Follow-up of circulatory changes secondary to deep venous thrombosis with special regards to radionuclide tests

The influence of circulatory changes, which are secondary to deep venous thrombosis (DVT) in the leg, on result of radionuclide tests was studied in eight patients. Strain gauge plethysmography, a radionuclide blood-pool test and phlebography were performed both in the acute phase and during recovery up to 6 months after the initial admission. Morphological and functional changes were correlated with results from repeatedly performed 99Tcm-plasmin tests, a test currently used for diagnosis of DVT. In the acute phase, the thrombotic leg showed an increase in pooled blood and, in the case of proximal thrombosis, also impaired venous outflow. During the 6-month follow-up complete recanalization was observed in three patients and partial recanalization in five. The circulatory changes were found to recover progressively and earlier than the morphological changes. The 99Tcm-plasmin test was pathological at admission in all patients. It was normalized in parallel with plethysmography and blood-pool test results, at a time when morphological recovery was still incomplete. These findings confirm that a positive 99Tcm-plasmin test reflects haemodynamic changes which are secondary to the DVT rather than a specific binding of the radiopharmaceutical to the thrombus. The 99Tcm-plasmin test was normalized from 1 to more than 26 weeks after an acute DVT. This finding is of practical importance when using radionuclide tests for evaluation of acute recurrent DVT.