Abstract:
An assembly for delivery and deployment of an inflation expandable stent within a vessel is comprised of a catheter, an inflation expandable stent, an expandable balloon, and a securement means such as a corrugated tube component or an expandable tube component. The tube component is mounted on the inner shaft beneath the balloon and provides increased securement to the stent in a reduced delivery diameter to maintain the stent on the catheter during delivery to the deployment site. The tube component is adhered to the inner shaft and has a plurality of ribs or is fluid expandable to no more than the delivery diameter. and may be comprised of more than one separately inflatable pouch expandable to provide the stent with a substrate seat with increased friction and to decrease the slack in stent recoil crimping. The assembly is used in a method for delivering and deploying a stent, and also adds safety when loading/crimping the stent onto a balloon.

Description:
REFERENCES TO CO-PENDING APPLICATIONS  
       [0001]    This application is a continuation-in-part of co-pending application Ser. No. 08/697,453 filed Aug. 23, 1996 entitled PRE-MOUNTED STENT DELIVERY DEVICE WITH INFLATABLE TUBE COMPONENT, herein incorporated by reference in its entirety.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to an assembly method for delivering and deploying an inflation expandable stent particularly within a lumen of a body vessel. More specifically, this invention relates to the provision of a securement component positioned over the inner catheter, and beneath a balloon and a loaded stent, to maintain the stent on the catheter assembly during delivery to a stent deployment site.  
           [0004]    2. Description of Relevant Art  
           [0005]    Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well-known. A stent is a general cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.  
           [0006]    Both self-expanding and inflation expandable stents are well-known and widely available. Self-expanding stents must be maintained under positive external pressure in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents (also known as balloon expandable stents) are crimped to their reduced diameter about the delivery catheter, positioned at the deployment site, and then expanded to the vessel by diameter by fluid inflation of the balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with enhanced stent securement and safer stent loading in the delivery and deployment of balloon expandable stents.  
           [0007]    In angioplasty procedure, there may be restenosis of the artery, which either necessitates another angioplasty procedure, a surgical bi-pass procedure, or some method of repairing or strengthening the area. To prevent restenosis and strengthen the area, a physician can implant an intravascular prosthesis for maintaining vascular patency, i.e. a stent, inside the artery at the lesion. The stent is expanded to a larger diameter for placement in the vasculature, often by the balloon portion of the catheter. Stents delivered to a restricted coronary artery, expanded to a larger diameter as by a balloon catheter, and left in place in the artery at the site of a dilated lesion are shown in U.S. Pat. No. 4,740,207 to Kreamer; U.S. Pat. No. 5,007,926 to Derbyshire; U.S. Pat. No. 4,733,665 to Palmaz; U.S. Pat. No. 5,026,377 to Burton et al.; U.S. Pat. No. 5,158,548 to Lau et al.; U.S. Pat. No. 5,242,399 to Lau et al.; U.S. Pat. No. 5,344,426 to Lau et al.; U.S. Pat. No. 5,415,664 to Pinchuck; U.S. Pat. No. 5,453,090 to Martinez et al.; U.S. Pat. No. 4,950,227 to Savin; U.S. Pat. No. 5,403,341 to Solar; U.S. Pat. No. 5,108,416 to Ryan et al.; and European Patent Application No. 707837A1 to Scheiban, all of which are incorporated herein by reference. A stent particularly preferred for use with this invention is described in PCT Application No. 96/03092-A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.  
           [0008]    In advancing a balloon expandable stent through a body vessel to the deployment site, there are a number of important considerations. The stent must be able to securely maintain its axial position on the delivery catheter. The stent, particularly its distal and proximal ends, are sometimes protected to prevent distortion of the stent, and minimize trauma to the vessel walls. Balloon expandable stent delivery and deployment assemblies are known which utilize restraining means that overlay the stent during delivery. U.S. Pat. No. 4,950,227 to Savin et al., relates to a balloon expandable stent delivery system in which a sleeve overlaps the distal or proximal margin (or both) of the stent during delivery. During inflation of the stent at the deployment site, the stent margins are freed of the protective sleeve(s) and the sleeves then collapse toward the delivery catheter for removal. A number of balloon expandable stent delivery and deployment assemblies do not use overlaying restraining members, such as the Savin sleeves, to position the stent for delivery. European Patent Application No. EP 055 3960A1 to Lau et al., uses an elastic sheath interspaced between the balloon and the stent. The sheath is said to act as a barrier to protect the balloon from the stent, allow uniform stent expansion, decrease balloon deflation time, prevent undesirable balloon flattening upon deflation and provide a friction substrate for the stent. The Lau sheath can be positioned on the inside or outside of the balloon. U.S. Pat. No. 5,409,495 to Osborne, similarly uses an elastic sleeve or sheath surrounding and in contact with the balloon for controlling the balloon radial expansion. In addition, Osborne is said to use restraining bands or a pair of balloons to achieve controllable stent expansion characteristics. U.S. Pat. No. 5,403,341 to Solar, relates to stent delivery and deployment assembly which uses a retaining sheath positioned about opposite ends of the compressed state. The retaining sheaths of Solar are adapted to tear under pressure as the stent is radially expanded, thus releasing the stent for engagement with the sheaths. U.S. Pat. No. 5,108,416 to Ryan et al. describes a stent introducer system which uses one or two flexible end caps and annular socket surrounding the balloon to position the stent during introduction to the deployment site. The content of all of these patents is incorporated herein by reference.  
