MXPA99006482A - Luminal endoprosthesis for ramification - Google Patents

Abstract

The invention relates to a luminal endoprosthesis for the ramifications of anatomical conduits in mammals, especially humans, and to a method for manufacturing this endoprosthesis. The latter includes at least one tubular structure with N radially compressible and extendable filaments and comprises at least one base element (12) with a multifilament structure delimiting a longitudinal cavity (14) open at its two ends (16, 18). This at least one base element (12) comprises two flexible segments (20, 22) extending one in a continuation of the other, substantially along the same axis in the absence of stress, and at least one lumen (24) opening into the cavity (14).

Description

LUMINAL ENDOPROTESIS FOR BRANCH DESCRIPTION OF THE INVENTION The invention is related to luminal endografts for branches (also called branches or bifurcations) of anatomical conduits in mammals, especially humans. The endoprosthesis according to the invention is more specifically related to the vascular system and the cardiovascular system where, in several places, there are shunts, branches, or bifurcations, the essential function of which is to provide a balanced supply of blood to the organs ., muscle tissue and connective tissue. The circulation of blood in the vessels causes several problems associated with the hydrodynamics and due to the structure and, in general, the shape of these vessels. Physiologists and morphologists generally accept "that the arrangement of the vessels is such that the circulation mechanically requires a minimum level of stress and that the surface of the walls assumes a minimum value." The luminal stents that have been developed up to now generally assume simple cylindrical or tubular shapes or, more rarely, a hyperboloid shape Such prostheses are described in particular in WO-A-83/03752 and GB-A-1 205 743. These prostheses include a tubular braided structure for an arterial conduit or other conduit and put in place, after compression of its diameter, using a tubular applied.These prostheses are not projected for their implant in a bifurcated shape.App attempts have been made to develop bifurcated forms of prostheses.These are essentially related to the union of the abdominal aorta, which is a large vessel, but the X investigations are very much in their beginning. The bifurcated prostheses for implantation in a conduit such as a blood vessel are known, in particular, from US Pat. No. 4,994,071. This prosthesis, made of intercapped metal rings, comprises a trunk. formed by a first series of interconnected rings, and at least a branch formed by a second series of interconnected rings, at least these two series are connected to each other by a flexible element, folded in such a way that corresponds to the angle between the branches in question. Place * said prosthesis in its place is extremely difficult, or even impossible. US Pat. No. 5,609,605 discloses a bifurcated stent made of two single diameter balloon endoprostheses placed side by side in a bifurcated lumen. EP-A-0 539 237 and WO 96/34580 describe devices for placing the bifurcated stent in place. These stents include a main body (trunk) and two limbs (branches) extending from the main body; They are made of a folded or folded blended fiber. The placement of said endoprostheses in arterial bifurcations is a long and delicate operation, especially taking into account the rigorous requirements with respect to orientation and function. In addition, the angle provided by the two branches does not necessarily correspond to the original angle between the vessels. EP-A-0 461 791 illustrates the difficulties involved in placing a bifurcated prosthesis in place, even in the case of an aneurysm of the abdominal aorta, where the vessels are of a very large diameter.

