Patent Description:
The use of endovascular procedures has been established as a minimally invasive technique to deliver a variety of clinical treatments in a patient's vasculature. A stent graft is an implantable device made of a tube-shaped surgical graft covering and an expanding or self-expanding metal frame. The stent graft is placed inside a blood vessel to bridge, for example, an aneurismal, dissected, or other diseased segment of the blood vessel, and, thereby, exclude the hemodynamic pressures of blood flow from the diseased segment of a blood vessel such as the aorta.

Document <CIT> relates to a catheter. Document <CIT> relates to a catheter. Document <CIT> relates to vascular repair devices. Document <CIT> relates to a stent graft delivery system having a rotatable single shaft tip capture mechanism. Document <CIT> relates to a controlled tip release stent graft delivery system and method.

Depending on the region of the aorta involved, the aneurysm may extend into areas having vessel bifurcations or segments of the aorta from which smaller "branch" arteries extend. For example, thoracic aortic aneurysms can include aneurysms present in the ascending thoracic aorta, the aortic arch, and/or branch arteries that emanate therefrom, such as subclavian or left or right common carotid arteries. In some cases, a branched stent graft can be used to treat such aneurysms. For example, a main stent graft can be deployed in the main vessel (e.g., aortic arch), and a supplemental, secondary stent graft can be deployed in the branched artery (e.g., left subclavian).

According to the invention, a stent graft delivery system comprises a stent graft cover and a tapered tip. The stent graft cover is configured to maintain a stent graft in a constricted configuration, and configured to slide relative to the stent graft to enable the stent graft to expand radially outwardly, wherein the stent graft cover extends along a first central axis. The tapered tip defines an opening therethrough that is configured to track along a guidewire, wherein the opening extends along a second central axis that is offset from the first central axis The tapered tip defines a second opening therethrough that is configured to track along a second guidewire.

According to another embodiment, a stent graft delivery system comprises a stent graft cover, a tapered tip, a tip capture mechanism, and a spindle. The stent graft cover is configured to maintain a stent graft in a constricted configuration, and configured to slide relative to the stent graft to enable the stent graft to expand radially outwardly. The tapered tip defines an opening therethrough that is configured to track along a guidewire. The tip capture mechanism has an inner member aligned with the opening, and the inner member has an inner lumen secured to the tapered tip and an outer lumen disposed about the inner lumen and configured to slide along an outer surface of the inner lumen. The spindle is aligned with the opening and has an inner surface contacting the inner lumen and an outer surface contacting the tapered tip to secure the tapered tip to the inner lumen.

According to another embodiment of the invention, a method of assembling a stent graft delivery system comprises fitting a barbed spindle about an outer surface of an inner lumen of an inner member, wherein the barbed spindle defines an opening extending about a central axis; press-fitting a tapered tip about an outer surface of the barbed spindle, wherein the tapered tip includes an opening extending about the central axis when press-fitted to the barbed spindle; and assembling a stent graft cover about a portion of the tapered tip such that a central axis of the stent graft cover is offset from the central axis of the opening of the barbed spindle, further comprising assembling a second lumen within the stent graft cover and aligned with a second opening of the tapered tip.

Further disclosed herein is a stent graft delivery system and method of assembling the same. The stent graft delivery system includes a stent graft cover configured to maintain a stent graft in a constricted configuration, and is configured to slide relative to the stent graft to enable the stent graft to expand radially outwardly. The stent graft cover extends along a first central axis. A tapered tip defining an opening therethrough is configured to track along a guidewire. The opening extends along a second central axis that is offset from the first central axis. This provides a delivery system with an opening in a leading edge that is not center relative to the outer stent graft cover.

Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.

Directional terms used herein are made with reference to the views and orientations shown in the exemplary figures. A central axis is shown in the figures and described below. Terms such as "outer" and "inner" are relative to the central axis. For example, an "outer" surface means that the surfaces faces away from the central axis, or is outboard of another "inner" surface. Terms such as "radial," "diameter," "circumference," etc. also are relative to the central axis. The terms "front," "rear," "upper" and "lower" designate directions in the drawings to which reference is made.

