Patent Application
20110118817
The present invention pertains to medical devices and methods for making and using medical devices. More particularly, the present invention pertains to stent delivery systems.
A wide variety of intracorporeal medical devices have been developed for medical use, for example, intravascular use. Some of these devices include stent delivery systems. These devices are manufactured by any one of a variety of different manufacturing methods and may be used according to any one of a variety of methods. Of the known stent delivery devices and methods for making and using the same, each has certain advantages and disadvantages. There is an ongoing need to provide alternative stent delivery devices as well as alternative methods for making and using stent delivery devices.
The invention provides design, material, manufacturing method, and use alternatives for stent delivery systems including self-expanding stent delivery systems. An example self-expanding stent delivery system may include an inner member. An outer sheath may be slidably disposed about the inner member. A self-expanding stent may be disposed between the inner member and the outer sheath. A rolling membrane may be attached to the outer sheath and to the inner member. A lubricious component may be disposed adjacent the outer sheath for reducing friction between the outer sheath and the membrane.
Another example self-expanding stent delivery system may include an inner member. An outer sheath may be slidably disposed about the inner member. A self-expanding stent may be disposed between the inner member and the outer sheath. A rolling membrane may be attached to the outer sheath and to the inner member. The rolling membrane may include a reinforcing member that may be configured to provide the rolling membrane with increased column strength such that the reinforcing member reduces buckling of the rolling membrane when the rolling membrane is rolled back upon itself.
Another example self-expanding stent delivery system may include an inner member. A sheath may be slidably disposed about the inner member. A self-expanding stent may be disposed between the inner member and the sheath. A rolling membrane may be attached to the sheath and to the inner member. The rolling membrane may include a radiopaque marker.
Another example self-expanding stent delivery system may include an inner member. An outer sheath may be slidably disposed about the inner member. A self-expanding stent may be disposed between the inner member and the outer sheath. A rolling membrane may be attached to the outer sheath and to the inner member. The rolling membrane may include a plurality of layers including a lubricious layer.
The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.
The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.
All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.
The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.
The ability to accurately deploy a stent within the vasculature may be an important feature considered when designing stent delivery systems. Some self-expanding stent delivery systems utilize a rolling membrane to improve deployment accuracy. In general, a rolling membrane is a structure that covers the stent during delivery and then “rolls” proximally to uncover the stent. The rolling motion of the membrane may help to reduce the likelihood that longitudinal shifting the stent may occur during deployment. Rolling membranes reduce longitudinal displacement of the stent that may occur when an outer sheath is proximally retracted to expose and deploy the stent in the vasculature.
Because stents (e.g., self-expanding stents) may have a tendency to exert an outward force on the membrane and/or the outer sheath, a potential exists that frictional forces may be created between the sheath and the membrane. These forces could result in the longitudinal displacement of the stent upon retraction of the outer sheath. In order to minimize the potential of these frictional forces being present, a clinician may inject a pressurized fluid into the lumen of the outer sheath so that the fluid is disposed between the membrane and the sheath. The pressurized fluid, which may include a lubricious or otherwise friction-reducing material (e.g., a lubricious hydrogel, saline, etc.), may be effective in reducing the potential of frictional forces influencing the position of the stent and, thus, may improve the accuracy of stent deployment.
An outer member 24 may be disposed on a portion of sheath 14. Outer member 24 may be similar in form and function to similar structures disclosed in U.S. Patent Application Pub. No. US 2007/0208350, the entire disclosure of which is herein incorporated by reference. Outer member 24 may be longitudinally fixed relative to inner member 12 and may further aid in the reduction of friction between sheath 14 and membrane 16. System 10, as well as numerous other contemplated stent delivery systems, may lack outer member 24.
