Claims:WE CLAIM:
1. A transjugular intrahepatic portosystemic shunt implant (100) comprising:
a. a first section (101) constituting 60% - 80% of the length ‘L’ of a shunt implant (100), the first section (101) including at least one row of closed cells (CC) at a first proximal end (101a) and a first distal end (101b) of the first section (101), the first section (101) further including a plurality of rows of open cells (OC) between the rows of closed cells (CC);
b. a second section (103) constituting 10% -40% of the length of the shunt implant (100), the second section (103) including a plurality of dumbbell shaped cells; and
c. a covering at least partially covering the shunt implant (100);
wherein the shunt implant (100) is made by laser cutting.
2. The shunt implant (100) as claimed in claim 1 wherein, struts of the closed cells (CC) and/or the open cells of the first section (101) include one or more of variable strut thickness and cell length along the length of the first section (101).
3. The shunt implant (100) as claimed in claim 1 wherein, the closed cells of the first section (101) include hexagonal shape at deployment.
4. The shunt implant (100) as claimed in claim 1 wherein, the open cells of the first section (101) include a lattice shape at deployment.
5. The shunt implant (100) as claimed in claim 1 wherein, the covering covers the first section (101) of the shunt implant (100).
6. The shunt implant (100) as claimed in claim 1 wherein, the covering is made of a polymer.
7. The shunt implant (100) as claimed in claim 1 wherein, the covering is made of one or more degradable or non-degradable polymers.
8. The shunt implant (100) as claimed in claim 1 wherein, the covering is provided on an inner side as well as outer side of the first section (101).
9. The shunt implant (100) as claimed in claim 1 wherein, the shunt implant (100) includes a crimped profile in a range of 0.15mm to 0.30mm.
10. The shunt implant (100) as claimed in claim 1 wherein, the covering is made of expanded polytetrafluoroethylene (ePTFE).
11. The shunt implant (100) as claimed in claim 1 wherein, the covering includes thickness in a range of 0.003mm to 0.12mm.
12. The shunt implant (100) as claimed in claim 1 wherein, mean cell spacing (MCS) of the closed cells ‘CC’ is less compared to the MCS of the open cells (OC).
13. The shunt implant (100) as claimed in claim 1 wherein, the length of the struts in the open cells ‘OC’ are in a range of 0.5mm to 4mm.
14. The shunt implant (100) as claimed in claim 1 wherein, the struts in the open cells ‘OC’ or the struts of open cells ‘OC’ and closed cells ‘CC’ are interconnected via links ‘L’.
15. The shunt implant (100) as claimed in claim 1 wherein, the link ‘L’ is one of a straight or curved configuration.
16. The shunt implant (100) as claimed in claim 1 is capable of being deployed through a delivery system of diameter 7Fr to 10Fr.
17. The shunt implant (100) as claimed in claim 1 wherein, the first section 101 includes a plurality of markers. , Description:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(Section 10 and Rule 13)

1. TITLE OF THE INVENTION:
INTRAHEPATIC IMPLANT
2. APPLICANT:
Meril Life Sciences Pvt. Ltd., an Indian company of the address Survey No. 135/139 Bilakhia House, Muktanand Marg, Chala, Vapi- 396191, Gujarat, India

The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF INVENTION
[001] The present invention relates to a medical implant, more specifically, a transjugular intrahepatic portosystemic shunt implant.
BACKGROUND
[002] The liver serves many essential functions within the body like removing waste products and foreign substances from the bloodstream, regulating blood sugar levels, and creating essential nutrients to synthesizing bile for digestion of food. In order to perform the said functions, the liver requires significant blood supply and around 75% of this blood supply comes from the portal venous system.
[003] Veins coming from the stomach, intestine, spleen, and pancreas merge into the portal vein, which then branches into smaller vessels and travels through the liver. In cases where the vessels in the liver are blocked due to liver damage, blood is not able to flow properly through the liver and hence, high pressure in the portal system is developed. This increased pressure in the portal vein may in turn cause development of large, swollen veins within the esophagus, stomach, rectum, or umbilical area (belly button), thereby leading to life-threatening complications. This condition is commonly referred as portal hypertension.
