Patent Publication Number: US-2023147439-A1

Title: Transcatheter pulmonic regenerative valve

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 16/666,319, filed Oct. 28, 2019, now U.S. Pat. No. 11,517,428, which claims the benefit of U.S. Application No. 62/754,102, filed August Nov. 1, 2018, the contents all of which are incorporated by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure is directed to artificial pulmonic valves and applications thereof, more particularly, pulmonic valves constructed of a bioabsorbable frame and regenerative tissue that can integrate with living tissue of a recipient of the artificial valve. 
     BACKGROUND 
     The human heart can suffer from various valvular diseases. These valvular diseases can result in significant malfunctioning of the heart and ultimately require replacement of the native valve with an artificial valve. Additionally, valvular diseases can affect children and adolescents, who are young and still growing and developing. When children or adolescents receive replacement valves, the artificial valves do not grow along with the recipient, as such, the artificial valves must be replaced in children to compensate for the growing heart. There are a number of known artificial valves and a number of known methods of implanting these artificial valves in humans. 
     Various surgical techniques may be used to replace or repair a diseased or damaged valve. Due to stenosis and other heart valve diseases, thousands of patients undergo surgery each year wherein the defective native heart valve is replaced by a prosthetic valve. Another less drastic method for treating defective valves is through repair or reconstruction, which is typically used on minimally calcified valves. The problem with surgical therapy is the significant risk it imposes on these chronically ill patients with high morbidity and mortality rates associated with surgical repair. 
     When the native valve is replaced, surgical implantation of the prosthetic valve typically requires an open-chest surgery during which the heart is stopped and patient placed on cardiopulmonary bypass (a so-called “heart-lung machine”). In one common surgical procedure, the diseased native valve leaflets are excised and a prosthetic valve is sutured to the surrounding tissue at the valve annulus. Because of the trauma associated with the procedure and the attendant duration of extracorporeal blood circulation, some patients do not survive the surgical procedure or die shortly thereafter. It is well known that the risk to the patient increases with the amount of time required on extracorporeal circulation. Due to these risks, a substantial number of patients with defective native valves are deemed inoperable because their condition is too frail to withstand the procedure. By some estimates, more than 50% of the subjects suffering from valve stenosis who are older than 80 years cannot be operated on for valve replacement. 
     Additionally, current artificial valves are static in size and do not grow or adjust to growing bodies. As such, children and adolescents suffering from valvular diseases require multiple procedures to replace artificial valves with larger valves to compensate for the recipient&#39;s growth. Since multiple procedures are required as children and adolescents grow, risks and dangers inherent to replacement processes increase with these individuals. 
     Further, because of the drawbacks associated with conventional open-heart surgery, percutaneous and minimally-invasive surgical approaches are garnering intense attention. In one technique, a prosthetic valve is configured to be implanted in a much less invasive procedure byway of catheterization. For instance, U.S. Pat. Nos. 5,411,522 and 6,730,118, which are incorporated herein by reference in their entireties, describe collapsible transcatheter heart valves that can be percutaneously introduced in a compressed state on a catheter and expanded in the desired position by balloon inflation or by utilization of a self-expanding frame or stent. 
     SUMMARY 
     Artificial heart valves and methods of use in accordance with embodiments of the invention are disclosed. In one embodiment, an implantable artificial heart valve includes a frame having a longitudinal axis extending between an inflow end of the frame and an outflow end of the frame, the inflow end of the frame being configured to receive antegrade blood flowing into the prosthetic valve when implanted, a leaflet structure positioned within the frame and constructed of a regenerative tissue, and an inner skirt positioned around an inner surface of the frame and extending along the longitudinal axis, the inner skirt is constructed of a second regenerative tissue. 
     In some aspects, the techniques described herein relate to a method of implanting an artificial heart valve using a catheter including accessing the vascular system of a patient, advancing a radially expandable artificial heart valve to the pulmonary artery of the patient, where the artificial heart valve is in a radially collapsed configuration and includes a frame having an inflow end portion defining an inflow end of the frame that is configured to receive antegrade blood flow into the artificial heart valve when implanted, and the frame also having an outflow end portion defining an outflow end of the frame opposite the inflow end of the frame, the prosthetic heart valve also including a leaflet structure positioned within the frame, an inner skirt positioned along an inner surface of the frame, where the leaflet structure is constructed of a regenerative tissue, and the inner skirt is constructed of a second regenerative tissue, where the regenerative tissue and the second regenerative tissue are capable of being integrated into native tissue, and where the artificial heart valve is mounted on a delivery apparatus, and delivering the radially expandable artificial heart valve to the pulmonary artery of the patient. 
     In some aspects, the techniques described herein relate to a method, where access to the vascular system of a patient is accomplished percutaneously. 
     In some aspects, the techniques described herein relate to a method, where access to the vascular system of a patient is accomplished by accessing the femoral vein. 
     In some aspects, the techniques described herein relate to a method, where the advancing step is performed by way of the femoral vein, inferior vena cava, tricuspid valve, and right ventricle. 
     In some aspects, the techniques described herein relate to a method, where the delivery apparatus is a catheter. 
     In some aspects, the techniques described herein relate to a method, where the catheter is a balloon catheter including a balloon, where the balloon is deflated, the radially expandable artificial heart valve is positioned over the balloon, and the delivering step is accomplished by inflating the balloon, where the inflating balloon radially expands the radially expandable artificial heart valve. 
     In some aspects, the techniques described herein relate to a method, where the catheter is a sheath catheter including an outer sleeve, the radially expandable artificial heart valve is disposed in the outer sleeve, and the delivering step is accomplished by retracting the outer sleeve, where the retracting sleeve allows the radially expandable artificial heart valve to expand. 
     In some aspects, the techniques described herein relate to a method, where the frame is constructed of a bioabsorbable material. 
     In some aspects, the techniques described herein relate to a method, where the bioabsorbable material is selected from poly(L-lactide), poly(D-lactide), polyglycolide, poly(L-lactide-co-glycolide), polyhydroxyalkanoate, polysaccharides, proteins, polyesters, polyhydroxyalkanoates, polyalkelene esters, polyamides, polycaprolactone, polylactide-co-polycaprolactone, polyvinyl esters, polyamide esters, polyvinyl alcohols, modified derivatives of caprolactone polymers, polytrimethylene carbonate, polyacrylates, polyethylene glycol, hydrogels, photo-curable hydrogels, terminal dials, poly(L-lactide-co-trimethylene carbonate), polyhydroxybutyrate, polyhydroxyvalerate, poly-orthoesters, poly-anhydrides, polyiminocarbonate, and copolymers and combinations thereof. 
     In some aspects, the techniques described herein relate to a method, where the frame further includes a plurality of commissure window frames to allow attachment of the leaflet structure. 
     In some aspects, the techniques described herein relate to a method, where the commissure window frames are constructed of a non-bioabsorbable material, and the frame is constructed of a bioabsorbable material. 
     In some aspects, the techniques described herein relate to a method, where the leaflet structure and inner skirt are constructed of the same regenerative tissue. 
     In some aspects, the techniques described herein relate to a method, where the leaflet structure includes a plurality of leaflets, each leaflet including a body portion having a free outflow edge, two opposing upper tabs extending from opposite sides of the body portion, and two opposing lower tabs, each lower tab extending from the body portion adjacent to a respective upper tab, the lower tabs extending from the body portion at opposite ends of the free outflow edge. 
     In some aspects, the techniques described herein relate to a method, where the lower tabs are folded about radially extending creases that extend radially from the opposite ends of the free outflow edge, such that a first portion of the lower tabs lies flat against the body portion of the respective leaflet, and the lower tabs are folded about axially extending creases such that a second portion of the lower tabs extends in a different plane than the first portion, where the radially extending creases and the axially extending creases are non-parallel. 
