WO2016196362A1

WO2016196362A1 - Sheath catheter with tearable sidewall strips for releasing self-expanding stents

Info

Publication number: WO2016196362A1
Application number: PCT/US2016/034813
Authority: WO
Inventors: Annette BRANGER; Eugene Serina; Nhan NGO
Original assignee: Branger Annette; Eugene Serina; Ngo Nhan
Priority date: 2015-05-29
Filing date: 2016-05-27
Publication date: 2016-12-08

Abstract

Described herein are devices and methods for retracting a sheath from a stent. The retractable sheath comprises a tubular liner having at least a portion concentrically disposed about the stent. The tubular liner comprises a tearable strip having a distal end attached to a retraction device. The retraction device is configured to retract the tearable strip proximally ahead of the everting discontinuous tubular liner.

Description

SHEATH CATHETER WITH TEARABLE SIDEWALL STRIPS FOR RELEASING SELF-EXPANDING STENTS

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/168,643, filed May 29, 2015, which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] Catheters often comprise a retractable sheath that surrounds a vascular stent.

Retractable sheaths are often used to keep self-expanding stents from expanding until the stent is delivered to the region of the vessel requiring support by the stent. Retracting the sheath in a proximal direction allows the self-expanding stent to expand in the vessel lumen, thereby providing support to a damaged region of the vessel. Stents can be coated with drugs (e.g., pharmaceutical compositions that inhibit restenosis or endothelial overgrowth of the implanted stent) and/or additional coatings. However, retraction of the sheath often generates high shear forces along the surface of the stent, which can damage the drug coating that is applied to the stent surface or create high deployment forces that makes it difficult for the physician to deploy the stent, especially for drug coated stents. The instant disclosure provides a retractable sheath that helps prevent damage to the surface of the stent and has a low deployment force.

BRIEF SUMMARY OF THE INVENTION

[0003] The present disclosure provides a retractable sheath for a catheter, the sheath having tearable sidewall strips (one or more) that are useful for releasing self-expanding stents from the catheter. Also provided are methods of using the retractable sheath for deploying a self- expanding stent in a vessel of a subject. The tearable sidewall strips provide the unexpected advantage of releasing the stent from the sheath without generating high shear forces between the sheath and the stent surface as in a conventional catheter, which can damage a drug coating on the surface of the stent or make deployment difficult.

[0004] In one aspect, a retractable sheath for deploying a stent is provided, the sheath comprising: a tubular liner having a portion concentrically disposed about the stent, wherein the tubular liner comprises a tearable strip having a distal end attached to a retraction device.

[0005] In some embodiments, the tearable strip comprises a strip or braided fiber or polymer that is attached to, adjacent to, embedded in, or capable of tearing the tubular liner. The distal end of the tubular liner can be attached to the retraction device, and the retraction device configured to retract the tearable strip proximally ahead of the discontinuous tubular liner. In some embodiments, distal end of the tubular liner is attached to a first retraction device, and the distal end of the tearable strip is attached to a second retraction device configured to retract the tearable strip proximally ahead of the discontinuous tubular liner. The retractable sheath can further comprise an axially moveable outer shaft. The retraction device can comprise an outer shaft of the sheath or a collar connected to one or more pull wires.

[0006] In a second aspect, a deployment system for a stent is provided, the deployment system comprising:

a catheter comprising an inner tube having a proximal end portion and a distal end portion;

a radially expandable stent concentrically disposed about the distal end portion;

a retractable sheath concentrically disposed about the stent;

the retractable sheath comprising a tubular liner concentrically disposed about the stent, wherein a proximal end of the tubular liner is attached to the inner tube at a location proximal to the stent, and a distal end of the tubular liner is attached to a first axially moveable retraction device;

wherein the tubular liner comprises a tearable strip having a distal end attached to a retraction device.

[0007] As in the first aspect, the tearable strip can comprise a strip or braided fiber or polymer attached, adjacent to, embedded in, or capable of tearing the tubular liner. For example, in any of the embodiments described herein, the tearable strip can comprises a strip or braided version of any of the following materials: a fiber, a polymer, a textile or a metal, embedded in, attached or adjacent to, or capable of tearing, the tubular liner. In some embodiments, the distal end of the tearable strip is attached to the first retraction device, and the first retraction device is configured to retract the tearable strip proximally ahead of the discontinuous tubular liner. The deployment system can further comprise a second axially moveable retraction device, wherein the distal end of the tearable strip is attached to the second retraction device, and the second retraction device is configured to retract the distal end of the tearable strip proximally ahead of the discontinuous tubular liner. [0008] In some embodiments, the inner tube comprises a guidewire lumen. In some embodiments, the inner tube comprises a stent stop postioned proximal to the stent.

