STENT GRAFTS AND METHODS OF ENHANCING FLEXIBILITY OF STENT GRAFTS BY THERMAL PLEATING

FIELD

One or more example embodiments described herein relate generally to stent grafts and methods of making and using stent grafts, and in specific embodiments, to stent grafts and methods of making stent grafts that are flexible.

BACKGROUND

Aneurysms are enlargements or bulges in blood vessels that are often prone to rupture and which therefore present a serious risk to patients. Aneurysms may occur in any blood vessel but are of particular concern when they occur in the cerebral vasculature or an aorta.

Abdominal aortic aneurysms (AAA's) are classified based on their location within the aorta as well as their shape and complexity. Aneurysms that are found below the renal arteries are referred to as infrarenal abdominal aortic aneurysms. Suprarenal abdominal aortic aneurysms occur above the renal arteries. Thoracic aortic aneurysms (TAA's) occur in the ascending, transverse, or descending part of the upper aorta.

Stent grafts have come into widespread use for the treatment of aneurysms. Various stent grafts provide a graft layer to reestablish a flow lumen through an aneurysm as well as a stent structure to support the graft. In general, an endoluminal repair using a stent graft involves accessing an aneurysm endoluminally through either or both common iliac arteries. The stent graft is then implanted to treat the aneurysm.

SUMMARY OF THE DISCLOSURE

One implementation of the present disclosure is a method for forming pleats in a stent graft. The method includes forming pleats in a graft material of the stent graft by compressing the stent graft, applying heat to the stent graft to thermally set the pleats in the graft material, and extending the stent graft to uncompress the stent graft after the pleats are thermally set.

In an embodiment, the applying of the heat may include applying an iron to creases of the pleats in the graft material.

In an embodiment, the iron may be heated between 320° C. to 390° C. prior to applying the iron to the creases.

In an embodiment, the compressing of the stent graft may include axially and/or circularly compressing the stent graft.

In an embodiment, the applying of the heat may include baking the stent graft in an oven for a predetermined time period after forming the pleats.

In an embodiment, the oven may be heated to 320° C. prior to baking the stent graft.

In an embodiment, the predetermined time period may be 5 minutes.

In an embodiment, the predetermined time period may be greater than 5 minutes.

In an embodiment, the forming of the pleats may include folding the graft material over an adjacent portion of the graft material.

In an embodiment, the folding of the graft material may include folding the graft material abluminally with respect to a lumen of the stent graft.

In an embodiment, the folding of the graft material may include folding the graft material adluminally with respect to a lumen of the stent graft.

In an embodiment, the forming of the pleats may include folding the graft material adluminally with respect to a lumen of the stent graft at a portion of the graft material, and folding the graft material abluminally with respect to the lumen of the stent graft at a different portion of the graft material.

In an embodiment, the forming of the pleats may include folding the graft material over an adjacent portion of the graft material to have a graft space between adjacent stent members that is greater on a greater curvature side of the stent graft than on a lesser curvature side of the stent graft.

In an embodiment, the method may further include increasing the graft space on the greater curvature side to decrease a radius of curvature of the stent graft.

Another implementation of the present disclosure is a stent graft including a graft formed of graft material, and a stent attached to the graft and including stent members. The graft material is folded between the stent members over an adjacent portion of the graft members to form a pleat, and the pleat has a graft space between corresponding stent members on a greater curvature side of the stent graft that is greater than on a lesser curvature side of the stent graft.

Another implementation of the present disclosure is a stent graft manufactured by a process including forming pleats in a graft material of the stent graft by axially and/or circularly compressing the stent graft, applying heat to the stent graft to thermally set the pleats in the graft material, and extending the stent graft to uncompress the stent graft after the pleats are thermally set.

In an embodiment, the applying of the heat may include applying an iron to creases of the pleats in the graft material.

In an embodiment, the applying of the heat may include baking the stent graft in an oven for a predetermined time period after forming the pleats.

In an embodiment, the forming of the pleats may include folding the graft material over an adjacent portion of the graft material.

In an embodiment, the folding of the graft material over an adjacent portion of the graft material may include folding the graft material to have a graft space between adjacent stent members that is greater on a greater curvature side of the stent graft than on a lesser curvature side of the stent graft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a stent graft in accordance with an embodiment prior to thermal setting of pleats.

