System for deploying an implant

Abstract

The present invention relates to a system for deploying an implant, optionally a TIPS stent graft, comprising a handle, a catheter extending from the handle, the catheter arranged to hold an implant in an implant holding portion at a distal end of the catheter, an implant fixation sheath arranged to surround the implant holding portion to secure an implant arranged in the implant holding portion, the implant fixation sheath, and a pull tab connected to the implant fixation sheath such that pulling the pull tab proximally pulls back the implant fixation sheath to release an implant arranged in the implant holding portion, the pull tab further comprising an engagement element arranged on the pull tab and moved proximally when the pull tab is moved proximally, the engagement element being arranged to engage with a first interference element arranged at a first fixed longitudinal position of the system for deploying the implant, the engagement between the engagement element and the first interference element providing tactile feedback to a user of the system that the implant fixation sheath has been pulled back a pre-set distance.

Description

[Technical field]

[0001] The present invention relates to a system for deploying an implant, optionally a TIPS stent graft. [Background technology]

[0002] To deploy (in other words, place or deploy) implants such as stents and stent grafts inside the human body, it is generally known to use a catheter that can be advanced through the patient's vascular system. The implant to be delivered is placed at the distal end of the catheter. The implant is typically covered by an implant fixation sheath that is crimped onto the delivery catheter and fixes the implant in place. Once the implant is positioned in the correct location inside the patient's body, the implant fixation sheath is retracted so that the implant can be deployed. In some cases, the implant is self-expanding, for example through the use of a shape memory alloy scaffold such as Nitinol, which expands at body temperature. Thus, when such an implant is exposed to the patient's bloodstream, the implant automatically expands to its delivery configuration.

[0003] One particular type of implant that presents its own challenges is a stent graft for use in a TIPS ("transjugular intrahepatic portosystemic shunt") procedure. In a TIPS procedure, a shunt is created between a patient's hepatic veins and portal veins, which extends through the patient's liver. The shunt acts as a blood bypass between these two veins and is used to treat portal hypertension. To stabilize the shunt, a special TIPS stent graft is placed inside the shunt to extend from the portal vein to the hepatic vein.

[0004] The TIPS stent graft is unusual in that it is only partially covered, with the covering material covering only one of the longitudinal ends, leaving each other longitudinal end uncovered, thus exposing the bare stent. This bare stent portion is then placed inside the portal vein and typically expands (flares) in place. This expanded portion of the stent graft serves to anchor the TIPS stent graft inside the portal vein, thus keeping it in place. However, because this portion of the base stent is uncovered, it presents little obstruction to blood flow and does not stop blood from flowing from the portal vein into the stent graft.

[0005] Then, the covered portion of the TIPS stent graft is deployed inside the shunt created through the liver parenchyma, and the other end of each of the TIPS stent grafts is finally placed in the hepatic vein. Thus, through the TIPS shunt thus placed, blood can bypass the liver and flow directly from the portal vein to the hepatic vein. This bypass relieves portal hypertension. Summary of the Invention [Problem to be solved by the invention]

[0006] One challenge with the placement of such stent grafts is the need to accurately position the uncovered and covered portions of the stent graft. On the one hand, it is important to ensure that the uncovered portion of the stent graft is provided entirely within the portal vein, because if this is not the case, blood will leak through the sidewall of the TIPS stent graft. On the other hand, if parts of the covered sections of the TIPS stent graft extend into the portal vein, they will at least partially obstruct blood flow and reduce the effective length of the TIPS shunt that can be covered using the lining portion of the TIPS stent graft. It is therefore desirable to be able to accurately place the TIPS stent graft such that the uncovered portion is entirely positioned within the portal vein, but the covered portion of the TIPS stent graft does not extend into this vein.

[0007] The present invention has been devised in view of the aforementioned problems and aims to provide a system for deploying an implant, optionally a TIPS stent graft, that makes it easier for surgeons to correctly deploy the implant. [Means for solving the problem]

[0008] The invention is defined by claim 1. Embodiments are defined in the dependent claims.

[0009] According to claim 1, a system for deploying an implant is provided. In an embodiment, such an implant may be a TIPS stent graft. It may also be some other kind of stent or stent graft (covered stent).

