STENT GRAFT TRIGGER WITH INDIRECT FIXATION

Disclosed herein are systems and methods for delivering a medical device to a body vessel of a patient. The medical device may be a stent graft, and the delivery assembly may include at least one loop that connects an end stent of the stent graft to a trigger wire of the delivery assembly, thereby providing indirect connection between the device to be delivered and the trigger wire.

FIELD

The present disclosure relates to an apparatus and method for delivering an implantable medical device, particularly a stent graft.

BACKGROUND

In aortic intervention, stented endovascular grafts are currently used for the treatment of aneurysms and aortic dissections. Stent grafts are commonly placed into such diseased vessels for structural support and to exclude blood flow to aneurysms. Therefore, they may be able to reduce or prevent further vessel expansion, and thus can reduce the likelihood of aneurysm rupture.

Proper placement of stent grafts aids in the success of such treatments. Good wall apposition and anchoring can help to reduce the occurrence of Type I and Type III endoleaks.

Different release mechanisms are currently used in endovascular graft delivery devices to unfold and/or attach stent grafts to vessel walls. These stents may include top stents that are located at an end of the endovascular graft, distal stents, and other stents that are located within the main body of the endovascular graft. As most stents used in these devices have barbs that attach to the vessel, the slow or controlled release of these stents or stented grafts can allow for accurate placement of the graft. If these stents are released without a controlled release mechanism during unsheathing, immediate engagement of the barbs is possible, which in turn may prevent readjustment of the positioning of the endograft.

Many such release mechanisms employ wires (such as nickel/titanium or stainless steel wires) to activate the release of the stent or stent graft. This release mechanism is designed such that it is easy to use, that it has a low profile, and that it functions reliably.

It has been a challenge to develop a medical device delivery assembly that quickly and reliably releases a stent graft or a stent thereof in such a way that the graft is repositionable.

SUMMARY

According to one aspect of the present disclosure, a system for deploying at least a portion of a stent is described. The system may include a cannula comprising a lumen. The system may include a guide member disposed over the cannula. The guide member may include an outer surface, and the guide member may define at least one curved channel therein. The at least one curved channel may define a trigger wire lumen. The guide member may include at least one access port through the outer surface to the curved channel. The system may include a trigger wire disposed in the trigger wire lumen.

According to another aspect of the present disclosure, a medical device assembly is described. The medical device assembly may include a cannula comprising a lumen, which may be a wire guide lumen. The medical device assembly may include a guide member disposed over the cannula. The guide member may have an outer surface and may comprise at least one curved channel therein. The at least one curved channel may define a trigger wire lumen which may be distinct from, or not in fluid communication with, the wire guide lumen. The guide member may include at least one access port through the outer surface to the curved channel. The medical device assembly may include a trigger wire disposed in the trigger wire lumen defined by the curved channel. The medical device assembly may include at least one loop disposed about the trigger wire and extending through the access port. The medical device assembly may include a stent graft disposed about the cannula, the stent graft including an end stent having an apex. The apex of the end stent may extend through the loop.

According to another aspect of the present disclosure, a method of delivering a stent graft is provided. The method may include moving a trigger wire distally in a medical device assembly that includes a trigger wire surrounded by a loop, the loop restraining an apex of an end stent of the stent graft. Moving the trigger wire distally such that the trigger wire passes completely through the loop may cause the apex to no longer be restrained. The method may include, when the trigger wire is moved distally, a plurality of apices being sequentially released. The method may include, when the trigger wire is moved distally, a plurality of apices being simultaneously released.

DETAILED DESCRIPTION

In the present application, the term “proximal end” is used when referring to that end of a medical device closest to the heart after placement in the human body of the patient, and may also be referred to as the inflow end (the end that receives fluid first), and the term “distal end” is used when referring to that end opposite the proximal end, or the one farther from the heart after its placement, and may also be referred to as the outflow end (that end from which fluid exits).