[004] In order to treat portal hypertension, transjugular intrahepatic portosystemic shunt (TIPS or TIPSS) was introduced in the year 1969. Transjugular Intrahepatic Portosystemic Shunt (TIPS) is an artificial channel in liver to pass the blood between a portal vein and a hepatic vein. TIPS have proven to be a promising procedure for safe decompression of the portal system and effective control of blood pressure flow.
[005] Ever since the advent of this procedure, various systems have been proposed. In recent practice, varied stent systems have been used as artificial channels. The stent systems may be manufactured by combining two stents made by either braiding or knitting. However, the conventional stent systems pose various challenges such as difficulty in deployment of the stent, inadequate performance of the stent due to improper flexibility at the implantation site, chances of dislocation of the stent at the junction of the portal and the hepatic vein, etc. In order to overcome aforesaid limitations of conventional stent systems, laser cut stents have been introduced. The conventional laser cut stents pose various limitations such as insufficient strength to be placed at the portal vein of the intrahepatic tract, inadequate kink resistance properties which may cause difficulty during deployment of the stent at the vein junction, rigid stent design which leads to need of a specific delivery mechanism to be deployed at the implantation site, etc.
[006] Therefore, an improved system for TIPS which overcomes the disadvantages of the conventional systems is required to be devised.
SUMMARY
[007] A transjugular intrahepatic portosystemic shunt implant is disclosed. The implant includes a first section constituting 60% - 80% of the length ‘L’ of a shunt implant, the first section including at least one row of closed cells at the beginning and the end of the first section, the first section further including a plurality of rows of open cells between the rows of closed cells. Further, the implant includes a second section constituting 10% -40% of the length of the shunt implant, the second section including a plurality of dumbbell shaped cells and a covering at least partially covering the shunt implant. The implant is manufactured by laser cutting.
BRIEF DESCRIPTION OF DRAWINGS
[008] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale.
[009] FIG. 1 depicts an implant 100 being deployed at an implantation site in accordance with an embodiment of the present invention.
[0010] Fig.2 depicts a covered and uncovered part of the implant 100 in accordance with an embodiment of the present invention.
[0011] FIG.3a depicts a laser cut design of the implant at crimped stage in accordance with an embodiment of the present invention.
[0012] Fig.3b depicts an exploded view of the implant 100 in accordance with an embodiment of the present invention.
[0013] Fig.4 depicts a second section of the implant 100 at crimped stage in accordance with an embodiment of the present invention.
[0014] Fig.4a depicts a first cell of the second section of the implant 100 in accordance with an embodiment of the present invention.
[0015] Fig.4b depicts a second cell of the second section of the implant 100 in accordance with an embodiment of the present invention.
[0016] Fig.5 depicts a flow chart involved in manufacturing of the implant 100 in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF DRAWINGS
[0017] Prior to describing the invention in detail, definitions of certain words or phrases used throughout this patent document will be defined: the terms "include" and "comprise", as well as derivatives thereof, mean inclusion without limitation; the term "or" is inclusive, meaning and/or; the phrases "coupled with" and "associated therewith", as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have a property of, or the like; Definitions of certain words and phrases are provided throughout this patent document, and those of ordinary skill in the art will understand that such definitions apply in many, if not most, instances to prior as well as future uses of such defined words and phrases.
[0018] Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, but mean “one or more but not all embodiments” unless expressly specified otherwise. The terms “including,” “comprising,” “having,” and variations thereof mean “including but not limited to” unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms “a,” “an,” and “the” also refer to “one or more” unless expressly specified otherwise.
[0019] Although the operations of exemplary embodiments of the disclosed method may be described in a particular, sequential order for convenient presentation, it should be understood that the disclosed embodiments can encompass an order of operations other than the particular, sequential order disclosed. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Further, descriptions and disclosures provided in association with one particular embodiment are not limited to that embodiment, and may be applied to any embodiment disclosed herein. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed system, method, and apparatus can be used in combination with other systems, methods, and apparatuses.
