Patent Application
20090171434
The present invention relates to stents, stent-grafts and other intraluminally implantable prostheses, and more particularly to apparatus and methods for loading prostheses into delivery catheters and other prosthesis-confining structures.
A variety of treatment and diagnostic procedures involve devices intraluminally disposed within the body of the patient. Among these devices are stents, including braided stents as disclosed in U.S. Pat. No. 4,655,771 to Wallsten. The Wallsten prostheses or stents are tubular, braided structures formed of helically wound filaments. These stents typically are deployed in a reduced radius state using a delivery catheter including an outer tube. When the stent is positioned at the intended treatment site, the outer tube of the delivery catheter is withdrawn, allowing the stent to radially expand into a substantially conforming surface contact with a blood vessel wall or other lumen-defining tissue.
An alternative stent construction to the braided Wallsten features plastically deformable strands or elements, usually formed of a ductile metal. Examples of such stents are shown in U.S. Pat. Nos. 4,776,337 to Palmaz and 5,716,396 to Williams, Jr. These stents do not require outer tubes or other features to maintain them in the reduced-radius state during delivery. Radial expansion at the treatment site, however, requires a dilatation balloon or other mechanism for radially enlarging the stent.
Regardless of whether the stents are self-expanding or plastically deformable, they generally have an open mesh or open frame construction, or otherwise are formed with multiple openings to facilitate radial enlargements and reductions, and to allow tissue in-growth. Either type of stent may be used to support a substantially fluid-impermeable material, frequently but not necessarily elastic, to provide a stent-graft for shunting blood or other body fluids past a weakened or damaged area such a lesion or stricture.
The structural strands or filaments of braided stents may be formed of metal, typically stainless steel, alloys including cobalt and alloys including titanium. Alternatively, the strands may be polymeric, formed of materials such as polyethylene terephthalate (PET), polypropylene (PP), polyetheretherketone (PEEK), high density polyethylene (HDPE), polysulfone (PSO), polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polycarbonate urethane (PC/PU), and polyurethane (PU). As another alternative, the structural strands of stents may be formed of bioabsorbable materials. Metallic stents typically are stronger and more resilient than stents formed of other materials. Nevertheless, there is an increased demand for prostheses formed of polymeric materials or bioabsorbable materials, particularly for use in the treatment of benign diseases and in other situations in which a removable prosthesis or a prosthesis with bioabsorbable structural strands is desirable.
Because of their superior structural strength and resiliency, self-expanding metal prostheses are well suited for preloading into catheters and other prosthesis delivery devices that maintain the prosthesis in a reduced-radius state, facilitating intraluminal delivery of the prosthesis to a designated treatment site. In the case of a radially self-expanding stent or other prosthesis, preloading entails elastically deforming the device to the reduced-radius state and maintaining the device in that state against an internal elastic restoring force of the stent. Upon release of the stent from the delivery device at the designated treatment site, the device radially expands via its restoring force and contacts the surrounding tissue or lumen. Typically, the surrounding tissue or lumen maintains the stent or prosthesis in a slightly radial compressed state, so that the internal restoring force of the stent continues to act radially against the tissue to anchor the device thereat.
Systems with preloaded prostheses are more convenient for the physician and contribute to the success of the procedure. With a prosthesis preloaded into a delivery system, there is no need for the attending physician to radially compress or otherwise manipulate the prosthesis, and his or her attention is more appropriately directed to intraluminal guidance and placement of the prosthesis. A preloaded prosthesis eliminates the time that otherwise would be needed to load a prosthesis, and this is particularly advantageous in time-critical procedures.
Metallic stents, metallic stent-grafts and other metallic prostheses may usually be maintained in their radially-reduced states without experiencing any material reduction in resilience. These devices may be loaded into the delivery system several minutes or several months, or longer, ahead of the deployment procedure. In other words, the duration in the radially compressed state does not materially affect the resilient properties of a metallic stent.
As noted above, implantable prostheses may be formed of polymeric and biodegradable materials, either in total or in part. Certain biodegradable materials, like polymers, may be used to fabricate radially self-expanding stents. In many procedures, polymeric or bioabsorbable prostheses are preferred over metallic devices, for example, due to the relative ease of removing a device intended for temporary implantation, or the capacity to be absorbed into the body.
When maintained in the reduced-radius state under a constant load for any appreciable length of time, a prosthesis formed of polymeric or bioabsorbable material may, however, undergo permanent or plastic deformation. When released from the catheter or other delivery device, such prosthesis may radially self expand to a diameter considerably less than its relaxed-state diameter prior to preloading. This phenomenon is commonly referred to as stress relaxation or “creep”. This phenomenon is aggravated when a polymeric or bioabsorbable prosthesis is exposed to elevated temperatures in its reduced-radius state, for example during a sterilization procedure, which may be performed prior the outset of the prosthesis deployment procedure.
To counteract this phenomenon of stress relaxation or creep, the polymeric or bioabsorbable prosthesis may be sterilized and/or stored in its relaxed state, i.e., not significantly reduced radial state, until just before it is to be used. When the physician is about to begin a procedure, he or she may load the polymeric prosthesis into the delivery system. Consequently, the prosthesis remains compressed in the reduced-radius state only for a short time, perhaps only several minutes. While such a procedure counteracts the problem of creep, the procedure is, however, more difficult and time consuming.
