Patent Description:
To prevent rupture, a stent graft of a tubular construction may be introduced into the blood vessel, for example intraluminally. Typically, the stent graft is deployed and secured in a location within the blood vessel such that the stent graft spans the aneurysmal sac. The outer surface of the stent graft, at its opposed ends, is sealed to the interior wall of the blood vessel at a location where the blood vessel wall has not suffered a loss of strength or resiliency. Blood flow in the vessel is thus channeled through the hollow interior of the stent graft, thereby reducing, if not eliminating, any stress on the blood vessel wall at the aneurysmal sac location. Therefore, the risk of rupture of the blood vessel wall at the aneurysmal location is significantly reduced, if not eliminated, and blood can continue to flow through to the downstream blood vessels without interruption.

Woven fabrics are useful in the construction of grafts due to their desirable mechanical properties and the ease and low cost of manufacturing such fabrics. However, existing woven fabrics cannot include certain shapes, such as tapers, without compromising the structural integrity of such fabrics (e.g., due to the potential for fraying). In view of this background, the present disclosure provides an improved woven graft material for use in a stent graft. <CIT> describes single tubular woven or bifurcated prostheses that have varying diameters and tapered transitions.

The invention is directed to an implantable graft according to independent claim <NUM>, to an implantable graft according to independent claim <NUM> and to a method according to independent claim <NUM>.

In one aspect, an implantable graft includes a main section having walls formed with a woven fabric, the main section having a main lumen extending therethrough. The implantable graft also includes a bifurcated section having walls formed with the woven fabric, where the bifurcated section extends from main section, where the bifurcated section includes a first branch and a second branch, and where the first branch and the second branch each include a branch lumen in fluid communication with the main lumen. At least one branch of the bifurcated section includes a branch taper formed by a seam connecting a first woven layer and a second woven layer. A seam extension extends outwardly along the seam of the branch taper, the seam extension being a single-layer woven structure.

In another aspect, an implantable graft includes a woven fabric forming walls of a first tubular section and a second section, the first tubular section having a first diameter and the second section having a smaller second diameter. A tapered section located between the first tubular section and the second section decreases in diameter as it extends from the first tubular section to the second section. A seam extension extending from a seam of the tapered section joins a first woven layer of the tapered section to a second woven layer of the tapered section. The seam extension includes a single-layer woven structure.

The embodiments will be further described in connection with the attached drawings. It is intended that the drawings included as a part of this specification be illustrative of the exemplary embodiments and should in no way be considered as a limitation on the scope of the present disclosure. Indeed, the present disclosure specifically contemplates other embodiments not illustrated but intended to be included in the claims.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein falling within the scope of the appended claims can be used in the practice or testing of the present invention. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

The term "implantable" refers to an ability of a medical device to be positioned at a location within a body, such as within a body lumen.

As used herein, the term "body vessel" means any tube-shaped body passage lumen that conducts fluid, including but not limited to blood vessels such as those of the human vasculature system, esophageal, intestinal, biliary, urethral and ureteral passages.

The term "branch vessel" refers to a vessel that branches off from a main vessel. The "branch vessels" of the thoracic and abdominal aorta include the celiac, inferior phrenic, superior mesenteric, lumbar, inferior mesenteric, middle sacral, middle suprarenal, renal, internal spermatic, ovarian (in the female), innominate, left carotid, and left subclavian arteries. As another example, the hypogastric artery is a branch vessel to the common iliac, which is a main vessel in this context. Thus, it should be seen that "branch vessel" and "main vessel" are relative terms.

The terms "about" or "substantially" used with reference to a quantity includes variations in the recited quantity that are equivalent to the quantity recited, such as an amount that is insubstantially different from a recited quantity for an intended purpose or function.

The term "stent" means any device or structure that adds rigidity, expansion force, or support to a prosthesis. The term "stent graft" as used herein refers to a prosthesis comprising a stent and a graft material associated therewith that forms a lumen through at least a portion of its length.

