Patent Publication Number: US-2021177587-A1

Title: Sealing Structures for Paravalvular Leak Protection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 14/547,595, filed on Nov. 19, 2014, which claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/906,076, filed on Nov. 19, 2013, the disclosures of which are hereby 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 ordinarily 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 For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.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 collapsible and expandable stent having a proximal end and a distal end and a valve assembly disposed within the stent, the valve assembly including a plurality of leaflets. The heart valve further includes a cuff annularly disposed about the stent and having a surplus portion capable of forming a sealing structure at the proximal end of the stent, the sealing structure having a deployed condition with a diameter in the deployed condition greater than a diameter of the proximal end of the stent. 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a collapsible and expandable stent having a proximal end and a distal end, a valve assembly disposed within the stent, the valve assembly including a plurality of leaflets and a cuff annularly disposed about the stent and having an attached end coupled to the stent and a free end extending past the proximal end of the strut and capable of forming a sealing structure for sealing gaps between the prosthetic heart valve and a native valve annulus. 
     In some embodiments, a method of making a prosthetic heart valve for replacing a native valve includes providing a collapsible and expandable stent having a proximal end and a distal end, coupling a valve assembly to the stent, the valve assembly including a plurality of leaflets, coupling a cuff to the stent so that a surplus portion of the cuff extends beyond the proximal end of the strut and converting the surplus portion of the cuff into a sealing structure at the proximal end of the stent, the sealing structure having a diameter greater than a diameter of the proximal end of the stent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present invention will now be described with reference to the appended drawings. It is to be appreciated that these drawings depict only some embodiments of the invention and are therefore not to be considered limiting of its scope. 
         FIG. 1  is a side elevational view of a conventional prosthetic heart valve; 
         FIG. 2A  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. 2B  is a highly schematic cross-sectional view showing a prosthetic mitral valve disposed within a native valve annulus; 
         FIGS. 3A and 3B  are highly schematic side views of one embodiment of a heart valve having a sealing portion intended to fill irregularities between the heart valve and the native valve annulus; 
         FIGS. 4A-E  are highly schematic side views of one method of delivering and deploying the heart valve of  FIGS. 3A and 3B  within the native valve annulus; 
         FIGS. 5A and 5B  are enlarged highly schematic partial side views of another embodiment of a heart valve having a sealing portion disposed at the annulus section; 
         FIG. 5C  is an enlarged highly schematic partial side view of another embodiment of a heart valve showing attachment ends of the elongated legs coupled to struts of a stent; 
         FIGS. 6A and 6B  are enlarged highly schematic partial side views of another embodiment of a heart valve having multiple sealing portions; 
         FIG. 7A  is an enlarged highly schematic partial side view of another embodiment of a heart valve having elongated legs with multiple eyelets; 
         FIG. 7B  is an enlarged highly schematic partial side view of another embodiment of a heart valve having wavy legs; 
         FIGS. 7C and 7D  are enlarged highly schematic partial side views of another embodiment of a heart valve having pairs of elongated legs in the extended and relaxed configurations, respectively; 
         FIGS. 8A-C  are highly schematic side views of heart valves having sealing rings disposed at various locations relative to the native leaflets; 
         FIGS. 9A and 9B  are enlarged highly schematic partial side views of another embodiment of a heart valve having elongated legs in the extended and relaxed configurations, respectively; 
         FIGS. 9C and 9D  are examples of the shortening of an elongated leg from the extended configuration of  FIG. 9A  to the relaxed configuration of  FIG. 9B ; 
         FIGS. 10A and 10B  are highly schematic side views of another embodiment of a heart valve having a sealing ring intended to fill irregularities between the heart valve and the native valve annulus; 
         FIGS. 10C-E  are highly schematic partial side views of elongated legs in a stretched configuration and two variations of bending the elongated legs; 
         FIG. 10F  is an enlarged partial perspective view of the bending of the elongated legs; 
         FIGS. 11A-F  are highly schematic partial side views of a heart valve showing variations of bending the elongated legs; 
         FIG. 12  is a highly schematic cross-sectional view showing a prosthetic heart valve disposed within a native valve annulus and having a sealing ring in its fully expanded state; 
         FIGS. 13A and 13B  are highly schematic side views of another embodiment of a heart valve having a sealing ring intended to fill irregularities between the heart valve and the native valve annulus; 
         FIG. 13C  is a schematic end view of the prosthetic heart valve of  FIGS. 13A and 13B  after formation of a sealing ring as seen from the annulus end toward the aortic end of the heart valve; 
         FIG. 13D  is a highly schematic side view of a variation of the embodiment shown in  FIGS. 13A-C ; 
         FIG. 14A  is a highly schematic side view of another embodiment of a heart valve having an undulating sealing ring intended to fill irregularities between the heart valve and the native valve annulus; 
         FIG. 14B  is a schematic end view of the prosthetic heart valve of  FIG. 14A  after formation of an undulating sealing ring as seen from the annulus end toward the aortic end of the heart valve; 
         FIG. 15A  is a highly schematic side view of another embodiment of a heart valve having a halo sealing ring intended to fill irregularities between the heart valve and the native valve annulus; 
         FIG. 15B  is a schematic end view of the prosthetic heart valve of  FIG. 15A  after formation of the halo sealing ring as seen from the annulus end toward the aortic end of the heart valve; 
         FIG. 16A  is a highly schematic side view of another embodiment of a heart valve having a sealing body with limbs intended to fill irregularities between the heart valve and the native valve annulus; and 
         FIG. 16B  is a schematic end view of the prosthetic heart valve of  FIG. 16A  after formation of the sealing body as seen from the annulus end toward the aortic end of the heart valve. 
     
    
    
     DETAILED DESCRIPTION 
     Despite the 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, 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 severe complications and possibly death 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 perivalvular leakage (also known as “paravalvular 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. Removing a fully deployed heart valve increases the length of the procedure as well as the risk of infection and/or damage to heart tissue. 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 perivalvular 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 transcatheter delivery and positioning of 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. Also as used herein, the terms “generally,” “substantially,” and “about” are intended to mean that slight deviations from absolute are included within the scope of the term so modified. 
     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. The 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 inventions herein are described predominantly in connection with their use with a prosthetic aortic valve and a stent having 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 a proximal or annulus end  130  to a 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  has a relatively small cross-section in the expanded condition, while aortic section  142  has a relatively large cross-section in the expanded condition. 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 positioned in annulus section  140  of the stent  102  and secured to the stent. 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  178 . 
