Patent Publication Number: US-2020289253-A1

Title: Graft having a pocket for receiving a stent and woven graft material forming a pocket

Description:
BACKGROUND 
     Aneurysms occur in blood vessels in locations where, due to age, disease or genetic predisposition, the blood vessel strength or resiliency is insufficient to enable the blood vessel wall to retain its shape as blood flows therethrough, resulting in a ballooning or stretching of the blood vessel at the limited strength/resiliency location to thereby form an aneurysmal sac. If the aneurysm is left untreated, the blood vessel wall may continue to expand, to the point where the remaining strength of the blood vessel wall is below that necessary to prevent rupture, and the blood vessel will fail at the aneurysm location, often with fatal result. 
     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. 
     While tubular stent grafts have been used with success, manufacturing processes remain inefficient and improved connections between the stent and graft body are desired. The present disclosure provides an improved stent graft and method of manufacture that improves the stent-to-graft connection while also increasing manufacturing efficiency relative to prior stent grafts. 
     BRIEF SUMMARY 
     In one aspect, the present disclosure describes a tubular graft for use in a stent graft. The tubular graft may include a first woven layer that forms a first side of the tubular graft, where the first woven layer has a set of first warp ends. A second woven layer may forma a second side of the tubular graft, where the second woven layer has a set of second warp ends, and where the second warp ends are distinct from the first warp ends. A woven pocket flap may extend from the first woven layer, where a pocket opening is defined between the woven pocket flap and the first woven layer, and where the woven pocket flap includes at least one common weft yarn with the first woven layer. 
     In another aspect, the present disclosure describes a stent graft. The stent graft may include a stent and a tubular graft, where the tubular graft includes a first woven layer and a pocket flap extending from the first woven layer. The pocket flap and the first woven layer may include at least one common weft yarn, where a portion of the stent is received by a pocket opening defined between the pocket flap and the first woven layer. 
     In another aspect, the present disclosure describes a method for forming a tubular graft. The method may include weaving a first woven layer that forms a first side of the tubular graft, the first woven layer having a set of first warp ends, weaving a second woven layer that forms a second side of the tubular graft, the second woven layer having a set of second warp ends, where the second warp ends are distinct from the first warp ends, and weaving a woven pocket flap extending from the first woven layer, where a pocket opening is defined between the woven pocket flap and the first woven layer, and where the woven pocket flap includes at least one common weft yarn with the first woven layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1  is an illustration showing a stent graft having a graft body with pockets that receive the stent in accordance with certain aspects of the present disclosure. 
         FIG. 2  is an illustration showing a view of a segment of the stent graft shown in  FIG. 1 , where the pockets are secured an underlying layer of the graft body via tack knots in accordance with certain aspects of the present disclosure. 
         FIGS. 3A-3C  are illustrations showing examples of points of securement for locking a portion of a stent within a graft pocket in accordance with certain aspects of the present disclosure. 
         FIG. 4  is an illustration showing a portion of a tubular graft body having woven pockets in accordance with certain aspects of the present disclosure. 
         FIG. 5  is an illustration showing a sectional view taken about line  5 - 5  of  FIG. 4 . 
         FIG. 6  is an illustration showing a weft insertion sequence for forming a plain tubular fabric for use in a graft body in accordance with certain aspects of the present disclosure. 
         FIG. 7  is an illustration showing a weft insertion sequence for forming a tubular fabric with two pockets for use in a graft body in accordance with certain aspects of the present disclosure. 
         FIG. 8  is an illustration showing a method (including certain steps of four separate weft insertion sequences) for forming a tubular fabric with two pockets having variable width (e.g., such as a triangular pocket) for use in a graft body in accordance with certain aspects of the present disclosure. 
         FIG. 9  is an illustration showing a method (including certain steps of four separate weft insertion sequences) for forming a tubular fabric with two pockets having variable width (e.g., such as a triangular pocket) for use in a graft body, where the sequence of  FIG. 9  is inverted relative to  FIG. 8 , in accordance with certain aspects of the present disclosure. 
         FIG. 10  is an illustration showing a woven fabric having pockets formed in accordance with certain aspects of the present disclosure, where floating warp ends extend from an edge of the pocket. 
         FIG. 11  is an illustration showing the woven fabric of  FIG. 10 , where the floating warp ends are removed, thereby allowing access to openings of the pockets. 
