FR2567405A1 - Filter for medical use. - Google Patents

Abstract

The present invention relates to a filter for medical use as well as its method of implantation by the endovenous route. According to the invention, the filter 1 comprising means 2 for fastening the filter onto the internal wall 4 of the vein 5 and filtration means 3, is characterised in that the fastening means 2 and the filtration means 3 are separate and may be folded separately in order to occupy a small volume and to allow percutaneous introduction of the said filter 1 via a percutaneous introducer 14 of small size. This filter will find an application in the medical field and more particularly will be intended to be implanted by the endovenous route in the inferior vena cava.

Description

 The present invention relates to a filter for medical use as well as to its endovenous implantation method.

 The filter of the present invention is more particularly a clot filter in particular intended to be implanted endovenously in the inferior vena cava.

 Filters are currently known for preventing the migration of clots from the lower veins of the body, into the heart and pulmonary artery to avoid embolism in certain patients. These filters are implanted endovenously but require a surgical approach for their introduction.

Generally, we use a filter called "filter
Greenfield ". These filters have two essential necessities: a first function of fixing the filter in the vein and a second need for filtration of the blood retaining possible clots. Currently, these two functions are devolved to the same elements.

 Indeed, these filters are made of elastic son preformed in a zig-zag joined by a cap. These wires being arranged to form a cone, the apex of which is the cap, the so-called zigzag forming the envelope of the cone. The ends of the wires are provided with mooring hooks which are inserted into the internal wall of the vein.

 In this type of filter, the fixing means therefore consist of elastic threads capable of bearing on the internal wall of the vein and complemented by the penetration of the mooring hooks in said wall. The filtration function is carried out by the zig-zag formed on the elastic threads, these zig-zag forming a weaving in space and preventing the passage of clots.

The principle of implantation of these so-called filters
Greenfield consists in introducing a filter through a small vein such as the jugular vein or the femoral vein, to guide and lead this filter towards the inferior vena cava where it will be fixed in a stable way when opening. He can then assume his function. filter.

 For current filters, their diameter in the folded position being relatively large, of the order of a centimeter, it is necessary to use an introducer comprising a tube of large section in which the folded filter takes place.

 To make the tube of this introducer penetrate into a small vein such as the jugular vein it is necessary to make a relatively difficult and long surgical intervention.

It is compulsory to incise the skin and the vein in order to be able to place the introducer which will guide the filter to the inferior vena cava.

 Although the current systems used give good results, their major drawback lies in the fact that they require a surgical approach sometimes difficult to support by a patient subject to embolism.

 The object of the present invention is to present a filter for medical use and to its endovenous implantation process which does not require surgical intervention.

 The main object of the present invention is to provide a filter which makes it possible to simplify the positioning by using a method of intra-cutaneous introduction which is faster and less aggressive for the patient.

 Other objects and advantages of the present invention will emerge during the description which follows, which is given for information only and which is not intended to limit it.

 According to the present invention, the filter for medical use, in particular intended to be implanted endovenously into the inferior vena cava, comprising means for fixing the filter on the internal walls of the vein and means of filtration, is characterized by the fact that the fixing means and the filtration means are dissociated and foldable separately to occupy a small volume and allow the per-cutaneous introduction of said filter via a small per-cutaneous introducer.

 The filter of the present invention allows the implementation of the endovenous implantation process, consisting in introducing said filter, essentially comprising fixing means and filtration means, through a peripheral vein such as the jugular vein or the vein femoral, said method being characterized by the fact that said filter is introduced percutaneously.

 The invention will be better understood if reference is made to the description below and to the accompanying drawings which form an integral part thereof.

 FIG. 1 illustrates a preferred embodiment of the filter according to the present invention.

 FIG. 2 represents a filter according to the present invention placed inside a per-cutaneous introducer.

 FIG. 3 represents a filter produced according to the present invention positioned in the inferior vena cava.

On the one hand, to be able to introduce the filter by a method of intra-cutaneous introduction and on the other hand, for the filter to be effective, this filter must meet two imperative conditions
- it must have in the insertion position a relatively small diameter allowing its introduction into a peripheral vein via a small per-cutaneous introducer, and,
- it must have in final position a stable fixing device and an effective filtration device in the inferior vena cava.

