1. Field of the Invention
The invention relates to a deployment system for an intraluminal medical device. More particularly, the invention relates to a deployment system having a support member on an inner member of a catheter that helps distribute loads more uniformly througout the intraluminal medical device during loading and delivery.
2. Related Art
Percutaneous transluminal angioplasty (PTA) is a therapeutic medical procedure used to increase blood flow through an artery. In this procedure, an angioplasty balloon is inflated within the stenosed vessel, or body passageway, in order to shear and disrupt the wall components of the vessel to obtain an enlarged lumen.
More recently, transluminal prostheses, such as stents, have been used for implantation in blood vessels, biliary ducts, or other similar organs of a patient in order to open, dilate or maintain the patency thereof. Such stents are often referred to as balloon expandable stents, as in U.S. Pat. No. 4,733,665 to Palmaz, as braided or self-expandable stents as in U.S. Pat. No. 4,655,771.
Balloon expandable stents can be impractical for use in some vessels, such as the carotid artery, due to their proximity to the surface of a patient's skin when deployed. Braided stents, on the other hand, pose other disadvantages, such as insufficient radial strength and the risk of unraveling of some of the fibers comprising the braided stent. Other types of self-exapnding stents, such as those comprising shape-memory materials, have thus been devised to address some of these risks. Even self-expanding stents, however, are susceptible to resistive forces during delivery that may cause the stent to undesirably bend, bunch, buckle or break as the stent is attempted to be pushed to its intended treatment site. Reactive forces can accumulate at portions of a stent as a result of such bending or bunching. Non-uniform deployment of the stent can occur as a result.
This tendency is particularly prevalent in newer stent designs that have reduced longitudinal stiffness properties in order to provide greater in situ flexibility. Buckling of the stent can further result in undesirable out-of-plane deflections of struts or segments of the stent, which may be particularly prevalent where a series of stents or stent grafts comprise the device. Such deflections risk penetration of the struts or segments into portions of the delivery sheath, or possibly the vessel wall, that can hinder deployment of the stent. Buckling can also lead to undesirable accumulations of reactive forces in portions of the stent that results in non-uniform deployment of the stent as described above. Of course, where resistive forces are so great that breaking of the stent occurs, the stent is no longer usable for its intended purpose. Resistive forces can also damage coatings where a coating stent is used, thereby also rendering the stent unusable. Premature deployment of self-expanding stents also tends to occur in a range of prior art systems.
U.S. Pat. Nos. 6,302,893 and 6,077,295 discloses a catheter having an elastomer inner member tube or sleeve on which a stent is positioned and an outer member positioned over the inner member or sleeve. Prior to delivery, the inner member tube or sleeve is heated until it fills and forms attachment projections in the open lattice structure of the stent. The outer member of the catheter retains the self-expanding stent from expanding radially outwardly as the attachment projections of the heated inner member tube or sleeve keeps the stent from undergoing axial or other movement until the outer sleeve of the catheter is withdrawn from over the inner member by relative axial movement of the inner member and the outer member. Upon withdrawal of the outer member, the self-expanding stent expands and extricates itself from the inner member tube or sleeve at an intended treatment site. The heat required to produce the attachment projections of the inner member tube or sleeve of the '893 or '295 patents can weaken bridging, or other portions, of a stent that is to be delivered however. Moreover, the requirement of heat to produce the attachment projections and filling of the open lattice structure of a stent is an additional step that can complicate the delivery of the stent, particularly where insufficient heat is provided rendering the stent susceptible to shifting during delivery as a result of under-developed attachment projections or other open lattice filling functions. Such heat also risks premature, or other, degradation of stent coatings, where the stent to be delivered is provided with such a polymeric, drug or other bio-active agent coating.
Still other delivery systems, such as in U.S. Pat. No. 6,468,298, include preformed protrusions or mechanically retractable grippers that extend from an inner member of a catheter delivery system in order to assist in maintaining a stent in place during delivery thereof. Such mechanically retractable grippers, when extended, engage the struts of a stent during delivery thereof, and when retracted, permit deployment of the stent at the intended treatment site. The mechanics of such grippers can complicate the delivery and deployment of a stent, particularly where the mechanics of such grippers fail. Moreover, such retractable grippers, or such preformed protrusions, must be provided with some degree of precision so as to align properly with the strut configuration of a stent in order to reliably engage, or disengage, the same during delivery.
In view of the above, a need exists for an intraluminal medical device delivery system that more simply and reliably delivers a stent or stent graft to an intended treatment site while more uniformly distributing forces throughout the stent or stent graft during loading and delivery thereof.
Various aspects of the systems and methods of the invention comprise an intraluminal medical device delivery system that simply and reliably delivers a stent or stent graft to an intended treatment site while distributing forces more uniformly throughout the stent or stent graft during loading and delivery.
