Patent Description:
<CIT> discloses an anti-reflux stent which includes an extended inner sleeve, a stent surrounding at least portion of the inner sleeve and a coating that bonds the stent to the inner sleeve. The inner sleeve includes a lumen through which food and liquid may pass, wherein at least a portion of the inner sleeve has a flexibility such that it collapses when the inner sleeve is not covered by the stent.

<CIT> discloses a tissue graft construct and method for repairing the inner linings of damaged vessels. The device comprises a cylindrical expandable member having a luminal and exterior surface, where a layer of submucosal tissue is fixed to the luminal or exterior surface of the expandable membrane. The graft device is preferably a vascular stent having a size for receiving the distal end of a catheter having an inflatable balloon.

An existing covered stent generally adopts a single-layer coating membrane structure or a two-layer coating membrane structure. After a stent having the single-layer coating membrane structure is implanted into a body, a metal stent would be exposed to blood and may be corroded after long time. The single-layer coating membrane structure is directly adhered and sealed to the inner wall of a blood vessel by the metal stent, causing low sealing property and low biocompatibility.

In the two-layer coating membrane structure, both the inner and outer surfaces of the metal stent are covered with membranes, and inner and outer coating membranes and the metal stent are combined into a whole by high-temperature thermal treatment. After this two-layer coating membrane structure is implanted into the body, the metal stent avoids being directly exposed to the blood to prevent corrosion of the metal stent and release of metal ions; and furthermore, the proximal end of the stent is directly adhered to the inner wall of the blood vessel by the coating membranes, achieving relatively high sealing property and high biocompatibility.

However, in the two-layer coating membrane structure, the inner and outer coating membranes are combined into a whole by the thermal treatment method, and thus may be torn under long-term impact of the blood on the proximal-end end surface and the distal-end end surface of the covered stent to further cause the exposure of the metal stent to the blood, which accelerates the corrosion of the metal stent to release the metal ions. Particularly, nickel ions released by a metal stent made of a nickel-titanium alloy in the blood have a carcinogenic effect. In addition, tear openings formed by the tearing of the inner and outer coating membranes on the proximal-end end surface and the distal-end end surface of the covered stent would slow down the blood flow to easily cause thrombosis in the tearing openings, and may increase the impact force of the flowing blood to the covered stent, thereby increasing the risk of stent displacement.

According to the present invention, a covered stent is provided as defined in claim <NUM>. The stent comprises a proximal-end end surface, a distal-end end surface and a peripheral surface located between the proximal-end end surface and the distal-end end surface, the peripheral surface comprising an inner surface and an outer surface opposite to the inner surface; the outer surface is covered with a first coating membrane, and the inner surface is covered with a second coating membrane; the covered stent further comprising a stent main body arranged between the first coating membrane and the second coating membrane, wherein the two ends of the second coating membrane are folded towards the outer surface and are connected with the second coating membrane through the stent main body, and the two ends of the first coating membrane are folded towards the inner surface and are connected with the second coating membrane, so as to cover the proximal-end end surface and the distal-end end surface.

The present invention further provides a membrane covering method as defined in claim <NUM>. The method of covering the stent includes:.

The present invention may prevent blood flow from directly impacting the coating membranes on the inner and outer surfaces of the proximal-end end surface and/or the distal-end end surface through a flanging design for the coating membranes on the proximal-end end surface and/or the distal-end end surface of the covered stent, thereby avoiding tearing of the coating membranes of the inner and outer surfaces caused by long-term blood flow impact and a series of adverse effects caused by the tearing of the coating membranes.

The present application will be further described below in combination with accompanying drawings, comparative examples and embodiments. In the drawings:.

To understand the technical features, objectives and effects of the present invention more clearly, embodiments and comparative examples are now described in detail in conjunction with the accompanying drawings.

As shown in <FIG>, a covered stent <NUM> is a tubular structure (used for forming a blood flow channel) with openings at two ends, and has a proximal-end end surface <NUM>, a distal-end end surface <NUM> and a peripheral surface <NUM> located between the proximal-end end surface <NUM> and the distal-end end surface <NUM>. The peripheral surface <NUM> includes an outer surface <NUM> and an inner surface <NUM> opposite to the outer surface <NUM>. The outer surface <NUM> and the inner surface <NUM> are respectively located on two sides of a stent main body <NUM>. In the present embodiment, the outer surface <NUM> is covered with a first coating membrane <NUM>, and the inner surface <NUM> is covered with a second coating membrane <NUM>. The first coating membrane <NUM> and the second coating membrane <NUM> have certain thicknesses and are generally made of a biocompatible macromolecular material, such as a PET (polyethylene terephthalate) membrane or PTFE (poly tetra fluoroethylene) membrane. The stent main body <NUM> is arranged between the first coating membrane <NUM> and the second coating membrane <NUM>. The first coating membrane <NUM> and the second coating membrane <NUM> are adhered by thermal treatment so as to clamp the stent main body <NUM> therebetween. The stent main body <NUM> is cut and expanded from a biocompatible plastic expansion material tubular product known in the art, and the tubular product may be medical stainless steel, or a cobalt-nobelium alloy, or a self-expansion material such as a nickel-titanium alloy. When made of a plastic expansion material, the stent main body <NUM> may be radially compressed in a delivery sheath tube and may be expanded to an initial shape and size through an inflatable balloon or an equivalent expansion mechanism. When made of the self-expansion material, the stent main body <NUM> may be radially compressed in the delivery sheath tube and recovers the initial shape and size in the absence of the compression of the delivery sheath tube. The stent main body <NUM> may be cut from the tube product or woven by a metal wire.