     In some aspects, the techniques described herein relate to a method, where the second portion of each lower tab is sutured to a respective upper tab. 
     In some aspects, the techniques described herein relate to a method, where the frame further includes tissue engaging elements to allow fixation of the artificial heart valve to the wall of a blood vessel. 
     In some aspects, the techniques described herein relate to a method, where the tissue engaging elements include a bioabsorbable glue to prevent the tissue engaging elements from expanding and allowing the artificial heart valve to be repositioned. 
     In some aspects, the techniques described herein relate to a method, where the regenerative tissue and second regenerative tissue are selected from polyglactin, collagen, and polyglycolic acid. 
     In some aspects, the techniques described herein relate to a method, where the regenerative tissue further includes extracellular matrix proteins selected from hydroxyproline, vitronectin, fibronectin and collagen type I, collagen type III, collagen type IV, collagen VI, collagen XI, collagen XII, fibrillin I, tenascin, decorin, byglycan, versican, asporin, and combinations thereof. 
     In some aspects, the techniques described herein relate to a method, where the inner skirt extends beyond at least one of the outflow end and inflow end of the frame and forms an outer skirt attached to an outer surface of the frame. 
     In some aspects, the techniques described herein relate to a method, where the frame further includes growth factors to promote integration of the regenerative tissue. 
     In some aspects, the techniques described herein relate to a method, where an outer diameter of the inflow end portion of the frame is smaller than an outer diameter of the outflow end portion of the frame. 
     In some aspects, the techniques described herein relate to a method, where the frame has a plurality of openings and portions of the leaflet structure protrude through the openings while the prosthetic valve is in the radially collapsed configuration. 
     In some aspects, the techniques described herein relate to a method, where the frame is included of a combination of bioabsorbable and non-bioabsorbable materials. 
     In some aspects, the techniques described herein relate to a method, where the regenerative tissue and the second regenerative tissue are capable of being integrated into native tissue. 
     Methods for treatment disclosed herein also encompass methods for simulating treatment, for example, for training and education. Such methods can be performed on any suitable platform, for example, cadavers, portions thereof (e.g., cadaver hearts and/or vasculature), human or non-human; physical models; in silico (e.g., on an anatomic ghost); or in any combination of these platforms. 
     Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the disclosure. A further understanding of the nature and advantages of the present disclosure may be realized by reference to the remaining portions of the specification and the drawings, which forms a part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings where: 
         FIG.  1 A  illustrates a cutaway view of the human heart in a diastolic phase. 
         FIG.  1 B  illustrates a cutaway view of the human heart in a systolic phase. 
         FIGS.  2 A- 2 E  illustrate sectional views of pulmonary arteries demonstrating that pulmonary arteries may have a variety of different shapes and sizes. 
         FIG.  3 A- 3 D  illustrate perspective views of pulmonary arteries demonstrating that pulmonary arteries may have a variety of different shapes and sizes. 
         FIG.  4 A  illustrates a side view an exemplary artificial valve in accordance with certain embodiments of the invention. 
         FIG.  4 B  illustrates a perspective view of an exemplary artificial valve in accordance with certain embodiments of the invention. 
         FIG.  4 C- 4 D  illustrate side views of exemplary artificial valves in accordance with certain embodiments of the invention. 
         FIG.  4 E  illustrates a side view of an exemplary artificial heart valve deployed in a blood vessel in accordance with certain embodiments of the invention. 
         FIGS.  5 A- 5 G  illustrate the assembly of an exemplary leaflet structure in accordance with certain embodiments of the invention. 
         FIGS.  6 A- 6 I  illustrate the assembly of exemplary commissure portions of the leaflet structures in accordance with certain embodiments of the invention. 
         FIGS.  7 A- 7 G  illustrate an exemplary frame of an artificial heart valve in accordance with certain embodiments of the invention. 
         FIGS.  8 A- 8 R  illustrate side views of exemplary tissue engaging elements in accordance with certain embodiments of the invention. 
         FIG.  9 A- 9 D  illustrate an example of the integration of regenerative tissue and the bioabsorption of a bioabsorbable materials of an artificial heart valve in accordance with certain embodiments of the invention. 
         FIG.  10 A  illustrates a cylindrical frame of an artificial heart valve in accordance with certain embodiments of the invention. 
         FIG.  10 B  illustrates an hourglass shaped frame of an artificial heart valve in accordance with certain embodiments of the invention. 
         FIGS.  11 A and  11 B  illustrate possible placement locations in the pulmonary artery of an artificial heart valves in accordance with certain embodiments of the invention. 
         FIG.  12    illustrates a cutaway view of the human heart in a systolic phase showing an exemplary path to implant an artificial heart valve using a catheter in accordance with certain embodiments of the invention. 
         FIG.  13    illustrates an artificial heart valve in a compressed state and mounted on a balloon catheter in accordance with certain embodiments of the invention. 
         FIGS.  14 A and  14 B  illustrate cross-sectional views of exemplary artificial heart valves in compressed states and mounted on catheters in accordance with certain embodiments of the invention. 
         FIGS.  15 A- 15 C  illustrate deployment of an exemplary embodiment of an artificial heart valve using a balloon catheter in accordance with certain embodiments of the invention. 
         FIG.  16 A- 16 E  illustrate deployment of an exemplary embodiment of an artificial heart valve using a sheath catheter in accordance with certain embodiments of the invention. 
     
    
    
     DETAILED DISCLOSURE OF THE INVENTION 
     Turning now to the diagrams and figures, embodiments of the invention are generally directed to artificial heart valves, and applications thereof. Although many embodiments are illustrated as being used within the pulmonary artery, other applications and other embodiments in addition to those described herein are within the scope of the technology, such that the artificial valves may be used in other areas of the anatomy, heart, or vasculature, such as the superior vena cava or the inferior vena cava. Additionally, embodiments of the technology may have different configurations, components, or procedures than those described herein. A person of ordinary skill in the art, therefore, will accordingly understand that the technology can have other embodiments with additional elements, or the technology can have other embodiments without several of the features shown and described below with illustrated in the figures herein. 
     It should be noted that various embodiments of artificial valves and systems for delivery and implant are disclosed herein, and any combination of these options may be made unless specifically excluded. Likewise, the different constructions of artificial valves may be mixed and matched, such as by combining any valve type and/or feature, tissue cover, etc., even if not explicitly disclosed. In short, individual components of the disclosed systems may be combined unless mutually exclusive or otherwise physically impossible. 
     For the sake of uniformity, in these Figures and others in the application the artificial valves are depicted such that the pulmonary bifurcation end is up, while the ventricular end is down. These directions may also be referred to as “distal” as a synonym for up or the pulmonary bifurcation end, and “proximal” as a synonym for down or the ventricular end, which are terms relative to the physician&#39;s perspective. 
       FIGS.  1 A and  1 B  illustrate cutaway views of a human heart H in diastolic ( FIG.  1 A ) and systolic ( FIG.  1 B ) phases. The right ventricle RV and left ventricle LV are separated from the right atrium RA and left atrium LA, respectively, by the tricuspid valve TV and mitral valve MV; i.e., the atrioventricular valves. Additionally, the aortic valve AV separates the left ventricle LV from the ascending aorta (not identified) and the pulmonary valve PV separates the right ventricle from the main pulmonary artery PA. Each of these valves has flexible leaflets extending inward across the respective orifices that come together or “coapt” in the flowstream to form one-way, fluid-occluding surfaces. The artificial valves of the present application are described primarily with respect to the pulmonary valve. Therefore, anatomical structures of the right atrium RA and right ventricle RV will be explained in greater detail. It should be understood that the devices described herein may also be used in other areas, e.g., in the inferior vena cava and/or the superior vena cava as treatment for a regurgitant or otherwise defective tricuspid valve, in the aorta (e.g., an enlarged aorta) as treatment for a defective aortic valve, in other areas of the heart or vasculature, in grafts, etc. 