     
    
    
     DETAILED DESCRIPTION 
     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 can be used in the practice or testing of the present invention. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. 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. 1  is an illustration showing a top view of a stent graft  100 , which may be an implantable stent graft for implantation into a patient body. Without limitation, the stent graft  100  may generally include a stent  102  and a tubular graft body  104  formed of a fabric and/or other suitable graft material (e.g., a woven fabric as described below). The graft body  104  may provide a fluid barrier such that a body fluid can flow through an inner lumen  132  defined by the tubular graft body  104 . While the stent  102  may include any suitable support structure, the depicted embodiment of the stent  102  includes several stent sections (e.g.,  102   a,    102   b,  etc.) that have several linear segments arranged in a zig-zag pattern. The segments of the stent  102 , at least when in an expanded state, provide support to the tubular graft body  104  such that it retains its tubular shape within a patient. While not shown, the stent  102  may also provide anchoring means (e.g., hooks, barbs, or other suitable devices) that anchor the stent graft  100  at an appropriate location within a body lumen when deployed. The stent  102  may be formed with an expandable structure (e.g., self-expanding or expandable upon receipt of an activation force) such that the stent graft  100  can be deployed in a collapsed state and then expanded into an operational state within the body. Optionally, the stent graft  100  may be removable from the body after an amount of time. 
     As shown, the graft body  104  may include pockets  110  for receiving at least a portion of the stent  102 . While the pockets  110  may receive any portion of the stent  102 , one exemplary embodiment includes several rows of triangular pockets  110  that receive apices of the respective stent sections  102   a,    102   b , etc. As shown (and as described in more detail below in  FIG. 2 ), the openings  112  of alternating pockets  110  in each pocket set (e.g., where a set corresponds to a single stent section) may face opposite directions (i.e., distal vs. proximal) to receive respective apices on opposite sides of the sections of the stent  102 . As described in more detail below, the pockets  110  may be defined by a two-layer fabric structure having an underlying base layer (e.g., substantially continuous with the areas surrounding the pocket) and a pocket flap, where the space between the base layer and the pocket flap defines a pocket opening. While the pockets  110  are shown as receiving the stent  102  is on the exterior side of the graft body  104 , it is contemplated that the stent  102  (and pockets) could instead be located on interior or lumen side of the of the graft body  104 . 
     While the pockets  110  are triangular in the depicted embodiment, they may have any other suitable shape. For example, if the stent  102  includes a different shape (e.g., unsuitable for receipt by a triangular pocket), the pockets  110  can be modified such that they have a shape suitable for receiving such a stent. Without limitation, at least one pocket that accords with the embodiments herein may have a semi-circular or other curved shape, a square shape or shape of another polygon, the shape of an elongated tube, etc. 
     Further, while the stent graft  100  herein is depicted as having a straight, single-lumen configuration (with multiple diameters), other configurations are also contemplated. For example, the teachings herein also apply to a stent graft that is bifurcated. The formation of pockets on the graft body  104  (as described in more detail below) is not dependent on whether the main body of the graft is straight or whether a straight section is followed by a bifurcated section, and it is contemplated that a bifurcated section may also have pockets appropriately positioned for receipt of one or more stents. 
       FIG. 2  shows a magnified view of the stent section  102   a  along with a set of respective triangular pockets  110 . As shown, the opening  112  of the lower pockets  110  face a first direction (e.g., upward from the perspective of  FIG. 2 ) and the openings  112  of the upper pockets  110  face an opposite second direction (downward). The openings  112  are formed between pocket flaps  114  and underlying base layer  116  (beneath the pocket flaps  114  from the perspective of  FIG. 2 ) of the graft body  104 , and the openings are accessible through respective mouths  152 . 
     An edge  119  of each of the pocket flaps  114  may be unsecured to the underlying base layer  116  to provide access to the openings  112  (e.g., to allow for receipt of a stent apex) through the mouth  152 . Other edges of the pocket flaps  114 , such as a second edge  120  and/or a third edge  122 , may be at least partially secured to the underlying base layer  116  of the graft body  104  if it is desirable to close those respective sides of the opening  112  off. In other embodiments (particularly when a triangular shape is used for the pockets), only the apices  124  of the pocket flaps  114  may be secured to the remainder of the graft body  104 , such as by the tack knots  126  shown in  FIG. 2 . Securement of the pocket flaps  114  to the remainder of the graft body  104  may be accomplished with any suitable structure or method. For example, the pocket flaps  114  may be secured via a woven or knitted structure (e.g., the woven structures described below), tacks, sewing threads, adhesives, mechanical clamps, etc. While the pocket flaps  114  have generally the same material as the remainder of the graft body  104  in the embodiments described herein (such as a woven material), this is not required. 
