Patent Application
20100204770
The present invention is directed to endoluminal prostheses for use in a body lumen. More particularly, the present invention is directed to a stent delivery system including a recapture component for partially collapsing a deployed stent in situ to permit repositioning of the stent.
A wide range of medical treatments are known that utilize “endoluminal prostheses.” As used herein, endoluminal prostheses are intended to mean medical devices that are adapted for temporary or permanent implantation within a body lumen, including both naturally occurring and artificially made lumens. Examples of lumens in which endoluminal prostheses may be implanted include, without limitation: arteries, such as those located within the coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; biliary tract; urethra; trachea; hepatic shunts; and fallopian tubes.
Various types of endoluminal prostheses are also known, each providing a component for modifying the mechanics of the targeted luminal wall. For example, stent prostheses are known for implantation within body lumens for providing artificial radial support to the wall tissue, which forms the various lumens within the body, and often more specifically within the blood vessels of the body.
To provide radial support to a blood vessel, such as one that has been widened by a percutaneous transluminal coronary angioplasty, commonly referred to as “angioplasty,” “PTA” or “PTCA”, a stent is implanted in conjunction with the procedure. Under this procedure, the stent may be collapsed to an insertion diameter and inserted into a body lumen at a site remote from the diseased vessel. The stent may then be delivered to the desired treatment site within the affected lumen and deployed, by self-expansion or radial expansion, to its desired diameter for treatment.
Recently, flexible stented valve prostheses and various delivery devices that can be delivered transvenously using a catheter-based delivery system have been developed for heart and venous valve replacement. These stented valves include a collapsible prosthetic valve attached to the interior of a tubular frame or stent, which can be either self-expanding or balloon expandable. The stented valves can also include a non-porous tubular portion or “stent graft” that can be attached to the interior or exterior of the stent to provide a generally tubular internal passage for the flow of blood when the valve leaflets are open. The graft can be separate from the valve and it can be made from any suitable biocompatible material including, but not limited to, fabric, a homograft, porcine vessels, bovine vessels, and equine vessels. The stented valve can be reduced in diameter, mounted on a catheter, and advanced through the circulatory system of the patient. Once the stented valve is positioned at the delivery site, the stent frame is expanded to hold the valve firmly in place. The prosthetic valve survives the compression and subsequent expansion in fully working form. One embodiment of a stented valve is disclosed in U.S. Pat. No. 5,957,949 to Leonhardt et al. entitled “Percutaneous Placement Valve Stent”, which is incorporated by reference herein in its entirety.
In all stent applications, particularly in stented valve applications, a fundamental concern is that the prosthesis be deployed in the vessel at the target location as precisely as possible. In an application where a stent is used to deliver therapeutic radiation to a target location, proper positioning of the prosthesis is vital to the efficacy of the treatment. However, accurate positioning of the stent prosthesis may be difficult due to complexities in the anatomy as well as other factors, and an initial deployment of the stent prosthesis may result in a less than optimal positioning or, even worse, an inoperable positioning. Thus there is a need in the art for a stent delivery system that permits in situ repositioning of a deployed stent that is less that optimally or improperly positioned.
Embodiments herein are directed to a stent delivery system for repositioning a deployed stent in situ. The stent delivery system includes a recapture component movable between a collapsed configuration and an expanded configuration. A deployable stent is connected to the recapture component such that the stent, after deployment may be at least partially collapsed when the recapture component is moved to the collapsed configuration. The stent and recapture component may be disconnected from each other in situ to allow for removal of the stent delivery system.
The foregoing and other features and advantages of the invention will be apparent from the following description of embodiments thereof as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. The drawings are not to scale.
Specific embodiments of the present invention are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Although the description of the invention is in the context of treatment of blood vessels, and venous and cardiac valve replacement, the invention may also be used in any other body passageways where it is deemed useful. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.
