Abstract:
Prosthetic valves that are adapted to be expanded into deployment and shrunk for repositioning and methods that are applicable to such valves.

Description:
BACKGROUND OF THE INVENTIONS 
       [0001]    Valve replacement is sometimes necessary in those instances where a patient experiences heart valve stenosis or regurgitation. Prosthetic valves typically include two structures, a leaflet device that consists of one or more leaflets which perform the opening and closing functions of the replaced biological valve and an anchor that holds the leaflet device in place. 
         [0002]    Valve replacement was for many years a highly invasive open heart procedure. During open heart surgery, the patient is placed under general anesthesia and connected to a heart-lung bypass machine so that blood can continue to circulate during the procedure. Access to the heart is obtained by way of a sternotomy. The defective valves were typically excised and prosthetic valves were implanted in their place. Although such procedures represented an advance in the area of heart valve stenosis and regurgitation treatment, there are a number of risks associated with open heart valve replacement procedures. Some risks, such as adverse reactions to the anesthesia, bleeding, and infections, are associated with surgical procedures in general. Other risks, such as death, stroke, heart attack, arrhythmia, and kidney failure, are more closely associated with open heart surgery. Surgical valve replacement may also be painful and require prolonged hosptialization. 
         [0003]    More recently, percutaneous heart valve replacement has been proposed as a less invasive alternative to open heart valve replacement procedures. Percutaneous valve replacement procedures often involve delivering a collapsed prosthetic valve to the deployment location (e.g. the mitral valve or aortic valve) on the distal end of a catheter. Once the prosthetic valve has reached the deployment location, the valve is deployed by expanding the anchor into contact with tissue in such a manner that the valve will not move. 
         [0004]    Percutaneous heart valve replacement has proven to be a significant advance because it eliminates many of the risks and other shortcomings associated with open heart valve replacement procedures. Nevertheless, the present inventor has determined that percutaneous heart valves, and the associated methods of deployment, are susceptibe to improvement. For example, the present inventor has determined that it can be quite difficult to move conventional prosthetic valves after they have been deployed in those instances where the deployment location is determined to be suboptimal. A subobtimal deployment location may, for example, be the result of less than optimal initial deployment of the valve or an anatomic shift that could occur years after a sucessful initial deployment. 
       SUMMARY OF THE INVENTIONS 
       [0005]    A prosthetic valve in accordance with one embodiment of a present invention includes an anchor that is configured to be expanded to a deployment size during the deployment process and to shrink to a smaller repositioning size when exposed to a condition that is not a normal body condition. A method in accordance with one embodiment of a present invention includes the step of shrinking a prosthetic valve by causing the valve anchor to transition from the martensitic state to the austenitic state. 
         [0006]    The present apparatus and methods provide a number of advantages over conventional apparatus and methods. For example, the present apparatus and methods allow valves that are at a less than optimal location to be simply and easily disengaged from the associated tissue structure (e.g. the tissue associated with the mitral valve or aortic valve), moved to a more optimal location and redeployed. Alternatively, if necessary, the disengaged valve may be percutaneously withdrawn from the patient. The present apparatus and methods are also less complicated than conventional apparatus and methods. As a result, the present apparatus, as compared to conventional valves, is easier to make and use, is less expensive, and may be deployed with a smaller delivery system to better facilitate percutaneous delivery. The present apparatus may also be deployed with a balloon or other inflatable structure, which physicians tend to be comfortable with. 
         [0007]    The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Detailed description of preferred embodiments of the inventions will be made with reference to the accompanying drawings. 
           [0009]      FIG. 1  is a side view of a prosthetic valve in accordance with one embodiment of a present invention. 
           [0010]      FIG. 2  is a front view of the prosthetic valve illustrated in  FIG. 1 . 
           [0011]      FIG. 3  is a side view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0012]      FIG. 4  is a plan view of a prosthetic valve and a delivery system in accordance with one embodiment of a present invention. 
           [0013]      FIG. 5  is a side view of a prosthetic valve and an expandable device in accordance with one embodiment of a present invention. 
           [0014]      FIG. 6  is a section view taken along line  6 - 6  in  FIG. 4 . 
           [0015]      FIGS. 7A-7D  are partial section views showing a prosthetic valve being deployed in accordance with one embodiment of present invention. 
           [0016]      FIGS. 8A-8F  are partial section views showing a prosthetic valve being repositioned and redeployed in accordance with one embodiment of present invention. 