     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, polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), ultra-high molecular weight polyethylene, silicone, urethane and the like. 
     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, commis sure 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 commis sure 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 condition. The delivery device may be introduced into a patient using a transfemoral, transapical, transseptal, transradial, transsubclavian, transaortic 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. 
     Problems may be encountered when implanting prosthetic heart valve  100 . For example, in certain procedures, collapsible valves may be implanted in a native valve annulus without first resecting the native valve leaflets. The collapsible valves may have critical clinical issues because of the nature of the stenotic leaflets that are left in place. Additionally, patients with uneven calcification, bi-cuspid aortic valve disease, and/or valve insufficiency cannot be treated well, if at all, with the current collapsible valve designs. 
     The reliance on unevenly calcified leaflets for proper valve placement and seating could lead to several problems, such as perivalvular leakage (PV leak), which can have severe adverse clinical outcomes. To reduce these adverse events, the optimal valve would anchor adequately and seal without the need for excessive radial force that could harm nearby anatomy and physiology. 
       FIG. 2A  is a highly schematic cross-sectional illustration of a prosthetic aortic valve  100 A disposed within native valve annulus  250 A. As seen in the figure, valve assembly  104 A has a substantially circular cross-section which is disposed within the non-circular native valve annulus  250 A. At certain locations around the perimeter of heart valve  100 A, gaps  200 A form between heart valve  100 A and native valve annulus  250 A. Blood flowing through these gaps and past valve assembly  104 A of prosthetic heart valve  100 A 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 A or to unresected native leaflets. 
       FIG. 2B  is a similar cross-sectional illustration of a prosthetic mitral valve  100 B disposed within native valve annulus  250 B. As seen in the figure, valve assembly  104 B has a substantially D-shaped cross-section which is disposed within irregularly-shaped annulus  250 B. At certain locations around the perimeter of heart valve  100 B, gaps  200 B form between heart valve  100 B and native valve annulus  250 B. Regurgitation and other inefficiencies may thus result in a prosthetic mitral valve. Though the following examples show aortic valves, it will be understood that the present devices and methods may be equally applicable to mitral heart valves. 
       FIGS. 3A and 3B  illustrate one embodiment of heart valve  300  intended to fill the irregularities between the heart valve and native valve annulus  250 A shown in  FIG. 2A . 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 . 
     Additionally, heart valve  300  may include a number of elongated legs  320  and a sealing portion  322  coupled to the elongated legs via eyelets  324  to mitigate perivalvular leakage. Attachment ends  325  of elongated legs  320  may be affixed to stent  306  near the proximal end  302  of heart valve  300 , and legs  320  may extend away from the distal end  304  of stent  306  and terminate at free ends  326 , which are unattached and free to move. As will be shown in subsequent examples, elongated legs  320  may instead be oriented in the opposition direction, being affixed near the proximal end  302  of heart valve  300  and extending toward the distal end  304  of the heart valve. Attachment ends  325  of elongated legs  320  may be affixed to stent  306  using welding, adhesive, or any other suitable technique known in the art. Additionally, legs  320  may be formed of a shape memory material such as those described above for forming stent  102  of  FIG. 1 , and may have an extended configuration and a relaxed configuration. In the extended configuration, shown in  FIG. 3A , elongated legs  320  may be substantially linear. Moreover, instead of being separately formed and affixed to stent  306  at attachment ends  325 , elongated legs  320  may be integrally formed with stent  306 , such as by laser cutting both stent  306  and elongated legs  320  from the same tube. 
     Sealing portion  322  may be attached to legs  320  to form a cylindrical tube around the interior or exterior of the legs. Sealing portion  322  may be attached to legs  320  via sutures, adhesive or any other suitable method. For example, each leg  320  may include eyelets  324  and sealing portion  322  may be attached to eyelets  324  via sutures (not shown). Where eyelets  324  are provided in this or any of the other embodiments described herein, they may be disposed at the free ends of legs  320  as illustrated in  FIG. 3A , or anywhere else along the length of the legs. Providing eyelets  324  along the length of legs  320  may better hold sealing portion  322  to the legs as the legs move between their extended and relaxed configurations. Moreover, it will be understood that other features such as indentations or notches may be used to couple two portions of the prosthetic valve using sutures. 
     Sealing portion  322  may be formed of the same material as cuff  312 , including natural materials such as, for example, bovine or porcine pericardium, or synthetic materials such as, for example, ultra-high-molecular-weight polyethylene (UHMWPE), or combinations thereof. In one example, sealing portion  322  may be formed by increasing the length of cuff  312  and extending it over the proximal end  302  and legs  320  of heart valve  300 . Alternatively, sealing portion  322  may be formed separately from cuff  312  and attached to eyelets  324  at the proximal end  302  of heart valve  300  to form a seam with cuff  312 . 
     In a variant of the foregoing, sealing portion  322  of heart valve  300  may be formed from a tubular section of braided fabric comprising a plurality of braided strands. The strands forming the braid may have a predetermined relative orientation with respect to one another (e.g., a helical braid). Moreover, sealing portion  322  may comprise a plurality of layers of braided fabric and/or other occluding material such that sealing portion  322  is capable of at least partially inhibiting blood flow therethrough in order to promote the formation of thrombus, endothelialization and epithelialization. 
     In such variants, sealing portion  322  may be formed of a passive material (e.g., one that does not change shape in response to a stimulus) so that it simply conforms to the shape of legs  320 . Alternatively, sealing portion  322  may be formed, for example, of a braided fabric mesh of a shape-memory material, of a super-elastic material, of a bio-compatible polymer, or of another material that is capable of being actuated between an extended configuration and a relaxed configuration. Sealing portion  322  may comprise a braided metal fabric that is both resilient and capable of heat treatment to substantially set a desired shape (e.g., the relaxed configuration shown in  FIG. 3B ). One class of materials which meets these qualifications is shape memory alloys, such as Nitinol. It is also understood that sealing portion  322  may comprise various materials other than Nitinol that have elastic and/or memory properties, such as spring stainless steel, trade named alloys such as Elgiloy®, and Hastelloy®, CoCrNi alloys (e.g., trade name Phynox), MP35N®, CoCrMo alloys, mixtures of such alloys or mixtures of metal and polymer fibers. Depending on the individual material selected, the strand diameter, number of strands, and pitch may be altered to achieve the desired properties for sealing portion  322 . Thus, sealing portion  322  may alternate between the extended configuration and the relaxed configuration due to the changing shape of legs  320  or alternatively it may itself alternate between the two configurations due to its own shape-memory material properties. 