     The right atrium RA receives deoxygenated blood from the venous system through the superior vena cava SVC and the inferior vena cava IVC, the former entering the right atrium from above, and the latter from below. The coronary sinus CS is a collection of veins joined together to form a large vessel that collects deoxygenated blood from the heart muscle (myocardium), and delivers it to the right atrium RA. During the diastolic phase, or diastole, seen in  FIG.  1 A , the venous blood that collects in the right atrium RA enters the tricuspid valve TV by expansion of the right ventricle RV. In the systolic phase, or systole, seen in  FIG.  1 B , the right ventricle RV contracts to force the venous blood through the pulmonary valve PV and pulmonary arteries into the lungs. In one exemplary embodiment, the devices described by the present application are used to replace or supplement the function of a defective pulmonary valve. During systole, the leaflets of the tricuspid valve TV close to prevent the venous blood from regurgitating back into the right atrium RA. 
     Referring to  FIGS.  2 A- 2 E and  3 A- 3 D , the illustrated, non-exhaustive examples illustrate that the main pulmonary artery can have a wide variety of different shapes and sizes. For example, as shown in the sectional views of  FIGS.  2 A- 2 E  and the perspective views of  FIGS.  3 A- 3 D , the length, diameter, and curvature or contour may vary greatly between main pulmonary arteries of different patients. Further, the diameter may vary significantly along the length of an individual main pulmonary artery. These differences can be even more significant in main pulmonary arteries that suffer from certain conditions and/or have been compromised by previous surgery. For example, the treatment of Tetralogy of Fallot (TOF) or Transposition of the Great Arteries (TGA) often results in larger and more irregularly shaped main pulmonary arteries. 
     Tetralogy of Fallot (TOF) is a cardiac anomaly that refers to a combination of four related heart defects that commonly occur together. The four defects are ventricular septal defect (VSD), overriding aorta (where the aortic valve is enlarged and appears to arise from both the left and right ventricles instead of the left ventricle as in normal hearts), pulmonary stenosis (a narrowing of the pulmonary valve and outflow tract or area below the valve that creates an obstruction of blood flow from the right ventricle to the main pulmonary artery), and right ventricular hypertrophy (thickening of the muscular walls of the right ventricle, which occurs because the right ventricle is pumping at high pressure). 
     Transposition of the Great Arteries (TGA) refers to an anomaly where the aorta and the pulmonary artery are “transposed” from their normal position so that the aorta arises from the right ventricle and the pulmonary artery from the left ventricle. 
     Surgical treatment for some conditions involves a longitudinal incision along the pulmonary artery, up to and along one of the pulmonary branches. This incision can eliminate or significantly impair the function of the pulmonary valve. A trans-annular patch is used to cover the incision after the surgery. The trans-annular patch can reduce stenotic or constrained conditions of the main pulmonary artery PA, associated with other surgeries. However, the trans-annular patch technique can also result in main pulmonary arteries having a wide degree of variation in size and shape (See  FIGS.  3 A- 3 D ). The impairment or elimination of the pulmonary valve PV can create significant regurgitation and, prior to the present invention, often required later open heart surgery to replace the pulmonary valve. 
     Turning to  FIGS.  4 A- 4 D , embodiments of the invention are illustrated. The illustrated valves are adapted to be implanted in the main pulmonary artery of a patient, although in other embodiments these embodiments can be adapted to be implanted in the other blood vessels, including the aorta and various native annuluses of the heart. The artificial valves  10  illustrated in  FIGS.  4 A- 4 E  are illustrated to show the inflow end at the bottom of the figure with an outflow end at the top of the figure, thus forming a longitudinal axis between the inflow and outflow ends of the artificial valves  10 . The inflow end is configured to receive antegrade blood flowing through circulatory system of a patient. In various embodiments, an artificial valve  10  comprises: a stent, or frame,  12 , a leaflet structure  14 , and an inner skirt  16 . In some embodiments, the inner skirt  16  extends the full length of the frame  12  along the longitudinal axis of the artificial valve  10 , such as illustrated in  FIGS.  4 A and  4 B . However, in additional embodiments, such as illustrated in  FIG.  4 C , the tissue forming the inner skirt  16  may be longer than the frame  12  and can be wrapped over one or both ends of the frame  12  to form an outer skirt  18 , thus reducing or eliminating exposure of the frame  12 , when placed into the pulmonary trunk. Further embodiments may comprise various means to secure the artificial valve  10  in the pulmonary trunk of the patient. In some embodiments, such as illustrated in  FIG.  4 D , the securing means will be tissue engaging elements  170  protruding from the frame  12 . These tissue engaging elements  170  can hold the frame  12  of the artificial valve  10  in place in the blood vessel of the patient. 
     Various embodiments of the artificial heart valve  10  are designed to be expandable, such that the frame  12  can be compressed into a collapsed configuration. As illustrated in  FIGS.  4 A- 4 E , various embodiments of an expandable, artificial heart valve by including a frame formed with angled struts to form a honeycomb-like structure. Additional details on expandable structures will be described below. 
     In some embodiments of the artificial heart, the materials used to construct these various elements can be permanent or stable to allow the removal and/or replacement of the artificial heart valve. In other embodiments, the materials used to construct these various elements can be chosen to allow the components to integrate with the body; for example, the tissue used for the skirt and/or leaflets may be regenerative tissue, which a body can integrate into the native blood vessel. Additionally, at least a portion of the frame of some embodiments can be selected from bioabsorbable materials to allow the degradation of the frame. Further embodiments may use both bioabsorbable materials for the frame and regenerative tissue for the leaflets and/or skirt, may allow the artificial heart valve to completely integrate and grow with a person&#39;s body. Details regarding materials and methods of construction of the various components described above will be described below. It should also be noted that various embodiments may use any combination of the above elements as the need arises to be effective in replacing the valve in a patient. 
       FIG.  4 B  illustrates a perspective view of the outflow end of an artificial valve  10  of some embodiments. As shown in  FIG.  4 B , some embodiments possess a leaflet structure  14 , which comprises three leaflets  40 , which can be arranged to collapse in a tricuspid arrangement, although additional embodiments can have a greater or fewer number of leaflets  40 . In various embodiments, individual leaflets  40  are joined at commissures  122 . In some embodiments, these commissures  122  may be sewn to the inner skirt  16 , while other embodiments may pass commissures  122  through commissure window frames  30  in order to attach the leaflet structure  14  to the frame  12 . Alternatively, certain embodiments may secure commissures  122  to both the inner skirt  16  and the frame  12  by sewing the commissures  122  to the inner skirt  16  and passing commissures  122  through commissure window frames  30 . Additional details on joining leaflets and commissures will be described in detail below. 
     In additional embodiments, the inner skirt  16  is secured to the frame  12  by suturing. Suturing the inner skirt  16  to the frame  12  can be done as the only means of securing the inner skirt  16  to the frame  12 , or suturing the inner skirt  16  to the frame  12  can be done in combination with securing the inner skirt  16  with the frame  12  using the commissure  122  of the leaflet structure  14 . Suturing the inner skirt  16  to the frame  12  can be done by means known in the art, such that the inner skirt  16  is secured to the frame  12  and can allow expansion of the artificial valve  10  in some embodiments. Such suturing methods are described in U.S. Pat. No. 9,393,110, the disclosure of which is incorporated herein by reference in its entirety. 
