US 20050080480 A1
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.
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 of
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 of
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 of
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 of
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 of
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 of
13. The system of
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 of
16. The removable stent of
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 of
19. The removable stent of
20. The removable stent of
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 of
23. The method of
24. The method of
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 of
26. The method of
27. The method of
28. The method of
29. The method of
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.
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.
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.
The removable stent 10 is an intraluminal prosthesis or device having proximal 22 and distal ends 24 that are open. The removable stent is generally tubular in shape and has an outer surface 30 which contains an inner lumen 32 that extends axially between collapsible proximal 22 and distal ends 24. A removable stent includes collapsing elements 40, which aid in collapsing or compressing the stent 10 for its removal from an intralumenal site. The collapsing element 40 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 the proximal end 22.
A removable stent 10 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.
In a preferred embodiment, as shown in
A collapsing element 40 can be of a variety of structural configurations. The collapsing element 40 is preferably located at or near the proximal end 22 of the removable stent 10 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 collapsing element 40 designed as a clasping structure that is located within the inner lumen 32 of the removable stent 10 as shown in
A hinged hook type of collapsing element 40 includes an upper region that is curved or shaped as a hook 44. The lower or bottom portion 46 of the collapsing element 40 is configured so as to enclose or wrap around a wire 43 of the stent so as to function as a hinge. The collapsing element 40 can be attached to a stent wire 43 at the inner surface of the removable stent. A hinged hook 44 can be designed or configured so as to snap onto a stent wire 43 with a portion 46 of the hinged hook disposed toward the outer surface of the stent. Once snapped into place, the hinged hook 44 can be pushed or slid along the stent wire 43, passing underneath a crossing wire 41, so as to position the book 44 underneath a cross wire 42 as shown in
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 to
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 of removal tools 62 can be used to remove a stent 10 of the present invention, as will be apparent to one skilled in the art. Referring to
In a preferred embodiment, a removal tool 62 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 the hooks 40 as shown in
As illustrated again in
A discontinuous lasso 120 can be a wire 128 that is woven in between the wires 26, 28 forming the removable stent 10. The discontinuous lasso 120 is connected to the removable stent 10 at a diamond 140 that is formed by the weaving of the wires 142 comprising the removable stent 10. The second end 124 of the discontinuous lasso 120 includes a ball 126 which protrudes into the lumen 32 of the stent 10, thereby allowing the user access to the discontinuous lasso 120 by insertion of a removal tool 150 into the lumen of the stent 10. The diameter of the ball 124 is slightly larger than the diagonal diameter of the diamond 140, thereby maintaining the ball 126 within the inner lumen 32 of the stent 10. When the removable stent 10 is expanded, the ball 126 is seated partly within a diamond 140. The removable stent 10 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 associated second end 124 which does not restrict expansion of the removable stent 10.
In another embodiment of the invention, shown in FIGS. 16 to 21, the removable stent 10 includes one or more eyelets or loops 170 formed at or near the ends of the elongate elements or wires 172 of the stent 10. The loops 170 can be shaped either before or after the wires 172 are assembled into the mesh-structure that forms the stent 10. The shape of the loops 170 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 a lasso 80. The design and alignment of the loops 170 at the ends of the wire elements 172 are configured to prevent the loops 170 and/or lasso 80 from projecting or extending into the interior of the stent 10. This, in turn, reduces the potential for encrustation or clot formation within the lumen of the implanted stent 10.
In one embodiment, at least one end of the wire element 172 is twisted or wound into a loop 170. Although the material characteristics of the wire element 172 maintain the end of the wire element 172 in a loop configuration, a resistance laser weld, crimp or other connection can be made at the location on the loop 170 where the wire element 172 crosses over itself. The resistance weld can be used to further secure the end of the wire element 172 in a permanent loop arrangement.
In an alternate embodiment, the elongate element 172 can be laser-cut, stamped or punched from a sheet of material. As shown in
In another embodiment of the invention, shown in
As shown in
In an alternate embodiment, the collapsing element of the removable stent 10 need not extend over the entire circumference of the removable stent 10 as a lasso or a noose does. As shown in
In one embodiment, the spiral or c-shaped member 180, 182 is attached or clipped onto the external surface of the stent 10. To constrict the stent 10, a removal tool is maneuvered between the external surface of the stent 10 and the lumen of the patient and engages/grasps the ends 184 of the clip member 180, 182. Using the tool, the ends 184 of the clip member 180, 182 are then moved toward each other and/or, depending on the desired degree of constriction of the stent 10, past each other. Radial constriction of the clip member 180, 182 causes inward collapse or radial contraction the stent 10. In an alternate embodiment, one end of the clip member 180, 182 is attached or secured to the stent 10 (not shown). As such, the removal tool need only grasp or engage the unattached end of the clip member 180, 182, moving the free end of the clip member 180, 182 toward and/or past the secured end. As with the previous embodiment, constriction of the clip member produces radial contraction of the stent 10, without causing the stent 10 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 lasso type collapsing element 120 can be a wire constructed of a material that is resistant to heat during resection, such as a flexible carbon fiber substance. In addition, the discontinuous lasso 120 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.
The removal attachment includes a base portion 202 that is tubular in shape. The base portion 200 has a front end 208 and a back end 210. The base portion 202 includes an element 204 disposed at the back end 210 which locks the removal attachment 200 to a delivery tool such as a grapple. The front end 208 of the removal attachment 200 includes prong(s) 212 that are configured or shaped as curved finger-like projections that extend outward or away from the removal attachment 200. 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 in
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.