DETAILED DESCRIPTION OF THE INVENTION

[0024] In FIGS. 1-4, a stent 100 that is an expandable prosthesis for a body passageway is illustrated. It should be understood that the terms “stent” and “prosthesis” are interchangeably used to some extent in describing the present invention, insofar as the method, apparatus, and structures of the present invention may be utilized not only in connection with an expandable intraluminal vascular graft for expanding partially occluded segments of a blood vessel, duct or body passageways, such as within an organ, but may so be utilized for many other purposes as an expandable prosthesis for many other types of body passageways. For example, expandable prostheses may also be used for such purposes as: (1) supportive graft placement within blocked arteries opened by transluminal recanalization, but which are likely to collapse in the absence of internal support; (2) similar use following catheter passage through mediastinal and other veins occluded by inoperable cancers; (3) reinforcement of catheter created intrahepatic communications between portal and hepatic veins in patients suffering from portal hypertension; (4) supportive graft placement of narrowing of the esophagus, the intestine, the ureters, the uretha, etc.; (5) intraluminally bypassing a defect such as an aneurysm or blockage within a vessel or organ; and (6) supportive graft reinforcement of reopened and previously obstructed bile ducts. Accordingly, use of the term “prosthesis” encompasses the foregoing usages within various types of body passageways, and the use of the term “intraluminal graft” encompasses use for expanding the lumen of a body passageway. Further in this regard, the term “body passageway” encompasses any lumen or duct within the human body, such as those previously described, as well as any vein, artery, or blood vessel within the human vascular system.

[0025] The stent 100 is an expandable lattice structure made of any suitable material which is compatible with the human body and the bodily fluids (not shown) with which the stent 100 may come into contact. The lattice structure is an arrangement of interconnecting elements made of a material which has the requisite strength and elasticity characteristics to permit the tubular shaped stent 100 to be moved or expanded from a closed (crimped) position or configuration shown in FIGS. 1 and 2 to an expanded or open position or configuration shown in FIGS. 2 and 3. Some examples of materials that are used for the fabrication of the stent 100 include silver, tantalum, stainless steel, gold, titanium or any type of plastic material having the requisite characteristics previously described. Based on the interlocking design of the stent 100 (greater detail provided later in this disclosure), when the stent 100 is deployed or expanded to its open position, even materials that tend to recoil to a smaller diameter or exhibit crushing or deformation-like properties are used for the stent 100 in accordance with the present invention. These are materials that are not used in traditional (prior art) stent designs. Some examples of these non-traditional stent materials that are used for the stent 100 in accordance with the present invention include deformable plastics, plastics that exhibit crushing or recoil upon deployment of the stent or polymers such as biodegradable polymers. Thus, the stent 100 in accordance with the present invention is also made of these type of plastics or polymers to include biodegradable polymers. Additionally, the biodegradable polymers used as material for the stent 100 can be drug eluting polymers capable of eluting a therapeutic and/or pharmaceutical agent according to any desired release profile.

[0026] In one embodiment, the stent is fabricated from 316L stainless steel alloy. In a preferred embodiment, the stent 100 comprises a superelastic alloy such as nickel titanium (NiTi, e.g., Nitinol). More preferably, the stent 100 is formed from an alloy comprising from about 50.5 to 60.0% Ni by atomic weight and the remainder Ti. Even more preferably, the stent 100 is formed from an alloy comprising about 55% Ni and about 45% Ti. The stent 100 is preferably designed such that it is superelastic at body temperature, and preferably has an Af temperature in the range from about 24° C. to about 37° C. The superelastic design of the stent 100 makes it crush recoverable and thus suitable as a stent or frame for any number of vascular devices for different applications.

[0027] The stent 100 comprises a tubular configuration formed by a lattice of interconnecting elements defining a substantially cylindrical configuration and having front and back open ends 102, 104 and defining a longitudinal axis extending therebetween. In its closed configuration, the stent 100 has a first diameter for insertion into a patient and navigation through the vessels and, in its open configuration, a second diameter, as shown in FIG. 3, for deployment into the target area of a vessel with the second diameter being greater than the first diameter. The stent 100 comprises a plurality of adjacent hoops 106a-106h extending between the front and back ends 102, 104. The stent 100 comprises any combination or number of hoops 106. The hoops 106a-106h include a plurality of longitudinally arranged struts 108 and a plurality of loops 110 connecting adjacent struts 108. Adjacent struts 108 or loops 110 are connected at opposite ends by flexible links 114 which can be any pattern such as sinusoidal shape, straight (linear) shape or a substantially S-shaped or Z-shaped pattern. The plurality of loops 110 have a substantially curved configuration.

