Abstract:
Stent-valves (e.g., single-stent-valves and double-stent-valves) and associated methods and systems for their delivery via minimally-invasive surgery are provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Conventional approaches for cardiac valve replacement require the cutting of a relatively large opening in the patient&#39;s sternum (“sternotomy”) or thoracic cavity (“thoracotomy”) in order to allow the surgeon to access the patient&#39;s heart. Additionally, these approaches require arrest of the patient&#39;s heart and a cardiopulmonary bypass (i.e., use of a heart-lung bypass machine to oxygenate and circulate the patient&#39;s blood). Despite their invasiveness, these surgical approaches may be reasonably safe for a first intervention. However, tissue adherences resulting from the first surgery may increase the risks (e.g., death) associated with subsequent valve replacement surgeries. See Akins et al., “Risk of Reoperative Valve Replacement for Failed Mitral and Aortic Bioprostheses”, Ann Thorac Surg 1998; 65:1545-52; and Weerasinghe et al., “First Redo Heart Valve Replacement—A 10-Year Analysis”, Circulation 1999; 99:655-658; each of which is incorporated by reference herein in its entirety. 
         [0002]    Synthetic valves and biological valves have been used for cardiac valve replacement with varying results. Synthetic valves rarely fail but require life-long anti-coagulant treatment to prevent blood from clotting (thrombosis) in and around the replacement valve. Such anti-coagulant treatment significantly limits patients&#39; activities and can cause various other complications. Biological valves do not require such anti-coagulation treatment but typically fail within 10-15 years. Thus, to limit the need for and risks associated with re-operation on failed biological valves, traditionally only patients with less than about 10-15 years to live have received biological valve replacements. Patients with longer life expectancies have received synthetic valves and anti-coagulant treatment. 
         [0003]    Attempts have been made to develop less-invasive surgical methods for cardiac valve replacement. These surgical methods, referred to as percutaneous heart valve replacement therapies (PHVT), use a catheter to deliver a replacement valve to an implantation site using the patient&#39;s vascular system. These PHVT attempts have various shortcomings, including their inability to ensure proper positioning and stability of the replacement valve within the patient&#39;s body. 
         [0004]    In view of the foregoing, it would be desirable to provide improved methods, systems, and devices for cardiac valve replacement. 
       SUMMARY OF THE INVENTION 
       [0005]    Some embodiments of the present invention are directed to systems, methods, and devices for cardiac valve replacement. For example, these methods, systems, and devices may be applicable to the full range of cardiac-valve therapies including the replacement of failed aortic, mitral, tricuspid, and pulmonary valves. In some embodiments, the present invention may facilitate a surgical approach whereby surgery is performed on a beating heart without the need for an open-chest cavity and heart-lung bypass. This minimally-invasive surgical approach may to reduce the risks associated with replacing a failed native valve in the first instance, as well as the risks associated with secondary or subsequent surgeries to replace failed artificial (e.g., biological or synthetic) valves. Stent-valves according to some embodiments of the present invention may include a valve component and at least one stent component (e.g., a single-stent-valve or a double-stent-valve). The valve component may include a biological or synthetic (e.g., is mechanical) valve and/or any other suitable material(s). The stent and valve components may be capable of at least two configurations: a collapsed configuration (e.g., during delivery) and an expanded configuration (e.g., after implantation). 
         [0006]    In some embodiments, the stent component of a stent-valve may include a first strut and a second strut with ends located at different positions along a longitudinal axis of the stent component, wherein the first strut and the second strut provide an axial resistance for anchoring the stent at an implantation site. Multiple installations of the first strut and the second strut may be provided, where such installations are positioned horizontally along a perimeter of the stent component. In some embodiments, the first strut and the second strut may be connected. 
         [0007]    Alternatively or additionally, the stent-component of a stent valve may include multiple locking elements protruding outwardly from an outer surface of the stent component, where each locking element includes a first end adjacent to the outer surface of the stent component and a second end spaced apart from the outer surface of the stent component. The second end of at least a first locking element may be located at a different position along a longitudinal axis of the stent component than the second end of at least a second locking element. For example, in one embodiment, the first locking element and the second locking element may have substantially the same lengths, and the first ends of the first and second locking elements may be positioned at multiple, different levels along the longitudinal axis or the stent component. In another embodiment, the first locking element and the second locking element may have different lengths, and the first ends of the first and second locking elements may be positioned at substantially the same level along the longitudinal axis of the stent component. 
