Patent Publication Number: US-2022211497-A1

Title: Methods of replacing prosthetic heart valves

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/666,099, filed Oct. 28, 2019, now U.S. Pat. No. 11,284,998, which is a continuation of U.S. patent application Ser. No. 16/298,616, filed Mar. 11, 2019, now U.S. Pat. No. 10,456,251, which is a continuation of U.S. patent application Ser. No. 16/197,280, filed Nov. 20, 2018, now U.S. Pat. No. 10,226,338, which is a continuation of U.S. patent application Ser. No. 15/403,458, filed Jan. 11, 2017, now U.S. Pat. No. 10,130,468, which is a continuation of U.S. patent application Ser. No. 14/571,141, filed Dec. 15, 2014, now U.S. Pat. No. 9,554,903, which is a continuation of U.S. patent application Ser. No. 13/954,822, filed Jul. 30, 2013, now U.S. Pat. No. 8,911,493, which is a continuation of U.S. patent application Ser. No. 11/441,406, filed May 24, 2006, now U.S. Pat. No. 8,500,798, which claims the benefit of U.S. Patent Application No. 60/684,443, filed on May 24, 2005, the entire disclosures of which are incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to prosthetic valves for implantation in body channels. More particularly, the present invention relates to prosthetic heart valves configured to be surgically implanted in less time than current valves. 
     BACKGROUND OF THE INVENTION 
     Due to aortic 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, either bioprosthetic or mechanical. When the 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 valves are deemed inoperable because their condition is too frail to withstand the procedure. By some estimates, about 30 to 50% of the subjects suffering from aortic stenosis who are older than 80 years cannot be operated on for aortic valve replacement. 
     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 by way of catheterization. For instance, U.S. Pat. No. 5,411,552 to Andersen et al. describes a collapsible valve percutaneously introduced in a compressed state through a catheter and expanded in the desired position by balloon inflation. Although these remote implantation techniques have shown great promise for treating certain patients, replacing a valve via surgical intervention is still the preferred treatment procedure. One hurdle to the acceptance of remote implantation is resistance from doctors who are understandably anxious about converting from an effective, if imperfect, regimen to a novel approach that promises great outcomes but is relatively foreign. In conjunction with the understandable caution exercised by surgeons in switching to new regimens of heart valve replacement, regulatory bodies around the world are moving slowly as well. Numerous successful clinical trials and follow-up studies are in process, but much more experience with these new technologies will be required before they are completely accepted. One question that remains unanswered is whether the new expandable valves will have the same durability as conventional prosthetic heart valves. 
     Accordingly, there is a need for an improved device and associated method of use wherein a prosthetic valve can be surgically implanted in a body channel in a more efficient procedure that reduces the time required on extracorporeal circulation. It is desirable that such a device and method be capable of helping patients with defective valves that are deemed inoperable because their condition is too frail to withstand a lengthy conventional surgical procedure. The present invention addresses this need. 
     SUMMARY OF THE INVENTION 
     Various embodiments of the present invention provide prosthetic valves and methods of use for replacing a defective native valve in a human heart. Certain embodiments are particularly well adapted for use in a surgical procedure for quickly and easily replacing a heart valve while minimizing time using extracorporeal circulation (i.e., bypass pump). 
     In one embodiment, a method for treating a native aortic valve in a human heart, comprises: 1) accessing a native valve through an opening in a chest; 2) advancing an expandable support structure to the site of a native aortic valve, the support structure being radially compressed during the advancement; 3) radially expanding the support structure at the site of the native aortic valve; and 4) mechanically coupling a valve member to the expanded support structure, wherein the valve member replaces the function of the native aortic valve. A further understanding of the nature and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals. 
     In one variation, the support structure is a stent, which may comprise a metallic frame. In one embodiment, at least a portion of the metallic frame is made of stainless steel. In another embodiment, at least a portion of the metallic frame is made of a shape memory material. The valve member may take a variety of forms. In one preferred embodiment, the valve member comprises biological tissue. The valve member further comprises a coupling portion configured to be connected to the support structure in a quick and efficient manner. In another variation of this method, the metallic frame is viewed under fluoroscopy during advancement of the prosthetic valve toward the native aortic valve. 
     The native valve leaflets may be removed before delivering the prosthetic valve. Alternatively, the native leaflets may be left in place to reduce surgery time and to provide a stable base for fixing the support structure within the native valve. In one advantage of this method, the native leaflets recoil inward to enhance the fixation of the metallic frame in the body channel. When the native leaflets are left in place, a balloon or other expansion member may be used to push the valve leaflets out of the way and thereby dilate the native valve before implantation of the support structure. 
     In another preferred embodiment, a method for treating a native aortic valve in a human heart, comprises accessing a native valve through an opening in a chest; advancing an expandable member to a position within the native aortic valve, the native aortic valve having at least two valvular leaflets; dilating the native aortic valve by expanding the expandable member to push aside the valvular leaflets of the native aortic valve; collapsing the expandable member and withdrawing the expandable member from the native aortic valve; advancing an expandable support structure to a position within the dilated native aortic valve, the support structure being radially compressed during the advancement; radially expanding the support structure within the dilated aortic valve, wherein the expanded support structure maintains the native aortic valve in the dilated condition; and coupling a valve member to the expanded support structure, wherein the valve member replaces the function of the native aortic valve. 
     In another aspect, an improved prosthetic valve comprises an expandable stent sized for implantation at the site of a native aortic valve, the stent having a coupling means (e.g., a plurality of tines extending from a first end thereof); and a valve member comprising three leaflets mounted on a base portion. The coupling means is configured for attachment to the valve member. Alternatively, the coupling means may be provided on the valve member or on both the stent and valve member. 
     A particularly useful configuration of the present invention is a two-stage prosthetic heart valve, comprising an expandable anchoring member sized to contact a heart valve annulus in an expanded state and a substantially non-expandable valve member configured for connection to the anchoring member. Desirably, the valve member includes a base ring surrounding an inflow end thereof, and the anchoring member comprises a tubular structure having connectors adapted to engage the base ring. The connectors may comprise prongs that change shape and engage the base ring. For example, the base ring may be made of a suture-permeable material, and the prongs are configured to pierce the base ring, or the prongs are shaped to wrap around the base ring. 
     In an exemplary embodiment, the valve member includes a plurality of discrete connectors spaced around a peripheral inflow end thereof, and the anchoring member comprises a tubular structure having a plurality of mating connectors spaced around a peripheral outflow end thereof. The connectors on the valve member and anchoring member engage one another by displacing the valve member toward the anchoring member. For instance, the connectors on either the valve member or anchoring member comprise latches, and the connectors on the other of the valve member or anchoring member comprise brackets, the latches configured to engage and lock to the brackets upon axial movement of the latches and brackets toward one another. Additionally, a plurality of guide filaments may be provided, at least one for each of the connectors on the anchoring member and slidingly received by the associated connector on the valve member. The guide filaments guide the valve member in proper orientation with respect to the anchoring member to ensure engagement of the mating connectors. 
     Desirably, the anchoring member comprises a stent having a wider outflow end than an inflow end thereof, wherein the valve member comprises a base ring surrounding an inflow end thereof that fits within the outflow end of the stent. In one embodiment, the valve member includes a suture-permeable base ring surrounding an inflow end thereof, and the anchoring member comprises a tubular structure having a suture-permeable fixation ring attached thereto, wherein the valve member connects to the anchoring member via sutures looped between the base ring and the fixation ring. 
     Another embodiment of the present invention comprises a two-stage prosthetic heart valve, having an expandable anchoring member sized to contact a heart valve annulus in an expanded state, a valve member, and an adapter sized to surround the valve member and engage the anchoring member, to connect the valve member and anchoring member. The adapter may be an annular ring or a wireform-shaped member that closely surrounds and conforms to cusps and commissures of a flexible leaflet valve member. 
     Whatever its shape, the adapter desirably includes a plurality of discrete connectors, and the anchoring member comprises a tubular structure having a plurality of mating connectors spaced around a peripheral outflow end thereof. The connectors on the adapter and anchoring member are configured to engage one another by displacing the adapter toward the anchoring member. For example, the connectors on either the adapter or anchoring member comprise latches, and the connectors on the other of the adapter or anchoring member comprise brackets, the latches being configured to engage and lock to the brackets upon axial movement of the latches and brackets toward one another. In addition, the valve member preferably has a base ring surrounding an inflow end thereof, and the adapter further includes a plurality of connectors adapted to engage and couple the adapter directly to the base ring. 
