The vessel "to be repaired" may typically be affected by one or more aneurisms or by degeneration necessitating the installation of tubing intended to channel the blood in the damaged portion(s), thus preventing the blood pressure from being allowed to be applied to the weakened walls of the vessel.
Up to the present, numerous vascular implants for the treatment of aneurisms have been proposed.
For several years, the installation of these implants by the percutaneous endoluminal route has been favoured.
Among these existing systems, WO-A-96/18361 proposes in particular a system comprising:
an implant having a body suitable for channelling the fluid in question along a single or branched tube extending generally along a major axis of the implant, at least in one configuration of the latter, which latter has a first configuration in order to be contained inside a flexible sheath, for the purpose of implantation in the canal, or a second configuration, once the implant is arranged in the canal outside the sheath, the first configuration having a radial dimension overall with respect to the said major axis which is smaller than the second configuration and the said body having a length along that axis; PA1 a device for installing the implant in the canal, the device comprising:
said flexible sheath, PA2 at least one retaining tie, to maintain the body substantially in the first configuration of the implant, PA2 and means for releasing the tie, in order to allow the implant to pass from its first to its second configuration.
WO-A-96/18361 provides for the combined use of ties for retaining the body of the implant in the "radially restricted" state of the implant and means for releasing the said ties, making it possible to control both the introduction of the body into the installation sheath and the actual step of implantation of the implant in the receiving anatomical canal.
But in reality, the action of the ties operates on two radially deployable tubular stents (or expanders), respectively arranged in "upper" (distal) and "lower" (proximal) portions of the implant.
However, between these two "upper" and "lower" levels, the release thread used to allow the stents to expand radially passes inside a central catheter round which the implant has been arranged, inside the implantation sheath.
Moreover, other threads or filaments are associated with the release and retaining means already mentioned, which makes the solution of WO-A-96/18361 complicated to carry out and difficult to use.
FIGS. 1 to 5 provide some exemplary embodiments of prior art vascular implants intended for the treatment of aneurisms, it being stated that practically all the existing configurations on this subject could be used, whether it is a question of an implant with armature (stent) which is self-expanding (that is to say, naturally having the capacity of deforming resiliently in a radial direction from a first, constricted diameter to a second, expanded diameter) or of an implant with an armature radially deployable by the effect of an internal force that can be created by means of an inflatable balloon which, when the time comes, is inflated inside the implant (as in U.S. Pat. No. 4,733,665, for example).
Typically, the sleeve or body 3 is a woven or non-woven fabric without inherent mechanical strength. In its radially deployed form in FIG. 1, it is in the form of a cylindrical tube of circular cross-section and having its axis la coinciding with that of the implant 1. It has a continuous wall.
An intermediate portion of the sleeve 3 might possibly be embossed in order to resist folding or kinking.
Axially, the sleeve 3 may have a length of between approximately 6 cm and 16 cm, with a diameter in its "radially deployed" state in FIG. 1 of between approximately 5 mm (iliac implantation) and 45 mm (aortic implantation). Its wall structure may be produced from polyethylene terephthalate (PET), or more generally from polyester or PTFE, with a wall thickness of the order of 0.10 mm to 0.80 mm.
For its implantation by means of a small diameter sheath (in particular by the percutaneous endoluminal route) and in order to ensure the application of the implant against the wall of the receiving canal, two tubular spring means 5, 7 have been provided, respectively arranged towards the proximal and distal ends of the sleeve 3. In the present instance these are two stents in the form of zigzags each defining a ring closed on itself, in the manner provided for in EP-A-177 330 or in WO-A-96/18361. To produce these stents, a metal wire (for example made of stainless steel) may be used which may have a diameter of the order of 0.5 mm, in order to produce a ring which is naturally radially expansible to change between a constricted ring diameter (FIG. 2) of approximately 2 mm to 9 mm and the naturally expanded diameter already indicated (FIG. 1).
In the radially constricted position in FIG. 2, it will be noted that the sleeve 3 has longitudinal folds.
In FIG. 3 there can be seen an implant 10 of the same type as that in FIGS. 1 and 2, except for the principal difference that the implant 10 is bifurcated. For this purpose the sleeve here identified by 13 has a principal section 13a which branches into two limbs 13b, 13c, one of which may be shorter than the other, imparting to the deployed tube 13a general inverted Y-shape.
At the free end of each of the sections 13a, 13b, 13c, an "expander" respectively 17a, 17b, 17c, shaped like the stents 5, 7, has been at least partially slid inside the corresponding section to which it can be fastened by any means, such as suture ties or clips.
In order to install the implant 10 in its receiving duct, by way of a device for implantation by the endoluminal route, each of the expanders is restricted radially and the two limbs 13b, 13c are applied one against the other so as to arrange the whole substantially along the general axis 10a.
In FIG. 4, the implant 20 is again in the form of a single tube with longitudinal axis 20a. But in the present instance the armature for radial deployment of the sleeve 23 (of the same type as the sleeve 3) is constituted by three tubes 25, 27, 29, each formed of a plurality of intersecting elongate elements consisting of a plurality of thin bars fixed to one another at their crossing points, so as to form a sort of grid radially deformable by the effect of an internal force (balloon or equivalent; see U.S. Pat. No. 4,733,665).
In FIG. 4, there have also been shown at 21 attachment hooks fixed respectively to the proximal section 25 and distal section 29 of the armature in order to hook the implant 20 into the wall of its receiving canal, in the radially deployed position. Such attachment hooks may of course be provided on the variants in FIGS. 1, 3 or 5.
In FIG. 5 only, there is shown another variant of an implant for aneurism, 30. The illustration shows diagrammatically an implant as disclosed in EP-A-836 452.
It will thus be observed that the vascular implant 30 comprises a proximal tubular armature 31 having one or more levels of filamentary winding in zigzags. This metallic armature is self-expanding, so that in the absence of radial constraint, it causes the distal portion 33a of the sleeve 33 which extends round it to be deployed radially. This first portion 33a is, like the sleeve 3, devoid of inherent mechanical strength, unlike the second portion 33b. This portion 33b, which axially extends the first, has naturally, in effect, a radially deployed tubular shape, in the manner of surgical vessel substitutes (see for example WO-A-88/06026 or U.S. Pat. No. 3,986,828).
The portion 33b is preferably impermeable to blood and is provided to be anastomosed to the receiving vessel in question, towards its proximal free end 36.
There is no stent (or equivalent means of radial deployment) with regard to the essential part at least of this anastomosable portion 33b which may be embossed and be manufactured, for example, from Dacron (registered trademark).