Stent graft and method for enhancing flexibility of stent graft by thermally forming pleats

Abstract

A method of forming pleats in a stent graft includes the steps of compressing the stent graft to form pleats in the graft material of the stent graft, applying heat to the stent graft to heat set the pleats in the graft material, and stretching the stent graft to decompress the stent graft after the pleats have been heat set. [Selection diagram] Figure 4

Description

Technical Field

[0001] [Cross - Reference to Related Patent Applications] This application claims priority and the benefit of U.S. Provisional Patent Application No. 62 / 532,737, filed Jul. 14, 2017, which is incorporated herein by reference in its entirety.

[0002] One or more exemplary embodiments described herein generally relate to stent grafts and methods of making and using stent grafts, and in certain embodiments relate to stent grafts and methods of making flexible stent grafts.

Background Art

[0003] An aneurysm is an enlargement or bulge within a blood vessel that is often prone to rupture and thus poses a serious risk to the patient. Aneurysms can occur in any blood vessel, but are of particular concern when they occur in the cerebrovascular system or the aorta.

[0004] Abdominal aortic aneurysms (AAAs) are classified based on their location within the aorta, as well as their shape and complexity. An aneurysm found below the renal arteries is called a juxtarenal abdominal aortic aneurysm. A suprarenal abdominal aortic aneurysm occurs above the renal arteries. Thoracic aortic aneurysms (TAAs) occur in the ascending, transverse, or descending portions of the upper aorta.

[0005] Stent grafts have become widely used for the treatment of aneurysms. Various stent grafts provide a graft layer that re - establishes a flow lumen through the aneurysm, as well as a stent structure that supports the graft. Generally, endovascular repair using a stent graft involves accessing the aneurysm endovascularly through one or both of the common iliac arteries. To treat the aneurysm, a stent graft is then implanted.

Summary of the Invention

Means for Solving the Problems

[0006] One embodiment of the disclosure of the present invention is a method of forming pleats in a stent graft. The method includes forming pleats in the graft material of the stent graft by compressing the stent graft, heating the stent graft to thermoset the pleats in the graft material, and stretching the stent graft to release the compression of the stent graft after the pleats are thermoset.

[0007] In an embodiment, the step of applying heat can include ironing the creases of the pleats in the graft material.

[0008] In an embodiment, the iron can be heated to between 320°C and 390°C before the step of ironing the creases.

[0009] In an embodiment, the step of compressing the stent graft can include compressing the stent graft axially and / or circumferentially.

[0010] In an embodiment, the step of applying heat can include baking the stent graft in an oven for a predetermined time after forming the pleats.

[0011] In an embodiment, the oven can be heated to 320°C before baking the stent graft.

[0012] In an embodiment, the predetermined time can be 5 minutes.

[0013] In an embodiment, the predetermined time can be longer than 5 minutes.

[0014] In an embodiment, the step of forming the pleats can include folding the graft material over adjacent portions of the graft material.

[0015] In an embodiment, the step of folding the graft material can include the step of folding the graft material in an outer lumen direction with respect to the lumen of the stent graft.

[0016] In an embodiment, the step of folding the graft material can include the step of folding the graft material in an inner lumen direction with respect to the lumen of the stent graft.

[0017] In an embodiment, the step of forming a fold can include the step of folding the graft material in an inner lumen direction with respect to the lumen of the stent graft at a portion of the graft material, and the step of folding the graft material in an outer lumen direction with respect to the lumen of the stent graft at a different portion of the graft material.

[0018] In an embodiment, the step of forming a fold can include the step of folding the graft material onto adjacent portions of the graft material such that there is a graft space between adjacent stent members on the larger curvature side of the stent graft that is larger than on the smaller curvature side of the stent graft.

[0019] In an embodiment, the method can further include the step of increasing the graft space on the larger curvature side to reduce the radius of curvature of the stent graft.

[0020] Another implementation of the disclosure of the present invention is a stent graft including a graft formed of a graft material and a stent including stent members attached to the graft. The graft material is folded between adjacent stent members at adjacent portions of the graft member to form a fold, and the fold has a graft space between corresponding stent members on the larger curvature side of the stent graft that is larger than on the smaller curvature side of the stent graft.

[0021] Another embodiment of the disclosure of the present invention is a stent graft manufactured by a process including the steps of forming pleats in the graft material of the stent graft by axially and / or circumferentially compressing the stent graft, applying heat to the stent graft to thermoset the pleats in the graft material, and stretching the stent graft to relieve compression after the pleats have been thermoset.

