Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Having marker
Reexamination Certificate
1996-08-22
2001-01-16
Millin, V (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Having marker
C623S001440, C623S001460, C606S194000, C606S195000, C606S198000
Reexamination Certificate
active
06174329
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to stents, and more particularly to coatings applied to stents to make them radiopaque and coatings to protect the stent and the radiopaque layer.
Stents are useful in the treatment of atherosclerotic stenoses in blood vessels and are generally tubular shaped devices which function to hold open a segment of a blood vessel, artery , heart valve or other body lumen. Stents are particularly suitable for use in supporting and holding open a coronary artery after an atherectomy or angioplasty procedure.
Generally, stents are made from a metal alloy, such as stainless steel, and have a hollow tubular shape with an outer wall surface resembling an open lattice configuration. In some prior art stents, the outer wall surface comprises intersecting wires or struts that are expanded beyond their elastic limit to plastically deform and hold open the body lumen in which they are implanted. Other stents are self-expanding and can be in the form of a coil wire that is biased open.
Stents made from stainless steel, for example, are radiolucent, due in part to the intersecting wires having a diameter of about 0.003 inch or less. Unless the metal or metal alloy used for making the stent has a high atomic weight and density, it is difficult to visualize in vivo during catheter introduction into the vessel, stent deployment, and post-operative diagnosis.
At least one prior art stent has an increased wire diameter, to approximately 0.004 inch, in order to make the stent more radiopaque. The disadvantages of a stent having thicker intersecting wires is a more rigid stent that tracks poorly through a tortuous vessel, is virtually inflexible when tracking on a curved section of vessel, it cannot be implanted easily in a curved section of a vessel, it may not deploy in a uniform cylindrical shape, and it has poor hemodynamics. The latter disadvantage, poor hemodyramics, can result in serious medical complications such as thrombosis.
SUMMARY OF THE INVENTION
The disadvantages of the prior art stents are overcome by the present invention in which a stent is provided that is sufficiently radiopaque, flexible, has a low profile, is substantially non-thrombogenic, and has a protective layer that will eliminate corrosion while still protecting the stent and other layers from mishandling.
The stent of the present invention includes an elongated tubular body that is substantially radiolucent and is formed from, for example, a stainless steel alloy. In order to increase the radiopacity of the stent, without the disadvantages of thicker wires, the stent, or a portion thereof, is coated with a thin radiopaque layer of material having high atomic weight, high density, sufficient surface area and sufficient thickness. With such a coating, the stent is sufficiently radiopaque to be seen with fluoroscopy, yet not so bright as to obstruct the radiopaque dye. This radiopaque layer covers at least a portion of the stent and can be formed from gold, tantalum, platinum, bismuth, iridium, zirconium, iodine, titanium, barium, silver, tin, alloys of these metals, or similar materials.
The radiopaque layer is thin, in one preferred embodiment it is about 1.0 to 50 microns thick. Since the layer is so thin, it is subject to scratching or flaking when the stent is being delivered intraluminally. Accordingly, it is an object of the invention to protect the stent and particularly the radiopaque layer with a more durable protective layer that is resistant to scratching and general mishandling.
Whenever two dissimilar metals are in direct contact, such as a stainless steel stent at least partly covered with a gold radiopaque layer, there is the potential to create the electrochemical reaction that causes galvanic corrosion. The by-product of corrosion (i.e., rust) will not be biocompatible or blood compatible, may cause a toxic response, and may adversely affect adhesion of the radiopaque material. Corrosion will occur if gold and another metal, like stainless steel, are in contact with the same bodily fluid (electrolyte). If the gold coating has any pinhole or has flaked or scratched off the surface, the underlying stainless steel will be exposed to the same fluid. Therefore, a galvanic reaction (battery effect) will occur. The use of a single protective coating covering the entire surface prevents this reaction. This is especially pertinent when the radiopaque layer partially covers the stainless steel stent. The protective layer of the present invention also prevents galvanic corrosion so that the stent is biocompatible.
In one embodiment of the invention, the radiopaque layer can be eliminated by incorporating a radiopaque material, such as barium or titanium oxide in the protective layer. In this embodiment, the stent is visible under fluoroscopy and it is protected by the protective layer, yet it will have a lower profile since it lacks a separate radiopaque layer.
The invention also includes the method of making the stent and applying the radiopaque layer and the protective layer. The radiopaque coating can be applied by dipping, spraying, painting, electroplating, evaporation, plasma vapor deposition, cathodic arc deposition, sputtering, laser welding or fusing, resistance welding, and ion implantation. The protective layer can be applied by dip coating, spray coating, spin coating, plasma deposition, condensation, electrochemically, electrostatically, electroplating, evaporation, plasma vapor deposition, cathodic arc deposition, sputtering, ion implantation, or use of a fluidized bed. The process for applying the radiopaque layer and the protective layer depends upon numerous factors which can include the type of material comprising the layer. These and other advantages of the invention will become more apparent from the following detailed description thereof and the accompanying exemplary drawings.
REFERENCES:
patent: 4086916 (1978-05-01), Freeman et al.
patent: 4699611 (1987-10-01), Bowden
patent: 4943346 (1990-07-01), Mattelin
patent: 5047050 (1991-09-01), Arpesani
patent: 5067491 (1991-11-01), Taylor, II et al.
patent: 5104404 (1992-04-01), Wolff
patent: 5222971 (1993-06-01), Willard et al.
patent: 5269802 (1993-12-01), Garber
patent: 5314444 (1994-05-01), Gianturco
patent: 5364354 (1994-11-01), Walker et al.
patent: 5423849 (1995-06-01), Engelson et al.
patent: 5562728 (1996-10-01), Lazarus et al.
patent: 5609629 (1997-03-01), Fearnot et al.
patent: 5628787 (1997-05-01), Mayer
patent: 5649951 (1997-07-01), Davidson
patent: 5674242 (1997-10-01), Phan et al.
patent: 0 380 668 A1 (1989-04-01), None
patent: 0 448 016 (1991-09-01), None
patent: 448 016 (1991-09-01), None
patent: 0 517 075 A1 (1992-12-01), None
patent: 0 679 372 (1995-11-01), None
patent: 0 679 373 (1995-11-01), None
patent: 679 372 (1995-11-01), None
patent: 679 373 (1995-11-01), None
patent: 2677872 A1 (1992-12-01), None
patent: WO/95/03010 (1995-02-01), None
patent: WO 95/03010 (1995-02-01), None
patent: WO 96 24393 (1996-08-01), None
patent: 96 24393 (1996-08-01), None
Callol Joseph R.
Yan John Y.
Advanced Cardiovascular Systems Inc.
Fulwider Patton Lee & Utecht LLP
Koh Choon P.
Millin V
LandOfFree
Protective coating for a stent with intermediate radiopaque... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Protective coating for a stent with intermediate radiopaque..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Protective coating for a stent with intermediate radiopaque... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543467