Unless otherwise indicated, for the delivery system the terms "distal" and "proximal" are used in the following description with respect to a position or direction relative to a treating clinician. "Distal" and "distally" are positions distant from or in a direction away from the clinician, and "proximal" and "proximally" are positions near or in a direction toward the clinician. For the stent-graft prosthesis, "proximal" is the portion nearer the heart by way of blood flow path while "distal" is the portion of the stent-graft further from the heart by way of blood flow path.

Although the description is in the context of treatment of blood vessels such as the aorta, coronary, carotid and renal arteries, the invention may also be used in any other body passageways where it is deemed useful.

Thoracic aortic aneurysms with disease progression extending into the aortic arch can be treated with a branched stent graft and delivery system. Branched stent graft delivery systems can be used to deliver and deploy stent grafts that are configured to couple with secondary stent grafts that extend into vessels or "branches" within a patient's vasculature, such as the thoracic aorta. For example, during a surgical procedure, a main guidewire may be fed into the vasculature and into a main vessel (e.g., aortic arch), and a secondary guidewire may be fed into a secondary vessel or branched artery (e.g., left subclavian). The stent graft delivery system can include a main lumen that tracks along the main guidewire, and a secondary lumen that tracks along the secondary guidewire. A main stent graft can be deployed in a main vessel, and a supplemental, secondary stent graft can be deployed in the branched artery. An example of such a surgical procedure is described in <CIT> titled Branched Stent Graft Delivery System.

<FIG> shows a branched stent graft delivery system <NUM> according to one embodiment. The branched stent graft delivery system <NUM>, also more simply referred to as a stent graft delivery system or a delivery system, includes an endovascular catheter and extends between a proximal end <NUM> and a distal end <NUM>. The terms "proximal end" and "distal end" are not intended to be limiting, as a surgical clinician may, during a procedure, in fact be located closer to the distal end <NUM> than the proximal end <NUM>. Therefore, the proximal end and the distal end may be referred to as a "first end" and a "second end," respectively.

A threaded screw gear <NUM> extends along an axis between the proximal end <NUM> and the distal end <NUM>. The threaded screw gear may be a multi-part shell configured to connect together to make a tubular screw gear. In one embodiment, the screw gear <NUM> is two half-shells configured to connect (e.g., snap or assemble) together.

A handle assembly <NUM> is provided for grip by the clinician. The handle assembly <NUM> may include two separable portions, namely a front grip <NUM> and an external slider <NUM>. The front grip <NUM> may be fixed relative to the screw gear <NUM>, and the external slider <NUM> may rotate about a threaded outer surface of the screw gear <NUM> to move linearly along the screw gear <NUM>. For example, during deployment of a stent graft, the external slider <NUM> is rotated to move toward the proximal end <NUM>. Since the external slider <NUM> is operatively coupled to a stent graft cover <NUM> surrounding the stent graft, the stent graft cover <NUM> is retracted with the linear movement of the external slider <NUM>. Meanwhile, a tip <NUM> at the distal end <NUM> of the delivery system <NUM>, which has openings to track over the guidewires, can remain steady within the vessel as the stent graft cover <NUM> is retracted away from the tip <NUM>. Retraction of the stent graft cover <NUM> allows the stent graft to expand within the patient's vessel. Once the stent graft is deployed, the entire stent graft delivery system <NUM> may be retracted from the patent's vessel.

