What is a Vena Tech LGM inferior vena cava (IVC) filter?

Updated: Oct 31, 2020
  • Author: Gary P Siskin, MD; Chief Editor: Kyung J Cho, MD, FACR, FSIR  more...
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Vena Tech LGM filter

The Vena Tech LGM filter was first developed and released in France by LG Medical; FDA approval was obtained in 1989. The filter is stamped and point-welded and manufactured from a biocompatible, nonferromagnetic metal alloy called Phynox (cobalt, chromium, iron, nickel, molybdenum). The filter is conical with 6 radiating, flat but slightly curved legs joining a central hub at the apex. At the base of the filter, each leg is attached to a flat side rail that contacts the wall of the IVC and thus acts as a vertical stabilizing strut.

The shape of each leg–side rail assembly resembles a skewed V or a check mark. A small spike is stamped approximately 13 mm from the cephalad end of each side rail, which provides longitudinal stability and prevents filter migration. In the original design, the side rails were 34 mm in length and the legs were 45 mm in length. In the latest design (introduced in 1991), the legs are 35.5 mm in length. The open filter is 38 mm in height. The base diameter is 30 mm and is suitable for deployment in IVCs as large as 28 mm in diameter. [30, 31] However, Millward et al reported successful insertion of a Vena Tech-LGM filter without significant migration in 4 patients with IVCs greater than 28 mm in diameter. [32] The filter is delivered through a 12F introducer sheath from either a jugular or femoral approach.

Incomplete opening of the Vena Tech LGM filter has been shown to affect the clot-trapping ability of the filter. In 1991, Reed et al reported an incomplete opening of the filter of as much as 41% when it was placed by the jugular approach, and they recommended that the filter not be inserted via this approach. [33] Murphy et al reported incomplete opening of the filter in 6% of filter insertions. [34] Rapid deployment by brisk retraction of the insertion cannula has been recommended to avoid incomplete opening.

A rate of as much as 6% of recurrent PE was reported in a number of long-term follow-up studies after insertion of the Vena Tech LGM filter. Of these patients, fatal PE occurred in 25-50%. The incidence of thrombosis at the insertion site was reported to be 8-23%. Murphy et al demonstrated a rate of 37% for filter thrombosis, with cephalad extension of thrombus seen in 20%. [34] Crochet et al reported a progressive decrease in IVC patency, with a rate of 66.8% at 9 years into the follow-up period. [35] Filter placement resulting from failed anticoagulation therapy for PE appeared to be the main predictor of IVC occlusion. Earlier, the Crochet et al reported IVC patency rates of 92% after 2 years, 80% after 4 years, and 70% after 6 years of follow-up monitoring. [36] In the same study, the authors reported an 18% rate of filter migration.

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