Claims:WE CLAIM:
1. A vena cava filter comprising
a. a body including a distal end, a proximal end and a plurality of hexagonal cells, each hexagonal cell including a plurality of legs, at least one of the plurality of legs including one or more barbs for preventing migration and promoting retainment of a filter; and
b. a retrieval member coupled to the proximal end of the body, the retrieval member including a pear-shape for accurate deployment and retrieval of the filter.
2. The filter as claimed in claim 1 wherein the retrieval member is coupled to a pusher including a complementary pear-shape hook for facilitating retrieval of the vena cava filter.
3. The filter as claimed in claim 1 wherein the body is made of one of nitinol, cobalt-chromium.
4. The filter as claimed in claim 1 wherein the plurality of legs includes seven legs.
5. The filter as claimed in claim 1 wherein the barbs are inclined with respect to a horizontal axis of the legs at a predefined angle.
6. The filter as claimed in claim 5 wherein the predefined angle is 120°.
7. The filter as claimed in claim 1 wherein the distal end and the proximal end are closed ends. , 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:
VENA CAVA FILTER AND METHOD OF MANUFACTURING THEREOF

2. APPLICANTS:
Meril Life Sciences Pvt Ltd, an Indian company, of the address Survey No. 135/139 Bilakhia House Muktanand Marg, Chala, Vapi-Gujarat 396191

3. 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 vena cava filter, more specifically the present invention relates to a barbed vena cava filter.
BACKGROUND
[002] Blood clotting and/or coagulation is the transformation of blood from a fluid to a semi-solid state resulting into formation of fibrinous solids. Formation of the blood clots may result in undesirable effects such as deep vein thrombosis (DVT). The DVT is a medical condition in which the blood forms clots within veins of legs resulting in migration of the blood clots to arteries in the lungs. The presence of blood clots in the arteries of lungs may be named as pulmonary embolism. The state of pulmonary embolism may arrest blood flow through the lungs leading to death of a patient. A filtering device can be deployed in the vena cava of a patient in such medical conditions.
[003] Conventional filters may have interconnected legs extending in a radial direction. The presence of extending legs may cause trauma to a blood vessel. Further, the conventional filter may pose a problem relating to misplacement of the filter during deployment and/or deflection of the filter after deployment in case of high blood pressure leading to a health risk for patients. Thus, there exists a need for an improved filter, that overcomes the deficiencies of conventional filter.
SUMMARY
[004] The present invention discloses a vena cava filter. The vena cava filter includes a body including a distal end, a proximal end and a plurality of hexagonal cells, each hexagonal cell including a plurality of legs, at least one of the plurality of legs including one or more barbs for preventing migration and promoting retainment of a filter, and a retrieval member coupled to the proximal end of the body, the retrieval member including a pear-shape for accurate deployment and retrieval of the filter. The retrieval member is coupled to a pusher including a complementary pear-shape hook for facilitating retrieval of the vena cava filter.
BRIEF DESCRIPTION OF DRAWINGS
[005] 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.
[006] FIG.1 illustrates a 3-D diagram of a vena cava filter in accordance with an embodiment of the present invention.
[007] FIG.2 illustrates a 2-D cross-sectional view of a vena cava after laser cutting in accordance with an embodiment of the present invention.
[008] FIG.3 illustrates a flow chart depicting a process involved in manufacturing of a vena cava filter in accordance with an embodiment of the present invention.
[009] FIG.4 illustrates a mold in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF DRAWINGS
[010] 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.
[011] Particular embodiments of the present disclosure are described herein below with reference to the accompanying drawings, however, it is to be understood that the disclosed embodiments are merely examples of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure.
[012] In accordance with the present disclosure, a vena cava (VC) filter and a method of manufacturing thereof is disclosed. In various embodiments, the VC filter may be used in various medical conditions for capturing thrombus and/or distal protection during vascular procedure. In an embodiment, the VC filter is implanted into the inferior vena cava (IVC) in order to prevent pulmonary emboli.
[013] The filter is not a permanent implant and may be retrieved back within a period of 12- 14 days from deployment. The filter may be used to break blood clots of bigger size into smaller fragments until the body’s lytic system starts to dissolve them in bloodstream. For example, the filter may break emboli having a diameter in a range of 4mm to 10mm into a smaller fragment of diameter in a range of 1mm to 3mm.
