Abstract:
A medical device comprises a catheter having a catheter shaft, a sheath and a rolling membrane. The sheath is being disposed about the catheter shaft and is longitudinally moveable relative thereto. A distal portion of the sheath defines a stent retaining region. The sheath is moveable between an extended position and a retracted position, wherein in the extended position the retaining region is disposed about a stent receiving region of the catheter shaft, and in the retracted position the sheath is removed from the stent receiving region. End regions of the rolling membrane are respectively engaged to a distal end of the sheath and a portion of the shaft proximal to the stent receiving region respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0002]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     Stents, grafts, stent-grafts, vena cava filters, vascular implants, and similar implantable medical devices, collectively referred to hereinafter as stents, are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents are typically mounted onto a catheter assembly for deployment within a body lumen. Stents may be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, etc. Stents may be used to reinforce body vessels and to prevent restenosis following angioplasty in the vascular system. They may be self-expanding, such as a nitinol shape memory stent, mechanically expandable, such as a balloon expandable stent, or hybrid expandable.  
         [0004]     Prior to delivery a stent or stents may be retained on a portion of the delivery catheter by crimping the stent onto the catheter, retaining the stent in a reduced state about the catheter with a removable sheath, sleeve, sock or other member or members, or by any of a variety of retaining mechanisms or methods. Some examples of stent retaining mechanisms are described in U.S. Pat. No. 5,681,345; U.S. Pat. No. 5,788,707; U.S. Pat. No. 6,066,155; U.S. Pat. No. 6,096,045; U.S. Pat. No. 6,221,097; U.S. Pat. No. 6,331,186; U.S. Pat. No. 6,342,066; U.S. Pat. No. 6,350,277; U.S. Pat. No. 6,443,880; U.S. Pat. No. 6,478,814 and U.S. patent application Ser. No. 09/664,268 entitled Rolling Socks and filed Sep. 18, 2000.  
         [0005]     In some systems for the delivery of a self-expanding stent, the stent is deployed by a pull back sheath system. When the stent is constrained within the system, the stent is exerting a force onto the inside diameter (ID) of the outer shaft or pull back sheath. The frictional interface between the stent and sheath may cause the sheath to negatively interact with the stent as the sheath is retracted during deployment. Lubricious coatings may be used to aid in reducing the frictional interface between the stent and sheath. In some cases, particularly those involving longer stents and thus greater frictional forces, the forces may be to great for the lubricant to compensate for. As a result, in some systems the frictional forces involved will prevent the catheter from being capable of properly deploying a stent of a desired length.  
         [0006]     Excess frictional interaction between the stent and sheath is of particular concern in systems deploying a stent that incorporates one or more therapeutic coatings thereon, as the coatings may be adversely affected by the frictional interface between the sheath and stent, particularly during sheath retraction.  
         [0007]     The present invention seeks to address these and/or other problems by providing catheter assemblies with a variety of embodiments and features which improve sheath retraction and stent deployment characteristics.  
         [0008]     All U.S. patents, applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.  
         [0009]     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.  
         [0010]     A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The present invention is directed to a variety of embodiments. For example, in at least one embodiment the invention is directed to a co-axial stent delivery system having a roll back inner membrane and an outer pull-back sheath. Prior to delivery of the stent the inner membrane is disposed directly about the stent and the pull back sheath is disposed about the membrane. A distal end of the membrane is engaged to a distal portion of the sheath and a proximal end of the membrane is engaged to a portion of the inner catheter shaft proximal of the stent retaining region of the catheter assembly. When the pull back sheath is retracted the membrane will be drawn along with the sheath and will roll back proximally along the length of the stent until the stent is fully exposed and deployed.  
         [0012]     In at least one embodiment a lubricious coating is positioned between the roll back membrane and the sheath.  
         [0013]     In at least one embodiment a lubricious coating is positioned between the stent and the roll back membrane.  
         [0014]     In at least one embodiment a fluid is present in a lumen or chamber defined by the roll back membrane and the sheath. The fluid may be sufficiently pressurized to maintain a gap between the membrane and sheath during retraction.  
