Stent delivery system allowing controlled release of a stent

A stent delivery system includes a stent having at least one eyelet and at least one rivet and a holder supporting the stent, wherein the holder includes a first section having a first diameter and a second section having a second diameter. A sheath covers the stent and the holder. The rivets are attached to each of the eyelets. A first inner diameter of the stent at the position of the rivets is smaller than a second inner diameter of the stent at other positions because the rivets protrude inwardly. A shoulder is formed on the holder due to the difference between the first diameter and the second diameter of the holder. The shoulder is positioned distally adjacent the rivets. The shoulder interferes with the protruding rivets, thereby restraining the longitudinal movement of the stent relative to the holder. Although the sheath is pulled back, the stent does not jump out of the stent delivery system. As a result, the stent delivery system allows the stent to be released in a controlled manner upon its deployment.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a stent delivery system. More particularly, the present invention relates to a stent delivery system that allows a stent to be released in a controlled manner upon its deployment.

2. Description of the Prior Art

Stents are well known and widely used in medical procedures. Stents are frequently used to treat various organs and vessels in the vascular system. In particular, stents are most commonly used to treat vascular diseases using endovascular procedures. Patients who suffer from vascular diseases typically develop stenosis of various arteries, i.e., blood vessels that are clogged or narrowed by substances that restrict blood flow. Traditionally, operations such as bypass surgery have been performed to treat the stenosis of arteries. Bypass surgery involves opening of the chest cavity, which is a very invasive procedure for patients.

The development of fluoroscopy was one of the first uses of non-invasive medical procedures. Fluoroscopy allows medical personnel to see internal organs and blood vessels of a patient from outside of the patient's body. Fluoroscopy is typically performed by introducing a catheter into a bodily passageway of the patient, for example, through one of the vessels in the leg. The catheter is a surgical instrument for withdrawing fluid from or introducing fluid or various medical devices into the body of a patient. In fluoroscopy, contrast media is introduced into the vessel that is to be observed. The catheter and the contrast media used in such procedures are well known in the art and are only described here generally for background.

After the contrast media is introduced and delivered through the blood vessel of the patient, physicians are able to see the state of the vessel. By using X-ray, physicians are able to spot possible areas of stenosis in the blood vessel. Once a narrowed portion of a blood vessel is identified, a stent is introduced to the spot of the clogged or narrowed blood vessels in order to provide a structural support. The stent generally expands within the vessel until it contacts the vessel wall. However, if the stenosis of the vessel is particularly acute, for example, greater than fifty percent, or if the substance causing the stenosis is calloused, the stent may not be able to fully expand. In those situations, a balloon is inserted to predilate the vessel. Upon implantation, the stent provides permanent structural support so that the blood vessel remains dilated. Using stents has the distinct advantage of providing both patients and physicians with a non-invasive method of treating problems of internal organs and blood vessels over traditional surgery.

Two types of the stents are generally employed: balloon-expandable stents and self-expandable stents. Although balloon-expandable stents have been used prior to introduction of the self-expandable stents, both types of the stents are currently used by physicians, depending on the area to be treated, the size of the vessel lumen, the state of the stenosis and the physician's experience and preference. For example, balloon-expandable stents are often preferable for treating critical arteries that are unlikely to experience pressure from external traumas. One of the advantages of balloon-expandable stents is that the implanted diameter of the stent can be precisely controlled. However, a disadvantage of balloon-expandable stents is that they can be catastrophically deformed when force from an external trauma is applied to the stent. As a result, the balloon-expandable stents are well suited for coronary vessels as opposed to peripheral vessels, which are frequently subject to external traumas.

With balloon-expandable stents, a balloon with a stent mounted thereon is introduced through a catheter and is inflated at the site of the narrowed vessel. The stent expands until it contacts and presses against the vessel wall. In contrast, self-expandable stents are capable of expanding without the use of a balloon. Self-expandable stents are generally made of spring metal, for example, nitinol or stainless steel. Spring metal used for making self-expandable stents typically has shape memory characteristics. Self-expandable stents are readily deformable by pressure applied thereto but return to their original shape like a spring after the pressure is removed.