[0009] The radially expandable stent can be a self-expanding, drug-coated stent.

[0010] In some embodiments, the stent has an axial length X, and the first and/or second retraction device is configured to move about twice (2X) length X when the sheath is retracted to deploy the stent.

[0011] In some embodiments, the deployment system further comprises a handle at the proximal end portion of the catheter for controlling the first and/or second retraction device, wherein the handle is configured to retract the tubular liner at least twice the axial length of the stent. The deployment system can further comprise an axially movable outer shaft. Thus, in some embodiments, the first and/or second retraction device comprises an axially movable outer shaft. In some embodiments, the first and/or second retraction device comprises a collar attached to one or more pull wires.

[0012] The catheter can be an over-the-wire catheter or a rapid-exchange catheter.

[0013] In a third aspect, a method of retracting a sheath covering a self-expanding stent is provided, the method comprising: tearing-away or splitting a side wall of the sheath by proximally retracting a tearable strip which may be attached, adjacent to or embedded in the side wall, wherein the sheath is folded over itself and partially everted at a distal end; and

proximally retracting and everting the radially discontinuous sheath in a rolling motion.

[0014] In a fourth aspect, a method of deploying a self-expanding stent in a vessel is provided, the method comprising: positioning a stent deployment system described above in the vessel; proximally retracting the tearable strip and tubular liner, thereby separating the side wall of the tubular liner and everting the discontinuous tubular liner in a rolling motion and permitting the stent to self-expand, and

deploying the self-expanding stent in the vessel.

[0015] In some embodiments of the methods described herein, the tearable strip is retracted by moving a first or second retraction device in a proximal direction. In some embodiments, the stent has an axial length X, and the first or second retraction device is retracted proximally at least about twice (2X) the length of the stent to deploy the stent. In some embodiments, the tubular liner is retracted at least twice the axial length of the stent. The first and/or second retraction device can comprise an outer shaft or a collar connected to one or more pull wires. In some embodiments, the stent is a drug coated stent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 illustrates one embodiment of the catheter sheath described herein.

[0017] Fig. 2 illustrates another embodiment of the catheter sheath described herein.

DEFINITIONS

[0018] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by a person of ordinary skill in the art. The term "a" or "an" is intended to mean "one or more." The term "comprise" and variations thereof such as "comprises" and "comprising," when preceding the recitation of a step or an element, are intended to mean that the addition of further steps or elements is optional and not excluded. Any methods, devices and materials similar or equivalent to those described herein can be used in the practice of this invention. The following definitions are provided to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.

[0019] The term "about," when modifying any amount, refers to the variation in that amount typically encountered by one of skill in the art, i.e., in the field of angioplasty catheter design. For example, the term "about" refers to the normal variation encountered in measurements for a given analytical technique, both within and between batches or samples. Thus, the term about can include variation of 1-10% of the measured amount or value, such as +/- 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% variation. The amounts disclosed herein include equivalents to those amounts, including amounts modified or not modified by the term "about."

[0020] When describing the catheter and retractable sheath herein, the term "distal" refers to further away from, and "proximal" refers to closer to the catheter handle, where the handle is used to control the catheter by a medical specialist. The term distal refers to further away from the heart, and the term proximal refers to closer to the heart, when describing the direction of a vessel herein.

[0021] The term "evert" or "everting" refers to turning the retractable sheath described herein outward or inside-out, for example in a rolling motion, such that the inner surface of the sheath that was directed toward the stent is now facing to the exterior, away from the stent (or central axis of the catheter).

[0022] The term "separating a side wall" of the sheath or tubular liner refers to creating a tear or an opening in the wall of the sheath or liner along the longitudinal axis, thereby creating a radially discontinuous tubular liner. In some embodiments, the side wall of the sheath or liner is a cylindrical wall. The process of progressively creating the tear in the sheath or tubular liner results in a loss of radial constraint, which permits the stent to self- expand. Proximally everting the tubular liner in a rolling motion prevents the liner from becoming trapped between the stent and the vessel wall.

[0023] The term "retract the tearable strip proximally ahead of the sheath" refers to the movement of the tearable strip relative to the sheath or tubular liner, where the tearable strip is retracted slightly ahead of the sheath in the proximal direction. This allows the tearable strip to begin ripping or tearing the sheath before the sheath begins moving in the proximal direction.