[0020] Furthermore, the described features, advantages, and characteristics of the embodiments may be combined in any suitable manner. One skilled in the relevant art will recognize that the embodiments may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments. These features and advantages of the embodiments will become more fully apparent from the following description and appended claims, or may be learned by the practice of embodiments as set forth hereinafter.
[0021] In accordance with the present disclosure, a medical implant to be employed as a transjugular intrahepatic portosystemic shunt (TIPS) is disclosed. The implant is useful for treatment of liver diseases such as portal hypertension, gastrointestinal bleeding, hepatic encephalopathy (HE), refractory ascites, etc. The implant of the present invention helps to establish a shunt through a portal vein and a hepatic vein for diverting the blood flow at an implantation site. The implantation site in the present invention corresponds to the intrahepatic tract of the liver. The implant helps to divert and increase the blood flow from the liver thereby reducing blood pressure in the portal vein as well as reducing any associated risk of bleeding of the dilated veins. The implant of the present invention has adequate flexibility, kink resistance at puncture site of the portal vein which provides better grip and/or avoids dislocation of the implant at the implantation site leading to improved performance of the implant.
[0022] The implant of the present invention is a self-expanding implant. The implant is manufactured as a single structure by a process of laser cutting. The single structure of the implant eases the process of deployment and/or avoid dislocation of the implant from the implantation site.
[0023] The single structure may comprise a plurality of sections depending upon geometry of the intrahepatic tract. The plurality of sections may have different design depending upon different locations of the intrahepatic tract. In an embodiment, the implant has two sections, a first section, constituting 60% -80% length of total length of the implant and a second section, constituting 10% -40% length of the total length of the implant.
[0024] The first section may be designed to be placed between a portal vein and a hepatic vein of the intrahepatic tract, also known as liver parenchyma. The first section acts as a shunt between the portal vein to the hepatic vein in order to divert excess blood flow from the portal vein. The first section includes a combination of open cells and closed cells. In an embodiment, the first section includes closed cell at the proximal and distal connected by the open cells in between. The open cells of one row are connected to another row via one of a straight or curved links to obtain desired flexibility, kink resistance and/or radial strength.
[0025] The first section of the implant includes high metal content which imparts high radial strength and kink resistance in order to act as a shunt to maintain adequate blood flow from the portal vein to the hepatic vein. The implant 100 may have radial strength in a range of 60N to 100N, more preferably 75N to 85N.
[0026] Further, the high metal content imparts adequate flexibility to the first section which facilitates easy navigation of the implant through the portal vein towards the hepatic vein without any damage to the vessels or the implant itself.
[0027] Moreover, the first section of the implant may have variable strut thickness and cell length over the entire length of the section depending upon anatomy of the intrahepatic tract. The variable strut thickness and cell length provides adequate flexibility in order to navigate the implant on bend curvature without any kinking and ease of deployment to the implantation site. Further, it may impart better holding capacity and strength to the implant which in turn helps to maintain crushing ability due to high forces and/or help to reside at the implantation site.
[0028] The second section is designed to reside in the portal vein of the intrahepatic tract. The second section may include unique dumbbell shaped cells. The aforesaid design of the cells provides greater area for blood flow through the portal vein. Further, the dumbbell shaped cells impart higher flexibility, sufficient radial strength, bending strength in order to efficiently deploy the implant at the portal vein without any risk of dislocation.
[0029] The implant of the present invention may be partly covered. In an embodiment, the first section of the implant is covered. The covering corresponds to a polymer covering having self-reinforcing properties, high radial resistance and resistance to damage caused by bile and other fluids. The polymeric covering further allows passage of the blood through the portal vein to the hepatic vein without any leakage through the implant surface.
[0030] The implant of the present invention is deployed via a 7Fr to 10Fr compatible delivery system. In an embodiment, the delivery system operates via a push-pull mechanism. The said delivery system allows easy and accurate placement of the implant in the intrahepatic tract.
