Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
2001-04-20
2002-05-07
Recla, Henry J. (Department: 3763)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C623S001460
Reexamination Certificate
active
06383215
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for reducing complications after implantation of an intravascular stent and, more particularly, for reducing the risk of restenosis due to stent implantation.
The invention further relates to a method for producing an intravascular stent reducing complications after implantation into a vessel and, more particularly, reducing the risk of restenosis due to stent implantation.
The invention further relates to the use of vessel healing substances after implantation of an intravascular stent and, more particularly, to the use of vessel healing substances during manufacture of an intravascular stent.
The invention finally relates to an arrangement for coating one or more intravascular stents with a coating substance.
An intravascular stent is a prosthesis which may be placed within a body passageway containing endothelial cells such as any vein, artery or blood vessel within the vascular system. Typically, the stent is inserted into a vessel and placed at a site of vascular occlusion. The stent is expanded at this site in order to contact the vessel wall, thereby widening the vessel and providing mechanical support for the wall. Stents are typically manufactured from special tubes of metal or other material compositions (e.g. stainless steel, tantalum, nitinol) or from coil or plait structures of metal and/or plastics. The stents may be inserted into the vessel in different ways. Before it is inserted, the stent can e.g. be arranged on a support and crimped thereupon. The support can be a balloon catheter. The crimped stent is then transported by means of the balloon catheter into the vessel to the site of stent placement. The stent is fixed in the vessel by being expanded, e.g. by increasing the internal pressure of the balloon catheter by means of a pump, e.g. a hand pump. Thereby, the structure of the stent is deformed and the stent urges against the wall of the vessel. After the balloon catheter has been removed, the stent is dimensionally stable in the vessel. A similar process is used for inserting so called self-expandable stents. These stents do not need any external pressure in order to expand, they expand due to restoring forces or due to the ambiance conditions (flow, temperature etc.). Thus, an inserted stent expands and support the vessel wall and can eliminate stenosis.
However, it has been found that the presence of a stent in a vessel can result in complications, e.g. restenosis. Restenosis can e.g. take place at the ends of the sent or in the stent itself (“in-stent stenosis”). It is believed that restenosis take place as a natural healing reaction due to the expansion of the vessel and the mechanical action of the stent on the wall of the vessel. Due to the uncontrolled migration and proliferation of medial smooth muscle cells the vessel is again stenosed. Also, the stent can cause undesirable local thrombosis.
Stents have been used for medical treatment since 1990. Since then, the experts deals in a large numbers of examinations and essays with the problem of complications after insertion of stents (see e.g. “Local drug delivery for prevention of restenosis” by A. Michael Lincoff et al. in Circulation 90(4), October 1994 and “New recipes for in-stent restenosis: cut, grate, roast or sandwich the neointima?” by C. Di Mario et al. in Heart 84(5), 2000).
Several different method for preventing complications due to stent implantation have been proposed. To address the problem of thrombosis the person receives anticoagulant and antiplatelet drugs (e.g. ticlopidin or aspirin). To address the problem of restenosis and in-stent stenosis the vessel can be expanded again by means of a balloon catheter. Often even bypass surgery is required. Furthermore, the stents can be coated with different substances such as heparin, collagen, fibrin or adhesion peptide coating in order to reduce the risk of restenosis. It is also known to coat the stent with DLC (“diamond-like carbon”) in order to reduce the risk of restenosis.
Such methods and stents are e.g. disclosed in U.S. Pat. Nos. 6,153,252, 6,140,127 and 5,591,227.
Prior attempts to reduce complications after implantation of an intravascular stent could not reduce the risk of restenosis in a satisfactory way. Restenosis and in-stent stenosis are still considered as unsolved problems. For example, in-stent stenosis is still observed in 20%-30% of the cases.
SUMMARY OF THE INVENTION
The object of the present invention is hence to reduce complications after implantation of an intravascular stent and, more particularly, to reduce the risk of restenosis due to stent implantation.
A more specific objects of the present invention is to provide an effective method for reducing complications after implantation of an intravascular stent and, more particularly, to reduce the risk of restenosis due to stent implantation.
Another object of the invention is to provide a method for producing an intravascular stent effectively reducing complications after implantation into a vessel and, more particularly, reducing the risk of restenosis due to stent implantation.
Still another object of the invention is to provide an effective method for coating one or more intravascular stents with a coating substance.
In accordance with the invention these objects are achieved by using 17beta-estradiol as vessel healing substance after implantation of an intravascular stent.
The invention is based on the knowledge that some of the complications after implantation of an intravascular stent (e.g. the risk of restenosis or in-stent stenosis) is caused by the excessive smooth muscle cell growth in the vessel wall. This excessive growth take place when the endothelium is injured. It has been shown that it takes about two month after implantation of a stent in a human body before it is covered by neointima and endothelial cell such that a continuous cell layer is developed.
The invention is further based on the knowledge that 17beta-estradiol (chemically described as 1,3,5(10)-estradien-3,17beta-diol having the chemical notation C
18
H
24
O
2
) on one hand inhibits the growth of smooth muscle cells and, on the other hand, stimulates the re-endothelialization. The present invention makes use of these effects in order to prevent restenosis and in-stent stenosis.
17beta-estradiol is a natural estrogen produced in the body itself. Thus, there are no problems concerning the biocompatibility when using 17beta-estradiol.
Thus, in accordance with one aspect of the invention the above mentioned objects are achieved through a method for reducing complications after implantation of an intravascular stent, comprising the steps of inserting an intravascular stent into a vessel to a site of intravascular stent placement and supplying 17beta-estradiol to the site of intravascular stent placement.
The supply of 17beta-estradiol can be effected before, during or after the implantation of the stent. However, it can be advantageous to supply 17beta-estradiol at least during the operation for implantation of the stent into the vessel or even simultaneously with the implantation of the stent into the vessel. This ensures that no additional surgical operation has to be done in order to supply the 17beta-estradiol. Furthermore, this increases the probability that the 17beta-estradiol is supplied to the proper place, namely the site of stent placement.
The quantity of 17beta-estradiol supplied to the site of stent placement can be chosen in dependence of the estimated healing time of the vessel after implantation of the stent. Preferably, the quantity of 17beta-estradiol is chosen such that the time of action of the 17beta-estradiol is substantially equal to the estimated healing time. Depending on the individual case, a quantity of 10-1000 &mgr;g 17beta-estradiol can be suitable. This quantity will, among other things, depend on the use of the 17beta-estradiol as one single dose acting within a few hours or as continuous (or discontinuous) supply over a longer period of time.
The supply of 17beta-estradiol during the i
Ho (Jackie ) Tan-Uyen T.
Mallinckrodt Robert R.
Mallinckrodt & Mallinckrodt
Recla Henry J.
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