         [0008]    In some embodiments, the stent component of a stent-valve may include at least a first commissural post and a second commissural post adjacent to a body of the stent component, where the external contours of the first and second commissural posts collectively form a generally concave shape. In some embodiments, each of the external contours may slope inwardly toward the center of the corresponding commissural post in the direction of the body of to the stent component. In other embodiments, external contours of adjacent commissural posts may be generally convexly shaped. 
         [0009]    In some embodiments, the valve component of a stent-valve may include an outer surface covered with fabric (e.g., at least a portion thereof, or substantially the entire surface). The valve component may include at least one suture along a free edge of the valve component and at least one suture along an inflow free edge of the valve component, where the fabric includes a skirt that extends below the valve component. A free edge of the skirt may be folded over a bottom portion of the corresponding stent component and sutured to the stent component. In some embodiments, substantially all or at least a portion of the fibers of the fabric are oriented +/−45 degrees with respect to a longitudinal axis of the valve component. Alternatively or additionally, the stent component may include at least one Y-shaped structure fixed to the valve component by one or more (e.g., 3) sutures forming a corresponding Y-shaped configuration. In some embodiments, the stent component comprises an annular groove and the free edge of the skirt is positioned within the groove. Alternatively or additionally, the free edge of the skirt comprises at least one cut oriented in the direction of a longitudinal axis of the stein component. In some embodiments, the annular groove may be at least partially filled with a fibrous, foam, or other biocompatible material. 
         [0010]    In still other embodiments of the present invention, a stent-valve delivery system is provided. A first assembly is provided that includes an outer sheath and a guide wire tubing. The delivery system also includes a second assembly including a stent holder configured for removable attachment to at least one attachment element of a stent-valve. The stent-valve may be positioned over the guide wire tubing of the first assembly. The first assembly and the second assembly may be configured for relative movement with respect to one another in order to transition from a closed position to an open position. In the closed position, the outer sheath may encompass the stent-valve still attached to the stent holder and thus constrain expansion of the stent-valve. In the open position, the outer sheath may not constrain expansion of the stent-valve and thus the stent-Valve may detach from the stent holder and expand to a fully expanded configuration. 
         [0011]    In some embodiments, the first assembly and the second assembly may be configured to transition from the closed position, to a partially-open position, to the open position. In the partially-open position, the stent-valve may expand partially but not detach from the steal holder because the outer sheath may still encompass the at least one attachment element of the stent-valve and the stent holder. When the stent-valve is in the partially-expanded configuration, it may be determined whether the stent-valve will be positioned correctly if the stent-valve is expanded to the fully expanded configuration. Alternatively or additionally, the functionality of the stent-valve may be tested (e.g., to determine whether the stent-valve will permit sufficient blood-flow) when the stent-valve is in the partially-expanded configuration. 
         [0012]    In some embodiments, the first assembly of the stent-valve delivery system may include a coil-reinforced outer sheath and/or a substantially dome-shaped tip, which may provide resistance to kinking due to the bending moment acting onto the delivery system during positioning within, for example, an aortic arch. 
         [0013]    In some embodiments, the stoat holder of the delivery system may include proximal and distal components positioned adjacent to one another (i.e., no gap). This may reduce or eliminate the risk of catching or damaging the outer sheath of the first assembly when closing the delivery device. 
         [0014]    In some embodiments, the stent holder may include at least one chamfered edge positioned adjacent to at feast one attachment pin of the stent holder, where the at least one attachment pin is configured for removable attachment to an attachment element of a stent component. The chamfered edge may assist with the release and expansion of the stent-valve from the stent holder when the stent holder is rotated axially. 
         [0015]    In still other embodiments of the present invention, an apparatus is provided for positioning and attaching a stent-valve comprising a plurality of attachment elements to a corresponding plurality of attachment pins of a stent holder. The apparatus may include an elongate, pliable member (e.g., suture or wire) configured to be threaded through the plurality of attachment elements. The apparatus may also include a tube for receiving the elongate, pliable member. Pulling the elongate, pliable member through the tubing while holding the tubing in a fixed position may collapse the stent-valve diameter to allow for engagement of the attachment elements to the attachment pins. 