[0024] The term "pull wire" refers to a non-elastic, flexible elongated member that is used to retract the tearable strip and/or tubular liner. In some embodiments, one or more pull wires are attached to a retractable collar. The pull wire can be made of, for example, a metal, a polymer, or a textile.

[0025] The term "discontinuous tubular liner" refers to a tubular liner or sheath that has a tear, slit, or opening in the wall of the liner or sheath that runs approximately along the longitudinal axis, in a distal to proximal direction with reference to the catheter. DETAILED DESCRIPTION OF THE INVENTION

[0026] Described herein is a retractable sheath for a catheter and methods of using the retractable sheath for deploying a stent in a subject, for example in a blood vessel of the subject. The retractable sheath allows a physician to remove the sheath from the stent without damaging a coating on the surface of the stent, such as a drug coating on a self- expanding stent. The drug coating on a stent is usually delicate and often tacky, and thus can be damaged by the friction of retracting a conventional sheath over the surface of the stent. This situation is often made worse by sheaths covering self-expanding stents, where the compressed stent exerts radial force against the sheath and forces the drug coating on the stent surface tightly against the sheath. The high shear force between the sheath and stent surface as the sheath is retracted can damage the drug coating. Further, longer self expanding stents, such as those used in the peripheral vasculature, can increase the shear force due to the increased surface area of the stent, and make higher deployment forces for physicians.

[0027] The retractable sheath described herein solves this problem by providing one or more tearable sidewall strips and everting the discontinuous tubular liner that allows the sheath to pull away from the stent without sliding along the surface of the stent or coating as the sheath is retracted. Pulling the tearable strip in a proximal direction tears the side wall of the sheath along the longitudinal axis, thereby allowing the self-expanding stent to expand. Further, the sheath is everted and retracted proximally, peeling off of (i.e., away from) the stent with minimal shear force, without friction against the stent much like a banana being peeled back. Thus, the retractable sheath described herein provides unexpected advantages including minimizing the damage to the surface of the stent. The retractable sheath described herein can also be used with catheters designed to deploy non-self-expanding stents, such as balloon expandable stents. Specific embodiments will now be described. The Retractable Sheath with Tearable Side Wall Strips

[0028] The retractable sheath described herein is typically part of a catheter assembly comprising an elongate, flexible catheter, the sheath, an inner tubular member, and a stent. In some embodiments, the retractable sheath is tubular in shape and circumferentially contacts or surrounds the compressed stent along the stent's longitudinal axis. In some embodiments, the retractable sheath provides sufficient radial restraint to hold the stent in its compressed state prior to retraction of the sheath. The sheath can be made of a trilayer of HDPE (High Density Polyethylene), PLEXAR®, and Nylon. The sheath comprises one or more tearable side wall strips that extend at least partially along the distal end of the sheath. The tearable side wall strip can be embedded in the material of the distal end portion of the sheath. In some embodiments, the distal end portion of the sheath, which comprises a tubular or annular opening, is partly folded over onto itself, thereby partially everting the sheath at the distal end. The sheath can further comprise a retraction device that is attached to the sheath, for example to the distal end of the partially everted sheath. In some embodiments, the distal end of the tearable strip is attached to the same retraction device. In some embodiments, the distal end of the tearable strip is attached to a different (second) retraction device.

[0029] In some embodiments, the sheath comprises a tubular inner liner, at least a portion of which concentrically surrounds, covers or is otherwise disposed about the stent. In some embodiments, the tubular liner is attached at one end (i.e., the proximal end) to the inner tubular member of the catheter assembly, and at the other end (i.e., the distal end) to a retraction device. The tubular liner can be at least slightly longer than the axial length of the stent that is deployed, but may be longer as required. For example, the tubular liner can vary in length from the axial length of the stent up to the length of the catheter or greater.

[0030] The tubular liner further comprises one or more tearable side wall strips. The tearable strip can be embedded in the tubular liner, for example, in the side wall of the tubular liner. The distal end of the tearable strip is attached to a retraction device, and the proximal end is attached to the inner tube of the catheter. In some embodiments, the tubular liner is manufactured such that the tearable strip emanates from a small tear or notch at the distal end of the everted tubular liner,. The notch facilitates tearing the side wall of the tubular liner when the tearable strip is retracted proximally. In some embodiments, the notch is about 2 mm deep, such that the distal end of the tearable strip is retracted about 2 mm ahead of the folded over distal region of the tubular liner. [0031] The tearable strip can be made of a variety of materials, for example, a metal ribbon or wire, a textile fiber, a polymer strip, or a braided fiber. In some embodiments, the tearable strip is made of polyetheretherketone (PEEK) or expanded polytetrafluoroethylene (ePTFE).

