US20060282149A1 - Apparatus and methods for deployment of multiple custom-length prostheses (II) - Google Patents

Abstract

Apparatus for delivering stents to body lumens include one or more tubular prostheses carried at the distal end of a catheter shaft, a sheath slidably disposed over the prostheses, and a guidewire tube extending from within the sheath to the exterior of the sheath through an exit port in a sidewall thereof A guidewire extends slidably through the guidewire tube. The sheath can be moved relative to the catheter shaft and the guidewire tube to expose the prostheses for deployment. Methods of delivering stents are also provided.

Description

FIELD OF THE INVENTION
• This invention relates generally to vascular catheters, and more specifically to stents and stent delivery catheters for deployment in the coronary arteries and other vessels.
BACKGROUND OF THE INVENTION
• Stenting has become an increasingly important treatment option for patients with coronary artery disease. Stenting involves the placement of a tubular prosthesis within a diseased coronary artery to expand the arterial lumen and maintain the patency of the artery. Early stent technology suffered from problems with restenosis, the tendency of the coronary artery to become re-occluded following stent placement. However, in recent years, restenosis rates have decreased dramatically. As a result, the number of stenting procedures being performed in the United States, Europe, and elsewhere has soared.
• Stents are delivered to the coronary arteries using long, flexible vascular catheters typically inserted through a femoral artery. For self-expanding stents, the stent is simply released from the delivery catheter and it resiliently expands into engagement with the vessel wall. For balloon expandable stents, a balloon on the delivery catheter is expanded which expands and deforms the stent to the desired diameter, whereupon the balloon is deflated and removed.
• Current stent delivery technology, however, suffers from a number of drawbacks. For example, current stent delivery catheters are not capable of customizing the length of the stent in situ to match the size of the lesion to be treated. While lesion size may be measured prior to stenting using angiography or fluoroscopy, such measurements may be inexact. If a stent is introduced that is found to be of inappropriate size, the delivery catheter and stent must be removed from the patient and replaced with a different device of correct size.
• Moreover, current stent delivery devices cannot treat multiple lesions with a single catheter. Current devices are capable of delivering only a single stent with a single catheter, and if multiple lesions are to be treated, a new catheter and stent must be introduced for each lesion to be treated.
• Further, current stent delivery devices are not well-adapted for treating vascular lesions that are very long and/or in curved regions of a vessel. Current stents have a discrete length that is relatively short due to their stiffness. If current stents were made longer so as to treat longer lesions, they would not conform well to the curvature of vessels or to the movement of vessels on the surface of the beating heart. On the other hand, any attempt to place multiple stents end-to-end in longer lesions is hampered by the inability to maintain appropriate inter-stent spacing and to prevent overlap of adjacent stents.
• Additionally, some stent delivery catheters and angioplasty balloon catheters, particularly those having movable external sheaths to enclose the stent or balloon, suffer from poor tracking and cumbersome interaction with guidewires. Some such catheters utilize an “over-the-wire” design in which the guidewire extends through an inner lumen of the catheter from its proximal end to its distal end, a design that makes catheter exchanges cumbersome and time-consuming. Rapid exchange designs have also been proposed for such catheters wherein the guidewire extends through the distal end of the catheter and out through a port in a sidewall of the sheath. However, in these designs the guidewire inhibits smooth retraction of the sheath and, if the sheath is retracted a substantial distance, the port can become so displaced from the distal end of the catheter that the guidewire does not slide smoothly as the catheter is moved.
• Finally, many stent delivery catheters suffer from inflexibility and high cross-sectional profile, which hamper endovascular positioning.
• For these and other reasons, stents and stent delivery catheters are needed which enable the customization of stent length in situ, and the treatment of multiple lesions of various sizes, without requiring removal of the delivery catheter from the patient. Such stents and stent delivery catheters should be capable of treating lesions of particularly long length and lesions in curved regions of a vessel, and should be highly flexible to conform to vessel shape and movement. Such stent delivery catheters should further be of minimal cross-sectional profile and should be highly flexible for endovascular positioning through tortuous vascular pathways.
BRIEF SUMMARY OF THE INVENTION
• The invention provides apparatus and methods for delivering prostheses or stents into body lumens. In one aspect of the invention, an apparatus for delivering a prosthesis into a target vessel comprises a flexible catheter shaft having proximal and distal ends and a first lumen therein. A tubular prosthesis is releasably carried near the distal end of the catheter shaft and is expandable to a shape suitable for engaging the target vessel. A sheath is disposed over the catheter shaft and the tubular prosthesis and is axially movable relative thereto. The sheath has proximal and distal ends, a sidewall, and an exit port in the sidewall between the proximal and distal ends. A guidewire tube extends through the exit port and has a distal extremity disposed within the tubular prosthesis and a proximal extremity disposed outside of the sheath, the guidewire tube being adapted for slidably receiving a guidewire therethrough.
• Preferably, the guidewire tube is slidable through the exit port so that the sheath slides relative to the guidewire tube as it is retracted to expose the prosthesis for deployment. Usually the guidewire tube is fixed relative to the catheter shaft, and may be attached thereto. If an expandable member is mounted to the catheter shaft for prosthesis expansion, the guidewire tube may extend through and attach to the expandable member.
• Because the guidewire tube exits the sheath in a distal extremity thereof the sheath has a low profile portion proximal to the exit port that has a smaller diameter than the portion distal to the exit port. Not only does this reduce the cross-sectional profile, but increases the flexibility of the device.
• The exit port may be cut into the sidewall of the sheath to face laterally, or alternatively oriented so as to face generally in a proximal direction. The exit port is usually positioned so as to be closer to the distal end of the sheath than to the proximal end thereof, and is preferably a distance of about 20-35 cm from the distal end of the sheath. With the sheath advanced fully distally over the catheter shaft, the proximal extremity of the guidewire tube exposed outside the sheath is preferably about 3-15 cm in length, although various lengths are possible, even as long or longer than the catheter shaft itself. The proximal end of the guidewire tube is preferably disposed a distance of less than about one-half the length of the catheter shaft from the distal end thereof, but in some embodiments may extend further proximally, even as far as the proximal end of the catheter shaft.
• The apparatus of the invention may be configured to deliver tubular prostheses that are either self-expanding or expandable by a balloon or other expandable member. When self-expanding prostheses are used, the sheath is adapted to constrain the prosthesis in a collapsed configuration. Upon retraction of the sheath, the prosthesis is released and self-expands to engage the vessel.
• For balloon-expandable prostheses, an expandable member is mounted to the catheter shaft near the distal end thereof. The tubular prosthesis is positionable over the expandable member for expansion therewith. Usually the expandable member will comprise a balloon in communication with an inflation lumen in the catheter shaft for delivery of inflation fluid to the balloon. The sheath is axially positionable relative to the expandable member and configured to restrain expansion of a selected portion of the expandable member. Preferably the sheath is reinforced to prevent expansion thereof by the expandable member.
• In a preferred aspect of the invention, the tubular prosthesis comprises a plurality of prosthesis segments. The sheath is axially movable relative to the prosthesis segments and configured to restrain expansion of a selectable number of prosthesis segments. In this way, lesions of various lengths may be treated by adjusting the length of the prosthesis in situ, without removal of the device from the body. In these embodiments, a pusher may be slidably disposed within the sheath proximal to the tubular prosthesis. The pusher has a distal end in engagement with the tubular prosthesis for moving the tubular prosthesis relative to the catheter shaft.
• In a further aspect of the invention, a method of delivering a prosthesis in a target vessel of a patient comprises inserting a guidewire through the patient's vasculature to the target vessel; slidably coupling a delivery catheter to the guidewire, the delivery catheter having a sheath and a guidewire tube, a proximal extremity of the guidewire tube being outside the sheath and a distal extremity of the guidewire tube being inside the sheath, the guidewire being slidably positioned through the guidewire tube; advancing the delivery catheter over the guidewire to the target vessel; retracting the sheath relative to the guidewire tube to expose a tubular prosthesis carried by the delivery catheter; and expanding the tubular prosthesis into engagement with the target vessel.
• Usually, the guidewire tube will extend through an exit port in the sheath, and the guidewire tube will slide through the exit port as the sheath is retracted. The method may include sealing the exit port around the guidewire tube to restrict fluid flow therethrough, but preferably the exit port allows some fluid flow to provide flushing of the distal portion of the catheter.
• In a preferred embodiment, an expandable member is fixed to a distal portion of the guidewire tube and the tubular prosthesis is positionable over the expandable member. The sheath is slidably disposed over the prosthesis and the expandable member and may be retracted a selectable distance to expose a desired length of the prosthesis and expandable member. The tubular prosthesis will then be expanded by expanding the expandable member. The sheath may be used to cover a proximal portion of the expandable member to constrain the proximal portion from expansion while a distal portion of the expandable member expands. Usually, the expandable member is inflatable and will be inflated by delivering inflation fluid to the expandable member through an inflation lumen in the catheter shaft. The guidewire tube preferably extends through the interior of the expandable member, which may be attached to the guidewire tube.