     As illustrated in  FIG.  4 B , the lower edge of leaflet structure  14  of various embodiments desirably has an undulating, curved scalloped shape (suture line  154  shown in  FIG.  4 A  tracks the scalloped shape of the leaflet structure). By forming the leaflets with this scalloped geometry, stresses on the leaflets are reduced, which in turn improves the durability of the valve. Moreover, by virtue of the scalloped shape, folds and ripples at the belly of each leaflet (the central region of each leaflet), which can cause early calcification in those areas, can be eliminated or at least minimized. The scalloped geometry also reduces the amount of tissue material used to form the leaflet structure  14 , thereby allowing a smaller, more even crimped profile at the inflow end of the valve. The leaflets  40  can be formed of various natural or synthetic materials, including pericardial tissue (e.g., bovine pericardial tissue), biocompatible synthetic materials, or various other suitable natural or synthetic materials as known in the art and described in U.S. Pat. No. 6,730,118, which is incorporated by reference herein in its entirety. In additional embodiments, the leaflets  40  and leaflet structure  14  can be formed of regenerative tissue to allow integration of the leaflets into the tissue of the patient. Details regarding the use and manufacture of regenerative tissue are described below. 
     A deployed artificial valve  10  according to some embodiments is illustrated in  FIG.  4 E . In this figure the artificial valve  10  has been placed in a blood vessel  900 , such as the main pulmonary artery, of a patient. The frame  12  contacts portions of the blood vessel wall  902  at points P. Points Pin some embodiments will include tissue engaging elements  170  as describe above. In some embodiments, inner skirt  16 , or in additional embodiments, the outer skirt  18 , can contact the blood vessel wall  902  to form a tissue contact, which may encourage the integration of regenerative tissue used in the valve construction, including the inner skirt  16 , outer skirt  18 , and leaflets (not shown). 
     Turning now to  FIGS.  5 A- 5 G , the construction of a leaflet structure is detailed in accordance with various embodiments. As best shown in  FIG.  5 A , each leaflet  40  in the illustrated configuration has an upper (outflow) free edge  110  extending between opposing upper tabs  112  on opposite sides of the leaflet. Below each upper tab  112  there is a notch  114  separating the upper tab from a corresponding lower tab  116 . The lower (inflow) edge portion  108  of the leaflet extending between respective ends of the lower tabs  116  includes vertical, or axial, edge portions  118  on opposites of the leaflets extending downwardly from corresponding lower tabs  116  and a substantially V-shaped, intermediate edge portion  120  having a smooth, curved apex portion  119  at the lower end of the leaflet and a pair of oblique portions  121  that extend between the axial edge portions and the apex portion. In some embodiments, the oblique portions can have a greater radius of curvature than the apex portion. In various other embodiments, each leaflet  40  can have a reinforcing strip  72  secured (e.g., sewn) to the inner surface of the lower edge portion  108 , as shown in  FIG.  5 B . 
     In embodiments, the leaflets  40  can be secured to one another at their adjacent sides to form commissures. A plurality of flexible connectors  124  (one of which is shown in  FIG.  5 C ) can be used to interconnect pairs of adjacent sides of the leaflets and to mount the leaflets to the frame of various embodiments. The flexible connectors  124  can be made from natural or synthetic materials, such as regenerative tissue as described below or a piece of woven PET fabric. It should be noted that other synthetic and/or natural materials can be used. Each flexible connector  124  can include a wedge  126  extending from the lower edge to the upper edge at the center of the connector. The wedge  126  can comprise a non-metallic material, such as, but not limited to, rope, thread, suture material, or a piece of regenerative tissue, secured to the connector with a temporary suture  128 . In various embodiments, the wedge  126  helps prevent rotational movement of the leaflet tabs once they are secured to the frame of certain embodiments. The connector  124  can have a series of inner notches  130  and outer notches  132  formed along its upper and lower edges. 
       FIG.  5 D  shows embodiments where the adjacent sides of two leaflets  40  are interconnected by a flexible connector  124 . In such embodiments, the opposite end portions of the flexible connector  124  can be placed in an overlapping relationship with the lower tabs  116  with the inner notches  130  aligned with the vertical edges of the tabs  116 . Each tab  116  can be secured to a corresponding end portion of the flexible connector  124  by suturing along a line extending from an outer notch  132  on the lower edge to an outer notch  132  on the upper edge of the connector. Three leaflets  40  can be secured to each other side-to-side using three flexible connectors  124 , as shown in  FIG.  5 E . 
     Referring now to  FIGS.  5 F and  5 G , in various embodiments the adjacent sub-commissure portions  118  of two leaflets can be sutured directly to each other. In the example shown, suture material is used to form in-and-out stitches  133  and comb stitches  134  that extend through the sub-commissure portions  118  and the reinforcing strips  72  on both leaflets. The two remaining pairs of adjacent sub-commissure portions  118  can be sutured together in the same manner to form the assembled leaflet structure  14 , which can then be secured to a frame in the following manner. 
       FIGS.  6 A- 6 G  show embodiments of one specific approach for securing the commissure portions  122  of the leaflet structure  14  to the commissure window frames  30  of the frame. First, as shown in  FIG.  6 A , the flexible connector  124  securing two adjacent sides of two leaflets  40  is folded widthwise and the upper tab portions  112  are folded downwardly against the flexible connector  124 . As shown in  FIGS.  6 A and  6 B , each upper tab portion  112  is creased lengthwise (vertically) to assume an L-shape having an inner portion  142  folded against the inner surface of the leaflet and an outer portion  144  folded against the connector  124 . The outer portion  144  can then be sutured to the connector  124  along a suture line  146 . Next, as shown in  FIG.  6 B , the commissure tab assembly (comprised of a pair of lower tab portions  116  connected by connector  124 ) is inserted through the commissure window frame  30 .  FIG.  6 C  is a side view of the artificial valve  10  showing the commissure tab assembly extending outwardly through the commissure window frame  30 . 
       FIGS.  6 D- 6 G  illustrate a method to secure commissures to a frame according to some embodiments. In particular,  FIG.  6 D  shows a cross-sectional view of a portion of the frame and leaflet structure showing the adjacent tab portions of two leaflets secured to a corresponding commissure window frame  30 , while  FIGS.  6 E- 6 G  illustrate perspective views of a portion of the frame and leaflet structure showing the adjacent tab portions of two leaflets secured to a corresponding commissure window frame  30 . As shown in  FIGS.  6 D and  6 E , the commissure tab assembly is pressed radially inwardly at the wedge  126  such that one of the lower tab portions  116  and a portion of the connector  124  is folded against the frame  12  on one side of the commissure window frame  30  and the other lower tab portion  116  and a portion of the connector  124  is folded against the frame  12  on other side of the commissure window frame  30 . A pair of suture lines  148  are formed to retain the lower tab portions  116  against the frame  12  in the manner shown in  FIG.  6 D . Each suture line  148  extends through connector  124 , a lower tab portion  116 , the wedge  126 , and another portion of connector  124 . Then, as shown in  FIGS.  6 D and  6 F , each lower tab portion  116  is secured to a corresponding upper tab portion  112  with a primary suture line  150  that extends through one layer of connector  124 , the lower tab portion  116 , another layer of connector  124 , another layer of connector  124 , and the upper tab portion  112 . Finally, as shown in  FIGS.  6 D and  6 G , the suture material used to form the primary suture line  150  can be used to further form whip stitches  152  at the edges of the tab portions  112 , 116  that extend through two layers of connector  124  sandwiched between upper tab portions  112  and lower tab portions  116 . 
