FR2645731A1 - System for preventing pulmonary embolisms - Google Patents

Abstract

The system essentially comprises a novel filter made of elastic wire and designed in such a way as to present two quasi-elliptical loops E1 and E2 which are coplanar and have a rounded proximal end M1 and a pointed distal end M2, placed in the inferior vena cava 30 with the aid of a catheter KT cooperating with a push device P with end-piece E. This system is designed to reduce the risk of pulmonary embolisms by stopping any clots originating from the veins of the lower limbs and/or the small pelvis.

Description

The subject of the present invention is:
An anti-pulmonary embolism system.

 We already know different types, actually used, of filters intended to be put in place in the inferior vena cava in order to stop the migration, towards the right heart, of clots coming from the veins of the lower limbs or the small pelvis.

 We can, in particular, cite the filters known under the names of Driller, Mobin-Uddin, Greenfield and Gunther.

 All these types of filters have in common that they have quasi-revolution structures, cylindrical or conical, which must be folded in a sheath then pushed into the lumen of a catheter towards the implantation area. Their introducer sheath with a diameter greater than three millimeters requires large caliber veins such as the internal jugular vein or the femoral vein.

 Once in place in the inferior vena cava, these filters are then released from their sheath and their structures are deployed by moderately widening the section of the vena cava. They are bulky, difficult to put in place, and sometimes traumatic for the tissues of the vena cava in which they come to anchor in several points of attachment. The bad positions and migrations of these filters are not exceptional.

 Another filter, imagined according to a different inventive idea, was proposed by the French patent Franceschi N02541901.

according to this idea, the filter would be produced using an elastic wire shaped to present ae permanently successive undulations in different planes. We would then take advantage of the elasticity of this wire to put it by traction in rectilinear form and thus transport it to the implantation zone. Arrived in this zone, pushed out of the catheter and released from it, it would then resume its initial wavy shape and would come to rest at several points on the aforementioned different planes against the walls of the vena cava.

 However, this proposal could not be the subject of medically acceptable practical achievements.

 Then, the same inventive idea of departure was taken up in the French patent application filed on December 31, 1987 by the Company Biomat, under the NO 87-18 472, having for title "Elastic anti-embolic filtering system for vena cava and its set of means for its implementation ", and supplemented by a request for addition filed on June 15, 1988 under NO 8808031.

 According to these requests, the elastic filtering system is a flexible steel wire with a remanence effect, for example of chromecobalt, of 0.3mm in diameter and of variable length from 25 to 30 cm. Its geometric shape determines two loops in the form of ellipses of perpendicular and equal coplanar axes, giving four points of permanent contact with the wall of the vena cava in which it is implanted and where it acts as a filter.

The two free ends of this filter are different:
- The first, introduced into the catheter then the vena cava, and called "proximal end" by medical convention, is terminated by a 2 am tip preceded by a coaxial cylinder guiding it into the lumen of the catheter. It is inclined by 45 relative to the two loops of the filter.

 - The second end of the filter, called "distal end" by medical convention, ends in a cylinder 3.5 mm long, 0.6 mm in diameter. It is integral with the tip of the pusher during its journey in the catheter.

The elastic filtering system is completed by a set of means for its installation:
- a 7F catheter (1 French = 1F = 0.33 mm) 100 cm long and 1.45 mm internal diameter, radiopaque;
-a 160 cm flexible teflon-coated J guide;
- a pusher formed of a flexible, braided stainless steel wire, diameter 0.7 mm, length 120 cm, the proximal end of which is made of a rigid cylinder 10 mm long and 1.3 mm in diameter carrying a slot at its free end and a recess in its center def5 mm in length, intended to receive the distal end of the filter.

The drawbacks of this elastic filtering system and its installation accessories are threefold:
1 - difficulty in positioning and risk of catching the filter in the catheter then in the vena cava due to the arrangement of its two free ends, proximal and distal;
2 - Unsuitability of the pusher for the safe placement of the filter, in the catheter, then in the vena cava;
3 - Absence of an accessory tool, but essential, to introduce the distal end of the filter, secured to the end of the plunger, in the distal orifice of the catheter 7F.

It is useful to explain these drawbacks in more detail:
1 - Difficulty installing the filter.

The proximal end of the filter has a sharp point which first enters the lumen of the 7F catheter and then that of the vena cava. This increased point is intended to prick itself, as soon as it leaves the proximal end-ut # t of the catheter, in the wall of the vena cava. This sharp proximal end of the filter then presents two risks:
On the one hand, in the catheter lumen, it is not protected but simply centered by its cylindrical weight
successive 3.5 mm long coaxial.