         [0016]    In some embodiments, an apparatus is provided for collapsing a diameter of a stent-valve to allow capture of the stent-valve within a sheath of a delivery system. The apparatus may include an elongate, substantially flat strip comprising a slit positioned perpendicular to a longitudinal axis of the strip. The elongate, substantially flat strip may include an end having a height less than a height of the slit, such that insertion of the end into the slit forms a loop. Upon placement of an expanded stent-valve within the loop, pulling the end through the slit causes a reduction of the loop diameter and thereby collapses the diameter of the stent-valve. The elongate, substantially fiat strip may be formed from any suitable material including, for example, polymer and metal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    For a better understanding of the present invention, reference is made to the following description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
           [0018]      FIG. 1  shows a stent component that includes single struts in a proximal section of the stent according to some embodiments of the present invention; 
           [0019]      FIG. 2  shows a stent component that includes double struts in a proximal section of the stent according to some embodiments of the present invention; 
           [0020]      FIGS. 3 and 4  show stern components that include multiple locking elements positioned at multiple, different levels such that at least one locking element is located more proximally than another locking element according to some embodiments of the present invention; 
           [0021]      FIGS. 5 and 6  show stent components having, respectively, convex and concave stem configurations according to some embodiments of the present invention; 
           [0022]      FIG. 7  shows a stent component that includes a reinforced proximal section and reinforced attachment elements according to some embodiments of the present invention; 
           [0023]      FIG. 8  shows a stent component that includes attachment elements positioned between commissural posts according to some embodiments of the present invention; 
           [0024]      FIG. 9  shows a fabric reinforcement for a valve component that covers all, or substantially all, of the valve outer surface and forms a skirt according to some embodiments of the present invention. 
           [0025]      FIG. 10  shows details regarding the suturing the valve component and fabric of  FIG. 9  to a stent according to some embodiments of the present invention. 
           [0026]      FIG. 11  shows a stern-valve that includes a multi- (e.g., three) component fabric reinforcement according to some embodiments of the present invention; 
           [0027]      FIG. 12  shows two configurations for the distal section of a stent-valve delivery system according to some embodiments of the present invention; 
           [0028]      FIGS. 13 and 14  show two configurations of a stent holder of stent-valve delivery system according to some embodiments of the present invention; 
           [0029]      FIG. 15  shows a stent holder with at least one chamfered edge according to some embodiments or the present invention; 
           [0030]      FIG. 16  shows a stent-valve delivery system in which a distal section of the delivery system has a reduced length according to some embodiments of the present invention; 
           [0031]      FIG. 17  shows a stent-valve delivery system with gear-box type release handle according to some embodiments of the present invention; 
           [0032]      FIG. 18  shows a stent-valve delivery system with a trigger type release handle according to some embodiments of the present invention; 
           [0033]      FIG. 19  shows a shaft of a stent-valve delivery system that has a bending stiffness which varies from its proximal to distal ends according to some embodiments of the present invention; 
           [0034]      FIG. 20  shows a positioning device for assisting a physician to implant a stent-valve at an appropriate location according to some embodiments of the present invention; 
           [0035]      FIGS. 21A-C  show a system and corresponding method for positioning and attaching a stent-valve to a stent holder of a delivery system according to some embodiments of the present invention; and 
           [0036]      FIGS. 22A-C  show a system and corresponding method for crimping a stent-valve onto a delivery system according to some embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]      FIG. 1  shows a stent component according to some embodiments that includes single struts  102  in a proximal section of the stent.  FIG. 2  shows a stent component according to some embodiments that includes two struts ( 202 ,  204 ) in a proximal section of the stent. Such double struts may increase the radial resistance to crush of the stent (e.g., axial resistance) and the out of plane bending stiffness of the stent proximal section, thus improving the anchoring of the stent within, for example, a failed biological valve or a calcified native annulus. In  FIG. 1 , multiple (e.g., 10-15 or more) installations of single strut  102  may be provided, for example, side-by-side around the circumference of the scent. In  FIG. 2 , first strut  202  and second strut  204  are provided, where second strut  204  may be a reinforcement within first strut  202 . 
