WO2014096810A1

WO2014096810A1 - Modular fenestrated assembly

Info

Publication number: WO2014096810A1
Application number: PCT/GB2013/053328
Authority: WO
Inventors: Robbie BRODIE; Vincent NELIS
Original assignee: Vascutek Limited
Priority date: 2012-12-18
Filing date: 2013-12-17
Publication date: 2014-06-26
Also published as: GB201222852D0

Abstract

A main graft (2) for a modular fenestrated assembly (1) consists of a graft sleeve having first and second ends (9 A, 9B), with a lumen extending therethrough, and bifurcated at a junction (6) to form two docking zones (8A, 8B), such that the lumen of the graft sleeve is divided into two smaller lumens after the bifurcation junction (6). The main graft (2) includes ring stents (7) located at end (9A) and on each docking zone (8A, 8B) at end (9B). The stents (7) may be attached to the graft sleeve by sewing. Leg grafts (3, 4) are sealingly engageable with either docking zone (8A, 8B) in zone (20), for example by expansion of a stent (7) at respective first ends (10A) of the first and second leg grafts (3, 4). A fenestration (5) is provided in either leg graft (3, 4).

Description

MODULAR FENESTRATED ASSEMBLY

The present invention relates to a modular stent graft assembly, and in particular to a modular fenestrated stent graft assembly for deployment by endovascular delivery.

Artificial prostheses consisting of a tubular conduit having an open lumen are well- known and are used in medicine to replace diseased or damaged natural body lumens, such as, for example, blood vessels or other hollow organs for example bile ducts, sections of intestine or the like. The most common use of such artificial prostheses is to replace diseased or damaged blood vessels.

A number of vascular disorders can be treated by use of an artificial prosthesis. One relatively common vascular disorder is an aneurysm. Aneurysm occurs when a section of natural blood vessel wall, typically of the aortic artery, dilates and balloons outwardly. Whilst small aneurysms cause little or no symptoms, larger aneurysms pose significant danger to a patient. Rupture of an aortic aneurysm can occur without warning and is usually fatal, so significant emphasis is placed on early diagnosis and treatment. With an increasingly ageing population, the incidence of aneurysm continues to rise in western societies.

Provided that an aneurysm is diagnosed prior to rupture, surgical treatment to repair the affected vessel wall is effective. Surgical treatment of aneurysm involves the replacement or reinforcement of the aneurismal section of aorta with a synthetic graft or prosthesis under general anaesthesia allowing the patient's abdomen or thorax to be opened (see Parodi et al., Annals of Vascular Surgery (1991) 5:491- 499). The patient will then have a normal life expectancy. Surgical repair of aneurysm is however a major and invasive undertaking and there has been much effort in developing less invasive methods. Currently, aneurysm repair generally involves the delivery by catheter of a fabric or ePTFE graft which is retained at the required location by deployment of metallic devices (stents). The ability to deliver the stent-graft device by catheter reduces the surgical intervention to a small cut-down to expose the femoral artery and, in suitable circumstances, the device can be deployed percutaneously. Catheter delivery is beneficial since the reduced invasive nature of the procedure allows utilisation of a local anaesthetic and leads to reduced mortality and morbidity, as well as decreased recovery time. For example, endovascular repair is typically used for repair of infra-renal abdominal aortic aneurysms where the graft is placed below the renal arteries. Many different types of devices useful for endovascular repair are now available, for example a resiliently engaging endovascular element described in US 6,635,080 (Vascutek) or a tubular fabric liner having a radially expandable supporting frame and a radiopaque marker element stitched to the liner as disclosed in US 6,203,568 (Medtronic). However, whilst the endovascular repair of aneurysms is now accepted as the method of choice, the technique has significant limitations and is not suitable for all patients.

Endovascular techniques involve the delivery of the prosthesis by catheter. Since the internal lumen of the catheter defines the maximum dimensions of the prosthesis to be inserted, much effort has been expended in the design of prostheses which can be packaged in a minimal volume, and are easy to deploy once positioned at the required location. One successful type of prosthesis consists of a stent graft comprising a conduit formed of a flexible sleeve attached to a rigid support or stent. The sleeve will typically be made of a fabric (usually a knitted or woven fabric) of ePTFE, PTFE, polyester (for example DACRON), polyethylene or polypropylene and may optionally be coated to reduce friction; discourage clotting or to deliver a pharmaceutical agent. The fabric will generally be porous on at least one surface to enable cell ingrowth. The stent may be balloon-expandable (eg. a PALMAZ stent made of rigid stainless steel wire), but could also be self-expandable and formed of a shape memory material, such as nitinol (a nickel-titanium alloy). Numerous different stent designs are known in the art (see for example braided stents described in EP 880949 or wire zig-zag stents described in US 4580568). The stent grafts are inserted using a delivery catheter and, once correctly located at the site requiring treatment, are deployed by the withdrawal of a delivery sheath of the delivery catheter. Balloon-expandable grafts are then caused to expand in diameter by inflation of a balloon located within the lumen of the graft. Self- expandable grafts radially expand upon release from the delivery sheath. Irrespective of the mode of expansion, once deployed, the stents hold the graft in location by contact with the inner wall of the blood vessel.