     Another aspect of the present invention is a system for retrofitting a conventional prosthetic heart valve, comprising an off-the-shelf, non-expandable prosthetic heart valve having a sewing ring capable of being implanted using sutures through the sewing ring in an open-heart procedure. An expandable anchoring member contacts and anchors to a heart valve annulus in an expanded state. Coupling means connects the prosthetic heart valve to the anchoring member, the prosthetic heart valve thus being attached to the heart valve annulus via the anchoring member. 
     In the system for retrofitting a conventional prosthetic heart valve, the anchoring member may comprise a tubular structure having a suture-permeable fixation ring attached thereto, wherein the coupling means comprises sutures looped between the base ring and the fixation ring. An adapter sized to surround the heart valve engages the anchoring member, to connect the heart valve and anchoring member. The adapter may be annular or wireform-shaped. Desirably, the adapter includes a plurality of discrete connectors, and the anchoring member comprises a tubular structure having a plurality of mating connectors spaced around a peripheral outflow end thereof, the connectors on the adapter and anchoring member being configured to engage one another by displacing the adapter toward the anchoring member. 
     A surgical method of implanting a prosthetic heart valve of the present invention in a patient involves providing a two-stage prosthetic heart valve comprising an expandable anchoring member and a valve member, the anchoring member being sized to contact a heart valve annulus in an expanded state and the valve member being configured to connect to the anchoring member. The patient is prepared for surgery by placing him/her on cardiopulmonary bypass. The surgeon creates a direct access pathway to the heart valve annulus that preferably permits direct (i.e., naked eye) visualization of the heart valve annulus. The anchoring member is delivered and expanded to contact the valve annulus, and the valve member is delivered and connected to the anchoring member. Preferably, the direct access pathway is created by performing open-heart surgery. The method may include balloon-expanding the anchoring member. Further, the valve member may be expandable and the method includes delivering the valve member in a compressed state and expanding it prior to connecting it to the anchoring member. 
     In one embodiment, the valve member and the anchoring member are provided with mating connectors, and the step of delivering and connecting the valve member to the anchoring member comprises axially displacing the valve member toward the anchoring member so that the mating connectors engage. In another embodiment, the anchoring member comprises a stent having an outflow end larger than an inflow end thereof, and the valve member comprises a non-expandable valve member having a base ring on an inflow end thereof sized to fit within the outflow end of the stent. The anchoring member may be provided with bendable connectors on an outflow end thereof, and the method includes causing the connectors to bend inward and engage a peripheral base ring of the valve member. For example, a bending tool may be used to bend connectors inward. 
     Another surgical method of implanting a two-stage prosthetic heart valve in a patient of the present invention includes providing an expandable anchoring member sized to contact a heart valve annulus in an expanded state, delivering and attaching the anchoring member to the heart valve annulus, providing a non-expandable valve member, and delivering and connecting the valve member to the anchoring member. The valve member and the anchoring member may be provided with mating connectors, and the step of delivering and connecting the valve member to the anchoring member comprises axially displacing the valve member toward the anchoring member so that the mating connectors engage. Desirably, the anchoring member comprises a stent having an outflow end larger than an inflow end thereof, and wherein the valve member comprises a base ring on an inflow end thereof sized to fit within the outflow end of the stent. The anchoring member may be provided with bendable connectors on an outflow end thereof, and the method includes causing the connectors to bend inward and engage a peripheral base ring of the valve member, such as by using a bending tool. 
     In an exemplary embodiment, the valve member includes a base ring on an inflow end thereof, and the method further includes providing an adapter sized to surround the valve member and seat on the base ring. The method therefore includes the step of delivering and connecting the valve member and coupling the adapter to the anchoring member. For instance, the adapter includes a plurality of discrete connectors, and the anchoring member comprises a tubular structure having a plurality of mating connectors spaced around a peripheral outflow end thereof. The step of coupling the adapter to the anchoring member comprises displacing the adapter toward the anchoring member to engage the mating connectors thereon. Additionally, the adapter may further have a plurality of connectors adapted to engage and couple the adapter directly to the base ring, and the method includes causing the connectors to engage the base ring. 
     In a still further surgical method of implanting a prosthetic heart valve in a patient, a prosthetic heart valve and a separate expandable anchoring member are provided. The prosthetic heart valve and anchoring member are positioned within a valve dilator/delivery tube having an exterior diameter sized to dilate a heart valve annulus. The valve dilator/delivery tube advances to the heart valve annulus, and the annulus is dilated using the valve dilator/delivery tube. The anchoring member is expulsed from the tube and expanded to contact the heart valve annulus. The prosthetic heart valve is then expulsed from the valve dilator/delivery tube, and connected to the anchoring member. 
     Another method of the present invention comprises retrofitting and rapidly implanting a conventional prosthetic heart valve in a patient. The method includes providing an off-the-shelf non-expandable prosthetic heart valve having a sewing ring capable of being implanted using sutures through the sewing ring in an open-heart procedure. An expandable tissue anchoring member sized to contact a heart valve annulus in an expanded state is delivered and expanded into contact with the heart valve annulus. Finally, the prosthetic heart valve is delivered and connected to the tissue anchoring member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained and other advantages and features will appear with reference to the accompanying schematic drawings wherein: 
         FIG. 1  is an exploded perspective view illustrating a preferred embodiment of a two-stage prosthetic valve comprising a stent portion and a valve member, wherein the valve member may be quickly and easily connected to the stent portion. 
         FIG. 2  illustrates the valve embodiment of  FIG. 1  after the valve member has been attached to the stent portion by crimping portions of the stent over the commissural points of the valve member. 
         FIG. 3  is an exploded perspective view of an alternative embodiment wherein the stent is provided with a plurality of tines configured to be crimped to a ring along the base of the valve member. 
         FIG. 4  illustrates the valve embodiment of  FIG. 3  after the valve member has been attached to the stent portion by crimping the tines on to the valve member. 
         FIG. 4A  is a sectional view through one side of the prosthetic heart valve of  FIG. 4  taken along line  4 A- 4 A and showing one configuration of tines connecting through a sewing ring portion of the valve member. 
         FIG. 5  is an exploded perspective view of an alternative embodiment wherein slotted posts are provided on the stent for coupling to protruding members on the valve member. 
         FIG. 5A  is an enlarged view of one of the slotted posts provided on the stent of  FIG. 5 . 
         FIGS. 6 and 6A  illustrate another alternative embodiment similar to  FIGS. 5 and 5A  wherein the posts are configured with L-shaped slots for locking the valve member to the stent. 
         FIG. 7  is a sectional view through a body channel that illustrates an alternative embodiment of prosthetic heart valves wherein first and second stents are provided for anchoring a valve member within the body channel. 
         FIG. 8  is an exploded perspective view of an alternative embodiment wherein the stent has a small diameter and a large diameter and wherein an expandable valve member is deployed within the large diameter. 
         FIG. 9A  is an exploded perspective view of another alternative embodiment of a two-part prosthetic valve wherein a ring portion along the base of the valve member snaps into a groove formed in the stent. 
         FIG. 9B  illustrates the embodiment of  FIG. 9A  with the valve member connected to the stent. 
         FIG. 10  is an exploded perspective view of another alternative embodiment wherein the valve member and the stent are provided with corresponding threaded portions for threadably engaging the valve member to the stent. 
         FIG. 11  is an exploded perspective view of an alternative prosthetic heart valve of the present invention having a valve member, stent, and a threaded locking ring for coupling the two together. 
         FIGS. 12A and 12B  are exploded and assembled perspective views of an alternative two-stage prosthetic heart valve having a valve member and tubular, expandable stent with tabs on an outflow end for coupling to the valve member. 
         FIGS. 12C and 12D  are sectional views through one side of the prosthetic heart valve of  FIG. 12B  schematically illustrating an exemplary tool that may be used to bend the tabs on the outflow end of the stent around a sewing ring of the valve member. 
         FIGS. 13A and 13B  are exploded and assembled perspective views of an alternative prosthetic heart valve of the present invention wherein a valve member and stent with tabs are coupled together in conjunction with a locking ring. 
