STENT SECUREMENT BY BALLOON MODIFICATION

Abstract: Improved stent securement in a balloon catheter including balloon modification.

Description: STENT SECUREMENT BY BALLOON MODIFICATION BACKGROUND OF THE INVENTION This invention relates to improved apparatus suitable for stent delivery and implantation. Stents are implantable devices which are placed within body lumens and the like, such as blood vessels. Stents are typically tubular in form, the diameter of which can be increased for implantation. They maybe made of plastic or metal. Stents are usually introduced for implantation percutaneously by means of a catheter and the diameter of the stent is increased by inflation of a balloon on the catheter. In one aspect, this invention relates to an improvement in the stent delivery system described in U.S. Patent 4,950,227 to Savin et al., entitled "Stent Delivery System" and issued on August 21, 1990. This patent is incorporated herein in its entirety by reference. That patent discloses a stent delivery system in which a catheter carries, on its distal end portion, a stent which is held in place around the catheter prior to and during percutaneous delivery by means of one and preferably two sleeves. The sleeves are positioned around the catheter with one end portion attached thereto and overlap an end portion(s) of the stent to hold it in place on the catheter in a contracted condition. Each sleeve is elastomeric in nature so as to stretch and release the stent when it expands for implantation. The stent is expandable by means of the expandable balloon on the catheter. SUMMARY OF THE INVENTION In a first aspect, this invention provides securement of a stent on a balloon by means of a folded or rolled end portion of the balloon itself. In another aspect of this invention the balloon configured as described above is used in combination with the elastic sleeves of the Savin et al. patent. Additionally, the balloon shape may be modified, as by enlarged cone portions, to facilitate the above improvements. Moreover, these features may be used alone or in combination and may be applied to one or both ends of the stent to secure it for delivery. BRIEF DESCRIPTION OF THE DRAWING(S) Figure 1 is an axial cross-section view of one embodiment of a balloon catheter of the present invention, showing the catheter operatively disposed in a body conduit. Figure 2 is an axial cross-section view of a balloon catheter, the balloon being rolled or folded onto the catheter cannula to encompass the ends of the stent carried by the balloon; Figure 3 is an enlarged cross-section view of one end of the balloon of Figure 2; Figure 4 is a schematic plane view of the distal end portion of a balloon catheter having a stent fixed to the catheter by means of folds in the balloon and retractable sleeves; Figures 5, 6, 7 and 8 are schematic views showing simultaneous expansion of a catheter balloon and stent and the resultant release of the stent from the balloon and retaining sleeves; Figure 9 is a schematic showing of a balloon of modified construction according to the invention; Figure 10 is an axial cross-section similar to Figure 1 showing the balloon of Figure 9 on a catheter with retractable sleeves, and Figure 11 is a schematic view in fragment of another embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS A stent-carrying balloon catheter is illustrated generally in Figure 1 and designated by the reference numeral 10. The catheter 10 is operatively disposed in a body conduit defined by walls 11 and includes an elongate cannula 12 having a distal end 14 and a proximal end (not shown). Catheter 10 includes a balloon 16 (inflated) having a distal end 18 and a proximal end 21. A central wall 27 is disposed between end wall 18 and 21 in a central region 30 of balloon 16. In this embodiment the end walls 18 and 21 are relatively thick and relatively small in diameter. This is in comparison to central wall 27 of balloon 16 which is relatively thin and relatively large in diameter. A pair of transition walls or cones 32 and 34 are of particular interest to the preferred embodiment of this invention. A stent 36 is shown on balloon 16 being expanded by the dilated balloon. Referring to Figures 2 and 3, the cones 32 and 34 of particular interest are discussed in more detail. As can be seen in the Figures, cone portions 32 and 34 are rolled or folded as at 32a and 32b under or over themselves and the catheter cannula 12 to encompass the ends 36a and 36b respectively of the stent thus securing it to the catheter. Upon inflation of balloon 16, folds 32a and 32b open to a configuration similar to that shown in Figure 1 to release the stent for expansion by the balloon. Referring to Figure 4, a stent delivery system 10 includes a balloon catheter 12 having a balloon 16 fixed to the catheter for remote inflation as is known in the art. The catheter includes an elongate cannula 46 and may include marker bands 44. Balloon 16 is shown in a somewhat contracted state. A stent 36 is positioned about balloon 16 on catheter 12 and held by two overlying retaining sleeves, a proximal one 40 and a distal one 42. Stent 36 may be of any known type. In this instance for example it may be a balloon expandable stent of stainless steel, such as the known types which are cut or etched from hypotubes. Sleeves 40 and 42 may be axially fixed along catheter 12 as by an adhesive (not shown). The sleeves overlap stent 36 at each of the stent ends or margin 36a and 36b as shown. Additionally, further securement of stent 36 is provided by balloon folds 32a and 32b similar to those shown in Figures 2 and 3. Sleeves 40 and 42 are comprised of elastomeric polymeric material such as rubber, urethane, styrenes, silicone, polyurethane, polyethylene, PET, ABS and polyimides. A lubricant additive such as silicone may be included in or on the sleeves. Additionally, further securement of stent 16 is provided by balloon folds 32a and 32b similar to those shown in Figures 2 and 3. Referring to Figures 5, 6, 7 and 8, the stent delivery system 10 of Figure 4 is inserted percutaneously by known technique into a body lumen or the like. As the stent is positioned (Figure 2), balloon 16 is expanded (Figures 6 and 7). During balloon expansion, stent 36 is also expanded and sleeves 40 and 42 deform elastically while balloon folds 32a and 32b open to release the stent. The balloon is then deflated by standard technique and catheter 12 with sleeves 40 and 42 is axially removed leaving stent 36 implanted (Figure 8). In some instances, only one sleeve may be provided at one end in the system. Also, only one fold may be provided in the balloon at one end. Preferably, the fold(s) are in the end regions of the balloon but could be located anywhere to accommodate the size stent used relative to the balloon length used. Referring now to Figure 9, a balloon 16 of modified construction according to the invention is shown. Balloon 16 includes a central body portion 30 of a nominal size, distal catheter attachment ends 18 and 21, and cone portions 32 and 34, also in end regions of the balloon. Cone portions 32 and 34 are larger in diameter, at least adjacent to their attachment to body 30, than the nominal body 30 size. A purpose of this construction modification in the balloon is to facilitate sleeve retraction as is shown in Figure 10. As can be seen from the Figure, when balloon 30 begins to inflate, the enlarged cones 32 and 34 increase in size to aid in sleeve 40 and 42 retraction to expose the stent 36 for expansion upon further inflation of the balloon. It is contemplated within the purview of this invention that the balloon, particularly in the region of the cones, may be physically modified so as to change the mechanical characteristics of the balloon in order to facilitate folding of the balloon. For example, this may be accomplished by forming slits or other apertures in those regions of the balloon. Sealing would be accomplished by the balloon fold or by covering by the sleeves. Such apertures might be formed in the balloon as made or formed in it later. For example, when the stent is crimped to the balloon, the stent ends maybe utilized to form apertures in the balloon material. Referring now to Figure 11 , which is a fragment schematic of a catheter system similar to those of the preceding Figures, a modified balloon construction is shown in which the stent 36 is positioned within a raised end 16a and 16b of balloon 16. Optionally, a dam 50 may be included as is known in the art. The balloon will preferably include raised end portions at both ends as shown. However, only one end, preferably the distal end 16a, could be raised. The raised relationship may be slitted by forming it in the balloon similar to the construction shown in Figure 9. Rotating sleeves may be optionally used in this embodiment. The above Examples and disclosure are intended to be illustrative and not exhaustive. These examples and 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 attached claims. 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 attached hereto.

