Patent Publication Number: US-11660184-B2

Title: Cuff stitching reinforcement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 14/548,723, filed Nov. 20, 2014 which claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/909,496, filed Nov. 27, 2013, the disclosure of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to heart valve replacement and, in particular, to collapsible prosthetic heart valves. More particularly, the present invention relates to collapsible prosthetic heart valves having improved cuff attachments. 
     Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery. 
     Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size. 
     When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient&#39;s heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn. 
     SUMMARY OF THE INVENTION 
     In some embodiments, a prosthetic heart valve includes a collapsible and expandable stent having a proximal end, a distal end, an annulus section adjacent the proximal end and an aortic section adjacent the distal end, the stent including a plurality of struts. A cuff may be coupled to the stent so that a flat, bottom edge of the cuff lies adjacent the proximal end of the stent. A pattern of stitches may be circumferentially disposed around the flat bottom edge of the cuff, the pattern of stitches alternating between stitches sewn to the cuff only and stitches sewn to both the cuff and the stent. 
     In some embodiments, a prosthetic heart valve may include a collapsible and expandable stent having a proximal end, a distal end, an annulus section adjacent the proximal end and an aortic section adjacent the distal end, the stent including a plurality of struts and a plurality of commis sure features. A cuff may be coupled to the stent so that a top edge of the cuff lies adjacent the plurality of commissure features and a plurality of tethers incorporated along the top edge of the cuff and coupled to the cuff only. 
     In some embodiments, a method of making a prosthetic heart valve may include (i) providing a collapsible and expandable stent having a proximal end, a distal end, an annulus section adjacent the proximal end and an aortic section adjacent the distal end, the stent including a plurality of struts, (ii) coupling a cuff to the stent so that a flat bottom edge of the cuff lies adjacent the proximal end of the stent, and (iii) sewing a pattern of stitches circumferentially around the flat bottom edge of the cuff, the pattern of stitches alternating between stitches sewn to the cuff only and stitches sewn to both the cuff and the stent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the presently disclosed heart valves are disclosed herein with reference to the drawings, wherein: 
         FIG.  1    is a side elevational view of a conventional prosthetic heart valve; 
         FIG.  2    is a highly schematic cross-sectional view showing another prosthetic heart valve disposed within a native valve annulus; 
         FIG.  3 A  is a developed view of a cuff having a series of peaks; 
         FIG.  3 B  is a perspective side view of the cuff of  FIG.  3 A  after the attachment portions of the cuff have been coupled together; 
         FIG.  4 A  is a partial schematic side view of a first variation of a prosthetic heart valve having a cuff coupled to a stent, the cuff having a plurality of cutouts; 
         FIG.  4 B  is a partial schematic side view of a second variation of a prosthetic heart valve having a cuff coupled to a stent, the cuff having a substantially straight inflow edge; 
         FIGS.  4 C- 4 D  are partial schematic side views of examples of cuffs having substantially straight inflow edges; 
         FIG.  4 E  is a highly schematic end view of the prosthetic heart valve of  FIG.  4 B  disposed within a native valve annulus; 
         FIG.  5    is a developed view of a cuff having stitches attached near the inflow end; 
         FIG.  6    is a highly schematic end view of the prosthetic heart valve of  FIG.  5    disposed within a native valve annulus; 
         FIGS.  7 A and  7 B  are a highly schematic end views of a prosthetic heart valve disposed within a generally elliptical native valve annulus, the prosthetic heart valve having and not having cuff inflow end stitches, respectively; and 
         FIG.  8    is a developed view of a cuff having stitches attached near the outflow edge. 
       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. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Inaccurate deployment and anchoring of a prosthetic heart valve may result in the leakage of blood between the implanted heart valve and the native valve annulus, commonly referred to as perivalvular (or “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, particularly when the native valve leaflets have not first been resected. To reduce the risk of leakage, adequate anchoring and sealing are helpful. Moreover, anatomical variations from one patient to another may affect wear and durability. 
