FR2814670A1 - Implantable blood clot filter has catheter of varying rigidity along its length and constant for at least half its length from distal end - Google Patents

Abstract

The implant consists of a catheter (3) with a wall (11) extending between its distal and proximal ends, and a blood filter with radial fingers (9) attached to its distal end. The catheter has a rigidity that varies along its length, being more rigid towards its distal end than its proximal end, and having a constant rigidity for over half its length measured from its proximal end, produced by stiffening elements (21, 23). The rigidity of the catheter wall is between 50 and 60 Shore D.

Description

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The invention relates to a device implantable in the body of a patient, up to a vessel, for retaining possible blood clots, the device comprising: - a catheter having an axis and a length (L) in the direction of this axis, with a proximal end and a distal end, - a blood filter placed at the distal end of the catheter and fixed to it, - the catheter being variably stiffened along its length, to be stiffer towards its distal end than towards its proximal end.

 The preferred field is that of vascular diseases where there are risks of thrombosis.

 TRI is particularly known, for certain vascular conditions, to use temporary blood filters in which the vascular filter is placed at the end of a catheter, or equivalent (operating rod remote from the filter, from outside the body of the patient, allowing in particular the removal of the filter at the end of the treatment period).

 US-A-5,484,424 (or its European correspondent EP-B-598,635) describes such a temporary blood filter whose catheter (or more generally the elongated maneuvering element) is of variable rigidity.

 This variable rigidity of the filter operating "catheter" is beneficial.

 The manner of obtaining this variable rigidity can however be further improved.

 In this regard, the patient's safety must be taken into account, with regard to the risks of migration of the filter into the vessel, of inappropriate rigidity on a proximal part inducing either a tendency for the catheter to wrap itself. , or a "tunneling" effect in the event that the proximal end of the catheter is housed under the skin with a locating element.

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A desired aim is also to limit the risks of the catheter bending towards its distal end, while promoting the centering of the filter with respect to the axis of the vessel, without the increase in rigidity reaching the area of the heart ( preferably).

- et que le cathéter soit par contre raidi vers son extrémité distale en étant ainsi sollicité pour y occuper une position essentiellement rectiligne, ceci sur une longueur de raidissement (f) contenue dans la longueur restante du cathéter, cette longueur de raidissement étant supérieure ou égale à environ 4 cm et inférieure à 30 cm environ. To avoid the drawbacks mentioned and to tend towards the objectives set, the invention proposes in particular: - that the rigidity of the catheter is considered to be constant over more than half of its length (L) measured from its proximal end,

- and that the catheter is on the other hand stiffened towards its distal end while being thus urged to occupy an essentially rectilinear position there, this over a length of stiffening (f) contained in the remaining length of the catheter, this length of stiffening being greater than or equal about 4 cm and less than about 30 cm.

 Concentrating the variation in rigidity over a limited length in the environment of the distal end thus makes this type of device even more reliable. And the effects of anti-kinking and centering of the catheter substantially in the axis of the vessel are all the more favored as the stiffening length of said catheter is between approximately 80 mm and 160 mm, this starting from the end distal of the latter.

 Quite particularly to prevent the catheter from rolling up on itself, and more generally a possible lack of rigidity on the distal side, another characteristic of the invention recommends that: - for stiffening over its stiffening length, the catheter be provided with stiffening means reported naturally rectilinear, - and the rigidity of its wall is essentially identical everywhere and between about 50 and 60 Shores D.

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To constitute these "added stiffening means", it is possible in particular to equip the catheter with a mandrel threaded into the internal conduit of the catheter.

 To act in stiffening of the catheter only from a certain curvature effect of the latter (distal side), an additional characteristic also advises that the stiffening mandrel of the catheter has, over at least part of its length (preferably where it is most deeply engaged in the conduit) a section smaller than the section of the internal conduit of this catheter.

 To further take into account the advantage of progressiveness in the variation of the force at the location of the transition between the stiffened zone and the whole non-stiffened part of the catheter, yet another characteristic of the invention recommends that the stiffening means are tapered, their section (transverse to the axis of the catheter) narrowing as one moves away from the distal end of the catheter in the direction of its proximal end. This has a beneficial effect on anti-wrinkling.

