Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Drug delivery
Reexamination Certificate
1998-09-29
2001-03-27
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Drug delivery
C623S001440, C623S001150, C623S023700
Reexamination Certificate
active
06206915
ABSTRACT:
TECHNICAL FIELD
This present invention relates to stents for placement within a vessel, such as a coronary artery, and more particularly, to stents designed for storing and releasing therapeutic drugs, such as those used in the treatment of restenosis.
BACKGROUND ART
Disease, injury and/or surgery can result in localized tissue damage within a vessel and possibly occlusion within the vessel. Angioplasty is a procedure which may be used to lessen the amount of occlusion, whereby a balloon is inserted into an occluded vessel and subsequently inflated to dilate the occluded area. In some instances, the balloon may damage the vessel wall during inflation. As a result, in about 30 to 50% of the cases, the initial increase in the vessel dimensions may be followed by a localized re-narrowing (i.e., restenosis) of the vessel at the occluded area over a period of about three to six months. Restenosis may be the results of hyperplasia within the neointima, vascular remodeling within the vessel, or shrinkage in the overall vessel dimensions. To prevent re-narrowing of the vessel, expandable stents, for example, have been implanted at the site of occlusion (i.e., constriction site), so that the a pathway may be maintain for fluid to flow therethrough.
There are a variety of methods currently used to implant an expandable stent within a vessel. A commonly used method first mounts an expandable stent in a non-expanded state on a balloon portion of a catheter. Subsequently, the catheter is maneuvered, with the stent thereon, along the vessel to the constriction site. Once the stent is at the constriction site, the balloon is dilated to expand the stent, and thus enlarging the vessel at the site of constriction. However, as with angioplasty, restenosis may subsequently result at the constriction site, despite the presence of the stent thereat. In particular, tissue growth may occur across the pattern of perforation (such a pattern is typically necessary to permit expansion of the stent from a non-expanded state) on the stent and into the stent lumen.
To reduce or prevent the occurrence of restenosis, there are stent designs which incorporate a therapeutic drug into or onto the stent body, which drug may diffuse or be released after the placement of the stent into a vessel. In one design, the therapeutic drug is coated onto the surface of the stent body. As fluid flows across the surface of the stent, the coat degrades and releases the therapeutic drug from the stent. However, such a design may permit the drug to be released too quickly. Consequently, the desired reduction in the occurrence of restenosis may not result. In another design, the therapeutic drug is incorporated into a strip of biodegradable material, and the strip placed onto the body of, for instance, a non-degradable stent. In this design, as the strip biodegrades the therapeutic drug is released at a rate at which the strip biodegrades. However, the use of a biodegradable strip may not provide a sufficient amount of a therapeutic drug necessary to reduce or prevent the occurrence of restenosis. With other designs, the therapeutic drug may be incorporated throughout the body or within different biodegradable layers of a biodegradable stent, so that the drug can be released as the stent biodegrades. The incorporation of the therapeutic drug into the body of the biodegradable stent may increase the total amount of drug over that used in the strip embodiment. However, the drug concentration must be so balanced so as not to affect the polymeric make-up of the stent, and thus the ability of the stent to biodegrade over a sufficiently long period during which restenosis may occur. At such a concentration, the amount of therapeutic drug may not be sufficient to reduce or prevent restenosis over the period necessary.
Accordingly, it is desirable to provide an expandable stent which can store a sufficient amount of therapeutic drug, which can vary the concentration of the drug without compromising the characteristics of the stent, and which can release the drug over a sufficiently long amount of time in a sufficient concentration to reduce and/or prevent the occurrence of restenosis.
SUMMARY OF THE INVENTION
The present invention is directed to a drug storing and metering stent designed for placement within a body vessel. In accordance with one embodiment of the invention, the stent, adapted to expand and remain in an enlarged diameter against the vessel wall, includes an outer member having a lumen and a cannulated inner member positioned within the lumen of the outer member. The stent further includes a space separating the inner member from the outer member and being situated between an outer surface of the inner member and the inner surface of the outer member. At least one protrusion is provided on at least one of the inner and outer members, and which protrusion extends across the space so as to create a friction fit between the inner and the outer members. As the stent is designed to deliver a therapeutic drug to a local site, for example, a constriction site caused by restenosis, a therapeutic drug may be disposed within the space between the inner and outer members. To maintain the drug within the space, the drug may be imbedded within a carrier, such as a bioabsorbable gel. The stent further includes a pattern of perforation extending from the outer member, across the space, and through the inner member. The presence of the perforation permits the stent to expand radially in diameter.
The stent may be manufactured, in accordance with one embodiment of the present invention, by positioning an inner tubular member having a predetermined outer diameter within an outer tubular member having a larger inner diameter so that they are substantially concentrically aligned. The difference between the diameters of the members defines a space between the first and second members. Once the members have been aligned at least one protrusion is caused to extend across the space from one of the inner and outer members. The protrusion must extend sufficiently across the space, so as to provide a friction fit between the inner and outer members. It should be appreciated that the protrusion or protrusions may be provided on the outer member, the inner member, or both, and may be provided on one or both members prior to the positioning of the inner member within the outer member. A therapeutic drug may next be disposed in the space between the outer and inner members. Thereafter, a pattern of perforation may be etched, for example, by laser, through the inner and outer members to provide the stent with the ability to expand. Alternatively, the perforation may be etched in the stent prior to the placement of the therapeutic drug within the space.
The stent, manufactured in accordance with an embodiment of the invention, may be placed within a vessel, for instance, a coronary artery, in a non-expanded state. Once it has been maneuvered to a site of interest, the stent may be expanded by a balloon catheter, so that with its expanded diameter, the stent is securely positioned within the vessel. The stent and the space between the outer and inner members may then be exposed to fluid flow within the vessel, so as to cause the therapeutic drug to be diffused or released into the vessel.
REFERENCES:
patent: 4417576 (1983-11-01), Baran
patent: 5707385 (1998-01-01), Williams
patent: 5733326 (1998-03-01), Tomonto et al.
patent: 5735897 (1998-04-01), Buirge
patent: 5788626 (1998-08-01), Thompson
patent: 5824050 (1998-10-01), Karwoski et al.
patent: 5843166 (1998-12-01), Lentz et al.
patent: 5858556 (1999-01-01), Eckert et al.
patent: 5948018 (1999-09-01), Dereume et al.
Fagan John R.
Shah Chirag B.
Jackson Suzette J.
Medtronic Ave Inc.
Sterne Kessler Goldstein & Fox P.L.L.C.
Willse David H.
LandOfFree
Drug storing and metering stent does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drug storing and metering stent, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drug storing and metering stent will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2479672