Patent Application
20080269865
1. Field of the Invention
This invention relates generally to medical apparatus and methods, and more specifically to vascular catheters, stents and stent delivery systems for use in the coronary arteries and other vessels.
Stenting is an important treatment option for patients with vascular occlusive disease. The stenting procedure involves placing a tubular prosthesis at the site of a lesion, typically within a diseased coronary artery. The procedure is performed in order to maintain the patency of the artery and is often performed after a primary treatment such as angioplasty. Early stent results suffered from high rates of restenosis, i.e. the tendency for the stented coronary artery to become re-occluded following implantation of the stent. However, in recent years, restenosis rates have decreased substantially, due in part to drug eluting stents as well as other improvements in stent delivery methods and stent technology. As a result, the number of stent related procedures being performed worldwide continues to dramatically increase.
Stents are typically either self-expanding or balloon expandable and they are delivered to the coronary arteries using long, flexible vascular catheters typically inserted percutaneously through the patient's 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, leaving the stent in place.
Current stent delivery technology suffers from a number of drawbacks which can make delivery of stents challenging. In particular, current stent delivery catheters often employ stents having fixed lengths. The proper selection of fixed length stents requires accurate knowledge of the lesion length being treated. While lesion length may be measured prior to stent deployment using angiography and fluoroscopy, these measurements are often inaccurate. Thus, if an improperly sized stent is introduced to a treatment site, the delivery catheter and stent must be removed from the patient and replaced with a different device having the correct size. This prolongs the procedure, increases waste and results in a more costly procedure.
The use of “custom length” stents as an alternative to fixed length stents has been proposed. One such approach for providing a custom length stent has been to use segmented stents for treatment in which only some of the stents are deployed for treatment. Several exemplary systems are described in several copending, commonly assigned applications which are listed below. In these systems, the stent segments are deployed by selective advancement over the delivery catheter. After delivering an initial group of segments, the catheter may be repositioned to a new treatment site and a further group of segments can then be deployed. These systems can enable treatment of multiple lesions with a single device and may contain up to fifty segments. While this technology represents a significant improvement over earlier stent delivery systems, in the case of smaller, more focal lesions or single lesions, only a small number of stent segments are needed and thus there is considerable waste when a large number of stent segments remain undeployed and end up being discarded at the end of the procedure.
Another challenge with existing “custom length” stent delivery systems is that to deliver multiple stent segments to multiple lesion sites requires an intricate delivery system that can be somewhat complex to use. Thus, a simpler delivery system that allows length customization with fewer prosthetic segments on the delivery catheter is desirable, especially for use in treating a single lesion. It is also desirable to protect stent segments on the delivery system from being improperly displaced, deformed or damaged during delivery and deployment.
For the above reasons as well as others, it would be desirable to provide improved prosthetic stents and delivery catheters. It would be particularly desirable to provide catheters which enable stent length to be customized yet have a minimal quantity of stent segments so as to treat common lesion lengths while minimizing stent segment waste. It is also desirable to provide a delivery system that is flexible and can track torturous vessels and that has a simple construction and is less costly and easy to use in deploying a selectable number of stent segments to a single treatment site.
2. Description of the Background Art
Prior publications describing catheters for delivering multiple segmented stents include: U.S. Publication Nos. 2004/0098081, 2005/0149159, 2004/0093061, 2005/0010276, 2005/0038505, 2004/0186551 and 2003/013266. Prior related unpublished co-pending U.S. patent applications include Ser. No. 11/148,713, filed Jun. 8, 2005 (Attorney Docket No. 14592.4002), entitled “Devices and Methods for Operating and Controlling Interventional Apparatus”; Ser. No. 11/148,545, filed Jun. 8, 2005 (Attorney Docket No. 14592.4005), entitled “Apparatus and Methods for Deployment of Multiple Custom-Length Prosthesis”; Ser. No. 11/344,464, filed Jan. 30, 2006 (Attorney Docket No. 021629-003500US), entitled “Apparatus and Methods for Deployment of Custom-Length Prostheses”; Ser. No. 60/784,309, filed Mar. 20, 2006 (Attorney Docket No. 021629-003600US), entitled “Apparatus and Methods for Deployment of Linked Prosthetic Segments”; Ser. No. ______, filed (Attorney Docket No. 021629-003800US), entitled “Custom Length Stent Apparatus”; and Ser. No. ______, filed (Attorney Docket No. 021629-004000US), entitled “Custom Length Stent Apparatus.” The full disclosures of each of these patents and applications are incorporated herein by reference.