Although numerous examples of trigger wire/release systems for the delivery of stent grafts exist and have been commercialized, such systems generally involve the direct connection of the device to be delivered to the delivery system. A release mechanism that secures a portion of the device indirectly to the delivery system may provide increased freedom of motion to the portion of the device to which it is connected. In some examples, the portion of the device that is connected may be a top stent; that is, the most proximal stent of the stent graft, which in some cases may be a suprarenal stent. However, other portions of the device, including other stents, may also be connected to the delivery system. Such indirect connection may also provide for a simplified release mechanism, including reducing the total number of trigger wires used in the delivery assembly.

An assembly providing for indirect connection between the device to be delivered and the assembly itself may provide for better control of release of the device in the body of the patient, and may also allow for greater freedom of movement of the device during delivery. Freedom of transverse, axial and rotational movement within the confines of the vessel walls can allow the device to conform itself to the natural vessel angulations, which in turn can improve wall apposition and sealing at the downstream stent sealing zone, and can reduce uneven localized forces experienced on barbs and at attachment sites, thereby reducing the changes of type I and type III endoleaks, perhaps even preventing them altogether.

As used herein, the term “direct” when used in reference to a connection between a stent portion of a stent graft to be released by a trigger wire and the trigger wire of the stent graft delivery assembly itself means that the trigger wire contacts the stent portion of the stent graft without contacting an intermediate component. “Indirect” means that the contact between the trigger wire and the stent portion of the stent graft to be released by the trigger wire is bridged by at least one additional component that is not the trigger wire and is not the stent portion of the stent graft.

FIG. 1Aillustrates an example of a delivery assembly10having a direct connection between the device to be delivered and a trigger wire. InFIG. 1A, a stent graft30is disposed about cannula20and an apex34of top stent32(or end stent) of the stent graft30is directly connected to a trigger wire40of the delivery assembly10at catch42. This connectivity can be observed in a number of commercially-available stent graft release systems. In this aspect, the cannula20has a lumen in which the trigger wire or trigger wires are contained, without sharing the space with a guide wire if one is employed.

FIG. 1Billustrates a delivery assembly110in which stent graft130is indirectly connected to trigger wire140. InFIG. 1B, the top stent132of stent graft130is indirectly connected near apex134, via loop150, to trigger wire140. The top stent132may have a sinuous structure that results in a plurality of apices134. The trigger wire140runs through cannula120of the delivery assembly110and can be manipulated by a medical practitioner to release the stent graft130when it is at the desired location in the vasculature of the patient. Such an arrangement may provide the benefit of a greater degree of motion of the top stent132during deployment, providing better adjustability of the diameter of the stent graft130, and providing the delivery assembly110with a relatively low profile.

FIG. 2illustrates one example of a portion of a delivery assembly210constructed in accordance with the principles of the present disclosure. The view ofFIG. 2illustrates a proximal portion of the assembly210, with tip270being the most proximal portion of the assembly210. Tip270may be made of a nylon or nylon copolymer for increased flexibility. The delivery assembly210has a stent graft230disposed thereon, but for clarity of illustration, only portions of top stent232(including apices234a,234b,234c,and so forth) are shown.

In the delivery assembly210as shown inFIG. 2, cannula220may be connected to guide member260. The cannula220may comprise two trigger wire lumens therethrough, through which the two trigger wires240aand240bextend. That is, the cannula220may instead include a central guide wire lumen, and may include separate trigger wire lumens formed therethrough. There may be individual lumens for each trigger wire, or the trigger wire lumens may be shared by multiple trigger wires.