           [0017]      FIG. 9  is a side view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0018]      FIG. 10  is a front view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0019]      FIG. 11  is a side view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0020]      FIG. 12  is a side, section view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0021]      FIG. 13  is a side, section view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0022]      FIG. 14  is a side, section view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0023]      FIG. 15A  is a side view of a prosthetic valve and an expandable device in accordance with one embodiment of a present invention. 
           [0024]      FIG. 16A  is a side view of a prosthetic valve on an unexpanded expandable device in accordance with one embodiment of a present invention. 
           [0025]      FIG. 16B  is a side view of a prosthetic valve on an expanded expandable device in accordance with one embodiment of a present invention. 
           [0026]      FIG. 16C  is a side view of an expanded expandable device in accordance with one embodiment of a present invention. 
           [0027]      FIG. 16D  is a side view of a prosthetic valve on an expanded expandable device in accordance with one embodiment of a present invention. 
           [0028]      FIG. 17  is a side view of an expandable device in accordance with one embodiment of a present invention. 
           [0029]      FIG. 18  is a side, cutaway view of an expandable device in accordance with one embodiment of a present invention. 
           [0030]      FIG. 19  is a side, cutaway view of an expandable device in accordance with one embodiment of a present invention. 
           [0031]      FIG. 20  is a side view of a prosthetic valve anchor in accordance with one embodiment of a present invention. 
           [0032]      FIG. 21  is a partial section view showing a prosthetic valve and delivery system in accordance with one embodiment of present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions. Additionally, although the present inventions are discussed below in the context of heart valves, the inventions herein also have application in other regions of the body such as, for example, the esophagus, stomach, ureter, vesica, biliary passages, lymphatic system, intestines, and veins outside the heart. 
         [0034]    As illustrated for example in  FIGS. 1 and 2 , a prosthetic valve  100  in accordance with one embodiment of a present invention includes a leaflet device  102  and an anchor  104 . The leaflet device  102  is configured to allow flow in one direction in response to a pressure differential across the prosthetic valve  100  and to prevent flow when the pressure differential is reversed. As such, the prosthetic valve  100  is well-suited for applications within the heart and may be used to replace one or more of the aortic, mitral, tricuspid and pulmonary valves. Although the present inventions are not limited to any particular leaflet device configuration, the exemplary leaflet device  102  includes three leaflets  102   a - c . The leaflets  102   a - c  may be in the form of biologic tissue leaflets (e.g. cadaver, bovine or porcine tissue) or synthetic leaflets (e.g. metal, polymer or engineered tissue). The leaflets  102   a - c  may be attached to the anchor  104  by, for example, welding, adhesive bonding, fusing, suturing, stapling, or some combination thereof. 
         [0035]    Turning to the exemplary anchor  104 , and as discussed in greater detail below in the context of  FIGS. 7A-7D  and  8 A- 8 F, the anchor is configured such that it may be delivered to a target location at a relatively small delivery size, mechanically deformed to a larger deployment size and, if necessary, activated in such a manner that it will shrink to a repositioning size that is smaller than the deployment size. The exemplary anchor  104  is also configured to remain at the repositioning size after actuation and will not expand back to the deployment size until it is again mechanically deformed. As a result, in those instances where a deployment location is suboptimal, the size of the anchor  104  can be reduced to a point where the prosthetic valve  100  can be disengaged from the surrounding tissue, repositioned and redeployed. In some implementations, the repositioning size will be small enough to facilitate percutaneous withdrawal of the valve from the patient, if necessary, in addition to repositioning of the valve for redeployment. 
         [0036]    The delivery, deployment and repositioning sizes will depend on the delivery method and the size of bodily region in which the valve is intended to be deployed. In the exemplary context of a prosthetic aortic valve that is delivered percutaneously, the delivery diameter of the exemplary anchor  104  may range from about 4 mm to about 6 mm, the deployment diameter of the anchor may range from about 24 mm to about 30 mm, and the repositioning diameter of the anchor may be about 1 mm or more smaller than the deployed diameter. For example, the repositioning diameter of the anchor  104  may range from slightly smaller than the delivery diameter to at least 1 mm smaller than the deployed diameter. The length of the anchor  104 , when expanded to the deployed diameter, may range from about 7 mm to about 20 mm, or longer if the anchor is intended to extend into the aorta and/or left ventricle. One example of a relatively long (i.e. longer than 20 mm) anchor is discussed below with reference to  FIG. 15 . 