         FIGS. 14A and 14B  are exploded and assembled perspective views of a still further prosthetic heart valve wherein a valve member and tubular, expandable stent are coupled together using a wireform-shaped adapter having tabs. 
         FIGS. 15A and 15B  are exploded and assembled perspective views of a prosthetic heart valve having a valve member and stent with locking bands on an outflow end. 
         FIGS. 16A and 16B  are exploded and assembled perspective views of an alternative prosthetic heart valve wherein a stent exhibits locking clips on an outflow end that are guided through mating slits on a locking ring to join the stent to a valve member. 
         FIGS. 17A and 17B  are exploded and assembled perspective views of an alternative prosthetic heart valve wherein a stent has brackets on an outflow end that receive guided locking clips on a locking ring to join the stent to a valve member. 
         FIG. 18  is a perspective view of an alternative stent for use in a prosthetic heart valve of the present invention. 
         FIG. 19  is a detailed sectional view through an inflow side of a prosthetic heart valve utilizing the stent of  FIG. 18  and showing a valve member base ring captured between two sets of prongs. 
         FIG. 20  is a perspective exploded view of a prosthetic heart valve having a tubular stent with upstanding tines and a valve member with an additional adapter ring arranged around a base ring. 
         FIG. 21  is an exploded perspective view of an exemplary prosthetic heart valve having an expandable stent and non-expandable valve member connected by an array of parachute sutures being removed from a storage jar. 
         FIGS. 22A-22C  are several views of the implantation of the prosthetic heart valve of  FIG. 21  assisted by a tubular valve dilator/delivery tube. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention attempts to overcome drawbacks associated with conventional, open-heart surgery, while also adopting some of the techniques of newer technologies which decrease the duration of the treatment procedure. The prosthetic heart valves of the present invention are primarily intended to be delivered and implanted using conventional surgical techniques, including the aforementioned open-heart surgery. There are a number of approaches in such surgeries, all of which result in the formation of a direct access pathway to the particular heart valve annulus. For clarification, a direct access pathway is one that permits direct (i.e., naked eye) visualization of the heart valve annulus. In addition, it will be recognized that embodiments of the two-stage prosthetic heart valves described herein may also be configured for delivery using percutaneous approaches, and those minimally-invasive surgical approaches that require remote implantation of the valve using indirect visualization. 
     One primary aspect of the present invention is a two-stage prosthetic heart valve wherein the tasks of implanting a tissue anchor and a valve member are somewhat separated and certain advantages result. For example, a two-stage prosthetic heart valve of the present invention may have an expandable tissue anchoring member that is secured in the appropriate location using a balloon or other expansion technique. A valve member is then coupled to the tissue anchoring member in a separate or sequential operation. By utilizing an expandable anchoring member, the duration of the initial anchoring operation is greatly reduced as compared with a conventional sewing procedure utilizing an array of sutures. The expandable anchoring member may simply be radially expanded outward into contact with the implantation site, or may be provided with additional anchoring means, such as barbs. The operation may be carried out using a conventional open-heart approach and cardiopulmonary bypass. In one advantageous feature, the time on bypass is greatly reduced due to the relative speed of implanting the expandable anchoring member. 
     For definitional purposes, the term “tissue anchoring member,” or simply “anchoring member” refers to a structural component of a heart valve that is capable of attaching to tissue of a heart valve annulus. The anchoring members described herein are most typically tubular stents, or stents having varying diameters. A stent is normally formed of a biocompatible metal wire frame, such as stainless steel or Nitinol. Other anchoring members that could be used with valves of the present invention include rigid rings, spirally-wound tubes, and other such tubes that fit tightly within a valve annulus and define an orifice therethrough for the passage of blood, or within which a valve member is mounted. It is entirely conceivable, however, that the anchoring member could be separate clamps or hooks that do not define a continuous periphery. Although such devices sacrifice some dynamic stability, these devices can be configured to work well in conjunction with a particular valve member. 
     The term “valve member” refers to that component of a heart valve that possesses the fluid occluding surfaces to prevent blood flow in one direction while permitting it in another. As mentioned above, various constructions of valve numbers are available, including those with flexible leaflets and those with rigid leaflets or a ball and cage arrangement. The leaflets may be bioprosthetic, synthetic, or metallic. 
     A primary focus of the present invention is the two-stage prosthetic heart valve having a first stage in which an anchoring member secures to a valve annulus, and a subsequent second stage in which a valve member connects to the anchoring member. It should be noted that these stages can be done almost simultaneously, such as if the two components were mounted on the same delivery device, or can be done in two separate clinical steps, with the anchoring member deployed using a first delivery device, and then the valve member using another delivery device. It should also be noted that the term “two-stage” does not necessarily limit the valve to just two parts, as will be seen below. 
     Another potential benefit of a two-stage prosthetic heart valve, including an anchoring member and a valve member, is that the valve member may be replaced after implantation without replacing the anchoring member. That is, an easily detachable means for coupling the valve member and anchoring member may be used that permits a new valve member to be implanted with relative ease. Various configurations for coupling the valve member and anchoring member are described herein. 
     It should be understood, therefore, that certain benefits of the invention are independent of whether the anchoring member or valve member are expandable or not. That is, various embodiments illustrate an expandable anchoring member coupled to a conventional valve member. However, the same coupling structure may be utilized for a non-expandable anchoring member and conventional valve member. Additionally, although a primary embodiment of the present invention is an expandable anchoring member coupled with a conventional valve member, both could be expandable and introduced percutaneously or through a minimally-invasive approach. Therefore, the invention should not be construed as being limited in these regards, but instead should be interpreted via the appended claims. 
     As a point of further definition, the term “expandable” is used herein to refer to a component of the heart valve capable of expanding from a first, delivery diameter to a second, implantation diameter. An expandable structure, therefore, does not mean one that might undergo slight expansion from a rise in temperature, or other such incidental cause. Conversely, “non-expandable” should not be interpreted to mean completely rigid or a dimensionally stable, as some slight expansion of conventional “non-expandable” heart valves, for example, may be observed. 
     In the description that follows, the term “body channel” is used to define a blood conduit or vessel within the body. Of course, the particular application of the prosthetic heart valve determines the body channel at issue. An aortic valve replacement, for example, would be implanted in, or adjacent to, the aortic annulus. Likewise, a mitral valve replacement will be implanted at the mitral annulus. Certain features of the present invention are particularly advantageous for one implantation site or the other. However, unless the combination is structurally impossible, or excluded by claim language, any of the heart valve embodiments described herein could be implanted in any body channel. 
     With reference now to  FIG. 1 , one preferred embodiment of an improved prosthetic valve  10  generally includes an expandable anchoring member or stent  20  and a valve member  30 . The stent provides a support structure for anchoring the valve member within a body lumen. Although a stent is described for purposes of illustration, any support structure capable of anchoring the valve member to the body lumen may be used. As will be described in more detail below, the prosthetic valve is configured such that the valve member may be quickly and easily connected to the stent. It should be noted here, that the anchoring members or stents described herein can be a variety of designs, including having the diamond-shaped openings shown or other configurations detailed below. The material depends on the mode of delivery (i.e., balloon- or self-expanding), and the stent can be bare strut material or covered to promote in-growth and/or to reduce paravalvular leakage. For example, a suitable cover that is often used is a sleeve of fabric such as Dacron. 
     The stent may be securely deployed in the body channel using an expandable member, such as, for example, a balloon. Because the stent is expanded before the valve member is attached, the valve member will not be damaged or otherwise adversely affected during the stent deployment. After the stent has been deployed in the body channel, the valve member may be connected to the stent. In one preferred application, the two-stage prosthetic valve is well-suited for use in heart valve replacement. In this application, the stent may be advantageously used to push the native leaflets aside such that the valve member can replace the function of the native valve. The anchoring members or stents described herein could include barbs or other such tissue anchors to further secure the stent to the tissue. In one preferred embodiment, the barbs are deployable (e.g., configured to extend or be pushed radially outward) by the expansion of a balloon. 
     In another advantageous feature, the two-stage prosthetic valve illustrated in  FIG. 1  provides a device and method for substantially reducing the time of the surgical procedure. This reduces the time required on extracorporeal circulation and thereby substantially reduces the risk to the patient. The surgical time is reduced because the stent may be deployed quickly and the valve member may be attached to the stent quickly. This simplifies and reduces the surgical time as compared with replacement valves that are sutured to the tissue after removing the native leaflets. 