As shown in <FIG>, two ends of the first coating membrane <NUM> and the second coating membrane <NUM> are folded inwards (namely inside the lumen of the covered stent) and are connected with the second coating membrane <NUM> through the stent main body <NUM> so as to cover the proximal-end end surface <NUM> and the distal-end end surface <NUM> of the covered stent <NUM>.

This first comparative example further provides a first comparative manufacturing method of the above-mentioned covered stent <NUM>, including that:.

The present disclosure may prevent blood flow from directly impacting the coating membranes on the proximal-end end surface and the distal-end end surface by a flanging design for the coating membranes covering the peripheral surface of the covered stent on the proximal-end end surface and the distal-end end surface of the covered stent, thereby avoiding tearing of the coating membranes on the inner and outer surfaces caused by long-term blood flow impact and a series of adverse effects caused by the tearing of the coating membranes.

As shown in <FIG>, a covered stent <NUM> is of a tubular structure (used for forming a blood flow channel) with openings in two ends, and has a proximal-end end surface <NUM>, a distal-end end surface <NUM> and a peripheral surface <NUM> located between the proximal-end end surface <NUM> and the distal-end end surface <NUM>. The peripheral surface <NUM> includes an outer surface <NUM> and an inner surface <NUM> opposite to the outer surface <NUM>. In the present embodiment, the outer surface <NUM> is covered with a first coating membrane <NUM>, and the inner surface <NUM> is covered with a second coating membrane <NUM>. The first coating membrane <NUM> and the second coating membrane <NUM> have certain thicknesses and are generally made of a biocompatible macromolecular material, such as a PET membrane or PTFE membrane. A stent main body <NUM> is arranged between the first coating membrane <NUM> and the second coating membrane <NUM>. The first coating membrane <NUM> and the second coating membrane <NUM> are adhered by thermal treatment so as to clamp the stent main body <NUM> therebetween. The stent main body <NUM> is cut and expanded from a biocompatible plastic expansion material tubular product known in the art, and the tubular product may be medical stainless steel, or a cobalt-nobelium alloy, or a self-expansion material such as a nickel-titanium alloy. When made of a plastic expansion material, the stent main body <NUM> may be radially compressed in a delivery sheath tube and may be expanded to an initial shape and size through an inflatable balloon or an equivalent expansion mechanism. When made of the self-expansion material, the stent main body <NUM> may be radially compressed in the delivery sheath tube and recovers the initial shape and size in the absence of the compression of the delivery sheath tube. The stent main body <NUM> may be cut from the tube product or woven by a metal wire.

As shown in <FIG>, two ends of the first coating membrane <NUM> and the second coating membrane <NUM> are folded outwards (namely outside the lumen of the covered stent) and are connected with the first coating membrane <NUM> through the stent main body <NUM> so as to cover the proximal-end end surface <NUM> and the distal-end end surface <NUM> of the covered stent <NUM>.

This second comparative example further provides a second comparative manufacturing method of the above-mentioned covered stent <NUM>, including that:.

As shown in <FIG>, a covered stent <NUM> is of a tubular structure (used for forming a blood flow channel) with openings in two ends, and has a proximal-end end surface <NUM>, a distal-end end surface <NUM> and a peripheral surface <NUM> located between the proximal-end end surface <NUM> and the distal-end end surface <NUM>. The peripheral surface <NUM> includes an outer surface <NUM> and an inner surface <NUM> opposite to the outer surface <NUM>. The inner surface <NUM> is covered with a second coating membrane <NUM>. As shown in <FIG>, two ends of the second coating membrane <NUM> are folded outwards (namely towards the outside of the lumen of the covered stent <NUM>). As shown in <FIG>, the outer surface <NUM> is covered with a first coating membrane <NUM>. As shown in <FIG>, two ends of the first coating membrane <NUM> are folded inwards (namely towards the inside of the lumen of the covered stent <NUM>). A stent main body <NUM> is also arranged between the first coating membrane <NUM> and the second coating membrane <NUM>. The first coating membrane <NUM> and the second coating membrane <NUM> are adhered by thermal treatment so as to clamp the stent main body <NUM> therebetween.

Claim 1:
A covered stent, comprising: a proximal-end end surface (<NUM>), a distal-end end surface (<NUM>) and a peripheral surface (<NUM>) located between the proximal-end end surface and the distal-end end surface, the peripheral surface (<NUM>) comprising an inner surface (<NUM>) and an outer surface (<NUM>) opposite to the inner surface (<NUM>); the outer surface (<NUM>) is covered with a first coating membrane (<NUM>), and the inner surface (<NUM>) is covered with a second coating membrane (<NUM>); the covered stent further comprising a stent main body (<NUM>) arranged between the first coating membrane (<NUM>) and the second coating membrane (<NUM>),
characterized in that the two ends of the second coating membrane (<NUM>) are folded towards the outer surface (<NUM>) and are connected with the second coating membrane (<NUM>) through the stent main body (<NUM>), and the two ends of the first coating membrane (<NUM>) are folded towards the inner surface (<NUM>) and are connected with the second coating membrane (<NUM>), so as to cover the proximal-end end surface (<NUM>) and the distal-end end surface (<NUM>).