Abstract:
This invention relates to catheters used for delivering medical devices. The catheter incorporates sleeves which aid in containing the medical device on the catheter, wherein the sleeves have portions comprising high modulus material to aid in the function of the sleeves.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to catheters used for delivering medical devices. The catheter incorporates sleeves which aid in containing the medical device on the catheter, wherein the sleeves have portions comprising high modulus material to aid in the function of the sleeves.  
         BACKGROUND OF THE INVENTION  
         [0002]    In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient through a vessel and advanced through therein until the distal end thereof is at a desired location in the vasculature. A guidewire and a dilatation catheter having a balloon on the distal end thereof are introduced through the guiding catheter with the guidewire sliding through the dilatation catheter. The guidewire is first advanced out of the guiding catheter into the patient&#39;s coronary vasculature and the dilatation catheter is advanced over the previously advanced guidewire until the dilatation balloon is properly positioned across the lesion. Once in position across the lesion, the flexible, expandable, preformed balloon is inflated to a predetermined size with a liquid or gas at relatively high pressures, such as greater than about four atmospheres, to radially compress the arthrosclerotic plaque of the lesion against the inside of the artery wall and thereby dilate the lumen of the artery. The balloon is then deflated to a small profile so that the dilatation catheter may be withdrawn from the patients vasculature and blood flow resumed through the dilated artery.  
           [0003]    In angioplasty procedures of the kind described above, there may be injury to or restenosis of the artery, which either necessitates another angioplasty procedure, a surgical by-pass operation, or some method of repairing or strengthening the area. To strengthen the area and help prevent restenosis, a physician can implant an intravascular prosthesis for maintaining vascular patency, commonly called 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.  
           [0004]    Stents delivered to a restricted coronary artery, expanded to a larger diameter 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, PCT Application No. 960 3092 A1, published Feb. 8, 1996, and U.S. Pat. No. 5,007,926 to Derbyshire, the content of which is incorporated herein by reference. Palmaz et al., 156  Radiology  73 (1985) and U.S. Pat. No. 4,733,665 describe introduction of a stent over a balloon catheter.  
           [0005]    The present invention is particularly directed to improved arrangements and configurations of sleeves for releasably covering the ends of the stent to prevent the stent ends from flaring and snagging to better facilitate delivery thereof. Examples of stent retaining sleeves can be found in Savin U.S. Pat. No. 4,950,227, U.S. application Ser. No. 09/407,836, filed Sep. 28, 1999 and U.S. application Ser. No. 09/668,496, filed Sep. 22, 2000  
           [0006]    All US patents and applications all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.  
           [0007]    Without limiting the scope of the invention in any way, the invention is briefly summarized in some of its aspects below.  
         SUMMARY OF THE INVENTION  
         [0008]    This invention concerns apparatus suitable for delivery of stents to body cavities. In general, stents are prosthetic devices which can be positioned within a body cavity, for example, a blood vessel of the body of a living human or in some other difficultly accessible place. The stent prosthesis is formed of a generally tubular body, the diameter of which can be decreased or increased. Stents are particularly useful for permanently widening a vessel which is either in a narrowed state, or internally supporting a damaged vessel. Such stents are typically introduced into the body cavity by use of a catheter. The catheter is usually of the balloon catheter type in which the balloon is utilized to expand the stent, which is positioned over the balloon, to place it in a selected location in the body cavity. The present invention is particularly directed to improved arrangements for releasably covering/securing the stent, particularly the ends thereof, to the catheter to prevent snagging of the stent ends and to facilitate delivery thereof. Depending on the type of stent used, the stent is held in place on the catheter and kept from flaring upward at its end(s) by means of at least one removable end covering means, or sock, over the stent, the stent having been fitted to the catheter over the balloon, as by crimping. Most specifically, this invention is directed to improved modifications of stent retaining sleeves.  