     When used for aortic valve replacement, the valve member  30  preferably has three leaflets  36  which provide the valvular function for replacing the function of the native valve. In various preferred embodiments, the valve leaflets may be taken from another human heart (cadaver), a cow (bovine), a pig (porcine valve) or a horse (equine). In other preferred variations, the valve member may comprise mechanical components rather than biological tissue. In one preferred embodiment, the valve is compressible in diameter. Accordingly, the valve may be reduced in diameter for delivery into the stent and then expanded. The three leaflets are supported by three commissural posts  34 . A ring  32  is provided along the base portion of the valve member. 
     With continued reference to  FIG. 1 , the stent  20  is provided with two diameters. A lower portion  22  has a small diameter and an upper portion  24  has a large diameter. The lower portion  22  is preferably sized to be deployed at the location of the native valve (e.g., along the aortic annulus). The upper portion  24  expands outwardly into the perspective cavity adjacent the native valve. For example, in an aortic valve replacement, the upper portion  24  expands into the area of the sinus cavities just downstream from the aortic annulus. Of course, care should be taken to orient the stent  20  so as not to block the coronary openings. The stent body is preferably configured with sufficient radial strength for pushing aside the native leaflets and holding the native leaflets open in a dilated condition. The native leaflets provide a stable base for holding the stent, thereby helping to securely anchor the stent in the body. To further secure the stent to the surrounding tissue, the lower portion may be configured with anchoring members, such as, for example, hooks or barbs (not shown). 
     The upper portion  24  of the stent  20  has a larger diameter sized for receiving the valve member  30 . A transition region  28  between the upper and lower portions of the stent body may be advantageously used to provide a seat for the bottom end of the valve member. The stent may further comprise a ridge (not shown) along an inner wall for providing a more definite seat portion within the stent. 
     With continued reference to  FIG. 1 , the prosthetic valve  10  is provided with a coupling mechanism for securing the valve member  30  to the stent  20 . The coupling mechanism may take a variety of different forms. However, in the illustrated embodiment, the stent body comprises three posts  26  which correspond to the three commissural points  34  on the valve member. The three posts  26  are preferably formed of a malleable material such that the posts  26  may be crimped over the commissural points on the valve member. A bending tool (not shown) may be provided for crimping the posts  26  over the commissures of the valve member, or the posts  26  may be hinged or made of the shape memory material so as to curl once implanted in the body. With reference to  FIG. 2 , the prosthetic valve  10  is illustrated in the assembled condition with the posts  26  crimped over the commissural points  34  of the valve member. In one variation, the three posts on the stent are formed with a recess for receiving the commissural points, such as in a snap-fit relationship. 
     In a preferred embodiment, the stent  20  is expandable, but the valve member  30  is a conventional, non-expandable prosthetic heart valve, such as the Carpentier-Edwards PERIMOUNT Magna® Aortic Heart Valve available from Edwards Lifesciences of Irvine, Calif. In this sense, a “conventional” prosthetic heart valve is an off-the-shelf (i.e., suitable for stand-alone sale and use) non-expandable prosthetic heart valve having a sewing ring capable of being implanted using sutures through the sewing ring in an open-heart procedure. An implant procedure therefore involves first delivering and expanding the stent  20  and the aortic annulus, and then coupling the valve member  30  thereto. Because the valve member  30  is non-expandable, the entire procedure is typically done using the conventional open-heart technique. However, because the stent  20  is delivered and implanted by simple expansion, the entire operation takes less time. This hybrid approach will also be much more comfortable to surgeons familiar with the open-heart procedures and conventional heart valves. Moreover, the relatively small change in procedure coupled with the use of proven heart valves should create a much easier regulatory path than strictly expandable, remote procedures. 
     A variation of the embodiment described in  FIGS. 1 and 2  may incorporate an expandable stent  20  and an expandable valve member  30 . Although not shown, the valve member  30  may be capable of expansion within the body, such as the Cribier-Edwards Aortic Percutaneous Heart Valve, also available from Edwards Lifesciences. Therefore, the valve  10  may be implanted without an open-heart procedure, and even without stopping heart. In such a remote procedure, the three posts  26  on the stent  20  may be made of a shape memory material having a temperature-induced shape change once implanted. Alternatively, a tool for bending the posts  26  may be delivered along with the valve  10  and utilized when the valve member  30  seats within the stent  20 . 
     With reference now to  FIG. 3 , an alternative prosthetic valve  10 A comprises a stent  40  provided with a bottom portion  42  and an upper flared portion  44 . A plurality of prongs or tines  46  is disposed along a top end of the flared portion  44 . The tines  46  are preferably bendable members configured to engage the ring portion  32  along the base of the valve member  30 . In one preferred embodiment, the tines  46  are crimped over the ring as shown in  FIG. 4 . If desired, the tines  46  may have pointed tips for passing through a fabric or other similar material along the ring portion of the valve member, such as seen in  FIG. 4A . 
     Once again, the stent  40  is desirably an expandable member that can be easily delivered and implanted at the body channel. The valve member  30  may be conventional, or may also be expandable. The illustrated embodiment shows a conventional valve  30  having the sewing ring portion  32  surrounding an inflow end. Sewing rings are typically made of suture-permeable material covered with cloth. The tines  46  may be sharp enough to pierce the material of the sewing ring portion  32  ( FIG. 4A ). In this regard, a conventional valve member  30  may be utilized without modification. In the alternative, the sewing ring portion  30  may be replaced with a more rigid peripheral band or ring, and the tines  46  are simply bent inward so as to fold over the ring and capture the valve member  31  on the top of the stent  40 . Desirably, a seat or rim of some sort is provided within the interior of the stent  40  so that the valve member  30  can easily be positioned therein. The tines  46  may be mechanically bent using a deployment tool (not shown), or they may be hinged or made of a shape memory material so as to curl inward upon reaching a certain temperature. 
     With reference now to  FIG. 5 , another alternative prosthetic valve  10 B comprises an anchoring member or stent  50  provided with a cylindrical portion  52  and three posts  54  extending upward from the cylindrical portion. Each post  54  may be slotted, as illustrated in the enlarged view of  FIG. 5B , or formed with an orifice. Radially protruding members  38  are provided along the ring portion  32  of the valve member  30  for mating with the posts on the stent. The exemplary slot has a thin neck portion  58  wherein engagement members, such as angled teeth, are provided. The teeth are angled such that the slot widens as the protruding member  38  is pushed downward into the slot. After passing through the teeth into the capture portion  59 , the protruding member  38  is securely captured. Because the teeth are angled in only one direction, an upward force will not cause the slot to widen, thereby capturing the protruding member. 
     With reference now to  FIG. 6 , yet another alternative embodiment of a component prosthetic valve  10 C is illustrated. The embodiment of  FIG. 6  is similar to the embodiment illustrated and described above with respect to  FIG. 5 . However, in this variation, the posts or connecting members  55  are provided with L-shaped slots  57  for receiving the protruding member disposed along the valve member. With reference to  FIG. 6A , an enlarged view of one preferred connecting member  55  is shown. The slot  57  of the connecting member  55  is shaped such that the protruding member  38  moves longitudinally into the slot and then rotationally to enter the capture portion. One or more teeth  58  may be provided for holding the protruding member in the capture portion. Alternatively, the protruding member  38  may be held in the slot  57  using friction or a mechanical locking member. In another alternative, a key lock system or “bayonet” attachment mechanism may be provided for coupling the valve member to the stent. 
     With reference now to  FIG. 7 , another alternative prosthetic valve  10 D is illustrated wherein the valve member  30  is captured and held between first and second stents  60 ,  62 . In use, the first stent  60  is expanded within a body channel such that the outer surface of the stent is in contact with the vessel wall  64 . The valve member  30  is then advanced through the body channel and into contact with the first stent. A ring  32  is preferably provided along the base portion of the valve member for contacting the outflow end of the first stent. The second stent is then advanced through the body channel and is deployed such that an inflow end of the second stent contacts a top surface of the ring  32  of the valve member for anchoring the valve member between the first and second stents. 
