Stent protector design

A catheter assembly comprises a catheter having a distal end and a longitudinal axis, a stent disposed about the distal end of the catheter, and a stent protector. The stent protector has a stent covering portion disposed about the stent and a catheter engagement portion that removably engages the stent protector to the catheter assembly. The stent covering portion is disposed about the stent without substantially engaging the stent.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable

FIELD OF THE INVENTION

This invention relates to catheter assemblies which are utilized in the delivery of implantable medical devices such as stents and to stent protectors employed on such devices.

BACKGROUND OF THE INVENTION

A stent is a medical device introduced to 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.

Stents and similar devices such as stent-grafts, expandable frameworks, and similar implantable medical devices, are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. 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 used to reinforce body vessels and to prevent restenosis following angioplasty in the vascular system. They 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 implanted into a body lumen. The stent protectors protect the stent from physical damage or contamination due to the transfer of unwanted material and are removed at the time of use to permit deployment of the stent. Examples of stent protectors are provided in U.S. Pat. No. 6,152,944 and U.S. Pat. No. 6,783,542.

Stent protectors have relied on a friction fit between the stent and the stent protector in order to hold the protector in place. However such intimate contact may not always be desirable. Stents are often used as a vehicle for delivering therapeutic agents (e.g. in the form of a coating on the stent). When removing the stent protector the friction fit could result in therapeutic agent being scraped off. In addition material from the stent protector can also be deposited onto the stent.

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 can be found in the Detailed Description of the Invention below.

BRIEF SUMMARY OF THE INVENTION

The invention is directed to stent protectors that are constructed to reduce or eliminate contact between the stent and the stent protector.

In some embodiments, the invention is a catheter assembly which comprises a catheter having a distal end and a longitudinal axis, a stent disposed about the distal end of the catheter, and a stent protector having a stent covering portion disposed about the stent and a catheter engagement portion. The catheter engagement portion of the stent protector provides engagement of the stent protector to the catheter remote from the stent so that the stent protector does not substantially engage the stent. In some embodiments the engagement location of the stent protector to the catheter is distal to the stent, in others it is proximal to the stent, in still others engagement is provided both distally and proximally of the stent.

In some embodiments, the catheter has raised portions to which the catheter engagement portion of the stent protector is engaged.

In some embodiments, the stent protector supports a portion of the catheter between proximal and distal support structures in the stent protector such that the stent does not contact the stent protector.

These and other embodiments of the invention are described and illustrated in the Drawings and the Detailed Description of the Invention below and/or are characterized in the claims annexed hereto.

DETAILED DESCRIPTION OF THE INVENTION

While this invention can 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. The stent protectors disclosed herein can be used for any type of stent (e.g. peripheral stents, bifurcated stents, and drug-eluting stents).

As used in the present application, the stent is not substantially engaged if any contact forces between the stent protector and the stent are less than those which occur between the stent protector and an engagement site on the catheter assembly remote from the stent. Suitably, any contact between the stent protector and the stent does not apply enough frictional or compressive force to disrupt a coating on the stent. Contact which occurs only during removal of the stent protector is not considered engaging contact, although in at least some embodiments of the invention the stent protector does not contact the stent at all while in place as part of the protective assembly and the stent protector can also be easily removed from the catheter without contacting the stent.

FIGS. 1 and 2depict catheter assemblies10having a stent20disposed about the distal end of a catheter30and a stent protector40disposed about the stent20. The stent protectors40have a narrowed portion42at the distal end engaging the catheter distal of the stent. InFIG. 1, moving proximally of portion42the stent protector progressively widens to an enlarged diameter in portion44. InFIG. 2the diameter changes to portion44in a more abrupt step-up manner.

In both cases the enlarged diameter portion44covers the stent20and maintains a space (i.e. the region between the widened wall portion and the stent) between the interior surface of the wall of the widened portion44and the stent such that the widened portion does not engage the stent and in at least some embodiments will not contact the stent at all during normal storage or removal.