[0010] The system includes a handle, the portion of the system intended for manipulation by an operator. The system further includes a catheter extending from the handle. The catheter is arranged for introduction into a patient's vasculature and is thus sufficiently thin and flexible to be advanced through a human blood vessel. A distal end of the catheter is provided with an implant retaining portion adapted for an implant to be positioned thereon such that the implant can be retained in the implant retaining portion while the catheter is advanced through the patient's vasculature to an implant deployment location.

[0011] An implant fixation sheath is further provided, arranged to surround the implant holding portion. When the implant fixation sheath surrounds the implant holding portion, it fixes the implant placed in the implant holding portion, for example by covering it. In an embodiment, such an implant fixation sheath may be made of a suitable plastic material. Those skilled in the art may envision other materials that may be used.

[0012] A pull tab, which in embodiments may be a pull string (i.e., a cord), is connected to the implant fixation sheath. The pull tab is arranged such that pulling the pull tab proximally pulls the implant fixation sheath back so as to at least partially release the implant disposed in the implant holding portion. In this context, "proximal" refers to the direction toward the operator of the system, and "distal" refers to the direction away from the operator, toward the patient. In embodiments, the pull tab may be made of a metal wire, but may also be made of a string made of a non-metallic material or some other suitable element arranged to exert a proximal tension on the implant fixation sheath, and thus be used to release the implant by gradually pulling back the implant fixation sheath.

[0013] The pull tab includes an engagement element disposed on the pull tab and moved proximally with the pull tab when the pull tab is moved proximally. The engagement element is disposed to engage with a first interference element. The first interference element is disposed at a first fixed longitudinal position of the system for deploying the implant. In an embodiment, the engagement element is disposed at a fixed longitudinal position on the handle.

[0014] The system is arranged such that the engagement between the engaging element and the first interfering element provides tactile feedback to a user of the system that the implant fixation sheath has been pulled back a preset distance. That is, the user can feel that the implant fixation sheath has moved a fixed preset distance when pulling back on the pull tab. This aids in the partial deployment of implants such as TIPS stent grafts, as the user knows by tactile feedback that the implant fixation sheath has been pulled back a preset distance and therefore uncovered a preset portion of the implant, and in a self-expanding implant, expanded. The tactile feedback therefore serves as an indication to the user that a preset portion of the implant has been uncovered and therefore partially deployed. Although described above primarily with respect to the deployment of TIPS stent grafts, the invention is also applicable to the deployment of bifurcated stent grafts for use in the treatment of abdominal aortic aneurysms.

[0015] In an embodiment, the system includes a pull tab retraction mechanism, which is a mechanism disposed on the system to assist in pulling back the pull tab. In an embodiment, the pull tab retraction mechanism is disposed on the handle. When the pull tab is pulled proximally using the pull tab retraction mechanism, the covering of the implant disposed on the implant holding portion is first partially and then completely removed. The pull tab retraction mechanism makes it easier for the clinician / operator to retract the implant fixation sheath.

[0016] In a further embodiment, the pull tab retraction mechanism comprises a thumb wheel coupled to a spindle. The thumb wheel is operable by a user. The spindle is arranged to wind up the pull tab to exert a proximal pull on the pull tab. That is, by manipulating the thumb wheel, the pull tab is pulled proximally to pull the implant fixation sheath proximally, thereby releasing the implant disposed in the implant holding portion. In another embodiment, instead of using a thumb wheel, the pull tab is retracted by a slider that is used to pull the pull tab back, such as that described in WO2008 / 017683A1.

[0017] In an embodiment, the tactile feedback provides prevention of further retraction of the pull tab. This prevention of further retraction ensures that the point at which the implant fixation sheath has been pulled back a pre-set distance cannot be missed by the operator, since it is not possible to retract the pull tab further. Hence, the corresponding system is very easy to use.

[0018] In a further embodiment, the system further comprises a first release mechanism for selectively releasing the prevention of further retraction of the pull tab by the engagement between the engaging element and the first interference element. That is, the pull tab cannot be prevented from being further retracted. Thus, if the engagement between the engaging element and the first interference element corresponds to partial deployment of the implant, releasing the prevention of further retraction of the pull tab can be advantageous to allow partial removal of the implant fixation sheath followed by complete removal of the implant fixation sheath. This aids in the deployment of implants that benefit from being deployed in two stages, such as a TIPS stent graft.