     The embodiment of  FIG. 7  employs a slightly different means for connecting the valve member  30  the anchoring member. Primarily, stents  60 ,  62  capture the ring  32  of the valve member  30  therebetween simply by providing upper and lower barriers to movement. The valve member  30  is desirably a non-expandable type, therefore the ring  32  is not overly susceptible to compression. By providing sufficient of the thickness of the stents  60 ,  62 , the valve member  30  remains sandwiched therebetween. In this regard, the outflow end of the first stent  60  and the inflow end of the upper stent  62  are preferably flat or blunt so as not to dig into the ring  32 . Because of the anchoring function of the stents  60 ,  62 , there is no need to suture the valve member  30 , and thus the ring  32  may be made relatively firm or rigid. Alternatively, the facing edges of the stents  60 ,  62  may be provided with barbs or other such piercing devices, and the ring  32  provided as a conventional suture-permeable sewing ring. 
     As noted above, the anchoring members or stents described herein could include barbs or other anchors to further secure the stent to the tissue. Further, the barbs could be deployable (e.g., configured to extend or be pushed radially outward) by the expansion of a balloon. Likewise, the stent can be covered to promote in-growth and/or to reduce paravalvular leakage. The cover would be similar to those on other valves, e.g., a Dacron tube or the like. 
     Alternatively, the valve member may be constructed with a tubular frame or cage for engaging one or both stents  60 ,  62 . In various preferred embodiments, the stents may be self-expanding or balloon-expandable. In one advantageous feature, the valve member  30  of this embodiment is not required to be mounted within a cylindrical frame or stent. Accordingly, the flow through area of the valve member may be maximized to improve valve function. In another variation, the first and second stents may be integrated as a single unit forming a chamber therebetween. In this variation, the valve member may be expanded within the chamber for securely deploying the valve member in the body channel. 
     With reference now to  FIG. 8 , another alternative embodiment of a two-stage prosthetic valve  10 E is illustrated wherein the anchoring member or stent  70  is provided with a varying diameter. More particularly, a lower portion  72  of the stent has a small diameter sized for implantation at a native valve annulus. In one preferred configuration, the small diameter is about 23 mm. The stent also has an upper portion  74  with a larger diameter for receiving an expandable valve member  30 A. In one preferred configuration, the larger diameter is about 29 mm. In this embodiment, the valve member  30 A is provided as a tubular body that is radially expandable. The valve leaflets are disposed along the interior of the valve member. 
     The stent  70  preferably includes a circular ridge  76  formed along the transition region between the large and small diameters. The ridge provides a seat for the base of the valve member  30 A. In one preferred embodiment, the ridge  76  incorporates a support wire  78  that extends at least partially through the ridge for strength and may be used to provide a radiopaque marker. The remaining portion of the ridge may be formed of Dacron or any other suitable material. The stent  70  may be comprised of a screen or mesh. A cover  75 , such as a polymer sheet, may be provided along at least a portion of the stent to help prevent leakage and enhance sealing. In addition, a sponge or cloth may be provided along the exterior portion of the stent for further enhancing sealing. 
     The stent  70  of  FIG. 8  may be self-expanding or balloon-expandable. When provided as a balloon-expandable stent, an expandable tapered (i.e., two diameter) balloon may be provided for deploying the stent. When configured for use with a stent having diameters of 23 mm and 29 mm, the balloon may have diameters of 22 mm and 28 mm, respectively. 
     With reference now to  FIGS. 9A and 9B , another alternative embodiment of a component prosthetic valve  10 F is provided wherein a valve member  30  is configured for connection with an anchoring member or stent  90 . In this embodiment, the stent  90  is provided with a groove  94  formed in an inwardly-directed circumferential member  92 . The groove extends at least partially around the inner portion of the stent and is sized to receive the ring portion  32  of the valve member  30 . In one preferred embodiment, the ring is configured to snap fit into the groove, as seen in  FIG. 9B . In another variation, the ring is made of a shape memory material configured to expand after deployment in the body. In this variation, the ring is configured to radially expand for securely anchoring itself within the groove. 
     With reference now to  FIG. 10 , yet another alternative embodiment of a component prosthetic valve  10 G is illustrated wherein the valve member  30  is configured for threadable engagement with an anchoring member or stent  100 . In this embodiment, the stent is provided on one end with a threaded region  102  along an inner wall configured for receiving a threaded flange portion  33  on the valve member  30 . The threaded flange portion is preferably provided along the ring  32  at the base of the valve member. During use, the stent is first deployed in the body channel. The stent may be deployed in a manner wherein the diameter of the threaded region remains substantially constant so as to not affect the threads. In one embodiment, the stent is substantially non-expandable and is delivered into the lumen in its fully expanded condition. This can be achieved by first stretching or dilating the delivery site for receiving the stent. In another embodiment, only the lower portion of the stent is expanded for engaging the tissue. In either embodiment, the valve member is threadably attached to the threaded flange on the stent after the stent has been firmly anchored in the body channel. This attachment means is configured such that the valve member advantageously connects to the stent through rotational movement. Accordingly, longitudinal forces applied to the valve member after implantation will have little or no effect on the integrity of the connection between the stent and valve. 
     With reference now to  FIG. 11 , an alternative prosthetic heart valve  10 H comprises a valve member  30 , an anchoring member or stent  110 , and a locking ring  112 . As before, the stent  110  desirably expands first at the implantation site, after which a conventional valve member  30  couples to the stent through the use of the locking ring  112 . However, the valve member  30  may also be expandable, and the stent  110  can take a variety of forms. In a preferred embodiment, the stent  110  comprises a latticework of balloon-expandable members adapted to be delivered to the implantation site in a collapsed or compressed state, and then expanded from within using a balloon. Of course, a self-expanding stent  110  could also be used, and additional anchoring means of such as exterior barbs may be provided to help prevent the stent from migrating after implantation. 
     A series of tabs or flanges  114  project slightly inwardly from an outflow end of the stent  110 . The flanges  114  are configured to mate with exterior threading  116  on a downwardly-projecting shoulder of the locking ring  112 . The number and configuration of the flanges  114  is selected to avoid interfering with radial expansion of the stent  110 , and also to mate with the threads  116  of the locking ring  112 . Desirably, a series of space-apart flanges  114 , for example eight, evenly spaced around the outflow rim of the stent  110  project inward therefrom a distance of between 1-3 mm. 
     An inner bore  118  of the locking ring  112  possesses a diameter large enough to pass over the entire valve member  30  except for the base ring  32 , which could be a sewing ring of a conventional heart valve. When coupled together, the locking ring  112  surrounds the valve member  30  and desirably includes an inner ledge that rests on the base ring  32  thereof. The inner diameter of the shoulder having the exterior threading  116  is sized larger than the base ring  32  and extends downwardly into engagement with the flanges  114 . By screwing down the locking ring  112 , the components can be easily and rapidly assembled. After implantation, removal and replacement of the valve member  30  merely requires releasing the locking ring  112  from any tissue ingrowth, unscrewing and removing it, and releasing the valve member  30  from the stent  110  by cutting away any tissue ingrowth therebetween. 
       FIGS. 12A and 12B  illustrate another prosthetic heart valve  10 I of the present invention having an expandable anchoring member or stent  120  coupled to a valve member  30 . Much like the valve  10 A of  FIGS. 3 and 4 , the outflow end of the stent  120  exhibits a series of spaced-apart tabs  122  that curl around the base ring  32  of the valve member  30 . In this embodiment, the stent  120  is a straight tube, and there are fewer tabs  122  (e.g., eight) than there are tines  46  in the valve  10 A. The tabs  122  may be bent using an auxiliary tool (not shown), or may possess a property permitting autonomous bending, such as temperature-induced movement. 
       FIGS. 12C and 12D  are sectional views through one side of the prosthetic heart valve  10 I of  FIG. 12B  schematically illustrating an exemplary tool that may be used to bend the tabs  122  on the outflow end of the stent  120  around the base ring  32  of the valve member  30 . It should be noted that the section is taken radially through one side of the system, and the tool will typically be annular or at least peripherally arranged to bend each one of the tabs  122 . The tool comprises a forming member  124  having a forming surface  125 . The forming member  124  slides within and relative to an outer anvil  126  having an inwardly angled portion  128  that directly surrounds and engages each of the tabs  122 . The forming surface  125  is curved such that axial displacement of the forming member  124  in the direction shown in  FIG. 12C  curls each of the tabs  122  inward to the shape of  FIG. 12D . In this embodiment, the tabs  122  wrap over the top of and restrain the base ring  32 . In other embodiments, the tool may be used to bend prongs so that they pierce the base ring  32 . It should be noted that the outer anvil  126  is primarily used for centering purposes to guide the forming member  124  toward the tabs  122 . 