In the embodiment shown in
In addition, stent delivery system includes an outer shaft component or outer tube 106 having a proximal end 110 coupled to hub 116 and a distal end 112 coupled to balloon 108. In the coaxial catheter construction of the illustrated embodiment, guidewire shaft 118 extends within outer tube 106 such that an annular inflation lumen 114 is defined between an inner surface of outer tube 106 and an outer surface of guidewire shaft 118. Other types of catheter construction are also amendable to the invention, such as, without limitation thereto, a catheter shaft formed by multi-lumen profile extrusion. Inflation lumen 114 extends between proximal and distal ends 110, 112 of outer catheter shaft 106 to allow inflation fluid received through an inflation port of hub 116 to be delivered to balloon 108. As would be understood by one of ordinary skill in the art of balloon catheter design, hub 116 provides a luer hub or other type of fitting that may be connected to a source of inflation fluid and may be of another construction or configuration without departing from the scope of the present invention.
A stent 130 is mounted over a recapture component 105 that is used to partially collapse and reposition stent 130 after deployment. Recapture component 105 is movable between a collapsed configuration and an expanded configuration. In the embodiment depicted in
Referring now to
Loops 134 are positioned circumferentially around balloon 108. In one embodiment, as shown in
Referring back to
As previously explained, sets of loops 134 are longitudinally aligned along the length of balloon 108. Tether 140 may be longitudinally woven or laced through loop lumens 136 and openings 128 of each row of longitudinally aligned loops 134. More particularly, tether 140 is laced in a distal direction along the length of the balloon, then back in a proximal direction along the length of the balloon, and so forth until the single line of tether 140 is woven through all rows of longitudinally aligned loops 134. If each set of loops 134 has an odd number of loops (for example, when loops 134B occur at three locations around the circumference of balloon 108B as explained above with reference to
In another embodiment, multiple tethers 140 may be utilized to simplify releasably connecting balloon 108 and stent 130 together. For example, independent tethers for each row of longitudinally aligned loops 134 may be utilized to simplify the lacing between balloon 108 and stent 130 and to lower friction when removing tethers in situ by pulling the proximal ends thereof. For example, when loops 134B occur at three locations around the circumference of balloon 108B as explained above with reference to
Tether 140 is an elongate flexible filament of biocompatible material having sufficient strength to aid in collapsing stent 130. In one embodiment, tether 140 is a monofilament. In various other embodiments, tether 140 may be a braid of a plurality of filaments of the same or different materials. In still other embodiments, tether 140 may include a braided sheath with a single filament core, or a braided sheath with a braided core. Tether 140 is constructed from a material that will not stretch and/or may be pre-stressed to prevent the tether from elongating during use. Suitable biocompatible materials for tether 140 include but are not limited to nylon, polyethylene, and polyester, as well as other high strength suture materials. In an embodiment, tether 140 may include one or more pre-stretched filaments of an ultra high molecular weight polyethylene, such as a filament made from DYNEEMA fibers. In an embodiment, tether 140 may also include a hydrophilic coating to aid in removing the tether from balloon 108 and stent 130 after proper deployment. Various embodiments hereof include tethers having diameters in the range of 0.015 inches and 0.050 inches in diameter. However, depending on the application, tethers having a diameter smaller than 0.015 inches or larger than 0.050 inches may be used.
Stent 130 may have any suitable configuration known in the art. For example, as shown in
As described in the embodiment of
In any of the embodiments described herein, the stent may include a valve located therein capable of blocking flow in one direction. The valve may be sealingly and permanently attached to the interior surface of the stent and/or graft material enclosing or lining the stent. The graft material may be a low-porosity woven fabric, such as polyester, Dacron fabric, or PTFE, which creates a one-way fluid passage when attached to the stent. The valve may be a bovine or porcine valve treated and prepared for use in a human, or may be a mechanical valve or a synthetic leaflet valve. For example, the stent may be a percutaneously implanted bovine or porcine valve treated and prepared for use in a human and sewn inside a laser-welded stent such as that described in U.S. Pat. No. 5,957,949, the contents of which were previously incorporated by reference. When a tissue valve is located within the stent, care should be taken that tether 140 does not pierce the tissue.
