Patent Publication Number: US-2021161666-A1

Title: Valve prosthesis and method for delivery

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention is related to an artificial heart valve frame. More specifically, the present invention is directed to an artificial valve prosthesis. 
     Background Art 
     The mitral valve is a functional organ composed of multiple dynamically interrelated units. During cardiac cycle, the fibrous skeleton, the anterior and posterior leaflets, the papillary muscles, the chordae tendinea, and the ventricular and atrial walls all interplay to render a competent valve. The complex interaction between the mitral valve and the ventricle by the subvalvular apparatus (the papillary muscles and the chordae tendinea) is essential in maintaining the continuity between the atrio-ventricular ring (which is part of the fibrous skeleton of the heart) and the ventricular muscle mass, which provides for the normal functioning of the mitral valve. 
     Cardiac valves, including the mitral valve, exhibit two types of pathologies: regurgitation and stenosis. In the case of the mitral valve, regurgitation is the abnormal leaking of blood from the left ventricle, through the mitral valve, and into the left atrium, when the left ventricle contracts. Stenosis is the narrowing of the orifice of the mitral valve of the heart. Regurgitation is the more common of the two defects. Either defect can be treated by a surgical repair. However, surgical procedures can lead to an interruption of the mitral annulus-papillary muscle continuity, which accounts for changes in geometry mechanics and performance of the left ventricle. These problems are lessened by the emerging techniques for minimally invasive mitral valve repair, but still many of those techniques require arresting the heart and funneling the blood through a heart-lung machine, which can also be traumatic for patients. 
     Under certain conditions, 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. 
     In addition, valve replacement can create additional problems including limitation of the mitral flow during exercise due to a small effective orifice area and high cardiac output imposed by a smaller size artificial valve. Further, the rigid structure of an artificial valve prevents the physiologic contraction of the posterior wall of the left ventricle surrounding the mitral annulus during systole. Also, myocardial rupture can result from excision or stretching of the papillary muscle in a thin and fragile left ventricle. Additionally, chordae rupture can also occur due to the chordae rubbing against the artificial valve over time, leading to increased heart wall stress. It has been shown that severing the chordae can lead to a 30% reduction in chamber function. Thus, mitral valve replacement has a high mortality rate in very sick, chronic heart failure patients. 
     The chordae tendinea, which connect the valve leaflets to the papillary muscles (PM) act like “tie rods” in an engineering sense. Not only do the chordae tendinea prevent prolapse of the mitral valve leaflets during systole, but they also support the left ventricular muscle mass throughout the cardiac cycle. To function adequately, the mitral valve opens to a large orifice area and, for closure, the mitral leaflets have an excess surface area (i.e. more than needed to effectively close the mitral orifice). On the other hand, systolic contraction of the posterior ventricular wall around the mitral annulus (MA) creates a mobil D-shaped structure with sphincter-like function which reduces its area by approximately 25% during systole, thus exposing less of the mitral leaflets to the stress of the left ventricular pressure and flow. 
     It has been long postulated that the structural integrity of the MA-PM continuity is essential for normal left ventricular function. Recent evidence supports the concept that preservation of the subvalvular apparatus with the MA-PM continuity in any procedure on the mitral valve is important for the improved long-term quality and quantity of life following valve replacement. Maintaining the MA-PM continuity, thus, appears to provide a substantial degree of protection from the complications associated with valve replacement. 
     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 through a patient&#39;s vasculature to the heart, where the prosthesis is then deployed in the native valve annulus. 
     Therefore, what is needed is a mitral valve prosthesis and method of implantation that minimizes the traumatic impact on the heart while effectively replacing native leaflet function. A consistent, reproducible, and safe method to introduce a prosthesis into the mitral position in a minimally invasive fashion could be attractive for numerous reasons: a) it can treat both functional and degenerative mitral regurgitation (MR); b) it can treat mitral stenosis; c) it can offer a remedy to inoperable patients, high risk surgical patients, and those that cannot tolerate bypass; d) it can allow a broad range of practitioners to perform mitral valve procedures; and/or e) it can enable more consistency in measuring outcome. 