           [0009]    In positioning a balloon expandable stent on the delivery catheter over the fluid expandable balloon, the stent must be smoothly and evenly crimped to closely conform to the overall profile of the catheter and the unexpanded balloon. It has been noted that, due to physical properties of the material used in manufacturing the stent (stainless steel, tantalum, platinum or platinum alloys, or shape memory alloys such as Nitinol™) there is a certain amount of “recoil” of the stent despite the most careful and firm crimping. That is the stent evidences a tendency to slightly open up from the fully crimped position and once the crimping force has been released. For example, in the typical stent delivery and deployment assembly, if the stent has been fully crimped to a diameter of approximately 0.0035″, the stent has been observed to open up or recoil to approximately 0.0037″. This phenomenon has been characterized as “recoil crimping”. Due to recoil crimping to this slightly enlarged diameter, it can be understood that the stent tends to evidence a certain amount of looseness from its desired close adherence to the overall profile of the underlying catheter and balloon. That is, the stent tends to have a perceptible relatively slack fit in its mounted and crimped position. During delivery, the stent can thus tend to slip and dislocate from its desired position on the catheter or even become separate from the catheter, requiring further intervention by the physician.  
           [0010]    Further, there is a possibility of damaging the balloon during the stent crimping as a result of pinching the balloon material between the metal stent and any metal (or protruding object) on the inner guide lumen (e.g. marker bands).  
           [0011]    According to the present invention, a securement means such as a corrugated (accordion-type) tube is secured over the Inner catheter beneath the balloon to compensate for the undesired looseness or slack that due to recoil crimping and to aid in securing the stent to the balloon, as well as protecting the balloon material from being sandwiched between the stent and any metal or protruding item which may be mounted on the inner shaft/guide wire lumen, for delivery of the stent. The corrugated tube provides additional volume for improved stent securement, i.e. more surface area to crimp onto, and also maintains flexibility. In addition, when metal marker bands are employed on the inner catheter, the tubing aids in preventing damage to the balloon during crimping/loading of the stent. The tubing, which may be inflatable, compensates for the perceptible looseness due to recoil crimping and secures the stent during tracking and delivery and provides a good friction fit to the stent and insures good contact between the stent and underlying balloon and catheter, instead of merely relying on the bulk of the flaccid balloon over the underlying catheter to hold the stent on. According to the present invention, the tubing component will compensate for slackness in the fit of the stent due to recoil crimping.  
           [0012]    According to another embodiment of the present invention, the securement means is an expandable tube component positioned under the expandable balloon to compensate for this undesired looseness or slack fit due to recoil crimping and to aid in securing the stent to the balloon and the catheter for delivery. The expandable tube component and the expandable balloon are each provided with separate, individually controllable fluid inflation sources. Once the stent has been fully crimped to conform to the overall profile of the catheter, the expandable balloon, and the underlying expandable tube component, the tube component is inflated. The tube component is inflated to at least the limits of the elastic deformation of the fully crimped stent. It is desirable to slightly further inflate the tube component to a pressure at which the fully crimped stent just begins to plastically deform. That is, the tube component many be inflated to a point at which the stent is just barely beginning to provide resistance to the expansion of the tube component, which is also characterized as a point at which the stent just barely begins to expand beyond the crimped position (taking into consideration the recoil crimping phenomenon). The desired pressure to which the tube component is inflated is characterized as the “securement pressure”. The application of securement pressure to the tube component compensates for the perceptible looseness due to recoil crimping and secures the stent during tracking and delivery. The application of securement pressure to the tube component provides a good friction fit to the stent and ensures good contact between the stent and the underlying balloon, “securement pressurized” tube component and catheter. The desired diameter of the stent upon the application of securement pressure to the tube component is characterized as the “delivery diameter”, because in this condition the stent can safely, reliably and securely be delivered to the pre-selected position within a body vessel. Instead of merely crimping the stent onto the balloon and the underlying catheter and relying on the bulk of the flaccid balloon to hold the stent on, according to the present invention, the expandable tube component will compensate for slackness in the fit of the stent due to recoil crimping. Prior to inflation of the tube component to the securement pressure, the physician preparing the assembly may manually sense a looseness of the stent in its position. When the tube component has been inflated to the necessary securement pressure, the physician will manually sense that the stent is securely retained or “stuck” in position. The expandable tube component is designed and constructed to be expandable to no more than is necessary to compensate for recoil crimping and is incapable of overexpanding to provide the pressure needed to fully expand the stent to its deployment position.  
