Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis
Reexamination Certificate
1999-09-17
2001-02-06
Buiz, Michael (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
C606S198000
Reexamination Certificate
active
06183503
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to stents adapted for use in providing structural support for the walls of body conduits.
2. Discussion of the Prior Art
Stents have been widely used in the body to provide structural support for the walls of body conduits. For example, stents have been used in the field of urology to provide structural support for the urethra, particularly in proximity to the prostate. Vascular stents have been particularly adapted for use in both veins and arteries to add support to weakened vascular walls, for example, in proximity to aneurysms. In each of these cases, the stent provides a tubular structure with sufficient hoop strength to support the walls while maintaining patency of the conduit.
Stents of the past have typically been provided in the form of a tube having a low-profile state facilitating insertion, and characteristics for being expanded to a high-profile state to provide structural support and lumen patency. Stents have been formed from various plastics, as well as a variety of metals and alloys. In some cases, stents have been formed as a tubular mesh that facilitates movement between the low-profile and high-profile states. Such a stent is disclosed and claimed in applicant's U.S. patent application Ser. No. 09/303,113, filed on Apr. 30, 1999, and entitled “Improved Ureteral Stent System Apparatus and Method,” which is incorporated herein by reference.
In order for the tubular stents to be formed of solid materials and also be expandable, the walls of the stents have needed to be cut, sometimes in intricate patterns, in order to facilitate expansion. Particularly in the case of metal stents, these small intricate patterns have been cut by lasers in an expensive and time-consuming fabrication process.
In accordance with one surgical operation, such a stent has been mounted over the balloon of a catheter and inserted in the low-profile state into the femoral artery. Then the catheter is advanced until the stent is moved into the desired location. At this point, the balloon as been inflated within the stent, moving its walls outwardly to the high-profile state. Then the balloon is deflated and the catheter withdrawn, leaving the stent to structurally support the body conduit.
The metal stents have been particularly desirable for their high hoop strength. Unfortunately, to provide such stents with the expansion characteristics desired, an intricate fabrication process is required. This, of course, adds to the expense associated with this type of stent.
SUMMARY OF THE INVENTION
The stent of the present invention overcomes these deficiencies of the prior art. It can be formed from inexpensive plastic filaments and woven to form a tubular mesh having a low-profile and a high-profile state. The mesh can be axially corrugated to further facilitate movement between these two states. In the high-profile state, the corrugations of the tube increase the thickness of the tubular wall, greatly enhancing its hoop strength. The stent can be easily manufactured at a greatly reduced cost of fabrication. In operation, the stent of the present invention can be inserted easily over a telescoping catheter having dual balloons. The balloons can be inflated and telescoped together to axially compress and radially expand the stent to the high-profile state. The balloons can then be deflated and the catheter withdrawn. When the stent is manufactured of thermoplastics, it can be heat-set so that it is automatically biased to the high-profile state.
In one aspect of the invention, a vascular stent is adapted to be disposed in the blood vessel of a patient. This stent includes a mesh formed in the configuration of a tube having an axis, the tube being expandable from a low-profile state to a high-profile state. The tube in the low-profile state has an elongate configuration with a wall having a first thickness and a first hoop strength. The tube in a high-profile state has a compressed configuration with the wall having a second thickness greater than the first thickness and a second hoop strength greater than the first hoop strength. The tube is formed with a plurality of convolutions, which are spaced in the low-profile state and non-spaced in the high-profile state.
In another aspect, the invention includes a vascular stent, including a tube formed in the configuration of a weave having a thickness and a plurality of convolutions facilitating movement of the tube between an insertion state and an operative state. The tube in the insertion state being stretched along the axis and having a first wall thickness generally equivalent to the thickness of the weave. The tube in the operative state being compressed axially to a length generally equivalent to twice the thickness of the weave multiplied by the number of convolutions.
In an additional aspect, the stent is adapted to be placed in a body conduit and includes a plurality of filaments forming a mesh with a first thickness, the mesh being disposed in the configuration of a tube having an axis. The tube is axially corrugated to facilitate movement between a low-profile state with a first wall thickness and high-profile state with a second wall thickness greater than the first wall thickness.
A further aspect of the invention relates to a method for using a stent to support a body conduit. The method includes the step of providing a stent having a woven tubular configuration with a plurality of convolutions disposed along an axis of the stent. A catheter is provided with an axis, and a first enlargement member together with a second enlargement member that are axially moveable relative to each other. The stent is mounted on the catheter between the first enlargement member and the second enlargement member. Then the catheter and the stent are inserted into the blood vessel with the stent in a low-profile state and having a first hoop strength. The size of each enlargement member is then increased and the members moved toward each other. This axially compresses the stent and provide the stent with the second hoop strength.
These and other features and advantages of the invention will become more apparent with a discussion of specific embodiments of the invention and reference to the associated drawings.
REFERENCES:
patent: 5007926 (1991-04-01), Derbyshire
patent: 6001117 (1999-12-01), Huxel et al.
Brustad John
Hart Charles C.
Hilal Said
Applied Medical Resources Corporation
Buiz Michael
King Anthony S.
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