• In a preferred aspect of the invention, the tubular prosthesis comprises a plurality of prosthesis segments, and the method includes positioning a first selected number of the prosthesis segments on the expandable member for expansion therewith. The method may further include positioning the sheath over a second selected number of the prosthesis segments to constrain expansion thereof. The first selected number of prosthesis segments may be positioned on the expandable member by pushing the first selected number with a pusher that is axially slidable relative to the expandable member.
• In alternative embodiments, the tubular prosthesis self-expands when the sheath is retracted. In embodiments in which the prosthesis comprises multiple prosthesis segments, the sheath may be retracted relative to a selected number of such segments to allow the segments to self-expand into contact with the vessel.
• In another aspect, the invention provides a balloon catheter for treating a target vessel that includes a flexible catheter shaft having proximal and distal ends and a first lumen therein. An expandable member is connected to the catheter shaft, and a sheath is disposed over the catheter shaft and the expandable member and is axially movable relative thereto. The sheath has an exit port in a sidewall thereof between its proximal and distal ends. A guidewire tube extends through the exit port and has a proximal extremity disposed outside of the sheath and a distal extremity disposed within the sheath that is coupled to the catheter shaft or the expandable member or both. The guidewire tube is adapted for slidably receiving a guidewire therethrough. The expandable member preferably comprises a balloon in fluid communication with the first lumen to receive inflation fluid therefrom. The sheath may be positionable to constrain a first selected portion of the expandable member from expansion while a second selected portion of the expandable member expands.
• In a preferred embodiment of the balloon catheter of the invention, a tubular prosthesis is disposed on the expandable member and is expandable therewith. The tubular prosthesis will preferably comprise a plurality of unconnected stent segments that are slidable relative to the expandable member. The sheath is positionable to expose a first selected portion of the stent segments while covering a second selected portion of the stent segments.
• In yet another aspect of the invention, an apparatus for delivering a prosthesis into a target vessel comprises a flexible catheter shaft having proximal and distal ends and a tubular prosthesis slidably coupled to the catheter shaft, the tubular prosthesis being expandable to a shape suitable for engaging the target vessel. A pusher is provided for moving the tubular prosthesis from a pre-deployment position to a deployment position near the distal end of the catheter shaft. The apparatus further includes a stop on the catheter shaft configured to engage the tubular prosthesis when the tubular prosthesis is in the deployment position.
• In one embodiment, an expandable member is coupled to the catheter shaft and the tubular prosthesis is adapted for expansion by the expandable member. The expandable member, e.g. balloon, has an interior, and the stop is preferably disposed within the interior of the expandable member. The stop may also be disposed outside of or on the exterior surface of the expandable member. Alternatively, the tubular prosthesis is self-expanding and expands upon being released from the catheter shaft.
• In a preferred aspect, a plurality of tubular prostheses are slidably coupled to the catheter shaft and are movable by the pusher to the deployment position. In addition, a sheath may be movably coupled to the catheter shaft and positionable over the tubular prosthesis or prostheses.
• In a further method of deploying a tubular prosthesis in a target vessel according to the invention a catheter shaft is positioned in a target vessel and the tubular prosthesis is moved distally relative to the catheter shaft while the catheter shaft remains in the target vessel until the prosthesis engages a stop near the distal end of the catheter shaft. The tubular prosthesis is then expanded to engage a wall of the target vessel.
• After expanding the tubular prosthesis, a second prosthesis (or any number of additional prostheses) may be moved distally relative to the catheter shaft until the second prosthesis engages the stop, and the second prosthesis then expanded to engage a wall of the target vessel. Alternatively, a second prosthesis may be moved distally relative to the catheter shaft simultaneously with moving the tubular prosthesis, and both the second prosthesis and the tubular prosthesis are expanded together to engage the wall of the target vessel. Usually, the tubular prosthesis and any additional prostheses are moved by a pusher movably coupled to the catheter shaft.
• The tubular prosthesis is preferably expanded by inflating a balloon coupled to the catheter shaft. Alternatively, the tubular prosthesis may be self-expandable.
• Further, the method may include retaining a second prosthesis in an unexpanded configuration on the catheter shaft while the tubular prosthesis is expanded. In one embodiment, the second prosthesis is retained within a sheath movably coupled to the catheter shaft.
• Further aspects of the nature and advantages of the invention will become apparent from the detailed description below taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a stent delivery catheter according to the invention with sheath retracted and expandable member inflated.
• FIG. 2A is a side cross-section of a distal portion of the stent delivery catheter ofFIG. 1 with expandable member deflated and sheath advanced distally.
• FIG. 2B is a side cross-section of a distal portion of the stent delivery catheter ofFIG. 1 with expandable member inflated and sheath retracted.
• FIG. 2C is a side cross-section of a distal portion of a stent delivery catheter illustrating radiopaque markers attached to the guidewire tube.
• FIG. 3 is a transverse cross-section through line3-3 ofFIG. 2A.
• FIG. 4 is a transverse cross-section through line4-4 ofFIG. 2A.
• FIG. 5A is a side view of a first embodiment of a stent segment according to the invention in an unexpanded configuration.
• FIG. 5B is a side view of the stent segment ofFIG. 5A in an expanded configuration.
• FIG. 6A is a side view of a second embodiment of a stent segment according to the invention in an unexpanded configuration.
• FIG. 6B is a side view of two of the stent segments ofFIG. 6A in an expanded configuration.
• FIGS. 7A-7E are side cut-away views of the stent delivery catheter of the invention positioned in a vessel with the stent segments ofFIGS. 5A-5B, illustrating various steps of delivering a prosthesis according to the method of the invention.
• FIG. 8 is a side cut-away view of the stent delivery catheter of the invention positioned in a vessel with the stent segments ofFIGS. 6A-6B in a deployed configuration.
• FIG. 9 is a perspective view of the distal portion of the stent delivery catheter of the invention with a portion of the outer sheath stripped away to reveal a garage member.
• FIG. 9A is an end view of a stop member.
• FIG. 10 is a planar view of a garage member.
• FIG. 11 is a side view of a garage member attached to a pair of mandrels.
• FIG. 12A is a side view of an expandable member in its expanded state.
• FIG. 12B is a side view of an expandable member in its contracted state and having a plurality of stent segments thereon.
• FIG. 12C is a side cross-section of an expandable member according to the invention.
• FIG. 13 is a side view of a pusher tube.
• FIG. 13A is a cross-sectional view of the pusher tube ofFIG. 13 taken at line A-A.
• FIGS.14A-B are side views of a stent segment embodiment having radiopaque markers affixed thereto.
• FIGS.15A-C are side views of stent segment embodiments having radiopaque marker coatings applied thereto.
• FIGS.15D-E are side views of multiple stent segments in their expanded configurations having radiopaque marker coatings applied thereto.
• FIG. 16 is a side view of a slider tube.
• FIG. 16A is a cross-sectional view of the slider tube ofFIG. 16 taken at line A-A.
• FIG. 17 is a side view of a slider body.
• FIG. 17A is a cross-sectional view of the slider body ofFIG. 17 taken at line A-A.
• FIG. 17B is an end view of the slider body ofFIG. 17.
• FIG. 18 is a side view of a slider cap.
• FIG. 18A is an end view of the slider cap ofFIG. 18.
• FIG. 19 is a perspective view of a slider seal.
DETAILED DESCRIPTION OF THE INVENTION
• The present application relates generally to copending U.S. patent application Ser. No. 10/637,713, entitled “Apparatus and Methods for Deployment of Vascular Prostheses,” filed Aug. 8, 2003, which application is hereby incorporated by reference.
• A first embodiment of a stent delivery catheter according to present invention is illustrated inFIG. 1.Stent delivery catheter20 includes acatheter body22 comprising anouter sheath25 slidably disposed over an inner shaft27 (not shown inFIG. 1). Anexpandable member24, preferably an inflatable balloon (shown in an inflated configuration), is mounted toinner shaft27 and is exposed by retractingsheath25 relative toinner shaft27. A taperednosecone28, composed of a soft elastomeric material to reduce trauma to the vessel during advancement of the device, is mounted distally ofexpandable member24. Astent30, which preferably comprises a plurality of separate orseparable stent segments32, is disposed onexpandable member24 for expansion therewith. Aguidewire tube34 is slidably positioned through a guidewiretube exit port35 insheath25 proximal toexpandable member24. Aguidewire36 is positioned slidably throughguidewire tube34,expandable member24, andnosecone28 and extends distally thereof.
• Ahandle38 is attached to aproximal end23 of thesheath25. Thehandle38 performs several functions, including operating and controlling thecatheter body22 and the components included in the catheter body. Various embodiments of a preferred handle and additional details concerning its structure and operation are described in co-pending U.S. patent application Ser. No. ______, filed Jun. 8, 2005, (Attorney Docket No. 14592.4002), entitled “Devices and Methods for Operating and Controlling Interventional Apparatus,” which application is hereby incorporated herein by reference. Embodiments of another preferred handle and details concerning its structure and operation are described in co-pending U.S. application Ser. No. 10/746,466, filed Dec. 23, 2003 (Attorney Docket No. 021629-002200US), entitled “Devices and Methods for Controlling and Indicating the Length of an Interventional Element,” which application is also hereby incorporated herein by reference.
