Abstract:
Heart valve prostheses are provided having a self-expanding frame that supports a valve body comprising a skirt and a plurality of coapting leaflets. The leaflets are constructed with four commissure points to reduce the stress and strain applied to the commissure points and to efficiently distribute and transmit forces along the leaflets and to the frame.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention is related to artificial heart valves. More specifically, the present invention is directed to an artificial valve prosthesis. 
         [0003]    2. Background Art 
         [0004]    Cardiac valves exhibit two types of pathologies: regurgitation and stenosis. Regurgitation is the more common of the two defects. Typically, either defect is treated by a surgical repair. Under certain conditions, however, the cardiac valve must be replaced. Standard approaches to valve replacement require cutting open the patient&#39;s chest and heart to access the native valve. Such procedures are traumatic to the patient, require a long recovery time, and can result in life threatening complications. Therefore, many patients requiring cardiac valve replacement are deemed to pose too high a risk for open heart surgery due to age, health, or a variety of other factors. These patient risks associated with heart valve replacement are lessened by the emerging techniques for minimally invasive valve repair, but still many of those techniques require arresting the heart and passing the blood through a heart-lung machine. 
         [0005]    Efforts have been focused on percutaneous transluminal delivery of replacement cardiac valves to solve the problems presented by traditional open heart surgery and minimally-invasive surgical methods. In such methods, a valve prosthesis is compacted for delivery in a catheter and then advanced, for example, through an opening in the femoral artery and through the descending aorta to the heart, where the prosthesis is then deployed in the aortic valve annulus. 
         [0006]    In view of the foregoing, it would be desirable to provide a valve prosthesis that is capable of conforming to a patient&#39;s anatomy while providing a uniform degree of rigidity and protection for critical valve components. Protection for critical valve components is essential to maintain reliability for the valve prosthesis. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    Provided herein are valve prostheses that generally include a self-expanding frame, where the valve prostheses are sutured to the self-expanding frame. Such configurations achieve numerous goals. For example, such configurations can: prevent the native leaflets from obstructing flow through the left ventricular outflow tract (LVOT); prevent the native leaflets from interacting with the prosthetic leaflets; recruit the native leaflets in minimizing perivalvular leaks; maintain proper alignment of the valve prosthesis; avoid systolic anterior mobility; and maintain valve stability by preventing migration of the valve into the atrium or ventricle. The design of the prosthesis also mimics the native valve and supports a non-round in vivo configuration, which better reproduces native valve function. 
         [0008]    In view thereof, disclosed herein are aspects of a valve prosthesis which is generally designed to include a valve body and a self expanding frame. The valve body includes a first leaflet, a second leaflet, and a third leaflet. Adjoining leaflets are sewn together to form a first commissure point, a second commissure point, a third commissure point, and a fourth commissure point. The four commissure points are sewn to the frame. 
         [0009]    In another exemplary embodiment, the valve prosthesis is designed to include a valve body including a first leaflet, a second leaflet, a third leaflet, and a fourth leaflet, and a self expanding frame. The first leaflet is attached to the second leaflet at a first point to form a first commissure point. The second leaflet is attached to the third leaflet at a second point to form a second commissure point. The third leaflet is attached to the fourth leaflet at a third point to form a third commissure point. The commissure points are sewn to the frame. 
         [0010]    Disclosed herein are aspects of a method of treating a valve disorder in a patient&#39;s heart including loading a valve prosthesis onto a delivery system, advancing the delivery system and valve prosthesis through an incision into the patient&#39;s vasculature and into the patient&#39;s heart, releasing the valve prosthesis from the delivery system, and withdrawing the delivery system from the patient&#39;s heart. The valve prosthesis includes a valve body and a self-expanding frame. The valve body includes a first leaflet, a second leaflet, and a third leaflet. Adjoining leaflets are sewn together to form a first commissure point, a second commissure point, a third commissure point, and a fourth commissure point. The four commissure points are sewn to the frame. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0011]    The accompanying figures, which are incorporated herein, form part of the specification and illustrate embodiments of a valve prosthesis. Together with the description, the figures further serve to explain the principles of and to enable a person skilled in the relevant art(s) to make, use, and implant the valve prosthesis described herein. In the drawings, like reference numbers indicate identical or functionally similar elements. 
           [0012]      FIG. 1  is a perspective view of a valve prosthesis, in accordance with an aspect of the disclosure. 
           [0013]      FIG. 2  is a side view of a valve prosthesis. 
           [0014]      FIG. 3  is a top view of a valve prosthesis. 
           [0015]      FIG. 4  is a top view of a valve prosthesis according to an alternate aspect of this disclosure. 