         [0037]    The ability to function in the intended manner at the intended location within the body notwithstanding, the anchor is not limited to any particular mechanical structure. The exemplary anchor  104  illustrated in  FIGS. 1 and 2 , which is intended for use within the heart, is in the form of a tubular wire mesh. More specifically, the exemplary anchor  104  includes first and second wires  106  and  108  that are angled back and forth and configured into an overall circular shape. The wires  106  and  108  are also secured to one another by, for example welding, bonding or adhesive, to form the tubular structure. Wire mesh structures may be configured in a variety of other ways. By way of example, but not limitation, an anchor may include one or more additional tubular wire structures  106  (or  108 ). There may also be some overlap of the wire structures  106  and  108 , if desired, in order to increase the stiffness of certain portions of the anchor. The exemplary anchor  104   a  illustrated in  FIG. 3  includes one or more wires  110  with portions that are transverse to one another and secured to one another. A single wire wound into a coil is another suitable anchor structure. The anchor  104  may also be formed from a tube with a solid wall or from a perforated sheet that is rolled into a tube, as is discussed below in the context of  FIG. 9 . It should also be noted that although the exemplary anchor members  104  and  104   a , are radially and longitudinally symetrical, they may also be radially and/or longitudinally assymetrical as necessary or desired. This aspect of the present inventions is discussed below in the context of  FIGS. 11-14 . 
         [0038]    With respect to materials, the present anchors are preferably formed from shape memory material that responds to a transition condition that is not a normal body condition. Thermally responsive shape memory materials, which change shape when heated to a predetermined temperature, are one example of a shape memory material that may be employed. Suitable materials include thermally responsive nickel-titanium alloys (e.g. the nickel-titanium alloy sold under the trade name NITINOL), copper-zinc-aluminum alloys, copper-aluminum-nickel alloys and polymers, each with a transition temperature that is slightly higher than the highest expected temperature within the body, i.e. a temperature that is not a normal body condition. The transition temperature should not, however, be high enough to cause appreciable tissue damage after short term exposure. A transition temperature of about 45° C. to 60° C. is suitable given the normal body temperature of 37° C. Alternatively, ferromagnetic shape memory materials, which change shape in response to the application of a magnetic field, may be employed. Given the fact that the body does not generate internal magnetic fields, a magnetic field is a transition condition that is not considered to be a normal body condition. 
         [0039]    Regardless of the material chosen for the anchor, the material must be “trained” to function in the manner described above. For example, an anchor formed NITINOL or some other thermally responsive shape memory material may be trained in the following manner. An anchor, such as one of the exemplary anchors  104  and  104   a , is initially constructed in any size other than the repositioning size. The anchor is then mechanically deformed to the repositioning size and heat treated to at least the transition temperature, e.g. heated to a temperature of at least about 45° C. to 60° C. in the case of NITINOL, to complete the training. As a result, when the anchor material is in the martensitic state and deformed, such as when the anchor is expanded from the delivery size to the deployment size at body temperature, it will remain deformed when the force responsible for the deformation is discontinued. Such deformation is referred to herein as “mechanical deformation.” However, when the anchor is heated to the transition temperature, it will transition to the austenitic state and return to the repositioning size to which it has been trained. The anchor will also remain in the repositioning size (i.e. the trained size) after cooling to body temperature and returning to the martensitic state. The anchor will only return to the larger deployment size if a deformation force is applied thereto. Ferromagnetic shape memory materials may be trained in a similar manner, albeit one that employs magnetic fields in place of heat. 
         [0040]    With respect to delivery and deployment, the exemplary prosthetic valve  100  may be delivered to the aortic, mitral, tricuspid and pulmonary valves, or any other target location, and deployed with any suitable device. One example of such a device is the catheter generally represented by reference numeral  200  and illustrated in  FIGS. 4-6 . The catheter  200  includes an elongate catheter body  202  with a balloon  204  (or other expandable device) on the catheter body distal end and a handle  206  on the catheter body proximal end. The balloon  204  may be used to hold the prosthetic valve  100  during delivery and also used to deploy and redeploy the valve. The catheter body  202  has infusion and ventilation lumens  208  and  210  that open into the interior of the balloon  204 , as well as a central guidewire lumen  212  for a guidewire  214 . In the illustrated embodiment, the guidewire lumen  212  extends to the proximal end of the catheter body  202  and the handle  206  includes a guidewire port  216 . Alternatively, the guidewire lumen  212  may extend only a few centimeters proximal of the balloon  204  and create an opening on the exterior of the catheter body  202  at that point. 