• Thehandle38 includes ahousing39 that encloses the internal components of the handle. Theinner shaft27 is preferably fixed to the handle, while theouter sheath25 is able to be retracted and advanced relative to thehandle38. Anadaptor42 is attached to thehandle38 at its proximal end, and is fluidly coupled to theinner shaft27 in the interior of the housing of thehandle38. Theadaptor42 is configured to be fluidly coupled to an inflation device, which may be any commercially available balloon inflation device such as those sold under the trade name “Indeflator™”, available from Guidant Corp. of Santa Clara, Calif. The adaptor is in fluid communication with theexpandable member24 via an inflation lumen in theinner shaft27 to enable inflation of theexpandable member24.
• Theouter sheath25 and guidewire36 each extend through aslider assembly50 located on thecatheter body22 at a point between its proximal and distal ends. Theslider assembly50 is adapted for insertion into and sealing within a hemostatic valve, such as on an introducer sheath or guiding catheter, while allowing relative movement of theouter sheath25 relative toslider assembly50. Theslider assembly50 includes aslider tube51, aslider body52, and aslider cap53. These components are illustrated in greater detail inFIGS. 16-19.
• In particular,FIGS. 16 and 16A show theslider tube51, which comprises an elongated cylindrical member having a first through-hole51 a and a second through-hole51b. The first through-hole51ahas a size to provide a slidable passageway for thecatheter body22, whereas the second through-hole51bhas a size to provide a slidable passageway for theguidewire34. Theslider tube51 is preferably formed from a polymeric material, such as PTFE, FEP, polyimide, nylon, or Pebax. Theslider body52 is illustrated inFIGS. 17 and 17A-B. Theslider body52 is also an elongated member having acylindrical section160 and atapered section161. The taperedsection161 has aninternal recess161 a that has an interior diameter that provides a snug fit with the external surface of theslider tube51. Thecylindrical section160 has aninternal recess160athat has an interior diameter that provides a snug fit with the external surface of theslider cap53. Theslider body52 also includes a first through-hole52asized to allow slidable passage of thecatheter body22, and a second through-hole52bsized to allow passage of theguidewire34. The slider body is preferably formed from a resilient, relatively incompressible material, such as polycarbonate, and has an exterior surface adapted for being clamped and sealed within a hemostasis valve, preferably being smooth and cylindrical in shape. Theslider cap53 is a relatively short cylindrical member having a first through-hole53asized to allow slidable passage of thecatheter body22, and a second through-hole sized to allow slidable passage of theguidewire34. Theslider cap53 has a size that provides a snug fit with theinternal recess160aof thecylindrical section160 of the slider body. Theslider cap53 is also preferably formed of a resilient, relatively incompressible material, such as polycarbonate.
• Aslider seal54 is illustrated inFIG. 19. The slider seal is a short, disc-shaped member having a size adapted to fit snugly within theinternal recess160aof thecylindrical section160 of the slider body. Theslider seal54 includes a first through-hole54asized to allow fluidly sealed, slidable passage of thecatheter body22, and a second through-hole54bsized to allow fluidly sealed, slidable passage of theguidewire34. The slider seal is preferably formed of a pliable, resilient material, such as a polymeric material or a silicone compound that is capable of providing a fluid-tight seal with the sheath and guidewire while allowing slidable movement thereof.
• Theslider assembly50 is constructed by installing the proximal end of theslider tube51 into theinternal recess161 a of the taperedportion161 of the slider body, taking care to align the first and second through-holes of each member appropriately. Theslider seal54 is installed in theinternal recess160aof thecylindrical portion160 of the slider body, and theslider cap53 is placed over theslider seal54 within theinternal recess160a, again taking care to ensure that the first and second through-holes of each component are properly aligned. The components are then bonded together by heating or by use of adhesives or other suitable means. The completedslider assembly50 is then placed over thecatheter body22 and theguidewire34 as shown inFIG. 1.
• Referring now toFIGS. 2A-2B,3 and4, which show a distal portion of the stent delivery catheter in cross-section, it may be seen thatsheath25 may be extended up to nosecone28 to fully surroundexpandable member24 andstent segments32. Agarage55 is attached to theouter sheath25 at thedistal end57 of the sheath. Thegarage55 is a generally cylindrical member having a relatively high circumferential strength such that it is able to prevent theexpandable member24 from inflating when the garage is extended over theinflatable member24. Thegarage55 preferably has a length at least as long as one of thestent segments32 carried by the catheter, but preferably less than the combined length of two such stent segments. Thegarage55 is shown in more detail inFIGS. 9-11, and is described more fully below. Aradiopaque marker56 is preferably formed integrally with or attached to the distal end of thegarage55 to facilitate visualization of the position of thesheath25 using fluoroscopy. Theradiopaque marker56 may have an axial length selected to provide a visual reference for determining the appropriate distance for stent segment separation, e.g., 2-4 mm, as described below.
• Theouter sheath25 further includes avalve member58 within thegarage55 preferably spaced proximally from the distal end57 a distance equal to, slightly larger than, or slightly smaller than the length of one of thestent segments32. For example, in a preferred embodiment, eachstent segment32 has a length of about 4 mm, and thevalve member58 is located approximately 5 mm from thedistal end57 of the sheath or the distal end of thegarage member55. In other embodiments, thevalve member58 may be spaced from the distal end57 a distance equal to about ¼-¾ of the length of onestent segment32, more preferably one-half the length of onestent segment32.Valve member58 preferably comprises a necked-down circumferential waist or inwardly extending ring-shaped flange60 configured to frictionally engagestent segments32 and thereby restrict the sliding movement ofstent segments32 distally relative tosheath25. Flange60 may be a polymeric or metallic material integrally formed withsheath25 or, preferably, with thegarage55, or a separate annular member bonded or otherwise mounted to the interior of thesheath25 or thegarage55. The geometry of flange60 may be toroidal with circular cross-section (like an O-ring) or it may have another cross-sectional shape such as triangular, trapezoidal, or pyramidal. Preferably flange60 is a polymer such as silicone or urethane sufficiently soft, compliant, and resilient to provide frictional engagement withstent segments32 without damaging the stent segment or any coating deposited thereon.Valve member58 will extend radially inwardly a sufficient distance to engage the exterior ofstent segments32 with sufficient force to allow the line ofstent segments32 remaining withinsheath25 to be retracted proximally withsheath25 so as to create spacing relative to those stent segments disposed distally ofsheath25 for deployment. At the same time,valve member58 should not exert so much force that it removes or damages the coating on the exterior surface ofstent segments32 assheath25 is retracted relative to the stent segments to expose a desired number ofstent segments32. In a preferred embodiment,stent segments32 have an outer diameter of about 0.040-0.050 in. (including coating) andsheath25 andgarage55 have inner diameter 0.041-0.051 in. so as to provide clearance of about 0.001 in. withstent segments32.Valve member58 has a preferred inner diameter about 0.003-0.008 in. less than that ofgarage55, or about 0.033-0.048″, so as to provide an interference fit withstent segments32.Valve member58 will preferably exert a force of about 0.5-5 lbs. on astent segment32 positioned within it. Various embodiments ofvalve member58 are described in copending application Ser. No. 10/412,714, Filed Apr. 10, 2003 (Attorney Docket No. 21629-000330), which is incorporated herein by reference.
• FIGS. 9-11 illustrate thegarage55, theradiopaque marker56, and thevalve member58 in greater detail. Thegarage55 is a cylindrical member that is preferably mounted to the distal end of theouter sheath25.FIG. 9 illustrates thegarage55 as it is oriented surrounding thestent segments32 aligned over the inner shaft. The distal portion of theouter sheath25 is shown stripped away inFIG. 9 to reveal the orientation of thegarage55. Thecylindrical garage55 is preferably formed of a metallic, polymeric, or other material and in a geometry to provide high radial strength and high axial flexibility. Superelastic alloys are preferred materials. A preferred garage material is Nitinol.
• The structure of thegarage55 is illustrated inFIG. 10, in which thegarage55 is shown in a planar form for clarity. Thegarage55 is preferably laser cut from a tube, but may also be cut, stamped, or otherwise formed from a sheet of material.
• A number of cut-outs or windows59 are preferably formed in the body of the garage to increase its axial flexibility. Preferably, thegarage55 is constructed in a manner and of materials that allow it to bend about a transverse axis. Although the number, size, and shape of the cut-outs59 may vary, the illustrated embodiment includes a preferred form. Thedistal end55aof thegarage55 is provided with no cut-outs in order to provide the greatest radial strength at the distal end of the sheath, where the restraining force against theexpandable member24 is the greatest. A pair of first cut-outs59ahaving oval or rectangular shape are formed a short distance from thedistal end55aof the garage, the pair of first cut-outs59abeing aligned circumferentially around the periphery of the garage. A series of narrow second cut-outs59bhaving a linear or slot-like shape are formed over the central portion of the body of thegarage55. Preferably, the second cut-outs59bare provided in a staggered formation to provide greater axial flexibility over the central portion of the garage. A series of third cut-outs59care located just proximally of the central portion of the garage. The third cut-outs59care of a similar size and shape to the first cut-outs59a, but are circumferentially staggered from the first cut-outs59a. A series of fourth rectangular or oval-shaped cut-outs59dare located just proximally of the third cut-outs, and are both narrower and shorter than the third cut-outs59c. Finally, a series of fifth cut-outs59ehaving a hexagonal shape are provided near theproximal end55bof the garage. Each of the fifth cut-outs59eis substantially wider (i.e., greater longitudinal length) than the other cut-outs59a-d. As noted below, the position of the fifth cut-outs corresponds with the location of thevalve member58.
