Variable depression stents (VDS) and billowing graft assemblies

A stent assembly includes support rings each having interconnected circumferentially alternating inner prongs and outer prongs. The inner prongs define an inner diameter around a longitudinal axis. The outer prongs define an outer diameter greater than the inner diameter. A graft engages the support rings and follows a waving peripheral path. The graft may be a billowing graft. A second graft may surround the first graft such that tunnels are defined between the first graft and second graft. A method of making a stent assembly includes diametrically expanding the support rings onto a mandrel, engaging a graft with the support rings, and removing the support rings and graft from the mandrel permitting the stent assembly to contract to a neutral state.

TECHNICAL FIELD

The present disclosure relates to devices that may be used to treat aortic aneurysms. The devices described may also be used for the treatment of thoracoabdominal, arch and ascending aneurysms.

BACKGROUND

Endovascular technology has revolutionized the treatment of abdominal aortic aneurysms. This technology has shifted the treatment of these deadly disorders from an invasive, morbid operation to a minimally invasive option with low morbidity and mortality and length of stay. Although many patients are candidates for this less invasive repair with conventional devices, a large group of patients are not treatable because of anatomical restrictions. Some of these patients may be candidates for treatment with conventional fenestrated endografts, however there are significant limitations to the use of that technology. These limitations are often secondary to poor iliofemoral access (because of the large profile of the current devices), angulations in the aorta, the degree of angulation and disease within the renal arteries, technical limitations with regard to the creation of the holes in the current endografts or a combination thereof. Another limitation to the current available technology is the fact that a device may need to be created for each individual patient, adding delays of between three to six weeks to the treatment of the patients and patients with urgent/emergent needs would be ineligible for this treatment.

SUMMARY

This summary is provided to introduce in a simplified form concepts that are further described in the following detailed descriptions. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it to be construed as limiting the scope of the claimed subject matter.

A stent assembly according to at least one embodiment includes a first support ring, a second support ring, and a billowing graft. Each support ring may be made of shape memory wire, stainless steel, or other materials. The first support ring has interconnected circumferentially alternating first inner prongs and first outer prongs, the first inner prongs defining a first inner diameter around a central longitudinal axis, and the first outer prongs defining a first outer diameter around the central longitudinal axis greater than the first inner diameter. The second support ring is spaced from the first support ring along the central longitudinal axis. The second support ring has interconnected circumferentially alternating second inner prongs and second outer prongs, the second inner prongs defining a second inner diameter around the central longitudinal axis, and the second outer prongs defining a second outer diameter around the central longitudinal axis greater than the second inner diameter. The billowing graft engages the first support ring and second support ring, the billowing graft following a waving peripheral path at least partially around at least one of the first support ring and second support ring.

In at least one example, a circumferential position of a particular first inner prong is aligned with a circumferential position of a particular second inner prong, and circumferential positions of two first outer prongs adjacent the particular first inner prong are aligned respectively with circumferential positions of two second outer prongs adjacent the particular second inner prong such that a longitudinal channel is defined along the aligned circumferential positions of the particular first inner prong and particular second inner prong.

In at least one example, the billowing graft billows along the longitudinal channel.

In at least one example, the billowing graft is attached to the two first outer prongs adjacent the particular first inner prong and to the two second outer prongs adjacent the particular second inner prong.

In at least one example, the billowing graft is free to billow radially outward from and radially inward toward the particular first inner prong and the particular first inner prong along the longitudinal channel.

In at least one example, at least one side stent is positioned at least partially within the longitudinal channel.

In at least one example, the first inner prongs have tips directed in a first longitudinal direction; and the first outer prongs have tips directed in a second longitudinal direction opposite the first longitudinal direction.

In at least one example, the first support ring further has a radially flat portion defined by at least two prongs that extend in opposite longitudinal directions, the at least two prongs of the radially flat portion of the first support ring being equidistant from the central longitudinal axis.

In at least one example, the first outer prongs and the at least two prongs of the radially flat portion of the first support ring are equidistant from the central longitudinal axis.

In at least one example, the second support ring further has a radially flat portion defined by at least two prongs that extend in opposite longitudinal directions, the at least two prongs of the radially flat portion of the second support ring being equidistant from the central longitudinal axis.

In at least one example, the radially flat portion of the first support ring has a circumferential position aligned with a circumferential position of the radially flat portion of the second support ring.

In at least one example, an angle subtended partially around the central longitudinal axis by the radially flat portion of the first support ring is approximately equal to an angle subtended partially around the central longitudinal axis by the radially flat portion of the second support ring.

In at least one example, the angle subtended partially around the central longitudinal axis by the radially flat portion of the first support ring is less than one hundred and eighty degrees.

In at least one example, the first inner prongs and first outer prongs are connected together by intermediate connecting segments; and the first inner prongs, first outer prongs and intermediate connecting segments together subtend a summation angle of greater than one hundred and eighty degrees around the central longitudinal axis.

In at least one example, the first support ring comprises a first portion including the first inner prongs and first outer prongs and a second portion including the radially flat portion of the first support ring; and the first portion of the first support ring is C-shaped and subtends an angle of greater than one hundred and eighty degrees around the central longitudinal axis.

In at least one example, the second inner prongs have tips directed in the first longitudinal direction; and the second outer prongs have tips directed in the second longitudinal direction opposite the first longitudinal direction.

In at least one example, the second outer prongs have tips directed in the first longitudinal direction; and the second inner prongs have tips directed in the second longitudinal direction opposite the first longitudinal direction.

In at least one example, at least one fenestration for receiving a vessel is formed through the billowing graft.

In at least one example, a radio-opaque marker is placed around the at least one fenestration.

In at least one example, the fenestration is formed through the billowing graft at a circumferential position corresponding to a circumferential position of a radially flat portion of the first support ring and a circumferential position of a radially flat portion of the second support ring.