     BRIEF SUMMARY OF THE INVENTION 
     Provided herein are mitral valve prostheses and methods for implanting the prostheses in the heart. The prostheses generally include a self-expanding frame and two or more support arms. A valve prosthesis is sutured to the self-expanding frame. Each support arm corresponds to a native mitral valve leaflet. At least one support arm immobilizes the native leaflets, and holds the native leaflets close to the main frame. Such configuration achieves numerous goals. For example, such configuration achieves one or more of the following: prevents the native leaflets from obstructing flow through the left ventricular outflow tract (LVOT); prevents the native leaflets from interacting with the prosthetic leaflets; recruits the native leaflets in minimizing peri-valvular leaks; maintains proper alignment of the valve prosthesis; avoid systolic anterior mobility; and maintains valve stability by preventing migration of the valve into the atrium or ventricle and prevents damage to the native chordae. Additionally, the prosthetic mitral valve frame can include two or more anchor attachment points. Each anchor attachment point can be attached to one or more anchors that help attach the mitral valve to the heart. Such configuration provides added stability to the prosthetic mitral valve and prevents damage to the native chordae. The design of the prosthesis also mimics the native valve and supports a non-circular in vivo configuration, which better reflects native valve function. 
     In view thereof, disclosed herein are aspects of a valve prosthesis which is generally designed to include a main frame including a first section, a second section, and a third section; a valve body connected to the frame, and a support frame including a first engagement arm and a second engagement arm connected to the main frame in the first section, where the first engagement arm is connected to the main frame in the first section at a first point and a second point, where in the second engagement arm is connected to the main frame in the first section at a third point and a fourth point, and where the first engagement arm and the second engagement arm include a radial portion where the respective arms extend in the radial direction. 
     In another exemplary aspect, disclosed herein are aspects of a valve prosthesis which is generally designed to include a valve body and a frame including a first portion connected to the valve body and a second portion adapted for implantation in a native valve annulus, the frame having a delivery configuration where the first portion is longitudinally adjacent to the second portion and an expanded configuration where the first portion is positioned within an interior area of the second portion. 
     In another exemplary embodiment, disclosed herein are aspects of a method of treating a valve disorder in a patient&#39;s heart which generally includes collapsing a valve prosthesis including a frame onto a delivery system to place a first portion of the frame adjacent a second portion of the frame, delivering the delivery system and valve prosthesis to a heart, expanding the valve prosthesis in the heart such that the first portion of the frame moves to be positioned within an interior area of the second portion of the frame, and withdrawing the delivery system from the heart. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       The accompanying figures, which are incorporated herein, form part of the specification and illustrate embodiments of a valve prosthesis frame and delivery system. 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. 
         FIG. 1  is a perspective view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 2  is a top view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 3  is a perspective view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 4  is a front view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 5  is a perspective view of a valve prosthesis according to an aspect of this disclosure. 
         FIG. 6  is a perspective view of a valve prosthesis according to an aspect of this disclosure. 
         FIG. 7  is a sectional view of a valve prosthesis frame in a collapsed configuration according to an aspect of this disclosure. 
         FIG. 8  is a sectional view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 9  is a schematic view of a valve prosthesis implanted in the heart according to an aspect of this disclosure. 
         FIG. 10  is a front view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 11  is a front view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 12  is a schematic view of a valve prosthesis implanted in the heart according to an aspect of this disclosure. 
         FIG. 13  is an assembly view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 14  is a front view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 15  is a front view of a portion of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 16  is an assembly view of a valve prosthesis frame according to an aspect of this disclosure. 
         FIG. 17  is a front view of a valve prosthesis frame according to an aspect of this disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description of a valve prosthesis and valve prosthesis frame 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. 
     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. As used herein the term “distal” is understood to mean downstream to the direction of blood flow. The term “proximal” is intended to mean upstream to the direction of blood flow. 
     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. The base of the valve leaflets is where the leaflet edges attach to the skirt and the valve frame. 
     Referring now to  FIGS. 1-4 , frame  100  is an exemplary aspect of the present invention. Frame  100  includes an inner portion  110 , an outer portion  120 , and connecting arms  130  connecting inner portion  110  to outer portion  120 . Inner portion  110  and outer portion  120  in frame  100  include a plurality of cells that form a cell pattern. The plurality of cells can be different sizes and/or shapes. 