The trigger wires240a/240bmay extend out of the cannula220via openings222a/222b,respectively (222bbeing on the opposite face of the cannula220as illustrated, not shown). The trigger wire240athen enters an entry port266ain the guide member260and extends proximally and in a helical fashion through a channel262a(which itself is curved, or helical) in the interior of guide member260, as will be described later in this disclosure. The channel262amay have a series of openings (264a/264b/264cin the variation as illustrated inFIG. 2) that provide the channel262awith fluid communication to the external environment. This also allows for access to portions of the trigger wire240a.The edges of the openings264may be chamfered, as shown. The trigger wire240amay then extend proximally through exit port268ainto an aperture272of the tip270, where an end of the trigger wire240aor240bmay be at least temporarily fixed or captured, or in some cases may remain unfixed. The path of trigger wire240bon the opposite side of delivery assembly210, not shown, may have similar features to that of the path of trigger wire240a.The trigger wires240a/240bmay have substantially straight proximal ends while engaged, or may have a looped configuration. The overall effect of such a construction may be to reduce the number of trigger wires employed by the delivery assembly.

In the illustrated delivery assembly210ofFIG. 2, the guide member260has six openings, including openings264a/264b/264c,through its outer surface. The openings open into channel262a.Likewise, openings264d/264e/264fopen into channel262b(not visible in the illustration). The trigger wire240ais accessible through openings264a/264b/264c,and the trigger wire240bis accessible through openings264d/264e/264f.The two trigger wires240aand240bmay run through trigger wire lumens defined in the cannula220of delivery assembly210, as seen inFIG. 4A, and may be operably connected to a handle (described with reference toFIG. 9). The trigger wires240a/240bmay be made of any suitable biocompatible or hemocompatible wire, including but not limited to a nickel/titanium alloy or stainless steel.

In another aspect, the delivery assembly may have a cross-section as illustrated inFIG. 4B. In this aspect, a guide wire lumen243′ runs centrally through the body241′ of the cannula220′, with individual trigger wire lumens240c/240d/240e/240frunning through the body241′. This allows the delivery assembly to be introduced over a guide wire. The cannula in this aspect is of sufficiently solid construction to endure forces experienced by the assembly, while being flexible enough to be adjustable in the anatomy.

FIG. 4Cillustrates another aspect of a delivery assembly cross section. In this aspect, cannula220″ is surrounded by sleeve225″, which contains trigger wires240g/240h/240i.The cannula220″ defines a lumen243″ in which a guide wire245″ can be contained.

In the illustrated aspect, the top stent232of stent graft230has six apices234a-234f,and the two trigger wires240a/240bof delivery assembly210each pass by three openings (256a-256cand256d-256f) in the guide member260, providing six total openings, one for each apex of the top stent232. In some aspects, the delivery assembly210may be constructed to have a number of openings equal to the number of apices of the top stent of the endograft to be delivered by the delivery assembly. Those of skill in the art will appreciate that designs having differing numbers of trigger wires, openings in the guide member, and channels formed in the guide member can be constructed in accordance with the principles of the present disclosure, depending on the specific application for which the delivery assembly is intended.

The guide member260may be of solid construction, aside from the channels262aand262b,or may have hollow portions other than the channels262a/262b.As illustrated, the guide member260has a substantially ellipsoid shape, but other shapes may be suitable as well, including spherical, rounded prismatic, and so forth. The channels262a/262bmay be machined in a solid piece of precursor material, or it may be additively manufactured to precisely control the size and shape of the channels for the trigger wires. The guide member260may be constructed without sharp edges at either end such that it will not damage the graft or the vessel during operation.

The guide member260may be made of any suitable material. In one aspect, the guide member260may be made of a metal, including but not limited to stainless steel, titanium, and other metals or metal alloys with biocompatible and hemocompatible properties. In another example, polymers including polyether ether ketone (PEEK), polyoxymethylene (DELRIN), polyethylene, and other biocompatible and hemocompatible polymers with comparable properties may be used.

As shown inFIG. 2, loops250, such as illustrated loops250a/250b/250c/250f(along with loops250dand250e,not shown) provide a connection between the stent graft230and the delivery assembly210. In this way, the device to be delivered is indirectly connected to the delivery assembly. The loops250a-250fare not considered to be a portion of the stent graft230, and may instead be considered to be a component of the delivery assembly210in some aspects, even when the loops are left with the stent graft inside the vasculature following delivery. Despite not being considered a portion of the stent graft230, the loops250a-250fmay nonetheless be delivered with the stent graft230to the body lumen of the patient. The loops250interact minimally with blood flow.

