Abstract:
A system for percutaneously introducing a prosthetic valve into a patient&#39;s vasculature comprises a balloon dilatation catheter, a prosthetic valve mounted coaxial to the dilatation balloon, and a pusher member comprising a longitudinally extending tubular member encompassing the shaft of the catheter. The distal end of the pusher member preferably corresponds to the proximal end of the stent component of the prosthetic valve. The pusher member provides enhanced longitudinal pushability for facilitating advancement of the prosthetic valve to a treatment site. The system is well-suited for advancing a prosthetic valve or other medical device through an introducer sheath having a relatively small inner diameter. The introducer sheath may be formed with a tapered proximal end portion for receiving the prosthetic valve and for reducing a diameter of the prosthetic valve during advancement therethrough.

Description:
RELATED APPLICATION  
       [0001]     The present application claims priority under 35 U.S.C. §119(e) to U.S. provisional application 60/584,903, filed Jun. 30, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to methods and devices for implanting medical devices in a human body. More particularly, the present invention relates to methods and devices for assistance in implanting a prosthetic valve in a patient&#39;s heart or other body duct.  
       BACKGROUND OF THE INVENTION  
       [0003]     The implantation of prosthetic valves using percutaneous techniques is a relatively new field of medicine. While percutaneous implantation has yet to achieve widespread acceptance, there are several companies developing such procedures and products. In this field, it has been found that stented valves are particularly well-suited for percutaneous advancement to a treatment site. Stented valves can be divided basically into two groups: self-expanding stented valves and expandable, i.e., internally-expanded, stented valves, which are most commonly expanded by balloons. Self-expanding stents are usually made from shape memory materials, such as nickel-titanium alloys, or Nitinol, which have a high elastic range. Balloon expandable stents are typically formed of a plastically deformable material having a high radial strength, such as such as stainless steel, platinum, iridium, cobalt-chromium, and the like.  
         [0004]     Before delivery to a treatment site, a self-expanding stented valve may be compressed and inserted into a small tube. The stented valve is guided, i.e., pushed or pulled, distally, through the tube to a desired location and then released from the restricting tube or sheath. The stent then expands to its set diameter, or until it is restrained from further expansion by lumen walls. The expansion is caused by the stent&#39;s internal elastic radial forces. In some cases an additional force applied by, for example, a balloon, expands the stent to its final diameter.  
         [0005]     A balloon expandable stented valve may be crimped from a large set diameter to a small crimped diameter and then moved into a patient&#39;s body ducts via an introducer sheath. After the stented valve reaches a desired position in the body, the stented valve is then expanded back to its set diameter by an external force, such as that created by an inflatable dilatation balloon.  
         [0006]     Although stented valves may be crimped or compressed to a smaller diameter for delivery purposes, it has been found that some degree of recoil occurs after the crimping or compression process. This is a particularly undesirable feature because the stented valve is typically advanced through an introducer sheath. Furthermore, the size of the introducer sheath is limited by the size of the entry into a patient&#39;s blood vessel. Therefore, due to recoil and other factors, when the size of the entry into the patient&#39;s blood vessel is small, it can be difficult or impossible to advance the stented valve through the introducer sheath.  
         [0007]     Accordingly, an urgent need exists for an improved system for assisting in the delivery of medical devices, such as stented prosthetic valves, into a patient&#39;s vasculature. It is desirable that such a system be particularly well-suited for use with prosthetic valves formed with self-expanding or balloon expandable stents. It is also desirable that such a system facilitates the delivery of prosthetic valves through introducer sheaths. The present invention addresses this need.  
       SUMMARY OF THE INVENTION  
       [0008]     Embodiments of the present invention provide devices and methods for delivering a medical device into a patient&#39;s vasculature. Preferred embodiments facilitate percutaneous delivery of a medical device via an introducer sheath. More particularly, embodiments of the present invention provide devices and methods for facilitating advancement of a stented prosthetic valve through an introducer sheath by enhancing pushabilty and/or reducing the diameter of the crimped prosthetic valve.  