 Although coaxial, this point can damage the wall of the catheter by friction or, in the event of too pronounced curvature of the catheter, prick into its wall and stop the progression of the entire filter system in the catheter.

 On the other hand, this sharp proximal end which comes to prick first in the wall of the vena cava determines a fixed point around which the whole of the flexible elastic flexible wire of the filter must return to its initial permanent shape in the lumen of the vein lower cellar.

 However, the fixed point is a major drawback because it counteracts the natural rotation of the wire on itself, and therefore its resumption in shape. It is therefore understood that two successive loops unwound on the same wire shaped in the same plane having the same direction of rotation are thwarted when they have to rewind in the lumen of the vein. The fixed point forces the wire to change its axis or plane in a conduit whose diameter is less than that of the loops of the filter. It makes the resumption in initial form of the filter very delicate.

 The immediate anchoring of the first released end can be the cause of incomplete recovery of shape in the vena cava, of bad position of the filter in the vena cava, of possible migration of the filter by absence of balance of the filter which is determined by its strong geometry, with four contact points on the venous wall.

 All this decreases the efficiency of the filter which is, like its good position, determined by its planar geometric shape in two ellipses flattening the venous lumen.

2 - The inadequacy of the pusher for fitting the filter into the catheter results from modifications of the ends of the filter according to the present invention and which will be explained below
3 - The "absence of an accessory tool" of installation.

 This third drawback of the "elastic filtering system and its means of implementation" consists in the impossibility of correctly introducing into the distal orifice of the 7F catheter the integral assembly formed by the tip of the pusher and the ex- distal filter half.

 The object of the present invention is to remedy all the drawbacks set out above.

 The invention stems from a systemic consideration of all the functional dimensions of the problem to be solved and of the goals to be achieved.

More specifically, the invention proposes to provide means which allow:
in terms of the very construction of the filter, to allow it, after it has been brought to the correct implantation zone and its release from the catheter, to be completely mechanically free to resume its permanent conformation designed to have, on the one hand, a position that is both correct and stable inside the vein and, on the other hand, a configuration optimally ensuring the filtering of blood flow in a flattened passage of the vein, and
b / in terms of the very design of the filter placement system, to have all the necessary and sufficient functional elements to carry out the medical placement of the filter with precision, speed and simplicity.

 The primary object of the present invention is therefore to propose a new conformation of the filter by modifying its two free ends.

 Its second purpose is to modify the rigid end piece of the pusher in which the sharp distal end of the filter fits.

 Its third purpose is to provide an essential accessory tool for introducing into the 7F catheter the integral assembly comprising the tip of the plunger and the distal end of the filter.

For these effects, the invention firstly relates to a pulmonary anti-embolism system, of the kind using a filter made of elastic wire shaped to have a general permanent shape of at least two substantially-coplanar quasi-elliptical loops and axes -perpendicular, being able to present momentarily in a rectilinear form to be able to be brought into a vena cava by pushing in a catheter, characterized in that it comprises:
a radiopaque proximal end of the filter produced in the form of a small cylinder with rounded end without roughness,
a radiopaque distal end of the filter produced in the form of a small cylinder terminated by a sharp point situated outside the planes of the two loops,
a pusher, of cylindrical shape to be able to be movable inside a catheter, and having in its end piece of the housings and longitudinal slots to receive respectively the unwound wire of the filter, then the cylinder of the ex distal end, and finally the distal sharp point, and
d / an introducer element of generally cylindroconical shape having an inner cylindrical channel of the same diameter as that of the catheter intended to receive the pusher assembled manually with the filter wire and the distal end and its sharp point and an extreme conical part to be able to s '' Engage in the larder orifice of the catheter.

The invention also relates to a method of medical implementation of such a system which successively comprises the following operations:
- a 7F catheter is percutaneously introduced into a peripheral vein
- this catheter is pushed under radioscopic control until the bifurcation of the inferior vena cava,
- the proximal end of the filter is manually inserted into the distal end of the catheter and the filter is unwound by pushing it inside the catheter until there is no more than the distal end near the orifice distal of the catheter,
- the introducer is threaded through its distal orifice on the plunger upstream of the rigid end piece,
- the distal end and the tip of the pusher are made integral,
the entire assembly is covered with the end and the end piece by translation of the introducer,
- the reliability of the coupling of the end with the end piece is checked by small movements back and forth in the introducer,
- the procedure is continued in the event of proven reliability, and it is re-assigned with other elements of the system in the event of an anomaly,
- the introducer is pushed into the distal catheter inlet,
- the pusher is actuated until the proximal end comes out of the catheter into the lumen of the vena cava in a position located below the renal veins and adjusted by radioscopic control,
the first and second loops of the filter are released by continuing the actuation of the pusher by radioscopically controlling their correct fitness capable of being improved by reciprocating movements and / or rotations of the pusher and / or low amplitude catheter,
- the procedure is continued in the event of a positive control and, in the event of a negative control, all or part of the filter integral with the pusher is removed and the filter unwinding procedure is resumed,
- the sharp distal end is released by a final push which introduces the tip into the vena cava and the end by spring effect is stuck in the wall of the vein,
- the plunger is removed from the catheter, and
- the catheter is removed from the vein.

