WO2007138608A1

WO2007138608A1 - A temporary, retrievable stent device system for use in a body conduit

Info

Publication number: WO2007138608A1
Application number: PCT/IN2006/000186
Authority: WO
Inventors: Baskaran Chandrasekar
Original assignee: Baskaran Chandrasekar
Priority date: 2006-06-01
Filing date: 2006-06-01
Publication date: 2007-12-06

Abstract

Described is a temporary and retrievable stent device system that is designed for use in a body conduit such as a blood vessel. The expansion and collapsing of the temporary stent device is controlled by a regulator (1) that is external to the body and is attached to the stent (12) device by a catheter (4). The regulator functions on the mechanism of rack-and-pinion which is mechanically operated, or, may also be operated electrically by a rechargeable/replaceable battery system. The invention can be used to provide precise and calibrated support to maintain optimal patency of a body conduit. The invention can be used for the local intramural delivery of drugs or agents for the prevention of restenosis, treatment of vulnerable plaque, can be used to seal dissections and aneurysms, and to prevent elastic recoil of vessel wall. The invention can be used for dilatation of stenoses in blood vessels without pre-dilatation with a balloon catheter. In another embodiment, the invention may also be used for the dilatation of strictures or narrowings of other body conduits.

Description

A TEMPORARY, RETRIEVABLE STENT DEVICE SYSTEM FOR USE IN A BODY CONDUIT

FIELD OF THE INVENTION The present invention relates generally to a medical device for use in a body conduit, and more specifically to a temporary and retrievable stent device system designed to provide precise and calibrated temporary support for maintaining patency of a body conduit. In addition, the invention is designed for local intramural delivery of drugs or agents in a body conduit, for example a blood vessel, for a purpose such as, but not limited to, restenosis prevention.

BACKGROUND OF THE INVENTION

For patients undergoing coronary angioplasty, acute closure of the vessel and restenosis (that is, the recurrence of blockage) are major factors limiting the outcome of the procedure. Stents that are permanently implanted at the site of angioplasty have been shown to decrease the incidence of acute closure and restenosis (Ref: Fischman DL, et al. for the Stent Restenosis Study Investigators. A randomized comparision of coronary-stent placement and balloon angioplasty in the treatment of coronary artery disease. N Engl J Med 1994;331:496; Serruys PW, et al. for the Benestent Study Group. A comparison of balloon-expandable-stent implantation with balloon angioplasty in patients with coronary artery disease. N Engl J Med 1994;331:489).

Despite the use of stents, restenosis still occurs in a significant proportion of patients. To overcome the critical problem of restenosis, drug-eluting stents have recently been made available. Drug-eluting stents are stents that are permanently deployed at the site of angioplasty and act as carriers of drugs that are released locally for the prevention of restenosis (Ref: Moses JW, et al. for the SIRIUS Investigators. Sirolimus-eluting stents versus standard stents in patients with stenosis in a native coronary artery. N Engl J Med 2003;349:1315-23; Stone GW, et al. One-year clinical results with the slow-release, polymer-based, paclitaxel-eluting TAXUS stent: the TAXUS-IV trial. Circulation 2004; 109: 1942-7). However, since currently available drug-eluting stents are permanently implanted in the vessel wall, they induce tissue reaction and also delay healing of the angioplasty site (Ref: Farb A, et al. Pathological analysis of local delivery of paclitaxel via a polymer-coated stent. Circulation 2001;104:473; Suzuki T, et al. Stent-based delivery of sirolimus reduces neointimal formation in a porcine coronary model. Circulation 2001:104-1188). The tissue reaction and delayed healing are well known in the practice of medicine to predispose to potential long-term life threatening complications such as death or heart attack (myocardial infarction) (Ref: McFadden EP, et al. Late thrombosis in drug-eluting coronary stents after discontinuation of antiplatelet therapy. Lancet 2004;364:1519-21; Virmani R, et al. Localized hypersensitivity and late coronary thrombosis secondary to a sirolimus-eluting stent: should we be cautious? Circulation 2004; 109:701-5).

Moreover, permanently implanted stents may impair the vessel geometry and prevent any favorable remodeling of the vessel wall tibat can occur after angioplasty. They may also entrap and obstruct side branches leading to ischemia or even myocardial infarction as a result in some patients.