In at least one embodiment, a method for forming a stent assembly includes: providing a first support ring having interconnected circumferentially alternating first inner prongs and first outer prongs, the first support ring having a neutral state in which the first inner prongs define a first inner diameter around a central longitudinal axis, and in which the first outer prongs define a first outer diameter around the central longitudinal axis greater than the first inner diameter; providing a mandrel having at least one portion with a diameter greater than the first outer diameter; diametrically expanding the first support ring from the neutral state and at least partially surrounding the at least one portion of the mandrel with the first outer prongs; at least partially surrounding the first outer prongs with a graft; engaging the graft with the first outer prongs; removing the first support ring and graft from the mandrel; and permitting the first support ring to diametrically contract to the neutral state such that the graft follows a waving peripheral path at least partially around the first support ring.

In at least one example, the at least one portion of the mandrel with a diameter greater than the first outer diameter is a first longitudinal portion of the mandrel having a first mandrel diameter greater than the first outer diameter. The mandrel further has a second longitudinal portion adjacent the first longitudinal portion of the mandrel. The second longitudinal portion of the mandrel has a second mandrel diameter that is less than the first mandrel diameter and greater than the first inner diameter. The method further comprises at least partially surrounding the second longitudinal portion of the mandrel with the first inner prongs.

In at least one example, the graft has an exterior side and an interior side and the graft has pockets defined along the interior side. Engaging the graft with the first outer prongs includes inserting the first outer prongs into the pockets.

In at least one embodiment, a stent assembly includes a first support ring, a second support ring, a first graft, and a second graft. The first support ring has interconnected circumferentially alternating first inner portions and first outer portions, the first inner portions defining a first inner diameter around a central longitudinal axis, and the first outer portions defining a first outer diameter around the central longitudinal axis greater than the first inner diameter.

The second support ring is spaced from the first support ring along the central longitudinal axis. The second support ring has interconnected circumferentially alternating second inner portions and second outer portions, the second inner portions defining a second inner diameter around the central longitudinal axis, and the second outer portions defining a second outer diameter around the central longitudinal axis greater than the second inner diameter. The first graft engages the first support ring and second support ring, the first graft following a waving peripheral path at least partially around each of the first support ring and second support ring. The second graft at least partially surrounds the first graft such that longitudinal tunnels are defined between first graft and second graft. The second graft may be supported by a wire skeleton or stents.

In at least one example: the first inner portions of the first support ring have circumferential positions aligned with circumferential positions of the second inner portions of the second support ring; the first outer portions of the first support ring have circumferential positions aligned with circumferential positions of the second outer portions of the second support ring; the first graft has radially depressed channels extending longitudinally at the circumferential positions of the first inner portions of the first support ring; and the longitudinal tunnels are defined between the radially depressed channels and the second graft.

DETAILED DESCRIPTIONS

These descriptions are presented with sufficient details to provide an understanding of one or more particular embodiments of broader inventive subject matters. These descriptions expound upon and exemplify particular features of those particular embodiments without limiting the inventive subject matters to the explicitly described embodiments and features. Considerations in view of these descriptions will likely give rise to additional and similar embodiments and features without departing from the scope of the inventive subject matters. Although the term “step” may be expressly used or implied relating to features of processes or methods, no implication is made of any particular order or sequence among such expressed or implied steps unless an order or sequence is explicitly stated.

Any dimensions expressed or implied in the drawings and these descriptions are provided for exemplary purposes. Thus, not all embodiments within the scope of the drawings and these descriptions are made according to such exemplary dimensions. The drawings are not made necessarily to scale. Thus, not all embodiments within the scope of the drawings and these descriptions are made according to the apparent scale of the drawings with regard to relative dimensions in the drawings. However, for each drawing, at least one embodiment is made according to the apparent relative scale of the drawing.

Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, caudal, cranial, etcetera, may be used throughout the specification in reference to the implants and surgical instruments described herein as well as in reference to the patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise. For example, the term “cranial” refers to the direction that is generally toward the head of the patient, and the term “caudal” refers to the direction that is generally toward the feet of the patient.

The design and geometrical shape of the endograft stent assemblies detailed in these descriptions permit separate access to the renal arteries, thus facilitating use with many anatomical variations. These designs allow for placement of parallel covered renal stents while reducing the likelihood of an endoleak along the renal stents, and reducing the risk of kinking and compression of the renal stents.

An embodiment of a support ring102is shown inFIGS. 1 and 2. The support ring102has two distinct diameters, namely an inner diameter110and a greater outer diameter120, defined respectively by alternating inner prongs112and outer prongs122of the support ring. The inner prongs112are connected to the outer prongs122by intermediate connecting segments130. The support ring surrounds a longitudinal axis104, and defines a longitudinal length106between oppositely directed tips114of the inner prongs112and tips124of the outer prongs122. In at least one embodiment, the support ring102is formed from one continuous wire. These descriptions nonetheless refer to segments of the support ring112as prongs, tips, and connecting segments for the purpose of detailing the support ring. InFIGS. 1 and 3, the tips114of the inner prongs112are shown as downwardly directed and the tips124of the outer prongs122are shown upwardly directed. This particular orientation is depicted for exemplary purposes. Other orientations may be preferred and are within the scope of these descriptions and the drawings.

For example,FIG. 3illustrates a stent frame400including three support rings, each generally within the scope of the descriptions of the support ring102. In particular, the stent frame400includes same-oriented upper and middle support rings102and202, and one oppositely oriented lower support ring302. More particularly, the lower support ring302is illustrated as having its inner prong tips314upwardly directed and its outer prong tips324downwardly directed. Thus,FIG. 3depicts one example of multiple support rings together forming a stent frame400having an inner diameter110and a greater outer diameter120.

FIG. 3illustrates the support rings102,202and302as approximately concentric with the longitudinal axis and spaced along the longitudinal axis104without expressly illustrating any interconnecting structure among the support rings. As further detailed in the following descriptions, the support rings in at least one embodiment are interconnected and maintained in their relative positions by a cover, for example the major cover graft502that generally surrounds the stent frame400inFIGS. 5 and 6.

