TIPS Stent Graft and Kit

Abstract

The present invention relates to a TIPS stent graft, comprising a tubular component having a lumen extending therethrough, the tubular component comprising a balloon expandable central section and a first and a second self-expanding section, the first and the second self-expanding section sandwiching the central section, the lumen extending through the first, central, and second sections, the stent graft being capable of selectively constricting the central section.

Claims

1. A Transjugular Intrahepatic Portosystemic Shunt (TIPS) stent graft, comprising: a tubular component having a lumen extending therethrough, the tubular component comprising: a balloon expandable central section; and a first self-expanding section and a second self-expanding section, the first and the second self-expanding sections sandwiching the central section, the lumen extending through the first self-expanding section, the central section, and the second self-expanding section, the TIPS stent graft being arranged so as to be capable of selectively restricting the central section.

2. The TIPS stent graft according to claim 1, the central section comprising a shape memory alloy having a transition temperature above body temperature, the central section being configured to assume a configuration which is more constricted than the first and second self-expanding sections in their expanded state when heated above its transition temperature.

3. The TIPS stent graft according to claim 1, further comprising a constriction means to selectively constrict the central section.

4. The TIPS stent graft according to claim 3, wherein the constriction means is a collar wrapped around the central section, the collar being arranged to selectively reduce its inner diameter to thereby constrict the central section.

5. The TIPS stent graft according to claim 4, wherein the collar is arranged to selectively reduce its inner diameter upon an application of heat.

6. The TIPS stent graft according to claim 4, wherein the collar comprises a metal.

7. The TIPS stent graft according to claim 4, the collar being arranged to heat up upon application of electric energy to thus reduce its inner diameter, the stent graft further comprising electrodes to supply electricity to the collar.

8. The TIPS stent graft according to claim 7, the electrodes being formed on an inside of the stent graft.

9. The TIPS stent graft according to claim 8, the electrodes comprising first and second electrodes, with the first electrode being provided on the first self-expanding section and with the second electrode being provided on the second self-expanding section.

10. The TIPS stent graft according to claim 4, the collar being formed as a cylinder.

11. The TIPS stent graft according to claim 4, the collar being formed as a coil.

12. The TIPS stent graft according to claim 1, wherein the collar comprises a shape memory alloy.

13. The TIPS stent graft according to claim 12, the shape memory alloy having a higher transition temperature than the first and second sections.

14. The TIPS stent graft according to claim 7, further comprising a catheter comprising electrodes arranged to supply energy to the electrodes of the stent graft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 shows a TIPS stent graft according to a first embodiment of the invention.

[0029] FIG. 2 shows a TIPS stent graft according to a second embodiment of the invention.

[0030] FIG. 3 shows an enlarged view of the TIPS stent graft of FIG. 2 in a use configuration.

[0031] FIG. 4 shows a TIPS stent graft according to a third embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows, schematically, the configuration of a TIPS stent graft according to a first embodiment of the invention. The stent graft 10 comprises a first self-expanding section 12 made of bare nitinol. This section 12 can be placed inside the portal vein of a patient and is configured so that it will be at its programmed size at temperatures higher than 20° C.

[0033] Central section 14 is an ePTFE covered nitinol section that has a transition temperature of higher than 37° C. (for example 50° C.). This section has a programmed small nominal diameter of 6 mm or less at body temperature. At that temperature, the material of the stent used in the central section 14 is (at least mostly) in the martensitic state. In that configuration, it is malleable without being permanently set. If this central section 14 is raised to a higher temperature then its transition temperature, it will return to its original small diameter.

[0034] Second section 16 is an ePTFE covered self-expanding nitinol section that is at a programmed size at temperatures larger than 20° C., for example at body temperature. Thus, at body temperature, it expands to the larger diameter.

[0035] When placing the stent graft 10 in the liver channel which has been created for the TIPS procedure, first and second sections 12 and 16 expand to their programmed full diameter. In the case of first self-expanding section 12, this helps in locating the stent graft and anchoring it in the portal vein. In the case of section 16, this helps in ensuring that there is no flow restriction in that section whilst also potentially helping with locating it and anchoring it.

