Fernando Lostalé

Animal experience in the Günther Tulip retrievable inferior vena cava filter.

AbstractPurpose: To assess the retrievability of the Gunther Tulip temporary inferior vena cava filter from a technical viewpoint, and consider the histopathologic changes that occur at the anchoring site of the filter prongs to the vein endothelium in Landrace pigs. Methods: Twenty-two Gunther Tulip retrievable filters were inserted in 22 experimental Landrace pigs via the jugular vein. Device implantation time was 0, 3, 7, 12, 14, 15, 16, 20, 30, 35 and 56 days. Study subjects were divided into two groups. In one group the filter was retrieved percutaneously via the jugular vein whereas in the other group it was removed surgically. The specimens obtained (vena cava and filter) were histopathologically examined. Prior to filter retrieval, a venacavography was obtained in all cases. Degree of retrieval difficulty was rated as follows: no difficulty (N), slight (S), mild (M), high (H) and unretrievable (U). Results: Of the 22 implanted filters, 11 should have been removed percutaneously but this was impossible in three cases (U). In four cases the device was retrieved with no difficulty (N); in two cases the degree of difficulty was mild (M) and in other two it was high (H) and slight (S) respectively. Retrieval difficulties were observed after 16 days. Starting from day 20, there was evidence of fibrosis with thick intimal proliferation and total filter prong involvement, which accounts for the difficulty in retrieving the device. Conclusions: It is advisable not to exceed a filter retrieval time of 16 days in view of the fibrotic changes reported. It might be necessary to perform a larger study with more animals and with retrieval times between 14 and 20 days.

Retrieval of Gunther Tulip optional vena cava filters 30 days after implantation: a prospective clinical study.

PURPOSE To report on the feasibility and safety of retrieval of the Günther Tulip optional vena cava filter 30 days after initial implantation. MATERIALS AND METHODS From March 2004 to September 2005, a single-center prospective study was undertaken in 35 patients who required inferior vena cava (IVC) filtration. All the Günther Tulip filters (GTFs) were implanted with the intention to be removed 30 days after initial implantation. A modified commercial dynamometer was used to measure the force required to remove the device. The degree of difficulty to remove the GTF was classified into four levels: N (no difficulty, force of 0-4.41 N), M (medium difficulty, force of 4.41-5.88 N), G (great difficulty, force of 5.88-9.8 N), and U (unable to remove). Clinical follow-up was performed 1, 3, 6, and 12 months after filter retrieval by review of medical records and imaging. RESULTS Two of the 35 patients experienced extensive thrombosis in the IVC as revealed by abdominal computed tomography, and their filters were left in place on a permanent basis. One patient died of respiratory and cardiac failure during follow-up within the first 30 days after GTF insertion. Filter retrieval was attempted in the remaining 32 patients, and 31 of these attempts were successful (98%). The force necessary to disengage the GTF from the caval wall was less than 9.8 N (N, 79%; M, 13%; G, 6%). Attempts to remove the GTF failed in only one patient (2%). On follow-up times ranging between 14 and 640 days (mean, 342.5 d), no complications or cases of recurrent pulmonary embolism were observed in this patient population. CONCLUSION The Günther Tulip optional IVC filter can be safely placed and retrieved percutaneously 30 days after initial implantation.

Retrievability of Uncoated Versus Paclitaxel-coated Günther-Tulip IVC Filters in an Animal Model

PURPOSE To compare in a pilot study, the retrievability and inferior vena cava (IVC) wall reaction elicited by uncoated and paclitaxel-coated Günther-Tulip filters in the animal model. MATERIALS AND METHODS Three groups with five pigs each underwent infrarenal IVC implantation of Günther-Tulip filters. Paclitaxel-coated filters were used in Groups A and B and uncoated filters were used in Group C. Filters were removed at 14, 19, 22, 26, and 30 days after implantation. A laparotomy was performed to remove filters from animals in group A and filters from animals in groups B and C that could not be retrieved via the right transjugular approach. Filter-induced venous wall changes were evaluated by examination of IVC venography, feasibility of filter removal at different implantation times, and laparotomy and microscopic findings. Feasibility of filter retrieval and venous wall changes were correlated. RESULTS IVC cavography showed no abnormality. Filters in animals in group B were uneventfully removed by a right jugular approach. Uncoated filter removal was not feasible in three of five animals in group C (19, 22, and 26 days). Microscopically, animals in group A had absent filter-induced IVC wall changes at 14, 19, 22, and 26 days and minimal changes at 30 days post implantation; animals in group B had absent filter-induced IVC wall changes at 14, 19, and 22 days and minimal changes at 26 and 30 days; animals in group C had moderate filter-induced IVC wall changes at 14 days and severe changes at 19, 22, 26, and 30 days. CONCLUSIONS This pilot study suggests that endothelial reaction to the presence of IVC filters in the porcine model is diminished by addition of paclitaxel coating to these filters. Further studies are necessary to substantiate these results.

