US20090018640A1 - Dual Taper Stent Protector - Google Patents

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

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of copending U.S. patent application Ser. No. 11/775,332, filed Jul. 10, 2007, the entire content of which is incorporated by reference herein.
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'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 5342307, 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 section2-2 inFIG. 1.
• FIG. 3 is a partial side view of the proximal end of a stent protector similar to that shown inFIG. 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 section6-6 inFIG. 5.
• FIG. 7 is a radial cross-section taken at section6-6 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 assembly10 with parts shown in hidden line illustrating one embodiment of astent protector40 according to the invention. Catheter assembly10 has aninner shaft12 and anouter shaft14.Distal tip13 is shown at the end of theinner shaft12. The distal end of each shaft is shown inFIG. 1.Balloon20 is disposed about the distal end of theouter shaft14 at the balloon proximal end32 and is disposed about the distal end of theinner shaft12 at the balloon distal end34.Balloon20 may be secured to theinner shaft12 and theouter shaft14 at itswaist portions16a,16busing any suitable method known in the art such as welding, adhesively, etc.
• Stent30 is disposed aboutballoon20 in the body region22 ofballoon20.FIG. 2 is a radial cross-section taken at section2-2 inFIG. 1.
• Stent protector40 is disposed aboutballoon20 andstent30. Stentprotector40 is designed so as to engage theproduct mandrel52. The outer surface (outer diameter) of theproduct mandrel52 is engaged by the inner surface (inner diameter) of thestent protector40. Whenstent protector40 is removed, theproduct mandrel52 is removed as well. In this embodiment,stent protector40 has a firststent covering region42, a firsttapered region44, asecond covering region46 which covers catheterdistal tip13, a secondtapered region48 and at least oneengagement region50.Engagement region50 engages theproduct mandrel52 which is removed prior to use, typically by the practitioner performing the procedure.Stent protector40, being engaged toproduct mandrel52, is likewise removed simultaneously. The secondtapered region48 tapers down to theengagement region50 which is crimped about theproduct mandrel52 to create an interference fit between the outer surface (outer diameter) of theproduct mandrel52 inner surface49 (inner diameter) of theengagement region50 of thestent protector40 and theproduct mandrel52.
• In another embodiment, thesecond covering region46 may optionally engage thecatheter tip13. In this embodiment, the firsttapered region44 tapers down to thesecond covering region46 which is crimped so as to create an interference fit between the inner diameter54 of thesecond covering region46 and the catheter tip13 (outer diameter). Likewise, in embodiments wherein a coating, such as a lubricious coating is disposed on thecatheter tip13, it may be desirable for engagement of thestent protector40 to engage the catheter assembly only at theengagement50 region which engages theproduct mandrel52.
• FIG. 2 is a radial cross-section taken at section2-2 inFIG. 1.
• In the above embodiments, the proximal end32 of thestent protector40 is shown having a non-tapered configuration. In this embodiment, thewall60 of said stent protector defines thelumen62 of thestent protector40 at the proximal end32 may be flared out slightly away from the catheter assembly10 about which it is disposed. This feature is shown inFIG. 3. Hereinafter, said feature is referred to as aflange61. Thus, in this embodiment, thestent protector40 has an open proximal end32. This flaredrim60 can facilitate placement of thestent protector40 over the catheter assembly10 and/or can facilitate removal of the stent protector at the time of use.
• In another embodiment shown inFIG. 4,stent protector40 may have a thirdtapered region64 at the proximal end32 which tapers to theballoon waist16awherein athird covering region66 ofstent protector40 coversballoon waist16a. Upon crimping, an interference fit may be created between the inner diameter68 of thethird covering region66 of thestent protector40 and the balloon waist441 disposed about theouter catheter shaft14. In this embodiment, thestent protector40 is further designed with a removal means such asperforations70, in this embodiment shown parallel with thelongitudinal axis72 of the catheter assembly10, so that thestent protector40 may be peeled away from the catheter assembly10 at the time of use.
• Thus, in this embodiment, thestent protector40 has a proximal end32 which is substantially closed around the balloon proximal waist44aand theouter catheter shaft14, further restricting movement of thestent protector40.
• Any suitable method of formingperforations70 in thestent protector40 may be employed. For example, a laser may be employed for formation of theperforations70 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 firststent covering region42 has an inner diameter D4awhich is greater than the outer diameter D4bof the stent so that no friction is created between theinner surface74 of thestent protector40 and theouter surface76 of thestent30. The enlarged diameter D4aof the firststent covering region42 of thestent protector40 covers thestent20 and maintains a space (i.e. the region between the widened wall portion and the stent) between theinner surface74 of the fiststent covering region42 and thestent30 such that theinner surface74 of the firststent covering region42 does not engage thestent30 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 fluoropolymers 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 theengagement region50, thesecond covering region46, thethird covering region66, 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'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 aninjection mold100 is shown inFIG. 5. In this embodiment,cavity110 ofmold100 has afirst half100aand asecond half100b, each having first covering regions142a,142b, firsttapered regions144a,144b, second covering regions146a,146bandengagement regions150a,150bfor formation of the stent protector.
• FIG. 6 is a radial cross-section taken at section6-6 inFIG. 5.FIG. 7 is a radial cross-section showing themold100 in an open configuration with thestent protector40 being released.
• Thestent protector40 may also be crimped about the catheter assembly.FIG. 8 is a longitudinal cross-section whereinheated crimpers200aand200bare applied externally to the catheter assembly and pressure and heat are used to conform thestent protector40 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 catheterdistal tip13. Where a lubricious coating is employed on thedistal tip13, it may be desirable for thestent protector40 to engage only theproduct mandrel52. Suitably, in such an embodiment the inner diameter D2aof thesecond covering region46 of the stent protector may suitably be greater than the outer diameter D2bof the catheterdistal tip13 so as to minimize damage to the lubricious coating.
• In other embodiments, thesecond covering region46 may be crimped onto the catheterdistal tip13 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 6545097, 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.