FIG. 2A is a flowchart of a method in accordance with an embodiment.

FIGS. 2B and 2C show methods that can be used with the method of FIG. 2A in accordance with various embodiments.

FIG. 3 shows a stent graft in an axially compressed state in accordance with an embodiment.

FIG. 4 shows an iron being used on graft material of a graft member of a stent graft in accordance with an embodiment to thermally lock in pleats in the graft material.

FIG. 5 shows a stent graft in accordance with an embodiment in a longitudinally extended state after pleats in graft material have been thermally set.

FIG. 6 shows a stent graft in accordance with an embodiment in a bent configuration after pleats in a graft member have been thermally set to form pleated sections in the stent graft.

FIG. 7A shows a stent graft in accordance with an embodiment having pleated sections that are tucked abluminally.

FIG. 7B shows an inner surface of a graft member of the stent graft of FIG. 7A.

FIG. 8A shows a stent graft in accordance with an embodiment having pleated sections that are tucked adluminally.

FIG. 8B shows an inner surface of a graft member of the stent graft of FIG. 8A.

FIG. 9A shows a stent graft in accordance with an embodiment having pleated sections that are tucked adluminally on a proximal end and abluminally on a distal end of the stent graft.

FIG. 9B shows an inner surface of a graft member of the stent graft of FIG. 9A.

FIG. 10 shows two embodiments of a stent graft to illustrate an effect of graft spacing between stent crowns on an achievable radius of curvature.

FIG. 11 shows an embodiment of a stent graft in a circularly compressed configuration.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings, which form a part of this specification. In the drawings, similar symbols typically identify similar items, unless context dictates 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 here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Various embodiments provide for an enhancement in the flexibility of stent grafts by thermal pleating the stent grafts. Various embodiments provide for endovascular stent graft flexibility enhancements by (1) manually pleating the graft material to nest the geometry of the stent graft in a preferred orientation, such as by axially compressing the stent graft; and (2) thermally treating the stent graft while in the compressed position so as to preferentially lock in the pleats to give the graft material a thermal memory to retain flexibility once the graft is extended again in length. Various embodiments allow for improving the flexibility of stent graft systems for vasculature applications by having pleats in the graft material that are thermally set.

Various embodiments provide for thermally locking in a preferable pleat geometry in a graft material of a stent graft. Such a thermally locked in pleat geometry for the graft material may allow, for example, each crown formed by a stent member of a stent that has a zig pattern within the graft material to consistently move relative to zigs of adjacent stent members without generating significant shear forces within the graft material even if the stent members are fully fused or sintered within the graft material. In various embodiments, thermally set pleats effectively reduce or minimize the randomness of crowns contacting to allow the crowns to uniformly tuck underneath or go over adjacent crowns as desired.

Various methods in accordance with various embodiments are provided herein for thermally locking in a preferable pleat geometry. One such method in accordance with various embodiments includes thermally ironing the pleats. In some such embodiments, the stent graft is initially axially compressed to produce a desired pleating pattern. In some embodiments, a soldering iron set to a temperature of, for example, 320° C. to 390° C. is then used to wipe the pleated areas between adjacent stent members with the tip or barrel of the iron to thermally lock in the fold or pleat in the graft material. In various embodiments, other suitable temperatures can be used for the iron for ironing the pleats. In various embodiments, once each of the folds or pleats are thermally locked at the desired areas in the graft material, the stent graft can be axially pulled back (or extended) to its natural or native length and will have flexibility that is improved (or greatly improved) over a non-pleated stent graft.

Another method in accordance with various embodiments for thermally locking in a preferable pleat geometry includes thermally baking the pleats. In some such embodiments, the stent graft is initially axially compressed to produce a desired pleating pattern. Also, in some such embodiments, the pleated part or parts of the stent graft is then placed in an oven set to a temperature of, for example, 320° C. or any other suitable temperature for a desired or predetermined time to thermally lock in the folds or pleats. In various embodiments the baking times in the oven are, for example, 5 minutes, 10 minutes, 20 minutes, and/or the like. However, the present disclosure is not limited thereto, and in other embodiments, other suitable baking times can be used. In some embodiments, 5 minutes may be preferable as a short amount of time to effectively lock in 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, once the folds or pleats are thermally locked at the desired areas in the graft material, the stent graft can be axially pulled back (or extended) to its natural or native length and will have flexibility that is improved (or greatly improved) over a non-pleated stent graft.