The invention generally provides for the delivery of prosthetic segments with a flexible delivery catheter capable of navigating torturous vessels such as the coronary arteries. The delivery catheter permits deployment of a selectable number of prosthetic segments at a single treatment site, thus allowing customization of prosthesis length while the delivery catheter is in a body lumen at a treatment site. Customization of prosthesis length in situ permits better matching of the prosthesis length to the lesion length being treated. The delivery catheter has a simplified design including a control mechanism on the catheter handle for selecting prosthetic segments for deployment and a stent valve or separator on the distal end of an outer shaft that facilitates deployment of the selected group of stent segments. A sheath protects the prosthetic segments from damage during delivery and deployment.
The terms “stent” and “stenting” are defined to include any of the array of expandable prostheses and scaffolds which are introduced into a lumen at a target treatment site and expanded in situ thereby exerting a radially outward force against the lumen wall. The prosthesis of the present invention comprises a closed or an open lattice structure and is typically fabricated from a malleable or elastic material. When a malleable material is used, such as stainless steel, gold, platinum, titanium, cobalt chromium and other alloys, the stent segments are typically expanded by balloon inflation, causing plastic deformation of the lattice so that it remains permanently deformed in the open position after deployment. When formed from an elastic material, including superelastic materials such as nickel-titanium alloys, the lattice structures are commonly constrained radially during delivery and upon deployment the constraining structure is removed, allowing the prosthesis to “self-expand” at the target site. The terms “stent,” “prosthetic segment” and “stent segments” refer broadly to all radially expansible stents, grafts, and other scaffold-like structures which are intended for deployment within a body lumen.
In a first aspect of the invention, an apparatus for delivering prosthetic segments in a body lumen comprises an elongated flexible member with proximal and distal ends and a plurality of prosthetic segments releasably arranged axially along the elongated flexible member near the distal end. The apparatus also has a sheath that is slidably disposed over at least a portion of the prosthetic segments and an outer shaft that is slidably disposed over at least a portion of the sheath. A separator is disposed on the outer shaft and is biased into engagement with at least one prosthetic segment so that the outer shaft may be retracted to separate a proximal group of prosthetic segments from a distal group of prosthetic segments which are to be deployed in the body lumen. The sheath is also positionable between the separator and the prosthetic segments to selectively disengage the separator from the prosthetic segments.
In preferred embodiments, the separator is adapted to apply substantially greater axial force against the prosthetic segments when the separator is retracted proximally than when the separator is advanced distally. Often, the sheath is configured to engage the outer shaft such that retraction of the sheath retracts the outer shaft. Both the sheath and outer shaft typically comprise an annular flange that allows the two members to engage one another. The apparatus also usually includes an expandable member near the distal end of the elongate flexible member and typically the expandable member is a balloon.
Often, the prosthetic segments are balloon expandable, although they may also be self-expanding. Additionally, the prosthetic segments may carry a therapeutic agent such as an anti-restenosis drug which may be released from the segments. The segments are often in the range of size from about 2 mm to about 10 mm, although they typically have a length about 3 mm to about 6 mm. In some embodiments, the prosthetic segments may have two or more lengths, while in other embodiments, the segments are substantially the same length. Often, the prosthetic segments have interleaved ends in engagement with each other prior to deployment although the segments may also be spaced apart prior to deployment. Spacing the segments apart allows the separator to engage the prosthetic segments at their distal ends. The separator often comprises a plurality of resilient fingers projecting radially inward. At least some of these fingers may be inclined so that the free ends of the fingers point proximally allowing the fingers to pass over the prosthetic segments as the separator is advanced distally but to engage a prosthetic segment when the separator is retracted proximally. In some embodiments, some of the fingers are composed of metal, while they may also be composed of a polymer. Some of the fingers may comprise a radiused end that substantially matches the curvature of the surface of the prosthetic segments thereby providing greater contact surface so as to facilitate engagement between the prosthetic segments and the separator as the separator is retracted proximally while allowing the separator to pass over the prosthetic segments during distal advancement of the separator.
