Abstract:
Apparatus and method deliver a prosthesis into a hollow body organ or blood vessel. The systems and methods make use of a catheter. A carrier on the distal end of the catheter is sized and configured to carry the prosthesis. A release mechanism and an enclosure mechanism on the distal end are operable to retain and enclose the prosthesis on the carrier. The release mechanism and the enclosure mechanism are also operable to selectively expose and release the prosthesis from the carrier for deployment in the hollow body organ or blood vessel.

Description:
RELATED APPLICATION 
     This application claims the benefit of United States Provisional Patent Application Ser. No. 60/488,753, filed Jul. 21, 2003, and entitled “Endoprosthesis Deliveiy Systems and Methods.” 
     FIELD OF THE INVENTION 
     The invention relates generally to the delivery of a prosthesis to a targeted site within the body, e.g., for the repair of diseased and/or damaged sections of a hollow body organ and/or blood vessel. 
     BACKGROUND OF THE INVENTION 
     The weakening of a vessel wall from damage or disease can lead to vessel dilatation and the formation of an aneurysm. Left untreated, an aneurysm can grow in size and may eventually rupture. 
     For example, aneurysms of the aorta primarily occur in abdominal region, usually in the infrarenal area between the renal arteries and the aortic bifurcation. Aneurysms can also occur in the thoracic region between the aortic arch and renal arteries. The rupture of an aortic aneurysm results in massive hemorrhaging and has a high rate of mortality. 
     Open surgical replacement of a diseased or damaged section of vessel can eliminate the risk of vessel rupture. In this procedure, the diseased or damaged section of vessel is removed and a prosthetic prosthesis, made either in a straight of bifurcated configuration, is installed and then permanently attached and sealed to the ends of the native vessel by suture. The prosthetic prosthesis for these procedures are usually unsupported woven tubes and are typically made from polyester, ePTFE or other suitable materials. The prosthesis are longitudinally unsupported so they can accommodate changes in the morphology of the aneurysm and native vessel. However, these procedures require a large surgical incision and have a high rate of morbidity and mortality. In addition, many patients are unsuitable for this type of major surgery due to other co-morbidities. 
     Endovascular aneurysm repair has been introduced to overcome the problems associated with open surgical repair. The aneurysm is bridged with a vascular prosthesis, which is placed intraluminally. Typically these prosthetic prostheses for aortic aneurysms are delivered collapsed on a catheter through the femoral artery. These prostheses are usually designed with a fabric material attached to a metallic scaffolding (stent) structure, which expands or is expanded to contact the internal diameter of the vessel. Unlike open surgical aneurysm repair, intraluminally deployed prostheses are not sutured to the native vessel, but rely on either barbs extending from the stent, which penetrate into the native vessel during deployment, or the radial expansion force of the stent itself is utilized to hold the prosthesis in position. These prosthesis attachment means do not provide the same level of attachment when compared to suture and can damage the native vessel upon deployment. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention provides apparatus and methods for delivering a prosthesis into a hollow body organ or blood vessel. The systems and methods include a catheter that is sized and configured for introduction into the hollow body organ or blood vessel. A carrier on the distal end of the catheter is sized and configured to carry the prosthesis. A release mechanism on the distal end is operable to retain the prosthesis on the carrier. The release mechanism is also operable to selectively release the prosthesis from the carrier for deployment in the hollow body organ or blood vessel. An enclosure mechanism on the distal end is operable to enclose the prosthesis on the carrier. The enclosure mechanism is also operable to selectively expose the prosthesis on the carrier, to thereby enable the release of the prosthesis from the carrier in response to selective operation of the release mechanism, which can occur separate from the operation of the enclosure mechanism or in conjunction with the enclosure mechanism. The systems and methods include at least one actuator, which is coupled to the release mechanism and the enclosure mechanism, to selectively operate the release mechanism and the enclosure mechanism, either separately or in conjunction. 
     Other features and advantages of the invention shall be apparent based upon the accompanying description, drawings, and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       The invention will be understood from the following detailed description of preferred embodiments, taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1A  is a perspective view of a prosthesis delivery catheter embodies features of the invention. 
         FIG. 1B  is an enlarged perspective view, with portions broken away and in section, of the distal end of the prosthesis delivery catheter shown in  FIG. 1A . 