The stent protector40can be designed to be open at its distal end, as shown inFIGS. 1 and 2. Alternatively, the stent protector can have a closed distal end which can be closed around the distal end33of catheter30so that proximal movement of the stent protector40on the catheter30is further restricted by the closed end contacting the distal end of the catheter.

The stent protectors40ofFIGS. 1 and 2can be slid off the catheter30when pulled in a distal direction with reduced friction between the stent protector40and stent20than would occur if the stent protector did not have a space between the widened portion and the stent.

In another embodiment a stent protector may be formed of two tubes of different diameter, overlapping and attached over a part of their length, but with the larger diameter tube extending beyond the smaller diameter tube and over the stent to form the stent covering portion of the stent protector. The smaller diameter tube provides engagement to the catheter assembly, for instance by frictionally engaging catheter at the catheter's distal tip.FIG. 3is illustrative.

InFIG. 3the stent protector40comprises an inner tube45and an outer tube48. The inner tube45and outer tube48are fixed together by adhesive, heat bonding, crimping, or the like. The inner tube45fits over the distal end33of the catheter30. In this embodiment the outer tube48has a greater length than the inner tube45and extends proximally to cover the stent20. Crimping the inner and outer tubes45,48together can be used to attach the two tubes together and at the same time reduce the diameter of the inner tube45to create a friction fit with the catheter.

The inner tube45can be of a length such that the proximal end of the inner tube does not extend to the distal edge of the stent thereby preventing contact between the inner tube45and the stent20. In some embodiments the inner tube fits over a catheter tip32that contacts one or more distal heat stakes or crimps37,38. InFIG. 3the distal crimp38can extend inwardly enough to restrict distal movement of the catheter tip32within the inner tube45.

In some embodiments, the catheter30has a marker band34and/or balloon edge36that has a diameter greater than that of the inner tube thereby restricting the proximal edge of the inner tube45to movement distal of the distal edge of the stent20.

The catheter engagement portion of the stent protector is located distally of the stent in the catheter assemblies ofFIGS. 1-3. In other embodiments catheter engagement may be located proximally of the stent or at both proximal and distal locations relative to the stent.

In another embodiment the stent protector may be a tubular member having an inner diameter large enough to cover a stent and catheter, without substantially engaging the stent, but which engages an enlarged diameter catheter engagement area on the catheter. In some such embodiments the tubular member compressively engages the catheter engagement area. Removal may be facilitated by providing a longitudinal or spiral slit through the tubular member. In some embodiments the tubular member substantially maintains its diameter from the proximal end to the distal end. In some embodiments a flared or tapered lead-in portion on the proximal and/or distal end of the stent protector can make it easier to place the stent protector over the catheter.

FIGS. 4a-5billustrate stent protectors40for use in the catheter assembly10ofFIG. 6. The stent protectors comprise a tube40having a slit41and a flared or tapered portion42. The stent protector40ofFIG. 4a-bhas a longitudinal slit41. The slit41maintains a space between the edges of the stent protector40as shown inFIG. 4a. In some embodiments, the slit allows the edges of the stent protector40to contact one another and even overlap as shown inFIG. 4b.

InFIGS. 5a-5cthe stent protectors40have slits41that coil in a longitudinal direction about the stent protector. The stent protector40has a flared or tapered lead-in portion42on the proximal and/or distal end of the stent protector40that can make it easier to place the stent protector40over the catheter30or can be used when removing the stent protector.

The stent protectors40illustrated inFIGS. 4a-5bcan be used with the catheter assembly10ofFIG. 6. The stent protectors40contact and engage to the protrusion31of catheter30. The protrusion31prevents contraction of the stent protector to the wall of the mounted stent and minimizes any incidental contact that may occur between the stent protector40and stent20. U.S. Pat. No. 6,152,944 discloses other stent protectors that can be used in the catheter assembly10ofFIG. 6.

FIG. 7illustrates a catheter assembly10having a stent protector40that has a hollow bulb design with an opening43. The hollow bulb has a narrowed portion42and a widened portion44. The narrowed portion42engages a raised portion31of the catheter30. The widened portion44of the stent protector40covers the stent20without engaging it. The stent protector40can be gripped at the widened portion44and pulled distally to remove the stent protector from the catheter without, or with only incidental, contact between the stent protector and the stent20. It should be noted that the distal end of the stent protector ofFIG. 7has a closed distal end. In other embodiments, not shown, the distal end can be open.