Retraction Device

[0032] The sheath and/or catheter assembly can further comprise a retraction device. The retraction device is configured to retract the distal end of the tearable strip proximally, such that the tearable strip rips open the side wall of the tubular liner in a proximal direction as the distal end of the tearable strip advances proximally. This can be accomplished by attaching the distal end of the tearable strip tautly to the retraction device. The distal end opening of the tubular liner is everted by partly folding the tubular liner outwardly over onto itself at the distal end. In operation, the distal end of the tearable strip is retracted proximally ahead of the discontinuous tubular liner by the retraction device, which results in the tearable strip opening the side wall of the tubular liner. Retracting the tubular liner allows the tubular liner to evert in a rolling motion. The distal end of the tearable strip and the distal end of the tubular liner can be attached to same retraction device, or the distal end of the tubular liner can be attached to a first retraction device and the distal end of the tearable strip can be attached to a second retraction device. If present, the second retraction device is configured to retract the tearable strip ahead of the tubular liner.

[0033] The catheter assembly can further comprise an axially movable tubular outer shaft that surrounds the retractable sheath or tubular liner. In some embodiments, the outer shaft extends to the distal end region of the catheter assembly such that it surrounds, but does not necessarily contact, the stent. Thus, the outer shaft can be concentrically disposed about the tubular liner at the distal end portion of the catheter, adjacent to the stent. In some embodiments, the outer shaft is in slidable contact with the tubular liner. In some

embodiments, the distal end of the outer shaft can be proximal to the stent, and does not need to be concentrically disposed about the tubular liner. In this embodiment, the tubular liner is at least 2X (twice) the length of stent.. In some embodiments, the distal end of the sheath or tubular liner is attached to the outer shaft. For example, the tubular liner can be attached to the distal end of the outer shaft, or attached to the outer shaft at any point along the length of the outer shaft. Similarly, the distal end of the tearable strip can be attached to the distal end of the outer shaft, or attached to the outer shaft at any point along its length. Thus, in these embodiments, the outer shaft functions as a retraction device, and is configured to proximally retract the tearable strip ahead of the discontinuous tubular liner. In some embodiments, the outer shaft is attached to the handle.

[0034] The retraction device can also comprise an annular collar connected to one or more pull wires. In some embodiments, the distal end of the tearable strip is attached to the collar. As described above, the retraction device comprising the annular collar is configured to retract the distal end of the tearable strip proximally ahead of the discontinuous tubular liner. In this embodiment, the outer shaft can surround the retraction device to confine the tubular liner almost completely within the catheter assembly, thereby preventing the tubular liner from contacting the interior lumen of the vessel as the sheath is retracted and the stent self- expands. In operation, the retraction device moves twice the axial distance of the outer shaft in order to evert and retract the tubular liner and expose the stent.

Expandable Stent

[0035] The stent is typically a radially expandable stent, such as a self-expanding or balloon expandable stent. In some embodiments, the stent is manufactured from a

pseudoelastic alloy (i.e., a shape memory metal) such as a nickel titanium alloy (e.g.,

NITINOL™).

Stent Coatings

[0036] The stent can also be a coated with a therapeutic drug (e.g., a drug-eluting stent). The drug can be eluted over time after the stent is deployed in the vessel of the subject. The drug can be selected from any therapeutically useful agent, including but not limited to, agents for inhibiting restenosis, inhibiting platelet aggregation, or encouraging

endothelialization. Some of the suitable agents may include smooth muscle cell proliferation inhibitors such as rapamycin, angiopeptin, and monoclonal antibodies capable of blocking smooth muscle cell proliferation; anti -inflammatory agents such as dexamethasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, acetyl salicylic acid, and mesalamine, lipoxygenase inhibitors; calcium entry blockers such as verapamil, diltiazem and nifedipine; antineoplastic/antiproliferative/anti-mitotic agents such as paclitaxel, 5- fluorouracil, methotrexate, doxorubicin, daunorubicin, cyclosporine, cisplatin, vinblastine, vincristine, colchicine, epothilones, endostatin, angiostatin, Squalamine, and thymidine kinase inhibitors; L-arginine; antimicrobials such astriclosan, cephalosporins,

