Flavio Castañeda

A Retrievable Nitinol Vena Cava Filter: Experimental and Initial Clinical Results

PURPOSE The authors describe the properties of a new retrievable nitinol vena cava filter and report experimental and initial clinical results. MATERIALS AND METHODS The filters, made of nitinol monofilament wire that forms a spiral cone and retrieval wire, were introduced through an indwelling 5.5-F transfemoral sheath into the infrarenal portion of the inferior vena cava in 10 sheep. In seven animals, four 4 x 30-mm radiopaque clots were injected below the filter to test its thrombus-trapping efficacy. Aspiration thrombectomy was then attempted, and the filter was removed. Follow-up venography was performed 1 week after placement in three other animals. After successful preclinical testing, the filter was implanted and retrieved in two patients. RESULTS All 10 filters were successfully and easily placed in sheep. All filters were thrombus-free at follow-up venography. All clots injected in the iliac veins were trapped by the filter and successfully removed by means of aspiration thrombectomy. All 10 filters were retrieved without difficulty. Temporary filter implantation and retrieval were accomplished in two patients for 5 and 7 days. In one patient, infrafilter thrombus was aspirated. Perisheath thrombosis occurred in both patients. One patient subsequently underwent permanent filter placement. CONCLUSION Temporary vena cava filtration is feasible. Potential advantages include easy placement, surveillance, and retrieval. One current limitation is pericatheter thrombosis, which may be eliminated by a less thrombogenic sheath.

New Thrombolytic Brush Catheter in Thrombosed Polytetrafluoroethylene Dialysis Grafts: Preclinical Animal Study

PURPOSE To assess the safety, efficacy, endothelial changes, and risks of pulmonary embolic events after the use of a new thrombolytic brush catheter in mature thrombosed polytetrafluoroethylene (PTFE) dialysis grafts in an animal model. MATERIALS AND METHODS Loop configuration PTFE grafts were implanted in the femoral vessels of 12 canines 4 weeks before mechanical thrombosis was performed. The thrombus was allowed to consolidate for 24 hours in 10 animals, 72 hours in one animal, and 7 days in one animal. Standard percutaneous criss-cross catheter access was performed, and a soft, low-speed, brush (6 mm in diameter), aided by 250,000 U of periprocedural urokinase, was utilized for thrombolysis. The native vessels, just distal to the anastomosis, and lungs were evaluated macro- and microscopically. RESULTS Thrombolysis was complete in all grafts with the exception of a small segment between the crossing of the access vascular sheaths. The total thrombolysis time ranged from 8 to 12 minutes; this included 5 minutes of pulse-spray lacing. No difference in thrombolysis time was found with regard to the age or amount of thrombus. Minimal endothelial changes were noted and no evidence of acute pulmonary embolus was found on necropsy or histologic studies. CONCLUSION This method offers a simple, safe, and efficient means of recanalization of thrombosed PTFE dialysis grafts in this canine model.

Pharmacomechanical Thrombolysis of Dialysis Access Grafts Using the MTI Castañeda Over-the-Wire Brush Catheter and Reteplase

Pharmacomechanical thrombolysis (PMT) has emerged as an alternate treatment used in most patients presenting with a thrombosed hemodialysis graft. Although the gold standard, surgical revision of thrombosed hemodialysis grafts is reserved for those cases of recurrent thrombosis despite the use of percutaneous techniques and for complicated cases after PMT. Nevertheless, as for every other procedure, PMT has its own set of limitations and cost issues. New mechanical devices have begun to emerge on the market to help accelerate clot dissolution with or without thrombolytic medications. These devices have decreased the time required to lyse clot and decrease the overall cost of percutaneous treatment. This article describes the use of the Microtherapeutics, Inc. (MTI) Castañeda over-the-wire brush and our experience with this device in the treatment of the clotted hemodialysis graft.

Experimental Evaluation of a Retrievable Vena Cava Filter

A new retrievable filter, consisting of a helical basket of ten stainless steel wires and a retrieval cable, was tested in 7 adult sheep. The filter was inserted into the infrarenal vena cava through a 9-F sheath and fixed subcutaneously by a stabilizing ball at the skin insertion site. An average of 15.6 days after the filter placement, a follow-up cavography and clot-trapping tests were performed. The filter was retrieved through a 9-F sheath. Although all of the filters were free of thrombi and all of the inferior venae cavae were patent with good flow, two caval stenoses were noted below the filter. All 4 x 30 mm clots were trapped by the filter. Five filters were retrieved successfully; however, two filters could not be retrieved. Although these initial animal studies have shown this basket-type filter to be less than ideal, the development of a filter than can be successfully retrieved is essential for expanding the application of vena cava filters.