         FIG. 2  is a perspective view of the prosthesis delivery catheter shown in  FIG. 1A , being positioned within an abdominal aortic aneurysm. 
         FIG. 3  is a perspective view of a straight endovascular prosthesis after deployment by the prosthesis delivery catheter shown in  FIG. 1A . 
         FIG. 4  is a perspective view of a bifurcated endovascular prosthesis after deployment by the prosthesis delivery catheter shown in  FIG. 1A . 
         FIG. 5A  is an enlarged perspective view, with portions broken away and in section, of the inner assembly which is located in the distal end of the prosthesis delivery catheter shown in  FIG. 1A . 
         FIG. 5B  is an enlarged perspective view, with portions broken away and in section, of the inner assembly which is located in the distal end of the prosthesis delivery catheter shown in  FIG. 5A , showing a prosthesis retained in a collapsed condition by restraining means prior to deployment. 
         FIG. 5C  is an enlarged perspective view, with portions broken away and in section, of the inner assembly which is located in the distal end of the prosthesis delivery catheter shown in  FIG. 5A , showing the prosthesis in an expanded condition after removal of the restraining means. 
         FIG. 6  is a side view, with portions broken away and in section, of the prosthesis delivery catheter shown in  FIG. 1A , showing the catheter retaining a prosthesis in a collapsed condition prior to deployment, the outer sheath being shown in an advanced position over the prosthesis. 
         FIG. 7  is a side view, with portions broken away and in section, of the prosthesis delivery catheter shown in  FIG. 6 , showing the catheter retaining a prosthesis in a collapsed condition prior to deployment, the outer sheath being shown in a position withdrawn from the prosthesis. 
         FIG. 8  is a side view, with portions broken away and in section, of the prosthesis delivery catheter shown in  FIG. 7 , showing the catheter retaining a prosthesis in a collapsed condition prior to deployment, with the pull wire still advanced to restrain radial expansion of the prosthesis. 
         FIG. 9  is a side view, with portions broken away and in section, of the prosthesis delivery catheter shown in  FIG. 8 , showing the prosthesis in a radially expanded condition after actuation of the pull wire to remove the restraining means. 
         FIG. 10  is a side view, with portions broken away and in section, of the prosthesis delivery catheter shown in  FIG. 9 , showing the withdrawal of the catheter from the prosthesis after its deployment. 
         FIG. 11A  is a simplified side view of the distal end of the prosthesis delivery catheter shown in  FIG. 5B , with the outer sheath removed, showing the releasing means retaining the prosthesis in a restrained condition. 
         FIG. 11B  is an end section view of the distal end of the prosthesis delivery catheter shown in  FIG. 11A , taken generally along line  11 B— 11 B in  FIG. 11A . 
         FIG. 11C  is a simplified side view of the distal end of the prosthesis delivery catheter shown in  FIG. 5B , with the outer sheath removed, showing an alternative embodiment of a restraining means for maintaining the releasing means in a desired orientation while retaining the prosthesis in a restrained condition. 
         FIGS. 12A and 12B  are simplified side views of the distal end of the prosthesis delivery catheter shown in  FIG. 5B , with the outer sheath removed, showing other alternative embodiments of a restraining means for maintaining the releasing means in a desired orientation while retaining the prosthesis in a restrained condition, without reliance upon the catheter tip component. 
         FIGS. 13A and 13B  are simplified side views of the distal end of the prosthesis delivery catheter shown in  FIG. 5B , with the outer sheath removed, showing other alternative embodiments of a restraining means for maintaining the releasing means in a desired orientation while retaining the prosthesis in a restrained condition, without reliance upon a tubular sleeve carried by the central shaft. 
         FIGS. 14A and 14B  are simplified side views of the distal end of the prosthesis delivery catheter shown in  FIG. 5B , with the outer sheath removed, showing other alternative embodiments of a releasing means with a cutting element for selectively releasing the prosthesis for use, together with an associated restraining means for maintaining the releasing means in a desired orientation for operation. 