[0031] Now referring to figures, FIG.1 depicts the implant 100 being disposed at the implantation site i.e. intrahepatic tract of the liver. The placement of the implant 100 is carried out via an endoluminal pathway through a jugular vein (not shown) which links a portal vein 1b disposed towards an inferior vena cava 1c to a hepatic vein 1d. As depicted in FIG. 1, the implant 100 is placed between the hepatic vein 1d and the portal vein 1b. The structure of the implant 100 is more clearly depicted in FIG. 2.
[0032] In accordance with Fig. 2, the implant 100 may include a body defined between a proximal end 100a and a distal end 100b. The implant 100 may include a length L between the proximal end 100a and the distal end 100b. The length L may be in a range of 40mm to 140mm, preferably 60mm to 120mm.
[0033] The implant 100 may be made of a metallic material. The metallic material may include without limitation, cobalt chromium, stainless steel, magnesium alloy or nitinol. In an embodiment, the implant 100 is made of nitinol owing to its self- expanding properties.
[0034] Further, the implant 100 has a plurality of sections to be deployed at different locations in the intrahepatic tract. Such sections may include distinct properties such as, without limitation, flexibility, softness and radial strength. In an embodiment, the implant 100 has a first section 101 and a second section 103 as depicted in Fig. 2. The first section 101 and the second section 103 may be connected together via s shaped links.
[0035] The first section 101 may include a length L1 defined between a first proximal end 101a and a first distal end 101b as depicted in Fig.3a. The first section 101 is designed to reside between the hepatic vein and the portal vein of the intrahepatic tract. The length L1 of the first section 101 may be 60% - 80% of the length ‘L’ of the implant 100. The length L1 of the first section 101 may depend upon the puncture site between the portal vein and the hepatic vein in the liver. The length ‘L1’ may range from 20mm to 120mm, more preferably 40mm to 100mm.
[0036] In an embodiment, the first section 101 has high metal content which imparts higher radial strength, kink resistance and less flexibility to the implant 100. The aforesaid properties of the implant 100 are required to effectively serve the purpose of a shunt at a region of high bending curves between the portal vein and the hepatic vein in order to maintain adequate blood flow.
[0037] Further, the first section 101 includes a plurality closed cells (CC) at both the first proximal end 101a and the first distal end 101b connected by open cells (OC) at the middle as represented in Fig.3b. The shape of the closed cell (CC) and the open cell (OC) may include without limitation hexagonal, diamond, lattice and rhombic shape in the deployed state. In an embodiment, the closed cell is hexagonal in shape while the open cell is lattice shaped. The closed cells (CC) may be connected to the open cells (OC) by a plurality of links “L”. As depicted in Fig. 3b, the link L may be a straight link. The combination of the closed cells (CC) and the open cells (OC) in the first section 101 imparts enhanced flexibility and/or facilitates easy deployment of the implant 100 at the implantation site.
[0038] The closed cells (CC) may be defined by a pair of zig zag struts 10a and 10b connected together by a straight link I. The thickness of the link ‘I’ may range from 0.08mm to 0.18mm, more preferably 0.10 mm to 0.14mm. Further, the length of the link “I” may range from 0.8mm to 1.6mm, more preferably 1.0mm to 1.4mm.
[0039] The total number of closed cells (CC) may range from 8-16 circumferentially, more preferably 10-14. However, it should be noted that the number of cells may also increase/decrease with increase/decrease in the diameter of the first section 101. The diameter of the first section 101 may range from 4mm to 14mm, more preferably 8mm to 12mm.
[0040] The outer length of the closed cell (CC) may be in a range of 4mm to 10mm, more preferably 6mm to 8mm. The inner length of the closed cell (CC) may be in a range of 3mm to 9mm, more preferably 5mm to 7mm. In an embodiment, the outer length of the closed cell (CC) is 7.2mm and the inner length of the closed cell (CC) is 6.4mm. The length of struts (10a & 10b) of the closed cell ‘CC’ may range from 4 mm to 10 mm, more preferably 6 mm to 8 mm.