[0019] In an embodiment, the engagement element comprises a protrusion fixedly disposed on the pull tab. The first interference element is a narrow opening on the inside of the handle, the opening being sized such that the protrusion engages a boundary of the opening to provide tactile feedback to the user. Such a configuration of the engagement element and the first interference element has high reliability.

[0020] In an embodiment, the pull tab is guided through an opening provided on the inside of the handle as the first interfering element, such a configuration providing good control of the path taken by the pull tab.

[0021] In an embodiment, a second interference element is further provided, disposed at a second fixed longitudinal position of the system for deploying the implant, the second fixed longitudinal position being different from the first fixed longitudinal position. The engagement element is disposed to engage with the second interference element to provide tactile feedback to the user. Again, for reasons similar to those described for the first interference element, this tactile feedback may provide useful information to the user, such as that if the pull tab is further retracted, deployment of the implant will commence (engagement between the second interference element and the engagement element corresponds to a configuration in which the implant fixation sheath fully covers the implant, but further retraction of the implant fixation sheath leads to partial removal of the implant's coverage).

[0022] In an embodiment, the tactile feedback of engagement between the engagement element and the second interference element is a prevention of further retraction of the pull tab, which leads to the advantages discussed above of the prevention of further retraction of the pull tab due to engagement between the engagement element and the first interference element.

[0023] Additionally, in embodiments, a second release mechanism is provided that selectively releases the engagement between the second interference element and the engagement element from preventing the pull tab from being pulled back. This allows the pull tab to be selectively pulled back further. The second release mechanism is optionally operable by a user-operable button, which makes the system easy to use. Again, similar advantages to those discussed with respect to the first release mechanism may be achieved.

[0024] It is according to an embodiment that the engagement between the second interference element and the engagement element corresponds to an implant fixation sheath that completely covers the implant retaining portion, i.e., this engagement may correspond to an initial configuration of the system (i.e., meaning the configuration of the system before it is advanced through the patient's vasculature).

[0025] According to an embodiment, the system comprises an implant, optionally a stent graft, and further optionally a TIPS stent graft, arranged in an implant holding portion, such that an implant, such as a stent graft or a TIPS stent graft, can be appropriately delivered by such a system.

[0026] In an embodiment, the implant is a self-expanding implant. By this is meant that the implant expands to a fully expanded configuration when warmed to body temperatures encountered within the human or animal body. Such a self-expanding implant comprises a scaffold of Nitinol, as an example of a shape memory alloy. However, other types of materials may also be used.

[0027] In embodiments, the engagement between the engaging element and the first interference element corresponds to a partial deployment of the implant, which may facilitate proper placement of the implant inside the patient's body. In embodiments where a TIPS stent graft is provided on the implant retaining portion, the engagement between the engaging element and the first interference element corresponds to a state where the uncovered portion of the TIPS stent graft is deployed, but the covered portion is still covered by the implant fixation sheath. [Brief description of the drawings]

[0028] [Figure 1] 1 illustrates a system according to an embodiment of the present invention. [Diagram 2] 2 illustrates the inside of the handle of the system of FIG. 1 in a first configuration. [Diagram 3] 3 illustrates the interior and second configuration of FIG. 2; [Figure 4] 2 illustrates the interior of the system of FIG. 1 in a third configuration; [Figure 5a] 1 illustrates steps that may be taken during deployment of a TIPS stent graft. [Figure 5b] 1 illustrates steps that may be taken during deployment of a TIPS stent graft. [Figure 5c] 1 illustrates steps that may be taken during deployment of a TIPS stent graft. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] FIG. 1 illustrates a system for deploying an implant according to an embodiment of the present invention. As can be seen in this figure, a handle 12 is provided with a first component 13 and a second component 15 arranged one on top of the other and connected to each other. At one end of the handle 12, a flexible tip 17 is provided. At the end of the flexible tip 17, a catheter 14 suitable for insertion into the vasculature of a patient is arranged. This catheter 14 can be advanced through the vasculature of a patient and can provide at its distal end an implant, such as a TIPS stent graft. The catheter 14 has an implant-holding portion (not shown) at its distal end and an implant fixation sheath (not shown) covering the implant-holding portion.