         FIGS. 15A and 15B  are simplified side views of the distal end of the prosthesis delivery catheter shown in  FIG. 5B , with the outer sheath removed, showing other alternative embodiments of a releasing means with a wedge element for selectively releasing the prosthesis for use, together with an associated restraining means for maintaining the releasing means in a desired orientation for operation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     I. Prosthesis Delivery Catheter 
       FIGS. 1A and 1B  show a prosthesis delivery catheter  10 . The purpose of the catheter  10  is to (i) contain and/or restrain a prosthesis  14  prior to its deployment (see  FIG. 1B ), (ii) deliver the prosthesis  14  through the vasculature to a desired location within the body, e.g., a hollow body organ or a blood vessel (see  FIG. 2 ), and (iii) controllably deploy the prosthesis  14  in the desired location (see  FIG. 3 ). 
     In the illustrated arrangement (see  FIG. 3 ), the prosthesis  14  takes the form of an endovascular, self-expanding stent prosthesis. In this respect, the prosthesis or prostheses  14  may have a wide variety of conventional configurations. It can typically comprise a fabric or some other blood semi-impermeable flexible barrier which is supported by a structure formed by stents  48 . The stent structure can have any conventional stent configuration, such as zigzag, serpentine, expanding diamond, or combinations thereof. The stent structure may extend the entire length of the prosthesis, and in some instances can be longer than the fabric components of the prosthesis. Alternatively, the stent structure can cover only a small portion of the prosthesis, e.g., being present at the ends. The stent structure may have three or more ends when it is configured to treat bifurcated vascular regions, such as the treatment of abdominal aortic aneurysms, when the stent prosthesis extends into the iliac arteries. In certain instances, the stent structures can be spaced apart along the entire length, or at least a major portion of the entire length, of the stent-prosthesis, where individual stent structures are not connected to each other directly, but rather connected to the fabric or other flexible component of the prosthesis. Still, it is contemplated that the stent structures could be attached to one another at discrete locations, e.g., in the proximal neck region. Such stent structures could comprise individual stents that are connected together when incorporated into the prosthesis, or stents that are manufactured in a joined condition prior to incorporation into the prosthesis. 
     The stents  48  may be elastic, e.g., comprised of a shape memory alloy elastic stainless steel, or the like. For elastic, expanding typically comprises releasing the stent structure from a constraint to permit the stent structure to self-expand at the implantation site. As will be described in greater detail, the catheter  10  places a sheath over the stent structure, in combination with releasable restraining means coupled to the stent structure, to maintain the stent structure in a radially reduced configuration during passage into the body. In this arrangement, self-expansion of the stent structure is achieved by pulling back on the sheath and release of the restraining means, to permit the stent structure to assume its larger diameter configuration. 
     Alternatively, the stent structure may be formed from a malleable material, such as malleable stainless steel of other metals. Expansion may then comprise applying a radially expansive force within the structure to cause expansion, e.g., inflating a delivery catheter within the stent structure in order to affect the expansion. In this arrangement, the positioning and deployment of the endoprosthesis can be accomplished by the use of an expansion means either separate or incorporated into the deployment catheter. This will allow the endoprosthesis to be positioned within the vessel and partially deployed while checking relative position within the vessel. The expansion can be accomplished either via a balloon or mechanical expansion device. Additionally, this expansion stabilizes the position of the endoprosthesis within the artery by resisting the force of blood on the endoprosthesis until the endoprosthesis can be fully deployed. Still, alternatively, the stent structure may comprise a combination of a self-expanding stent and a malleable stent structure. 
     In the illustrated embodiment (see  FIG. 2 ), the catheter  10  is shown it is being positioned over a guidewire  12  in a body lumen. The catheter  10  carries the prosthesis  14  in a radially reduced configuration to a targeted site. At the targeted site, the catheter  10  releases the radially reduced prosthesis  14 , which expands radially (see  FIG. 3 ). After partial or complete expansion or deployment of the prosthesis  14 , one or more fasteners are desirably introduced by a fastener attachment assembly to anchor the prosthesis  14  in place. Further details of the fastener attachment assembly can be found in U.S. patent application Ser. No. 10/307,226, filed Nov. 29, 2002, which is incorporated herein by reference. 
     The prosthesis  14  can be sized and configured to be either straight or bifurcated form.  FIG. 3  depicts a completely deployed straight prosthesis  14 .  FIG. 4  depicts a completely deployed bifurcated prosthesis. 
     For the purposes of illustration,  FIG. 2  shows the targeted site as being within an abdominal aortic aneurysm. Of course, the targeted site can be elsewhere in the body. 
