US20050080480A1 - Retrievable stent and method of use thereof - Google Patents

Abstract

A removable stent system and method for extraction of a removable stent from a target site is disclosed. The removable stent includes a removable stent having a collapsible end and a collapsing element configured for coupling with a removal tool. The collapsing element can be configured as a lasso or can be movable between two positions when deployed at a target site in vivo. The removable stent overcomes disadvantages and limitations of previous types of stents as well as overcoming complications during or following stent deployment in vivo. The removable stent further includes features that increase its ease of use and reduce the maneuvering required of devices or tools used to remove the stent. This then decreases the amount of effort required by the physician, the procedure time, and the level of discomfort experienced by a patient during the procedure.

Description

FIELD OF THE INVENTION
• The present invention relates generally to a removable stent and an assembly for its delivery or removal from a target site. The present invention particularly relates to a removable stent and system for its use in a medical procedure involving blood vessels, ducts, treatment of enlarged prostate gland, coronary artery disease and the like.
BACKGROUND OF THE INVENTION
• Stents are used in a wide variety of medical procedures where the permanent expansion of an occluded vessel is desired. Usually, stents are constructed of a metal cylinder that is implanted into a patient at the site of obstruction. In a patient suffering from an occluded vessel, balloon catheterization or balloon angioplasty is often the prescribed treatment. However, following such a procedure, restenosis or re-narrowing of the occluded tissue often occurs. Therefore, stents were developed and are used to optimize and improve the initial and long-term outcome in patients treated for an obstructed vessel. In addition to obstructions, stents are also used to provide support for a graft during healing of reconnected vessels. Diseases most often treated using a stent include coronary artery disease, benign prostatic hyperplasia (also referred to as an enlarged prostate gland), and other medical indications where expansion of a lumen, vessel or duct is desired. As such, a variety of stent systems have been developed for medical use. See, for example, U.S. Pat. No. 5,100,429; U.S. Pat. No. 4,762,128; and U.S. Pat. No. 4,800,882.
• Although the development of stents for use in medical procedures has been a major advance in treating a narrowed lumen, a variety of complications can and do occur in connection with either the delivery of the stent or, at a later time, following deployment of the stent in vivo. Such problems or complications include failure of proper deployment of the stent, misalignment, dislodgement, or damage of the stent after it is deployed, or re-occlusion of the vessel over time once the stent is inserted. In these cases, removal of the stent is desired. Devices and/or assemblies allowing for the extraction of a stent are known and include, for example, U.S. Pat. No. 5,474,563; U.S. Pat. No. 5,624,450 and U.S. Pat. No. 5,411,507. In particular, Hendrik, U.S. Pat. No. 5,624,450 describes an assembly for the removal of an implanted stent. The assembly entails use of an expandable element having an adhesive outer surface. The expandable element is connected to a pulling device. Insertion followed by expansion of the expandable element inside the faulty stent causes its attachment (adhesion) to the inner surface of the stent allowing the user to then “pull” the stent out. A particular disadvantage in this system is that it is unreliable, as attachment of the expandable element to the stent occurs by adhesion. As a result, a more reliable and effective removal system is desired.
• An example of an additional stent removal system may also be found in U.S. Pat. No. 5,474,563, which describes a system for removal of a cardiovascular stent device from a blood vessel. The system includes a self-expanding elastomeric stent and an extraction catheter for removal of the cardiovascular stent. The extraction catheter is especially designed so as to specifically engage with projections located on the stent. Removal of the stent occurs by engaging the extraction catheter with the projections. One disadvantage of this extraction system and other similar systems is the requirement for complex extraction instrumentation as well as specific and intricate maneuvering by the physician to engage the extraction tool with the stent.
• The above-described removal systems (and other similar devices not specifically described) offer advantages, including effectiveness and safety to both the user and the patient. However, it has been discovered that an obstacle or disadvantage to such devices is that their use is complicated. Additionally, even with the more simple removal systems, the susceptibility of separation of the removal device from the stent during use result in major limitations to the reliability of these systems.
• In view of the above, it is apparent that there is a need to provide a removable stent and a system which allows for reliable and minimally traumatic removal of a stent from an in vivo target site. There is also a need to provide a removable stent and system that is efficient, simpler to use for the physician and easy to maneuver in vivo. A reliable and efficient removal system would reduce the overall procedure time required, reduce possible trauma to the lumen wall during use, and therefore reduce patient discomfort during recovery. Such removal systems include properties that reduce the amount of effort required by the physician prior to and during use of the system as well as properties that ensure the system remain intact during removal of the stent.
OBJECTS AND SUMMARY OF THE INVENTION