In a preferred embodiment, the intraluminal medical device delivery system comprises a catheter system having an outer member, an inner member, a support member on the inner member of a catheter, and a self-expanding stent or stent graft fitted onto the support member. The stent or stent graft may comprise continuous or discontinous segments forming the stent or stent graft, or combinations thereof. At least one of the inner member and the outer member is axially movable relative to one another and the stent or stent graft is longitudinally supported by the support member as delivery of the stent or stent graft to an intended treatment site occurs.
The support member is preferably comprised of a material having a low modulus of elasticity that increases in modulus when the material is compressed. The stent or stent graft is crimped, i.e., reduced to a non-expanded state, onto the support member so as to mechanically compress the support member. The support member provides increased longitudinal stability to the stent or stent graft by more uniformly distributing resistive forces throughout the stent or stent graft during loading onto the inner member and support member of the delivery system and during delivery thereof to an intended treatment site. Because the stent or stent graft is crimped onto the support member, the stent or stent graft may be more readily moved forward or backward, i.e., towards or away from an intended treatment site, during delivery thereof, which aids re-positioning of the stent or stent graft to effect even more precise placement thereof, when desired or deemed medically preferred. The crimping of the stent or stent graft onto the support member also enables a series of two or more stents or stent grafts, or a series of continuous or discontinous segments of a single stent or stent graft, or a combination thereof, to be moved more readily in unison to effectuate emplacement thereof in an intended treatment site, as desired. The crimping of the stent or stent graft onto the support member in this manner also helps to maintain the stent or stent graft in place during delivery thereof to the intended treatment site, which helps minimize, or ideally eliminates, premature deployment of the stent or stent graft from the delivery catheter.
The support member can be comprised of various materials and morphologies provided it exhibits a soft, flexible, compliant nature. The materials can be any known or later developed version of a mechanically compressible material having a modulus of elasticity that increases upon compression, and that recovers some or all of its expanded state more slowly than does the stent or stent graft, or segments thereof, upon deployment at the intended treatment site. The morphologies of the support member can be any of a tube, a sleeve, a coating, or a film applied to the surface of the support member and onto which the stent, stent graft, or segments thereof are crimped prior to and during delivery to an intended treatment site.
Generally, the stent, stent graft, or segments thereof, is crimped onto the support member in order to aid stability of the stent, stent graft, or segments thereof, during loading and delivery. In some embodiments, however, portions of the support member protrude through open or accessible areas of the stent or stent graft, or segments thereof, so as to releasably grip the stent or stent graft, or segments thereof. Such gripping by protruding portions of the support member secures the stent, stent graft, or segments thereof, to the inner member of the delivery system even more than otherwise occurs by only crimping until delivery is effected, although crimping alone provides sufficient longitudinal stability to the stent, stent graft or segments thereof, to distribute forces effectively throughout the intraluminal medical device during loading and delivery thereof. Where a stent, stent graft or segments thereof is provided with a coating, the portions of the support structure that protrude through the open or accessible areas of the stent, stent graft, or segments thereof, also provide a barrier to the coating. Such barriers can extend the shelf life of the intraluminal medical device, and helps minimize undesirable or premature delamination of a coating from the device, in addition to the gripping function described above.
In some embodiments, the support member is attached to the inner member of the delivery system using adhesives. In other embodiments, the support member is attached to the inner member by marker bands crimped or swaged over the support member, thereby securing the support member to the inner member. Preferably, one marker band is located at a distal end of the support member, and another marker band is located at a proximal end of the support member. Radiopaque materials may comprise some or all of the marker bands to enhance visualization of the stent, stent graft or segments thereof, and the catheter during delivery and deployment of the intraluminal medical device.
A method of delivering an intraluminal medical device according to the invention generally comprises providing a catheter based delivery system with an outer member, an inner member, a mechanically compressible support member and a self-expanding intraluminal medical device, wherein at least one of the inner member and the outer member are longitudinally movable relative to one another, and the mechanically compressible support member is located along a distal portion of the inner member. The method further comprises loading the intraluminal medical device onto the support member by crimping so as to mechanically compress the support member, restraining the intraluminal medical device in its crimped state and the support member in its compressed state within the outer member, delivering the intraluminal medical device to an intended treatment site by one of pushing the inner member beyond a distal end of the outer member or by withdrawing the outer member while maintaining the inner member in place relative to the intended treatment site, resuming the expanded state of the intraluminal medical device at the intended treatment site and withdrawing the inner member and support member before the support member resumes its fully non-compressed state. The intraluminal medical device may be a stent, a stent graft, segments thereof, or a series of such stents, stent grafts or segments thereof.
The above and other features of the invention, including various novel details of construction and combinations of parts, will now be more particularly described with reference to the accompanying drawings and claims. It will be understood that the various exemplary embodiments of the invention described herein are shown by way of illustration only and not as a limitation thereof. The principles and features of this invention may be employed in various alternative embodiments without departing from the scope of the invention.
