Mechanical thrombolysis of venous thrombosis in an animal model with use of temporary caval filtration

Purpose: To test the effect of temporary caval filtration on pulmonary embo li when a mechanical thrombolytic device is used to treat venous thrombosis and to test the effects of a modified device on caval patency at 30-day fo llow-up. Materials and methods: In a canine model of iliocaval subacute thrombosis, mechanical thrombolysis was performed with use of an 8-F over-the-wire Arro w-Trerotola Percutaneous Thrombolytic Device (PTD) with a 9-mm (iliac) or 1 5-mm. (inferior vena cava [IVC]) basket. In six procedures, the device was made of nitinol monofilament, and in another six, it was made of braided st ainless steel. All procedures were performed with a nitinol expandable shea th (temporary filter) in the suprarenal IVC. Low-molecular-weight heparin w as given daily after the procedure. Venography, pulmonary arteriography, me asurement of blood gases, and pulmonary artery (PA) pressure measurement we re performed before and after the procedure and at 30-day follow-up. Pulmon ary arteriograms from the group treated with stainless-steel devices were c ompared to those from an earlier group of animals in which the identical pr ocedure was performed without caval filtration. The IVC was examined histol ogically. Results: Thrombolysis was successful in all animals. Rare segmental and sub segmental pulmonary emboli (PE) were seen arteriographically; compared to p rocedures without filters, there was a significant reduction in PE (P<.002) . However, a mild increase in pulmonary artery pressure, decrease in pH, an d increase in pCO(2) were observed postprocedurally. At 30-day follow-up (n =11), IVC patency was preserved in 45% (n=5) of animals overall. Caval pate ncy was significantly better in animals in which the combination of stainle ss-steel devices was used (five of six=83% vs zero with nitinol device; P=. 015). Histologically, the stainless-steel device caused little intimal inju ry and fibrosis-less than that seen with the nitinol device. Conclusions: Temporary filtration reduces, but does not completely eliminat e, PE during mechanical thrombolysis. The stainless-steel device results in less intimal injury and better caval patency than the nitinol device.