With brief reference now toFIGS. 4 and 5to appreciate advantages of the stent frame400, a first longitudinal side stent532aand a second longitudinal side stent532bare shown inFIG. 4as cradled within exterior longitudinal channels defined by the stent frame400. In such cradled engagement with the stent frame400, the side stents532aand532bare supported by the support rings in use when blood pressure is applied.FIG. 5includes also a major cover graft502generally surrounding the stent frame400, between the stent frame400and the side stents532aand532b. A central fluid flow channel504is defined within the major cover graft502along the longitudinal axis104. Longitudinal grooves for the side stents532aand532bare formed where the graft material is in contact with the side stents. Longitudinal fluid flow channels506aand506bare defined respectively within the side stents532aand532b. In other embodiments, additional parallel side stents can be included. In the stent assembly500ofFIG. 5, blood pressure can bear upon the major cover graft502from within, and arterial or aortic tissue can be contacted along the exterior of the stent assembly500, while the side stents532aand532bare supported and localized within the longitudinal grooves formed between the cover graft502and tissue by the support rings102,202and302of the stent frame400.

Returning toFIGS. 1 and 2to further describe each support ring, the inner prongs112and outer prongs122each subtend a circumferential angle as shown inFIG. 2. Each inner prong112is illustrated as subtending a greater circumferential angle116than the circumferential angle126subtended by each outer prong122. Other proportions than that expressly depicted inFIG. 2are within the scope of these descriptions. As shown best inFIG. 2, the circumferential angles116and126subtended by the inner prongs112and outer prongs122sum to a circumferential summation angle140that is less than three hundred and sixty (360) degrees such that the longitudinal axis is only partially circumferentially surrounded by the inner prongs112and outer prongs122connected by the intermediate connecting segments130.

The support ring102further includes a radially flat portion150, illustrated as having two commonly directed prongs152at the circumferential margins of the flat portion150and an oppositely directed central prong154. The radially flat portion150is distinct from other portions of the support ring100in that it lies in a cylindrical surface equidistant from the central longitudinal axis104, whereas the inner prongs112and outer prongs122lie at alternating respective near and far radial distances118and128from the axis104with the intermediate connecting segments130spanning the radial difference between the near and far radial distances118and128, which measure as halves of the inner and outer diameters110and120respectively. Thus, the support ring has a first circumferential portion subtending a first angle140and defined by alternating radially inner and outer prongs112and114with respect to the longitudinal axis104, and a second circumferential portion subtending a second angle142and defined by a radially flat portion150at a uniform distance from the central longitudinal axis104, that uniform distance being the far radial distance128. The sum of the subtended first angle140and the subtended second angle142is equal to three hundred and sixty (360) degrees. In the illustrated embodiment, the first portion is C-shaped as defined by the summation angle140being greater than one hundred and eighty (180) degrees.

As shown inFIGS. 1 and 3, each inner prong112is defined by a U-shaped element having two linear longitudinally extending portions connected by the tip114. Similarly, each outer prong122is defined by a U-shaped element having two linear longitudinally extending portions connected by the tip124. The connecting segments130are curvilinear, extending both longitudinally and radially. For example, when viewed along a side as shown inFIG. 3, from a view perpendicular to the longitudinal axis, the connecting segments130appear as S-shaped.

In the stent frame400ofFIG. 3, the inner prongs112of the support ring102, the inner prongs212of the support ring202, and the inner prongs312of the support ring302are aligned with regard to their circumferential positions. Similarly, the outer prongs122of the support ring102, the outer prongs222of the support ring202, and the outer prongs322of the support ring302, are aligned. Thus, the radial depressions132(FIG. 2), which are defined radially outward from the inner prongs112and circumferentially between the connecting segments130at either side of each inner prong112of support ring102, align with depressions similarly defined by corresponding portions of the support ring202. The depressions132are also aligned with depressions similarly defined by corresponding portions of the support ring302. As such, exterior longitudinal channels432are defined by the stent frame400to cradle the first longitudinal arterial stent532aand second longitudinal arterial stent532bas shown inFIG. 4. Additional longitudinal side stents may be similarly cradled in the unfilled exterior longitudinal channels. Thus, these descriptions refer to the variable depression stent (VDS) frame300with respect toFIG. 3. With regard to the assembly shown inFIG. 5, which includes the VDS frame300, the first longitudinal side stent532a, the second longitudinal side stent532b, and the major cover graft502, these description refer to a variable depression stent (VDS) assembly500.

In the stacked arrangement of support rings102,202and302in the stent frame400ofFIG. 3, circumferential channels partially surround the longitudinal axis104. In particular, a first circumferential channel434is defined radially outward from the inner prongs112of the support ring102longitudinally between the outer prongs122of the support ring102and the outer prongs222of the support ring202. Similarly, a second circumferential channel436is defined radially outward from the inner prongs212of the support ring202and inner prongs312of the support ring302longitudinally between the outer prongs222of the support ring202and the outer prongs322of the support ring302. Thus the stent frame400has the inner diameter110along the circumferential channels434and436, corresponding to the inner diameter110of the support rings102,202,302in those circumferential portions corresponding to the circumferential summation angle140(FIG. 2). The stent frame400has the outer diameter120elsewhere, including full circular peripheries at the longitudinal positions of the outer prongs122,222and322, and partial circular peripheries subtending the angle142(FIG. 2) corresponding to the longitudinal and circumferential positions of the radially flat portions150,250and350of the support rings. Thus, the stent frame400has a radially flat portion450corresponding to the circumferential locations of radially flat portions150,250and350of the support rings.

The VDS assembly500is shown inFIG. 6along the longitudinal axis as viewed from above the upper longitudinal end520of the assembly inFIG. 5. A billowing aspect of the major cover graft502can be understood from viewingFIG. 6. In the illustrated neutral state of the major cover graft502as shown inFIG. 6, a waving state of the graft502is seen due to the major cover graft502following a waving peripheral path around the stent frame400. The path length of the waving peripheral path of the major cover graft502is greater than an outer circumference of the stent frame400as prescribed by the outer diameter120defined by the outer prongs122,222and322of the support rings100,200and300. As such, when the stent frame400is in its diametrically neutral state as shown inFIG. 6, excess material of the graft502billows.