         [0015]     In at least one embodiment the invention is directed to a tri-axial system wherein a secondary lumen is formed between an intermediate shaft or mid-shaft and the inner shaft proximal to the stent retaining region. The proximal end of the roll back membrane may be engaged to a distal portion of the mid-shaft, thereby extending the secondary lumen into the stent retaining region of the catheter. The secondary lumen provides a flush path through which a fluid may be transported to the stent retaining region during or prior to delivery of the stent.  
         [0016]     These and other embodiments which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference should be made to the drawings which form a further part hereof and the accompanying descriptive matter, in which there is illustrated and described embodiments of the invention. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)  
       [0017]     A detailed description of the invention is hereafter described with specific reference being made to the drawings.  
         [0018]      FIG. 1  is a schematic longitudinal cross-sectional view of distal and proximal portions of an embodiment of the invention.  
         [0019]      FIG. 2  is a longitudinal cross-sectional view of the distal portion of the embodiment depicted in  FIG. 1  shown during retraction of the membrane and sheath.  
         [0020]      FIG. 3  is a longitudinal cross-sectional view of the embodiment depicted in  FIG. 1  shown with the membrane and sheath fully retracted from the stent.  
         [0021]      FIG. 4  is a longitudinal cross-sectional view of an alternative embodiment of the invention.  
         [0022]      FIG. 5  is a longitudinal cross-sectional view of an alternative embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     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.  
         [0024]     For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated.  
         [0025]     In at least one embodiment, an example of which is shown in  FIGS. 1-3 , a delivery system  10 , is depicted which includes a catheter  20  which is configured to deliver a stent  30 , which in at least one embodiment is a self-expanding stent.  
         [0026]     Catheter  20  includes a catheter shaft or inner shaft  22 , a portion of which defines a stent receiving region  24 . Catheter shaft  22  may further define a guidewire lumen  26  through which a guidewire  28  may be passed in order to advance the catheter to a predetermined position in a body lumen or vessel. Alternatively, the shaft  22  may be configured as a fixed-wire catheter.  
         [0027]     The catheter  20  may be any type of catheter desired and in some embodiments may include a catheter shaft  22  having a substantially hexagonal cross-sectional shape, such as is described in the Inventor&#39;s concurrently filed Application entitled Medical Device Delivery System having Attorney Docket number 10527-552001, the entire content of which is incorporated herein by reference.  
         [0028]     As shown in  FIG. 1 , a stent  30  may be a self-expanding stent which is disposed about the stent receiving region  24  of the catheter shaft  22 . In some embodiments the stent may be at least partially constructed from one or more of the following shape memory materials: nitinol, shape-memory polymer(s), etc., but may include other material or materials as well. In at least one embodiment the stent is at least partially constructed of stainless steel, cobalt, chromium, titanium, nickel, and any combinations or alloys thereof.  
         [0029]     In some embodiments the stent includes one or more areas, bands, coatings, members etc that is (are) detectable by imaging modalities such as X-Ray, MRI or ultrasound. In some embodiments at least a portion of the stent  30  is at least partially radiopaque.  
         [0030]     In some embodiments the stent  30  may include one or more therapeutic and/or lubricious coatings  50  applied thereto.  
         [0031]     A therapeutic agent may be included with the stent. In some embodiments the agent is placed on the stent in the form of a coating  50 . In at least one embodiment the coating  50  includes at least one therapeutic agent and at least one polymer agent.  
         [0032]     A therapeutic agent may be a drug or other pharmaceutical product such as non-genetic agents, genetic agents, cellular material, etc. Some examples of suitable non-genetic therapeutic agents include but are not limited to: anti-thrombogenic agents such as heparin, heparin derivatives, vascular cell growth promoters, growth factor inhibitors, Paclitaxel, etc. Where an agent includes a genetic therapeutic agent, such a genetic agent may include but is not limited to: DNA, RNA and their respective derivatives and/or components; hedgehog proteins, etc. Where a therapeutic includes cellular material, the cellular material may include but is not limited to: cells of human origin and/or non-human origin as well as their respective components and/or derivatives thereof. Where the therapeutic agent includes a polymer agent, the agent may be a polystyrene-polyisobutylene-polystyrene triblock copolymer (SIBS), polyethylene oxide, silicone rubber and/or any other suitable substrate.  