Accordingly, a typical procedure for implanting a self-expandable stent is as follows. First, the stent is delivered to the vessel area to be treated through a catheter in a compressed or collapsed state. In order to keep the stent compressed during delivery, a stent delivery system having a sheath and a holder is used. In general, the sheath is an outer cover and the holder is located inside the sheath. The sheath and the holder typically have a tubular shape. The self-expandable stent is interposed between the sheath and the holder. The sheath applies pressure to the stent, thereby maintaining the stent in the collapsed state. The holder supports and carries the stent until it is released from the stent delivery system. The stent delivery system is loaded into the catheter and delivered to the vessel where the stent is to be deployed.

Second, once the stent is positioned at the area to be treated, the stent is implanted by releasing the stent from the delivery system. To release the stent, the sheath is retracted so that the stent is exposed to the vessel. A holder band is typically positioned at the proximal end of the stent. The holder band basically prevents the stent from moving rearward as the sheath is retracted. Because the sheath directly contacts and presses against the stent, the stent has a tendency to move backward as the sheath. Thus, the holder band can restrain such movement of the stent, thereby allowing the stent to be released as the sheath is retracted. Once the sheath is withdrawn, the stent is freed from pressure and starts to expand. After the stent fully expands, the stent delivery system and the catheter are removed from the vessel.

The description of balloon-expandable stents and self-expandable stents is provided for general background only. However, regardless of the type of the stent that is used, physicians have many different preferred procedures and variations for implanting stents. Further, the techniques used for implanting stents are still developing and changing. In addition, procedures usually associated with one type of the stent may also be used with different types of the stents.

During the process of deploying a stent, a conventional stent delivery systems have difficulty in properly positioning the stent. As described above, the sheath first retracts to expose the stent. During that process, the stent may act like a spring. As a result, the stent may jump out of the sheath and be starting to expand. This problem most commonly occurs where the stent is a short stent. Short stents may quickly expand before the sheath is fully retracted. Once the stent starts to expand, it is not possible to compress the stent back into the delivery system in order to reposition the stent. Also, it is difficult to adjust the position of the stent once the stent contacts the wall of the vessel. Accordingly, a stent delivery system is desirable that is able to release a stent in a controlled manner upon deployment.

Currently, most stent delivery systems on the market do not have a controlled release mechanism. Accordingly, physicians must exercise extreme caution by slowly deploying the stent so that the distal end of the stent has time to contact the vessel wall before the proximal end of the stent exits the sheath. This method is inherently unreliable and is susceptible to uncontrolled release of the stent during deployment.

In U.S. Patent Publication Nos. 2002/0120322 and 2002/0120323, a similar problem was addressed. In these patent publications, an interlock system that engages male interlock structures on the stent with female interlock structures on an inner tubular member is described. As shown inFIG. 6Aof the Publications, the male interlock structures are positioned at the proximal and distal ends of the stent. The female interlock structures are formed to receive and be engaged with the male interlock structures. When the stent is in the collapsed state, the male and female interlock structures are coupled to each other.

When the sheath is retracted, the stent remains in the collapsed state until it is fully exposed. As the stent expands radially, the male interlock structures are free to radially move out of the female structures. By using this interlock system, it is possible to prevent the stent from moving longitudinally during expansion of the stent. However, this interlocking system adds extra costs in manufacturing the male and female interlocking structures. The male and female interlocking structures need to fit into each other accurately. Considering the size of the stent, the addition of male and female interlocking structures may require costly and burdensome processes. In addition, the stent may be subject to additional friction due to the interlocking structures. For example, if the interlocking structures are engaged with each other too tightly, the stent may be hindered from moving out of the stent delivery system.

U.S. Pat. No. 6,077,295 discloses a self-expandable stent delivery system. The system allows a physician to recapture a partially deployed stent. The physician can partially deploy the stent, and if the position of the stent is incorrect, the physician can manipulate control handles so that the sheath and the holder of the stent delivery system move axially in opposite directions. Specifically, the control handles can be manipulated so that the holder moves in a proximal direction, whereas the sheath moves in a distal direction. This system works on the assumption that it is possible to perform accurate manipulation of the control handles. However, it is uncertain that physicians can accurately manipulate the control handles once the stent is partially deployed. Thus, this system is still prone to errors in positioning the stent during deployment.

BRIEF SUMMARY OF THE INVENTION

By way of introduction only, a stent delivery system provides a stent and a holder supporting the stent. The stent and the holder are covered by a sheath. The stent, the holder and the sheath may have a tubular shape. The stent may be a self-expandable type. The stent delivery system is loaded into a catheter to be introduced into a patient's body and eventually to a blood vessel to be treated. When the stent delivery system is loaded, the stent is in a compressed state and is interposed between the holder and the sheath.