In other embodiments, the separator further comprises a hinge coupled to the fingers to allow the fingers to deflect radially and this facilitates passage of the separator over the sheath when the separator is advanced distally. Often the separator comprises an annular flange and this flange may be tapered or it can be a tapered conical nose. Other embodiments of the separator comprise a plurality of inclined ramps disposed on an inner surface of the outer shaft and these ramps may be separated by about ninety degrees. In still other embodiments, the separator may comprise a compliant sharp edge.
In another aspect of the present invention, a method for delivering prosthetic segments to a body lumen comprises introducing a plurality of prosthetic segments that are releasably arranged axially along an elongated flexible member, into a body lumen having a lesion with a lesion length at a first treatment site. An outer shaft having a separator is distally advanced relative to a group of prosthetic segments selected for delivery and the selected group typically has a combined length that matches the lesion length. A sheath, disposed between the separator and the prosthetic segments is then positioned until the separator is allowed to engage the prosthetic segments. The outer shaft is then retracted thereby creating a spacing between prosthetic segments in the selected group and one or more prosthetic segments remaining with the elongated flexible member. The selected group of prosthetic segments is then deployed at the first treatment site.
In still another aspect of the present invention, a method for selectively delivering prosthetic segments to a lesion in a treatment region in a body lumen comprises advancing a delivery catheter through the body lumen, which may be a blood vessel, to the treatment region. A plurality of prosthetic segments is often disposed axially along the delivery catheter. An outer shaft having a separator is distally advanced. A sheath disposed between the separator and the prosthetic segments is positioned until the separator is allowed to engage the prosthetic segments. The outer shaft can then be retracted proximally so as to create a spacing between prosthetic segments in the selected group and one or more prosthetic segments remaining with the elongate flexible member. Inflating a balloon disposed on the delivery catheter deploys the group of prosthetic segments while any remaining prosthetic segments stay with the delivery catheter.
Often, the sheath is configured to engage the outer shaft such that retraction of the sheath also retracts the outer shaft. Additionally, the prosthetic segments are typically balloon expandable, but they may also be self-expanding, and they are usually introduced into a blood vessel. Often, deploying the selected group of prosthetic segments comprises plastically deforming the selected group of prosthetic segments, and often this is accomplished with a balloon. Often, the plurality of prosthetic segments carries a therapeutic agent that is adapted to being released from the segments, and typically this agent is an anti-restenosis drug.
In some embodiments, the prosthetic segments have a length in the range from about 2 mm to about 10 mm, while in others, the segments have a length about 3 mm to about 6 mm. Often prosthetic segments have interleaved ends in engagement with each other prior to deployment, although the segments may also be spaced apart prior to deployment to allow the separator to engage the prosthetic segments at their distal ends.
Typically, the separator exerts substantially greater axial force against the prosthetic segments when the separator is retracted proximally than when the separator is advanced distally. In some embodiments, the separator comprises a plurality of resilient fingers projecting radially inward. Often, at least some of the fingers are inclined so that free ends of the fingers point proximally allowing the fingers to pass over the prosthetic segments as the separator is advanced distally but to engage a prosthetic segment when the separator is retracted proximally. Some of the fingers may be composed of metal, while in other embodiments, some of the fingers may be composed of a polymer.
In other embodiments, at least some of the fingers comprise a radiused end that substantially matches the curvature of the prosthetic segments thereby providing greater contact surface so as to facilitate engagement between the prosthetic segment and the separator as the separator is retracted proximally while allowing the separator to pass over the prosthetic segments during distal advancement of the separator. Some embodiments may include a separator that comprises a hinge coupled to the fingers. The hinge helps the fingers to deflect radially outward over the sheath when the separator is advanced distally. Often, the separator comprises an annular flange and the flange may be tapered or may have a tapered conical nose.
In still other embodiments, the separator comprises a plurality of inclined ramps that are disposed on an inner surface of the outer shaft. Often these ramps are separated by about ninety degrees. In yet other embodiments, the separator may comprise a sharp compliant edge.
These an other embodiments are described in further details in the following description related to the appended drawing figures.
