardiac efficiency and putting a greater strain on the heart muscle. Additionally, calcification of the aortic valve may affect performance and the interaction between the implanted valve and the calcified tissue is believed to be relevant to leakage, as will be outlined below. 
     Moreover, anatomical variations from one patient to another may cause a fully deployed heart valve to function improperly, requiring removal of the valve from the patient or performing an additional valve-in-valve procedure. Removing a fully deployed heart valve increases the length of the procedure as well as risks. Thus, methods and devices are desirable that would reduce the need to remove a prosthetic heart valve from a patient. Methods and devices are also desirable that would reduce the likelihood of paravalvular leakage due to gaps between the implanted heart valve and patient tissue. 
     There therefore is a need for further improvements to the devices, systems, and methods for positioning and sealing collapsible prosthetic heart valves. Specifically, there is a need for further improvements to the devices, systems, and methods for accurately implanting a prosthetic heart valve. Among other advantages, the present disclosure may address one or more of these needs. 
     As used herein, the term “proximal,” when used in connection with a prosthetic heart valve, refers to the end of the heart valve closest to the heart when the heart valve is implanted in a patient, whereas the term “distal,” when used in connection with a prosthetic heart valve, refers to the end of the heart valve farthest from the heart when the heart valve is implanted in a patient. When used in connection with devices for delivering a prosthetic heart valve or other medical device into a patient, the terms “trailing” and “leading” are to be taken as relative to the user of the delivery devices. “Trailing” is to be understood as relatively close to the user, and “leading” is to be understood as relatively farther away from the user. 
     The sealing portions of the present disclosure may be used in connection with collapsible prosthetic heart valves.  FIG. 1  shows one such collapsible stent-supported prosthetic heart valve  100  including a stent  102  and a valve assembly  104  as is known in the art. Prosthetic heart valve  100  is designed to replace a native tricuspid valve of a patient, such as a native aortic valve. It should be noted that while the disclosures herein relate predominantly to prosthetic aortic valves having a stent with a shape as illustrated in  FIG. 1 , the valve could be a bicuspid valve, such as the mitral valve, and the stent could have different shapes, such as a flared or conical annulus section, a less-bulbous aortic section, and the like, and a differently shaped transition section. 
     Prosthetic heart valve  100  will be described in more detail with reference to  FIG. 1 . Prosthetic heart valve  100  includes expandable stent  102  which may be formed from biocompatible materials that are capable of self-expansion, such as, for example, shape memory alloys, such as the nickel-titanium alloy known as “Nitinol” or other suitable metals or polymers. Stent  102  extends from proximal or annulus end  130  to distal or aortic end  132 , and includes annulus section  140  adjacent proximal end  130 , transition section  141  and aortic section  142  adjacent distal end  132 . Annulus section  140  may have a relatively small cross-section in the expanded configuration, while aortic section  142  may have a relatively large cross-section in the expanded configuration. Preferably, annulus section  140  is in the form of a cylinder having a substantially constant diameter along its length. Transition section  141  may taper outwardly from annulus section  140  to aortic section  142 . Each of the sections of stent  102  includes a plurality of struts  160  forming cells  162  connected to one another in one or more annular rows around the stent. For example, as shown in  FIG. 1 , annulus section  140  may have two annular rows of complete cells  162  and aortic section  142  and transition section  141  may each have one or more annular rows of partial cells  162 . Cells  162  in aortic section  142  may be larger than cells  162  in annulus section  140 . The larger cells in aortic section  142  better enable prosthetic valve  100  to be positioned in the native valve annulus without the stent structure interfering with blood flow to the coronary arteries. 
     Stent  102  may include one or more retaining elements  168  at distal end  132  thereof, retaining elements  168  being sized and shaped to cooperate with female retaining structures (not shown) provided on the deployment device. The engagement of retaining elements  168  with the female retaining structures on the deployment device helps maintain prosthetic heart valve  100  in assembled relationship with the deployment device, minimizes longitudinal movement of the prosthetic heart valve relative to the deployment device during unsheathing or resheathing procedures, and helps prevent rotation of the prosthetic heart valve relative to the deployment device as the deployment device is advanced to the target location and the heart valve deployed. 
     Prosthetic heart valve  100  includes valve assembly  104  preferably secured to stent  102  in annulus section  140 . Valve assembly  104  includes cuff  176  and a plurality of leaflets  178  which collectively function as a one-way valve by coapting with one another. As a prosthetic aortic valve, valve  100  has three leaflets  178 . However, it will be appreciated that other prosthetic heart valves with which the sealing portions of the present disclosure may be used may have a greater or lesser number of leaflets. 
     Although cuff  176  is shown in  FIG. 1  as being disposed on the luminal or inner surface of annulus section  140 , it is contemplated that cuff  176  may be disposed on the abluminal or outer surface of annulus section  140  or may cover all or part of either or both of the luminal and abluminal surfaces. Both cuff  176  and leaflets  178  may be wholly or partly formed of any suitable biological material or polymer such as, for example, Polyethylene terephthalate (PET), ultra-high-molecular-weight polyethylene (UHMWPE), or polytetrafluoroethylene (PTFE). 