The stent graft can be self-expanding, in that it includes structures that are shaped or formed from a material that can be provided with a mechanical memory to return the structure from a compressed or constricted delivery configuration to an expanded deployed configuration. The stent graft can include two main components: a tubular graft, and one or more stents for supporting and expanding the graft. The graft may be formed from any suitable graft material, for example and not limited to, a low-porosity woven or knit polyester, DACRON material, expanded polytetrafluoroethylene, polyurethane, silicone, or other suitable materials. In another embodiment, the graft material can also be a natural material such as pericardium or another membranous tissue such as intestinal submucosa. The stent is radially-compressible and expandable, is coupled to the graft material for supporting the graft material, and is operable to self-expand into apposition with the interior wall of a body vessel (not shown). Each stent can be constructed from a self-expanding or spring material, such as but not limited to Nitinol, stainless steel, a pseudo-elastic metal such as a nickel titanium alloy or nitinol, various polymers, or a so-called super alloy, which may have a base metal of nickel, cobalt, chromium, or other metal, or other suitable material. This allows the stent graft to expand when the stent graft cover <NUM> is retracted therefrom. The stent may be a sinusoidal patterned ring including a plurality of crowns or bends and a plurality of struts or straight segments with each crown being formed between a pair of opposing struts.

While the screw gear <NUM> is illustrated and described herein as having a threaded outer surface, it should be understood that in other embodiments, the screw gear is not threaded, the external slider <NUM> can slide linearly along the screw gear, or any other suitable mechanism may be used to retract the graft cover.

The stent graft delivery system <NUM> may also include an access port <NUM>. The access port <NUM> provides an opening for insertion, removal, or receiving of a secondary guidewire lumen, or branching lumen, for surrounding a secondary guidewire. The delivery system <NUM> can track along both the main guidewire and the secondary guidewire during delivery of the stent graft.

<FIG> illustrate various views of internal components of a distal end <NUM> of a stent graft delivery system, such as that illustrated in <FIG>. In other words, the structure shown in <FIG> and described below can be substituted for the distal end <NUM> of <FIG>.

The distal end <NUM> includes a tip <NUM>, also referred to as a tapered tip due to its tapered profile. The tapered tip <NUM> provides a leading edge of the delivery system <NUM>, and tracks over one or more guidewires. In particular, the tapered tip <NUM> includes a leading edge or front surface <NUM> that defines a cut-out or opening <NUM> configured to receive a main guidewire. The opening <NUM> can be an aperture in the material of the tapered tip <NUM> with an inner surface of the tapered tip <NUM> surrounding the main guidewire. The opening <NUM> is aligned with an inner member <NUM> within the stent graft cover <NUM>, as will be described below.

The tapered tip <NUM> can also include a second opening <NUM> configured to receive a secondary guidewire. This second opening <NUM> allows the delivery system <NUM> to track over the secondary guidewire simultaneously with the main guidewire. The second opening <NUM> is aligned with a secondary lumen <NUM> within the stent graft cover <NUM>, as will be described below.

The stent graft cover <NUM> is the outer-most sheath or lumen of the stent graft delivery system. The stent graft cover initially contains or surrounds a proximal portion of the tapered tip <NUM>, as well as the inner member <NUM>, the secondary lumen <NUM>, and a stent graft (not shown). As explained above, after insertion of the delivery system <NUM> to a desired location within the patient's vasculature, the surgical technician may utilize the handle to retract the stent graft cover <NUM>, allowing the stent graft to deploy. The stent graft cover <NUM> is an elongate tubular member defining a lumen from a proximal end to a distal end thereof. The stent graft cover <NUM> may be formed from a plurality of different materials or combination of materials; in one embodiment, the stent graft cover <NUM> is formed with a braided stainless steel wire with a flat or rounded cross section that is sandwiched between layers of PEBAX® or VESTAMID®.

The inner member <NUM> defines a hollow lumen, and can be two parts. For example, the inner member <NUM> can include an inner lumen or guidewire lumen <NUM>, and an outer lumen or capture lumen <NUM>. Each of the guidewire lumen <NUM> and the capture lumen <NUM> may be made from a high tensile polymer, such as polyether ether ketone (PEEK) or a polyimide. The capture lumen <NUM> is larger than the guidewire lumen <NUM> and receives the guidewire lumen <NUM> therein. The guidewire lumen <NUM> may be fixed to the tapered tip <NUM>, while the capture lumen <NUM> may be slideable along the outer surface of the guidewire lumen to slide toward the proximal end of the delivery system <NUM>. The guidewire lumen <NUM> may be fixed in alignment with the opening <NUM> of the tapered tip <NUM> to receive the main guidewire therethrough and track along the main guidewire during insertion into the patient.