           [0016]      FIG. 5  is a top view of a valve prosthesis according to an alternate aspect of this disclosure. 
           [0017]      FIG. 6  is a top view of a valve prosthesis according to an alternate aspect of this disclosure. 
           [0018]      FIG. 7  is a top view of a valve prosthesis according to an alternate aspect of this disclosure. 
           [0019]      FIG. 8  is a top view of a valve prosthesis according to an alternate aspect of this disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The following detailed description of a valve prosthesis refers to the accompanying figures that illustrate exemplary embodiments. Other embodiments are possible. Modifications can be made to the embodiments described herein without departing from the spirit and scope of the present invention. Therefore, the following detailed description is not meant to be limiting. 
         [0021]    The present invention is directed to a heart valve prosthesis having a self-expanding frame that supports a valve body. The valve prosthesis can be delivered percutaneously to the heart to replace the function of a native valve. For example, the valve prosthesis can replace a bicuspid or a tricuspid valve such as the aortic, mitral, pulmonary, or tricuspid heart valve. 
         [0022]    In one aspect of the invention, the valve body comprises three leaflets that are fastened together at enlarged lateral end regions to form commissural joints, with the unattached edges forming the coaptation edges of the valve. The leaflets can be fastened to a skirt, which in turn can be attached to the frame. The upper ends of the commissure points define an outflow or proximal portion of the valve prosthesis. The opposite end of the valve at the skirt defines an inflow or distal portion of the valve prosthesis. The enlarged lateral end regions of the leaflets permit the material to be folded over to enhance durability of the valve and reduce stress concentration points that could lead to fatigue or tearing of the leaflets. The commissural joints are attached above the plane of the coaptation edges of the valve body to minimize the contacted delivery profile of the valve prosthesis. 
         [0023]    Referring to  FIGS. 1 and 2 , from a top view, valve prosthesis  1  includes a circular frame  11 . Frame  11  can be any non-biological structure including wireforms, stents, and the like. In alternate aspects of the invention, frame  11  can be elliptical, D-shaped, or any other shape known to a person of ordinary skill in the art. From a side view, frame  11  can be tapered, cylindrical, conical, or any other shape known to a person of ordinary skill. Frame  11  can be a self-expanding structure formed by laser cutting or etching a metal alloy tube comprising, for example a shape memory material such as nickel titanium (nitinol). Alternatively, frame  11  can be a balloon expanding structure. Frame  11  can include a pattern of radial cells that make up the structure of frame  11 . The cell sizes can be modified during the formation of frame  11 , for example through an expansion step. In addition, the number of cells in a radial or axial direction can be modified to allow for a larger or fewer number of cells. Frame  11  can also include a cusp  91 . Cusp  91  can be a radiopaque imaging reference to assist in positioning the valve prosthesis  1  in a native valve annulus. Cusp  91  can also assist in anchoring frame  11  in the native valve annulus. 
         [0024]    Valve prosthesis  1  also includes a valve  21  that includes individual leaflets that are assembled to the skirt. The leaflets and skirt are formed from a natural or man-made material. Preferred materials for valve  21  include mammalian tissue, such as porcine, equine, or bovine pericardium, or a synthetic or polymeric material. In one aspect of the invention, valve  21  includes three leaflets  31   a - c.  Adjoining pairs of leaflets are attached to one another to form commissure points  41   a - d.  Leaflet  31   b  is attached to leaflet  31   a  by commissure points  41   a  and  41   d.  Leaflet  31   b  is attached to leaflet  31   c  by commissure points  41   b  and  41   c.  In a preferred embodiment, valve prosthesis  1  is biased to a closed position. Alternatively, valve prosthesis  1  can be biased to an open position. Free edges of leaflets  31   b  and  31   a  come together to form coaptation edge  51   a,  thereby creating a competent seal. Free edges of leaflets  31   b  and  31   c  come together to form coaptation edge  51   b,  thereby creating a competent seal. The length of coaptation edges  51   a  and  51   b  can be from approximately 24 mm to approximately 48 mm. In a preferred embodiment, the length of coaptation edges  51   a  and  51   b  is approximately 25 mm. 
         [0025]    In one aspect of the invention, the contact area between the leaflets at coaptation edges  51   a  and  51   b  is minimized to allow for quicker opening and closing of valve leaflets  31   a - c.  For example, at coaptation edge  51   a,  approximately 0.5 mm to approximately 6 mm of valve leaflets  31   a  and  31   b  touch along the length of coaptation edge  51   a.  However, the contact area of the leaflets at coaptation edges  51   a  and  51   b  is affected by the positioning of valve prosthesis  1  in the native anatomy. In one aspect of the invention, after implantation, valve prosthesis  1  takes approximately 0.06 seconds to open from a closed configuration. Valve prosthesis  1  takes approximately 0.04 seconds to close from an open configuration. Valve prosthesis  1  is also able to operate at approximately 167 ml/second of fluid. 
         [0026]    The bases of leaflets  31   a - c  are assembled to a skirt  71  and attached to frame  11 . Commissure points  41   a - d  are positioned on frame  11  such that leaflet  31   b  extends across the center of frame  11 , as shown in  FIG. 3 . Valve prosthesis  1  can include center member  81 . In one aspect of the invention, center member  81  attaches to frame  11  between commissure points  41   a  and  41   b  and between commissure points  41   c  and  41   d.  Center member  81  can be semi-rigid or rigid and can be a suture, nitinol wire, or a synthetic or polymeric material that will not generate a thrombotic response in a patient, or any other material known to a person of ordinary skill in the art. In one aspect of the invention, center member  81  is attached to frame  11  on the outflow side of leaflet  31   b.  Alternatively, center member  81  can be attached to frame  11  on the inflow side of leaflet  31   b.  Center member  81  restricts the movement of leaflet  31   b  and prevents leaflet  31   b  from collecting blood and parachuting in the outflow direction in the presence of blood flow. As a result, during blood flow, the free edges of leaflet  31   b  fold along center member  81  and minimize the area of leaflet  31   b  extending across the orifice area of valve prosthesis  1 . 
         [0027]    In another aspect of the invention, each commissure point is attached to frame  11  by sewing the commissure point to a cell of frame  11  such that each commissure point occupies an entire cell of frame  11 . Alternatively, each commissure point can be attached to frame  11  by sewing the commissure point to a portion of a cell of frame  11 . In a preferred embodiment, at least one cell of frame  11  is positioned between commissure points  41   a  and  41   b  and commissure points  41   c  and  41   d.  Further, at least two cells can be positioned between commissure points  41   b  and  41   c  and commissure points  41   a  and  41   d.  In one aspect of the invention, commissure points  41   a - d  are disposed longitudinally offset from coaptation edges  51   a - b  of the valve body, thereby permitting a smaller delivery profile. Due to the presence of leaflet  31   b  across the center of frame  11 , valve prosthesis  1  may require a delivery system that features an asymmetric member so that the delivery system doesn&#39;t interfere with leaflet  31   b.  Alternatively, a delivery system for valve prosthesis  1  can grasp the outer edge of frame  11  to deliver valve prosthesis  1  into a native valve annulus. 
         [0028]    The axial distance from the distal most portion of the base of the valve leaflets to the proximal most portion of the valve leaflets is the leaflet height, h 2 . The base of the valve leaflets is where the leaflet edges attach to the skirt and the valve frame. In a preferred embodiment, h 2  is from approximately 8 mm to approximately 15 mm. The axial distance between the distal and proximal portions of the commissure points is the commissure height, h 1 . In a preferred embodiment, h 1  is approximately 9 mm. 
         [0029]      FIG. 3  shows valve  21  in the closed state. Commissure points  41   a - d  attach to frame  11  and are positioned to form angles  61   a - d  between the respective commissure points with the center of frame  11  as the vertex of the angles. Angles  61   a  and  61   c  can be larger than angles  61   b  and  61   d.  In one aspect of the invention, angles  61   a  and  61   c  are approximately 170 degrees. In an alternate embodiment, one or more of angles  61   a - d  can be modified to optimize the function of valve prosthesis  1  by positioning one or more commissure points  41   a - d  at an alternate portion or cell of frame  11  or by modifying the shape of one or more of leaflets  31   a - c.  For example, angles  61   a  and  61   c  can be between approximately 160 degrees and 180 degrees. Angles  61   a  and  61   c  can also be between 90 degrees and 180 degrees. Modifying one or more of angles  61   a - d  can modify the length of coaptation edges  51   a  and/or  51   b.  A longer coaptation edge length correlates to less stress on commissure points  41   a - d.    
         [0030]    In a further aspect of the invention, leaflets  31   a  and  31   c  are approximately the same size. Alternatively, leaflets  31   a  and  31   c  can be different sizes. Modifying the sizes of leaflets  31   a  and  31   c  can also affect angles  61   a - d.  For example, if leaflets  31   a  and  31   c  are different sizes, angle  61   c  can be larger than angle  61   a,  or vice versa. 