     Leaflets  178  may be attached along their belly portions to cells  162  of stent  102 , with the commissure between adjacent leaflets  178  attached to commissure features  166 . As can be seen in  FIG. 1 , each commissure feature  166  may lie at the intersection of four cells  162 , two of the cells being adjacent one another in the same annular row, and the other two cells being in different annular rows and lying in end-to-end relationship. Preferably, commissure features  166  are positioned entirely within annulus section  140  or at the juncture of annulus section  140  and transition section  141 . Commissure features  166  may include one or more eyelets which facilitate the suturing of the leaflet commissure to stent  102 . 
     Prosthetic heart valve  100  may be used to replace a native aortic valve, a surgical heart valve or a heart valve that has undergone a surgical procedure. Prosthetic heart valve  100  may be delivered to the desired site (e.g., near the native aortic annulus) using any suitable delivery device. During delivery, prosthetic heart valve  100  is disposed inside the delivery device in the collapsed configuration. The delivery device may be introduced into a patient using a transfemoral, transaortic, transsubclavian, transapical, transseptal or any other percutaneous approach. Once the delivery device has reached the target site, the user may deploy prosthetic heart valve  100 . Upon deployment, prosthetic heart valve  100  expands so that annulus section  140  is in secure engagement within the native aortic annulus. When prosthetic heart valve  100  is properly positioned inside the heart, it works as a one-way valve, allowing blood to flow from the left ventricle of the heart to the aorta, and preventing blood from flowing in the opposite direction. 
       FIG. 2  is a highly schematic cross-sectional illustration of prosthetic heart valve  100  disposed within native valve annulus  250 . As seen in the figure, valve assembly  104  has a substantially circular cross-section which is disposed within the non-circular native valve annulus  250 . At certain locations around the perimeter of heart valve  100 , gaps  200  form between heart valve  100  and native valve annulus  250 . Blood flowing through these gaps and past valve assembly  104  of prosthetic heart valve  100  can cause regurgitation and other inefficiencies which reduce cardiac performance Such improper fitment may be due to suboptimal native valve annulus geometry due, for example, to calcification of native valve annulus  250  or to unresected native leaflets. 
       FIG. 3A  illustrates one embodiment of heart valve  300  intended to fill the irregularities between the heart valve and native valve annulus  250  shown in  FIG. 2 . Heart valve  300  extends between proximal end  302  and distal end  304 , and may generally include stent  306  and valve assembly  308  having a plurality of leaflets  310  and cuff  312 . Heart valve  300  may be formed of any of the materials and in any of the configurations described above with reference to  FIG. 1 . 
     Stent  306  may include a plurality of struts  320 . Certain struts  320  may terminate in retaining elements  321  at distal end  304 . Struts  320  may come together to form cells  322  connected to one another in one or more annular rows around the stent. Connected to struts  320  are a plurality of runners  330 , which are additional struts that bow or bulge out radially when stent  306  is expanded, as will be described in greater detail with reference to  FIGS. 3B and 3C . 
     In order to better appreciate the attachment and placement of runners  330 , stent  306  is shown in  FIG. 3B  in its collapsed configuration. For the sake of clarity, valve assembly  308  is not shown in this figure. In the collapsed configuration of stent  306 , each of cells  322  is also collapsed. Stent  306  extends from proximal or annulus end  302  of heart valve  300  to distal or aortic end  304 , and includes annulus section  340  adjacent proximal end  302 , aortic section  342  adjacent distal end  304 , and transition section  341  between annulus section  340  and aortic section  342 . Commissure features  345  may be positioned entirely within annulus section  340  or at the juncture of annulus section  340  and transition section  341  as shown. 
     One or more cells  322  may include runners  330 . An enlarged partial side view of cell  322  including a runner  330  is shown in  FIG. 3C . Four struts  320   a ,  320   b ,  320   c ,  320   d  may join to form cell  322 , each strut being attached to two adjacent struts. In the collapsed configuration of stent  306 , cell  322  may be stadium-shaped as shown. In the expanded configuration of stent  306 , cell  322  may shorten in the length direction of stent  306  between proximal end  302  and distal end  304 , and struts  320  may generally form a diamond shape ( FIG. 3D ). 
     Runners  330  may extend from first attachment end  335   a  where struts  320   a  and  320   c  meet to second attachment end  335   b  where struts  320   b  and  320   d  meet, and may be affixed to stent  306  by welding, adhesive, or any other suitable technique known in the art. Moreover, instead of being separately formed and affixed to stent  306  at attachment ends  335   a , 335   b , runners  330  may be integrally formed with stent  306 , such as by laser cutting both stent  306  and runners  330  from the same tube. Additionally, runners  330  may be formed of a shape memory material such as those described above for forming stent  102  of  FIG. 1 , and may have a substantially linear configuration in the collapsed configuration of heart valve  300  ( FIG. 3C ) and a curved or bowed configuration in the expanded configuration of heart valve  300  ( FIG. 3D ). 