       FIGS. 13A and 13B  illustrate another embodiment of a prosthetic valve  10 J having multiple components joined together. An anchoring member or stent  130  includes a plurality of tangs or flanges  132  on an outflow end. A valve member  30  seats adjacent the outflow end of the stent  130 , and a fixation ring  134  extends there around. Additionally, a plurality of tabs  136  project downward from the fixation ring  34 . Although not shown, the tabs  136  enable the fixation ring  34  to be coupled to the base ring  32  of the valve member  30  by mechanically bending the tabs, or configuring the tabs to curl upon reaching a certain temperature. As seen in  FIG. 13B , the flanges  132  extend around the outside of the fixation ring  134  and bend around the upper or outflow end thereof. Again, this can be accomplished using an auxiliary tool or through temperature-induced movement. Alternatively, the flanges  132  may be formed of a resilient polymer or metal having the shape seen in  FIG. 13B  such that they can be flexed outward around the fixation ring  134  and then snapped back into place to secure the ring around the valve member  30 . Although not shown, the interior of the fixation ring  134  is desirably contoured to mate with the base ring  32  of the valve member  30 . The fixation ring  134  can be made of any number of materials, including rigid, flexible, metallic, polymer, bioabsorbable, etc. One preferred configuration is a Teflon ring coated with anti-thrombogenic or anti-microbial compositions. 
       FIG. 14A  illustrates a still further prosthetic heart valve  10 K having an expandable anchoring member or stent  140 , a valve member  30 , and a wireform-shaped adapter  142 . The stent  140  and valve member  30  have been previously described. The adapter  142  has a shape similar to a so-called “wireform” used in the internal construction of many prior art bioprosthetic tissue valves. Indeed, the valve member  30  is desirably a Carpentier-Edwards PERIMOUNT Magna® Aortic Heart Valve made by Edwards Lifesciences, and including therewithin an Elgiloy wireform. The adapter  142  may be formed of biocompatible polymers or metals, preferably an alloy such as Nitinol. 
     The adapter  142  carries a plurality of securing tabs  144 ,  146 . In the illustrated embodiment, three lower securing tabs  144  are located at the apex of the three cusps of the wireform-shape, and two upper securing tabs  146  are located at each of the upstanding commissures of the wireform-shape, for a total of six at the commissures.  FIG. 14B  is a detailed illustration of the assembly of the stent  140 , valve member  30 , and adapter  142 . The base ring  32  of the valve member  30  seats on or just within the outflow end of the stent  140 , and the adapter  142  fits over the valve member and couples to it, as well as to the stent. In this regard, the cusps of the adapter  142  seat on or slightly outside the base ring  32  with the commissures surrounding and conforming to the commissures of the valve member  30 . The cusp securing tabs  144  bend up over the base ring  32  and down into engagement with the stent  140 . The two securing tabs  146  at each commissure of the adapter  142  bend or wrap around the corresponding valve member commissure. 
     Again, a supplemental tool may be used to accomplish the bending of the securing members  144 ,  146 , or they may exhibit temperature-changing properties. In the illustrated embodiment, the securing tabs  144 ,  146  are malleable, though other configurations are within the scope of the invention. For example, the lower securing tabs  144  may be barbs or tangs which pierce the base ring  32  and hook around the stent  140 , while the upper securing tabs  146  may be resilient straps that wrap around each one of the commissures of the valve member  30 . 
     To further secure the valve member  30  to the stent  140 , the stent includes a plurality of upstanding barbs  147  comprising spaced apart posts having teeth  140 . The adapter  142  possesses a plurality of outwardly projecting brackets  149  defining slots therethrough. As seen in  FIG. 14B , the barbs  147  pass through the base ring  32  and through the slots of the brackets  149  in the adapter  142 . The teeth  148  prevent removal of the barbs  147  from the slots. In this way, the stent  140  and adapter  142  are securely connected together, sandwiching the valve member  30  therebetween. 
     Another possibility is that the securing tabs  144 ,  146  are not initially carried by the adapter  142 , but instead are added after the assembly of the three components. For instance, staples or even sutures may be used after the valve member  30  seats on the stent  140 , and the adapter  142  is lowered around the valve member. Even if sutures are used, the time required relative to a conventional sewing operation is greatly reduced. Moreover, the structural support and anchoring properties of the wireform-shaped adapter  142  greatly enhances the overall integrity of the assembly. In this regard, securing tabs such as those shown may be placed more continuously around the adapter  142  so as to provide more uniform contact with the valve member  30 . One possible configuration is a series of small hooks or brackets extending along the undulating adapter  142  that loop over the corresponding undulating shape on the valve member  30 . The valve member  30  is therefore restrained from upward movement relative to the adapter simply by lowering the adapter  142  over the valve member. In such an arrangement, only the lower securing members need be actively attached, such as by causing their shape to change and bend into engagement with the stent  140 , as seen in  FIG. 14B . 
     A further prosthetic valve embodiment  10 L seen in  FIG. 15A  includes an expandable anchoring member or stent  150  and a valve member  30 . A plurality of fixation straps  152  ring the outflow end of the stent  150 . Four such straps  152  are shown, but more or less made be utilized. For example, three straps extending farther around the periphery of the outflow end of the stent  150  may be substituted. Conversely, four or more straps that overlap one another may be used. 
       FIG. 15B  illustrates the valve member  30  seated on top of the stent  150  with one of the straps  152  securing the two components together. Straps  152  may be attached at both of their ends to the stent  150 , and may comprise a resilient biocompatible material that stretches over the base ring  32  of the valve member  30 . Alternatively, the straps may be bent or folded over the base ring. In one variation, one end of each strap  152  may be initially free, and after the strap is looped over the base ring  32  is then attached to the stent  150 , somewhat like a belt configuration. The straps  152  may be formed of a variety of materials, typically cloth-covered so as to permit tissue ingrowth over a cloth-covered base ring  32  for enhanced long-term anchorage. One possible variation is to incorporate small barbs or Velcro-style hooks in each of the straps  152  so as to gain better purchase on the base ring  32 . 
       FIGS. 16A and 16B  illustrate a still further embodiment, wherein the prosthetic heart valve  10 M comprises a valve member  30 , expandable anchoring member or stent  160 , and coupling ring  162 . The coupling ring  162  defines a series of circumferentially-spaced apertures or slots  164  that receive upstanding hooks or latches  166  on the stent  160 . As seen in  FIG. 16B , the coupling ring  162  surrounds the commissures of the valve member  30  and seats on the base ring  32 , and the latches  166  extend through the slots  164  and are secured therein by outwardly directed teeth  168 . In the illustrated embodiment, the latches  166  each comprise a pair of parallel, spaced apart upstanding members, each with an outwardly directed tooth  168 , which may be cammed inward toward one another as they pass through the slots  164 . As the teeth  168  clear the slot  164 , the parallel members resiliently spring outward thus latching the stent  160  to the coupling ring  162 . The coupling ring  162  may further include a plurality of outwardly projecting tabs  172  that are bent or curl around the base ring  32 . 
     To aid in guiding the latches  166  through the slots  164 , one or more guide members may be used to direct the coupling ring toward the stent such that the slots are aligned with the latch members. For example, in the illustrated embodiment, a plurality of guide filaments  170  are attached to each one of the upstanding latch members and passed through the corresponding slots.  FIG. 16A  illustrates the pre-assembled valve  10 M with the guide filaments  170  extending up through each of the slots  164 . The implantation procedure comprises first delivering and expanding the stent  160 , and then advancing the valve member  30  to the position shown in  FIG. 16B . The coupling ring  162  is then parachuted down the array of guide filaments  170 , ultimately facilitating passage of the latches  166  through the slots  164 . The final assembly is seen in  FIG. 16B . in a preferred embodiment, each two guide filaments  170  comprises a strand of a single looped passing through small holes in each of the latch members. Removal of the guide filaments  170  is thus a simple matter of just pulling one of the strands, or severing the loop in between the latch members. Note that guide filaments could be used on any of the embodiments described herein to facilitate coupling of the separate components of the prosthetic heart valves. For example, in another variation, a wireform similar to the embodiment illustrated in  FIG. 14A  may also be used with a guiding filament. 