         [0031]    The configuration involving four commissure points can increase the coaptation length of the valve leaflets. As a result, the four commissure points experience less deflection than a valve having three commissure points. This allows the leaflets to maintain a rapid opening and closing time. The four commissure design also enables the valve prosthesis to maintain reliability with a low commissure height. The low commissure height allows valve prosthesis  1  to replace the native mitral valve. Furthermore, a low commissure height correlates to a valve prosthesis that is shorter in the axial direction that is easier to position and align in a native valve annulus. The four commissure points also enable the valve to maintain hemodynamic performance in a severely elliptical configuration by mitigating impact in the coaptive region. This configuration also provides a more uniform distribution of stresses along coaptation edges  51   a - b  of leaflets  31   a - c  allowing valve prosthesis  1  to exhibit greater reliability and a longer operating life than current catheter delivered valve prostheses. 
         [0032]    In an alternate aspect of the invention shown in  FIG. 4 , from a side view, frame  13  is an hourglass shape where the outflow portion flares out such that the diameter of the outflow portion of the frame is larger than the diameter of the inflow portion of the frame. In one aspect of the invention, commissure points  43   a - d  are angled outward from the center of frame  13 . In this configuration, the most proximal portions of commissure points  43   a - d  are further from the center of frame  13  than the distal portions of commissure points  43   a - d.  In an alternate embodiment, the commissure points can be angled inward towards the center of the frame. The commissure points can also be oriented vertically on the frame, as shown in  FIG. 3 . 
         [0033]      FIGS. 5-6  are top views of alternative aspects of the invention showing alternate frame shapes. In  FIG. 5 , from a top view, the frame is an elliptical shape. In this embodiment, leaflets  35   a  and  35   c  have approximately the same size and area and angles  65   a  and  65   c  are approximately equal. In a preferred embodiment, angles  65   a  and  65   c  are approximately 170 degrees. Furthermore, coaptation edges  55   a  and  55   b  are approximately equal in length. Similar to valve prosthesis  1  discussed in  FIGS. 1-3 , the size and area of leaflets  35   a - c  can be modified so that leaflets  35   a  and  35   c  do not have approximately the same size. The placement of commissure points  45   a - d  on frame  15  can also be modified to alter angles  65   a - d  in order to optimize the function of valve prosthesis  5 . 
         [0034]    In  FIG. 6 , from a top view, frame  17  is D-Shaped. In this aspect of the invention, leaflet  37   c  can have a larger area than leaflet  37   a  and corresponding angle  67   c  can be greater than angle  67   a.  As a result, coaptation edge  57   b  can have a greater length than coaptation edge  57   a.  Alternatively, leaflet  37   a  can be larger than leaflets  37   c  and corresponding angle  67   a  can be larger than angle  67   c.  In a preferred embodiment, angle  67   c  is approximately 170 degrees. In alternate aspects of the invention, the sizes of leaflets  37   a - c  and the angles  67   a - d  can be modified in order to optimize the function of valve prosthesis  7 . 
         [0035]      FIG. 7  shows an alternate valve prosthesis  101  having four leaflets  131   a - d  and four commissure points  141   a - d.  Leaflets  131   a  and  131   c  are approximately the same size having approximately the same area. In an alternate aspect of the invention, leaflets  131   a  and  131   c  can be different sizes. Leaflet  131   a  is attached to leaflet  131   b  at commissure point  141   a  and to leaflet  131   d  at commissure point  141   d.  Leaflet  131   c  is attached to leaflet  131   b  at commissure point  141   b  and to leaflet  131   d  at commissure point  141   c.  Free edges of leaflets  131   a  and  131   b  come together to form coaptation edge  151   a.  Free edges of leaflets  131   b  and  131   c  come together to form coaptation edge  151   b.  Free edges of leaflets  131   c  and  131   d  come together to form coaptation edge  151   c.  Free edges of leaflets  131   d  and  131   a  come together to form coaptation edge  151   d.  Free edges of leaflets  131   a  and  131   c  come together to form coaptation edge  151 e. Coaptation edges  151   a - e  thereby create a competent seal. In a preferred embodiment, the length of coaptation edge  151   e  is larger than the length of any of coaptation edges  151   a - d.    
         [0036]    Leaflets  131   a - d  are assembled to a skirt (not shown), similar to valve prosthesis  1 . Commissure points  141   a - d  are attached to frame  111  which is elliptical from a top view. Commissure points  141   a - d  are arranged to form angles  161   a - 161   d,  where the center of frame  111  is the vertex of the angles. Frame  111  can be any other shape known to a person of ordinary skill, including but not limited to circular, or D shaped from a top view, or tapered, conical, or cylindrical from a side view. In one aspect of the invention, angles  161   a  and  161   c  are larger than angles  161   b  and  161   d.  In a preferred embodiment, angles  161   a  and  161   c  are approximately 170 degrees. In an alternate embodiment, one or more of angles  161   a - d  can be modified to optimize the function of valve prosthesis  101  by positioning one or more commissure points  141   a - d  on an alternate portion of frame  111  or by modifying the shape or area of one or more of leaflets  131   a - d.  Modifying one or more of angles  161   a - d  can modify the length of coaptation edges  151   a - e.    