In particular, portions of the graft502overlying the circumferential positions of the exterior longitudinal channels432defined by the stent frame400are shown as billowed inward inFIG. 6. Portions of the graft502overlying the circumferential positions of the outer prongs122,222and322(see alsoFIG. 3), are maintained radially outward from the longitudinal channels432.

In use in which, for example, blood flows along central fluid flow channel504toward the lower longitudinal end522of the VDS assembly500, the graft502is expected to billow outwardly to contact arterial or aortic tissue along the exterior of the graft502. The side stents532aand532bare supported and localized within the longitudinal channels432between the major cover graft502and the tissue. This facilitates blood flow within the longitudinal fluid flow channels506aand506bdefined within the side stents532aand532b. The billowing properties of the graft will create a complete seal along the side stents532aand532b. As such, these descriptions refer to the VDS assembly500as having a billowing graft, referring to the billowing aspect of the major cover graft502.

Assembly of the billowing graft VDS assembly500, and other billowing graft VDS assemblies within the scope of these descriptions, can be understood in view ofFIGS. 7-9. InFIG. 7, the stent frame400ofFIG. 3in its neutral state is shown longitudinally aligned with a mandrel700. The mandrel700has alternating lesser and greater diameter portions. In particular, the mandrel has circumferential channels734and736defining lesser diameter portions corresponding to the circumferential channels434and436of the stent frame400at the longitudinal positions of the inner prongs112,212and312of the support rings102,202,302. The remainder of the mandrel700defines greater diameter portions corresponding to the remainder of the stent frame400, particularly the longitudinal positions of the outer prongs122,222and322of the support rings102,202,302. The lesser diameter710of the mandrel at the lesser diameter portions defined by the circumferential channels734and736is greater than the inner diameter110of the stent frame400in its neutral state (FIGS. 3 and 7). Similarly, the greater diameter720of the mandrel at the greater diameter portions is greater than the outer diameter420of the stent frame400.

Thus, the stent frame400and each support ring102,202and302is diametrically expanded onto the mandrel700inFIG. 8. In the expanded state ofFIG. 8, the stent frame400is ready for assembly with the graft502in a relatively taut condition of the graft. Once the graft is attached to the stent frame400in the expanded state, the stent frame400and graft502are removed from the mandrel as one piece, for example by removal of the mandrel from either longitudinal end of the stent frame400and graft502. By resilient properties of the stent frame400and each support ring102,202and302, the stent frame400returns to the neutral state ofFIG. 6, in which the waving state of the graft502is seen to show the billowing aspect of the major cover graft502as described with reference toFIG. 6.

The graft502generally maintains the support rings102,202and302as approximately concentric with the longitudinal axis and spaced along the longitudinal axis as shown inFIG. 3according to their longitudinal positions on the mandrel700when the graft502is attached.

As shown inFIG. 9andFIG. 10, in at least one embodiment the graft502includes pockets516along its interior side518(FIG. 10) at positions corresponding to the locations of the outer prongs122,222and322in the diametrically expanded state of the stent frame400when mounted on the mandrel700as shown inFIG. 8. The pockets516receive the prong tips to maintain attachment of the graft502to the stent frame400, for example as shown particularly inFIG. 9with regard to the tips124of the outer prongs122of the support ring102and the tips224of the outer prongs222of the support ring202. The graft502has circumferential excess relative to the circumference of the stent frame400prescribed by the outer diameter320when the neutral state of the stent frame is reached, for example upon removal from the mandrel700. By registering the graft502with the stent frame400at discrete attachment points about the circumference of the interior side518, the circumferential excess of the graft502is circumferentially distributed as waves as seen in the graft502inFIG. 6, and the billowing aspect of the major cover graft502is distributed and facilitated along its periphery.

Additionally, the graft502may be sewn to the stent frame400or attached in any other appropriate manner such as glue, suturing, lamination, or a mechanical fastener such as a clip. Thus, various attachment steps may be carried out while the, stent frame400and graft502are engaged with the mandrel700.

These descriptions refer here to materials and making of the support ring102, noting that the support rings202and302can be similarly made. In at least one embodiment, the support ring102is made of a memory shape wire, such as nitinol. Other biocompatible materials may be used. The memory shape wire is formed and heat treated in a fashion to create longitudinal and radial support. The ring102is formed such that the outer prongs122exert an outward radial force. In the illustrative embodiment, the outer prongs122exert a higher radial force than the inner prongs112.

The variation in radial force may be accomplished in a variety ways. For example, the outer prongs122may have a different Austenite finish temperature (“Af”) than inner prongs112. To do so, the inner prongs112would be insulated/masked during a high temperature and time heat set-processing. The entire ring102would be heated to a certain temperature before the inner prongs112are masked or insulated. The outer prongs122would then be exposed to a more aggressive heat-set process to achieve a high radial force, while the masking of the inner prongs112would result in a lower radial force. In at least one embodiment, the high radial force area would have an Af<30 degrees Celsius and the lower radial force area would have an Af somewhere in the range of 35-39 degrees Celsius.

Another method of achieving the variation in radial force may be to electropolish the entire ring102up to a certain point. The outer prongs122may then be masked before further electropolishing of the inner prongs112, thereby making the wire thinner in diameter in that section and resulting in a lower radial force. It should be appreciated that a combination of these two approaches may also be used. Additionally, in other embodiments, the radial force exerted by the outer prongs122may vary such that the force exerted by some of the outer prongs122is less than the force exerted by the inner prongs112. Similarly, the radial force exerted by the outer prongs122may vary such that the force exerted by some of the inner prongs112is greater the force exerted by the outer prongs122.

Whether made by these described materials and methods or others, the stent frame400is somewhat flexible, for example in order to stretch onto the mandrel700, and is resilient so as to return to its neutral dimensions to facilitate the billowing aspect of the major cover graft502. The flexible and resilient properties of the stent frame400also facilitate that the VDS assembly500conforms to shapes and dimensions of surrounding biological tissue in use while the side stents532aand532bare supported and localized within the longitudinal channels434between the cover graft502and the tissue.