In one embodiment, stent 130 is balloon expandable. Deployment of balloon expandable stent 130 is accomplished by tracking stent delivery system 100 through the vascular system of the patient until stent 130 is located within a stenosis at a predetermined treatment site. Once positioned, a source of inflation fluid is connected to an inflation port of hub 116 such that balloon 108 is inflated to expand stent 130 by the radial force of the balloon as is known to one of ordinary skill in the art. When fully expanded, stent 130 contacts the vascular wall to maintain the opening thereof. Stent deployment can be performed following treatments such as angioplasty, or during initial balloon dilation of the treatment site, which is referred to as primary stenting.
In another embodiment, stent 130 may be self-expanding such that balloon 108 is used only for repositioning of stent 130 as described above. Deployment of stent 130 may be facilitated by utilizing shape memory characteristics of a material such as nickel-titanium (nitinol). More particularly, shape memory metals are a group of metallic compositions that have the ability to return to a defined shape or size when subjected to certain thermal or stress conditions. Shape memory metals are generally capable of being deformed at a relatively low temperature and, upon exposure to a relatively higher temperature, return to the defined shape or size they held prior to the deformation. This enables the stent to be inserted into the body in a deformed, smaller state so that it assumes its “remembered” larger shape once it is exposed to a higher temperature, i.e., body temperature or heated fluid, in vivo. Thus, self-expanding stent 130 can have two states of size or shape, a contracted or compressed configuration sufficient for delivery to the treatment site and a deployed or expanded configuration having a generally cylindrical shape for contacting the vessel wall. In another embodiment in which stent 130 is self-expanding, stent 130 may be constructed out of a spring-type or superelastic material. When a self-expanding stent is used with the stent delivery system 100, a sheath (not shown) may be provided to surround and contain self-expanding stent 130 in a contracted or compressed position. Once self-expanding stent 130 is in position at a site of a stenotic lesion, the sheath may be retracted, thus releasing stent 130 to assume its expanded or deployed configuration.
Some examples of self-expanding and balloon-expandable stents that are suitable for use in embodiments of the present invention are shown in U.S. Pat. No. 4,733,665 to Palmaz, U.S. Pat. No. 4,800,882 to Gianturco, U.S. Pat. No. 4,886,062 to Wiktor, U.S. Pat. No. 5,133,732 to Wiktor, U.S. Pat. No. 5,292,331 to Boneau, U.S. Pat. No. 5,421,955 to Lau, U.S. Pat. No. 5,776,161 to Globerman, U.S. Pat. No. 5,935,162 to Dang, U.S. Pat. No. 6,090,127 to Globerman, U.S. Pat. No. 6,113,627 to Jang, U.S. Pat. No. 6,663,661 to Boneau, and U.S. Pat. No. 6,730,116 to Wolinsky et al., each of which is incorporated by reference herein in its entirety.
In any of the embodiments described herein, stent delivery system 100 may be modified to be of a rapid exchange (RX) catheter configuration without departing from the scope of the present invention such that guidewire shaft 118 extends within only distal portion 104. In such an embodiment, a proximal portion of outer catheter shaft 106 may include a metal hypotube with a guidewire transition area having a proximal guidewire port being positioned proximal of balloon 108.
Repositioning of stent 130 may be facilitated by the use of a guide catheter having reinforcement, such as a metal band, at the distal tip thereof. The guide catheter is placed over proximal shaft outer tube 106 and tether 140 with the distal reinforcement positioned slightly proximal of balloon 108. The guide catheter prevents deformation of outer tube 106 when tether 140 is pulled proximally to collapsible stent 130, with the distal reinforcement protecting the guide catheter's distal tip from being cut by tether 140 during the collapsing procedure. In an embodiment, the guide catheter includes a braided layer for shaft support, and includes a reinforced distal tip, such as a metal band surrounding the distal tip as described above, to avoid damage to the guide catheter tip when tension is applied to tether 140. Suitable embodiments of the guide catheter may include the EXPORT guide catheter or the LAUNCHER guide catheter, both manufactured by Medtronic, Inc. of Minneapolis, Minn.