           [0009]    In particular, the invention is directed to an improved stent delivery system designed to hold a stent over the balloon on a catheter, via the sleeve arrangements and to protect the stent from deformation, damage or premature release during delivery intraluminally, as well as snagging during transportation. It is also a purpose of the present invention to provide for easier and smoother removal of the sleeve retaining means. The stent is formed to its lowest geometrical diameter when loaded. The sleeves of the present invention incorporate high modulus compositions in the form of bands, which are positioned over the cone portion of the balloon on top of or beneath the socks and preferably bonded thereto. The sleeves aid in retaining the stent and holds the stent to the balloon (unexpanded) with little or no relative movement between the ID of the stent and the OD of the balloon/catheter arrangement. The bands are each preferably attached (adhered or welded) to the elastomeric socks or sleeves. One end of the sleeves cover the ends of the stent and the other end of the sleeves are respectively attached to the catheter. When the balloon under the stent is inflated, the bands, which are positioned on the tapered cone portion of the balloon, are driven primarily axially, resulting in the sleeves being pushed/pulled down the balloon cones to allow the stent to deploy. The positioning of the bands on the cones of the balloon allows for more of an axial force and movement of the socks when the balloon inflates rather then a radial force and provides a flatter profile as apposed to other arrangements. This allows for a steadier, smoother, more controlled removal of the sleeves instead of an abrupt release, which may happen with a primarily radial force. Since most stents which are deformed to a low diameter will increase in diameter somewhat after being deformed (spring back), the sleeves also somewhat prevent spring back and increase the friction fit between the stent and balloon.  
           [0010]    The present invention contemplates a stent delivery system having stent retaining sleeves having a high modulus ring or band, preferably a polymeric or metal band, located along the body of the sleeve. The high modulus band gives the sleeve improved retraction properties while allowing the stent edges to deploy. The present invention allows the stent ends to deploy at lower pressures, while assuring full retractions of the sleeves.  
           [0011]    Modifications to this embodiment are further described below.  
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]    [0012]FIG. 1 is a cross-sectional view, in longitudinal section, of the distal end portion of a balloon catheter having a stent fixed to the catheter by being crimped thereto over the balloon, the ends of the stent being covered by a first embodiment of the invention;  
         [0013]    [0013]FIG. 2 is similar to FIG. 1 in which the balloon is expanded and the stent has been released;  
         [0014]    [0014]FIG. 3 a - c  are side views of various ring configurations.  
         [0015]    [0015]FIG. 4 is a view of a modification of the embodiment shown in FIG. 1;  
         [0016]    [0016]FIG. 5 is a view of a modification of the embodiment shown in FIG. 1;  
         [0017]    [0017]FIG. 6 is a view of a modification of the embodiment shown in FIG. 1;  
         [0018]    [0018]FIG. 7 is a cross-sectional view, in longitudinal section, of the distal end portion of a balloon catheter having a stent fixed to the catheter by being crimped thereto over the balloon, the ends of the stent being covered by a further embodiment of the invention;  
         [0019]    [0019]FIG. 8 is similar to FIG. 7 in which the balloon is expanded and the stent has been released;  
         [0020]    [0020]FIG. 9 is a view of a modification of the embodiment shown in FIG. 7;  
         [0021]    [0021]FIG. 10 is a view of a modification of the embodiment shown in FIG. 7;  
         [0022]    [0022]FIG. 11 is a view of a modification of the embodiment shown in FIG. 7;  
         [0023]    [0023]FIG. 12 is a view of a modification of the embodiment shown in FIG. 7;  
         [0024]    [0024]FIG. 13 is similar to FIG. 11 in which the balloon is expanded and the stent has been released; and  
         [0025]    [0025]FIG. 14 is an alternative embodiment of the apparatus shown in FIG. 13.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    While this invention may be embodied in many different forms, there are shown in the drawings and described in detail herein specific embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.  
         [0027]    For the purposes of this disclosure, the term stent refers to stents, stent-grafts, grafts and other endoluminal prostheses whether self-expanding, balloon expandable, self-expanding and balloon expandable or otherwise expandable as are known in the art.  
         [0028]    In addition to the over-the-wire embodiments (example also found in U.S. Pat. No. 5,980,533) shown in FIGS.  1 - 4 , the inventive catheter system may also be provided in a rapid-exchange configuration. Examples of rapid-exchange catheters may be found in U.S. Pat. Nos. 5,534,007 and 5,833,706. The inventive stent delivery systems may also be made in fixed wire form. Examples of fixed-wire catheters may be found in U.S. Pat. No. 5,702,364.  