The stent may include at least one eyelet and at least one rivet attached to the eyelet. Each rivet protrudes inwardly, thereby making an inner diameter at the position of rivets smaller than an inner diameter at other positions of the stent. The holder may include at least one portion having an increased diameter. Because of the increased diameter, a circumferential surface of the portion is outwardly exposed and constitutes a shoulder. The shoulder is located distally adjacent each rivet. Each rivet overlaps and interferes with the shoulder. Thus, the stent is trapped by the shoulder of the holder.

Upon deployment of the stent, such trapping of the stent prevents the stent from jumping out of the stent delivery system. The stent remains within the stent delivery system until it is sufficiently deployed, even though the sheath is retracted and no pressure is applied to the stent. Accordingly, physicians can release the stent in a controlled manner.

One embodiment of a stent delivery system includes a holder having a bump (or a step) as an increased diameter portion. The bump is made of the same material as the holder and is integrally formed with the holder. A shoulder for the bump is a circumferential surface of the bump, which protrudes radially outwardly from the rest of the holder because of the increased diameter.

A second embodiment of a stent delivery system includes a holder having a sleeve. The sleeve may be made of the same material as the holder but it is a separate piece from the holder.

A third embodiment of a stent delivery system includes a holder having an integrated holder band. The holder is designed to have at least two increased diameter portions. One portion comprises a bump and the other portion comprises the holder band. A diameter of the holder band portion is generally larger than a diameter of the bump portion. The bump portion is positioned distally adjacent eyelets and rivets. Between the bump portion and the holder band, a groove is formed to receive the eyelets and the rivets.

Various designs, shapes and structures are available for a stent delivery system. The foregoing discussion of the embodiments has been provided only by way of introduction. Nothing in this section should be taken as a limitation on the following claims, which define the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, embodiments of a stent delivery system will be described. The following description is made only for explanation purposes and does not limit the scope of the claims.

FIG. 1shows a first embodiment of a stent delivery system1. The stent delivery system1comprises a sheath60and a holder10. The sheath60and the holder10have a tubular shape and extend from a proximal end5ato a distal end5b. A holder band30is positioned at the proximal end5a. A stent40is interposed between the sheath60and the holder10. The stent40comprises at least one eyelet70and at least one rivet50.

The sheath60applies pressure to the stent40so that the stent40remains in a collapsed state. The holder band30extends radially around the holder10as shown inFIGS. 1 and 2B. The holder band30may be made of any material but is preferably rigid and hard. The holder band30blocks a longitudinal movement of the stent40as the sheath60is pulled rearward. Thus, the holder band30prevents the stent40from moving along with the retracted sheath60.

Preferably, the stent40is in a collapsed state during delivery as shown inFIG. 1. The stent40is a self-expanding stent. Upon deployment, the stent40expands to provide structural support for a blood vessel. Preferably, the stent40is made of nitinol, but can also be made of numerous other materials known in the art. The stent40is typically spring elastic and has a natural tendency to expand from the collapsed state. Once pressure is removed, the stent40returns to its original expanded shape. Thus, it is preferred that the stent40is made of metal having shape memory characteristics.

The stent40typically has a cylindrical shape. The stent40comprises a plurality of struts41as shown inFIG. 2A. The plurality of struts41are interconnected with each other to constitute a plurality of rows. Neighboring rows are connected by longitudinal supports42.FIG. 2Ashows the stent having four eyelets70at both the proximal end5aand the distal end5bs of the stent40. Another longitudinal support43may connect another set of neighboring rows at a different angular position than longitudinal supports42. The longitudinal supports42,43interconnect the stent40along the length of the stent40between the proximal5aand distal5bends.

Referring back toFIG. 1, the eyelets70and the rivets50of the stent40are shown. The eyelets70are hollow and preferably ring shaped. The eyelets70are filled with rivets50. In other words, the eyelets70serves as a platform to receive the rivets50(FIG. 2A). The rivets50as shown inFIG. 1are flat and have circular shapes. The rivets50are made of radiopaque material so that they function as markers during the implantation of the stent40. Typically, the stent delivery system is not easily detectable by X-ray once it is introduced into the vessel of the patient. However, it is important for physicians to know the location of the stent delivery system during the implantation procedures so that they can accurately deploy the stent. Preferably, the rivets50are detectable by X-ray to provide the physician with a location indication. Although physicians may not see other parts of the stent delivery system, they can typically see the rivets50using X-ray visualization equipment. One of skill will readily understand the use of radiopaque markers and techniques that may be used to install the rivets into the eyelets of the stent.

