Abstract:
This invention features a device (1) comprising: at least one radially expansible segment (7, 8) with, in the expanded state, a transversal cross section substantially greater than the transversal cross section of one of the secondary ducts (3); one segment (6) with, in the expanded state, a truncated shape, corresponding to the shape of the bifurcation at the flared transition zone (11) which separates the main duct (2) from the secondary ducts (3), and a flexible link (9) between these two segments (6, 7), enabling their adjustment relative to each other, according to the orientation of the secondary duct (3) receiving the radially expandable segment (7) relative to the flared transition zone (11).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device permitting the treatment of bodily conduits in the area of a bifurcation, that is to say in the area where a principal conduit separates into two secondary conduits. It also relates to equipment for positioning this device. 
     This device can be used for the treatment of vascular bifurcations, in particular the carotid, femoral, iliac, popliteal, renal or coronary bifurcations, or nonvascular bifurcations, such as tracheal or biliary bifurcations, for example between the common bile and cystic ducts, or in the area of the bifurcation of the principal bile tract. 
     The treatment can consist in re-establishing the appropriate diameter of the bifurcation, in cases of arteriosclerosis or internal cell proliferation, in rectifying a localized or nonlocalized dissection in the wall of the conduit, or, in cases of aneurysm, in recreating a bifurcation of normal diameter, while eliminating the aneurysmal pouch. 
     DESCRIPTION OF THE PRIOR ART 
     It is known to treat narrowing of a rectilinear blood vessel by means of a radially expandable tubular device, commonly referred to as a stent. This device is introduced in the unexpanded state into the internal lumen of the vessel, in particular by the percutaneous route, as far as the area of narrowing. Once in place, it is expanded in such a way as to support the vessel wall and thus re-establish the appropriate cross section of the vessel. 
     The device can be made of a nonelastic material, and in this case is expanded by means of an inflatable balloon on which it is engaged, or can be self-expanding, that is to say made of an elastic material, expanding spontaneously when withdrawn from a sheath which is holding it in the contracted state. 
     The documents U.S. Pat. No. 4,733,665 and U.S. Pat. No. 4,886,062 are illustrative of existing devices and of corresponding positioning techniques. 
     A conventional stent is not entirely suitable for the treatment of a narrowing situated in the area of a bifurcation, since its engagement both in the principal conduit and in one of the secondary conduits can cause immediate or delayed occlusion of the other secondary conduit. 
     It is known to reinforce a vascular bifurcation by means of a device comprising two elements, each formed by helical winding of a metal filament. One of the two elements has two parts of diameter corresponding respectively to the diameter of the principal vessel and to the diameter of one of the secondary vessels, and is intended to be engaged on the one hand in this principal vessel and, on the other hand, in this secondary vessel. The other element has a diameter corresponding to the diameter of the other secondary vessel and is coupled to the first element, after the latter has been put into place, by engaging one or more of its turns in the turns of the first element. 
     This equipment permits reinforcement of the bifurcation but appears unsuitable for treating a vascular narrowing or an occlusive lesion, in view of its structure and of the low possibility of radial expansion of its two constituent elements. 
     Moreover, the shape of the first element does not correspond to the shape of a bifurcation, which has a widened transitional zone between the end of the principal vessel and the ends of the secondary vessels. Thus, this equipment does not make it possible to fully support this wall or to treat a dissection in the area of this wall. 
     In addition, the separate positioning of these two elements seems relatively difficult. 
     SUMMARY OF THE INVENTION 
     The present invention aims to overcome these various disadvantages by making available a device with which it is possible to treat a pathological condition in the area of a bifurcation, by fully supporting the vascular wall and by being relatively simple to position. 
     The device to which the invention relates comprises, in a manner known per se, segments delimiting longitudinal conduits, one of which is intended to be engaged through the bifurcation, and another of which is intended to be engaged in a secondary conduit of this bifurcation. 
     According to the invention, this device comprises: 
     at least one radially expandable segment which has, in the expanded state, a cross section substantially greater than the cross section of one of the secondary conduits; 
     a segment which has, in the expanded state, a truncated shape, corresponding to the shape of the bifurcation in the area of the widened transitional zone which separates the principal conduit from the secondary conduits; and 
     a flexible link between these two segments, permitting these to be oriented in relation to one another on the basis of the orientation of the secondary conduit, receiving said segment, in relation to said widened transitional zone. 