           [0013]    There are a number of descriptions of catheters which use a pair of coaxial, at least partially coextensive balloons. U.S. Pat. No. 5,512,051 to Want et al., describes a slip layered balloon made of a plurality of layers with a low friction substance between the layers. During expansion the layers are able to slide relative to each other softening the balloon while maintaining its strength. U.S. Pat. No. 5,447,497 to Sogard et al., relates to s a dual layered balloon, in which one balloon is compliant and the other is non-compliant, so that the balloon assembly has a non-linear compliance curve. U.S. Pat. No. 5,358,487 to Miller, describes a balloon catheter having an outer balloon surrounding an inner balloon. The inner balloon has a maximum inflation diameter less than that of the outer balloon, so that, upon inflation, the inner balloon bursts at a certain diameter, allowing the outer balloon to be further expanded. U.S. Pat. No. 5,290,306 to Totta et al., relates to a balloon catheter with an outer elastomeric sleeve to provide the balloon with pin hole and abrasion resistance. U.S. Pat. No. 5,049,132 to Shaffer et al., describes a first balloon and a second balloon, each having separate inflation lumens, the second balloon having apertures for controlled administration of a medication therethrough. U.S. Pat. Nos. 4,608,984 and 4,338,942 to Fogarty, each relate to a catheter with an inner non-elastic balloon and an outer elastic balloon. In each patent, the outer balloon aids in collapse and retraction of the inner balloon. U.S. Pat. No. 4,328,056 to Snooks, describes a method of making a double cuffed endotracheal tube component. However, none of these references show, suggest or render obvious an inner balloon, in conjunction with an outer deployment inflatable balloon, to provide securement pressure to a compressed stent during delivery to a site within a body vessel.  
           [0014]    The art referred to and/or described above is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists.  
         SUMMARY OF THE INVENTION  
         [0015]    The present invention is an assembly for delivery and deployment of an inflation expandable stent within a vessel. The assembly comprises a catheter, an expandable balloon mounted on the catheter, a stent securement means mounted on the catheter beneath or within the balloon, and a stent mounted on the balloon. The catheter has proximal and distal ends. The stent is inflation expandable from a delivery diameter to a deployment diameter. The delivery diameter is reduced from the deployment diameter for conforming the stent to the catheter. The stent, in its delivery diameter, is coaxially mounted on the catheter near the catheter distal end. The expandable balloon is coaxially mounted on the catheter axially within the stent. The balloon is designed and adapted for expansion of the stent from the delivery diameter to the deployment diameter upon application of fluid deployment pressure to the balloon. The securement means may be corrugated tubing mounted and adhered coaxially onto the catheter and situated between the balloon and the catheter itself. Alternatively, the securement means may be an expandable tube component mounted on the catheter. The expandable tube component is coaxially mounted on the catheter, axially within the expandable balloon. The expandable tube component is designed and adapted for fluid expansion to provide a securement pressure to the stent in the delivery diameter to maintain the stent in position on the catheter during delivery to the deployment site. The expandable tube component is sized and constructed to be fluid expandable to no more than the delivery diameter. The expandable tube component or corrugated tube is essentially equal in length to the stent and the stent is positioned on the assembly essentially coextensive with the tube component. When the stent is crimped and loaded onto the balloon, the balloon is situated therefore between the stent and the securement means. The securement means is preferably essentially equal to the length of the stent and the stent is positioned on the assembly essentially co-extensive with the tube component. The present invention is particularly directed to improved arrangements for releasably attaching the stent to the catheter to facilitate delivery thereof. Generally, the stent is held in place upon the catheter by means of an enlarged body carried by the catheter shaft within the balloon to which the stent and the balloon are fitted, as by crimping. The securement means on the catheter effectively holds the stent in place, takes up the slack due to recoil and protects the balloon material from being damaged during crimping.  
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0016]    [0016]FIG. 1 is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying corrugated tube component and the catheter.  
         [0017]    [0017]FIG. 2 is a side profile section, similar to FIG. 1, with the balloon and the stent fully inflated to deployment diameter.  
         [0018]    [0018]FIG. 3 is a perspective view of the corrugated tubing of the present invention.  
         [0019]    FIGS.  4 - 6  are side profile sections showing alternative embodiments of balloon expandable stent delivery and deployment assemblies, having the tubing component formed in a plurality of sections.  
         [0020]    FIGS.  7 - 8  are side profile sections showing alternative embodiments of the balloon expandable stent delivery and deployment assemblies, the tube component inflatable to add securement pressure.  
         [0021]    [0021]FIG. 9 is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying tube component and the catheter, and also having containment sleeves covering the ends of the stent.  
         [0022]    [0022]FIG. 10 is a side profile section showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying tube component and the catheter, and also having a pull-back wire attached to the tube component.  
         [0023]    [0023]FIG. 11 is a side profile section of an alternative embodiment showing a balloon expandable stent delivery and deployment assembly, with the stent crimped to delivery diameter onto the balloon, the underlying inflating tube component and the catheter and with the inflating tube component inflated to securement pressure.  
         [0024]    [0024]FIG. 12 is a side profile section, similar to FIG. 11, with the balloon and the stent fully inflated to deployment diameter.  
         [0025]    [0025]FIG. 13 is a side profile section showing an alternative embodiment of a balloon expandable stent delivery and deployment assembly, having a tube component formed in several sections.  