aminoglycosides, and nitorfurantoin; anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; nitric oxide (NO) donors such as lisidomine, molsidomine, NO-protein adducts, NO-polysaccharide adducts, polymeric or oligomeric NO adducts or chemical complexes; anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an RGD peptide-containing compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin antibodies, anti-platelet receptor antibodies, enoxaparin, hirudin, Warafin sodium, Dicumarol, aspirin, prostaglandin inhibitors, platelet inhibitors and tick antiplatelet factors; interleukins, interferons, and free radical scavengers; vascular cell growth promoters such as growth factors, growth factor receptor antagonists, transcriptional activators, and translational promoters; vascular cell growth inhibitors such as growth factor inhibitors (e.g., PDGF inhibitor— Trapidil), growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin; Tyrosine kinase inhibitors, chymase inhibitors, e.g., Tranilast, ACE inhibitors, e.g., Enalapril, MMP inhibitors, (e.g., Ilomastat, Metastat), GP Ilb/IIIa inhibitors (e.g., Intergrilin, abciximab), seratonin antagnonist, and 5-HT uptake inhibitors; cholesterol-lowering agents; vasodilating agents; and agents which interfere with endogeneus vascoactive mechanisms. Polynucleotide sequences may also function as anti-restenosis agents, such as pi 5, pi 6, pi 8, pi 9, p21, p27, p53, p57, Rb, nFkB and E2F decoys, thymidine kinase ("TK") and combinations thereof and other agents useful for interfering with cell proliferation. The selection of an active agent can be made taking into account the desired clinical result and the nature of a particular patient's condition and contraindications. In some embodiments, the agent is BA9™ (also known as Biolimus A9, INN: umirolimus).

[0037] In some embodiments, the stent comprises a coating that is useful in eluting a therapeutic drug from the surface of the stent (i.e., a drug eluting stent). Examples of such coatings include biocompatible coatings, drug-delivery coatings or polymer-free coatings. In some embodiments, the stent comprises a biocompatible coating comprising inorganic materials, such as gold, silicon carbide, iridium oxide, or titaniyum-nitride-oxide. In some embodiments, the stent comprises a polymer-free coating or surface, such as a microporous surface, a microstructured surface, a slotted tubular surface, a nanoporous surface, a nanoparticle coated surface, or surface coated with two therapeutic drugs (i.e., a dual polymer-free drug eluting stent).

[0038] In some embodiments, the stent comprises a coating containing the therapeutic drug, such that the drug elutes over time. For example, the coating can be a nonbiodregable polymer, such as but not limited to a polymer blend of poly(ethylene-co-vinyl acetate) and poly(n-butylmethacrylate), poly(styrene-b-isobutylene-b-styrene), a fluoropolymer and phosphorylcholine. In some embodiments, the coating comprises a biodegradable polymer, such as but not limited to poly(lactic acid) (PLA), poly(glycolic acid) and the copolymer, poly(lactic-co-glycolic acid) (PLGA), which can be fully degraded and metabolized by the human body.

[0039] With or without the inclusion of a drug, any of the stents described herein can be made from a bioabsorbable material. In one embodiment, the stent is a self-expanding bioabsorbable stent. In some embodiments, the stent comprises a bioabsorbable material and is mounted on a balloon, and the stent can be either balloon-expandable or self-expanding. In some embodiments, the tearable sidewall sheath deployment system described herein can be combined with a balloon catheter comprising an expandable stent or drug coated balloon. [0040] The stent can be designed for deployment in any vessel of the body of the subject. For example, the stent can be designed for deployment in the coronary arteries, the carotid artery, or peripheral arteries and veins. In embodiments for coronary arteries, the stent can be from about 10 mm to about 40 mm. In some embodiments, the stent is deployed in a peripheral vessel, such as a blood vessel in the leg of a subject. In embodiments for peripheral vessels, the stent is from about 40 mm to about 250 mm in axial length. In some embodiments, the stent comprises radiopaque markers at the distal and/or proximal end.

Deployment System

[0041] The retractable sheath described herein can be included in a deployment system for deploying a stent in a vessel of a subject. The deployment system comprises a catheter assembly described herein. In some embodiments, the catheter has an inner tube (also referred to as a "push rod") having a proximal end portion and a distal end portion. The inner tube has a region at the distal end portion configured for mounting a radially expandable stent thereon. The stent is mounted on the inner tube in the compressed or unexpanded

configuration. The inner tube further comprises a stent stop positioned proximal to the stent mounting region. The stent stop is configured to prevent the stent from moving in a proximal direction on the inner tube when the catheter is inserted into the vessel or the sheath is retracted. The inner tube also comprises a lumen for inserting a guidewire (the guidewire lumen). The distal end of the catheter can further comprise a distal tip configured to provide a smooth transition between the distal end of the catheter and the sheath or outer shaft and thereby minimize damage to the vessel wall when the catheter is inserted into the vessel.

