Stent graft connection arrangement

A connection socket (12) for an end of a stent graft or a side arm (10) of a stent graft. The connection socket has a first resilient ring (14) around the arm at its end, a second resilient ring (16) spaced apart along the arm from the first ring and optionally a zig zag resilient stent (20) between the first and second rings. Each of the rings is of slightly lesser diameter than the side arm. The zig-zag resilient stent can be a compression stent.

TECHNICAL FIELD

This invention relates to a stent graft used to restore the patency of a body lumen and in particular relates to a connection arrangement on such a stent graft.

BACKGROUND OF THE INVENTION

Where damage has occurred to an internal vessel of the human or animal body such as to a blood vessel either by disease or by trauma, it is possible to introduce to the blood vessel a stent graft by endoluminal techniques which will restore patency of the blood vessel across the damaged region. Often such damaged regions include branch vessels. To ensure the blood flow can go into the branch vessel, bifurcated or side branch stent grafts are used.

There can be a problem with such bifurcated or side branch stent grafts in that to provide a connection into a branch vessel from a stent graft through the bifurcation or side arm a connection arrangement is needed. There have previously been proposed socket type connections in which connection is achieved by overlap of an inner and outer tube, however, owing to movement of a stent graft due to migration or change in physiology such overlap connections can become dislodged.

A similar problem exists with side arm stent grafts in that once a side arm stent graft is deployed in place and a bridging stent graft or stent is be deployed to extend from the side arm into a branch vessel there can be a problem with successful retention of such a bridging stent into the side arm.

It is an object of this invention to provide solutions to these problems or to at least provide a practitioner with an alternative a branch connector system.

Throughout this specification the term distal when used with respect to a portion of the vasculature, a deployment device or a prosthesis is the end of the vasculature, deployment device or prosthesis further away in the direction of blood flow away from the heart and the term proximal means the portion of the vasculature, deployment device or end of the prosthesis nearer to the heart. When applied to other vessels similar terms such as caudal and cranial should be understood.

SUMMARY OF THE INVENTION

In one form the invention is said to reside in a connection socket for a stent graft having a tubular body of a biocompatible material, the socket comprising a first resilient ring around the tubular body at one end thereof and a second resilient ring spaced apart along the tubular body from the first ring.

Preferably the first resilient ring and the second resilient ring are of lesser diameter than the diameter of the tubular body. Preferably the connection socket further comprises a resilient stent between the first and second rings.

The resilient stent may be a zig zag resilient stent. Preferably the resilient stent is on the outside of the tubular body.

Preferably also the first and second rings are on the outside of the tubular body.

Preferably the first and second rings comprise a material selected from shape memory wire, stainless steel or plastics material. In one embodiment the first and second rings may comprise at least two turns of wire with each end terminating in a loop.

Preferably the zig zag resilient stent is comprised of a shape memory wire and the zig zag resilient stent defines a cylindrical form having a diameter less than that of the tubular body and is thus a self contracting stent, that is, when the stent is expanded beyond its rest diameter it tends to contract to return to its rest diameter.

In an alternative form the invention is said to reside in a stent graft comprising a main tube of a biocompatible graft material and a side arm being a tube of biocompatible graft material extending from the main tube and being in fluid communication therewith, a connection socket on the side arm for a bridging stent, the connection socket comprising a first resilient ring around the side arm adjacent to the distal end thereof, a second resilient ring spaced apart along the side arm from the first ring and a zig zag resilient stent between the first and second rings.

In an alternative form the invention is said to reside in a bifurcated stent graft comprising a main tube of a biocompatible graft material and a bifurcation defining first and second legs extending from the main tube and being in fluid communication with the main tube, each of the legs being formed from a tube of biocompatible graft material, a connection socket on at least one of the legs for a leg extension, the connection socket comprising a first resilient ring around the leg adjacent the distal end thereof, a second resilient ring spaced apart along the leg from the first ring and a zig zag resilient stent between the first and second rings.

The bifurcated stent graft may have a shorter and a longer leg and the connection socket may be on the shorter leg.

It will be seen that by this invention the portion of tubular graft material with the pair of rings and with a resilient stent between them there is provided an efficient sealing region into which can be deployed a self-expanding or a balloon expanded stent, either of which can be covered, and which when allowed to expand into the connection socket is in effect firmly gripped by the first and second rings and has a resilient connection with the zig-zag resilient stent between the first and second rings.

DETAILED DESCRIPTION

Now looking at the drawings and more particularly the first embodiment of connection socket according to the present invention shown inFIGS. 1 and 2.

The connection socket for this embodiment of the invention may be for a side arm for a stent graft or may be for a terminal end of a leg of a bifurcated stent graft or an aorta-uni iliac stent graft adapted to be deployed into the aortic bifurcation.

