Claims:We claim,

1. A self-expanding stent graft comprising plurality of shape memory alloy struts sewn on a tubular shaped surgical fabric at longitudinally substantially even distance from each other and a flared frame sewn at the distal end of the tubular fabric in a manner such that said flared frame longitudinally extends beyond the tubular fabric, wherein such struts being sinusoidal shaped and wherein such struts and flared frames being radially sewn to the fabric individually by way of blanket stitching.

2. The stent graft as claimed in claim 1, wherein the struts are W or V shaped with round corners.

3. The stent graft as claimed in claim 1 or 2, wherein the radius of curvature of the corners are in the range of 0.1mm to 0.9mm.

4 The stent graft as claimed in any preceding claim, wherein the struts comprise at least 5-8 peaks of height range of 10mm to 30mm.

5. The stent graft as claimed in any preceding claim, wherein wire diameter of the strut and flared frame ranges from 0.3mm to 0.6mm, thickness ranges from 0.15mm to 0.75mm and width ranges from 0.1mm to 0.45mm.

6. The stent graft as claimed in claim 1, wherein the struts and flared frame are stitched on the external surface of the tubular fabric.

7. The stent graft as claimed in claim 1, wherein the struts and flared frame are stitched on the internal surface of the tubular fabric.

8. The stent graft as claimed in claim in any preceding claim, wherein braided suture is used for stitching.

9. The stent graft as claimed in any preceding claim, wherein stitching of frames and stent with the vascular graft is a repeated pattern of double knot followed by left over right pattern and a final double knot to secure the ends, wherein the spacing between each stitch ranges from 3mm to 7mm.

10. The stent graft as claimed in claim 1, wherein the flared frame is of a shape similar to the shape of the struts.

11. The stent graft as claimed in any preceding claim, wherein the radius of the flared frame is greater than the graft.

12. The stent graft as claimed in any preceding claim, wherein the flared frame is provided with barbs at superior portion of the frame for fixing the graft at desired position.

13. The stent graft as claimed in any receding claim, wherein it comprises radiopaque marker stitched on the tubular fabric.

14. The stent graft as claimed in any preceding claim, wherein the weaving pattern of the surgical graft has Ends Per Inch (EPI) ranging from 120-125 & the Picks Per Inch (PPI) ranging from 78-82 causing smaller porosity to limit the blood to flow over.

15. A delivery device (100) for implantation of self-expandable stent graft (1) within a lumen of the body for treatment of aortic aneurysm comprising an elongated flexible tubular body having a movable tip (114) at the proximal end (P), a pushing mechanism (110) at the distal end (D), a gripping handle (101) with an actuating means and a supporting member (102) located adjacently at the middle of the said tubular body;
said tubular body comprises three longitudinally extended coaxial tubes (105,107,111) placed over each other; an outer tube (105) extending from the tip and engaged with the handle through a holding component (106), an inner tube (107) extending from a bumper (115) and connected to the said pushing mechanism through a holding component (112), and an innermost tube (111) engaging the said tip to the said pushing mechanism through a holding component (113);
said handle being mounted on a guiding rail (103), extending from the pushing mechanism to the supporting member (102), and is capable of being rotated on the guiding rail causing slow longitudinal movement of the outer tube facilitating partial deployment of a stent graft;
said actuation means is configured to disengage the said outer tube from the said guide rail facilitating faster longitudinal retraction of the outer tube and consequent further partial deployment of a stent graft; and
said pushing mechanism is adapted to cause proximal longitudinal movement of the innermost tube (111) and of the tip causing final deployment of the stent graft in the lumen of the body; and wherein the self-expandable stent graft (1) is configured to be mounted on the outer tube (105) in a radially compressed manner between the said tip (114) and the said bumper (115).

16. The device as claimed in claim 15, wherein the actuation means comprises a switch (104) and spring (108) mechanism adapted to engage or disengage with a mating thread (116) provided in the handle, with the thread of the guiding rail facilitating rotational or longitudinal movement of the outer tube.

17. The device as claimed in claim 15 or 16, wherein the handle has a holding component (106) adapted to cause longitudinal movement of the outer tube with the rotational movement of the handle.

18. The device as claimed in claim 15, wherein the pushing element comprises pushing switch (110) and holding component (113) adapted to cause longitudinal movement of the innermost tube and the tip for complete deployment of the stent graft.

19. The device as claimed in any of claims 15-18, wherein said bumper is distally located from the said tip between the said outer (105) and inner tube (107) and attached to the inner tube (107) and is configured to prevent the distal movement of the stent graft during retraction of the outer tube.