Bifurcated stent graft prostheses are known in the art for treatment of abdominal aortic aneurysm at the lower end of the aorta close to its bifurcation into the left and right iliac arteries. The bifurcated stent graft used to treat an aneurysm at this location typically comprises a main body portion located in the aorta which extends across the aneurysm so that it can be fixed in place by expansion of a stent onto healthy aortic wall proximal to the aneurysm. The main portion of the graft divides into two smaller legs, each leg extending down one of the iliac arteries with the distal end of each leg also being fixed by expansion of a stent. For ease of deployment, one leg can be created by use of a separate leg extension with graft assembly occurring in vivo. See EP 1063945 and US 5676696.

Depending on the location of an aneurysm, the graft can be adapted to suit the location necessary. For example, where an aneurysm extends down an iliac artery, the graft can include a further arm directed to an internal artery of the iliac artery as described in WO 2007/124053. Alternatively, where the graft is to be located to span across the junction of an intersection (eg. with the renal arteries), the graft can include an opening (fenestration) for alignment with one of the branch vessel(s) (see for example WO 99/29262 or EP 1673038). However, to date such fenestrated grafts must be individually designed for each patient since the anatomy of the vessel branches can vary significantly. Production of unique, individually designed and manufactured endografts having appropriate branch grafts or fenestrations which match the patient's individual anatomy requires meticulous design based on accurate pre-operative imaging data. The use of patient-specific designed grafts is expensive and requires significant pre- planning so that such grafts are not available in emergency situations. Moreover, the technical difficulties of aligning the fenestration to the branch vessel are significant, requiring precise axial and rotational control of the graft. No adjustments to the graft are possible during deployment, so that any errors in the initial diagnostic imaging or any changes in anatomy from the imaging stages cannot be rectified. An alternative approach requires the deliberate coverage of the branch vessel, which is clearly undesirable.

The desirability of conducting in vivo (in situ) fenestration of a graft has been also recognised in the art. McWilliams et al., (J. Endovasc Ther (2004) 11:170-174) describe the fenestration of a thoracic graft by passing a guide wire down the branch artery to pierce the fabric of the graft and then expanding the hole formed by inflation of a balloon. However, whilst such techniques require percutaneous retrograde access to the branch vessel for correct location of the fenestration, such access is possible for branches of the aortic arch but not for visceral vessels such as the renal or mesenteric arteries. Moreover, the requirement for retrograde access increases the complexity of the procedure.

There continues to be a need for a graft suitable for deployment at or near a vessel intersection, which is suitable for a range of patient anatomy and which avoids both the requirement for individual design and in vivo fenestration.

The requirement for such fenestrated grafts can apply to any vessel intersection, including without limitation, the renal arteries, mesenteric artery, brachiocephalic artery, carotid arteries or left subclarion artery. Graft fenestration design is particularly difficult in locations where two or more intersections are located within the length of the graft. The present invention provides a modular stent graft assembly comprising:

i) a main graft having a main graft sleeve with a main lumen therethrough; ii) a first leg graft having a first leg sleeve with a first lumen therethrough; and iii) a second leg graft having a second leg sleeve with a second lumen therethrough;

wherein said first leg graft and said second leg graft each have a fixing means to sealing engage to the main lumen of said main graft sleeve, and wherein a fenestration is located in at least one of said first leg sleeve or said second leg sleeve. The term "fenestration" is defined herein as a hole or opening within a graft or prosthesis (for example in the sidewall of the graft or prosthesis) or to the process of producing such a hole or opening. The fenestration can have any shape including, but not limited to, rectangular, triangular or curvilinear (eg. circular, oval or the like). The fenestration allows fluid communication from the exterior of the graft to the lumen of the graft.

Optionally each fenestration can be bound at its periphery by a strand of resilient material, for example nitinol wire or a strand of PEEK. The strand of resilient material can be sewn around the boundary of the fenestration so that the fenestration is kept open and also so that the edges of the fenestration are prevented from fraying.

Each graft sleeve can independently be formed from any flexible and biocompatible material. A woven or knitted fabric is suitable. Optionally the material used to form each or all of the graft sleeves is substantially impervious to fluid. Optionally, at least one surface of a graft sleeve will be sufficiently porous to facilitate cell ingrowth. Suitable materials include polyester, polyurethane, polyethylene, polypropylene, ePTFE, PTFE and the like. Each or any of the sleeves can independently be coated to reduce permeability or to deliver a biological agent.

For many intended purposes, each or any of the graft sleeve(s) can independently be formed with a constant diameter. However tapered grafts (i.e. where the diameter varies along its length) are also possible and are particularly useful for certain indications. A taper can be useful in assisting adequate docking of a leg graft with the main graft. In one embodiment, the first leg sleeve of the assembly has a fenestration in the side wall thereof.

In one embodiment, the second leg sleeve of the assembly has a fenestration in the side wall thereof.

In one embodiment, the first leg sleeve has a fenestration in the side wall thereof and the second leg sleeve has a fenestration in the side wall thereof.

The main graft will have a first end and a second end. The main sleeve has a lumen extending therethrough and bounded by the sleeve side walls (formed of fabric). Depending on the location for deployment of the assembly, the first end of the main graft may be proximal (i.e. closer to the heart) or distal (i.e. away from the heart). One end of the main graft comprises two docking zones. One docking zone accommodates the first leg graft and the other docking zone accommodates the second leg graft.

The first leg graft will have a first and second end. The first leg sleeve has a lumen extending therethrough and bounded by the sidewall of the sleeve. Depending on the location for deployment of the assembly, the first end of the first leg graft may be proximal (i.e. closer to the heart) or distal (i.e. away from the heart).