A temporary, retrievable stent, as compared to currently available permanently implanted stents, will not lead to tissue reaction and will also not delay healing of the angioplasty site. A temporary, retrievable stent will not impair vessel geometry or prevent favorable remodeling of the vessel wall, and will also not lead to entrapment and obstruction of side branches. Such a device could potentially avoid the major complications seen with currently available permanently implanted stents.

Some forms of temporary stents for providing support to the wall of coronary arteries have been described in U. S. Patent Nos. 6514191 and 6074338 to Popowski et al, U. S. Patent Nos. 6413273 and _,6348067 to Baum et al., U. S. Patent No. 6325813 to Hektmer, U. S. Patent Nos. 6090115 and 5964771 to Beyar et al., U. S.

Patent Nos. 5941895, 5733302 and 5643309 to Myler et al., U. S. Patent Nos. 5795318 and 5716410 to Wang, U. S. Patent No. 5730698 to Fischell et al. U. S. Patent No. 5449372 to Schmaltz et al., U. S. Patent No. 5222971 to Willard et al., U. S. Patent No. 5190058 to Jones et al., U. S. Patent No. 5034001 to Garrison et al., U. S. Patent No. 5037427 to Harada et aL, U. S. Patent No. 4998539 to Delsanti, and U. S. Patent No. 5002560 to Machold et al. None of the temporary stents described in the above patents envisage a uniform, controlled or calibrated and predictable expansion of the stent in relation to the diameter of the blood vessel, with the possible exception of systems using an expandable balloon. However, expandable balloon systems for stent expansion have important limitations such as significant recoil of the stent upon removal of the balloon, shortening of the stent length upon balloon expansion, injury to the vessel wall by the shoulder of the balloon during expansion, risk of migration or slippage of the mounted stent from the balloon during deployment with disastrous clinical consequences, and the need for a separate mechanism for stent removal. It is very important to be able to accurately control the size of expansion of the stent, as even a fraction of a millimeter of over sizing of the stent in relation to the blood vessel diameter can lead to severe injury to the vessel wall with resultant complications.

Furthermore, none of the temporary stents of the above mentioned patents are capable of local intramural drug delivery in patients undergoing angioplasty. Also, none of the temporary stents described in the above patents are known to be capable of use in restenosis prevention.

Therefore, there is an urgent need for a safe, temporary retrievable stent device system that can function without the limitations of currently known stent device systems. The present invention proposes to address such a need. The stent device in the present invention has a unique configuration, the expansion and collapsing of which is accurately controlled by means of a regulator located external to the body. Furthermore, the invention will be able to deliver drugs or agents locally intramurally ^"at the desired site and will be capable of use in restenosis prevention. The present invention is novel and is non-obvious over the art of record. SUMMARY OF THE INVENTION

The present invention is a temporary and retrievable stent device system designed for use in a body conduit, such as a blood vessel. The invention is intended, among other uses, to provide temporary support to the wall of a blood vessel, as for example after angioplasty, and to maintain optimal patency of a blood vessel. The invention has been specifically designed to achieve uniform, calibrated and predictable expansion of the supporting stent device, thereby ensuring avoidance of vessel wall injury.

The invention has a regulator at its proximal end that is external to the body.

The regulator is attached to a catheter which is introduced into a body conduit and has a stent device attached to its distal end. The stent device is made up of struts that have a unique configuration. Each strut has a central horizontal arm that is attached by means of hinges to short arms on either side. The short arms in turn are fixed in a radial fashion to a hub on each of the proximal and distal ends of the stent device. Expansion and collapsing of the stent device is easily achieved by the linear movement of a control cable one end of which is attached to the distal hub of the stent device and the other end of which is attached to the regulator. The regulator works on a rack-and-pinion mechanism.

The present invention can also be used to deliver drugs or agents locally intramurally for the prevention of restenosis in patients undergoing angioplasty, can be used to seal dissections and aneurysms, and to prevent elastic recoil of vessel wall.

The term "stent device" in the invention may be used interchangeably with the term "prosthesis" in the treatment of conduits in the body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG 1 : Shows a schematic representation of the stent device system according to the present invention in the unexpended or collapsed state. FIG 2: Shows a longitudinal sectional view of the stent device system of the present invention.