         [0026]    [0026]FIGS. 14, 15 and  16  are cross-sectional views taken along lines  44 ,  55  and  6 - 6  of FIG. 13, respectively.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    [0027]FIGS. 1 and 2 illustrate a side profile section showing an inflation expandable stent delivery and deployment assembly, generally designated  10 . Assembly  10  includes a catheter comprised of inner shaft  12  and outer shaft  13  of the coaxial type and an optional retractable delivery shaft  11  (typically called a guide catheter, shown retracted in FIG. 2), an inflation expandable balloon  14 , a corrugated/ribbed stent securement device  16 , optional marker bands  17  and an inflation expandable stent  18 . Any conventional type of catheter may be used, such as a catheter of the type generally used for PTA or PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. However, coaxial types as show are most preferred. The particular catheters  12  and  13  shown are formed of a biocompatible and hydrophilic compatible material, such as a lubricous polyimide or poly ethylene. Other suitable materials for the catheters  12  and  13  include nylons, urethanes, and polypropylene materials compatible with coatings such as silicone and/or hydrophilic coatings. In addition to hydrophilic compatible materials, any biocompatible material may be used. For example, polyethylene or polypropylene can be coated with a hydrophilic material to render them hydrophilic compatible. Suitable catheters for use according to the present invention include a number of catheters available from SciMed Life Systems, Inc., Maple Grove, Minn., the assignee of the present invention, such as BANDIT™, COBRA™, VIVA™, VIVA PRIMO™, MAXXUM™, MAXXUM ENERGY™ and RANGER™ catheters.  
         [0028]    Securement device  16  is fixed at its distal and/or proximal ends to inner shaft  12  at a position to be encompassed within the distal and proximal ends of the outer balloon  14 . According to art-recognized convention, the length L-B of the balloon  14  is defined as the length of the body portion of the balloon  14 , excluding the terminal cone sections  20 . As seen in FIG. 2, the body portion of the balloon  14  is generally cylindrical when in its deployed or inflated condition. Securement device/tube component  16  is illustrated as having terminal sections  21 , 22 . It is to be understood that, according to the present invention, either of the terminal sections  21 ,  22  may be relatively cone shaped, relatively vertical, relatively flat or of any other configuration known to those of skill in this art. A preferred length L-T of the tubing  16  is illustrated in FIGS.  1  and  2  as substantially equal to the length L-B of balloon  14 , and substantially equal to the length L-S of stent  1  S. However, according to the present invention, stent  18  should be supported by the underlying tube component  16  for a length sufficient to permit accomplishment of the stated purpose of the tube component  16 , to provide a superior securement and protective surface for stent  18  to maintain stent  18  in position with assembly  10  and to protect the balloon material during loading/crimping. It is also within the present invention for the tube component  16  to be slightly shorter than stent  18 , for example, the distal end  19  of stent  18  may extend distally beyond the distal end  22  of tube component  16  (not shown), so that the distal end  19  of stent  18  can be crimped over the distal end  22  of tube component  16  to prevent the distal end  19  of stent  18  from catching and tending to snag or further open as it is maneuvered within a body vessel. As has been explained above, tube component  16  is designed and constructed to have enough flexibility and have enough volume to no more than is necessary to compensate for recoil crimping of stent  18  and to closely accommodate (or even slightly over stress) the delivery diameter of stent  18 , taking into consideration the thickness of the intervening uninflated balloon  14 . Typically, the tube component  16  will have a consistent frequency of ribs, but may also vary by having intermittent groups of ribs along the tubing.  
         [0029]    The balloon and the crimped stent slightly conform to the undulations of the tube component for greater securement, but this conformation is not illustrated.  
         [0030]    Tube component  16  may be formed from a thermoplastic material, preferably a low modulus polymer, such as Surlyn™, Pebax and urethane. The device such as polypropylene, low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate (EVA), nylon, polyester and polyethylene terephthalate (“PET”), may be prepared through free blowing in a mold or inside a coil. Tubing is extruded with relatively thin walls and then free-blown in a mold, coil or other fixture to form the ribs/corrugation.  
         [0031]    A balloon  14  for use according to the present invention may be any conventional balloon for catheter delivery, such as a balloon of the type generally used for PTA and PTCA procedures. Typically, balloon  14  is fixed at its distal end to inner shaft  12  near the catheter distal end and at its proximal end to inner shaft  12 , near the distal end of the outer shaft  13 . Balloon  14  is inflatable through an inflation conduit  23 , i.e., the space between coaxial inner shaft  13  and outer shaft  13  of the catheter. The distal and proximal ends of balloon  14  are shown in FIGS. 1 and 2 positioned exterior the distal and proximal ends of tube component  16 , respectively, and of a length L-B generally equal to the length L-T of the tube component  16 . To be compatible with the tube component  16  illustrated in FIGS. 1 and 2 and described above, balloon  14  is inflatable at deployment to about the diameter of the body vessel in which the stent  18  is to be deployed. Balloon  14  may be formed of a compliant or non-compliant material, such as polyethylene or any standard balloon material. Compliant materials include low pressure, relatively soft or flexible polymeric materials, such as thermoplastic polymers, thermoplastic elastomers, polyethylene (high density, low density, intermediate density, linear low density), various co-polymers and blends of polyethylene, ionomers, polyesters, polyurethanes, polycarbonates, polyamides, poly-vinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyether-polyester copolymers, and polyetherpolyamide copolymers. Suitable materials include a copolymer polyolefin material available from E.I. DuPont de Nemours and Co. (Wilmington, Delaware), under the trade name Surlyn™ Ionomer and a polyether block amide available under the trade name PEBAX™. Non-compliant materials include relatively rigid stiff high pressure polymeric materials, such as thermoplastic polymers and thermoset polymeric materials, poly(ethylene terephthalate) (commonly referred to as PET), polyimide, thermoplastic polyimide, polyamides, polyesters, polycarbonates, polyphenylene sulfides, polypropylene and rigid polyurethanes, or combinations thereof. The balloon  14  typically has a wall thickness of about 0.0007-0.004″ for example.  