     If additional retention of the stent  102  is desirable after its insertion within a pocket opening, additional measures may be taken, some of which are shown in the non-limiting examples of  FIGS. 3A-3C . For example, referring to  FIG. 3A , the pocket flap  114  may be secured to the underlying base layer  116  at a point of securement  128  after the stent  102  is inserted to lock the stent  102  substantially in place, where the point of securement  128  is spaced from an edge of the pocket flap  114 . The point of securement  128 , which may be located just inside the apex of the stent  102  and between the two stent sections  106 , may be formed via thermally bonding, a sewn knot or other sewn structure, one or more applied adhesives, and/or any other suitable structure or method. For example,  FIG. 3B  shows a similar point of securement  128  that is formed with a tack knot. In some embodiments (such as that of  FIG. 3C ), the securement between the pocket flap  114  and the base layer  116  may be more extensive (and intentionally shaped) for enhanced control of the position of the stent  102  relative to the graft body  104 . For example, this embodiment includes a v-shaped section  131  formed by thermal bonding (or another securement means) that defines the interior v-shaped dimension of a pocket  110  that mimics the apex of the stent  102 . Optionally, non-essential portions of the pocket flap  114  may be removed, and such removal may be advantageous for decreasing the weight of the stent graft, to decrease the area of the graft fabric, to prevent or reduce the likelihood of loose graft material interfering with stent graft deployment and/or body functions, to maintain a low profile of the stent graft device, etc. The features shown in  FIGS. 3A-3C  and other securement structures may apply to any suitable pocket structure, including the woven pockets described in detail below. 
     In some embodiments, the material of the graft body  104  may be formed via weaving. Weaving generally involves a set of warp ends (or warp yarns/threads) that are aligned substantially in a first direction, and that are interwoven/interlaced with a plurality of weft yarns aligned substantially in a second direction, where the first direction and the second direction are substantially perpendicular. For example, when a weaving machine is used, the warp ends 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 yarns (also known as woof or fill yarns) may be the strands that are shuttled back and forth across the warp ends (while the warp ends are held in an “up” or “down” position by the loom) such that the warp ends and the weft yarns are together interwoven to define a structurally-sound woven fabric. The weaving process may take place on any suitable device (such as a narrow-width shuttle loom) using any suitable yarns materials, yarn types, yarn linear densities, and fabric parameters such as warp density, weft density, and weave design (e.g., plain, twill, rib, etc.). 
       FIG. 4  shows such an embodiment (with only two pockets for ease of description), where the warp direction (e.g., vertically from the perspective of  FIG. 4 , and along the lengthwise direction of the warp ends  130  shown in  FIGS. 6-9 ) is parallel to the longitudinal direction of the graft body  104  and its lumen  132 . The weft yarns (such as the weft yarns  134  as shown in  FIGS. 6-9 ) within the weave pattern, on the other hand, will generally extend around the circumference of the graft body  104 .  FIG. 5  shows a sectional view of the woven graft body  104  about line  5 - 5  in  FIG. 4  (except where the graft body  104  is in a flattened state rather than the fully-expanded state of  FIG. 4 ). 
     Referring to  FIGS. 4-5  (and also  FIG. 6 ), the graft material may be woven as a multi-layer fabric. The depicted embodiment includes four layers, but more or fewer layers are also contemplated. Specifically, the depicted embodiment includes a first layer  136  and a second layer  138 , where the first layer  136  and the second layer  138  are connected at their edges  140  (but separable between those edges  140 ). When initially removed from a loom, the first layer  136  and the second layer  138  may be in an overlapping and flat orientation, but once in an expanded state (e.g., with the assistance of a stent), a tubular structure (or other suitable structure with a lumen) may be formed. The lumen  132  may be defined between the first layer  136  and the second layer  138 , as shown. 
     The first layer  136  and the second layer  138  may each form roughly half of the tubular graft body  104 , and thus the overall diameter of the lumen  132  may be determined by the size of the first layer  136  and the second layer  138 . Thus, the number and/or the density of the of warp ends within the woven layers has a direct impact on the diameter of the graft body  104  (since it determines the width overall width of the layers), for example, and the length of the graft may be determined by a selected length of the warp ends (e.g., which may be cut to such a selected length after weaving is completed on the loom). Other weaving parameters and/or yarn parameters (e.g., warp and weft yarn thickness (linear density), warp density, weft density, and/or weave design) may provide the graft body  104  with certain functional characteristics, such as permeability, longitudinal and circumferential tensile strength, particular fatigue properties, and/or abrasion resistant. Post-processing steps may also impart functional characteristics, such as exposure to other materials, washing, and/or heat-setting to alter the woven dimensions and other characteristics of the material of the graft body  108 . 
     Additional woven layers may define pocket flaps, such as the depicted first pocket flap  114   a  and second pocket flap  114   b.  The unique weaving techniques described herein (e.g., with references to  FIGS. 6-8 ) provide an example of a weaving technique for forming such layers integrally with the remainder of the graft body  104 . Thus, the pocket flaps  114   a  and  114   b , when formed integrally with the other layers, will have at least one common warp end with the graft body  104  and also at least one common weft yarn. Advantageously, such a structure may have enhanced durability relative to embodiments where the pocket is formed separately and then connected via other means, particularly since the mechanical strength of the connection is not dependent on an external fastening device, and it may avoid potential exposure to other chemicals/materials (such as adhesives) that may deteriorate either the graft body or patient body tissue over a period of time. It may also have enhanced stability in the radial and longitudinal directions. Further, manufacturing efficiency may be improved relative to other woven embodiments since the pockets are formed without significant post-weaving connection steps. Additionally, integral formation of the graft pockets may reduce manufacturing time, reduce undesirable waste, reduce the necessity of adhesives and other materials that may be undesirable for use in a medical device, etc. 
     Several weavings techniques will now be described for forming different portions of the graft body  104  shown in  FIGS. 4-5 . Similar and/or identical techniques may be used to form graft bodies with different characteristics (i.e., with additional pockets, pockets having different shapes, etc.). For example, the weaving methods described herein, once understood, can be readily applied to form the graft of  FIG. 1  having pockets positioned for receiving a stent. It is noted that the following example sequences are for illustration only, and that certain adjustments and/or changes may be may be made without deviating from the teachings herein. 
       FIG. 6  shows an example of a weaving sequence (i.e., a weft insertion sequence) for forming plain tubular graft fabric. For example, the sequence of  FIG. 6  may form a first area  142  of the graft body  104  as shown in  FIG. 4 . Referring to  FIG. 6 , a first set of the warp ends  130  (or “first warp ends  130   a ”) may correspond with the first layer  136  (shown in  FIG. 5 ), and a second set of the warp ends  130  (or “second warp ends  130   b ”) may correspond with the second layer  138  ( FIG. 5 ). To form the tubular structure of the main graft body  104  ( FIG. 5 ), first warp ends  130   a  may refrain from crossing through the lumen  132  to the second layer  138 , and vice versa. 
     Four weft insertion steps are shown in  FIG. 6 , which may be repeated as necessary to form a plain tubular fabric of suitable length. In a first weft insertion step (i.e., “weft insertion  1 ”), the weft yarn  134  is inserted (e.g., via a shuttle portion of a loom as the warp ends are held selectively “up” or “down” via the weaving machine) such that approximately half of the first warp ends  130   a  are above, and about half are below, the weft yarn  134  (and where all of the second warp ends  130   b  are below the weft yarn  134 ). In the second weft insertion step, the weft yarn  134  returns through the fabric in a similar manner, this time such that about half of the second warp ends  130   b  are above, and about half are below, the weft yarn  134 . The third weft insertion step is similar to the first, except the first warp ends  130   a  switch their position (i.e., “up” vs. “down”) relative to the weft yarn  134  to lock a portion of the first layer  136  together and complete one side of the plain tubular structure. Similarly, the fourth weft insertion step is much like the second weft insertion step, except that the second warp ends  130   b  switch their positions to complete the plain weave structure of the second layer  138 . 
     Notably, while the warp ends  130  extending through the first layer  136  may be distinct from those extending from the second layer  138 , the weft yarns  134  may not. That is, a continuous weft yarn  134  may extend through both of the first layer  136  and the second layer  138  such that, when weaving is complete, it extends around the circumference of the graft body. While the weft yarn  134  of  FIG. 6  is shown as being continuous on only one side of the weave pattern (e.g., on the right side of  FIG. 6 ), it may also extend from one layer to the other on the other side of the weave pattern. Advantageously, the common weft yarns  134  may secure the first layer  136  to the second layer  138  at the edges  140 , completing the tubular structure of the main graft body  104 . It is noted that the edges  140  may be substantially undetectable as “edges” once weaving is complete. 
       FIG. 7  shows an example of a weaving sequence (i.e., a weft insertion sequence) for forming a tubular graft fabric having additional layers, such as layers for forming pocket flaps. For example, the sequence of  FIG. 7  may form a second area  144  of the graft body  104  as shown in  FIG. 4 . 
     Referring to  FIG. 7 , a first set of the warp ends  130  (or “first warp ends  130   a ”) may correspond with the first layer  136  (shown in  FIGS. 4-5 ), and a second set of the warp ends  130  (or “second warp ends  130   b ”) may correspond with the second layer  138 . Like the plain-tubular sequence described above, a set of first warp ends  130   a  may correspond with a first layer  136  and a second of second warp ends  130   b  may correspond with a second layer  138 . Additional subsets of warp ends may be isolated from the first and second warp ends  130   a,    130   b  for formation of other components. For example, in the depicted embodiment, a set of third warp ends  130   c  may be associated with the first pocket flap  114   a  (shown in  FIG. 5 ) and a set of fourth warp ends  130   d  may be associated with a second pocket flap  114   b.    
     The first four weft insertion steps of  FIG. 7  are nearly identical to the four weft insertion steps of  FIG. 6 , the only difference being the exclusion of the third warp ends  130   c  and the fourth warp ends  130   d  from those utilized in the first and second layers  136 ,  138 . Thus, it shall be understood that the first four weft insertion steps will create a small length of tubular woven fabric. Further, it should be noted that the third warp ends  130   c  and the fourth warp ends  130   d  are freely floating during these first four weft insertion steps, potentially blocking access to a pocket opening (where “float” is defined herein to mean that a section of a yarn that bypasses other yarns such that it extends without being interlaced/interwoven with another yarn). These floating warp ends are addressed below (with reference to  FIG. 10 ). 
     In the fifth insertion step, the weft yarn  134  extends into the third warp ends  130   c  while a section of the first warp ends  130   a  located immediately below are skipped (such that they are not interlaced with the pocket flap  114   a,  and thus float for a insignificantly small distance within the fabric, which may not be visible). Similarly, in a sixth weft insertion step, the weft yarn  134  extends into the fourth warp ends  130   d  and skips a section of the second warp ends  130   b  located immediately above the fourth warp ends  130   d.  The seventh and eighth weft insertion steps are respectively similar to the fifth and sixth insertion steps, except warp-end orientations are switched to complete a woven portion of each of the first pocket flap  114   a  and the second pocket flap  114   b  (as well as surrounding portions of the first layer  136  and the second layer  138 ). Since the weft yarn  134  extends directly into the respective first layer  136  or second layer  138  at the sides of the pocket flaps  114   a  and  114   b,  the side edges of the pocket flaps  114   a  and  114   b  (e.g., sides  120  and  122  shown in  FIG. 5 ) will be directly connected to the remainder of the graft body  104  by virtue of common weft yarn. In other words, a single segment of a weft yarn will extend continuously through a portion of the first layer  136 , into the pocket flap  114   a,  and then back into the first layer  136 . The same is true of a segment of the weft yarn and the second pocket flap  114   b.    
     Notably, none of the first warp ends  130   a  cross through the lumen  132  to the second layer  138 , nor do they cross through the opening of the first pocket  110   a  to the first pocket flap  114   a,  in any of the eight weft insertion steps of  FIG. 7 . The same is respectively true of the second warp ends  130   b.  This ensures formation of the openings  112  of the pockets  110  as well as the lumen  132 . These steps may be repeated as necessary to form a pocket of an appropriate size (though it should be recognized that merely repeating  FIG. 7  will form a pocket with a constant width). 
       FIG. 8  illustrates a weaving method for forming a shaped pocket, such as the triangular pocket  110  of  FIG. 4 , and it is noted that the specific steps of weft insertion are not included for in the illustration for purposes of concise description. A diagram  FIG. 8A  generally shows different portions of a pocket that are formed by the sequence portions (S 1 -S 4 ) depicted by  FIG. 8 . In short, the sequence portions S 1 -S 4  of  FIG. 8  may each follow the teachings of  FIG. 7  for forming a pocket extending from a tubular woven fabric, but the number of warp ends used to form the respective pocket flaps  114   a  and  114   b  varies moving from one sequence portion to the next. 
     More specifically, a first sequence portion (or “S 1 ” in  FIG. 8 ), a first pocket flap  114   a  may be formed with a set warp ends  130   c  (or “third” warp ends  130   c,  of which there are seven depicted) and a second pocket flap  114   b  may be formed with a set of warp ends  130   d  (or “fourth” warp ends  130   d,  of which there are seven depicted). As mentioned in the paragraph above, the specific weft insertion steps the sequence portions are not shown here (such as the weft insertion steps where the weft yarn  134  interlaces with the third and fourth warp ends  130   c,    130   d ), and such steps may be similar or identical to those described above with reference to  FIG. 7 . 
     After S 1  is executed at least once (and notably, it may be repeated), a second sequence portion S 2  may be initiated. S 2  may involve steps similar to those of S 1 , but the number of warp ends  130  associated with each pocket flap is different, in this case reduced (here shown as five warp ends, respectively, rather than seven). Thus, the area of the pocket flaps  114  formed by S 2  will have a smaller width that is smaller than the width formed by S 1 . S 3  and S 4  reduce the number of warp ends  130  used in the pocket flaps  114  further (to three and then one, respectively), such that the width of the pocket flaps  114  continues to decline as weaving continues. After S 4  is completed, the weaving machine may form pain tubular fabric (as shown in  FIG. 6 ), thus completing and continuing out of the woven pocket structure. While each subsequent sequence portion involves a reduction in warp ends utilized in a pocket flap, the number could also be increased to thereby increase the width of the pocket. In other embodiments, warp ends from one side of a pocket flap could be dropped from one side of that pocket flap, and others could be picked up on the other side, causing the newly-formed portion of the pocket flap to migrate its position. These techniques can be used to form one or more pockets with any suitable shape, position, orientation, etc. 
     While may shapes are contemplated, the pocket structures resulting from the sequence of  FIG. 8  are triangular, with relatively large widths formed at S 1 , decreasing widths moving to S 2  and then S 3 , and then reaching a triangle vertex at S 4 . If each of S 1 -S 4  is executed once, the sides of the triangle may be approximately linear, but this is not required. Further, the sequence portions S 2 -S 4  each drop one warp end from both sides of the respective pocket flaps, but more or less warp ends may be dropped (or picked up) at each sequence portion in other embodiments. 
       FIG. 9  is similar to  FIG. 8 , but its steps are inverted for forming an inverted triangle. Only  FIG. 8  is described in detail in these paragraphs, but the teachings from  FIG. 8  are applicable to  FIG. 9  in an inverted fashion. 
       FIG. 10  shows a portion of woven fabric  160  (e.g., for a graft body or for another application) with triangular pockets  110  formed utilizing the teachings of  FIGS. 4-9 . For example, two of the pockets  110   a - b  may be formed utilizing the teachings of  FIG. 8 , while a third pocket  110   c  may be inverted (e.g., utilizing a sequence similar to that of  FIG. 9 ), where surrounding areas may be formed utilizing the teachings of  FIG. 6 . While the woven fabric of  FIG. 10  is shown as a flat fabric, it may also be formed as a tubular graft body (as described above) with pockets on each respective side. 
     As mentioned briefly above, after the weaving process is complete, access to the pocket openings may be blocked by floating warp ends used at the initiation (or conclusion) of pocket formation. Referring to  FIG. 7 , for example, the warp ends  114   c  and  114   d  may float in the first four weft insertion steps, such that they float over the edge respective pocket flaps  114   a  and  114   b  (where the edge is initiated by weft insertion step  5 ). Thus, a cutting step (or other material removal or material alteration step) may be performed after weaving to provide access to the pocket openings. To illustrate, referring back to  FIG. 10 , each pocket  110  is associated with a set of floating warp ends  150  that block access to their respective pocket openings. In  FIG. 11 , these warp ends  150  have been cut away, resulting in pockets  110  with mouths  152  leading to their openings (e.g., for providing access for insertion of stent segments). To ensure the pocket flaps  114  do not unravel at their edges  140  after the cutting procedure, the edges  140  may be heat-processed and/or otherwise treated to finish the edge surface by at least partially securing the severed warp ends together. Optionally, warp ends may also be heat processed or otherwise secured at an area  156  (e.g., at the other end of where the floating warp ends were severed). 
     While the present invention has been described in terms of preferred embodiments, it will be understood, of course, that the invention is not limited thereto since modifications may be made to those skilled in the art, particularly in light of the foregoing teachings.