Randomized Controlled Study of an Absorbable Vena Cava Filter in a Porcine Model

Abstract

Purpose: To compare the safety and efficacy of an absorbable inferior vena cava (IVC) filter and a benchmark IVC filter in a porcine model.

Materials and methods: A randomized controlled Good Laboratory Practice study was performed in Domestic Yorkshire cross swine. Sixteen swine were implanted with an absorbable IVC filter (test device; Adient Medical, Pearland, Texas); 8 were implanted with a benchmark metal IVC filter (control device; Cook Medical, Bloomington, Indiana). All animals underwent rotational digital subtraction pulmonary angiography and cavography (anteroposterior and lateral) before filter deployment and 5 and 32 weeks after deployment. Terminal procedures and necropsy were performed at 32 weeks. The IVC, heart, lungs, liver, and kidneys were harvested at necropsy. The reported randomized controlled GLP animal study was conducted at Synchrony Labs, Durham, North Carolina.

Results: One animal died early in the test cohort of a recurring hemorrhage at the femoral access site resulting from a filter placement complication. All other animals remained clinically healthy throughout the study. No pulmonary embolism was detected at the 5- and 32-week follow-up visits. The absorbable filter subjects experienced less caval wall perforation (0% vs 100%) and thrombosis (0% vs 75%). The control device routinely perforated the IVC and occasionally produced collateral trauma to adjacent tissues (psoas muscle and aorta). The veins implanted with the absorbable filter were macroscopically indistinguishable from normal adjacent veins at 32 weeks except for the presence of radiopaque markers. Nontarget tissues showed no device-related changes.

Conclusions: Implantation of the absorbable IVC filter in swine proved safe with no pulmonary emboli detected. There was complete to near-complete resorption of the filter polymer by 32 weeks with restoration of the normal appearance and structure of the IVC.

Copyright © 2019 SIR. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1.

(a) Control (metal) Cook Celect filter and (b) test (absorbable) Adient Absorbable filter.

Figure 2.

Representative digital venacavogram frame for a control (metal) IVC filter in porcine taken at 5 weeks after filter placement. Note the filter struts have perforated the caval wall (arrows) defined by the contrast-filled IVC.

Figure 3.

Representative venacavogram frame for a test (absorbable) IVC filter in porcine at 5 weeks. Arrow denotes location of right renal vein influx. RO = radiopaque.

Figure 4.

Representative venacavogram frame for a test (absorbable) IVC filter in porcine at 32 weeks. Note the stent and basket portions have resorbed, leaving only the radiopaque (RO) markers in the caval wall.

Figure 5.

Group 2 metal IVC filter within IVC. Arrows indicate filter struts penetrating through the wall of the vein within the perivascular tissue; V = vein proximal to the implant site, the vein is distended by the filter and remodeled around the outer most struts.

Figure 6.

(a) Group 3 metal IVC filter within IVC. Arrows indicate filter struts penetrating through the wall into adjacent tissue (ie, skeletal muscle [M, white arrow] and aorta [A, black arrow]); V = vein proximal to the implant site where cephalic portion of the filter resides, the vein is distended by the filter and remodeled around the outer most struts. (b) Hematoxylin and eosin–prepared slide of filter strut penetrating the aorta (A). Arrow indicates cap of fibrocellular neointima covering the tip of the strut penetration within the lumen and arrowhead indicates filter strut penetrating the aorta.

Figure 7.

Group 1, absorbable IVC filter within IVC. The vein is normal and morphologically and structurally indistinguishable from unimplanted vein. V = vein proximal to implant site; arrow, filter tip embedded in the wall of the vein; arrowheads, filter barbs within the vein wall.

Figure 8.

(a) Group 1 absorbable IVC filter at 32 weeks using hematoxylin and eosin. Arrow, minimal inflammation (aggregate of lymphocytes) within the vein wall; dotted lines, clusters of foamy macrophages (biomaterial phagocytosis) at the location of the PDO suture from the stent section of the filter. Black frame shows area enlarged in (b). Arrowhead = hemosiderin; V = vein.

Figure 9.

(a) Group 2 metal IVC filter at 32 weeks using hematoxylin and eosin. Arrow, minimal focal para-strut inflammation. Black frame shows area detailed in (b). Arrowheads = filter struts embedded in the mature fibrocellular neointima; V = vein lumen.