     In the collapsed configuration, runner  330  may bisect cell  322  into first portion  360   a  and second portion  360   b . As the length of cell  322  shortens in the expanded configuration of heart valve  300 , the unchanged length of runner  330  causes the runner to bow or deflect outwardly of the curved surface defined by struts  320   a ,  320   b ,  320   c ,  320   d . Stent  306  may also be heat set such that struts  320  and runner  330  return to a predetermined shape in the fully expanded configuration (e.g., when no external forces are applied thereto). When cuff  312  ( FIG. 3A ) is coupled to the abluminal surface of annulus section  340  of stent  306 , the cuff is substantially tubular when runners  330  are not bowed outwardly. When runners  330  bow outwardly on the expansion of heart valve  300 , they form protuberances in cuff  312  to help seal heart valve  300  within the native valve annulus. 
     A method of delivering and implanting heart valve  300  will now be described with reference to  FIGS. 4A-D . A delivery system  400  may be used to deliver and deploy heart valve  300  in native valve annulus  250 , and may generally include sheath  410 , shaft  420 , atraumatic tip  430  and hub  440 . Sheath  410  may be slidable relative to shaft  420 . Heart valve  300 , including stent  306 , valve assembly  308  and runners  330 , may be disposed within sheath  410  about shaft  420  ( FIG. 4A ). Hub  440  may be coupled to shaft  420  and configured to mate with retaining elements  321  of heart valve  300 . Runners  330  of heart valve  300  may be disposed in the linear configuration of  FIG. 3C , substantially parallel to sheath  410 , during delivery. Specifically, though runners  330  are configured to return to their curved configuration, they may be kept substantially linear by being constrained within sheath  410 . By doing so, heart valve  300  may be delivered to the native valve annulus using delivery system  400  without increasing the radius of sheath  410 , avoiding the need to increase the crimp profile of the heart valve within delivery system  400 . A large delivery system may be incapable of being passed through the patient&#39;s vasculature, while a delivery system having a heart valve with a smaller crimp profile may be easier to navigate through a patient&#39;s body and may also reduce the length of the implantation procedure. In the example shown in  FIGS. 4A-D , delivery system  400  is delivered from the aorta toward the left ventricle as indicated by arrow  51 . If heart valve  300  or delivery system  400  includes echogenic materials, such materials may be used to guide delivery system  400  to the appropriate position using the assistance of three-dimensional echocardiography to visualize heart valve  300  within the patient. Alternative visualization techniques known in the art are also contemplated herein. 
     When delivery system  400  has reached the proper location (e.g., atraumatic tip  430  is just past native valve annulus  250 ), atraumatic tip  430  may be advanced slightly in the direction of arrow  51  toward the left ventricle by pushing shaft  420  toward atraumatic tip  430  while holding sheath  410  in place, which serves to decouple atraumatic tip  430  from sheath  410  ( FIG. 4B ). Sheath  410  may then be retracted in the direction of arrow S 2  toward the aorta. With sheath  410  slightly retracted, heart valve  300  begins to emerge from the sheath. As sheath  410  is further retracted in the direction of arrow S 2 , more of heart valve  300  is exposed until annulus section  340  is fully exposed and runners  330  become bowed ( FIG. 4C ). Thus, sheath  410  may be retracted until heart valve  300  is free to self-expand within native valve annulus  250 . While heart valve  300  is partially deployed (e.g., a portion of heart valve  300  is outside sheath  410 , but heart valve  300  is not fully detached from delivery system  400 ), if it appears that heart valve  300  needs to be recaptured and redeployed due to, for example, improper positioning or orientation, sheath  410  may be slid over shaft  420  in the direction of arrow  51  to recapture heart valve  300  within sheath  410 . During recapture, sheath  410  may push against bowed runners  330  to straighten them to the linear configuration shown in  FIG. 3C . This process may be repeated until heart valve  300  is properly positioned and deployed within native valve annulus  250 . 
     After sheath  410  has been fully retracted to expose heart valve  300 , runners  330 , now in their bowed or curved configuration, push cuff  312  outwardly against native valve annulus  250  and occlude gaps  200  between heart valve  300  and native valve annulus  250 , thereby reducing or eliminating the amount of blood that passes around heart valve  300  through gaps  200  ( FIG. 4D ). Retaining elements  321  of heart valve  300  may decouple from hub  440  as heart valve  300  fully expands, atraumatic tip  430  may be retracted through heart valve  300  in the direction of arrow S 2  and delivery system  400  may be removed from the patient. 
     Several variations of runners are described with reference to  FIGS. 5A-10B . In each variation, a collapsed cell is shown along with a schematic of the cell in the expanded configuration. As used herein the terms expanded and collapsed may refer to the configurations of a cell, a stent, a heart valve and a valve assembly interchangeably. 