         [0038]      FIGS. 3 and 4  show some embodiments of stent components that include multiple locking elements positioned at multiple, different levels, such that at least one locking element is located more proximally than another locking element. The locking elements may engage, for example, a failed biological valve or calcified native annulus. En  FIG. 3 , the portions of locking elements  302  located adjacent to the outer surface of the stent component are positioned at multiple, different levels ( 304   a, b, c ) and each locking element  302  has the same or similar length  306 . These locking elements may have a similar out of plane bending stiffness. In  FIG. 4 , the portions of locking elements  402  located adjacent to the outer surface of the stent component are positioned at the same level  404  and the locking elements  402  have multiple different lengths ( 406   a, b, c ). In the configuration of  FIG. 4 , the shorter locking elements  402  may have a higher out of plane stiffness. High out of plane bending stiffness may prevent a complete circular expansion of the stent-valve which could result in paravalvular leaks. 
         [0039]      FIGS. 5 and 6  show stent components according to some embodiments having different stem (e.g., commissural post) configurations according to some embodiments of the present invention. As shown in  FIG. 5 , each of the external contours (e.g., wires) of adjacent stems  502  and  504  may have a generally convex shape  506 .  FIG. 6  shows another embodiment in which the external contours of adjacent stems ( 602 ,  604 ) collectively form a generally concave shape  606 . In some embodiments, the concave shape may also have inward-sloping characteristic(s). For example, as shown in  FIG. 6 , each of the external arches slopes inwardly toward the center of the corresponding stem in the direction of the body  608  of the stent. The inclusion of a concavely-shaped stem may, for example, avoid the contact of the valve leaflets with the expanded stent during systole and improve ate blood flow to the coronary arteries. Other embodiments of stent components include, for example, stents that include both convexly- and concavely-shaped stems (e.g., a stent component including at least one stem  502  and at least one stem  602 ). 
         [0040]      FIG. 7  shows a stent component according to some embodiments that includes reinforcement of a proximal section of the stent with the connection of the double struts  702  (e.g., connection of struts  202  and  204  of  FIG. 2 ). This increases the radial force/resistance to crushing of the stent and the out of plane bending stiffness of the elements forming the proximal section, thus improving the anchoring of the stent-valve within the calcified annulus. Furthermore, the attachment elements are reinforced  704  to reduce the risk of kinking under compression during stent-valve release. Geometry  706  has also been changed (e.g., optimized) to locally reduce stresses and strains. 
         [0041]      FIG. 8  shows a stent component according to some embodiments in which the attachment elements  802  are positioned between the commissural posts. This may reduce the overall stent length and accordingly the length of the delivery system, thus avoiding its distal section entering deeply into the ascending aorta/aortic arch during stent-valve release. 
         [0042]      FIGS. 9 and 10  show additional details regarding stent-valves in accordance with some embodiments of the present invention. In  FIG. 9 , a fabric reinforcement is provided that covers all, or substantially all, of the valve outer surface down to the skirt  902 . This may prevent pulling out of sutures and wearing of the valve due to contact with the stein. A continuous suture  904  along the trimmed aortic sinus may be provided, which may allow for firm fixation of the valve to the stent commissural posts. Together with continuous suture  906  along the perimeter of the inflow margin, suture  904  may also increase seal integrity. The fabric that covers the skirt may be integral to and continuous with the fabric that extends between sutures  904  and  906 , although in other embodiments the skirt fabric and the fabric between sutures  904  and  906  may be two separate pieces of fabric that are joined by the sutures. In some embodiments, the fibers of the fabric may be oriented +/−45° with respect to the stent-valve longitudinal axis. This may allow the diameter of the skirt to self adapt to the diameter of the stent in its proximal grooved/flared section by slightly re-orienting the fiber direction (smaller angle within groove, larger angle within flared section). 
