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Lowers thrombosis risk: retrievable vein filter cuts risk of migration, fragmentation.

MIAMI BEACH -- A new design for inferior vena cava filters allows their endovascular removal when they are no longer needed.

About 45%-50% of patients who receive filters in their inferior vena cava need them temporarily, Dr. Bob Smouse said at the 16th International Symposium on Endovascular Therapy.

Removing a filter when it's no longer needed cuts the patient's risk of thrombosis and filter migration or fragmentation, said Dr. Smouse, an interventional radiologist in Peoria, Ill.

Until recently, all vena cava filters were designed for permanent placement. But several commercial models are now made with a hook at one end, and come with endovascular sheaths that can envelop the filter for safe relocation to a new site in the inferior vena cava. Relocation ensures that endothelialization does not prevent later removal.

Removable filters are as effective as permanent ones, and so all filters now used should be potentially retrievable if placed in patients who are candidates for removal, Dr. Smouse told this newspaper. Temporary placement may be best for patients who need a filter following trauma, or for patients on chronic warfarin treatment who need to stop the drug for surgery.

He reported placing 128 filters in 122 patients during August 2002 through June 2003. Every filter had an attempt at either removal or repositioning if it was still needed. Some repositioned filters were later removed or repositioned again.

Repositioning had to be done within 28 days, when endothelial growth on the filter prevented further movement. The longest period before repositioning in the series was 26 days but most were done 11-14 days after placement. The largest number of repositionings done in one patient has been five. Repositionings alone were done on 83 patients, and were successful in 78 (94%).

Removals were attempted in 51 patients and were successful in 47 (92%). Most failures occurred because the filter had tipped into the vascular wall, followed by endothelial growth that covered the retrieval hook.

New filter models come with a collar that centers the filter and prevents tipping, Dr. Smouse said. The entire series that he reported used the Gunther Tulip filter made by Cook. Other retrievable models are made by Baird and Cordis, he said in an interview with this newspaper.

Repositioning is something of a misnomer as the actual procedure involves capture within the sheath and immediate redeployment, more or less at the same site within the inferior vena cava, below the renal veins. All retrievals and repositionings were done by access through the right internal jugular vein using ultrasound guidance.


Philadelphia Bureau
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Title Annotation:Cardiovascular Medicine
Author:Zoler, Mitchel L.
Publication:Internal Medicine News
Date:Mar 1, 2004
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