Abstract:
A dual taper stent protector having a first stent covering region configured to cover a stent without substantially engaging the stent, a second covering region, and an engagement region for engaging a product mandrel removably disposed within a catheter shaft, and first and second tapered regions connecting the first stent covering region and the second stent covering region and the second covering region and the engagement region respectively, and to methods of making and using the same.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of catheter assemblies used for the delivery of medical devices, in particular stent delivery systems having stent protector means. 
     BACKGROUND OF THE INVENTION 
     A stent or similar device is an implantable medical device introduced into a body lumen and is well known in the art. Typically, a stent is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called “minimally invasive techniques” in which the stent, in a radially reduced configuration, optionally restrained in a radially compressed configuration by a sheath and/or catheter, is delivered by a stent delivery system or “introducer” to the site where it is required. The introducer can enter the body from an access location outside the body, such as through the patient&#39;s skin, or by a “cut down” technique in which the entry vessel is exposed by minor surgical means. The device is enlarged radially at the treatment site. 
     Stents can be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, fallopian tubes, coronary vessels, secondary vessels, etc. Stents can be self-expanding, expanded by an internal radial force, such as when mounted on a balloon, or a combination of self-expanding and balloon expandable (hybrid expandable). 
     Stent protectors are used to protect the stent before the stent and catheter assembly are introduced and subsequently the stent deployed and implanted into a body lumen. The stent protector protects the stent from physical damage or contamination due to the transfer of unwanted material and is removed at the time of use to permit deployment of the stent. Examples of stent protectors are provided in commonly assigned U.S. Pat. Nos. 6,991,639, 6,783,542, 6,764,504, 6,416,529, 6,152,944, 5,893,868, and 5,342,307, each of which is incorporated by reference herein in its entirety. 
     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. 
     Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a stent protector having an improved design and to methods of making and using the same. The stent protectors according to the invention are designed to reduce or eliminate contact between the stent and the stent protector. The improved stent protector reduces the possibility of damaging either the stent protector material on the inner surface of the stent protector and/or any stent coatings on the outer surface of a stent by frictional resistance resulting during deposition of the stent protector over a stent delivery assembly. 
     In one aspect, the present invention relates to a catheter assembly including a catheter having a distal end and a proximal end, a stent disposed about the distal end. The catheter assembly further includes a stent protector having a first covering region disposed about the stent, a second covering region disposed about the catheter tip. For shipping and storage, the catheter assembly is further disposed about a product mandrel which is removed prior to use. The stent protector further includes an n engagement region which engages the product mandrel. The engagement region is remote from the first covering region so that the first covering region of the stent protector does not substantially engage the stent. When the stent protector is removed the product mandrel goes with it or visa versa. 
     In some embodiments, a first tapered region may connect the first stent covering region to the second catheter tip covering region and a second tapered region may connect the second catheter tip covering region to the engagement region. The second tapered region tapers down to the product mandrel so that upon crimping, an interference fit is created between the inner diameter of the engagement region of the stent protector and the product mandrel. 
     Likewise, the first tapered region of the stent protector tapers down to the second covering region so that, if desired, upon crimping an interference fit may likewise be created between the inner diameter of the second covering region and the catheter tip. 
     In the above embodiments, at the proximal end of the balloon, the stent protector need not be tapered, and can further include a flange at the proximal end. 
     At a minimum, the stent protector is engaged to the product mandrel. 
     Alternative designs may include engagement at a catheter distal tip, and engagement at a catheter outer shaft at the proximal end of the protector. 
     The improved stent protectors according to the invention are particularly suitable for stents having coatings, such as drug eluting coatings, disposed thereon. 
     These and other aspects, embodiments and advantages of the present invention will become immediately apparent to those of ordinary skill in the art upon review of the Detailed Description and Claims to follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial side view showing the distal end of a catheter assembly with parts shown in hidden line illustrating one embodiment of a stent protector of the invention. 
