THE HELIX FILTER - A NEW VENA-CAVAL FILTER FOR THE PREVENTION OF PULMONARY-EMBOLISM

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  • 1 January 1985
    • journal article
    • research article
    • Vol. 26  (2) , 116-123
Abstract
The helix caval filter is a continuous band spiral composed of a highly elastic metal alloy. A vertical double-helix coil fixes the filter in the infrarenal vena cava by elastic expansion while a watch spring type horizontal coil works as the filtering element. The diameter of the filter can be reduced by torsion from 32 to 7 mm. Transvenous implantation was performed under fluoroscopy using a newly developed instrument featuring intraoperative angiographic control, high flexibility, a guidance system and a well-controlled release mechanism. The filter and the implantation technique were tested in a circulation system and in 10 dogs and 4 calves (follow-up 3-91 days). Two filters were released intentionally into the right atrium of a dog and a calf. Flow resistance of the filter was negligible up to > 10 l/min. Thrombi larger than 3.5 mm were filtered out reliably. Lethal complications, filter migrations or perforations did not occur in animal experiments. Filter coils which were in contact with the vessel wall became firmly incorporated within 3-4 wk. The patency rate of the vena cava was 80% (8/10) for dogs and 100% (4/4) for calves. Implantations in the right atrium did not cause any symptoms. The filter''s design allowed fixation without hooks or spikes and consequently makes transvenous extraction possible up to 7-10 days after implantation. Comparable clinical results could extend the indications for caval filter implantation and the decision which is still difficult today could be made easier.