20. The device as claimed in any of claims 15-19, wherein the outer sheath of the outer tube is made of a kinking resistant first polymer and inner sheath is made of friction resistant second polymer.

21. The device as claimed in claim 20, wherein first polymer is Pebax and the second polymer is PTFE.

22. The device as claimed in any of claims 15-20, wherein inner tube OD ranges between 1.25mm to 1.75mm, and ID ranges between 1.05mm to 1.25mm and inner most tube - OD ranges between 1.05mm to 1.35mm, and ID ranges between 0.95mm to 1.15mm.

23. The device as claimed in any of claims 15-21, wherein the device has radiopaque marker.

24. A system for implantation of self-expandable stent graft (1) comprising self-expandable stent graft as claimed any of claims 1-14 mounted on a delivery device as claimed in claims 15-23.

Dated this 13th day of June, 2019.

(SOUMEN MUKHERJEE)
IN/PA - 214
Applicants’ Agent
for seenergi IPR
, Description:FIELD OF THE INVENTION

The present invention relates to an Endovascular Stent Graft, its delivery system and the system therefor. The invention particularly related to an implantable endovascular device intended for the treatment of the aortic aneurysm and its delivery device as well as a system comprising a stent graft and the delivery device for implantation of the stent graft at the site of aortic aneurysm.

BACKGROUND OF THE INVENTION

Self-expanding stent grafts are more preferred over surgical approach due to fast patient recovery, low rate of morbidity and lower cost. Self-expanding endovascular stent grafts are widely used throughout the world for vascular surgery.
Specifically, fabric based endovascular self-expanding stent grafts have been developed for the treatment, replace, and bypass damaged area of vessel. Many fabric based tubular grafts are formed by weaving, braiding or knitting to provide outer surface to act as a layer to cover damaged or diseased endovascular portion. This type of fabric grafts are specially used for the Abdominal Aortic Aneurysm and Thoracic Aortic Aneurysm which are also referred as AAA and TAA. AAA is a localized enlargement of the abdominal aorta which is developed due to weakened wall of the abdominal aorta, whereas TAA is a localized enlargement of the thoracic aorta which is developed due to weakened wall of the thoracic aorta.
In prior arts, self-expanding endovascular grafts are fabricated from polymeric materials like PTFE (Poly-tetrafluoroethylene), PET (Polyethylene terephthalate), Teflon and Polyester of different weaving pattern ensuring high integrity against leakages. However, available endovascular stent grafts performance may hamper due to endo-leaks, stent abrading, prosthesis migration and stent graft thrombosis depending on stent design and suturing pattern. Further, the porosity of fabric may increase due to suturing with larger size of suture which may initiate endo-leaks and stent graft thrombosis.
US 7686842 discloses a SIS sandwich stent grafts for treatment of acute AAA rupture and short-term reaction of native aorta to their placement. The stent frame of the invention comprises at least one stent, and preferably a plurality of stents connected together such as, with monofilament line to define a stent frame. Accompanying the stent or stent frame is a sleeve or tube of a naturally occurring biomaterial. Such as collagen, which is highly desirable; particularly a special derived collagen material known as an extracellular matrix (ECM), such as small intestinal submucosa (SIS). A layer of the small intestine Submucosa (SIS) is disposed along at least the inside Surface and preferably also along the outside Surface of the stent frame. The SIS tube is affixed to the stent frame at the ends of the stent frame and preferably also at the connections of the stent bodies, such as by Sutures, and additional Sutures may optionally also be placed in the middle of every leg of each stent.
In prior art, the delivery system may include squeeze and release type of mechanism. The handle contains a trigger/switch and the guiding rail having threads in a step form or like helical structure. It also have three types of triggering movement through which the triggering gets locked or unlocked (slow backward movement), or can move freely without triggering (fast backward movement). When the physician squeezes the trigger; while in unlocked position, the handle moves backward through which the sheath which is connected with the handle also moves backward few inches ensuring partial deployment of the self-expandable stent graft. Then the trigger comes back to its initial position and again the trigger is squeezed for further movement, and the process goes on. Afterwards, when the physician feels comfortable about the partial deployment of the implant in the required zone, the switch is further pushed in a position through which the handle moves freely wherein the physician pulls the handle and may not need to squeeze the trigger again. After complete deployment of the implant, the physician pushes the handle back towards the initial position and recovers whole system.
However, such stent may not provide the required radial strength and flexibility also there is need to provide improved stent and better implantation device which is easy to use for high precision implantation of the stent graft in the treatment of aortic aneurysm.