         FIG. 2  is a radial cross-section taken at section  2 - 2  in  FIG. 1 . 
         FIG. 3  is a partial side view of the proximal end of a stent protector similar to that shown in  FIG. 1 . 
         FIG. 4  is a partial side view of the distal end of a catheter assembly with parts shown in hidden line illustrating another embodiment of the stent protector of the invention. 
         FIG. 5  is a portion of an injection mold for forming a stent protector according to the invention. 
         FIG. 6  is a radial cross-section taken at section  6 - 6  in  FIG. 5 . 
         FIG. 7  is a radial cross-section taken at section  6 - 6  illustrating the mold in an open configuration, showing both mold halves and the stent protector released therefrom. 
         FIG. 8  is a portion of a crimper for forming a stent protector about a catheter assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. 
     All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety. Any copending patent applications, mentioned anywhere in this application are also hereby expressly incorporated herein by reference in their entirety. 
     For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated. 
     Turning now to the figures,  FIG. 1  is a partial side view of the distal end of a catheter assembly  10  with parts shown in hidden line illustrating one embodiment of a stent protector  40  according to the invention. Catheter assembly  10  has an inner shaft  12  and an outer shaft  14 . Distal tip  13  is shown at the end of the inner shaft  12 . The distal end of each shaft is shown in  FIG. 1 . Balloon  20  is disposed about the distal end of the outer shaft  14  at the balloon proximal end  32  and is disposed about the distal end of the inner shaft  12  at the balloon distal end  34 . Balloon  20  may be secured to the inner shaft  12  and the outer shaft  14  at its waist portions  16   a ,  16   b  using any suitable method known in the art such as welding, adhesively, etc. 
     Stent  30  is disposed about balloon  20  in the body region  22  of balloon  20 .  FIG. 2  is a radial cross-section taken at section  2 - 2  in  FIG. 1 . 
     Stent protector  40  is disposed about balloon  20  and stent  30 . Stent protector  40  is designed so as to engage the product mandrel  52 . The outer surface (outer diameter) of the product mandrel  52  is engaged by the inner surface (inner diameter) of the stent protector  40 . When stent protector  40  is removed, the product mandrel  52  is removed as well. In this embodiment, stent protector  40  has a first stent covering region  42 , a first tapered region  44 , a second covering region  46  which covers catheter distal tip  13 , a second tapered region  48  and at least one engagement region  50 . Engagement region  50  engages the product mandrel  52  which is removed prior to use, typically by the practitioner performing the procedure. Stent protector  40 , being engaged to product mandrel  52 , is likewise removed simultaneously. The second tapered region  48  tapers down to the engagement region  50  which is crimped about the product mandrel  52  to create an interference fit between the outer surface (outer diameter) of the product mandrel  52  inner surface  49  (inner diameter) of the engagement region  50  of the stent protector  40  and the product mandrel  52 . 
     In another embodiment, the second covering region  46  may optionally engage the catheter tip  13 . In this embodiment, the first tapered region  44  tapers down to the second covering region  46  which is crimped so as to create an interference fit between the inner diameter  54  of the second covering region  46  and the catheter tip  13  (outer diameter). Likewise, in embodiments wherein a coating, such as a lubricious coating is disposed on the catheter tip  13 , it may be desirable for engagement of the stent protector  40  to engage the catheter assembly only at the engagement  50  region which engages the product mandrel  52 . 
       FIG. 2  is a radial cross-section taken at section  2 - 2  in  FIG. 1 . 
     In the above embodiments, the proximal end  32  of the stent protector  40  is shown having a non-tapered configuration. In this embodiment, the wall  60  of said stent protector defines the lumen  62  of the stent protector  40  at the proximal end  32  may be flared out slightly away from the catheter assembly  10  about which it is disposed. This feature is shown in  FIG. 3 . Hereinafter, said feature is referred to as a flange  61 . Thus, in this embodiment, the stent protector  40  has an open proximal end  32 . This flared rim  60  can facilitate placement of the stent protector  40  over the catheter assembly  10  and/or can facilitate removal of the stent protector at the time of use. 
