FR2764503A1 - Blood filter implant - Google Patents

Abstract

The filter, designed to be implanted temporarily in a blood vessel to trap blood clots and to be withdrawn afterwards, has a series of legs (112) which radiate from a central axis (xx) when implanted, at least one of which is a source of radioactivity. A variant of the design has a radiation emitter connected to a radioactive source. At least some of the filter's radial legs have outer thrust elements (115) which make contact with the wall of the blood vessel, and the radioactive source can be located on the periphery of a thrust element, while its half life is equivalent to the time for which the filter is implanted.

Description

 The field of the invention is that of devices or units for blood filtration that can be implanted inside a blood vessel to block clots therein.

 In particular, the invention relates to temporary blood filtration units, that is to say that one can remove after a certain period of implantation in the human body.

These filtration units, also more commonly called "blood filters", can be classified essentially in two categories:
The first is that of filters intended to be permanently implanted in patients for whom the risks of embolism are chronic. This type of filter commonly comprises a metal structure of frustoconical shape in its deployed state in the vessel to be treated, comprising a series of branches (or legs) connected to a common head and terminated by hooks allowing the final fixing of the filter to the wall of the vessel.

 The second category is that of filters intended to be temporarily implanted in a patient's vessel for which the risk of migration to the heart of blood clots exists only for a brief period, generally from a few days to a few weeks. This type of filter differs from permanent filters essentially in that it does not have hooks (or other means) for fixing to the wall of the vessel. Thus, each leg simply comes to bear on the wall of the vessel with the aid of "peripheral support zones", without however clinging to it. These filters are also connected, for the duration of their implantation, to a support rod (typically a catheter) which has the essential role of preventing them from moving and which allows their removal at the end of the implantation period.

 However, the Applicant has noticed that an important cause bothers or prevents the removal of "temporary blood filtration units", in particular after a relatively long implantation period (a few weeks), existed due to cell proliferation. , generally increasing over time, where the unit is located. This cell proliferation would occur in particular in reaction to the presence of the unit ("rejection" reaction) and would then form an aggregate which "would trap" the filtration unit and retain it at the vessel wall. There is therefore a risk of damage to this wall (tearing) if the practitioner has to use excessive force to remove the unit. In addition, the cell aggregates can detach from the vessel wall, and in particular from the peripheral areas of support with the unit and either accumulate in the legs of the unit with clots already trapped (reducing then the blood flow), or cross said filter towards the heart.

 The main object of the invention under these conditions is to facilitate the removal of a blood filtration unit, in particular after a relatively long implantation period, by avoiding harmful cell proliferation.

 The solution of the present invention therefore consists of a device for blood filtration comprising a blood filtration unit implantable in a vessel for retaining clots therein when it is implanted therein, and withdrawable from it after implantation, said unit being provided with a series of legs capable of occupying a radially implanted state deployed around a main axis while then presenting between them a filtration zone, characterized in that at least part of said legs comprises, or is, a source of radioactive emission. In other words, a portion (at least) of the filtration unit will emit radioactive radiation capable of destroying, or damaging, living cells in its immediate environment.

 The expression "at least part of said legs" is understood to mean a certain number of them, or even all of them, as well as a portion or the whole of at least one leg. The radiation thus created will reduce or suppress cell proliferation around the legs concerned. Thus, the legs are no longer trapped under a layer of cells which bind them to the wall of the vessel, the blood filtration unit can be removed more easily after implantation, even after several weeks. In addition, as cell proliferation is reduced or even suppressed, there will no longer be a risk that these portions of cell aggregates will become detached.

 Another solution of the present invention to the same problem consists in that, instead of the legs comprising (or being) a source of radioactive emission, said device comprises, as an alternative, irradiation means which are linked to a source of radioactive emission and can be implanted in the vessel so that they can be arranged substantially opposite the filtration unit, in its implanted state.

 In this way, the filtration unit, not irradiated, is implanted in a normal manner, and annexed means of irradiation are then used, that is to directly irradiate the unit (the annexed means being arranged facing this- (which then becomes a source of radioactive emission if the material used to make it allows), or to irradiate, in particular after a certain period of implantation of the unit, the immediate environment of the unit to destroy the cells that have accumulated around it.

 According to an additional consideration, at least some of said legs having at least one peripheral support zone intended to come substantially into contact with the wall of the vessel, the source of radioactive emission will preferably be located, or will preferably be adapted (case where the unit is installed non-irradiated) to be located, substantially at the location of this peripheral leg support zone. Thus, it will be possible to limit the radioactive zone of the unit and to concentrate the effect of the irradiation thus produced where it is necessary.