       FIG. 3B  illustrates the relaxed configuration of heart valve  300 . As noted above, legs  320  may have an extended configuration and a relaxed configuration. To effectuate this change in configuration, legs  320  may be curled and subjected to a heat setting process. This process may be accomplished in a series of steps. For example, legs  320  may be formed with a first curl and heat set, and then formed with a second curl and further heat set. The relaxed configuration of legs  320  may therefore include multiple curls due to the curling and heat setting process described above. Legs  320  may be straightened to the extended configuration (shown in  FIG. 3A  and described above) for cooperation with a delivery system as will be described below with reference to  FIGS. 4A-E , and may return to the curled, relaxed configuration after removal from the delivery system. As shown in  FIG. 3B , when heart valve  300  is permitted to return to its relaxed configuration, legs  320  may curl up toward distal end  304  and pull sealing portion  322  with them, rolling sealing portion  322  up in the process to form sealing ring  350  at proximal end  302  of heart valve  300 . Sealing ring  350  may have a radius larger than that of valve assembly  308 , the larger radius of sealing ring  350  being capable of filling any gaps between heart valve  300  and the native valve annulus (not shown). The length of sealing ring  350  may depend on the number of curls of legs  320 . For example, sealing ring  350  may have a length that is approximately one-half of the length of legs  320 . As shown in  FIG. 3B , sealing ring  350  is formed below proximal end  302  and may be suitable for a sub-leaflet application as will be described in greater detail below with reference to  FIGS. 8A-8C . Sealing ring  350  may be readily deformable to conform to the shape of the native valve annulus, portions of sealing ring  350  being configured to compress when pressed against the walls of the native valve annulus and other portions of sealing ring  350  being configured to radially expand in gaps, thereby filling the gaps between heart valve  300  and the native valve annulus. 
     A method of delivering and implanting heart valve  300  will now be described with reference to  FIGS. 4A-E . A delivery system  400  may be used to deliver and deploy heart valve  300  in native valve annulus  250 A, and may generally include sheath  410 , core  420 , atraumatic tip  430  and hub  440 . Sheath  410  may be slidable relative to core  420 . Heart valve  300 , including stent  306 , valve assembly  308 , legs  320  and sealing portion  322 , may be disposed within sheath  410  about core  420  ( FIG. 4A ). Hub  440  may be coupled to core  420  and configured to mate with retaining elements  360  of heart valve  300 . Elongated legs  320  of heart valve  300  may be disposed in the extended configuration of  FIG. 3A , substantially parallel to sheath  410 , during delivery. Specifically, though legs  320  are configured to return to their relaxed configuration by curling outwardly, they may be kept substantially linear by being constrained within sheath  410 . By doing so, sealing portion  322  and legs  320  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 the patient&#39;s body and may also reduce the operation time. In the example shown in  FIGS. 4A-E , 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 echocaradiography 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 A), atraumatic tip  430  may be advanced slightly in the direction of arrow  51  toward the left ventricle by pushing core  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. As seen in  FIG. 4B , with sheath  410  slightly retracted, legs  320  begin to emerge from the sheath and return to their relaxed configuration by curling outwardly with sealing portion  322 , which is attached thereto, curling along with legs  320 . As sheath  410  is further retracted in the direction of arrow S 2 , more of each leg  320  is exposed and curls upon itself ( FIG. 4C ) until legs  320  fully return to their relaxed configuration ( FIG. 4D ). Sealing portion  322  attached to curled legs  320  forms sealing ring  350 . At this juncture, stent  306  is still disposed within sheath  410  and heart valve  300  has not yet begun to expand. Sheath  410  may be retracted further until heart valve  300  is free to self-expand within native valve annulus  250 A. 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 core  420  in the direction of arrow  51  to recapture heart valve  300  within sheath  410 . During recapture, sheath  410  may push against legs  320  to straighten them to the extended configuration shown in  FIG. 4A . This process may be repeated until heart valve  300  is properly positioned and deployed within native valve annulus  250 A. After sheath  410  has been fully retracted to expose heart valve  300 , sealing ring  350 , being disposed at proximal end  302  of heart valve  300 , may occlude gaps  200  between heart valve  300  and native valve annulus  250 A, thereby reducing or eliminating the amount of blood that passes around heart valve  300  through gaps  200  ( FIG. 4E ). Retaining elements  360  of heart valve  300  may be decoupled from hub  440  and delivery system  400 , including atraumatic tip  430 , may then be retracted through heart valve  300  in the direction of arrow S 2  and removed from the patient. 
       FIGS. 5A and 5B  are enlarged schematic partial side views showing heart valve  500  having legs in an extended configuration and in a relaxed configuration, respectively. Heart valve  500  extends between proximal end  502  and a distal end (not shown) and generally includes stent  506  and a valve assembly (not shown for the sake of clarity) having a cuff and leaflets similar to those described above with reference to  FIGS. 3A and 3B . Heart valve  500  further includes elongated legs  520  and sealing portion  522  attached to elongated legs  520  at eyelets  524  via sutures. These elements may be formed of any of the materials described above with reference to  FIGS. 3A and 3B . Legs  520  may be attached to or formed integrally with stent  506  at attachment ends  525  to couple legs  520  to stent  506 . As seen in  FIG. 5A , legs  520  may be attached to stent  506  at eyelets  524  near the proximal end  502  of heart valve  500  at the top of the second row of cells  542  of stent  506 , and in their extended configuration, may extend substantially linearly toward the distal end of the valve, terminating at free ends  526 . 
       FIG. 5B  illustrates the relaxed configuration of legs  520 . Legs  520  may be biased so that, when they return to their relaxed configuration, they curl down toward the proximal end  502  of the valve. Due to the coupling of sealing portion  522  to legs  520 , the curling of legs  520  results in a similar curling of sealing portion  522 , causing it to roll down in the process to form upper sealing ring  550  within annulus portion  540  of heart valve  500 . Upper sealing ring  550  may have a radius larger than that of the valve assembly, and therefore may be capable of filling any gaps between heart valve  500  and the native valve annulus (not shown). As shown in  FIG. 5B , sealing ring  550  is spaced from proximal end  502  and may be useful for intra-leaflet applications that are described below with reference to  FIG. 8A-C . In at least some examples, sealing ring  550  may be positioned within annulus portion  540  so as to be directly radially outward of the leaflets of heart valve  500  (not shown). Heart valve  500  may be disposed within a delivery system, delivered to the native valve annulus and deployed therein using a delivery system that is the same as or similar to that described in  FIGS. 4A-E . 