 A more detailed description of the invention will now be provided, in conjunction with the accompanying drawings.

- la figure 3 montre une alternative de réalisation du système de raidissage distal du cathéter, dans un état désassemblé des éléments, - et la figure 4 montre la solution de la figure 3 dans un état assemblé. In these drawings: - Figure 1 shows a temporary filter as a whole, - Figure 2 shows the detail marked II in Figure 1,

- Figure 3 shows an alternative embodiment of the distal stiffening system of the catheter, in a disassembled state of the elements, - and Figure 4 shows the solution of Figure 3 in an assembled state.

 In the figures, and in particular in FIG. 1, a blood filter 1 is fixed to the distal end 3a of a catheter 3. This catheter, like the device as a whole, has a longitudinal axis 5 and, along this axis, a length (L) which can be of the order of 1 meter to 1.40 meters. Thus, the practitioner can implant, maneuver or remove the filter in a vessel

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éloigné de l'ouverture transcutanée d'accès qu'il a pratiquée pour pénétrer dans le corps du patient et guider le filtre, au bout de son cathéter, jusqu'à la zone vasculaire prévue pour l'implantation du filtre.

distant from the transcutaneous access opening which it made to penetrate the patient's body and guide the filter, at the end of its catheter, to the vascular zone provided for implantation of the filter.

 The catheter illustrated, compared to a flexible vascular implantable rod (wire guide type), has here the advantage of an internal conduit 6 (Figures 2 to 4), usable for injecting such or such product. However, the more accurate term for catheter is axially elongated means of maneuver away from the filter.

 In its design, such a blood filter / catheter assembly (or equivalent) is already described for example in US-A-5,484,424.

 It will only be recalled that the filter 1 is a typically metallic structure, radially expandable. It comprises a head 7 / 9a linked to the catheter and from which extend legs 9. In their naturally radially expanded position in FIG. 1, these legs define a generally conical corolla of axis 5, the base of which more small section is made up of zone 9a. In the radially tightened (constraint) position, the tabs 9 extend substantially parallel to the axis 5.

de cette paroi, et donc du cathéter en lui-même, peut être dans l'invention considérée comme constante sur plus de la moitié de la longueur (L), à partir de l'extrémité libre proximale 3b du cathéter. Even though the wall 11 of the catheter is locally surrounded by two radiopaque locating rings 13, 15, the intrinsic rigidity

of this wall, and therefore of the catheter itself, can be in the invention considered to be constant over more than half the length (L), from the proximal free end 3b of the catheter.

It should be noted that at this end, provision may be made to fix an implantable chamber (commonly called "access port") or a subcutaneous locating element (as for example described in US-A-5,300,086) to the catheter.
On the remaining length (length 1! 1 in FIG. 2 and 1! 2 in FIG. 4), the catheter 3 is mechanically stiffened so as to be urged to occupy there an essentially rectilinear position favorable to a (self)

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centrage du filtre dans le vaisseau et à un effet antiplicature dans la zone 17 (figures 2) ou 19 (figure 4), c'est-à-dire globalement dans l'environnement de la jonction filtre/cathéter.

centering of the filter in the vessel and an antiplication effect in zone 17 (FIGS. 2) or 19 (FIG. 4), that is to say globally in the environment of the filter / catheter junction.

 In practice, this stiffening length (Ê 1) or (Ê 2) is between approximately 4% of length L and less than L12 for a catheter of approximately 1200 mm long, and is, in any case, between 40 mm and 300 mm.

 It has been noted that beneficial effects, for a limited cost price and practically no appreciable negative effect on the behavior of the catheter at its proximal end and on its remaining length not stiffened (problem of winding, of unexpected migration of the end catheter) are obtained by selecting the stiffening length (1 1) or (e 2) between approximately 8% and 14% of the length L of the catheter, this starting from the distal end 3a of the latter, always for a catheter of about 1200 mm long, with a fixed limit anyway then (to a few centimeters) between 80 mm and 180 mm, since it was found that a "peak" of efficiency was obtained in this range, combining a real buffering effect on the stiffness of the catheter with an (axial) damping of the axial forces on the filter, without the catheter twisting in the vena cava, nor that the stiffening of the catheter goes up in the heart.