<FIG> is an illustration, useful for understanding the invention, showing a top view of a tubular woven graft <NUM>, which is an implantable graft for implantation to a patient body. <FIG> is an illustration showing a magnified view of the top layer of tubular graft of <FIG>. Referring to <FIG>, the graft <NUM> may be a portion of a stent graft, and thus the graft <NUM> may be associated with a stent (not shown). Further, the graft <NUM> is a woven graft having walls formed substantially of a woven fabric <NUM>. The woven fabric <NUM> may have a plurality of warp yarns (depicted as "warp ends <NUM>") aligned substantially in a first direction that are interwoven with a plurality of weft threads <NUM> aligned substantially in a second direction, where the first direction and the second direction are substantially perpendicular. For example, the warp ends <NUM> may be the lengthwise threads attached to a loom before weaving begins, and may be manipulated by a reed during the weaving process. The weft threads <NUM> (also known as woof or fill yarns) may be the strands that are shuttled back and forth across the warp ends <NUM> such that the warp ends <NUM> and the weft threads <NUM> together define the woven fabric <NUM>.

The graft <NUM> may include a main tubular section <NUM> and a bifurcated tubular section <NUM>, as shown in <FIG>. The main tubular section <NUM> may be configured for deployment in a vessel or other body lumen, such as an aorta of a human (or other) patient to treat an aneurysm. To allow blood flow through the main section <NUM>, a main lumen <NUM> may extend through the entire tubular woven graft that is constructed in the form of woven fabric <NUM>.

The bifurcated section <NUM>, which also may be formed with the tubular woven fabric <NUM>, extends from the main section <NUM>. In exemplary embodiment, the bifurcated section <NUM> may include a first branch <NUM> and a second branch <NUM> for deployment within branch vessels extending from the aorta (e.g., the iliac arteries of a human (or other) patient). The bifurcated section <NUM> may extend distally from the main section <NUM>, but it may alternatively extend a different direction from the main section <NUM> in other embodiments. The bifurcated section <NUM> includes a first branch <NUM> and a second branch <NUM> (and in some embodiments, more than two branches may be included). To allow blood flow through the branches, the first branch <NUM> and the second branch <NUM> each include a respective branch lumen <NUM>, <NUM> in fluid communication with the main lumen <NUM> of the main section <NUM>.

Optionally, the main section <NUM> may include a tapered portion <NUM> at its distal end <NUM> that extends from a cylindrical portion <NUM>. The tapered portion <NUM> may be frustoconical in shape and may decrease in diameter as it extends distally from the cylindrical portion <NUM> of the main section <NUM>. The tapered portion <NUM> may be advantageous to providing a smooth transition from the main section <NUM> to the bifurcated section <NUM>. For example, when the graft <NUM> is configured for use in and around the aorta, the tapered portion <NUM> may provide a smooth transition between the abdominal aorta and the common iliac arteries, but tapers for other body locations are also contemplated. In other embodiments, the main section <NUM> may lack the tapered second <NUM>, and thus the bifurcated section <NUM> may extend directly from the cylindrical portion <NUM>. When the tapered portion <NUM> is included, it may be formed with a woven structure as described in more detail below.

Similarly, the bifurcated section <NUM> includes a tapered section <NUM> where at least one of the branches includes a tapered structure. For example, the first branch <NUM> may include a first branch taper <NUM> and the second branch may include a second branch taper <NUM>. The first branch taper <NUM> and the second branch taper <NUM> may each include a respective frustoconical wall <NUM> that surrounds the branch lumens <NUM>, <NUM>. Advantageously, the first branch taper <NUM> and/or the second branch taper <NUM> may provide a smooth transition from a main vessel (e.g., the abdominal aorta) to smaller respective branch vessels.

<FIG> is an illustration depicting a diagram of a weaving orientation during formation of the graft <NUM>. As shown, the warp ends <NUM> extend substantially in the longitudinal direction of the graft <NUM>, and thus the weft threads <NUM> (<FIG>) extend substantially perpendicular to the longitudinal direction of the graft <NUM>. The warp ends <NUM> in <FIG> are depicted as extending through the graft <NUM>, and also beyond the limits of the graft walls (as they would appear during the weaving process prior to the graft <NUM> being removed from the loom).