         [0009]     In one preferred embodiment, a system for percutaneously introducing a prosthetic valve into a patient&#39;s vasculature comprises a balloon dilatation catheter having an elongate shaft and a dilatation balloon disposed along a distal end portion. A prosthetic valve is formed with an expandable stent member and a valvular structure and the prosthetic valve is positioned coaxially to the dilatation balloon. A pusher member is formed with a longitudinal slot for accepting the elongate shaft, the pusher member having a distal end corresponding to a proximal end of the expandable stent for transferring longitudinal forces to the expandable stent from a location outside the patient&#39;s vasculature, the pusher member being slidable relative to the elongate shaft. In one variation, the longitudinal slot comprises at least one area that is wider than a remaining portion of the slot. In another variation, a cover member is positioned over a distal end of the dilatation balloon, the cover member having two or more substantially equally spaced openings arranged around the cover member. The dilatation balloon may expand through the openings as the dilatation balloon is inflated. In another variation, a cover member is positioned over a distal end of the dilatation balloon, the cover member comprising a multitude of substantially equally sized members that form a substantially conical shape before the balloon is inflated. To create a seal between the pusher member and the introducer sheath, a cooperating sealing member may be provided that can be advanced distally over the pusher member. To further assist in the advancement of the prosthetic valve, the pusher member may further comprise at least one internal support member.  
         [0010]     In another preferred embodiment, a system for assisting in introduction and implantation in a body lumen of a crimped stent-mounted percutaneous valve assembly is provided wherein the valve assembly is carried on a delivery catheter comprising a shaft and stent expansion mechanism. The system includes a pusher member comprising a slotted tube that accepts the shaft, the distal end of the pusher member being sized for contact with a proximal end of the valve assembly. An introducer sheath is formed with a tapered opening configured to provide further crimping of the assembly when the valve assembly is longitudinally advanced through the tapered opening. A tapering is provided along a distal end of the valve assembly enabling the valve assembly to avoid catching on obstructions in the lumen. To increase the contact area between the distal end of the pusher member and the proximal end of the valve assembly, the slot in the pusher member may be relatively narrow along the distal end portion. A widening region may be provided along the pusher member proximal to the narrow portion for facilitating insertion of the catheter shaft into the slot. In yet another variation, the expansion mechanism may expand in such a fashion that the expansion mechanism contacts a portion of the body lumen, thereby anchoring the expansion mechanism and preventing longitudinal movement during deployment.  
         [0011]     In another preferred embodiment, a method of introducing a prosthetic valve into a body lumen comprises a first step of providing a balloon catheter having an elongate shaft and an expandable balloon, the prosthetic valve being disposed over the balloon. The elongate shaft is snapped into a slot formed in a pusher member, the pusher member having a distal end sized for contacting a proximal end of the prosthetic valve. An introducer sheath is inserted into the body lumen. The prosthetic valve is advanced through the introducer to a site of a native valve by applying longitudinal forces to the prosthetic valve via the pusher member. The pusher member is then withdrawn relative to the prosthetic valve and the balloon is inflated for expanding the prosthetic valve at the site of the native valve for replacing the function of the native valve. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     To better understand the present invention, and to appreciate its practical applications, the following drawings are provided and referenced hereafter. It should be noted that the drawings are given as examples only and in no way limit the scope of the invention as defined in the appended claims. Like components are denoted by like reference numerals:  
         [0013]      FIG. 1  illustrates a general view of a stented valve mounted on a balloon catheter, assembled with a pusher member, ready to be inserted through an introducer sheath;  
         [0014]      FIGS. 2 and 3  each illustrate a stented valve being pushed into an introducer sheath tube by a pusher member wherein in  FIG. 2  the diameter of the valve is larger than the tube&#39;s diameter and in  FIG. 3  the diameter of the valve has been reduced by advancing the valve into the sheath with the pusher member;  