 This is all the more true if the stiffening along 1! 1 or 1! 2 is obtained by means of a stiffening means reported naturally rectilinear, such as in particular the mandrel identified, as a whole 23 in FIG. 4, and if the rigidity of the wall 11 (identical everywhere, except for the negligible effect of the rings 13 and 15) is such that: - the hardness of the wall 11 is between approximately 40 and 80 Shores D, and is preferably equal to 55 Shores D 5.

 the thickness ep of the wall 11 (assumed to be constant everywhere) is between approximately 0.2 mm and 1.4 mm,

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- et le diamètre extérieur (pe (également supposé comme égal sur la grande majorité de la longueur du cathéter, hormis localement dans l'environnement immédiat de l'extrémité distale 3a, voire très localement à l'endroit des anneaux 13,15), est compris entre environ 1,3 mm et 3,3 mm.

- and the outside diameter (pe (also assumed to be equal over the vast majority of the length of the catheter, except locally in the immediate environment of the distal end 3a, or even very locally at the location of the rings 13,15), is between about 1.3 mm and 3.3 mm.

 This is of course linked to the preferred location for implantation of the device, namely the vena cava.

 FEP (fluoroethylene-polypropylene) or polypropylene is a particularly suitable choice of material for the catheter.

vaisseau. H assure la fixation mécanique entre le cathéter et le filtre 1. In Figure 2, the mandrel 21 of length 1! 1 is metallic (stainless steel, even titanium) and is not supposed to bend or bend in the

vessel. H provides mechanical fixation between the catheter and the filter 1.

 This mandrel 21 is frustoconical at its base, close to the filter (zone 25) then notched in the zone 27 which engages most deeply inside the conduit 6 of the catheter.

 An axial cavity 29, blind, receives a pin 31. The pin 31 comprises an enlarged base 33 and a barrel 35. It is the barrel 35 which enters the cavity 29, after having passed through an opening 37 formed where the legs 9 of the filter are joined together (meeting cone 9a).

 In FIG. 3, we can see in particular the tabs 9, the spindle 31 and the mandrel 21 (here called "elongated tip") in their disjoint state, while they are shown in their assembled state of fixing in FIG. 4. The cone 9a for joining the legs, the pin 31 and the enlarged base 21 ′ of the “mandrel” 21 in practice define the head 7 of the filter.

 While the mandrel 21 of Figure 2 is exclusively constituted in the manner presented above, and therefore closely engaged along its entire length inside the conduit 6 of the catheter from its distal end, and that moreover this catheter is type 7F (external diameter 2.31 mm and thickness 1.2 mm), the mandrel 23 of FIGS. 3 and 4 is constituted by the elongated end piece 21 (of shorter length) extended axially by a tapered stiffening rod of smaller diameter, 39, and appeared as

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favorable pour un cathéter de type 6F (épaisseur 0, 9 mm et diamètre extérieur 2 mm),
A noter également qu'il s'est avéré très approprié de prévoir une longueur (Ê 1) de l'ordre de 75 mm à 95 mmm pour le mandrin 21 de la figure 2, tandis que dans le cas des figures 3 et 4, il est apparu favorable que l'embout allongé 21 présente une longueur nettement inférieure à celle du mandrin 21 de la figure 2 (3 à 4 mm), tandis que le raidisseur 39 présente une longueur de l'ordre de 70 mm à 160 mm.

favorable for a type 6F catheter (thickness 0.9 mm and external diameter 2 mm),
Note also that it has proved very appropriate to provide a length (Ê 1) of the order of 75 mm to 95 mmm for the mandrel 21 of FIG. 2, while in the case of FIGS. 3 and 4, it appeared favorable that the elongated end piece 21 has a length considerably shorter than that of the mandrel 21 of FIG. 2 (3 to 4 mm), while the stiffener 39 has a length of the order of 70 mm to 160 mm.

 This stiffening rod 39 is tapered and its diameter is always less than the diameter (pi of the conduit 6, so that in the naturally rectilinear state of the catheter (as for example in FIG. 4), the rod 39 does not come into contact with the wall of the catheter: it is only in the event of sufficient curvature of the latter which risks creating kinking or biasing (offset) of the filter, that the rod 39 acts on the catheter to straighten the terminal part distal.