The loops250, when engaged with the stent apices234of the top stent232of the stent graft230and the trigger wire240of the delivery assembly210, define an attached state (or delivery state) for the stent graft230. This attached state allows freedom of motion to the stent apex such that it can move transversely, axially, and partially rotate about the cannula220so that this motion may enable the main body of the stent graft230(especially the proximal sealing section) to conform to the vessel wall during unsheathing of the graft prior to stent release by the trigger wires240a/240b.This is in contrast to known assemblies, particularly abdominal aortic aneurysm (AAA) stent grafts having a suprarenal stent, wherein the orientation of the delivery assembly in the vessel plays a larger role in governing the orientation of the remainder of the graft in the vessel, which in some cases may reduce efficiency in sealing and less perfect vessel wall apposition upon deployment.

The loops250may be made from any suitable biocompatible material. For instance, they may be made of a nondegradable suture material, including but not limited to polypropylene, polyester, Dyneema, or another hemocompatible pure or blended material. The loops250may also be made of a biocompatible or hemocompatible wire, such as one made from a nickel/titanium alloy or stainless steel.

An end portion of another delivery assembly910is illustrated inFIG. 3. InFIG. 3, like components are labeled similarly to those that are illustrated inFIG. 2. Delivery assembly910additionally includes sleeve925, which passes over and surrounds cannula920and covers a length of trigger wires940aand940b,thereby securing them and decreasing the profile of the delivery assembly910.

The sleeve925may be made of a biocompatible polymer, and may fit tightly enough to restrain the trigger wires940a/940bin the radial dimension, but loosely enough that it does not interfere with movement in the longitudinal dimension when the trigger wires940a/940bare manipulated. In this way, the trigger wires940a/940bmay contact, or run along the length of, the cannula920when the sleeve925is employed. The sleeve925may extend over opening922aand may extend over portions of the trigger wires940a/940b.In some aspects, the sleeve925may have a hole through it for positioning over or substantially over the opening922a,to allow the trigger wires940a/940bto pass through.

As illustrated inFIG. 3, the sleeve925may contact, or terminate just distal of, the guide member960. In some forms, the sleeve925may extend further in the proximal dimension, covering at least a portion of the guide member960. In another form, the sleeve925may extend over the entire guide member960, but may still allow for the release of loops950by the trigger wires940a/940b.In another form, the sleeve925may cover a portion of the tip970.

The guide member960may be attached or fixed to the cannula920, which may be made of a metal; to the sleeve925which may be made of a plastic or a polymer; or to both the cannula920or the sleeve925.

The various delivery assemblies illustrated and described throughout this explanation may optionally include a sleeve similar to sleeve925. For clarity, the sleeve has been omitted in figures other thanFIG. 3.

A number of variations on loops may be useful for indirect connection of the stent graft to the delivery assembly according to the principles of the present disclosure. In one aspect, and as shown inFIG. 5, the loops350a/350b/350cof delivery assembly310amay include loops of varying sizes depending on the distance from an opening356a/356b/356cto the respective apex of the top stent332to which it is to provide indirect connection. As shown, loop350chas a greater length than loop350b,and loop350bhas a greater length than loop350a.Such a configuration may be useful when the top stent332of the stent graft330has apices at the same or at similar heights compared to the remainder of the stent graft330. In some cases, multiple loops may share a single opening.

In a variation shown inFIG. 6, by contrast, the delivery assembly310bas configured has the same sized loops350g/350h/350iregardless of position. Such a construction may be of use when the top stent332of the stent graft330has apices (such as334g/334h/334i) of varying height.