FIG 3 : Shows a schematic representation of the stent device system of the present invention in the expanded state inside a blood vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG 1 illustrates the invention schematically. The invention consists of a regulator 1 that is external to the body. The regulator 1 has a knob 2 that is capable of rotation in a clockwise and anti-clockwise direction, which would lead to expansion and collapse respectively of the stent device. Markings 3 on the regulator permit the operator to gauge the degree of rotation of the knob 2, and thus be able to accurately control the degree of expansion of the stent device. The knob 2 has a safety lock mechanism (not shown) to prevent accidental or unintentional rotation of the knob. After deployment of the stent device, the regulator 1 is firmly secured to the patient's body by means of fasteners, clamps, sutures, straps, or by other means of securing the device system so as to prevent displacement of the stent device after deployment in a blood vessel. The regulator 1 is attached to a catheter 4 which has a lumen running along its entire length and houses the control cable/wire 10. The distal part of the catheter 4 has a second lumen running for a short distance only. The proximal opening 5a of the second lumen is located on the catheter 4 at a distance in the range of 15 cm to 60 cm from the distal tip of the catheter 4. The distal opening 5b of the second lumen is located on the catheter 4 at a distance in the range of 2 cm to 5 cm from the distal tip of the catheter 4. The second lumen will allow passage of a commercially available coronary guide wire 6 to facilitate rapid exchange of the catheter.

A hub 7 is fixed to the distal end of the catheter 4. The hub 7 may be discshaped or spherical and is preferably less than or equal to 3 mm in width. The hub 7 has a central opening 9 that may be guarded (optionally) by a membranous hemostatic valve to prevent retrograde flow of blood into the lumen of the catheter 4 from the blood vessel lumen when positioned inside a blood vessel. A control cable/wire 10 passes through the opening 9. The distal end of the control cable/wire 10 is attached to the center of another hub 8. The hub 8 may be disc-shaped or spherical and is preferably less than or equal to 3 mm in width. The farther side of the hub 8 tapers to a cone (with a rounded tip) and has a soft J-tipped flexible or highly flexible short guide wire 11 attached to it, to prevent injury to the wall of the conduit by the hub 8 when the device system is advanced into the conduit. The fixed guide wire 11 is less than 10 cm in length and is sufficiently radio-opaque to be visible under X-ray flouroscopy.

The stent device has several struts (ranging between 4 and 40 struts). Each strut has three segments: a longer horizontal segment 12a and, two shorter segments 12b one on each side of the horizontal segment 12a. In each strut, the horizontal segment 12a is attached on its either side to the two shorter segments 12b by hinge joints 13. For each strut, one shorter segment 12b is fixed in a radial fashion to the hub 7, and the other shorter segment 12b is fixed in a radial fashion to the hub 8. One or more of the horizontal segments 12a will have radio-opaque markers 14 at each end for accurate placement at the desired site in a conduit. The struts, hub 7, and hub 8 may be made of surgical-grade stainless steel, titanium, nitinol, cobalt-chromium or other biocompatible metal alloys, bio-compatible polymers, anodized aluminum, tantalum, a composite, or ceramic. The struts, hub 7, and hub 8 may or may not be coated with anti-thrombotic agents, or anti-coagulants, or platelet-inhibitors.

FIG 2 depicts the longitudinal sectional view of the invention. The regulator 1 houses the rack 17 that is capable of linear movement and a pinion 18. Rotation of the knob 2 rotates the pinion 18. Pinion 18 rotation may be achieved mechanically directly by turning of the knob 2. In another embodiment of the invention, rotation of the pinion 18 is achieved by an electric current from a rechargeable/replaceable battery system located within the casing of the regulator 1, wherein the flow of current from the battery system to the pinion 18 is controlled by rotation of the knob 2. The proximal end of the control cable/wire 10 is attached to the rack 17. The catheter 4 has a lumen 15 running along its entire length. -The lumen 15 houses the control cable/wire 10. The distal part of the catheter 4 has a second lumen 16 that carries a commercially available coronary guide wire 6 to facilitate rapid exchange of the catheter. The length of the catheter 4 from its distal tip to the point of attachment 20 between the catheter 4 and the regulator 1 will range between 90 cm to 165 cm. In another embodiment of the invention, the point of attachment 20 between the catheter 4 and the regulator 1, and the point of attachment 19 between the control cable/wire 10 and the rack 17 can be detached and reassembled according to clinical situation as determined by the operator to facilitate easy maneuvering of the catheter into the body conduit.

