Thrombus formation in deep venous thrombosis. A clinical approach to diagnosis and control of lysis efficacy.

The efficacy of fibrinolysis in deep venous thrombosis (DVT) depends on the age and organization of the thrombus as well as its localization. Up to now, indication for lysis therapy is defined according to the duration of clinical symptoms (less than 7 days). Our lysis results in urokinase therapy (n = 87) with high-dose and long-term regimen (mean 7.8 days), however, have shown no correlation between the duration of clinical symptoms (up to six weeks) and lysis efficacy (p less than 0.05). Therefore phlebographic criteria were established to allow the differentiation of fibrinolytic therapy depending on the site of the thrombus, its localization and the formation of collateral veins. In order to determine the state of thrombus organization, we used a new ultrasound Duplex system device (ARTIS, 7.5 Mhz, Picker International). In vivo experiments with induced thrombosis in human vena saphena magna demonstrate that echodensity of thrombi in ultrasound starts at the 11th-15th day. These findings are in good agreement with pathological studies of thrombus formation. Recent results of 24 patients with DVT indicate that echodensity of thrombus in ultrasound correlates with the course of organization and the efficacy of later lysis therapy.