OBJECTS OF INVENTION

The primary object of the present invention is to develop a self-expanding stent graft and a delivery system for easy and accurate deployment of graft in the body lumen.
It is another object of the invention to provide a self-expanding stent graft with smaller porosity which will limit the blood to flow over.
It is another object of the present invention to provide self-expanding stent with frames having larger diameter for better fixation and radial strength.
It is yet another object of the present invention to provide a delivery device capable of rapid, stress-free and smooth deployment of implant in the body lumen.
It is a further object of the present invention to provide a system comprising a self-expanding stent and a delivery device which provides for relatively easy and precise implantation of the self-expanding stent at the affected site of the body lumen.

SUMMARY OF THE INVENTION

The present invention provides a self-expanding stent graft comprising plurality of shape memory alloy struts sewn on a tubular shaped surgical fabric at longitudinally substantially even distance from each other and a flared frame sewn at the distal end of the tubular fabric in a manner such that said flared frame longitudinally extends beyond the tubular fabric, wherein such struts being sinosoidal shaped and wherein such struts and flared frames being radially sewn to the fabric individually by way of blanket stitching.
The struts are preferably W or V shaped with round corners and the radius of curvature of the corners are in the range of 0.1mm to 0.9mm. Preferably the struts comprise at least 5-8 peaks of height range of 10mm to 30mm.
Preferably wire diameter of the strut and flared frame ranges from 0.3mm to 0.6mm, thickness ranges from 0.15mm to 0.75mm and width ranges from 0.1mm to 0.45mm.
The struts and flared frame are stitched on the external surface of the tubular fabric wherein the struts and flared frame are stitched on the internal surface of the tubular fabric and braided suture is used for stitching.
Preferably stitching of frames and stent with the vascular graft is a repeated pattern of double knot followed by left over right pattern and a final double knot to secure the ends, wherein the spacing between each stitch ranges from 3mm to 7mm.
Preferably the flared frame is of a shape similar to the shape of the struts. In an embodiment the radius of the flared frame is greater than the graft.
Preferably the flared frame is provided with barbs at superior portion of the frame for fixing the graft at desired position.
The stent graft also comprises radiopaque marker stitched on the tubular fabric.
Preferably the weaving pattern of the surgical graft has Ends Per Inch (EPI) ranging from 120-125 & the Picks Per Inch (PPI) ranging from 78-82 causing smaller porosity to limit the blood to flow over.
The invention also discloses a delivery device for implantation of self-expandable stent graft within a lumen of the body for treatment of aortic aneurysm comprising an elongated flexible tubular body having a movable tip at the proximal end, a pushing mechanism at the distal end, a gripping handle with an actuating means and a supporting member located adjacently at the middle of the said tubular body; said tubular body comprises three longitudinally extended coaxial tubes placed over each other; an outer tube extending from the tip and engaged with the handle through a holding component , an inner tube extending from a bumper and connected to the said pushing mechanism through a holding component, and an innermost tube engaging the said tip to the said pushing mechanism through a holding component; said handle is mounted on a guiding rail which extends from the pushing mechanism to the supporting member, and is capable of being rotated on the guiding rail causing slow longitudinal movement of the outer tube facilitating partial deployment of a stent graft, the actuation means is configured to disengage the said outer tube from the said guide rail facilitating faster longitudinal retraction of the outer tube and consequent further partial deployment of a stent graft; and the pushing mechanism is adapted to cause proximal longitudinal movement of the innermost tube and of the tip causing final deployment of the stent graft in the lumen of the body; and wherein the self-expandable stent graft is configured to be mounted on the outer tube in a radially compressed manner between the said tip and the said bumper.
The actuation means comprises a switch and spring mechanism adapted to engage or disengage with a mating thread, provided in the handle, with the thread of the guiding rail facilitating rotational or longitudinal movement of the outer tube.
The handle has a holding component adapted to cause longitudinal movement of the outer tube with the rotational movement of the handle
The pushing element comprises pushing switch and holding component adapted to cause longitudinal movement of the innermost tube and the tip for complete deployment of the stent graft.
The bumper is distally located from the said tip between the outer and inner tube and attached to the inner tube and is configured to prevent the distal movement of the stent graft during retraction of the outer tube.
Preferably, the outer sheath of the outer tube is made of a kinking resistant first polymer and inner sheath is made of friction resistant second polymer, wherein first polymer is Pebax and the second polymer is PTFE.
Preferably the inner tube OD ranges between 1.25mm to 1.75mm, and ID ranges between 1.05mm to 1.25mm and inner most tube - OD ranges between 1.05mm to 1.35mm, and ID ranges between 0.95mm to 1.15mm.
The device also has radiopaque marker.
The invention also provides a system for implantation of self-expandable stent graft comprising self-expandable stent graft mounted on a delivery device.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1a-b show schematic view of weaving pattern of the fabric of the self-expanding stent.
Figure 2a-b is a schematic view of self-expanding frames and self-expanding stent.
Figure 3a shows the sinusoidal shape of the wire having property of shape memory.
Figure 3b is an exploded view of the self-expanding frame which shows the round corners around the edge.
Figure 3c-d illustrate view of the construction of self-expanding frame.
Figure 4 is a schematic view of mandrels required for shape setting.
Figure 5 is a schematic view of L-shape pins that are studded in the mandrels required for shape setting.
Figure 6a is a schematic view of laser cut stent with excluded barbs required for fixation of graft.
Figure 6b is an exploded view of the excluded barbs present in the laser cut stent.
Figure 6c is a schematic view of laser cut stent whose distal part is sewn over the proximal part of the vascular graft.
Figure 7: schematic view of the stitching pattern used to stitch the frames over the graft.
Figure 8: schematic view of radio-opaque wire and “o” shaped markers.
Figure 9 represents the section view of the delivery device of present invention.
Figure 10a represents the complete preview of present invention delivery system.
Figure 10b shows the handle movement over the guiding rail in rotational axis; and partial deployment of the self-expandable stent graft.
Figure 10c is a schematic view of the tip-capture mechanism which is useful while deployment.
Figure 11 shows the pushing mechanism and clip removal for forward movement of tip.
Figure 12a represents enlarged view of the self-expandable stent graft before tip forward movement.
Figure 12b represents enlarged view of the self-expandable stent graft after tip forward movement.
Figure 13 represents switch on the handle.
Figure 14 represents fully deployed self-expandable stent graft.
Figure 15 shows the gliding movement of the handle over the guiding rail.
Figure 16 shows the initial position of the handle of the delivery system; while re-sheathing the whole component after deployment of self-expandable stent graft
Figure 17 is a schematic view of the implant after successful deployment in the diseased vessel.

