Abstract:
A method and apparatus for reducing the longitudinal aspect of the catheter to stent force comprises at least one grip member for use with a stent delivery system. The grip engages a stent in the unexpanded state prior to delivery of the stent by retracting a stent retaining sheath. The grip comprises a body region having an outer diameter, a first end and a second end. The outer diameter of the first end is greater than the outer diameter of the second end. The grip is at least partially constructed from a polymeric material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     The use of stents, and other implantable medical devices such as grafts, stent-grafts, vena cava filters, etc, hereinafter referred to cumulatively as stents, to maintain the patency of bodily lumens is well known. 
     Stents are typically delivered via a catheter in an unexpanded configuration to a desired bodily location. Once at the desired bodily location, the stent is expanded and implanted in the bodily lumen. 
     Typically, a stent will have an unexpanded (closed) diameter for placement and an expanded (opened) diameter after placement in the vessel or the duct. Some stents are self-expanding; some stents are expanded mechanically with radial outward force from within the stent, as by inflation of a balloon; and some stents, known as hybrid stents, have one or more characteristics common to both self-expanding and mechanically expandable stents. 
     An example of a mechanically expandable stent and associated delivery system is shown in U.S. Pat. No. 4,733,665 to Palmaz, which issued Mar. 29, 1988, and discloses a number of stent configurations for implantation with the aid of a catheter. The catheter includes an arrangement wherein a balloon inside the stent is inflated to expand the stent by plastically deforming it, after positioning it within a blood vessel. 
     A type of self-expanding stent is described in U.S. Pat. No. 4,503,569 to Dotter which issued Mar. 12, 1985, and discloses a shape memory stent which expands to an implanted configuration with a change in temperature. Self-expanding stents are constructed from a wide variety of materials including nitinol, spring steel, shape-memory polymers, etc. 
     In many stent delivery systems, particularly those used to deliver a self-expanding stent, the stent is typically retained on the catheter via a retention device such as a sheath. The stent may be deployed by retracting the sheath from over the stent. To prevent the stent from being drawn longitudinally with the retracting sheath, many delivery systems provide the catheter shaft with one or more bumpers or hubs. 
     However it is known that in many cases when a sheath is withdrawn from a stent, particularly a self-expanding stent constructed of shape memory material, the stent may be displaced longitudinally relative to the catheter shaft as a result of so-called “stent jumping,” wherein when a sleeve or sheath is withdrawn from the stent during delivery the stent frictional forces and stent constrainment forces exerted by the retracting sleeve on the stent are less than those of the stent expansion force at an angle exiting the stent delivery system. As a result, in some instances, as the sheath is withdrawn from about the stent, the stent will tend to migrate or “jump” longitudinally relative to the stent mounting region of the catheter resulting in the imprecise delivery of the stent and/or distortion of the stent body. Because a portion of the stent is already expanding beyond the diameter of the catheter when stent jumping typically occurs, the presence of one or more hubs on the catheter shaft will typically not prevent stent jumping. 
     It would thus be desirable to provide a stent delivery system and/or one or more components thereof which may reduce or eliminate occurrences of stent jumping in order to improve the accuracy of stent placement within a vessel or other body space. 
     All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety. 
     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. 
     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 
     The present invention is directed to several embodiments which seek to improve the accuracy of stent placement and reduce the occurrence and severity of stent jumping. 
     For example, in at least one embodiment, the invention is directed to a stent delivery system that reduces the potential for stent jumping by providing one or more protrusions to which the stent, or one or more portions thereof, may be temporarily engaged during retraction of a stent retaining sleeve or sheath. The protrusions do not interfere with the radial expansion of the stent but will prevent the stent from moving longitudinally relative to the catheter. 