     As shown in  FIGS.  6 A and  6 D , in embodiments, the folded down upper tab portions  112  form a double layer of leaflet material at the commissures. The inner portions  142  of the upper tab portions  112  are positioned flat and abutting the layers of the two leaflets  40  forming the commissures, such that each commissure comprises four layers of leaflet material just inside of the commissure window frames  30 . This four layered portion of the commissures can be more resistant to bending, or articulating, than the portion of the leaflets  40  just radially inward from the relatively more rigid four layered portion. This causes the leaflets  40  to articulate primarily at inner edges  143  of the folded-down inner portions  142  in response to blood flowing through the valve during operation within the body, as opposed to articulating about the axial struts of the commissure window frames  30 . Because the leaflets articulate at a location spaced radially inwardly from the commissure window frames  30 , the leaflets can avoid contact with and damage from the frame. However, under high forces, the four layered portion of the commissures can splay apart about a longitudinal axis  145  ( FIG.  6 D ) adjacent to the commissure window frame  30 , with each inner portion  142  folding out against the respective outer portion  144 . For example, this can occur when an artificial valve is compressed and mounted onto a delivery shaft, allowing for a smaller crimped diameter. The four layered portion of the commissures can also splay apart about axis  145  when the balloon catheter is inflated during expansion of the valve, which can relieve some of the pressure on the commissures caused by the balloon and so the commissures are not damaged during expansion. 
     Additional embodiments may be used to secure the commissures by other methods.  FIGS.  6 H and  6 I  illustrate cross-sectional views of embodiments of commissures that utilize different methods to secure the commissures to a frame of certain embodiments. Specifically,  FIG.  6 H  illustrates a commissure tab assembly passing through a commissure window frame  30  and pressed radially inwardly at the wedge  126  such one lower tab portion  116  and a portion of the connector  124  is folded against the inner skirt  16  on one side of the commissure window frame  30 . A pair of suture lines  148  are formed to retain the lower tab portions  116  against the inner skirt  16 . Each suture line  148  extends through connector  124 , a lower tab portion  116 , the wedge  126 , and another portion of connector  124 . Then, each lower tab portion  116  is secured to the inner skirt  16  with a primary suture line  150  that extends through one layer of connector  124 , the lower tab portion  116 , another layer of connector  124 , and the inner skirt  16 . Additional suture lines  156  may be applied to the connector-tab-skirt assembly to provide additional strength and/or secure extra tissue that may be present. 
       FIG.  6 I  illustrates embodiments where the commissure tab assembly passes through an inner skirt  16  and presses radially inwardly at the wedge  126  such that the commissure tab assembly attaches to the inner skirt and does not attach to a frame. In such embodiments, each lower tab portion  116  is secured to the inner skirt  16  with a primary suture line  150  that extends through one layer of connector  124 , the lower tab portion  116 , another layer of connector  124 , and the inner skirt  16 . A pair of suture lines  148  may also be present to retain the lower tab portions  116  against the inner skirt  16 . Each suture line  148  extends through connector  124 , a lower tab portion  116 , the wedge  126 , and another portion of connector  124 . In some embodiments, each suture line  148  may further extend through the inner skirt  16 . Then, additional suture lines  156  may be applied to the connector-tab-skirt assembly to provide additional strength and/or secure extra tissue that may be present. 
     In various embodiments, after all commissure tab assemblies are secured to respective commissure windows, the lower edges of the leaflets  40  between the commissure tab assemblies can be sutured to the inner skirt  16 . Details on stitching leaflets to the inner skirt of an artificial valve can be found in U.S. Pat. No. 9,393,110 to Levi et al., the disclosure of which is incorporated herein by reference in its entirety. 
     In various embodiments, the tissue utilized for the inner skirt and leaflet structure, including leaflets, is regenerative tissue, such that the artificial valve will integrate into the body of the individual receiving the artificial valve. Suitable materials will allow the patient&#39;s body to fully integrate the material, such that the material will continue growing with the body of the patient. Such material will allow the valvular structure and skirt to grow in a concomitant manner as the patient&#39;s heart grows such that replacement is not required. Regenerative materials may include decellularized tissue from a natural source, which may require ligation of branching blood vessels. Alternatively, some embodiments will use an artificial construct to form the regenerative tissue, which are engineered and may not require steps to ligate portions. Examples of artificial tissue constructs include, but are not limited to tissue generated from polyglactin, collagen, and polyglycolic acid, which are formed into scaffolds or constructs. In some embodiments using artificial constructs, the artificial constructs include extracellular matrix proteins to allow integration of the tissue. Examples of regenerative tissue and methods of constructing these materials can be found in U.S. Pat. No. 6,666,886 to Tranquillo et al. and U.S. Pat. No. 9,657,265 to Dahl et al., the disclosures of which are incorporated herein by reference in their entireties. 
     In embodiments using polyglycolic acid scaffolds, the polyglycolic acid scaffolds are bioabsorbable and the extracellular matrix proteins will allow seeding of the host&#39;s tissue in order to incorporate the regenerative tissue into the patient&#39;s body. Examples of suitable extracellular matrix proteins include, but are not limited to, hydroxyproline, vitronectin, fibronectin and collagen type I, collagen type III, collagen type IV, collagen VI, collagen XI, collagen XII, fibrillin I, tenascin, decorin, byglycan, versican, asporin, and combinations thereof. In some embodiments, polyglycolic acid scaffolds will include the extracellular matrix proteins within the scaffold, while in other embodiments, extracellular matrix proteins will cover the polyglycolic acid scaffolds with extracellular matrix proteins. In yet further embodiments, the extracellular matrix proteins will be both within the polyglycolic acid scaffold and coating the polyglycolic acid scaffolds. 
     In certain embodiments, the skirt will merge with the pulmonary trunk tissue and provide an anchor point for the leaflets and provide structural support for the valve. Various embodiments will use different regenerative tissues for the skirt and the leaflets to provide an improved integration of the tissue. Such combinations may improve the flexibility of the leaflets, while maintaining more rigidity or strength in the skirt, which incorporates as a blood vessel wall. 
     Referring to  FIGS.  7 A and  7 B , a frame  12  in accordance with certain embodiments is shown. The frame  12  in the illustrated embodiment comprises a first, lower row I of angled struts  22  arranged end-to-end and extending circumferentially at the inflow end of the frame; a second row II of circumferentially extending, angled struts  24 ; a third row III of circumferentially extending, angled struts  26 ; a fourth row IV of circumferentially extending, angled struts  28 ; and a fifth row V of circumferentially extending, angled struts  32  at the outflow end of the frame. A plurality of substantially straight axially extending struts  34  can be used to interconnect the struts  22  of the first row I with the struts  24  of the second row II. The fifth row V of angled struts  32  are connected to the fourth row IV of angled struts  28  by a plurality of axially extending window frame portions  30  (which define the commissure windows  20 ) and a plurality of axially extending struts  31 . Each axial strut  31  and each frame portion  30  extends from a location defined by the convergence of the lower ends of two angled struts  32  to another location defined by the convergence of the upper ends of two angled struts  28 .  FIGS.  7 C- 7 G  are enlarged views of the portions of the frame  12  identified by letters A, B, C, D and E, respectively, in  FIG.  7 B . 
     In accordance with many embodiments, each commissure window frame portion  30  mounts to a respective commissure of the leaflet structure  14 . As can be seen each frame portion  30  is secured at its upper and lower ends to the adjacent rows of struts to provide a robust configuration that enhances fatigue resistance under cyclic loading of the valve compared to known cantilevered struts for supporting the commissures of the leaflet structure. This configuration enables a reduction in the frame wall thickness to achieve a smaller crimped diameter of the valve. In particular embodiments, the thickness T of the frame  12  ( FIG.  7 A ) measured between the inner diameter and outer diameter is about 0.48 mm or less. 
     The struts and frame portions of the frame collectively define a plurality of open cells of the frame. At the inflow end of the frame  12 , struts  22 , struts  24 , and struts  34  define a lower row of cells defining openings  36 . The second, third, and fourth rows of struts  24 ,  26 , and  28  define two intermediate rows of cells defining openings  38 . The fourth and fifth rows of struts  28  and  32 , along with frame portions  30  and struts  31 , define an upper row of cells defining openings  40 . The openings  40  are relatively large as compared to intermediate openings  38  and/or lower openings  36  and are sized to allow portions of the leaflet structure  14  to protrude, or bulge, into and/or through the openings  40  when the frame  12  is crimped in order to minimize the crimping profile. 
