US20080208327A1 - Method and apparatus for replacing a prosthetic valve - Google Patents

Abstract

In one aspect, the present disclosure concerns a percutaneously delivered adapter stent that is deployed within a previously implanted prosthetic valve and serves as an anchor or platform for implanting a percutaneously delivered replacement valve within the previously implanted valve. The adapter stent can be delivered to the implantation site via the patient's vasculature and positioned within the previously implanted valve. The stent can then be deployed to cause the stent to expand and become anchored to the inner surface of the previously implanted valve. Subsequently, the replacement valve can be positioned within the adapter stent and deployed to cause the replacement valve to expand and become anchored to the adapter stent. The adapter stent and the replacement valve can be mounted on the same catheter for delivery to the implantation site.

Description

FIELD
• The present invention relates to embodiments of a method and apparatus for replacing a previously implanted prosthetic valve, such as a surgically implanted prosthetic heart valve, without removing the previously implanted valve from the body.
BACKGROUND
• Prosthetic valves, such as prosthetic heart valves, are implanted in the body to replace a failing or diseased natural valve. Should the prosthetic valve begin to fail, it also may need to be replaced with another prosthetic valve. Surgically implanted, prosthetic heart valves, such as a prosthetic aortic valve, typically are replaced about every 15 years. The current method for replacing a surgically implanted, prosthetic heart valve involves open heart surgery wherein the patient's chest is opened and the existing prosthetic valve is removed and replaced with a new prosthetic valve. As can be appreciated, this is a traumatic and high risk procedure accompanied by substantial morbidity and mortality, and in some cases, cannot even be attempted due to the advanced age and/or medical condition of the patient.
• Therefore, it would be preferable to replace a prosthetic heart valve with a percutaneously implanted valve that is delivered to the implantation site via the patient's vasculature and deployed within the previously implanted valve. However, because existing prosthetic heart valves can vary widely in size and shape, there are substantial difficulties associated with the development and validation of a percutaneously delivered replacement valve that is compatible with different types of existing prosthetic heart valves. More particularly, difficulties arise because a replacement valve that does not conform to the geometry of the previously implanted valve may not be able to adequately anchor to the previously implanted valve and/or form an effective seal with the previously implanted valve.
SUMMARY
• In one aspect, the present disclosure concerns a percutaneously delivered adapter stent that is deployed within a previously implanted prosthetic valve and serves as an anchor or platform for implanting a percutaneously delivered replacement valve within the previously implanted valve. The replacement valve can be any known percutaneous valve. The adapter stent can be adapted to provide a suitable mounting platform for implanting a percutaneous replacement valve in a wide range of existing surgical valves, which typically vary widely in size and shape from patient to patient. In one advantageous feature, the adapter stent increases the frictional forces between the percutaneous replacement valve and the failing surgical valve, thereby providing a more predictable orientation and securement of the percutaneous replacement valve. Hence, this technique is particularly suited for replacing a surgically implanted prosthetic heart valve, but also could be used for replacing a percutaneously implanted prosthetic valve.
• The adapter stent can be delivered to the implantation site via the patient's vasculature and positioned within the previously implanted valve. The stent can then be deployed to cause the stent to expand and become anchored to the inner surface of the previously implanted valve. Subsequently, the replacement valve can be positioned within the adapter stent and deployed to cause the replacement valve to expand and become anchored to the adapter stent.
• In particular embodiments, the adapter stent and the replacement valve can be mounted on the same delivery catheter for delivery to the implantation site. In one implementation, for example, the adapter stent and the replacement valve can be crimped around respective first and second balloons of a double-balloon catheter. In this approach, the adapter stent is positioned in the previously implanted valve and expanded into contact with the previously implanted valve by inflating the first balloon. The catheter is then repositioned to place the replacement valve in the deployed adapter stent, after which the valve is expanded into contact with the adapter stent by inflating the second balloon. In another implementation, the adapter stent and the replacement valve are self-expandable. The self-expandable adapter stent and valve can be mounted on a common delivery catheter adapted to retain the stent and the valve in compressed positions while they are advanced through the patient's vasculature. Using the catheter, the adapter stent and the valve can be successively positioned and deployed within the previously implanted valve.