A stent frame according to these descriptions as flexible and resilient so as to return to neutral dimensions refers both to diametrically contracting to neutral dimensions after being diametrically expanded and diametrically expanding to neutral dimensions after being diametrically compressed. For example, upon removal from the mandrel700, the stent frame400, the stent frame diametrically contracts to neutral dimensions. Conversely, if diametrically compressed, the stent frame400is resiliently self-biased toward neutral dimensions and bears outward force upon any outer structure or tissue that constrains the stent frame400to less than its neutral diameter. This feature facilitates that a VDS stent assembly including such a frame conforms to anatomical dimensions to assure against endoleaks.

In at least one example, in which a first installed stent frame requires further support, a second self-expanding stent frame is inserted into the first self-expanding stent frame. For example, if anatomical dimension change over time after first installment of a frame-supported stent assembly, a second stent frame can be subsequently installed within the first stent frame. The second self-expanding stent frame then bears gentle outward force upon the interior of the first stent frame, further supporting the stent assembly, increasing the diameter of the first stent and urging it to conform to the new anatomical dimensions.

In the illustrated embodiment, the support ring102has eight (8) radial depressions132as shown inFIG. 2. The support rings202and302also have eight radial depressions each, such that the stent frame400has eight exterior longitudinal channels432. In other embodiments, a stent frame otherwise within the scope of these descriptions can have more than or less than eight exterior longitudinal channels.

Support rings102,202and302are illustrated as having the same inner diameters such that the stent frame400has the same inner diameter110defined by the inner prongs of each support ring. Similarly, support rings102,202and302are illustrated as having the same outer diameters such that the stent frame400has the same outer diameter120defined by the outer prongs of each support ring. In other embodiments, the dimensions of support rings along the length of a stent frame can vary, for example to suit the various anatomies of different patients. In at least one embodiment, the inner diameter110of the stent frame400is approximately thirty (30) millimeters and the outer diameter120is approximately thirty eight (38) millimeters. While the stent frame400is illustrated to have three support rings as shown inFIG. 3, other embodiments of stent frames within the scope of these descriptions can have any number of support rings.

Referring now toFIGS. 5 and 6, the stent frame400is shown with a covering described as the major cover graft502. This design and variations thereof are useful, for example, in endovascular reconstruction of the aorta wherever major aortic branches are involved. This includes the ascending aorta and the coronary arteries, the aortic arch and its branches, the thoracoabdominal aorta and the visceral arteries, the common iliac artery, and the hypogastric artery. Stent frames and grafts within the scope of these descriptions are useful in these and other anatomical regions.

The major cover graft502is used on the external surface of the stent frame400. The graft502may be formed as covered Z stents, mesh wire, braided stents and other constructions of stent like material and biologically inert coverings (e.g. PTFE, polyester, ePTFE etc.) impermeable to blood and serum. The major cover graft502covers the stent frame400partially or completely along its length or circumference. Once the graft502is applied to the stent frame400, the graft502defines walls of the exterior longitudinal channels432along which different branches of the aorta may be accessed and cannulated. The side stents532aand532band other stents and grafts can be placed in fluid communication with central fluid flow channel504. Thus, connections can be made through the major cover graft502to aortic branches such as coronary arteries, aortic arch branches, visceral branches and hypogastric arteries.

For example, inFIG. 5, a fenestration510is formed through the major cover graft502of the VDS assembly500to receive a vessel512, which represents an artery such as a superior mesenteric artery (SMA) or a stent or stent graft. The fenestration510permits fluid flow from the central fluid flow channel504to enter the vessel512, defining a lateral flow channel514through the major cover graft502at the fenestration510and along the vessel512. Such fenestrations may be located anywhere along the graft502where technically feasible with respect to the support rings within the graft. In the illustrated embodiment, the fenestration510is located at the front center of the frame. The fenestration510and other fenestrations formed to access fluid communication with the central fluid flow channel504may have various diameters and may be shaped as circular, oval, or other shapes. In the illustrated embodiment, the fenestration510represents an opening formed through the material of the major cover graft502in a location that does conflict with the support rings of the stent frame. In particular, the fenestration510is formed at a longitudinal and circumferential location between outer prongs222of the longitudinally central support ring202of the three support rings102,202and302of the support frame300. The fenestration510for an SMA vessel, stent, or graft is formed at a circumferential location corresponding to the radially flat portion450of the stent frame400.

While the stent frame400is illustrated to have three support rings as shown inFIG. 3, other embodiments of stent frames within the scope of these descriptions can have any number of support rings. Furthermore, while the support ring102has alternating inner prongs112, outer prongs122, radial depressions132, and a radially flat portion150, other embodiments of support rings within the scope of these descriptions can have other geometric configurations.

For example, a stent frame800according to at least one embodiment is shown inFIG. 11. The stent frame800includes, in order from top to bottom in the drawings, a first frustoconical support ring810, a first single diameter support ring820, the support ring102, the support ring302, a second frustoconical support ring830, a second single diameter support ring840, and a third single diameter support ring850. The stent frame800is configured to support a multi-path stent assembly having a longitudinal axis802along which a central fluid flow channel804is defined for blood flow in a downstream direction from a first end defined by the first frustoconical support ring810to a second end defined by the third single diameter support ring850. The stent frame800advantageously has a first diameter reduction at the first frustoconical support ring810and a second diameter reduction at the second frustoconical support ring830, such that flow along the central fluid flow channel804may be reduced by one or more flow channels that branch from the central fluid flow channel804in a stent assembly supported by the stent frame800. In at least one embodiment, the first longitudinal end of the stent frame800defined by the first frustoconical support ring810constitutes the cranial end of the stent frame800with reference to human anatomy, and the second longitudinal end defined by the third single diameter support ring850constitutes the caudal end of the stent frame800.

The first frustoconical support ring810is formed as a Z-stent having a first end812with a diameter greater than that of a second end814. The first end812is defined by turning points of the Z-stent extending outward from the longitudinal axis802. The second end814is defined by turning points of the Z-stent extending inward from the longitudinal axis802.

The single diameter support ring820is formed as a Z-stent in which turning points are equidistant from the longitudinal axis802. The support ring102and the support ring302are detailed in the preceding descriptions with reference toFIGS. 1-3.

The second frustoconical support ring830is formed as a Z-stent having a first end832with a diameter greater than that of a second end834. The first end832is defined by turning points of the Z-stent extending outward from the longitudinal axis802. The second end834is defined by turning points of the Z-stent extending inward from the longitudinal axis802.

The single diameter support rings820,840, and850are formed as Z-stents in which respective turning points are equidistant from the longitudinal axis802, defining a single respective diameter for each ring. The second and third single-diameter support rings840and850are illustrated having the same diameter in the stent frame800. The first single diameter support ring820is illustrated as having greater diameter than the second and third single-diameter support rings840and850, which are downstream of the diameter-reducing second frustoconical support ring830relative to the first single diameter support ring820.

Similar to the way the stent frame400ofFIG. 3can be covered with the major cover graft502, the stent frame800can be covered with a variety of coverings, at least three of which are represented inFIGS. 16-18. In each, the illustrated upper end represents the upstream longitudinal end of the stent assembly, and the illustrated lower end represents the downstream longitudinal end. In use, each serves as an endograft in which blood flows downstream through the longitudinal central channel of the stent assembly from a greater diameter upstream end to a lesser diameter downstream end, and one or more branches may direct blood flow from the central channel. For use in the aorta, the upstream end constitutes the cranial end of the stent frame800with reference to human anatomy, and the downstream end constitutes the caudal end of the stent frame800.

To attach the upstream end of the stent frame to host tissue, stabilizing elements may be connected to the first frustoconical support ring810as shown inFIGS. 12-15. As shown inFIG. 12, stabilizing elements860extending from the upstream end of the support ring810define a crown for engaging tissue. As shown inFIGS. 13 and 14, each stabilizing element869is wrapped around a respective prong816of the support ring810and formed from memory shape wire or stainless steel wire. Each stabilizing element860includes a barb862or hook that is uncovered and serves to fixate the endograft and add stability against the aortic wall.

Each stabilizing element860also includes a limb864(FIG. 13) that is covered by the covering material870inFIG. 15. As shown inFIG. 13-14, the limb864is positioned between the prongs816of the support ring810. The attachment point866of the stabilizing element860acts as a fulcrum for the limb864. In use, the barbs862engage the aorta, while the limbs864push outward against the covering material870as shown inFIG. 15to seal the covering material870against the aorta. In that way, the limbs864act as biasing elements. The covering material870represents, for example, the upper end of any one of the coverings shown inFIGS. 16-18.

Each stabilizing element860may be formed separately from stainless steel or other metal. It can be laser cut in whole together with the support ring810. The stabilizing elements860may be individually wrapped around a prong816. The shape of the element860as depicted allows for one end of the wire to “hook” into the aortic wall, thereby stabilizing the device and preventing migration of the endograft. The caudal end of the limb864will have an eccentrically directed angle and this portion of the wire will be located on the inside aspect of the graft coverage, in this embodiment the PTFE. By positioning the caudal end of the limb864at an angle in between each pair of prongs816, the endograft coverage will be pushed externally against the aortic wall to create additional points of contacts and seal. In addition, if the limbs864are captured towards the center of the graft with the delivery system, they can restrain the top stent and make the device easier to control.

InFIG. 16, a stent assembly900includes the stent frame800and a covering902sheathing the stent frame. The covering902is shown without any fenestrations. In this embodiment, the stent assembly900can be used below the kidney vessels.

InFIG. 17, a stent assembly1000includes the stent frame800and a covering1002sheathing the stent frame. The covering1002is shown with a single fenestration1004illustrated as a rectangular slot in the cranial end of the covering1002. The slot has an open cranial end1006such that the upper edge of the covering1002, interrupted by the open cranial end of the slot, partially surrounds the frame800. In this embodiment, the stent assembly1000can be used for aneurysms below the superior mesenteric artery (SMA). In such use, the single fenestration1004is used for both celiac artery and SMA stents or grafts.

InFIG. 18, a stent assembly1100includes the stent frame800and a covering1102sheathing the stent frame. A first fenestration1104is illustrated as a rectangular slot in the cranial end of the covering1102, in which the slot has an open cranial end1106such the upper edge of the covering1102, interrupted by the open cranial end of the slot, partially surrounds the frame800. A second fenestration1110is illustrated as a circular hole in the covering1102. In this embodiment, the stent assembly1100can be used for aneurysms below the celiac artery. In such use, the first fenestration1104and the separate second fenestration1110are used respectively as separate access fenestrations for the celiac artery and SMA stents or grafts. InFIG. 18, a portion of the far side of the stent frame is visible through the fenestration1110

InFIG. 18, a fenestration support ring1120surrounds the second fenestration1110. The fenestration support ring1120can be, for example, an eight (8) millimeter diameter ring formed from nitinol or other biocompatible materials, or can be constructed, for example, as described below with reference toFIG. 19. Placed around the second fenestration1110inFIG. 18, the fenestration support ring1120in at least one use receives and stabilizes the fenestration support of a branch in fluid communication with the stent assembly1100such as an SMA vessel or an SMA stent or graft.

The fenestration support ring1120may also serve as a radio-opaque marker during the placement procedure of the stent assembly1100. In such use, the fenestration support ring1120serves as “point zero” for the positioning and deployment of the stent assembly1100, or any stent assembly in which the fenestration support ring1120is included. Advantageously, the fenestration support ring1120for such use can be constructed of or with materials visible under X-ray or other medical imaging techniques.

A particular exemplary construction for the fenestration support ring1120is represented inFIG. 19. The fenestration support ring1120constructed as illustrated can serve as a radio-opaque marker. The fenestration support ring1120in this embodiment includes two supports1122formed as half-circles from a memory shape wire. Nitinol and/or other materials with the similar properties can be used to form the half-circle supports. The supports1122are wrapped with singular or multiple turns1124of a thin radio-opaque marker material such as platinum. The supports1122are connected by crimping their ends with connectors1126. In the illustrated embodiment, each connector1126is formed from gold, which also acts as a radio-opaque marker. In that way, the connectors1126and turns1124are visible on an x-ray image. The fenestration support ring1120therefore illustratively stabilizes the fenestration1110and makes the fenestration visible on an x-ray image. The marker1120may be connected to the frame800via glue or other adhesive, stitching, or heat treatment.