FIG 3 schematically illustrates the device system deployed inside a blood vessel 21. Clockwise rotation of the knob 2 causes movement of the distal hub 8 towards the proximal hub 7 leading to expansion of the stent device. At optimal expansion of the stent device, the horizontal segments 12a are in direct apposition with the vessel wall 22. The distal tip of the coronary guide wire 6 is withdrawn proximally before expansion of the stent device to prevent entrapment of the coronary guide wire 6 within the expanded struts. Similarly, anti-clockwise rotation of the knob

2 will lead to movement of the distal hub 8 away from the proximal hub 7 thus collapsing the stent device.

In Figures I₅ 2 and 3, each individual horizontal segment 12a is shown as being of straight-line in shape. In another embodiment, the horizontal segments 12a may instead be sinusoidal or wave-like or zigzag in shape or their variations thereof.

In another embodiment of the invention, the distal end of the control cable/wire 10 may be attached to the distal hub 8 by means of an intervening high-tensile spring or coil. The high-tensile spring or coil will facilitate the expanded device to return to its collapsed form at the time of device retrieval.

The catheter 4 should have sufficient torque, push-ability, and flexibility to be easily maneuvered- to reach the site of treatment in a body conduit, for example, a coronary artery. Some degree of radio-opacity of the catheter 4 to be visible under X- ray flouroscopy is also desirable. Therefore, to confer such properties, the catheter may be made with, either alone or in various combinations of, materials such as metals, metal alloys (nitinol, tantalum, cobalt-chromium, etc), plastics, polymers, composite, etc.

The control cable/wire 10 should be of sufficient stiffness and have sufficient tensile strength to facilitate easy collapsing and expansion of the stent device, and at the same time should be flexible enough so that the stent device can be positioned in any desired area of a body conduit, for example, coronary arteries. Therefore, to confer such properties, the control cable/wire 10 may be made with, either alone or in various combinations of, materials such as metals, metal alloys (nitinol, tantalum, cobalt-chromium, etc), plastics, polymers, composite, anodized aluminum, etc. The control cable/wire 10 may or may not be coated with anti-thrombotic agents, or anticoagulants, or platelet-inhibitors.

The thickness of the struts of the stent device will be determined by the amount of radial support required to maintain the optimal patency of a body conduit, for example, a blood vessel, and by the need to maintain the lowest profile of the collapsed stent device and to maximize flexibility of the stent device to facilitate easy positioning in any desired area of a body conduit, for example, a coronary artery. It is preferable that the strut thickness is in the range of 0.001 inches to 0.05 inches. However, the above thickness range mentioned indicate the preferred range only and should not be considered limiting with respect to the scope of the invention. The thickness ranges may vary according to the size of the stent device.

As an example to help better understand the invention, the procedure of deployment of the device and its retrieval in a body conduit, such as a coronary artery, is briefly described below. The example is for illustrative purposes only and should not be construed as in anyway to limit the scope of the invention. The device in its collapsed form is introduced over a commercially available coronary guide wire 6 into a standard coronary guiding catheter via the straight arm of a hemostatic adapter such as a Tuohy-Borst. The side-arm of the hemostatic adapter is attached to a commercially available manifold. The collapsed stent device is then maneuvered into the coronary artery to the desired site in the blood vessel. The collapsed stent device is accurately positioned at the desired site with the help of the radio-opaque markers 14 located on the horizontal segments 12a. The safety lock of the knob 2 of the regulator 1 is released and the knob 2 is rotated clockwise. The clockwise rotation of the knob 2 would activate the rack-and-pinion resulting in pulling of the control cable/wire 10. Pulling of the control cable/wire 10 will cause the distal hub 8 to move towards the proximal hub 7 leading to expansion of the stent device and apposition of the horizontal segments 12a with the vessel wall 22. The degree of expansion of the stent device can be accurately controlled by the regulator 1. The markings 3 on the regulator 1 can be easily calibrated such that clockwise turning of the knob 2 would effect accurate and predictable expansion of the stent device. For example, clockwise turning of the knob 2 by one division will cause stent device to expand by 0,25 mm. After optimal stent device expansion (determined with relation to the size of the reference vessel segment), the knob 2 is locked in position to prevent accidental or unintentional rotation of the knob. For device retrieval, the knob 2 is rotated anticlockwise after release of the safety lock, leading to movement of the distal hub 8 away from the proximal hub 7 thus collapsing the stent device. The collapsed stent device is then removed from the body as like any standard angioplasty catheter.