[014] The filter of the present invention includes a proximal end and a distal end. The filter is a closed structure on both the ends. The closed structure of the filter may provide dual filtration for prevention of pulmonary embolism. The filter may include a plurality of legs between the proximal end and the distal end. In an embodiment, the legs of the filter include a plurality of curved barbs angularly placed on the legs. The presence of angularly placed curved barbs may provide better holding ability, may minimize the risk of puncture to the vessel wall and/or deflection of the filter after implantation. In another embodiment, the filter includes a pear shaped hook on one of its proximal and the distal end for efficient deployment and/or retrieval from the implantation site.
[015] Now referring specifically to drawings, FIG. 1 illustrates a three-dimensional view of the filter 100. In an embodiment, the filter 100 is used in the IVC application. The filter 100 may be self- expandable in radial direction and/or may be deployed with the help of catheter. The profile of the catheter may be in a range of 6F to 10F and preferably in a range of 6F to 8F.
[016] The filter 100 may include a body having a proximal end 12, distal end 14 and a central portion 13. The central portion 13 extends between the proximal end 12 and the distal end 14. The filter 100 is illustrated in a deployed configuration. The deployed configuration is an expanded configuration of the filter 100 once it is implanted at a treatment site. In the deployed configuration, the filter 100 may be of a polygonal shape having a closed structure on the proximal end 12 as well as distal end 14. The closed ends of the filter 100 may provide dual filtration at a treatment site.
[017] The body of the filter 100 may be manufactured by means of without limitation braiding and/or laser cutting. In an embodiment, the filter 100 is manufactured by means of laser cutting. The material used for manufacturing the filter 100 may be a metallic alloy, degradable metal and/or biodegradable polymer or combination thereof. The material may possess shape memory property. The metallic alloy may include without limitation cobalt-chromium (Co-Cr) alloy, nickel-titanium alloy (nitinol) etc. The biodegradable material may include without limitation poly-l-lactide co-glycolide (PLGA), polydioxanone (PDO), poly dl-lactide-co-glycolide (PDLG), poly-l-lactide co-caprolactone (PLC) etc. The degradable metal may include without limitation magnesium, iron, zinc etc. In an embodiment, the filter 100 is manufactured by means of laser cutting of a nitinol tube. The nitinol is selected as it is having relatively higher biocompatibility, therefore it does not adversely affect blood vessels in a patient.
[018] When the filter 100 is deployed at the treatment site, large emboli having diameter of 4-10 mm may come in contact with the filter 100. The said emboli first contact the distal end 14 of the filter 100 and are thereby fragmented into smaller size, for example, the diameter is reduced to 50%-70% of the initial diameter. Further, the fragmented emboli may enter into the filter 100 through a plurality of cells 30 and may be further fragmented into smaller fragments with the help of the proximal end 12 inside the filter 100, for example, the diameter is further reduced to 10%-30% of the initial diameter.
[019] In an embodiment, the emboli having an initial diameter of 4mm to 10mm may be fragmented to a diameter of 1mm to 3mm. Such fragmented emboli of diameter in the range of 1mm to 3mm may be then dissolved by the body’s lytic system.
[020] The length and/or diameter of the filter 100 may be varied depending upon the application. In an embodiment, the length of the filter 100 is in a range of 47mm to 75mm and diameter is in a range of 10mm to 30mm for implantation in the inferior vena cava.
[021] The filter 100 may include at least one retrieval member. In an embodiment, the proximal end 12 has the retrieval member 20. The retrieval member 20 is made of the nitinol. The retrieval member 20 may be a hook like structure which may facilitate deployment and/or retrieval of the filter 100 efficiently from an implantation site with the help of a hook or a snare like device. The retrieval member 20 of the filter 100 may be of any shape such as without limitation, rectangular, pear shape, V- shape, trapezoidal shape etc. In an embodiment, the retrieval member 20 is a pear-shaped structure as depicted in FIG.2. The pear-shaped structure of the retrieval member 20 may enhance accuracy of deployment of the filter 100 and/or may avoid risk of slipping of the filter 100 during retrieval.
[022] The filter 100 may be deployed and/or retrieved with the help of a pusher (not shown). In an embodiment, the pusher may include a hook at an end. The hook may be in a shape of without limitation rectangular, V-shape, pear shape, etc. In an embodiment, the hook is in the pear shape. The hook of the pusher may be coupled with the pear-shaped hook of the filter 100. The coupling between the two complementary hooks may completely avoid the risk of misplacement and/or slipping of the filter 100 during deployment and/or retrieval.
[023] The central portion 13 of the filter 100 includes a plurality of cells 30, an independent leg 19, a first set of linking members 16 and a second set of linking members 18. Each cell 30 of the filter 100 may include a plurality of struts 17, and plurality of legs 10. The length and width of the struts 17 may directly influence the flexibility and strength of the filter 100. The struts 17 possess flexibility for uniform expansion of the filter 100 in the deployed state. The length and the width of the struts 17 may be in a range of 10 to 20mm and 60 microns to 150 microns respectively. In an embodiment, the length and the width are in a range of 12 to 16mm and 80 microns to 130 microns respectively.
