Results of a multicenter study of the retrievable Tulip Vena Cava Filter: early clinical experience.

PURPOSE: To evaluate clinically a new, retrievable vena caval filter in a multicenter study. METHODS: The Tulip filter is a stainless steel half-basket that is suitable for antegrade or retrograde insertion via an 8.5 Fr introducer sheath. The filter can be retrieved via the jugular approach using an 11 Fr coaxial retrieval system. Forty-eight filters were implanted via the femoral approach and 38 via the jugular approach in 83 patients. Follow-up examinations (plain films, colorcoded duplex sonography) were performed up to 3 years after filter insertion (mean 136 days) in 75 patients. Twenty-seven patients were screened by colorcoded duplex sonography for insertion site thrombosis. RESULTS: An appropriate filter position was achieved in all cases. Insertion problems occurred in 3 cases; these were not due to the filter design but to an imperfect prototype insertion mechanism that has now been modified (n = 2) or a manipulation error (n = 1). In 2 of these cases the filters were replaced percutaneously; 1 patient required venotomy for filter removal. No further complications due to filter insertion occurred. Two filters were used as temporary devices and were successfully removed after 6 and 11 days, respectively. There was 1 fatal recurrent pulmonary embolism (PE) and 2 non-fatal PE, 5 complete and 3 partial caval occlusions, and 3 caudal migrations of the filter. Insertion site venous thrombosis was not seen in the 27 patients monitored for this complication. CONCLUSION: Precise placement of the Tulip filter is feasible by either access route and the device appears mechanically stable. Further observations are needed to confirm that safe filter removal is practical up to 10 days after its insertion.

In vitro evaluation of vena cava filters.

PURPOSE: The authors tested in vitro nine caval filters to evaluate clot-trapping capacity and transfilter pressure gradients under varying experimental conditions. MATERIAL AND METHODS: The filtering efficiency of the stainless-steel Greenfield filter was evaluated in a modified flow model. A total of 2,100 clots were injected. In addition, controlled parameters simulating in vivo conditions were selected to appreciate clot-trapping capacity and pressure gradients for nine filters in horizontal and vertical positions, by using small (3 x 30 mm) and medium-sized (5 x 30 mm) clots. Statistical evaluation was performed for 3,600 clot deliveries. RESULTS: Depending on experimental conditions, the clot-trapping capacity of the Greenfield filter varied greatly (0%-78%) by using small and medium clots. Bird's Nest and Simon nitinol filters demonstrated the highest filtering efficiency (94%-100%) for small clots. Medium clots were effectively captured by Bird's Nest, Simon nitinol, Antheor, and Günther Tulip filters (79%-100%). CONCLUSION: Experimental parameters influence a filter's clot-trapping capacity. Bird's Nest filters demonstrated the highest clot-trapping capacity.

Renal artery stent placement: long-term results with the Wallstent endoprosthesis.

PURPOSE: To evaluate clinical success and long-term patency of a Wallstent in the renal artery. MATERIALS AND METHODS: Twenty-five Wallstents were placed in 21 patients to treat delayed restenosis after previous balloon angioplasty (n = 13) or inadequate immediate postangioplasty response (n = 8). Indications for angioplasty were hypertension in all patients and renal preservation in seven. Stenosis was atheromatous in 15 patients, involving ostium in seven. RESULTS: Stent placement was successful in all patients. At follow-up angiography (range, 12-60 months), four patients (20%) had stent restenosis. Of these, three had undergone treatment for restenosis after angioplasty and three had ostial lesions. Cumulative primary patency rate was 95%, 85%, and 77% at 7, 9, and 15 months, respectively. Hypertension was cured in three patients and improved in 18. CONCLUSION: Arterial stent placement has good clinical results and high long-term patency rates after conventional renal angiography or delayed restenosis, especially in ostial lesions.

Transjugular intrahepatic portosystemic shunt: evaluation with Doppler sonography.

To assess the potential role of ultrasound (US) in evaluating transjugularly inserted intrahepatic portosystemic shunts, the authors performed sonographic, including duplex and color Doppler, studies in 23 patients. Imaging was performed before, during the first week after, and 2-3 months after shunt placement. The prostheses were readily visualized and shunt patency was easily determined with Doppler US in all patients. The mean of the maximum blood flow velocity in the main portal vein increased from 7 (range, 3-16) cm/sec before shunting to 24 (range, 18-47) cm/sec 2-3 months after shunting. Flow reversal was detected in the intrahepatic portal branches in 16 (69%) of the 23 patients. US allowed prompt detection and management of two cases of incomplete stent expansion and one case of shunt stenosis due to pseudo-intimal hyperplasia. Sonography is a valuable tool for evaluation of changes in hepatic hemodynamics after transjugular intrahepatic shunt placement.

Color Doppler-US guidance in transjugular placement of intrahepatic portosystemic shunts.

Percutaneous placement of portosystemic shunts requires access to the portal system from a transjugular approach. Color Doppler sonography was used to direct the transjugular puncture in intrahepatic portosystemic shunt procedures in four patients. In each case, the technique allowed quick, safe transjugular puncture of the portal vein and close real-time monitoring of the procedure.

Treatment of femoropopliteal stenoses by means of self-expandable endoprostheses: midterm results.

An endovascular mechanical support that can be introduced percutaneously could be an attractive approach to preventing acute occlusion and restenosis following angioplasty. The self-expandable metallic endoprosthesis is characterized by its flexibility and elasticity. The authors report the results of 40 femoropopliteal implantations in 36 patients; the follow-up period was greater than 6 months in all patients. Lesion length exceeded 7 cm in 25% of cases and was 3-7 cm in 75%. Thirty percent of lesions were total occlusions. At hemodynamic and angiographic study, two types of complications were noted. In patients not receiving orally administered anticoagulants, six thromboses occurred early; no early thromboses were noted in the nine patients treated with acenocoumarol. Restenosis occurred in 10% of cases (maximum follow-up, 2 years) and was noted even in long lesions (greater than 7 cm). The authors believe that placement of this type of prosthesis is an attractive approach to preventing postangioplasty restenosis, provided that the conditions of anticoagulation are well controlled.