Therefore, it is an object of the present invention to provide a simple and reliable system for loading and deploying a body-insertable and radially expandable prosthesis, in particular one including polymeric material.
Another object is to provide a prosthesis loading and deployment system that affords positive control over the position of the prosthesis, both during its loading and later during its deployment.
A further object is to provide a process for loading a radially expandable prosthesis into a deployment device or other confining structure, with increased ease and simplicity to facilitate loading at the beginning of a deployment procedure.
Another object is to enhance the utility of the inner catheter or member of a prosthesis deployment system.
Yet another object is to provide an apparatus for loading a radially expandable prosthesis into a delivery catheter or other confining structure that reduces the time required for loading, and minimizes the risk of damage to the prosthesis and other components.
To achieve these and other objects, there is provided an apparatus for loading a radially expandable prosthesis into a prosthesis confining structure for maintaining the prosthesis in a reduced-radius state, such as a compressed state for a self-expanding stent or prosthesis or a pre-delivery or quiescent state for a balloon-expandable stent or prosthesis. The apparatus includes a prosthesis capturing device with a proximal capturing section that forms a compliant enclosure. The compliant enclosure may be open at a proximal end to allow insertion of a radially expandable prosthesis in an enlarged-radius state, such as relaxed or quiescent state for a self-expanding stent or prosthesis and an enlarged state for a balloon-expandable stent or prosthesis, into the enclosure, whereby the prosthesis is surrounded or at least partially surrounded by the enclosure, including over a distal region of the prosthesis. The capturing device may further include an elongate enclosure moving section, insertable into and movable distally along a lumen or other passage of the prosthesis confining structure to locate the enclosure, and thus also locate the radially expandable prosthesis so surrounded by the enclosure, adjacent a proximal entrance of the passage. The apparatus may further include an elongate control device having a distal end region insertable into a radially expandable prosthesis in the enlarged-radius state. The distal end region may be adapted for a releasable engagement with a radially expandable prosthesis when surrounded by the prosthesis in a reduced-radius state. When in the releasable engagement, the prosthesis may track axial movement of the control device. The enclosure moving section, with the enclosure and a radially expandable prosthesis so located and with the prosthesis surrounding the distal end region of the control device, may be movable distally to draw the enclosure and the prosthesis into the passage to cause a progressive radial compression of the enclosure and prosthesis, radially contracting the prosthesis to the reduced-radius state about the distal end region to effect the releasable engagement.
In one embodiment, the axial length of the enclosure is such that the proximal region of the radially expandable prosthesis, which is selected for insertion into the enclosure, remains outside the enclosure following its insertion. In some embodiments, the proximal region of the selected prosthesis constitutes at least one-half of the prosthesis length. Then, the enclosure moving section is operable to pull the enclosure distally through the lumen of a prosthesis confining structure until the enclosure is free of the lumen, with the proximal region of the prosthesis remaining in the lumen, still releasably engaged with the control device. This may eliminate the need to pull the proximal capturing section out from between the prosthesis and the confining structure. In some embodiments, the capturing device does not pull the prosthesis as it is removed, as there is less need to pin down the prosthesis at the distal end and less need to push an exposed prosthesis distal end into the confining structure to complete the loading function. Accordingly, several causes of prosthesis damage in prior loading devices may be eliminated.
The proximal capturing section can comprise an open mesh or open weave stent-engaging member. In one approach, the stent-engaging member is formed of helically wound, interbraided strands. This embodiment is well suited for use with a prosthesis formed of helical interbraided strands, because both the stent-engaging member and the prosthesis tend to elongate axially as they are radially compressed. Also, the respective braids have a tendency to engage one another, which may improve the capacity of the stent-engaging member to hold the prosthesis as the stent-engaging member and the prosthesis are drawn into the delivery catheter or other confining structure.
To provide the desired prosthesis retention quality, the control device may be constructed with a low durometer material or formed with a high friction surface along its distal tip. A prosthesis holding feature may be provided in the form of a prosthesis holding sleeve surrounding the control device, or several strips mounted to the control device. When used with open weave, open mesh or braided prostheses, the holding sleeve may comprise a compliant, low durometer material that tends to conform to the prosthesis as the prosthesis is compressed around it in the reduced-radius state. This helps to ensure that, when the control device and the outer catheter or other confining structures are moved axially relative to one another, the prosthesis follows the control device rather than the confining structure.
The holding feature can be mounted at the distal end of the control device. Alternatively, the holding feature can be proximally spaced apart from the control device distal end. This arrangement may be advantageous when the control device incorporates a catheter balloon, inflatable to radially expand either a ductile, e.g., plastically deformable, stent or a self-expanding stent at the intended treatment site. Typically, the balloon extends from a point near the distal end to a point just distally of the holding feature with the radially compressed stent overlying the balloon and feature.
In one version of the apparatus, the confining structure comprises a prosthesis delivery catheter incorporating an axially extended catheter lumen, and the control device comprises an inner member contained in the lumen and movable axially relative to the catheter to deploy a radially expandable prosthesis at a selected treatment site.
In other versions, the confining structure may be an intermediate device, for example either a loading tube or a loading capsule. The loading tube may have a diameter substantially the same as the diameter of a delivery catheter, whereby the tube is positionable to abut the catheter distal end to accommodate transfer of the prosthesis from the tube to the catheter. The tube is removable from the catheter, leaving the prosthesis and control device contained therein.
