| Stent delivery system -> Monitor Keywords |
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Stent delivery systemRelated Patent Categories: Prosthesis (i.e., Artificial Body Members), Parts Thereof, Or Aids And Accessories Therefor, Arterial Prosthesis (i.e., Blood Vessel), Stent Combined With Surgical Delivery System (e.g., Surgical Tools, Delivery Sheath, Etc.)Stent delivery system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060206187, Stent delivery system. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND [0001] 1. Technical Field [0002] The invention relates to a stent delivery system. More particularly, the invention relates to a stent delivery system having a holder interlocking and interfering with a stent. [0003] 2. Related Art [0004] Stents are commonly used to treat stenosis of various arteries. Where blood vessels are clogged or narrowed by substances that restrict blood flow, stents are delivered into such vessels and expanded to dilate blood vessels or maintain the dilated state of blood vessels. Expansion of stents may be made with or without the aid of a balloon. Balloon-expandable stents are expanded by inflating a balloon disposed beneath a stent. On the other hand, self-expandable stents are capable of expanding without the use of a balloon. For this purpose, self-expandable stents are generally made from shape memory or spring metal, such as nitinol or stainless steel, so that self-expandable stents are able to expand from a compressed state upon removal of pressures applied thereon. [0005] Determining the proper stent to use is the first step to deploying a stent. The proper stent is determined, in part, based on where a stent is to be deployed. For example, balloon-expandable stents are suitable for coronary arteries, whereas self-expandable stents are more suitable for peripheral arteries. However, the uses of balloon-expandable stents and self-expandable stents often overlap, and each type of stent may be used in a variety of applications. In addition, long lesions or tandem lesions require long coverage. Multiple short stents or a single long stent may be implanted in long lesions or tandem legions. [0006] Once deployed into a human body such as an artery, stents generally remain as permanent implants. Accordingly, stents need to comply with high quality standards and minor manufacturing defects on the stents may result in the manufacturing rejection of the stents. Stents are generally manufactured through complicated and labor-intensive processes. Stent manufacturing processes include laser cutting spring metal to form multiple, interconnected struts of a stent; sandblasting a stent to eliminate debris generated from the laser cutting, and electropolishing processes. Because of these processes, it is more difficult to manufacture long stents with high precision and quality than short stents, in part because a long stent is prone to manufacturing defects along the length compared to a short stent. Where a long stent is rejected due to manufacturing defects, material costs and manufacturing expenses substantially increase. [0007] Although defect-free long stents may be successfully manufactured, conventional stent delivery systems tend to improperly deploy long stents. This is particularly a problem in conventional stent delivery systems where uneven, high forces are applied at the proximal end to push a long stent out of the delivery system upon deployment. FIGS. 1A and 1B illustrate a conventional stent delivery system 1 for a self-expandable stent 10. The stent delivery system 1 includes the self-expandable stent 10, a holder 18 and a sheath 8. The sheath 8 radially constrains the stent 10 during delivery and is retracted when the stent 10 needs to be deployed as shown in FIG. 1B. The holder 18 is disposed beneath the stent 10 and supports the stent 10 during delivery. The stent 10 expands from a compressed state to an expanded state as shown in FIGS. 1A and 1B. The stent delivery system 1 is mounted on one end of a delivery catheter 50. The delivery catheter 50 has an outer tube 8 functioning as a sheath and a core 4, which longitudinally extends from a proximal end 20 to a distal end 22. The core 4 is connected to a hub 2 at the proximal end 20 and to a holder 18 at the distal end 22. The outer tube 8 is connected to a handle 7. A physician deploys the stent 10 by pulling the handle 7 towards the hub 2. As the outer tube 8 is retracted by pulling the handle 7, the stent 10 is exposed and starts expanding. The stent 10 is fully deployed when the handle 7 reaches the hub 2. However, the stent delivery system 1 often experiences problems when the stent to be deployed is long. Deployment of long stents often requires high concentrated force particularly at the proximal end 22 to push the long stent out of the stent delivery system 1. This frequently results in improper or inaccurate deployment of the long stent. [0008] In addition to improper deployment of long stents, the stent delivery system 1 presents other disadvantages as well. One disadvantage is that it is difficult to reduce the size of the stent delivery system 1. It is generally desirable for most stent delivery systems to have a low profile. Stent delivery systems that have lower profiles reduce possible damage to blood vessels during delivery and deployment of the stent. Further, stent delivery systems with lower profiles may be able to get to small and/or tortuous blood vessels. However, the sheath 8 substantially increases the overall profile of the stent delivery system 1. When the sheath 8 is retracted, the stent 10 may unexpectedly and/or uncontrollably move. As previously stated, because the stent 10 is made from spring metal, it tends to expand upon retraction of the sheath 8. This makes it difficult for physicians to accurately position the stent 10. Various attempts have been made to address this problem. For example, structures such as rings and shafts may