     As used herein, the term “proximal,” when used in connection with a prosthetic heart valve in the aortic position, 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. Also, as used herein, the word “about” is intended to mean that slight variations from absolute are included within the scope of the valve recited, for example, due to manufacturing tolerances. 
       FIG.  1    shows a 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 the native tricuspid valve of a patient, such as the 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 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  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 a deployment device configured to deploy the prosthetic valve  100  in the native valve annulus of a patient. 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), ultra-high molecular weight polyethylene, polyurethane, polyvinyl alcohol, silicone or combinations thereof. 
     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  of the stent. 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  of stent  102  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 condition. The delivery device may be introduced into a patient using a transfemoral, 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  200  disposed within native valve annulus  250 . As seen in the figure, stent  202  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  200 , crescent-shaped gaps  240  form between the heart valve and native valve annulus  250 . Blood flowing through these gaps and past valve assembly  204  of prosthetic heart valve  200  may be undesirable. 
       FIGS.  3 A and  3 B  illustrate the outer surface of a cuff before coupling to a stent. As shown, cuff  300  includes a generally parallelogram-shaped body  302 , a series of trapezoidal or triangular peaks  304   a ,  304   b , and  304   c  and a pair of attachment portions  306 . It will be understood, however, that cuff  300  may be formed in various geometric shapes and that illustrated configurations are merely exemplary. Peaks  304  may be used to couple cuff  300  to a stent. Body  302  extends longitudinally from an inflow end  320  to an outflow end  322 , peaks  304   a ,  304   b , and  304   c  being located near outflow end  322 . Attachment portions  306  are adapted to be coupled together to form cuff  300  into the wrapped or assembled configuration shown in  FIG.  3 B . Attachment portions  306  may overlap one another in the wrapped configuration, and may be coupled together using a suture, an adhesive or any other suitable means. Attachment portions  306  may also abut one another and couple together. Cuff  300  may be placed in the wrapped configuration before being coupled to a stent. Alternatively, cuff  300  may be first coupled to the stent after which attachment portions  306  may be coupled together. 
     Cuff  300  is coupled to a stent and to a number of leaflets to form a prosthetic heart valve. It will be understood that the components may be assembled using various techniques and in different orders. For example, the cuff may be coupled to the stent followed by the leaflets or the leaflets may be attached to the cuff followed by assembly of both to the stent. 
     Two variations of the final cuff-stent assembly are described below with reference to  FIGS.  4 A-C . In a first variation, shown in  FIG.  4 A , prosthetic heart valve  400 A includes stent  410 A formed of a plurality of struts  412 A, with cuff  420 A coupled to the stent. Cuff  420 A includes body  422 A extending between inflow end  430 A and outflow end  432 A. 
     Excess portions of cuff  420 A may unduly increase the crimp profile of heart valve  400 A and may also impinge on the effective orifice area (e.g., the entrance orifice through which blood flows to the valve assembly). In order to address these concerns, excess portions  440 A of body  422 A near inflow end  430 A may be trimmed using a cutting mandrel, a die or other suitable means. A fixation device may be useful in this trimming process. One fixation device useful for this purpose is shown in U.S. Provisional Patent Application Ser. No. 61/666,174 entitled “VALVE ASSEMBLY FOR CRIMP PROFILE” filed Jun. 29, 2012, the content of which is hereby incorporated by reference herein in its entirety. 
     The trimming of cuff  420 A may be accomplished either prior to or after the attachment of cuff  420 A to stent  410 A. After completion, cutouts  424 A, such as the semicircular cutouts shown in  FIG.  4 A , are formed in cuff  420 A at recurring positions along the edge near inflow end  430 A. In this variation, cutouts  424 A are configured to mitigate effective orifice area impingement of cuff  420 A during forward flow of blood through inflow end  430 A. Though cutouts  424 A may reduce the crimp profile of the device, in applications where prosthetic heart valve  400 A is implanted in an asymmetric annulus or in an annulus having heavily calcified regions as described above with reference to  FIG.  2   , cutouts  424 A may not adequately seal inflow end  430 A against the surrounding tissue. 
