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 said segment ( 7 ) relative to the flared transition zone ( 11 ).

Description:
This is a Continuationin-Part of application Ser. No. 09/011,214 filed Apr. 3, 1998. The entire disclosure of the prior application is hereby incorporated by reference herein in its entirety. Now U.S. Pat. No. 6,068,655. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus 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 apparatus. 
     This apparatus 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. 
     U.S. Pat. Nos. 4,733,665 and 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 apparatus 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 apparatus 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 apparatus comprises: 
     at least one radially expandable segment which has, in a predetermined expanded state, a cross section substantially greater than the cross section of one of the secondary conduits; and 
     a segment which has, in a predetermined expanded state, a truncated shape, corresponding to shape of the bifurcation in the area of the widened transitional zone which separates the principal conduit from the secondary conduits. 
     In some embodiments of this invention, this apparatus further comprises a flexible link between these two segments. 
     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 “secondary segment”, while the segment which has, in the expanded state, a truncated shape will be referred to hereinafter as the “truncated segment”. 
     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 apparatus 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 apparatus, with uniform support of the vascular wall, and thus without risk of this wall being damaged. 
     The two segments orient themselves suitably in relation to each other upon their expansion. 
     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 apparatus can permit treatment of an aneurysm by guiding the liquid through the bifurcation and thereby preventing stressing of the wall forming the aneurysm. 
     The segments can be made from tubes of material of a different diameter, with the tube for the truncated segment having a larger diameter than the tube for the secondary segment. The tubes may be comprised of the same material. The use of tubes of different diameters results in the truncated segment having a larger radial force, especially at larger diameters. 
     The apparatus 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 apparatus 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 may or may not be connected to each other and to the two aforementioned segments by means of flexible links, such as those indicated above. 
     The flexible links can be integral with one of the segments and separately connected to the other segment, or the flexible links can be separate pieces of material separately connected to both segments, such as by welding. 
     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 secondary segment, 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 the truncated 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 apparatus 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 apparatus 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 apparatus comprises, in a manner known per se, means for permitting the expansion of this apparatus 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 nonlimitiing 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  10   a  of the meshes  10  disposed longitudinally, as well as an increase in the angle formed between two facing edges  10   a.    
     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  10   a  pivot in relation to the transverse edges  10   b  of the meshes  10 , in such a way that the meshes  10  have, in this sate 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  5  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  57 , 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  190   a  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. 
     In addition, in other embodiments, the bridges  9  and  190  could be integral with one of the connected segments and separately connected, such as by welding, to the other connected segment. For example, bridge  9  which connects segments  6  and  7  could be integral with segment  6  and connected to segment  7 , or integral with segment  7  and connected to segment  6 . 
     In yet other embodiments, bridges  9  and  190  could be separate pieces of materials which are separately connected to segments  5 ,  6 ,  7  and  8  (or segments  105 ,  106 ,  107  and  108 ), such as by welding. In all of these embodiments, the segments  5  and  6  (and  105  and  106 ) can be made from different tubes of material than segments  7  and  8  (and  107  and  108 ). The tube from which segments  5  and  6  (and  105  and  106 ) are made may be a smaller diameter than the tube from which segments  5  and  6  (and  105  and  106 ) are made. The respective tubes may or may not be made of the same material. 
     Accordingly, bridges  9  and  190  can be made from one of these tubes, and thus be integral with segments  5  and  6  or segments  7  and  8  (or segments  105  and  106  or segments  107  and  108 ) or bridges  9  and  190  can be separate pieces of material. 
     When segments  5  and  6  (and  105  and  106 ) are made from tubes of a smaller diameter than segments  7  and  8  (and  107  and  108 ), the radial force of segments  7  and  8  (and  107  and  108 ) is larger than the radial force of segments  5  and  6  (and  105  and  106 ), especially at larger cross sections. 
     In further embodiments, bridges  9  and  190  are omitted such that the individual segments are spaced apart as necessary during installation and use. These individual segments are still delivered and implanted in the same core and sheath assembly.