Claims (7)

1. A method of making a protector, the protector comprising a first covering region having a diameter configured to cover a medical device without substantial frictional contact, a second covering region having a second diameter which is less than the first diameter, a first connecting region connecting said first covering region and said second covering region and an engagement region having a third diameter, the third diameter is less than the second diameter, the engagement region configured to engage a tubular portion of a catheter assembly, the engagement region located distally from the stent covering region and a second connecting region connecting said second covering region and said engagement region, the method comprising:

providing an injection mold, the mold having a first region of a first diameter corresponding to said first covering region of said protector, a second region of a second diameter which is less than the first diameter corresponding to said second covering region of said protector, a first tapered region connecting said first region and said second region, a third region having a diameter that is less than that of the second region corresponding to said engagement region of said protector, and a second tapered region connecting said second region and said third region; and

forming said protector in said injection mold.

2. The method ofclaim 1 further comprising disposing said protector about a catheter assembly and crimping said protector onto said catheter assembly with heat and pressure.

3. A mold for forming a protector for a medical device, the mold comprising:

a first region of a first diameter for forming a first covering region of said protector;

a second region of a second diameter which is less than the first diameter for forming a second covering region of said protector;

a first tapered region connecting said first region and said second region, said first tapered region for forming a first tapered protector region;

a third region having a diameter that is less than that of the second region, the third region for forming an engagement region of said protector, said engagement region sized for disposing said protector about a catheter shaft; and

a second tapered region connecting said second region and said third region of said mold, said second tapered region for forming a second tapered protector region.

4. A protector for a radially expandable medical device, the protector comprising:

a first covering region having a proximal end and a distal end, the first covering region having a first diameter;

a second covering region having a second diameter less than the first;

a first tapered connecting region between said first covering region and said second covering region;

an engagement region for engagement with a catheter shaft, the engagement region located distally from the second covering region and the second connecting region, the engagement region having a third diameter less than the second diameter; and

a second tapered region connecting said second covering region and said engagement region.

5. The protector ofclaim 4 having an opening at its proximal end, the opening having a diameter substantially the same as said first diameter.

6. The protector ofclaim 4, said protector disposed about an expandable medical balloon.

7. The protector ofclaim 5 disposed about a stent and said expandable medical balloon.

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