Referring now to FIG. 1, a stent graft 1 is shown, in accordance with an example embodiment. The stent graft 1 is a hollow tubular device having a graft member 10 forming a tubular wall with a proximal end 11 and a distal end 12 and defining an open lumen between the proximal end 11 and the distal end 12. While stent graft 1 as seen in FIG. 1 is depicted as being substantially tubular, it should be understood that stent graft 1 may be of any shape that is suitable for delivery to and placement in a target site of a patient. For example, portions of graft member 10 at either or both of proximal and distal ends 11 and 12 may be flared (inwardly or outwardly) or tapered (inwardly or outwardly). Furthermore, portions of graft member 10 may also include non-straight tubular portions, such as flared (inwardly or outwardly) portions, portions having bends or curvature, fenestrations, channels, bifurcated portions, and/or the like. Moreover, while the proximal and distal ends 11 and 12 are depicted as having a single open lumen, the present disclosure is not limited thereto. For example, one or both proximal end 11 and distal end 12 may be multi-lumen ends such as, for example, bifurcated open ends.

FIG. 1 shows the stent graft 1 in a longitudinally extended state prior to pleating. The stent graft 1 includes the 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 separate 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 undulating wires that are wound circumferentially along an axis in an open tubular configuration. The circumferentially wound undulating wire(s) may be circular or helical. Also, the circumferentially wound undulating wires may form zigs with peaks and valleys. For example, the stent member 20c is depicted as having a plurality of peaks 21 pointing towards the proximal end 11 of the stent graft 1 and a plurality of valleys 22 pointing towards 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 201 forms a crown with a plurality of peaks and valleys.

Each of the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 201 may be made, for example, from stainless steel, a nickel titanium alloy (NiTi) such as NITINOL, or any other suitable material, including, but not limited to, a cobalt-based alloy 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 201 may be balloon-expandable or self-expandable. In various embodiments, more than one stent member may be disposed at or near the proximal end 11 of the stent graft 1, such as two stent members as shown by the stent members 20a. Also, in various embodiments, more than one stent member may be disposed at or near the distal end 12 of the stent graft 1, such as two stent members as shown by the stent members 201. While the embodiment in FIG. 1 shows a particular number of stent members, it should be appreciated that, in various embodiments, any suitable number of stent members may be used.

In some embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 201 are attached to or laminated within the graft member 10. In some embodiments, the graft member 10 extends from the proximal end 11 to the distal end 12. In some other embodiments, the graft member 10 does not cover the entire length of stent graft 1, and may, for example, leave the proximal end 11, the distal end 12, or both uncovered. In various embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 201 are fully laminated or fused within the graft member 10. In this case, the possibility of graft material wear for the graft member 10 may be reduced, which is a function of relative motion between the components. In various embodiments, the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 201 are partially laminated, tethered, or free-floating within the graft member 10.

In various embodiments, the graft member 10 comprises graft material that is made from one or more polymers or other suitable materials. In some embodiments, the graft member 10 is made of polytetrafluoroethylene (ePTFE). In some embodiments, the graft member 10 is made of expanded polytetrafluoroethylene (ePTFE). In yet 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.

In some embodiments, the stent graft 1 can be longitudinally compressed to form a plurality of circumferential pleats with a predetermined orientation. In some embodiments, the stent graft 1 can be longitudinally compressed to form a continuous helical pleat in the case of a continuously wound wire. In various embodiments, each pleat involves a creased or folded surface of the graft material of the graft member 10, typically formed in areas 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 referred to herein as a pleated section of the stent graft 1. In various embodiments, each of a 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.

FIG. 2A is a flowchart of a method in accordance with an embodiment. FIGS. 2B and 2C show methods that can be used with the method of FIG. 2A. With reference to FIG. 2A, in step 100 a stent graft is compressed (e.g., axially or circularly) to form pleats in a graft material of the stent graft. In step 101, heat is applied to the stent graft to set creases for the pleats in the graft material. In step 102, the stent graft is pulled (or extended) so as to uncompress the stent graft after the pleats have been thermally set. With reference to FIGS. 2A and 2B, in various embodiments the applying heat of step 101 is performed as in step 103 by applying an iron to the pleats of the stent graft to set the creases for the pleats in the graft material. With reference to FIGS. 2A and 2C, in various embodiments the applying heat of step 101 is performed as in step 104 by placing the stent graft in an oven to bake the stent graft for a predetermined time period to thermally lock in the pleats.