     In some embodiments, the invention is directed to one or more bands or collars, that may be disposed about the catheter under the stent. Bands may be provided with a variety of surface features such as bumps, flaps, tabs, fins or other protrusions or surface features, against or about which a portion of the stent may be temporarily engaged. In at least one embodiment the bands are radiopaque. In some embodiments the a band is positioned adjacent to or at least partially under an end of the stent to allow the surface features of the band to engage the end affects of the stent while the remaining portion of the stent is freed to expand. In at least one embodiment, a stent is provided with one or more end regions which define a relatively large opening or gap in the stent structure to engage the surface features of an engagement band catheter shaft. 
     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) 
       A detailed description of the invention is hereafter described with specific reference being made to the drawings. 
         FIG. 1  is a perspective view of an embodiment of the invention. 
         FIG. 2  is a perspective view of the embodiment shown in  FIG. 1  wherein the band defines an alternative pattern of surface features. 
         FIG. 3  is a partial side view of a stent retaining region of a stent delivery catheter with the band of  FIG. 1  positioned thereon and engaged to a portion of a stent. 
         FIG. 4  is a perspective view of the band of  FIG. 1  wherein the surface features are provided by cutting and folding selected portions of the band. 
         FIG. 5  is a perspective view of the embodiment of  FIG. 1  wherein the surface features are tabs. 
         FIG. 6  is a cross-sectional view of the embodiment of  FIG. 1  wherein the surface features are substantially fin shaped. 
         FIG. 7  is a partial side view of the embodiment shown in  FIG. 2  wherein at least a portion of the stent defines an enlarged opening for engaging the band. 
         FIG. 8  is a cross-sectional side view of an embodiment of the invention. 
         FIG. 9  is a cross sectional side view of the embodiment of  FIG. 8  shown during stent delivery. 
         FIG. 10  is a cross sectional side view of the embodiment of  FIGS. 8 and 9  shown after the stent is fully deployed. 
     
    
    
     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. 
     For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated. 
     As mentioned above the present invention is embodied in a variety of forms. For example, in the embodiment shown in  FIG. 1  the invention is embodied in a stent retaining band or collar, indicated generally at  10 , which has an outer surface  12  comprising one or more protrusions  14 . As illustrated by  FIGS. 1 and 2  the protrusions  14  may have similar or differing dimensions and orientations relative to one another. In addition, the protrusions  14  may be arranged or positioned on the outer surface  12  by columns, rows, or any other pattern desired. 
     As is shown in  FIG. 3 , the pattern of protrusions  14  is determined, at least in part, based on the geometry of the stent  26  to which the protrusions  14  are designed to engage. As is shown, band  10  is constructed and arranged to be mounted on the shaft  16  of a catheter  18 . The band is positioned on a stent retaining portion  20  of the shaft  16 . Typically the band  10  is positioned such that one or more of the protrusions  14  pass at least partially through one or more of the openings  22  defined by the tubular wall  24  of a stent, stent-graft, graft, filter or other implantable medical device, hereinafter referred to collectively as a stent  26  or stents. 
     A band  10  may be positioned underneath one or both ends  30  of the stent  26 , or any other portion of the stent desired. In some embodiments the band  10  may have a length equal to or greater than the length of the stent  26 . 
     The protrusions  14  extend at least partially through the openings  22  to engage the portions or struts  28  of the stent  26  immediately adjacent thereto. In addition to, or as an alternative to positioning the protrusions  14  through one or more of the stent openings  22 , in some embodiments the protrusions  14  may be positioned adjacent to one or both of the ends  30  of the stent  26 . 
     In some embodiments of the invention, a stent  26  is provided with ends  30  whose struts  28  have been constructed to provide openings  22  which are enlarged or otherwise modified in order to more readily accommodate the positioning of the protrusions  14  therein. 
     In the various embodiments shown and described herein, the band  10  may be at least partially radiopaque so that the band  10  may be utilized as a marker band on a stent delivery catheter  18  such as is shown in FIGS.  3  and  8 - 10 . 