• The adapter stent in exemplary embodiments can comprise an expandable frame that mounts a flexible annular sealing member. The sealing member provides a seal between the previously implanted valve and the replacement valve to prevent or at least minimize blood flow between the original and replacement valves.
• The adapter stent may be configured to have a length that is greater than the length of the previously implanted valve that needs to be replaced. This allows the stent to extend over the entire inner surface of the previously implanted valve to provide sufficient surface area for anchoring the replacement valve and to ensure that the previously implanted valve does not interfere with the positioning and deployment of the replacement valve. In certain embodiments, the adapter stent, when expanded, has enlarged end portions that flare or extend radially outwardly past the adjacent ends of the previously implanted valve to assist in securing the adapter stent in place.
• In one representative embodiment, a method is provided for percutaneously implanting a replacement prosthetic valve at a site occupied by a previously implanted prosthetic valve. The method includes positioning an adapter stent within the previously implanted valve, deploying the adapter stent to cause the adapter stent to become anchored to the previously implanted valve, positioning the replacement valve within the deployed adapter stent, and deploying the replacement valve to cause the replacement valve to become anchored to the adapter stent.
• In another representative embodiment, a method of percutaneously implanting a replacement prosthetic valve in a patient at a site occupied by a previously implanted prosthetic valve includes advancing a catheter carrying an adapter stent through the patient's vasculature to position the adapter stent within the previously implanted valve. The catheter also carries the replacement valve. The method further includes deploying the adapter stent to cause the adapter stent to become anchored to the previously implanted valve, repositioning the catheter to position the replacement valve within the deployed adapter stent, and deploying the replacement valve to cause the replacement valve to become anchored to the adapter stent.
• In another representative embodiment, an assembly is provided for percutaneous replacement of a previously implanted prosthetic valve without removal of the previously implanted valve. The assembly comprises an adapter stent comprising a frame and an annular sealing member. The adapter stent is adapted to be deployed within the previously implanted valve. The assembly also includes a percutaneous, replacement prosthetic valve comprising a frame and a flexible valve member. The valve is adapted to be deployed within the deployed adapter stent such that the sealing member provides a seal between the previously implanted valve and the replacement valve.
• In yet another representative embodiment, an assembly for percutaneous replacement of a previously implanted prosthetic valve comprises a percutaneous, replacement prosthetic valve comprising a frame and a flexible valve member. The assembly also includes means for anchoring and sealing the replacement valve to the previously implanted valve, said means being separately deployable within the previously implanted valve prior to deploying the replacement valve within said means.
• The foregoing and other features and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a side elevation view of one embodiment of an assembly comprising a percutaneous prosthetic valve and an adapter stent for anchoring the prosthetic valve within a previously implanted prosthetic valve.
• FIG. 2 is a perspective view of the prosthetic valve shown inFIG. 1.
• FIG. 3 is a schematic side view of an embodiment of a double-balloon catheter showing the prosthetic valve and the adapter stent ofFIG. 1 crimped around respective balloons on the catheter for percutaneous delivery to an implantation site.
• FIGS. 4A-4G illustrate the successive steps of one specific embodiment of an implantation procedure employing the double-balloon catheter shown inFIG. 2 for implanting the adapter stent and the prosthetic valve inside a failing surgically implanted, prosthetic valve previously implanted in the aortic orifice of a patient.
• FIG. 5 is a schematic side view of one embodiment of delivery catheter that can be used to implant a self-expanding adapter stent and replacement valve inside a previously implanted valve.