Referring now to
In
In
Handle 106 includes a housing 110 which encloses the internal components of the handle 106. Handle 106 allows a physician operator to advance or retract outer shaft 124 and sheath 144, which determines the length of the prosthesis (number of segments) to be deployed. The handle 106 also permits connection of balloon 130 to an inflation source. The inner shaft 216 is preferably fixed to the handle housing 110, while both outer shaft 124 and sheath 144 are coupled to slide mechanisms 102 and 140, respectively. Slide mechanisms 102 and 140 allow both the outer shaft 124 and sheath 144 to be independently retracted and advanced relative to handle 106. An adaptor 108 is attached to handle 106 at its proximal end and is fluidly coupled to the inner shaft 216 in the interior of the housing of handle 106. The adaptor 108, preferably a Luer connector, is configured to be fluidly coupled with an inflation device which may be any commercially available balloon inflation device such as those sold under the trade name “Indeflator™,” manufactured by Abbott (formerly Guidant Corporation of Santa Clara, Calif.). The adaptor is in fluid communication with the inflatable balloon 130 via an inflation lumen in the inner shaft 216 to permit inflation of the inflatable balloon 130.
Additionally, a control mechanism on the handle 106 includes a slide mechanism 102 that translates along calibrated slot 104. Slide mechanism 102 is coupled with outer shaft 124 and is adapted to retract or advance the shaft 124 a selected distance. Initially, the distance is selected by advancing slide mechanism 102 distally along slot 104. This allows the physician operator to select the number of prosthetic segments 128 on the distal end of delivery catheter 100 that will be delivered. The slide mechanism 102 includes visual markers 148 so that an operator can easily determine how many stent segments have been selected. In preferred embodiments, slide mechanism 102 may have detents or a ratchet that provides audible or tactile feedback to the operator to facilitate operation of the stent delivery catheter 100 without requiring direct visualization during operation.
Handle 106 also comprises a second control mechanism 140 that translates along calibrated slot 142. Slide mechanism 140 is coupled with the sheath 144 and is adapted to retract or advance the sheath 144 a selected distance. After the number of prosthetic segments 128 has been selected as described above, slide mechanism 140 is retracted so as to cause proximal retraction of sheath 144. As sheath 144 is retracted, tabs 212 (
Additional details on materials and construction of other related handles are described in co-pending U.S. patent application Ser. No. 11/148,713, filed Jun. 8, 2005, (Attorney Docket No. 14592.4002), entitled “Devices and Methods for Operating and Controlling Interventional Apparatus,” and co-pending United States Publication No. 2005/0149159, entitled “Devices and Methods for Controlling and Indicating the Length of an Interventional Element,” and application Ser. No. ______, filed ______, 2006, (Attorney Docket No. 021629-003800US), entitled “Custom Length Stent Apparatus,” the full disclosures of which are incorporated herein by reference.
Both sheath 144 and outer shaft 124 along with guidewire 138 each extend through a slider assembly 132 slidably disposed on the catheter body 120 at a point between its handle 106 and expandable member 130. The slider assembly 132 is adapted for insertion into and sealing with a hemostasis valve, such as on an introducer sheath or guiding catheter, while still allowing relative movement of the outer shaft 124 and sheath 144 relative to the slider assembly 132. The slider assembly 132 includes a slider tube 118, a slider body 116, and a slider cap 114.
Outer shaft 124 and sheath 144 may be composed of any of a variety of biocompatible materials, such as but not limited to a polymer like PTFE, FEP, polyimide, Nylon or Pebax, and may be reinforced with a metallic or polymeric braid to resist radial expansion of inflatable balloon 130, and/or the like. Inflatable balloon 130 may be formed of a semi-compliant polymer such as Pebax, Nylon, polyurethane, polypropylene, PTFE or other suitable polymers. Additional aspects of the luminal prosthesis delivery system are described in U.S. patent application Ser. No. 10/306,813, filed Nov. 27, 2002 (Attorney Docket No. 021629-000320US); U.S. patent application Ser. No. 10/637,713, filed Aug. 8, 2003 (Attorney Docket No. 021629-000340US); U.S. patent application Ser. No. 10/738,666, filed Dec. 16, 2003 (Attorney Docket No. 021629-000510US); U.S. patent application Ser. No. 11/104,305, filed Apr. 11, 2005 (Attorney Docket No. 021629-003300US); and U.S. application Ser. No. 11/148,585, filed Jun. 8, 2005, the full disclosures of which are hereby incorporated by reference.