     As shown in  FIGS. 1A and 1B , the catheter  10  comprises an inner assembly  16 , an outer sheath  18 , and a handle assembly  20 . These components will now be individually described in greater detail. 
     A. The Inner Assembly 
     In the illustrated embodiment (see  FIG. 5A ), the inner assembly  16  comprises a central shaft  22 , which functions as a carrier for the prosthesis. The inner assembly also includes a catheter tip component  24 , a releasing means or mechanism  28  for retaining at least a portion of the prosthesis  14  in a radially compressed condition prior to deployment, a retaining means or mechanism  26  for maintaining the releasing means  28  in a desired relationship with the central shaft  22  during use, and a spacer  30 . 
     In the embodiment shown in  FIG. 5A , the central shaft  22 , the retaining means  26 , the releasing means  28 , and the spacer  30  are located within the confines of the outer sheath  18 . In this respect, the outer sheath  18  functions as an enclosure for the prosthesis on the carrier. In this arrangement, the catheter tip component  24  is attached the distal end of the central shaft  22 , and the distal end of the outer sheath  18  terminates adjacent the catheter tip component  24 . Thus, the catheter tip component  24  extends outward beyond the outer sheath  18 . The central shaft  22 , the releasing means  28 , and the outer sheath  18  connect to the handle assembly  20  at the proximal end of the catheter  10  (see  FIG. 1A ). In use (see  FIG. 5B ), the prosthesis  14  is contained in a cavity  32  defined between the central shaft  22  and the outer sheath  18  in the distal section of the catheter  10  (this arrangement is also shown in  FIG. 1B ). 
     The central shaft  22  extends from the handle assembly  20  (see  FIG. 1A ) to the catheter tip component  24 . The central shaft  22  may be made, e.g., from stainless steel or other suitable medical materials including other metals or polymers. The central shaft  22  desirably has at least one lumen  36  (see  FIG. 5A ), with an inner diameter between 0.010 and 0.120 inches, preferably between 0.03 and 0.06 inches and most preferably between 0.04 and 0.05 inches. 
     As described, the central lumen  36  allows for the insertion of a guide wire  12  up to 0.038″ diameter. The catheter tip component  24  also desirably has at least one lumen  38  (see  FIG. 5A ) configured to align with at least one lumen within the central shaft  22 . This lumen  38  allows for the insertion of a guide wire  12  through the central shaft  22  and through the catheter tip component  24  (see  FIG. 2 ). Typically this lumen will have an inner diameter between 010 and 0.120 inches, preferably between 0.03 and 0.06 inches and most preferably between 0.04 and 0.05 inches. 
     Preferably, the catheter tip component  24  is flexible and has a long, tapered distal end and a shorter, tapered proximal end. The maximum diameter of the catheter tip component  24  is approximately the same as the outside diameter of the distal end of the outer sheath  18 . The distal end of the catheter tip component  24  provides a smooth tapered transition from the lumen  38  containing the guide wire  12  to the distal edge of the outer sheath  18 . This feature aids in catheter insertion and navigation through tortuous anatomy over the guide wire  12 . The tapered section on the proximal end of the catheter tip component  24  prevents the catheter tip component  24  from inadvertently engaging the prosthesis  14 , portions of the surrounding anatomy, or an introducer sheath or the like during removal of the catheter  10  from the body. 
     Still referring to  FIG. 5A , the retaining means  26  holds the releasing means  28  in a desired, close relationship with the central shaft  22 . The retaining means  26  orients the releasing means  28  along the axis to of the central shaft  22  and allows the releasing means  28  longitudinal movement in this axis. In the embodiment shown in  FIGS. 5A ,  5 B, and  5 C, the retaining means  26  includes a small hole or recess  40  in the proximal end of the catheter tip component  24  and a tube  56  having a diameter sufficiently large to accommodate both the central shaft  22  and the releasing means  28 . In the embodiment shown in  FIGS. 5A ,  5 B, and  5 C, the tube  56  of the retaining means  26  is located over the central shaft  22  in alignment with and adjacent to the recess  40  on the catheter tip component  24 . The tube  56  is attached to the central shaft  22  in a manner in that retains a crescent shape lumen  42  between the tube  56  and the central shaft  22 . The releasing means  28  extends through this lumen  42  and into the recess  40 . 