• In view of the foregoing, it is an object of the present invention to provide a removable stent device that addresses the limitations and disadvantages associated with prior removal devices, yet meets the needs of the users.
• A further object of the invention is to provide a removable stent system that is efficient, requires minimal effort by the user and that is reliable.
• Still another object of the invention is to provide a removable stent assembly having a collapsing element configured around the circumference of the stent so as to allow retrieval of the stent by collapsing one end of the stent to a smaller diameter.
• A further object of the invention is to provide a stent removal system where removal of the stent can be achieved by use of a simple removal tool having a grasper attachment.
• In one aspect of the invention, a stent removal system for removing a stent from a target site in a patient is disclosed. The system can include a removable stent that is collapsible at a proximal end by engagement of a collapsing element with a removal tool. The collapsing element can be a lasso or a discontinuous lasso configured so as to collapse the proximal end of the removable stent for removal from a body site. Alternatively, the collapsing element can be a hook that is movable between an up and a down position. The removal tool is configured so as to allow coupling to the collapsing element of the removable stent. The removal tool can be configured as a tube having a slot at one end allowing for its coupling to the collapsing element. The stent removal system can also include a grasper element designed to aid in the removal of the stent by attachment to a removal tool or a delivery tool.
• An additional object of the invention is to provide a method of removing a stent in vivo using a stent removal system.
• These and other objects not specifically enumerated herein are believed to be addressed by the present invention which contemplates a stent removal system for removing a stent from a body site that includes a removable stent having a collapsible proximal end, a collapsing element and a removal tool.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a side view of a preferred embodiment of the present invention in situ including a removable stent having a collapsible proximal end, an inner lumen and a collapsing element;
• FIGS. 2A and 2B are enlarged views of the area of a removable stent having a hinged hook collapsing element depicting the hinged hook in upright (FIG. 2A) and down (FIG. 2B) positions;
• FIG. 3 is a cross-sectional view of a removable stent along the3-3 line ofFIG. 1;
• FIGS. 4A and 4B are cross-sectional views through the hinge region of a hook type of collapsing element;
• FIG. 5 is a side view of a removable stent including a removal tool for grasping a collapsing element of a removable stent;
• FIG. 6 is a cross-sectional view of a removable stent along line6-6 ofFIG. 5;
• FIG. 7 is a side view of a removable stent in situ with the proximal end in the collapsed position;
• FIG. 8 is a view of a removable stent having a lasso collapsing element;
• FIG. 9 is a cross sectional view through the proximal end of a removable stent having a lasso collapsing element;
• FIG. 10 is a view of a removal tool and a removable stent having a lasso collapsing element;
• FIG. 11 is a view of a removal tool grasping a removable stent;
• FIG. 12 is a view of a removable stent having a discontinuous lasso collapsing element;
• FIG. 13 is a cross sectional view through the proximal end of a removable stent having a discontinuous lasso collapsing element;
• FIG. 14 is a view of a removal tool grasping a removable stent;
• FIG. 15 a view of a removal tool grasping a removable stent;
• FIG. 16 is an enlarged view of an area of an alternate embodiment of a removable stent having eyelets or loops formed near the end of the stent;
• FIG. 17 is a detailed view of an alternate embodiment of the loop ofFIG. 16;
• FIG. 18 is an enlarged view of an area of an alternate embodiment of the removable stent ofFIG. 16;
• FIG. 19 is a partial view of the removable stent ofFIG. 16 having a lasso-type collapsing element;
• FIG. 20 is a partial side view of a removal tool and the removable stent ofFIG. 17;
• FIG. 21 is a side view of the removable stent ofFIG. 17 in a constricted configuration;
• FIG. 22 is a side view of a removable stent and an alternate embodiment of a collapsing element;
• FIG. 23 is a side view of a removable stent and an alternate embodiment of a collapsing element; and
• FIG. 24 is a view of a grasper device for attachment to a removal or a delivery tool.
DETAILED DESCRIPTION OF THE INVENTION
• FIG. 1 shows a representative view of aremovable stent10 in situ within abody vessel11. For convenience and ease of comprehension, the medical device referenced in the text and figures of the present disclosure is a stent. However, it should be noted that other medical devices or prosthesis including, but not limited to, balloons, stent coverings, vascular grafts, or other implantable devices, are also within the scope of the claimed invention.
• Theremovable stent10 is an intraluminal prosthesis or device having proximal22 and distal ends24 that are open. The removable stent is generally tubular in shape and has anouter surface30 which contains aninner lumen32 that extends axially between collapsible proximal22 and distal ends24. A removable stent includes collapsingelements40, which aid in collapsing or compressing thestent10 for its removal from an intralumenal site. The collapsingelement40 of the stent is a feature that aids in its efficient and easy removal from a body lumen As used herein, the term “proximal” is intended to refer to the end of the stent closest to the physician when deployed at a target site, or the end that will be collapsed for removal of the deployed stent from its target site. The “distal” end is intended to refer to that end which is opposite to theproximal end22.