• Turning toFIG. 11, thegarage55 is shown supported on aproximal mandrel150 and adistal mandrel152 to facilitate attachment of thevalve member58 andsheath25 thereto. The proximal mandrel is provided with an indentation or concavity adapted to receive and retain thevalve member58 in place for the purpose of attaching thevalve member58 to thegarage55 andouter sheath25. Theradiopaque marker56 may be placed over thedistal end55aof thegarage55. After the foregoing components have been properly aligned, theouter sheath25 is attached to theproximal end55bofgarage55, preferably by placing a piece of shrink tubing over the garage and distal end of the outer sheath and heating the assembly. Thegarage55 is thereby covered with a polymer material about its exterior. Of course various other attachment techniques may be used including heat treatment, adhesives, or other methods known to those skilled in the art.
• As thus described, thesheath25 has adistal extremity62 configured to surroundexpandable member24 andstent segments32 disposed thereon when in an unexpanded configuration.Distal extremity62 extends proximally to ajunction63, preferably aligned with the location of guidewiretube exit port35, wheredistal extremity62 is joined to aproximal extremity64 that extends proximally to handle38 (seeFIG. 1). In a preferred embodiment,distal extremity62 has a length of about 15-35 cm andproximal extremity64 as a length of about 100-125 cm.Proximal extremity64 may be constructed of a variety of biocompatible polymers, metals, or polymer/metal composites, preferably being stainless steel or Nitinol.Distal extremity62 may be a polymer such as PTFE, FEP, polyimide, nylon, or Pebax, or combinations of any of these materials. In a preferred form, thedistal extremity62 comprises a composite of nylon, PTFE, and polyimide. The distal extremity is preferably reinforced with a metallic or polymeric braid to resist radial expansion whenexpandable member24 is expanded.Sheath25 may further have a liner surrounding its interior of low friction material such as PTFE to facilitate relative motion ofsheath25,stent segments32, andpusher tube86.
• Preferably,proximal extremity64 has a smaller transverse dimension thandistal extremity62 to accommodate the added width ofguidewire tube34 within the vessel lumen, as well as to maximize flexibility and minimize profile. In one embodiment, shown inFIG. 3,distal extremity62 is a tubular member having a first outer diameter, preferably about 1.0-1.5 mm, andproximal extremity64 is a tubular member having a second, smaller outer diameter, preferably about 0.7-1.0 mm. At the junction ofproximal extremity64 withdistal extremity62, a proximally-facing crescent-shapedopening65 is formed between the two tubular members that creates guidewiretube exit port35. Excess space within crescent-shapedopening65 may be filled with a filler material such as adhesive or a polymeric material (e.g., Pebax).
• In an alternative embodiment (not shown), a hole is formed in the sidewall ofdistal extremity62 orproximal extremity64 to create guidewiretube exit port35. Proximally of guidewiretube exit port35, the wall ofsheath25 adjacent to guidewiretube34 is flattened or collapsible inwardly thereby reducing the transverse dimension ofsheath25 to accommodate the width ofguidewire tube34.
• Guidewire tube34 is slidably positioned through guidewiretube exit port35. The guidewiretube exit port35 may be configured to provide a total or partial fluid seal around the periphery ofguidewire tube34 to limit blood flow into the interior ofsheath25 and to limit leakage of saline (or other flushing fluid) out ofsheath25. This may be accomplished by sizing guidewiretube exit port35 appropriately so as to form a fairly tight frictional seal aroundguidewire tube34 while still allowing the sliding motion thereof relative tosheath25. Alternatively an annular sealing ring may be mounted in guidewiretube exit port35 to provide the desired seal. Preferably, however, the guidewiretube exit port35 is not totally fluid sealed, so as to provide a slight leakage or fluid flow to provide the ability to flush thedistal extremity62 of the catheter.
• Guidewiretube exit port35 will be positioned to provide optimal tracking ofstent delivery catheter20 through the vasculature and maximizing the ease with which the catheter can be inserted onto and removed from a guidewire to facilitate catheter exchanges. Usually, guidewiretube exit port35 will be positioned at a location proximal toexpandable member24 whensheath25 is extended fully distally up tonosecone28, but a distance of no more than one-half the length ofsheath25 fromdistal end57. In preferred embodiments for coronary applications, guidewiretube exit port35 is spaced proximally a distance of about 20-35 cm from thedistal end57 ofsheath25.
• Guidewire tube34 should extend proximally from guidewire tube exit port35 a distance at least as long as the longest possible stent that may be deployed, e.g., 30-200 mm depending upon the application, to allow for retraction ofsheath25 that distance while retaining a portion ofguidewire tube34 external tosheath25. Preferably theguidewire tube34 extends proximally a distance of about 35 to about 70 mm from the guidewiretube exit port35 whensheath25 is in a fully distal position, with the proximal end thereof disposed a distance of about 23-50 cm from the distal tip ofnosecone28. Wherestent delivery catheter20 is to be positioned through a guiding catheter, the proximal end ofguidewire tube34 will preferably be positioned so as to be within the guiding catheter whenexpandable member24 is positioned at the target site for stent deployment.Guidewire tube34 is preferably a highly flexible polymer such as PTFE, FEP, polyimide, or Pebax, and may optionally have a metal or polymer braid or fiber embedded in it to increase kink-resistance and tensile strength.
• Inner shaft27 forms aninflation lumen66 that is in communication with interior ofexpandable member24. Theinner shaft27 may be formed of a polymer material such as PTFE, FEP, polyimide, or Pebax, or theinner shaft27 may be a metal such as stainless steel or Nitinol.
• Expandable member24 has anexpandable balloon member70 that is joined to a non-expandabletubular leg72.Expandable balloon member70 is a semi-compliant polymer such as Pebax, polyurethane, or Nylon. Non-compliant, fully elastic, or other materials such as PTFE may also be used. Preferably, the compliance of the balloon member allows the expanded diameter ofballoon member70 to be adjusted by selecting the appropriate inflation pressure delivered thereto, thereby allowing customization of the deployed diameter ofstent segments32. For example, in one embodiment,balloon member70 may be inflated to a pressure of between about 5 and about 12 atmospheres, allowing the deployed stent diameter to be adjusted from about 2.0 mm to 4.0 mm. Of course, larger and smaller stent diameters are also possible by utilizing appropriate stent geometry and applying suitable inflation pressures.Tubular leg72 is preferably a polymer such as polyimide, PTFE, FEP, polyurethane, or Pebax and may optionally be reinforced with a metal or polymer braid or metal or polymer fibers.Tubular leg72 has an openproximal end74 through whichguidewire tube34 extends.Proximal end74 oftubular leg72 is fixed todistal end68 ofinner shaft27 and to guidewiretube34, forming a fluid-tight seal.Guidewire tube34 passes through the interior ofballoon member70 and is mounted tonosecone28, thereby providing a passage through the distal portion ofcatheter body22 through which guidewire36 may pass.Balloon member70 has adistal end76 that extends over anannular stop78, which is mounted to the distal end ofguidewire tube34 and/ornosecone28.Distal end76 ofballoon member70 may be bonded to stop78,guidewire tube34, and/ornosecone28. Thestop78 has a size and shape selected to engagestent segment32 and provide a stop against whichstent segments32 can be located in the ideal deployment position without being pushed beyond the distal end ofballoon member70. Additional details concerning stent stops suitable for use in the devices and methods described herein are disclosed in U.S. patent application Ser. No. 10/884,616, filed Jul. 2, 2004, (Atty. docket 21629-000360), which is hereby incorporated by reference herein.
• Preferably, thestop78 has a partial cylindrical shape, rather than a full cylindrical shape, as a relief to reduce interference withgarage55. For example,FIGS. 9 and 9A illustrate thestop78 having aflat portion81 formed on the opposed lateral surfaces of thestop78. A similar flat portion may be formed on the upper and lower sides of thestop78. The provision of flat portions on thestop78 allows thestop78 to limit distal movement of thestent segments32, while reducing interference betweenstop78 and the interior ofgarage55.
• Optionally, within the interior ofballoon member70 anannular base member80 is mounted toguidewire tube34 and has a diameter selected to urgeballoon member70 againststent segments32 in their unexpanded configuration, thereby providing frictional engagement withstent segments32. This helps to limit unintended sliding movement ofstent segments32 onballoon member70.Base member80 may be made of a soft elastomer, foam, or other compressible material.
• An additional option or alternative structure for limiting unintended sliding or movement of the stent segments is the provision on the distal exterior portion of theexpandable member24 of a layer ofmaterial84 having a high coefficient of friction so as to frictionally engage thestent segments32. See FIGS.12A-C. For example, a layer of apolymeric material84, such as polyurethane, will prevent thestent segments32 from sliding off the distal end of the balloon, and will cause thestent segments32 to stop in the desired location near the distal end of theexpandable member24. The layer ofmaterial84 is preferably formed over the entire circumference of the distal end of theexpandable member24, as shown in the Figures, but may alternatively be placed only at spaced intervals around the periphery. Thematerial layer84 is preferably formed of elastomeric materials and in a manner that allows it to expand and contract as theexpandable member24 expands and contracts. For example, thematerial layer84 may be applied by dipping theexpandable member24 in a liquid polymer, by spraying, or by attaching a sheet or tube of material over theexpandable member24 by adhesive or heat treatment. As thestent segments32 move distally relative to theexpandable member24 in its contracted state, the distal end of the most distal stent segment will come into contact with the layer ofmaterial84 and the friction force encountered by thestent segment32 will increase. This will inhibit or prevent additional relative movement between thestent segment32 and theexpandable member24. In addition, the increased frictional resistance may serve as a tactile indicator to the user of the position of thestent segment32 relative to theexpandable member24.Material layer84 may be of equal thickness along it length, or the thickness of thematerial layer84 may gradually increase in the distal direction to provide gradually increasing interference withstent segments32.Material layer84 may have an outer surface at the same height as the outer surface ofexpandable member24 to provide a smooth transition therebetween, ormaterial layer84 may be of greater height to provide a step that enhances engagement withstent segments32.