         [0043]      FIG. 10  shows details regarding the suturing the valve and fabric of  FIG. 9  to a stent according to some embodiments of the present invention. As shown, the proximal section of the skirt  1002  may be folded over the proximal flared/grooved proximal stent section. Y-shaped sutures  1004  may be provided that hold the valve firmly within the stent and increase seal integrity. In some embodiments, each Y-shaped connection may be made out of one or more independent sutures, where multiple sutures may be provided to avoid leakage in case of a rupture of any single stitch. Free floating edge  1006  of the skirt may be positioned within the groove of the stent and may serve as a further blood barrier by promoting clotting. In some embodiments, longitudinal cuts  1008  may be made along the free floating edge between the sutures to build flexible flaps around the circumference of the stent within the groove. This may improve the barrier effect and increase conformability of the skirt. Alternatively or additionally, the sealing of the prosthesis may be improved by at least partially filling the groove with a fibrous, foam like, or other suitable biocompatible material. The skirt may have a smooth inner surface to minimize blood shear at the annular inflow tract of the prosthesis. A more structured surface may be provided on the outer surface of the prosthesis in order to, for example, improve the sealing of the stent-valve at the implantation site. 
         [0044]      FIG. 11  shows a stent-valve according to some embodiments that includes a multi- (e.g., three) component fabric reinforcement. Each component may have a trapezoid geometry to accommodate the variation of the stent inner diameter over its longitudinal axis. When the components are sutured together, they may form a cylindrical or part-cylindrical skirt, which is flared at one extremity to avoid constraining the stent and thereby reducing its anchoring force within the annulus. 
         [0045]      FIG. 12  shows two configurations for a distal section of a stent-valve delivery system in accordance with some embodiments of the present invention. Distal configuration  1202  includes a generally dilator shaped, longer tip with an unreinforced outer stent sheath. In contrast, distal configuration  1204  includes a generally bullet or domed shaped, shorter tip with a coil-reinforced outer stent sheath. Several manufacturing technologies are available for manufacturing such coil-reinforced sheaths including, for example, extrusion of an inner and an outer tubing, coiling of a stainless steel wire, and assembling the three components by fusion bonding on a mandrel. Relative to distal configuration  1202 , distal configuration  1204  may have improved resistance to kinking due to the bending moment acting onto the delivery system during positioning within, for example, an aortic arch. More specifically, the coil-reinforced stent outer sheath may increase the mechanical kink resistance of the stent delivery system. The use of the bullet shaped tip with reduced length may decrease the bending moment of the delivery system. 
         [0046]      FIGS. 13 and 14  show two configurations of a stent holder of stent-valve delivery system in accordance with some embodiments of the present invention. In  FIG. 13 , the stent holder includes proximal and distal components separated by a gap  1302 . En some embodiments, the component actually holding the stent is the middle, metallic component. The distal component may be conically shaped to facilitate closing of the sheath and to avoid catching the pins. The proximal component may serve as a guide for the attachment elements of the stent and may prevent them from kinking under compression during stent-valve release. In some embodiments, the distal, metallic, and proximal components may be separate pieces, whereas in other embodiments they may be a single piece of solid construction. In  FIG. 14 , the proximal and distal components are positioned adjacent to one another and thus the gap is removed, which may reduce or eliminate the risk of catching or damaging the stent outer sheath  1304  when closing the delivery device. 
         [0047]      FIG. 15  shows another configuration of a stent holder in accordance with some embodiments of the present invention. As shown, one or both o f the edges ( 1502 ,  1504 ) located adjacent to element  1506  (e.g., pin) configured for removable attachment to a stent component may be chamfered. In some embodiments, the stent holder may include multiple (e.g., three) such elements  1506  and adjacent chamfered edge(s). The inclusion of chamfered edge(s) on the surface of the stent holder may help to release the stent-valve from element(s)  1506  of the stent holder when a rotational force is applied, for example, to a hold handle of the delivery system. 
         [0048]      FIG. 16  shows a stent-valve delivery system in which a distal section of the delivery system has a reduced length (e.g., the length which enters into the ascending aorta) relative to a delivery system with a chamfered distal tip. A hollow tip  1602  may be provided that encapsulates the attachment elements/stentholder assembly, which may provide for the reduced length. Placing the attachment elements between the commissural posts may allow for a further reduction in the length of the delivery system. 
         [0049]      FIG. 17  shows a stent-valve delivery system with gear-box type release handle according to some embodiments, which includes opened and closed positions. To move from one position to the other, a rotation of the handle is required prior to translation, thus reducing handling errors. 