[0041] Further, the thickness of struts (10a & 10b) of the closed cell (CC) at the first proximal end 101a and the first distal end 101b may be same or different. In an embodiment, the thickness of the struts (10a & 10b) at the first proximal end 101a is greater than the thickness of the struts (10a & 10b) at the first distal end 101b. The greater thickness of the struts (10a & 10b) at the first proximal end 101a imparts enhanced radial strength at junction of hepatic and portal vein making the process of deployment of the implant 100 easy.
[0042] The thickness of the struts (10a & 10b) at the first proximal end 101a may be in a range of 180micron to 280micron. Further, the thickness of the struts (10a & 10b) at the first distal end 101b may be in a range of 200 micron to 250 microns.
[0043] The length cell offset (CO) for the closed cell (CC) may be in a range of 4.5mm to 8.5mm, more preferably 5.5mm to 7.0mm. The mean cell spacing (MCS) of the closed cells ‘CC’ may be less as compared to the MCS of the open cell (OC). In an embodiment, the MCS of the closed cells ‘CC’ ranges from 2.0mm to 5.0mm, more preferably 3.5mm to 4.0mm and MCS of the open cells (OC) ranges from 2.5mm to 4.5mm, more preferably 2.8mm to 3.5mm.
[0044] The length of the struts in the open cells ‘OC’ may be in a range of 0.5mm to 4mm; more preferably 1.5mm to 3.5mm. The strut thickness of the open cells ‘OC’ may be in a range of 0.1mm to 0.5mm, more preferably 0.2mm to 0.4mm. The length cell offset ‘CO’ for the open cell (OC) may be in a range of 5.0mm to7.5mm; more preferably 6.0mm to7.0mm. The mean cell spacing ‘MCS’ of the open cell may be in a range of 2.5mm to 4.5mm more preferably 2.8mm to 3.5mm.
[0045] The struts in the open cells ‘OC’ are also interconnected via links ‘L’. Alternately, the struts of open cells ‘OC’ and closed cells ‘CC’ are interconnected via links ‘L’. However, the number of links ‘L’ in the open cells is less than the number of links ‘L’ in the closed cells ‘CC’. The link ‘L’ may be provided in a straight or curved configuration. In an embodiment, the link L is in straight configuration. The link ‘L’ may impart desired flexibility, kink resistance and/or radial strength to the first section 101.
[0046] The thickness of the links “L” may be same as the strut thickness of the cells. The thickness of the links “L” may be in a range from 0.3mm to 0.7mm, more preferably 0.4mm to 0.6mm. The length of the link ‘L’ may be in a range of 0.8mm to 1.6mm, more preferably 1.0 mm to 1.4 mm.
[0047] Further, the closed cells (CC) and open cells (OC) of the first section 101 may have variable strut thickness along the length L1 of the first section 101. The thickness of the struts may be varied depending upon the required flexibility and strength at the first proximal end 101a to the first distal end 101b.
[0048] The variable thickness of the struts may be achieved by grinding of the struts using files of diameter 2.00mm to 3.00mm Alternatively, variable strut thickness may be achieved through a process of electro-polishing where masking is performed to the desired area of the implant 100 followed by the electro-polishing process over the implant 100. The process may be repeated until desired strut thickness is achieved. Variable strut thickness may impart variable flexibility at different regions of the first section 101 of the implant 100. The variable flexibility may help to adequately align and accommodate the implant 100 in the intrahepatic without any kinking. Further, the variable strut thickness provides better holding capacity and/or strength to the implant 100 in order to maintain crushing ability due to high forces in the intrahepatic tract. Moreover, the variable strut thickness of the implant 100 makes it easier for the implant to be deployed at the implantation site.
[0049] In an exemplary embodiment, the strut thickness of closed cells (CC) of the first section 101 of the implant 100 at the first proximal end 101a and the first distal end 101b is in a range of 180micron to 280micron and the open cells (OC) at the middle portion of the first section 101 is in a range of 200 micron to 250 micron.