     The exemplary embodiment shows the latches  166  extending around the outside of the base ring  32  of the valve member  30 . It is entirely feasible, on the other hand, to design the latches  166  to pierce through the base ring  32 . Inclusion of the coupling ring  162  is suggested, because of its washer-like function in holding the assembly together. However, the latches  166  may be designed to pierce through and securely fasten to stent  160  to the base ring  32  without the use of the coupling ring  162 . In this regard, the latches  166  may be configured differently, or more than the number shown may be provided. For example, 4, 6, 8, or more single latch members having a configuration such as shown with a leading sharp point and rearwardly directed barb (much like a fishhook) could fight adequate anchorage through a conventional base ring  32  made of a silicone sponge covered with cloth. Those of skill in the art will understand that there are numerous alternatives available. 
     The stent  160  in  FIGS. 16A and 16B  has an outflow end that is preferably sized larger than its inflow end. More particularly, the outflow end is flared so as to receive therein the base ring  32  of the valve member  30 . In this way, a larger orifice valve member can be utilized than with a straight tubular stent. The reader is also reminded that at least the flared portion of the stent  160  is desirably provided with a sleeve of Dacron or other such fabric to help prevent paravalvular leaking between the base ring  32  and the surrounding native valve annulus. 
     With reference to  FIGS. 17A and 17B , yet another two-part prosthetic valve  10 N is configured for rapid deployment in a heart for replacing a defective native valve. In this version, an expandable anchoring member or stent  180  couples to a valve member  30  through the use of a coupling ring  182  in a manner similar to the last-described embodiment. The coupling ring  182  carries a plurality of latches  184  which mate with brackets  186  provided on the stent  180 . In the illustrated embodiment, the latches  184  again comprise a pair of spaced-apart latch members having outwardly directed teeth  188 , and the brackets  186  are simply apertures or slots in material loops that extend outward from the stent  180  adjacent its outflow end. Bringing the three components together, the latches  184  extend through the brackets  186  as seen in  FIG. 17B . To facilitate proper and rapid passage of the latches  184  through the brackets  186 , a plurality of guide filaments  190  loop through the brackets  186  and through holes provided in the latches  184 . Simply parachuting the coupling ring  182  down the filaments  190  aims the latches  184  through the brackets  186 . 
     At this stage, it is important to note that any of the fixation rings (i.e., locking ring  112 , fixation ring  134 , adapter  142 , coupling ring  162 , or coupling ring  182 ) described above could be designed to engage the surrounding tissue (annulus) and provide additional protection again paravalvular leakage. For example, a tissue growth factor or fibrin glue or the like may be coated on the exterior of any of these fixation rings for a better seal. Alternatively, the fixation rings might have an outer rim of fabric for encouraging tissue ingrowth. Moreover, the various fixation rings described and the base ring  32  of the valve member  32  may be constructed as a single component. For example, the base ring  32  could be configured to have slots (or any coupling member) in lieu of a separate fixation ring. 
     With reference now to  FIG. 18 , an alternative expandable anchoring member or stent  200  is illustrated wherein the anchoring member is configured to receive a valve member  30  to form a prosthetic heart valve. As illustrated in  FIG. 19 , a portion of the valve member is gripped between inwardly extending members located within the stent. More particularly, the stent  200  comprises a plurality of axial struts  202  connected by a number of rows of circumferential crown-shaped struts  204  to form a generally tubular structure. A lower or inflow end of the stent  200  includes a circumferential row of crown-shaped struts  206  that is larger than the others such that the inflow end of the stent flares outward. The upper rows  204  of circumferential struts define valleys (pointing downward) at the axial struts  202  and peaks (pointing upward) midway between each two adjacent axial struts. As seen from  FIG. 18 , therefore, the spaces defined between adjacent axial struts  202  and adjacent rows of circumferential struts  204  are preferably chevron-shaped, pointed upward. Conversely, the lower circumferential row of struts  206  has upper peaks at the axial struts  202  and lower valleys therebetween, resulting in elongated hexagon-shaped spaces between the lower two circumferential rows of struts. 
     The stent  200  possesses a plurality of prongs that extend inward therefrom to capture the valve member  30 . As seen in  FIG. 19 , the base ring  32  of the valve member  30  seats on a plurality of lower prongs  208 .  FIG. 18  shows the lower prongs  208  extending inward from the lower row of struts  206  at the valleys between adjacent axial struts  202 . The lower prongs  208  terminate in enlarged heads  210  to prevent damage to the base ring  32 . As seen in  FIG. 19 , the lower prongs  208  project inward farther than the expanded to defined by the upper portion of the stent  200 . Additionally, a plurality of upper prongs  212  extend inward from one of the upper rows of circumferential struts  204 . In the illustrated embodiment, there are four rows of circumferential struts  204 , and the upper prongs  212  project inward from the second lowest row. As seen in  FIG. 19 , the upper prongs  212  contact the base ring  32  of the valve member  30 . In this manner, the valve member  30  is captured between the lower prongs  208  and upper prongs  212 . 
     In the illustrated embodiment, the stent  200  includes twelve axial struts  202 , and one of each of the prongs  208 ,  212  between each adjacent pair of axial struts, resulting in twelve each of the lower and upper prongs. Of course, the number of prongs could be more or less depending on the configuration of the stent  200 . Further, there may be more than one prong between adjacent pairs of axial struts  202 , or the prongs may be provided only between every other pair. The prongs  208 ,  212  may be initially flat within the profile of the surrounding struts to prevent interference with an expansion-balloon. After stent deployment they may be bent inward into the angles shown using a tool (not shown). Alternatively, the balloon wall could be relatively thick and able to withstand puncture by the round heads of the prongs  208 ,  212  such that they are at all times biased inward and automatically assume the angles shown after balloon removal. 
     To deploy the prosthetic heart valve of  FIGS. 18 and 19 , the user advances the stent  200  in a collapsed state through the vasculature or a chest port into the target implantation site. Through self-expansion or balloon-expansion, the stent  200  expands into contact with the surrounding valve annulus. The valve member  30  then advances into position adjacent the outflow or upper end of the stent  200 . Desirably, the valve member  30  is a conventional non-expandable design, but could also be expandable, in which case it is then expanded prior to assembly with the stent  200 . 
     The outer diameter of the base ring  32  of the valve member  30  is sized approximately the same as the inner diameter of the tubular upper portion of the stent  200 . The valve member  30  advances from the outflow end of the stent  200  toward the inflow end until the base ring  32  contacts the circular row of upper prongs  212 . The upper prongs  212  are flexible, hinged, or otherwise capable of being displaced outward by the base ring  32  as the valve member  30  passes. Ultimately, the base ring  32  seats on the circular row of relatively non-flexible lower prongs  28  and the valve member  30  cannot be advanced farther. The spacing between the lower prongs  208  and the upper prongs  212  is such that the upper prongs  212  spring inward at the point that the base ring  32  seats on the lower prongs  208 . The upper prongs  212  may be formed with blunt heads like the lower prongs  208 , or may be straight or even sharp-pointed to pierce the base ring  32  and provided enhanced anchorage. In a preferred embodiment, both the lower prongs  208  and upper prongs  212  possess enlarged, blunt heads such that the base ring  32  is merely trapped between the two sets of prongs. 
     The design of the stent  200  of  FIG. 18  thus enables rapid deployment of a valve member therewithin, as well as positive tactile feedback to the user with valve member  30  is completely installed. Because the base ring  32  is sized closely within the stent  200 , good peripheral sealing is provided. To better enhance sealing, a peripheral skirt or layer of graft material may be added on the interior or exterior of the stent  200 . 