     In another embodiment shown in  FIG. 4 , stent protector  40  may have a third tapered region  64  at the proximal end  32  which tapers to the balloon waist  16   a  wherein a third covering region  66  of stent protector  40  covers balloon waist  16   a . Upon crimping, an interference fit may be created between the inner diameter  68  of the third covering region  66  of the stent protector  40  and the balloon waist  441  disposed about the outer catheter shaft  14 . In this embodiment, the stent protector  40  is further designed with a removal means such as perforations  70 , in this embodiment shown parallel with the longitudinal axis  72  of the catheter assembly  10 , so that the stent protector  40  may be peeled away from the catheter assembly  10  at the time of use. 
     Thus, in this embodiment, the stent protector  40  has a proximal end  32  which is substantially closed around the balloon proximal waist  44   a  and the outer catheter shaft  14 , further restricting movement of the stent protector  40 . 
     Any suitable method of forming perforations  70  in the stent protector  40  may be employed. For example, a laser may be employed for formation of the perforations  70  including, for example, UV Excimer lasers and Nd:Yag lasers. Other cutting methods include, but are not limited to, the use of razor blades, stamping dies, etc. 
     In any of the above embodiments, the first stent covering region  42  has an inner diameter D 4a  which is greater than the outer diameter D 4b  of the stent so that no friction is created between the inner surface  74  of the stent protector  40  and the outer surface  76  of the stent  30 . The enlarged diameter D 4a  of the first stent covering region  42  of the stent protector  40  covers the stent  20  and maintains a space (i.e. the region between the widened wall portion and the stent) between the inner surface  74  of the first stent covering region  42  and the stent  30  such that the inner surface  74  of the first stent covering region  42  does not engage the stent  30  during normal storage or removal. 
     The stent protectors as disclosed herein can be formed of any of a wide variety of suitable stent protector materials, for example, polymer materials including both thermoplastic elastomers and non-elastomers, and thermosetting materials. Examples of suitable polymer materials include, but are not limited to fluropolymers such as polytetrafluoroethylene (PTFE) and FEP, polyamides, i.e. nylons, silicones, and so forth. 
     Heat shrinkable materials may also be employed wherein the material is heat shrunk only in the desirable regions of the stent protector such as the engagement region  50 , the second covering region  46 , the third covering region  66 , or some combination thereof. 
     Heat shrinkable materials are typically thermoplastic, although in some instances thermoset materials may be employed, and include both elastomeric and non-elastomeric polymer materials. Suitable examples include, but are not limited to, polyolefins including, for example, homopolymers, copolymers and terpolymers of ethylene and propylene, fluoropolymers such as fluorinated ethylene-propylene (FEP), polytetrafluoroethylene (PTFE), polyvinylidene fluorides (PVFD) such as Kynar® PVFD&#39;s including Kynar® 500 available from Arkema Inc. in Philadelphia, Pa., copolymers of hexafluoropropylene (HFP), terpolymers of tetrafluoroethylene (TFE), ethylene-chlorotrifluoroethylene (ECTFE), VDF and HFP as well as perfluoromethylvinylether (PMVE), Viton® fluoropolymer elastomers available from Du Pont Performance Elastomers in Wilmington, Del., polyvinyl chloride (PVC), neoprene, silicon elastomers, polyamides including the nylons, polyether-block-amides, etc. 
     The stent protector may be formed using any suitable method known in the art. In one embodiment, a tubular member having a diameter substantially equal to the resultant diameter of the first stent covering region may be disposed about the catheter assembly where desired. In one embodiment, the engagement region may be formed by heat shrinking the material. In other embodiments, the tapered regions, the second covering region, the third covering region, and any combination thereof may also be created by heating shrinking the stent protector around the assembly in those regions only. 
