Our results demonstrate the preliminary safety and efficacy of a nearly completely absorbable filter in the inferior vena cava for short-term protection (<5 weeks) against pulmonary embolism.
Abstract
Purpose
To evaluate the immediate and long-term safety as well as thrombus-capturing efficacy for 5 weeks after implantation of an absorbable inferior vena cava (IVC) filter in a swine model.
Materials and Methods
This study was approved by the institutional animal care and use committee. Eleven absorbable IVC filters made from polydioxanone suture were deployed via a catheter in the IVC of 11 swine. Filters remained in situ for 2 weeks (n = 2), 5 weeks (n = 2), 12 weeks (n = 2), 24 weeks (n = 2), and 32 weeks (n = 3). Autologous thrombus was administered from below the filter in seven swine from 0 to 35 days after filter placement. Fluoroscopy and computed tomography follow-up was performed after filter deployment from weeks 1–6 (weekly), weeks 7–20 (biweekly), and weeks 21–32 (monthly). The infrarenal IVC, lungs, heart, liver, kidneys, and spleen were harvested at necropsy. Continuous variables were evaluated with a Student t test.
Results
There was no evidence of IVC thrombosis, device migration, caval penetration, or pulmonary embolism. Gross pathologic analysis showed gradual device resorption until 32 weeks after deployment. Histologic assessment demonstrated neointimal hyperplasia around the IVC filter within 2 weeks after IVC filter deployment with residual microscopic fragments of polydioxanone suture within the caval wall at 32 weeks. Each iatrogenic-administered thrombus was successfully captured by the filter until resorbed (range, 1–4 weeks).
Conclusion
An absorbable IVC filter can be safely deployed in swine and resorbs gradually over the 32-week testing period. The device is effective for the prevention of pulmonary embolism for at least 5 weeks after placement in swine.
© RSNA, 2017
Introduction
Pulmonary embolism (PE) is the third leading cause of death in the United States and accounts for approximately 100 000 deaths annually (1). Mechanical and pharmacologic therapies are effective modalities to prevent life-threatening PE (2). However, for patients in whom anticoagulation is contraindicated, inferior vena cava (IVC) filters are an effective adjunctive therapy for the prevention of PE (3–5). For this reason, the Eastern Association for the Surgery of Trauma guidelines suggests prophylactic filters in high-risk patients (6). Although the duration of protection against PE is variable in this patient population, 35 days is generally considered to be sufficient (7–11).
Conventional metallic filters are associated with acute and recurrent deep venous thrombosis, IVC thrombosis, and recurrent PE, and IVC filter migration, penetration, fracture, and embolization (12–16). To mitigate the long-term complications associated with permanent metallic filters, retrievable filters were developed to provide the patient with protection against PE during the anticoagulation contraindication period, after which the filter could be removed. However, in practice, many filters are never retrieved (17). Theoretically, an absorbable filter would be clinically advantageous, because it would protect the patient against PE during the period of contraindication to anticoagulation and then resorb, which would obviate an additional filter-retrieval procedure. We recently published our initial findings in three swine by using a novel absorbable IVC filter manufactured from polydioxanone (PDSII; Ethicon, Somerville, NJ) (18). The purpose of our study was to evaluate the immediate and long-term safety as well as thrombus-capturing efficacy for 5 weeks after implantation of an absorbable IVC filter in a swine model.
Materials and Methods
Animal Care
The institutional animal care and use committee approved our study. Animals were maintained in facilities approved by the Association for Assessment and Accreditation of Laboratory Animal Care and in accordance with current U.S. Department of Agriculture, Department of Health and Human Services, and National Institutes of Health regulations and standards. Eleven swine (nine domestic swine and two Yucatan miniature swine) were included in our study and underwent placement of an absorbable filter. This subcontracted study was funded through a Small Business Innovation Research phase II grant from the National Heart, Lung, and Blood Institute of the National Institutes of Health awarded to Adient Medical. The following authors reported the following conflicts of interests: M.E. is the owner and founder of Adient Medical; S.D. is an employee of Adient Medical; and S.Y.H., J.R.S., and M.J.W. serve on the scientific advisory board for Adient Medical. The protocol for this study and primary data will be available to the public.