FIG. 7Aillustrates the helical character of a curved channel362of a guide member360constructed in accordance with the principles of the present disclosure. The longitudinal axis A of the delivery assembly310is shown, as is a line H which is taken through a portion of the channel362. The lines A and H intersect to define helical angle α. Typically, the measure of angle α will be between about 5 degrees to about 85 degrees, or about 10 degrees and about 75 degrees, or between about 15 degrees and about 60 degrees, or about 20 degrees and about 45 degrees, or about 25 degrees and about 40 degrees, or about 30 degrees and 35 degrees, or about 30 degrees, or about 35 degrees, or about 45 degrees, or about 60 degrees.FIG. 7Billustrates the inner workings of guide member360ofFIG. 7A. Channel362acurves along the length of the guide member360, and channel362bmirrors it (that is, one of the channels may be a left-handed helix and the other may be a right-handed helix), formed at the same helical angle as channel362a.

FIG. 8Ashows a portion of a delivery assembly410which has a guide member460formed in a different shape. The guide member460includes two tubes472aand472bdefining the trigger wire channels, tubes472aand472bbeing twisted about one another to define the guide member460. Similar to other guide members illustrated herein, the guide member460has a number of openings464a/464b/464c/464fshown for access to the trigger wire housed therein from the outside of the assembly410.FIG. 8Bshows a cross-sectional view of the guide member460taken across line7B inFIG. 8A.

A full view of an exemplary delivery system500is shown inFIG. 9(not to scale). The delivery assembly510has a stent graft530mounted over the cannula520, which extends from handle590, through guide member560, and the proximal end526connects to tip570. Sleeve525is disposed over cannula520. The distal end524of the cannula520is connected to the handle590. An access port528may be in fluid communication with the cannula520. In some aspects, the handle590may include a thumbwheel592, which can be operably connected to the trigger wires540a/540b.Rotation of the thumbwheel in a first rotational direction may cause one or both of the trigger wires540a/540bto move distally, thereby releasing the stent graft530. Loops550connect the top stent532of the stent graft530indirectly to the delivery assembly510.

In some aspects, the stent graft may be crimped over the delivery assembly, and/or may be held in place by a sleeve positioned over the system including the stent graft and the delivery assembly.

A delivery system constructed in accordance with the principles of the present disclosure may provide a number of structural features that allow for varying release schemes. In system600shown inFIG. 10, the loops656a/656b/656care each connected to a respective apex634a/634b/634bof top stent632, with a single trigger wire640passing through all loops656a/656b/656c,to define an attached or delivery state. When the trigger wire640is pulled distally, loop650cwill release first, followed by loop650b,then loop650a.This represents a sequential or peak-by-peak release scheme into the detached, or delivered, state.

The delivery system700ofFIG. 11, by contrast, allows for simultaneous release of the apices734a/734b/734c.It does so by the construction of the trigger wire740, which includes branches721a/721b/721cangled away from the main body of the trigger wire740. The loops756a/756b/756care held in place by respective sleeves or restraints723a/723b/723c.When trigger wire740is pulled distally, the loops756a/756b/756cwill slide an equivalent distance along branches721a/721b/721cuntil they encounter and dislodge restraints723a/723b/723cand release.

In another aspect, delivery system800, shown inFIG. 12, provides for a sequential stepwise release of the apices834a/834b/834c.In this system800, two trigger wires840aand840bare employed, with two sets of loops850/852associated with one or both trigger wires840a/840b.As illustrated inFIG. 12, trigger wire840apasses through small loops856a/856b/856c,and both trigger wires840aand840bpass through large loops852a/852b/852c.In a variation on this construction, the loops852a/852b/852care only operably connected to the second trigger wire840b.

In one release scheme, trigger wire840amay first be pulled distally to allow the top stent832a greater degree of movement and/or expansion in the radial dimension. This may effectively cause a partial expansion of the stent graft830, so that the final position of the stent graft830can be approximated in the vasculature of the patient, and repositioned by the practitioner as necessary. The second trigger wire840bcan then be pulled distally to fully release the stent graft830such that it fully expands in the body vessel of the patient. Such a stepwise release may reduce the chances that a barb prematurely engages the vessel wall.

Features of any of the systems600/700/800may be used in combination with any of the other systems600/700/800according to the intended application.