       FIG. 5A  shows cell  522  of a stent having four struts  520   a ,  520   b ,  520   c ,  520   d , each strut being attached to two adjacent struts. In the collapsed configuration of the stent, cell  522  may be stadium-shaped as shown ( FIG. 5A ). Runner  530  may extend between two attachment ends  535   a ,  535   b . Specifically, runner  530  may be joined to third strut  520   c  at first attachment end  535   a  and to diagonally-opposed second strut  520   b  at second attachment end  535   b . Runner  530  may diagonally divide cell  522  substantially equally into first portion  560   a  and second portion  560   b  in the collapsed configuration. When cell  522  is placed in the expanded configuration ( FIG. 5B ), the cell may form a substantially diamond shape, with runner  530  stretching diagonally from strut second  520   b  to third strut  520   c  across the cell. Because attachment ends  535   a , 535   b  are closer to one another in the expanded configuration than in the collapsed configuration, runner  530  may bow outwardly to form a protuberance. 
       FIG. 6A  shows cell  622  of a stent having four struts  620   a ,  620   b ,  620   c ,  620   d , each strut being attached to two adjacent struts. Runner  630  may extend between two attachment ends  635   a ,  635   b  located at junctions of two struts (e.g., attachment end  635   a  is at the junction of struts  620   a  and  620   c , while attachment end  635   b  is at the junction of struts  620   b  and  620   d ) and bisect cell  622  into substantially equal first portion  660   a  and second portion  660   b  in the collapsed configuration. Runner  630  may be tapered as shown, having a larger width at attachment ends  635   a ,  635   b  than at its middle. A tapered runner  630  may provide added flexibility and may be easier to heat set so that it readily returns to the bowed configuration when cell  622  is expanded, as shown in  FIG. 6B . 
       FIG. 7A  shows cell  722  of a stent having four struts  720   a ,  720   b ,  720   c ,  720   d , each strut being attached to two adjacent struts. Unlike cell  322 , runner  730  is joined to cell  722  at a single attachment end  735   a  only and is able to deflect at free end  735   b  opposite attachment end  735   a . It will be understood that the single point of attachment may be disposed at any of struts  720   a ,  720   b ,  720   c ,  720   d  or at the intersection of any two struts (e.g., at the intersection of second strut  720   b  and fourth strut  720   d  as shown, or at the opposite end at the intersection of first strut  720   a  and third strut  720   c , or at the intersection of first strut  720   a  and second strut  720   b , or third strut  720   c  and fourth strut  720   d ). In the collapsed configuration, runner  730  fills a portion of cell  722  so that a U-shaped cutout  760   a  is formed within cell  722 . In the expanded configuration ( FIG. 7B ), runner  730  is capable of bowing radially outwardly to provide paravalvular sealing. 
       FIG. 8A  shows cell  822  of a stent having four struts  820   a ,  820   b ,  820   c ,  820   d , each strut being attached to two adjacent struts. Cell  822  includes a pair of runners  830   a ,  830   b  that are substantially parallel to one another in the collapsed configuration. First runner  830   a  is coupled to first strut  820   a  at first attachment end  835   a  and to second strut  820   b  at second attachment end  835   b , while second runner  830   b  is coupled to third strut  820   c  at third attachment end  835   c  and to fourth strut  820   d  at fourth attachment end  835   d . Moreover, first and second runners  830   a ,  830   b  are coupled to one another at midpoint  845 , which keeps runners  830   a ,  830   b  close together along a midline of the diamond shaped cell  822  in the expanded configuration ( FIG. 8B ). Twin runners  830   a ,  830   b  may provide a larger support surface over which a cuff may be stretched to better seal a heart valve within a native valve annulus. 
       FIG. 9A  shows another variation having twin runners. Cell  922  includes four struts  920   a ,  920   b ,  920   c ,  920   d , each strut being attached to two adjacent struts. Cell  922  includes a pair of runners  930   a ,  930   b  that are substantially parallel to one another in a collapsed configuration. First runner  930   a  is coupled to the junction of first strut  920   a  and third strut  920   c  at first attachment end  935   a  and to the junction of second strut  920   b  and third strut  920   d  at second attachment end  935   b , while second runner  930   b  is coupled to the same two junctions at third attachment end  935   c  and fourth attachment end  935   d . Runners  930   a ,  930   b  are not joined to one another except for having attachment ends near one another. When cell  922  expands, runners  930   a ,  930   b  bow outwardly and separate to provide scaffolding upon which a cuff may be stretched ( FIG. 9B ). Instead of the cuff being stretched out over a single bowed runner or dual bowed runners attached at a midpoint, stretching the cuff over twin bowed runners that are spaced apart from one another provides a greater support area. Thus, this separation of bowed runners  930   a ,  930   b  may provide a more uniform protuberance for better sealing of a heart valve within the native valve annulus. 