[0022] In an embodiment, the step of applying heat can include the step of annealing the creases of the pleats in the graft material.

[0023] In an embodiment, the step of applying heat can include the step of baking the stent graft in an oven for a predetermined time after forming the pleats.

[0024] In an embodiment, the step of forming pleats can include the step of folding the graft material over adjacent portions of the graft material.

[0025] In an embodiment, the step of folding the graft material over adjacent portions of the graft material can include folding the graft material such that there is a graft space between larger adjacent stent members on the larger curvature side of the stent graft rather than on the smaller curvature side of the stent graft.

Brief Description of the Drawings

[0026]

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DETAILED DESCRIPTION OF THE INVENTION

[0027] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, like symbols typically identify like items, unless the context indicates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized and other changes may be made without departing from the spirit or scope of the subject matter presented herein. Aspects of the disclosure of the invention as generally described herein and illustrated in the drawings can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are clearly envisioned and will be readily understood to form part of the present disclosure.

[0028] Various embodiments define the enhancement of the flexibility of a stent graft by thermally forming pleats in the stent graft. Various embodiments define the enhancement of intravascular stent graft flexibility by (1) manually forming pleats in the graft material, such as by axially compressing the stent graft to nest the shape of the stent graft in a preferred orientation, and (2) heat treating the stent graft while in the compressed position to impart a heat memory to the graft material such that the pleats are preferentially fixed and the flexibility is retained with the graft length again stretched. Various embodiments enable the improvement of the flexibility of a stent graft system for vascular applications by having thermoset pleats within the graft material.

[0029] Various embodiments define the thermal fixation of a preferred pleat shape within the graft material of a stent graft. Such a thermally fixed pleat shape for the graft material can, for example, be formed by a stent member of the stent such that each apex having a zigzag pattern within the graft material is always able to move relative to the zigzag of an adjacent stent member without generating significant shear forces within the graft material even when the stent member is fully fused or sintered within the graft material. In various embodiments, the thermoset pleats substantially reduce or minimize the irregularities of the contacting apices and enable the apices to be uniformly pushed under or beyond adjacent apices as needed.

[0030] This specification provides various methods according to various embodiments for thermally fixing a preferred pleat shape. One such method according to various embodiments includes the step of thermally ironing the pleats. In some such embodiments, the stent graft is first axially compressed to produce a desired pleat pattern. In some embodiments, a soldering iron set to a temperature, for example, from 320 °C to 390 °C, is then used to wipe the pleated area between adjacent stent members with the tip or barrel of the iron to thermally fix the creases or pleats in the graft material. In various embodiments, other suitable temperatures can be used with respect to the iron for ironing the pleats. In various embodiments, with each of the creases or pleats thermally fixed in a desired area within the graft material, the stent graft can be axially pulled back (or stretched) to its natural or original length and will have improved (or significantly improved) flexibility compared to a non-pleated stent graft.

[0031] Another method according to various embodiments for thermally fixing a preferred pleat shape includes the step of thermally baking the pleats. In some such embodiments, the stent graft is first axially compressed to produce a desired pleat pattern. Also in some such embodiments, one or more pleated portions of the stent graft are then placed in an oven set to a temperature of, for example, 320 °C or other suitable temperature for a desired or predetermined period of time to thermally fix the creases or pleats. In various embodiments, the baking time in the oven is, for example, 5 minutes, 10 minutes, and / or 20 minutes, etc. However, the disclosure of the present invention is not limited thereto, and in other embodiments, other suitable baking times can be used. In some embodiments, 5 minutes may be preferred as a short amount of time to substantially fix the pleats. In various embodiments, the baking method may be advantageous in that it is a non-contact method for producing the pleats. In various embodiments, with the creases or pleats thermally fixed in a desired region within the graft material, the stent graft can be axially pulled back (or stretched) to its natural or original length and will have improved (or significantly improved) flexibility compared to a non-pleated stent graft.