         [0015]      FIGS. 4 and 5  are top views of the mounted valve on the introducing balloon during and after crimping wherein  FIG. 4  shows the device while being crimped, and  FIG. 5  shows in a dashed line the final valve outer diameter after recoil;  
         [0016]      FIG. 6  illustrates an oblique view of a pusher member according to the invention, and  FIG. 7  is a cross-sectional view along line  7 - 7  in  FIG. 6 ;  
         [0017]      FIGS. 8 and 9  each illustrate a cross-sectional view of an assembled device including a shaft bushing;  
         [0018]      FIG. 10  is a cross-sectional view along the line  10 - 10  in  FIG. 8 ;  
         [0019]      FIGS. 11 and 12  illustrate a self-expandable stented valve being pushed by a pusher member through an introducer sheath;  
         [0020]      FIG. 13  illustrates a long pusher member assisting in introducing a prosthetic valve past a diseased valve and into its desired implantation location;  
         [0021]     FIGS.  14  to  23  illustrate the steps according to one preferred method for inserting a prosthetic valve into a native diseased valve through a long introducer sheath;  
         [0022]      FIG. 24  shows a detail of a valve assembly on a balloon with a tapered end, which will assist in passing a calcified native valve;  
         [0023]     FIGS.  25  to  27  show a balloon-based delivery device for introducing a prosthetic valve into its desired implantation location, the device having an additional portion on its tip creating a taper, improving the ability to pass through a calcified native valve; and  
         [0024]     FIGS.  28  to  30  show another a balloon-based delivery device for introducing a prosthetic valve into its desired implantation, the device having an additional portion on its tip creating a taper, improving the ability to pass through a calcific native valve. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     Preferred embodiments of the present invention provide devices and methods for facilitating advancement of a stented prosthetic valve through an introducer sheath to a treatment site. With reference now to the partial cross-sectional view of  FIG. 1 , for purposes of illustration, a balloon dilatation catheter  2  is shown. The balloon dilatation catheter  2  comprises a catheter shaft  4 , which extends distally through a non-inflated dilatation balloon  6 . The distal portion  8  of shaft  4  extends distally of the distal end  10  of dilatation balloon  6 . Catheter shaft  4  has at least one lumen (not shown) capable of slidably receiving a guidewire (not shown).  
         [0026]     The proximal end  12  of catheter  2  comprises a junction  16  in fluid communication with one or more manifolds  18  for entry of a guidewire, for example, or another device, substance, or fluid. For example, one manifold  18  may be in fluid communication with an inflation lumen (not shown) for dilatation balloon  6 , and another manifold  18  may be in fluid communication with a lumen (not shown) capable of receiving a guidewire, other device, or catheter (not shown).  
         [0027]     A stented valve  20  is positioned coaxial and adjacent to dilatation balloon  6 , where stented valve  20  is crimped onto deflated or non-inflated dilatation balloon  6 . Stented valve  20  has a proximal surface  24  that is adjacent to and in contact with a distal contact surface  26  of an elongate pusher member  28 . The stented valve generally comprises a substantially cylindrical stent portion which supports a valvular structure.  
         [0028]     Delivery system shaft  4  is nested in a groove  30  in pusher member  28 . The groove  30  preferably extends the entire length of pusher member  28 , which is essentially a modified tube as described below and having enough stiffness to enable translation of forces applied along the linear axis of pusher member  28  to prosthetic valve  20  as described below. In various preferred embodiments, the pusher member  28  may be machined from a polypropylene rod, or a similar rigid or semi-rigid, physiologically acceptable polymer or metal.  
         [0029]     An advantage of groove  30  is that it enables easy insertion of shaft  4  into pusher member  28  since dilatation catheter  2  has enlarged portions at each end. These enlarged portions would make it difficult or impossible to insert shaft  4  into pusher member  28  from the openings  32 ,  34  at the distal and proximal ends of the pusher member  28 , without groove  30  providing access to them. As illustrated, the proximal end  36  of pusher member  28  is preferably tapered.  