[0028] The flexible links 114 serve as bridges, which connect adjacent hoops 106a-106h at the struts 108 or loops 110. Each flexible link comprises two ends wherein one end of each link 114 is attached to one strut 108 or one loop 110 on one hoop 106a and the other end of the link 114 is attached to one strut 108 or one loop 110 on an adjacent hoop 106b, etc.

[0029] The above-described geometry better distributes strain throughout the stent 100, prevents metal to metal contact where the stent 100 is bent, and minimizes the opening between the features of the stent 100; namely, struts 108, loops 110 and flexible links 114. The number of and nature of the design of the struts, loops and flexible links are important design factors when determining the working properties and fatigue life properties of the stent 100. It was previously thought that in order to improve the rigidity of the stent, struts should be large, and thus there should be fewer struts 108 per hoop 106a-106h. However, it is now known that stents 100 having smaller struts 108 and more struts 108 per hoop 106a-106h improve the construction of the stent 100 and provide greater rigidity. Preferably, each hoop 106a-106h has between twenty-four (24) to thirty-six (36) or more struts 108. It has been determined that a stent having a ratio of number of struts per hoop to strut length which is greater than four hundred has increased rigidity over prior art stents which typically have a ratio of under two hundred. The length of a strut is measured in its compressed state (closed configuration) parallel to the longitudinal axis of the stent 100 as illustrated in FIG. 1.

[0030] FIG. 3 illustrates the stent 100 in its open or expanded state. As may be seen from a comparison between the stent 100 configuration illustrated in FIG. 1 and the stent 100 configuration illustrated in FIG. 3, the geometry of the stent 100 changes quite significantly as it is deployed from its unexpanded state (closed or crimped configuration/position) to its expanded state (open or expanded configuration/position). As the stent 100 undergoes diametric change, the strut angle and strain levels in the loops 110 and flexible links 114 are affected. Preferably, all of the stent features will strain in a predictable manner so that the stent 100 is reliable and uniform in strength. In addition, it is preferable to minimize the maximum strain experienced by the struts 108, loops 110 and flexible links 114 since Nitinol properties are more generally limited by strain rather than by stress. The embodiment illustrated in FIGS. 1-4 has a design to help minimize forces such as strain.

[0031] As best illustrated in FIG. 2, the stent 100, in the closed-configuration (crimped configuration wherein the stent 100 is crimped on the stent delivery device such as a catheter), has a plurality of pre-configured cells 120a. Each pre-configured cell 120a is defined by the struts 108 and loops 110 connected to each other respectively thereby defining an open area in the stent lattice 100. This open area is a space identified as the pre-configured cell 120a.

[0032] Each hoop 106a-106h has one or more (or a plurality of) pre-configured cells 120a. In one embodiment according to the present invention, the pre-configured cell 120a is a diamond-shaped area or space. However, it is contemplated in accordance with the present invention that the pre-configured cell 120a take the form of any desired alternative shape.

[0033] Additionally, the stent lattice 100 also includes at least one (or a plurality of) partial cells 120b. Each partial cell 120b is defined by struts 108 and one loop 110 of the respective hoops 106a-106h. In one embodiment according to the present invention, the partial cell 120b defines a semi-enclosed area or space having an open end in direct communication with a loop 110 from an adjacent hoop 106a-106h. In this embodiment according to the present invention, the flexible link 114 connects adjacent hoops, for example hoop 106b to hoop 106c, by having one end of flexible link 114 connected to an inner surface of loop 110 of a partial cell 120b of the hoop 106b and the opposite end of the flexible link 114 connected to loop 110 of the adjacent hoop 106c. Thus, in this embodiment, the flexible link 114 extends from one end of the partial cell 120b, for instance, of hoop 106b and extends through the semi-enclosed area of the partial cell 120b and is connected to loop 110 of the adjacent hoop 106c. In this embodiment according to the present invention, the flexible links 114 are connected between adjacent hoops 106a-106h by extension through the partial cells 120b. Additionally, the partial cell 120b is not only a semi-enclosed area or space defined by struts 108 and one loop 110 of each hoop 106, but the partial cell 120b may take the form of any desired semi-enclosed shape.

[0034] In this embodiment according to the present invention, each partial cell 120b of the stent lattice 100 exists while the stent 100 is in its crimped state or closed configuration, i.e. crimped to the delivery device such as a catheter.

