FR2672487A1 - Adaptable self-centring vein filter which can be implanted on the blood path - Google Patents

Abstract

The invention relates to an adaptable self-centring vein filter which can be implanted inside the vena cava and on its blood path in order to retain clots. This implantation is performed clinically by cardiovascular surgeons. It consists of six branches which are equipped with hooks sharpened at their ends (11), three longer branches which end in loops (12) made of elastic metal, all issuing from a cylindrical head (13). The assembly of the arched, concave (11) and simultaneously concave and convex (12) branches is deployed diametrally in the vein (6) in the shape of a corolla (14); of the anchoring of the branches (11) of the supports of the branches (12). The vein filter according to the invention is intended in particular to prevent the risks of embolism caused by blood clots.

Description

 The subject of the invention is an improved FILTER intended to be placed on the blood path, in particular on a VENOUS PATH, for the retention of blood clots.

 Filters of this type are known, and are for example described in patent US-A-3,952,747 and in patent application EN 84 14144 of September 14, 1984 filed by the applicant company.

 Generally, these filters are in the form of a small frustoconical basket which hangs inside a vein downstream of the path that we want to filter; it is generally the VEIN CELLAR reaching the heart. It is thus possible to stop, before their entry into the heart, any blood clots that may form and which may cause embolism.

 A difficulty specific to this kind of intervention is to correctly position the filter with its axis substantially in the axis of the vein in which it will hang. To facilitate this attachment, the filter tabs are usually fitted with hooks. In general, to introduce the filter into the vein, it is pushed into the latter by means of a conduit which crosses the vein and whose diameter is less than that of the latter. When the filter reaches the end of the duct (CATHETER), it is therefore released into the vein and the expansion of its hook-shaped legs ensures the anchoring of the filter.

It is obvious that such a drop is in practice extremely difficult to control, and there is in fact little chance that the basket filter occupies the most favorable position inside the vena cava. with its axis substantially parallel to the axis of the vein.

 The object of the invention is to avoid this difficulty.

 To this end, a filter according to the invention, of the type formed by elastic threads deployed substantially along a flared corolla, coming from a cylindrical and hemispherical head, is characterized in that certain at least aforementioned tabs are provided, at their ends of small hooks oriented externally and others of alternating camber looped at their ends, all generated by the opening perimeter of said corolla in a normal position of use.

 In this way, when the filter is introduced into the vein, the tabs curled at their ends leaving the duct with a slight rotation which has the effect of seeking an optimal position inside the vein substantially that of its axis.

 According to a preferred embodiment characteristic of the invention, the filter comprises at least; six legs provided with small hooks and three longer legs mentioned above, angularly distributed around the axis of the filter.

In this way we obtain a good automatic centering of the filter placed in the ideal place in the vein
According to a characteristic of a preferred embodiment of the invention, the legs provided with hooks are shorter than those which do not have them. In this way, when the filter is introduced into the vein, the legs not provided with hooks come to rest, always animated by their slight rotation, against the internal wall of the vein by centering the filter, before the other legs, shorter and provided with hooks do not deploy successively and do not come to hang on the internal wall of the vein.

The invention and its implementation will appear more clearly with the aid of the description which follows, given with reference to the appended drawings in which
FIG. 1 schematically shows in perspective a conventional filter manufactured according to the prior art,
FIG. 2 schematically shows the filter placed inside a vein, this filter being blocked obliquely in the vein and not parallel to its axis,
FIG. 3 shows, like FIG. 1, a filter modified in accordance with the invention,
FIG. 4 is a top view taken along the arrow F in FIG. 3,
FIG. 5 shows, like FIG. 2, the modified filter of the invention, placed in a vein and the axis of which substantially coincides with that of the vein,
FIG. 6 shows a top view of FIG. 5, made substantially along arrow F of this figure,
FIGS. 7, 8 and 9 show three successive stages of the installation of the filter of the invention in a vein, according to the respective planes BC and DE of FIG. 6,
FIG. 10 shows, on a larger scale, a detail of a sharp hook,
- Figures 11 and 12 show another detail of the loop made at the ends of the three legs called "stabilizers".

 With reference, first of all to FIGS. 1 and 2, a filter in accordance with the prior art essentially consists of lugs 1, for example four in number, substantially deployed in a conical corolla, the opening of which has been marked in dotted in 2, its legs being from a common ogival head 3. The legs are terminated at their free ends by hooks 4.

 The installation of such a filter, inside a vein, is known and commonly practiced. Reference may be made, for example on this subject, to the description which was made in the above-mentioned patent application 84 14144.

 In Figure 2 we see the filter 5 which has been placed inside a vein 6, the direction of blood flow being indicated by the arrow 7. The filter, as often happens is placed with its axis B clearly skewed with respect to axis 9 of the vein, which does not allow the filter to work in the best conditions.

 Referring to Figures 4 to 6, we see that a filter modified according to the invention, identified as a whole by the reference 10 comprises two different types of lugs. In the example illustrated, the filter has six tabs 11 and three tabs 12 made of flexible medical-grade stainless steel and modular sections with diameters 0.20 - 0.25 - 0.30 - 0.35 depending on the surgical choice made. The legs 11 and 12 being from a cylindrical head at the hemispherical end 13, also made of stainless steel with medical characteristics, diametrically modular from 1.50 mm to 1.80 mm and length 5 min.