Laparoscopic Demonstration of Vena Cava Wall Penetration by Inferior Vena Cava Filters in an Ovine Model

PURPOSE To verify the penetration of struts and hooks of two inferior vena cava (IVC) filters (Günther tulip retrievable filter [GTF] and Celect filter) through the vena cava wall and to assess local or systemic complications resulting from this penetration. MATERIALS AND METHODS Eight IVC filters were placed in the IVC of four ewes for 30 days (1 GTF and 1 Celect filter in each ewe). Angiographic and laparoscopic examinations of the animals were performed to demonstrate the penetration through the vena cava wall, and the filters were removed under laparoscopic control. Specimens were extracted for anatomicopathological and histologic examination. RESULTS Two-projection cavography showed a filter leg seemingly out of the vena cava in 19 of 32 legs (59.3%). Laparoscopy showed 7 real penetrating legs (5 Celect filters and 2 GTFs) out of the 14 legs that could be identified by laparoscopy owing to technique limitations. Neither laparoscopy nor necropsy showed any sign of wall hemorrhage or other injuries. Histologic examination showed intimal remodeling and slight thickening of adventitial tissue around filter legs. CONCLUSIONS GTFs and Celect filters can produce a real penetration 1 month after implantation. This penetration did not lead to any complications in the IVC or surrounding tissues and did not compromise the subjects health in any of the studied cases.

¿Cuál es el tiempo límite para retirar un filtro de vena cava? Filtros opcionales de vena cava inferior:: recuperación 90 días después de su implantación. Modelo ovino

Objetivo Estudiar la posibilidad y la seguridad de recuperar filtros opcionales de vena cava Gunther-Tulip (FGT) a los 90 dias de su implantacion inicial en un modelo animal ovino. Material y metodos Se implantaron 30 FGT en otras tantas ovejas hembras y se intento recuperarlos 90 dias despues de su implantacion. Se realizo cavografia convencional en todos los casos antes y despues de la recuperacion, para evaluar la permeabilidad de la vena cava. Se obtuvieron medidas de la vena cava y se documento la presencia de complicaciones relativas a la implantacion y recuperacion del filtro de vena cava inferior (VCI). Se midio la fuerza requerida para recuperar los filtros de vena cava con un dinamometro comercial modificado y adaptado al equipo de recuperacion de FGT. El estudio histologico se centro en la pared de la VCI. Resultados La implantacion se efectuo con exito en todos los casos (100%). Una oveja desarrollo un pequeno foco de trombosis en una de las patas del filtro y otra presento un trombo pequeno en el interior del filtro. Se intento la recuperacion del filtro en las 30 ovejas y, excepto en un caso, el resultado fue satisfactorio (96,6%). En la recuperacion de los 30 FGT, la fuerza necesaria para desenganchar las patas del filtro de la VCI fue menor de 12 newtons (N). No se observo ninguna complicacion en los cavogramas ni en la autopsia. Se observaron diferentes grados de fibrosis en el estudio histologico. Conclusiones En un modelo animal ovino, la recuperacion de FGT a los 90 dias de su implantacion es posible, segura y facil, y requiere poca fuerza (mediana: 4,2 N).

Stents traqueales metálicos autoexpandibles. Estudio comparativo de 3 tipos diferentes de stents en un modelo animal

INTRODUCTION The objective of this study was to assess tracheal reactivity after the deployment of different self-expandable metal stents (SEMS). MATERIAL AND METHODS Forty female New Zealand rabbits were divided into four groups. Three groups received three different SEMS: steel (ST), nitinol (NiTi), or nitinol drug-eluting stent (DES); the fourth group was the control group (no stent). Stents were deployed percutaneously under fluoroscopic guidance. Animals were assessed by multi-slice, computed tomography (CT) scans, and tracheas were collected for anatomical pathology (AP) study. Data from CT and AP were statistically analyzed and correlated. RESULTS The DES group had the longest stenosis (20.51±14.08mm vs. 5.84±12.43 and 6.57±6.54mm in NiTi and ST, respectively, day 30; P<.05), and higher granuloma formation on CT (50% of cases). The NiTi group showed the lowest grade of stenosis (2.86±6.91% vs. 11.28±13.98 and 15.54±25.95% in DES and ST, respectively; P<.05). The AP study revealed that the ST group developed intense proliferative reactivity compared to the other groups. In the DES group, a destructive response was observed in 70% of the animals, while the NiTi was the least reactive stent. CT was more effective in detecting wall thickening (positive correlation of 68.9%; P<.001) than granuloma (not significant). CONCLUSIONS The ST group developed granulomas and significant stenosis. NiTi was the least reactive stent, while DES caused significant lesions that may be related to drug dosage. This type of DES stent is therefore not recommended for the treatment of tracheobronchial stenosis.