         [0032]    A stent for use according to the present invention may be any conventional type of balloon expandable stent, including stents of the type used for PTA and PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. Suitable stent material is biocompatible stainless steel in the form of sheet metal, tube component wire or Nitinol. A preferred stent is described in PCT Application No. 960 3072 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference. All such stents are well-known in this art generally and additional examples are described in U.S. Pat. No. 5,507,768 to Lau et al.; in U.S. Pat. No. 5,458,615 to Klemm et al.; in U.S. Pat. No. 5,226,899 to Scheiban; in U.S. Pat. No. 4,875,480 to Imbert; in U.S. Pat. No. 4,848,343 to Wallsten et al.; and in U.S. Pat. No. 4,733,665 to Palmaz. Stent  18  as shown in FIGS. 1 and 2 is positioned on balloon  14 , which is over the underlying tube component  16 , at the distal end of the catheter. The length L-S of stent  18  is shown as essentially equal or slightly smaller than the length L-T of tube component  16  and is positioned on assembly  10  to be coextensive with tube component  16 . In this position, stent  18  is shown in FIG. 1 crimped to its delivery diameter D 1 , which is about 0.035-0.45″ for example.  
         [0033]    As discussed above, despite the most careful and firm crimping of stent  18  to closely conform to the overall profile of the catheter unexpanded balloon  14  and underlying tube component  16 , there is a certain amount of “recoil” of stent  18  or a tendency of stent  18  to slightly open from a desired hypothetical minimum crimped diameter. The actual minimum diameter achievable for fully crimped stent  18  on assembly  10  is referred to as stent  18  delivery diameter D  1 . This tendency of stent  18  to open or recoil slightly when crimped on assembly  10  has been characterized as “recoil crimping”. In FIG. 1, tube component  16  is shown at a diameter which is generally sufficient to compensate for any slack or looseness between crimped stent  18  and the overall profile of the catheter, the unexpanded balloon  14  and the underlying tube component  16  due to recoil crimping.  
         [0034]    [0034]FIG. 2 illustrates a side profile section showing a stent delivery and deployment assembly  10  of this invention with balloon  14  fluid inflated to its fully expanded position. As a result of the fluid inflation of the balloon  14 , stent  18  has also been fully expanded to its deployment diameter D 2  in which it can be deployed against the walls of a body vessel in which it is situated.  
         [0035]    [0035]FIG. 3 illustrates the preferred configuration of the tube component  16 . The tube component has a plurality of ribs  30  and is configured in a corrugated or accordion fashion. The ends of the tube component  16 ,  22  and  21 , are substantially rib-free so as to provide a flat surface to receive an adhesive and thereby bond to the inner shaft  12 . Preferable adhesives include cyanocrylates such as Loctite 4061/4011 or urethanes, such as H.B. Fuller 3507/3506. The tube component may also be heat bonded to the inner shaft. The ribs may vary in frequency and spacing.  
         [0036]    Tube component  16  may have different configurations in other embodiments, as shown in FIGS.  4 - 6 . The tube component  16  may be comprised of more that one piece of corrugated tubing (FIG. 4), a smaller single piece (FIG. 5) or one single piece of tubing sectioned into a plurality of ribbed sections, wherein the tubing is adhered to the inner shaft  12  in more than two locations (FIG. 6).  
         [0037]    [0037]FIG. 4 shows two pieces of tubing component  16   a ,  16   b . Both pieces are adhered to inner shaft  12  at adhesion points  32 . FIG. 5 discloses an embodiment which comprises one smaller piece of tube component  16  which is adhered to inner shaft  12  at adhesion points  32 . FIG. 6 discloses an embodiment which comprises one tube component  16  which has interrupted ribbed sections  34  adhered to the inner shaft  12 .  
         [0038]    [0038]FIGS. 7 and 8 illustrate an alternative embodiment in which the tubing component is inflatable to increase the securement pressure on the inside of balloon  14  when the stent is crimped onto the balloon so as to negated additional recoiling. The full expansion of the tube component  16  should only be slightly greater than the diameter of the inside of the balloon  14  when the stent  18  is fully crimped onto the balloon  14 .  
         [0039]    In FIG. 7, the inflating fluid comes through the guide wire lumen  12  under pressure from the proximal end or the distal end of the guide wire lumen  12 , preferably via a syringe, and fills the tubing component  16  through a one-way valve  47  (preferably resisting up to about 4 atm) in the inner catheter  12 .  
         [0040]    In FIG. 8, the tubing component  16  is inflated via an additional lumen  42  which extends from the proximal end of the catheter along the guide wire lumen  40 , much the same as any inflating lumen incorporated to inflate a balloon.  
         [0041]    In an alternative embodiment, as shown in FIG. 9, socks or sleeves  51  may be incorporated to stretch over the ends of the stent to prevent snagging and to secure the stent onto the balloon. Such sleeves are demonstrated in U.S. application Ser. No. 08/702,149, filed Aug. 23, 1996, and Ser. No. 08/701,979, filed Aug. 23, 1996, which are incorporated in their entirety herein by reference.  