In the bifurcated section <NUM> of the graft <NUM>, certain warp ends <NUM> may be dropped from the graft material (e.g., free from weft threads and thus not incorporated into the woven fabric <NUM>) in a located between the first branch <NUM> and the second branch <NUM>. When the machine direction is from distal-to-proximal (as depicted in <FIG>), the warp ends <NUM> may be picked up (e.g., interwoven with weft threads due to communication with the shuttle) at a junction <NUM> where the first branch <NUM> and the second branch <NUM> meet. A distal end of the main lumen <NUM> (<FIG>) may be located at a proximal end of the junction <NUM>.

The tapered portion <NUM> of the main section <NUM> may include a seam extension <NUM>. The seam <NUM> is used to create the tapered geometry in the tubular graft. The seam extension <NUM> may extend outwardly from a wall of the tapered portion <NUM>, as shown. The seam extension <NUM> may be defined by a location where the warp yarns forming the cylindrical portion <NUM> are transitioned into a single-layer woven structure (as described in more detail below with reference to <FIG>). Advantageously, and as described in more detail below, the tapered portion <NUM> may provide an area beyond the wall <NUM> of the tapered portion <NUM> where the warp ends <NUM> are locked/secured in place with respect to the weft threads such that the woven fabric <NUM> does not fray or otherwise unravel at a seam between upper and lower woven layers. <FIG> is an illustration showing a diagram of a cross-sectional construction of the cylindrical portion <NUM> of the main section <NUM> about A-A of <FIG>. Specifically, the perspective of <FIG> is from a proximal viewpoint looking distally through the main lumen <NUM>. While the cylindrical portion <NUM> is ovular in shape in <FIG>, it expand into a substantially cylindrical shape once the weaving process is complete and/or upon deployment into a patient body. During weaving, the cylindrical section may be formed by a two-layer woven structure where the top woven layer forms an upper side <NUM> of the cylindrical portion <NUM> and a bottom woven layer forms a lower side <NUM> of the cylindrical portion. During the weaving process, to prevent closing the main lumen <NUM>, the warp ends associated with the upper side <NUM> may remain only associated with the upper side <NUM>, and the warp ends associated with the lower side <NUM> may remain only associated with the lower side <NUM>. That is, the warp threads associated with the upper side <NUM> do not interweave with weft threads as they are forming the lower side <NUM>, and vice versa. The resulting structure is the tubular structure with the main lumen <NUM> extending therethrough, where the upper side <NUM> and the lower side <NUM> each define approximately half the perimeter of the cylindrical portion <NUM> (although it is also contemplated that one of the upper side <NUM> and the lower side <NUM> may be substantially larger than the other).

<FIG> is an illustration showing a diagram of a cross-sectional construction of the tapered portion <NUM> of the main section <NUM> about B-B of <FIG>. Specifically, the perspective of <FIG> is from a proximal viewpoint looking distally through the main lumen <NUM>. As shown, the tapered portion <NUM> is formed with a two layer woven structure similar to the structure of the cylindrical portion <NUM> as described above (with reference to <FIG>), but fewer warp ends may be included in the layer defining the upper side <NUM> and/or the layer defining the lower side <NUM> such that the diameter of the main lumen <NUM> within the tapered portion <NUM> of <FIG> is smaller than the diameter of the main lumen <NUM> in the cylindrical portion <NUM>. More particularly, the diameter of the main lumen <NUM> may incrementally decrease as the tapered portion <NUM> extends distally from the cylindrical portion <NUM> (as shown in <FIG>, above). The incremental decrease may be caused by incrementally decreasing the number of warp ends that are incorporated into the two layer woven structure with the upper side <NUM> and the lower side <NUM>.

In the tapered portion <NUM>, the upper side <NUM> and the lower side <NUM> may meet at a junction or seam <NUM>. As shown in <FIG>, two seam extensions <NUM> may extend outwardly from the wall <NUM> at the seam <NUM> where the upper side <NUM> and the lower side <NUM> meet. The warp ends and the weft threads in both the upper side <NUM> and the lower side <NUM> are incorporate into the woven structure of the seam extensions <NUM>. Thus, the seam extensions <NUM> may have a larger density (e.g., a higher thread density or thread count) than both the upper side <NUM> and the lower side <NUM> of the tapered portion <NUM>.