The horizontal segments 12a will carry the drug or agent to be released intramurally, preferably in the form of drug-loaded biodegradable and biocompatible microparticles or nanoparticles. Release of drug-loaded biodegradable and biocompatible microparticles or nanoparticles from the horizontal segments 12a into the vessel wall will occur when the stent device is optimally expanded with the horizontal segments 12a in apposition with the vessel wall.

The drug-loaded biodegradable and biocompatible microparticles or nanoparticles may be attached to (and released from) the surface of the horizontal segments 12a by means of biocompatible polymers (which may or may not be biodegradable) including phosphorylcholine, or, by viscous or gel-based mechanisms (example hydrogel), or, by glue-based mechanisms (example fibrin, collagen, etc), or, by other methods of binding (by use of any one or more of physical, chemical, or electrical methods). The drug-loaded biodegradable and biocompatible microparticles or nanoparticles may also be attached directly onto (and released from) the surface of the horizontal segments 12a (by use of any one or more of physical, chemical, or electrical methods). The drug-loaded biodegradable microparticles or nanoparticles will be released from the horizontal segments 12a into the wall of a conduit (intramurally) such as a blood vessel within a time duration of less than 24 hours (preferably less than 1 hour) after optimal expansion of the stent device at the desired site. Release of the drug-loaded biodegradable microparticles or nanoparticles from the horizontal segments 12a into the wall of the blood vessel may also be achieved by application of a magnetic field, an electrical field, or use of ultrasound.

The biodegradable and biocompatible microparticles or nanoparticles may carry a single drug or agent, or, may include a cocktail of microparticles or a cocktail of nanoparticles carrying multiple drugs or agents. The biodegradable and biocompatible microparticles or nanoparticles can be programmed to release the drug* or agent at the desired site over a period of several days or weeks. In the event of multiple drugs or agents, the different drugs or agents may be released over the same time period or over different time duration.

The biodegradable and biocompatible microparticles or nanoparticles may be loaded with either one or a combination of agents such as a drug, hormone, chemical, natural-derived or synthesized compound, pharmaceutical agent, genetic material, or peptide. One such use may be for the prevention of restenosis. Such agents for the prevention of restenosis may include but are not limited to antiproliferative agents, immunosuppressive agents, agents that enhance endothelial proliferation and function, hormones such as 17beta-estradiol, anti-inflammatory agents such as dexamethasone, inhibitors of extracellular matrix synthesis, inhibitors of oxidative stress (the redox process) after arterial injury, sulfated fucans (exemplified by fucoidan), heparin, etc. In another embodiment, the invention can be used for the prevention of restenosis without intramural drug delivery, by preventing elastic recoil of the blood vessel following angioplasty. Elastic recoil following angioplasty is a well-recognized risk factor for the development of restenosis (Ref : Dangas G, et al. Early changes in minimal lumen diameter after balloon angioplasty and directional coronary atherectomy. --J Invasive Cardiol 1998;10:372-5; Caixeta M, et al. Early luminal diameter reduction phenomenon after coronary angioplasty and its relation to the restenosis phenomenon. Arq Bras Cardiol 1997;69: 175-9). By virtue of its ability to provide precise, calibrated and predictable radial support to the vessel wall, the present invention can effectively neutralize the phenomenon of elastic recoil and thus prevent the development of restenosis without intramural drug delivery.

In another embodiment of the invention, in addition to the prevention of restenosis, the device system can be used for the dilatation of stenoses (or atherosclerotic narrowings) in a blood vessel without pre-dilatation with a balloon catheter.

