[Signs of high embolic risk in iliocaval floating thrombi].

Objective: To analyze the ultrasound characteristics of iliocaval floating thrombi in patients with deep vein thrombosis regarding embolic risk.

Material and methods: The study included 221 patients with deep vein thrombosis and iliocaval floating component. According to indications, all patients underwent implantation of infrarenal vena cava filter and received adequate anticoagulation. We analyzed the following parameters: length of floating clot, clot neck-to-stem ratio (minimum diameter of floating thrombus and diameter of clot attachment to occlusive thrombus), ratio of diameter of the clot neck to the widest part of the floating thrombus, as well as presence of large lateral inflow (internal iliac vein) near floating thrombus. Vena cava filter area was assessed regarding emboli. Ultrasound examinations were performed daily until primary endpoint (floating clot detachment or attachment to venous wall). The embolism group included 23 patients with clot detachment and cava filter embolism. The fixation group included 198 patients without cava filter embolism and floating thrombus attached to venous wall.

Results: The risk of floating thrombus detachment increases by 2.49 times in patients with floating clot 70-79 mm [odds ratio (OR) 2.49; 95% confidence interval (CI) (1.2; 5.16); p=0.02] and 4.8 times in case of length >80 mm [OR 4.8; 95% CI (1.34; 17.19); p=0.03]. Minimum diameter of floating clot divided into diameter of clot attachment <30% increases the risk of detachment by 2.81 times [OR 2.81; 95% CI (1.44; 5.48); p=0.01]. Large lateral tributary near the neck of the floating thrombus increases the risk of detachment by 1.99 times [OR 1.99; 95% CI (1.1; 3.71); p=0.04].

Conclusion: There are certain risk factors in patients with deep vein thrombosis, iliocaval floating thrombus and no contraindications to anticoagulation (clot length >70 mm, minimum diameter of floating clot divided into diameter of clot attachment <30% and large lateral tributary near the neck of the thrombus). These ones should probably be classified as a group with extremely high risk of fatal pulmonary embolism and need for endovascular prophylaxis of venous thromboembolic complications (cava filter implantation) in addition to anticoagulation.