Filter Manufacturing
Briefly, the absorbable filters (Adient Medical, Pearland, Tex) were braided from polydioxanone suture by using a mandrel to produce a filter measuring 47 mm (length) × 20 mm (diameter), which was previously described (18). The filter was designed in a conical fashion with a stent and conical portion (Fig 1); the conical component served as the capture basket. Four 2-mm stainless steel barbs were crimped onto the absorbable suture around the circumference of the filter to serve as anchors and radiopaque markers. A platinum iridium cylindrical radiopaque marker was fit into the tip of the filter. The filters were annealed in an oven at 71°C for 30 minutes and packaged for ethylene oxide sterilization.
Figure 1:
Photograph of the absorbable IVC filter made from polydioxanone suture. The filter is composed of a stent portion that adheres to the caval wall and a cone portion.
Preprocedure Preparation, Filter Deployment, and Follow-up
All interventional procedures were performed by a single operator (S.Y.H., with 8 years of experience). Filter placement procedures were performed through a percutaneous transfemoral venous technique. Eleven adult swine were sedated with an intramuscular injection of ketamine hydrochloride (15 mg/kg), acepromazine (0.15 mg/kg), and atropine sulfate (0.04 mg/kg). Anesthesia was induced with isoflurane (5%) administered by face mask. An endotracheal tube was then inserted, and anesthesia was maintained with isoflurane (1.5%–3%) and oxygen (0.8 L per minute).
Before catheter deployment of the filter, all swine were given a bolus of heparin (50 units per kilogram). Access from the right femoral vein to the right jugular vein was obtained to ensure that control of the filter was maintained throughout the procedure. The femoral access was sequentially dilated to accommodate a 16-F vascular sheath (Check-Flo Introducer; Cook Medical, Bloomington, Ind). By using a pigtail catheter positioned within the right common iliac vein, venacavography was performed to delineate the location of the renal veins and to assess the infrarenal IVC diameter. The filter was compressed and loaded over the wire into the introducer. An over-the-wire pusher was then used to advance the filter to the sheath tip. With slight forward pressure on the pusher, the sheath was pulled back to expose the filter. A balloon (Coda K032869; Cook Medical) was advanced over the wire into the conical and stent components of the filter. The balloon was inflated to a pressure of 10–18 mm Hg for 5–10 seconds to maintain wall apposition. The balloon was then removed and a pigtail catheter was reintroduced into the right iliac vein, and venacavography was performed.
Imaging follow-up with venacavography and computed tomography (CT) (GE LightSpeed; GE Healthcare, Waukesha, Wis) with and without intravenous contrast agent (iodixanol 320, GE Healthcare) was performed weekly for 6 weeks after filter implantation, biweekly from 7 to 20 weeks, and every 4 weeks thereafter. The following factors were evaluated by using CT: IVC thrombosis, narrowing, filter penetration, migration, PE, and access site thrombosis. For all swine, we evaluated at the same frequency as our imaging timeline serial hematologic samples for sodium, potassium, chloride, creatinine, white blood cell count, hemoglobin, platelets, prothrombin time, partial thromboplastin time, aspartate aminotransferase, alanine aminotransferase, and arterial pH, and partial pressure of carbon dioxide, partial pressure of oxygen, and oxygen saturation.
Administration of Autologous Thrombus
Ex vivo autologous thrombus was formed by aspirating blood from the each swine in a 3-mL syringe (19). The blood was then incubated at 4°C for 1 week. After incubation, any residual supernatant was discarded and the solid thrombus measuring 8 mm in diameter (range, 5–15 mm) by 26 mm in length (range, 18–55 mm) was loaded into a 16-F sheath, which was advanced into the central right iliac vein in seven swine surviving for 12, 24, and 32 weeks after filter deployment. For the seven swine, thrombus was deployed 0, 4, 4, 4, 14, 14, and 35 days, respectively, after filter deployment. After deployment, immediate venacavography and CT imaging of the chest (at pulmonary arterial phase) and abdomen and pelvis (at delayed venous phase) were performed to evaluate the extent of thrombus within the filter and CT evidence of PE.