These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
Referring still to
The support member 1113 is comprised of one or more materials that are processable into a mechanically compressible structure that exhibits a higher modulus of elasticity in its compressed state than in its non-compressed state. Such materials include, but are not limited to: polyurethane, polytetrafluoroethylene (in the form of expanded PFFE), silicone, rubbers (such as natural rubbers, EPDM rubbers, epichlorohydrin rubbers, or the like), polyamides, polyimides, fluoropolymers, hydrogels (such as hydroxyethylmethacrylate, polyvinylpyrrolidone, polysulfopropylacrylate, and the like), polyolefins, polyacrylates, methacrylates, or blends and co-polymers thereof, or any other known or later developed material in which its modulus of elasticity increases when in a mechanically compressed state, and that recovers its expanded state more slowly than does the intraluminal medical device, upon deployment of the device at the intended treatment site. The material comprising the support member is also deformable without heat so as to achieve fully the mechanically compressed state thereof solely by the crimping of the intralumnial medical device thereon. Where the material comprising the support member is a foam, the foam may be either an open cell foam or a closed cell foam. The morphologies of the support member can be any of a tube, a sleeve, a coating, or a film, any of which can be applied to the surface of the support member.
As a result of the mechanically compressible materials and morphologies comprising the support member 1113 according to the various embodiments of the invention described herein, stabilization and securement of the stent 1120 on the inner member 1111 and support member 1113 of the catheter delivery system 1110 occurs without heating of the inner member or the support structure, and without providing any additional mechanical members or formations on the surface of the inner member 1111 or support member 1113. Simpler, more reliable, loading and delivery of the stent 1120 to an intended treatment site is thus effected according to the invention.
In some embodiments, when the support member 1113 is mechanically compressed by crimping of the stent 1120 thereon, portions of the support member 1113 protrude between the open lattice-like areas of the stent 1120 so as to releasably grip portions of the stent 1120 with the protruding portions of the support member 1113. Such gripping can provide even more stability to the stent 1120 during loading or delivery thereof, although such gripping is not essential to achieving sufficiently increased stability of the stent to perform loading and delivery thereof to an intended treatment site. Where gripping of the stent 1120 occurs by protruding portions of the support member 1113, such gripping also acts as a barrier that minimizes damage to, and increase the shelf life of, the stent 1120. In particular, such gripping of the stent by the protruding portions of the support member 1113 can also comprise a barrier that minimizes damage to coatings, where such coatings are provided on the stent. Coatings can comprise polymers, drugs or other bio-active agents applied to the stent, as the artisan will readily appreciate, which coatings could more easily delaminate from the stent were the gripping barriers of the protruding portions of the support member not in place. In any event, expansion of the stent 1120 upon delivery to the intended treatment site releases the stent 1120 from the grip of the protruding portions of the support member 1113.
In still other embodiments, as shown in
In practice, delivery of an intraluminal medical device according to the invention generally comprises providing a catheter based delivery system having an outer member, an inner member, a mechanically compressible support member and a self-expanding intraluminal medical device, wherein at least one of the inner member and the outer member is longitudinally movable relative to one another and the mechanically compressible support member is located along a distal portion of the inner member. The method further comprises loading the intraluminal medical device onto the support member by crimping so as to mechanically compress the support member, restraining the intraluminal medical device in its crimped state and the support member in its compressed state within the outer member, delivering the intraluminal medical device to an intended treatment site by one of pushing the inner member beyond a distal end of the outer member or by withdrawing the outer member while maintaining the inner member in place relative to the intended treatment site, resuming the expanded state of the intraluminal medical device at the intended treatment site and withdrawing the inner member and support member so as to minimize damage to or interference with the device or vessel in which the device is emplaced from the support member as described hereinabove. In some embodiments, the method further comprises releasably gripping portions of the intraluminal medical device with protruding portions of the support member until delivery of the device is effected at the intended treatment site, whereafter expansion of the device releases the device from the grip of the protruding portions of the support member. Releasably gripping portions of the intraluminal medical device in this manner can further provide a barrier that minimizes undesirable, or premature delamination of coatings, where such coatings are provided on the intraluminal medical device. The intraluminal medical device may be a stent or stent graft, or segments thereof. The support member is comprised of materials and morphologies as described hereinabove.
The various exemplary embodiments of the invention as described hereinabove do not limit different embodiments of the systems and methods of the invention. The material described herein is not limited to the materials, designs or shapes referenced herein for illustrative purposes only, and may comprise various other materials, designs or shapes suitable for the systems and methods described herein, as should be appreciated by the artisan.
While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit or scope of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated herein, but should be construed to cover all modifications that may fall within the scope of the appended claims.