     Another variation, shown in  FIG. 10A , includes cell  1022  having four struts  1020   a ,  1020   b ,  1020   c ,  1020   d , each strut being attached to two adjacent struts. Runner  1030  is formed as a U-shaped nested strut in the collapsed configuration, being attached to two adjacent struts  1020   a ,  1020   c  at attachment ends  1035   a ,  1035   b , respectively. In the expanded configuration, runner  1030  bows radially outwardly to form a protuberance ( FIG. 10B ). Because bowed runner  1030  is attached to adjacent struts  1020   a ,  1020   c  in the same half of cell  1022  and stretches between two attachment points at about the same longitudinal position, in the expanded configuration, bowed runner  1030  extends laterally across cell  1022 . 
     Additionally, runners may be provided at a variety of locations on a stent. For example, in  FIG. 11A  heart valve  1100 A extends between proximal end  1102  and distal end  1104 , and may generally include stent  1106  and valve assembly  1108  having a plurality of leaflets  1110  and cuff  1112 . Heart valve  1100 A may be formed of any of the materials and in any of the configurations described above with reference to  FIG. 1 . 
     Stent  1106  may include a plurality of struts  1120 , which may come together to form cells such as cell  1122 A connected to one another in one or more annular rows around the stent. Connected to struts  1120  are a plurality of runners  1130 A, which are additional struts that bow or bulge out radially when stent  1106  is expanded, as will be described in greater detail with reference to  FIGS. 11B and 11C . As shown in  FIG. 11A , runners  1130 A are attached to the third full row of cells  1122 A from proximal end  1102  so that at least a portion of each runner is disposed radially outward of leaflets  1110 . In a second variation, shown in  FIG. 11B , heart valve  1100 B includes runners  1130 B attached to the first full row of cells  1122 B from proximal end  1102 . In yet another variation, shown in  FIG. 11C , heart valve  1100 C includes runners  1130 C attached to the bottom-most struts  1120 C so that they extend proximally of the proximal end  1102  of stent  1106 . It will be understood that the longitudinal position of runners  1130  may be varied anywhere within the annulus section and/or transition section. Additionally, multiple rows of runners may be disposed on stent  1106 . Moreover, each cell in an annular row of cells need not include a runner. Thus, there may be more runners in one annular row of cells than in another annular row of cells. 
       FIG. 12  is a highly schematic cross-sectional view showing heart valve  1200  having stent  1202 , valve assembly  1204  including leaflets  1208  and a cuff  1222 , and bowed runners  1230  supporting portions of cuff  1222 . As seen in  FIG. 12 , bowed runners  1230  extend radially outward from stent  1202  to press cuff  1222  into the gaps between heart valve  1200  and native valve annulus  250 . Cuff  1222  may be capable of promoting tissue growth between heart valve  1200  and native valve annulus  250 . For example, cuff  1222  may be innately capable or promoting tissue growth and/or may be treated with a biological or chemical agent to promote tissue growth, further enabling it to seal the heart valve within the native valve annulus. When runners  1230  are functioning properly, heart valve  1200  will be adequately sealed within native valve annulus  250  so that blood flows through leaflets  1208  of valve assembly  1204 , and so that blood flow through any gaps formed between heart valve  1200  and native valve annulus  250  is limited or reduced. 
     The preceding embodiments have illustrated a simplified arrangement in which a cuff is disposed on the abluminal surface of a stent and attached to runners such that the expansion of the runners pushes the cuff outwardly toward walls of the native valve annulus. Other configurations of the cuff are also possible as illustrated below. 
       FIG. 13  is a schematic developed view of a portion of heart valve  1300  including stent  1306  with cuff  1312  attached to same. For the sake of clarity, leaflets of the valve assembly are not shown. Stent  1306  includes a plurality of struts  1320  attached together to form diamond-shaped cells  1322  as has been described above. Three commissure features  1325   a ,  1325   b ,  1325   c  are also shown attached to struts  1320 . Runners  1330  are formed in each of cells  1322  in row R 1  located directly below commissure features  1325 . 
     Cuff  1312  is disposed on the luminal surface of stent  1306  (i.e.,  FIG. 13  is a schematic illustration of the exterior of heart valve  1300 ). Cuff  1312  may be formed of a polymer, a fabric or tissue, such as bovine, porcine, ovine, equine, kangaroo, PTFE, UHMWPE, PET, Dacron, PVA, Polyurethane, silicone or combinations thereof. Cuff  1312  includes diamond-shaped flaps  1350  for folding over certain cells  1322  in row R 1  that include runners  1330 . Each flap  1350  may be attached to cuff  1312  or formed integrally with cuff  1312  and may be folded at fold line F 1  from the luminal surface of stent  1306  to the abluminal surface of stent  1306  to cover runner  1330  as shown. A corresponding diamond-shaped suture pattern P 1  may attach a perimeter of flap  1350  to struts  1320  forming row R 1  of cells  1322  so that the bowing of runner  1330  pushes flap  1350  radially outward. 