 As shown in Figure 1, the filter 1 produced in a preferred manner, comprises means 2 for fixing the filter on the internal walls of the vein and means 3 for filtering the blood circulating in said vein. These different means 2 and 3 are produced and arranged in such a way that the filter is substantially in the form of a parachute.

 The fixing means 2 are elastic and are able to bear on the internal wall 4 of the vena cava 5 as illustrated in FIG. 3. They are essentially composed of elastic rods 6 and a cap 7.

Several elastic rods 6 converge towards the cap 7, forming a cone. The elastic rods 6 which are
more particularly in preferred embodiments 4 or 6 in number, are fixed in the cap 7. These elastic rods 6 in particular constituted by metallic wire are arranged such that they form the envelope of the cone and that in the normal position the base of this cone is a diameter greater than that of the inferior vena cava.

 These fastening means 2 are also foldable towards the inside of the cone, these by elasticity of the rods, so as to allow the formation of a much more acute cone whose base diameter is of the order of 2 at 5 mm.

In the different figures 1, 2 and 3, the diameter of the base of the cone in normal position is represented by D, the diameter of the base of the folded filter cane is represented by d and the internal diameter of the vena cava is represented by ss
The filtration means 3 consist of an element 8 which is flexible and permeable to blood flow. This element 8 is substantially in the form of a parabola at the edge of which the elastic rods 6 are fixed.

 These filtration means 3 can be constituted according to different embodiments by a flexible metallic grid, or by a synthetic or flexible plastic grid, or by a weaving of synthetic threads or by a non-degradable or possibly biodegradable textile fabric. This last characteristic being particularly interesting in the case of implantation of filter in a young subject, in fact, the disease being treated, the filter will be able to deteriorate to return a normal blood circulation.

 In the embodiment which has just been described, it is noted that the fixing means 2 and the filtration means 3 are dissociated and foldable separately to allow the introduction of said filter through the skin via an introducer. percutaneous of small dimension.

 As shown in Figure 2, the flexible element 8 and the elastic rods 6 are folded along the same axis and one behind the other to obtain a folded outer diameter d of dimension less than the diameter of the sheath 9 of introduction per-cutaneous. The longitudinal axis along which the element 8 and the rods 6 are folded is defined by the introduction of the filter 1 into the sheath 9; in fact, the longitudinal axis is parallel and coincides with the axis of said sheath 9.

 In order to be able to drive the filter 1 into its final position, the cap 7 supports, in addition to the elastic rods 6, a guide rod 10 capable of receiving the end of a stake 11 maneuvered from the outside 12, allowing the mobilization of the filter 1 in the introduction sheath 9. The support 11 at its end 13 has a housing in which the guide rod 10 is just inserted. The assembly of the rod 10 and the support 11 is carried out by respective friction of the two elements one on the other, the separation of these two elements being made when the filter 1 is fixed in the definitive position.

 The filter for medical use 1 which has just been described allows in particular the implementation of an endovenous implantation process and this by intra-cutaneous introduction.

 The main aim of the process is to place a filter, in particular intended to retain blood clots, in the inferior vena cava. introducing it through a peripheral vein such as the jugular or femoral vein.

The different stages of this process are as follows:
- the said peripheral vein is pricked with a needle and a metal guide is placed there,
- A per-cutaneous introducer 14 is introduced onto the metal guide, in particular consisting of a dilator and a sheath 9, the dilator serving to enlarge the orifice made with the needle so as to make it penetrate into the peripheral vein sheath 9 and --guide it inside the vein,
the percutaneous introducer is made to travel in said peripheral vein so that its terminal part opens into the vena cava where the filter is to be placed,
- the metal guide and the dilator are removed, the sheath 9 of the percutaneous introducer remaining in place and opening into the vena cava,
the fixing means 2 and the filtration means 3 of said filter 1 are folded back, separately to allow the introduction of the filter 1 into the sheath 9 of the percutaneous introducer 14,
the filter 1 thus folded is placed in the internal duct formed by the sheath 9, the diameter d of the folded filter being less than the internal diameter of the sheath 9,
- the filter 1 folded back in the sheath 9 of the introducer is made to travel into the vena cava, by means of the stake 11 operated from the outside 12, by pushing and sliding the filter in the sheath 9,
- The fastening means 2 and filtration 3 of said filter 1 are released to place the filter in the vena cava in the filtration position, this is achieved by pushing the filter 1 out of the end part of the sheath 9 opening into the vein cellar,
- the sheath 9 is then removed.