The second leg graft will have a first and second end. The second leg sleeve has a lumen extending therethrough and bounded by the sleeve side walls (formed of fabric). Depending on the location for deployment of the assembly, the first end of the second leg graft may be proximal (i.e. closer to the heart) or distal (i.e. away from the heart). In use, the main graft will be introduced into a main body vessel of a patient and deployed therein. Generally, the main graft will be introduced using endovascular techniques. Each of the first leg graft and the second leg graft will then be introduced and deployed. The sequence of deployment of the first leg and the second leg graft is not critical, provided that each leg graft is deployed after the main graft. The first end of the first leg graft will be located within the main graft sleeve and sealed thereto, typically by expansion of a stent on the first leg graft to sealingly engage with the inner luminal surface the main graft sleeve. The first end of the second leg graft will be located within the main graft sleeve and sealed thereto, typically by expansion of a stent on the second leg graft to sealingly engage with the inner luminal surface the main graft sleeve.

In one embodiment, the main graft sleeve is bifurcated at its second end to form two smaller lumens, which each act as a docking zone for a leg graft. Each bifurcated portion of the main graft is known as a "short trouser leg" within the art.

Use of a separate leg graft to extend a "short trouser leg" in this manner is known in the art, for example as described in US 5676696. An (optionally fenestrated) leg graft can be located into a docking zone by placement of one end of the leg graft into the tubular portion of the docking zone, such that the leg graft end sealingly engages with the docking zone. Sealing engagement can be achieved by expansion of a stent at the end of the leg graft inserted into the docking zone. The leg graft can be docked into the tubular portion at any rotational angle, allowing alignment of the fenestration to a branch vessel independently to that of a fenestration in the other leg graft.

The main graft can be bifurcated into two docking zones, each having a smaller lumen than the main lumen. Optionally, at least one docking zone can comprise a tubular portion (able to receive a leg graft in a sealing engagement) and a flange extension. The tubular portion is equivalent to a "short leg" as described above. The flange extension is an extension of the tubular portion, for example is a length of fabric (typically a section of a cylinder) which forms an extended docking zone able to overlap a leg graft. The flange extension provides a simple means to allow the docking zone to be held during insertion of the leg graft. Thus, the flange extension can be held under gentle tension during leg graft delivery and expansion, so avoiding inadvertent inversion of the docking zone due to insertion of the leg graft. Optionally a loop can be present at the end of the flange extension so that it can be held during deployment of the leg graft.

Generally, the first leg graft and second leg graft are inserted into the main graft so that the fenestrations in either or each of the first and second leg grafts align with an intersection to a branch vessel to allow blood flow thereto. Location of the fenestration(s) in the leg graft(s) of the assembly (as opposed to in the main graft) provides greater flexibility to accommodate a wider range of branch intersection configurations.

Optionally, at least a portion of each leg graft is extendable in length. An extendable portion can be provided by the inclusion of annular folds in the graft sleeve and/or by the use of a stretchable fabric (i.e. woven or elasticated). Annular folds (corrugations) can be present in the first leg sleeve and/or the second leg sleeve. Optionally the annular folds can be produced by heat-setting or crimping the leg sleeve fabric. Accordingly the distance between the main graft and the fenestration can be varied independently for each leg. This has the advantage that placement of the main body graft relative to the branch vessel is not critical at deployment. Where each leg graft includes a fenestration, there is also the advantage that two branch vessels which are at different longitudinal and/or rotational locations within a patient can easily be accommodated by the assembly of the invention, since the position of each fenestration can be individually adapted as required.

In an embodiment of the assembly of the present invention the main body graft is to be located proximal of the vessel intersection. Use of separate, optionally fenestrated, leg grafts provide an ability to separately accommodate two branch intersections which vary from each other in longitudinal location, size and/or angular (rotational) location.

Generally, the main graft will also comprise at least one stent attached to the first end of the main graft sleeve. The first end will usually be the proximal end of the main graft sleeve (i.e. located closer to the heart) but this orientation can be reversed if required. After deployment, the stent attached to the first end of the main graft sleeve will expand against the luminal surface of the body vessel into which the main graft is deployed. The stent can be formed from any resilient biocompatible material, as known in the art. The stent can be balloon expandable or self-expandable. Suitable materials include metals (eg. stainless steel, nitinol) and polymers, particularly engineering high modulus polymers such as polyether ether ketone (PEEK). PEEK polymers with shape memory behaviour can be used. Exemplary stent configurations are known in the art and include wire mesh stents, helices, coils, rings and other suitable configurations; see US 4735645, US 6635080 and US 6203568.

Generally, the first leg graft will also comprise at least one stent attached to the first end of the first leg graft. The first end will usually be the proximal end of the first leg graft (i.e. located closer to the heart) but this orientation can be reversed if required. After deployment, the stent attached to the first end of the first leg graft will expand against the luminal surface of the second end of the main sleeve into which the first leg graft is deployed. The stent can be formed from any resilient biocompatible material, as known in the art. The stent can be balloon expandable or self-expandable. Suitable materials include metals (eg. stainless steel, nitinol) and polymers, particularly engineering high modulus polymers such as polyether ether ketone (PEEK). PEEK polymers with shape memory behaviour can be used. Exemplary stent configurations are known in the art and include wire mesh stents, helices, coils, rings and other suitable configurations.