The delivery system also includes a tip capture mechanism, shown generally at <NUM>. The tip capture mechanism <NUM> is coupled to, and actuated by, the inner member <NUM>. In particular, according to the illustrated embodiment, the tip capture mechanism <NUM> includes a capture fitting <NUM> having a plurality of fingers <NUM> or prongs. The capture fitting <NUM> is configured to hold a stent, ring, loop, or other such structure of a proximal end of the stent graft. This allows the stent graft to be deployed (e.g., when the stent graft cover <NUM> is retracted) while its proximal end is held in a constricted manner during deployment. A proximal end of the capture fitting <NUM> is fixed to the capture lumen <NUM> to move with the capture lumen <NUM>. Once the stent graft is at least partially deployed, the capture lumen <NUM> can be slid toward the surgical technician relative to the guidewire lumen <NUM>, thereby releasing the fingers <NUM> of the tip capture fitting <NUM> from the stent, ring, loop, or the like of the stent graft. This releases the stent graft from the delivery system, and the entire catheter can then be removed from the patient. While one example of a tip capture mechanism has been described, any tip capture mechanism may be compatible with the present disclosure. For example, the tip capture mechanism may be configured such that the inner tube extends axially forward to move the tip forward relative to the outer tube and spindle, thereby releasing the stent graft. Other tip capture mechanisms may include a single tube, three or more tubes, or other systems.

The secondary lumen <NUM> is also provided within the stent graft cover <NUM>. The secondary lumen <NUM> is aligned with the opening <NUM> to receive the secondary guidewire therethrough, and track along the secondary guidewire during insertion into the patient's vasculature. The secondary lumen may be located radially outboard of the inner member <NUM>, but radially inward of the stent graft cover <NUM>.

In previous designs of stent graft delivery systems, the addition of a secondary lumen within the confines of the stent graft could present several issues. For example, packaging constraints within the delivery system would be compromised, requiring other components within the confines of the stent graft to be reduced in size while still maintaining feasibility. Moreover, a bulge could be created in the stent graft cover as the secondary lumen is bent around the stent graft components. Such a bulge can make the profile of the delivery system lager than the intended outer profile. There is also difficulty in maintaining alignment of the secondary lumen and the inner components. In many cases, the secondary lumen is forced to bend around the arms of the capture mechanism and can become bent or misshapen in a way that could compromise the lumen patency or at least increase wire friction through the lumen.

Therefore, according to various embodiments described herein, the tapered tip <NUM> is designed to allow for smaller components within the confines of the stent graft cover <NUM>. In embodiments, the front surface <NUM> and the opening <NUM> at the distal end of the tapered tip <NUM> is not concentric with the stent graft cover <NUM>. This allows other components of the delivery system, such as the inner member <NUM> and tip capture mechanism <NUM>, to also assume a location that is not concentric with the stent graft cover <NUM>. These components can be offset from center in a direction away from the secondary lumen <NUM>, giving more space for the secondary lumen <NUM> to assume and not be bent or create a bulge in the stent graft cover <NUM>. Also, this allows an easier retraction of the secondary lumen <NUM>, if necessary, during a surgical deployment prior to retraction of the stent graft cover <NUM>.

The nature of the offset can be seen in the <FIG>, and in particular <FIG>. The distal surface or front surface <NUM>, the opening <NUM>, the inner member <NUM>, and the tip capture mechanism <NUM> are all concentric and have a common first central axis <NUM>. Meanwhile, the stent graft cover <NUM> has a second central axis <NUM> that is offset from the first central axis <NUM>. The secondary lumen <NUM> is positioned toward the perimeter (e.g., touching or adjacent) of the stent graft cover <NUM>. The first central axis <NUM> is located away from the second central axis <NUM> in a direction away from the second central axis <NUM>. While the terms "first" and "second" are used herein, it should be understood that these terms are used merely to delineate and label the two components separately, and the terms can be interchangeable.