[0050] In another exemplary embodiment, the thickness of the first section 101 of the implant 100 is variable and distributed over five equal regions of 12mm along the length L1 of the first section 101 (depicted as R1, R2, R3, R4 and R5 in Fig. 3a). In an exemplary embodiment, the regions R1 and R5 have a strut thickness in a range of 180µm to 280µm, the regions R2 and R4 have a strut thickness in a range of 150µm to 250µm while the region R3 has a strut thickness ranging from 180µm to 200µm;
[0051] In yet another embodiment, the first section 101 has variable cell length over the length L1 of the implant 100 depending upon the required flexibility and strength at the first proximal end 101a to the first distal end 101b. The variable length of closed and open cells of the first section 101 may impart flexibility along with required radial strength which in turn facilitates adequate bending of the implant 100 during deployment in the intrahepatic tract.
[0052] In an exemplary embodiment, the closed cells (CC) at the first proximal end 101a and the first distal end 101b have length in a range of 6mm to 8mm, the open cells (OC) have length in a range of 3.8mm to 4.0mm towards the first proximal end 101a. In another exemplary embodiment, the cell length of the open cells (OC) may further reduce to 1.0mm-1.5mm leading to the length in a range of 2.4mm to 2.6mm towards the first distal end 101b of the first section 101.
[0053] Further, the first section 101 may include a plurality of markers (not shown). The markers may be placed at one of the first proximal end 101a and the first distal end 101b. In an embodiment, 2-10 markers are attached for enabling visibility of the implant 100 under fluoroscopy, more preferably 4-6 markers are used.
[0054] The markers may be made of metallic material such as without limitation, gold, platinum, platinum tungsten, platinum iridium. In an embodiment, the markers are made of platinum. The markers may be of any predefined shape without limitation, round shape, tube shape etc. In an embodiment, the shape of the markers used is tube shape. The diameter of the markers may be in a range of 0.3mm to 0.7mm, preferably 0.4mmto 0.6mm and thickness may be in a rage of 0.05mm to 0.4mm, preferably 0.1mm to 0.3mm. The markers may be disposed on the implant 100 by means of press fitting, laser welding etc.
[0055] Further, the second section 103 of the implant 100 may include a length L2 defined between a second proximal end 103a and a second distal end 103b. The length L2 may be in a range of 10mm to 30mm, more preferably 15mm to 25mm. In an embodiment, the length L2 of the second section 103 is 20mm.
[0056] The second section 103 has less metal content in comparison to the first section 101. The less metal content imparts high flexibility to the implant at the second section 103. The higher flexibility of the second section 103 makes the implant 100 to be held firmly inside the portal vein and form a proper grip at the implantation site.
[0057] The second section 103 may include a plurality of cells 10c as depicted in Fig.3a. The cells 10c may be provided in a predefined shape. The predefined shape may include without limitation dumbbell shape, fork shape, linear leaf shape, spear-shaped etc. In an embodiment, the cells 10c are of dumbbell shape. The cells 10c may be defined by a pair of dumbbell shape cells 10c1 and 10c2 as depicted in Fig.4. The number of cells may be in a range of 2-8, preferably 4-6. The dumbbell shape of the cells 10c may impart enhanced flexibility, adequate strength and kink resistance in order to provide enhanced gripping to the implant 100. Further, the aforesaid shape of cells 10c provide greater area for excess blood to flow from the portal vein to the hepatic vein without blocking the regular flow of the portal vein.
[0058] The cell 10c1 may include two portions, a first portion ‘A’ and a second portion ‘B’ as depicted in Fig.4a. In the depicted example, the first portion A is in the shape of a leaf while the second portion B is in the shape of a tube. The cell 10c1 may be provided towards the second proximal end 103a of the second section 103. The cell 10c1 is designed to reside at the portal vein puncture site and the vein internal space of the liver.
[0059] The length of the cell 10c1 maybe in a range of 8mm to 14mm, more preferably 10mm to 12mm. The length of the first portion ‘A’ may be in a range of 2mm to 7mm, more preferably 4mm to 5mm. The length of second portion ‘B’ may be in range of 4mm to 9mm, more preferably 6mm to 7mm.