         [0042]    In still another embodiment, as shown in FIG. 10, the tubing component  16  is slidable axially along the inner shaft  12  and is connected to a retracting wire  50  such that the tubing component may be retracted into the outer shaft  13  after the balloon has been inflated to reduce the profile of the balloon  14  when the catheter is removed. The tubing component, since it is not adhered to the inner shaft  12  in this embodiment, should fit tightly enough on the inner shaft to stay in place, but not too tightly so that it may be retracted by pulling on the retracting wire  50 .  
         [0043]    The method of using the stent delivery and deployment assembly  10  of this invention, as shown in FIGS. 1 and 2, is described as follows. The assembly  10  is constructed as described above. Stent  18  is compressed or crimped onto balloon  14 , tube component  16  and the catheter to a delivery diameter D 1 . This crimping can be done manually or with the aid of tooling specifically designed for the purpose either by the physician or the manufacturer. In the crimped position, stent  18  closely conforms to the overall profile of balloon  14 , tube component  16  and the catheter except for the slight slack or looseness due to recoil crimping. Tube component  16  is flexible enough to slightly collapse during crimping and rebound to the extent necessary to compensate for the slack or looseness due to recoil crimping, thus securing the stent. As a result, the stent does not move out of its position on the catheter during delivery or become separated from the catheter within a body vessel. The catheter distal end is delivered by standard techniques to the deployment site within the body vessel of interest. At this point, stent  18  is positioned as required by the physician and balloon  14  is fluid inflated by standard technique to expand stent  18  to its deployment diameter D 2 . During this expansion, stent  18  is expanded to fill the body vessel. Following deployment of stent  18 , balloon  14  is deflated and the assembly is retracted proximally and withdrawn from the body. If required by the procedure, the site of entry to the body is appropriately closed.  
         [0044]    The tube component provided by this invention increases stent securement force by increasing the frictional force between the tube component, the balloon wall and the internal diameter of the stent in its reduced crimped delivery diameter. The tube component is more flexible than a solid sheath under the expandable balloon, and thus the entire assembly has greater flexibility. This invention has particular advantages for assemblies in which the stent is provided for use as pre-crimped to the balloon and underlying catheter, by increasing the shelf life of the pre-crimped assembly. The tube component also protects the balloon material during crimping by acting as a buffer between the balloon material and whatever may be mounted on the inner shaft, such as marker bands  17 . The features and principles described for this invention are suitable for use with fixed wire, over-the-wire and single operator exchange assemblies.  
         [0045]    Another embodiment of the present invention is shown in FIGS. 11 and 12 which illustrate a side profile section showing an inflation expandable stent delivery and deployment assembly generally designated  110 . Assembly  110  includes a catheter comprised of inner shafts  112  and  113  and an outer shaft  115  of the coaxial type, an inflation expandable balloon  114 , an inflation tube component  116  such as an inner balloon and inflation expandable stent  118 . Any conventional type of catheter may be used, such as a catheter of the type generally used for PTA or PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. However, coaxial types as shown are most preferred. The particular catheter  112  shown is formed of a biocompatible and hydrophilic compatible material, such as a lubricous polyimide or polyethylene. Other suitable materials for the catheter  112  include nylons, urethanes, and polypropylene materials compatible with coatings such as silicone and/or hydrophilic coatings. In addition to hydrophilic compatible materials, any biocompatible material may be used. For example, polyethylene or polypropylene can be coated with a hydrophilic material to render them hydrophilic compatible. suitable catheters for use according to the present invention include a number of catheters available from Scimed Life Systems, Inc., Maple Grove, Minn., the assignee of the present invention, such as BANDIT™, COBRA™, VIVA™, and VIVA PRIMO™ catheters.  
         [0046]    Inflatable tube component  116  is fixed at its distal and proximal end to inner shaft  112  and at its proximal end to inner shaft  113  at a position to be encompassed within the distal and proximal ends of the outer balloon  114 . According to art-recognized convention, the length L-B of the balloon  114  is defined as the length of the body portion of the balloon  114 , excluding the terminal cone sections  120 . As seen in FIG. 12, the body portion of the balloon  114  is generally cylindrical when in its deployed or inflated condition. Tube component  116  is illustrated as having terminal sections  122  which are more relatively vertical than the cone sections  120  illustrated for the balloon  114 . However, it is to be understood that, according to the present invention, either of the terminal sections  120 ,  122  may be-relatively cone shaped, relatively vertical or of any other configuration known to those of skill in this art. A preferred length L-T of the tube component  116  is illustrated in FIGS. 11 and 12 as substantially equal to the length L-B of balloon  114 , and substantially equal to the length L-S of stent  112 . However, according to the present invention, stent  112  should be supported by the underlying tube component  116  for a length sufficient to permit accomplishment of the stated purpose of the tube component  116 , when inflated, to provide securement pressure for stent  112  to maintain stent  112  in position with assembly  110  during delivery. It is also within the present invention for tube component  116  to be slightly shorter than stent  112 , for example, the distal end  119  of stent  112  may extend distally beyond the distal end  121  of tube component  116  (not shown), so that the distal end  119  of stent  121  can be crimped over the distal end  121  of tube component  116  to prevent the distal end  119  of stent  112  from catching and tending to further open as it is maneuvered within a body vessel. As has been explained above, tube component  116  is designed and constructed to be inflatable to no more than is necessary to compensate for recoil crimping of stent  112  and to closely accommodate (or even slightly over-stress) the delivery diameter of stent  112 , taking into consideration the thickness of the intervening uninflated balloon  114 . Tube component  116  is inflated through the opening(s)  117  of inner shaft  112 . Typically, tube component  116  will have a wall thickness of about 0.0002-0.0007 inch and will be inflatable to no more than about 0.035.-0.045 inches.  