According to an additional consideration, the source of radioactive emission will preferably be:
- Or located substantially on an inner part of the support zone which is directed towards the main axis, in the radially deployed state of its legs.

 - Is adapted to be located substantially on an inner part of the support zone which is directed towards the main axis, in the radially deployed state of its legs and while the filtration unit is installed.

 Thus, the zone of direct contact between the wall of the vessel and the support zone of the filtration unit not being irradiated1 there is no risk of destruction of the a priori healthy cells from said wall to the location of the unit. The radioactive emission will therefore be concentrated in the areas of the filtration unit where proliferation most hinders its removal.

 According to yet another consideration, the source of radioactive emission from the blood filtration unit will preferably deliver radioactivity, the half-life of which will be substantially equal to the duration of implantation of said unit, this in order to limit the risks of contamination of the practitioner. when removing the filter and avoiding having too much radioactive waste (which at the same time makes it possible to avoid having to use overly large and costly containment devices and to set up overly restrictive sanitary conditions ). Preferably, the half life will be equal to the duration of implantation to within plus or minus 30%, with a maximum half life limited to one week beyond the withdrawal of the unit.

 The invention also relates to a method for producing in particular such a blood filtration unit. According to this method, after having shaped said blood filtration unit with its legs, it is preferable to irradiate at least a part of said legs, so that these themselves become a source of radioactive emission.

 According to an alternative, a source of radioactive emission will be reported on at least part of said legs.

 Preferably, the unit will be irradiated before implantation, but it is entirely possible to irradiate it once implanted.

 In the case where the unit is installed when it already constitutes a source of radioactive emission, the step of shaping the unit and the step of making it at least locally radioactive being dissociated, this is an additional guarantee of security for those responsible for complying with it. In addition, irradiating or bringing back a small quantity of radioactive material (for example using a welded sleeve or by covering the relevant part of the legs) is less expensive than if the unit had to be produced directly in radioactive material. .

 In the case where the unit is implanted non-irradiated, it is possible in particular to use additional irradiation means such as those described in patent US-A-5,484,384 and comprising in particular a catheter for irradiating the unit and / or irradiate the proliferating cells thereon. The first advantage of this solution is that it does not require the use of significant confinement means since the filter is shaped and implanted while it is not irradiated. The practitioner and his entourage are therefore protected during implantation. In addition, this prevents the filtration unit from starting to act on a priori healthy cells of the vessel wall. Finally, irradiation can possibly be carried out at any time after implantation of the unit.

According to an additional consideration:
- In particular, it will be possible to irradiate the unit, or bring back the source of radioactive emission, at the location of the peripheral support zone of its legs, at least in the interior part of this zone.

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 represents a temporary blood filtration unit of the prior art implanted inside a vessel,
FIG. 2 represents a blood filtration unit according to the present invention, also in its implanted state,
FIG. 3 shows a detail of the free end of a tab of the filtration unit according to the present invention, and
- Figure 4 illustrates another embodiment of a filtration unit according to the invention.

 Figure 1 shows a blood vessel (C) in a patient's body, typically the inferior vena cava leading to the heart. The direction of blood flow is represented by the arrow (F) directed from upstream (AM) downstream (AV), that is to say towards the heart (not shown). A temporary blood filtration unit 10, of the type used in the prior art, is shown. This is in its deployed state in the shape of a corolla around an axis 20 and is located inside the vessel (C), to block, between a series of legs 12 (or branches) connected to a common head 13 , possible blood clots or cellular aggregates transported by the blood towards the heart. The legs 12 each terminate in an end portion 15 which is free to bear, preferably not capable of damaging the wall (P) of the vessel (C) by piercing or tearing away tissue. This unit 10 is also connected, for the entire duration of its implantation, to a support rod 17.

 As can be seen, the free end portions 15 of the legs 12 are covered with cell aggregate (A), said cells proliferating from the wall (P) of the vessel (C) in the direction of the interior thereof. This cell proliferation (A) can increase throughout the duration of implantation of the unit. This is considered to be a problem with the removal of the filter from the vessel.

 Figures 2 to 4 show several preferred solutions of the present invention, and in particular the advantages it provides over the temporary blood filtration units proposed so far.

 A unit 110 for temporary blood filtration of axis xx ′, substantially of the type of that described in FIG. 1, is shown in FIG. 2. This unit 110 comprises a series of flexible metal legs 112 (for example six), of first substantially threadlike on a portion 112a and devoid of means for fixing to the wall (P) of the vessel (C), then each ending in a free end portion 115, preferably substantially in the form of a plate with rounded ends. The legs 112 are connected together (opposite to the part 115), for example by a common axial head 113. This unit 110 is further here here connected, for the entire duration of its implantation, to a flexible support rod 117 which has the essential role of preventing it from moving during implantation and which allows its removal at the end of the implantation period. Said rod 117 extends along one or more vessels (when the blood filtration unit 110 is implanted by the endoluminal route in the body of a patient at the chosen location), and exits from the body of the patient by a transcutaneous access route. Thus, the practitioner can advance, position and then remove the filtration unit 110 from outside the patient's body, using the rod 117 (or catheter) which remains integral with said unit 110 during all these steps.