     Alternatively, legs  520  may be attached to stent  506  at eyelets  524  and, in the extended condition, may extend substantially linearly toward the proximal end  502  of heart valve  500  so that free ends  526  are closer to proximal end  502  than attachment ends  525 . In this alternative example, legs  520  may curl upward toward the distal end to form sealing ring  550 . Thus, the location of attachment ends  525  and the direction of the curling of legs  520  may be used to vary the position of sealing ring  550  with respect to heart valve  500 . 
       FIG. 5C  is an enlarged schematic partial side view showing an alternate extended configuration of the elongated legs. Heart valve  500 C extends between a proximal end  502 C and a distal end (not shown) and generally includes stent  506 C and a valve assembly (not shown for the sake of clarity) having a cuff and leaflets similar to those described above with reference to  FIGS. 3A and 3B . Heart valve  500 C further includes elongated legs  520 C and sealing portion  522 C attached to elongated legs  520 C. These elements may be formed of any of the materials described above with reference to  FIGS. 3A and 3B . Legs  520 C may be attached to or formed integrally with stent  506 C at attachment ends  525 C to couple legs  520 C to stent  506 C. Specifically, legs  520 C may be coupled to one or more struts  541 C forming cells  542 C or a portion of a cell. Though the previous embodiments have shown attachment ends  525 C as being attached to or originating from an intersection of two struts  541 C, attachment ends  525 C may be coupled to or formed integrally with only one strut  541 C. In this example, four struts  541 C forming the four sides of cell  542 C intersect at four corners of the cell, and attachment ends  525 C are coupled to a single strut  541 C approximately halfway between two corners of the cell. It will be understood, however, that elongated legs  520 C may be coupled to any portion of stent  506 C and/or to any location along struts  541 C and/or to any number of struts. Elongated legs  520 C may curl from a relaxed configuration in the same manners described above in connection with  FIGS. 5A and 5B  to form a sealing ring. 
       FIGS. 6A and 6B  are schematic side views of another embodiment, showing heart valve  600  having legs in an extended configuration and a relaxed configuration, respectively. Heart valve  600  extends between proximal end  602  and a distal end (not shown) and generally includes stent  606  and a valve assembly (not shown for the sake of clarity) having a cuff and leaflets similar to those described above with reference to  FIGS. 3A and 3B . Heart valve  600  further includes first elongated legs  620  and first sealing portion  622 , which may be attached to first elongated legs  620  at eyelets  624  via sutures. In a configuration similar to that described above with reference to  FIGS. 5A and 5B , first legs  620  may be attached to or formed integrally with stent  606  at attachment ends  625  near the proximal end  602  of heart valve  600 , and may extend substantially linearly toward the distal end of the valve, terminating at free ends  626 . Heart valve  600  further includes second elongated legs  680  attached to stent  606  at second attachment ends  685 , which are located at proximal end  602  of the valve, and, in the extended condition, legs  680  extend substantially linearly away from the distal end of the valve to terminate at second free ends  686  beyond proximal end  602  of heart valve  600 . A second sealing portion  682 , similar to the sealing portion described above in connection with  FIGS. 3A and 3B , may be attached to legs  680 . 
       FIG. 6B  illustrates the relaxed configuration of the legs of heart valve  600 . First legs  620  may be biased so that, when they return to their relaxed configuration, they curl down toward the proximal end  602  of the valve, as shown in  FIG. 6B . Due to the coupling of first sealing portion  622  to first legs  620 , the curling of first legs  620  results in a similar curling of first sealing portion  622 , causing it to roll down in the process to form upper sealing ring  650  within annulus portion  640  of heart valve  600  (e.g. forming a ring at an intra-leaflet position). Likewise, when secondary legs  680  return to their relaxed configuration, they may curl up toward the distal end of heart valve  600 , pulling second sealing portion  682  with them to form lower sealing ring  690  (e.g., forming a ring at a sub-leaflet position). When heart valve  600  is implanted using a delivery system similar to that shown in  FIGS. 4A-E , lower sealing ring  690  may take shape first as the outer sheath of the delivery system is retracted, followed by upper sealing ring  650 . Additional methods may be used to actuate the formation of either of the sealing rings regardless of the delivery approach. 
       FIGS. 7A-D  illustrate several additional variants of a heart valve having sealing portions according to the present disclosure. In  FIG. 7A , heart valve  700 A extends between proximal end  702  and a distal end (not shown) and generally includes stent  706  and a valve assembly (not shown) having a cuff and leaflets. Heart valve  700 A further includes elongated legs  720  coupled to stent  706  near proximal end  702 , which legs  720 , in their extended configuration, may extend substantially linearly away from the distal end of the valve. A sealing portion  722  is coupled to legs  720 . In order to provide a more secure attachment of sealing portion  722  to legs  720 , each leg  720  may include multiple eyelets  724 A-D along its length, and sealing portion  722  may be coupled to legs  720  at each of the eyelets. Eyelets  724 A-D may be uniformly distributed along the length of each leg  720 , as seen in  FIG. 7A , resulting in better coupling of sealing portion  722  to legs  720  and a more uniform curling of sealing portion  722  in the formation of a sealing ring. 
     Although the elongated legs in all of the embodiments described above have a substantially linear configuration in the extended configuration, they may be formed with other configurations.  FIG. 7B  illustrates a heart valve  700 B having nonlinear elongated legs. Heart valve  700 B extends between proximal end  702  and a distal end (not shown) and includes stent  706  and a valve assembly having a cuff and leaflets as described above. Heart valve  700 B includes elongated legs  720 B that are curved or wavy in their extended configuration in contrast to the substantially linear legs of the previous embodiments. Wavy legs  720 B may couple to stent  706  at proximal end  702  of heart valve  700 B and extend away from the distal end thereof. Legs  720 B may be formed to curl in their relaxed configuration in a manner similar to the elongated legs described above. A sealing portion  722 B may be attached to legs  720 B so as to form a sealing ring in the relaxed configuration of the legs. 