Advantageously, the seam extensions <NUM> capture the warp ends that are dropped from the fabric of the tapered portion <NUM> as its diameter changes (e.g., due to incrementally dropping warp ends along the tapered portion <NUM> as its diameter decreases). For example, the warp ends <NUM> in the seam extension <NUM> may be included in the area <NUM> of <FIG> where no weft threads are located, and thus without the seam extension <NUM>, those same warp ends <NUM> may be relatively loose immediately adjacent to the graft wall, leaving them prone to fraying and/or otherwise compromising the structure of the wall <NUM> of the graft <NUM> at the seam <NUM> shown in <FIG>. Referring to <FIG>, by including the seam extension <NUM>, the woven structure adjacent to the seam <NUM> may have enhanced durability (e.g., it may be resistant to fraying). In some embodiments, a fusible material (e.g., a yarn or strand with a suitable melting point for heat-processing) may be included in the seam extensions <NUM>, which may be head processed at least in the seam extensions <NUM> to lock the warp yarns and/or the weft threads in place. The fusible material may be included with a yarn or strand (e.g., with at least one of the warp ends or weft threads), or it may be included separately (e.g., in a post-weaving manufacturing step). In some embodiments, a similar locking effect may be achieved in the seam extension <NUM> without (or in addition to) heat processing, such as by including an adhesive in the seam extension <NUM>. For example, some options for yarn materials include polyethylene terephtalate (PET) or ePTFE, which may be biocompatible and/or hemocompatible. Any other suitable biocompatible and/or hemocompatible material can be used.

<FIG> is an illustration showing a diagram of a cross-sectional construction of the bifurcated section <NUM> about C-C of <FIG>. Specifically, the perspective of <FIG> is from a proximal viewpoint looking distally through the first branch lumen <NUM> of the first branch <NUM> and the second branch lumen <NUM> of the second branch <NUM>. As shown, each of the first branch <NUM> and the second branch <NUM> may be formed of a two layer woven structure similar to the two layer woven structure described above to form the cylindrical portion <NUM> (<FIG>) and the tapered portion <NUM> (<FIG>). However, referring to <FIG>, a space <NUM> may be located between the first branch <NUM> and the second branch <NUM> where centrally-located warp ends <NUM> are dropped and thus not incorporated into either of the first branch <NUM> and the second branch <NUM>. The space <NUM> between the first branch <NUM> and the second branch <NUM> may grow gradually as the first branch <NUM> and the second branch <NUM> extend away from the main section <NUM> (<FIG>), and such growth may be caused by tapering at least one of the first branch <NUM> and the second branch <NUM> in a manner similar to as described above with reference to <FIG>. A taper is included with at least one of the branches, the at least one corresponding seam extension is also included.

For example, referring to <FIG>, a first branch seam extension <NUM> that extends outwardly from a wall <NUM> of the first branch <NUM> and a second branch seam extension <NUM> that extends outwardly from a wall <NUM> of the second branch <NUM>. The branch seam extensions <NUM>, <NUM> are formed with a single-layer woven structure where the warp ends from the two layer woven structure of the respective branch <NUM>, <NUM> are incorporated into the single-layer woven structure. Like the seam extension <NUM> (<FIG>) described above, the branch seam extensions <NUM>, <NUM> of <FIG> may be advantageous for providing a space where the warp ends <NUM> (and/or the weft threads) are secured/locked in place to inhibit fraying along the junctions or seams <NUM> between an upper side and a lower side of the branches <NUM>, <NUM> as they taper.

While only one seam area is shown per branch in <FIG>, it is contemplated that each branch may include two seam areas, particularly if the branches <NUM>, <NUM> taper along both seams/junctions where the upper sides and lower sides of the branches <NUM>, <NUM> meet. Further, while the first branch <NUM> and the second branch <NUM> are mirror-images of each other, this is not necessarily true in all embodiments. It is contemplated that only one of the branches <NUM>, <NUM> may include a seam extension (e.g., particularly if only one branch tapers), and the seam extensions <NUM>, <NUM> of the branches <NUM>, <NUM> do not necessarily need to be the same size.

