Objective: To establish a rat model of venous thromboembolism (VTE).
Methods: One hundred and forty-four SD rats were randomly divided into 2 equal groups: VTE-A group, undergoing local blocking of left femoral artery with micro vessel clip to cause deep vein thrombosis (DVT), and VTE-B group undergoing local blocking of left femoral artery with micro vessel clip in addition of administration of thrombin slowly injected from the distal end of the femoral vein blocked by micro clip. The rate of swelling limbs was observed. One, 4, and 7 days later 6 rats from each group were killed with their femoral veins taken out to observe the thrombosis rate by light microscopy. Other 18 rats in each group underwent injection of the thrombi from left femoral vein solution in normal saline into the right femoral vein 1, 4, and 7 days after DVT formation to establish model of DVT-pulmonary thromboembolism (PTE). The 6 rats of each group [VTE-A-D(n)P(n) and VTE-B-D(n)P(n) groups] were killed 1, 4, and 7 days after DVT-PTE formation respectively with their lungs taken out to observe the rate of PTE by light microscopy.
Results: (1) On day 1 after DVT, the successful rate of DVT was 100% in both VTE-A and VTE-B groups, and the swelling limb rate of the VTE-B group was 37.5% (27/72), significantly higher than that of the VTE-A group [16.7% (12/72), P = 0.005]. On day 7 after DVT, the positive thrombus rate of the VTE-B group was 83.3% (20/24), significantly higher than that of the VTE-A group [41.7% (10/24), P = 0.003]. One, 4, and 7 days after DVT, there were reddish, mixed, and organized thrombi in both VTE-A and VTE-B groups. (2) Tachypnea and tachycardia occurred immediately and disappeared spontaneously within 30 - 60 minutes when solution of thrombi was injected into pulmonary arteries via the right femoral veins. One rat died in the VTE-B-D(1)P(1) group 12 h after the embolization and was anatomically confirmed to suffer from fresh massive emboli lodged in pulmonary arteries. The successful rates of DVT-PTE model were 100% (18/18), 83.3% (15/18), and 44.4% (8/18) in the VTE-A-D(1)P(n), VTE-A-D(4)P(n), and VTE-A-D(7)P(n) groups respectively, and were 94.4% (17/18), 100% (18/18), and 83.3% (15/18) in the VTE-B-D(1)P(n), VTE-B-D(4)P(n), and VTE-B-D(7)P(n) groups respectively. The successful rate of DVT-PTE model in the VTE-B-D(7)P(n) group was higher than that in the VTE-A-D(7)P(n) group (P = 0.015). The thrombi in pulmonary arteries caused by the 4 or 7 days thrombi of DVT showed lower dissolubility in both VTE-A and VTE-B groups.
Conclusions: A new rat model of VTE (DVT-PTE) has been successfully established. The successful rate of VTE can be increased when thrombin is slowly injected from the distal end of femoral vein blocked by micro clip in addition.