In this embodiment the tube10may be a side arm for a stent graft or may be a terminal end of a leg of a bifurcated stent graft or of an aorta-uni iliac stent graft. The tube10has a socket arrangement12into which may be placed a self-expanding stent, a balloon expandable stent or a composite stent or leg extension. The tube10has a first ring14stitched to its terminal end and a second ring16spaced apart from the first ring14. Each ring14and16is formed from at least two turns and preferably three turns of a shape memory wire such as nitinol wire and the ends of the nitinol wire terminate in loops18. The use of the loops18prevent sharp ends from the nitinol wire from digging into the vasculature into which the stent graft is deployed. The rings14and16are stitched to the tube10by stitching15. The rings14and16can alternatively be formed from stainless steel wire, plastics material or other suitable material. Stitching of the loops on the rings to the biocompatible graft material also prevents the resilient rings from being expanded by the pressure of a self expanding or balloon expandable stent placed therein and expanded.

Between the first ring14and the second ring16is a stent20formed from a resilient material. The resilient stent20is formed from nitinol wire, for instance, and defines a cylindrical form having a diameter less than that of the tube10whereby to define a self contracting stent and hence when sewn on to the outside of the tube10using stitching22it provides a diameter reducing effect on the tube10. A further self-expanding stent24can be placed on the tube10to maintain patency of the tube.

The rings14and16provide a firm expansion restricting structure into which a balloon expandable covered or uncovered stent can be expanded or into which a stent including a self expanding stent can be deployed and the resilient stent20between them assists with gripping the balloon expandable covered or uncovered stent or a graft including a self expanding stent to provide a good seal.Also provided on the tube10are radiopaque markers26adjacent each of the rings14and16. These markers enable the physician to visualize the side arm and rings during an operation to assist with correct placement of a leg extension into the tube10.

FIG. 3shows an alternative embodiment of connection socket according to the present invention. In this embodiment the tube30may be a side arm for a stent graft or may be a terminal end of a leg of a bifurcated stent graft or of an aorta-uni iliac stent graft. The tube30has a socket arrangement32into which may be placed a self-expanding stent, a balloon expandable stent or a composite stent or leg extension. The tube30has a first ring34stitched to its terminal end and a second ring36spaced apart from the first ring34. Each ring34and36is formed from at least two turns and preferably three turns of a shape memory wire such as nitinol wire and the ends of the nitinol wire terminate in loops38. The use of the loops38prevent sharp ends from the nitinol wire from digging into the vasculature into which the stent graft is deployed. The rings34and36are stitched to the tube30by stitching35. The rings34and36can alternatively be formed from stainless steel wire, plastics material or other suitable material.

The rings34and36provide a firm expansion restricting structure into which a balloon expandable covered or uncovered stent can be expanded or into which a graft including a self expanding stent can be deployed.

When a balloon expandable stent or balloon expanded covered stent46is placed into the socket12, of the type shown inFIG. 1, as shown inFIGS. 4 and 5and expanded the rings14and16provide firm locking for the balloon expanded covered stent46and the resilient stent20which is expanded by the balloon expanded stent while it is being balloon expanded provides a compressive effect to keep tension on the balloon expanded stent46. The balloon expandable covered stent46comprises a mesh of a shape memory metal47such as nitinol or stainless steel and a cover48of a biocompatible graft material such as woven or non-woven material selected from the group comprising Dacron and expanded PTFE or an elastomeric biocompatible material such as Thoralon®. By this means a firm connection and an improved seal can be obtained between a stent leg or arm10and a bridging stent46. A similar gripping effect can be obtained with the use of a self-expanding stent, a composite stent or other form of leg extension.

Thoralon® is a polyurethane multi-polymer comprising a high flex life elastomer base with a surface modifying agent comprising siloxane which is manufactured by Thorotec Corporation (Pleasanton, Calif. USA). It will be noted fromFIG. 5that the balloon expanded covered stent46extends within the tube10to past the inner ring16and that the balloon expanded covered stent46is deformed around each of the rings to assist with locking of the balloon expanded covered stent46onto the tube10. In one particular embodiment the side tube10may have a diameter of 8 mm and hence a circumference of 26 mm. Each of the rings may have a diameter at rest of 7 mm and the resilient stent20formed from nitinol wire may have a diameter at rest of 6 mm. The first and second rings14and15may be spaced apart by 10 mm and the length of the resilient stent20may be 6 mm. Hence there may be a gap between the rings and the resilient stent at each side of the stent of 2 mm.