     As best shown in  FIG.  7 D , in various embodiments the lower end of the strut  31  is connected to two struts  28  at a node or junction  44 , and the upper end of the strut  31  is connected to two struts  32  at a node or junction  46 . In some embodiments, the strut  31  can have a thickness S 1  that is less than the thicknesses S 2  of the junctions  44  and  46 . The advantage of this differential thickness is illustrated below in  FIGS.  14 A- 14 B  showing a portion of the frame  12  in a crimped state. 
     In many embodiments, the frame  12  is configured to prevent or at least minimize possible over-expansion of the valve at a predetermined balloon pressure, especially at the outflow end portion of the frame, which supports the leaflet structure  14 . In one aspect, the frame is configured to have relatively larger angles  42   a ,  42   b ,  42   c ,  42   d ,  42   e  between struts. The larger the angle, the greater the force required to open (expand) the frame. When the frame  12  is in its compressed state (e.g., mounted on a balloon). The vertical distance between the ends of the struts is greatest when the frame is compressed, providing a relatively large moment between forces acting on the ends of the strut in opposite directions upon application of an opening force from inflation of the balloon (or expansion of another expansion device). When the frame expands radially, the vertical distance between the ends of the strut decreases. As the vertical distance decreases, so does the moment between forces. Hence, it can be seen that a relatively greater expansion force is required as the vertical distance and the moment between the ends of the strut decreases. Moreover, strain hardening (stiffening) at the ends of the strut increases as the frame expands, which increases the expansion force required to induce further plastic deformation at the ends of the strut. As such, in various embodiments, the angles between the struts of the frame can be selected to limit radial expansion of the frame at a given opening pressure (e.g., inflation pressure of the balloon). In particular embodiments, these angles are at least 110 degrees or greater when the frame is expanded to its functional size, and even more particularly these angles are at least 120 degrees or greater when the frame is expanded to its functional size. 
     Also, as can be seen in  FIG.  7 B , in some embodiments, the openings  36  of the lowermost row of openings in the frame are relatively larger than the openings  38  of the two intermediate rows of openings. This configuration allows the frame, when crimped, to assume an overall tapered shape that tapers from a maximum diameter at the outflow end of the valve to a minimum diameter at the inflow end of the valve. When crimped, the frame  12  has a reduced diameter region extending along a portion of the frame adjacent the inflow end of the frame. The diameter of the lower portion region is reduced compared to the diameter of the upper portion of the frame. When the valve is deployed, the frame can expand to the cylindrical shape shown in  FIG.  7 A . 
     In some embodiments, the frame may be constructed of a material, such that the frame remains intact in the body when introduced, while other embodiments may be constructed of materials that are bioabsorbable, such that the frame eventually degrades in the body. Materials which can be used to construct the frame are discussed in detail below. When constructed of a plastically-expandable material, the frame  12  (and thus the valve  10 ) can be crimped to a radially compressed state on a delivery catheter and then expanded inside a patient by an inflatable balloon or equivalent expansion mechanism. When constructed of a self-expandable material, the frame  12  (and thus the valve  10 ) can be crimped to a radially compressed state and restrained in the compressed state by insertion into a sheath or equivalent mechanism of a delivery catheter. Once inside the body, the valve can be advanced from the delivery sheath, which allows the valve to expand to its functional size. 
     As noted above, in various embodiments, the frame  12  will include tissue engaging elements  170  to secure the artificial valve  10  to the blood vessel of a patient.  FIGS.  8 A- 8 R  illustrate various possible tissue engaging elements that may be placed on frame  12 . In the embodiment of  FIG.  8 A , the tissue engaging element  170  comprises a shaft  450  formed with a diamond-shaped window  451  near its distal tip  452 , which can be sharp enough to penetrate tissue. In such embodiments, the shape may be set so that window  451  is biased toward being open in an expanded configuration as shown in  FIG.  8 A . Prior to delivery of the device, window  451  may be pinched closed and a bioabsorbable glue  455  may be injected into window  451  to hold it in a closed configuration as shown in  FIG.  8 B . Upon deployment of the device, the distal tip  452  can penetrate the native tissue, e.g. blood vessel wall, as shown in  FIG.  8 C . The glue  455  within window  451  maintains it in a closed configuration for a period of time to allow the operator to reposition or remove the device if necessary. If left in position, the glue  455  erodes, allowing the window  451  to reopen into the expanded configuration which will retain the tissue engaging element  170  in the tissue as shown in  FIG.  8 D . 
     In the embodiment shown in  FIGS.  8 E- 8 H , the tissue engaging element  170  comprises an arrowhead-shaped tip  453  having two or more wings  454  biased to be angled radially outward and pointing in a proximal direction as shown in  FIG.  8 E . A bioabsorbable glue or coating  455  can be applied over the arrowhead tip  453  to hold the wings  454  in a radially contracted configuration as shown in  FIG.  8 F . In the contracted configuration, the device  100  is deployed such that the tissue engaging element  170  pierces the native tissue as shown in  FIG.  8 G . The bioabsorbable coating  455  then erodes gradually until it allows the wings  454  to return to the laterally expanded configuration shown in  FIG.  8 H , thus retaining the tissue engaging element  170  in the tissue. 
     A further embodiment is shown in  FIGS.  8 I- 8 L . In this embodiment, the tissue engaging element  170  comprises a helical tip  456  in an unbiased state. A bioabsorbable coating  455  may be used to retain the helical tip  456  in a straightened configuration as shown in  FIG.  8 J . The tissue engaging element  170  can penetrate the tissue in the contracted configuration, and when the bioabsorbable coating  455  erodes sufficiently to allow the helical tip  456  to return to its deployed configuration, the tissue engaging element  170  can be retained in the tissue. 
       FIGS.  8 M- 8 R  are enlarged side views of embodiments of additional tissue engaging elements that can be incorporated on various device structures (referred collectively as “ST”), such struts, connectors, posts, arms, and/or ribs which may be incorporated into device features, such as the anchoring member no or valve support  120 . For example, the additional tissue engaging elements may comprise one or more cut-out protrusions  350  ( FIGS.  8 M and  8 N ) in place of or in addition to tissue engaging elements  170 . In a collapsed or straightened configuration, as shown by the side view of  FIG.  8 O , cut-out protrusion  350  maintains low relief relative to the surface of structure ST to maintain a low profile during delivery. As the device  100  expands and structure ST changes to its deployed configuration (e.g. a curvature as shown in  FIG.  8 P ), the protrusion separates from the ST to a higher relief. The protrusion  350  may also be configured to grab subannular tissue, pulling the cut-out protrusions even farther away from structure ST. The device structures ST may also be shaped to include sharp protrusions  352  along one or more of its edges or faces, as illustrated in  FIG.  8 Q , or may also include pointed scale-like protrusions  354 , as shown in  FIG.  8 R . 
     Suitable plastically-expandable materials that can be used to form a transcatheter frame  12  and tissue engaging elements  170  that remains intact in a body in accordance with various embodiments include, without limitation, stainless steel, a nickel based alloy (e.g., a cobalt-chromium or a nickel-cobalt-chromium alloy), Nitinol, certain polymers, or combinations thereof. In particular embodiments, frame  12  is made of a nickel-cobalt-chromium-molybdenum alloy, such as MP35N® alloy (SPS Technologies, Jenkintown, Pa.), which is equivalent to UNS R30035 alloy (covered by ASTM F562-02). MP35N®/1TNS R30035 alloy comprises 35% nickel, 35% cobalt, 20% chromium, and 10% molybdenum, by weight. 
