EARLY AND LATE RESULTS AFTER BIRDS NEST FILTER PLACEMENT IN THE INFERIOR VENA-CAVA - CLINICAL AND DUPLEX ULTRASOUND FOLLOW-UP

From February 1989 to November 1992, 61 Bird's Nest filters were placed in the infrarenal vena cava in 61 patients (36 men and 25 women; mean age +/- s.d., 63 +/- 15, range (16-83). In 27 (44.3%), the filter was inserted because of contraindication to anticoagulation, in 19 (31.1%) for anticoagulation failure and in 15 (24.6%) as prophylaxis against pulmonary embolism in high risk patients. All the filters were introduced by percutaneous puncture of the femoral vein after preliminary screening venography demonstrated that the iliac vein was free of thrombus. Two deaths occurred within 24 h of filter placement (periprocedure mortality 3.3%) while five other patients died within 1 month (30 day cumulative mortality 11.5%). At follow up, 2-40 months later (mean +/- s.d., 17 +/- 9), a further 13 patients had died (cumulative mortality 32.8%). At 36 months, the probability of survival, calculated by the Kaplan-Meier Product Limit Method, was 55% (95% confidence intervals 37-74%). Apart from the two patients dying within 24 h, none of the early or late deaths were attributable to the procedure and there were no recurrent pulmonary emboli. Thirty-seven of the surviving 41 patients were recalled for clinical examination and Duplex ultrasound interrogation of the vena cava and the lower limb veins. No new venous thromboses in the legs were observed and no increase or onset of leg swelling was reported. The vena cava patency was 100% in these 37 patients. Considering that the annual attack rate for deep venous thrombosis in New South Wales, Australia is 60 per 100 000, and for pulmonary embolism 45 per 100 000, vena caval filter placement is an effective but underused resource.