Generally, the second leg graft will also comprise at least one stent attached to the first end of the second leg graft. The first end will usually be the proximal end of the second leg graft (i.e. located closer to the heart) but this orientation can be reversed if required. After deployment, the stent attached to the first end of the second leg graft will expand against the luminal surface of the second end of the main sleeve into which the second leg graft is deployed. The stent can be formed from any resilient biocompatible material, as known in the art. The stent can be balloon expandable or self-expandable. Suitable materials include metals (eg. stainless steel, nitinol) and polymers, particularly engineering high modulus polymers such as polyether ether ketone (PEEK). PEEK polymers with shape memory behaviour can be used. Exemplary stent configurations are known in the art and include wire mesh stents, helices, coils, rings and other suitable configurations.

Each stent can be independently formed of any suitable biocompatible material having the necessary resilience to fold inwardly into a first folded configuration (i.e. for packaging) and to adapt a second open configuration (i.e. after deployment).

Optionally, one or more ring stents can be attached to the first end of any or each of the main graft, first leg graft or second leg graft. The ring stents can each be formed from nitinol wire and will typically include multiple windings of nitinol wire. Each stent can be attached to the external surface of the graft sleeve or to the internal (luminal) surface of the graft sleeve. Generally, it is more convenient to attach the stents to the external (non-luminal) surface of the sleeve.

In one embodiment, the first end of the main graft sleeve comprises a pair of ring stents which, after deployment, together hold the graft sleeve in position within the body vessel. Optionally, the two stents can be formed of nitinol wire. The ring stent closest to the first end of the main graft sleeve can be of a shallow sinusoidal configuration, with the second ring stent (further along the graft sleeve) being of sinusoidal or circular configuration. Optionally, a stabilising stent member (or a pair of such members) as described in PCT/GB2012/051236 or GB 2491481can be located between the two ring stents. In one embodiment, the first end of the first leg graft sleeve comprises a pair of ring stents which, after deployment, together hold the graft sleeve in position within the main graft. Optionally, the two stents can be formed of nitinol wire. The ring stent closest to the first end of the first leg graft sleeve can be of a shallow sinusoidal configuration, with the second ring stent (further along the graft sleeve) being of sinusoidal or circular configuration. Optionally, a stabilising stent member (or a pair of such members) as described in PCT/GB2012/051236 or GB 2491481 can be located between the two ring stents. In one embodiment, the first end of the second leg graft sleeve comprises a pair of ring stents which, after deployment, together hold the graft sleeve in position within the main graft. Optionally, the two stents can be formed of nitinol wire. The ring stent closest to the first end of the second leg graft sleeve can be of a shallow sinusoidal configuration, with the second ring stent (further along the graft sleeve) being of sinusoidal or circular configuration. Optionally, a stabilising stent member (or a pair of such members) as described in PCT/GB2012/051236 or GB 2491481 can be located between the two ring stents.

The number of strands of wire in a ring stent can be varied according to the diameter of wire utilised and the size of graft. The number of strands wound can vary from 2 to 120 or even more, but would typically have 10 to 30 strands forming the ring stent. Any diameter wire which maintains the required resilience can be used. Suitable diameters for the wire can be selected from a range of 0.1 mm to 2 mm, for example 0.5 mm to 1 mm.

Each stent can conveniently be positioned externally of the graft sleeve.

Conveniently, each stent is attached to the graft sleeve by sewing, but any other suitable means of attachment to the graft sleeve (eg. adhesive or heat bonding) could alternatively be used. Optionally each leg graft can include a series of ring stents. Such stents can typically be formed of multiple windings of nitinol wire. Optionally the stents can be attached to the exterior of the first and/or second graft sleeve, by stitching, in a sinusoidal (saddle-shaped) configuration. Use of ring stent(s) on each leg graft is beneficial since the lumen is held in an open configuration whilst retaining the ability of the leg graft to be folded or concertinaed to allow adjustment of length.

A stent which is ring-shaped (annular) will have an inner circumference substantially identical to (preferably identical to) the outer circumference of the graft sleeve (the tubular graft). By "substantially identical to" we refer to a circumference which is equal to or up to 5% greater than the outer circumference of the graft sleeve, preferably which is equal to or up to 2% greater than the outer circumference of the graft sleeve and more preferably equal to or up to 1% greater than the outer circumference of the graft sleeve.

A stent which is sinusoidal or "saddle shaped" refers to a circular ring stent formed of a material which is sufficiently resilient to be distorted so that a first pair of diametrically opposed points on the circumference of the ring are displaced in one axial direction whilst a second pair of diametrically opposed points, centrally located on the circumference between the first pair, are displaced in the opposing axial direction to form a symmetrical saddle shape. For convenience, the first pair of points can be described as "peaks", with the second pair of points described as "valleys". The degree of axial displacement between the first pair of points and the second pair of points (which axial displacement is also termed the "saddle height"), is a function of the original circumference of the ring stent prior to its distortion, relative to the final circumference of a circle within which the distorted (saddle shaped) configuration can be located. Thus, the ratio of final circumference: original circumference provides a simplistic notation of the axial displacement. Generally the final circumference will be the outer circumference of the graft sleeve to which the stent is to be attached. The percentage oversize of the undistorted inner circumference of the circular stent relative to the outer circumference of the graft sleeve also gives a convenient measure of the saddle shape adopted, and can be calculated as:

Oversize % = [Stent inner diameter - Graft sleeve outer diameter] x 100%

Graft sleeve outer diameter

Optionally the first end of the main graft sleeve can comprise two stents: a first stent being a saddle-shaped stent and a second stent being a ring stent or saddle-shaped stent. Thus in one embodiment the main graft sleeve can comprise two saddle shaped stents. The terminal first stent can be formed of a continuous loop of resilient material (nitinol or PEEK or the like) having a sinusoidal (saddle) shape as described above. This first saddle shaped stent can have a saddle height of 4 to 8 mm and is conveniently located at one end of the graft sleeve. A second stent formed in a continuous loop and either in circular form with an inner circumference substantially identical to the outer circumference of the graft sleeve or in a sinusoidal shape (as described above for the first stent) is also present and is adjacent the first stent. The second stent can also be formed from resilient material (nitinol or PEEK or the like). The resilient material can be formed as an elongate strand and wound into a loop. Conveniently these two stents are spaced 5 to 13 mm apart (for example 5 to 8 mm at the closest point) and provide good sealing of the main graft against the luminal wall of the blood vessel.

Each of the first and second leg grafts can independently comprise 2, 3, 4 or 5 separate saddle shaped stents. Optionally the size of the valleys and peaks in the saddle shaped stents can increase monotonically between the stents. Optionally saddle shaped stents with two different saddle heights can be present, differentiated by their saddle height. For example one saddle shaped stent type can have a saddle height of 4 to 8 mm, and a further saddle shaped stent type can have a saddle height of 8 to 15 mm. The stents can be placed 12 to 25 mm apart. One or more stents of each saddle shape can be present. Conveniently the spacing of each stent in the first leg and/or second leg graft is such that the peak of one stent is traversely aligned with the valley of its immediate neighbour. Optionally, the peaks and valleys of each stent element are longitudinally aligned with the peaks and valleys, respectively, of its immediate neighbour. This arrangement provides increased axial and tensional stiffness.

Conveniently, the second leg and/or the first leg graft can also include at least one stent at its end, which stent is able to seal against the luminal surface of the body vessel.

Additionally or alternatively the distal end of each or either leg(s) can include a "locking ring" and/or a taper to provide a docking zone for a further leg extension.

The components of the assembly can each be inserted into the patient using a delivery catheter and, once correctly located at the site requiring treatment, deployed by the withdrawal of a delivery sheath of the delivery catheter. Balloon- expandable grafts are then caused to expand in diameter by inflation of a balloon located within the lumen of the graft. Self-expandable grafts radially expand upon release from the outer tube. Irrespective of the mode of expansion, once deployed, the stents hold the main graft in location by contact with the inner walls of the blood vessel, and each leg graft by contact with the luminal wall of the main graft sleeve.

Since each graft will need to be compressed for loading into the catheter and during delivery, in general terms, each stent is formed from the minimum amount of material possible. Thus, for stents on the distal portion of each leg, the stents advantageously comprise the minimum material to enable the patency of the appropriate sleeve lumen at the required diameter to be maintained. Likewise, stents forming at least a part of the fixing means (i.e. at the proximal ends of the body and leg grafts) is formed from the minimum amount of material able to provide the stent with adequate radial force for sealing and/or for migration resistance. In one embodiment, each graft can remain attached to its catheter after the sheath is retracted. A suitable graft of this type is the ANACONDA^® graft of Vascutek Ltd., UK (see US 6,635,080).

In one embodiment, where the assembly is to be inserted in a blood vessel, the method of the invention employs grafts which can be at least partially collapsed to allow blood flow between the outer surface of the graft and the inner lumen of the blood vessel until correction location has been achieved. Such perfusion avoids the risk of ischemia and consequent damage to tissue.

In one aspect, the present invention provides a modular endovascular stent graft assembly comprising:

a) a main graft comprising a main graft sleeve having a first end and a second end with a lumen extending therethrough;

b) a first docking zone and a second docking zone formed by bifurcation of the main graft sleeve;

c) a first leg graft comprising a first leg sleeve having a first end and a second end with a lumen extending therethrough;

d) a second leg graft comprising a second leg sleeve having a first end and a second end with a lumen extending therethrough;

e) first fixing means to sealingly engage said first leg graft to said main graft sleeve and second fixing means to sealing engage said second leg graft to said main graft sleeve; and

f) a fenestration located in a side wall of the first leg sleeve or the second leg sleeve.

In a further aspect, the present invention provides an implantable stent graft assembly comprising:

i) a compliant and substantially fluid impervious tubular main sleeve having a proximal end and a distal end with a conduit therethrough;

ii) a first ring stent formed from multiple windings of wire of a shape memory material, attached to said main sleeve at said proximal end; iii) a bifurcation of said main sleeve, so that said main sleeve forms a first docking zone and a second docking zone at its distal end;

iv) a compliant and substantially fluid impervious tubular first sleeve having a proximal end and a distal end with a conduit therethrough;

v) a second ring stent formed from multiple windings of wire of a shape memory material attached to said first sleeve at said proximal end;

vi) a compliant and substantially fluid impervious tubular second sleeve having a proximal end and a distal end with a conduit therethrough;

vii) a second ring stent formed from multiple windings of wire of a shape memory material attached to said second sleeve at said proximal end; and viii) a fenestration in said first sleeve and/or said second sleeve.

In a further aspect, the present invention provides a method of treating a target site proximate to a branch vessel intersection, said method comprising inserting an assembly according to the present invention so that a fenestration in said first or second leg graft is aligned with said branch vessel.

In a further aspect, the present invention provides a method of treating a target site proximate to first and second branch vessel intersections, said method comprising inserting an assembly according to the present invention so that a fenestration in the first leg graft is aligned with said first branch vessel and a fenestration in the second leg graft is aligned with said second branch vessel.