In the case of a stent graft to be deployed into the common iliac artery with the side arm adapted to extend towards the internal iliac artery the side arm may have a diameter of 8 mm and a length after the join of up to 25 mm. It will be realised that for stent grafts to be deployed into the ascending or descending aorta with side arms to extend into their respective branch vessels other lengths and diameters will be applicable.FIG. 6shows a side branch stent graft or prosthesis of the type adapted for deployment into the iliac arteries, for instance, such that a bridging stent can extend from the side arm into the internal iliac or hypogastric artery.

The stent graft70has a main tubular body72and a side arm74. Both the main tubular body and the side arm are formed from a seamless tube of a biocompatible graft material such as Dacron. A triangular aperture is formed in the main tube and a bevel cut into the inner end of the side arm and the side arm stitched into the triangular aperture with stitching78. The side arm has a connection socket arrangement76at its distal end77. The connection socket arrangement76comprises a first ring79stitched to its terminal or distal end77and a second ring80spaced apart from the first ring79. Each ring79and80is formed from at least two turns and preferably three turns of nitinol wire and the ends of the nitinol wire terminate in loops81. The use of the loops81prevents sharp ends from the nitinol wire from digging into the vasculature into which the stent graft is deployed. Also the loops81enable the ends of the wires forming the rings to be stitched to the fabric of the graft which assists with preventing the rings from expanding in use. Between the first ring79and the second ring80is a stent82formed from a resilient material. The resilient stent82is formed from nitinol wire, for instance, and is made to be of a size which at rest is slightly smaller than the diameter of the side arm74and hence when sewn on to the outside of the side arm74it provides a diameter reducing effect on the side arm74.

When a bridging stent, such as a balloon expandable stent, is placed into the socket76and expanded, the rings79and80provide firm locking for the balloon expanded stent and the resilient stent82which is expanded by the balloon expanded stent while it is being balloon expanded, provides a compressive effect to keep tension on the balloon expanded stent. By this means a firm connection and an improved seal can be obtained between the side arm and a bridging extension. A similar gripping effect can be obtained with the use of a bridging extension in the form of a self-expanding stent, a composite stent or other form of leg extension.

FIG. 7shows an embodiment of a bifurcated stent graft or prosthesis with a connection socket according to this invention. The bifurcated prosthesis90has a generally inverted Y-shaped configuration having a body portion91, a shorter leg92and a longer leg93. The body of the prosthesis is constructed from a tubular woven biocompatible synthetic material such as dacron. At the proximal end94of the prosthesis90is a first zigzag stent95which extends beyond the end of the prosthesis and has distally extending barbs96. The prosthesis has a number of zigzag stents mounted to it and extending along its length. The stent97nearest the proximal end94is inside the tubular material so that the outside presents a smooth surface which in use engages against the inner wall of the vessel into which it is deployed to provide a barrier to the flow of blood. The stent98nearest the distal end99of the longer leg93is also inside the tubular material so that the outside presents a smooth surface which in use engages against the inner wall of the vessel into which it is deployed to provide a barrier to the flow of blood. Between these internal stents the rest of the stents100are arranged on the outside of the tubular material so that they present minimal restriction to the flow of blood through the prosthesis and present minimal sites for the growth of thromboses within the prosthesis. Each stent is sewn to the tubular material as shown particularly at101.

The shorter leg92has a connection socket102at it distal end. The connection socket comprises a first ring113stitched to its terminal or distal end103and a second ring112spaced apart from the first ring113. Each ring113and112is formed from at least two turns and preferably three turns of nitinol wire and the ends of the nitinol wire terminate in loops114. The use of the loops114prevent sharp ends from the nitinol wire from digging into the vasculature into which the stent graft is deployed. Between the first ring113and the second ring112is a stent116formed from a resilient material. The resilient stent116is formed from nitinol wire, for instance, and is made to be of a size which is at rest slightly smaller than the diameter of the shorter leg92and hence when sewn on to the outside of the shorter leg92using stitching118it provides a diameter reducing effect on the shorter leg.

In use the prosthesis according to this embodiment of the invention is adapted for fitting into aorta such that the proximal end94is just distal of the renal arteries and the first zigzag stent95extends up to or over the renal arteries. As the stent is constructed from thin wire it does not obstruct the renal arteries if it extends over them. The longer leg93extends down one of the iliac arteries and the shorter leg terminates in the aorta just short of the other iliac artery at the aortic bifurcation. An extension prosthesis104is adapted for fitting into the connection socket102on the shorter leg. The extension prosthesis104is constructed from a tubular synthetic material such as dacron and has terminal internal stents105and a plurality of external intermediate stents106.

Throughout this specification various indications have been given as to the scope of this invention but the invention is not limited to any one of these but may reside in two or more of these combined together. The examples are given for illustration only and not for limitation.

Throughout this specification and the claims that follow unless the context requires otherwise, the words ‘comprise’ and ‘include’ and variations such as ‘comprising’ and ‘including’ will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.