Referring toFIGS. 1 and 2A, the stent40is collapsed onto the holder10, and accordingly, the inner diameter of the stent40may be designed to be slightly larger than that of the holder10, and the outer diameter may be smaller than that of the sheath60. Specifically, the stent40has an outer diameter that is about the same as the inner diameter of the sheath60. Typically, the outer diameter of the stent40is about 0.076 inch and the inner diameter of the sheath60is also about 0.076 inch. The sheath60directly contacts and presses against the outer surface of the stent40. On the other hand, the inner diameter of the stent40is normally larger than the diameter of the holder10.

The stent40comprises a first portion and a second portion having two different inner diameters. The first portion has a first inner diameter D1and the second portion has a second inner diameter D2as shown inFIG. 1. The first inner diameter D1is smaller than the second inner diameter D2. The first portion of the stent40comprises the eyelets70and the rivets50. For example, the stent40may have four eyelets70where the rivets50are attached to fill hollow portions of the eyelets70as shown inFIG. 2A. Turning back toFIG. 1, the first inner diameter D1at the point where the rivets50are located is different from the second inner diameter D2at the body of the stent40. This difference in D1and D2derives from the construction of the eyelets70and rivets50. In particular, the rivets50inwardly protrude from surfaces of the eyelets70where the each rivet is attached, thereby forming the smaller inner diameter D1. As a result, the first portion is where the eyelets70and rivets50are formed as the radiopaque marker, as shown inFIG. 1. The second portion is the rest of the stent body. InFIG. 2A, the stent40has another first portion at the distal end5b.

The difference between D1and D2is relatively small and does not need to be particularly large. For example, D1is about 0.054 inch, whereas D2is about 0.060 inch. The difference between D1and D2is typically about 0.006 inch. However, the difference between D1and D2could be as small as 0.001˜0.002 inch total. Alternatively, other values for D1and D2are possible.

InFIG. 1, the holder10includes a proximal section, i.e., a first section11having a first diameter H1and a second section having a second diameter H2. The second section comprises a bump20.FIG. 2Bshows the second section20of the holder10is designed to comprise the bump20at the midsection of the stent body. The bump20may start from the midsection of the holder10and extend toward the eyelets70. The holder10further comprises a distal section, i.e., a third section13having a third diameter H3and disposed distally relative to the second section20. The first diameter H1and the third diameter H3are smaller than the second diameter H2. The first diameter H1is the same as, or alternatively, smaller than the third diameter H3. If the first diameter H1and the third diameter H3are the same, the holder10has the same diameter H1or H3throughout its body except the second section20, i.e., the bump20. Like the inner diameters D1, D2of the stent40as above, the difference between diameters H1and H2of the holder are typically relatively small. For example, H1may be as small as 0.053 inch and H2may be about 0.059 inch. Accordingly, the difference between H1and H2is about 0.006 inch.

Because the stent40is radially collapsed onto the holder10, the second diameter H2of the holder is typically smaller than the second inner diameter D2of the stent. The second diameter H2, however, could be the same as the second inner diameter D2, if the holder10and the stent40are made of material that permits a tight tolerance. In addition, the first diameter H1of the holder10is generally smaller than the first inner diameter D1of the stent. The second diameter H2of the holder, however, is larger than the first inner diameter D1and smaller than the second inner diameter D2, as shown inFIG. 1.

Referring again toFIG. 2B, the difference in the first and the second diameters H1and H2results in a radially exposed circumferential surface, or a shoulder21. The shoulder21is about 0.006 inch total and about 0.003 inch per side in this embodiment. However, the shoulder may have different dimensions. As shown inFIG. 1, the shoulder21overlaps and interferes with the first portion of the stent40(i.e., inner diameter D1). The overlapping distance is equal to the difference between the first inner diameter D1and the second diameter H2of the holder10and may be about 0.0025 inch per side. Thus, the shoulder21may directly contact the side edges of the rivets50.

The dimensions for the diameters D1, D2, H1, H2and the shoulder21are provided above for description purposes only. Various dimensions and materials for the holder10and the stent40are possible as long as there is interference between the shoulder21and a portion of the stent40. Another consideration for the diameter of the stent40is that its first inner diameter D1is preferably as large as possible (i.e., rivets inwardly protrude as little as possible) so that the stent40smoothly deploys from the delivery system. On the other hand, the rivets need to protrude inwardly a sufficient extent to provide interference with the shoulder21.