[024] The number of legs in the filter 100 may directly influence the ability of emboli entrapment and/or fragmentation. The filter 100 may include an odd number of legs. In an embodiment, the filter 100 has seven legs. The seven legs may include the legs of the cells 30 and the independent leg 19. Each of the legs 10 and the independent leg 19 may be provided circumferentially and/or uniformly spaced with respect to a longitudinal axis of the filter 100. The legs of the filter 100 may be in a straight configuration. The length and width of each leg 10 and 19 of the filter 100 may be same and/or different. In an embodiment, the length of each leg 10 and 19 may be in a range of 20 mm to 30 mm. In an embodiment, the length of each leg 10 and 19 is in a range of 23 mm to 27 mm. The width of the legs 10 and 19 may be equal and/or larger than the strut members 16, 18. In an embodiment, the width of the legs 10 and 19 is larger than the strut members 16, 18 in order to adequately hold the filter 100 and/or to provide better entrapment and/or fragmentation of the emboli at an implantation site. The width of the leg 10 and 19 may be in a range of 50 microns to 180 microns. In an embodiment, the width of the legs 10 and 19 is in a range of 75 microns to 150 microns.
[025] The legs 10 and 19 of the filter 100 may include at least one cut 31 and its corresponding barb 32. The cuts 31 may be located at various predefined locations on the leg 10, such as at a proximal end, distal end or between the proximal end and the distal end of the leg 10. The cuts 31 may be provided in any shape such as curved shape, needle shape, conical shape etc. In an embodiment, the cuts 31 are of curved shape.
[026] In an embodiment, the barbs 32 may be provided at a predefined of angle of inclination, say A, with respect to a horizontal axis of legs 10. The predefined angle of inclination A of the barbs 32 may be in a range of 80° to 160°. In an embodiment, the predefined angle of inclination A of the barb 32 is 120° with respect to the leg 10 of the filter 100.
[027] In another embodiment, the barbs 32 are provided in curved shape. The barbs 32 of the filter 100 are flexible in order to conform to the geometry of the implantation site. The presence of the angularly placed curved barbs 32 on each of the leg 10 of the filter 100 may mitigate the risk of deflection of the filter 100 and/or risk of piercing the wall of inferior vena cava in a patient.
[028] The legs 10 of the cell 30 of the filter 100 may connect with the struts 17. The struts 17 may connect with the legs 10 to provide a circular geometry to the filter 100. The circular geometry of the filter 100 may facilitate easy and/or accurate deployment of the filter 100 using a sheath (not shown). In an embodiment, two legs 10a, 10b may connect to the four struts 17a, 17b, 17c and 17d at an angle of inclination to make a hexagonal structure of the cell 30 as depicted in FIG. 1. The angle of inclination between the struts 17 and the legs 10 may depend upon the size of vena cava vessel. The angle of inclination between the struts 17 and the legs 10 may be in a range of 80° to 160°. In an embodiment, the angle of inclination between the struts 17 and the legs 10 is in a range of 100° to 140°.
[029] The first set of linking members 16 of the central portion 13 of the filter 100 may connect the cell 30 to the proximal end 12 and the second set of linking members 18 may connect the cell 30 to the distal end 14 of the filter 100. The first set of linking members 16 and the second set of linking members 18 may include any number of linking elements depending upon the size of the filter 100. In an embodiment, the first set of linking members 16 may include three linking elements. Similarly, the second set of linking members 18 may include three linking elements. In another embodiment, one of the first set of linking members 16, say 16a, may connect the independent leg 19 to the proximal end 12 and one of the second set of linking members 18, say 18a, may connect the independent leg 19 to the distal end 14 of the filter 100 as depicted in FIG.1
[030] The process of manufacturing of the filter 100 is now explained with the help of a flow chart. FIG. 3 illustrates an exemplary process involved in manufacturing of the filter 100. The filter 100 may be manufactured by laser cutting of a nitinol tube and/or by braiding of nitinol strands over a mandrel. In an exemplary embodiment, the filter 100 is manufactured by laser cutting of the nitinol tube.
[031] The process of manufacturing of the VC filter 100 commences at a step 301. At this step, the nitinol tube (not shown) is cut to form the retrieval member 20, the set of legs 10, the first set of strut members 16, the second set of strut members 18 and cuts 31 in the nitinol tube as depicted in FIG.2.