[0036] The physician would then use a balloon to open up the central section 14 to its intended diameter (typically 8-10 mm). This would be larger than its nominal diameter of 6 mm or less. The material would stay in this expanded shape without being damaged as long as the liver tissue does not collapse the stent. If in that configuration, the pressure balance is acceptable, no further steps are necessary.

[0037] Should the physician later need to reduce the flow through the stent graft 10 (due to hepatic encephalitis or for other reasons), he needs to only raise the temperature of the central section 14 above the transition temperature. This may be accomplished by inserting a heater via a catheter, by applying a voltage to the stent or by any other method such as, for example, induction heating to raise the local temperature to, for example, 50° C. for a short period. It may also be possible to do this using an MRI device or some other method which heats up the stent graft noninvasively.

[0038] When the temperature of the stent is raised above the transition temperature of the central section 14, the material of the central section 14 will be reset to its pre-programmed small diameter, which will reduce the flow through the stent graft 10. If the thus achieved default setting of the cross-sectional diameter of the stent graft 10 is acceptable, no further action is required. On the other hand, if the physician needs to reopen the central section 14 to a larger diameter, he could do this by letting the central section 14 cool down to body temperature and by re-expanding it with a balloon to its desired size.

[0039] This would, effectively, allow for the placement of a 9 or 10 mm diameter stent graft in the first instance. If the stent is too big, it can be reset to 6 mm or smaller and then resized to 7 or 8 mm. This procedure could be repeated as many times as necessary to set the correct diameter.

[0040] Since central section 14 would be covered with ePTFE or other suitable materials, the covering would to prevent bile or other fluids from the liver from entering the bloodstream. This also means that surrounding tissue would not crawl into the stent graft 10, so the change in diameter when expanding or constricting the stent graft 10 should not cause damage to the surrounding liver tissue even after several weeks or months of implantation.

[0041] FIG. 2 shows a more detailed view of a second embodiment of the present invention. A stent graft 110 comprises a first self-expanding section 112 and a second self-expanding section 116. Together with the central section 114, they constitute the tubular component 111 of the TIPS stent graft 110. As can be seen from the drawing, a lumen 113 extends through the stent graft 110 from one end to the respective other end.

[0042] Provided so as to surround the central section 114 is a coil 120 made of nitinol. This coil is connected via wires 121 to electrodes 122, 124 which are shown in FIG. 3. By means of those electrodes 122, 124, a current can be led through the coil 120 which will heat up that coil 120. If this heating up heats up the coil 120 beyond its transition temperature, the coil 120 will assume a configuration with a smaller circumference, thereby constricting the central section 114.

[0043] FIG. 3 shows in more detail the stent graft 110 shown in FIG. 2 in a configuration where a catheter 130 has been introduced. The catheter 130 has two expanded sections 140 which hold electrodes 142, 144. Those electrodes abut against electrodes 122, 124 of the stent graft. Provided between the expanded sections 140, 141 is a narrower section 139 which is provided inside the central section 114. When applying a voltage to the electrodes 142, 144 of the catheter 130 through wires provided in the inside of the catheter 130 (not shown), a current flows through the wire constituting the coil 120. The coil 120 will then heat up and, if heated above its transition temperature, assume a more constricted configuration, as discussed previously with respect to FIG. 2.

[0044] FIG. 4 shows a third embodiment of the present invention. Between a first self-expanding section 212 and a second self-expanding section 216, a central section 214 with a smaller diameter is arranged. This section is surrounded by a tubular collar 220. This collar is, in turn, connected to electrodes (not shown) provided on the inside of the stent graft 210. When applying a voltage to those electrodes, a current flows through the collar 220 which again causes the collar 220 to heat up and to shrink and to thus assume a constricted configuration. In turn, this reduces the cross-sectional area of the stent graft 210. The further details of the stent graft 210 are identical to what is shown in FIG. 3.