• FIG. 6 is a side elevation view of another embodiment of an adapter stent that can be used to anchor a replacement valve within a previously implanted prosthetic valve.
• FIG. 7 illustrates another embodiment of an implantable assembly for replacing a previously implanted prosthetic valve.
• FIG. 8 illustrates the assembly ofFIG. 7 deployed within a previously implanted surgical valve.
DETAILED DESCRIPTION
• As used herein, the singular forms “a,” “an,” and “the” refer to one or more than one, unless the context clearly dictates otherwise.
• As used herein, the term “includes” means “comprises.” For example, a device that includes or comprises A and B contains A and B but may optionally contain C or other components other than A and B. A device that includes or comprises A or B may contain A or B or A and B, and optionally one or more other components such as C.
• In one aspect, the present disclosure concerns a percutaneously delivered adapter stent that is deployed within a previously implanted prosthetic valve and serves as an anchor or platform for implanting a percutaneously delivered replacement valve within the previously implanted valve. As used herein, the term “stent” refers generally to any luminal structure. The replacement valve can be any known percutaneous valve. The adapter stent can be advanced through the patient's vasculature and positioned within the previously implanted valve. The adapter stent can then be deployed to cause the adapter stent to expand and become anchored to the inner surface of the previously implanted valve. The replacement valve can then be positioned within the adapter stent and deployed to cause the replacement valve to expand and become anchored to the adapter stent. In one respect, the adapter stent is configured to increase the frictional forces between the replacement valve and the failing previously implanted valve, thereby providing a more predictable orientation and securement of the replacement valve. In the following description, the adapter stent and the replacement valve are shown and described in connection with replacing a previously implanted aortic valve. However, the embodiments described herein can also be used to replace prosthetic valves implanted at other locations in the heart or in other body channels having native valves, such as veins or other organs.
• FIG. 1 shows anassembly10 comprising a percutaneousprosthetic heart valve12 and anadapter stent30, according to one embodiment. Theadapter stent30 can be deployed within a failing, previously implanted valve, such as the prostheticaortic valve60 shown inFIG. 4A. Once theadapter stent30 is deployed within the previously implanted valve, thenew valve12 can be deployed within theadapter stent30 to replace the previously implantedvalve60. The previously implantedvalve60 shown in the figures is a surgical valve (i.e., a valve implanted via open heart surgery), although theadapter stent30 and thereplacement valve12 can also be deployed within a previously implanted percutaneous valve.
• Thevalve12 and theadapter stent30 are each crimpable or compressible to a reduced diameter for percutaneous delivery to the implantation site, such as using a delivery catheter. When expanded to their functional size (FIG. 1), the outer diameter of thevalve12 desirably is approximately equal to the inner diameter of the adapter stent and the outer surface of thevalve12 generally conforms to an inner surface portion of theadapter stent30 to promote attachment of thevalve12 to theadapter stent30. Methods for implanting theadapter stent30 and thevalve12 are described in greater detail below.
• As shown inFIGS. 1 and 2, thevalve12 in the illustrated embodiment includes anannular frame14 that mounts aflexible valve member16. Theframe14 in the illustrated embodiment comprises a plurality of angularly-spaced axial struts, or support members,18 that extend axially (longitudinally) along the frame and a plurality of support posts, or beams,20 (one of which is shown inFIGS. 1 and 2) spaced in the illustrated example at 120-degree intervals from each other around theframe14. The support posts20 can be formed withapertures22 to facilitate attachment of thevalve member16 to theposts20, such as, for example, by suturing thevalve member16 to the posts. Theframe14 can also include a plurality of axially-spaced, circumferential bands, or struts,24 attached to theaxial struts18 and the support posts20. Thestruts24 are formed with multiple bends that allow theframe14 to be crimped to a smaller diameter for delivery to an implantation site and expanded to its functional size for anchoring the valve assembly to theadapter stent30 at the implantation site. For example, each of thestruts24 in the illustrated configuration includes a plurality oflinear strut members26a,26barranged in a zig-zag or saw-tooth configuration defining bends between adjacent strut members.