         [0041]    The handle  206  in the exemplary catheter  100  also includes infusion and ventilation ports  218  and  220  that are connected to the catheter body infusion and ventilation lumens  208  and  210 . A fluid source (not shown) may be connected to the infusion and ventilation ports  216  and  218  and used to inflate the balloon  204  during deployment of the prosthetic valve  100 . The fluid source may also be used to circulate fluid heated to the transition temperature during repositioning. A sheath  222 , which may be positioned over the prosthetic valve  100  during delivery in order to prevent the anchor  104  from damaging non-target tissue and/or unintended expansion of the anchor, may also be provided. The sheath  222  may be moved proximally from its position over the prosthetic valve  100  just prior to reaching the target location, or after reaching the target location but prior to deployment. 
         [0042]    With respect to dimensions and material, the exemplary catheter body  202  will typically be about 5 mm in diameter and may be formed from any suitable biocompatible material. Such materials include, for example, biocompatible thermoplastic materials such as Pebax® material, polyethylene, or polyurethane. The balloon  204  will preferably be formed from material that is relatively high in thermal conductivity. Suitable materials for the balloon include thermally conductive biocompatible materials such as silicone, polyisoprene, Nylon, Pebax®, polyethylene, polyester and polyurethane. The uninflated and fully inflated sizes of balloon  204  will depend on the delivery and deployment sizes of the prosthetic valve with which it is intended to be used. The balloon  204  may also be provided with radiopaque markers (discussed below in the context of  FIGS. 16A-16C ), either on the balloon itself or on portions of the catheter body  202  within the balloon. Such markers help the physician align the balloon with the valve  100 . 
         [0043]    Referring to  FIG. 5 , the exemplary prosthetic valve  100  will typically be crimped onto the balloon  204  prior to the start of the delivery and deployment procedure. More specifically, the prosthetic valve  100  will be placed, while at the repositioning size, over the uninflated balloon  204 . The valve  100  will then be compressed, such that the anchor  104  is mechanically deformed radially inwardly down to the delivery size, and secured to the uninflated balloon  204  by mechanical interference and friction, as is illustrated in  FIG. 5 . 
         [0044]    As noted above, the exemplary prosthetic valve  100  may be used, in the context of the heart, to replace one or more of the aortic, mitral, tricuspid and pulmonary valves. An aortic valve replacement is shown in  FIGS. 7A-7D  for illustrative purposes only. Flouroscopy may be used to monitor the position of the prosthetic valve  100  during the procedure. Referring first to  FIG. 7A , the guidewire  214  may be advanced into the left ventrical LV by way of the aorta A using a retrograde approach. Antegrade and hybrid approaches may also be employed. The catheter body  202  may then be adavanced over the guidewire  214  with the prosthetic valve  100  crimped onto the balloon  204  and the sheath  222  ( FIG. 4 ) over the prosthetic vavle. The sheath  222  may be withdrawn once the prosthetic valve  100  and balloon  204  are adjacent to the aortic valve AV, as is shown in  FIG. 7A . Turning to  FIG. 7B , the catheter body  202  may then be advanced until the prosthetic valve  100  and balloon  204  displace the aortic valve leaflets AVL and the prosthetic valve is aligned with the aortic valve annulus AVA. The balloon  204  may then be inflated, as illustrated in  FIG. 7C , by filling the balloon with fluid that is below the transition temperature of the thermally responsive shape memory anchor material. The anchor  104 , which has remained in the relatively small delivery size up to this point, will be expanded to the deployment size by the balloon  204 . The anchor  104  will also be mechanically deformed by the expansion and, accordingly, will remain at the deployment size after the balloon  204  has been deflated and withdrawn from the aortic valve annulus AVA, as illustrated in  FIG. 7D . Withdrawal of the balloon  204  will also allow the leaflet device  102  to return to its normally closed orientation. 
         [0045]    The same process would be employed in those instances where the anchor is formed from a ferromagnetic shape memory material. Here, however, the temperature of the fluid used to inflate the balloon  204  will not effect the anchor. 