[0060] The curved radius of the first portion ‘A’ may be in a range of 0.2mm to 0.6mm, more preferably 0.3mm to 0.5mm. The curved length of first portion ‘A’ is in range of 0.5mm to 1.1mm, more preferably 0.7mm to 0.9mm.
[0061] Similarly, the cell 10c2 may include two portions, a first portion ‘C’ and a second portion ‘D’ as depicted in Fig.4b. In the depicted example, the first portion C is in the shape of a leaf while the second portion D is in the shape of a dart end. The cell 10c2 may be provided towards the second distal end 103b of the second section 103. The cell 10c2 is designed to reside at the portal vein surface of the liver. The first portion ‘C’ is longer than the second portion ‘D’ in order to provide better gripping at the implantation site.
[0062] The length of the cell 10c2 maybe in a range of 7mm to 13mm, more preferably 9mm to 11mm. The length of the first portion ‘C’ may be in a range of 4mm to 9mm, more preferably 6mm to 7mm. The length of second portion ‘D’ may be in range of 1mm to 5mm, more preferably 2.5mm to 3.5mm.
[0063] The curved radius of the first portion ‘C’ may be in a range of 0.2mm to 0.6mm, more preferably 0.3mm to 0.5mm. The curved length of the first portion ‘C’ is in range of 0.5mm to 1.1mm, more preferably 0.7mm to 0.9mm.
[0064] Further, the implant 100 may be provided with a covering over an outer surface and/or an inner surface of the implant 100. In an embodiment, the implant 100 includes the covering over the first section 101. The covering may be provided on an inner side as well as outer side of the first section 101. The covering on both sides of the implant 100 provides enhanced strength to the first section 101, enhanced resistance against leakage and/or avoid restenosis due to stent surface.
[0065] The covering may be a polymeric covering being composed of one or more degradable or non-degradable polymers over the implant 100. The non-degradable polymers may include, without limitation, polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), silicone, fluorinated ethylene propylene (FEP), etc. The degradable polymers may be selected from say, polylactic acid (PLLA), poly (lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), etc. In an embodiment, expanded polytetrafluoroethylene (ePTFE) is used. The covering may be provided to impart self-reinforcing properties, high radial resistance and resistance to damage caused by bile and other fluids to the implant 100. The covering further allows passage of the blood through the portal vein to the hepatic vein without any leakage through the implant surface.
[0066] In an embodiment, the covering 105 is made of expanded polytetrafluoroethylene (ePTFE). This ePTFE may include an unsintered membrane with a low thickness. The thickness on both sides of implant 100 may be same or different. In an embodiment, the thickness on both the sides is same, which is in a range of 0.003mm to 0.12mm, more preferably from 0.005mm to 0.09mm. The low thickness of ePTFE helps to maintain the low profile of the implant 100 in the crimped state. The crimped profile of the implant 100 may be in a range of 0.15mm to 0.30mm, more preferably 0.20mm to 0.25mm. The low crimped profile of the implant 100 makes the implant 100 to be compatible with a delivery system of diameter 7Fr to 10Fr.
[0067] In another embodiment, the covering is provided over the second section 103 of the implant 100.
[0068] In yet another embodiment, the covering is provided over the entire surface of the implant 100.
[0069] In accordance with an embodiment of the present invention, Fig. 5 depicts a flowchart of a process involved in manufacturing of the implant 100. The process commences at a step 401. At step 501, a nitinol tube of thickness 0.2mm to 0.3mm is laser cut. The laser cutting may be performed by means of a laser cutting machine where, a high-power laser beam is directed upon the nitinol tube in a controlled environment under predefined parameters. The predefined parameters may include a gas pressure in a range of 10 bar to 20 bar, preferably 12 bar to 15 bar, power is 50W to 110W and, preferably 70W to 90W, pulse width is 0.005 ms to 0.025 ms, preferably 0.010 ms to 0.015 ms, diameter of the laser beam is 10 µm to 25 µm, preferably 15 µm to 20 µm.