FIGS. 8a-billustrate a catheter assembly10having a stent protector40that has a proximal open end43, the shape of which is reconfigurable. InFIG. 8athe proximal open end43of the stent protector40has a first size wherein the stent protector40is in contact with the catheter30and engages it at the dotted line45. The open end43of the stent protector40can be reconfigured to a larger second size by forcing the open end to a larger configuration as shown inFIG. 8b. The larger second size of the stent protector40allows the stent protector40to be removed from the catheter without engaging the stent. InFIGS. 9a-ba transition between an embodied proximal open end43is shown in cross-section. Corresponding toFIG. 8a,FIG. 9ashows the smaller configuration as crescent shaped and having small radius45. Application of radially outward pressure in the direction of the arrow46will cause the opening43to adopt the open configuration ofFIG. 9bwhich corresponds toFIG. 8band illustrates the larger configuration as substantially circular. Application of radially inward pressure in the direction of the arrow46as shown inFIG. 9bwill cause the opening43to return to the configuration ofFIG. 9a.

The stent protector inFIGS. 8a-9bcan be bi-stable in that the larger configuration and the smaller configuration of the smaller catheter engagement portion are stable positions and those positions between the two positions are unstable. Spring metal materials, a number of crosslinked plastics, and some engineering thermoplastic resins can be configured in this way. It should be noted that other shaped openings can be used other than those illustrated inFIGS. 8a-9b. The stent protector10can also have stable configurations over a wide variety of positions between those shown inFIGS. 9aand9b.

InFIGS. 10a-ba stent protector40is shown. The stent protector has a catheter engagement portion47formed by flattening the distal end of stent protector40. In the catheter assembly10ofFIG. 11the stent protector40is engaged to a catheter30. The flattened distal end47frictionally grips the catheter30. The stent protector40can be pulled distally to remove it from the catheter30. The stent covering portion44is widened in order to prevent engagement of the stent protector40to the stent20.

As shown inFIGS. 12a-b, the catheter engagement portion47of the stent protector can have squeeze points that are squeezed together to release the stent protector from the catheter30. InFIG. 12athe catheter engagement portion47of stent protector40grips catheter30thereby engaging the stent protector to the catheter. By applying a force52to squeeze points50the cross-sectional area of catheter engagement portion47is increased, as shown inFIG. 12b. The stent protector40can then be removed from the catheter30. Elastomers, such as silicones, elastomeric polyurethanes and thermoplastic elastomers, and various plastic foam materials may be suitable materials for such embodiments of the invention.

The catheter engagement portion47as illustrated inFIGS. 12a-bcan be used on one or both of the proximal end and distal end of the stent protector40. An embodiment with engagement portion47located both proximally and distally of the stent is shown inFIG. 13. The proximal catheter engagement portion47in some embodiments as shown inFIG. 14can be wider than the distal catheter engagement portion in order to better accommodate the stent and catheter as it is inserted through the opening55upon squeezing the squeeze points50together.

As shown inFIG. 15the stent protector40of catheter assembly10has a catheter engagement portion47having petals49. The petals49can be formed by slitting the catheter engagement portion47far enough that when the petals49are separated and expanded radially the stent and catheter can pass through the diameter without the stent20engaging or contacting the stent protector40. InFIG. 16athe petals49engage the catheter30. Upon being separated and expanded radially as shown inFIG. 16b, the stent protector40is released from the catheter30. In some embodiments the petals will have a shape memory so that the engaged and expanded position of the petals are bi-stable.

FIGS. 17-21pertain to a catheter assembly wherein a portion of the catheter is supported within the stent protector. The stent is disposed about the catheter between a proximal and a distal catheter engagement portion of the stent protector.