     In a second variation, shown in  FIG.  4 B , prosthetic heart valve  400 B includes stent  410 B formed of a plurality of struts  412 B, with cuff  420 B coupled to the stent. Unlike heart valve  400 A, cuff  420 B of heart valve  400 B is not trimmed along either inflow end  430 B or outflow end  432 B, leaving a substantially flat edge  424 B near inflow end  430 B. Flat edge  424 B may align with the proximal ends of struts  412  near inflow end  430 B. Flat edge  424 B may present some drawbacks as explained below. 
       FIGS.  4 C- 4 D  are partial schematic side views of examples of cuffs having untrimmed inflow edges. In  FIG.  4 C , prosthetic heart valve  400 C includes stent  410 C formed of a plurality of struts  412 C, with cuff  420 C coupled to the stent. Cuff  420 C is rolled on itself near inflow end  430 C to create halo  436 C, a ring-like portion of cuff  420 C that extends past flat edge  424 C. Halo  436 C may be formed of the same material as cuff  420 C or a different material. Additionally, halo  436 C may be integrally formed with cuff  420 C or may be formed of a different portion of tissue, fabric or other cuff material that is coupled to cuff  420 C through adhesive, suture or other suitable techniques. In  FIG.  4 D , prosthetic heart valve  400 D includes stent  410 D formed of a plurality of struts  412 D, with cuff  420 D coupled to the stent. Cuff  420 D is rolled on itself near inflow end  430 D to create parachute  436 D. 
       FIG.  4 E  is a highly schematic end view illustrating prosthetic heart valve  400 B of  FIG.  4 B  disposed within native valve annulus  250  as seen through inflow end  430 B. When cutouts, such as those shown in  FIG.  4 A , are not formed in cuff  420 B, portions of the cuff may bend inwardly during forward flow of blood. Specifically, bent portions  440  of cuff  420 B that are not directly attached to struts  412 B of stent  410 B fold inwardly toward the central axis of prosthetic heart valve  400 B, diminishing the effective orifice area  450  through which blood may flow. In some experiments, it has been found that bent portions  440  may diminish the total effective orifice area  450  by as much as about 10% to about 20%. Moreover, blood flowing through regions near bent portions  440  may be directed outside of cuff  420 B as opposed to flowing through orifice area  450  of the valve assembly, leading to perivalvular leakage. Thus, bent portions  440  may cause regurgitation and other inefficiencies which reduce cardiac performance Similar issues may also arise in examples having untrimmed portions as shown in  FIGS.  4 C and  4 D . 
     Several techniques will be described to reduce the formation of bent portions in the cuff and to avoid constriction of the effective orifice area through the prosthetic heart valve.  FIG.  5    illustrates one such technique, which uses stitches to reduce bent portions of the cuff. For the sake of illustration, cuff  500  is shown flat, as if stretched out and only a portion of a stent is shown in detail. Cuff  500  includes body  502 , a series of large peaks  504   a ,  504   b , and  504   c  projecting from one edge of body  502 , and a pair of attachment portions  506 , one on each longitudinal end of body  502 . To minimize the formation of bent portions of the cuff during use, as shown in  FIG.  4 E , a stitching technique may be applied along flat edge  524  of body  502  near inflow end  530 . In one example, a stitch pattern P may be disposed along flat edge  524  to eliminate or minimize bending of the cuff. 
     An enlarged detailed view of  FIG.  5    is shown of body  502  as well as portions of select struts  552   a ,  552   b  (shown in broken lines) to which body  502  will be attached. For the sake of clarity, the remaining portions of the stent are not shown. As shown in the detailed view, when two struts  552   a  and  552   b  join at the inflow end of stent  550 , a horseshoe  554  is formed. Stitch pattern P may include a first horseshoe locking stitch L 1  anchored at each horseshoe  554 . Between adjacent horseshoe locking stitches L 1 , stitch pattern P may include additional locking stitches L 2  sewn to cuff  500  only, as shown in the enlarged detailed view in  FIG.  5   . Each locking stitch may include two threads that entwine together at the cuff. Although  FIG.  5    shows two such locking stitches L 2  between adjacent horseshoe locking stitches L 1 , cuff  500  may include a greater or lesser number of locking stitches L 2  as desired. To get from one horseshoe locking stitches L 1  to another, any type of stitch may be used though locking stitches L 2  are shown which minimize bulkiness. Thus, stitch pattern P may begin at the attachment portion  506  at one end of cuff  500  and form a recurring pattern of a single horseshoe locking stitch L 1  coupling cuff  500  to a horseshoe  554  of stent  550  and two additional locking stitches L 2  sewn to the cuff only. Stitch pattern P may begin and end in the attachment portions  506  so that the beginning and end knots are hidden when the cuff  500  is fully attached to stent  550  and the attachment portions are joined together. 