Other documents such as US 5,609,627 and US 5,639,278 describe a stent in the form of pants with added limbs, which very often causes disturbance of blood flow. Bifurcation angles differ from one person to another and from one population to another. They are smaller and more asymmetrical in older people than in younger subjects. The bifurcations are more asymmetrical in men than in women. Comparative studies have shown that the bifurcation angles in Asian people are wider than in Caucasian ones. Hydrodynamics also teaches that the thickness of arterial walls differs from one population to another. When these walls are thin, the effort necessary to transport the blood increases. It is also known that when the vessels are very large, the blood volume increases beyond what is necessary. These factors promote aneurysms (dilation of the arterial wall). The considerations detailed above show that it will be necessary to adapt the design of a bifurcation to each anatomical site, and also that this design should take into account the differences between the different types of populations, between men and women, between the young and the elderly, etc. . In practice, it is not possible to provide custom-made bifurcations for each patient. This would in fact risk causing problems associated with waiting periods and pr ohibitiv e costs. Therefore, it has been sought to develop a luminal endoprosthesis which can be adapted to practically all branches of the anatomical conduits, and in particular those of the vascular and cardiovascular system. Another object of the invention is that this stent should be easy to place in its place. Another object is to allow the possibility of placing said endoprosthesis in places where until now they have been inaccessible. The subject of the invention is a luminal endoprosthesis for branching an anatomical duct, including at least one radially compressible and extending tubular structure which comprises at least one base element comprising a structure of multiple filaments with N filaments delimiting a longitudinal cavity open at both ends. At least this base element comprises two flexible segments, respectively a first single segment and a second single segment, extending one in a continuation of the other, substantially along the same axis in the absence of stress, and at least one lumen opening within of the longitudinal cavity at the junction between the first segment and the second segment, the same metal filaments forming the structure of the first segment and the second segment. According to a first preferred embodiment, in a base element, the first element (or trunk) has a cross section greater than that of the second segment (or branch). According to a second representation, the first segment and the second segment of a base element have transverse cuts which are practically identical. These stents generally comprise two base elements, in their interlocked state, the first respective segments of each of these two base elements are coupled one inside the other, and assuming, in this position, the cross sections which are essentially identical, the second segment of one of the base elements is coupled to a lumen of the other base element. At least one of the base elements advantageously comprises a sleeve made of biocompatible material, such as a polyester, polyurethane or polyethylene type polymer, or another type of biocompatible material. The structure of each base element can be braided advantageously using metal filaments made of an elastic alloy for medical use or filaments with memory of its shape. The braid is advantageously formed by crossing over two layers of N / 2 filaments. The first segment of each of the two base elements may comprise a larger cross section. According to a representation, the second segment of at least one of the base elements comprises a part with a larger cross section. In the absence of stress, the filaments of the braided structure intersect at an angle and in a diameter which will vary depending on the desired application. In a preferred manner, the cross section of the trunk of a base element is equal to at least four times that of its branch and / or a lumen of a base element has a cross section at least equal to a quarter of that of the trunk. or at least equal to that of the branch. Another subject of the invention is a method for fabricating braided structures with multiples for a stent as described hereinabove, and whose method comprises the following operations: braiding the filaments, made of a bi-material tibial elastic, super elastic or with memory of its shape around a first mandrel, along the length and the diameter corresponding to the branches of a base element, fixing at least one auxiliary mandrel parallel to the first mandrel, such auxiliary mandrel includes a first end and a second end, of cross section corresponding to those of a lumen, such first end is inserted in a straight line with the braid in progress, upstream of the braiding point, the second end is placed downstream of the braiding point, the assembly (first mandr i 1 -mandr i 1 auxiliary) has a cross section corresponding to that of a trunk of a base element, continue braiding around or assembly (first auxiliary mandrel mandrel) along a length corresponding to at least one of the trunk of a base element, causing the lumen of a lumen to be braided around the first end of the auxiliary mandrel. This method can additionally comprise the following operation: continue the braiding around the assembly (first mandr 1 -mandr i 1 auxiliary) along a length corresponding to at least twice that of the trunk of a base element, - separate the second end of at least one auxiliary mandrel of the first mandrel, said second end having a cross section corresponding to that of a lumen of a base element, - continuing the braiding in the first mandrel along a length and a diameter which corresponds to the branch of a base element, causing the turning of a second lumen to be braided around the second end of the auxiliary mandrel, - decoupling the obtained braid and the mandrels, - cutting the braid obtained in two elements different bases. When the auxiliary mandrel comprises at least one flexible part, the spacing between the second end of the auxiliary mandrel and the main mandrel can be effected by bending down such second end in the braid in progress. further, at least one enlarged part can be placed in the first mandrel along the length corresponding to one of the future branches. An enlarged part of larger diameter than the assembly (first mandr 1 - mandr 1 auxiliary) can be placed in this assembly along the length corresponding to the future trunks. The manufacturing method, as described, may comprise the insertion of a single auxiliary mandrel or of two auxiliary mandrels. The invention is also related to a method for manufacturing the braided structures with many filaments for the base element of a stent as described above, which method comprises the following operations: braiding the filaments, made of an elastic biocompatible material, super elastic or with memory of its shape, around a first mandrel, along the length and the diameter corresponding to one of the segments of the base element, - fixing an auxiliary mandrel perpendicular to the first mandrel, such auxiliary mandrel has a cross section corresponding to those of the desired lumen of the auxiliary mandrel, such auxiliary mandrel is inserted at a level of the braiding point of the braid in progress, - continuing the braiding around the assembly (first mandr 1 -mandr i 1 auxiliary) throughout of a length that corresponds at least to that of the contact (first mandr i 1 -mandr i 1 auxiliary), causing the turning of a l The braid is wound around the end of the auxiliary mandrel, the braiding continues in the first mandrel, along a length corresponding to the other segment of the base element, the braid obtained from the first braid and the first mandrel, the application of an auxiliary mandrel. advantageously it is repeated during the braiding of the element in such a way that several different lumens are formed. When the filaments with memory of their shape are used, the above operations are completed by thermal operations obtained by the metal to memorize a predetermined nominal shape. An advantage of the endoprosthesis according to the invention is that it usually adapts to any type of branching or bifurcation, particularly that of the arterial system, and at any angle, and this without taking into account age, sex of the subject and the population to which the subject belongs; it is therefore universal. The shape of the developed endoprosthesis is simple and flexible, and in this way it agrees with the anatomical place as such, by means of which it is possible to avoid the problems of positioning, migration, thrombosis and adaptation to the geometry of the original branching of each patient. The endoprosthesis according to the invention can be made with numerous variations in terms of cross section, length and angle of intersection of the filaments, and can be made from numerous materials. The stent according to the invention can be made in machines currently used to obtain traditional tubular stent grafts.