Claims: What Is Claimed Is: 1. In a stent-carrying balloon catheter in which a balloon is positioned within a stent for expanding same upon dilation of the balloon, the improvement comprising a circumferential fold in the balloon body over a portion of the balloon itself, the fold encompassing a circumferential end portion of the stent for securing it in place until dilation of the balloon. 2. The improvement of claim 1 in which the fold is in the region of at least one end portion of the balloon. 3. The improvement of claim 1 in which there are two folds in the balloon one each encompassing an end respectively of the stent. 4. The improvement of claim 3 in which the two folds are in the region of opposite ends of the balloon. 5. In a stent delivery system comprising: a catheter including a distal balloon constructed and arranged to carry and release a stent; a stent positioned around the distal balloon of the catheter, the stent having a contracted condition and being expandable to an expanded condition, the stent having at least an end portion lying over the distal balloon of the catheter, and an elastomeric sleeve of polymeric composition carried in the region of the balloon and positioned around the catheter, the sleeve having a first end attached to the catheter and a second end lying over the end portion of the stent, the sleeve fixing the end of the stent on the catheter when the stent is in the contracted condition, the catheter and stent being cooperatively constructed and arranged for expansion of the stent and axial removal of the sleeve from the margin of the stent upon delivery of the stent for implantation, the improvement comprising: a circumferential fold in the balloon body over a portion of the balloon itself, the fold encompassing a circumferential end portion of the stent between the balloon and the sleeve. 6. The improvement of claim 5 in which the fold is in the region of at least one end portion of the balloon. 7. The improvement of claim 5 in which there are two folds in the balloon, one each encompassing an end respectively of the stent. 8. The improvement of claim 7 in which the two folds are in the region of opposite ends of the balloon. 9. A balloon for balloon catheters, the balloon being constructed and arranged to have a body portion and opposite cone end portions in which the cone end portions are of a larger diameter respectively adjacent to the body portions than the diameter of the body portion in that adjacent region. 10. A balloon for balloon catheters, the balloon having a nominal body size and enlarged cone ends. 11. In a stent delivery system comprising: a catheter including a distal balloon constructed and arranged to carry and release a stent; a stent positioned around the distal balloon of the catheter, the stent having a contracted condition and being expandable to an expanded condition, the stent having at least an end portion lying over the distal balloon of the catheter, and an elastomeric sleeve of polymeric composition carried at the end region of the balloon and positioned around the catheter, the sleeve having a first end attached to the catheter and a second end lying over the end portion of the stent, the sleeve fixing the end of the stent on the catheter when the stent is in the contracted condition, the catheter and stent being cooperatively constructed and arranged for expansion of the stent and axial removal of the sleeve from the margin of the stent upon delivery of the stent for implantation, the improvement comprising: the balloon having a nominal body size and enlarged cone ends. 12. The stent delivery system of claim 11 in which the balloon is constructed and arranged to have a body portion and opposite cone end portions in which the cone end portions are of a larger diameter respectively adjacent to the body portion than the diameter of the body portion in that adjacent region. 13. In a stent-carrying balloon catheter in which a balloon is positioned within a stent for expanding same upon dilation of the balloon, the improvement comprising at least one enlarged end portion on the balloon. 14. The improvement of claim 13 in which both balloon ends are enlarged.

Inventors: HANSON SCOTT M, PEDERSON GARY J JR, SEPPALA JAN D, SMITH SCOTT R, VRBA ANTHONY C, HANSON, SCOTT, M., PEDERSON, GARY, J., JR., SEPPALA, JAN, D., SMITH, SCOTT, R., VRBA, ANTHONY, C.
Applicants: SCIMED LIFE SYSTEMS INC, SCIMED LIFE SYSTEMS, INC.
Application year: 2000
Main classification: A61F2
IPC codes: A61F2, A61M25