<FIG> is an illustration showing a diagram of a cross-sectional construction of the bifurcated section <NUM> about D-D of <FIG>. Specifically, the perspective of <FIG> is from a proximal viewpoint looking distally through the first branch lumen <NUM> of the first branch <NUM> and the second branch lumen <NUM> of the second branch <NUM>. As shown in <FIG>, the first branch <NUM> and the second branch <NUM> do not include a seamed area. This lack of a seamed area is due to the first branch <NUM> and the second branch <NUM> extending with a substantially constant diameter in this location, and therefore a seamed area at this location may not be necessary since no warp ends are dropped at this location from the respective two-layer woven structures forming the tubular branches as they are woven in a shuttle weaving machine as explained earlier.

<FIG> is an illustration showing a close-up view of the proximal portion <NUM> of the bifurcated section of the graft <NUM>. As shown, the first branch seam extension <NUM> of the first branch <NUM> and the second branch seam extension <NUM> of the second branch may meet at a branch junction <NUM> (i.e., the location where the first branch <NUM> and the second branch <NUM> meet). Within a distal junction area, a common seam extension <NUM> may exist, and therefore no warp ends may be unused between the first branch <NUM> and the second branch <NUM> in the junction <NUM>. The common seam extension <NUM> may extend to the main section <NUM>.

Seamed areas such as those described above may have any one of a variety of shapes. Certain examples are shown in the illustrations of <FIG>. While the following examples reference the seam extension <NUM> (e.g., of the main section <NUM>), similar and/or identical shapes may be used for the branch seamed areas <NUM>, <NUM> (see <FIG>). One example is shown in <FIG>, where a seam extension <NUM> has a rectangular shape at its distal end <NUM>. Such a shape may be formed where the warp ends <NUM> are dropped from the distal end at the same time during weaving, and/or such that each of the dropped warp ends <NUM> enter the seam extension <NUM> at a common weft thread.

<FIG> shows another potential shape of the seam extension <NUM>. In <FIG>, the seam extension <NUM> includes a slanted shape at its distal end <NUM>, which may be formed by dropping the warp ends <NUM> gradually. For example, if weaving in the proximal direction (i.e., from distal-to-proximal), each successive shuttle motion during weaving may pick up an additional warp end <NUM> that was previously unused until reaching a warp end <NUM> that will eventually form the outer edge <NUM> of the main section <NUM>.

In <FIG>, the depicted seam extension <NUM> extends beyond the outer edge <NUM> of the cylindrical portion <NUM> of the graft <NUM>. Thus, some of the warp ends <NUM> used in the seam extension <NUM> may not be used elsewhere in the graft <NUM>. To illustrate, the warp end 130a of <FIG> may be picked up by the seam extension <NUM> at the proximal end of the seam extension <NUM> and dropped at the distal end of the seam extension <NUM>, but it may be free from the woven material of the graft <NUM> at locations proximal of the seam extension <NUM> and also at locations distal of the seamed area. <FIG> depicts the seam extension <NUM> as also extending beyond the outer edge <NUM> of the cylindrical portion <NUM> of the graft <NUM>, but with slanted edges rather than the squared edges as shown in <FIG>.

<FIG> is an illustration showing the graft <NUM> having trimmed seam extensions <NUM> and branch seam extensions <NUM>, <NUM>. For example, the seam extensions <NUM> may initially be relatively wide (e.g., have a relatively large dimension extending outwardly from the wall of the graft <NUM>) such that the warp ends and/or the weft threads remain relatively secure after the weaving process. Advantageously, the structure of the graft <NUM> may be retained even prior to a fusing or other securement process post-weaving. After weaving, the seam extensions <NUM> may be secured (e.g., fused) as described above. Once secured, the relatively large width of the seam extensions <NUM> may no longer be necessary, so they may be trimmed. The trimming process may include cutting the seam extensions <NUM> with scissors, a knife, a punch, or any other suitable cutting device, and it may be performed manually by a manufacturing professional or automatically with the use of a machine. Advantageously, by trimming the seam extensions <NUM>, it may be ensured that the seam extensions <NUM> do not irritate or damage a body surface (e.g., an inner diameter surface of an artery), do not inhibit deployment of the graft <NUM>, etc..