[0035] Moreover, in one embodiment according to the present invention, each pre-configured cell 120a has one loop 110 terminating in a male end 130 and the other loop defining the pre-configured cell 120a terminating in a female and 140. Thus, in this embodiment in accordance with the present invention, the male end 130 of one loop 110 and the female end 140 of the other loop 110 of the pre-configured cell 120a are positioned opposite each other thereby defining opposite ends of the pre-configured cell 120a, for example opposite ends of the diamond-shaped area in this embodiment.

[0036] In one embodiment in accordance with the present invention, the male end 130 has a substantially convex configuration and the female end 140 has a substantially concave configuration. In general, the female end 140 is designed such that it is shaped to receive and mateably connect with the male end 130. Accordingly, in this embodiment, the substantially concave surface of the female end 140 mateably connects with the substantially convex shape of the male end 130 when the stent lattice 100 is moved to the open configuration or state (deployed or expanded state) such as shown in FIGS. 3 and 4.

[0037] As best illustrated in FIG. 4, when the stent lattice 100 is deployed or expanded to its open position or configuration, the male end 130 of the loop 110 of one hoop 106, for example 106b, mateably connects with the female end 140 of an opposite loop 110 of an adjacent hoop, for example 106c, thereby forming a locked joint 150. The male end 130 and the female end 140 may take the form of any desired shape or configuration that permits the male end 130 to mateably connect with the female end 140 in order to form the locked joint 150. For example, the male end 130 and the female end 140 may be shaped respectively in order to form portions of a dove-tail such that the locked joint 150 has or forms a dove-tail configuration. Other shapes for the male end 130 and female end 140 forming the locked joint 150 are also contemplated herein.

[0038] Accordingly, when the stent lattice 100 is deployed or expanded to the open position (open configuration of the stent 100), adjacent hoops 106a-106h interlock with each other at the newly formed joints 150 mateably connecting adjacent hoops 106a-106h. For example, when the stent lattice 100 is moved to its open configuration, the hoop 106b mateably connects or interlocks with the adjacent hoop 106c and the hoop 106c interlocks with the adjacent hoop 106d, etc. Thus, the points of interlocking or mateable connection are located at the newly formed locked joint 150 between each pair of adjacent hoops 106 as shown. Thus, each locked joint 150 is formed by at least one loop 110 of one hoop 106 (for example 106b, wherein the male end 130 of this loop 110 mateably connects with the female end 140 of another loop 110), i.e. an adjacent loop on an adjacent hoop 106, for example loop 110 on the hoop 106c which is directly opposed from the male end 130 of loop 110 of the hoop 106b. Therefore, the adjacent hoops 106a-106h, are mateably connected to or locked to each other respectively at each locked joint 150 formed in a manner such as described above.

[0039] Upon the mateable connection or linking of the male end 130 to the female end 140 (on the loops 110 of adjacent hoops 106), a formed cell 120c is created or formed between adjacent locked joints 150 form by a pair of interlocking, adjacent hoops 106, for example, 106a and 106b, etc. Each formed cell 120c is a fully enclosed area or space defined by the struts 108 loops 110 and locked joints 150 formed by the adjacent hoops 106, i.e. linking of hoop 106a to hoop 106b, linking of hoop 106b to adjacent hoop 106c, etc. Accordingly, the partial cell 120b (FIG. 2) of the stent lattice 100 in its crimped configuration, becomes the formed cell 120c when linked or coupled by the locked joint 150 between adjacent hoops 106 as shown in FIG. 4.