 The invention will be better understood with the aid of the following description of a preferred embodiment.

This description will be made with reference to the accompanying drawings, in which:
FIG. 1 is a plan view of the filter element,
FIG. 2 is a top view of this same filter,
FIG. 3 is a plan view of the first proximal end of the filter,
FIG. 4 is a plan view of the second distal end of the filter,
FIG. 5 represents the method of anchoring the distal end of the filter in the end piece of the pusher,
FIG. 6 represents the mode of cooperation of the introducer element with the distal end of the catheter,
Figures 7 to 13 illustrate the method of placing the filter in the catheter and then in the vena cava.

 1 - Now, we will first proceed to the description of the pulmonary anti-embolism system according to the invention.

 11 - Filter element (figures 1 to .4).

 This filter (F) is made of elastic radioopague wire and is shaped to have the general shape already known of two quasi-ellipses (El) and (E2) substantially coplanar and with perpendicular axes.

 It differs from the prior art known in that, to slide without risking altering the internal wall of the catheter 7F and not to prevent the return to the original shape of the filter (F) in the vena cava, this filter (F ) has a first proximal free end (M1) (Figure 3), with a hemispherical tip (1) (rounded, soft, softened) non-traumatic (without tip) extended by a cylinder (3) of 1.3mm diameter on 3.5mm in length.

 As will be seen in more detail below, this end (M1) comes first from the lumen of the catheter 7F. In the vena cava the free end (M1) precedes the first loop of the filter which, gradually, coils without constraint, lying along the wall. The direction of rotation of the wire is respected.

 The second distal free end (M2) of the filter F, (Figure 4), has a direction perpendicular to the axis of symmetry of the two loops (Figure 1) and makes an angle of about 45c relative to the planes of the ellipses (Figure 2). The end (M2) has a 2 mm coaxial tip (5) succeeded by a cylinder (7) with a diameter of 0.6 mm and a length of 3 mm. So that the end (M2) does not damage the lumen of the catheter 7 #, it is housed as will be seen later in the end piece (Eiu pusher (P) designed for this purpose. The end piece of the pusher and the distal end (M2) are only attached during their placement in the lumen of the catheter and throughout their journey in this cat-heter 7F.

12- Pusher (Figures 5 and 6)
The rigid end piece (E) of the pusher rR) has a length of 15 mm sufficient to be able to comprise, in addition to a first coaxial slot (9) and a central recess (11) of 5 mm, a second slot distal coaxial (15) close to the flexible cable 6mm long and 0.35mm wide, to receive and protect the sharp point (5) from the end (M2) of the filter (F).

13 - Auxiliary installation tool (figure 6). (I)
A rigid polyurethane introducer / is essential for the correct introduction of the distal end (M2) of the filter (F) and of the rigid end piece (E) of the plunger (P) which are engaged by hand before they are put in place. place in the distal catheter port (KT).

 The base (17) of the catheter (KT), over an internal length of 11 mm, has an internal lumen with a diameter of 4 mm significantly greater than that of the clean lumen (19) of the catheter (1.45 mm) which follows it. . The junction of the two lights is made by a cylindrical-conical piece (23).

 It is not possible to manually insert the tip (E) and the end (M2) together into the catheter base (KT).

Only a tool adapted to this base allows the introduction of lt ~ m-- end (E) and the end (M2) integral
The introducer (I) is made of rigid polyurethane, length 45 mm, external diameter 3 mm. Its internal diameter over its entire length is identical to that of the catheter lumen (KT), i.e. 1.45mu Its 6 mm conical proximal end fits exactly to the internal truncated cone of the base of the distal orifice catheter (KT).

 2 - We will now describe the process of setting up the filtering system in the vena cava.

The filter system includes:
- The catheter (KT),
- The filter (F), at the ends (M1) and (M2),
- The introducer (I), and
~ The pusher (P) with nozzle (E).