Other characteristics and advantages of the invention will be obvious when following the description of various representations, applied here to the blood system, referring to the attached figures, of which is: Figure 1 is a schematic view of a part of the vascular system including a Typical series of branch configurations, Figure 2 is a general perspective view of an anatomical branch, Figures 3 and 4 are schematic perspective views of two base elements (attached, then separated) of the stent according to the invention, - Figure 5 is a cut away perspective view and an endoprosthesis placed in an aneurysm (of the abdominal aorta), - Figure 6 is a perspective view of a step in the fabrication of the structures of the base element of a stent, - Figure 7 is a perspective view of an alternative fabrication of the structures of the element base, Figures 8 and 9 are perspective views during and after manufacture, respectively, of an alternative representation of the base elements of the stent, Figures 10 and 11 are perspective views during and after manufacture, respectively, of another alternative representation of the base elements of the stent, - Figure 12 is a cut away perspective view of an endoprosthesis according to the invention after it has been placed in the bifurcation of a carotid, Figures 13 and 14 are perspective views during and after the manufacture, respectively, of a third alternative representation of the base elements of the endoprosthesis; and Figures 15 and 16 are schematic (cut) perspective views of an aortic iliac aneurysm, respectively with a stent according to the prior art and with a stent according to the invention. Figure 1 shows, in schematic representation, a place that presents typical branches, represented in detail in Figure 2. The figure distinguishes in particular the place 2 which consists of a bifurcation in the form of a "from the left main trunk 3 towards the artery right circumflex 4 and the left anterior coronary artery 5. In place 6, the two branches, ie 7 (right anterior descending coronary artery) and 8 (the left circumpleja), join the anterior left coronary artery 5 at the same level, forming a "?" branch. For small arteries, there is a close relationship between the velocity of the blood and the dimension of the artery. The smaller the diameter, the lower the blood velocity and the greater the tendency for the artery to become blocked. In contrast, when the vessels are too large, the blood volume increases beyond what is necessary. This factor promotes aneurysms (dilation of the arterial wall). The geometry of the various bifurcated forms influences the blood flow, especially at the site of the branch, decreasing it and creating local turbulence. Research carried out by various researchers has shown that there is a relationship between high blood velocity, shear stress at the site of branching, and the appearance of sclerotic lesions along the arterial wall. Figure 2 shows in this way the zones of particular stress in the bifurcation "?", That is to say a zone of low effort 9 (low frequency zone) and a zone of high stress 10 in the furcation. It is also known that the vibration of the artery at low frequency, due to the low blood velocity, can be highly destructive to the artery. It should also be taken into account that in older subjects, the branching angle of the branches becomes smaller with age and as a result can form an atheroma 11. The same phenomenon can appear in the iliac arteries. Figures 3 and 4 show, in perspective, the structures of two base elements 12 of the endoprosthesis according to the invention. In Figure 3, the structures of these base elements are still attached (12a, 12b) in relation to a manufacturing method which will be described later. Figure 4 shows the structures of these separate elements 12a and 12b.