Alternatively a loading capsule, at least near its proximal end, may have a lumen substantially equal in diameter to a delivery catheter lumen. The capsule may be positionable with its proximal end in confronting relation to the distal end of a delivery catheter, to accommodate a proximal transfer of the prosthesis from the capsule to the catheter. This version can advantageously employ a socket designed to establish the confronting relation while releasably maintaining the capsule and catheter coaxially aligned. If desired, the capsule lumen can have a larger diameter over most of its length, necked down to equal the catheter lumen diameter at the capsule proximal end. This may facilitate the use of the capturing device to load the prosthesis into the capsule.
Another aspect of the present invention is a package or assembly including the prosthesis capturing device, a radially expandable prosthesis in the enlarged-radius state surrounded by the capturing device enclosure, and/or the elongate control device. If desired, the assembly or package further can include a prosthesis delivery catheter or other confining structure. In addition, the package can incorporate a tray or other support for maintaining the various components in a desired configuration, particularly with the prosthesis contained in the enclosure, and optionally with the control device distal end surrounded by the prosthesis. The assembly may also provide a convenient vehicle for simultaneously sterilizing these components, and for transporting and otherwise handling these components both before and after the sterilization stage.
In further embodiments, a stent loading and deploying device may include a stent confining device for maintaining a radially expandable stent in a reduced-radius state suitable for delivering the stent to an intraluminal treatment site. The device may have a stent capturing device including a proximal capturing section forming a compliant enclosure open at a proximal end to allow insertion of the stent, when in an enlarged-radius state, into the enclosure to be surrounded by the enclosure along a distal region of the stent. The capturing device may further include an elongate enclosure moving section insertable into and movable distally through a passage running axially along the stent confining device, to locate the enclosure, and the stent when so contained in the enclosure, adjacent a proximal entrance of the passage. The deployment device may further include an elongate stent control device having a distal end region insertable into the stent when the stent is in the enlarged-radius state. The distal end region may be adapted for a releasable engagement with the stent when surrounded by the stent with the stent in the reduced-radius state, whereby the stent tends to follow axial movement of the control device. The moving section, with the enclosure and stent so located and with the stent surrounding the distal end region, may be movable distally to draw the enclosure and stent into the passage and to progressively radially compress the enclosure and stent, thereby radially contracting the stent to the reduced-radius state about the distal end region to effect the releasable engagement.
Further in accordance with the invention, there may be provided a process for loading a radially expandable stent into a confining structure for maintaining the stent in a reduced-radius state, comprising the following steps:
The process further can include providing a retaining feature along the control device distal end region. Then, the stent may be maintained in surrounding relation to the retaining feature, with the releasable engagement comprising engagement of the stent directly with the retaining feature.
The stent may have a proximal region extending away from the enclosure when captured in the enclosure. This proximal region may be aligned with the retaining feature. Then, after the enclosure and stent are drawn into the confining device, the enclosure and stent may be movable further distally until the enclosure is free of the confining device, while the proximal region of the stent remains in the passage, releasably engaged with the retaining feature. This may facilitate removal of the enclosure from the confining structure and may permit the pulling of the control device proximally to draw the stent completely back into the passage after the enclosure is removed. When the confining device is a delivery catheter, this may position the stent for intraluminal delivery to an intended treatment site.
In accordance with a further aspect of the invention, the control device can incorporate a releasable coupling between the distal end region comprising a distal tip section incorporating the retaining feature, and a proximal region or section that typically forms most of the control device axial length. For example, the connection can employ complementary threads, a pin in one of the section insertable into a groove in the other, or a snap fit. In any event, the coupling may permit a stent or prosthesis to be loaded into an intermediate confining structure such as a loading tube or loading capsule, using just the distal tip section of the control device. The tip section may be relatively short, e.g. from about 1 cm to 10 cm, desirably from about 1 cm to about 5 cm, including less than 3 cm, and is much easier to manipulate during loading than the complete control device, which can have a length of 80 cm or more, for example from about 80 cm to about 300 cm, including from about 80 cm to about 200 cm. The proximal section can be loaded into a delivery catheter and coupled to the assembly that includes the distal tip section, the stent, and the loading tube or capsule containing them. Then, the assembled control device can be used to transfer the stent to the delivery catheter as previously described.
A variety of distal tip sections, for example a tip section carrying only a holding sleeve and a tip section including a balloon catheter as well, can be provided for use with a single control device proximal section. Further, a variety of distal tips representing different procedures may be used with the proximal section. For example, a control device proximal section might be used with a dilating distal tip to enlarge a lumen at an intended treatment site, then with a different distal tip for loading and deploying a stent to the treatment site, and finally with a balloon distal tip to radially enlarge a stent after its implantation for a more secure fixation.
Thus in various embodiments, radially expandable stents and other prostheses can be loaded into delivery catheters and other confining structures with relative ease and simplicity, immediately before an implantation procedure. This allows the physician to select a device most suitable for the procedure at hand, even when the device is subject to creep or otherwise not suitable for long term maintenance in a reduced-radius state. The present system not only may reduce the time required for on-site loading, but may also minimize the risk of damage to the prosthesis and other components, by allowing manipulation of the prosthesis without pushing against or crimping one of its ends. Further, the same control device used to position the prosthesis during loading, may also be used to control the prosthesis relative to a delivery catheter during deployment. Device loading can be further simplified by intermediate confining devices such as loading tubes and capsules, and by forming the control device with a distal tip section removably coupled to the remainder of the device. In both cases, the user is able to manipulate and load relatively short components, in lieu of the much longer delivery catheter and inner member needed during deployment.
For a further understanding of the above objects and advantages, reference is made to the following detailed description and to the drawings, in which:
Turning now to the drawings, there is shown in
System 16 employs several components, some of which are involved in loading stent 18 and others are involved in stent deployment. The later components include an elongate, pliable outer catheter or tubing 20 constructed of a biocompatible polymer. Suitable polymers include, but are not limited to, polytetrafluoroethylene (PTFE), polypropylene (PP), or polyethylene terephthalate (PET). A central lumen 22 runs axially through catheter 20, from a proximal end 24 to a distal end 26 of the catheter 20. During a deployment procedure, catheter 20 may be inserted by distal end 26 and is then guided intraluminally to a selected treatment site, while proximal end 24 remains outside the body.
The outer catheter 20 is shown in section to reveal stent 18 and an elongate stent control device or inner member 28. The control device 28 may be formed of a biocompatible polymer such as, but not limited to, PTFE, PP, PET or polyamide (PA), commonly referred to as nylon. Control device 28 is flexible and pliable to allow bending when negotiating body lumens, including but not limited to blood vessels, and also has sufficient axial stability to permit a physician to control the position of distal end 26 by manipulating proximal end 24.
Stent 18 may be of open weave or mesh construction and, in some embodiments, may be formed of multiple interbraided helically wound strands or filaments. Stent 18, however, is not limited to a braided stent and other stent configurations may suitably be used. Useful biocompatible materials include but are not limited to biocompatible metals, biocompatible alloys, biocompatible polymeric materials, including synthetic biocompatible polymeric materials and bioabsorbable or biodegradable polymeric materials, materials made from or derived from natural sources and combinations thereof. Useful biocompatible metals or alloys include, but not limited to, nitinol, stainless steel, cobalt-based alloy such as Elgiloy, platinum, gold, titanium, tantalum, niobium, polymeric materials and combinations thereof. Useful synthetic biocompatible polymeric materials include, but are not limited to, polyesters, including polyethylene terephthalate (PET) polyesters, polypropylenes, polyethylenes, polyurethanes, polyolefins, polyvinyls, polymethylacetates, polyamides, naphthalane dicarboxylene derivatives, silks and polytetrafluoroethylenes. The polymeric materials may further include a metallic, a glass, ceramic or carbon constituent or fiber. Useful and nonlimiting examples of bioabsorbable or biodegradable polymeric materials include poly(L-lactide) (PLLA), poly(D,L-lactide) (PLA), poly(glycolide) (PGA), poly(L-lactide-co-D,L-lactide) (PLLA/PLA), poly(L-lactide-co-glycolide) (PLLA/PGA), poly(D,L-lactide-co-glycolide) (PLA/PGA), poly(glycolide-co-trimethylene carbonate) (PGA/PTMC), polydioxanone (PDS), Polycaprolactone (PCL), polyhydroxybutyrate (PHBT), poly(phosphazene) poly(D,L-lactide-co-caprolactone) PLA/PCL), poly(glycolide-co-caprolactone) (PGA/PCL), poly(phosphate ester) and the like, and any one of the materials identified in U.S. Pat. No. 6,245,103, the contents of which are incorporated herein by reference by their entirety. Further, the stent 18 may include materials made from or derived from natural sources, such as, but not limited to collagen, elastin, glycosaminoglycan, fibronectin and laminin, keratin, alginate, combinations thereof and the like. Further, the stent 18 may be made from polymeric materials which may also include radiopaque materials, such as metallic-based powders or ceramic-based powders, particulates or pastes which may be incorporated into the polymeric material. For example, the radiopaque material may be blended with the polymer composition from which the polymeric filament is formed, and subsequently fashioned into the stent as described herein. Alternatively, the radiopaque material may be applied to the surface of the metal or polymer stent. Various radiopaque materials and their salts and derivatives may be used including, without limitation, bismuth, barium and its salts such as barium sulfate, tantalum, tungsten, gold, platinum and titanium, to name a few. Additional useful radiopaque materials may be found in U.S. Pat. No. 6,626,936, which is herein incorporated in its entirety by reference. Metallic complexes useful as radiopaque materials are also contemplated. The stent 18 may be selectively made radiopaque at desired areas along the stent 18 or made be fully radiopaque, depending on the desired end-product and application. Further, portions of the stent 18, for example stent filaments, may have an inner core of tantalum, gold, platinum, iridium or combination of thereof and an outer member or layer of nitinol to provide a composite filament for improved radiocapicity or visibility. Alternatively, the stent 18 may also have improved external imaging under magnetic resonance imaging (MRI) and/or ultrasonic visualization techniques. MRI is produced by complex interactions of magnetic and radio frequency fields. Materials for enhancing MRI visibility include, but are not limited to, metal particles of gadolinium, iron, cobalt, nickel, dysprosium, dysprosium oxide, platinum, palladium, cobalt based alloys, iron based alloys, stainless steels, or other paramagnetic or ferromagnetic metals, gadolinium salts, gadolinium complexes, gadopentetate dimeglumine, compounds of copper, nickel, manganese, chromium, dysprosium and gadolinium. To enhance the visibility under ultrasonic visualization the stent 18 of the present invention may include ultrasound resonant material, such as but not limited to gold. Other features, which may be included with the stent 18 of the present invention, include radiopaque markers; surface modification for ultrasound, cell growth or therapeutic agent delivery; varying stiffness of the stent or stent components; varying geometry, such as tapering, flaring, bifurcation and the like; varying material; varying geometry of stent components, for example tapered stent filaments; and the like. In any event, stent 18 is an example of a radially self-expanding, i.e. elastically compressible to a reduced-radius, providing an axially-elongated state for positioning within catheter 20 near distal end 26 as shown in
Control device 28 includes a distal tip 30 and a proximal end 32 disposed proximally of catheter proximal end 24. This may allow a physician to manipulate the control device 28, moving it axially relative to catheter 20, usually with the aid of a hub or handle (not illustrated). When stent 18 is radially compressed in the reduced-radius configuration about distal tip 30, the stent 18 is designed to be maintained in a releasable engagement with the control device 28, and thus tends to track or follow axial movement of the control device 28. Accordingly, with the distal end 26 of catheter 20 positioned at the treatment site, the catheter 20 may be withdrawn proximally while the control device or inner member 26 is held in place. Because of its releasable engagement with control device 28, stent 18 likewise tends to stay in place rather than following proximal movement of the outer catheter 20, whereupon stent 18 is progressively released from the outer catheter 20 for radial self-expansion. After complete release and expansion of the stent 18, catheter 20 and control device 28 are proximally withdrawn.
Even after stent 18 is partially released, it should continue to track axial movement of control device 28, so long as the distal region of the stent 18 is radially compressed about distal tip 30. This feature allows the stent 18 to be recaptured or re-constrained after a partial deployment. Should the need arise to reposition a partially deployed stent 18, control device 28 can be held stationary while catheter 20 is moved distally to recapture the stent 18. Alternatively, the catheter 20 can be held stationary while the control device 28 is moved distally to recapture the stent 18. In other words, either of the catheter 20 and/or the control device 28 may be held or moved relative to one and the other. Then, after the assembly is moved to reposition the stent 18 as desired, catheter 20 can be moved in the proximal direction, releasing the stent 18 once again.
System 16 further includes a stent loading component in the form of a stent capturing device 34. At the proximal end of the device 34 is a stent-capturing section, such as stent-engaging member 36, which may function as a distensible stent-engaging member. The stent-engaging member or basket 36 may be formed with multiple helically wound interbraided strands 36′, so that it is similar in construction to stent 18. At the distal end 38 of the stent-engaging member 36, at least some of the strands or filaments 36′ may be gathered to reduce the stent-engaging member diameter and integrally couple the stent-engaging member 36 to an elongate, pliable moving member or stent-engaging member puller 40. The stent-engaging member puller 40 may be formed of a polymer such as polyvinyl chloride (PVC), PEEK, PP, PA or any of the above-described polymers. Other suitable materials for the stent-engaging member puller 40 may include metals such as stainless steel, nitinol and/or any of the above-described metals and/or alloys. Stent-engaging member puller 40 may be constructed to have axial stiffness, but alternatively can be formed as pliable and inextensible in the nature of a metallic coil, chain, or thread, configured to exert sufficient tension to pull stent-engaging member 36 into and through catheter 20 or another stent-confining structure.
Stent-engaging member 36 may be compliant, and may be resilient as well, depending on the material selected for the stent-engaging member strands 36′. The stent-engaging member 36 may be open at its proximal end 44 to receive stent 18 in a relaxed or enlarged-radius state as shown near the stent-engaging member in broken lines. This is generally the shape assumed by stent 18 when it is not subject to any external forces. As compared to its configuration when loaded into catheter 20, stent 18 in the relaxed state has a larger radius and shorter axial length. In any event, the opening at proximal end 44 is large enough to receive stent 18 when in the relaxed state. At the same time, that part of stent-engaging member 36 that surrounds stent 18 is shorter than the axial length of the stent 18, and in some embodiments no more than about half the stent length. In other words, a proximal region of the stent 18 extends beyond the stent-engaging member 36, and may constitute at least one-half of the stent length.
Alternative stents and prostheses may be formed according to non-braided configurations in which the stent, whether in the relaxed state or the reduced-radius state, has substantially the same axial length. Capturing device 34 is suitable for this type of stent as well. Preferably, the stent-engaging member 36 used with a “non-shortening” stent or prosthesis likewise is configured such that its radial reduction does not lead to any substantial axial elongation. Alternatively, a braided stent-engaging member is selected such that, despite any axial elongation accompanying radial contraction, a proximal region of the radially contracted stent remains free of the stent-engaging member.
As seen in
One purpose of system 16 is to afford a convenient and reliable loading of stent 18 into outer catheter 20 for deployment. In many systems, stents or other prostheses are loaded into their respective delivery catheters well in advance of the anticipated procedure, and provided to the physician in preloaded form.
Although stents formed of stainless steel and other metals are generally well suited for advance loading, stents formed of many polymeric materials and biodegradable materials generally are not, because they are susceptible to a phenomenon known as stress relaxation or “creep”, in which the stent, maintained in its reduced-radius state for any appreciable length of time, tends to loose at least some of its resiliency. While such a stent may radially self-expand upon release from a catheter or other confining structure, its relaxed-state diameter is often less than before the stent was constrained. Further, in many procedures it is necessary or desirable to sterilize the stent or prosthesis just prior to deployment. Sterilization frequently entails exposure of the stent to elevated temperatures, e.g. 40° C. or higher. For prostheses susceptible to creep, these higher temperatures can increase the tendency of stress relaxation.
When a stent subject to the creep phenomenon is maintained in its relaxed or enlarged-radius state until commencement of a deployment procedure, there remains a need to radially compress the stent and maintain it in its reduced-radius state, but only for several minutes. For most materials, this can help to avoid or minimize the creep phenomenon. System 16, by providing for a convenient and reliable loading of a stent into a delivery catheter, may allow the physician to select from a broader range of stent materials. The physician can choose materials with reference to the tissue being treated and the time the stent is expected to remain at the treatment site, with less concern about whether the stent material is suitable for preloading.
Further, should it be necessary or desirable to sterilize stent 18 during manufacturing, sterilization can be accomplished while the stent remains in its relaxed, enlarged-radius state. The components that come into contact with stent 18 during the procedure may be sterilized as well. Such components, such as capturing device 34, control device 28 and outer catheter 20, may be configured in an assembly or package that also includes the stent, for simultaneous sterilization. A package suitable for this approach is illustrated in
Accordingly, the utility of a prosthesis susceptible to creep is enhanced when it is maintained in a relaxed, enlarged-radius state until the beginning of a deployment procedure, and further when it is maintained in the relaxed state while being sterilized.
In
The loading sequence beyond the ready position is shown in
At this point, stent-engaging member pulling member 40 can be pulled distally to draw stent-engaging member 36, stent 18 and control device 28 through lumen 22 until the stent-engaging member 36 and stent 18 reach distal end 26 of the catheter 20. In some embodiments, however, the components may be controllable, individually or in combination. The components are moved further in the distal direction until capturing device 34 is free of the outer catheter 20. At this point the distal region of stent 18 may be disposed outside the catheter 20 and may expand radially as shown in
With the catheter 20, stent 18 and control device 28 arranged as shown in
In either event, with the outer catheter distal end 26 at the treatment site, control device 28 is held in place, while outer catheter 20 is moved in the proximal direction, by manipulating a hub or handle along the proximal portions of these components that remain outside the body. Any of these components or handles may be moved relatively to one and the other, including simultaneous movement. As the catheter 20 is proximally withdrawn, distal region 50 of stent 18 is released from catheter 20 and undergoes radial self-expansion, encountering surrounding tissue of the body lumen as seen in
Returning to
Tubular loading member 54 can be formed of any suitable polymer, for example, but not limited to, polycarbonate (PC), PA, PTFE or PET. Tubular member 54 can have an outer diameter comparable to an outer diameter of the delivery catheter, although this is not required. A lumen 62 runs through the tubular member, and has an inner diameter greater than the outside diameter of control device 56. In particular, the lumen diameter is selected to maintain a stent in a reduced-radius state about distal tip 60.
Tubular member 54 requires an axial length sufficient only to maintain a stent or other prosthesis in its reduced-radius, axially-elongated state. Consequently, the tubular member 54 is much shorter than the catheter used for intraluminal delivery of the prosthesis, e.g. from about 50 centimeters to about 100 centimeters shorter. These lengths are non-limiting, and the procedure at hand governs the size of the delivery catheter, the prosthesis (and thus the tubular member), and other components. As just noted, capturing device 58 of system 52 can be used to load the stent into tubular member 54 rather than into a delivery catheter. Thus, a pull member 64 of capturing device 58 can be much shorter than puller 40 of capturing device 34, even when stent-engaging members 36 and 66 are substantially the same size.
Capturing device 58 may be used to load a stent 68 into tubular member 54 in much the same manor as capturing device 34 is used to load stent 18 into outer catheter 20. The capturing device 58 is inserted into member 54 by puller 64, and then moved distally until stent-engaging member 66 is located near a proximal end 70 of the tubular member 54 as seen in
From this position, pull member 64 is moved distally or the tubular member 54 is advanced until stent 68 resides entirely within tubular member 54, as shown in
At this stage, control device 56 can be moved proximally relative to delivery catheter 72, thus to draw stent 68 and tubular member 54 toward the delivery catheter, positioning a proximal end of the tubular member in confronting relation to a distal end of catheter 72 as shown in
In system 52, the diameter of lumen 62 of tubular loading member 54 preferably is equal to the diameter of a lumen 74 of catheter 72. This better insures that catheter 72, like tubular member 54, can maintain the stent in its reduced-radius state about distal tip 60 so that the stent tends to track axial movement of the control device. If desired, a retaining feature like holding sleeve 46 is mounted on distal tip 60. Further, the delivery catheter can be enlarged at the distal end, to form a socket to receive tubular member 54. Moreover, tubular member 54 can be modified to easily move inside catheter 72. The tubular member 54 may be lubricated, may have ribs or bumps to reduce contact area and/or may include low friction materials or portions.
As compared to system 16, system 52 requires an extra component in the form of tubular member 54. Stent loading with system 52 requires the additional step of drawing the stent from the tubular member to the delivery catheter. Nonetheless, system 52 may be preferred. Loading the stent or other prosthesis into tubular member 54, as compared to loading stent 18 into catheter 20, may be easier and less distracting to the physician, primarily because of the reduced length of capturing device 58 and tubular member 54. While stent deployment with system 52 still requires components of greater axial length, namely catheter 72 and control device 56, the control device can be loaded into the delivery catheter well in advance of the procedure, when time is not critical. Stent loading with the shorter components in system 52 can also reduce the risk of accidental dropping and/or the stent can come preloaded with the catheter 72 to avoid possible contamination of the components. The preloading may by performed by the manufacturer or supplier of the system or may be prepared by a practitioner's assistant prior to use by the practitioner. Thus, system 52 affords a level of convenience that can reduce risk to the patient associated with procedural delays, particularly in time-critical procedures.
With reference to
As member 98 is pulled in the distal direction, stent-engaging member 100 and stent 96 may be progressively radially compressed as shown in
At this stage, distal tip 106 of control device 80 including a retaining sleeve 108 can be moved distally to be surrounded by proximal region 102 of the stent 96, as shown in
At this stage, proximal end 90 of the capsule and a distal end 110 of a delivery catheter 112 may be placed in confronting, centered relation to one another. Preferably, control device 80 has been preloaded into catheter 112 as described in connection with system 52. With the capsule and catheter maintained in confronting relation, control device 80 can be pulled proximately, which draws stent 96 proximally into the catheter as seen in
Loading system 76 provides shorter components for stent loading, thus to afford the advantages discussed above in connection with system 52. Further advantages arise due to the controlled variance in the wall thickness of the capsule. Transfer of the stent to the delivery catheter requires alignment and engagement of the stent and the control device. The thinner wall (larger lumen diameter) along most of the capsule length allows stent 96 to expand to a larger diameter when contained in the capsule. This is particularly important along the distal region of the stent, where stent-engaging member 100 remains captured between the stent and capsule just before its removal. The larger diameter substantially reduces the force necessary to pull stent-engaging member 100 away from the stent and capsule, and minimizes any tendency in stent 96 to follow distal travel of the stent-engaging member. Larger diameters may also reduce plastic deformation of the stent.
Moreover, the confronting relation of the capsule and catheter can eliminate the need to insert the capsule into the catheter when transferring the stent. The capsule walls can have more thickness, and the capsule lumen can be larger in diameter over the majority of the capsule length, necked down near the proximal end to match the diameter of catheter lumen 116.
To use socket 140 during loading, catheter 112 can be inserted distally into lumen 142. Then, control device 80 is inserted into lumen 116 to position distal tip 106 proximate the catheter distal end, extending just beyond socket 140. Alternatively, the control device can be inserted into the catheter before inserting the catheter into the socket.
In either event, with stent 96 partially loaded into capsule 82 (see
At this stage, control device 80 can be pulled in the proximal direction relative to catheter 112. Stent 96, releasably engaged with the control device, should move proximally with the control device and thereby is transferred from capsule 82 into the catheter. Alignment socket 140 can provide for a more convenient and more reliable transfer of the stent into the delivery catheter while demanding less of the physician's time and attention. The socket 140 accurately centers capsule 82 relative to catheter 112 as the capsule is inserted into lumen 142. Centering is maintained during insertion, until the capsule engages the delivery catheter. Then, as the physician moves control device 80 proximally to draw stent 96 into the catheter, socket 140 is designed to maintain the desired confrontation and alignment.
The releasable coupling can provide for a more convenient loading of stent 130 into the capsule, particularly when disposing the distal tip within the proximal region of the stent, and when moving the stent and distal tip into the capsule, as shown in
Regardless of the style of coupling, loading of the stent or other prosthesis may be more convenient and less demanding of the physician's attention when the control device has a detachable distal tip. Another advantage of the releasable coupling is that a variety of different distal tips can be connected, alternatively, to the same proximal section of a control device. For example,
In one version of this device, stent 180 is radially self-expanding, in which case the stent is deployed by moving the control device distally to release the stent for radial self-expansion. Balloon 178 is a dilation balloon, inflatable against stent 180 after its release, to press the stent radially outwardly into contact with surrounding tissue for a more secure fixation or to reopen the lumen during placement of the stent. Other dilating mechanisms, such as but not limited to a mechanical cage, may suitably be used as a substitute for balloon 178 or in addition to balloon 178.
Alternatively, stent 180 may be a plastically deformable or balloon-expandable stent. In such cases, the loading and deployment system preferably employs an intermediate component such as capsule 82 or tubular member 54. If desired, the intermediate component can be used to radially compress the stent to a diameter equal to or less than the diameter of the lumen through the delivery catheter. In this case stent 180 may not radially expand against the delivery catheter wall when loaded into the catheter, and requires inflation of balloon 178 for its radial expansion. The stent-engaging member of the capturing tool, and the capsule or other intermediate component, can provide a progressive, controlled radial reduction of the stent to the reduced-radius state. Because of the tendency of plastic deformation, the stent may remain compressed until expanded with the balloon. The confining structure is not needed to maintain a compressive force on the stent. This simplifies transfer of the stent to the delivery catheter.
The retaining sleeves described above are one embodiment to providing the releasable engagement of the stent and control device when the stent is in its reduced-radius state.
While the preferred construction of the capturing device stent-engaging member is an interbraiding of generally helical strands as described, alternative constructions can be deployed here as well, e.g. a stent-engaging member composed of a fabric mesh, or a more tightly woven fabric. In another alternative, strands can be interbraided for the complete length of a capturing device, tightly braided along a “pulling member” section of the device and forming a more open or expanded braid at the end forming the stent-engaging member. In yet another alternative illustrated in
The prosthesis loading and deployment systems of this invention have been described in the context of on-site use by the physician to load a stent or other prosthesis just minutes before that prosthesis is intraluminally delivered and deployed at the treatment site. The loading systems have utility in a variety of other situations as well. For example, where radially self-expanding prostheses (for example when formed of metal) are suitable for preloading and long-term maintenance in the radially-reduced state, the loading systems described herein can be used to preload the prostheses into delivery catheters to provide for faster, simpler and more reliable preloading of these implantable devices.
At its distal end 210, channel 208 can open to a larger compartment 212 designed to accommodate stent 18, 58, 96 in the relaxed state, a stent-engaging member 36, 100 of a capturing device 34, 58, 78 and the proximal portion of a loading tube or capsule 82, 126. Distally of compartment 212, the recess 206 can be narrowed to provide a neck 214 that accommodates a clamp 216 which may be formed of elastomeric material. Clamp 216 may frictionally engage the loading tube 82, 126 and container 202 to releasably secure tube 82, 126 within the recess 206. Beyond neck 214, capsule 82, 126 may extend distally into a distal compartment 218 designed to accommodate the loading capsule 82, 126 and a pulling member 40, 64, 98 of the capturing device 34, 58, 78.
Stent 18, 58, 96, and to a lesser extent the stent-loading components involved, determine the size of container or tray 202 and the compartments 212, 214, 218 of recess 206. Proximal channel 208 should have a diameter larger than the outer diameter of the control device 28, 56, 80 intended for use with stent 18, 58, 96 to accommodate a distal insertion of the control device distal end 28, 56, 80 into the stent 18, 58, 96. Medial compartment 220 requires a width (vertical dimension in the
Packaging assembly 200 can facilitate stent loading by maintaining the stent 18, 58, 96 and certain loading components in place, allowing the physician to direct his or her attention to other concerns, e.g. proper alignment of an inner catheter or other control device when pulling the stent 18, 58, 96 into the loading capsule 82, 126. Using channel 208 to guide distal travel of a control device 28, 56, 80, the physician can align the distal tip of the control device within the stent 18, 58, 96. Then, while moving pulling member distally to draw the stent-engaging member and stent 18, 58, 96 into loading capsule, the physician can move the control device 28, 56, 80 distally to maintain the desired distal tip position, using channel 208 as a guide. Thus, the capturing device 34, 58, 78, stent 18, 58, 96 and control device 28, 56, 80 can be moved distally in concert, while clamp 216 grips loading capsule 82, 126 to maintain its location relative to tray 202, until the stent is completely contained within the capsule 82, 126, in its reduced-radius state.
Then, with clamp 216 continuing to maintain capsule 82, 126, the physician can continue to move pulling member 40, 64, 98 and the control device distally in concert, until stent-engaging member 36, 100 is free of the capsule 82, 126, then can move the control device 28, 56, 80 proximally to draw stent 18, 58, 96 back into capsule 82, 126 as previously described.
Thus, a salient advantage of the packaging assembly 200 is that it can facilitate an accurate alignment of the control device 28, 56, 80 with the stent 18, 58, 96 during use of the capturing device 34, 58, 78 to draw the stent 18, 58, 96 distally into the loading capsule 82, 126. A further advantage of the package assembly is that it can facilitate sterilization of the stent 18, 58, 96 and loading components. According to one approach, the entire packaging assembly as shown in
Thus in accordance with the present invention, a variety of prosthesis loading and deploying systems are provided. These systems facilitate on-site loading of prostheses just prior to delivery and deployment procedures, and thus allow the physician to use prostheses that are well suited to the procedure, but not necessarily suited for remaining constrained in a reduced-radius state for extended periods of time. All of the systems advantageously employ control devices that are operable to move a prosthesis in either axial direction when the prosthesis is constrained about the control device in a reduced-radius state. Some of the systems use capsules, tubular members or other intermediate components that are shorter and therefore easier to handle than delivery catheters. Other systems employ control devices with detachable distal tips. The result is a more convenient and simplified loading of stents and other prostheses, allowing physicians to direct their attention more appropriately to the procedure at hand.
Moreover, any of the above-described tubular components which are disposable within the outer catheter tube may be splittable, for example be able to be pulled back out of the catheter in a banana-peel like manner. Furthermore, any of the above-described prosthesis or stent retaining sleeves may them selves be expandable when removed from the catheter. Still furthermore, any the components of the invention may be packaged separately or in any combination.
While various embodiments of the present invention are specifically illustrated and/or described herein, it will be appreciated that modifications and variations of the present invention may be effected by those skilled in the art without departing from the spirit and intended scope of the invention. Further, any of the embodiments or aspects of the invention as described in the claims or in the specification may be used with one and another without limitation.
This application claims the benefit of U.S. Provisional Application No. 61/017,184, filed Dec. 28, 2007, the content of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61017184 | Dec 2007 | US |
