FR2772258A1 - CORONARY ENDOPROSTHESIS - Google Patents

Abstract

The invention concerns a coronary prosthesis for vascular shoring, covered with a microporous membrane.

Description

CORONARY ENDOPROSTHESIS
The present invention relates to a coronary stent for vascular support.

There are known in the prior art endoprostheses formed by a wire frame or an openwork metal sheet, the purpose of which is to support the vascular wall. For example, the French patent
FR2727854 describes a self-expanding endoprosthesis, intended for the maintenance of walls of anatomical canals. The endoprosthesis according to the invention comprises: 2 n external longitudinal elements, and 2 n other intermediate longitudinal elements, distributed parallel around the axis of the endoprosthesis, and offset relative to each other along this axis. A plurality of rings distributed along the axis of the endoprosthesis secure the longitudinal elements. These elements each have the shape of a zigzag shaped wire.

 French patent FR2722678 describes a bifurcated prosthesis comprising a flexible sheath for channeling the fluid circulating in the conduit, longitudinal stabilizers functionally linked to the sheath along which they extend and expandable spring means for passing the stabilizers from a state tightens to a radially expanded state.

 Another French patent FR2714815 also describes an elastic prosthesis of the "stent" type, for widening a stenosed part of a blood vessel. The prosthesis is made up of several elastic threads wound in helical turns of the same direction. The wires are axially interposed with one another in a substantially cylindrical configuration. Preferably, the wires are not fixed to each other. The turns have a shorter pitch P1 in the middle part than in the other parts (of the length of the prosthesis, which prevents a wire from moving by "screwing" between the others. The ends of the wires can be all in the same plane or axially offset.

 Another French patent FR2702954 describes an intraluminal implant comprising a prosthesis made of a continuous helix of a zigzag metal wire and loops which connect adjacent vertices of the metal wire. The prosthesis is compressible and self-expanding substantially to a precompressed configuration. The device also includes an implant fixed to the prosthesis and made of a suitable biocompatible material.

 Finally, patent FR2678508 relates to a device for the reinforcement of vessels of the human body of the type comprising an elongated reinforcement matching the internal wall of the vessel to be reinforced. According to the invention, in order to allow continuous junctions to be made, in particular at the bifurcations, at least two devices are provided comprising self-locking turns enabling continuous connections to be made.

 The introduction of a foreign body, however, produces cell proliferation at the level of the stent meshes. This proliferation causes after a few months a decrease in the harmful vascular lumen.

 The object of the present invention is to avoid this drawback by proposing a stent preventing, or at least reducing, cell proliferation.

 To this end, the invention relates in its most general sense to a stent covered by a micro-porous membrane.

 Preferably, the coronary stent according to the invention is covered with a membrane allowing the passage of molecules with a molecular weight which can vary from 1,000 to 60,000 depending on the diameter of the pores of the membrane.

 Preferably, the membrane has a thickness of between 0.1 mm and 0.2 mm.

 According to a preferred embodiment, the membrane is a dialysis membrane.

 According to a variant, the membrane is treated by ion bombardment, in order to precisely adjust the diameter of these pores.

 The endoprosthesis is formed by an openwork metallic structure having meshes alternating with a network of wires or shoring walls. This metallic structure is generally expandable using a balloon. The outer surface of this metallic structure is covered by a porous membrane (dialysis) with a thickness of 0.1 mm.

 This membrane is a biocompatible membrane made up of a sieve allowing the passage of molecules whose molecular weight can vary from 1,000 to 60,000 depending on these pores.

 This membrane can be formed by a dialysis membrane for hemodialysis usually in the form of flat sheets, sheathed sheets or hollow fibers of polysaccharide ether. This membrane is deposited on the expandable support structure.

 The membrane may also be a polysulfone membrane in the form of a hollow fiber comprising, on its inner surface, a layer of dense skin having no observable pores and on its outer surface micropores having an average pore diameter of 50 to 500 nm with a fractional surface porosity of 5 to 50%.

 Another example of a membrane capable of coating the support structure is a membrane in the form of a hollow fiber for the dialysis of blood, formed by spinning in the molten state of a block copolymer.

Claims (6)

 1 - Coronary endoprosthesis for vascular shoring, characterized in that it is covered by a micro-porous membrane.  2 Coronary endoprosthesis according to claim 1 characterized in that the microporous membrane is of the type allowing the passage of molecules with a molecular weight (PM) which can vary from 1,000 to 60,000 depending on the diameter of its pores.  3 - Coronary endoprosthesis according to claim 1 characterized in that the microporous membrane is of the type allowing the passage of molecules with a molecular weight (PM) of the order of 60,000.  4 - Coronary endoprosthesis According to at least one of the preceding claims, characterized in that the membrane has a thickness of between 0.1 mm and 0.2 mm.  5 - Coronary endoprosthesis according to at least one of the preceding claims, characterized in that the membrane is a dialysis membrane.  6 - Coronary endoprosthesis according to at least one of the preceding claims, characterized in that the membrane is treated by ion bombardment.