In each of the aspects described above for treatment of a target site, the target site can include an aneurysm which is treated through deployment of the assembly. Optionally the aneurysm is a thoracic aortic aneurysm.

In each of the aspects described above for treatment of a target site, the assembly according to the present invention can be inserted so that the bifurcation junction is proximal to the branch vessel intersections. Where two branch vessel intersections are present but are not located 180° to each other (due to the patient's natural anatomy), the modular assembly described above can be used to accommodate the angular alignment of the fenestrations as required.

Additionally, each graft of the assembly is desirably inserted using endovascular techniques.

Preferred or alternative features of each aspect or embodiment of the invention apply mutatis mutandis to each other aspect or embodiment of the invention, unless context demands otherwise.

The present invention will now be further described by reference to the following figures in which:

Figure 1 is a schematic illustration of a main graft for a first embodiment of a modular assembly according to the invention;

Figure 2A is a schematic illustration of a first leg graft for use in a modular assembly according to the present invention; Figure 2B is a schematic illustration of a second leg graft for use in a modular assembly according to the present invention;

Figure 3 is a schematic illustration of the assembled modular assembly of Figures 1, 2A and 2B;

Figure 4 is a schematic illustration of an assembled modular assembly according to the present invention having a second embodiment main graft;

Figure 5 shows a schematic illustration of an assembled modular assembly according to the present invention having a third embodiment main graft (E) with a schematic illustration of how the main body of this graft type is folded back onto itself (A to D); and Figure 6 illustrates an alternative embodiment of a partially assembled modular assembly according to the present invention, in which the main graft is according to a fourth embodiment. In more detail, Figure 1 illustrates a first embodiment of a main graft (2) for use in a modular assembly (1) according to the present invention. The main graft (2) consists of a graft sleeve having a first end (9A) and a second end (9B) with a lumen extending therethrough. The main graft sleeve is bifurcated at a junction (6) to form two docking zones (8A, 8B). Thus the lumen of the graft sleeve in main body portion (2) is divided into two smaller lumens (of docking zones (8A, 8B)) after the bifurcation junction (6). The main graft (2) includes a number of ring stents (7) formed by multiple windings of nitinol wire. As illustrated, main graft (2) has four ring stents (7), two located at end 9A and one on each docking zone (8A, 8B) at end (9B). Optionally one or more ring stents (7) can be located on the main sleeve in a sinusoidal or saddle shaped form. The main sleeve of main graft (2) can be formed from any suitable knitted or woven fabric, for example woven polyester. The stents (7) can be attached to the exterior surface of the main sleeve by any suitable means, but can conveniently be attached by sewing using a suitable biocompatible thread, for example suture thread. The bifurcated graft can be woven in a one piece format, for example as described in WO 02/27085. The main graft (2) has a lumen which is in fluid communication with the lumen of each docking zone (8A, 8B).

Figure 2A illustrates a first leg graft (3) for use with the main graft (2) shown in Figure 1. Leg graft (3) has first end (10A) and a second end (10B). Leg graft (3) is formed from any suitable biocompatible flexible material, for example woven polyester. Leg graft (3) will usually also include a number of stents (7) which may be of annular or sinusoidal (saddle shaped) configuration. The stents (7) can be formed from multiple windings of nitinol wire and can be attached by any suitable means, including stitching. Whilst leg graft (3) is illustrated as having 5 stents (7), the number of stents required can be varied depending on the length and circumference of the leg graft (3). However, the presence of a stent (7) at first end (10A) is required for sealing engagement. Thus stent (7) at end (10A) acts as a fixing means for first leg graft (3). In use first leg graft (3) is inserted into the lumen of docking zone (8A) or of docking zone (8B) of the main graft (2) of Figure 1 and sealed thereto, for example, by expansion of stent (7) located at end (10A). The stent or pair of stents located at the first end (10A) of the first leg graft (3) of Figure 2A form a sealing zone able to dock with a docking zone (8A) or of docking zone (8B) of Figure 1 and seal thereto. However, other forms of sealing engagement are possible, for example the use of a balloon expandable Z-stent or other stent type.

As illustrated first leg graft (3) includes a fenestration or aperture (5) in the fabric material forming the sleeve of first leg (3). The fenestration (5) can be bounded by nitinol wire to hold the aperture open and to prevent fraying of the aperture edges.

Figure 2B illustrates a second leg graft (4) for use with the main graft (2) shown in Figure 1. Leg graft (4) has first end (10A) and a second end (10B). Leg graft (4) is formed from any suitable biocompatible flexible material, for example woven polyester. Leg graft (4) will usually also include a number of stents (7) which may be of annular or sinusoidal (saddle shaped) configuration. The stents (7) can be formed from multiple windings of nitinol wire and can be attached by any suitable means, including stitching. Whilst leg graft (4) is illustrated as having 5 stents (7), the number of stents required can be varied depending on the length and circumference of the leg graft (4). However, the presence of a stent (7) at first end (10A) is required for sealing engagement. Thus stent (7) at end (10A) acts as a fixing means for second leg graft (4). In use second leg graft (4) is inserted into the lumen of docking zone (8A) or of docking zone (8B) of the main graft (2) of Figure 1 and sealed thereto, for example, by expansion of stent (7) located at end (10A). The stent or pair of stents located at the first end (10A) of the second leg graft (4) of Figure 2B form a sealing zone able to dock with a docking zone (8A) or of docking zone (8B) of Figure 1 and seal thereto. However, other forms of sealing engagement are possible, for example the use of a balloon expandable Z-stent or other stent type.