     Inner portion  110  can be configured to be expandable. In one aspect of the invention, inner portion  110  is self-expandable and can be formed of a shape memory alloy such as NITINOL. Other biocompatible metals can also be used. Outer portion  120  can also be formed of a shape memory alloy such as NITINOL, or other biocompatible metals. Inner portion  110  and outer portion  120  can be integrally formed and connected by connecting arms  130 . Connecting arms  130  can also be formed of a shape memory alloy such as NITINOL, or other biocompatible metals. In an alternate aspect of the invention, the inner portion and the outer portion of the frame can comprise separate modular components that are attached to one another, for example as shown in  FIG. 17 . As shown in  FIG. 17 , inner portion  5110  is attached to outer portion  5120  by connections  5130  to form frame  5100 . 
     In one aspect of the invention, inner portion  110  is designed to flex and deform so as to mimic the natural cardiac movements of the heart through the cardiac cycle. In another aspect of the invention, inner portion  110  is designed in a rigid fashion to avoid flexing or deformation during the cardiac cycle. 
     Frame  100  can be attached to valve  200  to form valve prosthesis  10 . Valve  200  can include leaflets  210  and a covering  220 . In one aspect of the invention, covering  220  is a biocompatible fabric or other biocompatible material. In an alternate aspect of the invention, covering  220  can be tissue, for example bovine or porcine pericardium. In one aspect of the invention, valve  200  is connected to frame  100  in inner portion  110 . The object of the present valve prosthesis is to mimic the native valve structure. In one aspect of the invention, valve  200  can be sewn onto inner portion  110  as described in U.S. Patent Application Publication No. 2008/0071368, which is incorporated herein by reference in its entirety. In one aspect of the disclosure, valve  200  can be formed of a biocompatible synthetic material, synthetic polymer, an autograft tissue, xenograft tissue, or other alternative materials. In a further aspect of the invention, valve  200  can be a tri-leaflet bovine pericardium valve, a bi-leaflet valve, or any other suitable valve. 
     Outer portion  120  can be formed in a straight fashion (i.e., cylindrical and parallel to the longitudinal axis of frame  100 ) or in a flared fashion (i.e., diverging away from the longitudinal axis of frame  100 ). In one aspect of the invention, outer portion  120  bulges outward from inner portion  110 . In a further aspect of the invention, outer portion  120  can be an elliptical shape. In a further aspect, the proximal end of outer portion  120  is flared outward. In one aspect of the disclosure, outer portion  120  is wider than the native valve at the native valve annulus. Such a configuration prevents migration of prosthesis  10  into the ventricle and improves sealing of prosthesis  10  against the atrial wall. In an aspect of the invention, outer portion  120  can have an hourglass profile. 
     In one aspect of the invention, inner portion  110  can be approximately 17 mm to approximately 40 mm in diameter. In a further aspect of the invention, outer portion  120  can be approximately 30 mm to approximately 70 mm in diameter. 
     The plurality of cells forming a cell pattern in frame  100  permit frame  100  to adapt to the specific anatomy of the patient, thereby reducing the risk of valve prosthesis migration and reducing the risk of perivalvular leakage. In one aspect of the invention, valve prosthesis  10  is configured to be disposed in the mitral annulus of a patient&#39;s left ventricle. 
     Typically, heart valve prostheses aim to create laminar blood flow through the prosthesis in order to prevent lysis of red blood cells, stenosis of the prosthesis, and other thromboembolic complications. Outer portion  120  is designed to conform to a patient&#39;s anatomy and to anchor valve prosthesis  10  in the patient&#39;s natural valve annulus to prevent lateral movement or migration of valve prosthesis  10  due to normal movement of the heart. 
     Inner portion  110  is configured to be expandable and can be self-expandable. Inner portion  110  can be formed of a shape memory alloy such as NITINOL. Other biocompatible metals can also be used. Outer portion  120  can also be formed of a shape memory alloy such as NITINOL, or other biocompatible metals. Inner portion  110  and outer portion  120  can be integrally formed. In this aspect, inner portion  110  is connected to outer portion  120  with connecting arms  130 . In an alternate aspect of the invention, inner portion  110  and outer portion  120  can comprise separate modular components that are attached to one another. In one aspect of the invention, inner portion  110  is designed to flex and deform so as to mimic the natural cardiac movements of the heart through the cardiac cycle. In another embodiment, inner portion  110  is designed in a rigid fashion to avoid flexing or deformation during the cardiac cycle. 