InFIGS. 17-18bthe stent protector40has a clam shell design. The clam shell has a first section51and a second section53which mate along edges52when closed. The stent protector40supports a portion of a catheter30between proximal and distal support structures54,56. The catheter has a stent20mounted therein which is located between the support struts54,56. The stent protector40is designed to fold over the portion of the catheter and stent20between the proximal and distal supports54,56such that widened portion44of the stent protector covers the stent without contacting it. It should be noted that, while illustrated as half-sections, in other embodiments the first section and the second section can vary greatly in size to one another.

A clam shell stent protector optionally can have clasps58used for keeping the stent protector closed as shown inFIGS. 18aand 18bwhich respectively depict side and end views of the stent protector40in the closed position. The clasp58extends about the support structure54to secure the first half51and the second half53together in the closed position. In some embodiments the clasp58extends over a shorter portion of the support structure than illustrated inFIGS. 17-18b; in other embodiments the clasp58may extend over a longer portion of the support structure than illustrated inFIGS. 17-18b. In other alternatives a clasp may be centered longitudinally on the device or even extend over the entire device. In some embodiments a clasp may extend over both mating edges52. In other embodiments the two sections may be hinged along at least a portion of one of the mating edges52so that the clasp structure if provided need only extend over a portion or portions of the other mating edge.

As shown inFIGS. 19-21the stent protector40can have a cradle configuration having a base51and a cap53. InFIG. 19the base51includes two supports60supporting a catheter30with a stent20disposed between the supports60. The catheter can rest within the slots62. The slots62can have a width that closely matches the diameter of the catheter portion disposed therein, thereby frictionally engaging the catheter to the base51. In some embodiments the supports include clasps or other fasteners to further engage the catheter30to the base51of the stent protector.

The supports60of the base can fittingly engage an optional cap53, shown inFIG. 20. The cap53fits over the supports60of base51; in some embodiments it snaps over the supports. When the cap53and base51are engaged as illustrated inFIG. 21, the stent20is supported between the supports60and within the space62between the base51and the cap53.

The features of the various figures are illustrative and can be combined in other ways not shown. As non-limiting examples, the catheter engagement mechanism illustrated proximally of the stent inFIG. 6can be located distally of the stent or both proximally and distally thereof. Likewise a bi-stable engagement mechanism as inFIGS. 9aand 9b, which is proximally of the stent inFIGS. 8aand 8b, can be readily adapted for a distal engagement or for engagements at both proximal and distal locations relative to the stent. The same is true of the petalled engagement mechanism inFIGS. 15, and 16a-b.

The stent protectors as disclosed herein can be formed of a wide variety of polymer materials (e.g. PTFE, FEP, Nylons, silicones, engineering resins, crosslinked resins, thermoplastic elastomers, etc). In some embodiments the stent protector40can be formed of braided fiber. In some embodiments the protectors, or portions thereof, may be fabricated of metals, for instance spring metals, or metal/polymer laminates.

In some embodiments the stent, the delivery system or other portion of the assembly can include one or more areas, bands, coatings, members, etc. that is (are) detectable by imaging modalities such as X-Ray, MRI, ultrasound, etc. In some embodiments at least a portion of the stent and/or adjacent assembly is at least partially radiopaque.

In some embodiments the at least a portion of the stent is configured to include one or more mechanisms for the delivery of a therapeutic agent. The agent will be in the form of a coating or other layer (or layers) of material in any suitable form placed on a surface region of the stent, which is adapted to be released at the site of the stent's implantation or areas adjacent thereto. Alternately, the therapeutic agent can reside in a reservoir formed within or on the stent using suitable configurations or arrangements. The stent protectors of the invention are especially suited for protecting stents provided with such coatings.

A therapeutic agent can 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 can include but is not limited to: DNA, RNA and their respective derivatives and/or components; hedgehog proteins, etc. Where a therapeutic agent includes cellular material, the cellular material can 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 polymer agent can be a polystyrene-polyisobutylene-polystyrene triblock copolymer (SIBS), polyethylene oxide, silicone rubber and/or any other suitable substrate.

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. The various elements shown in the individual figures and described above can be combined or modified for combination as desired. 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”.

This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art can recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.