The Greenfield Vena Cava Filter: Caval Perforation
As stated previously, when the filter springs open during insertion, its struts engage the wall of the vena cava with some force. Penetration of the caval wall by the sharp anchoring prongs is necessary to prevent filter migration. Whether the prongs actually perforate the cava is not documented, but there have been no reported complications attributed to this. However, strut perforation can take place in a minority of cases, particularly if there is angled insertion, or if an effort is made to alter the position of a filter after it has been extruded. Methods used to assess filter position have included computerized tomography, ultrasound, and venacavography. Strut perforation has been the potential cause of two retroperitoneal hematomata, one case mimicking intestinal obstruction, and one case of reversible hematuria. Long-term experience with patients both treated and untreated with anticoagulants has not revealed other complications. generic wellbutrin
There have been no reported cases of an infected Greenfield filter. This concern was raised by such a report involving a Mobin-Uddin umbrella and led Peyton et al to examine the effect of Greenfield filter insertion in a canine model of septic embolism. These studies suggest that sepsis is not an absolute contraindication to filter placement, and that the device can be sterilized if contamination takes place. In addition, it was recommended that prophylactic antibiotics be administered to filtered patients in whom bacteremia could arise due to dental or surgical manipulation.
Little is known about the morbidity/mortality impact of thrombolytic therapy administered following insertion of the Greenfield filter. Four patients are reported in the literature in whom filters were in place prior to such treatment. Few details are given; however, no complication attributable to the presence of the filter was noted. Given the absence of significant complications during insertion into anticoagulated patients, it may be safe to administer thrombolytic agents shortly after filter placement. However, further observations in this regard are needed.
Having established the excellent long-term patency record of this filter, some have begun placing the device in a suprarenal position when I VC thrombus location prevents lower placement, or in other special contexts, as follows: recurrent thromboem-boli with I VC thrombus extending to or above the renal veins despite adequate anticoagulation; recurrent thromboemboli secondary to renal vein thrombosis despite adequate anticoagulation; recurrent thromboemboli from a previous IVC interruption despite adequate anticoagulation; recurrent thromboemboli with a large patent left ovarian vein (with or without thrombus) as a possible source of embolus despite adequate anticoagulation; presence of a perirenal IVC thrombus when anticoagulation is contraindicated; after renal transplant surgery if contraindications to anticoagulation exist; and in the presence of renal cell carcinoma with extension of tumor thrombus into the vena cava. Initial concerns over adverse renal consequences of potential suprarenal occlusion have not materialized. Thus far, 35 patients have been reported with a filter placed above the renal veins. There were no complications or caval occlusions and renal function remained unchanged in all patients.