     In  FIGS. 7C and 7D , another example is shown in which heart valve  700 C extends between a proximal end  702  and a distal end (not shown) and includes stent  706  and pairs of elongated legs  720 C,  720 D. Heart valve  700 C further includes a valve assembly having a cuff and leaflets and a sealing portion (none of which are shown for the sake of clarity). In the extended configuration of the legs, shown in  FIG. 7C , legs  720 C,  720 D are formed in pairs that originate at a common attachment end  725  at the apex of a cell at proximal end  702  and extend away from the distal end of heart valve  700 C in substantially linear configurations to terminate in independent free ends  726 . As shown in their relaxed configuration in  FIG. 7D , legs  720 C,  720 D may curl upward toward the distal end of heart valve  700 C along with the attached sealing portion, as previously described, to form a sealing ring. This configuration may provide additional structure for forming and supporting the sealing ring. 
     As will be appreciated from the embodiments described above, the elongated legs may be attached at the proximal end of a heart valve or anywhere in the annulus portion of the valve. Additionally, in their extended configuration, the elongated legs may extend either toward or away from the distal end of the heart valve, and in their relaxed configuration, may curl in either direction. By varying the points of attachment and the orientation of the elongated legs, sealing rings may be formed at different locations along the valve. In some applications, damaged or calcified native valve leaflets may not be resected prior to implantation of a prosthetic heart valve. The location of the sealing rings may be modified to accommodate the unresected native valve leaflets. 
       FIGS. 8A-8C  illustrate heart valves  800 A-C disposed within a native valve annulus adjacent unresected native leaflets  803 . In  FIG. 8A , heart valve  800 A includes sealing ring  850 A at a proximal end thereof and configured to be disposed below native leaflets  803  (i.e., in a sub-leaflet location). Sealing ring  850 A may be at least partially disposed below native leaflets  803  and may contact the native leaflets to provide a seal between heart valve  800 A and native leaflets  803 .  FIG. 8B  illustrates heart valve  800 B having a sealing ring  850 B spaced distally of the proximal end of the valve and configured to be disposed within native leaflets  803  to provide a seal between heart valve  800 B and native leaflets  803  (i.e., in an intra-leaflet location).  FIG. 8C  illustrates a heart valve  800 C having a sealing ring  850 C spaced further distally of the proximal end of the valve and configured to be disposed above the free edges of native leaflets  803  to provide a seal between heart valve  800 C and native leaflets  803  (i.e., in a supra-leaflet location). Thus, sealing rings  850 A-C may be disposed at various locations relative to native leaflets  803 . It will be appreciated that combinations of any of these sealing rings may be possible. For example, a heart valve may include two sealing rings, a first sealing ring  850 A configured to be disposed below native leaflets  803 , and a second sealing ring  850 C configured to be disposed above the free edges of native leaflets  803 . When sealing ring  850 A is disposed below the native valve leaflets  803  ( FIG. 8A ), it may prevent heart valve  800 A from migrating into the aorta. When sealing ring  850 C is disposed above the native valve leaflets ( FIG. 8C ), it may prevent heart valve  800 C from migrating into the left ventricle. Thus, with this and similar configurations, sealing rings may be used to anchor a heart valve in the native valve annulus, thereby preventing the heart valve from migrating from its intended position. 
       FIGS. 9A and 9B  illustrate a heart valve  900  pursuant to another embodiment having sealing features to mitigate perivalvular leakage. Heart valve  900  of  FIG. 9A  extends between a proximal end  902  and a distal end (not shown) and includes a stent  906 , a valve assembly (not shown) including a cuff and leaflets, and elongated legs  920 . Legs  920  may be attached to stent  906  at attachment ends  925  near the proximal end  902  of heart valve  900  and, in the extended configuration of the legs shown in  FIG. 9A , may extend substantially linearly away from the distal end of the valve, terminating in free ends  926 . A sealing portion  922  may be attached to legs  920  in the same manner as the sealing portions described above. When legs  920  of heart valve  900  return to their relaxed configuration, instead of curling over themselves as shown in the previous embodiments, they may axially collapse to form an undulating shape, as seen in  FIG. 9B . As a result of this collapse, portions of legs  920  may billow radially out from the profile of the annulus portion  940  of heart valve  900  by an additional distance di to form distended portion  928 . As shown in  FIG. 9B , multiple distended portions  928  may be formed. Each distended portion  928  may extend circumferentially to form a sealing ring  929  or a portion of a sealing ring. 
       FIG. 9C  illustrates a first example of an elongated leg  920 C that is capable of collapsing axially to form distended portion  928 . In this first example, leg  920 C may be substantially linear and have a first length L 1  in an extended configuration. Leg  920 C may be heat set or otherwise configured to axially collapse to an undulating shape  920 C′ having a shorter length L 2  in the relaxed configuration. When leg  920 C assumes undulating shape  920 C′ it will not only shorten, but will also form convex regions  930 C along its length that collectively define distended portions  928  of sealing ring  929 .  FIG. 9D  illustrates another example in which an elongated leg  920 D having a length L 1  in an extended configuration shortens to an N-shape  920 D′ having a length L 3  in the relaxed configuration. Legs  920 D form convex regions  930 D along their lengths that collectively define distended portions  928  of heart valve  900 . It will be understood that  FIGS. 9C and 9D  illustrate only two possible examples for forming distended portions  928  and that various techniques and shapes may be used to alternate between a substantially linear elongated leg in the extended configuration and a shortened shape having convex regions in the relaxed configuration. 
       FIGS. 10A and 10B  illustrate a heart valve  1000  in accordance with another embodiment. Heart valve  1000  extends between proximal end  1002  and distal end  1004 , and may generally include stent  1006  and valve assembly  1008  having a plurality of leaflets  1010  and cuff  1012 . Additionally, heart valve  1000  may include a number of elongated legs  1020  and a sealing portion  1022  coupled to the elongated legs via eyelets  1024  to mitigate perivalvular leakage. Legs  1020  may be formed of a shape memory material such as those described above with reference to  FIGS. 3A and 3B  and may have an extended configuration and a relaxed configuration. Attachment ends  1025  of elongated legs  1020  may be affixed to stent  1006  near proximal end  1002  of heart valve  1000 , and legs  1020  may extend away from the distal end  1004  of stent  1006  and terminate at eyelets  1024 . In this example, sealing portion  1022  may be in the form of a generally toroidal-shaped sealing ring  1050 , regardless of whether legs  1020  are in their extended or relaxed configuration. As used herein, the terms “toroid” and “toroidal” are not limited to a circle revolved about an axis external to the circle, which is parallel to the plane of the figure and does not intersect the figure, but also include the revolving of other plane geometrical figures such as, for example, an oval, a triangle, a square and the like. Sealing ring  1050  may be formed of a braided fabric comprising a plurality of braided strands, although it will be understood that any of the other materials described above with reference to  FIGS. 3A and 3B  may be used as well. In the extended configuration of legs  1020 , sealing ring  1050  may be spaced away from proximal end  1002  by the length of the legs. 