In another embodiment, the invention can be used in the treatment of a patient with vulnerable atherosclerotic plaque. The biodegradable and biocompatible microparticles or nanoparticles may be loaded with either one or a combination of agents such as a drug, hormone, chemical, natural-derived or synthesized compound, pharmaceutical agent, genetic material, or peptide, that may have one or more functions as an anti-thrombotic, or, anti-inflammatory, or, that facilitates endothelial regeneration. Such agents may include but are not limited to anti-thrombotic agents, fibrinolytic agents, anti-platelet agents, anti-coagulants, antiproliferative agents, immunosuppressive agents, anti-inflammatory agents such as but not limited to dexamethasone, or agents that enhance endothelial proliferation and function, hormones such as 17beta-estradiol, agents to decrease plaque size, statins, HDL-

- cholesterol mimetic agents, inhibitors of extracellular matrix synthesis, inhibitors of oxidative stress (redox process), inhibitors of matrix-metalloproteinases, sulfated fucans (exemplified by fucoidan), etc. In another embodiment, the invention can be used for the local intramural delivery of drugs or agents in patients with severe ischemia (myocardial or peripheral) for the induction of neovascularization (arteriogenesis, angiogenesis, post-natal vasculogenesis). The drug or agent that is delivered locally, may act regionally and/or may be released in a gradual and sustained manner from the biodegradable and biocompatible microparticles or nanoparticles over a pre-determined period of time of several days or weeks into the lumen of the vessel to act downstream for the induction of neovascularization. For the purpose of induction of neovascularization, the biodegradable and biocompatible microparticles or nanoparticles may be loaded with either one or a combination of agents such as a drug, hormone, chemical, natural- derived or synthesized compound, pharmaceutical agent, genetic material, or peptide capable of induction of neovascularization. Examples include but are not limited to 17beta-estradiol, vascular endothelial growth factor, fibroblast growth factor, sulfated fucans (exemplified by fucoidan), heparin, low-molecular weight heparin, etc.

In another embodiment, the invention can be used for the local intramural delivery of drugs or agents in patients with acute coronary syndrome such as acute myocardial infarction, unstable angina, or non-ST elevation myocardial infarction. The drug (s) or agent (s) delivered locally, may act regionally for the prevention of restenosis and/or may be released in a gradual and sustained manner from the biodegradable and biocompatible microparticles or nanoparticles over a predetermined period of time of several days or weeks into the lumen of the vessel to act downstream to reduce the size of myocardial infarction and/or to induce favorable remodeling of the infarct segment. For such a purpose, the biodegradable and biocompatible microparticles or nanoparticles may be loaded with either one or a combination of agents such as a drug, hormone, chemical, natural-derived or synthesized compound, pharmaceutical agent, genetic material, or peptide capable of said- function (s), namely, prevention of restenosis and/or reduction in the. size of myocardial infarction and/or induction of favorable remodeling of the infarct segment. The drugs or agents to be released from the horizontal segments 12a as drug- loaded biodegradable and biocompatible rnicroparticles or nanoparticles are preferably in the form of biodegradable and biocompatible microspheres or nanospheres. The biodegradable and biocompatible material with which the drug or agent is loaded may be polymeric or non-polymeric. Examples of polymeric biodegradable and biocompatible microparticles or nanoparticles include but are not limited to preparations from, either alone or a combination of, poly(lactide-co-glycolide) (PLGA or PLAGA), poly(D, L-lactic acid) (PLA), poly(epsilon-caprolactone) (PCL), or any other biodegradable and biocompatible polymer capable of being loaded with the intended drug or agent. Examples of non-polymeric materials (also referred to as bioabsorbable or biocorrodible) include but are not limited to preparations from, either alone or a combination of, metals or metal alloys, for example iron, magnesium, etc. Besides microspheres or nanospheres, other physical forms as micro-pellets or nano- pellets, micro-filaments or nano-filaments, micro-tubules or nano-tubules, micro-foils or nano-foils, etc., may also be used as drug-loaded biodegradable and biocompatible microparticles or nanoparticles. In other embodiments, other forms of sustained drug release such as but not limited to drug-loaded liposomes, or predominantly water- based vesicles, or, derived from amphiphiles may also be used.

In another embodiment, the invention can be used in peripheral arteries such as the arteries supplying the limbs, renal arteries, subclavian arteries, or carotid arteries in the prevention of restenosis, treatment of vulnerable plaque, induction of neovascularization, dilatation of stenosis, or to maintain optimal patency of a blood vessel, to seal dissections, and to prevent elastic recoil in these arteries.