[0070] At step 503, the laser cut tube is subjected to a process of grinding. The process of grinding is performed in order to remove slug, bur or unwanted particles from the surface of the laser cut nitinol tube. The process of grinding may be performed by circular axial shaft shaped diamond files for removing slug and burs produced by laser cutting process inside nitinol tube.
[0071] At step 505, after removal of the slug and burs from the laser cut tube, a process honing is performed in order to impart surface finish to laser cut tube. The process of honing is performed by filing the surface of the laser cut tube with a diamond file. The diamond file may be applied with an abrasive gel in order to achieve finished surface. After honing process, the implant is washed washed under purified water to remove any excessive gel from an inner surface of the tube.
[0072] At step 507, post honing, the laser cut tube is further expanded with the help of mandrel in order to impart desired shape to the implant 100. The mandrel may be made of steel alloy such as mild steel alloy, stainless steel alloy etc. In an embodiment, the mandrel is made of stainless steel SS304 and SS316 material, preferably SS316 material.
[0073] At step 509, after shape setting, the laser cut tube is polished by a process of sand blasting. The process of sand blasting is performed by injecting a stream of abrasive material on a surface under high pressure. The aforesaid process helps to smooth the rough surface by removing micro particles or contaminants from the surface.
[0074] At step 511, the laser cut tube was covered with ePTFE layer to form the implant 100. The covering may be performed on the implant surface via for example, heating, coating, gluing etc. In preferred embodiment, an ePTFE layer is covered on an inner and an outer surface of the implant 100 by applying heat which secures the polymer onto the implant 100. The said covering may be easily expanded without reducing the flexibility of the implant 100.
[0075] For providing the covering over the first section 101 of the implant 100, a mandrel is mounted with the implant 100 having the ePTFE layer is heated at a temperature of about 150°C to 300°C for 05min to 30 min; more preferably 180°C to 220°C for 10min to 25 min respectively. To shrink the ePTFE layer properly, a heat shrink tube is laid over the ePTFE layer for protecting the outer surface which is directly in contact to heat. The dimensions of the heat shrink tube may be more than the implant dimensions, particularly the diameter. The heat shrink tubes used in the present invention may include fluorinated ethylene propylene, PTFE, nylon, pebax etc. In an embodiment, fluorinated ethylene propylene is used. Subsequently, the mandrel having the implant 100 is cooled at the normal temperate to gain the strength of graft bonding. The mandrel 20 may be cooled for say, 1 min to 15 mins; more preferably 5mins to 10 mins. Post cooling, the heat shrink tube is removed.
The invention will now be described with the help of following examples.
[0076] Example 1(Prior art): A conventional implant made by a process of knitting having a first section and a second section was used. The first section included zig zag shaped open cells and was covered by a polymeric layer. The implant was deployed between the portal vein and the hepatic vein. The second section included diamond shaped cells and was deployed in the portal vein.
[0077] It was observed that the implant of Example 1 had difficulties during deployment due to the implant structure. Further, it was observed that the said implant needed more precision for deployment at the implantation site. Also, the implant was prone to migration and dislocation from the implantation site due to improper deployment at target location and high blood pressure at portal vein.
[0078] Example 2 (Present Invention): An implant having a single laser cut construction with two sections, a first section and a second section, was used. The first section included a combination of lattice-shaped open cells and hexagonal-shaped closed cells with a PTFE covering was deployed between the portal vein and the hepatic vein. The second section included a plurality of dumbbell shape cells and was deployed in the portal vein.
[0079] It was observed that the implant was easily deployed in the veins without any special precaution (under in-vitro simulation model). Also, the enhanced flexibility of the second section of the implant at the portal vein provided firm grip at the tortuous portal vein. Further, the enhanced radial strength of the first section of the implant provided a rigid shunting structure to maintain excess blood flow from the portal vein towards the hepatic vein.
[0080] The scope of the invention is only limited by the appended patent claims. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention is/are used.