     Returning to  FIG. 5A , the spacer  30  provides support for the outer sheath  18  and, by occupying space within the outer sheath  18 , reduces the amount of air entrapped within the catheter  10 . The distal end of the spacer  30  desirably terminates adjacent the proximal end of the prosthesis  14  (as  FIG. 5B  shows). In this arrangement (see  FIG. 5B ), the cavity  32  containing the prosthesis  14  extends from the proximal end of the catheter tip component  24  to the distal end of the spacer  30 . As  FIG. 5A  shows, the spacer  30  is positioned over the central shaft  22  and releasing means  28  and the proximal end of the spacer  30  is connected to the handle assembly  20 . Typically, the spacer  30  can have an outer diameter slightly less than the inner diameter of the outer sheath  18 . The spacer  30  can comprise a single lumen or an array of multiple lumens for passage of the various components within the spacer  30 . 
     The releasing means  28  holds the prosthesis  14  in a desired configuration prior to deployment (see  FIG. 5B ) and selectively releases the prosthesis  14  for deployment (see  FIG. 5C ). In the illustrated embodiment, the proximal end of the releasing means  28  is connected to an actuator or control button or knob  46  in the handle assembly  20  (see  FIG. 1A ) . As  FIG. 5B  shows, the releasing means  28  extends along the outside of the central shaft  22 , through the inside of the spacer  30 , and continues distally through the inside of the prosthesis  14 . The releasing means  28  passes through the prosthesis  14  and the retaining means  26 . 
     As  FIG. 5B  best shows, the prosthesis  14  is retained by the releasing means  28  along the central shaft  22  in the cavity  32 , which extends between the proximal end of the catheter tip component  24  and the distal end of the spacer  30 . In the illustrated embodiment, the releasing means  28  includes a wire  58  that extends along the central shaft  22 . The distal end of the wire  58  passes through the crescent shape lumen  42  of the retaining means  26 , and is ultimately captured in the hole or recess  40  of the retaining means  26  in the proximal end of the catheter tip component  24 . The distal end of the wire  58  is thereby kept in a desired relationship along the central shaft  22 . The proximal end of the wire  58  is coupled to the control button  46 , such that fore and aft movement of the button  46  advances the wire  58 , respectively, distally and proximally. 
     As  FIG. 5B  shows (and which is further shown in more schematic form in  FIGS. 11A ,  11 B, and  11 C), the retaining means  28  includes sutures  44  and/or equivalent structures, which are attached to one or more stents  48  on the prosthesis  14 . The sutures  44  are, in turn, looped around the wire  58  of the releasing means  28 , when the wire  58  is in its distal-most position, as  FIG. 5B  shows. Proximal advancement of the wire  58  (using the control button  46 ) withdraws the wire  58  from the suture loops  44 , as  FIG. 5C  shows. 
     In the illustrated embodiment (see  FIG. 5B  as well as  FIGS. 11A ,  11 B, and  11 C), the suture loops  44  are attached to one or more stents  48  at the distal end of the prosthesis  14 . It should be appreciated, however, that suture loops  44  could be attached to stents  44  elsewhere in the prosthesis  14 , and/or the other components of the prosthesis  14  as well. 
     The suture loops  44  and wire  56  of the embodiment of the releasing means  28  just described retain the prosthesis  14  to the central shaft (see  FIG. 5B ). The suture loops  44  and the wire  56  keep the prosthesis  14  from moving proximally as the outer sheath  18  is retracted. The releasing means  28  also keeps the stents  48  that are coupled to the suture loops  44  in a radially compressed condition as the outer sheath  18  is removed. The suture loops  44  and wire  56  prevent the distal end of the prosthesis  14  from self-expanding until the releasing means  28  has been withdrawn. In the illustrated embodiment, the withdrawal of the releasing means  28  is accomplished by operating the control button  46  to move the wire  58  proximally, withdrawing the wire  58  from the hole or recess  40  and away from the suture loops  44 . Once the releasing means  28  is withdrawn, the restrained components of the prosthesis  14  are freed to self expand, as  FIG. 5C  shows. 