FIG. 20is a perspective view of a stent frame1200according to at least one embodiment.FIG. 21is a perspective view of an endograft stent assembly1300that includes the stent frame1200at least partially covered by a graft1304. The design and geometrical shape of the endograft stent assembly1300permits separate access to the renal arteries, thus facilitating use with many anatomical variations of juxtarenal and suprarenal aneurysms. The design allows for placement of parallel covered renal stents while reducing the likelihood of an endoleak along the renal stents, and reduces the risk of kinking and compression of the renal stents. When the outside of a graft is covered or partially covered with fibers of thrombogenic material, the external force that parallel stents exert on the graft and its thrombogenic material creates longitudinal grooves that seal along the parallel stents.

The stent frame1200can be constructed of a metal alloy, including a memory shape wire such as nitinol. Other biocompatible materials may be used. In at least one example, the memory shape wire is cut and heat treated in a fashion to create longitudinal and radial support. The stent frame1200includes circumferential wires1202shaped to define circumferential waves that are aligned longitudinally to define longitudinal channels. A radial variation is defined between the crests (radial maxima) and nadirs (radial minima) of the circumferential waves. In at least one example, the radial variation is approximately three (3) millimeters. In other examples, the radial variation may be in the range of two to four (2-4) millimeters. The circumferential distance between the crests can be, for example, in the range of three to fifteen (3-15) millimeters. Like the stent frame400that includes a radially flat portion450(FIG. 3), the stent frame1200has a radially flat portion for locating an SMA vessel, stent, or graft that branches from the interior of the endograft stent assembly1300.

The stent frame1200includes longitudinal wires1204that extend between the circumferential wires. Each circumferential wire1202is spaced, for example at 5-20 mm, from the next and has a wave shape to define the longitudinal channels. The circumferential positions of the longitudinal wires1204alternate in a staggered fashion.

The endograft stent assembly1300includes a fenestration support ring1320, which, in the illustrative embodiment, is an 8 mm nitinol ring. The fenestration support ring1320is positioned or created within the stent frame1200with its center point at approximately thirty four (34) millimeters below the top edge1302of the stent1300. The fenestration support ring1320in at least one use receives the visceral or SMA stent placed during the placement procedure. The fenestration support ring1320also serves as “point zero” for the positioning and deployment of the endograft stent assembly1300. A second ring (not shown) may be positioned cranial of the SMA fenestration support ring1320, with its center approximately fifteen (15) millimeters cranial to the fenestration support ring1320. The center of the second ring may be at 12:30 clock position relative to the SMA fenestration support ring1320, and the diameter of the second ring may measure between eight and ten (8-10) millimeters.

The stent frame1200may be formed as one unit. In at least one embodiment the stent frame1200approximately one hundred (100) millimeters in longitudinal length. The proximal aspect of the stent frame1200is wavy tubular extending thirty four (34) millimeters proximal to the center point of the visceral or SMA fenestration support ring1320. The distal aspect extends fourteen (14) millimeters below the center point of the SMA fenestration support ring. At this level, the stent frame1200includes a distal extension1210that funnels to eighteen (18) millimeters or more in diameter over a distance of ten to twenty (10-20) millimeters. This distal extension1210is approximately fifty to sixty (50-60) millimeters long, with at least the most distal forty (40) millimeters measuring at least eighteen (18) millimeters in diameter. In at least one embodiment, the most anterior portion of the proximal part of this stent frame1200is curved flat and does not have any waves or channels.

As shown inFIGS. 20 and 21, the stent frame1200includes a crown of barbed stents1220extending from its top edge1222at its most cranial aspect. In the endograft stent assembly1300, the barbed stents1220are uncovered and serve to fixate the endograft stent assembly and add stability against the aortic wall. Each barbed stent1220is formed of memory shape wire. In one embodiment, the barbed stents1220are formed in a figure-of-eight fashion with the top of the component containing a hook facing the external surface of the stent. In another embodiment, the hook may be attached to the proximal end of a wire. The middle of the wire is equipped with a small round hole for placement of a trigger wire. The barbed stents1220are shaped to extend outwards to a 45 degree angle on the horizontal plane upon deployment.

In the illustrated embodiment ofFIG. 21, the graft1304is partially covered with microfibers or other thrombogenic material1310along the 3 and 9 o'clock aspects of it, with the center of the fenestration support ring1320defining 12 o'clock. The microfibers1310assist in filling any remaining gutters as a source of endoleak along parallel renal stents. In other embodiments, hydrogel or other sealing materials may be used to coat the external surface of the endograft in order to fill in any gutters alongside the parallel renal stents. A fenestration1330is defined by the graft1304as a rectangular slot in the cranial end of the graft, in which the slot has an open cranial end. A second fenestration is illustrated as a circular hole in the graft1304in a location corresponding to the SMA fenestration support ring1320. In use, the fenestration1330and the separate second fenestration are used respectively as separate access fenestrations for the celiac artery and SMA stents or grafts.

FIG. 22is a perspective view of a stent frame1400according to at least one embodiment.FIG. 23is a perspective view of an endograft stent assembly1500that includes the stent frame1400at least partially covered by a graft1502.

FIGS. 24 through 28illustrate components of an iliac limb assembly1600. All dimensions given in these descriptions correspond at least to one embodiment without limiting the scope of these descriptions to one such embodiment.