     As noted above, legs  1020  may have an extended configuration and a relaxed configuration.  FIG. 10B  illustrates the relaxed configuration. When legs  1020  of heart valve  1000  are permitted to return to their relaxed configuration, they may curl up toward distal end  1004  and pull sealing ring  1050  over proximal end  1002  of heart valve  1000  so that sealing ring  1050  is at least partially disposed over valve assembly  1008  and/or cuff  1012 . Sealing ring  1050  may have a radius larger than that of valve assembly  1008 , the larger radius of sealing ring  1050  being capable of filling any gaps between heart valve  1000  and the native valve annulus (not shown). Thus, in this embodiment, sealing ring  1050  is already formed in both the extended and relaxed configurations of legs  1020 , but is brought into place for sealing when legs  1020  curl upward in the relaxed configuration. 
       FIGS. 10C-E  illustrate the extended configuration of legs  1020  and two examples of the relaxed configuration of legs  1020 . As seen in  FIG. 10C , in the extended configuration, legs  1020  are coupled to stent  1006  of heart valve  1000  near proximal end  1002  and are substantially linear between eyelets  1024  and attachment ends  1025 . In one example shown in  FIG. 10D , elongated legs  1020  are configured to curl toward the distal end (not shown) of heart valve  1000 , each elongated leg  1020  being bent straight back so that substantially the entire leg lies in a single plane Z. Alternatively, as shown in  FIG. 10E , each elongated leg  1020  may also be bent with respect to the plane of attachment Z such that it ends in a second plane Z′ which forms an angle α with respect to plane of attachment Z. The angle between the two planes may be between about 1 degree and about 60 degrees. By bending leg  1020  in such a manner, leg  1020  may be more conformable, aiding in the transition between the extended and the relaxed configurations. 
       FIG. 10F  is an enlarged partial perspective view showing the bending of the elongated legs of heart valve  1000 F. Heart valve  1000 F may extend between a proximal end  1002 F and a distal end (not shown) and includes stent  1006 F and elongated legs  1020 F, each having an eyelet  1024 F. Elongated legs  1020 F may be coupled to stent  1006 F at attachment ends  1025 F. It may be difficult to bend elongated legs  1020 F due to the thickness and width of the legs. Elongated legs  1020 F therefore may be twisted along their longitudinal axes in order to more easily bend the legs. In addition to twisting, elongated legs  1020 F may be bent as described above with reference to  FIG. 10E . The twisting and bending of elongated legs  1020  may weaken the legs so that a desired stiffness is achieved for proper extension and relaxation of the legs. 
       FIGS. 11A-F  are highly schematic partial side views of heart valves, showing variations in how the elongated legs are bent in the relaxed configuration. In a first example, heart valve  1100 A includes stent  1106  and elongated legs  1120 A coupled thereto ( FIG. 11A ). Elongated legs  1120 A of heart valve  1100 A bend in the shape of a semicircle, and sealing portion  1122 A, which is attached to elongated legs  1120 A, curls with the elongated legs to form a sealing ring  1150 A in the shape of a semicircle revolved about an axis external to the semicircle, which is parallel to the plane of the figure and does not intersect the figure. In a second example, heart valve  1100 B includes stent  1106  and elongated legs  1120 B coupled thereto ( FIG. 11B ). Elongated legs  1120 B of heart valve  1100 B bend to form an almost complete circle, and sealing portion  1122 B, which is attached to elongated legs  1120 B, curls with the elongated legs to form a sealing ring  1150 B in the shape of an ellipsoid revolved in the manner described above.  FIG. 11C  illustrates another example in which heart valve  1100 C includes stent  1106  and elongated legs  1120 C, which bend in multiple curls to form sealing portion  1122 C into a spiral-shaped sealing ring  1150 C in the shape of a revolved curl. It will be understood from these examples that the elongated legs may include any number of curls or portions of curls. 
     Moreover, the elongated legs may take a number of shapes other than curls. For example, in  FIG. 11D , heart valve  1100 D includes elongated legs  1120 D coupled to stent  1106 . Elongated legs  1120 D are configured to bend in the shape of a triangle as shown, sealing portion  1122 D bending with them to form sealing ring  1150 D in the shape of a revolved triangle.  FIG. 11E  illustrates another example of heart valve  1100 E having elongated legs  1120 E coupled to stent  1106 . Elongated legs  1120 E curl in a substantially elliptical shape having a major axis m 1  disposed at an upward angle β 1  with respect to an axis x extending in the radial direction of heart valve  1100 E. In this example, major axis m 1  forms an upward angle β 1  of about 40 degrees with respect to axis x, causing sealing portion  1122 E to form sealing ring  1150 E in the shape of a distally-pointing revolved ellipsoid. In an alternative configuration, elongated legs  1120 F may be coupled to stent  1106  of heart valve  1100 F as shown in  FIG. 11F . Elongated legs  1120 F curl in a substantially elliptical shape as in  FIG. 11E , the ellipse having a major axis m 2  disposed at a downward angle β 2  with respect to an axis x extending in the radial direction of heart valve  1100 F. In this example, major axis m 2  forms a downward angle β 2  of about 40 degrees with respect to axis x, causing sealing portion  1122 F to form sealing ring  1150 F in the shape of a proximally-pointing revolved ellipsoid. It will be understood that various modifications may be made to any of these basic shapes of the elongated legs. For example, the foregoing shapes may be inverted when the elongated legs extend toward the distal end of a heart valve (e.g., a triangle that is inverted from that shown in  FIG. 11D ). Thus, the elongated legs may take any desired shape to form sealing rings of various profiles and radiuses to adequately seal the region between the heart valve and the native valve annulus. 