         [0047]    Inflating tube component  116  may be formed of either compliant or non-compliant balloon materials. Compliant materials include low pressure, relatively soft or flexible polymeric materials, such as thermoplastic polymers, thermoplastic elastomers, polyethylene (high density, low density, intermediate density, linear low density), various co-polymers and blends of polyethylene, ionomers, polyesters, polyurethanes, polycarbonates, polyamides, poly-vinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyether-polyester copolymers, and polyetherpolyamide copolymers. Suitable materials include a copolymer polyolefin material available from E.I. DuPont de Nemours and Co. (Wilmington, Del.), under the trade name Surlyn™ Ionomer and a polyether block amide available under the trade name PEBAX™. Non-compliant materials include relatively rigid of stiff high pressure polymeric materials, such as thermoplastic polymers and thermoset polymeric materials, poly(ethylene terephthalate) (commonly referred to as PET), polyimide, thermoplastic polyimide, polyamides, polyesters, polycarbonates, polyphenylene sulfides, polypropylene and rigid polyurethanes.  
         [0048]    A balloon  114  for use according to the present invention may be any conventional balloon for catheter delivery, such as a balloon of the type generally used for PTA and PTCA procedures. Typically, balloon  114  is fixed at its distal end to inner shaft  112  near the catheter distal end and at its proximal end to outer shaft  115 . Balloon  114  is larger in diameter than tube component  116 , because balloon  114  must be able to expand to a larger diameter than tube component  116 . Balloon  114  is inflatable through an inflation conduit  123 , i.e., the space between coaxial inner shaft  113  and outer shaft  115  of the catheter. The distal and proximal ends of balloon  114  are shown in FIGS. 11 and 12 positioned exterior to the distal and proximal ends of tube component  116 , respectively, and of a length L-B generally equal to the length L-T of the tube component  116 . To be compatible with tube component  116  illustrated in FIGS. 11 and 12 and described above, balloon  114  is inflatable at deployment to about the diameter of the body vessel in which the stent  118  is to be deployed. Balloon  114  may be formed of a compliant or non-compliant material, of the types of compliant materials described herein above, such as polyethylene or any standard balloon material. Balloon  114  typically has a wall thickness of about 0.0007-0.004 inch for example.  
         [0049]    A stent for use according to the present invention may be any conventional type of balloon expandable stent, including stents of the type used for PTA and PTCA angioplasty procedures, for prostate therapy, and TTS endoscopic catheters for gastrointestinal use. Suitable stent material is biocompatible stainless steel in the form of sheet metal, tube component wire or Nitinol. A preferred stent is described in PCT Application No. 960 3072 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference. All such stents are well known in this art generally and additional examples are described in U.S. Pat. No. 5,507,768 to Lau et al.; in U.S. Pat. No. 5,458,615 to Klemm et al; in U.S. Pat. No. 5,226,889 to Sheiban; in U.S. Pat. No. 4,875,480 to Imbert; in U.S. Pat. No. 4,848,343 to Wallsten et al., and in U.S. Pat. No. 4,733,665 to Palmaz. Stent  118  as shown in FIGS. 11 and 12 is positioned on balloon  114 , the underlying inflatable tube component  116  and the distal end of the catheter. The length L-S of stent  118  is shown as essentially equal or slightly smaller than the length L-T of tube component  116  and is positioned on assembly  110  to be co-extensive with tube component  116 . In this position, stent  118  is shown in FIG. 11 crimped to its delivery diameter D 1 , which is about 0.035-0.045 inch for example.  
         [0050]    As discussed above, despite the most careful and firm crimping of stent  118  to closely conform to the overall profile of the catheter unexpanded balloon  114  and underlying inflatable tube component  116 , there is a certain amount of “recoil” of stent  118  or a tendency of stent  118  to slightly open from a desired hypothetical minimum crimped diameter. The actual minimum diameter achievable for fully crimped stent  118  on assembly  110  is referred to as the stent  118  delivery diameter D 1 . This tendency of stent  118  to open or recoil slightly when crimped on assembly  110  has been characterized as “recoil crimping”. In FIG. 11, inflatable tube component  116  is shown inflated to a diameter which is generally sufficient to compensate for any slack or looseness between crimped stent  118  and the overall profile of the catheter, the unexpanded balloon  114  and the underlying inflatable tube component  116  due to recoil crimping.  
         [0051]    [0051]FIG. 12 illustrates a side profile section showing a stent delivery and deployment assembly  110  of this invention with balloon  114  fluid inflated to its fully expanded position. As a result of the fluid inflation of the balloon  114 , stent  118  has also been fully expanded to its deployment diameter D 2  in which it can be deployed against the walls of a body vessel in which it is situated.  