     In order to deploy valve prosthesis  10  in a patient&#39;s native valve, valve prosthesis  10  can be compacted and loaded onto a delivery device for advancement through a patient&#39;s vasculature. In the collapsed configuration, inner portion  110  and outer portion  120  are positioned in series such that inner portion  110  is adjacent outer portion  120  along the longitudinal axis.  FIGS. 3-4  illustrate the relative positioning between inner portion  110 , outer portion  120  and connecting arms  130  in the collapsed configuration. In the collapsed configuration, inner portion  110  is longitudinally positioned at a first end of frame  100 , outer portion  120  is longitudinally positioned at a second end of frame  100 , and connecting arms  130  are longitudinally positioned between inner portion  110  and outer portion  120 . 
     Frame  100  is shape set such that upon deployment at a patient&#39;s native valve annulus, inner portion  110  moves inside outer portion  120  and remains in that position, as shown in  FIGS. 1-2 and 6 . In an alternate aspect, outer portion  120  moves to surround inner portion  110 . In one aspect of the invention, the entire inner portion  110  is positioned within the interior area of outer portion  120 . As disclosed herein, the interior area is defined as the radial and longitudinal space bounded by an inner diameter and a length of a segment of the frame. In this aspect, the longitudinal length of inner portion  110  is less than or equal to the length of outer portion  120 . In an alternate aspect of the invention, in the expanded configuration, a section of inner portion  110  is positioned within the interior area of outer portion  120  and a second section of inner portion  110  is positioned outside of the interior area of outer portion  120 . In one aspect of the invention, the longitudinal length of inner portion  110  is greater than the longitudinal length of outer portion  120 . In this aspect, longer inner portion  110  can be used with relatively longer valve leaflets so as to increase valve durability as compared to a valve prosthesis with shorter valve leaflets. 
     Positioning inner portion  110  within outer portion  120  reduces the projection distance of frame  100  into the patient&#39;s left ventricle. If the left ventricle of a prosthetic valve is too large, the left ventricle flow tract can become obstructed. This obstruction in turn negatively affects how blood flows through the heart and into the aorta. Therefore, a low left ventricle projection distance is desired, as provided by frame  100 . 
     Referring now to  FIGS. 7-12 , frame  100  can include one or more engagement arms  310 . Engagement arms  310  can be attached to inner portion  110  to anatomically match the native valve leaflets. Upon implantation, outer engagement arms  310  clamp and immobilize the native valve leaflets, and hold the native leaflets close to outer portion  120 . As shown in  FIG. 9 , in one aspect of the disclosure, valve prosthesis  10  can be placed in mitral annulus  410 . Proper seating of valve prosthesis  10  at the mitral annulus  410  is achieved by engagement arms  310  capturing the native mitral valve leaflets. The radial force generated by valve prosthesis  10  in the atrium against engagement arms  310  creates a “sandwich effect” by pinching the native mitral valve leaflets and atrial tissue against outer portion  120  of valve prosthesis  10 . The native mitral valve leaflet acts as a sealing mechanism around valve prosthesis  10 . In addition, engagement arms  310  can add tension onto the native chordae to reduce peri-valvular leakage and increase valve stability. 
     In one aspect of the invention, engagement arms  310  are attached to inner portion  110  at connection  320 . Each engagement arm can include a bend  312 , a horizontal component  314 , and a second bend  316  in order to better match the native valve anatomy. Horizontal component  314  extends engagement arms  310  in the radial direction. In one aspect of the invention as shown in  FIG. 9 , valve prosthesis  10  can include two engagement arms  310  to capture the native valve leaflets. Engagement arms  310  are connected to each other and to inner portion  110  at a common point at connection  320 . 
     In a further aspect of the invention shown in  FIG. 10 , each engagement arm  1310  can be connected to inner portion  1110  at a different point such that frame  1100  includes two connections  1320  for each engagement arm  1310 . Attaching each engagement arm  1310  to frame  1100  at different connections  1320  reduces the tension imparted onto the native chordae by engagement arms  1310 . It is desirable to impart tension onto the native chordae with valve frame engagement arms. However, excessive tension can cause the native chordae to rupture which reduces the effectiveness of the valve prosthesis. 