System 10 may also include a lubricious component 26. In general, lubricious component 26 is a structural feature (e.g., a member, component, part, element, feature, etc.) that is configured to reduce frictional forces between sheath 14 and membrane 16 that may be present when sheath 14 is retracted to deploy stent 18, for example as shown in
As the name suggest, lubricious component 26 may be formed or otherwise include a lubricious material. Because of this, lubricious component 26 may help reduce frictional forces between sheath 14 and membrane 16 and allow sheath 14 to be smoothly retracted while minimizing the possibility that stent 18 is displaced. Lubricious component 26 may vary in form. In at least some embodiments, lubricious component 26 is a tube (e.g., a “floating” tube) disposed between sheath 14 and membrane 16. By virtue of being a floating tube, lubricious component 26 may be understood to be free of attachment to essentially any component of system 10. Accordingly, lubricious component 26 may be free to move when sheath 14 is retracted without being encumbered by any other part of system 10.
In alternative embodiments, for example as shown in
In the embodiments mentioned above, lubricious component 26/126 may comprise a distinct member that is disposed between sheath 14 and membrane 16. However, alternative embodiments are contemplated where lubricious component 26 is adhered to membrane 16 or where lubricious component 26 is a layer of or coating on membrane 16.
Multi-layer membrane 216 may have essentially the same thickness as typical membranes (e.g., about 0.0005 to about 0.007 inches or so, or about 0.001 to about 0.005 inches or so). Alternatively, membrane 216 may be slightly thicker (e.g., about 0.0007 to about 0.01 inches or so, or about 0.0015 to about 0.006 inches or so) or thinner (e.g., about 0.0004 to about 0.005 inches or so, or about 0.0007 to about 0.004 inches or so) than typical membranes. It can be appreciated that essentially membrane 216 may have any suitable thickness without departing from the spirit of the invention.
The individual layers 228/230 (and/or other layers that may be included with membrane 216) may have a thickness on the order of about 0.00003 to about 0.0004 inches or so (e.g., about 1-10 microns or so), or about 0.00003 to about 0.0001 inches or so (e.g., about 1-5 microns or so), or about 0.0001 to about 0.0004 inches or so (e.g., about 5-10 microns or so).
First layer 228 may include a suitable polymer such as a polyether block amide (e.g., PEBAX®) or any other suitable material. Second layer 230 may include a low friction or lubricious material such as polytetrafluoroethylene. Alternatively, second layer 230 may include other lubricious materials such as high-density polyethylene (HDPE), ultra high modulus polyethylene (UHMPE), or any other suitable material. Layers 228/230 may be arranged so that second layer 230 (e.g., formed of or otherwise including a lubricious material) is disposed adjacent sheath 14 so that second layer 230 can reduce friction between sheath 14 and membrane 216.
Numerous other materials are contemplated for layers 228/230 including those listed herein and other suitable materials. For example, first layer 228 may include a material having a first durometer or hardness and second layer 230 may include a material having a second durometer or hardness different from the first durometer. In at least some of these embodiments, first layer 228 may include a polyether block amide such as PEBAX® 72D and second layer 228 may include a polyether block amide such as PEBAX® 40D. One or more additional layers may also be disposed or coated onto layers 228/230.
The multi-layered membrane 216 may be formed in essentially any suitable manner. For example, membrane 216 may be coextruded. Alternatively, layers 228/230 may be provided separately and attached together, for example, using a heat bond, reflow, an adhesive, or any other suitable bonding technique. One example adhesive or tie layer that may be used to bond layers 228/230 may be OREVAC® resin, available from Arkema. In some embodiments, layers 228 may be blown, stretched, or otherwise expanded so as to thin layer 228, layer 230, or both. In other embodiments, one or more of layers 228/230 may be formed by a coating process that may including mixing the material used to form the layer with an appropriate solvent, coating the material onto a surface (e.g., on the other layer), and then allowing the solvent to volatize leaving behind the coating that forms the layer.
While membrane 216 is illustrated as having two layers 228/230, this is not intended to be limiting.
