Placement of a spring filter during interventional treatment of deep venous thrombosis to reduce the risk of pulmonary embolism

Purpose: To assess the efficacy of the Spring filter during interventional treatment of deep venous thrombosis in vivo. Material and Methods: A model of inferior vena cava thrombosis was used. Part I: The thrombus was treated by the pulse-spray technique (PT) (urokinase 250,000 IU; n = 7) or a rotatory basket catheter, Thrombolizer (MT) (activated with compressed air at 7 atm; n = 5). Part II: Following placement of a Spring filter, the animal underwent PT (n = 5) or MT (n = 5). Based on the results of part I, the treatment protocol was modified (PT, urokinase 500,000 IU; MT, compressed air at 8 atm). Embolus volumes trapped by the filter and found in the lungs were calculated and the filtering efficacy quantified. Results: Part I: Pulmonary emboli (1 to 4 mm in diameter) were observed in 3 animals in the PT group and 1 animal in the MT group, respectively. Median reduction in thrombus volume was 21% and 4% by PT and MT, respectively. Part II: In the PT group, 58% and 100% of the total embolus load was trapped in 2 animals, while the filter failed to trap emboli (1 to 1.5 mm in diameter) in 1 animal. In the remaining 2 animals, no embolus was found trapped by the filter or in the lungs. In the MT group, 55-97% (median 83%) of the embolus load was trapped. Emboli found in the lungs did not exceed 4 mm in diameter. Conclusion. Preceding interventional treatment of venous thrombosis with placement of the Spring filter reduced the embolic burden on the lungs.