| Custom-length self-expanding stent delivery systems with stent bumpers -> Monitor Keywords |
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Custom-length self-expanding stent delivery systems with stent bumpersRelated Patent Categories: Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor, Arterial Prosthesis (i.e., Blood Vessel), Stent Combined With Surgical Delivery System (e.g., Surgical Tools, Delivery Sheath, Etc.)Custom-length self-expanding stent delivery systems with stent bumpers description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20080077229, Custom-length self-expanding stent delivery systems with stent bumpers. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] 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 [0002] 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.TM.). [0003] 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. [0004] 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. [0005] 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. [0006] 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 [0007] 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. [0008] 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. [0009] 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. [0010] 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. [0011] 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. [0012] 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. [0013] 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. [0014] 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. [0015] 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. [0016] 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. [0017] 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 [0018] FIG. 1 is a side, partially cut-away view of a prosthesis delivery catheter according to one embodiment of the present invention. [0019] 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. [0020] 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. 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