• In a preferred embodiment as shown inFIG. 12C,expandable member24 is molded with a circumferential channel, stepped geometry, and/or with reduced wall thickness near its distal end so as to have a smaller outer diameter in the region where thematerial layer84 is to be applied to accommodate the thickness ofmaterial layer84. In this way, the outer wall of theexpandable member24 andmaterial layer84 will be smooth and continuous without an abrupt change in elevation, allowingstent segments32 to slide smoothly from theexpandable member24 to thematerial layer84. Alternatively,expandable member24 and/ormaterial layer84 may have an outer diameter or wall thickness that is stepped outwardly or that gradually increases in the distal direction so as to increase the frictional resistance withstent segments32. In alternative embodiments,material layer84 may have surface features such as bumps, ridges, projections, or scales to increase friction againststent segments32.
• Annularradiopaque markers82 may be mounted to theguidewire tube34, facilitating visualization of the location ofballoon member70 with fluoroscopy and enabling appropriate positioning ofstent segments32 onballoon member70. Referring toFIG. 2C, theradiopaque markers82 are preferably located at regular intervals along the length of theguidewire tube34. In a particularly preferred form, theradiopaque markers82 are spaced at intervals that are related to the length ofindividual stent segments32, such as being at intervals equal to the stent segment lengths, one-half of stent segment length, double stent segment length, or the like. Stated otherwise, the distance between the distal ends of adjacent markers82 (or the proximal ends ofadjacent markers82, or the mid-points ofadjacent markers82, etc.) are provided equal to the stent segment lengths, one-half of stent segments length, double stent segment length, or the like. Locating multipleradiopaque markers82 on theguidewire tube34 at regularly spaced intervals provides a visual reference for determining the location and number ofstent segments32 onexpandable member24 under fluoroscopy. Further, the length ofexpandable member24 andstent segments32 exposed during retraction ofsheath25 may be determined under fluoroscopy by observing the position ofmarker56 ongarage member55 relative to marker(s)82 onguidewire tube34. Alternatively, only asingle marker82 at or near the distal end ofballoon member70 may be used, or markers may be placed at both the distal end and proximal end of thebase member80, or markers may be placed at other locations onnosecone28,guidewire tube34, orinner shaft27. Such markers may be made of various radiopaque materials such as platinum/iridium, tantalum, gold, and other materials.
• Stent segments32 are slidably positioned overballoon member70. Depending upon the number ofstent segments32 loaded instent delivery catheter20,stent segments32 may be positioned over bothballoon member70 andtubular leg72. In an exemplary embodiment, each stent segment is about 2-20 mm in length, more preferably 2-8 mm in length, and 3-50 stent segments may be positioned end-to-end in a line overballoon member70 andtubular leg72.Stent segments32 preferably are in direct contact with each other, but alternatively separate spacing elements may be disposed between adjacent stent segments, the spacing elements being movable with the stent segments alongballoon member70. Such spacing elements may be plastically deformable or self-expanding so as to be deployable withstent segments32 into the vessel, but alternatively could be configured to remain onballoon member70 following stent deployment; for example, such spacing elements could comprise elastic rings which elastically expand withballoon member70 and resiliently return to their unexpanded shape whenballoon member70 is deflated. The spacing elements could be pushed to the distal end ofballoon member70 againststop78 asadditional stent segments32 are advanced distally.
• Stent segments32 are preferably a malleable metal so as to be plastically deformable byexpandable member24 as they are expanded to the desired diameter in the vessel. Alternatively,stent segments32 may be formed of an elastic or super elastic shape memory material such as Nitinol so as to self-expand upon release into the vessel by retraction ofsheath25.Stent segments32 may also be composed of polymers or other suitable biocompatible materials including bioabsorbable or bioerodable materials. In self-expanding embodiments,expandable member24 may be eliminated or may be used for predilatation of a lesion prior to stent deployment or for augmenting the expansion of the self-expanding stent segments.
• In preferred embodiments,stent segments32 are coated with a drug that inhibits restenosis, such as Rapamycin, Paclitaxel, Biolimus A9 (available from BioSensors International), analogs, prodrugs, or derivatives of the foregoing, or other suitable agent, preferably carried in a durable or bioerodable polymeric or other suitable carrier material. Alternatively,stent segments32 may be coated with other types of drugs and therapeutic materials such as antibiotics, thrombolytics, anti-thrombotics, anti-inflammatories, cytotoxic agents, antiproliferative agents, vasodilators, gene therapy agents, radioactive agents, immunosuppressants, and chemotherapeutics. Several preferred therapeutic materials are described in U.S. Published Patent Application No. 2005/0038505, entitled “Drug-Delivery Endovascular Stent and Method of Forming the Same,” filed Sep. 20, 2004, which application is hereby incorporated by reference herein. Such materials may be coated over all or a portion of the surface ofstent segments32, orstent segments32 may include apertures, holes, channels, pores, or other features in which such materials may be deposited. Methods for coatingstent segments32 are described in the foregoing published patent application. Various other coating methods known in the art may also be used, including syringe application, spraying, dipping, inkjet printing-type technology, and the like.
• Stent segments32 may have a variety of configurations, including those described in copending application Ser. No. 10/738,666, filed Dec. 16, 2003 (Attorney Docket No. 21629-000510), which is incorporated herein by reference. Other preferred stent configurations are described below.Stent segments32 are preferably completely separate from one another without any interconnections, but alternatively may have couplings between two or more adjacent segments which permit flexion between the segments. As a further alternative, one or more adjacent stent segments may be connected by separable or frangible couplings that are separated prior to or upon deployment, as described in co-pending application Ser. No. 10/306,813, filed Nov. 27, 2002 (Attorney Docket No. 21629-000320), which is incorporated herein by reference.
• Apusher tube86 is slidably disposed overinner shaft27. The structure of thepusher tube86 is illustrated inFIG. 13, and its location within thecatheter body22 is best shown in FIGS.2A-B. Thepusher tube86 contains three primary sections, adistal extension88, aribbon portion89, and aproximal portion90. Theproximal portion90 extends from thehandle38 over theinner shaft27 and to theribbon portion89. Theproximal portion90 is preferably formed of a tubular material to provide high column strength but adequate flexibility to extend through the vasculature from an access site to the coronary ostia or other target vascular region. A preferred material is stainless steel hypotube. Theribbon portion89 of the pusher tube corresponds with the location of theguidewire exit port35 on theouter sheath25. Theribbon portion89 is formed of a partial-tube, see, e.g.,FIG. 13A, in order to provide an opening to allow theguidewire tube34 to pass through to theexit port35. The proximal portion of theribbon portion89 is formed out of the same tubular material that makes up theproximal portion90 of the pusher tube, e.g., stainless steel hypotube. The proximal portion of theribbon portion89 is joined to the distal portion of theribbon89, such as by aweld91 or the ribbon portion and proximal portion may be formed from the same hypotube which is laser cut in the appropriate geometry. Thedistal extension88 is preferably formed of a slotted tube of rigid material, such as stainless steel or Nitinol. The slotted tube making up thedistal extension88 includes a number ofcylindrical rings92 interconnected bylongitudinal connectors93, thereby defining a plurality oftransverse slots97 arranged in pairs along the length of the distal extension. Each pair of slots is disposed opposite one another ondistal extension88, thus defining a pair of opposing,longitudinal connectors93. Thelongitudinal connectors93 are flexible so as to be capable of bending around a transverse axis. Each pair oftransverse slots97 is oriented at90 degrees relative to the adjacent pair ofslots97, so that the pairs oflongitudinal connectors93 alternate between those oriented vertically and those oriented horizontally. This allowsdistal extension88 to bend about either a horizontal and vertical transverse axes, thus providing a high degree of flexibility. Of course, the pairs oftransverse slots97 could be oriented at various angles relative to adjacent pairs to provide flexibility about more than two axes. The slots provided in the slotted tube allows thedistal extension88 to be more axially flexible than it would be without the slots, while still retaining high column strength. It is preferable to providetransverse slots97 andcylindrical rings92 that each have a width that is approximately the same as the length of astent segment32. In addition or alternatively, thetransverse slots97 andcylindrical rings92 may be spaced apart by a known fraction or multiple of the stent segment length. In this way, a detent mechanism may be provided on the interior surface of thesheath25, with one or more detents that releasably engage the cylindrical rings92 formed in thedistal extension88 to provide a tactile feedback based upon the distance that theouter sheath25 is retracted relative topusher tube86. Anesting tip94 is formed on the distal end of thedistal extension88. The nesting tip preferably includes a plurality of fingers shaped and oriented to engage and interleave with the proximal end of the mostproximal stent segment32. As described elsewhere herein,stent segments32 preferably have axial extensions or projections on each end which interleave with those on the adjacent stent segment.Tip94 ofpusher tube86 preferably has a geometry with axial projections similar to or complementary to those ofstent segments32 so as to interleave therewith.
• Preferably, theproximal portion90 of the pusher tube has a diameter that is smaller than the diameter of thedistal extension88. Thus, the stainless steel hypotube material making up theproximal portion90 of the pusher tube and part of theribbon portion89 may have a first diameter, while the slotted tube making up thedistal extension88 and the distal portion of theribbon89 may have a second, larger diameter. As noted above, the slotted tube and the hypotube are preferably joined by aweld91 formed in theribbon portion89.