Necropsy and Histologic Analysis
Animals with a filter were assigned to survive 2 weeks (n = 2), 5 weeks (n = 2), 12 weeks (n = 2), 24 weeks (n = 2), and 32 weeks (n = 3). The predetermined end points were chosen to assess the filter for formation of endothelial tissue (2 weeks), filter integrity at the end of the proposed indication period (5 weeks), and degree of filter resorption (12, 24, and 36 weeks). At necropsy, the IVC, lungs, heart, liver, kidneys, and spleen were removed from each animal. Histologic changes were evaluated with hematoxylin-eosin staining. Presence of polydioxanone in the samples was assessed by passing specimens under polarized light.
Sample Size Calculation and Statistical Methods
The number of animals for the proposed study was determined with the objective of having a reasonable chance of observing at least one complication (eg, access site thrombosis, 1%; filter embolization, 2%; recurrent PE, 5%; IVC occlusion, 10%; and death, 1%). These complication rates were adapted from guidelines for filter placement established by the Society of Interventional Radiology (20). To determine the number of animals necessary to observe at least one filter-related complication, we considered a binomial distribution where the probability of observing a complication in any one animal as a value between 0.10 (corresponding to the 10% event rate for IVC occlusion) and 0.19 (corresponding to the summation of probability for complications listed previously). The range of probabilities is provided because it is not known a priori whether the complication events encountered in this study would be mutually exclusive or independent. The corresponding probability of overall success among the animals is equal to (1 − p)N, where p is probability and N is number of animals. Thus, the probability of observing at least one complication is the complement [1 − (1 − p)N]. Consequently, the probability of observing at least one complication in the first 2 weeks is 0.686–0.902 (11 swine) and the probability of observing at least one complication in the first 5 weeks is 0.613–0.850 (nine swine). Results were reviewed by all the authors and results were decided by consensus for cases in which there was a discrepancy. Continuous variables were evaluated with Student t test. A P value less than .05 was considered to indicate statistical significance.
Results
Preprocedure Preparation, IVC Filter Deployment, and Follow-up
The 11 filters were deployed in the intended infrarenal IVC location. However, one filter required more advanced maneuvers to be fully deployed. In this particular case, the filter was advanced through the sheath into an infrarenal location. The sheath was then pulled back to expose the filter and the balloon was advanced into the filter. After venoplasty, the balloon was deflated and retracted. The filter, however, pulled back with the balloon, indicating that the filter was not engaged against the caval wall. The sheath was then advanced to the most inferior portion of the filter and the balloon catheter was retracted, eventually disengaging itself from the filter. The balloon catheter was then removed and a new balloon catheter was advanced, and serial insufflation was performed beginning from the caudal portion of the filer by progressing cranially. No complications other than this incident were noted. Specifically, there was no IVC thrombosis, filter penetration, or access site thrombosis.
CT imaging demonstrated narrowing that involved the IVC in the region of the stent portion of the filter. The degree of narrowing, measured by using CT, is presented in Table 1. The luminal narrowing peaked 5 weeks after filter deployment and measured 38.0%. After week 5, the luminal area gradually returned to baseline dimensions. Figure 2 shows changes in the IVC at fluoroscopy and CT with pathologic correlation at 2, 5, 12, 24, and 32 weeks after filter deployment. Similar to the changes observed with the caval lumen, the degree of wall thickening appeared to peak during weeks 4–6 after filter implantation and then gradually regressed toward the baseline dimensions thereafter. This also appeared to coincide with IVC wall hyperplasia observed by using pathologic analysis (see Necropsy and Histologic Analysis). Of note, IVC wall thickening and luminal narrowing were exacerbated by the swine with the difficult filter deployment; wall thickening peaked at weeks 5 and 6 after filter deployment, with luminal diameter decreasing from 1.4 × 0.8 cm (baseline, area 0.88 cm2) to 0.4 × 0.4 cm (week 5 and 6, area 0.13 cm2) within the stent component of the filter. At the time of necropsy for this swine, the IVC dimensions measured 1.2 × 0.6 cm (week 24, area 0.82 cm2). Figure 3 depicts the degree of caval luminal narrowing over the course of the study for all swine included in the study (n = 11, includes the swine with the complicated filter deployment) and for only the swine with uncomplicated filter deployments (n = 10). If the swine with the poorly deployed filter were excluded from the caval narrowing calculations, then the average IVC luminal narrowing would peak at 30.7% versus 38.0%.