     As illustrated and described, the releasing means  28  is coupled to one restrained component of the prosthesis  14 . It should be appreciated, however, that the releasing means  28  can be coupled to the prosthesis  14  at two or more restrained regions, so that withdrawal of the releasing means  28  frees the prosthesis at two or more restrained regions. It should also be appreciated that the releasing means  28  can comprise more than a single releasing element. For example, multiple, individual releasing wires  58  could be coupled to the prosthesis  14  at different regions, so that release of separate regions of the prosthesis  14  can be individually controlled. 
     B. The Outer Sheath 
     The outer sheath  18  also serves to restrain the stents  48  on the prosthesis  14  from expanding and allows for a control deployment of the prosthesis  14  within the body. In the illustrated arrangement, the outer sheath  18  is connected to an actuator or a collar or knob  50  on the handle assembly  20 . As  FIG. 5A  shows, the outer sheath  18  extends distally over the spacer  30  and prosthesis  14  and terminates adjacent the proximal and of the catheter tip component  24 . Typically, the outer sheath  18  can be made of a polymer tube and be free of structural reinforcement. 
     In the illustrated embodiment (see  FIG. 5A ), the outer sheath  18  is tapered due to the difference in outer diameters of the catheter tip component and the spacer  30 . The larger diameter of the outer sheath  18  is intended to contain the main body of the prosthesis  14  and the smaller diameter would contain the leg portion or portions of the prosthesis  14 , if present (as in the embodiment shown in  FIG. 4 ). The smaller diameter continues proximally to the handle assembly  20 . This tapered feature of the outer sheath  18  also allows for better blood circulation passed the catheter. 
     C. Handle Assembly 
     The handle assembly  20  provides the operator with longitudinal and rotational control of the catheter  10  within the body and provides access to the actuator or control means for deploying the prosthesis  14 . 
     In the illustrated embodiment, the handle assembly  20  comprises a handle body  52  and the sliding knob or collar  50  which is connected to the proximal and the of the outer sheath  18 , and the knob or button  46  which is attached to proximal end of the releasing means  28 . In the illustrated embodiment, the central shaft  22  is captured within the handle and has a guide wire receiving luer  34  connected to its proximal end, which is located at the proximal end of the handle assembly  20 . This design prevents the position of the prosthesis  14  from moving relative to the handle body  52  while the outer sheath  18  is retracted. 
     To withdraw the outer sheath  18  from the prosthesis  14  (see  FIGS. 6 and 7 ), the sliding knob  50  is moved proximally until the distal end of the outer sheath  18  is free of the prosthesis  14  (see  FIG. 8 ). The portion or portions of the prosthesis  14  that are not coupled to the releasing means  28  (which, in the illustrated embodiment comprise the proximal region of the prosthesis  14 ) are free to self-expand, as  FIG. 8  shows. However, the portions of the prosthesis  14  that are coupled to the releasing means  58  (which, in the illustrated embodiment comprise the distal region of the prosthesis  14 ) are still restrained from self-expansion, despite withdrawal of the outer sheath  18 , as  FIG. 8  also shows. The stent structure of the prosthesis  14  is thereby kept restrained closely against the central shaft tube  22  while the outer sheath  18  is retracted. The retaining means  26  prevents the prosthesis  14  from moving relative to the central tube  22  during retraction of the outer sheath  18 , which potentially minimizes blood flow through the prosthesis  14  during the deployment process. Furthermore, as described, the prosthesis  14  is not “pushed out” of the catheter. The prosthesis  14  therefore need not have longitudinal stiffness or a stent structure with a “spine”. 
     To withdraw the releasing means  28  (see  FIGS. 8 and 9 ), the sliding button  46  is moved proximally until the distal end of the releasing means  28  is withdrawn from the restraining means  26 . The prosthesis is thereby free to fully self-expand, as  FIG. 9  and  FIG. 5C  show. As described, the prosthesis  14  is not released immediately from distal end to proximal end as the sheath  18  is withdrawn. As the outer sheath  18  is retracted, the prosthesis  14  is pulled in tension, which “stretches” the prosthesis to its proper length and stent spacing. The distal stent or stents  48  are released in a secondary operation, which follows the withdrawal of the outer sheath  18  (as shown in  FIGS. 5C ,  8 , and  9 ). Final placement of distal end of the prosthesis  14  can therefore comprise a final step in the deployment process. 
