Venous thromboembolism: Detection by duplex scanning

Purpose: The usefulness of transcranial Doppler monitoring in identifying emboli in the arterial circulation has been established. We attempted to extend this technique to identify embolism in the venous circulation and to note any changes in embolism rate with anticoagulation. Methods: From March to July 1993, 218 patients were evaluated by duplex scan for deep venous thrombosis. Results: Sixty patients had positive study results; 26 scans (43%) demonstrated embolism. In five patients (19%) the emboli were also seen on a B-mode image, enabling us to estimate embolus size, which ranged from 200 to 5000 mu m. Embolus counts varied from 5 to 800 per minute. Deep venous thrombosis was located in the iliofemoral vein in 2 patients, superficial femoral/profunda vein in 8, saphenofemoral junction in 1, popliteal vein in 1, and the calf in 10. Concomitantly, studies of 158 patients were negative for deep venous thrombosis; embolism was detected in 4 patients (3%) in this group. In patients taking heparin, the embolus count decreased 50% or more within 24 hours, and all embolism was abolished within 72 hours. Two patients died of pulmonary embolus. Conclusion: Patients with duplex scans that are positive for deep venous thrombosis have a high incidence of ongoing embolism. Heparin appears effective in eliminating the microemboli detected. The relationship among microembolism, deep venous thrombosis, and clinically significant pulmonary embolism remains to be elucidated.