     For the sake of simplification, the segment which has, in the expanded state, a cross section substantially greater than the cross section of one of the secondary conduits will be referred to hereinafter as the &#34;secondary segment&#34;, while the segment which has, in the expanded state, a truncated shape will be referred to hereinafter as the &#34;truncated segment&#34;. 
     The secondary segment is intended to be introduced into the secondary conduit in the contracted state and to bear, in the expanded state, against the wall of this conduit. This expansion not only makes it possible to treat a narrowing or a dissection situated in the area of this conduit, but also to ensure perfect immobilization of the device in the conduit. 
     In this position of the device, the truncated segment bears against the wall of the conduit delimiting the widened transitional zone of the bifurcation, which it is able to support fully. A narrowing or a dissection occurring at this site can thus be treated by means of this device, with uniform support of the vascular wall, and thus without risk of this wall being damaged. 
     By virtue of the flexible link which connects them, the two segments orient themselves suitably in relation to each other upon their expansion. The device additionally has a unitary character, and is therefore relatively easy to implant. 
     Preferably, at least the truncated segment is covered by a wall which gives it impermeability in a radial direction. 
     This wall makes it possible to trap, between it and the wall of the conduit, the particles which may originate from the lesion being treated, such as arteriosclerotic particles or cellular agglomerates, and thus to avoid the migration of these particles in the body. 
     Moreover, the device can permit treatment of an aneurysm by guiding the liquid through the bifurcation and thereby preventing stressing of the wall forming the aneurysm. 
     The device can comprise several secondary segments, placed one after the other, to ensure supplementary support of the wall of the secondary conduit and, if need be, to increase the anchoring force of the device in the bifurcation. To this same end, the device can comprise, on that side of the truncated segment directed toward the principal conduit, at least one radially expandable segment having, in the expanded state, a cross section which is substantially greater than the cross section of the principal conduit. 
     These various supplementary segments can be connected to each other and to the two aforementioned segments by means of flexible links, such as those indicated above. 
     Preferably, the flexible link between two consecutive segments is made up of one or more bridges of material connecting the two adjacent ends of these two segments. Said bridge or bridges are advantageously made of the same material as that forming the segments. 
     According to a preferred embodiment of the invention, each segment has a meshwork structure, the meshes being elongated in the longitudinal direction of the device, and each one having a substantially hexagonal shape; the meshes of the truncated segment have a width which increases progressively in the longitudinal sense of the device, in the direction of the end of this segment having the greatest cross section in the expanded state. 
     This increase in the width of the meshes is the result of an increase in the length of the edges of the meshes disposed longitudinally and/or an increase in the angle formed between two facing edges of the same mesh. 
     In addition, the truncated segment can have an axis not coincident with the longitudinal axis of the device, but oblique in relation to this axis, in order to be adapted optimally to the anatomy of the bifurcation which is to be treated. In this case, the widths of the meshes of this segment also increase progressively, in the transverse sense of the device, in the direction of a generatrix diametrically opposite that located in the continuation of the bridge connecting this segment to the adjacent segment. 
     The device can be made of a metal with shape memory, which becomes malleable, without elasticity, at a temperature markedly lower than that of the human body, in order to permit retraction of the device upon itself, and to allow it to recover its neutral shape at a temperature substantially corresponding to that of the human body. This metal is preferably the nickel/titanium alloy known by the name NITINOL. 
     The equipment for positioning the device comprises, in a manner known per se, means for permitting the expansion of this device when the latter is in place. These means can comprise a removable sheath in which the device is placed in the contracted state, when this device is made of an elastic material, or a support core comprising an inflatable balloon on which the device is placed, when this device is made of a nonelastic material. 
     In either case, this equipment comprises, according to the invention, means with which it is possible to identify, through the body of the patient, the longitudinal location of the truncated segment, so that the latter can be correctly positioned in the area of the widened zone of the bifurcation. 
     In the case where the expansion of this same segment is not uniform in relation to the axis of the device, the equipment additionally comprises means with which it is possible to identify, through the body of the patient, the angular orientation of the device in relation to the bifurcation, so that that part of this segment having the greatest expansion can be placed in a suitable manner in relation to the bifurcation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     To ensure that it is fully understood, the invention is again described hereinbelow with reference to the attached diagrammatic drawing which shows, by way of nonlimiting example, two preferred embodiments of the device to which the invention relates. 