• Aremovable stent10 can be of the type that is self expanding, or of the type that is expandable using a balloon mechanism. Methods for the construction, manufacture or deployment of self-expanding stents are known in the art and are described, for example, in U.S. Pat. No. 5,356,423 as well as in U.S. Pat. No. 4,655,772. Balloon expandable stents are also known in the art and are described, for example, in U.S. Pat. No. 4,893,623. Alternatively, the stent can be expandable by any other means, or can be of any variety of expandable prostheses or intralumenal implantation devices that include an element capable of collapsing or constricting the stent from an end, such as the proximal end.
• Referring toFIG. 1, aremovable stent10 can be constructed so as to have amesh structure26. The mesh can be made of elongate elements, such as metal wires, that are woven, braided, or stamped. Alternatively, the mesh-work can be formed from any other type of material or structure so long as it is biocompatible and of sufficient rigidity so as to support patency of a body lumen or target site when implanted in vivo. Biocompatible materials suitable for such construction include, for example, stainless steel, alloys, composite materials, or plastics. The removable stent can also be constructed of a flexible or non-metallic material such as an elastic polymer or rubber, medical-grade nylon or polyester, or any material that is either itself collapsible or can be formed or configured to be compressible.
• In a preferred embodiment, as shown inFIGS. 1 and 7, theremovable stent10 is a braidedtubular mesh26, constructed of a collection of wires28 (approximately 24 in number) held together by friction. The wires are formed or woven in such a way so as to facilitate and maintain radial expansion of the stent when deployed in vivo (SeeFIG. 1), while also allowing for radial compression of the stent when pulled along its longitudinal axis (FIG. 7). The expansion/compression feature of theremovable stent10 is designed such that application of a pulling force along the stent's longitudinal (x-x) axis results in radial compression and reduced lumen diameter. Release of the longitudinal force returns the stent to its deployed radially expanded dimension. This feature of the removable stent is similar to the mechanism employed in a child's Chinese handcuff toy.
• A collapsingelement40 can be of a variety of structural configurations. The collapsingelement40 is preferably located at or near theproximal end22 of theremovable stent10 as this is generally the end from which the physician will first encounter the stent during a removal procedure. In a preferred embodiment, a removable stent can include a collapsingelement40 designed as a clasping structure that is located within theinner lumen32 of theremovable stent10 as shown inFIGS. 1 and 3.FIG. 3 is a cross-sectional view of a removable stent taken along the3-3 line at theproximal end22 of theremovable stent10 ofFIG. 1. Such a collapsing element40 (also referred to herein as a “hinged hook” or a “hook”) is movable between a first and a second position. Therefore, as illustrated inFIG. 2 thehook elements42 can be lifted into an upright or “up” position (FIG. 2A) for engagement with and extraction by a removal tool, or can be pushed into a “down” position (FIG. 2B) where it lays flat against theinner wire surface42 of the removable stent when the stent is deployed in vivo. As illustrated inFIG. 3, when in the “up” position, thehooks40 protrude away from theinner surface30 of the stent into theinner lumen32. A removable stent having a hinged hook type of collapsingelement40 will preferably include 2 to 3, or 3 to 4 hooks, spaced equally along the inner circumference orsurface30 of the removable stent.
• FIGS. 2A and 2B are enlarged views illustrating a hook type of collapsingelement40 of a removable stent when deployed in vivo. When in the first or “down” position (FIG. 2B), thehook element40 resides substantially parallel to or flat against the inner surface of across wire42 of a stent. The ability of thehook40 to lay flat against the inner surface of the removable stent (“down” position) is particularly advantageous in that such a collapsingelement40 will not interfere with the patency, impede the flow, or increase the possibility of clot formation of a fluid through the stent. This is of particular concern when a stent is deployed in a blood vessel. A collapsingelement40 that is movable between an up and a down position allows for placement of the collapsingelement40 into a more accessible position for engagement with a removal tool. This aspect of the present invention provides a more versatile and effective removable stent.
• A hinged hook type of collapsingelement40 includes an upper region that is curved or shaped as ahook44. The lower orbottom portion46 of the collapsingelement40 is configured so as to enclose or wrap around awire43 of the stent so as to function as a hinge. The collapsingelement40 can be attached to astent wire43 at the inner surface of the removable stent. A hingedhook44 can be designed or configured so as to snap onto astent wire43 with aportion46 of the hinged hook disposed toward the outer surface of the stent. Once snapped into place, the hingedhook44 can be pushed or slid along thestent wire43, passing underneath a crossing wire41, so as to position thebook44 underneath across wire42 as shown inFIG. 2B.