InFIGS. 24 and 25, a dual channel tubular stent is shown including graft material, such as ePTFE, supported by Z-stents. The dual channel stent has two internal channels separated longitudinally by a septum1602, for example for a distance of five (5) millimeters or more. The septum1602is shown in longitudinal end view inFIG. 25. The diameter of the upstream dual channel part of the tubular stent is twenty six (26) millimeters to twenty eight (28) millimeters in at least one example. The main tube divides, for example after the first five (5) millimeters, into two approximately cylindrical tubes1604and1606, one longer than the other, each measuring approximately thirteen (13) millimeters in diameter in at least one example. The longer tube1604extends in at least one example for a distance of at least one hundred (100) millimeters. The shorter tube1606extends in at least one example for approximately twenty (20) millimeters. In at least one particular use, the longer tube1604constitutes a first iliac limb stent for connecting a first side or channel of the dual channel tubular stent to a first iliac artery. In that example, the shorter tube1606constitutes a junction by which a second iliac limb stent1608(FIG. 8), for connection to a second iliac artery, can be connected to the second side or channel of the dual channel tubular stent.

A graft tube1610reinforced with Z stents is shown inFIG. 26. Combining the structures ofFIGS. 24 and 26, by placing the graft tube1610(FIG. 26) around the upstream dual channel part of the tubular stent (FIG. 24) produces an iliac bifurcation device1600(FIG. 27) that can be moved cranially and caudally within the main body of the endograft1500shown inFIG. 23. This will help in controlling and adjusting the location of the placement of the iliac limb stents1604and1608in the iliac arterial system.FIG. 28shows the second iliac limb stent1608for engagement with the shorter tube1606inFIG. 24.

By placing the iliac bifurcation at a maximum cranial location possible within the iliac limb system as illustrated and described here, there is room to move the second iliac limb stent1608up or down and adjust the desired length remaining for engagement with an iliac artery. The two flow channels for the two iliac limb stents1604and1608are separated by the septum1608throughout the upstream dual channel part of the tubular stent. The septum1602prevents the upstream cranial end of the second iliac limb stent1608, as the position of the stent1608is adjusted, from obstructing the flow entering the first iliac limb stent1604on the other side of the septum1602. This permits a range of human anatomy dimensions to be served by one set of components (FIGS. 24-28).

FIG. 29illustrates a multi-branch stent assembly1700in a state of partial assembly or installation, with the longer first iliac limb stent1604in engagement, at its caudal downstream end, with a first iliac artery.FIG. 30illustrates the multi-branch stent assembly1700ofFIG. 29, in use in a human aorta, with the second iliac limb stent1608in engagement, at its caudal downstream end, with the second iliac artery. InFIGS. 29 and 30, the multi-branch stent assembly1700includes the stent assembly1000ofFIG. 17.

To achieve the installation shown inFIG. 30, the stent assembly1000is first installed. In at least one such example, a fenestration support ring or other radio-opaque marker serves as “point zero” for the positioning and deployment of the stent assembly1000, during the placement procedure in order to properly place the stent assembly for engagement with the anatomical SMA and celiac artery.

Lower portion of side stents523aand523bare then engaged with the renal arteries as shown inFIG. 30, with upper longitudinal portions of the side stents523aand523bcradled within and supported by the exterior longitudinal grooves of the stent assembly1000.

Subsequent to installation of the stent assembly1000, the first iliac limb stent1604can be positioned in different locations by the telescoping engagement of the upstream end of the dual channel tubular stent with the downstream end of the stent assembly1000. The adjustable telescoping engagement of the dual chamber stent with the stent assembly1000defines a functional length adjustment for the first iliac limb stent1604relative to the engage first iliac limb artery. The position of the dual chamber tubular stent is selected to engage the first iliac limb stent1604with the first iliac limb artery. Once the engagements ofFIG. 29are achieved as desired, the second iliac limb stent1608can be engaged with the second iliac artery as shown inFIG. 30.

Thus, an endovascular device (endograft) for treatment of complex abdominal aneurysms involving the kidney vessels is provided. The device can go above the kidney vessels, while blood flows to the kidneys and the gut vessels are preserved. In the parallel endograft technique in which stents523aand523bare installed alongside the aortic endograft, the aortic endograft does not crush the kidney stents or create gutters that may otherwise cause leaks of blood alongside the grafts. These are advantages of these variable depression stent (VDS) and billowing graft assemblies.

FIG. 31is a longitudinal end view of a tunneled graft stent assembly1800according to yet another embodiment in which multiple longitudinal channels defined by a first circumferential graft are covered by a second circumferential graft1802to form tunnels. InFIGS. 5 and 6, open longitudinal channels432are defined along the exterior of the graft502, and the longitudinal side stents532aand532bmay be laterally supported by the aortic wall in some uses. InFIG. 31, the graft502is further covered by a second graft1802and covered longitudinal tunnels1832are defined between the inner graft502and outer graft1802. The covered longitudinal tunnels1832may constitute stents or receiving stents therein inFIG. 31in lieu of, for example, the longitudinal side stents532aand532binFIGS. 5 and 6. In the tunneled graft stent assembly1800, parallel flow channels defined in the longitudinal tunnels don't require further lateral support and thus the tunneled graft stent assembly1800may be placed within an aneurysm.

As illustrated inFIG. 32, device1800is shown for thoracoabdominal device placement. As illustrated, device1800is placed in a thoracoabdominal area and renal stents1850are extending into the tunnels1832, and the celiac1854and SMA1856are also received within the device. Members1608interconnect the iliac arteries as previously described. In this manner, the parallel stents1850don't need lateral support and this allowed the device1800to be placed in the middle of an aneurysm.

FIG. 33is a longitudinal end view of a stent assembly1900with an inflatable seal component1902according to at least one embodiment. In at least one example, the stent assembly1900has an inflatable component1902on a graft1904. The inflatable component1902has a deflated state and an inflated state. The assembly1900with one or more inflatable seal components1902can be put in place, with the inflatable component1902in its deflated state, together with parallel stents1906. When the assembly1900is placed, and the inflatable seal component1902is inflated as shown inFIG. 33, longitudinal grooves are formed around the parallel stents1906. The infusion of the inflatable component1902with special polymers while the parallel stents1906are in place will create longitudinal grooves along the parallel stents1906after the polymers harden inside the inflatable component1902.

Particular embodiments and features have been described with reference to the drawings. It is to be understood that these descriptions are not limited to any single embodiment or any particular set of features, and that similar embodiments and features may arise or modifications and additions may be made without departing from the scope of these descriptions and the spirit of the appended claims.