     FIG. 1 is a side view thereof, according to a first embodiment; 
     FIG. 2 is a perspective view of this device in a state of radial contraction, and, in partial cutaway, of the equipment allowing it to be positioned; 
     FIG. 3 is a longitudinal sectional view of the bifurcation to be treated; 
     FIGS. 4 to 6 are views of this bifurcation similar to FIG. 3, during three successive stages of positioning of the device; 
     FIG. 7 is a view, similar to FIG. 3, of a bifurcation presenting an aneurysm, in which the device is placed, and 
     FIG. 8 is a side view of the device according to a second embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows an expandable device 1 permitting the treatment of bodily conduits in the area of a bifurcation, that is to say, as is shown in FIG. 3, in the area where a principal conduit 2 separates into two secondary conduits 3. 
     The device 1 comprises four successive segments 5, 6, 7, 8, of meshwork structure, which are connected to one another via three bridges of material 9. 
     The meshes 10 of these segments are elongated in the longitudinal direction of the device 1 and have in each case a substantially hexagonal shape. 
     The segment 5 has a tubular shape and has a diameter which is substantially greater than the diameter of the principal conduit 2. 
     The segment 6 has meshes 10 whose width increases progressively, compared to that of the meshes of the segment 5, on the one hand in the longitudinal sense of the device 1, in the direction of the end of the segment 6 situated opposite the segment 5, and, on the other hand, in the transverse sense of the device 1, in the direction of a generatrix diametrically opposite that located in the continuation of the bridge 9. 
     This increase in the width of the meshes 10 results from an increase in the length of the edges 10a of the meshes 10 disposed longitudinally, as well as an increase in the angle formed between two facing edges 10a. 
     This segment 6 thus has a truncated shape with an axis which is oblique in relation to the longitudinal axis of the device 1. This shape corresponds to the shape of the bifurcation in the area of the widened transitional zone 11 which separates the end of the principal conduit 2 from the ends of the secondary conduits 3. 
     The segments 7 and 8 are identical to each other and have a tubular shape with a diameter which is substantially greater than the diameter of one of the secondary conduits 3. 
     The bridges of material 9 connect the adjacent ends of the segments 5 to 8 and have a small width, so that they can undergo a certain flexion, making it possible to orient these segments in relation to one another, in particular the segment 6 in relation to the segment 7. 
     The device 1 is made by appropriate cutting of a sheet of nickel/titanium alloy known by the name NITINOL, then folding the resulting blank into a circle and welding the parts of this blank which come into proximity with each other. 
     This alloy is malleable at a temperature of the order of 10° C., but can recover its neutral shape at a temperature substantially corresponding to that of the human body. 
     FIG. 2 shows the device 1 in a state of radial contraction, obtained by cooling its constituent material. During this contraction, the edges 10a pivot in relation to the transverse edges 10b of the meshes 10, in such a way that the meshes 10 have, in this state of contraction, a substantially rectangular shape. 
     By virtue of this contraction, the segments 5 to 8 have a cross section which is smaller than that of the conduits 2 and 3, and they can be introduced into these, as will be described hereinafter. 
     The device 1 is engaged on a central support core 15, and is then contracted radially on the latter. This core 15 comprises an axial abutment such as a shoulder (not visible in FIG. 2) which has a diameter smaller than that of the device 1 when this device is expanded, but greater than the diameter of this device 1 when the latter is contracted. This abutment consequently permits the axial immobilization of the device 1 on the core 15 when the latter is contracted. 
     A sheath 16 is then engaged on the device 1 in order to hold it in its contracted state. This sheath 16 includes four radiopaque markers 20, 21, 22, 23 impressed on it, containing, for example, a barium compound. Three markers 20, 21, 22 have an annular shape and extend round the whole periphery of the sheath 16. They are situated, respectively, in the area of the free ends of the segments 5 and 8 and in the area of the bridge 9 separating the segments 6 and 7. The fourth marker 23 is situated at substantially the halfway point of the generatrix of the segment 6 situated in the continuation of the bridge 9 and of the diametrically opposite generatrix. It has a diamond shape and a small thickness. 
     The core 15 has a longitudinal axial hole permitting its engagement on a guide wire 25 (FIGS. 4 to 6). This wire 25 can be engaged, by the percutaneous route, in the conduit 2, by way of the zone 11, and then in one of the conduits 3, through which it can slide, and comprises a cone 26 of synthetic material, situated in front of the assembly consisting of core 15, device 1 and sheath 16. 
     The bifurcation 30 shown in FIG. 3 has excrescences 31 which create a narrowing in cross section, which impedes the flow of the liquid circulating in the conduits 2 and 3. In the case of a vascular bifurcation, these excrescences are due, for example, to arteriosclerosis or cellular growth. 