DETAILED DESCRIPTION

According to the present invention self-expanding stent is used to repair damaged vessel. When the stent graft is implanted within the natural diseased vessel, it eventually decreases the chances of vessel puncture and thereof increases blood-tight vascular connection. The defects that are being treated by self-expanding stent graft are aortic aneurysm, aortic dissections, and other diseases related to abdominal and thoracic aorta. When self-expanding stent graft is implanted in the abdominal or thoracic aorta, the stent frame forms a seal in the diseased portion of the vessel and it gradually affixes there.

Implant Fabric
The fabric or sleeve of self-expanding stent graft is of tubular in shape and is made up of a woven graft material within its overall length. The fabric can be mainly manufactured by weaving or knitting technique. Material of fabric includes Poly-tetrafluoroethylene (PTFE), polyurethanes, PET (Polyethylene terephthalate), Teflon, polyesters, fluorinated polymers such as poly-tetrafluoroethylene (PTFE), expanded PTFE and poly (vinylidene fluoride); poly-siloxanes, including poly-dimethyl siloxane; and polyurethanes, including polyether-urethanes, polyurethane ureas, polyether-urethane ureas, polyurethanes containing carbonate linkages and polyurethanes containing siloxane segments can also be used to manufacture graft. The fabric material includes a polymeric sheet made with a textile type construction because the fibers provide a flexible array in sheet or tubular form so that the graft material may be provided with a predetermined high degree of flexibility which is a provide advantage for the delivery and deployment. Apart from poly-fabric biological derived materials can be used including but not limited to such as bovine vessels, fixed pericardium, peritoneum and other preserved animal origin material. In preferred embodiment, the fabric material of the graft is biocompatible polyester. Yet in another embodiment, preferred textile material which will be used as polymeric sheets; is made up from polyethylene terephthalate and PTFE (Poly-tetrafluoroethylene). Polyester is selected as fabric material because they are inexpensive, easily handled practically, has better physical characteristics and have excellent biocompatibility.
In the present embodiment, fabric is manufactured by weaving technique. Fabric construction of woven textiles is such that it includes weft woven and warp woven fiber arrays. The different flexibility characteristics of the various woven formations may be beneficially adapted to the functional requirement of the particular graft material application. In preferred embodiment, the weaving fabric can be made from one or multiple yarns. The term filament means the number of fibers woven with warp or weft loops in a single thread. In preferred embodiment, the diameter of the fiber yarn ranges between 1 micron to 100 microns, preferably between 10 microns to 50 microns, more preferably between 15 microns to 30 microns. The thread construction is made up of multifilament structure which means it is jumbled combination of fibres of the yarn and this fibre is known as filament. The number of filaments in multifilament structure of the fabric ranges between 60 to 120 filaments per thread, more preferably between 70 to 100 filaments per thread. In preferred embodiment, the denier of the fabric yarn ranges between about 100 to 200 deniers, preferably between 120 deniers to 190 deniers, more preferably between 140 deniers to 180 deniers. Porosity of fabric depends on the arrangement and spacing between two fibers. The individual filament of graft comprises a maximum spacing from 1 micron to 200 microns; more preferably about 10 microns to about 180 microns. Most preferably, the spacing between the fibers of the textile lies from about 25 micron to about 150 microns. An illustration of the weaving pattern is depicted in Figure 1a and Figure 1b.