• In addition, a hook type of collapsing element can be configured so as to include tab components, which allow it to be easily snapped or clipped onto a stent wire. Referring toFIGS. 4A and 4B detailed cross-sectional views through thehinge portion46 of ahook44 illustrate two exemplary designs of tab components of a hook hinge region. In the first design (FIG. 4A), thetab gap element8 is an extension of thehinge portion46 that, when pressed, will become captured in thehinge latch47 which is an extension of thehook44. In the second design (FIG. 4B), thehinge latch47 is pressed such that it becomes captured by thetab gap element8. Both of these hinge designs allow rotational movement of thecross wire43 relative to thehook44. That is, thehinge46 portion of ahook type44 of collapsingelement40 allows the collapsing element to be movable between its deployed, “down” position and a removable “up” position. A hingedhook44 type of collapsing element as described herein is also advantageous in that the tab gap design reduces undesired movement of thehook element44 between its two positions (upright or down) by virtue of how the tab gap design is comprised around and in frictional contact with thecross wire43. Therefore, a hinged hook is preferably manufactured of a material that maintains a certain degree of resistance so as to ensure the collapsing element remains in either the up or the down position, as is desired by the physician during use. A hinge material can be manufactured of a same material as the stent wire, such as stainless steel or plastic. An optimal method of fabricating and handling a hinged hook is by continuous metal stamping on a band or a ribbon.
• A stent of the present invention can be removed from an intralumenal site by collapsing one of its ends, such as the proximal end, with the aid of a removal tool. Several types ofremoval tools62 can be used to remove astent10 of the present invention, as will be apparent to one skilled in the art. Referring toFIG. 5, aremoval tool62 suitable for use with a hook type of collapsingelement40 can be designed to havecoupling structure64 for engaging thehook elements40. Thestent10 can then be collapsed beginning at itsproximal end22 using theremoval tool62 to grasp thehooks40 and to apply a pulling force.FIG. 6 illustrates a cross-sectional view of a removable stent havinghook elements40 engaged with a removal tool. As indicated inFIG. 6, application of a rotational force on the constrictingelements40 via the coupling means64 collapses thestent10 radially inward.
• In a preferred embodiment, aremoval tool62 can take the form of a standard stone basket tool. One such tool includes a stone basket as manufactured by Cook Urologic. In this embodiment, the strands forming the basket of the tool engage thehooks40 as shown inFIG. 6.
• FIG. 7 illustrates astent10 of the present invention during removal from anintralumenal site11. Radial constriction begins at theproximal end22 of thestent10 extending toward thedistal end24 longitudinally, as thestent10 is pulled by aremoval tool62 coupled to the collapsingelements40. Radial compression and collapse of thestent10 beginning with theproximal end22 allows the physician to easily withdraw or ensnare thestent10 into an endoscope sheath for its removal from an in vivo intralumenalsite11. This aspect of theremovable stent10 is particularly advantageous to achieving the goals of the invention in that astent10 having a collapsible end allows for easy manipulation of thestent10 into a catheter or endoscope sheath to completely remove thestent10 from the patient's body.
• Referring toFIG. 8, a collapsing element can also be configured as alasso80 situated around the circumference of theproximal end22 of astent10. Thelasso80 is constructed of a wire which functions as a noose capable of constricting or tightening itself around theoutside surface82 of thestent10. Thelasso80 can include aloop region84, which allows for engagement of aremoval tool101 to grasp and remove the stent10 (seeFIG. 10). Theloop region84 of thelasso80 is disposed internally within thestent10 with the remainder of the lasso wire86 wrapped externally around thestent10. Alternatively, thelasso80 can be woven into and out of thestent surface82. Therefore, thelasso80 is preferably incorporated substantially around the circumference on theoutside surface30 of thestent10.
• As illustrated again inFIG. 9, the inner lumen90 of theremovable stent10 has a cross-sectional diameter, along its x-x, or its y-y axis, which dimensions can vary depending on use.FIG. 9 shows a cross-sectional view of aremovable stent10 when expanded. The diameter of the inner lumen90 can vary between a relatively larger diameter such as when the stent is deployed, and a significantly smaller diameter. Therefore, when theproximal end22 of thestent10 is collapsed, through constriction of thelasso80, the inner lumen will have a reduced cross-sectional diameter allowing for its extraction from an intralumenal site (seeFIG. 11). This aids the physician in removing the stent from its target site with minimal damage or trauma to the surrounding tissue.
• FIGS. 10 & 11 shows views from internal perspectives (inside viewing outward) of aremovable stent10 during collapse and removal of thestent10. Thelasso80 type of collapsing element functions by radial contraction, which collapses aremovable stent10 from an expanded diameter (FIG. 10) to a reduced diameter (FIG. 11). Theloop region84 of the lasso86 protrudes into the inner lumen of theremovable stent10, thereby allowing the physician to grasp thelasso84 by ahook element102 disposed at the end of the removal tool101 (FIG. 10). Constriction of theproximal end22 of thestent10 is achieved by rotating theremoval tool101, which causes the lasso to twist upon itself, thus also collapsing thestent10. Alternatively, the lasso can be designed to include internal elements such as a ball, a hook, or a loop that assists in locating as well as operating the lasso. Thelasso80, therefore, constricts or collapses theproximal end22 of theremovable stent10 by radial tightening88 of the lasso86 upon itself A lasso type of collapsing element can be constructed from permanent materials (stainless steel, or metal wire, for example) or from temporary degradable materials.