[0042] The deployment system further comprises a retractable sheath described herein concentrically disposed about the stent. In some embodiments, the retractable sheath comprises a tubular liner described above concentrically disposed about the stent. A proximal end of the tubular liner is attached to the inner tube at a location proximal to the stent mounting region. In one embodiment, the tubular liner is attached to the inner tube at a location proximal to the stent stop. The distal end of the tubular liner is attached to an axially moveable retraction device. The tubular liner comprises a tearable strip having a distal end attached to the retraction device, and a proximal end attached to the inner tube, for example, at a location proximal to the stent mounting region or proximal to the stent stop. In one embodiment, the tearable strip comprises a braided fiber, and the braided fiber is embedded in the material of the tubular liner. In some embodiments, the deployment system comprises an axially moveable outer shaft that is concentrically disposed about and/or in slidable contact with the tubular liner.

[0043] In order to retract the sheath, a retraction device is required. Thus, the deployment system comprises a retraction device configured to retract the tearable strip proximally ahead of the sheath. In one embodiment, the retraction device is an axially moveable outer shaft. In one embodiment, the retraction device comprises an annular collar attached to one or more pull wires. In some embodiments, the deployment system further comprises a second axially movable retraction device. The distal end of the tearable strip can be attached to the second retraction device, whereas the distal end of the tubular liner is attached to an axially moveable first retraction device. The deployment system further comprises a handle at the proximal end portion of the catheter for controlling the first and/or second retraction devices. In some embodiments, the handle is configured to retract the sheath, pullwires or tubular liner twice the axial length of the stent. For example, if the stent has an axial length X, the retraction device is retracted about twice (2X) length X when the sheath is retracted to deploy the stent. Likewise, the tubular liner and tearable strip also move twice (2X) length X when the sheath is retracted. This 2 to 1 ratio is typical of sheaths that are everted to deploy the stent.

[0044] In some embodiments the retraction device attached to the tubular liner is surrounded by an outer shaft. This outer shaft can surround the retraction device to confine the majority of the tubular liner within the catheter assembly, thereby preventing the tubular liner from contacting the interior lumen of the vessel as the sheath is retracted and the stent self-expands. In this configuration the retraction device is retracted about twice (2X) the axial length X of the stent, whereas the outer shaft is retracted IX the axial length X of the stent, at the rate the stent is exposed.

[0045] The handle can comprise a single or multiple mechanisms for proximally retracting the sheath and/or retraction device(s). Examples of such mechanisms include wheels, knobs, toggles, or sliding mechanisms. As described above, in some embodiments, the retraction device comprises an annular collar attached to one or more pull wires, and the outer shaft circumferentially surrounds the retraction device. In some embodiments in which two retraction devices are used, one for the tearable strip and one for the tubular liner, the handle may comprise one or more mechanisms that may or may not be linked for retracting the two sheaths at the same speed and distance. Examples of suitable sheath retraction devices are described in US Patent No. 8,500,789, and the references cited therein, which are

incorporated by reference in their entirety herein. In the embodiments of two retracting sheaths where one shaft is designed to keep the tubular liner from significant contact with the vessel wall, the handle may comprise a first wheel attached to a pull wire for retracting the annular collar, and a second wheel attached to the outer shaft. The physician retracts the sheath(s) by turning the wheels, which are configured such that the annular collar moves twice the axial distance of the outer shaft as the sheath is retracted. In some embodiments, the handle comprises a single wheel having two different diameters configured such that turning the wheel retracts the two different sheath s/shafts at two different speeds or distances, such that the tubular liner/strip attached to the collar moves 2X, and the outer shaft moves IX. In some embodiments the handle comprises other means of linking and controlling the two different sheath/shaft speeds or distances by one handle mechanism, as in a gun tackle two pulley system, such that the tubular liner/strip attached to the collar moves 2X, and the outer shaft moves IX.

[0046] The deployment system can comprise an over-the- wire catheter or a rapid exchange catheter. METHODS

[0047] The retractable sheath described herein is useful for deploying a stent in the vessel of a subject, for example to treat a pathological condition in the vessel. Thus, methods of using the retractable sheath will now be described.

[0048] In one embodiment, the method comprises the steps of tearing away or splitting a side wall of the sheath by proximally retracting one or more tearable strips attached, adjacent to or embedded in the sheath (e.g., in a side wall of the sheath), permitting the stent to expand, and proximally retracting and everting the discontinuous sheath in a rolling motion,.