The invention in another embodiment can be used to treat stenosis in iatrogenic arterio-venous fistulae, such as, in patients undergoing hemodialysis.

Ih another embodiment, the invention- can be used in the treatment of dissections and aneurysms (both true and false aneurysms) in blood vessels. In such an embodiment, a bio-compatible membrane (such as but not limited to PTFE, Dacron, etc.) can be attached circumferentially to the horizontal segments 12a, linking the horizontal segments 12a (either completely encircling or partly encircling). When the stent device is expanded, the horizontal segments 12a along with the circumferentially attached membrane will seal off the dissection or aneurysm by excluding it from the lumen of the blood vessel, thus functioning like a temporary and retrievable tubular graft. The abluminal or outer surface of the bio-compatible membrane may also be coated with pro-coagulant compounds or materials to enhance sealing of the dissection or aneurysm.

In another embodiment, the invention may also be used for the dilatation of strictures or narrowings of other body conduits, such as but not limited to, the venous system, trachea, bronchus, alimentary tract, biliary tract, ureter, urethra, etc.

Besides the local intramural delivery or agents for the above mentioned uses, the invention in another embodiment can be used to deliver drugs or agents locally intramurally for purposes such as treatment of diseases of body conduits such as, cancer, benign tumors, ulcers, inflammation, scars, infection, to stop bleeding arising from body conduits (with or without use of pro-coagulants), variceal bleeding, etc.

Although the present embodiment describes the use of a rack-and-pinion mechanism for control of movement of the control cable/wire 10, in other embodiments other mechanisms such as linear induction motor, gears, pulleys, or other mechanical system, electrical system, magnetic system, electro-magnetic (solenoid) system, or compressed air or gas system may be used to control movement of the control cable/wire 10.

Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled ,„ in the art and it is intended to cover in the appended claims all such modifications and equivalents.

Claims

CLAIMS :

1. A temporary, retrievable stent device system for use in a body conduit, said stent device a strut assembly including a plurality of struts (12), each strut including a central horizontal arm (12a) and one short arm (12b) on either side of the horizontal arm (12a) attached by means of hinges; a first hub (7) to which the other ends of first set of short arms are attached in a radial fashion; a second hub (8) to which the other end of second set of short arms are attached in a radial fashion; a catheter (4) including a first lumen running from its proximal end to its distal end; the first hub (7) being fixed to the distal end of the catheter (4); a regulator (1) for regulating the expansion and collapse of the strut assembly which is attached to the proximal end of the catheter (4) and located external to the body; a control cable / wire (10) which is attached between the regulator (1) and the second hub (8) and is housed inside the catheter (4); the regulator (1) includes a knob (2) which is capable of rotation in a clockwise and anti-clockwise direction to expand and collapse, respectively, the strut assembly to provide precise and calibrated temporary support for maintaining patency of the body conduit.

2. The stent device system as claimed in claim 1, wherein the first hub (7) and the second hub (8) are preferably disc-shaped or spherical.

3. The stent device system as claimed in claim 1, wherein the first hub (7) and the second hub (8) are preferably less than or equal to 3mm in width.

4. The stent device system as claimed in claim 1, wherein the first hub (7) includes a central opening to allow the control cable / wire (10) to pass through.

5. The stent device system as claimed in claim 4, wherein the central opening of the first hub (7) may be guarded by a membranous hemostatic valve to prevent retrograde flow of blood into the lumen of the catheter (4) from the blood vessel.

6. The stent device system as claimed in claim I₃ wherein the catheter (4) comprises a second lumen located close to its distal end for a coronary guide wire (6) to facilitate rapid exchange of the catheter (4).

7. The stent device system as claimed in claim 6, wherein the proximal opening (5 a) of the second lumen is located on the catheter (4) at a distance in the range of 15 to 60cm from the distal tip of the catheter (4).

8. The stent device system as claimed in claim 6, wherein the distal opening (5b) of the second lumen is located on the catheter (4) at a distance in the range of 2 to 5 cm from the distal tip of the catheter (4).

9. The stent device system as claimed in claim 1, wherein the farther side of the second hub (8) tapers to a core with a rounded tip and has a flexible guide wired (11) attached to it to prevent injury to the wall of the conduit by the hub

(8) when the stent device system is advanced into the conduit.