     Panels  1352  formed of the same or different material than cuff  1322  may be coupled to all cells or to certain cells  1322  where folding is difficult. Specifically, panels  1352  may be coupled to cuff  1312  and/or struts  1320  of cells  1322  of row R 1  located directly below commissure features  1325 , while flaps  1350  may be provided for all other cells  1322  in row R 1 . Panels  1352  may be formed from segments of material that are initially not attached to cuff  1312 , and may be attached to cells  1322  under commissure features  1325  using a diamond pattern of sutures similar to that of pattern P 1 . For the sake of clarity, only one panel  1352  is shown under the left-most commissure feature  1325   a  and no panels are shown under commissure features  1325   b , 1325   c  so that the shape of cuff  1312  may be appreciated. It will be understood, however, that panels  1352  may be coupled to cells  1322  located under commissure features  1325   b  and  1325   c.    
       FIG. 14  is a schematic developed view of a portion of heart valve  1400  including stent  1406  and cuff  1412  attached to the stent. Stent  1406  includes struts  1420  forming cells  1422 , commissure features  1425 , and runners  1430 . Heart valve  1400  includes first flaps  1450   a  that are similar to flaps  1350  of  FIG. 13  described above. Heart valve  1400  differs from heart valve  1300  in that second flaps  1450   b  are also formed under commissure features  1425 . Specifically, instead of panels that initially are separate from and later are attached to the cuff, cuff  1412  includes second flaps  1450   b  that fold 180 degrees at fold line F 2  and then attach to cell  1422  under commissure feature  1425  to form two layers of cuff sandwiching runner  1430 . For the sake of clarity, only one second flap  1450   b  is shown under commissure feature  1425   a . Thus, cuff  1412  may be integrally formed from a single piece of material, disposed on the luminal surface of stent  1406  and include flaps on the abluminal surface to cover runners  1430 . 
       FIG. 15  is a similar developed view of a portion of heart valve  1500  including stent  1506  with cuff  1512  attached thereto. Stent  1506  includes struts  1520  forming cells  1522 , commissure features  1525 , and runners  1530 . Various methods of folding flaps over runners  1530  are shown. In each example, flap  1550  is folded to a position over cell  1522  indicated by a diamond in broken lines. For example, flap  1550   a  is capable of folding diagonally downward to position  1550   a ′, while flaps  1550   b  fold diagonally upward toward position  1550   b ′. Flap  1550   c  may fold straight down to position  1550   c ′ and flap  1550   d  may fold diagonally downward to position  1550   d′.    
       FIGS. 16A and 16B  illustrate yet another example of cuff  1612  for covering a plurality of runners  1630  using flaps  1650 .  FIG. 16A  illustrates the preassembled state in which cuff  1612  includes three flaps  1650   a ,  1650   b  and  1650   c  that will be horizontally folded over runners  1630  and main portion  1660  of the cuff that covers six cells  1622 . Cuff  1612  may be formed of a single piece of material or may be formed as a composite cuff with multiple portions. For example, in  FIG. 16A , first flap  1650   a  and second flap  1650   b  may be formed of a first piece of material, main portion  1660  may be formed of a second piece of material and third flap  1650   c  may be formed of a third piece of material. All three pieces may be sutured or otherwise coupled together to form a triple composite cuff. 
     As seen in the assembled state ( FIG. 16B ), first flap  1650   a  and second flap  1650   b  have been folded horizontally so that first flap  1650   a  extends to position  1650   a ′ over first runner  1630   a , and second flap  1650   b  extends to position  1650   b ′ over second runner  1630   b . Flap  1650   c  has been folded horizontally (in a direction opposite to first flap  1650   a  and second flap  1650   b ) to position  1650   c ′ over third runner  1630   c . Flaps  1650  may then be sutured to their respective cells around their perimeters 
     In  FIG. 17 , heart valve  1700  includes stent  1706  and cuff  1712 , as well as runners  1730  in row R 1  of cells  1722 . Instead of folding flaps as described above, individual panels  1750  are sutured around their perimeter to each cell  1722  in row R 1  as shown. Panels  1750  may be formed of the same material as cuff  1712 , or from a different material. Because runners  1730  bow outwardly, panels  1750  may be slightly larger than the underlying cells  1722 , such as first panel  1750   a , so as to not impede the outward bowing. Additionally, panels  1750  may be formed with a specific fiber orientation, compliance, thickness or the like to allow for the bowing. Pockets formed between cuff  1712  and panels  1750  may be filled with a liquid, a gel, a powder or other media to help support the outward bulging of the panels and thereby help mitigate paravalvular leakage. One example of the filler media may be a solution of polyvinyl alcohol (PVA). As cuff  1712  and panels  1750  contact blood upon the implantation of prosthetic heart valve  1700 , the filler media may swell in size, increasing the size and specifically the diameter of the pockets between the cuff and the panels. The enlarged pockets thus fill the gaps between the native valve annulus and the prosthetic heart valve, minimizing or preventing paravalvular leakage. 