         [0030]     While groove  30  extends longitudinally along the length of pusher member  28 , it preferably has a distal narrowing  38 , to provide the largest possible contact between pusher member  28  and the contact surface  24  of prosthetic valve  20  at pushing contact area  26 . A relative widening  40  of groove  30  may be provided to facilitate passing shaft  4  through narrowing  38 . Widening  40  with tapered edges  42  allows the operator to more easily snap the shaft  4  through narrowing  38 . Optionally pusher member  28  may have at least one support member  44 .  
         [0031]     Pusher member  28  is preferably constructed to be sufficiently pliable such that its walls can be pushed apart when shaft  4  is pushed against narrowing  38 , thereby enabling insertion of shaft  4  through groove  30  into pusher member  28  even when narrowing  38  is narrower than shaft  4  itself.  
         [0032]     Pusher member contact area  26  is the point of contact between pusher member  28  and distal end  24  of prosthetic valve  20 . Pusher member  28  therefore can be used to translate force applied along the longitudinal axis of pusher member  28  directly to prosthetic valve  20 . This approach differs from the traditional technique whereby a delivery system shaft  4  is alone used to push a prosthetic valve into and through an introducer sheath. Such direct pushing protects dilatation balloon  6  and minimizes or avoids the possibility of kinking of shaft  4 . It will be appreciated by those skilled in the art that pusher member  28  enables the application of large longitudinal forces to a prosthetic valve or other medical device, thereby enabling passage through smaller introducer sheaths. It will also be appreciated that pusher member  28  may be used to transmit rotational forces to the prosthetic valve for maneuvering the valve into a desired alignment before or during deployment.  
         [0033]      FIG. 2  illustrates an implantable prosthetic valve  48  mounted on a delivery system dilatation balloon  50  and pushed by a pusher member  52 . More particularly,  FIG. 2  depicts prosthetic valve  48  being pushed into an introducer sheath  54 . In the illustrated embodiment, the outer diameter  56  of implantable prosthetic valve  48  is slightly larger than the inner diameter  58  of introducer sheath  54 .  
         [0034]     With reference to the partial cross-sectional drawings shown in  FIGS. 2 and 3 , the delivery system comprising a balloon dilation catheter shaft  62 , a dilatation balloon  50 , a prosthetic valve  48 , and a pusher member  52  is advanced into the introducer sheath  54 . The proximal end  64  of introducer sheath  54  is slightly flared. The taper in the proximal end  64  of introducer sheath  54 , together with the direct pushing force applied by pusher member  52  to prosthetic valve  48  at pusher member contact area  66 , enable reduction of valve outer diameter  56  to a size similar to that of sheath  54  inner diameter  58 .  FIG. 3  illustrates prosthetic valve  48  after having been advanced into introducer sheath  54  wherein the diameter  56  of prosthetic valve  48  has been reduced due to application of force by pusher member  52  and the geometry of taper  64 .  
         [0035]     Optionally pusher member  52  may have at least one internal support  68 . Each such support  68  will have a passageway  70  for catheter shaft  62  that comprises an opening  72  commensurate with the groove or slot (not shown here). Thus, each support may have a semi-annular shape that provides additional support to pusher member  52  and/or to catheter shaft  62 .  
         [0036]     A limiting factor when a prosthetic valve is inserted is the fact that, after crimping, the valve diameter increases from its smallest possible diameter due to recoil. This effect can be seen with reference to  FIGS. 4 and 5 , wherein a top view is shown of a prosthetic valve  74  assembled on a folded or non-inflated balloon  76 . In  FIG. 4 , the jaws  78  compress the prosthetic valve assembly to its smallest diameter. Balloon  76  has a central lumen  80 , which may receive a guidewire  82 .  FIG. 5  shows the device assembly after it is released from the crimping device. With the crimping force released, the assembly recoils (expands) slightly until reaching its post-recoil circumference as shown by dotted line  84 . When the prosthetic valve assembly is pushed by pusher member  28  (as shown in  FIG. 2 ) against taper  28 , the circumference of the assembly is advantageously reduced from the post-recoil circumference  84  to a reduced circumference  86 .  