To accommodate for this offset-axis relationship, the internal components may be reduced in size. For example, the tip capture mechanism <NUM> may be reduced in size, to allow the components to be offset from their original, central positioning. This creates more space for the secondary lumen <NUM>.

This also allows for the tapered tip <NUM> to be assembled to (e.g., pressed into) the delivery system late in the assembly process, in which the tapered tip <NUM> can be precisely positioned, rotationally, to optimize engagement with the secondary lumen <NUM>. In other words, once the secondary lumen <NUM> is assembled and in place within the stent graft cover <NUM>, the tapered tip <NUM> can be assembled to the remainder of the delivery system at a rotational alignment such that the opening <NUM> is aligned with the secondary lumen <NUM>.

To facilitate attachment during assembly, a spindle <NUM> is provided. The spindle <NUM> is a barbed insert for attachment of the tapered tip <NUM> to the inner member <NUM>. The spindle <NUM> is shown in the cross-sectional view in <FIG>, in isolation in <FIG> and attached about the guidewire lumen <NUM> in <FIG>. The spindle <NUM> is configured to align with the tip capture device <NUM> along the first central axis <NUM> to hold the stent graft in place during delivery (e.g., the stent apices may be held between the spindle <NUM> and the capture fitting <NUM>). The spindle <NUM> is fixed to the tapered tip <NUM>, and does not move with the capture lumen <NUM> or stent graft cover <NUM> during deployment of the stent graft. In previous designs, a spindle was overmolded onto a tapered tip, but this can create difficulty with non-concentric arrangements. Instead, in embodiments herein the spindle <NUM> is a separate component and separately assembled to the tapered tip <NUM>.

In one embodiment, a portion of the delivery system may be pre-assembled or preloaded such that the tapered tip <NUM> may be assembled to the guidewire lumen <NUM>, which is inserted into the capture lumen <NUM>, and the tapered tip <NUM> is pressed onto the spindle <NUM>. This eliminates a need for any threaded screw fit, and instead provides a simple press-fit attachment between the tapered tip <NUM> and the spindle <NUM>. The tapered tip <NUM> may be formed to include an inner surface <NUM> that creates a widened portion of the opening <NUM> at a proximal end of the tapered tip <NUM>. The inner surface <NUM> of the widened opening can be pressed around and fit about an exterior surface <NUM> of the spindle <NUM>.

To facilitate the press-fit attachment, the exterior surface <NUM> of the spindle <NUM> may be provided with surface features configured to inhibit movement. In particular, the exterior surface <NUM> can include a first set of barbs <NUM> and a second set of barbs <NUM>. The first set of barbs <NUM> may include one or more fins, projections, or the like that extend annularly about the first central axis <NUM>. As can be seen in <FIG>, these barbs <NUM> may be formed to be angled such that a proximal end of the barbs <NUM> extends further radially outward compared to a distal end of the barb <NUM>. This angle inhibits the tapered tip <NUM> from pulling away from the spindle <NUM> after assembly. The barbs <NUM> may be flattened or otherwise compressed once the tapered tip <NUM> is pressed over the barbs <NUM>.

The second set of barbs <NUM> may include one or more circumferentially-spaced fins each extending in an axial direction along the exterior surface <NUM>. These barbs <NUM> are configured to inhibit rotation between the tapered tip <NUM> and the spindle <NUM>.

To facilitate the press-fit attachment between the guidewire lumen <NUM> and the tapered tip <NUM>, the exterior surface of the guidewire lumen <NUM> may be provided with one or more barbs <NUM>. The barbs <NUM> may be similar to the first set of barbs <NUM>, being disposed annularly about the first central axis <NUM>. While not shown, the guidewire lumen <NUM> may also be provided with one or more barb that is similar in design to the second set of barbs <NUM>.