FIG. 3 shows the stent graft 1 in an axially compressed state in accordance with an embodiment. With reference to FIGS. 1, 2A, and 3, step 100 of axially compressing the stent graft 1 in FIG. 1 can result in the axially compressed version of the stent graft 1 as shown in FIG. 3, according to an embodiment. In various embodiments, the stent graft 1 is axially compressed by bringing the distal end 12 closer to the proximal end 11, which creates pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k where the graft material of the graft member 10 creases between the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 201, such that the stent members 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, and 201 at least partially overlaps with (e.g., passes over or under) corresponding adjacent stent members.

FIG. 4 shows an iron 50 being used on the graft material of the graft member 10 of the stent graft 1 in accordance with an embodiment to thermally lock in the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k. With reference 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 pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k of the stent graft 1 to set the creases for the pleats 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 to (e.g., wiped over) each of the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k around a circumference of the stent graft 1. In various embodiments, the temperature of the iron 50 is set to a temperature between 320° C. and 390° C., for example. In various other embodiments, other suitable temperatures are used for the iron 50.

Additionally and/or alternatively, the manually compressed stent graft 1 as seen in FIG. 3 may be heated evenly or substantially evenly to set the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k, such as, for example, by baking the stent graft 1 in an oven as shown in step 104 of FIG. 2C. With reference to FIGS. 2C and 3, the temperature of the oven may be set based on the baking time and the thickness of the graft member 10, and may be, for example, about 280° C.-300° C., 300° C.-320° C., 320° C.-340° C., 340° C.-360° C., or within any other suitable temperature range. The baking time may 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 for setting the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k. In various example embodiments, three manually compressed stent grafts are placed in an oven of 320° C. for 5, 10, and 20 minutes, respectively. After baking, all three stent grafts are thermally set to the predetermined pleat orientation, and are able to retain the same orientation when compressed again naturally.

FIG. 5 shows the stent graft 1 in a longitudinally extended state after the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k have been thermally set. 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 a continuous helical pleat. With reference to FIGS. 2A, 4, and 5, in various embodiments, the step 102 is performed on the stent graft 1 to pull (or extend) the stent graft 1 to uncompress the stent graft 1 from the axially compressed state as in FIG. 4 to the longitudinally extended state as in FIG. 5 after the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k have been thermally set. The stent graft 1 in FIG. 5 is shown to include the pleated sections 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h, 40i, 40j, 40k, and 40l.

The pleated section 40a of the stent graft 1 includes the stent members 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 pleat 30a and the pleat 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 pleat 30b and the pleat 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 pleat 30c and the pleat 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 pleat 30d and the pleat 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 pleat 30e and the pleat 30f.

The pleated section 40g of the stent graft 1 includes the stent member 20g and a portion of the graft member 10 between the pleat 30f and the pleat 30g. The pleated section 40h of the stent graft 1 includes the stent member 20h and a portion of the graft member 10 between the pleat 30g and the pleat 30h. The pleated section 40i of the stent graft 1 includes the stent member 20i and a portion of the graft member 10 between the pleat 30h and the pleat 30i. The pleated section 40j of the stent graft 1 includes the stent member 20j and a portion of the graft member 10 between the pleat 30i and the pleat 30j. The pleated section 40k of the stent graft 1 includes the stent member 20k and a portion of the graft member 10 between the pleat 30j and the pleat 30k. The pleated section 40l of the stent graft 1 includes the stent members 201 and a portion of the graft member 10 between the pleat 30k and the distal end 12.

The stent graft 1 with predetermined or pre-set pleat orientation in accordance with various embodiments provides several advantages. Circumferential pleats provide space for longitudinal movement between stent members or crowns, thereby improving longitudinal flexibility during longitudinal compression and/or expansion, and improving radial flexibility as movement is permitted in the radial direction upon bending or even longitudinal compression. The pre-set pleats provide an advantage over random pleats because random pleats that are formed by compressing a stent graft, and especially those that protrude radially outward, tend to prevent longitudinal compression and generate internal forces within a stent graft that lead to kinking. Various embodiments disclosed herein overcome the problem of random pleating by predetermining and locking in the orientation of the pleats before the stent graft is longitudinally compressed (or uncompressed) or radially bent, thereby allowing the stent graft to automatically form a consistent and predetermined pleat orientation when radially bent or longitudinally compressed for loading, delivery, or implantation. A uniformed pleat orientation allows the stent members or crowns to consistently move relative to adjacent crowns without generating significant shear forces within the graft material.

FIG. 6 shows the stent graft 1 in accordance with an embodiment in a bent configuration after the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k in the graft member 10 have been thermally set to form the pleated sections 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h, 40i, 40j, 40k, and 401 in the stent graft 1. The stent graft 1 has improved kink resistance when bent due to the thermally set pleats. In some embodiments, the stent graft 1 is able to conform, for example, around a pin with a 0.325 inch diameter without kinking. In various embodiments, during bending, the pleats 30a, 30b, 30c, 30d, 30e, 30f, 30g, 30h, 30i, 30j, and 30k in the graft member 10 move under the bending force according to their preset orientation. This permits the stent graft 1 to bend about 180° or greater without having a substantial reduction in diameter in any portion of the bend. Thus, openness of a lumen of the stent graft 1 is maintained or substantially maintained, particularly in the area of the bend. This results in a higher-performing stent graft as blood flow is diminished only slightly, or not at all in the bend. In contrast, a stent graft without the preset pleats (e.g., circumferential or helical) may have a deformed portion when undergoing a similar degree of bending, where the deformed portion may cause a partial closing of a lumen resulting in suboptimal performance.

By longitudinally compressing a stent graft from a longitudinally extended configuration to a compressed configuration, pleats (e.g., a plurality of circumferential pleats or pleats forming a continuous helical pleat) of predetermined orientation can be formed such that the pleated sections nest within corresponding adjacent pleated sections along an axis. In various embodiments, circumferential pleats in any desired orientation may be pretreated thermally to lock the pleats in the desired orientation such that when the stent graft is longitudinally compressed again in a natural setting, for example, during stent graft loading, delivery, or implantation, the compressed stent graft will memorize and resume the preset pleat orientation. In various embodiments, a stent graft is manually compressed longitudinally to form a uniform abluminal pleat orientation. Each of the circumferential pleats is then ironed to set the creases in the graft member. After the ironing step, the stent graft is manually pulled back to its extended state. Such thermal pretreatment allows the stent graft to memorize the preset pleat orientation when being compressed again naturally. The pleats may also be pretreated thermally to form a uniform adluminal orientation, or a combination of abluminal and adluminal orientation, as desired.

FIG. 7A shows a stent graft 70 in accordance with an embodiment including 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, 741, and 74m that have zig valleys that are tucked abluminally with respect to adjacent zig peaks. The stent graft 70 includes the pleated sections 74a, 74b, 74c, 74d, 74e, 74f, 74g, 74h, 74i, 74j, 74k, 741, and 74m that are preset through an intentional compression to be nested such that all of those pleated sections are tucked abluminally with respect to each other (that is, a more proximal pleated section is radially raised to cover a portion of its immediately distally adjacent pleated section). This causes the pleats to be formed in the stent graft 70 such that the crown valleys of the stent members are tucked abluminally with respect to each other. FIG. 7B shows an inner surface 75 of the graft member 73 of the stent graft 70 of FIG. 7A in accordance with an embodiment with pleats 77a, 77b, 77c, 77d, 77e, and 77f that form a “rough” inner surface due to the abluminal nesting orientation of the pleated sections 74a, 74b, 74c, 74d, 74e, 74f, 74g, 74h, 74i, 74j, 74k, 741, and 74m.

FIG. 8A shows a stent graft 80 in accordance with an embodiment including a graft member 83 with a proximal end 81 and a distal end 82 and having pleated sections 84a, 84b, 84c, 84d, 84e, 84f, 84g, 84h, 84i, 84j, 84k, 841, 84m, 84n, 84o, 84p, 84q, 84r, and 84s that have zig valleys that are tucked adluminally with respect to adjacent zig peaks. The stent graft 80 includes the pleated sections 84a, 84b, 84c, 84d, 84e, 84f, 84g, 84h, 84i, 84j, 84k, 841, 84m, 84n, 84o, 84p, 84q, 84r, and 84s that are preset through an intentional compression to be nested such that all of those pleated sections are tucked adluminally with respect to each other (that is, a more distal pleated section is radially raised to cover a portion of its immediately proximally adjacent pleated section). This causes the pleats to be formed in the stent graft 80 such that the crown valleys of the stent members are tucked adluminally with respect to each other to create reduced shear stress in the graft material. FIG. 8B shows an inner surface 85 of the graft member 83 of the stent graft 80 of FIG. 8A in accordance with an embodiment with pleats 87a, 87b, 87c, 87d, 87e, and 87f that form a “smooth” inner surface throughout the stent graft 80 due to the adluminal nesting orientation of the pleated sections.

In yet some other embodiments, some of the pleated sections may be predetermined to be tucked adluminally, while others may be tucked abluminally. For example, in some embodiments, proximal pleated sections are tucked adluminally, while distal pleated sections are tucked abluminally. FIG. 9A shows a stent graft 90 in accordance with an embodiment including a graft member 93 with a proximal end 91 and a distal end 92 and having pleated sections 94a, 94b, 94c, 94d, 94e, 94f, 94g, 94h, 94i, 94j, 94k, 941, 94m, 94n, 94o, 94p, 94q, and 94r. The stent graft 90 includes the pleated sections 94a, 94b, 94c, 94d, and 94e that are preset through an intentional compression to be nested such that all of those pleated sections are tucked adluminally with respect to each other. The stent graft 90 includes the pleated sections 94f, 94g, 94h, 94i, 94j, 94k, 941, 94m, 94n, 94o, 94p, 94q, and 94r that are preset through an intentional compression to be nested such that all of those pleated sections are tucked abluminally with respect to each other. FIG. 9B shows an inner surface 95 of the graft member 93 of the stent graft 90 of FIG. 9A in accordance with an embodiment with pleats 97a, 97b, 97c, 97d, 97e, 97f, 97g, and 97h, where the pleats 97a, 97b, 97c, 97d, and 97e form a “smooth” inner surface due to the adluminal 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 abluminal nesting orientation of the remaining pleated sections. Various embodiments provide for a mechanical interlocking with modular components.

In various embodiments, a blood flow pattern in a stent graft may be controlled and modified by selecting the orientation of the pleats. For example, when the valleys of the stent crowns are tucked abluminally, the inner surface of the stent graft lumen is “rough” and may disrupt blood flow. On the other hand, when the valleys of the stent crowns are tucked adluminally, the inner surface of the stent graft lumen is “smooth,” resulting in a desirable blood flow pattern and reduced shear stress on the graft material. Further, when the pleats are helical pleats, the inner surface of the stent graft lumen has a spiral pattern (which can have pleats that are tucked adluminally or abluminally), which may induce or maintain a desirable spiral blood flow pattern.

FIG. 10 illustrates the effect of graft spacing between stent members or crowns on an achievable radius of curvature. Each of stent graft 200 on the left and stent graft 300 on the right has a greater curvature side 205 and 305 and a lesser curvature side 210 and 310, respectively. The stent graft 200 on the left has a 2 mm graft space 215 between the crowns of the stent body at the greater curvature side 205, while stent graft 300 on the right has a 4 mm graft space 315 between the crowns of the stent body at the greater curvature side 305. 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 lesser curvature side 210 and 310 opposite the greater curvature side 205 and 305, respectively. The increased graft spacing on the greater curvature side 305 allows stent graft 300 to achieve a smaller radius of curvature when compared to the stent graft 200 due to the larger pleats which allow more nesting of the stent zig geometry. For example, the stent graft 200 has a curvature with an end-to-end length of L₁(of about 125 mm), whereas the stent graft 300 has a curvature with an end-to-end length of L₂(of about 80 mm), where L₁is greater than L₂. In various embodiments, thermally pretreating a stent graft that has been longitudinally compressed allows for pleats to be formed that are consistent with a predetermined orientation. In various embodiments, each pleated section may include one crown or more than one crown, and pleated sections in different portions of the stent graft may include different numbers of crowns or otherwise have different width or spacing, to accommodate the shape of the stent graft, and to achieve a desired dimension and physical characteristics.

FIG. 11 shows a stent graft 1000 in accordance with an embodiment in a circularly compressed configuration. In the circularly compressed configuration, the stent graft 1000 with circular pleating can be formed. The stent graft 1000 with circular pleating has partial pleats 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 1301 that are thermally set in the graft member 110 on a lesser curvature side 130 of the stent graft 1000, but a greater curvature side 120 of the stent graft 1000 does not have pleats. For example, the partial pleats 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 1301 may be thermally set by applying heat to the partial pleats 130a, 130b, 130c, 130d, 130e, 130f, 130g, 130h, 130i, 130j, 130k, and 1301 via an iron and/or baking the circularly compressed stent graft 1000 having the partial pleats. The stent graft 1000 with the circular pleating has improved conformability in a curved configuration with improved kink resistance. Thus, openness of a lumen of the stent graft 1000 is maintained or substantially maintained, while conforming to the curved configuration. This results in a higher-performing stent graft as blood flow is diminished only slightly, or not at all in the curved portion. In contrast, a stent graft without the preset circular pleating may have a deformed portion when undergoing a similar degree of curvature, where the deformed portion may cause a partial closing of a lumen resulting in suboptimal performance.

By circularly compressing a stent graft from a longitudinally extended configuration to a circularly compressed configuration, partial pleats (e.g., pleats on the lesser curvature and no pleats on the greater curvature of the graft material) of predetermined orientation can be formed such that the partial pleated sections nest within corresponding adjacent partial pleated sections along the curvature. In various embodiments, partial pleats in any desired orientation may be pretreated thermally to lock the partial pleats in one or more desired curved orientations such that when the stent graft is circularly compressed again in a natural setting, for example, during stent graft loading, delivery, or implantation, the compressed stent graft will memorize and resume the preset curved orientations. In various embodiments, a stent graft is manually compressed circularly to form a uniform abluminal partial pleat orientation. Each of the partial pleats is then thermally set by applying heat (e.g., by ironing or baking) to set the partial pleats in the graft member. After the thermal application step, the stent graft is manually pulled back to its extended state. Such thermal pretreatment allows the stent graft to memorize the preset partial pleat orientation when being circularly compressed again naturally. The partial pleats may also be pretreated thermally to form a uniform adluminal partial pleat orientation, or a combination of abluminal and adluminal partial pleat orientation, as desired.

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

Various embodiments provide stent grafts with improved flexibility due to pleating that allows a nitinol zig pattern of stent members freedom to move over adluminally formed pleats. Various pleats are formed to create a preferential nesting pattern for maximum flexibility. In some embodiments, a portion of the pleating is abluminal (valley of nitinol crown for example) while the adjacent portion of the pleating is adluminal (peak of nitinol crown for example). In various embodiments, the stent is fully laminated or fused within the graft material, thereby reducing concerns about wear, since wear rate is a function of relative motion between components, and subsequent corrosion. In some embodiments, a fully laminated or fused stent within graft material has an advantage over embodiments where the stent is partially laminated, tethered, or free-floating within the graft material, since there can be less wear.

Various embodiments provide for producing pleats in a preferred directional orientation to create a smooth lumen in a stent graft. This allows for reducing or eliminating an undesirable random pleating in which there may be protrusions into the lumen in such a way that may disrupt blood flow. Various embodiments provide an advantage of improved kink resistance and improved flexibility. Various embodiments provide a fast method for locking in pleats. For example, in various embodiments, a non-contact oven pleating method allows for locking in pleats in as little as 5 minutes time.

The embodiments disclosed herein are to be considered in all respects as illustrative, and not restrictive of the invention. The present invention is in no way limited to the embodiments described above. Various modifications and changes may be made to the embodiments without departing from the spirit and scope of the invention, as defined by the following claims and their equivalents.

STENT GRAFTS AND METHODS OF ENHANCING FLEXIBILITY OF STENT GRAFTS BY THERMAL PLEATING

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

International Classifications

Abstract

Description

Claims

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

PCT Information

Provisional Applications (1)