The manner of using the stent delivery system1is now apparent. The catheter is introduced into the patient's vessel. The stent delivery system1is then moved along with the catheter until the vessel portion to be treated is reached. During the delivery, the stent40remains in the collapsed state as shown inFIG. 1. The sheath60applies the needed pressure on the stent40to keep the stent40in the collapsed state.

Upon deployment of the stent40, the sheath60is slowly retracted and the stent40is exposed. The stent40does not jump out of the stent delivery system1because the eyelets70and rivets50of the stent40are trapped by the shoulder21of the bump20. The rivets50partially or wholly overlap and interfere with the shoulder21. As a result, the stent40is temporarily restrained from longitudinal movement relative to the holder10, even though the sheath60is retracted and the stent40is no longer subject to complete constraint. The stent40remains within the delivery system1until it radially expands. Once the stent40sufficiently expands, the eyelets70and rivets50expand away from the first section11and the second section21of the holder10. Thus, the first inner diameter D1of the stent40becomes much larger than the second diameter H2of the bump20upon expansion of the stent40.

Based on the above, it is possible to release the stent40in a more controlled manner than conventional stent delivery systems. Physicians do not need to expend extra energy exercising extreme caution to slowly release the stent40. Moreover, no additional structures or processes are required to accomplish the controlled release. Therefore, the stent delivery system1of this embodiment provides a cost effective and readily controllable stent delivery device. Furthermore, the stent delivery system does not add extra expenses to manufacturing and loading of the stent into the stent delivery system. The stent delivery system1simply requires the process of designing the bump20at the midsection of the holder10. The differences between D1and D2of the stent40do not need any further manufacturing step or process. Therefore, manufacturing costs are substantially minimized.

Furthermore, the second diameter H2may be designed to have a different value. A change of the second diameter H2results in a change in the difference between the first inner diameter D1of the stent40and the second diameter H2of the holder10, which directly affects the overlapping distance between the shoulder21and the rivet50. Trapping effect of the rivets50by the shoulder21is changed and adjustable by simply changing the value of the second diameter H2. In addition, it is also possible to change the first inner diameter D1. The change of the first diameter D1also results in a change of the overlapping distance between the shoulder21and the rivets50, thereby affecting the trapping effect by the shoulder21. Thus, the degree of trapping may be easily modified as desired.

FIG. 3shows a second embodiment of a stent delivery system200. The stent delivery system200includes a sheath260, a stent210and a holder220. The stent210has a first portion comprising eyelets215and rivets216attached to the eyelets215. The first portion has a first inner diameter D1, which is smaller than a second inner diameter D2. The stent210has a second portion having the second inner diameter D2as shown inFIG. 3. The holder220comprises a proximal section, i.e., a first section211, a second section and a distal section, i.e., a third section213. The first section211has a first diameter H1and the second section has a second diameter H2, which is larger than H1. The third section213has a third diameter H3, which is smaller than or the same as the first diameter. The diameters H1, H2and the inner diameters D1, D2have small dimensions. A holder band240is positioned at a proximal end250ato block the rearward movement of the stent210when the sheath260is retracted.

In the second embodiment, the second section comprises a sleeve230. As shown inFIG. 3, the sleeve230extends around radially, preferably, the midsection of the holder220to provide the second diameter H2. The sleeve230is made of the same material as the holder220. The sleeve230is designed to provide a shoulder223. The shoulder223is formed due to the difference between the first diameter H1and the second diameter H2. The shoulder223is positioned distally adjacent the first portion of the stent210, and in particular adjacent the rivets216. Accordingly, the rivets216interfere with and are trapped by the shoulder223, thereby restraining the longitudinal movement of the stent210relative to the holder220. The overlapping distance between the rivets216and the shoulder223is equal to the difference between the first inner diameter D1and the second diameter H2, which may be about 0.0025 inch per side. Once the stent210starts to be deployed, it radially expands. Upon radial expansion of the stent210, the rivets216are no longer trapped by the shoulder223.