     With reference to  FIG. 20 , another embodiment of a prosthetic heart valve  220  comprises a tubular, expandable anchoring member or stent  222 , a valve member  30 , and an adapter ring  224  for coupling the two components together. The stent  222  and manner of connecting the stent to the valve member  30  is similar to embodiment of  FIGS. 3 and 4 , and also the embodiment of  FIG. 12 , in that a plurality of tines  226  project upward from the stent  222 . However, instead of the tines  226  piercing or curling around the base ring  32  of the valve member  30 , the tines interact with the adapter ring  224 . In particular, the adapter ring  224  attaches around the lower periphery of the base ring  32 , preferably via a secure stitch line formed during assembly of the valve member  30 . The tines  226  pierce or otherwise engage the adapter ring  224  instead of the base ring  32  to couple the valve member  30  to the stent  222 . The supplemental adapter ring  224  provides an added margin of safety that helps prevent damage to the valve member  30  by the tines  226 . For instance, if the tines  226  are configured to pierce and curl inward, they are farther away from the inner flexible leaflets  36  of the valve member which are susceptible to puncture or tearing. 
     With reference to  FIG. 21 , yet another embodiment of a prosthetic heart valve  230  comprises an anchoring member or stent  232  coupled to a valve member  30  via a plurality of sutures  234 . The components of the valve  230  are shown exploded above a container or jar  236  used to store the components. In this regard, the entire assembly, including the attachment sutures  234 , may be stored together in the jar  236  so as to be ready for deployment. Alternatively, only the stent  232  and valve member  30  may be stored in the jar  236 , and the sutures  234  added just prior to deployment but before the actual operation. Still further, the stent  232  can be stored dry in a sterile container, while the valve member  30  having bioprosthetic leaflets may be stored separately in a suitable preservative fluid such as glutaraldehyde. In any event, details of the prosthetic heart valve  230  will be described below with reference to  FIGS. 22A through 22C . 
       FIGS. 22A through 22C  show the components of the prosthetic heart valve  230  in conjunction with a valve dilator/delivery tube  240 . The usage of the delivery tube  240  will be described below. The stent  232  comprises an expandable, tubular structure formed of a plurality of axial struts  242  joined by a plurality of angled circumferential struts  244 . In this embodiment, there are four rows of circumferential struts  244 , the upper two pointing upward, and the lower two pointing downward. The result is a series of both diamond-shaped and chevron-shaped openings. Three axial bars  246  substitute for the narrower struts  242  at three evenly-spaced positions around the stent  232 . As seen in the view of  FIG. 22B , the commissures  34  of the valve member  30  align with the axial bars  246 . 
     With reference now to the sectional view of  FIG. 22C , the stent  232  additionally comprises an inner fixation ring  250  and an outer sealing ring  252 . Both these rings  250 ,  252  attach to the struts of the stent  232  independently, or to each other through the struts. For example, a series of sutures (not shown) can be used to join the inner ring  250  and outer ring  252  in a relatively continuous circumferential line around the stent  232 . These rings are desirably made of suture-permeable, typically compressible material such as silicone rubber, or may be rolled up fabric cuffs. In any event, the inner fixation ring  250  couples to the valve member  30 , while the outer sealing ring  252  help prevent leakage around the stent  232 . 
     As seen in  FIG. 22A , the attachment sutures  234  extend upward within the stent  232  from the inner fixation ring  250 . In this regard, each two strands of the attachment sutures  234  may be defined by looping a single length of suture downward and back upward through the fixation ring  250 . The circular array of sutures  234  then passes through corresponding sectors of the base ring  32  of the valve member  30 . Again, this can be done at the time of valve assembly, just prior to the valve replacement procedure, or after the stent  232  has been implanted. Those of skill in the art will understand the process of lining up the circular array of attachment sutures  234  into the appropriate locations around the base ring  32  to permit the valve member  32  to parachute down the sutures until it contacts the fixation ring  250 . 
     The entire procedure will now be described in conjunction with use of the valve dilator/delivery tube  240 . As mentioned above, the valve replacement procedures described herein are sometimes done without removing the existing native valve. The annulus and valve leaflets are often heavily calcified, and sometimes provide a serious impediment to passage and implant of a replacement valve, even a valve that is initially quite small and balloon expanded. To help widened the orifice in which the prosthetic valve  230  will be implanted, the delivery tube  240  receives all of the valve components therein and acts as a protective sleeve and dilator. In a preferred embodiment, just the sealing ring  252  extends out of the delivery tube  240  at an inflow or leading end thereof. 
     First, the attachment sutures  234  are preinstalled within the fixation ring  250  and, while maintaining a non-crossing circular array, are passed through the delivery tube  240  to be accessible out the upper end. The sutures  234  are then passed through the appropriate locations within the base ring  32  of the valve member  30 . Of course, this can be done during fabrication of the prosthetic heart valve  230 , though some structure for maintaining the relative position and orientation of two components is required. In any event, a holder (not shown) attached to the valve member  30  is used to advance the valve member along the array of sutures  234  and within the delivery tube  240 , into the approximate position seen in  FIG. 22A . 
     When the patient has been prepared, and an access opening to the target implantation site created, the assembly of the prosthetic heart valve  230  within the delivery tube  240  advances into the body. The leading end comprises the sealing ring  252  and an outwardly bulged portion  254  in the delivery tube  240 . For installation in the aortic annulus, the delivery tube  240  advances down the ascending aorta until the stent  232  lines up with the annulus (with the help of radiopaque markers or the like). The outwardly bulged portion  254  in the delivery tube  240  helps open up the calcified annulus. Even if the native valve is resected, sometimes the annulus will shrink a little prior to implant of the valve. The valve dilator/delivery tube  240  thus helps open up the annulus to permit implant of a desired diameter valve. The contour of the bulged portion  254  is relatively smooth, and the material may be Teflon or other such highly lubricated surface so that the tube easily slips through the annulus. A slight back-and-forth movement may be required to fully open the annulus. 
     At this stage, the delivery tube  240  retracts relative to the stent  232 , through the use of a pusher (not shown) for example, such that the stent  232  may fully expand into the annulus. The stent  232  may be self-expanding and thus be only partially expanded within the delivery tube  240 . When the delivery tube  240  is removed, the stent  232  springs outward into firm engagement with the annulus. Alternatively, a balloon (not shown) may be used to accomplish the final expansion of the stent  232 , which configuration would require a catheter passing through the center of the valve leaflets  34 . If the stent  232  is balloon expandable, consideration must be taken of the continual attachment of the valve to the guide sutures  234 . On the other hand, if the stent  232  is self-expanding, then typically an auxiliary sheath would be provided to hold the stent in the contracted condition. 
     When the user is satisfied that the stent  232  is properly positioned, the valve member  30  is advanced using the aforementioned holder (not shown). As the valve member  30  advances, care is taken to ensure that the attachment sutures  234  remain untangled and taut. Ultimately, the valve member  30  seats on the fixation ring  250  as seen in  FIGS. 22B and 22C . At this point, the user ties off and severs the attachment sutures  234  in a conventional manner. The provision of the sealing ring  252  directly adjacent and surrounding the fixation ring  250  greatly enhances the ability of the prosthetic valve  230  to resist paravalvular leaking. 
     In one advantageous feature, preferred embodiments of the component based prosthetic valves described herein may be used with existing technology. For example, certain stent embodiments may be configured for attachment to sewing rings provided on existing prosthetic valves. In other cases, the valve member requires only small variations in order to be used with the component-based system. Not only will this contribute to a lower price for the final valve, but also lend familiarity to the system for surgeons who might be hesitant to adopt a completely new system. 
     It will be appreciated by those skilled in the art that embodiments of the present invention provide important new devices and methods wherein a valve may be securely anchored to a body lumen in a quick and efficient manner. Embodiments of the present invention provide a means for implanting a prosthetic valve in a surgical procedure without requiring the surgeon to suture the valve to the tissue. Accordingly, the surgical procedure time is substantially decreased. Furthermore, in addition to providing an anchoring member for the valve, the stent may be used to maintain the native valve in a dilated condition. As a result, it is not necessary for the surgeon to remove the native leaflets, thereby further reducing the procedure time. 
     It will also be appreciated that the present invention provides an improved system wherein a valve member may be replaced in a more quick and efficient manner. More particularly, it is not necessary to cut any sutures in order to remove the valve. Rather, the valve member may be disconnected from the stent (or other support structure) and a new valve member may be connected in its place. This is an important advantage when using biological tissue valves or other valves having limited design lives. Still further, it will be appreciated that the devices and methods of the present invention may be configured for use in a minimally invasive approach (e.g., through a small incision between the ribs) or in a percutaneous procedure while still remaining within the scope of the invention. 
     While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description and not of limitation. Therefore, changes may be made within the appended claims without departing from the true scope of the invention.