In some embodiments, one or more of layers 328/330/332 (and/or one or more of layers 228/230) may be formed of or otherwise include a radiopaque material. For example, layer 330 may include a radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of system 10 in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler such as bismuth subcarbonate (Bi2O2(CO3)), barium sulfate (BaSO4), etc., and the like. In some embodiments, the radiopaque material may include any of those materials disclosed in U.S. Pat. No. 6,599,448, the entire disclosure of which is herein incorporated by reference. Additionally, other radiopaque marker bands and/or coils, or radiopaque coatings or layers may also be incorporated into the design of system 10 (e.g., at membrane 16/116/216), for example as discussed below, to achieve the same result.
The thickness of the layer including the radiopaque material (e.g., layer 328, 330, and/or 332) may vary. For example, the thickness of the layer including the radiopaque material may be about 0.0001 to about 0.001 inches or so (e.g., about 5-25 microns) or about 0.001 to about 0.004 inches or so (e.g., about 25-100 microns).
In some embodiments, the layer including a radiopaque material (e.g., layer 328, 330, and/or 332) may extend along substantially the length of membrane 316. In other embodiments, the layer including a radiopaque material may extend along a portion of the length of membrane 316. In still other embodiments, the layer including a radiopaque material may extend along multiple portions of the length of membrane 316 and, thus, form a plurality of discrete radiopaque sections.
Another feature that may be desirable in a rolling membrane stent delivery system may be to increase the column strength or “pushability” of the membrane. This may help the membrane, for example, remain properly placed over stent 18 while advancing system 10 to the desired location within the anatomy. Additionally, this may reduce the chances that the membrane will buckle when sheath 14 is retracted. In at least some embodiments, any of the membranes disclosed herein may include a reinforcing member to increase the column strength thereof. For example,
Reinforcing members 436/536 may be formed of any suitable material so as to provide the desired increase in column strength. For example, reinforcing members 436/536 may include a polymer such a polyether block amide, nylon, a poly paraphenylene terephthalamide (for example, KEVLAR®), a polymer having a relatively high durometer, or other materials. In some embodiments, reinforcing members 436/536 may include a metal or metal alloy such as those listed herein. Reinforcing members 436/536 may include a single filament or member (e.g., a single coil 536) or a plurality of filaments or members (e.g., a multi-filament braid 436). In embodiments that utilize multiple filaments, each of these filaments may include the same materials or some or all of the filaments may include different materials. Furthermore, some or all of the filaments may be or otherwise include one or more fibers or strands that are coupled together to form one or more of the filaments.
Bands 638a/638b/638c may help to aid in the visualization of system 10 and may provide a clinician with a visual indicator of the progress of the deployment of stent 18. For example, prior to deployment of stent 18 bands 638a/638b/638c may be disposed distally of bumper 20, which may also be made from or include a radiopaque material. As sheath 14 is proximally retracted, bands 638a/638b/638c may begin to migrate proximally as shown in
While
The materials that can be used for the various components of system 10 (and/or other systems disclosed herein) may include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to inner member 12, sheath 14, and membrane 16. However, this is not intended to limit the invention as the discussion may be applied to other similar members and/or components of members or systems disclosed herein.
Inner member 12, sheath 14, and membrane 16, and/or other components of system 10 may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, combinations thereof, and the like, or any other suitable material. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS® 400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material.
As alluded to above, within the family of commercially available nickel-titanium or nitinol alloys, is a category designated “linear elastic” or “non-super-elastic” which, although may be similar in chemistry to conventional shape memory and super elastic varieties, may exhibit distinct and useful mechanical properties. Linear elastic and/or non-super-elastic nitinol may be distinguished from super elastic nitinol in that the linear elastic and/or non-super-elastic nitinol does not display a substantial “superelastic plateau” or “flag region” in its stress/strain curve like super elastic nitinol does. Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol. Thus, for the purposes of this disclosure linear elastic and/or non-super-elastic nitinol may also be termed “substantially” linear elastic and/or non-super-elastic nitinol.