         [0046]    It should be noted here that the aortic valve leaflets AVL are displaced toward the left ventricle LV during the delivery and deployment procedure illustrated in  FIGS. 7A-7D . This may be reversed, i.e. the aortic valve leaflets AVL may be displaced toward the aorta A, in other procedures that involve the exemplary prosthetic valve  100 . 
         [0047]    In either case, there will invariably be some instances where the initial deployment location of the prosthetic valve  100  is suboptimal. For example, the location illustrated in  FIG. 7D  could be deemed to be too close to the left ventricle LV. There will also be some instances where the initial deployment location is optimal and a subsequent situation arises (e.g. an anatomic shift) that results in a suboptimal valve location. Such subsequent situations could arise soon after the catheter is withdrawn, or at a later time, up to many years after the initial deployment. The present prosthetic valve  100 , which may be disengaged from the aortic valve annulus AVA, repositioned and redeployed in the exemplary manner illustrated in  FIGS. 8A-8F , is especially useful in these situations. 
         [0048]    At the outset of the disengagement portion of the repositioning procedure, the catheter body  202  may be moved distally until the balloon  204  is again aligned with the prosthetic valve  100 , as illustrated in  FIG. 8A . There may also be some instances where the catheter  200  will simply remain in the location illustrated in  FIG. 7C  (and  8 A) until the accuracy of the initial deployment has been evaluated. Turning to  FIG. 8B , the balloon  204  may then be inflated into contact with the valve anchor  104  with fluid heated to a temperature above the transition temperature of the material used to form the anchor (about 45° C. to 60° C. in the exemplary embodiment). Preferably, the relatively high temperature fluid will be continuously infused into the balloon  204 , and ventilated from the balloon, in order to offset the loss of heat to the surrounding blood that is normally only about 37° C. The heat from the fluid will warm the anchor  104  to at least the transition temperature of the material (e.g. NITINOL) from which the anchor is formed, typically in just a few seconds. In response to being heated to the transition temperature, and as illustrated in  FIG. 8C , the anchor material will transition to the austenitic state and the anchor  104  will shrink down to the repositioning size to which it was trained. Shrinkage of the anchor  104  may also cause some deformation of the balloon  204 . At this point, the anchor  104  will be disengaged from the aortic valve annulus AVA. In other words, although a portion of the anchor  104  may be in contact with tissue depending on the position of the catheter body  202 , the anchor will be readily movable relative to the aortic valve annulus AVA. 
         [0049]    The temperature of the fluid circulating through the balloon  204  may, at this point, be reduced to a temperature below the transition temperature (e.g. body temperature or room temperature), thereby returning the thermally responsive shape memory anchor material to the martensitic state. The anchor  104  will remain at the repositioning size after cooling to the temperature below the transition temperature. As illustrated for example in  FIG. 8D , the volume of fluid within the balloon  204  may, if desired, also be slightly reduced to the point where the balloon is only as big as is necessary to hold the prosthetic valve  100 . The prosthetic valve  100  may then be moved with the catheter  200  to the more optimal location illustrated in  FIG. 8D . The balloon  204  may then be inflated, as illustrated in  FIG. 8E , by filling the balloon with fluid that is below the transition temperature of the anchor material. The anchor  104 , which has remained in the repositioning size up to this point, will again be expanded to the deployment size. The anchor  104  will also be mechanically deformed by the expansion and, accordingly, will remain in the deployment size after the balloon  204  has been deflated and withdrawn from the aortic valve annulus AVA, as illustrated in  FIG. 8F . Withdrawal of the balloon  204  will also allow the leaflet device  102  to return to its normally closed orientation. 
         [0050]    A substantially similar procedure would be employed in those instances where the anchor is formed from a ferromagnetic shape memory material and  FIGS. 8A-8F  may be used to desribe such a procedure. In the case of ferromagnetic shape memory material, however, the temperature of the fluid used to inflate the balloon (note  FIGS. 8B and 8E ) will not effect the anchor. Instead, the anchor will be subjected to a magnetic field that will actuate the ferromagnetic shape memory material when the anchor is to be shrunk from the deployment size down to the repositioning size (note  FIG. 8C ). The magnetic field will be removed after the anchor reaches the repositioning size and the anchor will remain in the repositioning size until it is again mechanically deformed by the balloon ( FIG. 8E ). 
         [0051]    Although the present inventions have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. 