         [0037]      FIGS. 6 and 7  are perspective and cross-sectional views, respectively, of one preferred embodiment of a pusher member  94 . Pusher member  94  has a groove  96  along its entire length. Near the distal end  98  of pusher member  94 , the groove  96  has a narrow portion  100 , maximizing the pushing contact area  102 . The groove  96  is preferably tapered on its edges and widened at point  104  to provide means for sliding the delivery system shaft into the groove  96 . Distal end bore  106  of pusher member  94  is the receptacle for the delivery system&#39;s balloon (not shown).  
         [0038]      FIG. 8  provides a cross-sectional view along the length of pusher member  110 . The mounted delivery system comprises catheter shaft  112 , balloon  114 , and prosthetic valve  116 . Groove  120  is cut along the entire length. The depth of the groove changes according to different functions along the pusher member. At the pusher member distal end  122 , prosthetic valve  116  is preferably concentric to pusher member  110  so it can be pushed symmetrically through the introducer sheath. Accordingly, in the illustrated embodiment, the depth of groove  120  changes along the length of pusher member.  
         [0039]     The delivery system and pusher member  110  are inserted through a standard introducer sheath (not shown) and are preferably sealed, in this case with bushing  124 , which has a flexible proximal surface  126  and a distal opening  128 . Therefore, the depth of groove  120  and delivery system shaft  112  create a complete sealing boundary, as seen in  FIG. 9 , optionally over the proximal end of an introducer sheath (not shown). Bushing  124  is made of a stretchable material, preferably a biologically compatible polymer, which can seal the shaft and can also seal the entire pusher member, as shown in  FIG. 9 . A taper  130  is added to the pusher member to facilitate moving the sealing bushing  124  onto the pusher member  110 .  
         [0040]      FIG. 10  represents a cross-section of  FIG. 8  across line  10 - 10 , where catheter shaft  112  resides within groove  120  of pusher member  110 .  
         [0041]      FIG. 11  is a partial cross-sectional view of an alternative configuration wherein a self-expandable stented prosthetic valve  132  is pushed by a pusher member  134  through an introducer sheath  136  over a guidewire  138 . In this case, introducer sheath  136  is guided through a patient&#39;s aorta  140  to a stenotic aortic valve  142 , as shown in  FIG. 12 . After advancement to the desired location, prosthetic valve  132  pushed out of introducer sheath  136 . Alternatively, the valve may be released by withdrawing introducer sheath  136  relative to the prosthetic valve  132 .  
         [0042]     To facilitate advancement through stenotic valve  142  with sheath  136 , a tapered distal tip  144  may be formed or attached to the distal portion  146  of pusher member  134 . Before introducer sheath  136  is passed through the stenotic aortic valve  142 , tapered tip  144  tip is first passed through introducer sheath  132 . Tapered tip  144  is preferably formed with flexible walls  148  and notches  152  that allow it to pass through sheath  136  and, when released out of sheath  136 , to expand to the outer diameter of sheath  136 . In that way a smooth transition is created between sheath  136  and tapered tip  144 , allowing a smooth passage into the left ventricle. Valve mount  154  is proximally adjacent to tapered tip  144  and can carry the self-expanding prosthetic valve payload. Alternatively, valve mount  154  can be replaced by an assembly of an inflatable balloon (not shown) surrounded by a stented valve, with the balloon later inflated to expand the valve to its final set diameter.  