       FIG. 12  is a highly schematic cross-sectional view showing heart valve  1200  having stent  1202 , valve assembly  1204  including a cuff (not shown) and leaflets  1208 , and elongated legs  1250  supporting a sealing portion  1260 . Legs  1250  have curled up to form sealing ring  1270  and heart valve  1200  has been disposed within native valve annulus  1280 . As seen in  FIG. 12 , sealing ring  1270  has radially expanded to fill gaps  200  shown in  FIG. 2 , and may be capable of promoting tissue growth between heart valve  1200  and native valve annulus  1280 . For example, sealing portion  1260  may be innately capable of promoting tissue growth and/or may be treated with a biological or chemical agent to promote tissue growth, further enabling sealing ring  1270 , when expanded, to seal the heart valve within the native valve annulus. Alternatively, the expanded sealing ring  1270  may be sufficiently dense to adequately seal around heart valve  1200  without the need for major tissue growth. Sealing portion  1260  may also be double-layered and in embodiments having a mesh sealing portion, it may include tighter braiding to more completely occlude the space between heart valve  1200  and native valve annulus  1280 . When sealing ring  1270  is functioning properly, heart valve  1200  will be adequately sealed within native valve annulus  1280  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  1280  is limited or reduced. 
       FIGS. 13A-C  illustrate a heart valve  1300  in accordance with another embodiment. Heart valve  1300  extends between proximal end  1302  and distal end  1304 , and may generally include stent  1306  formed of a plurality of struts  1307 , and valve assembly  1308  having a plurality of leaflets  1310  and a cuff  1312 . Cuff  1312  may include surplus portion  1322  that extends past the most-proximal struts  1307  of stent  1306 . In some examples, surplus portion  1322  may longitudinally extend between about 10 mm and about 20 mm proximally from the most-proximal struts  1307  of stent  1306 . Surplus portion  1322  may be formed of the same material as the rest of cuff  1312  and may be formed integrally therewith from a single piece of material. Alternatively, surplus portion  1322  may be formed of a different material than cuff  1312  that is sutured, glued or otherwise affixed to the proximal end of cuff  1312 . 
       FIG. 13B  illustrates heart valve  1300  after surplus portion  1322  has been rolled to form sealing ring  1350 A. After assembly of cuff  1312  to stent  1306 , surplus portion  1322  may be rolled in the direction of distal end  1304  until it is aligned with the proximal-most struts  1307  to form sealing ring  1350 A. In this example, surplus portion  1322  is rolled into a generally toroidal-shaped sealing ring  1350 A near proximal end  1302  of heart valve  1300  (e.g., at a subannular position). Sealing ring  1350 A may be formed of one complete revolution of surplus portion  1322 , or of a series of revolutions (e.g., two, three or more revolutions of surplus portion  1322 ). 
     Sealing ring  1350 A may maintain its shape through a variety of methods, such as by being tied to select struts  1307  of stent  1306 . In one example, as seen in the enlarged schematic view of  FIG. 13B , end struts  1360   a  and  1360   b  of stent  1306  meet to form a horseshoe-shaped end  1370  having a partial slot  1372  therebetween. A number of locking stitches LS 1  may be tied around horseshoe-shaped ends  1370 , and specifically around each slot  1372  and sealing ring  1350 A to keep the sealing ring from unfurling. Locking stitches LS 1  may be formed of a suture, string or any other suitable biocompatible thread. It will be understood that, though three locking stitches are shown around the circumference of the heart valve to couple sealing ring  1350 A to stent  1306 , any number of locking stitches may be used. Other techniques for maintaining the shape of sealing ring  1350 A may also be used including adhesive, glue or the like. Sealing ring  1350 A may have a radius larger than that of valve assembly  1308 , the larger radius of sealing ring  1350 A being capable of filling any gaps between heart valve  1300  and the native valve annulus (not shown). 
       FIG. 13C  illustrates prosthetic heart valve  1300  in native valve annulus  1380  after formation of sealing ring  1350 A as seen from proximal end  1302  (e.g., as seen from the annulus end toward the aortic end of the heart valve). Sealing ring  1350 A has been secured to stent  1306  via a series of locking stitches LS 1 . The outer diameter of stent  1306  at the proximal end is indicated with a dashed-line. Sealing ring  1350 A extends radially outward from the outer diameter of stent  1306  at the proximal end of heart valve  1300  by a radial distance r 1 . In at least some examples, radial distance r 1  may be between about 1 mm and about 2.5 mm. 
       FIG. 13D  illustrates heart valve  1300 D, which is a variant of heart valve  1300  of  FIGS. 13A-C . Heart valve  1300 D extends between proximal end  1302  and distal end  1304 , and may generally include stent  1306  formed of struts  1307 , and valve assembly  1308  having a plurality of leaflets  1310  and a cuff  1312 . A surplus portion  1322 D of cuff  1312  has been rolled to form sealing ring  1350 D in a manner similar to that described above, except that sealing ring  1350 D has been rolled to a position closer to distal end  1304  and leaflets  1310  than sealing ring  1350 A (e.g., at an intra-annular position). After rolling surplus portion  1322 D and forming sealing ring  1350 D at the appropriate position, locking stitches LS 2  may be coupled to sealing ring  1350 D and select struts  1307  of stent  1306  to secure the sealing ring in place. 
       FIGS. 14A-B  illustrates a heart valve  1400  in accordance with another embodiment. Heart valve  1400  extends between proximal end  1402  and distal end  1404 , and may generally include stent  1406  formed of struts  1407 , and valve assembly  1408  having a plurality of leaflets  1410  and a cuff  1412 . Cuff  1412  may include a surplus portion  1422  that extends proximally past the most-proximal struts  1407  of stent  1406 . In some examples, surplus portion  1422  may extend between about 5 mm and about 20 mm from the most-proximal struts  1407  of stent  1406 . Surplus portion  1422  may be formed of the same material as the rest of cuff  1412  and may be integrally formed therewith of a single piece of material. 
     In this example, surplus portion  1422  is formed of a thickened material that is configured to circumferentially buckle in an accordion-like fashion at certain locations to form undulating sealing ring  1450  when heart valve  1400  is released from a delivery device. Undulating sealing ring  1450  allows for more surface area to fill in and around voids. Furthermore, undulating sealing ring  1450  is capable of being folded in an organized manner for loading and delivery. Terminal sutures TS 1  may attach portions of surplus portion  1422  to selected struts  1407  to aid in the formation of undulating ring  1450 . In some examples, sutures TS 1  are the same sutured that are used to attach cuff  1412  to the struts  1407  so that no extra steps or bulk is added. Undulating ring  1450  is annularly disposed around proximal end  1402  of heart valve  1400 . Undulating ring  1450  alternates between a series of peaks  1460  and valleys  1470  and radially expands to a diameter greater than the diameter of the proximal end of stent  1406 . Undulating ring  1450  may include thin porcine pericardial tissue about between about 0.005 inches and about 0.007 inches in thickness or UHMWPE or PET fabric between about 0.003 inches and about 0.005 inches in thickness. 