• Referring toFIGS. 12-15, in a further embodiment of the present invention, the collapsing element of aremovable stent10 need not extend over the entire circumference of theremovable stent10 as a lasso or a noose, but can be a collapsing element that is a discontinuous type of lasso. Referring toFIG. 12, the collapsing element includes adiscontinuous lasso120 having afirst end122 and asecond end124. Thefirst end122 is attached or anchored to theproximal end22 of theremovable stent10. This attachment can be permanent if desired. Thesecond end124 of the collapsing element ordiscontinuous lasso120 is not attached to the stent, but is freely associated with thestent10. This allows for the free expansion of the stent as needed in vivo. At least a portion of the discontinuous lasso between its first and second ends is juxtaposed, adjacent or interwoven to theouter surface30 of thestent10.
• Adiscontinuous lasso120 can be awire128 that is woven in between thewires26,28 forming theremovable stent10. Thediscontinuous lasso120 is connected to theremovable stent10 at adiamond140 that is formed by the weaving of thewires142 comprising theremovable stent10. Thesecond end124 of thediscontinuous lasso120 includes aball126 which protrudes into thelumen32 of thestent10, thereby allowing the user access to thediscontinuous lasso120 by insertion of aremoval tool150 into the lumen of thestent10. The diameter of theball124 is slightly larger than the diagonal diameter of thediamond140, thereby maintaining theball126 within theinner lumen32 of thestent10. When theremovable stent10 is expanded, theball126 is seated partly within adiamond140. Theremovable stent10 can, therefore, freely expand to any given cross-sectional diameter without being restricted by its collapsing element. The design of a discontinuous lasso type of constricting element allows for a freely associatedsecond end124 which does not restrict expansion of theremovable stent10.
• Referring toFIGS. 14 & 15, in order to collapse and remove a stent having a discontinuous lasso type of collapsingelement120, aremoval tool150 is used. An example of such a tool is shown inFIG. 14. Theremoval tool150 can be configured as a cylindrically shaped tube having aslot152 disposed at its end. The removal tool should be sufficiently rigid so as to allow the user to easily maneuver and engage theball126 of the collapsingelement122 into theslot152. Theslot152 is slid underneath theball126 of the collapsing element120 (FIG. 14), thereby lifting theball126 out of its seating within thestent10. Once theball126 is lifted, theremoval tool150 is twisted, wrapping the wire of thediscontinuous lasso128 around the outer surface of theremoval tool150. Because the pulling force of thediscontinuous lasso120 and the holding force of theremovable stent10 are at thetip154 of the removal tool150 (FIG. 14) theproximal end22 of thestent10 is easily collapsed (FIG. 15), enabling the physician to pull or withdraw the collapsed stent away from the implanted site in vivo.
• In another embodiment of the invention, shown in FIGS.16 to21, theremovable stent10 includes one or more eyelets orloops170 formed at or near the ends of the elongate elements orwires172 of thestent10. Theloops170 can be shaped either before or after thewires172 are assembled into the mesh-structure that forms thestent10. The shape of theloops170 can include “p”-shaped, helical, twisted, oval, circular, diamond, square or any other similar configuration that forms a hole capable of receiving and/or capturing a cord-like member, such as alasso80. The design and alignment of theloops170 at the ends of thewire elements172 are configured to prevent theloops170 and/or lasso80 from projecting or extending into the interior of thestent10. This, in turn, reduces the potential for encrustation or clot formation within the lumen of the implantedstent10.
• In one embodiment, at least one end of thewire element172 is twisted or wound into aloop170. Although the material characteristics of thewire element172 maintain the end of thewire element172 in a loop configuration, a resistance laser weld, crimp or other connection can be made at the location on theloop170 where thewire element172 crosses over itself. The resistance weld can be used to further secure the end of thewire element172 in a permanent loop arrangement.
• In an alternate embodiment, theelongate element172 can be laser-cut, stamped or punched from a sheet of material. As shown inFIG. 17, at least oneloop170 is formed at an end of the stampedelement172. Other embodiments of forming theloop170, though not specifically described herein, are also included within the scope of the claimed invention.
• Referring toFIG. 16, the mesh-structure of thestent10 is formed from two sets or groups ofparallel wires172. The first set ofparallel wires174 is placed at approximately a 90 degree angle with respect to the second set ofparallel wires176, forming a diamond-shapedpattern178 ofwire elements172. However, the actual placement of the two sets ofparallel wires174,176 may vary within the range of 10 degrees to 170 degrees. As shown inFIG. 16, aloop170 is formed at or near an end of everyother wire172 of the first set ofparallel wires174. The configuration of the first set ofwires174, in particular the placement of thewires172 so that each wire end rests on the external surface of a wire element172 (whereby the external surface of thewire element172 corresponds to theoutside surface82 of thestent10, not shown) from the second set ofwires176, further enhances the constriction characteristics of thestent10. In addition, this configuration also prevents potential flaring of the distal end of thestent10 as theproximal end22 of thestent10 is constricted or collapsed during stent removal. Flaring of the distal end of thestent10 not only impedes stent removal, but also causes the wire ends to anchor or embed into the wall tissue of the lumen. Thus, the loop design at the ends of thewire elements172 also mitigates potential tissue trauma associated with the stent removal procedure.
• In another embodiment of the invention, shown inFIG. 18, a total of at least threeloops170 are formed at the ends of thewires172 near theproximal end22 thestent10. In general, theloops170 are formed at the ends of thewires172 and a lasso-type element is woven through theloops170. Placement of theloops170 at the ends of thewires172 improves user accessibility to the lasso for facilitatedstent10 removal. In another embodiment, theloops170 can be formed anywhere within the region approximately twodiamonds178 distal to or 10 mm or 5 mm (0.39 inches or 0.020 inches) from the ends of thewire elements172.