     It should be appreciated that the knob  50  can comprise a separate component that is not part of the handle assembly  20 , i.e., on the outer sheath  18 . 
     II. Use of the Prosthesis Delivery Catheter 
     During use, the catheter  10  is navigated over the guide wire  12  to the desired location within the body (as  FIG. 2  shows). In the illustrated embodiment, deployment of the prosthesis  14  is achieved in a two step process. First, by pulling the knob or collar  50  on the handle assembly  20  proximally, the outer sheath  18  is retracted and exposes the prosthesis  14  (as  FIGS. 6 and 7  show). The unrestrained portion or portions of the prosthesis  14  self-expand, as  FIG. 8  show. As  FIGS. 6 and 7  show, during retraction of the outer sheath  18 , the prosthesis  14  maintains its position relative to the central shaft  22  due to the releasing means  28  connected to the prosthesis  44 . 
     In the second step of the deployment process, following the withdrawal of the outer sheath  18 , the control button or knob  46  on the handle assembly  20  is moved proximally (see  FIGS. 8 and 9 ). This causes the distal end of the releasing means  28  to be withdrawn and allows the restrained stent or stents  44 , and the prosthesis  14  as a whole, to self-expand radially (as  FIGS. 5C and 9  show). The prosthesis  14  enlarges to contact the internal walls of the vessel or hollow body organ, as  FIG. 3  shows. The catheter  10  can then be withdrawn (as  FIG. 10  shows). 
     It should be appreciated that the withdrawal of the outer sheath  18  and the withdrawal of the releasing means  28  can be accomplished in a single step process. In this arrangement, a single activation mechanism can be jointly coupled to the outer sheath  18  and the releasing means  28 , so that the outer sheath  18  and releasing means  28  are withdrawn in a single step. 
     III. Alternative Embodiments 
     In the embodiment shown in  FIGS. 11A to 11C  (as already described), the distal end of a movable component of the releasing means  28  (e.g., the wire  58 ) extends along the central shaft  22  in a manner prescribed and controlled by the restraining means  26 , i.e., between a tube  56  carried by the central shaft  22  and a recess  40  located in the proximal end of the catheter tip component  24 . It is in the region between the tube  56  and the recess  40 , that a stationary component of the releasing means  28 , which is attached to the prosthesis  14  (e.g., the suture loops  44 ), is operatively coupled to the movable component of the releasing means  28 . Movement of the movable component  58  out of this region releases the stationary component  44 . The overall objective of the restraining means  26  is achieved: the restraining means  26  serves to maintain the movable component  58  of the releasing means  28  in a desired operative alignment with the central shaft  22 , as well as in a desired operative relationship with the stationary component  44  of the releasing means  28 , such that quick and certain release of the prosthesis  14  occurs. 
     The releasing means  28  and the restraining means  26  can be variously constructed to meet this objective. For example, in the alternative embodiment shown in  FIG. 12A , the distal end of the movable component  58  of the releasing means  28  extends along the central shaft  22  in a manner prescribed and controlled by the restraining means  26 , i.e., between adjacent, spaced apart tubes  60 A and  60 B, without dependence upon additional support by the catheter tip component  24 . Each tube  60 A and  60 B surrounds the central shaft  22  in the same fashion as the single tube  56  shown in  FIGS. 11A to 11C . The movable component  58  of the releasing means  28  is held in the region between the two tubes  60 A and  60 B in operative association with the stationary component  44  of the releasing means  28 , and can be quickly and certainly withdrawn from this region to release the prosthesis  14 . In a similar alternative arrangement (see  FIG. 12B ), the distal end of the movable component  58  of the releasing means  28  extends along the central shaft  22  between adjacent, spaced apart external tubes  62 A and  62 B, again without dependence upon additional support by the catheter tip component  24 . In  FIG. 12B , the tubes  62 A and  62 B project along the exterior of the central shaft  22 , but do not surround it. Still, it should be appreciated that a single external support tube like tube  62 A or  62 B could, alternatively, be used in a hybrid combination with the recess  40  in the catheter tip component  24 , if desired. 