 FIG. 2 represents the filter 1 placed in a percutaneous introducer 14 allowing the implantation process described above.

Indeed, the sheath 9 of the introducer 14 is placed in a peripheral vein 15, inside the sheath 9 is folded the filter 1, the support 11 rests on the guide rod 10 of the filter which allows the filter to travel to its final position by working it from the outside.

 FIG. 3 represents the filter 1 placed in the filtration position in the lower vena cava 5. The fixing means 2 in particular constituted by the flexible rods 6 are such that when the filter is pushed out of the introduction sheath 9 they resume naturally their starting position coming to bear on the internal wall 4 of the vein 5, in fact, the constitution of the filter 1 deployed is such that the diameter D is greater than the internal diameter of the vena cava 5. The forces created by these elastic rods 6 are sufficient to cause a slight ovoid deformation 16 of the vena cava 5 as shown in FIG. 3.

 It should be noted that in the pre ferential embodiment, the ends 17 of the flexible rods 6 are sharp. In this way, they can penetrate slightly into the internal wall 4 of the vena cava 5.

 In addition, when the filter 1 unfolds in the use position, the filtration means 3 secured to the ends 17 of the flexible rods 6 are deployed. As a result, the filtration means 3 cooperate with the fixing means 2 to hold the filter 1 in position in the vena cava 5. In fact, the flow of blood circulating in the vein 5 creates forces which are applied to the cap 8 of filter 1 and which tend to penetrate the sharp ends 17 into the wall 4 of the vena cava 5.

 The embodiment which has just been described is given for information only, and other implementations of the present invention, within the reach of ordinary skill in the art, could be adopted without however get out of it.

Claims (8)

 1. Filter for medical use (1), in particular intended to be implanted endovenously into the inferior vena cava (5), comprising means for fixing (2) the filter to the internal wall (4) of the vein ( 5) and filtration means (3), characterized in that the fixing means (2) and the filtration means (3) are separate and foldable separately to occupy a small volume and allow percutaneous introduction of said filter ( 1) by means of a small percutaneous introducer (14).  2. A filter for medical use according to claim 1, characterized in that it has elastic fixing means (2) able to bear on the internal wall (4) of the vena cava (5).  3. Filter for medical use according to claims 1 and 2, characterized in that it comprises filtration means (3) essentially composed of a flexible element (8), permeable, at the edge of which are fixed the fixing means elastic (2).  4. Filter for medical use according to claims 1 and 3, characterized in that the flexible element (8) and the elastic fixing means (2) are folded along a longitudinal axis, defined by the introduction of the filter (1 ) in the sheath (9), one behind the other to obtain an outer diameter (d) folded with a dimension smaller than the diameter of said introduction sheath (9).  5. Filter for medical use according to claim 3, characterized in that it comprises a cap (7) which supports elastic rods (6) and a guide rod (10) capable of receiving the end of a stake (11), operated from the outside (12), allowing the mobilization of the filter (1) in the insertion sheath (9) to drive the filter (1) in its final position.  6. Filter for medical use according to claim 1, charac ters by the fact that the filtration means (3) consist of a flexible metallic or plastic grid, or a weaving of synthetic son, or a textile fabric non-degradable, or a bio-degradable textile fabric.  7. Filter according to claims 1 and 3, characterized in that the fixing means (2) consist of flexible elastic metal son whose ends (17) are sharp.  8. Filter for medical use according to claims 1 and 7, characterized in that the filtration means (3) cooperate with the fixing means (2) to hold the filter (1) in position in the vena cava (5) , the flow of blood circulating in the vein (5) creating forces applied to the filter tending to penetrate the sharp ends (17) in the wall (4) of the vena cava (5).