• As shown inFIGS. 19 and 20, thelasso80 type collapsing element is woven or threaded through theloops170 of thestent10. In one embodiment, thelasso80 type collapsing element is a flexible closed-loop or ring-like structure. When thestent10 is in an expanded configuration, portions of thelasso80 extending between eachloop170 are easily accessible for engagement from the end of thestent10 in vivo using a standard alligator gripper orcustom removal tool178. As such, thestent10 is removed from the lumen of the patient by twisting theremoval tool178 so that thelasso80 wraps around the outer surface of theremoval tool178 or pulling the lasso axially. Because the pulling force of thelasso80 and the holding force of theremovable stent10 are at the tip of theremoval tool178, theproximal end22 of thestent10 is easily collapsed, enabling the physician to pull or withdraw thecollapsed stent10 away from the implanted site in vivo. Referring toFIG. 21, during constriction of theproximal end22 of thestent10, thelasso80 is configured so that it acquires a folded profile. The folded configuration of thelasso80 prevents portions of thelasso80 from hanging into the lumen and causing associated blockages or clot formations. As such, any slack or folds in thelasso80 is generally held or captured between the external surface of thestent10 and the tissue wall of the patient's lumen.
• In an alternate embodiment, the collapsing element of theremovable stent10 need not extend over the entire circumference of theremovable stent10 as a lasso or a noose does. As shown inFIGS. 22 and 23, the collapsing element can be adiscontinuous spiral180 or c-shaped182 clip member. In general, thespiral180 or c-shaped182 clip member can be fabricated from a rigid or semi-rigid material. As with theelongate elements172 of thestent10, theclip member180,182 can be fabricated from a variety of materials including, but not limited to, laser cut, woven, braided, or stamped. Various other material types and configurations may also be used provided that the type of material or structure is biocompatible and of sufficient rigidity so as to support constriction of thestent10. Examples of suitable biocompatible materials include, but are not limited to, stainless steel, alloys, composite materials, plastics, or other non-metallic materials such as an elastic polymer or rubber, medical-grade nylon or polyester.
• In one embodiment, the spiral or c-shapedmember180,182 is attached or clipped onto the external surface of thestent10. To constrict thestent10, a removal tool is maneuvered between the external surface of thestent10 and the lumen of the patient and engages/grasps theends184 of theclip member180,182. Using the tool, theends184 of theclip member180,182 are then moved toward each other and/or, depending on the desired degree of constriction of thestent10, past each other. Radial constriction of theclip member180,182 causes inward collapse or radial contraction thestent10. In an alternate embodiment, one end of theclip member180,182 is attached or secured to the stent10 (not shown). As such, the removal tool need only grasp or engage the unattached end of theclip member180,182, moving the free end of theclip member180,182 toward and/or past the secured end. As with the previous embodiment, constriction of the clip member produces radial contraction of thestent10, without causing thestent10 to rotate within the lumen of the patient.
• Due to the dynamic nature of living tissue, ingrowth can occur around an implanted stent. As a result, it is sometimes necessary for the physician to resect or cut the implanted stent away from the surrounding tissue. As such, heated methods of resection are often used to cut the stent out. Therefore, a lassotype collapsing element120 can be a wire constructed of a material that is resistant to heat during resection, such as a flexible carbon fiber substance. In addition, thediscontinuous lasso120 can be coated with an anti-adhesive substance such as heparin, or other pharmaceutical or chemical agent which aids in preventing adherence of tissue to the collapsing element.
• As disclosed above, a collapsing element can be configured in a number of ways and is preferably designed so as to allow the user to grasp the stent and collapse the proximal end of the stent. It should be noted, however, that also included in the present invention is a removable stent having a collapsing element whose location is not at or restricted to the proximal end of the stent. For example, a collapsing element can be disposed anywhere along the length of the stent so long as the collapsing element is designed so as to be capable of collapsing an end of the stent. This allows for removal of the stent from an intraluminal site with minimal damage to adjacent tissue or intraluminal wall of the target site.
• A variety of tools or devices can be used to grasp the collapsing element of a removable stent. In addition to the removal tool as described above, stone or basket extractors or grasping forceps known in the art can be used with the present invention. For example, with a removable stent having a hinged hook type of collapsing element, a physician can use a basket extractor to engage and grasp the hinged hooks. Using a stone extractor, for example, the physician will first position the hooks into their upright position (while viewing the deployed stent through a cystoscope). Once upright, the physician then engages the wires of the extractor with the hooks, thereby grasping the stent by the collapsing elements. By collapsing the wires of the extractor, the physician also pulls on the collapsing elements, thereby collapsing the proximal end of the stent. Once collapsed, the stent can then be pulled into the sheath of the cytoscope.