 It can be seen that the unit 110 can be installed in the same way as in the prior art. Indeed, the portions 112a of the legs 112 define here, in their radially deployed unstressed state, substantially a cone (or a corolla) of axis xx ', and extend towards the base of greater diameter of said cone than the portions 112a delimit, by a substantially cylindrical zone also of axis xx 'defined by the free end parts 115.

For the implantation of the unit 110, the legs 112 are typically radially tightened and the unit 110 is introduced (at the end of its flexible extension 117) into the vessel (C), inside a sheath (typically an external catheter) for introduction, not shown (in particular by the so-called "SELDINGER" technique).

 Once released, the legs 112 of the unit 110 therefore deploy by themselves radially by withdrawal of the sheath and the free end portions 115 (devoid of means for fixing to the wall (P) of the vessel (C) of so as not to oppose the withdrawal or the axial displacement of the unit 110) then simply come into contact with said wall (P) thereby defining "peripheral bearing zones" or "contact portions". The legs 112 thus deployed, and in particular the portions 112a, then define a "trap" (a sort of spider web) to block the passage of possible blood clots (or aggregates of other types of cells transported by blood) going to the heart.

 In addition to its main function which is to filter the blood, at least part of the legs 112 comprises, or is, a source of radioactive emission. This radioactive source can be constituted by, or attached to, the entire length of one or more tab (s) 112 (filiform central portion 112a of main filtration and free end portion 115), but is preferably constituted by, or attached to, the peripheral bearing zones between said legs and the wall of the vessel in the implanted position of the filtration unit, also called "contact portions". In this case, these "radioactive" zones are constituted by the free end portion 115 of each of the legs 112 (see FIG. 3), and preferably by the interior part 116 of the support zone 115 (more precisely on its surface outer peripheral or on a small thickness of that i) directed towards the main axis xx ′, that is to say towards the interior of the vessel.

 Two methods of producing a blood filtration unit 110 in accordance with the invention are however particularly possible.

 According to a first method, once the unit 110 is conformed with its legs 112, and before implantation, it is irradiated on the portion (s) of chosen leg (s) (115 in this case) by any means (for example by direct irradiation by radiation), and with any type of suitable radioactive source (cobalt for example). We will choose a material which, once irradiated, becomes itself a source of radioactive emission.

 According to another method, a radioactive source can be added to at least part of the legs 112 of the unit 110, for example by covering the portion (s) of the selected leg (s) (116 in l 'occurrence) with a radioactive material, or by attaching an outer perimeter sleeve made of a radioactive material (irradiated metal or intrinsically radioactive material).

 In these two preferred embodiments, the unit 110 thus irradiated is then enclosed in a confinement means, such as a lead box the thickness of which will be compatible with the radioactivity delivered by said unit 110, until time of its implementation.

 The blood filtration unit 110, once irradiated (or comprising a radioactive source), is then implanted in the blood vessel (C) to be treated by a known method, typically by endoluminal percutaneous route, or by stripping, and takes the position illustrated by figure 2.

 In the two embodiments presented, the irradiated portion of the legs 112 (in this case the part 116) therefore acts as a source of radioactive emission. This radioactive emission source preferably has a radioactivity whose half-life is substantially equal to the duration of implantation of said unit 110 at more or less 30% and this in order not to generate radioactive waste that is too dangerous and difficult to clear after unit 110 is removed. The doses of radiation emitted by the unit 110 will preferably not be too strong but sufficient to suppress, or more probably prevent, cell proliferation on the legs 112.

 Over a few millimeters deep (or even less), around the radioactive portions of the unit 110 (parts 116), the radioactivity emitted by them a priori destroys cell proliferation by killing said cells.

Thus, the cell proliferation in question is reduced or nonexistent on the support zone of the legs 112, in particular on the part 116 directed towards the interior of the vessel (C) of the free end parts 115. The invention therefore makes it possible to provide a number of advantages already mentioned, and in particular it facilitates the removal of the unit 110 and potentially increases the duration of implantation of the unit 110 in the patient's body.