[0032] Referring now to FIG. 1, there is shown a stent graft 1 according to an exemplary embodiment. The stent graft 1 is a hollow tubular device having a graft member 10 that forms a tubular wall having a proximal end 11 and a distal end 12 and defines an open lumen between the proximal end 11 and the distal end 12. Although the stent graft 1 as shown in FIG. 1 is depicted as being substantially tubular, it should be understood that the stent graft 1 can be of any shape suitable for delivery to and placement at a target site in a patient. For example, each portion of the graft member 10 at either or both of the proximal end 11 and the distal end 12 may be expanded (inwardly or outwardly) or tapered (inwardly or outwardly). Further, each portion of the graft member 10 may also include non-linear tubular portions such as expanded (inwardly or outwardly) portions, portions having bends or curves, perforations, channels, and / or branched portions. Further, although the proximal end 11 and the distal end 12 are depicted as having a single open lumen, the disclosure of the present invention is not limited thereto. For example, one or both of the proximal end 11 and the distal end 12 may be a multi-lumen end, such as a branched open end, for example

[0033] FIG. 1 shows a stent graft 1 in a longitudinally stretched state before pleat formation. The stent graft 1 includes a graft member 10 and also includes stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l. In some embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l are connected to each other as a single stent, while in other embodiments, they are separated from each other. In various embodiments, each of the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l is made of a corrugated wire wound circumferentially along an axis in an open tubular configuration. The circumferentially wound corrugated wire may be circular or helical. The circumferentially wound corrugated wire can also form a zigzag having peaks and valleys. For example, the stent member 20c is depicted as having a plurality of peaks 21 directed toward the proximal end 11 of the stent graft 1 and a plurality of valleys 22 directed toward the distal end 12 of the stent graft 1. In various embodiments, each of the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l forms a crown having a plurality of peaks and valleys.

[0034] Each of the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l can be made from any other suitable material including, for example, stainless steel, nickel-titanium alloys (NiTi) such as NITINOL, or, without limitation, cobalt-based alloys such as ELGILOY, platinum, gold, titanium, tantalum, niobium, and / or combinations thereof. Each of the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l may be balloon-expandable or self-expandable. In various embodiments, more than one stent member can be disposed at or near the proximal end 11 of the stent graft 1, such as two stent members as shown by stent member 20a. Similarly, in various embodiments, more than one stent member can be disposed at or near the distal end 12 of the stent graft 1, such as two stent members as shown by stent member 20l. Although the embodiment of FIG. 1 shows a specific number of stent members, it must be recognized that in various embodiments, any suitable number of stent members can be used.

[0035] In some embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l are attached to or laminated within the graft member 10. In some embodiments, the graft member 10 extends from a proximal end 11 to a distal end 12. In some other embodiments, the graft member 10 does not cover the entire length of the stent graft 1 and can be left uncovered, for example, at the proximal end 11, the distal end 12, or both. In various embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l are completely laminated or fused within the graft member 10. In this case, the possibility of graft material wear against the graft member 10, which is a function of relative movement between components, can be reduced. In various embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l are partially laminated, tethered, or freely floating within the graft member 10.

[0036] In various embodiments, the graft member 10 includes a graft material made of one or more polymers or other suitable materials. In some embodiments, the graft member 10 is made of expanded polytetrafluoroethylene (ePTFE). In some embodiments, the graft member 10 is made of expanded polytetrafluoroethylene (ePTFE). In still some other embodiments, the stent graft 1 may include at least one additional polymer layer, such as a drug eluting layer for eluting a bioactive agent from the stent graft 1 after implantation.

[0037] In some embodiments, the stent graft 1 can be compressed longitudinally to form a plurality of circumferential pleats having a predetermined orientation. In some embodiments, the stent graft 1 can be compressed longitudinally and, in the case of continuously wound wire, form continuous helical pleats. In various embodiments, each pleat is accompanied by a creased or folded surface of the graft material of the graft member 10 typically formed in the region of the graft member 10 between the locations of the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l. Each portion of the stent graft 1 between two adjacent pleats is herein referred to as a pleated section of the stent graft 1. In various embodiments, each of the plurality of circumferential pleats is disposed between the crowns formed by the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l.

[0038] FIG. 2A is a flow diagram of a method according to an embodiment. FIGS. 2B and 2C illustrate methods that can be used with the method of FIG. 2A. Referring to FIG. 2A, in step 100, the stent graft is compressed (e.g., axially or circumferentially) to form pleats in the graft material of the stent graft. In step 101, heat is applied to the stent graft to cure the creases for the pleats in the graft material. In step 102, the stent graft is pulled (or stretched) to relieve the compression of the stent graft after the pleats are thermally cured. Referring to FIGS. 2A and 2B, in various embodiments, the step of applying heat in step 101 is performed as in step 103 by applying an iron to the pleats of the stent graft to cure the creases for the pleats in the graft material. Referring to FIGS. 2A and 2C, in various embodiments, the step of applying heat in step 101 is performed as in step 104 by placing the stent graft in an oven and baking the stent graft for a predetermined time to thermally fix the pleats.