• An additional aspect of the present invention comprises a removal attachment or grasper for use with a delivery tool to engage or grasp the removable stent.FIG. 24 shows a view of aremoval attachment200 that can be used with a removal tool. Alternatively, such an attachment can be attached or used with a stent delivery tool. Removal tools suitable for use with a removal attachment include those described herein as well as others known in the art, such as the Urolume Delivery System. Stent delivery tools suitable for use with a removal attachment include the Urolume Delivery System.
• The removal attachment includes abase portion202 that is tubular in shape. Thebase portion200 has afront end208 and aback end210. Thebase portion202 includes anelement204 disposed at theback end210 which locks theremoval attachment200 to a delivery tool such as a grapple. Thefront end208 of theremoval attachment200 includes prong(s)212 that are configured or shaped as curved finger-like projections that extend outward or away from theremoval attachment200. The prong(s)212 can be manipulated so as to grasp or hook a collapsing element of a removable stent. One aspect of the removal attachment that is particularly advantageous to achieving the goals of the invention is that it is designed to be adaptable with a wide variety of tools used in the art for delivery and/or removal of a stent.
• Method For Extraction of a Removable Stent
• The methods and devices of the present invention provide simple, accurate and stable removal of a stent or prosthesis from an intraluminal or other, site in vivo. The features of the invention, as described herein, provide a removable stent and system that is reliable and less awkward or cumbersome for the physician to use.
• The present invention can be used for a variety of medical treatments where removal of a stent from a patient is or may be desirable. For example, in the treatment of an enlarged prostate gland, a stent is often placed in the patient's urethra, intraluminally at the site of compression by the enlarged prostate. The deployed stent is often intended as a permanent means of providing support and radial expansion to the constricted urethra so that urine flow from the bladder through the compressed site is remedied. However, failure of the implanted stent to function properly can occur. For example, over time, tissue ingrowth from the urethral wall through the openings of the stent wall can occur, resulting in reobstruction or restenosis of the lumen. The present invention is particularly advantageous in that it has elements allowing for its easy access, and removal in vivo should the need arise to remove or explant the stent after deployment. Therefore, the present invention can function as a permanently implanted stent or as a temporary or removable stent in vivo. Use of the present invention in medical indications requiring stent treatment adds a precautionary measure not provided in permanent stent implants or prostheses.
• Depending upon the location of the deployed stent and/or the physician's preference, a removable stent can be extracted using a removal tool and withdrawn into a catheter or a sheath of a viewing instrument. For example, as shown inFIG. 10, with aremovable stent10 having a lasso type of collapsingelement80, aremoval tool101 having ahooked end102 is first inserted into a patient's urethra through a viewing instrument, up to the site of the deployed stent. Once at the stent, the physician engages the hooked end of theremoval tool101 with theloop84 portion of the collapsingelement80. The physician maneuvers by twisting or rotating the removal tool so as to cause thelasso80 to constrict upon itself. Tightening of thelasso80 around thestent10 collapses theproximal end22 of the removable stent10 (FIG. 11). The collapsed end of the removable stent is then easily aimed into the lumen of an extraction catheter or the sheath of a cystoscope. Once inside the lumen, thestent10 is extracted by further pulling on thelasso80, which is coupled to the stent. The remainder of thestent10 is then pulled away from and out of its in vivo site.
• Alternatively, as described previously, where a stent having an alternative collapsing element configuration is to be removed, there are a variety of commercially available devices that can be used as the removal tool. If the deployed stent comprises a swinging hook type of collapsing element, a removal tool such as a loop snare, wire basket stone extractor, stone forceps, or other device can also be used to grasp and withdraw the deployed stent. These types of devices are known in the art, available commercially, and described, for example, in U.S. Pat. No. 5,330,482. A basket retrieval device can be used to catch or engage the stent from its internal lumen. As described previously, when deployed in a target site, a removable stent can have a hinged hook collapsing element in a down position so as not to impede the fluid flow. In order to collapse the proximal end of the stent, the physician can position the hook(s) into an upright or up position. The resistive characteristics of the hinge portion of the hook maintains the collapsing element in the up position, allowing the physician to manipulate the wires of the basket retrieval device until they engage with the hooks. Retraction of the basket pulls on the collapsing element, which collapses the proximal end of the stent. The stent is withdrawn and removed from the patient.
• The systems and methods of the present invention provide accurate, easy to use and stable grasping of a stent allowing for its safe removal from a target site in vivo. The features of the invention, as described herein, also provide a removable stent that is less awkward or cumbersome for the physician to use.
• Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.
• All publications and patent applications in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