Table 1.
Cross-sectional Area of the IVC in the Region of the Stent Portion of the Filter over Time
Note.—Data in parentheses are range. Areas were modeled as an ellipse and measured on the basis of the cross-sectional diameters of the IVC at contrast agent–enhanced CT imaging. Swine were euthanized and relevant tissues were harvested at the following time points: 2 weeks (n = 2), 5 weeks (n = 2), 12 weeks (n = 2), 24 weeks (n = 2), and 32 weeks (n = 3). NA = not applicable.
*Unable to obtain CT images for two swine during the time period referenced.
†Unable to obtain CT images for one swine during the time period referenced.
Figure 2:
Changes involving the IVC at baseline and after deployment of IVC filter (cone and stent delineated by double-headed arrows in top row) on fluoroscopic images (top row), axial CT images (middle row, white arrows), and hematoxylin-eosin–stained slides (bottom row) for five different swine. On the baseline fluoroscopic image, note right (arrowhead) and left (double arrowhead) renal vein inflow. Filters were deployed in an infrarenal position. Baseline histologic slides were not obtained because animals were not immediately killed after filter deployment. Axial CT and hematoxylin-eosin–stained images were obtained through the stent component of the filter and demonstrate hyperplasia of the inferior caval wall, which is most pronounced at weeks 2 and 5 after filter deployment. The embedded fragments of polydioxanone (black arrows) are located within the caval wall and gradually degrade with evidence of granulomatous inflammation (ie, multinucleated giant cells, histiocytes, and lymphocytes; arrowheads in bottom row), which are difficult to identify by week 32.
Figure 3:
Graph of the average luminal area of the IVC within the stent portion of the filter plotted against time. Area calculations were on the basis of CT imaging and the area of the lumen was modeled as an ellipse. Vertical bars represent maximum and minimum values at each time point.
Animals were followed clinically for signs of distress throughout the study (eg, poor appetite, lack of socialization, and lethargy). No deaths occurred as a result of the filter. One of the 11 swine marked for the 12-week study end point was killed early at 9 weeks after filter implant. This swine was involved in an altercation with another swine and soon afterward became acutely lethargic and withdrawn. Conservative measures to comfort the swine were unsuccessful and it was decided to humanely kill the swine. Necropsy demonstrated a ruptured right hemidiaphragm, right lung collapse, and intrathoracic gastric displacement related to trauma. For all swine, serial hematologic samples did not differ significantly from baseline values throughout the study (Table 2).
Table 2.
Serial Hematologic Parameters (Average) for All Swine Included in the Study
Note.—Samples were obtained while the swine was mechanically ventilated. ALT = alanine aminotransferase, AST = aspartate aminotransferase, Cr = creatinine, Hgb = hemoglobin, pCO2 = partial pressure of carbon dioxide, pO2 = partial pressure of oxygen, PT = prothrombin time, PTT = partial thromboplastin time, SO2 = saturation of oxygen in arterial blood, WBC = white blood cell.
Administration of Autologous Thrombus
Iatrogenic thrombus was successfully deployed inferior to the filter in seven swine. All thrombi were captured and maintained inferior to the absorbable filter until autologous thrombolysis at follow-up CT imaging (median time to complete thrombolysis after clot deployment, 3 weeks; range, 1–4 weeks). Importantly, there was no evidence of PE at follow-up CT imaging (mean, 146 days; range, 59–225 days). A representative image from venacavography immediately after thrombus deployment is shown in Figure 4.
Figure 4:
Venacavogram immediately after iatrogenic thrombus deployment from the IVC below the level of the filter. The thrombus (*) was captured completely with no evidence of PE at immediate follow-up CT examination of the chest during the pulmonary arterial phase of contrast-agent enhancement (not shown).