• In alternative embodiments, the frame can have other configurations. For example, one or more of thecircumferential bands24 can have a curved or serpentine shape rather than a zig-zag shape. Further, theframe14 can include various attachment elements (not shown), such as barbs, staples, flanges, and the like for enhancing the ability of the frame to anchor to theadapter stent30.
• Theframe14 can be made from any of various suitable ductile and/or elastic materials and is typically made of a metal, such as stainless steel, titanium, or other biocompatible metals. Theframe14 or components thereof can also be made from a shape memory alloy such as nickel titanium (NiTi) shape memory alloys, as marketed, for example, under the trade name Nitinol. The shape-memory components allow thevalve12 to be self-expandable; that is, thevalve12, when restrained in a radially compressed state by an outer restraint (e.g., a sheath covering the valve), automatically expands to its functional size when the outer restraint is removed.
• Thevalve member16 can have a leafed-valve configuration, such as the tricuspid valve configuration shown in the illustrated embodiment. Thevalve member16 can be formed from three pieces of pliant material connected to each other at seams aligned withposts20 to form collapsible leaflets28 (FIG. 2). Thevalve member16 can be made from biological matter, such as natural tissue, pericardial tissue (such as bovine, porcine or equine pericardium), a harvested natural valve or other biological tissue. Alternatively, thevalve member16 can be made from biocompatible polymers or similar materials.
• Various other prosthetic valve configurations also can be used. Examples of other valves that can be utilized are disclosed in U.S. Pat. No. 6,730,118, U.S. Pat. No. 6,767,362, and U.S. Pat. No. 6,908,481, which are incorporated herein by reference.
• Theadapter stent30 in exemplary embodiments includes anexpandable frame32 that mounts a flexibleannular sealing member34. Theframe32 is shown inFIG. 1 in its expanded, functional size, and is configured to be crimpable to a reduced diameter for percutaneous delivery, such as on a delivery catheter. Theframe32 can be made from any of various suitable ductile and/or elastic materials and is typically made of a metal, such as stainless steel, titanium, or other biocompatible metals. Theframe14 or components thereof can also be made from a shape memory material, which allows thestent30 to be self-expandable.
• Theframe32 is the illustrated embodiment comprises a plurality of longitudinally extending, zig-zag struts36 joined to each other atjunctures38. Theframe32 has a length L measured between the opposite ends thereof that desirably is greater than the length of the previously implanted valve that needs to be replaced. In this manner, theframe32, when deployed within the previously implanted valve, can extend over the entire inner surface area of the previously implanted valve to provide sufficient surface area for anchoring thereplacement valve12 and to ensure that the previously implanted valve does not interfere with the positioning and deployment of thereplacement valve12. In particular embodiments, for example, the length L of the frame is about 10 mm to about 40 mm, with about 30 mm being a specific example,
• As shown, theframe32 in exemplary embodiments has a generally cylindricalintermediate portion44 extending between theopposite end portions40,42, which are enlarged or flared relative to theintermediate portion44 when the frame is expanded. Eachend portion40,42 desirably expands to a diameter that is greater than the diameter of the previously implanted valve. Hence, when theadapter stent30 is deployed within the previously implanted valve, theend portions40,42 can extend radially outwardly past the adjacent ends of the previously implanted valve to assist in securing the adapter stent in place.
• In alternative embodiments, theframe32 can have various other shapes or configurations. For example, theframe32 can be generally cylindrical or tubular along its entire length without enlarged end portions. Theframe32 optionally can be provided with various attachment elements (not shown), such as barbs, staples, flanges, and the like for enhancing the ability of the frame to anchor to the previously implanted valve60 (FIG. 4A). If desired, theframe32 may be provided with attachment elements along the inner surface for enhancing the ability of theframe32 to securely engage theframe14 of the percutaneously deliveredreplacement valve12.