Claims (29)

1. A removable stent comprising a stent and a lasso:

the stent having an inner lumen, an outer surface and two opened ends, wherein at least one opened end is collapsible; and

the lasso positioned toward the end of the stent that is collapsible, wherein a portion of the lasso is engageable with a removal tool within the inner and/or outer lumen of the stent.

2. The removable stent ofclaim 1, further comprising a lasso having a loop disposed within the inner lumen of the removable stent.

3. A removable stent, comprising:

a stent having an inner lumen, an outer surface, and two opened ends, wherein at least one opened end is collapsible; and

a collapsing element having first and second ends, the first end coupled to the stent and the second end being free, wherein at least a portion of the collapsing element between its first and second end is coupled to the outer surface of the stent, and the second end is substantially within the inner lumen of the stent.

4. The removable stent ofclaim 3 further comprising a ball coupled to the second end of the collapsing element.

5. A removable stent comprising:

a stent having an inner lumen, an outer surface, and two opened ends, wherein at least one opened end is collapsible; and

a collapsing element located on said stent, said collapsing element being movable between a first and a second position, wherein the collapsing element is in a down position when in the first position.

6. The removable stent ofclaim 5 wherein the collapsing element is a hinged hook

7. A stent removal system comprising:

a removable stent having an inner lumen, an outer surface, two opened ends, wherein at least one opened end is collapsible;

a lasso positioned toward the end of the stent that is collapsible, wherein a portion of the lasso is disposed within the inner and/or outer lumen and includes an engagement coupling for receiving a removal tool; and

a removal tool having at least one end configured for engaging with said engagement coupling.

8. The system ofclaim 7 wherein said engagement coupling comprises at least one of a loop, a ball, and a hook

9. A stent removal system comprising:

a stent having an inner lumen, an outer surface, and two opened ends, wherein at least one opened end is collapsible;

a collapsing element having a first end and a second end, the first end coupled to the stent and the second end being free, wherein a portion of the collapsing element between the first and second end is in contact with the outer surface of the stent and the second end is within the inner lumen of the stent; and

a removal tool having at least one end configured to engage said free end of the collapsing element.

10. The system ofclaim 9 wherein the collapsing element comprises a wire having a first end and a second end, wherein the first end is coupled to the outer surface of the removable stent and the second end is at least one of a ball, a loop and a hook disposed within the inner lumen of the stent.

11. A stent removal system comprising:

a stent having an inner lumen, an outer surface, and two opened ends, wherein at least one opened end is collapsible;

a collapsing element movable between a first and a second position, wherein the collapsing element is normally placed in the first position when deployed in a target site in vivo; and

a removal tool having a first and a second end, wherein the first end is configured to engage the collapsing element.

12. The system ofclaim 11, further comprising a grasper element configured for attachment to the removal tool.

13. The system ofclaim 12 wherein the grasper element is configured for attachment to a stent delivery tool.

14. A removable stent comprising:

a stent having an inner surfact, an outer surface, and two open ends, wherein at least one open end is collapsible and includes at least one loop disposed towards said open end; and

a collapsing element supported by said at least one loop.

15. The removable stent ofclaim 14 wherein portions of said collapsing element extend between at least two loops, said portions begin accessible for engagement with a removal tool.

16. The removable stent ofclaim 14 wherein said collapsing element contains flexures enabling a folded profile during constriction of said open end of said stent.

17. A removable stent comprising:

a stent having an inner lumen, an outer surface, and two open ends, wherein at least one open end is collapsible; and

a collapsing element clipped onto said external surface of said stent.

18. The removable stent ofclaim 17 wherein said collapsing element is c-shaped.

19. The removable stent ofclaim 17 wherein said collapsing element is spiral shaped.

20. The removable stent ofclaim 17 wherein ends of said collapsing element are accessible for engagement with a removal tool maneuvered between said external surface of said stent and a lumen of a patient.

21. A method of removing a stent from a target site comprising:

providing a removable stent having an inner lumen, an outer surface, a collapsible end and a collapsing element, wherein at least a portion of said collapsing element contacts said outer surface of said removable stent;

maneuvering a tool toward said removable stent such that said tool engages said collapsing element;

compressing said collapsible open end of said removable stent through continued engagement of said collapsing element; and;

removing said removable stent from said target site.

22. The method ofclaim 21 wherein said tool is maneuvered within said inner lumen of said removable stent.

23. The method ofclaim 22 wherein said collapsing element comprises a lasso having a loop disposed within said inner lumen of said removable stent.

24. The method ofclaim 23 wherein said collapsing element comprises a wire having a first end and a second end;

said first end coupled to said stent and said second end being free, wherein a portion of said wire between the first end and said second end is in contact with said outer surface of said stent and said second end is within said inner lumen of said stent.

25. The method ofclaim 24 wherein said second end of said wire comprises at least one selected from the group consisting of a ball, a loop, and a hook

26. The method ofclaim 21 wherein said collapsing element is movable between an up and a down position when deployed in said target site in vivo.

27. The method ofclaim 26 wherein said collapsing element is a hinged hook.

28. The method ofclaim 21 wherein said tool is maneuvered toward said collapsible end of said stent and said collapsing element comprises a closed-loop structure woven through and accessible at said collapsible end.

29. The method ofclaim 21 wherein said tool is maneuvered between said outer surface of said stent and a lumen at said target site.

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