Method of making a stent

Abstract: A bifurcated stent for insertion into a bifurcated vessel such as a blood vessel. In one embodiment, a first sheet is formed into a first leg, a second sheet is formed into a second leg, a third sheet is formed into a stem, and the two legs are attached to the stem. In a second embodiment, a first sheet is formed into a member having a first leg and half of a stem, a second sheet is formed into a second member having a second leg and half of a stem, and the two stem halves are combined to form the bifurcated stent. In a third embodiment, the stent comprises two sections that are serially inserted and assembled within the vessel at the site of the bifurcation to be treated.

Description: Field of the Invention The present invention relates to stents, and more particularly to a method of making bifurcated stents for insertion within a branching vessel. Background of the Invention Stents are well known in the art. They are typically formed of a cylindrical metal mesh which can expand when pressure is internally applied. Alternatively, they can be formed of wire wrapped into a cylindrical shape or sheets of material formed into a cylindrical shape. Stents are devices which are usually implanted within bodily conduits including the vascular system to reinforce collapsing, partially occluded, weakened, or abnormally dilated sections of the blood vessel. Stents also have been successfully implanted in other areas, e.g., the urinary tract or the bile duct to reinforce such bodily conduits. U.S. Patent No. 4,994,071 (MacGregor) discloses an expandable, bifurcating stent having a main cylindrical lattice formed from interconnected flexible wire. Two additional cylindrical lattices, having smaller diameters than the main lattice, are similarly constructed. The main lattice includes a flexible wire interconnecting the main lattice to one of the additional lattices. A second flexible wire interconnects the main lattice to the other additional lattice. The flexible wires form backbones that extend axially along the length of the main lattice and along each of the additional lattices. One disadvantage of this bifurcating stent is the complex nature of the interconnection of the flexible wires forming the backbones with the loop structure of each lattice. Summary of the Invention The present invention solves these and other disadvantages of the prior art by providing a method of fabricating a stent as set forth in the accompanying claim 1. Advantageous embodiments of this method are claimed in dependent claims 2 to 6. Brief description of the drawings FIG. 1 shows a sheet used to form a first expandable tubular member; FIG. 2 shows the sheet of FIG. 1 after it has been formed into a first expandable tubular member; FIG. 3 shows the first expandable tubular member of FIG. 2 with catheters inserted into the longitudinal bore and the side branch aperture; FIG. 4 shows the first expandable tubular member of FIG. 3 after expansion with an unexpanded second tubular member being introduced into the side branch aperture; FIG. 5 shows the first expandable tubular member of FIG. 4 after expansion with an unexpanded second tubular member disposed in the side branch aperture; FIG. 6 shows the second tubular member of FIG. 5 after it has been expanded; FIGS. 1 to 6 show the method of making a bifurcated stent in accordance with the invention. FIG. 1 shows a sheet 300 used to form a first expandable tubular member 301. The sheet 300 has a longitudinal axis 302, a circumferential axis 303, a proximal end 304, a distal end 305, a first side 306, a second side 307, a third side 308, a fourth side 309, a fifth side 310, and a sixth side 311. The sheet 300 may be provided with a variety of patterns, however, in a preferred embodiment the sheet 300 is provided with a plurality of expandable cells 312 adapted to be substantially flexible prior to expansion of the first tubular member 301 and substantially rigid after expansion of the first tubular member 301. In an especially preferred embodiment the flexible cells 312 of the sheet 300 are substantially uniform as shown in FIG. 1. The first side 306 of the sheet 300 has a proximal portion 313 having a proximal end 314 and a distal end 315. The first side 306 also has a distal portion 316 having a proximal end 317 and a distal end 318. The second side 307 of the sheet 300 has a proximal end 319 and a distal end 320 and is disposed between the proximal end 304 of the sheet 300 and the distal end 305 of the sheet 300. The third side 308 of the sheet 300 has a proximal end 321 and a distal end 322 and is disposed between the distal end 320 or the second side 307 and the distal end 305 of the sheet 300. The fourth side 309 of the sheet 300 is disposed between the proximal end 314 of the proximal portion 313 of the first side 306 and the proximal end 319 of the second side 307. The fifth side 310 of the sheet 300 is disposed between the distal end 318 of the distal portion 316 of the first side 306 and the distal end 322 of the third side 308 and is provided with a length L1 that is shorter than the length L2 of the fourth side 309. In a preferred embodiment, the length L1 of the fifth side 310 and the length L2 of the fourth side 309 are in a ratio of about 5:7, i.e., the fifth side 310 has a length L1 that is about 70% of the length L2 of the fourth side 309. In an especially preferred embodiment the sheet 300 is etched with a plurality of substantially uniform cells 312 as previously discussed and the number of cells disposed along the circumferential axis 303 of the fifth side 310 and the number of cells disposed along the circumferential axis 303 of the fourth side 309 are in a ratio of about 5:7. A sixth side 311 is disposed between the second side 307 and the third side 308. In an especially preferred embodiment, the first side 306, second side 307, and third side 308 are substantially parallel to each other and the fourth side 309, fifth side 310, and sixth side 311 are substantially parallel to each other and the first side 306, second side 307, and third side 308 are substantially perpendicular to the fourth side 309, fifth side 310, and sixth side 311. To make the first expandable tubular member 301, the second side 307 of the sheet 300 is attached via attaching means to the proximal portion 313 of the first side 306 of the sheet 300 and the third side 308 of the sheet 300 is attached via attaching means to the distal portion 316 of the first side 306 of the sheet 300 to form a first expandable tubular member 301 having a longitudinal bore 323 defining a longitudinal axis 324 as shown in FIG. 2. The attaching step may be carried out utilizing a variety of attaching means well known to those skilled in the art as suitable for this purpose, however, in a preferred embodiment the attaching step is carried out utilizing screwing, crimping, soldering, welding, or spot welding. In the embodiment shown in FIG. 2 spot welding 325 has been utilized. After the sides have been attached as discussed above, the fourth side 309 defines a proximal tubular member aperture or stent aperture 326 communicating with the longitudinal bore 323, and the fifth side 310 defines a distal tubular member aperture or stent aperture 327 communicating with the longitudinal bore 323 as shown in FIGS. 2 and 5. The sixth side 311 and the proximal end 321 of the third side 308 and the proximal end 317 of the distal portion 316 of the first side 306 define a side branch aperture 328 (as shown in FIGS. 2-5) sized and adapted to receive and secure a second expandable tubular member 329 (shown in FIGS. 5-6). The branch aperture 328 has a diameter D1 that is larger than the diameter D2 of the unexpanded stent, i.e., the branch aperture 328 is larger than the proximal and distal apertures 326 and 327 of the first tubular member 301 both before and after the tubular member 301 is expanded. The first expandable tubular member 301 is then delivered to a bifurcated vessel having a first lumen and a second lumen so that the first expandable tubular member is disposed within the first lumen and the branch aperture communicates with the second lumen. In a preferred embodiment, delivery is via a balloon catheter as previously discussed. After it has been positioned, the first expandable tubular member is expanded in an amount sufficient to secure the first expandable tubular member in the first lumen. A second expandable tubular member 329 is then prepared having a proximal end 330 and a distal end 331 and having longitudinal bore 332 therethrough. The second expandable tubular member 329 (shown in FIGS. 4, 5, and 6) may be patterned in the same way as the sheet 300 as previously discussed. In a preferred embodiment the cells 312 of the sheet 300 used to make the first expandable tubular member 301 and the cells 312' of the second expandable tubular member 329 are substantially uniform. The second expandable tubular member 329 is delivered into the longitudinal bore 323 of the first tubular member 301, as shown in FIG. 4, and is advanced into and beyond the branch aperture 328, as shown in FIG. 5, so that the distal end 331 of the second expandable tubular member 329 is disposed within the second lumen and the proximal end 330 of the second expandable tubular member 329 is disposed within the longitudinal bore 323 of the first tubular member 301. The second expandable tubular member 329 is then expanded in an amount sufficient to secure the second expandable tubular member 329 within the second lumen and within the branch aperture 328 of the first tubular member 301 as shown in FIG. 6. Among the advantages that this embodiment provides is that this stent provides a large branch aperture that facilitates the introduction of the second tubular member into the side branch or second lumen. In addition, this stent is especially suitable for the performance of serial bifurcation stenting and also for stenting around a side branch before it is occluded.