 The rod 39 may be metallic. It is fixed in an axial recess 41 of the end piece 21. As can be seen, and to best fulfill its function, its section decreases towards the proximal end of the catheter.

 As has already been noted, it is important that the stiffening means are rectilinear, so as to obtain in particular the desired effects of antiplicature and self-alignment of the filter in the general axis 5 of the device. If the catheter and its stiffening means are not urged towards a rectilinear state and do not remain essentially coaxial, the aimed goals are not achieved.

 Note, however, that instead of the illustrated stiffening means, one could have considered using a covering membrane having a stiffness greater than that of the catheter wall and doubling (in particular internally) its wall (around its conduit 6, in the way

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 of a scabbard) over a length which could be comparable to the length l2.

 If such a covering membrane is used, the mandrel (or elongated tip) 21 advantageously has an axial internal conduit for delivering a treating product through the catheter and the filter head (or drawing blood).

 The rigidity of this membrane, or lining, will preferably be greater than that of the wall of the catheter.

Claims (9)

 1. Device implantable in the body of a patient, up to a vessel, to retain possible blood clots therein, the device comprising: - a catheter (3) having an axis (5) and a length (L) in the direction of this axis, with a proximal end (3b), a distal end (3a), and a wall (11) between these ends, - a blood filter (1) placed at the distal end of the catheter and linked to it ,

 - the catheter being stiffened variably over its length, to be stiffer towards its distal end than towards its proximal end, characterized in that:

 - the rigidity of the catheter (3) is considered constant over more than half of its length (L) measured from its proximal end (3b), - and the catheter is on the other hand stiffened towards its distal end (3a) in thus being urged to occupy an essentially rectilinear position there, this over a stiffening length (1, 2) contained in the remaining length of the catheter, this stiffening length being greater than or equal to approximately 40 mm and less than approximately 300 mm.  2. Device according to claim 1, characterized in that the stiffening length is between approximately 80 mm and 180 mm, from the distal end (3a) of the latter.  3. Device according to claim 1 or claim 2, characterized in that: - for stiffening over its stiffening length (t 1, 1! 2), the catheter is provided with stiffening means reported naturally rectilinear (21,23 ) <Desc / Clms Page number 10>  - and the rigidity of its wall (11) is essentially identical everywhere and between approximately 50 and 60 Shores D.

 4. Device according to any one of the preceding claims, characterized in that the catheter is stiffened by lining its wall, over its stiffening length, by a lining membrane.  5. Device according to any one of claims 1 to 3, characterized in that: - the catheter has an axial internal duct (6), - over its stiffening length, the catheter is stiffened by adding an internal mandrel ( 21,23) in its axial duct.  6. Device according to claim 5, characterized in that the stiffening mandrel comprises, from the distal end (3a) of the catheter: - a first part (21) tightly engaged in the internal conduit of the catheter and directly fixed to the filter , - and a second part (39) fixed to the first part, at a distance from the distal end of the catheter, and whose cross section at the axis of the catheter is less than the cross section of the internal conduit of the catheter.  7. Device according to claim 5, characterized in that the mandrel (23,39) for stiffening the catheter (3) has, over at least part of its length, parallel to the axis of the catheter, a cross section at l axis of said catheter lower than the section of the internal conduit (6) of this catheter.  8. Device according to any one of claims 3 to 7, characterized in that the stiffening means (23,39) are tapered, over at least part of their length, parallel to the axis of the catheter, their cross section to the axis of the catheter narrowing while moving away from the distal end of the catheter (3) towards its proximal end. <Desc / Clms Page number 11>

9. Device according to claim 1, characterized in that: - the stiffening length of the catheter (3) is between approximately 80 mm and 180 mm, counting from the distal end (3a) of the latter, - the rigidity of the wall (11) of the catheter is essentially identical everywhere and between approximately 50 and 60 Shores D, - the catheter has an axial internal duct (6), - for its stiffening over said stiffening length (2), the catheter is provided with an internal mandrel (23) disposed in its axial duct, and - the catheter stiffening mandrel (23) has, over at least part of its length, parallel to the axis of the catheter, a section transverse to the axis of said catheter less than the section of the internal conduit (6) of this catheter.