Patent Abstract:
an absorbable vascular filter is disclosed for deployment within a vessel for temporary filtering of body fluids . a preferred embodiment is the placement of such absorbable vascular filter within the inferior vena cava to filter emboli for the prevention of pulmonary embolism for a limited duration in time . once protection from pe is complete , the filter is sequentially biodegraded according to a planned schedule determined by the absorption properties of the filter components . hence the temporary absorbable vascular filter obviates the long term complications of permanent ivc filters such as increased deep vein thrombosis , while also circumventing the removal requirement of metal retrievable ivc filters .

Detailed Description:
embodiments of the present invention will now be described in detail with reference to the drawings , which are provided as illustrative examples so as to enable those skilled in the art to practice the invention . notably , the figures and examples below are not meant to limit the scope of the present invention to a single embodiment , but other embodiments are possible by way of interchange of some or all of the described or illustrated elements . wherever convenient , the same reference numbers will be used throughout the drawings to refer to same or like parts . where certain elements of these embodiments can be partially or fully implemented using known components , only those portions of such known components that are necessary for an understanding of the present invention will be described , and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention . in the present specification , an embodiment showing a singular component should not be considered limiting ; rather , the invention is intended to encompass other embodiments including a plurality of the same component , and vice - versa , unless explicitly stated otherwise herein . moreover , applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such . further , the present invention encompasses present and future known equivalents to the components referred to herein by way of illustration . referring to the embodiment depicted in fig1 a - e , an absorbable vascular filter 1 consists of an outer , circumferential element 2 for supporting a plurality of absorbable filter capture elements ( 30 - 32 , 40 - 41 ). the capture elements are purposely designed to be biologically absorbed and / or degraded in a sequential manner to avoid simultaneous detachment of the entire filter causing an unexpected embolus . the sequential bioabsorption / biodegradation is illustrated in fig1 b - e where decomposition begins with the proximal capture elements 30 , progressing to the middle section capture elements 31 , and finally full bioabsorption / biodegradation as depicted in fig1 e . such engineered , sequential bioabsorption / biodegradation of the capture elements can be achieved with numerous synthetic materials . the goal is to select the absorbable filter materials to match a desired filter indwell time . per the prior background section , a filter indwell time of 6 weeks would be suitable for an ivc filter to prevent pe following trauma or in conjunction with major surgeries . plausible synthetic materials include : polydioxanone ( pdo , pds )— colorless , crystalline , biodegradable synthetic polymer of multiple repeating ether - ester units . in suture form , pds ii ( ethicon , somerville , n . j .) size 4 / 0 and smaller maintains 60 %, 40 %, and 35 % of its tensile strength at 2 , 4 , and 6 weeks respectively . for pds ii size 3 / 0 and larger , it retains 80 %, 70 %, and 60 % of its tensile strength at 2 , 4 , and 6 weeks respectively . in addition to providing wound support for 6 weeks , pds ii suture is fully absorbed in 183 - 238 days via hydrolysis making it a strong candidate for ivc filter applications . basically absorption is minimal in the first 90 days and is essentially complete in 6 months . finally , pds has a low affinity for microorganisms and possesses minimal tissue reaction . polytrimethylene carbonate ( maxon )— similar to pds in absorption profile yet with slightly higher breaking strength . maxon ( covidien , mansfield , mass .) maintains 81 %, 59 %, and 30 % of its tensile strength at 2 , 4 , and 6 weeks respectively , and is fully hydrolyzed in 180 - 210 days . polyglactin 910 ( vicryl )— braided multifilament coated with a copolymer of lactide and glycolide ( polyglactin 370 ). in suture form , vicryl ( ethicon ) size 6 / 0 and larger maintains 75 %, 50 %, and 25 % of its tensile strength at 2 , 3 , and 4 weeks respectively and is fully absorbed in 56 - 70 days . polyglycolic acid ( dexon )— similar to polyglactin , made from polyglycolic acid and coated with polycaprolate . dexon has similar tensile strength and absorption profile as polyglactin . poliglecaprone 25 ( monocryl )— synthetic copolymer of glycolide and e - caprolactone . monocryl ( ethicon ) maintains 50 %- 70 % and 20 %- 40 % of its tensile strength at 1 and 2 weeks respectively and is fully absorbed in 91 - 119 days . polylacticoglycolic acid ( plga ) copolymer of monomers glycolic acid and lactic acid . different forms and properties of plga can be fabricated by controlling the ratio of lactide to glycolide for polymerization . like the other synthetic absorbable materials , plga degrades by hydrolysis with the absorption profile dependent on the monomer ratio ; the higher content of glycolide , the faster degradation . however , the 50 : 50 copolymer exhibits the fastest degradation at 2 months . since the polymer degrades in the body to produce lactic acid and glycolic acid , both being normal physiological substances , plga poses minimal systemic toxicity . as a specific example of engineering capture elements to sequentially degrade following the period of pe protection , the proximal capture elements 30 , 41 could be fabricated with pds ii size 4 / 0 ( 0 . 