     However, some embodiments possess bioabsorbable frames and tissue engaging elements which may be constructed of suitable materials including, without limitation, poly(L-lactide) (PLLA), poly(D-lactide) (PDLA), polyglycolide (PGA), poly(L-lactide-co-glycolide) (PLGA), polyhydroxyalkanoate (PHA), polysaccharides, proteins, polyesters, polyhydroxyalkanoates, polyalkelene esters, polyamides, polycaprolactone, polylactide-co-polycaprolactone, polyvinyl esters, polyamide esters, polyvinyl alcohols, modified derivatives of caprolactone polymers, polytrimethylene carbonate, polyacrylates, polyethylene glycol, hydrogels, photo-curable hydrogels, terminal dials, poly(L-lactide-co-trimethylene carbonate), polyhydroxybutyrate; polyhydroxyvalerate, poly-orthoesters, poly-anhydrides, polyiminocarbonate, and copolymers and combinations thereof. 
     Additionally, some embodiments with bioabsorbable frames will be reinforced with reinforcing compositions. Reinforcing compositions for bioabsorbable frames can include magnesium and magnesium alloys. Magnesium and its alloys are biocompatible, bioabsorbable and easy to mechanically manipulate presenting an attractive solution for reinforcing bioabsorbable polymer stents. Radiological advantages of magnesium include compatibility with magnetic resonance imaging (MRI), magnetic resonance angiography and computed tomography (CT). Vascular stents comprising magnesium and its alloys are less thrombogenic than other bare metal stents. The biocompatibility of magnesium and its alloys stems from its relative non-toxicity to cells. Magnesium is abundant in tissues of animals and plants, specifically Mg is the fourth most abundant metal ion in cells, the most abundant free divalent ion and therefore is deeply and intrinsically woven into cellular metabolism. Magnesium-dependent enzymes appear in virtually every metabolic pathway is also used as a signaling molecule. Magnesium alloys which are bioabsorbable and suitable for reinforcing bioabsorbable polymer stents include alloys of magnesium with other metals including, but not limited to, aluminum and zinc. In one embodiment, the magnesium alloy comprises between about 1% and about 10% aluminum and between about 0.5% and about 5% zinc. 
     The magnesium alloys of the present invention include but are not limited to Sumitomo Electronic Industries (SEI, Osaka, Japan) magnesium alloys AZ31 (3% aluminum, 1% zinc and 96% magnesium) and AZ61 (6% aluminum, 1% zinc and 93% magnesium). The main features of the alloy include high tensile strength and responsive ductility. Tensile strength of typical AZ31 alloy is at least 280 MPa while that of AZ61 alloy is at least 330 MPa. 
     Reinforcing bioabsorbable polymeric materials with bioabsorbable magnesium materials can be accomplished with one of the methods including, but not limited to, the use of bioabsorbable magnesium wire, magnesium fibers either wound around or within a polymeric stent or impregnated within a bioabsorbable polymeric frame. 
     In certain embodiments, the specific material used for the frame and tissue engaging elements is chosen to allow absorption of the frame by the body of the patient undergoing valve replacement. The absorption properties of these materials may be selected based on time a body absorbs or incorporates the particular material. Thus, different materials or combinations of materials may be used to ensure that the frame dissolves after regenerative tissue integrates with the patient&#39;s tissue. As such, if integration of the tissue occurs in less than one year, then frame materials that will hold the valve&#39;s integrity for more than one year will be desirable. For example, if integration of the regenerative tissue occurs in a 6-12 month time frame, the frame should hold its integrity for at least one year and be fully absorbed by the body over the period of 3, 6, 9, or 12 months. Thus, at the end of 24 months, the artificial valve will be fully integrated into the body with very little or no remnants of the frame remaining. 
       FIGS.  9 A- 9 D  illustrate an example of the process of integration and absorption of the frame.  FIG.  9 A  illustrates an embodiment of an artificial valve  10  implanted in the pulmonary trunk of a patient. As seen in this figure, the frame  12  is intact and the inner skirt tissue has not integrated with the patient&#39;s tissue. In  FIG.  9 B , the tissue portions, including the inner skirt  16 , has integrated with the patient&#39;s tissue, while the frame is still present to provide support for the artificial valve  10  during this process.  FIGS.  9 C and  9 D  illustrate a full integration of the artificial valve  10 , where the tissue has integrated and the frame has been absorbed. 
     Further, some embodiments will utilize a combination of non-bioabsorbable materials and bioabsorbable materials in the frame. Using a combination of bioabsorbable and non-bioabsorbable materials will allow some parts of the frame to degrade, while certain portions will remain intact in the body of the patient to continue to provide support over time. Certain embodiments are made of a bioabsorbable frame comprising non-bioabsorbable commissure windows. In embodiments having non-bioabsorbable commissure windows and a bioabsorbable frame, the frame will degrade over time, but the commissure windows will remain permanent in the body to provide additional support to the leaflets by permanently securing the commissures of the valvular structure.  FIG.  9 D  illustrates an embodiment where the tissue has fully integrated with the patient&#39;s body, the frame has been absorbed, and the commissure window frames  30  are made of a non-bioabsorbable material and remain present in the body after the frame has been fully absorbed. 
     Additional embodiments will include growth factors in the frame and tissue engaging elements. Growth factors can stimulate or promote the integration of the regenerative tissue with the patient. Examples of growth factors that can be used in embodiments include, but are not limited to, transforming growth factor alpha (TGF-alpha), transforming growth factor beta (TGF-beta), basic fibroblast growth factor (bFGF), vascular epithelial growth factor (VEGF), and combinations thereof. In certain embodiments, growth factors are incorporated within the frame material, while some embodiments have the growth factors coating the frame material. In additional embodiments, the growth factors are both incorporated in the frame material and coating the frame material. The growth factors can be formulated to release over time or may release as the frame degrades during the bioabsorption process. 
     Although specific artificial valve shapes have been shown in Figures thus far, it will be understood that these shapes may vary depending on the specific application. Turning now to  FIGS.  10 A and  10 B , various exemplary shapes of artificial valves in accordance with embodiments are illustrated. As illustrated above and in  FIG.  10 A , frames can be cylindrical in nature in order to fit in the pulmonary trunk of a patient. Cylindrical frames may be suitable for placement in a blood vessel at a point away from the native valve, such that the artificial valve supplements a faulty or defective valve in the patient. However, some embodiments will utilize an hourglass-shaped frame for the artificial valve, as illustrated in  FIG.  10 B . Hourglass frames may provide certain advantages for artificial valves, such that an hourglass-shaped valve may be placed at the native position of the valve. In this way, and hourglass valve may replace the native valve rather than supplement the valve. The hourglass valve accomplishes this task by being placed at a position where waist of the hourglass frame provides space for the native valve flaps. 
     Examples of the placement of the artificial valve  10  in the main pulmonary artery PA are illustrated in  FIGS.  11 A- 11 B . In  FIGS.  11 A- 11 B , a cutaway of a heart H is shown in the systolic phase. When the heart is in the systolic phase, the pulmonic valve (not shown) opens, and blood flows from the right ventricle RV and through the pulmonary artery PA.  FIG.  11 A  illustrates the position of an artificial valve  10  deployed downstream of the native pulmonic valve, in accordance with various embodiments. In  FIG.  11 B , the artificial valve  10  of some embodiments is deployed at the site of the pulmonic valve, thus replacing the native valve of the patient. 
