US20080077229A1 - Custom-length self-expanding stent delivery systems with stent bumpers - Google Patents

Abstract

Custom-length self-expanding stent delivery systems and methods enable precise control of prosthesis position during deployment. The stent delivery systems carry multiple stent segments and include a stent bumper for helping control the axial position of the stent segments during deployment. This enables the deployment of multiple prostheses at a target site with precision and predictability, preventing stent segment recoil and ejection from the delivery device and thus eliminating excessive spacing or overlap between prostheses. In particular embodiments, the prostheses of the invention are deployed in stenotic lesions in coronary or peripheral arteries or in other vascular locations.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 10/944,282 (Attorney Docket No. 021629-003000US) now U.S. Pat. No. 7,300,456 which is a continuation-in-part of U.S. patent application Ser. No. 10/879,949 (Attorney Docket No. 021629-002700US), filed Jun. 28, 2004, all of which are hereby incorporated fully by reference.
BACKGROUND OF THE INVENTION
• Stents are tubular prostheses designed for implantation in a vessel to maintain patency of the vessel lumen. Stents are used in various vessels throughout the body, including the coronary arteries, femoral arteries, iliac arteries, renal artery, carotid artery, vascular grafts, biliary ducts, trachea, and urethra. Stents are typically implanted by means of long, flexible delivery catheters that carry the stents in a compact, collapsed shape to the treatment site and then deploy the stents into the vessel. In some applications, balloon expandable stents are used. These stents are made of a malleable metal such as stainless steel or cobalt chromium and are expanded by means of a balloon on the tip of the delivery catheter to plastically deform the stent into contact with the vessel wall. In other applications, self-expanding stents are used. These are made of a resilient material that can be collapsed into a compact shape for delivery via catheter and that will self-expand into contact with the vessel when deployed from the catheter. Materials commonly used for self-expanding stents include stainless steel and elastic or superelastic alloys such as nickel titanium (Nitinol™).
• While self-expanding stents have demonstrated promise in various applications, such stents face a number of challenges. One such challenge is that in some cases the disease in a vessel may be so extensive that a stent of very long length, e.g. 30-200 mm, is called for. Currently available stents are typically less than 30 mm in length, and suffer from excessive stiffness if made longer. Such stiffness is particularly problematic in peripheral vessels such as the femoral arteries, where limb movement requires a high degree of flexibility in any stent implanted in such vessels.
• To overcome the stiffness problem, the idea of deploying multiple shorter stents end-to-end has been proposed. However, this approach has suffered from several drawbacks. First, currently available delivery catheters are capable of delivering only a single stent per catheter. In order to place multiple stents, multiple catheters must be inserted, removed and exchanged, heightening risks, lengthening procedure time, raising costs, and causing excessive material waste. In addition, the deployment of multiple stents end-to-end suffers from the inability to accurately control stent placement and the spacing between stents. This results in overlap of adjacent stents and/or excessive space between stents, which is thought to lead to complications such as restenosis, the renarrowing of a vessel following stent placement. With self-expanding stents the problem is particularly acute, because as the stent is released from the catheter, its resiliency tends to cause it to eject or “watermelon seed” distally from the catheter tip by an unpredictable distance. During such deployment, the stent may displace not only axially but rotationally relative to the delivery catheter resulting in inaccurate, uncontrollable, and unpredictable stent placement.
• Interleaving stents or stent segments such as those disclosed in co-pending U.S. patent application Ser. No. 10/738,666 (Attorney Docket No. 021629-000510US), filed Dec. 16, 2003, which is incorporated herein by reference, present even greater challenges to conventional delivery systems. Interleaving stents have axially extending elements on each end of the stent that interleave with similar structures on an adjacent stent. Such interleaving minimizes the gap between adjacent stents and increases vessel wall coverage to ensure adequate scaffolding and minimize protrusion of plaque from the vessel wall. However, such interleaving requires that the relative rotational as well as axial positions of the adjacent stents be maintained during deployment to avoid metal overlap and excessive gaps between stents. Conventional delivery systems suffer from the inability to control both the axial and rotational positions of self-expanding stents as they are deployed. These issues are addressed, in part, in co-pending U.S. patent application Ser. No. 10/879,949, which was previously incorporated by reference. “Watermelon seeding” of self-expanding stents, where the resiliency of the stents causes them to eject distally from the catheter tip by an unpredictable distance, continues to be a challenge.
• What are needed, therefore, are stents and stent delivery system that overcome the foregoing problems. In particular, the stents and stent delivery systems should facilitate stenting of long vascular regions of various lengths without requiring the use of multiple catheters. Such stents and delivery systems should also provide sufficient flexibility for use in peripheral vessels and other regions where long and highly flexible stents might be required. In addition, the stents and stent delivery systems should enable the delivery of multiple stents of various lengths to one or more treatment sites using a single catheter without requiring catheter exchanges. Further, the stents and stent delivery systems should facilitate accurate and repeatable control of stent placement and inter-stent spacing to enable deployment of multiple self-expanding stents end-to-end in a vessel at generally constant spacing and without overlap. In particular, the stents and delivery systems should enable the deployment of interleaving stents or stent segments with precision and control over the axial spacing of each stent or segment.
BRIEF SUMMARY OF THE INVENTION
• The present invention provides prostheses, prosthesis delivery systems, and methods of prosthesis deployment that enable the precise and controllable delivery of multiple prostheses using a single delivery catheter. The prostheses, delivery systems, and methods of the invention provide for the precise control of prosthesis placement so that inter-prosthesis spacing is maintained at a constant and optimum distance. In some embodiments, both axial and rotational displacement of the prostheses relative to the delivery catheter is controlled during deployment, enabling the delivery of multiple prostheses that interleave with one another without overlap. The prostheses, prosthesis delivery systems, and methods of the invention further enable the length of prostheses to be customized in situ to match the length of the site to be treated. The invention is particularly useful for delivery of self-expanding prostheses, but balloon expandable prostheses are also contemplated within the scope of the invention. The invention is well-suited to delivery of stents to the coronary arteries and to peripheral vessels such as the popliteal, femoral, tibial, iliac, renal, and carotid arteries. The invention is further useful for delivery of prostheses to other vessels including biliary, neurologic, urinary, reproductive, intestinal, pulmonary, and others, as well as for delivery of other types of prostheses to various anatomical regions, wherever precise control of prosthesis deployment is desirable.
• In a first aspect of the invention, a catheter system for delivery of a stent to a body lumen includes a stent delivery catheter and a plurality of stent segments. The stent delivery catheter includes a sheath having a first lumen, a shaft extending through the first lumen and slidable relative to the sheath, and a stent bumper mounted to the shaft distally of the sheath and movable from a contracted shape to an expanded shape. The plurality of self-expanding stent segments is carried within the first lumen in a collapsed configuration, and the segments are adapted to resiliently expand from the collapsed configuration to an expanded configuration. The stent segments are deployable from the first lumen so as to expand into the expanded configuration, while the stent bumper is configured to engage a first stent segment during deployment thereof to maintain its position relative to an adjacent stent segment disposed proximal to the first stent segment.
• In a number of embodiments, the stent bumper in the expanded shape has an outer diameter sized to contact an inner wall of the body lumen. The bumper may thus prevent distal migration of the stent segments and be stable in the vessel, without tilting, deflecting or slipping. In some embodiments, at least a portion of the stent bumper includes a lubricious surface for contacting one or more of the stent segments. For example, a proximal surface or portion of the stent bumper may have such a coating.
• The bumper itself may have any of a number of suitable shapes, sizes and configurations, and may be made of any suitable material or combinations of materials. In some embodiments, for example, the stent bumper may comprise an expandable basket, a plurality of expandable blades, rods or petals, an expandable disk, a proximal portion of a nosecone at the distal end of the catheter shaft, or the like. In a preferred embodiment, the stent bumper comprises an inflatable balloon. In such embodiments, the catheter typically further includes an inflation lumen in the shaft (or elsewhere in the catheter), which is in fluid communication with the inflatable balloon. In some embodiments, the balloon is adapted to be deflated, positioned within the deployed first stent segment, and re-inflated to the expanded shape. Optionally, the balloon in the expanded shape may be adapted to further expand the deployed first stent segment. In an alternative embodiment, an elongate balloon is used, the balloon having an axial length at least as long as two stent segments. In one embodiment, for example, the axial length of the elongate balloon is between about 20 mm and about 250 mm. In such embodiments, the catheter may further include an inner sheath disposed over the balloon, with the inner sheath being retractable to expose a portion of the balloon to allow it to be inflated from the contracted shape to the expanded shape. In some embodiments, the balloon is adapted to be expanded within one or more deployed stent segments to further expand the segments.
• Any suitable stents or stent segments may be used. Examples of self-expanding stents are described in U.S. patent application Ser. No. 10/879,949, which was previously incorporated by reference, but any other suitable self-expanding stents or stent segments may be substituted in various embodiment. In some embodiments, balloon expandable stents may be used. In various embodiments, the stent segments may be made of Nitinol, other superelastic alloys, stainless steel, cobalt chromium, other resilient metals, polymers or any other suitable material. Additionally, each stent segment may have any suitable length. In some embodiments, for example, each stent segment has a length of between about 3 mm and about 30 mm, and more preferably between about 4 mm and about 20 mm. Furthermore, any suitable number of stent segments may be loaded onto the catheter in various embodiments. For example, some embodiments may include between 2 and 50 segments. In some embodiments, the catheter may additionally include a pusher slidably disposed over the shaft, proximal to the stent segments, for advancing the stent segments relative to the sheath or holding the stent segments in place while the sheath is retracted.
• In another aspect of the invention, a method of delivering a stent to a body lumen involves: positioning a stent delivery catheter in the body lumen, the delivery catheter carrying at least first and second stent segments; expanding a stent bumper on the delivery catheter; releasing the first stent segment from the delivery catheter into the body lumen proximal to the stent bumper, the first stent segment self-expanding into an expanded configuration in the body lumen, wherein the stent bumper engages the first stent segment during expansion thereof to maintain its position relative to the delivery catheter; and releasing the second stent segment from the delivery catheter into the body lumen adjacent to the first stent segment.
• In a preferred embodiment, expanding the stent bumper involves inflating a balloon. Optionally, such a method may further include, before releasing the second stent segment: deflating the balloon; positioning the deflated balloon within the expanded first stent segment; and inflating the balloon, wherein the balloon engages the second stent segment during expansion thereof to maintain its position relative to the delivery catheter and the first segment. In some embodiments, inflating the balloon within the first segment further expands the first segment. The method may further involve: deflating the balloon; positioning the deflated balloon within the expanded second stent segment; and inflating the balloon, wherein the balloon engages a third stent segment during expansion thereof to maintain its position relative to the delivery catheter and the first and second segments. These steps of deflating, positioning and inflating may be repeated as many times as desired to deploy a desired number of stent segments.
• In an alternative embodiment, before expanding the balloon, a portion of the balloon is exposed from the distal end of an inner sheath that is disposed over the balloon. Such a method may optionally further involve, before releasing the second stent segment: exposing an additional portion of the balloon from the distal end of the inner sheath, the additional portion disposed within the expanded first stent segment; and inflating the balloon, wherein the balloon engages the second stent segment during expansion thereof to maintain its position relative to the delivery catheter and the first segment. In some embodiments, inflating the additional portion of the balloon further expands the expanded first stent segment.
• Rather than inflating a balloon, in alternative embodiments expanding the stent bumper involves deploying one or more other structures on the catheter device. In one embodiment, for example, a basket of resilient polymer or metal mesh is expanded. In some embodiments, expanding the stent bumper involves releasing one or more shape-memory members from constraint. For example, the shape-memory member(s) may include blades, rods, petals, rings or the like, made of metal, polymer or other resilient material.
• The stents may be released from the delivery catheter via any suitable means. In one embodiment, for example, releasing each stent segment involves maintaining an axial position of the stent segments relative to the delivery catheter using a pusher member of the catheter and retracting an outer sheath disposed over the stent segments. Alternatively, releasing each stent segment may involve maintaining an axial position of an outer sheath disposed over the stent segments relative to the delivery catheter and advancing the stent segments out of a distal end of the sheath using a pusher member of the catheter.
• Further aspects of the nature and advantages of the invention will be apparent from the following detailed description of various embodiments of the invention taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a side, partially cut-away view of a prosthesis delivery catheter according to one embodiment of the present invention.
• FIGS. 2A and 2B are side cross-sectional views of a distal portion of a prosthesis delivery catheter with a stent bumper in a vessel according to one embodiment of the present invention, showing outer shaft retracted with prosthesis partially deployed, and prosthesis fully deployed, respectively.
• FIGS. 3A-3F are side cross-sectional views of a distal portion of a prosthesis delivery catheter with a stent bumper in a vessel according to one embodiment of the present invention, demonstrating a method for deploying stents in a vessel.
• FIGS. 4A-4C are side cross-sectional view of a distal portion of a prosthesis delivery catheter with a stent bumper in a vessel according to another embodiment of the present invention, demonstrating an alternative method for deploying stents in a vessel.
• FIG. 5 is a side cross-sectional view of a distal portion of a prosthesis delivery catheter with a stent bumper in a vessel according to another embodiment of the present invention.
• FIG. 6 is a side cross-sectional view of a distal portion of a prosthesis delivery catheter with a stent bumper in a vessel according to another embodiment of the present invention.
• FIG. 7 is a side cross-sectional view of a distal portion of a prosthesis delivery catheter with a stent bumper in a vessel according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• Referring toFIG. 1, a first embodiment of aprosthesis delivery catheter20 according to the invention is illustrated.Delivery catheter20 may have any of various constructions, including those described in co-pending U.S. patent application Ser. No. 10/637,713, (Attorney Docket No. 021629-000340US), filed Aug. 8, 2003; Ser. No. 10/874,859 (Attorney Docket No. 021629-000350US), filed Jun. 22, 2004; and Ser. No. 10/884,616, (Attorney Docket No. 021629-000360US), filed Jul. 2, 2004, all of which are hereby incorporated by reference.Delivery catheter20 has ahandle assembly21 and anelongated catheter body22 that includes three concentric tubular shafts, all axially slidable relative to one another: anouter shaft24, apusher26, and aninner shaft28. A distal portion ofdelivery catheter20 is shown schematically and in partial cutaway view for clarity. The distal portion, as well as other portions ofdelivery catheter20 may include additional features not shown. For example, a typical embodiment includes a guidewire tube/lumen for allowing passage of a guidewire. Such features are described in further detail, for example, in the co-pending patent applications described immediately above.
• Outer shaft24 has adistal extremity46 defining afirst lumen48. A plurality of stents50 (or stent segments) are disposed in a collapsed configuration withinfirst lumen48.Stents50 are preferably composed of a resilient material such as stainless steel or Nitinol so as to self-expand from the collapsed configuration to a radially expanded configuration when deployed fromfirst lumen48. Whilestents50 as illustrated have a wave-like or undulating pattern in a plurality of interconnected circumferential members, the pattern illustrated is merely exemplary and the stents of the invention may have any of a variety of strut shapes, patterns, and geometries. From 2 up to 10 or more stents may be carried byouter shaft24. Optionally, avalve member49 is mounted withinfirst lumen48 to facilitate separating thosestents50 to be deployed from those to remain withinouter shaft24, as described in co-pending U.S. patent application Ser. No. 10/412,714 (Attorney Docket No. 021629-000330US), filed Apr. 10, 2003, which is incorporated herein by reference.
• Coupled withinner shaft28 is anexpandable stent bumper60. In various embodiments,stent bumper60 may comprise an expandable wire or mesh basket, an expandable ring, shape-memory members such as petals, blades, prongs or other protrusions, or any of a number of other configurations. In a preferred embodiment, as shown,stent bumper60 is an inflatable balloon. In some embodiments,stent bumper60 is inflatable via an inflation lumen disposed withininner shaft28. Such an inflation lumen may alternatively be disposed on an outer surface ofinner lumen28 or the like. In some embodiments,stent bumper60 may be attached to, or a proximal extension of, anosecone36 ofdelivery catheter20. When expanded,stent bumper60 helps control the deployment ofstents50. For example, ifstent bumper60 is expanded and astent50′ is deployed out of the distal end ofcatheter body46,stent bumper60 has a diameter large enough, in its expanded configuration, to stop deployedstent50′ from moving distally, thus preventing “watermelon seeding” ofstent50′. The operation ofstent bumper60 will be described further below with reference to subsequent drawing figures.
• Handleassembly21 has arotatable retraction knob52 coupled to a shaft housing53, to whichouter shaft24 is fixed. By rotatingretraction knob52,outer shaft24 may be retracted proximally relative topusher26 andinner shaft28. Aswitch56 engages and disengagespusher26 withouter shaft28, so thatpusher26 either moves withouter shaft24 or remains stationary asouter shaft24 is retracted.Indicia58 on shaft housing53 indicate the extent of retraction ofouter shaft28 by distance, number of stents, or other suitable measure. Other aspects ofhandle assembly21 are described in co-pending application Ser. No. 10/746,466 (Attorney Docket No. 021629-002200US), filed Dec. 23, 2003, which is hereby incorporated by reference. Except as stated otherwise, any of the embodiments of the stent delivery catheter described below may incorporate the features, and be otherwise constructed as, just described.
• With reference now toFIGS. 2A and 2B, in some embodiments, astent delivery catheter180 includes anstent bumper160 comprising an inflatable balloon.Delivery catheter180 has a plurality ofstents182 disposed in anouter shaft184. Aninner shaft186, with adistal nosecone190, extends throughouter shaft184 andstents182 and is axially movable relative thereto. A pusher shaft (not shown) is slidably disposed overinner shaft186 and engagesstents182 for purposes of deployingstents182 fromouter shaft186 and repositioning the remainingstents182 withinouter shaft186, as in earlier embodiments. In this embodiment,stents182 comprise a plurality ofstruts191 forming a series ofrings192 interconnected atjoints193. Eachring192 has a series ofclosed cells194 interconnected circumferentially and having an “I” shape in the unexpanded configuration. Other aspects ofstents182 are described in co-pending U.S. application Ser. No. 10/738,666, which was previously incorporated by reference.
• Asouter shaft184 is retracted to deploy one ormore stents182, at least adistal ring192′ is configured to expand into engagement withstent bumper160 before the entire length ofstent182 is deployed from outer shaft184 (FIG. 2A). Oncedistal ring192′ is engaged withstent bumper160, the remainder ofstent182 is deployed (FIG. 2B),stent bumper160 thus preventing “watermelon seeding” ofstent182 fromcatheter180. Eachstent182 has at least two, and preferably four ormore rings192, each ring being about 2-5 mm in length, givingstent182 an overall length of at least about 8-20 mm. Of course, stents of shorter or longer length are also contemplated within the scope of the invention. Lesions longer than eachstent182 may be treated by deployingmultiple stents182 end-to-end. Advantageously, eachstent182 can be deployed precisely at a desired spacing from a previously-deployedstent182 becausestent bumper160 prevents unwanted overlapping of, or gaps between,stents182 caused by watermelon seeding.
• Rings192 are preferably formed from a common piece of material and are integrally interconnected atjoints193, makingjoints193 relatively rigid. In this embodiment, the majority of flexibility betweenrings192 is provided bystruts191 rather than byjoints193. Alternatively, joints193 may comprise welded connections betweenrings192 which are also fairly rigid. As a further alternative,joints193 may comprise hinge or spring structures to allow greater deflection betweenadjacent rings192.
• In various alternative embodiments, any of a number of alternative stents with alternative designs, shapes, sizes, materials and/or the like may be used. For example, a number of exemplary self-expanding stents that may be used withdelivery catheter180 are described in co-pending U.S. patent application Ser. Nos. 10/879,949 and 10/738,666, which were previously incorporated by reference.Stents192 may be made of any suitable material, such as but not limited to Nitinol™, a superelastic alloy, stainless steel, cobalt chromium, other resilient metals, resilient polymers or the like. In some embodiments,stent192 may be balloon expandable, rather than self-expanding, although this description focuses on the preferred self-expanding embodiments.
• Various alternative types of interconnecting structures between adjacent stents and between the stents and the pusher shaft are also possible within the scope of the invention, including those described in co-pending application Ser. No. 10/738,666, previously incorporated by reference. Such interconnecting structures may also be breakable or frangible to facilitate separation as the stent expands. In addition, a mechanism such as an expandable balloon or cutting device may be disposed at the distal end ofdelivery catheter180 to assist in separatingstents192 upon deployment. Further, the interconnections between stents may be different than the interconnection between the proximal-most stent and the pusher shaft. For example, the pusher shaft may have hooks, magnets, or other mechanisms suitable for releasably holding and maintaining traction on the proximal end of a stent until it is deployed.
• Referring toFIGS. 3A-3F, a method for deploying stents in a vessel is shown schematically. InFIG. 3A, astent delivery catheter210 is positioned within a vessel V, such that anosecone212 attached to the distal end of aninner shaft216 ofcatheter210 is distal to a lesion L.A stent bumper260 coupled withinner shaft216 is expanded (in this case an inflated balloon) to contact the vessel wall. Multiple stents250 (or stent segments) are housed within anouter shaft220 or sheath ofcatheter210, and apusher214 is used to maintain the axial position ofstents250 relative toouter shaft220.
• InFIG. 3B,outer shaft220 is retracted relative tostents250 andinner shaft216, whilepusher214 maintains the relative axial position ofstents250. Asouter shaft220 is retracted, adistal stent250′ begins to be deployed out of its distal end.Distal stent250′contacts stent bumper260, which preventsstent250′ from ejecting (“watermelon seeding”) distally.FIG. 3C showsdistal stent250′ fully deployed within the vessel V.
• As shown inFIG. 3D, after a firstdistal stent250′ has been fully deployed,stent bumper260 may be deflated, repositioned withdistal stent250′, and re-expanded. In some cases, this re-expansion helps further expanddistal stent250′, thus enhancing its ability to prop open the vessel V. Turning toFIG. 3E, after re-expansion ofstent bumper260,outer shaft220 may again be retracted relative tostents250 andinner shaft216, thus deploying a seconddistal stent250″. Seconddistal stent250″contacts stent bumper260, thus again avoiding watermelon seeding, which might causestents250″ and250′ to overlap.FIG. 3F shows firstdistal stent250′ and seconddistal stent250″ fully deployed within the vessel. This process may be repeated as many times as desired, to deploy as many stents250 (or stent segments) as desired.
• Referring now toFIGS. 4A-4C, in an alternative embodiment, astent delivery catheter310 may include astent bumper360 that comprises an elongate inflatable balloon. In such an embodiment, firstdistal stent250′ is deployed the same way as shown inFIGS. 3A-3C. As shown inFIG. 4A, after deployment of firstdistal stent250′, asheath322 disposed over a proximal portion ofstent bumper360 is retracted proximally to expose an additional portion ofstent bumper360, and the newly exposed portion of the inflatableballoon stent bumper360 is inflated within firstdistal stent250′. As described above,stent bumper360 in some embodiments may be used to further expand an already-expandeddistal stent250′.
• As shown inFIG. 4B, seconddistal stent250″ is then deployed from the distal end ofouter shaft220 to contactstent bumper360. InFIG. 4C, seconddistal stent250″ is fully deployed,sheath322 has been retracted farther proximally, and an additional portion ofstent bumper360 has been inflated within seconddistal stent250″. This process may be repeated as many times as desired to deploy asmany stents250 as desired.
• Referring now toFIG. 5, an alternative embodiment of astent delivery catheter410 includes anexpandable wire structure460 that acts as a stent bumper.Wire structure460 acts analogously to the stent bumpers described above. In the embodiment shown,wire structure460 is made of shape memory, super-elastic or other resilient material and assumes its expanded shape when exposed from the distal end of asheath422.Sheath422 may be retracted farther proximally to expose additional portions ofwire structure460 to help deployadditional stents250. In other embodiments, a wire ring or tube, expandable wire basket, mesh basket or the like may be pushed by a proximal pusher member or pulled by a puller coupled to its distal end to force the expandable stent bumper to buckle or otherwise expand.
• In another embodiment, and with reference now toFIG. 6, astent delivery catheter510 include astent bumper560 comprising multiple self-expanding petals562 (or alternatively prongs, blades, bristles or the like) coupled to anouter shaft522 slidable overinner shaft216.Petals562 are normally disposed withinnosecone212 and deploy/expand wheninner shaft216, to whichnosecone212 is attached, is advanced distally relative toouter shaft522, thereby exposingpetals562.Nosecone212 may be advanced further to allow greater expansion ofpetals562 or to expose additional sets ofpetals562.Petals562 may be made of metal, polymer or any other suitable resilient material(s).
• Referring now toFIG. 7, in another embodiment, astent delivery catheter610 includes astent bumper660 comprising multiple self-expandingprongs662 coupled withinner shaft216. Before deployment, prongs662 are disposed with asheath632 slidably disposed overinner shaft216. Whensheath632 is retracted proximally relative toinner shaft216 and/orinner shaft216 is advanced relative tosheath632,prongs662 are exposed, thus allowing them to assume their expanded configuration, as shown. After deployingfirst stent250′, which is prevented from watermelon seeding bystent bumper660,sheath632 may be retracted farther proximally and/orinner shaft216 may be advanced farther distally to expose a second set of prongs662 (not shown). Asecond stent250 may then be deployed to contact the second set ofprongs662. In various embodiments, any number ofstent bumpers660/sets ofprongs662 may be included, for promoting deployment of any number ofstents250.Prongs662 may be made of any resilient material, such as Nitinol, spring stainless steel, or other shape-memory or super-elastic materials.
• While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, improvements and additions are possible without departing from the scope thereof, which is defined by the claims.

Claims (20)

1. A catheter system for delivery of a stent to a body lumen comprising:

a stent delivery catheter comprising:

a sheath having a first lumen;

a shaft extending through the first lumen and slidable relative to the sheath;

a stent bumper mounted to the shaft distally of the sheath and movable from a contracted shape to an expanded shape; and

a plurality of self-expanding stent segments carried within the first lumen in a collapsed configuration, the stent segments being adapted to resiliently expand from the collapsed configuration to an expanded configuration, and

wherein the stent segments are deployable from the first lumen so as to resiliently expand into the expanded configuration, the stent bumper being expandable independently of the stent segments and configured in the expanded shape to engage a first stent segment during deployment thereof to maintain its position relative to an adjacent stent segment disposed proximal to the first stent segment, and

wherein the sheath is disposed over the balloon and the sheath is retractable to expose a portion of the stent bumper to allow it to expand from the contracted shape to the expanded shape.

2. A system as inclaim 1, wherein the stent bumper in the expanded shape has an outer diameter sized to contact an inner wall of the body lumen.

3. A system as inclaim 1, wherein the stent bumper in the expanded shape has an outer diameter sized to contact an inner wall of at least one of the expanded stents.

4. A system as inclaim 1, wherein the stent bumper comprises an inflatable balloon.

5. A system as inclaim 4, wherein the balloon is adapted to be deflated, positioned within the deployed first stent segment, and re-inflated to the expanded shape.

6. A system as inclaim 5, wherein the balloon in the expanded shape is adapted to further expand the deployed first stent segment.

7. A system as inclaim 1, wherein the axial length of the elongate balloon is between 20 mm and 250 mm.

8. A system as inclaim 1, wherein each of the stent segments has a length of between 3 mm and 30 mm.

9. A system as inclaim 1, wherein the plurality of stent segments comprises between 2 and 50 segments.

10. A system as inclaim 1, further comprising a pusher slidably disposed over the shaft, proximal to the stent segments, for advancing the stent segments relative to the sheath or holding the stent segments in place while the sheath is retracted.

11. A system as inclaim 1, wherein the stent bumper is adapted to be moved to the expanded shape while at least a portion of the stent segments remain in the collapsed configuration.

12. A system as inclaim 1, wherein the stent bumper engages the first stent segment as it expands thereby maintaining position of the first stent segment relative to the sheath.

13. A system as inclaim 1, wherein two or more stent segments are deployed sequentially without repositioning the delivery catheter relative to the body lumen.

14. A system as inclaim 1, wherein the stent bumper maintains the position of each stent segment during deployment such that adjacent stent segments do not overlap and a spacing between adjacent stent segments is no more than about 1 mm after deployment.

15. A method of delivering a stent to a body lumen comprising:

positioning a stent delivery catheter in the body lumen, the delivery catheter carrying at least first and second stent segments;

expanding a stent bumper on the delivery catheter;

releasing the first stent segment from the delivery catheter into the body lumen after the stent bumper has been fully expanded, the first stent segment resiliently self-expanding into an expanded configuration in the body lumen, wherein the stent bumper expands independently of the first stent segment and engages the first stent segment during expansion thereof to maintain its position relative to the delivery catheter;

before releasing the second stent segment, contracting the stent bumper;

positioning the contracted stent bumper within the expanded first stent segment;

re-expanding the stent bumper, wherein the stent bumper engages the second stent segment during expansion thereof to maintain its position relative to the delivery catheter and the first segment; and

releasing the second stent segment from the delivery catheter into the body lumen adjacent to the first stent segment,

wherein the stent bumper maintains the position of each stent segment during deployment such that adjacent stent segments do not overlap and a spacing between adjacent stent segments is no more than about 1 mm after deployment.

16. A method as inclaim 15, wherein expanding the stent bumper comprises inflating a balloon.

17. A method as inclaim 16, further comprising, before inflating the balloon, exposing a portion of the balloon from the distal end of an inner sheath disposed over the balloon.

18. A method as inclaim 15, wherein releasing each stent segment comprises:

maintaining an axial position of the stent segments relative to the delivery catheter using a pusher member of the catheter; and

retracting an outer sheath disposed over the stent segments.

19. A method as inclaim 15, wherein releasing each stent segment comprises:

maintaining an axial position of an outer sheath disposed over the stent segments relative to the delivery catheter; and

advancing the stent segments out of a distal end of the sheath using a pusher member of the catheter.

20. A method as inclaim 15, wherein the first and second stent segments are released sequentially without repositioning the delivery catheter relative to the body lumen.

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