Necropsy and Histologic Analysis
Neointima formation indicative of filter formation of endothelial tissue was observed in the swine at 2, 5, 12, 24, and 32 weeks (n = 11). Between 2 and 12 weeks, there was fibromuscular proliferation with neovascularization and minimal inflammatory reaction. At 24 weeks, there was a prominent granulomatous inflammatory component (ie, multinucleated giant cells, histiocytes, and lymphocytes) at the implantation site indicative of filter resorption. At 32 weeks (three swine), the filter was not identified in one swine, while in the other two swine, the filter fibers had been reduced to small fragments up to approximately 40 μm with reduced granulomatous inflammation relative to swine at the earlier 24-week time point. Representative images of the IVC wall at 2, 5, 12, 24, and 32 weeks after implantation are shown in Figure 2. The filters were completely intact at 2 weeks (n = 2), 5 weeks (n = 2), and 12 weeks (n = 2). The suture fibers demonstrated evidence of fragmentation by 24 weeks after implantation.
Of note, there were two foci of polydioxanone fragments identified in the pulmonary parenchyma; one focus was identified in a swine at 24 weeks after implantation and another focus in a swine at 32 weeks after implantation. The suture identified in the lung measured approximately 30 μm and was surrounded by macrophages, and the semicrystalline filter fragments were confirmed with polarized light (Fig 5). In addition to these two foci of granulomatous inflammation, there were additional small scattered areas of granulomatous inflammation throughout the pulmonary parenchyma of all the swine, which were not associated with polydioxanone. The qualitative degree of granulomatous inflammation observed in the IVC wall and lungs is listed in Table 3. No granulomatous inflammation was observed in the other organs harvested: heart, liver, kidneys, and spleen. However, medial hyperplasia of small terminal coronary and pulmonary arterioles was observed in multiple animals.
Figure 5a:
Slides show filter fragments in the lung tissue of a swine. (a) Hematoxylin-eosin–stained lung tissue filter fragments (arrow and arrowhead) within terminal pulmonary arterioles in a swine that was euthanized at 24 weeks after filter deployment. (b) Confirmation of the polydioxanone filter fragments (arrow and arrowhead) was performed by passing the slide under polarized light. Fragments were surrounded by granulomatous inflammation, which is similar to findings identified in the cava wall. Fragments measured 11 × 31 μm (arrow) and 13 × 13 μm (arrowhead).
Table 3.
Qualitative Grading of Granulomatous Inflammation with or without Birefringent Material
Note.—Birefringent material refers to polydioxanone fragments. Data are for each swine, separated by a comma. Grading schema: 0, no significant lesion; 1, rare, ≤10%; 2, mild, 10%–20%; 3, moderate, 20%–50%; and 4, severe, >50%.
*Evidence of an underlying enzootic pneumonia, frequently from Mycoplasma hyopneumoniae, was present in the lungs of some swine included in the study.
Figure 5b:
Slides show filter fragments in the lung tissue of a swine. (a) Hematoxylin-eosin–stained lung tissue filter fragments (arrow and arrowhead) within terminal pulmonary arterioles in a swine that was euthanized at 24 weeks after filter deployment. (b) Confirmation of the polydioxanone filter fragments (arrow and arrowhead) was performed by passing the slide under polarized light. Fragments were surrounded by granulomatous inflammation, which is similar to findings identified in the cava wall. Fragments measured 11 × 31 μm (arrow) and 13 × 13 μm (arrowhead).
Discussion
This large animal study showed the preliminary safety and efficacy of an absorbable IVC filter. For all 11 filters, there was no evidence of IVC thrombosis, permanent IVC narrowing, filter penetration, PE, access site thrombosis, or death. However, there was one case of filter migration during deployment that required secondary maneuvers to ensure adequate device capture and repositioning. This event resulted in an overall filter-related complication rate of 9.1% (one of 11 filter deployments).