Claims: A method of making a stent comprising the steps of: a) preparing a sheet (300) having a proximal end (304), a distal end (305), a longitudinal axis (302), and a circumferential axis (303), the sheet (300) provided with: a first side (306) having a proximal portion (313) having a proximal end (314) and a distal end (315) and a distal portion (316) having a proximal end (317) and a distal end (318); a second side (307) having a proximal end (319) and a distal end (320), the second side (307) disposed between the proximal end (304) of the sheet (300) and the distal end (305) of the sheet (300); a third side (308) having a proximal end (321) and a distal end (322), the third side (308) disposed between the distal end (320) of the second side (307) and the distal end (305) of the sheet (300); a fourth side (309) disposed between the proximal end (314) of the proximal portion (313) of the first side (306) and the proximal end (319) of the second side (307); the fourth side having a length (L2); a fifth side (310) disposed between the distal end (318) of the distal portion (316) of the first side (306) and the distal end (322) of the third side (308), the fifth side (310) having a length (L1) that is shorter than the length (L2) of the fourth side (309); and a sixth side (311) disposed between the second side (307) and the third side (308); b) rolling the sheet (300) to form a first tubular member (301) having a side branch aperture (328) communicating with a longitudinal bore (323) of the first tubular member (301); c) attaching the second side (307) to the proximal portion (313) of the first side (306) and the third side (308) to the distal portion (316) of the first side (306) so that the fourth side (309) defines a proximal stent aperture (326) communicating with the longitudinal bore (323), the fifth side (310) defines a distal stent aperture (327) communicating with the longitudinal bore (323), and the sixth side (311) and the proximal end (321) of the third side (308) and the proximal end (317) of the distal portion (316) of the first side (306) define the side branch aperture (328) communicating with the longitudinal bore (323) and sized and adapted to receive and secure a second tubular member (329). The method of claim 1, further comprising the step of disposing and securing a second tubular member (329) having a proximal end (330) and a distal end (331) and having longitudinal bore (332) therethrough within the side branch aperture (328) of the first tubular member (301). The method of claim 1 or 2, wherein the attaching step c) is carried out utilizing screwing, crimping, soldering, welding or spot welding. The method of one of the preceeding claims, wherein the fifth side (310) has a length that is about 70 % of the length of the fourth side (309). The method of one of the preceeding claims, wherein the branch aperture (328) is larger than the proximate and distal apertures (326, 327) of the first tubular member (301). The method of one of the preceeding claims, wherein the first, second and third sides (306, 307, 308) are substantially parallel to each other and the fourth, fifth and sixth sides (309, 310, 311) are substantially parallel each other. The method of one of the preceeding claims, wherein the first, second and third sides (306, 307, 308) are substantially perpendicular to the fourth, fifth, and sixth sides (309, 310, 311).

Inventors: PINCHASIK GREGORY, RICHTER JACOB, PINCHASIK, GREGORY, RICHTER, JACOB
Applicants: MEDINOL LTD, MEDINOL LTD.
Application year: 1999
Main classification: A61F2
IPC codes: A61F2