     In one specific embodiment, the stent protector is formed using an injection molding process. For illustration only, a longitudinal cross-section of a portion of one embodiment of an injection mold  100  is shown in  FIG. 5 . In this embodiment, cavity  110  of mold  100  has a first half  100   a  and a second half  100   b , each having first covering regions  142   a ,  142   b , first tapered regions  144   a ,  144   b , second covering regions  146   a ,  146   b  and engagement regions  150   a ,  150   b  for formation of the stent protector. 
       FIG. 6  is a radial cross-section taken at section  6 - 6  in  FIG. 5 .  FIG. 7  is a radial cross-section showing the mold  100  in an open configuration with the stent protector  40  being released. 
     The stent protector  40  may also be crimped about the catheter assembly.  FIG. 8  is a longitudinal cross-section wherein heated crimpers  200   a  and  200   b  are applied externally to the catheter assembly and pressure and heat are used to conform the stent protector  40  about the catheter assembly. 
     These are only examples of methods of making the stent protector disclosed herein. The invention is not limited by the method employed and other methods may be used as well. 
     The present invention finds particular utility wherein stent coatings are employed. Stent coatings may incorporate a polymer material. There are any suitable polymer materials which are employed in stent coatings are such polymer materials are well known in the art. 
     In some embodiments, the stent coating may include bioresorbable polymers. Examples of bioresorbable polymers include, but are not limited to, polyhydroxyalkanoates such as polyhydroxyvalerate (PHV), polyhydroxybutyrate (PHB), poly(hydroxybutyrate-co-valerate) (PHBV) and polycaprolactone (PCL), poly(L-lactic acid) (PLA), poly(lactide-co-glycolide) (PLGA), polydioxanone, polyorthoesters, polyanhydrides, poly(glycolic acid), poly(D,L-lactic acid), poly(glycolic acid-co-trimethylene carbonate), polyphosphoesters, polyphosphoester urethanes, poly(amino acids), cyanoacrylates, poly(trimethylene carbonate), poly(iminocarbonate), copoly(ether-esters) (e.g. PEO/PLA), polyalkylene oxalates, polyphosphazenes and biomolecules such as fibrin, fibrinogen, cellulose, starch, collagen, hyaluronic acid, etc., and mixtures thereof. 
     Some of these polymers may be susceptible to hydrolysis in the presence of moisture. 
     Lubricious coatings are also commonly employed on various components of a catheter assembly and are also well known in the art. Lubricious coatings include both hydrophilic and non-hydrophilic polymer materials. Commonly employed hydrophilic polymer materials include those referred to in the art as hydrogels. 
     Lubricious coatings may be employed on any component of the catheter assembly and are commonly employed on the balloon body, waist and cones, or any combination thereof, as well as on the outer catheter shaft and the catheter distal tip  13 . Where a lubricious coating is employed on the distal tip  13 , it may be desirable for the stent protector  40  to engage only the product mandrel  52 . Suitably, in such an embodiment the inner diameter D 2a  of the second covering region  46  of the stent protector may suitably be greater than the outer diameter D 2b  of the catheter distal tip  13  so as to minimize damage to the lubricious coating. 
     In other embodiments, the second covering region  46  may be crimped onto the catheter distal tip  13  as discussed previously. 
     Any of the coatings may incorporate a therapeutic agent therein. The terms, “therapeutic agent”, “drug”, “pharmaceutically active agent”, “pharmaceutically active material”, “beneficial agent”, “bioactive agent”, and other related terms may be used interchangeably herein and include genetic therapeutic agents, non-genetic therapeutic agents and cells. A drug may be used singly or in combination with other drugs. Drugs include genetic materials, non-genetic materials, and cells. 
     Examples of drugs can be found in commonly assigned U.S. Pat. Nos. 7,105,175, 7,014,654, 6,899,731, 6,855,770 and 6,545,097, each of which is incorporated by reference herein in its entirety, and in commonly assigned U.S. Patent Application Publication No. 2004/0215169, the entire content of which is incorporated by reference herein. 
     The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. 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.