The deployment technique relied on obtaining access from the right internal jugular vein to the right common femoral vein and used a 16-F sheath in the right common femoral vein for device deployment to maintain control of the device until satisfactory deployment. The size of the swine femoral vein varied from 6 to 8 mm, similar in size to the 16-F deployment sheath with an outer diameter of 6.7 mm. At each follow-up interval, CT imaging of the femoral vein showed no evidence of access site thrombosis.
Hyperplasia of the IVC wall occurred after device implantation, which accounted for temporary IVC narrowing observed in all swine. Although the data in our study suggest that caval wall hyperplasia and luminal narrowing begins to regress 6–8 weeks after filter deployment, additional studies are needed to assess the long-term effect on the caval wall. Analysis would ideally also include a comparison with conventional metallic filters. Of note, there was increased hyperplasia of the caval wall involving the swine with the difficult filter deployment. It is possible that during the manipulation required to extract the balloon catheter, the retention barbs on the filter or, potentially, the filter itself caused caval wall injury, which exacerbated the wall hyperplasia and luminal narrowing.
The character and distribution of the mild edema and granulomatous inflammation identified in the lungs of the animals in our study can be seen with Mycoplasma hyopneumoniae, a frequent infection found in domestic swine. Thus, for the granulomatous lesions identified in the lungs, it is difficult to know whether the lesions arise from polydioxanone breakdown or an underlying enzootic pneumonia. Follow-up studies will likely benefit from the use of pathogen-free swine. The significance of the medial hyperplasia identified within the coronary and pulmonary arterioles is also unknown. Because there was no control arm in our study, it is not possible to ascertain whether these lesions were incidental aging changes, secondary to simultaneous disease processes, or potentially related to the hemodynamic changes resulting from the implantation of the absorbable polydioxanone filter.
The absorbable filter was 100% effective at capturing iatrogenic autologous thrombus ranging in size from 5 to 15 mm in diameter by 18–55 mm in length and deployed 0 to 35 days after filter placement. The intended duration of protection against life-threatening PE for this absorbable filter is 35 days after placement. In one swine, thrombus was deployed at 35 days after filter placement and the thrombus was successfully captured and held through resorption at 8 weeks. This indicated that the proposed prophylactic period of protection from PE of 5 weeks is most likely achievable. Furthermore, on the basis of our previous pilot study (18) in which polydioxanone was implanted into the jugular vein of swine, the strength of polydioxanone suture remained above 70% baseline strength until 6 weeks after filter deployment. It is important to note that filter degradation occurs by hydrolysis and this does not begin to occur until the filter is exposed to blood, provided it is stored in a moisture-barrier package.
Partially absorbable filters were previously studied in preclinical models (21,22). These partially absorbable filters are composed of a metallic strut to stabilize the filter against the caval wall. The filter in our study is nearly entirely composed of an absorbable material and dissolves completely without definite evidence of long-term sequelae in the IVC wall. Serum chemistries, complete blood count, liver function enzymes, coagulation profiles, and arterial blood gases remained normal for swine throughout the entirety of our study.
Similar to other IVC filters currently on the market, there is a theoretical risk of guidewire entrapment (23). There is also the possibility that passing catheters and wires through the filter may cause the filter to become deformed. Although the physical properties of polydioxanone may mitigate these risks, this would need to be further investigated. It should also be noted that in our study, a 16-F sheath was placed in the right common femoral vein over a Bentson guidewire (Cook Medical) to deploy iatrogenic thrombus. The Bentson guidewire was advanced beyond the filter and removed under careful fluoroscopic viewing for each animal that underwent thrombus deployment without any incidents of guidewire entrapment (n = 5). Preclinical investigations are currently underway to enhance the radiodensity of polydioxanone without sacrificing strength or affecting resorption (24).