As illustrated second leg graft (4) includes a fenestration or aperture (5) in the fabric material forming the sleeve of second leg (4). The fenestration (5) can be bounded by nitinol wire to hold the aperture open and to prevent fraying of the aperture edges.

The assembled modular assembly (1) is shown in Figure 3 and shows the sealing zone (20) achieved by overlapping first end (10A) of each leg graft (3, 4) within the lumen of docking zones (8A) and (8B) respectively. In an alternative embodiment fenestration (5) need not be present in first leg graft (3). Alternatively the fenestration (5) can be omitted from second leg (4). As illustrated in Figure 3, each of first leg graft (3) and second leg graft (4) include 6 ring stents (7) along its length. Depending on the length of each leg graft (3), (4) the number of ring stents (7) can be varied. These rings stents (7) may be of sinusoidal (saddle shaped) form or may be circular. The ring stents (7) maintain the patency of leg grafts (3), (4) and assist bending of the leg graft without kinking to accommodate the patient's anatomy. The ring stents (7) may be formed from multiple windings of nitinol wire and attached to the exterior surface of leg grafts (3), (4), for example by stitching. The fabric material may itself be corrugated or crimped. For example, the fabric material forming the sleeve of first leg graft (3) and/or of second leg graft (4) can be corrugated by heat setting into crimps prior to attachment of the ring stents (7). In use both the ring stents (7) and the corrugations in the sleeve for first leg graft (3) and/or second leg graft (4) mean that it is possible for the length of the leg graft to fenestration (5) to be shortened by partly folding or bunching the fabric of the sleeve of the leg graft in order to align fenestration (5) with the target branch vessel.

Figure 4 illustrates an assembled modular assembly according to the present invention, which is similar to that illustrated in Figure 3, but with an alternative format of main graft (2). Main graft (2) is similar to that shown in Figure 1, but the docking zone (8A) created after the bifurcation point (6) includes a flange extension (30), terminating in loop (33). The addition of flange (30) to docking zone (8A) means that following insertion of a leg graft, flange (30) lies alongside leg graft (4). Loop (33) is advantageously included at the point of the flange (30) and can be held during deployment of main graft (2) so that flange (30) is held in an extended form during insertion and docking of the leg graft. Flange (30) is conveniently formed from the same material as the sleeve of main graft (2). Although Figure 4 shows only docking zone (8A) as including flange (30), in alternative embodiments docking zone (8B) could include the flange (30) or both docking zones (8A), (8B) could include flanges. Flange (30) provides a simple means for attachment to the delivery system even after deployment of main graft (2). Thus, the short docking zone of main graft (2) can be held securely during insertion of the leg graft (4). This avoids inadvertent inversion of the docking zone by the extension leg delivery system.

Figure 5E illustrates an assembled modular assembly according to the present invention similar to that shown in Figure 3, but having an alternative configuration for main graft (2). Essentially main graft (2) is folded back onto itself, such that the proximal sealing stent (7) is sewn onto main graft (2) at the location of fold (24) in main graft (2). This arrangement allows a higher bifurcation point for the graft assembly which can be beneficial for certain types of patient anatomy. Leg grafts (3), (4) are located and secured in short trouser legs (22), such that the end (23) of each leg graft (3), (4) is secured above the end of short trouser leg (22) but below the bifurcation of legs (22). Body (2) extends proximally to line (24), usually defined by a stent (7) having sealing and migration resistant functionality, and is then folded back over towards legs (22). Each leg (3), (4) includes a fenestration (5) which can be angularly adjusted through rotation of leg (3) or (4) as required. Figs 5 A to D show views of a graft similar to that shown in Fig 5E, and illustrate the folding of body (2) in the direction of the arrows (Figs 5A, B & C) to form fold (24).

Figure 6 illustrates a partially assembled modular graft assembly according to the present invention in which main graft (2) again includes a bifurcation (6). In this embodiment each docking zone (8A, 8B) comprises a tubular portion having a large aperture (15) located therein. A tubular section of docking zone (8A, 8B) is located above and below aperture (15). As illustrated in Figure 6, the partially assembled modular assembly includes a second leg graft (4), which can be as described for Figure 2B, inserted into its docking zone (8A) such that the first end (10A) is approximately level with bifurcation (6), and is sealed thereto by expansion of stent

(7) located at end (10A) of leg graft (4). Stent (7) expands onto the upper tubular section of docking zone (8A) and forms a blood tight connection between main graft (2) and leg graft (4). A portion of the second leg graft (4) is exposed through large aperture (15) of the docking zone (8) and leg graft (4) extends beyond the aperture through the further tubular portion (44). The second end (10B) of leg graft (4) can be held completely within tubular portion (44) or can protrude therefrom as illustrated. Docking zone (8) can be unstented, since the stents (7) of the leg graft inserted therein will maintain the patency of this portion of the assembly. However, for convenience, a ring stent can be located at second end (10B) of the docking zone

(8) to facilitate entry of leg graft (4). The fenestration (5) of leg graft (4) is present in the portion of leg graft (4) which is exposed by large aperture (15). Thus fenestration (5) can align with the branch vessel and permit blood flow thereto. A first leg graft (3) optionally including a fenestration (5) can be inserted into docking zone (8B) as described above for leg graft (4) to complete the modular assembly.