A distal portion of another embodiment of stent delivery system 400 is illustrated in
In an embodiment, hooks 446 may be wires having a hook or curved shape that are sufficiently stiff to engage stent 130. Wire hooks 446 may be attached to balloon 408 during a post-processing step, such as by melting the material of the balloon wall around each wire such that the hook of the wire radially extends from an outside surface of the balloon, or alternatively by adhesive. Hooks 446 may be positioned circumferentially around balloon 408 with sets of hooks 446 longitudinally spaced along the length of balloon 408 as described above with respect to loops 134. As shown in
If it is desired to adjust the positioning of stent 130 after initial deployment, balloon 408 is deflated with hooks 446 engaged into stent 130. As stent 130 is directly connected to balloon 408, deflation of balloon 408 urges stent 130 into at least a partially collapsed configured such that stent 130 may be repositioned and redeployed. Once stent 130 is positioned precisely at the target location and no further adjustments are desired, balloon 408 and stent 130 are disconnected such that stent delivery system 400 may be removed from the patient. In order to remove stent delivery system 400, balloon 408 may be manufactured to deflate in a particular way such that hooks 446 disengage stent 130.
Another embodiment of stent delivery system 500 is illustrated in
More particularly, tubular component 550 is expanded and contracted by relative movement between an inner tube 556 and an outer tube 558 that are operably attached to tubular component 550, as discussed below. Tubular component 550, inner tube 556, and outer tube 558 cooperate to provide an expansion framework that is controlled to be movable between a reduced-diameter or collapsed configuration and an enlarged-diameter expanded configuration. Inner tube 556 extends within the lumen of outer tube 558, and is movable in an axial direction along and relative to outer tube 558. Coaxial tubes 556, 558 extend the length of stent delivery system 500 such that the proximal ends thereof (not shown) extend out of the patient and may be manipulated by a clinician. A proximal end 549 of tubular component 550 is attached to a distal end 559 of outer tube 558 and a distal end 551 of tubular component 550 is attached to a distal end 557 of inner tube 556. While holding a proximal end 564 of outer tube 558 fixed, inner tube 556 may be proximally retracted within outer tube 558. When inner tube 556 is proximally retracted, the attachment point between tubular component 550 and outer tube 558 remains fixed such that tubular component 550 radially expands.
Although embodiments are described with inner tube 556 being movable relative to outer tube 558 to expand tubular component 550, it should be apparent to one of ordinary skill in the art that tubular component 550 is expanded by shortening the distance between ends 549, 551 thereof. Thus, in another embodiment, tubular component 550 may be expanded by distally advancing outer tube 558 while holding inner tube 556 stationary. In addition, tubular component 550 may be expanded by a combination of distally advancing outer tube 558 and proximally retracting inner tube 556. Tubes 556, 558 may include radiopaque markers, such as metal annular bands 562, at distal ends 557, 559, respectively, to aid in fluoroscopic visualization of system 500 during delivery and stent deployment.
Tubular component 550 may be attached to outer tube 558 and inner tube 556 in any suitable manner known in the art. For example, the connection may be formed by welding, such as by resistance welding, friction welding, laser welding or another form of welding such that no additional materials are used to connect tubular component 550 to tubes 556, 558. Alternatively, tubular component 550 can be connected to tubes 556, 558 by soldering, by the use of an adhesive, by the addition of a connecting element there between, or by another mechanical method.
Referring back to
Tubular component 550 may have any suitable configuration known in the art. For example, as shown in
Mechanically-expandable tubular components according to embodiment hereof are preferably constructed of implantable polymeric or metallic materials having good mechanical strength while maintaining a minimized delivery profile. Non-exhaustive examples of polymeric materials for the tubular component are polyurethane, polyethylene terephalate (PET), nylon, polyethylene, PEBAX, or combinations of any of these, either blended or co-extruded. Non-exhaustive examples of metallic materials for the tubular component are stainless steel, cobalt based alloys (605L, MP35N), titanium, tantalum, superelastic nickel-titanium alloy, or combinations of any of these.
While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.