• As best shown in FIGS.2A-B, thepusher tube86 extends longitudinally within theouter sheath25 and over theinner shaft27 through most of the length of thecatheter body22. Thedistal extension88 is slidable over thetubular leg72 and engages thestent segment32 at the proximal end of the line ofstent segments32. At its proximal end (not shown), thepusher tube86 is coupled to an actuator associated with the handle38 (seeFIG. 1). In this way, thepusher tube86 can be advanced distally relative toinner shaft27 to urge thestent segments32 distally over the expandable member24 (or, alternatively, thepusher tube86 may be held in position while retracting theexpandable member24 relative to stent segments32) until the stent segments engage thestop78. In addition, thepusher tube86 can be used to hold thestent segments32 in place on theexpandable member24 while thesheath25 is retracted to expose a desired number ofstent segments32, as shown inFIG. 2B. As noted above, theproximal portion90,ribbon portion89, anddistal extension88 of the pusher tube are preferably constructed of stainless steel, but they may alternatively be constructed of a variety of biocompatible polymers, metals, polymer/metal composites, alloys, or the like.
• It can be seen that withsheath25 retracted a desired distance,expandable member24 is allowed to expand when inflation fluid is delivered throughinflation lumen66, thereby expanding a desired number ofstent segments32 exposed distally ofsheath25. The remaining portion ofexpandable member24 and the remainingstent segments32 withinsheath25 are constrained from expansion bysheath25.
• FIG. 2B further illustrates that whensheath25 is retracted relative toexpandable member24, guidewiretube exit port35 becomes further away from the point at which guidewire36 exits theproximal end74 oftubular leg72, increasing the distance that guidewire36 must pass within the interior ofsheath25. Advantageously,guidewire tube34 provides a smooth and continuous passage from thetubular leg72 through guidewiretube exit port35, eliminating any problems that might result from changing the alignment of the two. This is particularly important in the present invention where the stent delivery catheter may carry a large number ofstent segments32 andsheath25 may be retracted a substantial distance relative toexpandable member24, resulting in substantial misalignment of guidewiretube exit port35 relative totubular leg72.
• In order to confirm the positioning of thestent segments32 on theexpandable member24, fluoroscopy is used to visualize thestent segments32 relative to themarkers82 located on theinner shaft27. In addition, by fluoroscopic visualization of themarker56 located on thegarage55 at the distal end of theouter sheath25, the user can see the extent of retraction of thesheath25 relative to theexpandable member24 and view the location of the exposedstent segments32 relative to thesheath25. Visualization of thestent segments32 is further enhanced with the use of radiopaque markers and/or materials in or on the stent segments themselves. Markers of radiopaque materials may be applied to the exterior ofstent segments32, e.g, by applying a metal such as gold, platinum, a radiopaque polymer, or other suitable coating or mark on all or a portion of the stent segments. Examples of such markers are illustrated in FIGS.14A-B. In those Figures,radiopaque markers95 are attached to a plurality of circular openings formed in the body of thestent segment32. Six such markers are formed in a circumferentially aligned pattern in theFIG. 14A example, while three markers are formed in another circumferentially aligned pattern in theFIG. 14B example. The markers may be discs, buttons, or other members that are welded in place, or they may be provided as rivets or rivet-type members that are installed in a sized hole or eyelet. Alternatively,stent segments32 may include a radiopaque cladding or coating or may be composed of radiopaque materials such as L-605 cobalt chromium (ASTM F90), other suitable alloys containing radiopaque elements, or multilayered materials having radiopaque layers. See, for example, FIGS.15A-C, where three patterns of radiopaque coatings are illustrated. InFIG. 15A, acoating96 of radiopaque material is provided in a broad circumferential center stripe on thestent segment32. InFIGS. 15B and C, smaller circumferential stripes ofradiopaque coatings96 are formed on the proximal and distal ends of thestent segment32, such as being formed only on the axial projection portions of the stent segment32 (seeFIG. 15C). In yet another alternative,stent segments32 may have a geometry conducive to fluoroscopic visualization, such as having struts of greater thickness, sections of higher density, or overlapping struts.
• Preferably, the radiopaque markers are configured so as to provide an indication of the number, location, and/or relative spacing of eachstent segment32 when deployed end-to-end in a line in a vessel or other body lumen. This allows the operator to determine howmany stent segments32 have been deployed at a vascular site, and the spacing betweenadjacent stent segments32. The radiopaque markers allow the operator to visualize with fluoroscopy the divisions betweenadjacent stent segments32 by observing radiopaque markers on the ends and/or a middle portions of eachstent segment32. For example, in the embodiment ofFIG. 15D, the operator may visualize a central stripe on each segment to allow an accounting of the number and location of deployedsegments32. In the embodiments ofFIG. 1SE, the operator may visualize two adjacent radiopaque stripes where two segment ends are disposed side-by-side. If the segments are close together, the operator sees a single wide stripe, while if the segments are separated by a gap, the operator may see two parallel stripes, thus providing an indication of the segment spacing as well as number.
• Some of the possible materials that may be used instent segments32 include (by ASTM number):
• F67-00 Unalloyed Titanium
• F75-01 Cobalt-28 Chromium-6 Molybdenum Alloy
• F90-01 Wrought Cobalt-20 Chromium-15 Tungsten-10 Nickel Alloy
• F136-02a Wrought Titanium-6 Aluminum-4 Vanadium ELI Alloy
• F138-00, F139-00 Wrought 18 Chromium-14 Nickel-2.5 Molybdenum Stainless Steel Bar or Sheet
• F560-98 Unalloyed Tantalum
• F562-02 Wrought 35 Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy
• F563-00 Wrought Cobalt-20 Nickel-20 Chromium 3.5 Molybdenum-3.5 Tungste-5 Iron Alloy
• F688 Wrought Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy
• F745-00 18 Chromium-12.5 Nickel-2.5 Molybdenum Stainless Steel
• F799-02 Cobalt-28 Chromium-6 Molybdenum Alloy
• F961-96 Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy
• F1058-02 Wrought 40 Cobalt-20 Chromium-16 Iron-15 Nickel-7 Molybdenum Alloy
• F1091-02 Wrought Cobalt-20 Chromium-15 Tungsten-10 Nickel Alloy
• F1108 Titanium-6 Aluminum-4 Vanadium Alloy
• F1295-01 Wrought Titanium-6 Aluminum-7 Niobium Alloy
• F1314-01 Wrought Nitrogen-strengthened 22 Chromium-13 Nickel-5 Manganese-2.5 Molybdenum Stainless Steel Alloy
• F1241-99 Unalloyed Titanium Wire
• F1 350-02 Wrought 18 Chromium-14 Nickel-2.5 Molybdenum Stainless Steel Wire
• F1377-98a Cobalt-28 Chromium-6 Molybdenum Powder coating
• F1472-02a Wrought Titanium-6 Aluminum-4 Vanadium Alloy
• F1537-00 Wrought Cobalt-28 Chromium-6 Molybdenum Alloy
• F1580-01 Titanium and Titanium-6 Aluminum-4 Vanadium Alloy Powder coating
• F1586-02 Wrought Nitrogen Strengthened 21 Chromium-10 Nickel-3 Mnaganese-2.5 Molybdenum Stainless Steel Bar
• F1713-96 Wrought Titanium-13 Niobium-13 Zirconium Alloy
• F1813-01 Wrought Titanium-12 Molybdenum-6 Zirconium-2 Iron Alloy
• F2063-00 Wrought Nickel-Titanium Shape Memory Alloys
• F2066-01 Wrought Titanium-15 Molybdenum Alloy
• F2146-01 Wrought Titanium-3 Aluminum-2.5 Vanadium Alloy Seamless Tubing
• F2181-02a Wrought Stainless Steel Tubing.
• FIGS.5A-B illustrate a portion of a first embodiment of astent segment32. The Figures illustrate a portion of thestent segment32 in a planar shape for clarity. Thestent segment32 includes twoparallel rows98A,98B of I-shapedcells100 formed into a cylindrical shape around an axial axis A. Eachcell100 includes upper and loweraxial slots102 and a connectingcircumferential slot104. The upper andlower slots102 are bounded by upperaxial struts106, loweraxial struts107, curved outer ends108 and curved inner ends110. Eachcircumferential slot104 is bounded by an outercircumferential strut109 and an innercircumferential strut111. Each I-shapedcell100 is connected to the adjacent I-shapedcell100 in thesame row98A or98B by acircumferential connecting strut113. All or a portion ofcells100 inrow98A merge or join withcells100 inrow98B at the inner ends110, which are integrally formed with the inner ends110 of theadjacent cells100.
• In a preferred embodiment, a spacingmember112 extends outwardly in the axial direction from a selected number of outer circumferential struts109 and/or connectingstruts113. Spacingmember112 preferably itself forms asubcell114 in its interior, but alternatively may be solid without any cell or opening therein. For those spacingmembers112 attached to outer circumferential struts109,subcell114 preferably communicates with I-shapedcell100. Spacingmembers112 are configured to engage the curved outer ends108 of anadjacent stent segment32 so as to maintain appropriate spacing between adjacent stent segments. In one embodiment, spacingmembers112 haveouter ends116 with two spaced-apartprotrusions118 that provide a cradle-like structure to index and stabilize the curvedouter end108 of the adjacent stent segment. Preferably, spacingmembers112 have an axial length of at least about 10%, more preferably at least about 25%, of the long dimension L of I-shapedcells100, so that the I-shapedcells100 of adjacent stent segments are spaced apart at least that distance. Because spacingmembers112 experience little or no axial shortening during expansion ofstent segments32, this minimum spacing between stent segments is maintained both in the unexpanded and expanded configurations.
• FIG. 5B showsstent segment32 ofFIG. 5A in an expanded configuration. It may be seen thatcells100 are expanded so that upper andlower slots102 are diamond shaped withcircumferential slots104 remaining basically unchanged. This results in some axial shortening of the stent segment, thereby increasing the spacing between adjacent stent segments. The stent geometry is optimized by balancing the amount of axial shortening and associated inter-segment spacing, the desired degree of vessel wall coverage, the desired metal density, and other factors. Because the stent is comprised of multipleunconnected stent segments32, any desired number from 2 up to 10 or more stent segments may be deployed simultaneously to treat lesions of any length. Further, because such segments are unconnected to each other, the deployed stent structure is highly flexible and capable of deployment in long lesions having curves and other complex shapes.
• As an additional feature,circumferential slots104 provide a pathway through which vessel side branches can be accessed for catheter interventions. Shouldstent segment32 be deployed at a location in which it covers the ostium of a side branch to which access is desired, a balloon dilatation catheter may be positioned throughcircumferential slot104 and expanded. This deformscircumferential struts109,111 axially outward, thereby expandingcircumferential slot104 and further expanding upper andlower slots102, as shown in phantom inFIG. 5B. This provides a relativelylarge opening120 through which a catheter may be inserted throughstent segment32 and into the side branch for placing stents, performing angioplasty, or carrying out other interventions.