         [0029]    The system may be adapted for use with a medical device such as a stent, for example, a self-expanding, balloon expandable or combination self-expanding and balloon expandable stent. The system may also be used for delivery of other medical devices for use in the body as well including, but not limited to, ultrasonic devices, laser devices, vena cava filters, implantable drug delivery devices and the like.  
         [0030]    The inventive medical systems disclosed herein may also be provided with any of the features disclosed in U.S. Pat. Nos. 6,096,056, U.S. 6,068,634, U.S. 6,036,697, U.S. 6,007,543, U.S. 5,968,069, U.S. 5,957,930, U.S. 5,944,726, U.S. 5,653,691 and U.S. 5,534,007.  
         [0031]    The stent delivery system may also comprise various coatings as are known in the art, including lubricious coatings to facilitate movement of the various parts of the system, as well as collagen-type coatings. More information concerning suitable coatings may be found in U.S. Pat. No. 5,443,907, and U.S. application Ser. Nos. 08/382,478, 09/306,939 and 09/316,502.  
         [0032]    Referring to FIGS. 1 and 2, a stent delivery system  10  includes a catheter such as an over-the-wire or rapid exchange. Balloon catheters are preferred herein as best examples of catheters having an expandable distal end portion constructed and arranged for expanding the outer diameter of the catheter from a contracted state to an expanded state. FIGS. 1 and 2 shows a catheter  10  having a outer shaft  16 , a guide wire lumen  18  with marker band secured thereto  15  and a distal tip  17 . A balloon  14  is fixed to the distal end of the catheter by adhesive or welding attachment of the proximal end  13  to the outer shaft  16  of the catheter and the distal end  19  to the inner shaft  18  of the catheter. Other arrangements known in the art may be used. Balloon  14  is shown in FIG. 1 in its contracted state and in FIG. 2 in its expanded state. A stent  20  is held about balloon  14  by two overlying retaining sleeves, or socks,  22  and  24 , which cover the ends  30 ,  32  of the stent, respectively.  
         [0033]    Various types of stents may be used with balloon expansion. For example, the stent may be a self-expanding stent which upon release self-expands and is further expanded or is merely aided in release by balloon expansion from the sleeves. Such stents may self-expand elastically or may be thermally induced such as stents formed of nitinol or other shape memory metals or materials.  
         [0034]    Any kind of stent may be delivered by the system of the invention, including plastically deformable or elastically deformable, and they may be of any configuration or structure so long as they can be loaded at a low diameter and deployed at a larger diameter, i.e., have a contracted condition and being expandable to an expanded condition of large diameter.  
         [0035]    Stent  20  may be any of the various types known in the art, either balloon expandable or self-expandable. Exemplary stents are shown in U.S. Pat. No. 4,735,665; U.S. Pat. No. 4,950,227; EPO application 707 837 A1, and U.S. Pat. No. 5,445,646. All of these patents are incorporated herein by reference and are intended to be exemplary only and not limiting. Various materials including stainless steel, tantalum, shape memory alloys and plastic may be used.  
         [0036]    Stent  20  is radially compressed, as by crimping to a contracted condition, against balloon  14  to a relatively small loaded diameter having an OD of 0.044 inches for example, although it has a larger released diameter in the expanded condition. Various sized stents may be used  
         [0037]    Sleeves  22  and  24  may be formed of any material suitable for catheter sleeves. By way of example, sleeves may be made of an expandable material, including a broad class of elastomers, such as urethanes, styrenics, silicones, natural rubbers, nylons, segmented polyamide-polyether-polyesters sold under the Pebax® (Pebax), polyesters (Arnitel), latex, polyether amide, polyolefin copolymer (POC) or Surlyn™, by way of example only. The material should be formable into a thin walled tube. Only one sleeve may be provided at one end of the stent, such as the distal end. However, the use of a pair of sleeves, one at each end of the stent, is typical.  
         [0038]    For example, polyurethane tubing or the like can be used, having a Shore D scale hardness of preferably 70A-55D and having, for example, an ID of 0.032-0.038 inches and a wall thickness of 0.002-0.004 inches. Of course, the ID and wall thickness may be dictated by the size of stent being used. Sleeves  22  and  24  are axially connected along catheter  10  to the proximal end of balloon  14  at  26  and to the distal end of balloon  14  at  27  by means of adhesive  26 ,  27  or welding. Other methods of connecting the sleeves to the catheter such as welding or by utilizing a frictional gripping force which is produced due to the elasticity of the sleeve, all methods are well known in the art.  