The sheath is folded over itself and at least partially everted at the distal end prior to proximally retracting the tearable strip(s). The tearable strip(s) is retracted proximally ahead of the partially everted discontinuous sheath, such that the side walls of the sheath separate along the lengthening tear and the sheath everts or rolls outward as the tearable strip(s) is retracted proximally. [0049] Also described is a method of deploying a self-expanding stent in a vessel, for example a blood vessel of a subject. The method comprises positioning a stent deployment system described herein in the vessel, and retracting a tearable strip attached, adjacent to, embedded in, or capable of tearing a tubular liner, thereby separating the wall of the tubular liner which permits the stent to self-expand and deploy in the vessel. The proximal retraction of the tubular liner prevents the liner from becoming trapped between the stent and vessel wall. As above, the tubular liner is partially everted at the distal end prior to proximally retracting the tearable strip.

[0050] In the above methods, the distal end of the tearable strip is attached to a retraction device, and is retracted by moving the retraction device in a proximal direction such that the tearable strip moves proximally ahead of the discontinuous sheath or tubular liner. In some embodiments, the sheath or tubular liner is attached to a first retraction device, and the tearable strip is attached to a second retraction device, and the second retraction device is configured to retract the distal end of the tearable strip proximally ahead of the sheath or tubular liner. In some embodiments, the stent has an axial length X, and the stent is deployed by retracting the retraction device proximally about twice (2X) the axial length of the stent. In some embodiments, the tubular liner and tearable strip are retracted at least about twice the axial length of the stent. Further, in the above methods, the stent can be coated with a therapeutic drug or agent and/or coating. [0051] Non-limiting examples will now be described.

EXAMPLES

[0052] Example 1 describes one embodiment of a deployment system described herein.

[0053] Figure 1 illustrates a deployment system (10) comprising a catheter (not shown) having a stent disposed at the distal end. Fig. 1 shows three different stages of deploying the stent by pulling the tearable strip in a proximal direction, thereby everting and tearing the tubular liner which allows the stent to self-expand. The stent (15) is covered by a tubular liner (20) having a proximal end (25) attached to a push rod (30) proximal to a stent stop (40), and a distal end (45) attached to an axially movable outer shaft (50). The tubular liner is partially folded over itself (i.e., everted) in an outward direction at the distal end. The tubular liner comprises a notch in the folded over, partially everted section, and the pull tab (60) for a tearable strip (70) emanates from the notch. The pull tab (60) at the distal end of the tearable strip (70) is also attached to the outer shaft (50) at the location of the notch. To deploy the stent (15), the outer shaft is retracted proximally by moving the handle (90) proximally, which pulls the tearable strip proximally and tears the liner along the longitudinal axis, which everts the liner and exposes the stent. The stent is now free to self-expand. The outer shaft, the tearable strip, and the liner move twice (2X) the axial length of the stent (X). [0054] Example 2 describes another embodiment of the deployment system described herein.

[0055] Figure 2 illustrates a deployment system (100) comprising a catheter (not shown) having a stent (115) disposed at the distal end. Fig. 2 shows three different stages of deploying the stent by pulling the tearable strip in a proximal direction, thereby everting and tearing the tubular liner which allows the stent to self-expand. The catheter will typically comprise a guide wire (112) and a distal tip (114). As in Fig. 1, the stent is covered along its axial length by a tubular liner (120). The deployment system further comprises a retraction device (110) comprising an annular collar or ring (135) attached to one or more pull wires (150), which are attached to a handle at the proximal end of the catheter (not shown). The tubular liner has a proximal end (125) attached to a push rod (130) proximal to the stent stop (140), and a distal end (145) attached to the annular collar (135). The liner is folded over itself and partially everted at the distal end (145), and has a notch (165) in the folded over region. As described in Example 1, the distal end of a tearable strip (170) emanates from the notch, and is also attached to the annular collar (135) at the location of the notch in the liner. The deployment system further comprises an axially moveable outer shaft (180) that surrounds the tubular liner. The outer shaft is connected to the handle at the proximal end of the catheter (not shown).

[0056] To deploy the stent, the physician proximally retracts the annular ring (135) using the handle connected to the pull wires (150). This pulls the tearable strip (170) proximally such that the tearable strip tears open the tubular liner (120) as the annular ring (135) is retracted, and also pulls the tubular liner in a proximal direction resulting in the eversion and retraction of the discontinuous tubular liner. The outer shaft (180) is simultaneously retracted by the handle, which is configured to retract the annular collar twice the distance the outer shaft is retracted. The outer shaft thus surrounds the tubular liner as it is everted and retracted from the stent, which keeps the everted liner inside the deployment system and prevents the loose liner from contacting the vessel lumen. [0057] It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.