Each base element 12 comprises a braided structure with multifilaments which delimits a longitudinal cavity 14 open at its two ends 16, 18. Each base element 12 is made of two segments, hereinafter referred to as first segments or "trunks". "20 and second segments or" branches "22 (the trunks 20 in Figure 4 each have a larger cross section than the corresponding branches 22). A lumen 24 is formed in each base member 12 and opens within the longitudinal cavity 14 at a level of connection between the two segments 20, 22. The structure of each base element 12 is formed here by twisted filaments N in two layers (each layer being formed by filaments N / 2). The filaments N of the structure of each base element 12 extends without interruption from one end to the other (16, 18) of this element 12, the lathe of each lumen 24 thus "braid" in each structure. Each structure is braided by metal filaments made of elastic alloy for medical use or filament with memory of its shape. Applying it to an external stress, it can be compressed to a fraction of its initial diameter (the reduction in diameter is accompanied by the proportional longitudinal elongation), and in this state it can be introduced, via an applicator known by itself, through an incision and within the circulatory system of the subject, in the appropriate place. In the uncompressed state, ie before the stent is placed in place, or when the stent is in place, the filaments forming the two layers intersect to form an angle which is such that it is possible to obtain a good relationship, from the mechanical point of view, between the resistance to radial compression and the flexibility of the endoprosthesis. Figure 5 shows the disposition of an endoprosthesis 25 placed in an aneurysm 26 of the abdominal aorta 27. As indicated above, the first base element 12a is introduced through an incision within one of the iliac arteries 28. The applicator ( not shown) is inserted up to the abdominal aorta 27, upstream of the aneurysm 26. The applicator is gradually withdrawn, leaving in its place the element 12a, the trunk 20a, which aligns the aorta 27 to a level of the aneurysm 26, and the branch 22a in the iliac artery 28. The angle between the trunk 20 and the branch 22 of the base element 12a automatically adapts to the physiological divergences between the abdominal aorta 27 and the iliac artery 28. The lumen 24a of the first base element 12a is arranged in line with the mouth of the other iliac artery 29. A second base element 12b is introduced via the other iliac artery 29 and the lumen 24a into the trunk 20a. When the endoprosthesis is in place, the two trunks 20a and 20b are thus coupled one inside the other, the branch 22b of the second element extends within the iliac artery 29. The two branches 22a and 22b, being flexible, spontaneously they assume the angle of the original physiological branch. The two lumens 24a and 24b, arranged opposite from each other, do not induce any turbulence or any relative loss of pressure between the two blood vessels. The endoprosthesis in this way assumes totally the same functions as the healthy branch.

The structure of the endoprosthesis around the lumens 24a, 24b is strong and stable, which prevents these lumens from being crushed even during insertion into the catheter. The element 12a is internally aligned by a sleeve (not shown) made of biocompatible polymeric material and designed to serve as a support for the regeneration of the tissues. Because one of these two trunks 20a and 20b of the base elements 12 is engaged in the other, this sleeve is sandwiched between two structures, and this allows more safety. The slight divergences of the filaments at the ends of each structure (as shown in Figure 3) provides excellent anchoring for the stent in the body tissues and stability due to the coupling of the two trunks 20a and 20b. Figure 6 illustrates a method specially developed for manufacturing by braiding, of the structures of the base element 12 of the stent 25. This method allows two base elements of corresponding dimensions to be manufactured in a single operation. The method begins with a conventional braiding operation: the filaments N are entangled in two layers, in opposite directions, around a first cylindrical mandrel 30. This braid, in the diameter of the branch 22a of the base element 12a, is continuous as length of a length corresponding to that of the desired branch 22a. An auxiliary mandrel 32 is then arranged in parallel to the first mandrel 30; an end 34 of the auxiliary mandrel 32, whose cross section is in relation to that of the desired lumen 24, is placed against the braid in progress. The braiding of the filaments N is continued, this is around the assembly (first mandrel 30-auxiliary mandrel 32) along a length corresponding at least to that of the two trunks 20a, 20b of the base elements 12a, 12b . When the desired length has been reached, the end 36 of the auxiliary mandrel 32 is removed from the first mandrel 30. For the mandrel 32, it is possible to use a flexible material or a foldable shape: in this case, the mandrel is simply removed by bending this end 36 backwards in the braid in progress. The braiding is then continued in the first mandrel 30 along the length corresponding to that of the branch 22b of the base element 12b. After separation of the mandrels, the braid presents the appearance shown in Figure 3. It allows two structures to be obtained as depicted in Figure 4. The described method allows great variety in the shapes of the base elements 12, and, consequently, stents made with different base elements 12 are adapted to practically all anatomical sites. It should be emphasized that the base elements are formed in a single operation while the known bifurcated stems or stems have to be enslaved. The braid shown in Figure 7 is made using two auxiliary mandrels 32 of the same length. It applies in the case of branches in the form of? (as shown in place 6 of Figure 2) by combining two base elements 12 (see Figure 4) with a base element 38 having two lumens 24. The superposition of the three layers of trunks 20 of the base elements maintain permeability of the artery.