Claims

1 A modular stent graft assembly comprising:

(i] a main graft having a main graft sleeve with a main lumen therethrough;

(ii] a first leg graft having a first leg sleeve with a first lumen therethrough; and

(iii] a second leg graft having a second leg sleeve with a second lumen therethrough; wherein said first leg graft and said second leg graft each have a fixing means to sealing engage to the main lumen of said main graft sleeve, and wherein a fenestration is located in at least one of said first leg sleeve and said second leg sleeve.

A modular stent graft assembly as claimed in claim 1, wherein a fenestration is provided by forming a hole or opening within a side wall of a portion of the first leg graft or within a side wall of a portion of the second leg graft

A modular stent graft assembly according to claim 1 or claim 2, wherein each fenestration has a periphery bound by a strand of resilient material.

4. A modular stent graft according to claim 3, wherein the resilient material is selected from nitinol wire or polyether ether ketone (PEEK].

5. A modular stent graft assembly according to any one of the preceding claims,

wherein the graft sleeve is a tapered graft sleeve.

6. A modular stent graft assembly according to any one of claims 1 to 5, wherein the first leg sleeve of the assembly has a side wall, and comprises a fenestration in the side wall of the first leg sleeve, and the second leg sleeve of the assembly has a side wall, and comprises a fenestration in the side wall of the second leg sleeve.

7. A modular stent graft assembly according to any one of the preceding claims

wherein the main graft sleeve is bifurcated at one end to form two smaller lumens.

8. A modular stent graft assembly as claimed in any preceding claim, wherein the main graft sleeve comprises two docking zones, one docking zone accommodating the first leg graft and the other docking zone accommodating the second leg graft

9. A modular stent graft assembly according to claim 8, wherein at least one leg graft has a stent at the end of the leg graft, and said at least one leg graft is insertable into a docking zone of the main graft sleeve, and is sealingly engageable with the docking zone of the main graft sleeve by expansion of the stent when inserted into the docking zone.

10. A modular stent graft assembly according to claim 8 or 9, wherein at least one docking zone comprises a tubular portion adapted to receive a leg graft in a sealing engagement, and a flange extension of the tubular portion to form an extended docking zone that is able to overlap a leg graft when the leg graft is inserted into the docking zone.

11. A modular stent graft assembly according to any one of the preceding claims, wherein at least portion of one or both of said first and second leg grafts is extendable in length.

12. A modular stent graft assembly according to claim 11, wherein the extendable portion comprises annular folds and/or a stretchable fabric portion.

13. A modular endovascular stent graft assembly comprising:

a] a main graft comprising a main graft sleeve having a first end and a second end with a lumen extending therethrough;

b] a first docking zone and a second docking zone formed by bifurcation of the main graft sleeve;

c] a first leg graft comprising a first leg sleeve having a first end and second end with a lumen extending therethrough;

d] a second leg graft comprising a second leg sleeve having a first end and a second end with a lumen extending therethrough;

e] first fixing means to sealingly engage said first leg graft to said main graft sleeve and second fixing means to sealing engage said second leg graft to said main graft sleeve; and

f] a fenestration located in a side wall of the first leg sleeve or the second leg sleeve.

14. An implantable stent graft assembly comprising:

i. a compliant and substantially fluid impervious tubular main sleeve having a proximal end and a distal end with a conduit therethrough;

ii. a first ring stent formed from multiple windings of wire of a shape memory material, attached to said main sleeve at said proximal end;

iii. a bifurcation of said main sleeve, so that said main sleeve forms a first docking zone and a second docking zone at its distal end;

iv. a compliant and substantially fluid impervious tubular first sleeve having a proximal end and a distal end with a conduit therethrough;

v. a second ring stent formed from multiple windings of wire of a shape memory material attached to said first sleeve at said proximal end;

vi. a compliant and substantially fluid impervious tubular second sleeve having a proximal end and a distal end with a conduit therethrough

vii. a second ring stent formed from multiple windings of wire of a shape memory material attached to said second sleeve at said proximal end; and viii. a fenestration in said first sleeve and/or said second sleeve.

15. A method of treating a target site proximate to a branch vessel intersection, said method comprising inserting an assembly according to any one of claims 1 to 14, so that a fenestration in said first or second leg graft is aligned with a branch vessel of said branch vessel intersection.

16. A method of treating a target site proximate to first and second branch vessel

intersections said method comprising inserting an assembly according to any one of claims 1 to 14, so that a fenestration in the first leg graft is aligned with a first branch vessel and a fenestration in the second leg graft is aligned with a second branch vessel of the respective branch vessel intersections.

17. A method of assembling a modular stent graft assembly comprising:

providing a main graft sleeve with a main lumen therethrough;

providing a first leg graft having a first leg sleeve with a first lumen therethrough and second leg graft having a second leg sleeve with a second lumen therethrough wherein the main graft sleeve comprises a bifurcated portion providing a first docking zone and second docking zone; inserting the first leg graft into a lumen of the first docking zone and sealingly attaching the first leg graft to the first docking zone.

18. A method according to claim 17, wherein a second leg graft is inserted into a lumen of the second docking zone and sealingly attached to the second docking zone.

19. A method according to claim 17, or claim 18, wherein the sealing attachment step is carried out by the expansion of a stent located at an end of the respective leg graft

20. A method according to any one of claims 17 to 19, wherein a portion of the main graft sleeve is folded back over a surface of the main graft sleeve.