       FIG. 18  is a schematic developed view of a portion of heart valve  1800  including stent  1806  and cuff  1812  attached to the stent. Stent  1806  includes struts  1820  forming cells  1822 , commissure features  1825 , and runners  1830 . In  FIG. 15 , runners  1330  were formed in each of cells  1322  in row R 1  located directly below commissure features  1325 . In the instant example, runners  1830  are provided in each of the cells in row R 2  located in the second full row below commissure features  1825 . Flaps  1850   a  and  1850   b  fold vertically downward to positions  1850   a ′ and  1850   b ′, respectively, sandwiching certain runners  1830  between cuff  1812  and the flaps. Other runners  1830  may be covered with individual panels (not shown) as described above with reference to  FIG. 17 . 
       FIG. 19  illustrates another variation in which heart valve  1900  includes flaps  1950   a - f  which are arranged to fold over runners  1930  in row R 2 . Flaps  1950   a - f  may be unitarily formed with cuff  1912  and cut at certain edges depending on their intended position to create individual diamond-shaped flaps. Flaps  1950   a - f  may be folded either diagonally or vertically downward to positions  1950   a ′-f, respectively. In another variation of folding flaps over the runners in second row R 2 ,  FIG. 20  illustrates heart valve  2000  having runners  2030  and flaps  2050   a - f  that are foldable directly upward to the abluminal surface onto positions  2050   a ′-f as shown. In a further variation of the  FIG. 20  embodiment, individual panels as shown in  FIG. 17  may be disposed over each of runners  2030  in second row R 2 . Such panels may be enlarged or chosen based on specific properties as discussed above with reference to  FIG. 17 . 
     In  FIG. 21 , heart valve  2100  includes stent  2106  and attached cuff  2112 . Stent  2106  includes a plurality of cells  2122  and runners  2130  in second row R 2  of the cells. Cuff  2112  is attached to the luminal surface of stent  2106 . Instead of individual panels or folded flaps, heart valve  2100  includes a unitary sheet of material  2150  coupled to the abluminal surface of stent  2106 . Sheet  2150  may be sized to extend over all cells  2122  in second row R 2  and may be attached to cuff  2112  using suture pattern s 21 . Suture pattern S 21  extends around the perimeter of sheet  2150  with the exception of edges E 1 , which may be left unattached to cuff  2122 . Blood flowing in a retrograde direction when heart valve  2100  is implanted in a patient may enter into a pocket P 21  formed between sheet  2150  and cuff  2112  at edges E 21  and causes the pocket to expand. In one variation of this embodiment, cuff  2112  and sheet  2150  may be unitarily formed such that a single piece of material is folded from the luminal surface over the bottom of the stent and forms a second layer on the abluminal surface of the stent. In one example, such a fold or transition may be made distal to the runners. 
       FIG. 22A  is a schematic developed view of heart valve  2200  including stent  2206  and attached cuff  2212 A. Stent  2206  includes struts  2220  forming cells  2222 , commissure features  2225 , and runners  2230 . Three rows of cells, R 1 , R 2 , R 3  are shown below commissure feature  2225 . In this example, runners  2230  are disposed in row R 3  of incomplete cells defined at the proximal end of stent  2206 , and are attached to the bottom-most struts  2220  of stent  2206  in a manner similar to the stent described in connection with the embodiment of  FIG. 11C . Individual panels  2250  may be sutured over each portion of a cell having a runner. In a slight variation, shown in  FIG. 22B , cuff  2212 B may be disposed on the luminal surface of a stent (not shown) and include a plurality of triangular flaps  2260  that may be folded upwardly at fold line F 22  and extend over the runners on the abluminal surface of the stent. Thus, flaps  2260  may take the place of individual panels  2250  from  FIG. 22A . 
     In  FIG. 23 , heart valve  2300  includes stent  2306  and attached cuff  2312 . Stent  2306  includes a plurality of cells  2322  arranged in three rows, R 1 , R 2 , R 3  below commissure feature  2325 . Runners  2330  are disposed in row R 3  of incomplete cells  2322  at the proximal end of the stent. Cuff  2312  is attached to the luminal surface of stent  2306 . Heart valve  2300  further includes a unitary sheet of material  2350  coupled to the abluminal surface of stent  2306  so as to overlie runners  2330 . Sheet  2350  may be sized to extend over all incomplete cells  2322  in row R 3  and may be attached to cuff  2312  using a stitch pattern S 23  around the perimeter of sheet  2350 . Thus, cuff  2312  and sheet  2350  may form a continuous pocket P 23 , which functions similarly to individual pockets P 21  of  FIG. 21  described above. 
