Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Patent
1996-06-14
1998-03-31
Milano, Michael J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
A61F 206
Patent
active
057333270
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a stent for liberating a drug which is introduced into a vascular system such as blood vessels, and more particularly to a stent used for a local dosage of the drug.
BACKGROUND ART
For instance, in angioplasties, vascular walls are likely to be damaged by insertion of a catheter such as a balloon catheter or an atheroma-resecting catheter thereinto so that there occurs proliferation of the tunica intima due to a healing reaction in the vascular walls, which frequently results in a so-called restenosis.
Such restenosis is caused by a hyperplasia of smooth muscle cells and a majority of the recurrence of the disease is ascertained by an angiography, for example, 3 months after the angioplasty operation.
The frequency of the restenosis sums to about 30 to 40% though it varies depending upon facilities used in the angioplasty operation. If any restenosis does not occur 3 months after the operation, it is suggested that the restenosis is no longer caused subsequently.
Meanwhile, any method for preventing the aforementioned restenosis has not yet been established. However, attempts, which have been made for this purpose until now, include methods in which an instrument such as a stent or an atheroma-resecting catheter is used, or other methods to which genetic engineering is applied or in which drugs such as an antimetabolite, e.g., a carcinostatic agent, a fibroblast hyperplasia-preventing agent, or the like are used.
However, in the event that the catheter, for example, the atheroma-resecting catheter, is used to prevent the restenosis of blood vessels, patients suffer from significant pain and such an operation can be repeated only in a limited manner.
In addition, introduction of the stent into a portion subjected to the angioplasty provides some effect to prevent obliteration of blood vessels. However, since the stent itself has no function for restricting hyperplasia of smooth muscle cells and preventing the restenosis, the essential problem still remains unsolved. Moreover, upon the introduction of the stent into a portion subjected to the angioplasty, there is a possibility that thrombus will occur. Under these circumstances, in the event that the stent is used, in order to prevent occurrence of such thrombus, there has been proposed a method in which dosage of an antithrombotic agent such as dextran, aspirin, warfarin, or the like is used.
On the other hand, it is considered that dosage of drugs capable of restricting hyperplasia of smooth muscle cells is effective to prevent restenosis without use of instruments such as the stent, because such dosed drugs can function so as to prevent restenosis itself. However, in this case, some problems have been posed with respect to the dosage method of these drugs.
Similarly, in the event that the stent is used together with the antithrombotic agent to prevent thrombus, some problems have been also posed on the dosage of the antithrombotic agent.
In consequence, a locally limited dosage is regarded as an effective method for dosage of the drugs capable of restricting hyperplasia of smooth muscle cells or the antithrombotic agent. The locally limited dosage is carried out by a method in which a so-called dispatch catheter is used, a method in which a sweat balloon catheter is used, a method in which a double balloon catheter is used, a method in which the drugs are selectively introduced through a catheter, or the like.
The dispatch catheter is composed of a non-porous polyurethane sheath and a spiral coil wound around the polyurethane sheath. Drugs to be dosed are supplied into the spiral coil so that the drugs can be brought into contact with walls of blood vessels. The sweat balloon catheter contains a balloon having a microporous structure. When such a sweat balloon catheter is used, drugs are gradually dosed through fine pores of the balloon into an interior of the blood vessels. The double balloon catheter contains two balloons by which opposite ends of the portion subjected to the angioplasty are closed such tha
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Igaki Keiji
Tamai Hideo
Milano Michael J.
Nguyen Tram Anh T.
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