In some cases, linear elastic and/or non-super-elastic nitinol may also be distinguishable from super elastic nitinol in that linear elastic and/or non-super-elastic nitinol may accept up to about 2-5% strain while remaining substantially elastic (e.g., before plastically deforming) whereas super elastic nitinol may accept up to about 8% strain before plastically deforming. Both of these materials can be distinguished from other linear elastic materials such as stainless steel (that can also can be distinguished based on its composition), which may accept only about 0.2-0.44% strain before plastically deforming.
In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy is an alloy that does not show any martensite/austenite phase changes that are detectable by DSC and DMTA analysis over a large temperature range. For example, in some embodiments, there may be no martensite/austenite phase changes detectable by DSC and DMTA analysis in the range of about −60° C. to about 120° C. in the linear elastic and/or non-super-elastic nickel-titanium alloy. The mechanical bending properties of such material may therefore be generally inert to the effect of temperature over this very broad range of temperature. In some embodiments, the mechanical bending properties of the linear elastic and/or non-super-elastic nickel-titanium alloy at ambient or room temperature are substantially the same as the mechanical properties at body temperature, for example, in that they do not display a super-elastic plateau and/or flag region. In other words, across a broad temperature range, the linear elastic and/or non-super-elastic nickel-titanium alloy maintains its linear elastic and/or non-super-elastic characteristics and/or properties and has essentially no yield point.
In some embodiments, the linear elastic and/or non-super-elastic nickel-titanium alloy may be in the range of about 50 to about 60 weight percent nickel, with the remainder being essentially titanium. In some embodiments, the composition is in the range of about 54 to about 57 weight percent nickel. One example of a suitable nickel-titanium alloy is FHP-NT alloy commercially available from Furukawa Techno Material Co. of Kanagawa, Japan. Some examples of nickel titanium alloys are disclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which are incorporated herein by reference. Other suitable materials may include ULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available from Toyota). In some other embodiments, a superelastic alloy, for example a superelastic nitinol can be used to achieve desired properties.
In at least some embodiments, portions or all of inner member 12, sheath 14, and membrane 16 may also be doped with, made of, or otherwise include a radiopaque material including those listed herein or other suitable radiopaque materials.
In some embodiments, a degree of MRI compatibility is imparted into system 10. For example, to enhance compatibility with Magnetic Resonance Imaging (MRI) machines, it may be desirable to make inner member 12, sheath 14, and membrane 16, in a manner that would impart a degree of MRI compatibility. For example, inner member 12, sheath 14, and membrane 16, or portions thereof, may be made of a material that does not substantially distort the image and create substantial artifacts (artifacts are gaps in the image). Certain ferromagnetic materials, for example, may not be suitable because they may create artifacts in an MRI image Inner member 12, sheath 14, and membrane 16, or portions thereof, may also be made from a material that the MRI machine can image. Some materials that exhibit these characteristics include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nitinol, and the like, and others.
Some examples of suitable polymers that may be used to form inner member 12, sheath 14, and membrane 16, and/or other components of system 10 may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like. In some embodiments the sheath can be blended with a liquid crystal polymer (LCP). For example, the mixture can contain up to about 6% LCP.
In some embodiments, the exterior surface of the system 10 may include a coating, for example a lubricious, a hydrophilic, a protective, or other type of coating. Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves device handling and exchanges. Lubricious coatings improve steerability and improve lesion crossing capability. Suitable lubricious polymers may include silicone and the like, polymers such as high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), polyarylene oxides, polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers may be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. Some other examples of such coatings and materials and methods used to create such coatings can be found in U.S. Pat. Nos. 6,139,510 and 5,772,609, the entire disclosures of which are incorporated herein by reference.
It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention's scope is, of course, defined in the language in which the appended claims are expressed.