 FIGS. 7 to 13 make it possible to understand the method of placing in the catheter (KT), then in the vena cava, the filter (F) according to the invention using the pusher (P) with nozzle and the introducer. (I).

 The catheter (KT) 7F is placed first in the vena cava percutaneously from a peripheral vein (preferably by the upper limb). It is first used to do a cavography.

 By the distal end of the catheter (KT) the filter (F) is introduced by hand. The first proximal free end (M1) enters the first into the lumen of the catheter (KT). Its softened end (1) slides easily by simple pressure on the filter shaped into two coplanar ellipses but then unrolled.

 After having pushed the two loops of the unwound filter (F), it remains to introduce the rectilinear terminal segment located in a plane at 45c and comprising the sharp distal end (M2).

 The introducer (I) is threaded through its distal orifice on the pusher (P) upstream of the rigid end piece (E) as shown in Figure 7.

 The end (M2) is then placed in the slots (9) and (15) and the central recess of the end piece (E). To keep them together, (given the spring effect of the end wire (M2),), the introducer (I) is removed in the opposite direction of its introduction on the pusher (P) to cover the assembly of the end (M2) and of the end piece (E) as shown in FIG. 8. The reliability of the coupling of the end (M2) with the end piece (E) is checked by small movements of va and back in the introducer (I). The procedure is continued in the event of proven reliability, and it is repeated with other elements of the system in the event of an anomaly.

 The introducer (I) containing the pusher (P) with the end piece (E) filled by the end (M2) of the filter (F) is then introduced into the distal orifice (17) of the catheter (KT) (figure 9).

 The pressure on the cable of the pusher (P) makes it possible to advance the assembly (E, M2) integral in the lumen of the catheter (KT). The introducer (I) can be removed from the distal orifice of the catheter (KT); it remains on the pusher (P).

 Under radioscopic control, the filter can now be pushed to the proximal orifice (25) of the catheter (KT) which is located below the renal veins.

 The release of the filter (F) begins, under radioscopic control, by the exit into the lumen of the vena cava of the softened end (M1) (figure 10) It slides on the venous wall (30) according to the movement resumption in permanent form of the first loop of the filter (F) (figure ll). The second loop follows the same direction of rotation as the first loop, free of any movement in the venous lumen. The vein deforms along the plane of the two loops of the filter (F), (Figure 12). This recovery in the shape of the filter (F) can be improved by reciprocating and / or rotating movements of the pusher and / or the catheter of low amplitude. The definitive release of the sharp end (M2) is not carried out. only after checking the correct position of the filter (F) in the vena cava and its resumption in perfect shape.

 As soon as the catheter (KT) is ejected from the tip (E) of the pusher (P) containing the end (M2), the sharp distal end (M2) is released by its spring effect from the notch (recess and slit of the pusher) and will prick at an angle of about 45o in the venous wall, (Figure 13). The installation of the filter (F) is complete.

 The pusher P is withdrawn through the catheter (KT). Then it is the catheter's (KT) turn to be removed from the vein by simple pull to its percutaneous entry orifice.

 Although, in the example described above, very precise values have been given to the different measures of diameters and / or lengths of the different elements, it should be understood that these are optimal values observed resulting from numerous experiments carried out.

Claims (1)

 REV # ENDI CAT ION  -Anti-pulmonary anti-embolism system of the kind using a filter made of elastic thread shaped to have a general permanent shape of at least two substantially elliptical loops essentially coplanar and of axes quasi-per # endicular, which may present momentarily under a rectilinear shape to be able to be closed in the inferior vena cava by pushing in a catheter, characterized in that it comprises:  a radiopaque proximal end (M1) of the filter (F) produced in the form of a small cylinder with rounded end without roughness, (FIGS. 1 to 3).  b / a radiopaque distal end (M2) of the filter (F), produced in the form of a small cylinder (7) terminated by a sharp point (5) situated outside the planes of the two loops, (Figures 2 and 13).  a pusher (P), (FIG. 5), of cylindrical shape so as to be able to be mobile inside a catheter (KT), and having in its tip (E) housings (11) and longitudinal slots (9 and 15 ) to receive respectively the unwound thread of the filter, then the cylinder of the distal end, and finally the sharp distal tip, and  d / an introducer element (I) (FIG. 6), of generally cylindro-conical shape having an internal cylindrical channel of the same diameter as that of the catheter intended to receive the pusher assembled manually with the filter wire and the extre - distal mite and its sharp point and an extreme conical part in order to be able to engage in the wider entry orifice of the catheter, (Figures 8 and 9).