[032] The nitinol tube may be an oxide free tube. The cutting may be performed by any means such as without limitation liquid jet machining, laser cutting, abrasive jet machining, etc. In an embodiment, the cutting of the nitinol tube is performed by means of laser cutting. The diameter and/or thickness of the nitinol tube may directly influence the strength of the filter 100. The diameter and the thickness of the nitinol tube may be in range of 1 mm to 4 mm and 150 microns to 500 microns respectively. In an embodiment, the diameter of the nitinol tube is in a range of 1.5mm to 3mm and thickness is in a range of 250 microns to 350 microns.
[033] The laser cutting may be performed with a laser beam of pulse width in a range of 0.01ms to 0.05ms. The laser cutting may also be performed with an inert gas. The inert gas may be without limitation argon, nitrogen etc. In an embodiment, the inert gas is argon. The pressure of argon is in a range of 2 bars to 18 bars, preferably 6 to 7 bars.
[034] Further at step 303, the filter 100 obtained at the previous step (as shown in FIG.2) is subjected to a process of honing to produce an internal smooth surface of the filter 100. The process of honing may be performed by means of an abrasive stone. The process may include inserting a mandrel inside the filter 100 to remove debris from the internal surface of the filter 100. A lubricant may also be used for easy removal of the debris.
[035] At step 305, the filter 100 is subjected to a process of shape setting. The shape setting may be performed means of heat treatment in a mold 200 as depicted in FIG. 4. The mold may be customized to yield a required shape of the filter 100. In an embodiment, the mold 200 is provided in a cylindrical shape. The mold 200 may have a length 20mm and diameter 30mm.
[036] The laser cut tube (as depicted in FIG.2) is mounted on the mold 200. The mold 200 may include at least two grooves 40 and 42. The grooves 40, 42 may hold the struts 16, 18 (as depicted in FIG.2) for further processing as mentioned in paragraphs 35 and 36.
[037] At this step, the filter 100 is placed on the mold 200 and the barbs 32 of the legs 10 of the filter 100 are inclined with respect to a horizontal axis of the fitler100. The barbs 32 may be inclined manually with the help of forceps. The barbs 32 may be inclined at a predefined angle of inclination, say A. The predefined angle of inclination A may be in a range of 100° to 160°. In an embodiment, the predefined angle of inclination A is in a range of 80° to 140°. The inclined barbs 32 avoids piercing and/or harming the wall of blood vessel. Further, the inclined barbs 32 may prevent deflection of the filter 100 at the implantation site.
[038] Following inclination of the barbs 32, the filter 100 is shape set by heat treatment at a temperature in a range of 480°C to 600°C, preferably in a range of 490°C to 540°C and more preferably at 500°C to 520°C. In an embodiment, the heat treatment is performed at a temperature of 505°C. The time duration of heat treatment may be in range of 1 to 13 minutes, preferably 03 to 08 minutes. In an embodiment, the heat treatment is performed for a time duration of 05 minutes. Subsequently the filter 100 is subjected to a process of quenching for a time duration of 20 minutes. The process of quenching may release the stress generated during the heat treatment.
[039] At step 307, the filter 100 is subjected to process of sand blasting. The process of sand blasting may be performed by means of aluminum oxide powder. The aluminum oxide powder is allowed to strike on an outer surface of the filter 100 at a predefined frequency for a predefined period of time. The predefined frequency and the predefined time may be in a range of 45 to 85 Hz and 3minutes to 10 minutes. In an embodiment, the frequency is in range of 55 to 65 Hz and time is 5minutes to 8minutes. The pressure exerted by the powder may vary in a range of 20 psi to 90 psi, preferably in a range of 30 psi to 60 psi. The process sand blasting may produce highly smooth outer surface of the filter 100 due to abrasion with the aluminum powder. The process of sand blasting may also remove oxide layers, striations left by laser cutting in previous step, decrease propensity for micro cracking and/or provide light texture to the outer surface of the filter 100.
[040] Lastly, at step 309, the filter 100 is subjected to a process of electropolishing. The process of electropolishing is performed by immersing the filter 100 in solution of electrolytes and passing the current at a predefined voltage for a predefined time duration. The electrolytes may be concentrated acid solution such as mixture of perchlorates with acetic anhydride and methanolic solutions of sulfuric acid. The voltage used for the electro polishing is from 3V to 9V, preferably from 4V to 8V and the current is from 0.3A to 1.5A, preferably from 0.6A to 1.2A. The predefined time duration is in a range of 1 minutes to 8 minutes, preferably 2 to 6 min.
[041] 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.