As can be seen in <FIG>, the offset-axis relationship of the delivery system can yield a tapered tip with varying thicknesses of material. For example, referring to <FIG>, the tapered tip <NUM> has a thicker amount of material above the opening <NUM> than below. Said another way, there is more material of the tapered tip on the side of the first central axis <NUM> closer to the second opening <NUM> than the other side of the first central axis <NUM>. The first central axis <NUM> is not the centerline of the taper of the tapered tip <NUM>. <FIG> illustrate various embodiments for varying the thickness of the tapered tip on either side of the opening <NUM>. Varying the shape or thickness of the tapered tip <NUM> can provide a preferential bending direction during insertion into the vasculature.

The tapered tips of <FIG> include the structure of the tapered tip <NUM> described above, unless described otherwise. <FIG> shows a tapered tip <NUM>' according to one embodiment. The tapered tip <NUM>' has a first portion <NUM> on the side of the opening <NUM> closer to the second opening <NUM>, and a second portion <NUM> on the side of the opening <NUM> away from the second opening <NUM>. The first portion <NUM> is generally conical in shape, generally constantly increasing in thickness (e.g., between the opening <NUM> and the outer surface) from the front surface <NUM> toward the rear. The outer surface of the first portion <NUM> is generally linear. Meanwhile, the second portion <NUM> has an outer surface that is concave. Therefore, the second portion <NUM> is not generally conical in shape, as the thickness of the second portion is not constant. This can influence the tracking performance of the delivery system in a first manner, with a first preferred bending direction that may allow for easier tracking and device placement.

<FIG> shows a tapered tip <NUM>" according to another embodiment. The tapered tip <NUM>" has a first portion <NUM> on the side of the opening <NUM> closer to the second opening <NUM>, and a second portion <NUM> on the side of the opening <NUM> away from the second opening <NUM>. The first portion <NUM> has an outer surface that is generally concave, and the second portion <NUM> has an outer surface that is generally concave. The outer surfaces of the two portions <NUM>, <NUM> can be pitched or concave at different degrees of magnitude. For example, the second portion <NUM> can be more concave than the first portion <NUM>. Moreover, the outer surfaces of both the first and second portions <NUM>, <NUM> can be angled such that the thickness of both portions is equal or substantially similar for at least a majority of the length of the portions <NUM>, <NUM>. This can influence the tracking performance of the delivery system in another manner, with another preferred bending direction that may allow for easier tracking and device placement.

<FIG> shows a tapered tip <NUM>‴ according to another embodiment. The tapered tip <NUM>‴ has a first portion <NUM> on the side of the opening <NUM> closer to the second opening <NUM>, and a second portion <NUM> on the side of the opening <NUM> away from the second opening <NUM>. The second portion <NUM> may have an outer surface that is generally linear, creating a conical shape of the second portion <NUM>. Meanwhile, the outer surface of the first portion <NUM> may be concave. Opposite to the embodiment of <FIG>, in this embodiment, the thickness of the second portion <NUM> may exceed the thickness of the first portion <NUM> for at least a majority of the length of the portions <NUM>, <NUM>. This can influence the tracking performance of the delivery system in another manner, with another preferred bending direction that may allow for easier tracking and device placement.

Claim 1:
A stent graft delivery system (<NUM>) comprising:
a stent graft cover (<NUM>) configured to maintain a stent graft in a constricted configuration, and configured to slide relative to the stent graft to enable the stent graft to expand radially outwardly, wherein the stent graft cover (<NUM>) extends along a first central axis; and
a tapered tip (<NUM>) defining an opening (<NUM>) therethrough that is configured to track along a guidewire, wherein the opening (<NUM>) extends along a second central axis that is offset from the first central axis, wherein the tapered tip (<NUM>) defines a second opening (<NUM>) therethrough that is configured to track along a second guidewire.