15 mm dia . ), while the middle capture elements 31 , 40 fabricated with size 2 / 0 ( 0 . 3 mm dia . ), and finally the distal capture elements 32 fabricated with size 2 ( 0 . 5 mm ) pds ii suture . as an alternative to assembling a plurality of capture elements , the vascular filter can be fabricated with absorbable or non - absorbable composite mesh . candidates for a mesh capture system include polypropylene such as c - qur ( atrium medical corp . hudson n . h . ), polypropylene encapsulated by polydioxanone as in proceed ( ethicon , somerville , n . j . ), polypropylene co - knitted with polyglycolic acid fibers as in bard sepramesh ip composite ( davol , inc ., warwick , r . i . ), polyethylene terephathalate as in parietiex composite ( covidien , mansfield , mass . ), and eptfe used in dualamesh ( w . gore & amp ; assoc . inc ., flagstaff , ariz .). regarding the circumferential element 2 in fig1 and 2 that serves to support the capture elements of the absorbable vascular filter and maintain filter positioning within the vessel upon expansion , either an absorbable material such as described above or non - absorbable material can be utilized . a non - absorbable material would essentially serve as a permanent stent , lasting well beyond the life of the absorbable capture elements . this may be an important option in cases where the vessel needs assistance in maintaining patency . both types of circumferential elements 2 would likely incorporate barbs 79 ( refer fig2 ) to maintain filter positioning upon deployment . plausible non - absorbing materials for constructing the circumferential element include : nitinol , elgiloy , phynox , 316 stainless steel , mp35n alloy , titanium alloy , platinum alloy , niobium alloys , cobalt alloys , and tantalum wire . fig2 a - 2 h illustrate another embodiment of the absorbable vascular filter wherein the absorbable capture elements 60 - 64 are mounted to a simple circumferential element 2 held against the vessel wall 70 with barbs 79 . here again the circumferential element 2 can be fabricated with absorbable or non - absorbable materials of the like described above . an enlarged cross - sectional view of the capture element assembly 65 is shown in fig2 b . notice that the sequential degradation of the capture elements is achieved by varying the diameter of the chosen absorbable material . for example , the inner capture element 60 could be pds ii 4 / 0 ( 0 . 15 mm dia .) resulting in the fastest absorption as illustrated in fig2 d at time t 1 , followed by capture element 61 degradation being pds ii 3 / 0 ( 0 . 20 mm dia .) at time t 2 in fig2 e , followed by capture element 62 degradation being pds ii 2 / 0 ( 0 . 30 mm dia .) at time t 3 in fig2 f , followed by capture element 63 degradation being pds ii 0 ( 0 . 35 mm dia .) at time t 4 in fig2 g , and finally the degradation of the last capture element 64 constructed of pds ii 1 ( 0 . 40 mm dia .) at time t 5 in fig2 h . overall , a gradual progression of degradation is designed purposely following a prophylactic window of 6 weeks for trauma and major surgery applications . a preferred installation of the absorbable vascular filter is via intravenous insertion with a catheter requiring only a local anesthetic as illustrated in fig3 a - e . here the filter is collapsed and compressed within a delivery catheter comprised of an outer sheath 71 and internal applicator or stabilizer 73 on a central rod 72 as illustrated in fig3 a . for ivc filter deployment , the delivery catheter is inserted into the patient &# 39 ; s vasculature of convenient location , such as the femoral vein . subsequently , the delivery catheter is fed through the vasculature until reaching the desired deployment location , typically just inferior to the renal veins . next the compressed filter 50 is allowed to expand upon sliding the exterior sheath 71 in the distal direction while simultaneously holding the stabilizer rod 72 steady ( refer fig3 b ). once the exterior sheath 71 is withdrawn distally away from the filter , the stabilizing rod 73 can also be retracted distally as depicted in fig3 c . consequently as a thrombosis event releases an embolus 80 , the embolus is captured by the absorbable vascular filter and is prevented from traveling to the heart and lungs thereby preventing a potentially fatal pe ( refer fig3 d ). following the desired prophylactic time window for filter utilization ( approximately 6 weeks in many applications ), the filter is biologically absorbed resulting in the absence of any foreign material in the vessel as depicted in fig3 e . although the present invention has been described with reference to specific exemplary embodiments , it will be evident to one of ordinary skill in the art that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention . accordingly , the specification and drawings are to be regarded in an illustrative rather than a restrictive sense . goldhaber s z , ortel t l . the surgeon general &# 39 ; 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