         [0050]      FIG. 18  shows a stent-valve delivery system with a trigger type release handle according to some embodiments. In such embodiments, translational movement for opening the delivery system and releasing the stent-valve may be provided by pressing the trigger, thus releasing a braking system and pushing forward the metal shaft connected to the stent cuter sheath. This system advantageously allows a one hand release of the stent-valve, whereas the other hand takes care of the positioning of the implant. The design of this release handle may be similar to, for example, products commercially available for dispensing, for example, silicone. 
         [0051]      FIG. 19  shows a mid section of a stent-valve delivery system according to some embodiments, which may include a shaft having a bending stiffness which varies from its proximal to distal ends. A stiff proximal shaft may provide for pushability of the delivery system, whereas the flexible distal section may allow for an improved trackability in curves. The shaft may include openings (e.g., water jet cut openings) along its longitudinal axis ( FIG. 17 and 19 ), where the openings may be oriented towards two perpendicular axes with respect to the shaft cross section. 
         [0052]      FIG. 20  shows a positioning device for assisting a physician to implant a stent-valve at an appropriate location according to some embodiments. The positioning device comprises three self expanding (e.g. nitinol) fingers or feelers constrained within an outer sheath, which may be co-axially slideable into the stent-valve delivery system. By retracting the outer sheath, the feelers start to expand and can be positioned under the inflow tract of, for example, the aortic valve under fluoroscopic assistance. By exerting a slight force towards the annulus, the three fingers may act as a landmark for implanting the stent-valve. 
         [0053]      FIGS. 21A-C  show a system and corresponding method for positioning and attaching a stent-valve to stent holder in accordance with some embodiments of the present invention. As shown in FIG,  21 A, a suture or other pliable, continuous element  2102  (e.g., wire) may be threaded through the attachment elements of the stent component and then through a cannula or tubing  2104 . By pulling the suture and holding the tubing, the stent-valve diameter may be collapsed and the attachment elements may engage the element(s) (e.g., pins  2106 ) of the stent holder. In some embodiment, both ends of the suture are free (such that both ends are fed through the tube and then pulled). In other embodiments, one end of the suture is free whereas the other end is fixed (e.g., to the tubing), such that only one end of the suture is thread through the tubing and pulled. Subsequently, outer sheath  2108  may be pulled proximally over the attachment elements, as shown in  FIGS. 21B and 21C . The suture may then be removed by pulling it back through the attachment elements. 
         [0054]      FIGS. 22A-C  show a system and corresponding method for crimping a stent-valve onto a delivery system according to some embodiments.  FIG. 22A  shows a thin, flat (e.g., polymer or metallic) strip  2202  with a slit  2204  perpendicular to its longitudinal axis and having a wide edge  2206  at one end and a narrower edge  2208  at the opposite end. When the narrow edge is inserted into the slit (i.e., the slit having a greater height than a height of the narrow edge), the strip forms a loop. As shown in  FIGS. 22B and 22C , when a stent-valve is placed within the loop, pulling on the edges at the two extremities of the strip causes a reduction of the loop diameter  2210  thereby crimping the stent-valve. The crimped stent-valve can then be stepwise constrained by the outer sheath  2212 . Generally, the positioning and crimping systems shown in  FIGS. 21A-C  and  22 A-C provide for ease of use by physicians or other technicians. In some embodiments, these positioning and crimping systems may be low cost and disposable, and may be delivered as sterile accessories together with the delivery system and/or the stent-valve. 
         [0055]    Thus it is seen that stent-valves (e.g., single-stent-valves, double-stent-valves) and associated methods and systems for surgery are provided. Although particular embodiments have been disclosed herein in detail, this has been done by way of example for purposes of example and illustration only, and is not intended to be limiting with respect to the scope of the appended claims, which follow. To that end, any reference to measurements, distances and the like, are for illustrative/example purposes. In particular, it is contemplated by the applicant that various substitutions, alterations, and modifications may be made without departing from the spirit and scope of the invention as defined by the claims. Other aspects, advantages, and modifications are considered to be within the scope of the following claims. The claims presented are representative of some of the inventions disclosed herein. Other, unclaimed inventions are also contemplated. The applicant reserves the right to pursue such inventions in later claims.