• FIGS. 6A-6B illustrate a second embodiment of astent segment32 according to the invention. InFIG. 6A, a portion ofstent segment32 is shown in a planar shape for clarity. Similar to the embodiment ofFIG. 5A,stent segment32 comprises twoparallel rows122A,122B of I-shapedcells124 formed into a cylindrical shape around axialaxis A. Cells124 have upper and loweraxial slots126 and a connectingcircumferential slot128. Upper andlower slots126 are bounded by upperaxial struts130, loweraxial struts132, curved outer ends134, and curved inner ends136.Circumferential slots128 are bounded by outercircumferential strut138 and innercircumferential strut140. Each I-shapedcell124 is connected to the adjacent I-shapedcell124 in the same row122 by acircumferential connecting strut142.Row122A is connected to row122B by the merger or joining of curved inner ends136 of at least one (and preferably three) of upper andlower slots126 in eachcell124.
• One of the differences between the embodiment ofFIGS. 6A-6B and that ofFIGS. 5A-5B is the way in which spacing is maintained between adjacent stent segments. In place of thespacing members112 of the earlier embodiment, the embodiment ofFIG. 6A includes abulge144 in upper and loweraxial struts130,132 extending circumferentially outwardly fromaxial slots126. These giveaxial slots126 an arrowhead or cross shape at their inner and outer ends. Thebulge144 in each upperaxial strut130 extends toward thebulge144 in a loweraxial strut132 in thesame cell100 or in anadjacent cell100, thus creating aconcave abutment146 in the space between eachaxial slot126.Concave abutments146 are configured to receive and engage curved outer ends134 ofcells124 in the adjacent stent segment, thereby maintaining spacing between the stent segments. The axial location ofbulges144 along upper and loweraxial struts130,132 may be selected to provide the desired degree of inter-segment spacing.
• FIG. 6B shows twostent segments32 ofFIG. 6A in an expanded condition. It may be seen thataxial slots124 are deformed into a circumferentially widened modified diamond shape withbulges144 on the now diagonal upper and loweraxial struts130,132.Circumferential slots128 are generally the same size and shape as in the unexpanded configuration.Bulges144 have been pulled away from each other to some extent, but still provide aconcave abutment146 to maintain a minimum degree of spacing between adjacent stent segments. As in the earlier embodiment, some axial shortening of each segment occurs upon expansion and stent geometry can be optimized to provide the ideal intersegment spacing.
• It should also be noted that the embodiment ofFIGS. 6A-6B retains the feature described above with respect toFIGS. 5A-5B to enable access to vessel side branches blocked bystent segment32. Should such side branch access be desired, a dilatation catheter may be inserted intocircumferential slot128 and expanded to provide an enlarged opening through which a side branch may be entered.
• Referring now toFIGS. 7A-7E, the use of the stent delivery catheter of the invention will be described. While the invention will be described in the context of coronary artery treatment, it should be understood that the invention is useful in any of a variety of blood vessels and other body lumens in which stents are deployed, including the carotid, femoral, iliac and other arteries, as well as veins and other fluid-carrying vessels. A guiding catheter (not shown) is first inserted into a peripheral artery such as the femoral and advanced to the ostium of the target coronary artery. A guidewire GW is then inserted through the guiding catheter into the coronary artery A where lesion L is to be treated. The proximal end of guidewire GW is then inserted throughnosecone28 andguidewire tube34 outside the patient's body andstent delivery catheter20 is slidably advanced over guidewire GW and through the guiding catheter into the coronary arteryA. Slider assembly50 is positioned within the hemostasis valve at the proximal end of the guiding catheter, which is then tightened to provide a hemostatic seal with the exterior of theslider body52.Stent delivery catheter20 is positioned through a lesion L to be treated such thatnosecone28 is distal to lesion L. During this positioning,sheath25 is positioned distally up tonosecone28 so as to surroundexpandable member24 and all of thestent segments32 thereon.
• Optionally, lesion L may be pre-dilated prior to stent deployment. Pre-dilation may be performed prior to introduction ofstent delivery catheter20 by inserting an angioplasty catheter over guidewire GW and dilating lesion L. Alternatively,stent delivery catheter20 may be used for pre-dilation by retractingsheath25 along withstent segments32 to expose an extremity ofexpandable member24 long enough to extend through the entire lesion. This may be done whiledelivery catheter20 is positioned proximally of lesion L or withexpandable member24 extending through lesion L. Fluoroscopy enables the user to visualize the extent of sheath retraction relative to lesion L by observing the position ofmarker56 on thegarage55 contained at the distal end of thesheath25 relative to themarkers82 formed on theguidewire tube34 beneath theexpandable member24. To allowstent segments32 to move proximally relative toexpandable member24, force is released frompusher tube86 andvalve member58 engages and draws the stent segments proximally withsheath25. Thepusher tube86 is retracted along with theouter sheath25 by use of an actuator provided on thehandle38. With the appropriate length ofexpandable member24 exposed,expandable member24 is positioned within lesion L and inflation fluid is introduced throughinflation lumen66 to inflateexpandable member24 distally ofsheath25 and thereby dilate lesionL. Expandable member24 is then deflated and retracted withinsheath25 while maintaining force onpusher tube86 so thatstent segments32 are positioned up to the distal end ofexpandable member24, surrounded bysheath25.
• Following any predilatation,stent delivery catheter20 is repositioned in artery A so thatnosecone28 is distal to lesion L as shown inFIG. 7A.Sheath25 is then retracted as inFIG. 7B to expose the appropriate number ofstent segments32 to cover lesion L. Again, fluoroscopy can be used to visualize the position ofsheath25 by observingmarker56 thereon relative tomarker82 withinexpandable member24. Assheath25 is drawn proximally, force is maintained againstpusher tube86 so thatstent segments32 remain positioned up to the distal end ofexpandable member24. It should also be noted thatsheath25 moves proximally relative toguidewire tube34, which slides through guidewiretube exit port35. Advantageously, regardless of the position ofsheath25,guidewire tube34 provides a smooth and continuous passage for guidewire GW so that stent delivery catheter slides easily over guidewire GW.
• With the desired number ofstent segments32 exposed distally ofsheath25, it is preferable to create some spacing between the stent segments to be deployed and those remaining enclosed within thesheath25. This reduces the risk of dislodging or partially expanding thedistal-most stent segment32 withinsheath25 whenexpandable member24 is inflated. Such spacing is created, as shown inFIG. 7C, by releasing force againstpusher tube86 and retracting both thepusher tube86 and the sheath25 a short distance simultaneously. The engagement ofvalve member58 withstent segments32 moves thosestent segments32 withinsheath25 away from thosestent segments32 distal tosheath25. The length of this spacing is preferably equal to the length of about ½-1 stent segment, e.g., in one embodiment about 2-4 mm. By observingradiopaque marker56 onsheath25, the operator can adjust the spacing to be suitable in comparison to the length ofmarker56, which preferably has a length equal to the desired spacing distance.
• Expandable member24 is then inflated by delivering inflation fluid throughinflation lumen66, as shown inFIG. 7D. The exposed distal portion ofexpandable member24 expands so as to expandstent segments32 thereon into engagement with lesion L. If predilatation was not performed, lesion L may be dilated during the deployment ofstent segments32 by appropriate expansion ofexpandable member24.Sheath25 constrains the expansion of the proximal portion ofexpandable member24 and thosestent segments32 withinsheath25.
• Expandable member24 is then deflated, leavingstent segments32 in a plastically-deformed, expanded configuration within lesion L, as shown inFIG. 7E. The alternative embodiment ofstent segment32 illustrated inFIGS. 6A-6B is shown in a similarly expanded condition inFIG. 8. Withstent segments32 deployed,expandable member24 may be retracted withinsheath25, again maintaining force againstpusher tube86 to slidestent segments32 toward the distal end ofexpandable member24.Expandable member24 is moved proximally relative tostent segments32 until the distal-most stent segment engages stop78 (FIGS. 2A-2B), thereby placingstent segments32 in position for deployment.Stent delivery catheter20 is then ready to be repositioned at a different lesion in the same or different artery, and additional stent segments may be deployed. During such repositioning,guidewire tube34 facilitates smooth tracking over guidewire GW. Advantageously, multiple lesions of various lengths may be treated in this way without removingstent delivery catheter20 from the patient's body. Should there be a need to exchangestent delivery catheter20 with other catheters to be introduced over guidewire GW,guidewire tube34 facilitates quick and easy exchanges.
• It should be understood that when the movement of the pusher tube, sheath, or stent segments is described in relation to other components of the delivery catheter of the invention, such movement is relative and will encompass both moving the sheath, pusher tube, or stent segments while keeping the other component(s) stationary, keeping the sheath, pusher tube or stent segments stationary while moving the other component(s), or moving multiple components simultaneously relative to each other.
• While the foregoing description of the invention is directed to a stent delivery catheter for deploying stents into vascular lumens to maintain patency, it should be understood that various other types of wire-guided catheters also may embody the principles of the invention. For example, balloon catheters for angioplasty and other purposes, particularly those having a slidable external sheath surrounding the balloon, may be constructed in accordance with the invention. Other types of catheters for deployment of prosthetic devices such as embolic coils, stent grafts, aneurism repair devices, annuloplasty rings, heart valves, anastomosis devices, staples or clips, as well as ultrasound and angiography catheters, electrophysiological mapping and ablation catheters, and other devices may also utilize the principles of the invention.
• Although the above is complete description of the preferred embodiments of the invention, various alternatives, additions, modifications and improvements may be made without departing from the scope thereof, which is defined by the claims.