Figure 8 shows another variant of the described method. In this variant, use is made of an enlarged part 40 mounted on the level of the first mandrel 30 with the auxiliary mandrel 32. The shape of the base element 42 thus obtained has a widening 43, as can be seen in Figure 9 , by means of which it is possible to compensate for a probable narrowing of a neck of an abdominal aneurysm. The enlarged part 40 can also be placed on the first mandrel 30 much higher or much lower than the auxiliary mandrel 32, as shown in Figure 11. The use of a stent using a base member representing said widening 43 is illustrated in Figure 12: one of the base elements 12 has a widening 43 which is made to coincide with the carotid sinus 46 at the bifurcation of a common carotid artery 48 in the internal carotid 50 and the external carotid 52. Figure 13 illustrates another variant of the method, whose variant is obtained by placing another auxiliary mandrel 54, whose cross section roughly corresponds to that of the desired lumen 24, almost perpendicular to the first mandrel 30.

In the case shown, the first segment 20 and the second segment 22 have the same diameter, corresponding to that of the first mandrel 30. The lumen of the lumen 24 is braided in the structure of the base element 56. The auxiliary mandrel 54, which is represented here as cylindrical, it can assume various shapes and cross sections. A base element 58, provided with two different lumens 24 arranged in the same generation line, is shown in Figure 14. The base member 56, 58 can be used in combination with another base element 12 (see Figure 4) especially for derivations of vessels, the trunk 20 of the base element 12 has a cross section in relation to one of the segments of the base elements 56. This is to say, as a function of the configuration of these places, the two variants of the manufacturing methods they can be combined with each other for the production of a composite stent. Two other ways of forming an endoprosthesis is, each time using a simple base element 12, 56, are illustrated in Figure 16.

By way of comparison, Figure 15 shows a traditional operating procedure for this type of injury (aneurysm) 26 which involves the use of a prior art stent 060, and deflecting the affected section of vessel 62 and creating a 064 lead. Although the present stent was described as self-expanding, it is obvious that the same principle applies to plastically deformable stents such as balloon-associated stents.

Claims (20)

1. A luminal endoprosthesis for branching an anatomical duct, including at least one radially compressible and extending tubular structure characterized in that it comprises at least one base element comprising a continuous multifocal structure that delimits an open longitudinal cavity in its two ends, this at least one base element comprises - two flexible segments, respectively a first single segment and a second single segment, extending one in a continuation of the other, substantially along the same axis in the absence of tension, - at least one lumen that opens within a longitudinal cavity at the junction between the first segment and the second segment, the same filaments forming the structure of the first segment and the second segment.

2. The endoprosthesis according to the rei indication 1, characterized in that in a base element, the first segment (or trunk) has a cross section greater than that of the second segment (or branch).

3. The stent according to claim 1, characterized in that the first segment and the second segment of a base element have transverse cuts which are essentially identical.

4. The luminal endoprosthesis according to any of the preceding claims, characterized in that it comprises two base elements in their entangled state, the first respective segments of each of these two elements are coupled one inside the other and assuming, in this position, trans sections. ersales which are essentially identical, the second segment of one of the base elements is coupled in a lumen of the other base element.