         [0052]    Tube component  116  may have a shape other than the cylindrical shape described and illustrated with regard to the embodiment shown in FIGS. 11 and 12. Further, the tube component may be comprised of more than one separately inflatable pouch. For example, as illustrated with regard to FIG. 13, the tube component of an alternative stent delivery and deployment assembly generally designated  130  can be comprised of three separately inflatable pouches  136 ,  138 ,  140 . The pouches  136 ,  138 ,  140  are each separately inflatable through their respective inflation conduits  137 ,  139 ,  141 , and each of the pouches  136 ,  138 ,  140  can be inflatable to a different extent. The conduits are formed in the wall of shaft  132  as can be seen in FIGS.  14 - 16 . The stent delivery and deployment assembly  130  of FIG. 13 is also comprised of a catheter having inner shaft  132  and outer shaft  135 , a balloon  134 , with its balloon inflation conduit  139  and the balloon terminal cone sections  144 , and a stent  142 . As has been explained above with reference to FIGS. 11 and 12, stent  142  is crimped to closely conform to the overall profile of the catheter the unexpanded balloon  134  and the underlying inflatable pouches  136 ,  138   140 . Even with the most careful and firm crimping, there is a certain amount of “recoil” of the stent  142  or a tendency of stent  142  to slightly open from a desired hypothetical minimum diameter. In FIG. 13, the first  136  and third  140  pouches are inflated to a slightly larger size than the second pouch  138 . As discussed above, the inflation of the pouches  136 ,  138 ,  140  to this configuration is generally sufficient to compensate for any slack or looseness between the crimped stent  142  and the overall profile of the catheter, the unexpanded balloon  134  and the underlying inflatable pouches  136 ,  138 ,  140  due to recoil crimping. Once pouches  136 ,  138   140  have been inflated to the configuration shown in FIG. 13, stent  142  is firmly secured against axial movement with regard to assembly  130 . The distal  146  and proximal  148  ends of stent  142  are protected from any possible unwanted contact with vessel walls during maneuvering, which helps to protect the vessel walls from abrasion and also helps to protect the ends  146 ,  148  of stent  142  from distortion. Additionally, stent  142  may be of a length such that it fits over pouch  140  and pouch  136  as well as over pouch  138 .  
         [0053]    The method of using the stent delivery and deployment assembly  110  of this invention, as shown in FIGS. 11 and 12, is described as follows. The assembly  110  is constructed as described above. Stent  118  is compressed or crimped onto balloon  114 , inflatable tube component  116  and the catheter to a delivery diameter D 1 . This crimping can be done manually or with the aid of tooling specially designed for the purpose either by the physician or the manufacturer. In the crimped position, stent we closely conforms to the overall profile of balloon  114 , inflatable tube component  116  and the catheter except for the slight slack or looseness due to recoil crimping. Tube component  116  is fluid inflated to the extent necessary to compensate for this slack or looseness due to recoil crimping. The pressure of force required to inflate tube component  116  to this extent is also referred to as securement pressure, i.e., the force or pressure needed to secure stent  112  in this position. It is to be noted that, since tube component  116  is designed and constructed to be capable of filly expanding to no more than the size necessary to compensate for recoil crimping, there is no possibility of stent  112  expanding or beginning to open to a larger diameter. Thus, there is no hazard of stent  112  moving out of its position on the catheter during delivery or of becoming separated from the catheter within a body vessel. The catheter distal end is delivered by standard techniques to the deployment site within the body vessel of interest. At this point, stent  112  is positioned as required by the physician and balloon  114  is fluid inflated by standard technique to expand stent  121  to its deployment diameter D 2 . During this expansion, stent  112  is expanded to fill the body vessel. Following deployment of stent  112 , balloon  114  and optionally, tube component  116  are deflated and the assembly  110  is retracted proximally and withdrawn from the body. If required by the procedure, the site of entry to the body is appropriately closed.  
         [0054]    The method of using the stent delivery and deployment assembly  130  of this invention, as shown in FIG. 13, is similarly described. The assembly  130  is constructed as described above. Stent  142  is compressed or crimped to closely conform to the overall profile of balloon  134 , inflatable pouches  136 ,  138 ,  140  and the catheter except for the slight slack or looseness due to recoil crimping. Pouches  136 ,  138 ,  140  are each fluid inflated to the profile shown in FIG. 13 through separate fluid inflation conduits (not shown) to securement pressure to compensate for this slack or looseness and to secure stent  142  in this position. The overall configuration of pouches  136 ,  138   140  further serves to position stent  142  against axial dislocation during delivery. The catheter is delivered by standard techniques to the deployment site within the body vessel of interest. At this point, stent  142  is positioned as required by the physician and balloon  134  is fluid inflated by standard technique to expand and deploy stent  142 . Following deployment of stent  142 , balloon  134  and, optionally, pouches  136 ,  138   140  are deflated and the assembly  130  is retracted proximally and withdrawn form the body. If required by the procedure, the site of entry to the body is appropriately closed.  
         [0055]    The inflation tube component provided by this invention also maximizes stent securement force by optimizing the frictional force between the inflating tube component, the balloon wall and the internal diameter of the stent in its reduced crimped delivery diameter. The inflation tube component is more flexible than a solid sheath under the expandable balloon, and thus the entire assembly has greater flexibility. This invention has particular advantages for assemblies in which the stent is provided for use as pre-crimped to the balloon and underlying catheter, by increasing the shelf life of the pre-crimped assembly. The features and principles described for this invention are suitable for use with fixed wire, over-the-wire and single operator exchange assemblies.  
         [0056]    It should be understood that the various elements and materials of all embodiments could be utilized in each of the other embodiments if desired.  
         [0057]    The above examples and disclosures are intended to be illustrative and not exhaustive. These examples and descriptions will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.