[0030] The handle 12 has a recess 33 on its upper side, positioned so that the surgeon can place his or her thumb. Opposite the recess 33, the handle 12 is provided with two protrusions 35 positioned to help the surgeon hold the device and handle and prevent them from slipping off. The surgeon can grip his or her hand around the handle 12 with his or her thumb in the recess 33 and the remaining fingers positioned between the protrusions 35 so that the handle 12 is held securely. The protrusions 35 are provided at two locations spaced apart along the length of the handle 12.

[0031] A thumbwheel 22 is disposed on the handle 12 so as to protrude from an opening in the handle 12 provided inside the recess 33. The thumbwheel 22 has a surface structured to increase its frictional force to make its operation easier. The thumbwheel 22 is coupled to a spindle (not shown), which is coupled to a pull tab 16, which will be discussed further below with reference to Figures 2-4. The pull tab 16 is coupled to an implant fixation sheath, such that proximal movement of the pull tab 16 pulls the implant fixation sheath proximally, thus uncovering the implant holding portion, thus deploying the implant held in the implant holding portion. By operating the thumbwheel 22, the pull tab 16 wraps around the spindle and the pull tab 16 is pulled proximally (to the left in Figure 1).

[0032] In FIG. 1, a first release mechanism 28 and a second release mechanism 24 are provided. The first release mechanism 28 is actuated by a button, and the second release mechanism 24 is operable by a slider. When the second release mechanism 24 is not actuated, a structure discussed below with reference to FIGS. 2-4 prevents the implant fixation sheath from being pulled back, and the covering of the implant holding portion cannot be even partially removed. That is, the implant provided in the implant portion cannot be even partially deployed unless the second release mechanism 24 is actuated. However, when the slider of the second release mechanism 24 is slid to an actuated position, this prevention of the pull tab 16 from being pulled back in the proximal direction is released, whereby rotation of the thumb wheel 22 can pull the pull tab 16 in the proximal direction. This allows partial deployment of the implant disposed in the implant holding portion at the distal end of the catheter 14.

[0033] When the pull tab 16 is pulled further proximally by operating the thumb wheel 22, the pulling of the pull tab 16 in the proximal direction is prevented by engagement with a first interference element 26, which will be discussed further below. This engagement may also be selectively released by actuating a first release mechanism 28 by pressing an associated button. This releasable prevention of further retraction of the pull tab 16 may correspond to partial deployment of an implant disposed at the distal end of the catheter 14. In the case of a TIPS stent graft provided at the distal end of the catheter 14, this may correspond to selective partial release of the uncovered portion of the stent graft. As previously pointed out, this is highly advantageous when it comes to deploying and placing a TIPS stent graft in the human liver. Once the uncovered portion is deployed, the surgeon may actuate the first release mechanism to release the prevention of further retraction of the pull tab 16, thus completely releasing the implant.

[0034] In the structure illustrated in FIG. 1, different positions and portions of the catheter 14 are marked. Position A indicates the position to which the implant fixation sheath extends when the implant retaining portion is fully covered. This position corresponds to the position where the pull tab 16 is prevented from being pulled back further by the unactuated second release mechanism 24. When the second release mechanism 24 is actuated, the implant fixation sheath can be pulled back beyond the distance indicated by the letter "D". This partial pullback corresponds to a state where only the uncovered portion of, for example, the TIPS stent graft is exposed to the patient's body.

[0035] The portion designated by E corresponds to a fully complete retraction of the implant fixation sheath such that the entire covering of the implant holding portion (and therefore of the implant) is removed so that the implant may be deployed. This corresponds to the fully deployed configuration.

[0036] The portion designated by C is the portion of the catheter 14 that is not used for delivery of the implant, i.e., this portion serves to provide sufficient length of the catheter 14 to reach the deployment location of the implant.

[0037] The catheter 14 may provide a lumen therein suitable for guiding a guidewire, which may extend through a connector 19 at the proximal end of the handle 12, which may be a Luer connector.

[0038] Figure 2 illustrates an inside view of the lower part 13 of the handle 12 in a configuration in which the implant fixation sheath extends to point A illustrated in Figure 1, i.e. the implant holding portion is completely covered. The lower part 13 of the handle 12 is made of a plastic shell having a semi-cylindrical shape that bulges from the distal end 50 towards the central portion. This allows the handle 12 to be gripped ergonomically. At the distal end 50 a semi-spherical cutout 32 is provided through which the pull tab 16 extends. This pull tab 16 is guided through the interior of the lower part 13 and is wound on a spindle (not shown) attached to the thumb wheel 22.

[0039] On the inside of the lower part 13, reinforcing ribs 32 are provided which serve to provide mechanical stability to the lower part 13. These reinforcing walls 32 have notches through which the pull tab 16 is guided, i.e., these notches serve to stabilize the path of the pull tab 16. Near the distal end 50 of the lower part 13, a metal plate 30 is provided with a hole through which the pull tab 16 is guided, this plate 16 also serves to stabilize the path taken by the pull tab 16. This plate 30 is attached (clipped) to one of the ribs 32.

[0040] Proximally to the plate 30, there is a leaf spring 20, one end of which is held in a rib 34 provided in the wall of the lower part 13. This leaf spring 20 is bent. Its bent portion abuts against an engagement element 18 in the form of a ring-shaped protrusion fixedly arranged on the pull tab 16. The bent portion of the leaf spring 20 abuts against the most proximal portion of the engagement element 18 so as to prevent the engagement element 18 from moving in the proximal direction. This then prevents the pull tab 16 from moving in the proximal direction. The leaf spring 20 is coupled to a slider 24, the sliding movement of which bends the leaf spring 20, and the bent portion disengages from the engagement element 18. In this configuration, the engagement element 18 can move in the proximal direction and the pull tab 16 can be moved in the proximal direction. This then allows the implant fixation sheath to be pulled back across the area indicated as "D" in FIG. 1. Thus, the bent portion of the leaf spring 20 constitutes a second interference element.

[0041] Further proximally on the leaf spring 20 there is provided a first interference element 26 having the form of a U-shaped plastic plate coupled to a push button 28. The pull tab 16 is guided through a recess in the U-shaped plate 26. When the push button 28 is pressed, the U-shaped plate 26 is depressed deep enough that the pull tab 16 no longer extends through the recess in the U-shaped plate 26. The recess in the U-shaped plate 26 is sized so that the engaging element 18 does not fit such that the engagement between the engaging element 18 and the U-shaped plate 26 prevents the engaging element 18 from moving through the recess, but is wide enough to allow the remaining part of the pull tab 16 to pass freely.

[0042] Figure 3 illustrates a configuration in which the engagement element 18 has been disengaged from the second interference element in the form of leaf spring 20 and the pull tab 16 has been pulled proximally to move the implant fixation sheath across portion D in Figure 1. As can be seen in Figure 3, in this configuration, the engagement element 18 now abuts the first interference element 26. Proximal movement of the engagement element 18 is prevented by this abutment, since the push button 28 has not been depressed.

[0043] 4, push button 28 is pressed as indicated by the arrow and there is no longer any engagement between first interference element 26 and engaging element 18. Thus, pull tab 16 can be pulled proximally, and engaging element 18 can also be pulled to a position more proximal than proximal of the currently positioned first interference element 26. In this configuration, the implant fixation sheath can be moved across region E illustrated in FIG. 1 to fully deploy the implant provided in the implant retaining portion.

[0044] Thus, the device described above provides the surgeon with clear tactile feedback as to when retraction of the implant fixation sheath has begun and when the implant has been partially uncovered, so that the surgeon knows when the implant has been partially uncovered and can ensure that the thus uncovered portion is properly seated.

[0045] For example, in the case of a TIPS stent graft, the surgeon can ensure that the uncovered portion of the TIPS stent graft is positioned in the portal vein, for example using X-ray imaging of markers on the TIPS stent graft. The surgeon can then feel that the uncovered portion is fully positioned inside the portal vein by noticing that it abuts the junction between the TIPS shunt and the portal vein (as a mechanical resistance to the proximal pullback of the TIPS stent graft to be deployed). Thus, very accurate and convenient positioning of the TIPS stent graft is possible, since the surgeon knows that only the uncovered portion has been uncovered, but that the coverage of this portion has been completely removed.

[0046] Therefore, when wishing to place a TIPS stent graft using the design described above, the following steps, also shown in part in Figures 5a to 5c, are performed by the surgeon.

[0047] A step of creating a TIPS shunt connecting the patient's hepatic vein (HV) and portal vein (PV).

[0048] Inserting a catheter 14 into the patient's vasculature and, in an embodiment using a guidewire (not shown), advancing its tip through the TIPS shunt and into the portal vein.

[0049] Releasing the prevention of pull-back of the pull tab 16 by the engagement between the second interference element 20 and the engagement element 18 (not shown).

[0050] Pulling back the implant fixation sheath to release the uncovered portion 102 of the TIPS stent graft 100 until further retraction is prevented by engagement between the first interference element 26 and the engagement element 18 (FIG. 5a).

[0051] Positioning the uncovered portion of the TIPS stent graft inside the portal vein PV.

[0052] Releasing the prevention of further pulling back of the pull tab 16 by the engagement between the first interference element 27 and the engagement element 18 .

[0053] Pulling back the implant fixation sheath to fully release the TIPS stent graft 100 (FIGS. 5b, 5c).

[0054] It should be noted that although the present invention has been described primarily with respect to the placement of a TIPS stent graft, the present invention is equally applicable to the placement of a bifurcated stent graft for the treatment of abdominal aortic aneurysms.

Claims

1. A system (10) for deploying an implant, the system comprising: A handle (12); a catheter (14) extending from the handle (12), the catheter positioned to hold an implant in an implant holding portion at a distal end of the catheter; an implant fixation sheath disposed around the implant holding portion to fix an implant disposed in the implant holding portion; a pull tab (16) connected to the implant fixation sheath, wherein pulling the pull tab proximally pulls back the implant fixation sheath to release an implant disposed in the implant holding portion, the pull tab further comprising an engaging element (18) disposed on the pull tab (16) and moved proximally when the pull tab (16) is moved proximally, the engaging element (18) being positioned to engage with a first interference element (26) disposed at a first fixed longitudinal position of the system for deploying the implant; Equipped with engagement between the engaging element (18) and the first interference element (26) provides tactile feedback to a user of the system that the implant fixation sheath has been pulled back a preset distance and prevents further retraction of the pull tab (16); The system (10) further comprises a pull-tab retraction mechanism, the pull-tab retraction mechanism being arranged to pull the pull-tab (16) in a proximal direction to release an implant disposed in the implant holding portion; the pull tab retraction mechanism comprises a thumbwheel (22) coupled to a spindle, the spindle being positioned to wind up the pull tab (16) so as to exert a proximal pull on the pull tab (16); the system further comprises a first release mechanism (28) distinct from the pull tab retraction mechanism for selectively releasing the prevention of further retraction of the pull tab (16); the engagement element (18) comprises a protrusion fixedly attached to the pull tab (16), and the first interference element (26) comprises an opening in the interior of the handle (12), the opening being sized such that the protrusion engages a boundary of the opening to provide tactile feedback to the user; The pull tab (16) is guided through the opening provided inside the handle (12) as part of the first interference element (26).

2. The system of claim 1 , wherein the first release mechanism (28) is operable by a user-operable button.

3. 3. The system of claim 1, further comprising a second interference element (20) positioned at a second fixed longitudinal position of the system for deploying the implant, the engagement element (18) positioned to engage the second interference element (20) to provide tactile feedback to the user.

4. The system of claim 3 , wherein the tactile feedback is an inhibition of pull-back of the pull tab (16).

5. 5. The system of claim 3 or 4, further comprising a second release mechanism (24) that selectively releases the prevention of retraction of the pull tab (16) due to the engagement between the second interference element (20) and the engagement element (18).

6. The system of claim 5, wherein the second release mechanism (24) is operable by a slider.

7. 7. The system of claim 3, wherein the engagement between the second interference element (20) and the engagement element (18) corresponds to the implant fixation sheath completely covering the implant holding portion.

8. The system of claim 1 , further comprising an implant disposed in the implant holding portion.

9. The system of claim 8 , wherein the implant is a stent graft.

10. The system of claim 9 , wherein the implant is a TIPS stent graft.

11. 11. The system of any one of claims 8 to 10, wherein the implant is a self-expanding implant.

12. The system of any one of claims 8 to 11, wherein the engagement between the engaging element (18) and the first interference element (26) corresponds to partial deployment of the implant.

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