     Band  10  may be constructed of a wide variety of materials including but not limited to metals, plastic, rubber, silicone, polymers, etc. Where the band  10  is at least partially constructed of metal, in at least one embodiment the metal is a radiopaque metal such as platinum, gold, iridium, etc. In at least on embodiment the metal is a biocompatible metal such as including but not limited to stainless steel, nitinol, cobalt and alloys thereof. Some polymer materials suitable for use in construction of the band  10  include one or more polyetheramide block copolymers, such as the ester linked polyetheramides sold under the trade mark PEBAX®; polyetherester block copolymer such as sold under the ARNITEL® and HYTREL®; nylon, polyethylene, etc. 
     The protrusions  14  may be constructed of the same or different material as the rest of the band or band body  15 . 
     As indicated above the protrusions  14  may be of any shape or configuration. For example in the embodiments shown in  FIGS. 1-2  the protrusions are raised portions or bumps on the surface  12  of the band and may be formed by a variety of forming mechanisms including for example molding the band and protrusions into the shape shown. In some embodiments the protrusions  14  may be made from altering the inner shaft  16  to homogeneous with the material of the band  10 . Protrusions  14  may also be separate elements which are welded, stamped, punched, adhesively engaged, injection molded, melted or otherwise positioned and/or engaged onto the surface  12  of the band  10 . However, as is shown in  FIG. 4 , protrusions  14  may also be formed by cutting out one or more openings  40  into the band  10 . The material or flap  42  cut from the tube  10  remains integral and engaged to the tube  10  along at least one line or point of engagement  44 . The resulting flap  42  of tube material is oriented to extend at least partially outward from the tube surface  12  to act as a protrusion  14 . Where multiple flaps  42  are provided for, flaps  42  may be of any shape desired and may be of a uniform or different configuration relative to one another. 
     Alternatively, the band  10  may be provided with one or more flaps  42  to act as protrusions  14  without cutting or otherwise providing the band  10  with openings flaps or slots  40  from the band  10  by molding or otherwise shaping the band  10  to include flap style protrusions  14  such as are shown in  FIG. 5 . 
     As a result of the plastic or deformable nature of the material of the band  10 , in some cases one or more protrusions  14  may be provided by pinching and or pulling selected portions of the band  10  together and radially outward in order to form one or more substantially fin shaped protrusions  14  such as is shown in  FIG. 6 . A band  10  may be provided with substantially fin shaped protrusions by manipulating a band  10  in the manner described or by molding or other wise forming the tube  10  with the protrusions already in place. 
     As indicated above, the shape, size and arrangement of the protrusions of the band are selected in order to temporarily engage at least a portion of a stent when the stent is engaged to the stent retaining area  20  of a delivery catheter. As is shown in  FIG. 7 , where the band  10  employs flap, fin or other somewhat elongated protrusions  14 , the protrusions are designed to be positioned within the spaces or openings  22  between adjacent struts  28  of the stent  26 . 
     When a stent delivery catheter  18 , such as is shown in  FIG. 8  being advanced through a vessel  50 , is equipped with one or more bands  10 , the one or more protrusions  14  of the bands  10  will engage the stent  26  in the manner described above. 
     As is shown in  FIG. 9 , when the catheter  18  has been positioned within the vessel  50  at a desired location, the stent retaining sheath  52  is retracted from the stent retaining area  20  to expose the stent  26  for delivery. In the embodiment shown, the protrusions  14  on the band  10  positioned adjacent to the distal end  56  of the stent  26 , will continue to engage the stent  26  until the sleeve  52  is fully retracted off of the stent  26 , such as is shown in  FIG. 10 . As a result of the engagement between the protrusions  14  and the stent  26 , the band  10  acts to anchor the stent  26  to the shaft  16  thereby preventing longitudinal jump of the stent  26  relative to the catheter  18 . Thus the stent  26  is deployed from the catheter  18  and into the intended area of the vessel  50  with improved precision and reliability. 
     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. 
     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. 
     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.