On Studying the Interaction Between Different Stent Models and Rabbit Tracheal Tissue: Numerical, Endoscopic and Histological Comparison

Stenting technique is employed worldwide for treating atherosclerotic vessel and tracheal stenosis. Both diseases can be treated by means of metallic stents which present advantages but are affected by the main problem of restenosis of the stented area. In this study we have built a rabbit trachea numerical model and we have analyzed it before and after insertion and opening of two types of commercial stent: a Zilver® FlexTM Stent and a WallStentTM. In experimental parallel work, two types of stent were implanted in 30 New Zealand rabbits divided in two groups of 10 animals corresponding to each stent type and a third group made up of 10 animals without stent. The tracheal wall response was assessed by means of computerized tomography by endoscopy, macroscopic findings and histopathological study 90 days after stent deployment. Three idealized trachea models, one model for each group, were created in order to perform the computational study. The animal model was used to validate the numerical findings and to attempt to find qualitative correlations between numerical and experimental results. Experimental findings such as inflammation, granuloma and abnormal tissue growth, assessed from histomorphometric analyses were compared with derived numerical parameters such as wall shear stress (WSS) and maximum principal stress. The direct comparison of these parameters and the biological response supports the hypothesis that WSS and tensile stresses may lead to a greater tracheal epithelium response within the stented region, with the latter seeming to have the dominant role. This study may be helpful for improving stent design and demonstrates the feasibility offered by in-silico investigated tracheal structural and fluid dynamics.

Pharmacokinetic Study of Paclitaxel Concentration after Drug-Eluting Balloon Angioplasty in the Iliac Artery of Healthy and Atherosclerotic Rabbit Models.

PURPOSE To assess whether the presence of an atherosclerotic lesion may alter the deposition kinetics of paclitaxel on the arterial wall after drug-eluting balloon (DEB) angioplasty, as well as paclitaxel concentrations in serum and in the recovered balloons. MATERIALS AND METHODS Three New Zealand White rabbit models were created: an atheroma group (arterial mechanical injury and hyperlipidic diet; group A), a prelesional group (fat arterial infiltration, hyperlipidic diet; group B), and a control healthy group (group C). Forty-five animals underwent DEB angioplasty in the iliac artery. Arteries and serum samples were analyzed by liquid chromatography/tandem mass spectrometry at 1, 24, 48, 72, and 96 hours (arteries) and at 1, 6, 12, and 24 hours (serum). Recovered balloons were analyzed by UV chromatography. Histologic and statistical analyses were also performed. RESULTS Group A showed significantly higher arterial paclitaxel concentrations in the first hour after DEB angioplasty (632.05 ng/mg ± 125.75 in group A vs 179.55 ng/mg ± 45.64 and 168.54 ng/mg ± 83.48 in groups B and C, respectively; P < .05). Paclitaxel was undetectable in serum at 24 hours in all groups, but the amount was significantly higher (P < .05) in group B at 1, 6, and 12 hours. The paclitaxel amount in navigated balloons from group A was significantly lower than in other groups (P < .05). CONCLUSIONS Paclitaxel concentration in an atherosclerotic lesion model immediately after DEB angioplasty is nearly fourfold higher than in a healthy artery. Paclitaxel remains in the bloodstream longer when a universal state of fat arterial infiltration is achieved. These findings could have clinical implications, as studies testing commercial drug-eluting devices on healthy animals may be underestimating paclitaxel arterial uptake.

Removal of Retrievable Inferior Vena Cava Filters 90 Days After Implantation in an Ovine Model: Is There a Time Limit for Removal?

OBJECTIVE To study the feasibility and safety of removing retrievable Günther-Tulip vena cava filters (GTFs) 90 days after their implantation in an ovine model. MATERIAL AND METHODS Thirty GTFs were implanted in 30 ewes and retrieval was attempted at 90 days. Conventional cavography was performed in all cases before and after retrieval in order to evaluate inferior vena cava patency and record dimensions. The presence of complications related to placement and retrieval of the filter from the inferior vena cava was also recorded. The force required to remove the filters was measured using a modified commercial dynamometer adapted to the GTF retrieval set. Histologic study focused on the inferior vena cava wall. RESULTS Implantation was performed successfully in all cases (100%). One ewe developed a small focus of thrombosis around 1 of the legs of the filter and another presented a small thrombus within the filter. Retrieval of the filter was attempted in all 30 sheep at 90 days and the result was satisfactory in all but 1 case (96.6%). None of the GTFs required a force greater than 12 N to disengage the hooks of the filter from the wall. No complications were detected on venacavography or at autopsy. Variable degrees of fibrosis were observed in the histologic study. CONCLUSIONS Retrieval of GTFs 90 days after implantation in an ovine model was feasible, safe, and easy, and required little force (median, 4.2 N).

Stent‐induced tracheal stenosis can be predicted by IL‐8 expression in rabbits

Bare metal stents may cause complications like fibrous encapsulation, granulation and tracheal stenosis. We investigated the behaviour of three commercially available stents in vivo (rabbits) and in vitro (coculture of those stents with epithelial and fibroblast cell lines). Also, we investigated whether development of tracheal stenosis could be predicted by any biological marker.