       FIG. 14B  illustrates prosthetic heart valve  1400  in native valve annulus  1480  after formation of undulating sealing ring  1450 , as seen from proximal end  1402  (e.g., as seen from the annulus end toward the aortic end of the heart valve). Surplus portion  1422  has buckled to form undulating sealing ring  1450 . The outer diameter of stent  1406  at the proximal end is indicated with a dashed-line. Undulating ring  1450  extends radially outward from the outer diameter of stent  1406  at the proximal end of heart valve  1400  by a radial distance r 2 . In at least some examples, radial distance r 2  may be between about 1.0 mm and about 10.0 mm. Radial distance r 2  may also be between about 1.0 mm and about 2.5 mm. 
     In another variation ( FIGS. 15A and 15B ), heart valve  1500  extends between proximal end  1502  and distal end  1504 , and may generally include stent  1506  formed of struts  1507 , and valve assembly  1508  having a plurality of leaflets  1510  and a cuff  1512 . Cuff  1512  may include an extended surplus portion  1522  that extends proximally past the most-proximal struts  1507  of stent  1506 . In some examples, surplus portion  1522  may extend between about 5.0 mm and about 10.0 mm from the most-proximal struts  1507  of stent  1506 . Surplus portion  1522  may be formed of the same material as the rest of cuff  1512  and may be integrally formed therewith of a single piece of material. 
     In this example, surplus portion  1522  deploys into a flat sealing halo  1550 , which flares radially outward to a diameter greater than the diameter of the proximal end of stent  1506 .  FIG. 15B  illustrates prosthetic heart valve  1500  in native value annulus  1580  after formation of sealing halo  1550 , as seen from proximal end  1502  (e.g., as seen from the annulus end toward the aortic end of the heart valve. The outer diameter of stent  1506  at the proximal end is indicated with a dashed-line. Sealing halo  1550  extends radially outward from the outer diameter of stent  1506  at the proximal end of heart valve  1500  by a radial distance r 3 . In at least some examples, radial distance r 3  is between about 2 mm and about 10 mm. 
     In another variation ( FIGS. 16A and 16B ), heart valve  1600  extends between proximal end  1602  and distal end  1604 , and may generally include stent  1606  formed of struts  1607 , and valve assembly  1608  having a plurality of leaflets  1610  and a cuff  1612 . Cuff  1612  may include an extended surplus portion  1622  that extends proximally past the most-proximal struts  1607  of stent  1606 . In some examples, surplus portion  1622  may extend between about 2 mm and about 10.0 mm from the most-proximal struts  1607  of stent  1606 . Surplus portion  1622  may be formed of the same material as the rest of cuff  1612  and may be integrally formed therewith of a single piece of material. 
     In this example, surplus portion  1622  forms sealing body  1650  having a number of independently moveable limbs  1660 , which flare out radially.  FIG. 16B  illustrates prosthetic heart valve  1600  in native valve annulus  1680 , as seen from proximal end  1602  (e.g., as seen from the annulus end toward the aortic end of the heart valve). Surplus portion  1622  has flared radially outward to form sealing body  1650  and limbs  1660  have also spread apart. The outer diameter of stent  1606  at the proximal end is indicated with a dashed-line. Sealing body  1650  extends radially outward from the outer diameter of stent  1606  at the proximal end of heart valve  1600  by a minimum radial distance of at least r 4 . In at least some examples, radial distance r 4  is between about 2.0 mm and about 10.0 mm. 
     While the inventions 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. The sealing rings described may also have a circular, D-shaped or elliptical cross-section. Additionally, though the sealing structures 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. 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a collapsible and expandable stent having a proximal end and a distal end and a valve assembly disposed within the stent, the valve assembly including a plurality of leaflets. The heart valve further includes a cuff annularly disposed about the stent and having a surplus portion capable of forming a sealing structure at the proximal end of the stent, the sealing structure having a deployed condition with a diameter in the deployed condition greater than a diameter of the proximal end of the stent. 
     In some examples, the surplus portion may include at least one of a metallic mesh, a shape-memory material, a polymeric material or a tissue material. The sealing structure may include a toroid formed by rolling the surplus portion upon itself. The stent may include horseshoe-shaped ends and the toroid is coupled to at least some of the horseshoe-shaped ends via a plurality of locking sutures. The plurality of locking sutures may include three locking sutures. The stent may include an annulus section and the toroid may be disposed proximal to the annulus section of the stent. The stent may include an annulus section and the toroid may be disposed about the annulus section of the stent. The sealing structure may include an undulating sealing ring having a plurality of alternating peaks and valleys. The stent may include a plurality of struts and the surplus portion is coupled to selected ones of the struts via terminal sutures to enable circumferential buckling of the surplus portion into the undulating sealing ring. The sealing structure may include a flat sealing halo. The sealing structure may include a body having a plurality of independently moveable limbs. The diameter of the sealing structure in the deployed condition may have a diameter greater than the diameter of the proximal end of the stent by between about 2.0 mm and about 10.0 mm. 
     In some embodiments, a prosthetic heart valve for replacing a native valve includes a collapsible and expandable stent having a proximal end and a distal end, a valve assembly disposed within the stent, the valve assembly including a plurality of leaflets and a cuff annularly disposed about the stent and having an attached end coupled to the stent and a free end extending past the proximal end of the strut and capable of forming a sealing structure for sealing gaps between the prosthetic heart valve and a native valve annulus. 
     In some examples, a free end is configured to roll upon itself to create a toroid. The free end may be configured to flare out radially to form a flattened halo adjacent the proximal end of the stent. The free end may include a body having a plurality of independently moveable limbs. 
     In some embodiments, a method of making a prosthetic heart valve for replacing a native valve includes providing a collapsible and expandable stent having a proximal end and a distal end, coupling a valve assembly to the stent, the valve assembly including a plurality of leaflets, coupling a cuff to the stent so that a surplus portion of the cuff extends beyond the proximal end of the strut and converting the surplus portion of the cuff into a sealing structure at the proximal end of the stent, the sealing structure having a diameter greater than a diameter of the proximal end of the stent. 
     In some examples, a converting step includes rolling the surplus portion of the cuff into a toroid shape. The method may further include securing the surplus portion to the stent via at least one suture to maintain the toroid shape. 
     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.