[0039] Figure 3 shows the stent graft 1 in a state of being axially compressed according to an embodiment. Referring to FIGS. 1, 2A, and 3, the step 100 of axially compressing the stent graft 1 of FIG. 1 can, according to an embodiment, result in an axially compressed version of the stent graft 1 as shown in FIG. 3. In various embodiments, the stent graft 1 is axially compressed by bringing the distal end 12 closer to the proximal end 11, which creates the folds 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k, where the graft material of the graft member 10 forms creases between the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l, and the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 20l at least partially overlap (e.g., pass over or under) the corresponding adjacent stent members.

[0040] Figure 4 shows an iron 50 used to thermally fix the folds 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k in the graft material of the graft member 10 of the stent graft 1 according to an embodiment. Referring to FIGS. 2A, 2B, and 4, in various embodiments, the step 101 of applying heat to the stent graft 1 includes the step 103 of applying the iron 50 to each of the folds 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k of the stent graft 1 to cure the creases for the folds 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k in the graft material of the graft member 10. In various embodiments, the iron 50 is applied (e.g., wiped over) to each of the folds 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k around the circumference of the stent graft 1. In various embodiments, the temperature of the iron 50 is set to a temperature, for example, between 320°C and 390°C. In various other embodiments, other suitable temperatures are used for the iron 50.

[0041] In addition to and / or instead of this, the manually compressed stent graft 1 as seen in FIG. 3 can be heated evenly or substantially evenly, for example, by baking the stent graft 1 in an oven as shown in step 104 of FIG. 2C to cure the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k. Referring to FIGS. 2C and 3, the temperature of the oven can be set based on the baking time and thickness of the graft member 10, for example, to be about 280°C - 300°C, 300°C - 320°C, 320°C - 340°C, 340°C - 360°C, or any other suitable temperature range. The baking time can be, for example, about 5 - 10 minutes, 10 - 15 minutes, 15 - 20 minutes, 20 - 25 minutes, 25 - 30 minutes, or any other suitable time range to cure the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k. In various exemplary embodiments, three manually compressed stent grafts are placed in an oven at 320°C for 5 minutes, 10 minutes, and 20 minutes respectively. After baking, all three stent grafts are thermoset in a predetermined pleat orientation and can maintain the same orientation when naturally compressed again.

[0042] FIG. 5 shows a stent graft 1 in a state where the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k are stretched longitudinally after being thermoset. In some embodiments, the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k are a plurality of circumferential pleats. In some embodiments, the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k form continuous spiral pleats. Referring to FIGS. 2A, 4, and 5, in various embodiments, after the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k are thermoset, step 102 is performed on the stent graft 1 to draw (or stretch) the stent graft 1, releasing the compression of the stent graft 1 from the axially compressed state as shown in FIG. 4 to the axially stretched state as shown in FIG. 5. The stent graft 1 of FIG. 5 is shown including pleated sections 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h, 40i, 40j, 40k, and 40l.

[0043] The pleated section 40a of the stent graft 1 includes the stent member 20a and a portion of the graft member 10 between the proximal end 11 and the pleat 30a. The pleated section 40b of the stent graft 1 includes the stent member 20b and a portion of the graft member 10 between the pleats 30a and 30b. The pleated section 40c of the stent graft 1 includes the stent member 20c and a portion of the graft member 10 between the pleats 30b and 30c. The pleated section 40d of the stent graft 1 includes the stent member 20d and a portion of the graft member 10 between the pleats 30c and 30d. The pleated section 40e of the stent graft 1 includes the stent member 20e and a portion of the graft member 10 between the pleats 30d and 30e. The pleated section 40f of the stent graft 1 includes the stent member 20f and a portion of the graft member 10 between the pleats 30e and 30f.

[0044] The pleated section 40g of the stent graft 1 includes the stent member 20g and the portion of the graft member 10 between the pleats 30f and 30g. The pleated section 40h of the stent graft 1 includes the stent member 20h and the portion of the graft member 10 between the pleats 30g and 30h. The pleated section 40i of the stent graft 1 includes the stent member 20i and the portion of the graft member 10 between the pleats 30h and 30i. The pleated section 40j of the stent graft 1 includes the stent member 20j and the portion of the graft member 10 between the pleats 30i and 30j. The pleated section 40k of the stent graft 1 includes the stent member 20k and the portion of the graft member 10 between the pleats 30j and 30k. The pleated section 40l of the stent graft 1 includes the stent member 20l and the portion of the graft member 10 between the pleat 30k and the distal end 12.

[0045] The stent graft 1 having a pre-determined or pre-set orientation of the pleats according to various embodiments provides several advantages. The circumferential pleats provide a space for longitudinal movement between stent members or crowns, thereby improving longitudinal flexibility during longitudinal compression and / or expansion, and also improving radial flexibility since it can move radially during bending or longitudinal compression. The pre-set pleats provide an advantage over irregular pleats because irregular pleats formed by compressing the stent graft, particularly those protruding radially outward, tend to impede longitudinal compression and generate internal forces that cause twisting within the stent graft. The various embodiments disclosed herein overcome the problem of irregular pleats by pre-determining and fixing the orientation of the pleats before the stent graft is longitudinally compressed (or decompressed) or radially bent, thereby enabling the stent graft to automatically form a consistent and pre-determined pleat orientation when radially bent or longitudinally compressed for loading, delivery, or implantation. The uniform pleat orientation enables the stent material or crowns to move consistently relative to adjacent crowns without generating large shear forces within the graft material.

[0046] FIG. 6 shows a stent graft 1 according to an embodiment in a bent configuration after the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k within the graft member 10 have been thermoset and the pleated sections 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h, 40i, 40j, 40k, 40l have been formed within the stent graft 1. The stent graft 1 has improved torsional resistance during bending due to the thermoset pleats. In some embodiments, the stent graft 1 can conform without twisting, for example, around a pin having a diameter of 0.325 inches. In various embodiments, during bending, the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k within the graft member 10 move according to their pre-set orientations under the bending force. This enables the stent graft 1 to bend by about 180° or more without a substantial reduction in diameter at any portion of the bend. Accordingly, the lumen opening of the stent graft 1 is maintained or substantially maintained, particularly in the region of the bend. This results in a higher performance stent graft since the blood flow is either only slightly reduced or not reduced at all at the bend. In contrast, a stent graft without pre-set pleats (e.g., circumferential or helical) may have a deformed portion when subjected to a similar degree of bending, where the deformed portion may cause a partial closure of the lumen and result in sub-optimal performance.

[0047] By longitudinally compressing a stent graft from a longitudinally stretched configuration to a compressed configuration, pleated sections can be formed into a predetermined orientation of pleats (e.g., pleats forming a plurality of circumferential pleats or continuous helical pleats) such that the pleated sections nest within corresponding adjacent pleated sections along the axis. In various embodiments, any desired orientation of circumferential pleats can be thermally pre-treated to fix the pleats in the desired orientation such that when the stent graft is longitudinally compressed again by natural hardening, for example, during loading, delivery, or implantation of the stent graft, the compressed stent graft will remember and recover the preset pleat orientation. In various embodiments, the stent graft is manually compressed longitudinally to form a uniform outward luminal pleat orientation. Next, each of the circumferential pleats is annealed to harden the creases within the graft member. After the annealing step, the stent graft is manually pulled back to its stretched state. Such thermal pre-treatment enables the stent graft to remember the preset pleat orientation when naturally compressed again. The pleats may also be thermally pre-treated to form a uniform inward luminal orientation or a combination of outward luminal and inward luminal orientations as needed.

[0048] Figure 7A shows a stent graft 70 according to an embodiment having a graft member 73 with a proximal end 71 and a distal end 72 and having pleated sections 74a, 74b, 74c, 74d, 74e, 74f, 74g, 74h, 74i, 74j, 74k, 74l, and 74m having zigzag valleys folded outwardly lumenally with respect to adjacent zigzag peaks. The stent graft 70 includes pleated sections 74a, 74b, 74c, 74d, 74e, 74f, 74g, 74h, 74i, 74j, 74k, 74l, and 74m which are preset to be nested by intentional compression such that all of their pleated sections are folded outwardly lumenally with respect to one another (i.e., a more proximal pleated section is radially lifted and covers a portion of the immediately adjacent distal pleated section). Thereby, the pleats are formed in the stent graft 70 such that the valleys at the crown of the stent member are folded outwardly lumenally with respect to one another. Figure 7B shows the inner surface 75 of the graft member 73 of the stent graft 70 of Figure 7A according to an embodiment having pleated sections 77a, 77b, 77c, 77d, 77e, 77f which form a "rough" inner surface due to the outward lumenal nesting orientation of the pleated sections 74a, 74b, 74c, 74d, 74e, 74f, 74g, 74h, 74i, 74j, 74k, 741, and 74m.

[0049] FIG. 8A shows a stent graft 80 according to an embodiment including a graft member 83 having proximal end 81 and distal end 82 and having zigzag valleys 84a, 84b, 84c, 84d, 84e, 84f, 84g, 84h, 84i, 84j, 84k, 84l, 84m, 84n, 84o, 84p, 84q, 84r, and 84s that are folded lumenally inwardly with respect to adjacent zigzag peaks. The stent graft 80 includes zigzag sections 84a, 84b, 84c, 84d, 84e, 84f, 84g, 84h, 84i, 84j, 84k, 84l, 84m, 84n, 84o, 84p, 84q, 84r, and 84s that are pre-set to be nested by intentional compression such that all of these zigzag sections are folded lumenally inwardly with respect to one another (i.e., a more distal zigzag section is radially lifted and covers a portion of the immediately adjacent proximal zigzag section). Thereby, the valleys at the apex of the stent member are folded lumenally inwardly with respect to one another to reduce the stress generated within the stent material, and the folds are formed in the stent graft 80. FIG. 8B shows the inner surface 85 of the graft member 83 of the stent graft 80 of FIG. 8A according to an embodiment having zigzag sections 87a, 87b, 87c, 87d, 87e, and 87f that form a “smooth” inner surface over the entire stent graft 80 due to the lumenal nesting orientation of the zigzag sections.

[0050] In still some other embodiments, some of the pleated sections can be pre-determined to be folded in a lumen-inward manner, while others are folded in a lumen-outward manner. For example, in some embodiments, the proximal pleated section is folded in a lumen-inward manner, while the distal pleated section is folded in a lumen-outward manner. FIG. 9A shows a stent graft 90 according to an embodiment including a graft member 93 having a proximal end 91 and a distal end 92 and having pleated sections 94a, 94b, 94c, 94d, 94e, 94f, 94g, 94h, 94i, 94j, 94k, 94l, 94m, 94n, 94o, 94p, 94q, and 94r. The stent graft 90 includes pleated sections 94a, 94b, 94c, 94d, and 94e, which are pre-set to be nested by intentional compression such that all of these pleated sections are folded in a lumen-inward manner relative to each other. The stent graft 90 includes pleated sections 94f, 94g, 94h, 94i, 94j, 94k, 941, 94m, 94n, 94o, 94p, 94q, and 94r, which are pre-set to be nested by intentional compression such that all of these pleats are folded in a lumen-outward manner relative to each other. FIG. 9B shows the inner surface 95 of the graft member 93 of the stent graft 90 of FIG. 9A according to an embodiment having pleated sections 97a, 97b, 97c, 97d, 97e, 97f, 97g, and 97h, where the pleated sections 97a, 97b, 97c, 97d, and 97e form a "smooth" inner surface due to the lumen-inward nesting orientation of the pleated sections 94a, 94b, 94c, 94d, 94e, and 94f, while the other pleats form a "rough" inner surface due to the lumen-outward nesting orientation of the remaining pleated sections. Various embodiments define a mechanical interlock with modular components.

[0051] In various embodiments, the blood flow pattern within the stent graft can be controlled and modified by selecting the orientation of the pleats. For example, when the valleys of the stent crown are folded in a lumen-outward manner, the inner surface of the stent graft lumen may be "rough" and disrupt blood flow. On the other hand, when the valleys of the stent crown are folded in a lumen-inward manner, the inner surface of the stent graft lumen is "smooth", resulting in a desirable blood flow pattern and reducing shear stress on the graft material. Further, when the pleats are helical pleats, the inner surface of the stent graft lumen has a helical pattern (which can have pleats folded in a lumen-inward or lumen-outward manner), which can induce or maintain a desirable helical blood flow pattern.

[0052] Figure 10 illustrates the effect of the graft spacing between stent members or between the crowns on the achievable radius of curvature. Each of the left stent graft 200 and the right stent graft 300 has a greater curvature side 205 and 305 and a smaller curvature side 210 and 310, respectively. The left stent graft 200 has a 2 mm graft space 215 on the greater curvature side 205 between the crowns of the stent body, and the right stent graft 300 has a 4 mm graft space 315 on the greater curvature side 305 between the crowns of the stent body. Each of the stent graft 200 and the stent graft 300 has a smaller (or negative) graft space between the crowns of the stent body on the smaller curvature sides 210 and 310, respectively, opposite to the greater curvature sides 205 and 305. By increasing the graft spacing on the greater curvature side 305, the stent graft 300 can achieve a smaller radius of curvature compared to the stent graft 200, which is due to the large folds that allow more nesting of the stent zigzag shape. For example, the curvature of the stent graft 200 has a length L1 (about 125 mm) from end to end, and the curvature of the stent graft 300 has a length L2 (about 80 mm) from end to end, and L1 is greater than L2. In various embodiments, thermally pre-treating the longitudinally compressed stent graft enables the formation of folds that match a predetermined orientation. In various embodiments, each folded section can include one crown or more than one crown, and the folded sections of different parts of the stent graft can include different numbers of crowns or otherwise have different widths or spacings to accept the shape of the stent graft to achieve desired dimensions and physical properties.

[0053] Figure 11 shows a stent graft 1000 according to an embodiment in an annular compression configuration. In the annular compression configuration, a stent graft 1000 having circular pleats can be formed. The stent graft 1000 having circular pleats has thermoset partial pleats 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 130l on the smaller curvature side 130 of the graft member 110, while the larger curvature side 120 of the stent graft 1000 has no pleats. For example, the partial pleats 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 130l can be thermoset by applying heat to the partial pleats 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 130l through an iron and / or by firing the annularly compressed stent graft 1000 having partial pleats. The stent graft 1000 having circular pleats has improved conformity in a curved configuration with improved torsional resistance. Accordingly, the lumen opening of the stent graft 1000 is maintained or substantially maintained while conforming to the curved configuration. Thereby, the blood flow is only slightly reduced or not reduced at all in the curved portion, resulting in higher performance of the stent graft. In contrast, a stent graft without pre-set circular pleats may have a deformed portion when curved to a similar degree, and the deformed portion may cause partial closure of the lumen, resulting in suboptimal performance.

[0054] By compressing the stent graft annularly from a longitudinally stretched configuration to an annularly compressed configuration, partial pleats in a predetermined orientation (e.g., there are pleats on a graft material with a smaller curvature and no pleats on a graft material with a larger curvature) can be formed, and as a result, the pleated sections are nested within corresponding adjacent pleated sections along the curvature. In various embodiments, the partial pleats in any desired orientation are thermally pre-treated to fix the partial pleats in one or more desired curved orientations, so that when the stent graft is again annularly compressed by natural hardening, for example, when the stent graft is loaded, delivered, or implanted, the compressed stent graft will remember and recover the preset curved orientation. In various embodiments, the stent graft is manually annularly compressed to form a uniform outwardly luminal partial pleat orientation. Next, each partial pleat is thermally cured (e.g., by annealing or firing) to cure the partial pleat in the graft member. After the step of applying heat, the stent graft is manually pulled back to its stretched state. Such thermal pre-treatment enables the stent graft to remember the preset partial pleat orientation when it is again naturally annularly compressed. The partial pleats may also be thermally pre-treated to form a uniform inwardly luminal partial pleat orientation or a combination of outwardly luminal and inwardly luminal partial pleat orientations as needed.

[0055] In some embodiments, the stent graft can be formed to have circular pleats on a portion thereof and axial pleats (e.g., circumferential or helical pleats) on another portion thereof. In this case, as described above with reference to FIG. 11, a portion of the stent graft can be compressed annularly to form circular pleats, and as described above with reference to FIG. 5, another portion of the stent graft can be compressed axially to form axial pleats. For example, such a stent graft can be particularly useful in the case of the descending chest where the upper portion of the aorta is curved (thus suitable for receiving the circular pleated portion of the stent graft), while the descending section is relatively straight (thus suitable for receiving the axially pleated portion of the stent graft). However, the disclosure of the present invention is not limited thereto, and it must be recognized that in various embodiments, the stent graft may include any number of circular pleated portions and axially pleated portions as needed or desired.

[0056] Various embodiments provide a stent graft with improved flexibility due to pleats that allow the nitinol zigzag pattern of the stent member to move freely across the internally luminal formed pleats. The various pleats are formed to produce a preferred nested pattern to maximize flexibility. In some embodiments, a portion of the pleat is externally luminal (e.g., the valleys of the nitinol crowns), while an adjacent portion of the pleat is internally luminal (e.g., the peaks of the nitinol crowns). In various embodiments, the stent is fully laminated or fused to the graft material, thereby reducing concerns regarding wear as the wear rate is a function of the relative movement between components and subsequent corrosion. In some embodiments, a stent fully laminated or fused to the graft material has the advantage of less wear over embodiments where the stent is partially laminated, tethered, or freely floating within the graft material.

[0057] Various embodiments define creating pleats in a direction favorable for creating a smooth lumen in a stent graft. This enables reducing or eliminating undesirable irregular pleats that may be present with protrusions into the lumen in a way that impedes blood flow. Various embodiments provide the advantages of improved torsional resistance and improved flexibility. Various embodiments provide a fast method of securing the pleats. For example, in various embodiments, a non-contact oven pleating method enables securing the pleats in only 5 minutes.

[0058] The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The present invention is not limited in any way to the above-described embodiments. Various modifications and changes can be made to the embodiments without departing from the spirit and scope of the invention as defined by the following claims and their equivalents.

Description of the Reference Numerals

[0059] 1 Stent graft 10 Graft member 30a Pleat 50 Iron

Claims

1. A method of forming pleats in a stent graft, comprising: forming pleats by compressing the stent graft in the polymeric graft material of the stent graft; applying heat to the stent graft to thermoset the pleats in the polymeric graft material; after the pleats are thermoset, axially pulling back the stent graft to its original length to relieve the compression of the stent graft; and the step of forming the pleats includes folding the polymeric graft material over an adjacent portion of the polymeric graft material, the method.

2. The method according to claim 1, wherein the step of applying heat includes applying an iron to the crease of the pleats in the polymeric graft material.

3. The method according to claim 2, wherein the iron is heated to between 320 °C and 390 °C before applying the iron to the crease.

4. The method according to claim 1, wherein the step of compressing the stent graft includes compressing the stent graft axially and / or circumferentially.

5. The method according to claim 1, wherein the step of applying heat includes baking the stent graft in an oven for a predetermined time after forming the pleats.

6. The method according to claim 5, wherein the oven is heated to 320 °C before baking the stent graft.

7. The method according to claim 5, wherein the predetermined time is 5 minutes.

8. The method according to claim 5, wherein the predetermined time is longer than 5 minutes.

9. The method according to claim 1, wherein the step of folding the polymeric graft material includes folding the polymeric graft material outside the lumen with respect to the lumen of the stent graft.

10. The method according to claim 9, wherein the step of folding the polymeric graft material includes folding the polymeric graft material inside the lumen with respect to the lumen of the stent graft.

11. The step of forming the pleats includes: folding the polymeric graft material inside the lumen with respect to the lumen of the stent graft at a portion of the polymeric graft material; folding the polymer graft material outwardly with respect to the lumen of the stent graft at different portions of the polymer graft material; The method according to claim 1, comprising: **Claim 12** The step of forming the fold includes folding the polymer graft material at adjacent portions of the polymer graft material such that a larger graft space is provided between adjacent stent members on a larger curvature side of the stent graft than on a smaller curvature side of the stent graft. The method according to claim 1. **Claim 13** The method according to claim 12, further comprising increasing the graft space on the larger curvature side to reduce the radius of curvature of the stent graft. **Claim 14** A method of manufacturing a stent graft, forming a fold in the polymer graft material of the stent graft by axially and / or circumferentially compressing the stent graft; applying heat to the stent graft to thermoset the fold in the polymer graft material; after the fold has been thermoset, stretching the stent graft to relieve the compression of the stent graft; comprising: The step of forming the fold includes folding the polymer graft material at adjacent portions of the polymer graft material. **Claim 15** The method according to claim 14, wherein the step of applying heat includes applying an iron to the fold of the polymer graft material. **Claim 16** The method according to claim 14, wherein the step of applying heat includes baking the stent graft in an oven for a predetermined time after forming the fold. **Claim 17** The step of folding the polymer graft material at adjacent portions of the polymer graft material includes folding the polymer graft material such that a larger graft space is provided between adjacent stent members on a larger curvature side of the stent graft than on a smaller curvature side of the stent graft. The method according to claim 1.

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