         [0039]    Sleeves  22  and  24  overlap stent  20  at each of its ends  30  and  32 , respectively. Rings or bands  34  are affixed around the sleeves  22 ,  24  via adhesion, such as an adhesive, or welding. The bands  34  may be embedded into the sleeve. The bands are made of a higher modulus material relative to the sleeve material. The band material may have higher strength and less elongation than the material of the sleeve. The bands also may be any material which forms a closed curve or any polygonal structure, or a combination of the two. In an alternative embodiment, the bands may also be discontinuous and forming generally circular or polygonal shapes. Preferably, the bands are made of a material which effectively retains a substantially annular shape. One function of the rings is to more effectively and smoothly draw the sleeve off of the ends of the stent, by creating more axial movement of the ring  34 .  
         [0040]    Bands  34  are positioned over the cone portion of the balloon  14 , in this example mid-way up the cone, when the balloon is in its collapsed configuration. By way of example, bands  34  may have Shore D scale hardness of greater than 55, such as with PEBAX, PET, nylon, plastic, such as polyimide or polyethylene, or metal, such as platinum, gold, stainless steel or nitinol.  
         [0041]    Referring to FIG. 2, in its expanded state balloon  14  has an enlarged diameter with tapered cone portions  36  and  38  at each end thereof. Stent  20  is released from sleeves  22  and  24  upon expansion of balloon  14  due to the axial/radial force created by balloon causing the sleeves to recede. The sleeves may recede away from the stent in any manner.  
         [0042]    In at least one manner, the bands draw the sleeves gradually outward, bunching the sleeves between the bands  34  and the fixed position of the sleeves on the catheter. The combination of radial and axial forces are applied to the ring  34 . Since the rings resist the radial force, they are driven primarily axially, dragging the sleeves off of the ends of the stent and balloon, while maintaining the sleeves close to the balloon. The increased axial pressure allows for a more controlled and steady release of the stent and balloon, as opposed to a sudden release which may happen when the primary force on the sleeve is in the radial direction. As seen in FIG. 2 the stent deploys. The sleeves contract about balloon  14  when it is deflated. Deflation allows balloon  14  and sleeves  22  and  24  along with catheter  10  to be axially removed from the body.  
         [0043]    In assembling polyurethane sleeves, they can be temporarily swelled by exposure to a solvent such as toluene, alcohol, or others as known in the art, or lubricated then pushed on the ends of the stent. The sleeves are then bonded to the balloon ends with an adhesive or the like. The sleeves may also be lubricated to prevent resistance when in use.  
         [0044]    Other embodiments are within the claims to this invention. For example, referring to FIGS.  3 A-C, the bands in the Figures may take the form of a shaped ring (FIG. 3A), shaped to surround the cone of the balloon, rings (FIG. 3B), or wire coils (FIG. 3C). The spiral of the coil may be cut only partially into the body as a spiral cut or it may be cut all the way through as shown. The cross-section of the bands can take any form, such as squares or any regular polygon as well.  
         [0045]    FIGS.  4 - 6  show different positions and configurations for the bands. Only the distal end of the catheter is shown for illustrative purposes. It should be understood that two sleeves, one on either end of the balloon, may be utilized.  
         [0046]    In FIG. 4, the sleeve  24  has two bands  34 , one being partially embedded on the inside of the sleeve and one partially embedded on the outside of the sleeve  24 . Preferably, the bands are in mirroring positions relative to the sleeve  24  over the cone portion.  
         [0047]    In FIG. 5, the bands  34  are substantially embedded within the sleeve  24 . This allows the profile of the catheter to be reduced.  
         [0048]    In FIG. 6, the sleeves comprise two portions  36 ,  38  separated by the bands  34 . In this embodiment, portions  36 ,  38  of the sleeve  24  are attached on either side of the band  34  via adhesion or welding or via an integral connection. It should be understood that the bands need not be spherical as shown. Various cross-sectional shapes may be incorporated  
         [0049]    FIGS.  7 - 12  illustrate further embodiments of the invention. These figure show two-piece sleeves, wherein one piece comprises material as described above in reference to band  34 , that being high modulus material, and one piece comprises material as described above in reference to sleeves  22  and  24 , that being lower modulus material. Hereafter, the two pieces which make up the sleeves will be referred to as high modulus (HM) bands and low modulus (LM) bands. The use of the words “low” and “high” are meant to indicate the level of modulus for the two pieces of the sleeves, each relative to the other. For example, the HM bands have a higher modulus relative to the LM bands.  