         [0052]    By way of example, and as illustrated in  FIG. 9 , an exemplary anchor  104   c  is formed from a sheet of shape memory material with a plurality of perforations  114 . The perforations may be any suitable shape or size or any suitable combination of different shapes and/or sizes. The exemplary anchor  104   d  illustrated in  FIG. 10  is identical to the anchor  104  but for the inclusion of protrusions  116  that are used to further secure the anchor to the target tissue region after deployment. Other surface structures, such as hooks or surface irregularities, may also be employed. 
         [0053]    Turning to  FIGS. 11-14 , anchors in accordance with the present inventions may also be configured such that the size or geometry of the structures that define the anchors are something other than constant. Referring first to  FIG. 11 , the exemplary anchor  104   e  includes a plurality of wires  110   e  that are transverse to one another and secured to one another at their longitudinal ends. The cross-sectional size of the wires  110   e  (i.e. diameter in the case of a circular wire) may vary over the length of the wires. In the illustrated embodiment, the cross-sectional size is smallest at the longitudinal mid-point (or some other point between the longitudinal ends), and increases from there to each of the longitudinal ends, where the cross-sectional size is largest. This may also be reversed, such that the cross-sectional size of the wires is largest at the mid-point or some other point between the longitudinal ends. The wire cross-sectional size may, alternatively, be smallest at one longitudinal end, largest at the other, and tapered therebetween. There may also be regions of constant cross-sectional size combined with regions of varying cross-sectional size as well as instances where some wires in an anchor are configured differently than others. 
         [0054]    The tubular anchor  104   f  illustrated in  FIG. 12  has a constant outer diameter and an inner diameter that varies such that the wall thickness of the tube is greatest at the longitudinal ends. This may also be reversed so that the wall thickness is greatest at the mid-point or some other point between the longitudinal ends. Alternatively, as illustrated in  FIG. 13 , the wall thickness is constant over a portion of the length of the anchor  104   g  and variable over another. This may consist of a constant wall thickness from one longitudinal end to the mid-point, or some other point between the longitudinal ends, and an increasing wall thickness from this point to the other longitudinal end (as shown), a decreasing wall thickness from the this point to the other longitudinal end, or any other combination of constant and non-constant wall thicknesses. As illustrated for example in  FIG. 14 , the anchor  104   h  has a non-constant wall thickness as well as a non-constant overall cross-sectional size. More specifically, the overall diameter of the anchor  104   h  increases from one longitudinal end to the other. Other types of variations in the overall cross-sectional size are contemplated. For example, the overall diameter of the anchor  104   h  could, alternatively, be greatest at the longitudinal ends whether or not the wall thickness is constant. The tubular anchors illustrated in  FIGS. 12-14  may also include apertures, such as those discussed above with reference to  FIG. 9 , or slots. 
         [0055]    An exemplary valve  100   a  with a relatively long anchor  104   i  is illustrated in  FIG. 15 . The anchor  104   i  includes a plurality of tubular wire structures  106  and  108  secured to one another by, for example welding, bonding or adhesive. The relatively long anchor  104   i  will typically be longer than 20 mm and may be used, for example, to secure the valve  100   a  to tissue within the aorta and/or left ventricle. 
         [0056]    Alternative balloon structures are also contemplated. The exemplary balloon  204   a , which is illustrated in its uninflated state in  FIG. 16A  and its inflated state in  FIG. 16B , includes a distal portion  205  that is slightly larger than the proximal portion  207 . The larger distal portion  205  prevents distal movement of the valve  100  after the valve has been crimped onto the uninflated balloon  204   a  during delivery and recovery of the valve. When the balloon  204   a  is inflated, it prevents the valve  100  from sliding distally off the catheter  200 , especially as the anchor  104  shrinks from the deployed size to the repositioning size. It should be noted that the difference in cross-sectional size (i.e. diameter) is somewhat exaggerated in  FIGS. 16A and 16B . In practice, the difference in diameter will be such that the deflated diameter of the balloon distal portion  205  will be small enough to pass through the valve  100  after the anchor has been expanded to the deployment size. Typically, the distal portion  205  will be about 1 mm to about 3 mm larger in diameter than the proximal portion  207  when the balloon  204  is inflated. Turning to  FIG. 16C , the exemplary balloon  204   b  includes proximal and distal portions  205   b  that are slightly larger than the portion  207   b  therebetween. 