<FIG> is an illustration showing the graft <NUM> having a meltable yarn <NUM> that extends along the seam <NUM> of the graft <NUM>. When no tapers are included in the graft <NUM>, the meltable yarn <NUM> may simply be a warp end <NUM> having a particular material, but in exemplary embodiments the warp end <NUM> is included along the seam <NUM> of the tapered portion <NUM>, and thus the meltable yarn <NUM> may extend diagonally with respect to the warp ends <NUM> (at least in the tapered portion <NUM>). To include the meltable yarn <NUM>, the weaving machine that manufactures the graft <NUM> may include an open reed. The meltable yarn <NUM> can therefore be independently manipulated relative to the warp ends <NUM> and placed along the seam <NUM>, as desired.

The meltable yarn <NUM> may include any suitable material, such as a thermoplastic polymer material having a melting point configured to fuse when heat processed. That is, a material of the meltable yarn <NUM> may at least partially melt when heated and then solidify when later cooled to enhance the structure of the seam <NUM>. For example, the meltable yarn <NUM> may be a yarn including a low melting polyester or other bio and hemocompatible thermoplastic with a melting point lower than the melting point of base material from which the body of the graft is constructed. For example, the melting point of the meltable yarn <NUM> may be about <NUM> degrees Celsius or less, such as less than about <NUM> degrees Celsius. In addition, any other irreversibly meltable/fusible polymeric or natural yarn can be used for this purpose. Advantageously, the meltable yarn <NUM> can be heat-processed after the weaving process to seal/secure the woven threads along the structure of the seam <NUM> to enhance the strength and durability of the graft <NUM>. While only one strand of the meltable yarn <NUM> is depicted, it is contemplated that a plurality of meltable yarns <NUM> may be included together and/or separately.

<FIG> is an illustration showing the graft <NUM> where optional meltable yarns <NUM> extend along the first branch <NUM> and the second branch <NUM>, including along the first branch taper <NUM> and the second branch taper <NUM>. The meltable yarns <NUM> may include any of the aspects described above with reference to the meltable yarn <NUM>. In <FIG>, the meltable yarns <NUM> are shown as terminating at a location <NUM> that is just proximal of the junction <NUM>. The meltable yarn is part of the top warp yarn layers but not interwoven into the top layer of the graft <NUM> until location <NUM>. Alternatively, the meltable yarn can be fed to the weaving zone as an external yarn using a separate bobbin and then can be interwoven with the base material staring from point <NUM> using an open reed weaving procedure.

The aspects and features described above may also apply to grafts having different shapes, and many graft shapes are contemplated. For example, one geometry of an iliac leg graft <NUM> is shown in <FIG>, which is formed of a woven fabric <NUM>. The graft <NUM> may lack a bifurcated section, but otherwise may be similar to the graft <NUM> described above. Referring to <FIG>, the graft <NUM> has a first tubular section <NUM> and a second tubular section <NUM>, where the second tubular section <NUM> has a smaller diameter than the first tubular section <NUM>. A tapered section <NUM> is located between the first tubular section <NUM> and the second tubular section <NUM>. Like the embodiments described above, a seam extension <NUM> may be located on each side of the tapered section <NUM>. The seam extension <NUM> may incorporate any of the features and aspects described with respect to the seam extensions discussed above.

Claim 1:
An implantable graft (<NUM>), comprising:
a main section (<NUM>) having walls formed with a woven fabric (<NUM>), the main section having a main lumen (<NUM>) extending therethrough; and
a bifurcated section (<NUM>) having walls formed with the woven fabric, wherein the bifurcated section extends from main section, wherein the bifurcated section includes a first branch (<NUM>) and a second branch (<NUM>), and wherein the first branch and the second branch each include a branch lumen (<NUM>,<NUM>) in fluid communication with the main lumen,
wherein at least one branch of the bifurcated section includes a branch taper (<NUM>,<NUM>) formed by a seam connecting a first woven layer and a second woven layer, and
wherein a seam extension (<NUM>, <NUM>) extends outwardly along the seam of the branch taper, the seam extension being a single-layer woven structure
wherein warp ends and weft threads in both the first woven layer and the second woven layer are incorporated into the woven structure of the seam extension such that the seam extension has a higher thread density than both the first woven layer and the second woven layer in the at least one branch.