Factors influencing the recanalisation rate of deep venous thrombosis

After an acute episode of deep venous thrombosis (DVT) resolution of venous thrombi is followed. However, the complete recanalisation occurs only in about a half of the patients. Therefore, the disease is accompanied by different sequellae like post-thrombotic syndrome. Factors that contribute to lysis of thrombi remain poorly understood. Therefore, the aim of our study was to investigate whether levels of the circulating inflammatory markers and other factors like fibrinolytic parameters, sex, and extent of the thrombotic occlusion are related to the recanalisation rate.

The study included 49 patients with idiopathic DVT in the stable phase of the disease (4-6 months after the diagnosis). All patients were evaluated for the presence of risk factors of atherosclerosis. Using Duplex ultrasound patients were examined in acute phase of the disease (before start of treatment), and at the end of the observation period (after 4 to 6 months). Each affected venous segment was classified as completely recanalised, partially obstructed, or completely occluded. Blood was collected for laboratory analysis of the fibrinolytic activity and circulating inflammatory markers.

Complete recanalisation occurred more frequently in distal (popliteal) than in proximal venous thrombosis (57% vs. 43%, P≤0.01), and the recanalisation rate was lower in patients with more extended thrombosis (increased thrombus load). The recanalisation rate (partial and total) was higher in females than in males: 87% vs. 73%, P=<0.05. Risk factors of atherosclerosis had no influence on the recanalisation rate of the occluded deep veins. Out of the endogenic fibrinolytic markers, t-PA activity only was significantly related to the recanalisation rate. The recanalisation was shown to be related to some circulating cytokines. The multivariate analysis, including inflammatory markers and the recanalisation of deep veins as dependent variables showed that IL-6 and P-selectin were the only statistically significant independent predictors of the recanalisation rate.

The results of our study show that 4 - 6 months after an acute episode of DVT complete recanalisation of the occluded veins occurred in about 50%. The recanalisation rate is related to the extent of venous thrombosis, is lower in proximal occlusions and is higher in females than in males. In patients with increased cytokine levels and decreased t-PA activity recanalisation is less likely.