     Such a stitching technique allows the prosthetic heart valve to achieve a small crimp profile when collapsed for delivery, while securing each section of cuff  500  to stent  550  and minimizing bending of cuff tissue into the flow area. Additionally, it is common to create a stent  550  having a fully-expanded diameter that is greater than the diameter the stent will have in use. Thus, stitch pattern P may have the added benefit of ensuring optimal valve performance by limiting cuff  500  from over-expanding outside the optimal use range. Finally, stitch pattern P may reduce or eliminate the inward bending of cuff  500  at inflow end  530 , thereby improving sealing by providing a larger landing zone and maintaining the effective orifice area through which blood may flow, while at the same time increasing the landing area along which the native valve annulus may be positioned relative to the prosthetic heart valve allowing easier placement by the physician. Larger landing areas may provide more forgiving placement accuracy. Stitch pattern P may provide these benefits while not unduly increasing the crimp profile of the prosthetic heart valve. 
       FIG.  6    is a highly schematic end view illustrating prosthetic heart valve  600  disposed within native valve annulus  250 . Prosthetic heart valve  600  includes cuff  620  coupled to stent  610 . A stitching technique as described with reference to  FIG.  5    has been applied to cuff  620 . Specifically, stitch pattern P has been applied along the circumference of cuff  620  at its inflow end. Because of the stitching technique, bent portions  630  of the cuff are reduced, leading to a larger effective orifice area  650  through which blood may flow and more adequate sealing with surrounding tissue at the inflow end of prosthetic heart valve  600 . 
     The advantages of the stitching technique described above will also be readily seen when a prosthetic heart valve is implanted in an irregularly-shaped or elliptical native valve annulus.  FIGS.  7 A and  7 B  are highly schematic cross-sectional illustrations of prosthetic heart valves  700 A and  700 B disposed within an elliptical native valve annulus  250 . Prosthetic heart valve  700 A includes cuff  720 A coupled to stent  710 A, but does not employ the stitching technique described above. When prosthetic heart valve  700 A is deployed in elliptical native annulus  250 , bicuspid or mitral valves and subjected to blood flow, bent portions  730 A are formed, reducing the effective orifice area  750 A through which blood may flow. Prosthetic heart valve  700 B is similar to heart valve  700 A, and includes cuff  720 B coupled to stent  710 B. However, in prosthetic heart valve  700 B, the stitching technique described above with reference to  FIG.  5    has been applied to cuff  720 B. When prosthetic heart valve  700 B is deployed in elliptical native annulus  250  and subjected to blood flow, the formation of bent portions  730 B is minimized, leading to great apposition of cuff  720 B to stent  710 B, a larger effective orifice area  750 B through which blood may flow, and more adequate sealing with surrounding tissue at the inflow end of the prosthetic heart valve. 