     In another illustrative, alternative embodiment (see  FIG. 13A ), the distal end of the movable component  58  of the releasing means  28  extends within a lumen in the  66  central shaft  22 , exiting through an aperture  64  in the shaft  22  and into a recess  40  in the catheter tip component  24 . The movable component  58  of the releasing means  28  is held in the region between the aperture  64  and the recess  40  in operative association with the stationary component  44  of the releasing means  28 , and can be quickly and certainly withdrawn from this region to release the prosthesis  14 . In a similar alternative arrangement (see  FIG. 13B ), the distal end of the movable component  58  of the releasing means  28  extends within a lumen  68  the central shaft  22  between adjacent, spaced apart apertures  70  and  72 . The movable component  58  exits the aperture  72  and enters a recess  40  in the catheter tip component  24 . The movable component  58  of the releasing means  28  is held in the region between the aperture  72  and the recess  40  in operative association with the stationary component  44  of the releasing means  28 , and can be quickly and certainly withdrawn from this region to release the prosthesis  14 . 
     In yet another illustrative, alternative embodiment (see  FIGS. 14A and 14B ), the restraining means  26  includes a single tube  74  carried by the central shaft  22 , through which the movable component  58  of the releasing means  28  passes. The tube  74  can comprise a surrounding tube of the type shown in  FIG. 12A  (as  FIGS. 14A and 14B  show) or an external tube of the type shown in  FIG. 12B . 
     In this arrangement, the releasing means  28  includes a suture loop  76  carried by the proximal end of the catheter tip component  24  and a cutting element  78  carried on the distal end of the movable component  58  of the releasing means  28 . The suture loop  76  passes through the suture loops  44  on the prosthesis  14 , as well as through the cutting element  78 . The cutting element  78  on the distal end of the movable component  58  of the releasing means  28  extends along the central shaft  22  in a manner prescribed and controlled by the restraining means  26 , i.e., through and beyond the tube  74 , and in operative association with the suture loops  44  and  76 , which, in this embodiment, comprise the stationary components of the releasing means  28 . This occurs without dependence upon additional support by the catheter tip component  24 . Withdrawal of the movable component  58  moves the cutting element  78  through the suture loop  76 , cutting the suture loop  76  and releasing the prosthesis  14  (as  FIG. 14B  shows). 
     In yet another illustrative, alternative embodiment (see  FIGS. 15A and 15B ), the restraining means  26  includes a single tube  80  carried by the central shaft  22 , through which the movable component  58  of the releasing means  28  passes. As the tube  74  shown in  FIGS. 14A and 14B , the tube  80  can comprise a surrounding tube of the type shown in  FIG. 12A  (as  FIGS. 15A and 15B  show) or an external tube of the type shown in  FIG. 12B . 
     In this arrangement, the releasing means  28  includes a wedge element  84  carried on the distal end of the movable component  58  of the releasing means  28 . The wedge element  84  nests within a mating wedge surface  86  formed in the proximal end of the catheter tip component  24 . Advancement of the movable component  58  moves the wedge element  84  into the registration within the wedge surface  86  (as  FIG. 15A  shows) and out of registration with the wedge surface  86  (as  FIG. 15B  shows). The releasing means  28  in this arrangement further includes alternative embodiments of suture loops  82  or  82 ′, which are pinched between the wedge element  84  and the wedge surface  86  when the element  84  and the surface  86  are in registration, as  FIG. 15A  shows. The embodiment of the suture loop  82  comprises a closed loop  82  carried by a prosthesis stent  48 . The embodiment of the suture loop  82 ′ comprises an open loop  82 ′ carried by the proximal end of the catheter tip component  24  and looped through a prosthesis stent  48 . When either embodiment of the suture loop  82  or  82 ′ is pinched between the wedge element  84  and the indented surface  86 , expansion of the prosthesis  14  is restrained (as  FIG. 15A  shows) . When the movable component  58  of the releasing means  28  is advanced proximally, the wedge element  84  is freed from registration within the wedge surface  86 , freeing the loops  82  or  82 ′, thereby releasing the prosthesis  14  for expansion, as  FIG. 15B  shows. 
     The preferred embodiments of the invention are described above in detail for the purpose of setting forth a complete disclosure and for the sake of explanation and clarity. Those skilled in the art will envision other modifications within the scope and sprit of the present disclosure. 
     The above described embodiments of this invention are merely descriptive of its principles and are not to be limited. The scope of this invention instead shall be determined from the scope of the following claims, including their equivalents.