5. The stent according to any of the preceding claims, characterized in that at least one base element comprises a sleeve made of a biocompatible material.

6. The stent according to any of the preceding claims, characterized in that the structure of each base element is tightened.

7. The stent according to rei indication 6, wherein the structure of each base element is braided using metal filaments made of an elastic alloy for medical use.

8. The endoprosthesis according to the rei indication 6, characterized in that the structure of each of the base elements is braided using filaments with memory of its shape.

9. The endoprosthesis according to any of the preceding claims, characterized in that the first segment of the base element comprises a part of greater cross section.

10. The stent according to any of the preceding claims, characterized in that the second segment of at least one of the base elements comprises a part of greater cross section.

11. The stent according to the indication 2, characterized in that the cross section of the trunk of a base element is equal to at least four times that of its branch.

12. The stent according to any of claims 2 and 11, characterized in that a lumen of a base element has a cross section at least equal to 1/4 of that of the trunk or at least equal to that of 1 to branch.

13. A method for manufacturing braided structures of various sizes for a stent according to any of claims 2 to 12, characterized in that it comprises the following operations: braiding the filaments, made of a material chosen from among the materials of biocompatible elastic alloys, super elastic and with memory of their shape, around a first mandrel along the length and diameter corresponding to the branch of a base element, - fix at least one auxiliary mandrel in parallel to the first mandrel, such auxiliary mandrel includes a first end and a second end, transverse cut corresponding to those of a lumen, the first end being inserted in a straight line with the braid in progress, upstream of the braiding point, the second end is placed downstream of the braiding point, the assembly (first mandr 1 -mandr i 1 auxiliary) has a cross section corresponding to that of a trunk of a base element, - continue braiding around the assembly (first auxiliary mandrel-mandrel) causing the lumen of one lumen to be braided around the first end of the auxiliary mandrel, continuing the braiding around the assembly (first mandr 1 -mandr i 1 auxiliary) throughout of a length corresponding to at least that of the trunk of a base element.

14. The method of manufacture according to claim 13, characterized in that it further comprises the following operations: continuing the braiding around the assembly (first mandr 1 -mandr i 1 auxiliary) along a length corresponding to at least the double that of the trunk of the base element, - separating the second end of at least one auxiliary mandrel from the first mandrel, said second end has a cross section corresponding to that of the lumen of a base element, continuing the braid in the first mandrel , along a length and a diameter corresponding to the branch of the base element, causing a second lumen to be braided around the second end of the auxiliary mandrel, - uncoupling the obtained braid and the mandrels, - Cut the braid obtained into two base elements.

15. The method of manufacture according to the rei indication 13, characterized in that the auxiliary mandrel comprises at least one flexible part, the separation between the second end of the auxiliary mandrel and the main mandrel is made by folding down the second end in the braid in progress .

16. The manufacturing method according to any of claims 13 to 15, characterized in that at least one enlarged part is placed in the first mandrel along the length corresponding to one of the future branches of a base element.

17. The method of manufacture according to any of claims 13 to 16, characterized in that an enlarged part of a larger diameter than the assembly (first auxiliary mandrel mandrel), is placed in this assembly along a length corresponding to the future trunks of the base elements.

18. The method of manufacture according to any of claims 13 to 17, characterized in that it comprises the insertion of a simple auxiliary mandrel.

19. The method of manufacture according to any of claims 13 to 17, characterized in that it comprises the insertion of at least two auxiliary mandrels.

20. The method of manufacturing the braided structures with multifilaments for a base element of a stent according to any of claims 3 to 10, wherein the following operations are performed: - braiding the filaments, made of a material chosen from among biocompatible materials with memory of its shape, super elastic and elastic, around a first mandrel, along the length and diameter corresponding to one of the first and second segments of the base element, - fix an auxiliary mandrel essentially perpendicular to the first mandrel, said auxiliary mandrel has a cross section corresponding to that of the desired lumen of the base element, such an auxiliary mandrel is inserted at the level of the stitch point, - continuing the braiding around the assembly (first mandrel). 1 -mandr i 1 auxiliary) along a length corresponding at least to that of the contact (first mandr 1 -mandr i 1 auxiliary ), causing the lumen of a lumen to be wound around the end of the auxiliary mandrel.