       FIG.  8    illustrates another example of a cuff for promoting the sealing of the prosthetic heart valve against surrounding tissue and maximizing the effective orifice area through which blood may flow through the prosthetic heart valve. Cuff  800  includes body  802 , a series of peaks  804   a ,  804   b , and  804   c  at the outflow end  832  of body  802 , and a pair of attachment portions  806 , one on each longitudinal end of body  802 . Body  802  extends between inflow end  830  and outflow end  832 . To minimize the formation of bent portions of the cuff during use, as shown in  FIG.  4 E , a tethering technique may be applied near outflow end  832  of cuff  800 . In one example, a plurality of horizontal tethers T 1  may be used to attach peaks  804   a ,  804   b , and  804   c  to one another. Though cuff  800  is shown in the flat configuration, it will be understood that when the cuff is in the wrapped configuration, one set of tethers T 1  attach peak  804   a  to peak  804   c . Vertical tethers T 2  attach the horizontal tethers T 1  to one another, creating a net-like structure or web. By adding tethers T 1  and T 2  near outflow end  832  of cuff  800 , the landing zone of the prosthetic heart valve is increased without unduly increasing its crimp profile. In general, a longer landing zone corresponds to better sealing. In some variations, instead of using separate horizontal tethers T 1  and vertical tethers T 2 , a preformed webbing, netting or mesh may be attached to the top of body  802  or peaks  804   a ,  804   b ,  804   c  to increase the landing zone in a similar manner. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. 
     In some embodiments, a prosthetic heart valve, includes a collapsible and expandable stent having a proximal end, a distal end, an annulus section adjacent the proximal end and an aortic section adjacent the distal end, the stent including a plurality of struts. A cuff may be coupled to the stent so that a flat, bottom edge of the cuff lies adjacent the proximal end of the stent. A pattern of stitches may be circumferentially disposed around the flat bottom edge of the cuff, the pattern of stitches alternating between stitches sewn to the cuff only and stitches sewn to both the cuff and the stent. 
     In some examples, the pattern of stitches may include a plurality of locking stitches. The pattern of stitches may include a recurring pattern comprised of a first type of stitch and a second type of stitch. The first type of stitch may be a locking stitch sewn to the cuff only. The second type of stitch may be a locking stitch sewn to the cuff and at least a portion of the stent. The recurring pattern may include two adjacent stitches of the first type followed by a single stitch of the second type. The plurality of struts may form horseshoe-shaped portions at the proximal end of the stent, and the pattern of stitches may couple the cuff to the horseshoe-shaped portions. The pattern of stitches may include locking stitches sewn only to the cuff between the horseshoe-shaped portions. 
     In some embodiments, a prosthetic heart valve may include a collapsible and expandable stent having a proximal end, a distal end, an annulus section adjacent the proximal end and an aortic section adjacent the distal end, the stent including a plurality of struts and a plurality of commis sure features. A cuff may be coupled to the stent so that a top edge of the cuff lies adjacent the plurality of commissure features and a plurality of tethers incorporated along the top edge of the cuff and coupled to the cuff only. 
     In some examples, the stent may include a plurality of commissure features and the top edge of the cuff includes a plurality of peaks coupled to the commissure features. The plurality of tethers may include at least one vertical tether and at least one horizontal tether. Adjacent ones of the plurality of peaks may be coupled to one another via the at least one horizontal tether. The at least one vertical tether may be coupled to the at least one horizontal tether. The at least one vertical tether may include multiple vertical tethers disposed between the plurality of peaks. 
     In other embodiments, a method of making a prosthetic heart valve may include (i) providing a collapsible and expandable stent having a proximal end, a distal end, an annulus section adjacent the proximal end and an aortic section adjacent the distal end, the stent including a plurality of struts, (ii) coupling a cuff to the stent so that a flat bottom edge of the cuff lies adjacent the proximal end of the stent, and (iii) sewing a pattern of stitches circumferentially around the flat bottom edge of the cuff, the pattern of stitches alternating between stitches sewn to the cuff only and stitches sewn to both the cuff and the stent. 
     In some examples, sewing a pattern of stitches may include forming a plurality of locking stitches. Sewing a pattern of stitches may include sewing a recurring pattern comprised of a first type of stitch and a second type of stitch. Sewing a pattern of stitches may include sewing a first type of stitch that is a locking stitch sewn to the cuff only. Sewing a pattern of stitches may include sewing a second type of stitch that is a locking stitch sewn to the cuff and at least a portion of the stent. The plurality of struts may form horseshoe-shaped portions at the proximal end of the stent, and sewing a pattern of stitches may include sewing the cuff to the horseshoe-shaped portions. 
     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.