be added to an inner holder adjacent the proximal end. These structures may engage the proximal end of a stent in order to longitudinally restrain the stent. When the sheath is retracted, the distal end of the stent is first exposed into the blood vessel. Because the proximal end of the stent is temporarily restrained by these structures, the stent may not abruptly move in response to the retraction of the sheath. However, the structures, such as rings and shafts, may be counterproductive to accurate deployment of stents because they trap the stent which must be expanded. In addition, such structures require sophisticated design, which increases manufacturing expenses. [0009] The stent delivery system 1 may not be optimal for delivering and deploying drug coated stents. The stent 10 may include drug coatings on the outer surface thereof. Drugs may be coated on the stent 10 for various purposes. For example, drugs may prevent the formation of scar tissue on the vessel walls or reduce restenosis. Contrary to these benefits, some drug coatings may cause unfavorable consequences if applied improperly. For example, drugs, such as scar prevention drugs, may be highly incompatible with blood. Thus, when drugs that are coated on the stent 10 come into contact with blood, the drugs may cause problems such as blood clots. For this reason, it is desirable that drugs are disposed only on the outer surface of the stent 10. Because the outer surface of the stent 10 is pressed against the vessel walls upon expansion, blood does not flow between the outer surface of the stent 10 and the vessel walls. However, the conventional stents 10 usually contain drug coatings on the sides and inner surfaces which come into contact with the blood. Drug coating material is typically sprayed on a stent 10 when it is in an expanded state. Because the stent 10 is self-expandable, it is generally not possible to spray the drug coating material on the compressed stent 10 since the outer surface of the stent 10 is constantly pressed against the inner surface of a transfer tube or a sheath 8 when it is compressed. When the drug coating material is sprayed on the expanded stent 10, it easily covers the sides and inside surfaces of the stent 10 through the openings between the struts of the stent 10. Further, the stent has relatively large openings when it is expanded. This reduces the efficiency of spraying because a substantial amount of sprayed drugs passes through the openings. [0010] Even if drugs may be adequately sprayed on the expanded stent 10, they may be lost in the course of manufacturing (e.g., loading into the delivery system) and the deployment processes of the stent 10. The stent 10 must be compressed, for example, by rolling it down to a smaller diameter. During this compression process, shear force or mechanical trauma is applied to the stent 10 and a substantial amount of the drug coating may be lost. Further, when the stent 10 is pushed into the sheath 8 and the sheath 8 is later retracted rearward to deploy the stent 10, a substantial portion of the drug coating may be lost. Accordingly, there is a need for a stent delivery system that overcomes the foregoing drawbacks. SUMMARY [0011] The invention provides a stent delivery system that comprises at least one stent and a holder. The stent is expandable from a compressed state to an expanded state. The holder interlocks and interferes with the stent in the compressed state. An outer diameter of the holder contacts an inner diameter of the stent. For example, the holder may be blowmolded onto an inner surface of the stent in the compressed state. Various other processes are possible to interlock the stent with the holder. The stent delivery system may or may not include sheath. In one embodiment, the sheath may radially constrain the stent. In other embodiment, the sheathless stent delivery system may include a stimulator configured to apply a predetermined force to an inner surface of the holder. [0012] In yet another embodiment, a stent delivery system includes a holder having a pattern or impression. The pattern or impression interlocks and interferes with the stent in the compressed state. The pattern or impression may be formed by a blowmolding process. The pattern or impression does not extend through the stent and contacts side surfaces of the stent. Alternatively, or additionally, the pattern or impression may extend through the stent in the compressed state. [0013] In yet another embodiment, a stent delivery system includes at least one stent having a plurality of radial openings. The radial openings are defined in part by side surfaces of the stent. The stent delivery system further includes a holder having a portion extended from an outer diameter of the holder. The portion of the holder contacts the side surfaces of the stent. Accordingly, the portion restricts longitudinal movement of the stent relative to the holder. When an expansion force of the stent exceeds the restraining force of the holder, the stent is expanded to the expanded state. The stent delivery system further includes a sheath radially constraining the stent. Alternatively, or additionally, the stent delivery system includes no sheath. Instead of the sheath, the portion of the holder further extends around a portion of an outer diameter of the stent. Thus, the portion of the holder may radially constrain the stent. This sheathless stent delivery system further includes means for stimulating an inner surface of the holder, thereby to release the stent from the holder. The stent delivery system further includes a tip attached to the holder at one end of the stent. The holder is made from one of polyethylene terephathalate, crosslink nylon and irradiated polyethelene. [0014] In yet another embodiment, a sheathless stent delivery system includes at least one stent and a holder blowmolded onto an inner surface of the stent in the compressed state. The stent includes