Results of long-term venacavography study after placement of a Greenfield vena caval filter.

Digital subtraction venacavography (DSV) as a follow-up examination was performed in 46 patients after placement of a standard stainless steel Greenfield vena caval filter (SGF). DSV is an exact method of visualizing the lumen of the inferior vena cava as well as intraluminal or captured thrombi. Eccentric filters with an angulation of more than 15 degrees were found in 8 patients causing a higher risk of pulmonary embolism from smaller emboli and propagating thrombi. Penetration of the caval wall by filter struts was however frequent (41%), without any damage to adjacent structures as demonstrated by CT scans. The long-term caval patency rate was 90%, with 4 cases of caval thrombosis. Two patients with an occluded inferior vena cava showed no venostasis. Although changes of the filter position usually remain asymptomatic, regular follow-up examinations seem necessary to recognize any impairment of the filter's clot trapping efficiency. Filters should only be used in patients with a risk of recurrent pulmonary embolism despite anticoagulation and patients with contraindications to anticoagulation therapy.