     Methods of treating a patient (e.g., methods of treating heart valve dysfunction/regurgitation/disease/etc.) may include a variety of steps, including steps associated with introducing and deploying an artificial valve in a desired location/treatment area. Some embodiments are placed in a patient through surgical means, while other embodiments are placed in position by transcatheter insertion. For example,  FIG.  12    illustrates an artificial valve of various embodiments being deployed by a catheter  3600 . The artificial valve  10  can be positioned and deployed in a wide variety of different ways. Access can be gained through the femoral vein or access can be percutaneous. Generally, any vascular path that leads to the pulmonary artery may be used. In one exemplary embodiment, a guidewire followed by a catheter  3600  is advanced to the pulmonary artery PA by way of the femoral vein, inferior vena cava, tricuspid valve and right ventricle RV. The artificial valve  10  of certain embodiments is placed in the right ventricular outflow tract/pulmonary artery PA, while the artificial valve  10  of other embodiments is place at the position of the native valve. Any and all of the methods, operations, steps, etc. described herein can be performed on a living animal or on a non-living cadaver, cadaver heart, simulator, anthropomorphic ghost, analog, etc. 
     Multiple types of catheters can be used to deliver the artificial valve into the pulmonary trunk of a patient. Some embodiments use a balloon catheter where the valve is compressed around a balloon which expands the frame into the pulmonary trunk. Other embodiments will use a sheath catheter, which compresses the artificial valve into a sheath, and the frame expands on its own as it is removed from the sheath. In embodiments using a balloon catheter, the artificial valve may be compressed around a balloon, such as illustrated in  FIG.  13   . 
       FIG.  13    shows an artificial valve  10  mounted on an elongated shaft  180  of a delivery apparatus, forming a delivery assembly for implanting the artificial valve  10  in a patient&#39;s body in accordance with various embodiments. The artificial valve  10  is mounted in a radially collapsed configuration for delivery into the body. The shaft  180  comprises an inflatable balloon  182  for expanding the balloon within the body, the crimped artificial valve  10  being positioned over the deflated balloon  182 . As further shown, the artificial valve  10  comprises commissure portions of the leaflets extending radially outwardly through corresponding commissure window frames  30  to locations outside of the frame and sutured to the side struts of the commissure window frame  30 . To minimize the crimp profile of the valve, the commissure window frames  30  can be depressed radially inwardly relative to the surrounding portions of the frame, such as the frame portions extending between adjacent commissure windows, when the valve is radially compressed to the collapsed configuration on the shaft  180 . For example, the commissure window frames  30  of the frame can be depressed inwardly a radial distance of between about 0.2 mm and about 1 mm relative to the portions of the frame extending between adjacent commissure window frames  30  when the artificial valve  10  is radially collapsed. In this way, the outer diameter of the outflow end portion the valve comprising the commissure portions can be generally consistent, as opposed to the commissure portions jutting outward from the surrounding portions of the artificial valve  10 , which could hinder delivery of the valve into the body. Even with the radially depressed commissure window frames  30 , the outer diameter of the inflow end portion of the frame can still be smaller than, or about equal to, the outer diameter of the outflow end portion of the frame when the valve is radially collapsed on the shaft, allowing for a minimal maximum overall diameter of the valve. By minimizing the diameter of the valve when mounted on the delivery shaft, the assembly can contained within a smaller diameter catheter and thus can be passed through smaller vessels in the body and can be less invasive in general. 
       FIGS.  14 A and  14 B  show cross sections of the compressed artificial valve  250  mounted on a balloon catheter.  FIG.  14 A  illustrates an embodiment with a frame  202  having axially spaced struts  210  engineered to be relatively smaller in width, thus allowing spaces between struts  210  in a crimped configuration. In this configuration, the crimped artificial valve  250  will allow portions of the leaflets to protrude outwardly through the openings, as indicated by  216  on  FIG.  14 A . Because of this outward protrusion, the artificial valve  250  may be compressed into a smaller diameter than would normally exist. In comparison, a cross section of known artificial valves is demonstrated in  FIG.  14 B . In this embodiment, the struts are not engineered to have a smaller width, thus disallowing gaps and outward protrusion of the leaflets. As such, the outer diameter of the crimped artificial valve will be larger. 
       FIGS.  15 A- 15 C  show a prosthetic heart valve assembly  600  comprising an embodiment of a frame  602  for a prosthetic valve mounted on a balloon  606  of a delivery shaft  604 . The frame  602  can be similar in shape to the cylindrical frame illustrated in  FIG.  10 A  and can comprise an inflow end portion  610 , an outflow end portion  612  and an intermediate portion  614 . For clarity, the other components of the valve, such as the leaflets and the skirts, are not shown. The frame  602  can have a reduced thickness at the inflow end portion  610  and at the outflow end portion  612 , relative to the thickness of the intermediate portion  614 . Due to the thinner end portions, when the balloon  606  is inflated the end portions  610 ,  612  offer less resistance to expansion and expand faster than the intermediate portion  614 , as shown in  FIG.  15 B . Because the end portions expand faster than the intermediate portion, the frame  602  becomes confined on the balloon  606 , inhibiting the frame from sliding towards either end of the balloon and reducing the risk of the frame sliding off the balloon prematurely. As shown in  FIG.  15 C , further inflation of the balloon can cause the intermediate portion  614  of the frame to expand to the same final diameter as the end portions  610 ,  612  for implantation, after which the balloon can be deflated and removed. Controlling the position of the valve on the balloon can be important during delivery, especially with frames that foreshorten during expansion and move relative to the balloon. In the embodiment shown in  FIGS.  15 A- 15 C , the intermediate portion  614  of the frame can be held constant relative to the balloon while the two end portions foreshorten towards the intermediate portion due to the “dog-bone” effect of the balloon. Any conventional means can be used to produce the frame  602  with reduced thickness at the end portions  610 ,  612 , such as sanding down the end portions with an abrasive, sand paper, or the like. In one embodiment, the end portions  610 ,  614  of the frame have a thickness of about 0.37 mm while the intermediate portion  614  has a thickness of about 0.45 mm. 
     Additional embodiments will use a sheath catheter to deploy artificial valves.  FIGS.  16 A- 16 E  illustrate a distal portion of an exemplary embodiment of a catheter  3600  for delivering and deploying the artificial valve  10 . The catheter  3600  can take a wide variety of different forms. In the illustrated example, the catheter  3600  includes an outer tube/sleeve  4910 , an inner tube/sleeve  4912 , an artificial valve connector  4914  that is connected to the inner tube  4912 , and an elongated nosecone  28  that is connected to the artificial valve connector  4914  by a connecting tube  4916 . 
     The artificial valve  10  can be disposed in the outer tube/sleeve  4910  (See  FIG.  16 A ). Elongated legs  5000  can connect the artificial valve  10  to the artificial valve connector  4914  (See  FIG.  16 A ). The elongated legs  5000  can be retaining portions that are longer than the remainder of the retaining portions  414 . The catheter  3600  can be routed over a guidewire  5002  to position the artificial valve  10  at the delivery site. 
     Referring to  FIGS.  16 B- 16 E , the outer tube  4910  is progressively retracted with respect to inner tube  4912 , the artificial valve connector  4914 , and the elongated nosecone  28  to deploy the artificial valve  10 . In  FIG.  16 B , the artificial valve  10  begins to expand from the outer tube  4910 . In  FIG.  16 C , a distal end  14  of the artificial valve  10  expands from the outer tube  4910 . In  FIG.  16 D , the artificial valve  10  is expanded out of the outer tube, except the elongated legs  5000  remain retained by the artificial valve connector  4914  in the outer tube  4910 . In  FIG.  16 E , artificial valve connector  4914  extends from the outer tube  4910  to release the legs  5000 , thereby fully deploying the artificial valve. During deployment of an artificial valve in the circulatory system, similar steps may be used and the artificial valve may be deployed in a similar way. 
     Doctrine of Equivalents 
     While the above description contains many specific embodiments, these should not be construed as limitations on the scope of the disclosure, but rather as an example of one embodiment thereof. Accordingly, the scope of the disclosure should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.