       FIG. 24  illustrates heart valve  2400  including stent  2406  and attached cuff  2412 . Stent  2406  includes a plurality of cells  2422  arranged in three rows, R 1 , R 2 , R 3  below commissure feature  2425 . Runners  2430  are disposed in third row R 3  of incomplete cells  2422  at the proximal end of the stent. Instead of a unitary sheet of material or individual panels, cuff  2412  includes upper portion  2450  and lower portion  2452  and fold line F 24  separating the two portions. Fold line F 24  is disposed along the tops of the incomplete cells in third row R 3 . Lower portion  2452  is divided into individual, substantially rectangular segments  2454 . Upper portion  2450  is attached to the luminal surface of stent  2406 . At fold line F 24 , rectangular segments  2454  may be folded from the luminal surface to the abluminal surface of stent  2406 , each segment passing through the center of cell  2412 . Segments  2454  of lower portion  2452  may then be stitched to adjacent segments and to runners  2430 . To aid in securing segments  2454  of lower portion  2452 , each runner  2430  may include a horseshoe  2460  at its free end and segments  2454  may be sutured to horseshoes  2460 , which may prevent lower portion  2452  from riding up runner  2430  during assembly or use. In some variations, eyelets or other similar features may be disposed at the free ends of the runners. Thus, a portion of cuff  2412  is disposed on the luminal surface of stent  2406  and a second portion of cuff  2412  is disposed over runners  2430  and on the abluminal surface of stent  2406 . 
     While the devices disclosed herein have been described for use in connection with heart valve stents having a particular shape, the stent could have different shapes, such as a flared or conical annulus section, a less-bulbous aortic section, and the like, as well as a differently shaped transition section. Additionally, though the runners and cuffs have been described in connection with expandable transcatheter aortic valve replacement, they may also be used in connection with other expandable cardiac valves, as well as with surgical valves, sutureless valves and other devices in which it is desirable to create a seal between the periphery of the device and the adjacent body tissue. 
     Moreover, although the disclosures herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present disclosure. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present claims. 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a stent extending between a proximal end and a distal end and including a plurality of struts forming cells, the stent having a collapsed condition and an expanded condition. At least one runner is coupled to a cell, the at least one runner being configured to transition from a first configuration to a second configuration when the stent moves from the collapsed condition to the expanded condition, the at least one runner projecting radially outwardly from the cell in the second configuration. A valve assembly is disposed within the stent, the valve assembly including a plurality of leaflets, a cuff at least partially disposed on a luminal surface of the stent and a covering material disposed on an abluminal surface of the stent and covering the at least one runner in the second configuration. 
     In some examples, the at least one runner is substantially linear in the first configuration, and/or the at least one runner is bowed in the second configuration, and/or the cuff includes at least one flap configured to fold from the luminal surface to the abluminal surface of the stent to form the covering material, and/or the flap folds over a selected strut from the distal end toward the proximal end of the stent, and/or the flap folds over a selected strut from the proximal end toward the distal end of the stent, and/or the flap folds diagonally over a selected strut, and/or the at least one runner comprises multiple runners and the covering material includes a plurality of individual panels, each of the plurality of individual panels being disposed over one of the multiple runners, and/or the covering material includes at least one diamond-shaped panel disposed over at least one cell, and at least one flap integrally formed with the cuff and configured to fold from the luminal surface to the abluminal surface of the stent, and/or the stent further includes commissure features and the at least one runner coupled to selected cells in a first row of the cells proximal of the commissure features, and/or the stent further includes commissure features and the at least one runner coupled to selected cells in a second row of the cells proximal of the commissure features, and/or a plurality of runners coupled to proximal-most struts of the stent and extending proximally of the proximal end of the stent, and/or each of the plurality of runners extends from a first end joined to a strut to a free end, and/or each free end has a horseshoe shape, the covering material being sutured to the horseshoe shape, and/or the covering material includes a sheet of material circumferentially disposed on the abluminal surface of the stent so as to extend over a row of cells. 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a stent extending between a proximal end and a distal end and including a plurality of struts forming cells and a plurality of runners, the stent having a collapsed condition and an expanded condition, the struts defining a first diameter and the runners defining a second diameter, the second diameter being greater than the first diameter. A valve assembly is disposed within the stent, the valve assembly including a plurality of leaflets and a cuff at least partially disposed on a luminal surface of the stent and partially disposed on an abluminal surface of the stent to cover the runner. 
     In some examples, the stent includes a plurality of commissure features and the cuff includes an upper portion and a lower portion, the upper portion being disposed on the luminal surface of the stent and coupled to the commissure features and the lower portion being disposed on the abluminal surface of the stent so as to cover the plurality of runners, and/or the lower portion is divided into individual segments capable of passing through the cells from the luminal surface to the abluminal surface, and/or the cuff transitions from the luminal surface to the abluminal surface distal to the plurality of runners, and/or each of the individual segments is coupled to an adjacent segment and a runner. 
     It will be appreciated that the various dependent claims and the features set forth therein can be combined in different ways than presented in the initial claims. It will also be appreciated that the features described in connection with individual embodiments may be shared with others of the described embodiments.