 According to another preferred solution of the invention illustrated in FIG. 4, a “traditional” blood filtration unit 110 is implanted which emits no radioactivity. Once implanted in the vessel at the chosen location, use is made of irradiation means 120 connected to a source of radioactive emission (not shown) which is placed inside the conduit opposite the unit 110. , preferably between the corolla defined by its extended legs. For this, one introduces, preferably by the endoluminal route, for example a catheter 120 connected to an external radioactive source. The unit can for this purpose have an axial passage (orifice) in its head 113.

 The radioactive emission thus produced by the irradiation means 120 will irradiate the environment close to the unit, and in particular at least the internal part 116 of its support zone 115. In this case, the unit which can itself becoming a source of radioactive emission if its constituent material allows it, acts as described above.

 Also, these irradiation means 120 can be used to irradiate part of the vessel wall, in particular if cell proliferation has already started in reaction to the implantation of the unit. The practitioner can thus wait for the right moment to irradiate before removing the unit, and in particular by checking, for example by radiography, the state of cell proliferation on the support zones of this. In this case, the practitioner can wait until a certain "thickness" of cell has been created around the unit 110 (in particular parts 116) to start irradiating.

The removal of the unit 110 will be facilitated in the same way as previously by destruction of the cellular aggregates.

 Of course, the invention is in no way limited to the preferred embodiment described here. Any filter designed to be removable from a vessel after being implanted in it is suitable.

Thus, in particular, the blood filtration unit 110 could be of the “temporary / permanent” type such as that described in the US patent.
A4 990 156, in which case only the legs of the part of the unit intended to be
deployed and active, outside the introductory sheath, during the
"temporary establishment" period, will include, or be, an area
irradiated.

Claims (8)

Claims  1. Device for blood filtration comprising a blood filtration unit (110) implantable in a vessel (C) for retaining clots therein when it is implanted therein, and removable from it after implantation, said unit (110) being provided with a series of legs (112) suitable for occupying a radially implanted state deployed around a main axis (xx ') while then presenting between them a filtration zone, characterized in that at least part of said legs (112) includes, or is, a source of radioactive emission.  2. Device for blood filtration comprising a blood filtration unit (110) implantable in a vessel (C) for retaining clots therein when it is implanted therein, and withdrawable from it after implantation, said unit (110) being provided with a series of legs (112) suitable for occupying a radially implanted state deployed around a main axis (xx ') while then presenting between them a filtration zone, characterized in that it also comprises means (120) of irradiation linked to a source of radioactive emission and implantable in said vessel (C) so as to be able to be arranged substantially opposite the filtration unit (110) in its implanted state.  3. Device according to claims 1 or 2, characterized in that, at least some of said tabs (112) having a peripheral support zone (115) intended to come substantially into contact with the wall (P) of the vessel (C) , the radioactive emission source is located, or adapted to be located, substantially at the location of this peripheral support zone (115) of the tabs (112).  4. Device according to claim 3, characterized in that the source of radioactive emission is:  - either located substantially on an inner part (116) of the support zone (115) directed towards the main axis (xx '), in the radially deployed state of the tabs (112),  - Is adapted to be located opposite an inner part (116) of the support zone (115) directed towards the main axis (xx '), in the radially deployed state of the legs (112) while the the filtration unit (110) is installed.  5. Device according to any one of the preceding claims, characterized in that the half-life of the radioactive emission source is substantially equal to the duration of implantation of said unit.  6. Method for producing a blood filtration unit (110) to be implanted in a vessel (C) for retaining clots therein when it is implanted therein, and for removing from said vessel (C) after implantation, the method comprising a step in which conforms said unit (110) so that it has an axis (xx ') and comprises tabs (112) suitable for occupying a radially constricted state or a state radially deployed around said axis (xx'), characterized in that that, after having shaped said blood filtration unit (110) with its legs (112), at least part of said legs (112) are irradiated, so that these themselves become a source of radioactive emission.  7. Method for producing a blood filtration unit (110) to be implanted in a blood vessel (C) to retain clots therein when it is implanted therein, and to remove from said vessel (C) after implantation, the method comprising a step in which said unit (110) is conformed so that it has an axis (xx ') and comprises tabs (112) suitable for occupying a radially constricted state or a radially deployed state around said axis (xx'), characterized in that, after having shaped said blood filtration unit (110) with its legs (112), and before implanting it in the vessel (C), a source is reported, on at least part of said legs (112), radioactive emission.  8. Method according to any one of claims 6 to 7, characterized in that,  - During the shaping step, the tabs (112) are produced so that, in their radially deployed state, at least some of said tabs have a peripheral support zone (115) designed to come substantially into contact with the wall (P) of the vessel (C), and  - The unit (110) is irradiated, or the source of radioactive emission is reported, at the location of said peripheral support zone (115) of its legs, at least in the interior part (116) of this zone.