Implant Framework
In-order to hold the fabric and achieve adequate radial strength in self-expanding stent grafts, few materials such as outer frames, laser cut stent are incorporated. In a preferred embodiment, outer frames are designed by many ways like braiding, laser cutting or winding technique. More preferably winding and laser cutting technique is used to develop framework to support the fabric. Materials used for the frame work is metal or polymeric material. Metal frame works include but not limited to materials like stainless steel, cobalt chromium, nickel-titanium alloy or nitinol. In preferred embodiment, the metal frame work and the stent is made up of materials like alloy of nickel and titanium; known as nitinol. The nitinol framework is sewn to the exterior surfaces of the body of the self-expanding stent graft (1) as illustrated in the Figures 2a & 2b. The self-expanding graft also includes a self-expanding stent known as anchor stent (4) which is sewn partially with the proximal part of the body. These nitinol frames (3) that are radially connected to the fabric material (2) with the help of sutures which provides radial strength to the stent graft to withstand against higher abdominal aortic blood pressure. Further radial force of the stent helps in fixation with the vessel wall and hence it diminishes the chances of the graft from migration. Stent frames are shaped such that it matches with the diameter of the expanded graft fabric. However, in the present embodiment, the shape of stent is such that the diameter of the stent remains larger than the diameter of the expanded graft. So that when the graft is expanded, the larger diameter of the stent imparts a greater radial force to the graft and hence the graft attaches tightly within diseased vessel. In some embodiment, the grafts may also include shapes similar to two legs which is also known as bifurcated graft. These bifurcated grafts are specifically used in abdominal region in-case of larger lesion in the abdominal region.
The shape of stent is like sinusoidal valve as shown in Figure 3a. As illustrated in Figure 3b, the corners of stents have a radius that it will not damage or puncture the vessel while coming in contact with it. The radius of curvature of the fillet corners are between 0.1mm to 0.9mm, preferably between 0.2mm to 0.8mm, more preferably between 0.3mm to 0.7mm.
In preferred embodiment, frames are in “W” shape, as it gives a greater radial force and covers larger surface area of graft. “W” shape frame also helps in achieving flexibility which is required in torturous vessels after implantation. Diameter of the wire of these frames ranges from 0.1mm to 0.8mm, preferably between 0.2mm to 0.7mm, more preferably around 0.3 to 0.6mm. As shown in Figure 3c the design of “W” shape frames (3) include four common points which are then patterned peripherally in same fashion to complete the construction. In this embodiment the height from point A to B ranges preferably between 3mm to 8mm, more preferably between 5mm to 6.5mm, moreover the height from B to C point ranges from preferably between 1mm to 6mm, more preferably between 3mm to 4.5mm, and the height from point C to D point ranges preferably between 3mm to 8mm, more preferably between 5mm to 6.5mm.
Numbers of frames are used to construct the graft according to graft length. In the preferred embodiment, number of frames ranges from 5 frames to 20 frames per graft when the length of graft ranges from 100mm to 250mm.
In an embodiment, also Figure 3d the “V” shape frames (3’) are used as a support graft framework. The number of waves ranges preferably between 5 to 10 waves over the periphery, more preferably ranges between 6 to 9 waves over the periphery. The height of these frames preferably ranges between 12mm to 20mm; more preferably ranges between 14mm to 18mm. The frames have round corners such that the self-expanding stent graft will not penetrate or damage the surrounding vessels while deploying in the thoracic region and also after post treatment.
In preferred embodiment, the frames are initially formed on various sizes of mandrels, as shown in Figure 4 as per desired diameter of graft. The mandrels are made up Stainless Steel (314 grade) and the diameter of mandrel ranges from 16mm to 36mm respectively. The wires are winded over the periphery of the mandrel over some pins in-order to give the sinusoidal shape and round corners. As shown in Figure 5 the pins are in L-shape and are extruded perpendicularly from the axis of the mandrel such as the wires can get hold of the shape and won’t slip from the mandrel. After this, wires are then annealed to the desired shape of the graft with round corners. The pins locations are depicted on the mandrels as per the final “W” shape design.
In preferred embodiment, the anchor stent (frame) used at distal part of the graft as shown in Figure 6a which arrangement is such that 60 to 70 % of stent area remains exposed from the graft. The strut width of the stent varies from 0.1mm to 0.5mm, preferably from 0.15mm to 0.45mm, more preferably from 0.25mm to 0.40mm; thickness of the frame varies from 0.15mm to 0.75mm, preferably from 0.25mm to 0.70mm, more preferably from 0.35mm to 0.65mm. The height of the flare frame ranges from around 10mm to 30mm, preferably from 15mm to 27mm, more preferably from 17mm to 23mm. The distance of frame from one particular corner to the bottom frames adjacent corner is equal to its longitudinal axis. But by this configuration frame is connected and have constant distance among them, which helps in maintaining the radial force around the graft, thus the graft remains intact and are in tight configuration with the diseased vessel. In preferred embodiment, frame (4) at distal end of graft is designed in such a manner that it flares outwards from the longitudinal axis and hence its diameter is greater than that of the graft which helps to lock the graft within the vessel to prevent migration. The holding frame of the graft is sewn only towards the end portion as shown in (6) in Figure 6c. Graft with self-expanded flare frame includes suprarenal barbs (5) at superior portion of frame which helps to fix the graft at the desired position. As shown in Figure 6b the barbs are further expanded and hence will have a greater diameter circumferentially than the flared region.