• The sealingmember34 provides a seal between the previously implantedvalve60 and thereplacement valve12 to prevent or at least minimize blood flow between the valves. As shown inFIG. 1, the sealingmember34 desirably extends nearly the entire length of theframe32 to maximize the surface area that can contact the previously implantedvalve60 and thereplacement valve12. In other embodiments, however, the sealing member can extend along only a portion of theframe32, such as theintermediate portion44. With reference to the embodiment shown inFIG. 1, the sealingmember34 is secured to the inner surface of theframe32. Alternatively, the sealing member can be secured to the outer surface of theframe32 as shown inFIG. 6 to prevent the leakage of blood. In another implementation, a sealingmember34 can be secured to both the inner and outer surfaces of theframe32.
• In particular embodiments, the sealingmember34 is made of a natural or synthetic biocompatible elastomeric material, such as foam rubber, thermoplastic elastomers (e.g., polyurethanes) or other polymeric elastomers, such as a polymeric sponge. The sealingmember34 can be secured to or formed on the frame using any suitable techniques or mechanisms, such as by suturing the sealing member to the frame or co-molding the sealing member to the frame. The sealingmember34 also can be formed on the frame using conventional coating techniques, such as spray coating, dip coating, or roll coating.
• Thevalve12 and theadapter stent30 can be implanted using a double-balloon catheter.FIG. 3, for example, shows the distal end portion of an exemplary embodiment of a double-balloon catheter, indicated at70. Thecatheter70 includes ashaft72, on which there are mounted first and second, spaced-apart balloons74,76, respectively, between a respective pair ofrings80,82. Theadapter stent30 and thereplacement valve12 are crimped around thefirst balloon74 and thesecond balloon76, respectively. Theshaft72 contains two lumens (not shown), each of which is fluidly connected to arespective balloon74,76 for successive and separate inflation of each balloon. Theshaft72 also contains another lumen to accept aguide wire78 so that the catheter can be advanced over theguide wire78 for guiding the catheter through the patient's vasculature.
• Thecatheter70 can be introduced percutaneously into the patient's vasculature (e.g., into a peripheral artery such as the femoral artery) and advanced to the implantation site. For example, for replacing a prosthetic aortic valve, the catheter in certain embodiments has a length of at least about 80 cm, usually about 90-100 cm, to allow transluminal positioning of the shaft from the femoral and iliac arteries to the ascending aorta. Alternatively, the shaft may have a shorter length, e.g. about 20-60 cm, for introduction through the iliac artery, through the brachial artery, through the carotid or subclavian arteries, or through a penetration in the aorta itself. In the femoral approach, the catheter desirably is long enough and flexible enough to traverse the path through the femoral artery, iliac artery, descending aorta and aortic arch. At the same time, the catheter desirably has sufficient pushability to be advanced to the ascending aorta by pushing on the proximal end, and has sufficient axial, bending, and torsional stiffness to allow the physician to control the position of the distal end, even when the catheter is in a tortuous vascular structure. Alternatively, the catheter may be passed through a port between ribs in the patient's thorax above the heart and through an incision in the heart wall (e.g., through the apex of the left ventricle) or through an incision in the aortic arch, in a so-called minimally-invasive procedure.
• A procedure for implanting thevalve12 and theadapter stent30 using thecatheter70, according one embodiment, is illustrated inFIGS. 4A-4G.FIG. 4A illustrates the previously implantedvalve60 implanted in the aortic annulus between theleft ventricle chamber86 and the ascendingaorta88. As noted above, the illustratedvalve60 is a surgical valve, although theadapter stent30 and thereplacement valve12 can also be implanted within an existing percutaneous valve. Thecatheter70 can be introduced percutaneously into the patient's vasculature and advanced to the implantation site using known techniques. For example, a blood vessel (e.g., the femoral artery) typically is dilated using a conventional dilator to allow an introducer sheath to be inserted into the blood vessel. Theguide wire78 can then be inserted into the blood vessel via the introducer sheath and advanced to the implantation site. Subsequently, thecatheter70 can be advanced over theguide wire78 to position theadapter stent30 in the previously implantedvalve60. More precisely, theadapter stent30 desirably is positioned such that theend portions40,42 are located outside the adjacent ends of the previously implantedvalve60, as shown inFIG. 4B.
• As depicted inFIG. 4C, theballoon74 is then inflated to deploy theadapter stent30, which expands to its functional size and engages the inner surface of the previously implantedvalve60. As shown, in its expanded stated, theend portion40,42 flare radially outwardly past the adjacent ends of the previously implanted valve to assist in retaining theadapter stent30 in place against thevalve60. In addition, theadapter stent30, in the illustrated example, also extends over the entire inner surface area of the existingvalve60 and causes theflexible leaflets62 of the valve to expand radially outwardly, thereby providing a surface area suitable for mounting thereplacement valve12.