         [0033]     In some embodiments the at least a portion of the stent may include a stent covering. The covering may be constructed of a variety of materials such as Dacron, PTFE, etc. In at least one embodiment the covering comprises at least one therapeutic agent.  
         [0034]     In the various embodiments described herein the stent  30  is preferably configured to be at least partially self-expanding or have self-expanding characteristics. As used herein the term “self-expanding” refers to the tendency of the stent to return to a predetermined diameter when unrestrained from the catheter, such as in the manner depicted in  FIGS. 1-3 . In the present embodiment when the stent is disposed about the stent receiving region  24  of the catheter shaft  22 , the stent is restrained in its reduced diameter or pre-delivery configuration by retractable sheath  40  which is disposed about the entire length of the stent  30  prior to delivery.  
         [0035]     The sheath  40  includes a stent retaining region  42 , which refers to that region of the sheath  40  which is disposed about the stent  30  prior to delivery. Engaged to a portion of the stent retaining region  42  is a roll back sleeve or membrane  44 . To deliver the stent  30 , the sheath  40  is retracted proximally, which causes the membrane  44  to roll back off of the stent in the manner illustrated in  FIGS. 2-3 .  
         [0036]     In some embodiments the membrane  44  comprises a distal end region  43  and a proximal end region  45 . The proximal end region  45  is engaged to a portion of the inner shaft  22  proximal to the stent receiving region  24 .  
         [0037]     The distal end region  43  of the membrane is engaged to a distal end portion  47  of the sheath  40  at an engagement region  46 . The membrane  44  and sheath  40  may be engaged together by any mechanism and/or configuration desired. For example region  43  and portion  47  may be engaged together by chemical, or adhesive welding or bonding, fusion or heat welding, ultrasonic welding, etc.; they may be mechanically engaged along complementary surfaces; an additional component such as a fastener or other device may be utilized to secure the components together, etc. In some embodiments the membrane  44  and the sheath  40  may be butt-welded or joined, or lap-welded or joined.  
         [0038]     As is shown in  FIG. 1 , in at least one embodiment the distal end region  43  of the membrane  44  can be folded back upon itself to engage the distal end region of the sheath  40 . This results in effectively engaging the inside surface (i.e. that surface which at its proximal extent is in contact with the exterior of the stent)  56  of the membrane  44  to the inside surface  57  of the sheath  40 . This folded arrangement provides the membrane  44  with a continuous bend region  59  which not only aids in providing the membrane  44  with the tendency to roll back upon itself rather than buckle or slide during retraction, but also aids in the formation of a potential gap between the membrane  44  and sheath  40  proximal to their engagement region  46 .  
         [0039]     As illustrated in the various figures this “gap” functions as a fluid lumen or chamber  60  into which a fluid, represented by arrows  62 , from a fluid source  76  (such as a syringe, etc) may be transported via a fluid port  73  at the proximal end region  74  of the catheter  20 . The proximal end region  74  of the catheter may have any handle configuration desired and may have any desired mechanism for regulating the flow of fluid  62  into and/or out of the chamber  60 . In at least one embodiment the catheter  20  may include a pressure gauge  75  or other mechanism for monitoring and regulating to volume, flow rate, and/or pressure of the fluid  62  with in the catheter.  
         [0040]     In a proximal region of the catheter the fluid chamber  60  acts as a lumen to transport the fluid distally into the area of the stent retaining region of the sheath  40 . The proximal portion of the chamber or lumen  60  is defined by the sheath  40  and the inner shaft  22 . As indicated, the distal region of the chamber  60  is defined by the sheath  40  and the membrane  44 .  