Frame-Fabric Stitching
The fabric are sewn to the frames and holding frame to make tubular structure with the help of suture. Suture may be multifilament or monofilament depending on the application. In the present embodiment, frames are sewn on the outer side of tubular graft, although it may be sewn on the inner side of tubular graft as per application. To sew the fabric 2/0 to 10/0 size sutures are used, preferably from 3/0 to 8/0 size sutures are used, more preferably from 4/0 to 7/0 size sutures are used for fabric stitching. The stitching is done left over right pattern with single suture. Suture material includes but not limited to polyurethane, PLGA (Poly Lactic-co-Glycolic Acid), polypropylene, PTFE, ePTFE, etc. In an embodiment, suture used for stitching is of multifilament polyester.
In an embodiment, all frames are stitched manually over fabric with help of multi-filament polyester braided suture. The first frame is stitched on fabric by leaving 3mm to 6mm gap from the upper side of the fabric. After this every frame are stitched by giving minimum 1mm to 15mm gap, more preferably 3mm to 12mm gap and most preferably 4mm to 10mm gap. These specific gaps will provide sufficient radial strength to graft. In this embodiment, holding stent is sewn at the bottom strut such that it will hold the side edges of fabric and will not disturb the blood flow after implantation. This stitching pattern which is used to stitch the frames over the vascular graft is known as blanket stitch as illustrated in Figure 7. The stitching is done by placing the suture (7) in the needle and tying a knot (8) in the end of the suture. Then the needle is sent up by starting it from below the fabric which will hide the end knot. Then the thread is pulled, and circled back around to make the first loop around the edge by sending the needle under the bottom layer and is brought out on top in the exact place where it was started. Then the needle is brought through the loop. Now the joint is brought about a 1/4 of an inch and the needle is sent through the bottom layer, up to the top. Now thread is pulled by leaving a small loop. At last the needle is pulled through the loop tightly. The stitch spacings are too close; so it prevents any edge of stent from extending further from the outer tubular area of the stent graft which helps graft to immerse out easily from the sheath while deployment. In the preferred embodiment the spacing between each stitch ranges preferably between 1mm to 10mm, more preferably between 3mm to 5mm. Extra suture tentacles are removed/trimmed and bent from both holding stent and frame-fabric stitching portion. These tentacles may result in disturbing blood cells and may induce clotting or thrombosis at treatment site.
The proximal corners or apices of the frame are sewn with the fabric graft, but the unsown distal end of frame has a larger radius of curvature compared to the round corners of the proximal part of the frame. In this embodiment, the strut radius of the corner of distal part of the flared frame is in range of 0.3mm to 0.7mm, whereas the distal part of the stent is having 1.3mm - 1.7mm of radius. The reason behind keeping greater radius of curvature around those corners is because it won’t pierce or damage the vessel walls after placement. The anchor frame while expanding covers larger surface area then the body frames of the graft. This is so made such that it helps the graft from dislocating over the vessel walls after placement.
In an embodiment, for the radiopacity and precision placement of graft, radio-opaque markers are placed over fabric surface. Radiopaque marker of “O” shape and a straight wire is used in self-expanding stent graft for better visibility under fluoroscope. As shown in Figure 8, three or greater number of “O” shaped markers (9) are stitched over the radial axis of the proximal and the distal part of the graft. Radio-opaque wire is stitched from distal to upper in a straight form along with its longitudinal axis. Hence, radio-opaque marker is helpful for precise placement of the graft over the diseased vessel. These markers can be made by using radio-opaque material includes but not limited to platinum, gold, alloys of platinum-iridium, platinum-tungsten, etc. In the preferred embodiment, radio-opaque markers are made up of alloy of platinum-tungsten due to its better fluoroscopic property.