[0040] In accordance with the present invention, the stent 100 has flexible links 110 that may be on one or more of the following components of the stent lattice: the hoops 106a-106h, the loops 110, and/or the struts 108. Moreover, the components of the stent lattice, i.e. hoops, loops, struts and flexible links, have drug coatings or drug and polymer coating combinations that are used to deliver drugs, i.e. therapeutic and/or pharmaceutical agents including: antiproliferative/antimitotic agents including natural products such as vinca alkaloids (i.e. vinblastine, vincristine, and vinorelbine), paclitaxel, epidipodophyllotoxins (i.e. etoposide, teniposide), antibiotics (dactinomycin (actinomycin D) daunorubicin, doxorubicin and idarubicin), anthracyclines, mitoxantrone, bleomycins, plicamycin (mithramycin) and mitomycin, enzymes (L-asparaginase which systemically metabolizes L-asparagine and deprives cells which do not have the capacity to synthesize their own asparagine); antiplatelet agents such as G(GP)IIbIIIa inhibitors and vitronectin receptor antagonists; antiproliferative/antimitotic alkylating agents such as nitrogen mustards (mechlorethamine, cyclophosphamide and analogs, melphalan, chlorambucil), ethylenimines and methylmelamines (hexamethylmelamine and thiotepa), alkyl sulfonates-busulfan, nirtosoureas (carmustine (BCNU) and analogs, streptozocin), trazenes-dacarbazinine (DTIC); antiproliferative/antimitotic antimetabolites such as folic acid analogs (methotrexate), pyrimidine analogs (fluorouracil, floxuridine, and cytarabine), purine analogs and related inhibitors (mercaptopurine, thioguanine, pentostatin and 2-chlorodeoxyadenosine {cladribine}); platinum coordination complexes (cisplatin, carboplatin), procarbazine, hydroxyurea, mitotane, aminoglutethimide; hormones (i.e. estrogen); anticoagulants (heparin, synthetic heparin salts and other inhibitors of thrombin); fibrinolytic agents (such as tissue plasminogen activator, streptokinase and urokinase), aspirin, dipyridamole, ticlopidine, clopidogrel, abciximab; antimigratory; antisecretory (breveldin); antiinflammatory: such as adrenocortical steroids (cortisol, cortisone, fludrocortisone, prednisone, prednisolone, 6α-methylprednisolone, triamcinolone, betamethasone, and dexamethasone), non-steroidal agents (salicylic acid derivatives i.e. aspirin; para-aminophenol derivatives i.e. acetominophen; indole and indene acetic acids (indomethacin, sulindac, and etodalac), heteroaryl acetic acids (tolmetin, diclofenac, and ketorolac), arylpropionic acids (ibuprofen and derivatives), anthranilic acids (mefenamic acid, and meclofenamic acid), enolic acids (piroxicam, tenoxicam, phenylbutazone, and oxyphenthatrazone), nabumetone, gold compounds (auranofin, aurothioglucose, gold sodium thiomalate); immunosuppressives: (cyclosporine, tacrolimus (FK-506), sirolimus (rapamycin), azathioprine, mycophenolate mofetil); angiogenic agents: vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) platelet derived growth factor (PDGF), erythropoetin,; angiotensin receptor blocker; nitric oxide donors; anti-sense oligionucleotides and combinations thereof, cell cycle inhibitors, mTOR inhibitors, and growth factor signal transduction kinase inhibitors. It is important to note that one or more of the lattice components (e.g. hoops, loops, struts and flexible links) are coated with one or more of the drug coatings or drug and polymer coating combinations. Additionally, as mentioned above, the stent 100 is alternatively made of a polymer material itself such as a biodegradable material capable of containing and eluting one or more drugs, in any combination, in accordance with a specific or desired drug release profile.

[0041] The method of utilizing the stent 100 according to the present invention includes first identifying a location, for example, a site within the vessel in a patient's body for deployment of the stent 100. Upon identifying the desired deployment location, for example a stenotic lesion or vulnerable plaque site, a delivery device, such as a catheter carrying the stent 100 crimped to a distal end of the catheter such that the stent 100 is in its closed configuration, is inserted within the vessel in the patient's body. The catheter is used to traverse the vessel until reaching the desired location (site) wherein the distal end of the catheter is positioned at the desired location (site), for instance the lesion, within the vessel. At this point, the stent 100 is deployed to its open configuration by expanding the stent 100 such as by inflation if the stent 100 is a balloon expandable stent or by uncovering or release of the stent 100 if the stent 100 is a self-expanding (crush recoverable) type stent. If a cover is utilized to further protect and secure the stent 100 to the catheter distal end when the stent 100 is a self-expanding stent, the cover is removed from the distal end of the catheter prior to expansion of the stent 100, for instance, through use of an expandable member such as an inflatable balloon.

[0042] Upon expanding the stent 100 to its open configuration, the expandable member (balloon) is then collapsed, for instance through deflation of the expandable member, whereby the catheter is removed from the deployment site of the vessel and patient's body altogether.

[0043] As mentioned previously, the unique design of the stent 100, i.e. the interlocking of adjacent hoops 106 upon deployment of the stent 100, allows for a wide array of materials, not previously used with prior art stents, to be used with the stent 100 in accordance with the present invention. These include materials normally prone to crushing, deformation or recoil upon deployment of the stent. These materials include plastics and polymers to include biodegradable polymers such as drug eluting polymers.

[0044] While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.