This study has several important limitations. First, there was no control arm. During our pilot study (three swine), there were no complications associated with filter placement. Thus, we felt that excluding a control or sham arm would be appropriate. Our study had the power to detect adverse events with a probability of 83.2% during the first 5 weeks. However, as the number of swine decreased, the probability of being able to detect an adverse event related to the filter also decreased. Histopathologic analysis of the caval wall in the region of the filter demonstrated stromal thickening and a granulomatous inflammatory process composed of multinucleated giant cells, histiocytes, and lymphocytes. Further studies in humans will need to be performed to assess the degree of wall thickening and more accurately follow the timeline of resolution. Second, the absorbable filter in our study is not radiopaque and may prove problematic for patients who undergo catheterization of the IVC after filter placement. Third, the mechanism of polydioxanone resorption relies on hydrolysis. There is no reason that this would change as the filter is placed in humans. Nonetheless, filter integrity and strength retention would need to be verified. Finally, it should be noted that our study was not performed in a good laboratory practice facility and, therefore, it was not good laboratory practice compliant. A subsequent good laboratory practice study is currently underway.
In conclusion, our results demonstrate the preliminary safety and efficacy of a nearly completely absorbable IVC filter for short-term protection (<5 weeks) against PE. For patient populations in whom prophylaxis against PE is warranted (eg, patients with trauma and who are orthopedic preoperative), an absorbable filter can provide short-term protection against PE when anticoagulation is contraindicated. Absorbable filters offer the chief advantage of preventing life-threatening PE without the need for a second invasive procedure to remove the device. Although additional trials in animals and humans are needed to verify the findings of our preclinical study, our results are encouraging and indicate that an absorbable filter made from polydioxanone can be safe and effective.
Advances in Knowledge
■ An absorbable inferior vena cava (IVC) filter made from polydioxanone can be safely deployed in swine and resorbs over approximately 32 weeks.
■ The polydioxanone components of the filter induce a foreign body granulomatous reaction in the adjacent caval wall, and the foreign body granulomatous reaction causes circumferential caval wall thickening, which results in a decrease in cross-sectional area from 1 cm2 (range, 0.71–1.00 cm2) to 0.62 cm2 (range, 0.13–0.92 cm2) at 4–6 weeks after filter deployment; the cava cross-sectional area gradually returns to baseline approximately 32 weeks after filter deployment.
■ The absorbable IVC filter was able to capture iatrogenic thrombus measuring approximately 8 × 26 mm administered 1–4 weeks after device deployment without evidence of pulmonary embolism (PE).
Implications for Patient Care
■ An absorbable filter offers short-term protection from life-threatening PE without the need for device retrieval.
Acknowledgments
Acknowledgements
This article is a posthumous publication for Michael J Wallace. His guidance and vision brought this project to fruition.
Received August 22, 2016; revision requested October 31; revision received March 17, 2017; accepted April 5; final version accepted April 26.
Study supported by National Heart, Lung, and Blood Institute (R44HL 127734).
Disclosures of Conflicts of Interest: S.Y.H. Activities related to the present article: disclosed grants from Adient Medical. Activities not related to the present article: disclosed membership on a Scientific Advisory Board for Adient Medical and received stock options for this membership. Other relationships: disclosed no relevant relationships. M.E. Activities related to the present article: disclosed salary paid by Adient Medical. Activities not related to the present article: disclosed pending patent applications in the US including 13/403790, 15/174973, 15/586210, 15/586123, and 15/592043; additionally, patents are pending in Brazil, Japan, Canada, India, Republic of Korea, Australia, and Europen Patent Office; issued patent in China ZL 201280010783.0. Other relationships: disclosed no relevant relationships. M.J.M. Activities related to the present article: disclosed a grant from Adient Medical. Activities not related to the present article: disclosed no relevant relationships. Other relationships: disclosed no relevant relationships. D.A.D. disclosed no relevant relationships. A.M. disclosed no relevant relationships. S.D. Activities related to the present article: disclosed partial salary from Adient Medical. Activities not related to the present article: disclosed stock options from Adient Medical. Other relationships: disclosed no relevant relationships. L.R.H. disclosed no relevant relationships. M.P.M. disclosed no relevant relationships. J.R.S. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: disclosed stock options and member of the Medical Advisory Board for Adient Medical. Other relationships: disclosed no relevant relationships. M.J.W. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: disclosed membership on the Scientific Advisory Board. Other relationships: disclosed no relevant relationships.
Abbreviations:
- IVC
- inferior vena cava
- PE
- pulmonary embolism
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