Delivery System Components & Description
Present invention relates to the delivery device that offers simple and rapid implantation of a self-expandable stent graft within the lumen body without applying excessive force.
The delivery device (100) comprising an elongated flexible tubular body having a movable tip (114) at the proximal end (P), a pushing mechanism (110) at the distal end (D), a gripping handle (101) with an actuating means and a supporting member (102) located adjacently at the middle of the said tubular body. The gripping handle can have a suitable shape for ease of operation. The tubular body comprises three longitudinally extended coaxial tubes (105, 107, 111) placed over each other; an outer tube (105) extending from the tip and engaged with the handle through a holding component (106), an inner tube (107) extending from a bumper (115) and connected to the said pushing mechanism through a holding component (112), and an innermost tube (111) engaging the said tip to the said pushing mechanism through a holding component (113). The handle is mounted on a guiding rail (103). The guide rail extends from the pushing mechanism to the supporting member (102). The gripping handle is capable of being rotated on the guiding rail causing slow longitudinal movement of the outer tube facilitating partial deployment of a stent graft.
Material of various tube include stainless steel, cobalt chromium, nitinol, Pebax, PEEK, PTFE etc. In present invention, inner (107) and inner most tube (111) are made up of stainless steel while outer sheath (105) is made up of Pebax and PTFE. The inner diameter of tube outer sheath ranges from preferably 10 Fr to 24Fr, more preferably 16 Fr to 22 Fr. The hardness of outer sheath range from preferably 35 durometer to 90 durometer, more preferably ranges from 50 durometer to 75 durometer.
The forward or backward movement of handle is achieved by gliding of handle on guiding rail. In order to rotate or slide the gripping handle (101) a guiding rail (103) having threads of custom pitch is present for rotational movement and slow delivery with precise initial positioning of self-expandable stent graft. The gripping handle (101) has a shape that is more comfortable and easily adaptive to physician. Further, grooves on handle helps for proper gripping and rapid turning of handle.
The delivery system further includes a dome shaped element that works as a supportive member (102) to support and keep the components of the delivery system in place. However, supportive member can have other suitable shape also. The supportive member (102) is attached with the proximal part of the guiding rail; hence the guiding rail works as a pillar for the delivery system. These supporting components may include the distal portion of guiding rail (103), outer sheath (105), the inner tube (107) and the innermost tube (111). Further delivery system comprises a bumper (115) that is attached on inner tube and lies in between the surface of the outer sheath and the inner tube. Bumper helps to keep the self-expandable stent graft in stable condition and also acts as pusher for implant deployment.
The guiding rail has an exterior thread which includes custom pitch to assist rotational movement of the delivery handle. The pitch of the thread ranges preferably between 5mm and 10mm, more preferably between 6 mm and 8 mm. Through the guiding rail, the handle (101) glides/rotates up and down as required by moving handle backward or forward. At the proximal end of the guiding rail (103) the supportive member is attached along with guiding rail. Towards the distal end of the guiding rail the pushing mechanism (110) and the clip (109) are attached for deployment purpose. The delivery handle further includes a mating thread element (116) that mates with the thread of the guiding rail (103). The mating thread (116) is located in between the delivery handle (101). Further, mating thread is connected with the switch (104) of the delivery system which directs engagement and disengagement of mating thread with the guiding rail whenever required; engagement for slower delivery and disengagement for faster delivery. Engagement prevents longitudinal movement of handle and allows rotational movement. On the flip side, disengagement prevents rotational movement of handle and allows longitudinal movement. The delivery system further comprises a switch (104) and a spring (108) in the handle as shown in Figure 9, which constitutes the actuation mechanism. The spring may be in a conical or helical form. In present invention, spring is conical. The material of spring includes but not limited to nitinol, Iron, stainless steel, mild steel and other materials. In present invention the spring is made up of stainless steel.
When self-expandable stent graft (1, 117) is deployed partially in the preferred location, then operator can glide the handle (101) in the longitudinal axis instead of rotational axis by pressing the switch (104). Since pushing of switch (104) leads to breakdown of the mating thread from the guiding rail due to compression force of the spring (108).
The delivery system includes a tip (114) which is used as a guiding element while inserting the delivery system into the lumen. Material of tip includes but not limited to PTFE (Polytetrafluoroethylene), Pebax, polyamide, Nylon and other materials. In present invention, tip is made up of Pebax. Further, tip contains flared portion of self-expandable stent graft in compressed state as represented in Figure 10c.