     In a further aspect of the invention shown in  FIGS. 11-12 , frame  2100  can have engagement arms of varying lengths in the longitudinal direction. This varying length of the engagement arms is provided to accommodate the longer anterior leaflet of the native mitral valve. In this aspect, posterior engagement arm  2312  is shorter in the longitudinal direction than anterior engagement arm  2314 . Posterior engagement arm  2312  and anterior engagement arm  2314  can be connected to frame  2100  at connections  2320  on inner portion  2110 . As shown, a section of inner portion  2110  is within an interior area of outer portion  2120 . 
     Referring now to  FIGS. 13-15 , engagement arms  3310  can include connecting segments  3340  that connect the respective connections  3320  to provide a continuous structure. In this aspect, the continuous engagement arm structure ensures symmetry of engagement arms  3310 , simplifies assembly of engagement arms  3310  onto frame  3100 , and enhances the overall frame strength. Engagement arms  3310  can also include additional struts  3350  that extend between connections  3320  of each engagement arm  3310 . Struts  3350  prevent native valve leaflets from bulging through the engagement arms  3310 . In addition, struts  3350  and connecting segments  3340  can make the resulting valve prosthesis assembly stiffer in the radial direction. The stiffer valve prosthesis is better able to maintain a circular expanded cross section against fluid pressures exerted on the valve prosthesis. Maintaining a circular cross section provides better valve performance and increases the longevity of the valve prosthesis. 
     In a further aspect of the invention, engagement arms  3310 , connecting segments  3340 , and additional struts  3350  can be covered with a covering  3220 . Covering  3220  can be a biocompatible fabric or can be tissue, for example porcine or bovine pericardium. Covering  3220  can prevent the native valve leaflets from bulging through engagement arms  3310 , can reduce metal to metal abrasion between engagement arms  3310  and frame  3100 , and can protect the native chordae from abrasion against engagement arms  3310 . In an alternate aspect of the invention, covering  3220  only covers engagement arms  3310 . 
     In an alternate aspect of the invention shown in  FIG. 16 , engagement arms  4313  can be connected to a connecting segment  4340  and can form a continuous arm structure. Connecting segments  4340  can include a series of struts that extend circumferentially and are geometrically identical in structure to the corresponding struts on frame  4100 . In this aspect, engagement arms  4310  can be connected to connecting segment  4340  at connections  4320 . The continuous arm structure provided by connecting segment  4340  can simplify assembly of the valve prosthesis and enhances the overall strength of frame  4100  in the radial direction. In a further aspect of the invention, engagement arms  4313  and connecting segment  4340  can be covered by a covering (not shown). The covering can be a biocompatible fabric or can be tissue, for example porcine or bovine pericardium. 
     In a further aspect of the invention, engagement arms can be integrally formed into the valve prosthesis frame. 
     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 a delivery device. This frame design requires a loading system to crimp valve prosthesis  10  to the delivery size. 
     The valve prosthesis and inner member can then be loaded into a delivery sheath of conventional design. In one aspect of the invention, valve prosthesis and can be delivered transfemorally. In this aspect, the delivery device and valve prosthesis can be 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, into the left ventricle, and mid-way across the defective mitral valve. Once positioning of the catheter is confirmed, the delivery device can deploy valve prosthesis  10  in the native annulus. 
     As the valve prosthesis expands, it traps the leaflets of the patient&#39;s defective valve against the valve annulus, retaining the native valve in a permanently open state. The outer portion of the valve prosthesis expands against and aligns the prosthesis within the mitral annulus, while the inner portion withdraws into an interior area of the outer portion to reduce the projection of the valve prosthesis into the left ventricle. 
     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. In the transapical procedure, the inner portion of the frame can be inserted first and the outer portion can then be moved distally such that it sits at the mitral annulus. In this configuration, the back pressure of blood flow from the left ventricle won&#39;t cause the inner portion of the frame to be pushed back into its original configuration where the inner portion and outer portion are longitudinally adjacent to each other. 
     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. 
     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.