10. The stent device system as claimed in claim 9, wherein the flexible guide wire (11) is less than 10cm in length and is sufficiently radio-opaque to be visible under x-ray fluoroscopy.

11. The stent device system as claimed in claim 1, wherein the strut assembly includes at least 4 to 40 struts.

12. The stent device system as claimed in claim 1, wherein one or more of the horizontal arm (12a) of the strut includes radio-opaque markers (14) at both the ends for accurate placement of the stent at the desired site in a conduit.

13. The stent device system as claimed in claim 1, wherein the struts, the first hub (7) and the second hub (8) are preferably made of surgical-grade stainless steel, titanium, nitinol, cobalt-chromium or other bio-compatible metal alloys, bio-compatible polymers, anodized aluminum, tantalum, a composite, or ceramic.

14. The stent device system as claimed in claim 1, wherein the struts, the first hub and the second hub may or may not be coated with anti-thrombotic agents, or anti-coagulants, or platelet-inhibitors.

15. The stent device system as claimed in claim 1, wherein the regulator (1) includes a rack (17) and a pinion (18) assembly to control the expansion and collapse of the strut assembly.

16. The stent device system as claimed in claim 1, wherein the pinion of the regulator can be controlled manually or electrically by rotating the knob of the regulator.

17. The stent device system as claimed in claim 1, wherein the horizontal arm of the strut can be straight-line or sinusoidal or wave-like or zigzag in shape, or their variations thereof.

18. The stent device system as claimed in claim 1, wherein the distal end of the control wire (10) is preferably attached to the second hub (8) by means of an intervening high-tensile spring or coil.

19. The stent device system as claimed in claim 1, wherein the catheter is made with, either alone or in various combinations of, materials such as metals, metal alloys (nitinol, tantalum, cobalt-chromium, etc), plastics, polymers and composite.

20. The stent device system as claimed in claim 1, wherein the control wire (10) is made with, either alone or in various combinations of, materials such as metals, metal alloys (nitinol, tantalum, cobalt-chromium, etc), plastics, polymers, composite and anodized aluminum.

21. The stent device system as claimed in claim 1, wherein the cable wire (10) may or may not be coated with anti-thrombotic agents, or anti-coagulants, or platelet-inhibitors.

22. The stent device system as claimed in claim 1, wherein , the struts are preferably of the thickness ranging from 0.001 to 0.05 inches.

23. The stent device system as claimed in claim 1, wherein the horizontal arm of the strut carry the drug or agent to be released intramurally, preferably in the form of drug-loaded biodegradable and biocompatible microparticles or nanoparticles.

24. The stent device system as claimed in claim 23, wherein the drug-loaded biodegradable and biocompatible microparticles or nanoparticles may be attached to (and released from) the surface of the horizontal segments (12a) by means of biocompatible polymers (which may or may not be biodegradable) including phosphorylcholine, or, by viscous or gel-based mechanisms (example hydrogel), or, by glue-based mechanisms (example fibrin, collagen, etc), or, by other methods of binding (by use of any one or more of physical, chemical, or electrical methods). The drug-loaded biodegradable and biocompatible microparticles or nanoparticles may also be attached directly onto (and released from) the surface of the horizontal segments 12a.

25. The stent device system as claimed in claim 23, wherein the biodegradable and biocompatible microparticles or nanoparticles may carry a single drug or agent, or, may include a cocktail of microparticles or a cocktail of nanoparticles carrying multiple drugs or agents.

26. The stent device system as claimed in claim 23, wherein the biodegradable and biocompatible microparticles or nanoparticles may be loaded with either one or a combination of agents such as a drug, hormone, chemical, natural-derived or synthesized compound, pharmaceutical agent, genetic material, or peptide.

27. The stent device system as claimed in claim 1, wherein the regulator (1) includes a locking mechanism to prevent accidental or unintentional rotation ofthe knob (2).

28. Use of a temporary retrievable stent device system that is made of a number of struts that can be expanded inside a body conduit (for example a blood vessel) to provide precise and calibrated temporary support for maintaining patency of the body conduit, for use such as dilatation of stenoses, for local intramural delivery of drugs or agents for applications such as but not limited to prevention of restenosis, treatment of vulnerable plaque, induction of neovascularization, limitation of infarct size and inducing favorable remodeling after acute myocardial infarction.