a plurality of struts interconnected with one another to form multiple openings therebetween, and the holder includes a plurality of extensions that extend through the multiple openings of the stent. The holder wraps around a portion of an outer surface of the stent, thereby to retain the stent in the compressed state. The sheathless stent delivery system further includes a stimulator adapted to apply a predetermined force to an inner surface of the holder, thereby to release the stent from the holder. For example, the stimulator includes a ball that has a diameter larger than an inner diameter of the holder. The ball is attached to a wire that extends through a hollow interior of the holder. The ball is configured to stimulate the inner surface of the holder as the ball is pulled rearward. The ball is made from a rigid material such as steel. The sheathless system may have an outer diameter smaller than about 0.0540 inch. [0015] In yet another embodiment, a sheathless stent delivery system includes a container positioned inside the holder and storing a liquid supplied thereto. Preferably, the liquid may be compatible with blood. The stent is released from the holder in response to increased pressure of the container. For example, the container may include an occluder. [0016] In yet another embodiment, a stent delivery system includes a holder and a plurality of stents longitudinally arranged one after another. The plurality of stents are expandable from a compressed state and an expanded state. The holder is blowmolded onto an inner surface of stents in the compressed state. The plurality of stents may be different in size, length and/or flexibility. At least one of the plurality of stents may include a drug coating. [0017] In yet another embodiment, the invention provides a method for deploying a stent disposed on a blowmolded holder. The method includes delivering a stimulator attached to a wire to a predetermined deployment site and delivering the compressed stent and the holder to the deployment site by threading the wire through an interior of the holder. The wire may extend from a proximal end to a distal end. The method further includes stimulating an inner surface of the holder by retracting the stimulator toward the proximal end. A diameter of the stimulator is larger than an inner diameter of the holder. The method also includes releasing the stent from the holder, thereby to expand the stent to the expanded state. [0018] In yet another embodiment, a deploying method includes delivering the compressed stent and the holder into a predetermined deployment site and delivering a container into the deployment site and positioning the container inside the holder. The deployment method further includes supplying a quantity of liquid into the container and stimulating an inner surface of the holder in response to an increased pressure of the container. The increased pressure is responsive to supply of the liquid. The method further includes releasing the stent from the holder, thereby to expand the stent to the expanded state. [0019] In yet another embodiment, a deploying method includes (a) delivering the plurality of stents in the compressed state and the holder to a predetermined deployment site and (b) retracting the sheath toward a proximal end to the extent that a first stent is exposed wherein the first stent is disposed distally adjacent a distal end. The method further includes (c) expanding the first stent from the compressed state to the expanded state, (d) retracting the sheath toward the proximal end to the extent that a second stent is exposed wherein the second stent is disposed proximally adjacent the first stent and (e) repeating the step of (a)-(d) until remaining stents are expanded. [0020] In yet another embodiment, a method for manufacturing a stent delivery system is provided. The stent delivery system includes compressing the stent to the first diameter, inserting the stent into a first tube and placing a second tube inside the first tube and inside an inner diameter of the stent. The second tube is airtight. The manufacturing method further includes applying pressure and heat suitable to the second tube, thereby to blowmold the second tube against the stent. The method further includes cooling down the first tube, the stent and the second tube without any pressure. The method also includes inserting the stent and the second tube into a sheath as the first tube is removed, and sealing an end of the second tube during blowmolding and removing the seal after the blowmolding. [0021] The pressure may range between 30 psi and 90 psi. The heat may range between 200.degree. F. and 280.degree. F. Specifically, the pressure may range between 35 psi and 45 psi and the heat ranges between 210.degree. F. and 220.degree. F. More specifically, the pressure is about 40 psi and the heat ranges between 210.degree. F. and 220.degree. F. In other embodiment, the pressure ranges between 85 psi and 95 psi and the heat ranges between 230.degree. F. and 280.degree. F. More specifically, the pressure is about 90 psi and the heat is about 250.degree. F. [0022] In yet another embodiment, a method for manufacturing a sheathless stent delivery system is provided. The method includes compressing the stent from an expanded state to a compressed state, blowmolding the holder against the stent by applying suitable heat and pressure, and applying a drug coating material on an outer surface of the stent in the compressed state. The drug coating material does not cover an inner surface and side surfaces of the stent. The step of applying the drug coating material includes spraying the drug coating material. Continue reading about Stent delivery system... Full patent description for Stent delivery system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Stent delivery system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. 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