         [0041]     While the fluid  62  may be in the form of a coating, such as a lubricious hydrogel, saline, etc. which aids in reducing the potential frictional interactions between the sheath  40  and membrane  44 , in some embodiments however a volume of fluid  62  may be injected into the lumen  60  under a predetermined pressure which is maintained during the stent delivery process depicted in  FIGS. 2 and 3 . The use of fluid  62  under pressure keeps the gap between the sheath  40  and membrane  44  open throughout the retraction process effectively minimizing any sliding friction therebetween, as well as limiting the frictional forces resulting from the stent&#39;s tendency to push outward against the sheath  40 . As illustrated in  FIG. 2 , in addition to the above, the pressure exerted by the fluid  62  against the membrane  44  maintains the membrane  44  over the stent and provides the folded over membrane  44  with a turgid-like state sufficient to retain a portion of the stent  30  thereunder in the reduced state until the membrane  44  is retracted.  
         [0042]     In some embodiments the pressure exerted by fluid  62  on the membrane  44  may be monitored and regulated by the pressure gauge  75 , such as is shown in  FIG. 1 . A desired pressure of fluid  62  may be maintained within the chamber  60  by the use of any of a variety of devices such as stop-cocks, relief valves, etc.  
         [0043]     When the sheath  40  and the membrane  44  are fully withdrawn from about the stent  30 , the stent is delivered into a desired location within a body lumen or vessel.  
         [0044]     Because the sheath  40 , and particularly the distal portion or stent retaining region  42  of the sheath, is configured to retain the stent  30  in its reduced or pre-delivery diameter, in some embodiments at least the stent retaining region  42  of the sheath  40  is constructed to have sufficient hoop strength to prevent the stent from expanding off of the stent receiving region  24  until the sheath  40  is retracted. At least the stent retaining region  42  of the sheath  40  may be constructed from one or more of the materials including but not limited to: polymer materials such as Pebax, Hytrel, Arnitel, Nylon, etc. In at least on embodiment the stiffness of the sheath  40  can be varied by changing the polymer durometers from the proximal end to the distal end by any manner desired.  
         [0045]     In some embodiments the sheath  40  comprises a multi-layer construction wherein one or more materials are layered, braided or otherwise combined to form the sheath  40 .  
         [0046]     In some embodiments the sheath  40  may be provided with a PTFE liner or such a liner may be absent. Where a liner is provided, an inner PTFE liner may be braided with an additional polymer as desired.  
         [0047]     In at least one embodiment the sheath  40  is of the same or similar construction as a guide catheter.  
         [0048]     In some embodiments the sheath  40  is at least partially constructed of a clear polymer. Such a clear polymer may be used to provide the sheath  40  with a substantially clear distal end region. The clear distal end would allow for viewing the stent or implant device in a constrained state under the sheath.  
         [0049]     In at least one embodiment the inside of the sheath is coated for enhanced lubricity.  
         [0050]     While the stent retaining region  42  of the sheath  40  is typically constructed to have greater hoop strength than the membrane  44 , the sheath may be less flexible than the membrane  44  as well.  
         [0051]     The membrane  44  may be at least partially constructed of one or more of a variety of flexible materials such as including but not limited to: Pebax, PET, Nylon, POC, Polyurethane, etc. In some embodiments the material of the membrane  44  may include those which are nanoceramic for added durability. In some embodiments the membrane  44  is at least partially made from one or more polymers with surface alterations such as plasma treatment for enhanced lubricity. In at least one embodiment the membrane  44  comprises one or more layers of material. In at least one embodiment one or both sides of the membrane  44  are coated and/or provided with surface enhancements. Coating can include silicones or other substances to enhance lubricity.  
         [0052]     In at least one embodiment the membrane  44  is at least partially constructed from those materials from which medical balloons are known to be manufactured from. Such membrane material may be blown or extruded to any dimensions desired. The wall thickness of the membrane may vary and may be about 0.001 inches to no more than about 0.005 inches thick. In at least one embodiment the thickness of the membrane is less than about 0.001 inches.  