Claims (15)

1. Apparatus for delivering a prosthesis into a target vessel of a patient, comprising:

a flexible catheter having proximal and distal ends, said catheter comprising an outer sheath and an inner shaft; and

a plurality of tubular prostheses releasably carried near the distal end of the catheter over the inner shaft and deployable therefrom in selectable numbers, the outer sheath disposed over the prostheses and being axially movable relative thereto;

wherein at least a portion of the tubular prostheses have a radiopaque marker disposed thereon such that the number of prostheses deployed from the catheter at one time may be visualized.

2. Apparatus as inclaim 1 wherein the radiopaque marker is disposed only on a portion of each prosthesis.

3. Apparatus as inclaim 1 wherein the radiopaque marker comprises a circumferential stripe on at least one end of each prosthesis.

4. Apparatus as inclaim 1 wherein each prosthesis has a plurality of axial projections extending from at least one end thereof, the axial projections being configured to interleave with axial projections on an adjacent prosthesis, and the radiopaque marker is disposed on the axial projections.

5. Apparatus as inclaim 1 wherein the radiopaque marker comprises a circumferential stripe in a middle region of each prosthesis.

6. Apparatus as inclaim 1 wherein the radiopaque marker covers only a portion of the prosthesis.

7. Apparatus as inclaim 1 wherein the radiopaque marker comprises a coating on the surface of the prostheses.

8. Apparatus as inclaim 1 wherein the radiopaque marker comprises a radiopaque component coupled to the prosthesis.

9. Apparatus as inclaim 1 wherein the radiopaque marker is a material selected from gold, silver, platinum, titanium, iridium, and tungsten.

10. Apparatus as inclaim 1 wherein the radiopaque marker is configured so as to indicate the location of each prosthesis in a line of prostheses deployed end-to-end in a vessel.

11. A method of determining the number of prostheses deployed in a vessel comprising:

deploying from a catheter a plurality of prostheses end-to-end in a vessel; and

visualizing radiopaque markers on at least a portion of the prostheses, the radiopaque markers indicating the location of each deployed prosthesis relative to other of the deployed prostheses.

12. A method as inclaim 11 wherein the prostheses have axial projections on each end thereof, the axial projections on each prosthesis interleaving with the axial projections on the adjacent prosthesis.

13. A method as inclaim 12 wherein the radiopaque marker is disposed on the axial projections.

14. A method as inclaim 11 further comprising retaining at least one prosthesis in the catheter while the plurality of prostheses are deployed in the vessel.

15. A method as inclaim 11 further comprising selecting the number of prostheses to deploy in the vessel from a total number of prostheses carried by the catheter.

Images