The six legs 11 are staggered lengths, terminated by small hooks sharpened three sides and slightly inverted as shown in the detail plan
G.

 The 3 legs 12 are also of staggered lengths, terminated by small polished loops folded over the tangency of the wire as shown in the detail plane H.

 More precisely, if we designate by 14 the opening perimeter of the corolla formed by the filter, and if we designate by 15 the cylinder generated by a generating line parallel to the axis 16 of the cone formed by the filter 10 and moving by describing the line 15, the tabs 12 are in non-traumatic support on the wall of the cylinder 15.

In other words, when the filter is in place in the vein 6, as illustrated in FIG. 5, the tabs 12, called "stabilizers" will be pressed while seeking their optimal support against the internal wall of the vein 6 by centering thus automatically the axis 16 of the filter 10 on the axis 9 of the vein 6. In fact the cylinder 15 and the vein 6 substantially coincide, the curve 15 ′ having been defined as the perimeter of the opening corolla of the filter in its normal position of use.

 The advantage of choosing legs 12 a little longer than the legs 11 will now appear with the help of the description of FIGS. 7 to 9 explaining the installation of the filter. In these figures, we find the vein 6 traversed by the bloodstream in the direction of the arrow 7.

 The installation of the filter is done through an introduction tube marked 20 designated in the "DESILET" technique. The filter 10 is pushed inside the tube 20 by a pusher 21.

 The particularity of the invention makes it possible to use a desilet with a much smaller diameter 7 F (FRENCH), ie a lumen with a diameter of 2.40 min, less traumatic during surgical intervention.

 It should be noted that the anterior filters are installed using a 10 F diameter mesh (FRENCH) and more, that is to say a lumen with a minimum diameter of 3.40 mm.

 In FIG. 7, the filter appears with its legs 12 already coming out of the tube still animated by their natural rotation. Note that the tube 20 is not parallel to the axis of the vein, as often happens. FIG. 8 indicates, an instant later when the filter is more extended, the tabs 11 still having their rear ends trapped inside the tube 20, continuing the pushing on the pusher 21. Each tab provided with hooks is released alternately and grips the internal wall of the vein which is substantially self-centering in the axis of said vein under the corolla effect deployed by the elasticity of the wires and their respective conformation.

 An instant later, all the legs will be released from the tube 20 which can be removed, and we will be in the position illustrated in FIGS. 5 and 6.

 Of course, the invention is in no way limited to the illustrated embodiments described, the number of legs being able to vary, as well for the "stabilizers" as for those provided with hooks, as well as their shape and nature.

 In general, the legs 11 and 12 may be of slightly different configuration.

 One end of the legs 12 called "stabilizer" can be provided with a "sensor" in the form of a small spring made of very flexible stainless steel wire illustrated according to FIG. 12. This appendix has the effect of allowing those skilled in the art to be able quickly, in addition to large clots, to systematically "trap" tiny particles of these so-called clots which embolize the venous circulation and to control their periodicity of migration.

Claims (9)

 1. - FILTER intended to be placed on the blood path, in particular on a venous path for the retention of blood clots and for the control of migration of their tiny particles, of the type formed by flexible legs, made of elastic threads, deployed substantially according to a conical and flared corolla coming from a cylindrical and hemispherical head, characterized in that certain legs at least aforementioned 12 are called "STABILIZERS" and have the effect of placing the filter in a position substantially parallel to the substantially cylindrical wall 15 generated by a generating line parallel to the axis 16 of the said flared corolla and describing as a guideline the opening perimeter 14 of the said corolla in an optimal position of use.  2. - FILTER according to claim (1), characterized in that the tabs provided with hooks 11 of stepped lengths alternately gripping the internal wall of the vein 15.  3. - FILTER according to claim (1) or claim (2), characterized in that it comprises at least six tabs 11 provided with the above hooks and distributed angularly around the aforementioned axis 16 of the filter.  4. - FILTER according to one of the preceding claims, characterized in that it comprises at least three tabs 12 devoid of said hooks "stabilizers" above and angularly distributed around the aforementioned axis 16 of the filter.  5. - FILTER according to one of the preceding claims, characterized with regard to the possibility of being able, if necessary, to adapt on the end of one of the legs 12 a "sensor" for controlling the periodic migration of tiny particles clots embolizing the venous circulation, illustrated in figure 12.  6. - FILTER according to one of the preceding claims, characterized by the possibility of modulating the filter by adapting it to legs of variable sections allowing it to be placed more sensitive by those skilled in the art according to the verifiable fragility of certain veins , without changing its configuration.  7. - FILTER according to one of the preceding claims, characterized by its adaptation and its implementation using a "fin" of smaller diameter 7 F (GATHERED) than the desilets used for the establishment of filters of this type.  8. - FILTER according to one of the preceding claims, characterized by its embodiment composed of six legs 11 and three legs 12 maintained at a circumferential spacing of 400 relative to each other, the aforementioned three 12 called "stabilizers".  9. - FILTER according to one of the preceding claims, characterized by its filtering power and controllable by the "sensor" and more particularly the flexible wires which constitute it are made of any elastically deformable material usually used for the manufacture of VASCULAR FILTERS and preferably medical grade stainless steel.