         [0043]     In  FIG. 13 , a preferred implantation process of a stented valve  160  mounted on an inflation balloon  162 , which is part of a delivery system, is illustrated. In one advantageous feature, a bendable (i.e., flexible) pusher member  164  pushes directly on the stented valve  160 . Although pusher member is bendable, pusher member is substantially rigid along its longitudinal axis for transmitting longitudinal forces to the stented valve. The absence of the pusher member would require pushing the stented valve over a guidewire  166  via the catheter shaft  168 . The shaft has much less rigidity and pushing force than the pusher and in many cases would become twisted, and in some cases kinked, disabling the delivery of the valve to the desired location. In stenotic valves, the case is even worse since passing a stenotic valve  170  to place the prosthetic valve is very difficult and requires significant pushing forces. The pusher member described here enables one to achieve effective pushing forces all the way to the stenotic valve and across it.  
         [0044]     With reference to FIGS.  14  to  23 , preferred methods of using the delivery system will now be described in more detail. With reference to  FIG. 14 , one preferred method of use generally comprises insertion of a guiding sheath into a native calcified valve followed by implantation of a prosthetic percutaneous valve. An introducer sheath  174  is a flexible tube that can be made of various materials and could include a braided layer and have a PTFE layer in its outer and inner surfaces. The PTFE layer can be replaced with a hydrophilic or lubricious material. The purpose of sheath  174  is to provide a pathway from entry through a patient&#39;s femoral artery to the patient&#39;s aortic valve. To optimally achieve that purpose sheath  174  should be flexible enough to take the aortic arc curve and possibly torturous blood vessels. It should also have a minimal friction coefficient, as reflected by the materials and coatings indicated. A dilator  176  is inserted through introducer sheath  174 . Dilator  176  has a tapered distal tip  178  that facilitates passage through a calcified aortic valve. Passing the calcified aortic valve could be difficult, and a tapered tip with no shoulders is required to pass it in an optimal way. A transition point  180  between dilator  176  and introducer sheath  174  is smooth. Dilator distal tip  178  has a lumen  184  suitable for a guidewire.  
         [0045]     In  FIG. 15 , sheath  174  with dilator  178  comprising a guidewire  186  is shown positioned through a calcified aortic valve  188  into a patient&#39;s left ventricle  190 . In  FIG. 16 , the proximal portion of sheath  174  is shown with the proximal portions of dilator  176  and guidewire  186 .  
         [0046]     As shown in  FIGS. 17 and 18 , dilator  176  is withdrawn from introducer sheath  174  over guidewire  186 . The distal end of sheath  174  preferably remains slightly distal to calcified aortic valve  188 . A prosthetic valve may then be inserted through the introducer sheath to the implant site.  FIG. 19  shows a delivery system  190  with a pushable shaft  192 , prosthetic valve  194 , and dilatation balloon  196 . With reference now to  FIG. 20 , a delivery system in accordance with a preferred embodiment of the present invention, similar to the devices described above, especially in  FIG. 1 , generally comprises a catheter shaft  202 , a prosthetic valve  204 , a dilatation balloon  206 , and a pusher member  208 . Both of these delivery devices will push the valve through the tube to the desired location.  
         [0047]     The delivery system with the valve is pushed through the tubular sheath until it emerges from the distal end, opposite the native valve leaflets.  FIG. 21  shows the exposure of a prosthetic valve  212 . The sheath  214  is pulled back, while the pusher member  216 , balloon  218 , and catheter shaft  220  are held in place. Then, pusher member  216  is pulled back while the delivery system is held in place. The crimped valve is now opposite the native leaflets ready for inflation. The distal ends of sheath  214 , pusher member  216 , and catheter shaft  220  are shown in  FIG. 22 .  FIG. 23  shows the last stage of inflating balloon  218  and expanding prosthetic valve  212 .  