• Thereafter, theballoon74 is deflated (FIG. 4D) and thecatheter70 is retracted slightly to position thereplacement valve12 within the deployed adapter stent30 (FIG. 4E). Thesecond balloon76 is then inflated to deploy thereplacement valve12, which expands to its functional size and engages the inner surface of the adapter stent30 (FIG. 4F). Once thereplacement valve12 is deployed, theballoon76 can be deflated and thecatheter70 can be removed from the body (FIG. 4G).
• Theadapter stent30, as well as thevalve12, can be positioned at the implantation site with the assistance of fluoroscopy and radiopaque markers, ultrasonic imaging, and the like. For example, rings80,82 on thecatheter shaft72 can be made of any of various suitable metals that are visible during fluoroscopy for use in positioning the adapter stent and/or the valve. Alternatively, radiopaque markers can be provided on portions of theadapter stent30 and/or thevalve12.
• In an alternative approach, thereplacement valve12 can be mounted on thefirst balloon74 and theadapter stent30 can be mounted on thesecond balloon76. In this approach, theadapter stent30 is first deployed within the previously implantedvalve60 while thefirst balloon74 and thereplacement valve12 are positioned in theaorta88. After theadapter stent30 is deployed, thecatheter70 is advanced further into theleft ventricle86 to position thefirst balloon74 and thereplacement valve12 within the deployedadapter stent30. Thereplacement valve12 can then be deployed by inflating thefirst balloon74.
• As noted above, theframe32 of theadapter stent30 and theframe14 of thereplacement valve12, or portions thereof, can be made of a shape-memory material, which allows theadapter stent30 and thevalve12 to be self-expandable.FIG. 5 is a schematic view of the distal end portion of a delivery catheter, indicated at90, which can be used to implant a self-expanding replacement valve and adapter stent in the previously implantedvalve60. Thecatheter90 includes ashaft92 and an outer sheath94, which is moveable longitudinally relative to theshaft92. Theshaft92 can include a lumen for receiving aguide wire78. Thevalve12 and theadapter stent30 are mounted to theshaft92 in their compressed states. The outer sheath94 extends over thevalve12 and theadapter stent30 to retain the valve and adapter stent in their compressed states until each is positioned for deployment at the implantation site.
• Thecatheter90 can be introduced into the body and advanced through the patient's vasculature in the same manner as theballoon catheter70. Theadapter stent30 is first positioned in the previously implantedvalve60 and the outer sheath is retracted to expose theadapter stent30, which permits the adapter stent to expand into contact with the previously implanted valve. Thecatheter90 is then advanced slightly to position thevalve12 in the deployedadapter stent30. The outer sheath94 can then be retracted to expose thevalve12, which permits the valve to expand into contact with the adapter stent.
• Although less desirable, theadapter stent30 and thereplacement valve12 can be delivered and implanted at the site of the previously implanted valve using separate catheters. For example, theadapter stent30 and thevalve12 can be mounted on separate balloon catheters. In this approach, theadapter stent30 is implanted using a first balloon catheter, which is then removed from the body to allow a second balloon catheter carrying the replacement valve to be inserted into the body.
• As noted above, surgical valves, such asvalve60, typically vary widely in size and shape from patient to patient. Advantageously, theadapter stent30 can be adapted to provide a suitable mounting platform for implanting a percutaneous replacement valve in a wide range of surgical valves varying in size and shape.
• FIG. 7 illustrates another exemplary embodiment of anassembly100 comprising a percutaneousprosthetic valve12 and anadapter stent102. Theadapter stent102, likeadapter stent30, includes a radially compressible andexpandable frame102 that mounts a flexibleannular sealing member106.FIG. 8 illustrates theadapter stent102 and theprosthetic valve12 deployed within a previously implantedsurgical valve60. Theadapter stent102 has a length L that is preferably greater than the length of the previously implantedvalve60 but need not be longer than thenew valve12. In certain embodiments, theadapter stent102 has a length L of about 10 mm and thenew valve12 has a length of about 20 mm.
• In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. I therefore claim as my invention all that comes within the scope and spirit of these claims.

Claims (25)

1. A method of percutaneously implanting a replacement prosthetic valve at a site occupied by a previously implanted prosthetic valve, the method comprising:

positioning a stent within the previously implanted valve;

deploying the stent to cause the stent to become anchored to the previously implanted valve;

positioning the replacement valve within the deployed stent; and

deploying the replacement valve to cause the replacement valve to become anchored to the stent.

2. The method ofclaim 1 wherein the stent and the replacement valve are mounted on a common delivery catheter, which is used to position stent and the replacement valve at their respective deployment positions.

3. The method ofclaim 2 wherein:

the stent is mounted on a first balloon of the catheter and the replacement valve is mounted on a second balloon of the catheter;

deploying the stent comprises inflating the first balloon to cause the stent to expand and engage the previously implanted valve; and

deploying the replacement valve comprises inflating the second balloon to cause the replacement valve to engage the stent.

4. The method ofclaim 2, wherein:

the stent is self-expandable and is retained in a radially compressed state on the catheter by a sheath; and

deploying the stent comprises withdrawing the sheath from the stent to allow the stent to expand and engage the previously implanted valve.

5. The method ofclaim 4, wherein:

the replacement valve is self-expandable and is retained in a radially compressed state on the catheter by the sheath; and

deploying the replacement valve comprises withdrawing the sheath from the replacement valve to allow it to expand and engage the stent.

6. The method ofclaim 1, wherein:

the stent has a length that is greater than the length of the previously implanted valve and enlarged opposite end portions that are greater in diameter than an intermediate portion of the stent when the stent is deployed; and

when the stent is deployed, the enlarged opposite end portions of the stent are positioned outside of the previously implanted valve to assist in retaining the deployed stent in place.

7. The method ofclaim 1, the stent comprises an annular sealing member that creates a seal between the previously implanted valve and the replacement valve once deployed.

8. The method ofclaim 7, wherein the sealing member comprises an elastomer.

9. The method ofclaim 8, wherein the sealing member comprises sponge rubber.

10. The method ofclaim 1, wherein the previously implanted valve is located in the aortic annulus of a patient and the stent and the replacement valve are delivered to the deployment site via the aorta.

11. The method ofclaim 1, wherein the replacement valve comprises a frame and a valve member secured to the stent.

12. A method of percutaneously implanting a replacement prosthetic valve in a patient at a site occupied by a previously implanted prosthetic valve, the method comprising:

advancing a catheter carrying a stent through the patient's vasculature to position the stent within the previously implanted valve, the catheter also carrying the replacement valve;

deploying the stent to cause the stent to become anchored to the previously implanted valve;

re-positioning the catheter to position the replacement valve within the deployed stent; and

deploying the replacement valve to cause the replacement valve to become anchored to the stent.

13. The method ofclaim 12 wherein:

the stent is mounted on a first balloon of the catheter and the replacement valve is mounted on a second balloon of the catheter;

deploying the stent comprises inflating the first balloon to cause the stent to expand and engage the previously implanted valve; and

deploying the replacement valve comprises inflating the second balloon to cause the replacement valve to engage the stent.

14. The method ofclaim 12, wherein when the stent is deployed, opposite end portions of the stent extend outside opposite ends of the previously implanted valve and flare radially outwardly with respect to the opposite ends of the previously implanted valve.

15. An assembly for percutaneous replacement of a previously implanted prosthetic valve without removal of the previously implanted valve, the assembly comprising:

an adapter stent comprising a frame and an annular sealing member, the adapter stent being adapted to be deployed within the previously implanted valve; and

a percutaneous, replacement prosthetic valve comprising a frame and a flexible valve member, the valve being adapted to be deployed within the deployed stent such that the sealing member provides a seal between the previously implanted valve and the replacement valve.

16. The assembly ofclaim 15 wherein the sealing member comprises an elastomer.

17. The assembly ofclaim 15, wherein the sealing member extends substantially the entire length of the frame of the adapter stent.

18. The assembly ofclaim 15, wherein the sealing member is mounted on the outside of the frame of the adapter stent.

19. The assembly ofclaim 15, wherein the sealing member is mounted on the inside of the frame of the adapter stent.

20. The assembly ofclaim 15, wherein the frame of the adapter stent has an inlet end portion, an outlet end portion, and an intermediate portion extending between the end portions, the end portions being greater in diameter than the intermediate portion.

21. The assembly ofclaim 15, wherein the frame of the adapter stent has a length of at least about 10 mm.

22. The assembly ofclaim 15, wherein the frames of the replacement valve and the adapter stent are self-expandable.

23. The assembly ofclaim 15, wherein the replacement valve is a prosthetic heart valve.

24. An assembly for percutaneous replacement of a previously implanted prosthetic valve without removal of the previously implanted valve, comprising;

a replacement prosthetic valve having a frame and a flexible valve member, the replacement prosthetic valve being radially expandable and collapsible; and

means for anchoring and sealing the replacement valve to the previously implanted valve, said means being separately deployable within the previously implanted valve prior to deploying the replacement valve within said means.

25. The assembly ofclaim 24, wherein said means comprises an expandable frame and an annular sealing member secured to the frame.

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