Delivery catheter 100 also includes a separator or “stent valve” disposed near the distal end of outer shaft 211 and an exemplary embodiment of this is seen in
Separator 206 contacts and engages prosthetic segments 202. As shown in
Prosthesis 126 is composed of one or more prosthetic segments 128. Prosthetic stent segments 128 are disposed over an inflation balloon 130. Each stent segment is about 2-20 mm in length, more typically about 2-10 mm in length and preferably being about 2-8 mm in length. Usually 2-20, more typically 2-10 and preferably 2-6 stent segments 128 may be positioned axially over the inflation balloon 130 and the inflation balloon 130 has a length suitable to accommodate the number of stent segments. Stent segments 128 may be positioned in direct contact with an adjacent stent segment so that segment ends are interleaved or there may be a spacing between segment ends. When the segments are spaced apart from one another, the spacing is typically between 0.5 mm and 1 mm. Furthermore, the stent segments 128 may be deployed individually or in groups of two or more at a single treatment site within the vessel lumen.
Prosthetic stent segments 128 are preferably composed of a malleable metal so they may be plastically deformed by inflation balloon 130 as they are radially expanded to a desired diameter in the vessel at the target treatment site. The stent segments 128 may also be composed of an elastic or superelastic shape memory alloy such as Nitinol so that the stent segments 128 self-expand upon release into a vessel by retraction of the sheath 124. In this case, an inflation balloon 130 is not required but may still be used for predilation of a lesion or augmenting expansion of the self-expanding stent segments (e.g. postdilation or tacking). Other materials such as biocompatible polymers may be used to fabricate prosthetic stent segments and these materials may further include bioabsorbable or bioerodable properties.
Stent segments 128 may have any of a variety of common constructions, such as but not limited to those described in U.S. patent application Ser. No. 10/738,666 filed Dec. 16, 2003 (Attorney Docket No. 02169-000510US), which was previously incorporated by reference. Constructions may include for example, closed cell constructions including expansible ovals, ellipses, box structures, expandable diamond structures, etc. In addition, the closed cells may have complex slotted geometries such as H-shaped slots, I-shaped slots, J-shaped slots, etc. Suitable open cell structures include zigzag structures, serpentine structures, and the like. Such conventional stent structures are well described in the patent and medical literature. Specific examples of suitable stent structures are described in the following U.S. patents, the full disclosures of which are incorporated herein by reference: U.S. Pat. Nos. 6,315,794; 5,980,552; 5,836,964; 5,527,354; 5,421,955; 4,886,062; and 4,776,337.
In preferred embodiments, prosthetic stent segments 128 may be coated, impregnated, infused or otherwise coupled with one or more drugs that inhibit restenosis, such as Rapamycin, Everolimus, Paclitaxel, analogs, prodrugs, or derivatives of the aforementioned, or other suitable agents, preferably carried in a durable or bioerodable polymeric carrier. Alternatively, stent segments 128 may be coated with other types of drugs or therapeutic materials such as antibiotics, thrombolytics, anti-thrombotics, anti-inflammatories, cytotoxic agents, anti-proliferative agents, vasodilators, gene therapy agents, radioactive agents, immunosuppressants, chemotherapeutics and/or stem cells. Such materials may be coated over all or a portion of the surface of stent segments 128, or stent segments 128 may have a porous structure or include apertures, holes, channels, or other features in which such materials may be deposited.
Referring now to
The length of the lesion to be treated is typically visualized by introducing contrast media into the target vessel V and observing the resulting image under a fluoroscope. Radiopaque markers 226, 228, one at the distal end of the balloon 204 and one at the distal end of the outer shaft 211 may be used to visualize the length of stent segments 202 exposed for deployment relative to the target lesion. This is accomplished by advancing the delivery catheter 200 so that radiopaque marker 226 is at the distal edge of the lesion and then outer shaft 211 is advanced until radiopaque marker 228 is at the proximal edge of the lesion. Retraction of sheath 208 engages outer shaft 211 and then both sheath 208 and outer shaft 211 are retracted distally, resulting in a number of stent segments 218 being selected to match the length of lesion L, as shown in
Additionally, once annular flange 212 on the sheath 208 has passed through stent valve 206, stent valve 206 is no longer disposed over sheath 208. The stent valve 206 now engages the distal-most prosthetic segment 202 in the group of prosthetic segments remaining with the delivery catheter 200, and this is shown in
Referring now to
While the exemplary embodiments have been described in some detail for clarity of understanding and by way of example, a variety of additional modifications, adaptations and changes may be clear to those of skill in the art. Hence, the scope of the present invention is limited solely by the appended claims.