     The device 1 permits treatment of this bifurcation by re-establishing the appropriate diameter of the conduits 2, 3 and of the widened zone 11. 
     In practice, as can be seen in FIG. 4, the assembly consisting of core 15, device 1 and sheath 16 is engaged on the wire 25 as far as the cone 26. By means of its sliding action, this wire 25 permits the engagement and then the guiding of this assembly in the conduit 2, the zone 11 and then the conduit 3. The cone 26 facilitates the sliding of the assembly and reduces the risk of trauma. 
     The marker 22 makes it possible to visualize, with the aid of a suitable radiography apparatus, the position of the bridge 9 separating the segments 6 and 7, and thus to visualize the location of the segment 6 so that the latter can be correctly positioned in relation to the widened zone 11. 
     With the markers 20 and 21 it is possible to ensure that the segments 5 and 8 are correctly positioned, respectively, in the principal conduit 2 and the secondary conduit 3. 
     The marker 23 is, for its part, visible in a plan view or an edge view, depending on whether it is oriented perpendicular or parallel to the radius of the radiography apparatus. It thus makes it possible to identify the angular orientation of the device 1 in relation to the bifurcation 30, so that the part of the segment 6 having the greatest expansion can be placed in an appropriate manner in relation to the zone 11. 
     The sheath 16, which has a length such that it opens out beyond the opening having permitted introduction of the assembly, is then progressively withdrawn, as is shown in FIGS. 5 and 6, in order to permit the complete expansion of the device 1. 
     The latter is reheated by the body temperature, and this permits its expansion. 
     After complete expansion of the device 1, the core 15 and the wire 25 are withdrawn. 
     FIG.7 shows that the device 1 can also be used to treat an aneurysm 40. The segment 6 and a part of the segment 5 are then covered by a polyester film 41, impermeable to the liquid circulating in the conduits 2 and 3, which film is sewn onto them. The device then guides this liquid through the bifurcation 30 and consequently prevents stressing of the wall forming the aneurysm 40. 
     FIG. 8 shows a device 100 according to the invention, having segments 105, 106, 107, 108 and a bridge 109 connecting the segments 106 and 107, with a structure similar to that of the segments 5 to 8 and of the bridge 9 in the device shown in FIG. 1. 
     In the device 100, two consecutive segments, excluding the segments 106 and 107, are connected by six omega-shaped bridges 190. The curved central part 190a of these bridges 190 has a multidirectional elasticity permitting the appropriate longitudinal orientation of the various segments in relation to one another. 
     The advantage of these bridges 190 is that they provide the device with longitudinal continuity, which facilitates the passage of said device into a highly curved zone and which eliminates the need to reduce this curvature, which is always dangerous in the cases of arteriosclerosis, so as to permit the passage of the device. 
     The invention thus provides a device permitting the treatment of a pathological condition in the area of a bifurcation 30. This device has the many advantages indicated above, in particular those of ensuring a perfect support of the vessel wall and of being relatively simple to position. 
     It goes without saying that the invention is not limited to the embodiment described hereinabove by way of example, but instead embraces all the variant embodiments. 
     Thus, the device 1, 100 can comprise several segments 5, 8, 105, 108 placed one after the other, in order to ensure supplementary support and, if need be, to increase the hold of the device in the bifurcation 30. 
     The core 15 could comprise an inflatable balloon, either to effect the expansion of the device 1, in the case where the latter is made of a nonelastic material, or to ensure the total expansion of a self-expanding device 1 after the latter has been put into place. 
     The markers 20 to 23 could be impressed on the core 15 or directly on the device 1, in particular on the bridge 9, 109, and not on the sheath 16. 
     The segment 6, 106 could have an axis coincident with the longitudinal axis of the device, and not oblique in relation to this axis, if such is rendered necessary by the anatomy of the bifurcation which is to be treated. 
     In addition, the segment 7, 107 could itself have, in the expanded state, a widened shape corresponding to the shape of the widened connecting zone via which, in certain bifurcations, the secondary conduits 3 are connected to the widened transition zone 11. This segment 7, 107 would thus have a shape corresponding to the shape of this widened connecting zone, and would ensure perfect support thereof. 
     The bridges 190 between two consecutive segments could be greater or smaller in number than six, and they could have a shape other than an omega shape, permitting their multidirectional elasticity, and in particular a V shape or W shape.