         [0037]    In an alternate aspect of the invention shown in  FIG. 8 , from a top view, frame  113  is D-Shaped. In this aspect of the invention, leaflet  133   c  has a larger area than leaflet  133   a  and corresponding angle  163   c  is greater than angle  163   a.  Furthermore, leaflet  133   a  is larger than leaflets  133   b  and  133   d  and corresponding angle  163   a  can be larger than angles  163   b  and  163 d. In a preferred embodiment, angle  163   c  can be 170 degrees. In alternate aspects of the invention, the sizes of leaflets  37   a - c  and the angles  67   a - d  can be modified to optimize the function of valve prosthesis  103 . Similar to valve prosthesis  101  discussed above with respect to  FIG. 7 , leaflets  133   a - d  come together to form coaptation edges  153   a - e.  In a preferred embodiment, the length of coaptation edge  153   e  is greater than the length of any of coaptation edges  153   a - d.    
         [0038]    The valve prosthesis can replace the function of a tricuspid or bicuspid heart valve including the mitral valve, the aortic valve, the pulmonary valve, or the tricuspid valve. The valve can be delivered, for example, transeptally, transapically, transradially, or transatrially. 
         [0039]    Implantation of the valve prosthesis will now be described. As discussed above, the valve prosthesis preferably comprises a self-expanding frame that can be compressed to a contracted delivery configuration onto an inner member of a delivery catheter. The valve prosthesis and inner member can then be loaded into a delivery sheath of conventional design, e.g., having a diameter of less than 20-24 French. Due in part to the fact that the commissure points are longitudinally offset from the coaptation edges of the leaflets, and due to the ability to maintain a lower commissure height, it is expected that the valve prosthesis can achieve a significantly smaller delivery profile than previously-known percutaneously-deliverable replacement valves. 
         [0040]    The delivery catheter and valve prosthesis are then advanced in a retrograde manner through the femoral artery and into the patient&#39;s descending aorta. The catheter then is advanced, under fluoroscopic guidance, over the aortic arch, through the ascending aorta and mid-way across the defective aortic valve. Once positioning of the catheter is confirmed, the sheath of the delivery catheter can be withdrawn proximally, thereby permitting the valve prosthesis to self-expand. 
         [0041]    As the valve prosthesis expands, it traps the leaflets of the patient&#39;s defective aortic valve against the valve annulus, retaining the native valve in a permanently open state. The outflow section of the valve prosthesis expands against and aligns the prosthesis within the ascending aorta, while the inflow section becomes anchored in the aortic annulus of the left ventricle, so that the skirt reduces the risk of perivalvular leaks. 
         [0042]    Alternatively, the valve prosthesis can be delivered through a transapical procedure. In a transapical procedure, a trocar or overtube is inserted into the left ventricle through an incision created in the apex of a patient&#39;s heart. A dilator is used to aid in the insertion of the trocar. In this approach, the native valve (e.g. the mitral valve) is approached from the downstream relative to the blood flow. The trocar is retracted sufficiently to release the self-expanding valve prosthesis. The dilator is preferably presented between the valve leaflets. The trocar can be rotated and adjusted as necessary to properly align the valve prosthesis. The dilator is advanced into the left atrium to begin disengaging the proximal section of the valve prosthesis from the dilator. 
         [0043]    In an alternate aspect of the invention, the valve prosthesis can be delivered through a transatrial procedure. In this procedure, the dilator and trocar are inserted through an incision made in the wall of the left atrium of the heart. The dilator and trocar are advanced through the native valve and into the left ventricle of heart. The dilator is then withdrawn from the trocar. A guide wire is advanced through the trocar to the point where the valve prosthesis comes to the end of the trocar. The valve prosthesis is advanced sufficiently to release the self-expanding frame from the trocar. The trocar can be rotated and adjusted as necessary to properly align the valve prosthesis. The trocar is completely withdrawn from the heart such that the valve prosthesis self-expands into position and assumes the function of the native valve. 
         [0044]    The foregoing description has been presented for purposes of illustration and enablement, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Other modifications and variations are possible in light of the above teachings. The embodiments and examples were chosen and described in order to best explain the principles of the invention and its practical application and to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention.