| Devices and methods for controlling expandable prostheses during deployment -> Monitor Keywords |
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Devices and methods for controlling expandable prostheses during deploymentRelated 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.), Expandable Stent With Constraining MeansDevices and methods for controlling expandable prostheses during deployment description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050288766, Devices and methods for controlling expandable prostheses during deployment. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 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, to name some examples. Stents are typically implanted by means of long and 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.). [0002] 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. [0003] 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. [0004] Interleaving stents or stent segments such as those disclosed in co-pending application Ser. No. 10/738,666, 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. [0005] 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. Moreover, the stents and delivery systems should enable the deployment of interleaving stents or stent segments with precision and control over both the axial spacing and rotational position of each stent or segment. BRIEF SUMMARY OF THE INVENTION [0006] 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. [0007] In a first aspect of the invention, a prosthesis delivery catheter includes an outer shaft having a first lumen; a plurality of self-expanding tubular prostheses carried within the first lumen, the prostheses being adapted to radially expand upon deployment from the first lumen; a deployment mechanism for deploying a selected number of the prostheses from the first lumen; and a control member interactive with the prostheses to control expansion of the prostheses when the prostheses are deployed from the first lumen. [0008] The control member may comprise a plurality of axially-extending wires, the prostheses being coupled to the wires and axially slidable thereon, the wires being radially deflectable to allow controlled expansion of the prostheses. The wires may have free distal ends configured to move radially outward as the prostheses expand. The distal ends of the wires may be retractable into the outer shaft following deployment of the selected number of prostheses. The prostheses may have sidewalls with a plurality of openings, the wires being threaded through the openings. The wires may form a loop extending around the outside of the prostheses and through the inside of the prostheses, wherein the wires can be withdrawn from around the prostheses following deployment thereof. In such case, at least one end of each wire is releasable to allow the wire to be withdrawn following prosthesis deployment. [0009] The delivery catheter may further comprise an inner shaft disposed in the first lumen, the prostheses being slidably disposed around the inner shaft, wherein a distal end of each wire is releasably coupled to the inner shaft. A nosecone may be attached to the inner shaft distally of the prostheses, the distal end of each wire being releasably coupled to the nosecone. The inner shaft may also have an inner lumen and at least one port in communication with the inner lumen, wherein the control wires are slidably disposed through the inner lumen and the port. [0010] The control member may also comprise a sleeve disposed around the prostheses, the sleeve being expandable to allow controlled expansion of the prostheses. The sleeve may be elastomeric, an expandable mesh or woven material, or other expandable structure. When expanded, the sleeve may form a cone shape that flares in the distal direction. The sleeve may be slidable relative to the outer shaft. The sleeve may have at least one longitudinal slit therein whereby it expands by splitting at the longitudinal slit. The sleeve may have a pair of opposing edges bordering the longitudinal slit, a cone shape being formed by moving the edges at an angle relative to each other. The sleeve may also have a plurality of longitudinal sections or beams separated by longitudinal slits, the longitudinal sections being deflectable outwardly to allow controlled expansion of the prostheses. A retainer may be releasably coupled to the longitudinal sections to selectively prevent radial deflection thereof. The retainer may comprise a capsule coupled to an inner shaft slidably disposed through the first lumen, longitudinal sections being received in the capsule. [0011] The deployment mechanism of the delivery catheter may comprise a pushing element slidably disposed in the first lumen, the pushing element being in engagement with at least one of the prostheses to advance the prostheses distally relative to the outer shaft. In preferred embodiments, the prostheses are self-expandable, made of resilient or shape memory materials such as stainless steel, Nitinol or suitable polymers. Such self-expanding prostheses are held in an unexpanded state within the outer shaft until deployed therefrom, whereupon they resiliently expand to an expanded shape in contact with the vessel wall or lesion. The delivery systems of the invention will also be useful with balloon expandable prostheses. In either case, expandable balloons, valve members, and other mechanisms may also be included in the delivery catheter to facilitate stent deployment. [0012] In a further aspect of the invention, the prostheses are releasably interconnected to each other. In this case, the control member may comprise an interconnection structure on the pushing element, the interconnection structure being releasably coupled to at least one of the prostheses to resist distal movement of the prostheses relative to the outer shaft. [0013] In addition to controlling axial position of the stents relative to the delivery catheter and/or to each other during deployment, the control member of the delivery catheter is preferably configured to maintain rotational position of the prostheses relative to each other. This facilitates the delivery of stents having axially interleaving elements and prevents excessive spacing or overlap between such elements [0014] In still another aspect of the invention, a prosthesis delivery catheter for delivering prostheses into a vessel lumen comprises an outer shaft having a first lumen; a plurality of self-expanding tubular prostheses carried within the first lumen, the prostheses being adapted to radially expand upon deployment from the first lumen; a deployment mechanism for deploying a selected number of the prostheses from the first lumen; and an anchor member adapted to engage the vessel to limit movement of the outer shaft relative thereto when a prosthesis is being deployed. In one embodiment, the anchor member comprises an expandable member mounted on an inner shaft, the inner shaft being slidably disposed in the first lumen. The expandable member preferably comprises a balloon. The expandable member may be configured to expand within a deployed prosthesis in the vessel lumen. The expandable member is preferably configured to remain expanded within the deployed prosthesis while a second prosthesis is deployed adjacent to the deployed prosthesis. This maintains the relative positions of the deployed prosthesis and the delivery catheter so the second prosthesis is deployed at a predictable distance from the deployed prosthesis. [0015] In another aspect of the invention, a prosthesis delivery catheter for delivering prostheses into a vessel lumen comprises an outer shaft having a first lumen; a plurality of self-expanding tubular prostheses carried within the first lumen, the prostheses being adapted to radially expand upon deployment from the first lumen, each prosthesis comprising a distal portion and proximal portion, the distal portion being configured to expand into engagement with the vessel while the proximal portion is at least partially disposed in the first lumen; and a deployment mechanism for deploying a selected number of the prostheses from the first lumen. Preferably, the distal portion is configured to engage the vessel prior to deployment of the proximal portion so that the prosthesis remains in a generally constant position relative to the catheter as the proximal portion is deployed. [0016] In one embodiment, the distal and proximal portions of the prostheses are interconnected by at least one spring member, the spring member having a retracted shape and an elongated shape and being biased into the retracted shape, wherein deployment of the distal portion into the vessel elongates the spring into the elongated shape. In such a case, the deployment of the proximal portion into the vessel allows the spring to return at least partially to the retracted shape to draw the proximal portion toward the distal portion. [0017] In still another aspect, the invention provides a method of delivering one or more prostheses to a treatment site in a vessel comprising positioning a delivery catheter at the treatment site, the delivery catheter carrying a plurality of self-expanding prostheses; selecting a desired number of the prostheses to deploy; deploying the desired number of prostheses from the delivery catheter into the vessel, each prosthesis expanding into contact with the vessel upon deployment; and controlling the axial displacement of each of the selected number of prostheses relative to the delivery catheter during the deployment thereof. [0018] In one embodiment, the axial displacement is controlled by an expandable sleeve disposed around the desired number of prostheses. The method may further include retracting the sleeve from around the prostheses after the prostheses have been deployed. The axial displacement may also be controlled by a plurality of wires coupled with the desired number of prostheses. The wires may be threaded through openings in each of the prostheses, and may be retracted from the prostheses after the prostheses have been deployed. [0019] The method may further include controlling the rotational displacement of the selected number of prostheses relative to the delivery catheter and/or relative to each other during the deployment thereof. [0020] The axial displacement of the prostheses may be controlled by expanding an expandable member in the vessel during deployment of at least a portion of the desired number of prostheses. Alternatively, the axial displacement may be controlled by first expanding a distal portion of a first of the prostheses into engagement with the vessel while a proximal portion of the first of the prostheses remains in the delivery catheter, then expanding the proximal portion of the first of the prostheses into engagement with the vessel. [0021] As a further alternative, the prostheses may be releasably interconnected while in the delivery catheter, wherein the axial displacement is controlled by connecting at least one of the prostheses to a restraining member in the delivery catheter. In this case, the selected number of prostheses becomes detached from the prostheses remaining in the delivery catheter upon deployment. [0022] 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. 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