The outer layer of sheath (105) is made up of Pebax having different type of grades which may include but not limited to Pebax 7233, Pebax 5533, Pebax 7232 and others. Also the sheath consists of metallic construction which may be of braided or coiled type configuration in the middle layer. In the present invention, the sheath is having coiled type configuration which ensures high resistance against kinking and also have better strength and flexibility. The inner layer of the sheath (105) is made up of PTFE material so that the self-expandable stent graft can come out from the sheath with less friction resistance. The size of the sheath ranges between 17 Fr to 25 Fr; also the sheath includes a radio-opaque marker band at the distal most part of the delivery system. Because of this marker band, the sheath can be viewed under fluoroscope while implanting the self-expandable stent graft into the lumen for better placement in the defect region.
Rotation of handle (101) leads to upwards and downward movement of holding component (106) and ultimately results in backward/forward movement of outer sheath (105). However the sheath (105) will not rotate in circular manner during the process instead it will move in a longitudinal manner, which reduces the damage to lumen.
The self-expandable stent graft is loaded inside the outer sheath in a radially compressed manner. The self-expandable stent graft is located between the tip (114) and the bumper (115) of the delivery system. The bumper is attached with the inner tube of the delivery system. It is located in the distal region of the delivery system behind the self-expandable stent graft and is used as pusher element for deployment of self-expandable stent graft.
At the distal region of delivery system, a clip (109) and a pushing switch (110) are present which are required while deploying the self-expandable stent graft. The clip is made up of rubber grade material so when needed, it can be pulled out with ease. The material includes but not limited to EPDM, fluorocarbon, neoprene, nitrile, silicone etc. Inside the pushing mechanism, a holding component (113) is present which is connected with the innermost tube. Further this innermost tube is connected with the tip (114) of the delivery system.
Initially, proximal part of delivery system is being guided towards the diseased zone of the body. The proximal part of the system includes tip, outer sheath, bumper, inner tube and innermost tube. After delivering the sheath towards the diseased zone, as shown in Figure 10a & 10b the handle is rotated along the guiding rail in-order to move the outer sheath in backward direction towards the distal end. With the pulling of sheath, the self-expandable stent graft comes out partially as shown in Figure 10b. The self-expandable stent graft possesses a retracting force while pulling the sheath which makes it difficult to deploy, but because of the bumper (115) attached with the inner-tube (107) the implant gets pushed outwards by opposing the retracting force of the self-expandable stent graft.
Once self-expandable stent graft is partially deployed in the perfect position, operator can remove the clip which is present in the distal region of the delivery system as shown in Figure 11. After removing the clip (109), the operator pushes the pushing component (110) towards the proximal side of the delivery system as shown in Figure 11. This pushing switch is connected with the secondary holding component (113) of the delivery system. This holding component is further connected with the innermost tube (111) of the delivery system which is fixed with the tip as mentioned earlier. Hence when the physician pushes the pusher component, the innermost tube gets pushed because of which the tip of the delivery system moves towards the proximal side and radially compressed flared frame (4, 118) of the self-expandable stent graft booms out and gets fixated in the vessel region of the body as shown in Figure 17. In Figure 12a, the image depicts the self-expandable stent graft that is in partially deployed state and the flared frames being radially compressed inside the tip; and in Figure 12b, the image depicts the flared frames in a deployed condition after pushing the pushing switch which further pushes the tip.
After deploying the flared frames of the self-expandable stent graft, when the physician feels comfortable about the position of the graft, the switch (104) of the delivery system present in the handle is pushed which dislocates the mating thread from the guiding rail. While pushing the switch, the handle is being pulled backwards along the longitudinal axis of the guiding rail, instead of rotating it as shown in Figure 13. Hence with the movement of handle, the sheath (105) retracts back simultaneously. With the retraction of sheath the self-expandable stent graft gets deployed rapidly.
When the self-expandable stent graft is fully deployed in the vessel of the body as shown in Figure 14, then the handle (101) is again pushed back to its initial position while pressing the switch (104) as shown in Figure 15. Afterwards the pushing mechanism is also pulled backwards because of which the tip also reaches to its initial position as shown in Figure 16. Afterwards the whole delivery system is retracted from the body. Figure 17 shows the defected aneurysm and the self-expanding stent graft after deployment.
The present invention has been described with the help of some embodiments, which are no way limiting and various modifications are possible without departing from the scope of the invention as described above or defined in the claims herein below.