Like the previous embodiment, the stent210does not jump out of the stent delivery system200. The stent210remains in the collapsed state until it radially expands upon its deployment, and the stent210is allowed to be released in a controlled manner. The stent delivery system200provides additional advantages in that the second diameter H2of the holder220is easily changeable by using a sleeve having a different diameter. As described above, a change in the second diameter H2results in change in the trapping effect because the overlapping distance between the shoulder and the rivets is changed. The sleeve structure facilitates this process by providing a simplified way of changing shoulder223and the resulting trapping effect.FIG. 3shows one sleeve230covering the holder220and supporting the rivets216. Alternatively, two or more sleeves may be used if necessary.

A third embodiment of a stent delivery system300is shown inFIG. 4. The stent delivery system300includes a stent310, a holder320and a sheath330. The holder320includes a bump321and is designed to make the holder band340an integrated part. Accordingly, the holder320includes a proximal section, i.e., a first section326, a second section having the bump321, a distal section (i.e., a third section327), and a holder band section (i.e., a fourth section328), as shown inFIG. 4. The holder band340needs to have a distance (P) that is sufficient to receive eyelets315of the stent310. Accordingly, the holder band section328has a diameter H4, which is larger than the two diameters H1and H2, as shown inFIG. 4. As discussed above, the diameters H1and H2are about 0.053 and 0.059 inch, respectively. The diameter H4is about 0.075 inch. Each distance P, as shown inFIG. 4, is typically 0.022 inch per side. The width W of each eyelet315is about 0.025˜0.027 inch. The third diameter H3is the same as or larger than the first diameter H1. The dimensions provided for H1, H2, P and W are exemplary only and may be larger or smaller than the described values.

Because the holder band340is formed as an integrated part of the holder320, a groove360is disposed between the holder band340and the bump321. The depth of the groove360is about the same as the distance P of the holder band340and is about 0.022 inch per side. As shown inFIG. 4, the eyelets315and the rivets316are positioned in each groove360.

The holder band340is made of the same material as the holder320. Any material, such as metal, plastic or polymer, which preferably provides rigid, hard characteristics, may be used. For example, tungsten or stainless steel is used to make the holder. Alternatively, other materials are possible for the holder320and the holder band340. The stent delivery system300reduces additional manufacturing costs because the holder band340is readily made during the process of manufacturing the holder320.

In this embodiment, the shoulder323traps the eyelets315and the rivets316upon the deployment of the stent310. The shoulder323partially or wholly overlaps and interferes with the rivets316. The overlapping length between the shoulder323and the rivets316is equal to the difference between the first inner diameter D1of the stent310and the second diameter H2of the holder320. The difference between the first inner diameter D1and the second diameter H2is about 0.005 inch. Because of the trapping of the rivets316by the shoulder323, longitudinal movement of the stent310relative to the holder320is temporarily restrained and the stent310is prevented from jumping out of the stent delivery system300. Because the groove360receives the eyelets315and the rivets316on the opposite side of the shoulder323, it may further contribute to the trapping effect. In addition, the second diameter H2may be changed, which results in a change of the overlapping distance between the shoulder323and the rivets316. The trapping effects may be further increased or decreased depending on changes of the overlapping length. In addition, the value of the first inner diameter D1may be changed as well. The change of the first inner diameter D1also affects the trapping effect. This makes it possible to modify the degree of trapping effect as desired. Because only changes to the diameters D1and H2are required, no additional costly or complex processes is necessary. Thus, it is possible to provide a stent delivery system that is cost-efficient and has a more controlled release than the conventional stents.

As described in connection with various embodiments, the invention provides a stent delivery system employing a difference between inner diameters of the stent. The difference in the inner diameters of the stent is utilized to trap a portion of the stent until the stent is fully deployed. Such trapping prevents the stent from jumping out of the stent delivery system when the stent is being deployed. Thus, the stent can be released in a controlled manner.

The stent delivery system includes a holder that is designed to have an increased diameter. The holder includes a bump portion having an increased diameter. Alternatively, the holder includes a sleeve extending radially around the holder or an integrated holder band. These structural designs are intended to increase the diameter of the holder for the purpose of trapping a portion of the stent.

Although various embodiments of the invention have been described in connection with a stent delivery system, the invention is not limited to the described embodiment of the stent delivery system. The invention may be applicable to other medical systems or methods that involve implantation of a device or structure like a stent. The application of the invention may be more useful if the device or structure has characteristics of self-expansion.

Various embodiments of the invention have been explained, but they do not represent the scope of the invention. For example, it is apparent to those having ordinary skill in the art that modification and change may be made with the invention. It is therefore intended in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.