Fig. 1. Initial vena cavogram shows a patent IVC with no evidence of clot or anomaly.		Fig. 2. Spot film of the filter after deployment. The filter has failed to open fully; the inferior portion of the filter is constrained and the cone held closed while the cephalad tips of the stabilizing legs are splayed.
Case Reference No. CC-1097-01 A 47-year-old woman with steroid-dependent asthma and congestive heart failure was referred for placement of an inferior vena cava (IVC) filter. She had recently been diagnosed with acute right lower extremity deep venous thrombosis, and was considered to have a contraindication to heparin therapy because of two previous episodes of hemorrhage from esophageal ulcerations. A right internal jugular vein approach was chosen for filter placement. An initial vena cavogram shows a patent IVC (Fig. 1). The diagnostic catheter was exchanged for the deployment sheath of a Vena-Tech LGM filter (B. Braun Medical, Inc., Evanston, IL). The filter was deployed, but it showed an unusual configuration afterwards (Fig. 2). A vena cavogram obtained after filter deployment showed that the tip of the filter protruded outside the column of contrast material that represented the IVC (Fig. 3). Further injections of contrast material with oblique positioning revealed that the filter had been deployed in the right gonadal vein (Fig. 4). Gentle attempts to retrieve the filter were performed with a loop snare, but these proved unsuccessful because the filter was firmly fixed inside the vein. A second filter was deployed in the infrarenal inferior vena cava without incident.		Fig. 3. Vena cavogram after filter deployment shows the caudal tip of the filter protruding lateral to the caval column of contrast material (arrow). Fig. 4. Right posterior oblique repeat vena cavogram, with injection of contrast material near the filter. Arrows show the right gonadal vein.
The case illustrates a complication of filter deployment which, to our knowledge, has not previously been reported formally, even in the recent excellent review by Kaufman et al (AJR 1995; 165:1281­1287). Specifically, the misplaced filter in this instance relates to the presence of a caval tributary vein which, because of its shallow angle of confluence, is nearly parallel to the IVC and partially overlaps it in the AP projection. Thus, it is easily entered from a cephalad approach, and it may be difficult to recognize that a deployment sheath has slipped into the orifice of the tributary on fluoroscopy following catheter exchange. Questions 1) It is our general sense (based on anecdotal evidence from various sources) that this problem may be occurring without being recognized fully. Specifically, we believe that examples of these misplacements have been misdiagnosed as (1) incomplete filter opening, (2) renal vein malpositioning, or (3) caval perforation by the filter. Has anyone else seen this complication? 2) In general, we like the internal jugular approach for filter deployment, although the complication described here would seem to be one to which a femoral approach should not be subject. Does anyone have any further comments on the relative pros and cons of the internal jugular approach? 3) Performance of preprocedural vena cavography through the deployment sheath might decrease the chances that this deployment problem will occur. Does anyone see any problems with this strategy? 4) We think that this potential deployment pitfall should not be unique to the Vena-Tech LGM filter. It seems that, given their mechanisms for deployment, all of the currently available filters in the United States have a similar misplacement potential. Do you agree? Related cases: MM#96-32 Caval thrombosis and thrombolysis after filter placement Case 797_01 -- Incompletely formed nitinol filter MM#96-33 Stainless steel Greenfield filter maldeployments and migration