         [0048]     With reference now to  FIG. 24 , a valve delivery system is inserted into a tubular introducer sheath  222 , the delivery system comprising an inflatable balloon  224 , a crimped valve  226 , a pusher member  228 , and a guiding tip  230 . Guiding tip  230  has a tapered shape enabling safe passage of sheath  222  through a patient&#39;s calcified valve (not shown). It is desirable to have a tapered shape with no shoulders or irregular contours that might get caught on the calcified valve, preventing passage of tube  222 . The delivery system shown in  FIG. 24  is inserted over a guidewire  232 . In this embodiment of the present invention, the delivery system is pushed by pusher member  228  in a fashion similar to devices shown in the drawings described above.  
         [0049]     With reference to FIGS.  25  to  27 , yet another embodiment of a balloon-based delivery device for introducing a prosthetic valve into its desired implantation location is shown. A stented prosthetic valve  234  is coaxially mounted on an inflatable balloon  236  covered by a tapered sleeve  238 , preferably having “windows” or openings  240 . This sleeve creates a continuous tapered shape, eliminating the effect of a shoulder, which normally disturbs the delivery device when trying to pass through a calcified aortic valve (not shown). Sleeve  238  either extends to the same (or a greater) diameter as (than) valve  234  at point  242 . Sleeve  238  can be made of a thin flexible material that creates a tapered shape when crimped.  
         [0050]     When balloon  236  is inflated, as shown in  FIG. 26 , portions  246  of balloon  236  protrude through windows  240  to create a dog-bone shape, which shape prevents prosthetic valve  234  from shifting on the balloon during inflation. As balloon  236  continues to inflate, at least one weakened area  248  on tapered sleeve  238  tears, allowing sleeve  238  to open and allowing balloon  236  to inflate to its full, final diameter. Although a preferred embodiment of a tapered sleeve is described for purposes of illustration, any suitable cover member configuration may be employed. Furthermore, a tapered sleeve similar to tapered sleeve  238  (or other cover member) could be provided on the proximal portion of balloon  236 , either in addition to or instead of tapered sleeve  238 .  
         [0051]     With reference to FIGS.  28  to  30 , yet another embodiment of a balloon-based delivery device is shown.  FIG. 28  illustrates an inflated inflatable balloon  252  having a plurality of flaps  254  attached to the distal portion  256  of balloon  252  and arranged in a “tent-like” fashion. Flaps  254  are sized to come together when balloon  252  is deflated ( FIG. 29 ), to form a tapered shape  258  having a proximal inner diameter corresponding to the outer diameter of a prosthetic valve  260 . Prosthetic valve  260  is shown mounted on balloon  252  in  FIG. 30 . The proximal ends  264  of flaps  254  are crimped to a tapered shape, creating a continuous area between the taper and the prosthetic valve that will pass easily through a calcified aortic valve. The proximal end of the assembly between the stent and balloon creates a shoulder which in this case does not interfere in the insertion of the valve to the aortic native valve. However, the distal end would have had the same shoulder in the absence of flaps  254 .  
         [0052]     The materials and dimensions for the embodiments of the invention described herein are either known to or would be readily apparent to those skilled in the art. More specifically, balloon dilatation catheters and guidewires useful according to the invention are readily available commercially from suppliers such as Cook, Johnson &amp; Johnson, Boston Scientific, and the like. Prosthetic valves are described in the literature, including U.S. patents. See, for example, U.S. Pat. Nos. 3,755,823, 4,056,854, 4,106,129, 4,222,126, 4,297,749, 4,343,048, 4,580,568, 4,777,951, 5,032,128, 5,037,434, 5,411,552, 5,840,081, 5,855,601, 5,855,602, and 6,171,335, all of which are incorporated herein by reference. Other members described herein can be fabricated from physiologically acceptable materials such as known polymers such as polypropylene, polyethylene, copolymers thereof, PTFE, and the like. The dimensions of the longitudinal members described herein will preferably range from about 100 to about 300 cm in length and from about 8 to about 20 mm in diameter.  
         [0053]     The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood, however, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims.