Patent Description:
In order to deploy implants such as stents and stent grafts inside a human body, it is generally known to use catheters that can be advanced through a patient's vasculature. At the distal end of the catheters, the implant to be delivered is arranged. This implant is typically crimped down on the delivery catheter and is covered with an implant retaining sheath that retains it in place. Once the implant has been positioned at the correct place inside the patient's body, the implant retaining sheath is retracted so that the implant can be deployed. In a number of cases, the implant is self-expanding, for example due to the use of a scaffolding made of a shape memory alloy such as nitinol, and will expand at body temperature. Accordingly, once such an implant is exposed to a patient's bloodstream, it will automatically expand to its delivery configuration.

One particular type of implant that presents its own challenges are stent grafts for use in a TIPS ("transjugular intrahepatic portosystemic shunt") procedure. In a TIPS procedure, a shunt is created between the hepatic vein and the portal vein of a patient, with the shunt extending through the patient's liver. This shunt, which serves as a blood bypass between those two veins, is used to treat portal hypertension. To stabilize the shunt, a specialised TIPS stent graft is placed inside the shunt so as to extend from the portal vein to the hepatic vein.

A TIPS stent graft is unusual in that it is only partially covered: the covering material only covers one of the longitudinal ends whilst the respective other longitudinal end is uncovered and thus reveals the bare stent. This bare stent portion is then placed inside the portal vein and will typically expand (flare out) at that position. This flared part of the stent graft serves to anchor the TIPS stent graft inside the portal vein and thus keep it in place. Since, however, that part of the base stent is not covered, it will provide little obstruction to blood flow so that it will not stop blood from flowing into the stent graft from the portal vein.

Subsequently, the covered portion of the TIPS stent graft is deployed inside the shunt that has been created through the liver parenchyma so that the respective other end of the TIPS stent graft ends up in the hepatic vein. Accordingly, through the thus placed TIPS shunt, blood can bypass the liver and flow directly from the portal vein to the hepatic vein. This bypass alleviates portal hypertension.

One challenge with placing such stent grafts is that there is a need to accurately position the uncovered portion and the covered portion of the stent graft. On the one hand, it is important to ensure that the uncovered part of the stent graft is fully provided within the portal vein, since otherwise, blood could leak through the sidewalls of the TIPS stent graft. On the other hand, if parts of the covered section of the TIPS stent graft extend into the portal vein, they would at least partially obstruct blood flow and also reduce the effective length of the TIPS shunt that can be covered using the lined part of the TIPS stent graft. Accordingly, it is desirable to be able to accurately place the TIPS stent graft so that the uncovered portion is fully positioned within the portal vein, but without the covered portion of the TIPS stent graft extending into that vein.

<CIT> discloses a system for deploying a stent comprising a handle and a catheter extending from the handle. The catheter comprises feedback or braking means (e.g., tactile feedback means) to indicate when the distal end of the sheath of the catheter has reached a defined position on the stent during proximal and/or distal movement of said sheath along said stent or to cause a braking effect when the distal end of the sheath has moved beyond a certain position along the stent.

The present invention has been conceived in view of the previously mentioned challenges and aims at providing a system for deploying an implant, optionally a TIPS stent graft, that makes it easier for a surgeon to correctly deploy that implant.

According to claim <NUM>, a system is provided for deploying an implant. Such an implant can, in embodiments, be a TIPS stent graft. It can also be some other kind of stent or stent graft (covered stent).

The system comprises a handle that is that part of the system that is intended for manipulation by an operator. The system furthermore comprises a catheter that extends from the handle. The catheter is arranged for being introduced into a patient's vasculature so that it is sufficiently thin and flexible for being advanced through human blood vessels. At the distal end of the catheter, an implant holding portion is provided that is suitable for having the implant arranged thereon so that the implant can be held at the implant holding portion whilst advancing the catheter through a patient's vasculature to the implant deployment position.

Further provided is an implant retaining sheath that is arranged so as to surround the implant holding portion. When it surrounds the implant holding portion it will retain an implant that is arranged at the implant holding portion, for example by covering it. Such an implant retaining sheath can, in embodiments, be made of a suitable plastic material. The skilled person will be able to envisage other material that can be used.

Connected to the implant retaining sheath is a pull tab that could, in embodiments, be a pull string. This pull tab is arranged so that a proximal pull on the pull tab pulls back the implant retaining sheath so as to at least partially release an implant arranged at the implant holding portion. In the present context, "proximal" denotes a direction towards the operator of the system whilst "distal" denotes a direction away from the operator and towards the patient. The pull tab, which can, in embodiments, be made of a metal wire but could also be made of a string made of a non-metallic material or some other suitable element arranged for exerting a proximal tensile force on the implant retaining sheath, is therefore used for releasing the implant by gradually pulling back the implant retaining sheath.

The pull tab comprises an engagement feature that is arranged on that pull tab and that is moved proximally together with the pull tab when the pull tab is moved proximally. This engagement feature is arranged to engage with a first interference feature. This first interference feature is arranged at a first fixed longitudinal position on the system for deploying the implant. In embodiments, the engagement feature is provided at a fixed longitudinal direction on the handle.

The system is arranged so that an engagement between the engagement feature and the first interference feature provides tactile feedback to a user of the system that the implant retaining sheath has been pulled back a pre-set distance. That is, the user can feel, when pulling back the pull tab, that the implant retaining sheath has moved a certain pre-set distance. This aids in the partial deployment of an implant such as a TIPS stent graft since the user then, by the tactile feedback, knows that a pre-set distance of the implant retaining sheath has been pulled back and, accordingly, a pre-set portion of the implant has been uncovered and, in the context of a self-expanding implant, has expanded. Accordingly, the tactile feedback serves as an indication to the user that a pre-set portion of the implant has been uncovered and has thus been partially deployed. Whilst so far described mainly in terms of the deployment of a TIPS stent graft, the invention is also applicable to the deployment of bifurcated stent grafts for use in treating abdominal aortic aneurysms.

In embodiments, the system comprises a pull tab withdrawal mechanism which is a mechanism that is arranged on the system for aiding in pulling back the pull tab. In embodiments, the pull tab withdrawal mechanism is arranged on the handle. When the pull tab is pulled proximally using the pull tab withdrawal mechanism, an implant arranged at the implant holding portion is first partially and then completely uncovered. Such a pull tab withdrawal mechanism makes it easier for the clinician/operator to withdraw the implant retaining sheath.

According to the invention, the pull tab withdrawal mechanism comprises a thumbwheel coupled to a spindle. The thumbwheel is operable for a user. The spindle is arranged for winding up the pull tab so as to exert a proximal pull on that pull tab. That is, by means of operating the thumbwheel, the pull tab is pulled proximally so as to pull the implant retaining sheath proximally to thereby release an implant arranged at the implant holding portion. In other embodiments, instead of using a thumbwheel, the pull tab is withdrawn by means of a slider that is used for pulling the pull tab back, such as described in <CIT>.

In embodiments, the tactile feedback provides a blocking of further withdrawal of the pull tab. This blocking of further withdrawal ensures that the point where the implant retaining sheath has been pulled back a pre-set distance cannot be missed by an operator since it would be impossible to withdraw the pull tab further. Accordingly, a corresponding system is highly user-friendly.

In further embodiments, the system further comprises a first release mechanism for selectively releasing the blocking of further withdrawal of the pull tab by the engagement between the engagement feature and the first interference feature. That is, the further withdrawal of the pull tab can be unblocked. Therefore, if the engagement between the engagement feature and the first interference feature corresponds to a partial deployment of the implant, the release of the blocking of further withdrawal of the pull tab can be advantageous in that one can then, subsequent to the partial removal of the implant retaining sheath, have a full removal of the implant retaining sheath. This aids in deploying an implant for which it is helpful that it is deployed in two stages, such as a TIPS stent graft.

In embodiments, the engagement feature comprises a protrusion that it is fixedly arranged on the pull tab. The first interference feature is a narrow opening provided inside the handle, where the opening is sized so that the protrusion engages with the boundaries of the opening to provide the tactile feedback to the user. Such a configuration of the engagement feature and the first interference feature has a high degree of reliability.

In embodiments, the pull tab is led through the opening provided inside the handle as part of the first interference feature. Such a configuration provides a good control of the path taken by the pull tab.

In embodiments, there is further provided a second interference feature that is arranged at a second fixed longitudinal position on the system for deploying an implant, where the second fixed longitudinal position is different from the first fixed longitudinal position. The engagement feature is arranged so as to engage with the second interference feature so as to provide tactile feedback to the user. Again, for reasons analogous to those set out regarding the first interference feature, this tactile feedback can provide useful information to the user, for example that the deployment of the implants would begin if the pull tab is retracted further (so that the engagement between the second interference feature and the engagement feature corresponds to a configuration where the implant retaining sheath covers the implant completely but where any further withdrawal of the implant retaining sheath would lead to the implant being partially uncovered).

In embodiments, the tactile feedback of the engagement between the engagement feature and the second interference feature is a blocking of further withdrawal of the pull tab which leads to the advantages described previously regarding the blocking of further withdrawal of the pull tab due to an engagement between the engagement feature and the first interference feature.

There is furthermore, in embodiments, provided a second release mechanism for selectively releasing the blocking of withdrawal of the pull tab by the engagement between the second interference feature and the engagement feature. This allows for selectively pulling the pull tab further back. The second release mechanism is optionally operable by means of a user operable button which makes for an easy-to-use system. Again, similar advantages to those discussed with respect to the first release mechanism can be achieved.

It is according to embodiments that the engagement between the second interference feature and the engagement feature corresponds to the implant retaining sheath fully covering the implant holding portion. That is, this engagement could be made to correspond to the initial configuration of the system (i.e. the configuration of the system it is meant to be in before being advanced through a patient's blood vessels).

According to embodiments, the system comprises an implant, optionally a stent graft, even more optionally a TIPS stent graft, that is arranged at the implant holding portion. With such a system, an implant such as a stent graft or a TIPS stent graft can be suitably delivered.

In embodiments, the implant is a self-expanding implant. By this, it is meant that the implant will expand to a fully expanded configuration when warmed up to the body temperature experienced inside a human or animal body. Such a self-expanding implant can comprise a nitinol scaffolding as an example of a shape memory alloy. However, other types of material can also be used.

In embodiments, the engagement between the engagement feature and the first interference feature corresponds to a partial deployment of the implant. This can make it easy to suitably place the implant inside a patient's body. In embodiments where a TIPS stent graft is provided on the implant holding portion, the engagement between the engagement feature and the first interference feature would correspond to the uncovered portion of the TIPS stent graft being deployed whilst the cover portion is still covered by the implant retaining sheath.

<FIG> shows a system for deploying an implant according to an embodiment of the invention. As can be seen from this Figure, a handle <NUM> is provided that comprises a first component <NUM> and a second component <NUM> that are arranged on top of each other and that are connected to one another. At one end of the handle <NUM>, a flexible tip <NUM> is provided. At the end of the flexible tip <NUM>, a catheter <NUM> that is suitable for insertion into a patient's vasculature is arranged. This catheter <NUM> can be advanced through a patient's vasculature and can provide, at the distal end thereof, implant such as a TIPS stent graft. The catheter <NUM> has provided thereon an implant holding portion (not shown) at the distal end thereof as well as an implant retaining sheath (not shown) that covers the implant holding portion.

The handle <NUM> has provided on its upper surface a recess <NUM> that is arranged so that a surgeon can rest his or her thumb thereon. At the opposite side of the handle <NUM> relative to the recess <NUM>, two protrusions <NUM> are provided that are arranged so as to help the surgeon in holding the device and the handle and to prevent it from slipping. A surgeon can grip with his or her hand around handle <NUM> so that his or her thumb rests on the recess <NUM> whilst the remaining fingers are arranged between the protrusions <NUM> so that the handle <NUM> is securely held. The protrusions <NUM> are provided at two longitudinal spaced apart positions of the handle <NUM>.

A thumbwheel <NUM> is arranged on the handle <NUM> so that it sticks out of an opening of the handle <NUM> that is provided inside the recess <NUM>. The thumbwheel <NUM> has a structured surface that increases friction thereof so as to make operating it easier. The thumbwheel <NUM> is coupled to a spindle (not shown) that is, in turn, coupled to the pull tab <NUM> that will be discussed further below with reference to <FIG>. This pull tab <NUM> is coupled to the implant retaining sheath so that a proximal movement of the pull tab <NUM> will pull the implant retaining sheath proximally to thus uncover the implant holding portion and to thus deploy an implant that is held at the implant holding portion. By operating the thumbwheel <NUM>, the pull tab <NUM> will be wound onto the spindle so that the pull tab <NUM> is pulled proximally (to the left hand side in <FIG>).

In <FIG>, a first release mechanism <NUM> and a second release mechanism <NUM> are provided. The first release mechanism <NUM> is to be actuated by means of a button whilst the second release mechanism is operable by means of a slider. When the second release mechanism <NUM> has not been operated, a structure to be discussed below with reference to <FIG> will block a withdrawal of the implant retaining sheath so that the implant holding portion cannot even be partially uncovered. That is, unless the second release mechanism <NUM> has been actuated, an implant provided at the implant portion cannot even be partially deployed. However, when sliding the slider of the second release mechanism <NUM> to the actuated position, this blocking of proximal withdrawal of the pull tab <NUM> will be released so that thereby, a rotation of the thumbwheel <NUM> can pull the pull tab <NUM> proximally. This allows for a partial deployment of an implant that is arranged at the implant holding portion at the distal end of the catheter <NUM>.

When the pull tab <NUM> is pulled further proximally by means of operating the thumbwheel <NUM>, the proximal pulling of the pull tab <NUM> will be blocked by an engagement with a first interference feature <NUM> to be discussed further below. Also that engagement can be selectively released by means of actuating the first release mechanism <NUM> by means of pushing the associated button. This releasable blocking of further withdrawal of the pull tab <NUM> can correspond to a partial deployment of the implant arranged at the distal end of the catheter <NUM>. In the case of a TIPS stent graft provided at the distal end of the catheter <NUM>, this can correspond to the selective and partial release of the uncovered portion of that stent graft. As pointed out before, this is highly advantageous when it comes to deploying and placing a TIPS stent graft in a human liver. Once the uncovered portion has been deployed, the surgeon can actuate the first release mechanism to release the blocking of further withdrawal of the pull tab <NUM> to thus completely release the implant.

In the structure shown in <FIG>, different positions and portions have been marked up on the catheter <NUM>. The position A denotes the position up to which the implant retaining sheath extends when the implant holding portion is fully covered. This position corresponds to the position where the further withdrawal of the pull tab <NUM> is blocked by means of the second release mechanism <NUM> not being actuated. When the second release mechanism <NUM> is actuated, the implant retaining sheath can be pulled back over a distance denoted by the letter "D". This partial withdrawal corresponds to only the uncovered portion of, e.g., a TIPS stent graft being exposed to the patient's body.

The portion denoted by E corresponds to a sufficiently full withdrawal of the implant retaining sheath that the entirety of the implant holding portion (and thus of the implant) is uncovered so that the implant can be deployed. This would correspond to the full deployment configuration.

The portion denoted by C is that portion of the catheter <NUM> that is not used for carrying the implant. That is, this portion serves to provide enough of a length of the catheter <NUM> so as to reach the deployment position of the implant.

The catheter <NUM> can have provided therein a lumen suitable for leading a guidewire therethrough. This guidewire can extend, at the proximal end of the handle <NUM>, through a connector <NUM> that can be a Luer connector.

<FIG> shows an inside view of the lower part <NUM> of the handle <NUM> in a configuration where the implant retaining sheath extends up to the point A shown in <FIG>. That is, the implant holding portion is fully covered. The lower part <NUM> of the handle <NUM> is made of a plastic shell that has a semi-tubular shape that bulges out when going from the distal end <NUM> towards the central portion. This allows for ergonomically gripping the handle <NUM>. At the distal end <NUM>, a hemispherical cut out <NUM> is provided through which the pull tab <NUM> extends. This pull tab <NUM> is led through the interior of the lower part <NUM> and is to be rolled up on a spindle (not shown) attached to thumbwheel <NUM>.

Provided inside the lower part <NUM> are reinforcing ribs <NUM> that serves so as to provide mechanical stability to the lower part <NUM>. Those reinforcing walls <NUM> have a notch through which the pull tab <NUM> is led. That is, those notches serve to stabilise the path of the pull tab <NUM>. Close to the distal end <NUM> of the lower part <NUM> is provided a metallic plate <NUM> having a hole provided therein through which the pull tab <NUM> is led. Also this plate <NUM> serves to stabilise the path taken by the pull tab <NUM>. This plate <NUM> is attached (clipped) to one of the ribs <NUM>.

Provided proximally relative to the plate <NUM> is a leaf spring <NUM> that is, at one of its ends, held by ribs <NUM> provided on a wall of the lower part <NUM>. This leaf spring <NUM> is bent. Its bent portion abuts against an engagement feature <NUM> in the form of a ring like protrusion fixedly arranged on the pull tab <NUM>. The bent portion of the leaf spring <NUM> abuts against the proximal-most portion of the engagement feature <NUM> so that it prevents a proximal movement of the engagement feature <NUM>. In turn, this prevents a proximal movement of the pull tab <NUM>. The leaf spring <NUM> is coupled to the slider <NUM> so that a sliding movement of the slider <NUM> will bend the leaf spring <NUM> so that the bent portion gets out of engagement with the engagement feature <NUM>. In that configuration, a proximal movement of the engagement feature <NUM> is possible so that the pull tab <NUM> can be moved proximally. This then allows for a pulling back of the implant retaining sheath across the portion denoted by the region "D" in <FIG>. The bent portion of the leaf spring <NUM> thus constitutes the second interference feature.

Provided even further proximally relative to the leaf spring <NUM> is the first interference feature <NUM> that has the shape of a U-shaped plastic plate that is coupled to a pushbutton <NUM>. The pull tab <NUM> is led through the recess of the U-shaped plate <NUM>. When the pushbutton <NUM> is depressed, the U-shaped plate <NUM> is pushed down sufficiently far that the pull tab <NUM> no longer extends through the recess of the U-shaped plate <NUM>. The recess of the U-shaped plate <NUM> is sized so that the engagement feature <NUM> cannot fit through it so that the engagement between the engagement feature <NUM> and the U-shaped plate <NUM> blocks a movement of the engagement feature <NUM> through that recess whilst being sufficiently wide to allow the rest of the pull tab <NUM> to freely pass through it.

<FIG> shows a configuration where the engagement between the second interference feature in the form of the leaf spring <NUM> and the engagement feature <NUM> had been released and where the pull tab <NUM> has been pulled proximally so that the implant retaining sheath has moved across the portion D in <FIG>. As can be seen from <FIG>, in that configuration, the engagement feature <NUM> now abuts against the first interference feature <NUM>. Since the pushbutton <NUM> has not been depressed, a proximal movement of the engagement feature <NUM> is prevented by that abutment.

In the configuration that is shown in <FIG>, the pushbutton <NUM> has been depressed, as indicated by an arrow, so that there is now no longer an engagement between the first interference feature <NUM> and the engagement feature <NUM>. Accordingly, it is possible to pull the pull tab <NUM> proximally so that also the engagement feature <NUM> can now be pulsed to a position that is proximal to now arranged proximally of the first interference feature <NUM>. In that configuration, the implant retaining sheath can be moved across the region E shown in <FIG> to fully deploy the implant that is provided on the implant holding portion.

Thus, with the device described previously, a surgeon is given clear tactile feedback as to when implant retaining sheath withdrawal begins and when the implant has been partially uncovered. The surgeon could thus, once he or she knows that the implant has been partially uncovered, ensure that the thus uncovered portion is properly placed.

For example in the case of a TIPS stent graft, the surgeon could ensure that the flared uncovered portion of the TIPS stent graft is arranged in the portal vein, for example using X-ray imaging of markers that are provided on the TIPS stent graft. The surgeon could then feel that the flared portion is completely arranged inside the portal vein by noticing the flared portion abutting against the junction between the TIPS shunt and the portal vein (as a mechanical resistance against proximal withdrawal of the TIPS stent graft to be deployed). Accordingly, since the surgeon knows that only the uncovered portion has been uncovered but that this portion has been uncovered completely, a highly accurate and user-friendly positioning of the TIPS stent graft is possible.

Accordingly, the following steps would be taken by a surgeon when wishing to place a TIPS stent graft using the previously described design, which are also partially illustrated in <FIG>)-c):.

Claim 1:
System (<NUM>) for deploying an implant, the system comprising:
- a handle (<NUM>),
- a catheter (<NUM>) extending from the handle (<NUM>), the catheter being arranged for holding an implant at an implant holding portion at a distal end of the catheter,
- an implant retaining sheath, the implant retaining sheath being arranged so as to surround the implant holding portion so as to retain an implant that is arranged at the implant holding portion,
- a pull tab (<NUM>), the pull tab (<NUM>) being connected to the implant retaining sheath so that a proximal pull on the pull tab pulls back the implant retaining sheath so as to release an implant arranged at the implant holding portion,
the pull tab (<NUM>) further comprising an engagement feature (<NUM>) that is arranged on the pull tab (<NUM>) and that is moved proximally as the pull tab (<NUM>) is moved proximally, the engagement feature (<NUM>) being arranged to engage with a first interference feature (<NUM>) arranged at a first fixed longitudinal position on the system for deploying the implant, wherein an engagement between the engagement feature (<NUM>) and the first interference feature (<NUM>) provides tactile feedback to a user of the system that the implant retaining sheath has been pulled back a pre-set distance, further comprising a pull tab withdrawal mechanism, the pull tab withdrawal mechanism being arranged pull the pull tab (<NUM>) proximally so as to release an implant arranged at the implant holding portion,
the pull tab withdrawal mechanism comprising a thumbwheel (<NUM>) coupled to a spindle, the spindle being arranged for winding up the pull tab (<NUM>) so as to exert a proximal pull on the pull tab (<NUM>).