         [0050]    In FIGS.  7 - 8 , as in FIGS.  1 - 2 , a balloon catheter is shown in its collapse form and in its expanded form, respectively. The stent retaining sleeves  40 ,  42  comprise two pieces. Sleeves  40 ,  42  comprise a HM band  48  and a LM band  50 . In this embodiment, one end of the HM bands  48  is connected to the balloon at  46  and  47  in the same manner as described above, while the remaining ends of the HM bands are in abutting connection  52  with the LM bands  50 . The remaining ends of the LM bands  50  cover the corresponding end margins of the stent  20 .  
         [0051]    FIGS.  9 - 12  show different positions and configurations for the sleeves. Only the distal end of the catheter is shown for illustrative purposes. It should be understood that two sleeves, one on either end of the balloon, may be utilized.  
         [0052]    In FIG. 9, sleeve  54  comprises two pieces. The LM band  56  extends from being attached via conventional means to the balloon at point  58  to over the margin of the stent  20 . The HM band  60  is attached to the LM band  56  over point  58  extending partially up the cone portion of the balloon.  
         [0053]    In FIG. 10, sleeve  64  comprises two pieces. The HM band  64  extends from being attached via conventional means to the balloon at point  66  to partially up the cone portion of the balloon  14 . The LM band  68  is attached to the HM band  64  over point  66  extending along the balloon  14  over the margin of the stent  20 .  
         [0054]    In FIG. 11, sleeve  70  also comprises two pieces. The HM band  72  extends from being attached via conventional means to balloon at point  73  to partially up the cone portion of the balloon  14 . The HM band  72  is in overlapping connection with the LM band  74  at point  75 . The LM band  74  extends from point  75  to over the margin of the stent  20 . In this embodiment, the HM band  72  overlaps the LM band  74 .  
         [0055]    In FIG. 12, sleeve  76  also comprises two pieces. The HM band  78  extends from being attached via conventional means to balloon at point  79  to partially up the cone portion of the balloon  14 . The HM band  78  is in overlapping connection with the LM band  80  at point  81 . The LM band  74  extends from point  81  to over the margin of the stent  20 . In this embodiment, the LM band  80  overlaps the HM band  78 .  
         [0056]    It should be understood that the present application contemplates embodiments as described above where the LM bands and the HM bands are exchanged.  
         [0057]    It should also be understood that the sleeves may be attached to the catheter or the waist portions of the balloon, for example at point  73 , via adhesion or in direct contact via welding.  
         [0058]    FIGS.  13 - 14  show examples of the retraction of the sleeves when the balloon is expanded. The size of the balloons appear to be constant, however, it should be understood that the illustration is directed to the action of the sleeves during expansion and deployment of the stent.  
         [0059]    In FIG. 13 the sleeve  84  comprises a LM band  86  and a HM band  88 . During expansion of the balloon  14 , the sleeve  84  recedes, or folds back onto itself. In this embodiment, the LM band  86  comprises a majority of the recession, while the HM band  88  retains more of its original shape. This is due in part to the relative stiffness of the HM band  88  as compared to the LM band  86 . The exact manner in which the sleeves recede may vary. FIG. 14 illustrates a similar recession of an alternative sleeve wherein the LM bands  86  are attached to the catheter at point  79  and the HM bands  88  extend further onto the balloon. Similarly, the LM band  86  has a greater tendency to recede than does the HM band  88 .  
         [0060]    All of the patent, applications or publications referred to above are herein incorporated by reference in their entirety.  
         [0061]    The above examples and disclosure are intended to be illustrative and not exhaustive. These examples and description 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 claims, where the term “comprising” means “including, but not limited to”. 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. Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim  1  should be alternatively taken as depending from all previous claims). In jurisdictions where multiple dependent claim formats are restricted, the following dependent claims should each be also taken as alternatively written in each single dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below (e.g. claim  6  may be taken as alternatively dependent from any of claims 2-5, claim 4 may be taken as alternatively dependent from claim 3; etc.).