Claims

WHAT IS CLAIMED IS:

1. A retractable sheath for deploying a stent, the sheath comprising: a tubular liner having a portion concentrically disposed about the stent, wherein the tubular liner comprises a tearable strip having a distal end attached to a retraction device.

2. The retractable sheath of claim 1, wherein the tearable strip comprises a strip or braided fiber or polymer that is embedded in the tubular liner.

3. The retractable sheath of claim 1, wherein a distal end of the tubular liner is attached to the retraction device, and the retraction device is configured to retract the tearable strip proximally ahead of the discontinuous tubular liner.

4. The retractable sheath of claim 1, wherein a distal end of the tubular liner is attached to a first retraction device, and the distal end of the tearable strip is attached to a second retraction device configured to retract the tearable strip proximally ahead of the discontinuous tubular liner.

5. The retractable sheath of claim 1, further comprising an axially moveable outer shaft.

6. The retractable sheath of claim 1, wherein the retraction device comprises an outer shaft or a collar connected to one or more pull wires.

7. A deployment system for a stent, the deployment system comprising: a catheter comprising an inner tube having a proximal end portion and a distal end portion;

a retractable sheath concentrically disposed about the stent;

the retractable sheath comprising a tubular liner concentrically disposed about the stent, wherein a proximal end of the tubular liner is attached to the inner tube at a location proximal to the stent, and a distal end of the tubular liner is attached to a first axially moveable retraction device; wherein the tubular liner comprises a tearable strip having a distal end attached to the retraction device.

8. The deployment system of claim 7, wherein the tearable strip comprises a strip or braided version of any of the following materials: a fiber, a polymer, a textile or a metal, embedded in, attached or adjacent to, or capable of tearing, the tubular liner.

9. The deployment system of claim 7, wherein the distal end of the tearable strip is attached to the first retraction device, and the first retraction device is configured to retract the tearable strip proximally ahead of the discontinuous tubular liner.

10. The deployment system of claim 7, further comprising a second axially moveable retraction device, wherein the distal end of the tearable strip is attached to the second retraction device, the second retraction device configured to retract the distal end of the tearable strip proximally ahead of the discontinuous tubular liner.

11. The deployment system of claim 7, wherein the inner tube comprises a guidewire lumen.

12. The deployment system of claim 7, wherein the inner tube comprises a stent stop postioned proximal to the stent.

13. The deployment system of claim 7, wherein the radially expandable stent is a self-expanding, drug-coated stent.

14. The deployment system of claim 7, wherein the stent has an axial length X, and the first retraction device is configured to move about twice (2X) length X when the sheath is retracted to deploy the stent.

15. The deployment system of claim 10, further comprising a handle at the proximal end portion of the catheter for controlling the first and/or second retraction device, wherein the handle is configured to retract the tubular liner at least twice the axial length of the stent.

16. The deployment system of claim 7, further comprising an axially movable outer shaft.

17. The deployment system of claim 10, wherein the first and/or second retraction device comprises the outer shaft of claim 16 or a collar attached to one or more pull wires.

18. The deployment system of claim 7, wherein the catheter is an over-the- wire catheter.

19. The deployment system of claim 7, wherein the catheter is a rapid- exchange catheter.

20. A method of retracting a sheath covering a self-expanding stent, comprising:

tearing-away or splitting a side wall of the sheath by proximally retracting a tearable strip, wherein the sheath is folded over itself and partially everted at a distal end; and proximally retracting and everting the sheath in a rolling motion, permitting the stent to expand.

21. A method of deploying a self-expanding stent in a vessel, the method comprising:

positioning the stent deployment system of any of claims 7-19 in the vessel; proximally retracting the tearable strip and tubular liner, thereby separating the side wall of the tubular liner and everting the discontinuous tubular liner in a rolling motion and permitting the stent to self-expand, and

deploying the self-expanding stent in the vessel.

22. The method of claim 20 or 21, wherein the tearable strip is retracted by moving a first or second retraction device in a proximal direction.

23. The method of claim 22, wherein the stent has an axial length X, and the first or second retraction device is retracted proximally at least about twice (2X) the length of the stent to deploy the stent.

24. The method of claim 23, wherein the tubular liner is retracted at least twice the axial length of the stent.

25. The method of claim 22, wherein the first and/or second retraction device comprises an outer shaft or a collar connected to one or more pull wires.

26. The method of claim 20 or 21, wherein the stent is coated with a drug and/or coating.