         [0057]    The exemplary balloons  204   a  and  204   b  also include radiopaque markers  236 . In the illustrated embodiments, the markers  236  are provided on the larger balloon portions  205  and  205   b . Alternatively, or in addition, radiopaque markers may be provided on the smaller balloon portions  207  and  207   b . Radiopaque markers may, alternatively, be carried by the catheter body  202  within the balloons at locations aligned with those discussed above and/or on other portions of the catheter body. 
         [0058]    The balloons  204   a  and  204   b  may also be used to carry and deploy a valve that includes an anchor with an overall diameter that, when deployed, is greatest at one or both of the longitudinal ends. As illustrated for example in  FIG. 16D , a valve  100   b  that has been delivered in a crimped state, where the diameter of the anchor is essentially constant over its length, may be expanded during deployment by a balloon  204   c  in such a manner that the diameter of the anchor is greatest at the longitudinal ends. The balloon  204   c  is identical to balloon  204   b  but for the locations of the markers  236 . 
         [0059]    The manner in which the balloon heats the anchor  104  may also be varied. As illustrated for example in  FIG. 17 , the balloon  204   d  includes conductive regions  224  and  226  that may be used to conduct current through the anchor  104  and resistively heat the anchor above the transition temperature. The use of resistive heating obviates the need for heated fluid and the circulation thereof within the balloon. Accordingly, the catheter body  202   a  includes a single fluid lumen that may be used to both infuse and ventilate fluid in and out of the balloon  204   d . Another heating apparatus that does not involve direct heating of the fluid is one or more resistive heaters carried on the exterior or interior of the balloon wall or between the plies of material used to form the balloon. 
         [0060]    Another alternative is to heat the fluid while it is in the balloon. To that end, and as illustrated for example in  FIG. 18 , a pair of electrodes  228  and  230  may be mounted on the catheter body  202   a  within the balloon  200 . The single fluid lumen, which terminates at an aperture  232 , may be used to inflate the balloon with a conductive fluid such as saline. Current will be transmitted from one electrode to the other in order to resistively heat the conductive fluid. The single fluid lumen may also be used to ventilate fluid from the balloon  200  when necessary. 
         [0061]    Still another exemplary catheter configuration is illustrated in  FIG. 19 . The catheter illustrated in  FIG. 19 , which is intended for use with anchors such as the exemplary anchor  104   j  illustrated in  FIG. 20  that are formed from ferromagnetic shape memory materials, includes a selectively actuatable magnet  234  in place of the electrodes  228  and  230 . The magnet  234  may be used to generate a magnetic field sufficient to cause the associated anchor to shrink from the deployment size to the repositioning size. It should be noted here that anchors formed from ferromagnetic shape memory materials may also have any of the other configurations discussed above. 
         [0062]    Anchors in accordance with the present inventions may also be heated with fluid, at the appropriate heating temperature, that is simply supplied to the bodily region where the valve is deployed. Suitable fluids include saline and contrast fluid. The catheter  200   a  illustrated in  FIG. 21 , which is substantially similar to the catheter  200 , is one example of a device that can heat the valve anchor in this manner. The catheter  200   a  includes a catheter body  202   a  with a single infusion and ventilation lumen that terminates within the balloon  204 . A fluid tube  238 , which has an outlet  240  near the proximal end of the balloon  204 , is carried on the exterior of the catheter body  202   a . Alternatively, the catheter body could be provided with an internal heated fluid lumen that has an outlet at a location similar to that of the outlet  240 . In either case, the catheter  200   a  may also be provided with an occlusion balloon  242  which, in combination with the balloon  204 , will prevent blood from cooling the heated fluid being supplied to the anchor  104 . In still other implementations, the fluid tube  238  (or internal heated fluid lumen) may be omitted and the heated fluid simply supplied by way of the space between the outer surface of the catheter body  202   a  and in inner surface of the delivery sheath  222  ( FIG. 1 ). 
         [0063]    Prosthetic valves in accordance with the present invention may also include a coating over the anchor, or at least over the anchor surfaces that will be in contact with tissue, that prevents anchor/tissue adhesion. Adhesion prevention facilitates valve repositioning that may be required long after the initial deployment. Polymeric coatings may, for example, be employed for this purpose. Coatings including anti-thrombotic drugs and/or other therapeutic drugs may also be applied to the anchor and released therefrom over time. 
         [0064]    The present inventions also include any and all combinations of the elements from the various embodiments disclosed in the specification, and systems that comprise sources of heated fluid and/or current for resistive heating in combination with any of the device described above and/or claimed below. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.