         [0053]     In the embodiments depicted in  FIG. 1  prior to delivery the membrane  44  is a single layer membrane folded over upon itself at the distal end region  43  whereupon it is engaged to the sheath  40 . When the sheath  40  is retracted, the membrane  44  is pulled back off of the stent  30  as the outside fold  52  of the membrane rolls proximally on top of the inner fold  54  proximally until the entire membrane  44  is rolled off of the stent  30  such as is depicted in  FIGS. 2-3 .  
         [0054]     During retraction of the membrane  44 , the outer fold  52  of the membrane  44  will roll proximally on top of the inner fold  54  until the entire membrane  44  is rolled off of the stent  30  as depicted in  FIG. 3 . As discussed above in some embodiments a lubricant or other fluid  62  may be provided within the lumen  60  to encourage the rolling action of the folds  52  and  54  and/or separate the folds. The fluid  62  may be any type of “inflation fluid” such as may be utilized in balloon catheters which are known, and/or may be any sort of biocompatible fluid or lubricant such as is described in U.S. Pat. No. 5,693,034, the entire content of which is incorporated herein by reference. In some embodiments fluid  62  is a liquid.  
         [0055]     In some embodiments a hub, flange, protrusion(s), marker or other member  70  and  72  may be positioned proximally and/or adjacent to the stent receiving region  24 . In some embodiments member  72  may also be provided with a diameter sufficiently greater than the diameter of the stent in the reduced state, to thereby prevent the stent from being inadvertently displaced in the proximal direction. Alternatively, the stent  30  may be crimped onto, or disposed about, one or more of the members  70  and/or  72 , and/or the catheter  20  may be provided any of the variety of stent retaining mechanisms that are known. Members  70  and/or  72  may also include any known or later developed type of fixation system for reducing the likelihood of stent displacement prior to and/or during deployment.  
         [0056]     Members  70  and/or  72  may be configured to be detectable by imaging modalities such as X-Ray, MRI or ultrasound. In some embodiments at least a portion of one or both members is at least partially radiopaque.  
         [0057]     Turning now to the embodiment depicted in  FIG. 4 , in the embodiment shown, the catheter  20  is provided with a secondary lumen  80  which is formed between an intermediate shaft or mid-shaft  82  and the inner shaft  22  proximal to the stent receiving region  24 . In this embodiment, the proximal end region  45  of the membrane  44  is engaged to a distal portion  84  of the mid-shaft  82 . This modified system  10  provides a secondary lumen  80  which extends into the stent receiving region  24  of the catheter  20  which underlies the membrane  44 . The secondary lumen  80  provides a flush path through which a fluid  64  may be transported to the stent receiving region  24  during or prior to delivery of the stent  30 .  
         [0058]     Fluid  64  may be similar or different than fluid  62 .  
         [0059]     Flushing the stent receiving region  24  prior to delivery of the stent  30  and/or prior to use of the device  10  will not only purge the region  24  of air but will also act to reduce frictional engagement of the stent  30  and the membrane  44  prior to and/or during retraction of the membrane  44 . Flushing can also be used to hydrate the shaft walls and/or the stent.  
         [0060]     In some embodiments, a system  10  of the type shown in  FIGS. 1-3  may also be provided with a flush path for flushing the stent receiving region  24  of the catheter  20  prior to use. In at least one embodiment, an example of which is depicted in  FIG. 5 , a flush path is defined by the guidewire lumen  26  and one or more holes or ports  86  through the stent receiving region  24  of the catheter shaft  22 . Ports  86  provide fluid communication between the guidewire lumen  26  and the stent receiving region  24 . By blocking or plugging the distal end of the guidewire lumen  26  with a shipping mandrel or other device  88 , fluid  64  injected under pressure into the guidewire lumen  26  at the proximal end region  74  of the catheter  20  will be forced through the ports  86  to flush the stent receiving region  24 . In some embodiments the ports  86  may be configured as a one-way valve to allow fluid to exit the guidewire lumen  26  but not re-enter.  
         [0061]     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. 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.  
         [0062]     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 singly dependent claim format which creates a dependency from a prior antecedent-possessing claim other than the specific claim listed in such dependent claim below.  
         [0063]     This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.